WO2016038736A1 - 操舵制御装置 - Google Patents
操舵制御装置 Download PDFInfo
- Publication number
- WO2016038736A1 WO2016038736A1 PCT/JP2014/074249 JP2014074249W WO2016038736A1 WO 2016038736 A1 WO2016038736 A1 WO 2016038736A1 JP 2014074249 W JP2014074249 W JP 2014074249W WO 2016038736 A1 WO2016038736 A1 WO 2016038736A1
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- WIPO (PCT)
- Prior art keywords
- steering
- current command
- command value
- steering torque
- torque
- Prior art date
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
- B62D5/046—Controlling the motor
- B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
- B62D5/046—Controlling the motor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
- B62D6/02—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits responsive only to vehicle speed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
- B62D6/08—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits responsive only to driver input torque
- B62D6/10—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits responsive only to driver input torque characterised by means for sensing or determining torque
Definitions
- the present invention relates to a steering control device, and more particularly to a steering control device that assists the steering of a vehicle driver.
- the current command value 2 calculated from a signal proportional to the differential value of the steering torque suppresses the road vibration generated when traveling on a rough road or the like from being transmitted to the driver. There is also an effect.
- the phase margin at the crossing frequency of the open loop characteristic of the steering control device is improved by calculating the current command value 1 with the steering torque subjected to phase compensation.
- the stability of the control system can be improved and self-excited vibration can be suppressed.
- adding the current command value 2 changes the open loop characteristics near the crossover frequency.
- ⁇ Self-excited vibration occurs.
- phase compensation it is necessary to design the phase compensation so that the open loop characteristics including the current command value 1 and the current command value 2 are stable, and there is a problem that the design becomes complicated.
- the current command value 2 when the current command value 2 is changed, it is necessary to redesign the phase compensation. Therefore, it takes a design man-hour to change the current command value 2 and select whether to use the current command value 2 or not. There was a problem.
- the present invention has been made to solve such a problem. Even when the current command value 2 calculated from the differential value of the steering torque is added to the current command value 1, the stability of the control system is reduced.
- An object of the present invention is to obtain a steering control device that can suppress the change of the current command value 2 and easily select whether or not the current command value 2 is used.
- the present invention is a steering control device for assisting steering by a driver of a steering wheel of a vehicle, the steering torque detecting unit detecting the steering torque of the steering wheel, and the vehicle speed detecting unit detecting the vehicle speed of the vehicle.
- a first current command for the motor based on the steering torque detected by the steering torque detector and the vehicle speed detected by the vehicle speed detector.
- a first current command value calculating unit that calculates a value, a steering torque differentiating unit that calculates a differential value of the steering torque detected by the steering torque detecting unit, and a notch filter, and using the notch filter
- a notch filter processing unit for filtering a differential value of the steering torque, and the filtered steering torque
- a second current command value calculation unit for calculating a second current command value for the motor on the basis of the differential value of the motor, and a sum of the first current command value and the second current command value.
- a current drive unit that drives the motor so that the values of the currents flowing through the filter coincide with each other, and the second current command value calculation unit replaces the filtered differential value of the steering torque with the filter.
- a notch frequency of the filter is set to be higher than a mechanical resonance frequency of the steering control device and lower than the first crossing frequency.
- the steering control device When the steering control device according to the present invention filters the differential value of the steering torque with the notch filter, the notch frequency set to a value higher than the mechanical resonance frequency of the steering control device and lower than the cross frequency of the open loop characteristic is obtained.
- a filter process is performed with a notch filter, and a current command value 2 is calculated from a signal obtained by the filter process.
- FIG. 1 is a configuration diagram showing a steering control device according to Embodiment 1 of the present invention.
- a steering shaft 2 is connected to the steering wheel 1.
- a pair of steered wheels 3 are connected to the steering shaft 2 via tie rods.
- the left and right steered wheels 3 are steered according to the rotation of the steering shaft 2 connected to the steering wheel 1.
