CN110595796B - Simulation experiment method for urban circulation working condition of parallel hydraulic hybrid electric vehicle - Google Patents
Simulation experiment method for urban circulation working condition of parallel hydraulic hybrid electric vehicle Download PDFInfo
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Abstract
The invention relates to the technical field of hydraulic hybrid power, and discloses a simulation experiment method for urban circulation working conditions of a parallel hydraulic hybrid electric vehicle, which simulates the speed change of the parallel hydraulic hybrid electric vehicle under the urban circulation working conditions through a laboratory bench control motor; the physical element truly reflects the working state of the hydraulic system of the parallel hydraulic hybrid electric vehicle; and the upper computer simulates the working states of an automobile engine, a gearbox and the like according to the real-time working state of the hydraulic element, so that the working state of the parallel hydraulic hybrid electric vehicle under the urban circulation working condition is obtained. The experiment table of the experiment method comprises the following components: the system comprises an energy accumulator, a hydraulic pump/motor, a pump station, a pressure sensor, a torque coupler, a dynamometer and a motor.
Description
Technical Field
The invention relates to the technical field of hydraulic hybrid power, in particular to a simulation experiment method for urban circulation working conditions of a parallel hydraulic hybrid power automobile.
Background
With the rapid development of industrial technologies worldwide, the problems of energy shortage and environmental pollution become more serious. The hydraulic hybrid power technology is considered as one of effective schemes for solving the problems of energy crisis and environmental pollution, the hydraulic hybrid power has the advantages of high power density, high energy circulation efficiency and the like, and can provide larger braking torque in the braking process and obviously improve the energy-saving effect of the hybrid power vehicle. The hydraulic hybrid vehicle is a hybrid vehicle which outputs power simultaneously or in a time-sharing manner by controlling and coordinating an engine and a hydraulic auxiliary driving device. The hydraulic hybrid power system has high power density, energy is stored in a hydraulic energy mode, no chemical energy conversion of the energy is generated, and the braking energy recovery efficiency is high. The hydraulic system has fast response and fast energy charging and discharging, can play a role in occasions with frequent energy exchange, and is suitable for vehicles with frequent starting and stopping conditions.
The hydraulic hybrid electric vehicle is a complex mechanical, hydraulic and electrical aggregate, and if a large number of real vehicle tests are directly carried out by building real vehicles in the early stage of development of the whole vehicle, a large amount of manpower, material resources and financial resources are consumed, and the design and development cycle is prolonged; the characteristics of system components are difficult to be completely embodied by adopting computer simulation completely, and the result is greatly different from the actual result. Therefore, in the development of the hydraulic hybrid electric vehicle, it is necessary to develop a method for performing a semi-physical experiment by fusing computer technology.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a simulation experiment method for urban circulation working conditions of a parallel hydraulic hybrid electric vehicle, which simulates the urban circulation working conditions of the parallel hydraulic hybrid electric vehicle on an experiment table.
The technical scheme of the invention is as follows:
a simulation experiment method for urban circulation working conditions of a parallel hydraulic hybrid electric vehicle specifically comprises the following steps:
the method comprises the following steps: converting the speed of the hydraulic hybrid electric vehicle under the urban circulation working condition into the rotating speed of the output end of the vehicle gearbox so as to be simulated by a motor;
step two: calculating the real-time speed of the automobile according to the real-time rotating speed of the output end of the automobile gearbox, and determining the gear of the transmission and the real-time rotating speed of the engine in the current state;
step three: according to the speed u of the hydraulic hybrid electric vehicle under the urban circulation working conditionaCalculating the given angular acceleration of the output end of the automobile gearbox, and further judging the driving mode and the braking of the automobile according to the given angular acceleration of the output end of the automobile gearboxA mode, a parking mode and a constant speed driving mode;
step four: calculating the required torque at the output end of the torque coupler according to the given acceleration of the automobile;
step five: determining the opening degree of a swash plate of the hydraulic pump according to the maximum torque which can be provided by the mechanical end of the hydraulic pump and the required torque of the output end of the torque coupler, which are obtained by calculating the current pressure state of the accumulator;
step six: determining real-time engine torque in a driving state or mechanical braking torque in a braking state according to the torque required by the output end of the torque coupler and the torque which can be provided by the hydraulic pump;
step seven: and determining the oil consumption of the engine and obtaining the oil saving rate according to the real-time rotating speed and torque of the engine and the universal characteristic curve of the engine.
