CN117125053A - Road adhesion coefficient estimation method and torque control method and device - Google Patents

Road adhesion coefficient estimation method and torque control method and device Download PDF

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Publication number
CN117125053A
CN117125053A CN202210552596.0A CN202210552596A CN117125053A CN 117125053 A CN117125053 A CN 117125053A CN 202210552596 A CN202210552596 A CN 202210552596A CN 117125053 A CN117125053 A CN 117125053A
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China
Prior art keywords
state
adhesion
torque
wheel
road surface
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CN202210552596.0A
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Chinese (zh)
Inventor
廉玉波
凌和平
石明川
袁跃旭
李鹏翔
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BYD Co Ltd
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BYD Co Ltd
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Priority to CN202210552596.0A priority Critical patent/CN117125053A/en
Publication of CN117125053A publication Critical patent/CN117125053A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
    • B60W30/02—Control of vehicle driving stability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W10/00—Conjoint control of vehicle sub-units of different type or different function
    • B60W10/04—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units
    • B60W10/08—Conjoint control of vehicle sub-units of different type or different function including control of propulsion units including control of electric propulsion units, e.g. motors or generators
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/02—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to ambient conditions
    • B60W40/06—Road conditions
    • B60W40/064—Degree of grip
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • B60W50/0098—Details of control systems ensuring comfort, safety or stability not otherwise provided for
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • B60W2050/0001—Details of the control system
    • B60W2050/0043—Signal treatments, identification of variables or parameters, parameter estimation or state estimation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2520/00—Input parameters relating to overall vehicle dynamics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2710/00—Output or target parameters relating to a particular sub-units
    • B60W2710/08—Electric propulsion units
    • B60W2710/083—Torque
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/72—Electric energy management in electromobility

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Human Computer Interaction (AREA)
  • Control Of Driving Devices And Active Controlling Of Vehicle (AREA)

Abstract

The embodiment of the invention discloses a road adhesion coefficient estimation method and a torque control device, wherein the road adhesion coefficient estimation method comprises the following steps: acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel; judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and the threshold value; the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a third adhesion state when the rate of change of the acceleration of the wheel angular velocity is between the first threshold value and a second threshold value and the duration exceeds a preset duration, and the corresponding first adhesion rate is calculated according to the first adhesion state or the vehicle parameter in the third adhesion state to obtain a first target value; and determining the road adhesion coefficient according to the first target value. By the embodiment of the invention, the trend of the vehicle slip is prejudged in advance according to the change rate of the acceleration of the angular speed of the wheel.

Description

Road adhesion coefficient estimation method and torque control method and device
Technical Field
The invention relates to the technical field of automobiles, in particular to a method and a device for estimating road adhesion coefficient and a method and a device for controlling torque.
Background
Under the safety control scene of the automobile, the road adhesion coefficient has a particularly important effect, and the automobile can sense the road adhesion condition under different road conditions through the road adhesion coefficient, so that different control strategies can be made, and the safe and stable running of the automobile can be ensured.
In the prior art, the calculation of the road adhesion coefficient has a certain hysteresis, such as for a slip event of a vehicle, the road adhesion coefficient is usually calculated according to the fed back vehicle parameters after the vehicle has already performed the slip event relative to the road surface, that is, the road adhesion coefficient is calculated according to the vehicle parameters at a later time, so as to perform corresponding control, and the hysteresis can affect the safe and stable running of the vehicle.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: how to reduce the hysteresis of road attachment coefficient calculation.
In order to solve the above technical problems, an embodiment of the present invention provides a method for estimating a road adhesion coefficient, including:
acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel;
Judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a third adhesion state when the rate of change of the acceleration of the wheel angular velocity is between the first threshold value and a second threshold value and the duration exceeds a preset duration, the first threshold value being greater than the second threshold value;
calculating a corresponding first attachment rate according to the vehicle parameters in the first attachment state or the third attachment state to obtain a first target value;
and determining the road adhesion coefficient according to the first target value.
Optionally, the calculating the corresponding first attachment rate according to the vehicle parameter in the first attachment state or the third attachment state to obtain the first target value includes:
recording as a marking time when the road surface attaching state is the first attaching state or the third attaching state;
calculating a plurality of first adhesion rates according to the vehicle parameters at a plurality of marking moments;
a first target value is determined from a plurality of the first attachment rates.
Optionally, the determining the first target value according to the plurality of first attachment rates includes:
when the interval between two adjacent marking moments is larger than the preset time interval, taking the first attachment rate of the previous marking moment as a first target value;
when the interval between two adjacent marking times is less than or equal to the preset time interval, the first attachment rate at the latter marking time is taken as a first target value.
Optionally, the determining the road adhesion coefficient according to the first target value includes: the first target value is taken as a road adhesion coefficient.
Optionally, the determining the road adhesion coefficient according to the first target value includes:
calculating a corresponding second attachment rate according to the vehicle parameters in the second attachment state; wherein the road surface adhesion state is the second adhesion state when the rate of change of the acceleration of the wheel angular velocity is smaller than the second threshold value;
determining a second target value based on at least one of the second attachment rates;
and determining the road adhesion coefficient according to the first target value and the second target value.
Optionally, the determining the road adhesion coefficient according to the first target value and the second target value includes:
Determining an adhesion difference value of the first target value and the second target value;
determining the first target value as a road surface adhesion coefficient under the condition that the absolute value of the adhesion difference value is larger than a preset adhesion difference value;
and determining the second target value as the road surface adhesion coefficient under the condition that the absolute value of the adhesion rate difference value is smaller than or equal to a preset adhesion rate difference value.
Optionally, the determining a second target value according to at least one of the second attachment rates includes:
and determining a plurality of corresponding second attachment rates according to the vehicle parameters in the second attachment states, and selecting the maximum value of the second attachment rates as a second target value.
Optionally, the second threshold is half of the first threshold.
The embodiment of the invention also provides a torque control method, which comprises the following steps:
acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel;
judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the first threshold value being greater than the second threshold value;
In the first attachment state, controlling the motor torque corresponding to the wheels to be reduced until the road surface attachment state exits from the first attachment state;
and in the second attaching state, controlling the motor torque corresponding to the wheels to rise until the road surface attaching state enters the first attaching state.
Optionally, when the rate of change of the acceleration of the wheel angular velocity is between the first threshold value and the second threshold value and the duration exceeds a preset duration, the road surface adhesion state is a third adhesion state, the method further comprising:
and in the third attaching state, controlling the motor torque corresponding to the wheels to rise until the road surface attaching state enters the first attaching state.
Optionally, the method further comprises:
obtaining a road adhesion coefficient;
and determining the equivalent torque of the adhesion capacity of the road surface according to the road surface adhesion coefficient.