Preferably, the formula for converting the speed of the hydraulic hybrid vehicle under the urban cycle condition into the rotating speed of the output end of the vehicle gearbox is as follows,
in the formula, n is the given rotating speed of the output end of the torque coupler, namely the given rotating speed of the motor; u. ofaThe theoretical speed of the urban cycle working condition; i.e. i0Is the transmission ratio of a main speed reducer of an automobile; r is the wheel radius.
Preferably, the real-time rotating speed of the output end of the automobile gearbox is measured through a rotating speed sensor, the real-time automobile speed is calculated through the following formula,
in the formula usReal-time vehicle speed; n issFor the real-time speed, i, of the output of the torque coupler0Is the transmission ratio of a main speed reducer of an automobile; r is the wheel radius;
judging the gear of the gearbox according to a preset gear shifting rule so as to obtain the real-time rotating speed of the engine;
the real-time rotational speed calculation expression of the engine is as follows,
ne＝nimig
in the formula, neThe real-time rotating speed of the engine; i.e. imIs the gear ratio of the torque coupling; i.e. igIs the transmission ratio of the gearbox.
Preferably, the expression for a given acceleration of the vehicle is as follows,
wherein a is the given acceleration of the automobile; u. ofaThe speed of the hydraulic hybrid electric vehicle under the urban circulation working condition is a given speed; u. ofan-1△ t is the time interval of two given vehicle speeds;
a given angular acceleration at the output of the vehicle transmission is calculated by the following formula,
where the given angular acceleration of the output of the gearbox is used.
Preferably, the running mode of the automobile is judged by a given speed and a given angular acceleration of the output end of the gearbox;
when the given angular acceleration is larger than zero, judging that the automobile is in a driving mode;
when the given angular acceleration is less than zero, judging that the automobile is in a braking mode;
when the given angular acceleration is equal to zero and the given vehicle speed is equal to zero, judging that the vehicle is in a parking mode;
and when the given angular acceleration is equal to zero and the given vehicle speed is not equal to zero, judging that the vehicle is in a constant-speed driving mode.
Preferably, the calculation expression of the required torque at the output of the torque coupler is as follows,
in the formula, Treq-qThe driving torque required by the output end of the torque coupler in the driving mode; t isreq-zThe braking torque required by the output end of the torque coupler in the braking mode; m is the mass of the automobile; f is a rolling resistance coefficient; cDIs the air resistance coefficient; a is the frontal area of the automobile.
Preferably, the expression for the torque that the hydraulic pump can provide is as follows,
in the formula, TpTorque that the hydraulic pump can provide; p is a radical ofxIs the accumulator pressure; p is a radical ofzThe pump station outlet pressure; vgIs the pump displacement; and pi is the circumferential ratio.
Preferably, when the automobile is in a driving mode, the mechanical braking torque is zero, and the real-time torque of the engine is calculated by the torque which can be provided by the hydraulic pump and the driving torque required by the output end of the torque coupler in the driving mode;
the calculation expression of the real-time torque of the engine in the drive mode is as follows,
in the formula, TeIs the real-time torque of the engine; t ispTorque which can be provided by a hydraulic pump and is collected by a torque sensor; t isreq-qThe driving torque required by the output end of the torque coupler in the driving mode;
when the automobile is in a braking mode, the real-time torque of the engine is zero, and the mechanical braking torque is calculated by the torque which can be provided by the hydraulic pump and the braking torque required by the output end of the torque coupler in the braking mode;
the mechanical braking torque in the braking mode is calculated by the following formula,
Tm＝Treq-z-Tp
in the formula, TmIs a mechanical braking torque; t ispTorque which can be provided by a hydraulic pump and is collected by a torque sensor; t isreq-zThe braking torque required at the output of the torque coupler in braking mode.
Preferably, a corresponding engine universal characteristic data table is checked through the real-time rotating speed and the real-time torque of the engine to obtain the fuel consumption rate of the engine;
the computational expression of the fuel consumption of the engine is as follows,
wherein Q is the fuel consumption of the engine; beIs the fuel consumption rate of the engine; t iseIs the real-time torque of the engine; n iseThe real-time rotating speed of the engine; t is time.
Preferably, the fuel saving ratio is calculated as follows,
wherein η is the oil saving rate, QcThe fuel consumption of the traditional vehicle under the urban circulation working condition is realized; and Q is the fuel consumption of the engine.
Compared with the prior art, the invention has the following advantages:
1. the experimental method for simulating the urban circulation working condition of the parallel hydraulic hybrid electric vehicle is used in the development stage of the hydraulic hybrid electric vehicle, can improve the research and development efficiency and reduce the research and development cost.
2. The experimental method for simulating the urban circulation working condition of the parallel hydraulic hybrid electric vehicle can be used for researching a control strategy and determining the optimal control strategy.
3. The experimental method for simulating the urban circulation condition of the parallel hydraulic hybrid electric vehicle can accurately simulate the actual running condition of the hydraulic hybrid electric vehicle.
4. Compared with other experimental methods, the experimental method for simulating the urban circulation condition of the parallel hydraulic hybrid electric vehicle has the obvious advantages of high simulation precision, low test cost, small occupied space and the like.
Drawings
FIG. 1 is a flow chart of a simulation experiment method of urban circulation conditions of a parallel hydraulic hybrid electric vehicle according to the invention;
FIG. 2 is a schematic structural diagram of a test bench in the simulation experiment method for urban circulation conditions of the parallel hydraulic hybrid electric vehicle according to the invention.
In the figure: 1. the system comprises an energy accumulator, 2 parts of a dynamometer, 3 parts of a motor, 4 parts of a first pressure sensor, 5 parts of a second pressure sensor, 6 parts of a pump station, 7 parts of a hydraulic pump and 8 parts of a torque coupler.
Detailed Description
Features of exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers can indicate functionally identical or similar elements. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The invention controls the motor in a constant-rotating-speed control mode through the experiment table to simulate the speed change of the parallel hydraulic hybrid electric vehicle under the urban circulation working condition; the working state of the hydraulic system of the parallel hydraulic hybrid electric vehicle is truly reflected through physical elements such as the energy accumulator 1, the hydraulic pump 7, the pump station 6 and the torque coupler 8; and the upper computer simulates the working states of an automobile engine and a gearbox according to the real-time working state of the hydraulic element, so that the working state of the parallel hydraulic hybrid electric vehicle under the urban circulation working condition is obtained.
Preferably, the laboratory bench comprises an accumulator 1, a dynamometer 2, an electric machine 3, a pressure sensor, a pumping station 6, a hydraulic pump 7 and a torque coupler 8. The pressure sensors include a first pressure sensor 4 and a second pressure sensor 5.
Preferably, a hydraulic pump may be used as the motor.
The energy accumulator 1 is connected with a pump port A of the hydraulic pump 7, the pump station 6 is connected with a pump port B of the hydraulic pump 7, the mechanical end of the hydraulic pump 7 is connected with a second input end of the torque coupler 8, a first input end of the torque coupler 8 is empty, and an output end of the torque coupler 8 is sequentially connected with the dynamometer 2 and the motor 3.