Optionally, in the second attachment state, controlling the motor torque corresponding to the wheel to rise until the road surface attachment state enters the first attachment state includes:
in the second attaching state, if the current torque is smaller than the attaching capability equivalent torque and the absolute value of the torque difference value of the attaching capability equivalent torque is larger than a first preset torque difference value, adding the first preset torque difference value to the attaching capability equivalent torque by taking the first preset torque difference value as a first step length until the absolute value of the torque difference value of the attaching capability equivalent torque is smaller than or equal to the first preset torque difference value;
If the current torque is smaller than the attaching capability equivalent torque and the torque difference between the current torque and the attaching capability equivalent torque is smaller than or equal to a first preset torque difference, taking the attaching capability equivalent torque as the motor output torque;
after the adhesion capacity equivalent torque is used as the motor output torque, if the road surface adhesion state is still the second adhesion state, the adhesion capacity equivalent torque is increased by a second step length until the road surface adhesion state enters the first adhesion state; wherein the second step size is smaller than the first step size;
and under the third attachment state, controlling the motor torque corresponding to the wheels to rise until the road surface attachment state enters the first attachment state, wherein the method comprises the following steps of:
in the third attaching state, if the current torque is smaller than the attaching capability equivalent torque and the torque difference between the current torque and the attaching capability equivalent torque is smaller than or equal to a first preset torque difference, increasing the attaching capability equivalent torque by a third step length until the pavement attaching state enters the first attaching state; wherein the third step size is smaller than the second step size.
Optionally, the determining the equivalent torque of the adhesion capability of the road surface according to the road surface adhesion coefficient includes:
Acquiring axle load and wheel rolling radius;
and determining the equivalent torque of the adhesion capability of the road surface according to the axle load, the rolling radius of the wheels and the road surface adhesion coefficient.
Alternatively, obtaining the road surface adhesion coefficient includes referring to the estimation method of the road surface adhesion coefficient as described above.
The embodiment of the invention also provides a device for estimating the road adhesion coefficient, which comprises the following steps:
the first acceleration change rate determining module is used for obtaining the angular speed of the wheel and obtaining the change rate of the acceleration of the angular speed of the wheel according to the angular speed of the wheel;
the first road surface adhesion state judging module is used for judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and the threshold value; wherein the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a third adhesion state when the rate of change of the acceleration of the wheel angular velocity is between the first threshold value and a second threshold value and the duration exceeds a preset duration, the first threshold value being greater than the second threshold value;
a first target value obtaining module for calculating a corresponding first attachment rate according to the vehicle parameter in the first attachment state or the third attachment state to obtain a first target value;
And the road surface adhesion coefficient determining module is used for determining the road surface adhesion coefficient according to the first target value.
The embodiment of the invention also provides a torque control device, which comprises:
the second acceleration change rate determining module is used for obtaining the angular speed of the wheel and obtaining the change rate of the acceleration of the angular speed of the wheel according to the angular speed of the wheel;
a second road surface adhesion state judging module for judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular velocity of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the first threshold value being greater than the second threshold value;
the first attaching state torque control module is used for controlling the motor torque corresponding to the wheels to be reduced in the first attaching state until the road surface attaching state exits from the first attaching state;
and the torque control module is used for controlling the motor torque corresponding to the wheels to rise in the second attaching state until the road surface attaching state enters the first attaching state.
In the embodiment of the invention, the change rate of the acceleration of the wheel angular velocity is obtained according to the wheel angular velocity, the road surface attachment state of the wheel is judged according to the change rate of the acceleration of the wheel angular velocity and the threshold value, when the change rate of the acceleration of the wheel angular velocity is larger than the first threshold value, the road surface attachment state is the first attachment state, when the change rate of the acceleration of the wheel angular velocity is between the first threshold value and the second threshold value and the duration exceeds the preset duration, the road surface attachment state is the third attachment state, the first threshold value is larger than the second threshold value, and then the corresponding first attachment rate is calculated according to the first attachment state or the vehicle parameter under the third attachment state, so as to obtain the first target value, and the road surface attachment coefficient is determined according to the first target value.
According to the torque control method, torque control is carried out according to the attached state of the wheels on the road surface, so that the attached state of the wheels on the road surface is switched between the second attached state close to the first attached state and the first attached state close to the second attached state, the torque is fluctuated in a small range, and the driving stability of the vehicle is improved.
Drawings
In order to more clearly illustrate the technical solutions of the present invention, the drawings that are needed in the description of the present invention will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort to a person skilled in the art.
FIG. 1 is a diagram of an overall architecture according to one embodiment of the present invention;
FIG. 2 is a flowchart illustrating a method for estimating road adhesion coefficient according to an embodiment of the present invention;
FIG. 3a is a graph showing torque versus slip ratio according to one embodiment of the present invention;
FIG. 3b is a schematic diagram showing an example of estimating road adhesion coefficient according to an embodiment of the present invention;
FIG. 4 is a flow chart of steps of a method of torque control according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of an example of torque control provided by an embodiment of the present invention;
FIG. 6a is a schematic diagram of a torque control effect provided by an embodiment of the present invention;
FIG. 6b is a schematic illustration of another torque control effect provided by an embodiment of the present invention;
FIG. 7 is a block diagram showing a road adhesion coefficient estimating apparatus according to an embodiment of the present invention;
fig. 8 is a block diagram of a torque control apparatus according to an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects solved by the invention more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
In the embodiment of the invention, as shown in fig. 1, on one hand, the attachment state of the road surface is judged by the rotation speed of the wheels, namely, whether the torque exceeds the attachment capacity of the road surface, and on the other hand, the attachment rate of the front and rear axles is calculated by vehicle parameters such as the longitudinal acceleration, the gradient, the front and rear motor torque, the wheelbase, the front and rear wheelbase, the centroid height and the like of the whole vehicle.
After the attachment rate and the attachment state are obtained, the maximum attachment rate of the front and rear axles, namely the attachment capacity coefficient of the road surface, can be calculated according to the attachment rate and the attachment state, then the attachment capacity equivalent torque of the road surface is calculated by combining the front and rear axle loads and the rolling radius of the wheels, and further the torque control can be performed according to the attachment capacity equivalent torque.
In torque control, the torque requirement of the road surface adhesion capability can be met by adjusting the obtained total torque requirement by adopting the adhesion capability equivalent torque.
Referring to fig. 2, a flowchart illustrating a method for estimating a road adhesion coefficient according to an embodiment of the present invention may specifically include the following steps:
in step 201, the angular velocity of the wheel is obtained, and the rate of change of the acceleration of the angular velocity of the wheel is obtained from the angular velocity of the wheel.
In a specific implementation, the wheel angular velocity may be read by a wheel speed sensor of the vehicle, the wheel angular velocity may include a wheel angular velocity of a wheel of a front axle of the vehicle and a wheel angular velocity of a wheel of a rear axle of the vehicle, and further, the acceleration of the wheel angular velocity may be calculated according to the read wheel angular velocity, the acceleration of the wheel angular velocity is a derivative of the wheel angular velocity, and then the change rate of the acceleration of the wheel angular velocity may be calculated according to the acceleration of the wheel angular velocity, the change rate of the acceleration of the wheel angular velocity is a derivative of the acceleration of the wheel angular velocity, that is, the change rate of the acceleration of the wheel angular velocity is a second derivative of the wheel angular velocity.
And 202, judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and the threshold value. The road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a third adhesion state when the rate of change of the acceleration of the wheel angular velocity is between the first threshold value and a second threshold value and the duration exceeds a preset duration, the first threshold value being greater than the second threshold value.
Wherein a value between the first threshold and the second threshold includes the first threshold and the second threshold, and a value between the first threshold and the second threshold.
As for the road surface adhesion state of the wheels, which can reflect whether the longitudinal driving force provided by the current torque in the vehicle to the wheels exceeds the adhesion capability of the road surface, the following is specifically analyzed:
the dynamics equations of the contact points of the front axle wheels and the rear axle wheels with the road surface are as follows:
wherein J is w Equivalent total moment of inertia, ω, of the front or rear axle wheels f 、ω r The angular velocities of the front axle wheel and the rear axle wheel are respectively, specifically the average value of the angular velocities of the two wheels on each axle,the derivatives of the angular velocities of the front and rear axle wheels, respectively, i.e. the acceleration of the angular velocity, T f 、T r The motor output torque i for the front axle wheel or the rear axle wheel, respectively f 、i r Main speed reducer speed ratios of a front shaft and a rear shaft respectively, F X1 、F X2 Road surface longitudinal driving forces respectively received by the front axle wheels and the rear axle wheels, specifically the sum of the road surface longitudinal driving forces received by the two wheels on each axle, r t The wheel rolling radius is the front axle wheel or the rear axle wheel.
Respectively representing the longitudinal driving force actually used for accelerating by the front axle wheel and the rear axle wheel, T f i f 、T r i r Characterizing the longitudinal driving force provided by the current torque of the motor to the front axle wheels and the rear axle wheels respectively, F X1 r t 、F X2 r t Longitudinal driving forces are respectively provided for the front axle wheels and the rear axle wheels for the road surface.
As can be seen in conjunction with fig. 3a, as the current torque of the motor increases, the current torque of the motor provides the longitudinal driving force to the wheels (as T in fig. 3a f i f Corresponding curve) is gradually increased, the road surface provides the longitudinal driving force to the wheels (as shown by F in fig. 3a X1 r t Corresponding curve) increases as well.
When the current torque of the motor provides a longitudinal driving force to the wheels greater than the maximum value of the longitudinal driving force provided to the wheels by the road surface (F in fig. 3a X1 r t The highest point of the corresponding curve), i.e., the longitudinal driving force provided by the current torque to the wheels exceeds the adhesion capability of the road surface, the following situations may occur thereafter:
1. the acceleration of the wheel angular velocity accelerates.
2. Along with the acceleration of the angular velocity of the wheels, the acceleration of the angular velocity of the wheels is larger than the acceleration of the speed of the whole vehicle, so that the slip rate is increased, and the phenomenon of slipping is aggravated.
The slip rate may be indicative of the severity of slip as the vehicle progresses, which may be expressed as follows:
where s is slip ratio, v is vehicle speed, and ω is wheel angular velocity.
3. The road surface may provide a longitudinal driving force to the wheels (e.g. F in fig. 3a X1 r t The corresponding curve) is further reduced, thereby exacerbating cases 1 and 2.
Based on the above, the road surface adhesion state of the wheel can be judged by combining the change rate of the acceleration of the angular velocity of the wheel with a threshold value, wherein the threshold value can comprise a first threshold value and a second threshold value, and the value range of the first threshold value can be 10rad/s 3 To 100rad/s 3 The second threshold may be half of the first threshold.
When the change rate of the acceleration of the angular velocity of the wheel is greater than a first threshold value, the road surface attachment state can be judged to be a first attachment state, namely, the longitudinal driving force provided by the current torque of the motor to the wheel exceeds the road surface attachment capability, and when the change rate of the acceleration of the angular velocity of the wheel is located between the first threshold value and a second threshold value and the duration exceeds the preset duration, if the value range of the preset duration is 10ms to 50ms, the road surface attachment state is judged to be a third attachment state, namely, the longitudinal driving force provided by the current torque of the motor to the wheel approaches the road surface attachment capability.
Step 203, calculating a corresponding first attachment rate according to the vehicle parameters in the first attachment state or the third attachment state to obtain a first target value.
In the case where the wheels are in the first attaching state or the third attaching state, the vehicle parameter may be acquired, and further the first attaching rate may be determined according to the vehicle parameter, and the first target value, that is, the attaching rate of the first target, may be determined according to the first attaching rate.
For the front axle attachment rate and the rear axle attachment rate, the equivalent gradient of the whole vehicle can be determined according to the acceleration of the whole vehicle and the gradient of the road surface in the vehicle parameters, and then the attachment rate can be determined according to the torque distribution ratio and the equivalent gradient in the vehicle parameters.
Specifically, for the equivalent gradient, the acceleration of the whole vehicle can be measured from the obtained acceleration sensor of the whole vehicle, the gradient of the road surface is read from the output signal of the gradient estimation related module, and then the equivalent gradient of the whole vehicle is calculated according to the acceleration of the whole vehicle and the gradient of the road surface, and the following formula is shown:
wherein q is a longitudinal acceleration sensor signal, A x And the acceleration of the whole vehicle is that theta is the gradient of the road surface, and g is that of gravity.
For the torque distribution ratio, the torque distribution ratio may be a torque distribution ratio of any one of the front axle or the rear axle, the torque distribution ratio of the other axle may be calculated by subtracting the total ratio, specifically, the current torque may be read from the motor controller output signal, the torque of the front axle and the torque of the rear axle may be included, and then the torque distribution ratio may be calculated according to the torque of the front axle and the torque of the rear axle, as shown in the following formula:
Wherein ψ is the torque distribution ratio of the rear axle, T r T is the torque of the rear axle f Is the torque of the front axle.
After the equivalent gradient and the torque distribution ratio are obtained, the attachment rates of the front axle tire and the rear axle tire can be calculated respectively by combining the whole vehicle wheelbase, the front axle base, the rear axle base and the whole vehicle centroid height, and the following formulas are shown:
wherein,the attachment rates of the front axle tire and the rear axle tire are respectively, L is the wheel base of the whole vehicle, a is the front wheel base, b is the rear wheel base, h g The mass center height of the whole vehicle.