Preferably, as shown in fig. 2, the outlet of the accumulator 1 is connected to a first pump port, i.e., port a, of the hydraulic pump 7, and the pump station 6 is connected to a second pump port, i.e., port B, of the hydraulic pump 7. The mechanical end of the hydraulic pump 7 is connected with the second input end of the torque coupler 8, the first input end of the torque coupler 8 is empty, the output end of the torque coupler 8 is sequentially connected with the dynamometer 2 and the motor 3, and the first pressure sensor is arranged between the outlet end of the energy accumulator and the first pump port of the hydraulic pump 7 and is configured for collecting the pressure of the energy accumulator in real time; the second pressure sensor 5 is arranged between a second pump port of the hydraulic pump 7 and an outlet of the pump station 6, and is configured to acquire the outlet pressure of the pump station 6 in real time. The speed change of the hydraulic hybrid electric vehicle under the urban circulation working condition is simulated through the motor 3, specifically, the speed of the vehicle is converted into the rotating speed of the output end of the gearbox through wheels and a main reducer, and the upper computer controls the motor of the experiment table to operate at the rotating speed, so that the simulation of the vehicle is realized; the rotational speed of the output of the motor vehicle gearbox equals the rotational speed of the output of the torque coupler 8.
The real object element truly reflects the working state of a hydraulic system on an automobile, namely, the pressure of the energy accumulator 1 is acquired by the first pressure sensor 4 in real time, and the outlet pressure of the pump station 6 is acquired by the second pressure sensor 5 in real time.
Judging the working mode of the automobile by the angular acceleration of the output end of the gearbox obtained by converting the speed of the automobile: specifically, when the vehicle is in a driving mode, the hydraulic pump 7 functions as a motor to convert the pressure potential energy in the accumulator 6 into kinetic energy, and at the moment, the mechanical end of the hydraulic pump 7 provides driving torque to drive the electric motor to rotate.
When the vehicle is in the braking mode, the hydraulic pump 7 acts as a hydraulic pump, converting kinetic energy into pressure potential energy in the accumulator, at which time the mechanical end of the hydraulic pump 7 provides the braking torque.
The displacement change of the hydraulic pump 7 is controlled by the result of the comparison of the maximum torque that can be provided by the mechanical side of the hydraulic pump 7, calculated from the current pressure state of the accumulator 1, with the torque demand at the output of the torque coupling 8.
The upper computer simulates the working states of an automobile engine and a gearbox according to the real-time working state of the hydraulic element. The gear of the gearbox is obtained by judging according to a real-time speed converted from the acquired real-time rotating speed of the output end of the gearbox and a preset gear shifting rule; the rotating speed of the engine is calculated according to the collected real-time rotating speed of the output end of the gearbox and the gear of the gearbox; the torque of the engine is calculated according to the required driving torque of the output end of the gearbox and the driving torque provided by the mechanical end of the hydraulic pump 7; the mechanical braking torque of the vehicle is calculated from the demanded braking torque at the output of the gearbox and the braking torque provided by the mechanical side of the hydraulic pump 7.
The gear shifting rule is that the vehicle speed is less than or equal to 10 kilometers per hour and is a first gear; the speed is more than 10 kilometers per hour and less than 20 kilometers per hour, and the speed is two grades; the speed is more than or equal to 20 kilometers per hour and less than 40 kilometers per hour, and the third gear is adopted; the speed is more than or equal to 40 kilometers per hour and less than 60 kilometers per hour, and the fourth gear is adopted; the speed is greater than or equal to 60 kilometers per hour, and the speed is five gears.