In an embodiment of the present invention, step 203 may include:
a substep 11 of recording a marking time when the road surface adhesion state is the first adhesion state or the third adhesion state.
Each time the first attachment state or the third attachment state is entered, the time at which the user is aware of the time is the mark time.
A substep 12 calculates a plurality of first adhesion rates based on the vehicle parameters at the plurality of marking moments.
At each marking time, a first attachment rate may be calculated from the vehicle parameters, resulting in a plurality of first attachment rates.
And a substep 13 of determining a first target value according to a plurality of first attachment rates.
After obtaining the plurality of first attachment rates, a first target value may be determined based on the plurality of first attachment rates.
In an embodiment of the present invention, the sub-step 13 may include:
in the substep 131, when the interval between two adjacent marking moments is greater than the preset time interval, the first attachment rate at the previous marking moment is taken as the first target value.
In a specific implementation, since the marking moments are recorded in advance, the time interval of two adjacent marking moments can be determined, which can be the time interval of the two nearest marking moments.
When the time interval is greater than the preset time interval, for example, the value of the preset time interval may range from 10ms to 100ms, and the first attachment rate at the previous marking time may be the first target value.
In the substep 132, when the interval between two adjacent marking moments is smaller than or equal to the preset time interval, the first attachment rate at the following marking moment is taken as the first target value.
When the time interval is less than or equal to the preset time interval, the first attachment rate at the later marking time may be taken as the first target value.
In an embodiment of the present invention, the first attachment rate in one first attachment state may be set as the first target value, or the first attachment rate in one third attachment state may be set as the first target value.
And 204, determining the road adhesion coefficient according to the first target value.
After the first target value is obtained, a road surface adhesion coefficient may be determined from the first target value, and the road surface adhesion coefficient may be used to characterize the adhesion capability of the road surface.
In an embodiment of the present invention, step 204 may include:
the first target value is taken as a road adhesion coefficient.
In a specific implementation, the first target value may be directly taken as the road surface adhesion coefficient.
In an embodiment of the present invention, step 204 may include:
a substep 21 of calculating a corresponding second attachment rate according to the vehicle parameters in the second attachment state; wherein the road surface adhesion state is the second adhesion state when the rate of change of the acceleration of the wheel angular velocity is smaller than the second threshold value.
When the rate of change of the acceleration of the angular velocity of the wheel is smaller than the second threshold value, it may be determined that the road surface adhesion state is the second adhesion state, that is, the longitudinal driving force provided by the current torque of the motor to the wheel is not exceeded and does not approach the road surface adhesion capability, and in entering the second adhesion state, the second adhesion rate may be calculated according to the acquired vehicle parameters.
A sub-step 22 of determining a second target value based on at least one of said second attachment rates.
After the second attachment rate is obtained, a second target value may be determined based on the at least one second attachment rate.
In one embodiment of the present invention, sub-step 22 may include:
and determining a plurality of corresponding second attachment rates according to the vehicle parameters in the second attachment states, and selecting the maximum value of the second attachment rates as a second target value.
For a plurality of mark timings in the second attachment state, a plurality of second attachment rates can be obtained, and further, the largest second attachment rate can be selected therefrom as the second target value.
Specifically, the second attachment rate at the later marking time may be compared with the second attachment rate at the earlier marking time, with the larger second attachment rate being taken as the second target value.
In an embodiment, the second target value may be the second adhesion rate at a single time.
And a substep 23 of determining a road adhesion coefficient according to the first target value and the second target value.
After the first target value and the second target value are obtained, the road surface adhesion coefficient may be determined based on the first target value and the second target value.
In an embodiment of the present invention, the substep 23 may include:
In a substep 231, an adhesion difference between the first target value and the second target value is determined.
After the specific implementation, a difference between the first target value and the second target value may be calculated, resulting in an adhesion difference value.
And a substep 232 of determining the first target value as the road surface adhesion coefficient when the absolute value of the adhesion difference value is greater than the preset adhesion difference value.
In the case where the absolute value of the adhesion difference is larger than the preset adhesion difference, for example, the preset adhesion difference may have a value ranging from 0.1 to 0.5, and the first target value may be determined as the road surface adhesion coefficient.
In the substep 233, the second target value is determined to be the road surface adhesion coefficient when the absolute value of the adhesion rate difference is less than or equal to the preset adhesion rate difference.
In the case where the absolute value of the adhesion difference is less than or equal to the preset adhesion difference, the second target value may be determined as the road surface adhesion coefficient.
The invention is illustrated below in connection with fig. 3 b:
1. the road surface adhesion state of the front axle tire or the rear axle tire, the adhesion rate C, and the corresponding time point t are input.
2. The first target value a is calculated as follows:
2.1, judging whether the road surface adhesion state is the first adhesion state max-or the third adhesion state max0.
2.2 recording the marking time t when the road surface adhesion state is the first adhesion state max-or the third adhesion state max0 k And determine the t k First adhesion rate n=c (k) at time.
2.3 recording the marking time t when the road surface adhesion state is again the first adhesion state max-or the third adhesion state max0 k+1 。
2.4 calculating the time interval t of two marking moments k+1 -t k And determine the time interval t k+1 -t k Whether or not it is greater than a preset time interval T 1 At time interval t k+1 -t k Is greater than a preset time interval T 1 In the case of (2), t k A is given as a first target value at a first attachment rate n at a time interval t k+1 -t k Less than or equal to a preset time interval T 1 In the case of (2), t k+1 The first adhesion rate C (k+1) at the time is set as the first target value a.
3. The second target value e is calculated as follows:
3.1, if the road surface adhesion state is the second adhesion state max+, judging whether the second adhesion rate C (i) at the later time i is larger than the second adhesion rate C (i-1) at the later time i-1, and further regarding the larger second adhesion rate as a second target value e.
4. And calculating an adhesion difference value e-a of the first target value a and the second target value e, and judging whether the absolute value of the adhesion difference value e-a is larger than a preset adhesion difference value K.
5. In the case where the absolute value of the adhesion difference e-a is larger than the preset adhesion difference K, the first target value a is taken as the road surface adhesion coefficientIn the case where the absolute value of the adhesion difference e-a is smaller than or equal to the preset adhesion difference K, the second target value e is taken as the road surface adhesion coefficient +.>
In the embodiment of the invention, the change rate of the acceleration of the wheel angular velocity is obtained according to the wheel angular velocity, the road surface attachment state of the wheel is judged according to the change rate of the acceleration of the wheel angular velocity and the threshold value, when the change rate of the acceleration of the wheel angular velocity is larger than the first threshold value, the road surface attachment state is the first attachment state, when the change rate of the acceleration of the wheel angular velocity is between the first threshold value and the second threshold value and the duration exceeds the preset duration, the road surface attachment state is the third attachment state, the first threshold value is larger than the second threshold value, and then the corresponding first attachment rate is calculated according to the first attachment state or the vehicle parameter under the third attachment state, so as to obtain the first target value, and the road surface attachment coefficient is determined according to the first target value.
Referring to fig. 4, a flowchart illustrating steps of a method for torque control according to an embodiment of the present invention may specifically include the following steps:
in step 401, the angular velocity of the wheel is obtained, and the rate of change of the acceleration of the angular velocity of the wheel is obtained from the angular velocity of the wheel.
Reference is made to the above description of step 201 for a description of step 401.
Step 402, judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the first threshold value being greater than the second threshold value.
Reference is made to the above description of step 202, sub-step 21 for a description of step 402.
In an embodiment of the present invention, the method may further include:
obtaining a road adhesion coefficient; and determining the equivalent torque of the adhesion capacity of the road surface according to the road surface adhesion coefficient.
In a specific implementation, the road surface adhesion coefficient may be obtained as described above with reference to step 103, and then the road surface adhesion capability equivalent torque may be determined based on the road surface adhesion coefficient.
In an embodiment of the present invention, the determining the equivalent torque of the adhesion capability of the road surface according to the adhesion coefficient of the road surface includes: acquiring axle load and wheel rolling radius; and determining the equivalent torque of the adhesion capability of the road surface according to the axle load, the rolling radius of the wheels and the road surface adhesion coefficient.
In specific implementation, the rolling radius of the wheel can be obtained first, the axle loads of the front axle and the rear axle can be obtained through calculation, then the axle loads and the rolling radius of the wheel can be used for converting the road surface adhesion coefficient into the adhesion capacity equivalent torque of the road surface, and the following formula can be adopted:
wherein T is fmax 、T rmax Equivalent torque of the adhesion capability of the front axle and the rear axle respectively,road adhesion coefficients of front axle and rear axle, F z1 、F z2 The axle loads of the front axle and the rear axle respectively, r t Is the rolling radius of the wheel.
The axle load can be calculated according to the whole vehicle mass, the gravity acceleration, the road gradient, the front axle base, the rear axle base, the whole vehicle mass center height and the whole vehicle acceleration, and the following formula is shown:
wherein F is z1 、F z2 The axle loads of a front axle and a rear axle respectively, M is the mass of the whole automobile, g is the gravity acceleration, a is the front axle base, b is the rear axle base, L is the axle base of the whole automobile, and h g The mass center height of the whole vehicle.
Step 403, in the first attachment state, controlling the motor torque corresponding to the wheels to decrease until the road surface attachment state exits the first attachment state.
In the case of the first adhesion state, that is, the current torque of the motor provides the longitudinal driving force to the wheels exceeding the road adhesion capability, the motor torque corresponding to the wheels can be controlled to be reduced until the road adhesion state exits from the first adhesion state and enters into the second adhesion state, for example, the motor torque can be reduced according to the step length with the value ranging from-200 Nm to-10 Nm.
And step 404, in the second attachment state, controlling the motor torque corresponding to the wheels to rise until the road surface attachment state enters the first attachment state.
In the second attachment state, that is, when the current torque of the motor provides the longitudinal driving force to the wheels that does not exceed the road attachment capability, the torque of the motor corresponding to the wheels can be controlled to rise until the road attachment state enters the first attachment state.
In an embodiment of the present invention, step 404 may include:
and a substep 31, in the second attachment state, if the current torque is smaller than the attachment capacity equivalent torque and the absolute value of the torque difference between the current torque and the attachment capacity equivalent torque is larger than a first preset torque difference, adding the first preset torque difference to the attachment capacity equivalent torque by taking the first preset torque difference as a first step length until the absolute value of the torque difference of the attachment capacity equivalent torque is smaller than or equal to the first preset torque difference.
Under the condition that the current torque is smaller than the attaching capability equivalent torque, the absolute value of the torque difference between the current torque and the attaching capability equivalent torque can be calculated, and when the absolute value of the torque difference is larger than a first preset torque difference, if the value range of the first preset torque difference can be 10Nm to 100Nm, that is, the difference between the current torque and the attaching capability equivalent torque is larger, the first preset torque difference can be the first step size, the attaching capability equivalent torque is increased, and the attaching capability equivalent torque is gradually approached.
And step 32, if the current torque is smaller than the attachment capacity equivalent torque and the torque difference between the current torque and the attachment capacity equivalent torque is smaller than or equal to a first preset torque difference, taking the attachment capacity equivalent torque as the motor output torque.
When the absolute value of the torque difference is smaller than or equal to the first preset torque difference, that is, the difference between the current torque and the adhesion equivalent torque is smaller, the adhesion equivalent torque can be directly used as the motor output torque to control the torque rise.
A substep 33, after taking the equivalent torque of the attaching capability as the output torque of the motor, if the road surface attaching state is still the second attaching state, increasing the equivalent torque of the attaching capability by a second step length until the road surface attaching state enters the first attaching state; wherein the second step size is smaller than the first step size.
After the equivalent torque of the adhesion capability is taken as the output torque of the motor, whether the road surface adhesion state enters the first adhesion state from the second adhesion state or not can be detected again, if so, the torque is controlled in a mode of the first adhesion state, and if not, the torque increase can be controlled continuously with a smaller second step length.
In an embodiment of the present invention, when the rate of change of the acceleration of the angular velocity of the wheel is between the first threshold value and the second threshold value and the duration exceeds the preset duration, the road surface adhesion state may be a third adhesion state, and the method may further include:
and in the third attaching state, controlling the motor torque corresponding to the wheels to rise until the road surface attaching state enters the first attaching state.
In the third attachment state, that is, the longitudinal driving force provided by the current torque of the motor to the wheels approaches the road attachment capability, the torque of the motor corresponding to the wheels can be controlled to rise until the road attachment state enters the first attachment state.
In an embodiment of the present invention, in the third attachment state, controlling the motor torque corresponding to the wheel to rise until the road surface attachment state enters the first attachment state may include:
In the third attaching state, if the current torque is smaller than the attaching capability equivalent torque and the torque difference between the current torque and the attaching capability equivalent torque is smaller than or equal to a first preset torque difference, increasing the attaching capability equivalent torque by a third step length until the pavement attaching state enters the first attaching state; wherein the third step size is smaller than the second step size.
When the current torque is smaller than the attachment capacity equivalent torque, if the absolute value of the torque difference is smaller than or equal to the first preset torque difference, that is, the difference between the current torque and the attachment capacity equivalent torque is smaller, the torque increase can be continuously controlled by a smaller third step.
The invention is illustrated below in connection with fig. 5:
1. the current torque demand T_req is increased by taking Step0 as a Step length, the value range of Step0 can be 10Nm to 100Nm, the actual torque (namely the current torque) of the motor at the moment K is T_actl, and the equivalent torque of the attachment capability is T_max.