Fig. 1 shows a flow chart of a simulation experiment method for urban circulation conditions of a parallel hydraulic hybrid electric vehicle according to the invention, which specifically comprises the following steps:
the method comprises the following steps: converting the speed of the hydraulic hybrid electric vehicle under the urban circulation working condition into the rotating speed of the output end of the vehicle gearbox so as to be simulated by the motor 3;
preferably, the formula for converting the speed of the hydraulic hybrid vehicle under the urban cycle condition into the rotating speed of the output end of the vehicle gearbox is as follows,
where n is the given speed at the output of the torque coupler 8, i.e. the motor 3Fixing the rotating speed; u. ofaThe theoretical speed of the urban cycle working condition; i.e. i0Is the transmission ratio of a main speed reducer of an automobile; r is the wheel radius;
step two: calculating the real-time speed of the automobile according to the real-time rotating speed of the output end of the automobile gearbox, and determining the gear of the transmission and the real-time rotating speed of the engine in the current state;
preferably, the real-time rotating speed of the output end of the automobile gearbox is measured through a rotating speed sensor, the real-time automobile speed is calculated through the following formula,
in the formula usReal-time vehicle speed; n issFor the real-time speed, i, at the output of the torque coupler 80Is the transmission ratio of a main speed reducer of an automobile; r is the wheel radius;
judging the gear of the gearbox according to a preset gear shifting rule so as to obtain the real-time rotating speed of the engine;
ne＝nimig
in the formula, neThe real-time rotating speed of the engine; i.e. imIs the gear ratio of the torque coupling 8; i.e. igIs the transmission ratio of the gearbox;
step three: according to the speed u of the hydraulic hybrid electric vehicle under the urban circulation working conditionaCalculating the given angular acceleration of the output end of the automobile gearbox, and judging a driving mode, a braking mode, a parking mode and a constant-speed driving mode of the automobile according to the given angular acceleration of the output end of the automobile gearbox;
preferably, the expression for calculating a given acceleration of the vehicle is as follows,
wherein a is the given acceleration of the automobile; u. ofaThe speed of the hydraulic hybrid electric vehicle under the urban circulation working condition is a given speed; u. ofan-1Given for the last moment△ t is the time interval of two given vehicle speeds;
a given angular acceleration at the output of the vehicle transmission is calculated by the following formula,
where the given angular acceleration of the output of the gearbox is used.
And judging the running mode of the automobile according to the given speed and the given angular acceleration of the output end of the gearbox.
When the given angular acceleration is larger than zero, judging that the automobile is in a driving mode;
when the given angular acceleration is less than zero, judging that the automobile is in a braking mode;
when the given angular acceleration is equal to zero and the given vehicle speed is equal to zero, judging that the vehicle is in a parking mode;
and when the given angular acceleration is equal to zero and the given vehicle speed is not equal to zero, judging that the vehicle is in a constant-speed driving mode.
Step four: calculating the required torque at the output end of the torque coupler 8 according to the given acceleration of the automobile;
preferably, the calculation expression of the required torque at the output of the torque coupler is as follows,
in the formula, Treq-qThe driving torque required at the output of the torque coupler 8 in the driving mode; t isreq-zThe braking torque required at the output of the torque coupler 8 in braking mode; m is the mass of the automobile; f is a rolling resistance coefficient; cDIs the air resistance coefficient; a is the frontal area of the automobile;
step five: determining the opening degree of a swash plate of the hydraulic pump 7 according to the maximum torque which can be provided by the mechanical end of the hydraulic pump 7 and the required torque of the output end of the torque coupler 8, which are obtained by calculating the current pressure state of the accumulator 1;
preferably, the pressure of the accumulator is acquired in real time by the second pressure sensor 5.
Step six: the engine real-time torque in the driving state or the mechanical braking torque in the braking state is determined based on the torque required at the output of the torque coupler 8 and the torque that can be provided by the hydraulic pump 7.
Preferably, the expression of the torque that the hydraulic pump 7 can provide is as follows,
in the formula, TpTorque that the hydraulic pump 7 can provide; p is a radical ofxIs accumulator 1 pressure; p is a radical ofzThe outlet pressure of the pump station 6; vgIs the pump displacement; and pi is the circumferential ratio.
When the automobile is in a driving mode, the mechanical braking torque is zero, and the real-time torque of the engine is calculated by the torque which can be provided by the hydraulic pump 7 and the driving torque required by the output end of the torque coupler 8 in the driving mode;
preferably, the calculation expression of the real-time torque of the engine in the drive mode is as follows,
in the formula, TeIs the real-time torque of the engine; t ispTorque that the hydraulic pump 7 can provide that is gathered for the torque sensor; t isreq-qThe driving torque required at the output of the torque coupler 8 in the driving mode;
when the automobile is in a braking mode, the real-time torque of the engine is zero, and the mechanical braking torque is calculated by the torque which can be provided by the hydraulic pump 7 and the braking torque required by the output end of the torque coupler 8 in the braking mode.
The mechanical braking torque in the braking mode is calculated by the following formula,
Tm＝Treq-z-Tp
in the formula, TmIs a mechanical braking torque; t ispTorque that the hydraulic pump 7 can provide that is gathered for the torque sensor; t isreq-zThe braking torque required at the output of the torque coupler 8 in braking mode;
step seven: determining the oil consumption of the engine and obtaining the oil saving rate according to the real-time rotating speed and torque of the engine and the universal characteristic curve of the engine;
preferably, a corresponding engine universal characteristic data table is checked through the real-time rotating speed and the real-time torque of the engine to obtain the fuel consumption rate of the engine;
preferably, the computational expression of the fuel consumption of the engine is as follows,
wherein Q is the fuel consumption of the engine; beIs the fuel consumption rate of the engine; t iseIs the real-time torque of the engine; n iseThe real-time rotating speed of the engine; t is the time of day and t is,
the oil saving rate is calculated by the following formula,
wherein η is the oil saving rate, QcThe fuel consumption of the traditional vehicle under the urban circulation working condition is realized; q is the fuel consumption of the engine;
as shown in fig. 1, the experimental bench for simulating the urban circulation condition of the parallel hydraulic hybrid electric vehicle comprises: the system comprises an energy accumulator 1, a hydraulic pump 7, a pump station 6, a first pressure sensor 4, a second pressure sensor 5, a torque coupler 8, a dynamometer 2 and a motor 3.
The pressure of the energy accumulator 1, the rotating speed of the hydraulic pump 7, the pressure of the outlet of the pump station 6 and the rotating speed of the output end of the torque coupler 8 are acquired through the first pressure sensor 4, the second pressure sensor 5 and the dynamometer.
The speed of a motor is converted into the rotating speed of the output end of an automobile gearbox under the urban circulation working condition through a formula, namely the rotating speed of the output end of a torque coupler 8, a test bench controls a motor 3 to operate according to the rotating speed in a constant rotating speed control mode, the working state of the hydraulic hybrid electric vehicle under the urban circulation working condition is simulated, and an upper computer of the test bench calculates the real-time rotating speed of the engine according to the rotating speed of the output end of the automobile gearbox and the gear shifting rule of the gearbox.
The motor drives the hydraulic pump 7 to rotate through the torque coupler 8, and a pump station is used for replacing a low-pressure energy accumulator in a real vehicle in order to prevent the hydraulic component from being damaged by system air suction in the test process. When the automobile is in a braking mode, the hydraulic pump 7 plays a role of a hydraulic pump, low-pressure oil in the pump station 6 is pumped into the energy accumulator 1, the pressure of the energy accumulator 1 plays a role in blocking the flow of the oil to form a resistance effect on the rotation of the hydraulic pump 7, and the output end of the hydraulic pump 7 provides braking torque; when the automobile is in a driving mode, the hydraulic pump 7 plays a role of a motor, the direction and the size of the displacement of the hydraulic pump are adjusted according to pressure signals collected by the pressure sensor and system required torque, high-pressure oil in the high-pressure energy accumulator is released, the pressure difference of an inlet and an outlet of the hydraulic pump forms a driving effect on the hydraulic pump 7, and the output end of the hydraulic pump 7 provides driving torque.
In the braking process of the automobile, when the braking strength is greater than 0.7, the automobile is judged to be emergency braking, at the moment, the braking is purely mechanical braking, the hydraulic system does not work, and the braking torque is not provided; when the braking torque required by the vehicle is less than or equal to the braking torque which can be provided by the hydraulic system, the displacement of the hydraulic pump 7 is adjusted according to the requirement of the system intensity to reasonably control the magnitude of the braking torque.
In the braking process of the automobile, the hydraulic pump 7 charges oil into the energy accumulator 1, and if the pressure of the energy accumulator 1 reaches the limit pressure, the excess oil discharged by the hydraulic pump overflows through an overflow valve and returns to a pump station.