2. It is determined whether the road surface adhesion state is the first adhesion state max-.
3. When the road surface adhesion state is the first adhesion state max-, torque reduction is performed in steps of Step3, and Step3 may have a value ranging from-200 Nm to-10 Nm, that is, t_req (k+1) =t_req (k) +step2.
4. Under the condition that the road surface adhesion state is the first adhesion state max-, calculating an absolute value T_actl-T_max of a torque difference value of the current torque T_actl and the adhesion capacity equivalent torque T_max, and judging whether the absolute value T_actl-T_max of the torque difference value is smaller than a first preset torque difference value Step0.
5. In the case that the absolute value t_act-t_max of the torque difference is greater than or equal to the first preset torque difference Step0, the torque is continuously increased with Step0 as a Step size.
6. In the case where the absolute value t_act-t_max of the torque difference is smaller than the first preset torque difference Step0, it is further determined whether the road surface adhesion state is the second adhesion state max+.
7. In the case where the road surface adhesion state is the second adhesion state max+, then the adhesion-ability equivalent torque may be directly taken as the motor output torque, i.e., t_req (k+1) =t_max.
8. After the equivalent torque of the adhesion capability is taken as the output torque of the motor, whether the road surface adhesion state is the second adhesion state max+ or not can be judged again, if the road surface adhesion state is the second adhesion state max+, the torque increase can be continuously controlled by a smaller second Step length Step1, the value range of Step1 can be 10Nm to 100Nm, and if the road surface adhesion state is not the second adhesion state max+, the torque control can be performed by a strategy under the corresponding adhesion state.
9. When the road surface adhesion state is not the second adhesion state max+, that is, the road surface adhesion state is the third adhesion state max0, the torque increase can be continuously controlled with the smaller third Step 2.
In the embodiment of the invention, the change rate of the acceleration of the angular velocity of the wheel is obtained according to the angular velocity of the wheel, the road surface attached state of the wheel is judged according to the change rate of the acceleration of the angular velocity of the wheel and the threshold value, when the change rate of the acceleration of the angular velocity of the wheel is larger than the first threshold value, the road surface attached state is in the first attached state, when the change rate of the acceleration of the angular velocity of the wheel is smaller than the second threshold value, the road surface attached state is in the second attached state, the first threshold value is larger than the second threshold value, then the motor torque corresponding to the wheel is controlled to be reduced in the first attached state until the road surface attached state exits the first attached state, and the motor torque corresponding to the wheel is controlled to be increased in the second attached state until the road surface attached state enters the first attached state, so that the torque is controlled to be close to the attached capacity of the road surface according to the attached state of the wheel, the accuracy of the torque control is improved, and the safe and stable running of the vehicle is ensured.
The beneficial effects of the present invention are described below with reference to fig. 6a and 6 b:
as shown in fig. 6a, in which the torque demand T is controlled by using the equivalent torque of the road surface as the torque reference value, and as shown in fig. 6b, in which the torque demand T is not controlled by using the equivalent torque of the road surface as the torque reference value, the following advantages are obtained when the torque demand T is controlled by using the equivalent torque of the road surface as the torque reference value:
1. in the torque increasing stage, the equivalent torque of the adhesion capability of the road surface is used as the torque increasing reference value of the front axle torque and the rear axle torque, the torque increasing rate can be adjusted after the maximum torque increasing rate reaches the reference value, and compared with a general torque increasing step size limiting mode, the response time can be effectively reduced.
2. After the torque reduction control is carried out to a vehicle stable state, a torque recovery stage is carried out to calculate the adhesion capability equivalent torque of the road surface to be used as a torque increase reference value of the front axle motor and the rear axle motor, so that the phenomenon that wheels slip again due to unlimited torque increase is avoided, and the torque reduction control is triggered.
In the prior art, whether slipping occurs or not is judged according to the difference value of the actual slipping rate and the preset slipping rate, and the slip judgment result can be obtained only after the wheel speed rises to the slipping phenomenon. In addition, the torque is controlled according to the slip ratio, and the torque range to be adjusted from the slip state to the normal state is larger and the time required is longer due to the hysteresis of judgment (see fig. 6 b).
According to the torque control method, the torque is controlled according to the slip trend, namely the first attachment state and the second attachment state, the torque is timely reduced under the first attachment state, namely the slip trend is generated, the slip risk is avoided, the torque is increased again after the torque is reduced to enter the second attachment state from the first attachment state, namely the torque is controlled until the first attachment state is reentered, namely the torque is timely increased to enable the wheels to enter the first attachment state again after the first attachment state enters the second attachment state from the first attachment state, and the torque is timely reduced to enable the wheels to enter the second attachment state again after the second attachment state enters the first attachment state, so that the stay time of the road surface attachment state of the wheels in the first attachment state and the second attachment state is short, the control range of the torque is also in a small range, particularly in a small range of the attachment capacity equivalent axis of the road surface, fluctuation (see fig. 6 a), and the driving stability of the vehicle is improved. In addition, since the wheels have a tendency to slip in the first attachment state, but no slip occurs, the running safety of the vehicle is also ensured.
It should be noted that, for simplicity of description, the method embodiments are shown as a series of acts, but it should be understood by those skilled in the art that the embodiments are not limited by the order of acts, as some steps may occur in other orders or concurrently in accordance with the embodiments. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred embodiments, and that the acts are not necessarily required by the embodiments of the invention.
Referring to fig. 7, a block diagram of a road adhesion coefficient estimating apparatus according to an embodiment of the present invention may specifically include the following modules:
the first acceleration change rate determining module 701 is configured to obtain a wheel angular velocity, and obtain a change rate of acceleration of the wheel angular velocity according to the wheel angular velocity.
A first road surface adhesion state judging module 702, configured to judge a road surface adhesion state of a wheel according to a change rate of acceleration of the angular velocity of the wheel and a threshold value; the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a third adhesion state when the rate of change of the acceleration of the wheel angular velocity is between the first threshold value and a second threshold value and the duration exceeds a preset duration, the first threshold value being greater than the second threshold value.
A first target value obtaining module 703, configured to calculate a corresponding first attachment rate according to the vehicle parameter in the first attachment state or the third attachment state, so as to obtain a first target value.
The road surface adhesion coefficient determination module 704 determines the road surface adhesion coefficient based on the first target value.
In an embodiment of the present invention, the first target value obtaining module 703 may include:
a marking time recording sub-module, configured to record a marking time when the road surface adhesion state is the first adhesion state or the third adhesion state;
a plurality of first attachment rate calculation sub-modules for calculating a plurality of first attachment rates according to the vehicle parameters at a plurality of marking moments;
and the first target value determination submodule is used for determining a first target value according to the first attachment rates.