The real-time torque of the engine is obtained by subtracting the driving torque which can be provided by the hydraulic pump 7 from the required driving torque at the output end of the torque coupler 8 and calculating the transmission ratio of the gearbox, when the driving torque provided by the hydraulic pump 7 can meet the required driving torque at the output end of the torque coupler 8, the driving torque is provided by the hydraulic pump 7, and the real-time torque of the engine is zero; the mechanical braking torque is calculated by subtracting the braking torque provided by the hydraulic pump 7 from the braking torque at the output end of the torque coupler 8, when the braking torque provided by the hydraulic pump 7 can meet the braking torque required at the output end of the torque coupler 8, the braking torque is provided by the hydraulic pump 7, and the mechanical braking torque is zero.
The universal characteristic curve of the engine can be checked according to the real-time torque and the real-time rotating speed of the engine, the fuel consumption rate of the engine at the current moment is obtained, the fuel consumption of the whole urban circulation working condition is obtained through superposition, and the fuel saving rate of the hydraulic hybrid electric vehicle can be obtained by comparing the fuel consumption of the traditional vehicle under the urban circulation working condition.
Finally, it should be noted that: the above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A simulation experiment method for urban circulation working conditions of a parallel hydraulic hybrid electric vehicle is characterized by comprising the following steps:
the method comprises the following steps: converting the speed of the hydraulic hybrid electric vehicle under the urban circulation working condition into the rotating speed of the output end of the vehicle gearbox so as to be simulated by a motor;
step two: calculating the real-time speed of the automobile according to the real-time rotating speed of the output end of the automobile gearbox, and determining the gear of the transmission and the real-time rotating speed of the engine in the current state;
step three: according to the speed u of the hydraulic hybrid electric vehicle under the urban circulation working conditionaCalculating the given angular acceleration of the output end of the automobile gearbox, and judging a driving mode, a braking mode, a parking mode and a constant-speed driving mode of the automobile according to the given angular acceleration of the output end of the automobile gearbox;
step four: calculating the required torque at the output end of the torque coupler according to the given acceleration of the automobile;
step five: determining the opening degree of a swash plate of the hydraulic pump according to the maximum torque which can be provided by the mechanical end of the hydraulic pump and the required torque of the output end of the torque coupler, which are obtained by calculating the current pressure state of the accumulator;
step six: determining real-time engine torque in a driving mode or mechanical braking torque in a braking mode according to the torque required by the output end of the torque coupler and the torque which can be provided by the hydraulic pump;
step seven: and determining the oil consumption of the engine and obtaining the oil saving rate according to the real-time rotating speed and torque of the engine and the universal characteristic curve of the engine.
2. A parallel hydraulic hybrid vehicle city cycle simulation experiment method as claimed in claim 1, wherein the formula for converting the speed of the hydraulic hybrid vehicle under the city cycle into the rotational speed of the vehicle transmission output is as follows,
in the formula, n is the given rotating speed of the output end of the torque coupler, namely the given rotating speed of the motor; u. ofaThe vehicle speed is the urban cycle working condition; i.e. i0Is the transmission ratio of a main speed reducer of an automobile; r is the wheel radius.
3. A simulation experiment method of urban cycle conditions of a parallel hydraulic hybrid electric vehicle according to claim 2, wherein the real-time rotation speed of the output end of the transmission of the vehicle is measured by a rotation speed sensor, the real-time vehicle speed of the vehicle is calculated by the following formula,
in the formula usReal-time vehicle speed; n issFor torque couplingReal-time speed of the output of the combiner, i0Is the transmission ratio of a main speed reducer of an automobile; r is the wheel radius;
judging the gear of the gearbox according to a preset gear shifting rule so as to obtain the real-time rotating speed of the engine;
the real-time rotational speed calculation expression of the engine is as follows,
ne＝nimig
in the formula, neThe real-time rotating speed of the engine; i.e. imIs the gear ratio of the torque coupling; i.e. igIs the transmission ratio of the gearbox.
4. A parallel hydraulic hybrid vehicle city cycle simulation experiment method as claimed in claim 3, wherein the expression of the given acceleration of the vehicle is as follows,
wherein a is the given acceleration of the automobile; u. ofaThe speed of the hydraulic hybrid electric vehicle under the urban circulation working condition is a given speed; u. ofan-1△ t is the time interval of two given vehicle speeds;
a given angular acceleration at the output of the vehicle transmission is calculated by the following formula,
where the given angular acceleration of the output of the gearbox is used.
5. A parallel hydraulic hybrid vehicle city cycle simulation experiment method according to claim 4, wherein the driving mode of the vehicle is determined by a given vehicle speed and a given angular acceleration at the output of the gearbox;
when the given angular acceleration is larger than zero, judging that the automobile is in a driving mode;
when the given angular acceleration is less than zero, judging that the automobile is in a braking mode;
when the given angular acceleration is equal to zero and the given vehicle speed is equal to zero, judging that the vehicle is in a parking mode;
and when the given angular acceleration is equal to zero and the given vehicle speed is not equal to zero, judging that the vehicle is in a constant-speed driving mode.
6. A parallel hydraulic hybrid vehicle city cycle simulation experiment method according to claim 5, wherein the calculation expression of the required torque at the output of the torque coupler is as follows,
in the formula, Treq-qThe driving torque required by the output end of the torque coupler in the driving mode; t isreq-zThe braking torque required by the output end of the torque coupler in the braking mode; m is the mass of the automobile; f is a rolling resistance coefficient; cDIs the air resistance coefficient; a is the frontal area of the automobile.
7. A parallel hydraulic hybrid vehicle city cycle simulation experiment method as claimed in claim 6, wherein the expression of the torque that the hydraulic pump can provide is as follows,
in the formula, TpTorque that the hydraulic pump can provide; p is a radical ofxIs the accumulator pressure; p is a radical ofzThe pump station outlet pressure; vgIs the pump displacement; and pi is the circumferential ratio.
8. A simulation experiment method of urban cycle conditions of a parallel hydraulic hybrid electric vehicle according to claim 7, wherein when the vehicle is in a driving mode, the mechanical braking torque is zero, and the real-time torque of the engine is calculated from the torque that can be provided by the hydraulic pump and the driving torque required at the output end of the torque coupler in the driving mode;
the calculation expression of the real-time torque of the engine in the drive mode is as follows,
in the formula, TeIs the real-time torque of the engine; t ispTorque which can be provided by a hydraulic pump and is collected by a torque sensor; t isreq-qThe driving torque required by the output end of the torque coupler in the driving mode;
when the automobile is in a braking mode, the real-time torque of the engine is zero, and the mechanical braking torque is calculated by the torque which can be provided by the hydraulic pump and the braking torque required by the output end of the torque coupler in the braking mode;
the mechanical braking torque in the braking mode is calculated by the following formula,
Tm＝Treq-z-Tp
in the formula, TmIs a mechanical braking torque; t ispTorque which can be provided by a hydraulic pump and is collected by a torque sensor; t isreq-zThe braking torque required at the output of the torque coupler in braking mode.
9. A parallel hydraulic hybrid vehicle city cycle simulation experiment method as claimed in claim 8, wherein the engine fuel consumption rate is obtained by looking up the corresponding engine universal characteristic data table through the real-time rotation speed and the real-time torque of the engine;
the computational expression of the fuel consumption of the engine is as follows,
wherein Q is the fuel consumption of the engine; beIs the fuel consumption rate of the engine; t iseIs the real-time torque of the engine; n iseThe real-time rotating speed of the engine; t is time.
10. A parallel hydraulic hybrid vehicle city cycle simulation experiment method as claimed in claim 9, wherein the calculation formula of the fuel saving ratio is as follows,
wherein η is the oil saving rate, QcThe fuel consumption of the traditional vehicle under the urban circulation working condition is realized; and Q is the fuel consumption of the engine.
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