In an embodiment of the present invention, the plurality of first attachment rate determining first target value sub-modules may include:
a preceding marking time determining unit configured to take a first attachment rate at a preceding marking time as a first target value when an interval between two adjacent marking times is larger than a preset time interval;
and a subsequent marking time determining unit configured to take the first attachment rate at the subsequent marking time as a first target value when the interval between the adjacent two marking times is less than or equal to the preset time interval.
In an embodiment of the present invention, the road adhesion coefficient determining module 704 may include:
the first target value is used as a coefficient submodule and is used for taking the first target value as a road adhesion coefficient.
In an embodiment of the present invention, the road adhesion coefficient determining module 704 may include:
a second attachment rate calculation submodule for calculating a corresponding second attachment rate according to the vehicle parameters in the second attachment state; wherein the road surface adhesion state is the second adhesion state when the rate of change of the acceleration of the wheel angular velocity is smaller than the second threshold value;
a second target value determination sub-module for determining a second target value based on at least one of the second attachment rates;
and the combined second target value determining coefficient submodule is used for determining the road surface adhesion coefficient according to the first target value and the second target value.
In an embodiment of the present invention, the determining a coefficient sub-module in combination with the second target value may include:
an adhesion-difference-value determining unit configured to determine an adhesion difference value of the first target value and the second target value;
a road surface adhesion coefficient determining unit configured to determine a first target value as a road surface adhesion coefficient when an absolute value of the adhesion difference value is greater than a preset adhesion difference value;
And a road surface adhesion coefficient determining unit configured to determine the second target value as a road surface adhesion coefficient when the absolute value of the adhesion difference is less than or equal to a preset adhesion difference.
In an embodiment of the present invention, the second target value determining submodule may include:
and selecting a maximum value unit, which is used for determining a plurality of corresponding second attachment rates according to the vehicle parameters in the plurality of second attachment states, and selecting the maximum value of the plurality of second attachment rates as a second target value.
In an embodiment of the present invention, the second threshold is half of the first threshold.
Referring to fig. 8, a block diagram of a torque control apparatus according to an embodiment of the present invention is shown, which may specifically include the following modules:
the second acceleration change rate determination module 801 obtains the change rate of the acceleration of the wheel angular velocity from the wheel angular velocity by acquiring the wheel angular velocity.
A second road surface adhesion state determination module 802 for determining a road surface adhesion state of the wheel based on a rate of change of acceleration of the wheel angular velocity and a threshold value; the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the first threshold value being greater than the second threshold value.
The first adhesion state torque control module 803 is configured to control the motor torque corresponding to the wheels to decrease in the first adhesion state until the road adhesion state exits the first adhesion state.
And the second adhesion state torque control module 804 is used for controlling the motor torque corresponding to the wheels to rise in the second adhesion state until the road adhesion state enters the first adhesion state.
In an embodiment of the present invention, when the rate of change of the acceleration of the angular velocity of the wheel is between the first threshold value and the second threshold value and the duration exceeds the preset duration, the road surface adhesion state is a third adhesion state, and the apparatus may further include:
and the torque control module is used for controlling the motor torque corresponding to the wheels to rise in the third attaching state until the road surface attaching state enters the first attaching state.
In one embodiment of the present invention, the apparatus further comprises:
the road surface adhesion coefficient acquisition module is used for acquiring the road surface adhesion coefficient;
and the adhesion capacity equivalent torque determining module is used for determining the adhesion capacity equivalent torque of the road surface according to the road surface adhesion coefficient.
In an embodiment of the present invention, the second adhesion state torque control module 804 may include:
a sub-module is added in a first step length, and is used for adding the first preset torque difference value to the attaching capability equivalent torque until the absolute value of the torque difference value of the attaching capability equivalent torque is smaller than or equal to the first preset torque difference value if the current torque is smaller than the attaching capability equivalent torque and the absolute value of the torque difference value of the attaching capability equivalent torque is larger than the first preset torque difference value in the second attaching state;
the adhesion capacity equivalent torque output sub-module is used for taking the adhesion capacity equivalent torque as the motor output torque if the current torque is smaller than the adhesion capacity equivalent torque and the torque difference between the adhesion capacity equivalent torque and the adhesion capacity equivalent torque is smaller than or equal to a first preset torque difference;
the second step-size increasing submodule is used for increasing the attaching capacity equivalent torque by a second step size until the pavement attaching state enters the first attaching state if the pavement attaching state is still the second attaching state after the attaching capacity equivalent torque is used as the motor output torque; wherein the second step size is smaller than the first step size;
In an embodiment of the present invention, the torque control module in the third attachment state may include:
a sub-module is added in a third step, and is used for adding the third step to the equivalent torque of the attaching capability until the pavement attaching state enters the first attaching state if the current torque is smaller than the equivalent torque of the attaching capability and the torque difference between the current torque and the equivalent torque of the attaching capability is smaller than or equal to a first preset torque difference; wherein the third step size is smaller than the second step size.
In an embodiment of the present invention, the attachment capability equivalent torque determination module may include:
the axle load and radius acquisition sub-module is used for acquiring the axle load and the rolling radius of the wheel;
and the combined axle load and radius determining submodule is used for determining the equivalent torque of the adhesion capability of the road surface according to the axle load, the rolling radius of the wheels and the road surface adhesion coefficient.
In one embodiment of the present invention, obtaining the road surface adhesion coefficient includes referring to the road surface adhesion coefficient estimating means as described above.
An embodiment of the present invention further provides an electronic device, which may include a processor, a memory, and a computer program stored on the memory and capable of running on the processor, where the computer program when executed by the processor implements the above road adhesion coefficient estimation method or torque control method.
An embodiment of the present invention also provides a computer-readable storage medium having a computer program stored thereon, which when executed by a processor implements the above road adhesion coefficient estimation method or torque control method.
For the device embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments for relevant points.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (16)

1. A method for estimating road adhesion coefficient, the method comprising:
acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel;
judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a third adhesion state when the rate of change of the acceleration of the wheel angular velocity is between the first threshold value and a second threshold value and the duration exceeds a preset duration, the first threshold value being greater than the second threshold value;
Calculating a corresponding first attachment rate according to the vehicle parameters in the first attachment state or the third attachment state to obtain a first target value;
and determining the road adhesion coefficient according to the first target value.
2. The method of claim 1, wherein calculating the corresponding first attachment rate based on the vehicle parameter in the first or third attachment state to obtain the first target value comprises:
recording as a marking time when the road surface attaching state is the first attaching state or the third attaching state;
calculating a plurality of first adhesion rates according to the vehicle parameters at a plurality of marking moments;
a first target value is determined from a plurality of the first attachment rates.
3. The method of claim 2, wherein said determining a first target value based on a plurality of said first attachment rates comprises:
when the interval between two adjacent marking moments is larger than the preset time interval, taking the first attachment rate of the previous marking moment as a first target value;
when the interval between two adjacent marking times is less than or equal to the preset time interval, the first attachment rate at the latter marking time is taken as a first target value.
4. A method according to any one of claims 1-3, wherein said determining the road adhesion coefficient from said first target value comprises: the first target value is taken as a road adhesion coefficient.
5. A method according to any one of claims 1-3, wherein said determining the road adhesion coefficient from said first target value comprises:
calculating a corresponding second attachment rate according to the vehicle parameters in the second attachment state; wherein the road surface adhesion state is the second adhesion state when the rate of change of the acceleration of the wheel angular velocity is smaller than the second threshold value;
determining a second target value based on at least one of the second attachment rates;
and determining the road adhesion coefficient according to the first target value and the second target value.
6. The method of claim 5, wherein said determining a road adhesion coefficient based on said first target value and said second target value comprises:
determining an adhesion difference value of the first target value and the second target value;
determining the first target value as a road surface adhesion coefficient under the condition that the absolute value of the adhesion difference value is larger than a preset adhesion difference value;
And determining the second target value as the road surface adhesion coefficient under the condition that the absolute value of the adhesion rate difference value is smaller than or equal to a preset adhesion rate difference value.
7. The method of claim 6, wherein said determining a second target value based on at least one of said second attachment rates comprises:
and determining a plurality of corresponding second attachment rates according to the vehicle parameters in the second attachment states, and selecting the maximum value of the second attachment rates as a second target value.
8. The method of claim 1, wherein the second threshold is half of the first threshold.
9. A method of torque control, the method comprising:
acquiring the angular velocity of the wheel, and obtaining the change rate of the acceleration of the angular velocity of the wheel according to the angular velocity of the wheel;
judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the first threshold value being greater than the second threshold value;
In the first attachment state, controlling the motor torque corresponding to the wheels to be reduced until the road surface attachment state exits from the first attachment state;
and in the second attaching state, controlling the motor torque corresponding to the wheels to rise until the road surface attaching state enters the first attaching state.
10. The method of claim 9, wherein the road surface adhesion state is a third adhesion state when a rate of change of acceleration of the wheel angular velocity is between the first threshold value and the second threshold value and a duration exceeds a preset duration, the method further comprising:
and in the third attaching state, controlling the motor torque corresponding to the wheels to rise until the road surface attaching state enters the first attaching state.
11. The method according to claim 10, wherein the method further comprises:
obtaining a road adhesion coefficient;
and determining the equivalent torque of the adhesion capacity of the road surface according to the road surface adhesion coefficient.
12. The method of claim 11, wherein in the second attachment state, controlling the increase in motor torque corresponding to the wheel until the road attachment state enters the first attachment state comprises:
In the second attaching state, if the current torque is smaller than the attaching capability equivalent torque and the absolute value of the torque difference value of the attaching capability equivalent torque is larger than a first preset torque difference value, adding the first preset torque difference value to the attaching capability equivalent torque by taking the first preset torque difference value as a first step length until the absolute value of the torque difference value of the attaching capability equivalent torque is smaller than or equal to the first preset torque difference value;
if the current torque is smaller than the attaching capability equivalent torque and the torque difference between the current torque and the attaching capability equivalent torque is smaller than or equal to a first preset torque difference, taking the attaching capability equivalent torque as the motor output torque;
after the adhesion capacity equivalent torque is used as the motor output torque, if the road surface adhesion state is still the second adhesion state, the adhesion capacity equivalent torque is increased by a second step length until the road surface adhesion state enters the first adhesion state; wherein the second step size is smaller than the first step size;
and under the third attachment state, controlling the motor torque corresponding to the wheels to rise until the road surface attachment state enters the first attachment state, wherein the method comprises the following steps of:
In the third attaching state, if the current torque is smaller than the attaching capability equivalent torque and the torque difference between the current torque and the attaching capability equivalent torque is smaller than or equal to a first preset torque difference, increasing the attaching capability equivalent torque by a third step length until the pavement attaching state enters the first attaching state; wherein the third step size is smaller than the second step size.
13. The method according to any one of claims 9-12, wherein said determining the road adhesion capability equivalent torque from the road adhesion coefficient comprises:
acquiring axle load and wheel rolling radius;
and determining the equivalent torque of the adhesion capability of the road surface according to the axle load, the rolling radius of the wheels and the road surface adhesion coefficient.
14. The method of claim 11, wherein obtaining the road adhesion coefficient comprises referring to the method of any one of claims 1-8.
15. An apparatus for estimating road adhesion coefficient, the apparatus comprising:
the first acceleration change rate determining module is used for obtaining the angular speed of the wheel and obtaining the change rate of the acceleration of the angular speed of the wheel according to the angular speed of the wheel;
The first road surface adhesion state judging module is used for judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular speed of the wheel and the threshold value; wherein the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a third adhesion state when the rate of change of the acceleration of the wheel angular velocity is between the first threshold value and a second threshold value and the duration exceeds a preset duration, the first threshold value being greater than the second threshold value;
a first target value obtaining module for calculating a corresponding first attachment rate according to the vehicle parameter in the first attachment state or the third attachment state to obtain a first target value;
and the road surface adhesion coefficient determining module is used for determining the road surface adhesion coefficient according to the first target value.
16. A torque-controlled apparatus, the apparatus comprising:
the second acceleration change rate determining module is used for obtaining the angular speed of the wheel and obtaining the change rate of the acceleration of the angular speed of the wheel according to the angular speed of the wheel;
a second road surface adhesion state judging module for judging the road surface adhesion state of the wheel according to the change rate of the acceleration of the angular velocity of the wheel and a threshold value; wherein the road surface adhesion state is a first adhesion state when the rate of change of the acceleration of the wheel angular velocity is greater than a first threshold value, and is a second adhesion state when the rate of change of the acceleration of the wheel angular velocity is less than a second threshold value, the first threshold value being greater than the second threshold value;
The first attaching state torque control module is used for controlling the motor torque corresponding to the wheels to be reduced in the first attaching state until the road surface attaching state exits from the first attaching state;
and the torque control module is used for controlling the motor torque corresponding to the wheels to rise in the second attaching state until the road surface attaching state enters the first attaching state.
CN202210552596.0A 2022-05-20 2022-05-20 Road adhesion coefficient estimation method and torque control method and device Pending CN117125053A (en)

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CN202210552596.0A CN117125053A (en) 2022-05-20 2022-05-20 Road adhesion coefficient estimation method and torque control method and device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210552596.0A CN117125053A (en) 2022-05-20 2022-05-20 Road adhesion coefficient estimation method and torque control method and device

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CN117125053A true CN117125053A (en) 2023-11-28

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