- a torque sensor 4 is disposed on the steering shaft 2 and detects a steering torque acting on the steering shaft 2.
- the motor 5 is connected to the steering shaft 2 via the speed reduction mechanism 6, and the steering assist torque generated by the motor 5 can be applied to the steering shaft 2. Further, the vehicle speed of the vehicle is detected by a vehicle speed sensor 7.
- the current flowing through the motor 5 is detected by the current sensor 8.
- the control unit 9 calculates the steering assist torque that should be generated by the motor 5, obtains the current of the motor 5 necessary to generate the steering assist torque as a current command value, and controls the motor 5.
- the control unit 9 includes a microcomputer provided with a memory including a ROM and a RAM, and a current drive unit 10 (not shown) that drives the motor current so that the current flowing through the motor 5 matches the current command value corresponding to the steering assist torque. 2).
- control unit 9 which is the main part of the present invention will be described with reference to the block diagram shown in FIG. 2 and the flowchart shown in FIG. Note that the operation shown in the flowchart is repeatedly executed at a preset period.
- the control unit 9 includes a current drive unit 10, a current command value 1 calculation unit 11, a differentiator 12, a notch filter processing unit 13, a current command value 2 calculation unit 14, and an adder 15. Has been.
- the current command value 1 calculation unit 11 receives the vehicle speed detected by the vehicle speed sensor 7 and the steering torque detected by the torque sensor 4.
- the current command value 1 calculation unit 11 calculates a current command value 1 based on the vehicle speed and the steering torque.
- the current command value 1 is a motor current designation value for generating a steering assist torque generated by the motor 5 to assist the driver's steering. A method of calculating the current command value 1 will be described later.
- the differentiator 12 calculates a differential value of the steering torque detected by the torque sensor 4.
- the notch filter processing unit 13 has a notch filter.
- the notch filter processing unit 13 filters the steering torque differential value output from the differentiator 12 with a notch filter.
- the current command value 2 calculation unit 14 receives the vehicle speed detected by the vehicle speed sensor 7 and the differential value of the steering torque filtered by the notch filter processing unit 13. .
- the current command value 2 calculation unit 14 calculates the current command value 2 based on the vehicle speed and the filtered steering torque differential value. A method for calculating the current command value 2 will be described later.
- the current command value 2 calculation unit 14 may obtain the current command value 2 using only the differential value of the filtered steering torque without using the vehicle speed.
- the adder 15 adds the current command value 1 calculated by the current command value 1 calculation unit 11 and the current command value 2 calculated by the current command value 2 calculation unit 14 to obtain a current command value for the motor 5. Calculate.
- the current drive unit 10 receives the current command value from the adder 15 and the current value of the motor 5 detected by the current sensor 8. The current driver 10 drives the current that flows through the motor 5 so that the current value of the motor 5 matches the current command value.
- control unit 9 Next, the operation of the control unit 9 will be described based on the flowchart of FIG.
- step S1 the vehicle speed V is detected by the vehicle speed sensor 7. Further, the torque sensor 4 detects the steering torque Thdl.
- the current command value 1 calculation unit 11 calculates the current command value 1 from the vehicle speed and the steering torque.
- the current command value 1 calculation unit 11 may obtain the current command value 1 by further using vehicle state information from other sensors in addition to the vehicle speed and the steering torque.
- the current command value 1 is a motor current command value for generating a motor torque (steering assist torque) that assists the driver's steering.
- the current command value 1 may be calculated by a known technique of the following steering control device. For example, as shown in FIG. 4, an assist map that defines the relationship among the steering torque Thdl, the vehicle speed V, and the current command value 1 to the motor 5 is created in advance.
- a current command value 1 corresponding to the steering torque Thdl and the vehicle speed V is read from this assist map, and used as a basic assist command value.
- this assist map is generally determined so that the current command value 1 increases and the gradient increases as the steering torque Thdl increases as a quadratic function. . Further, it is determined that the current command value 1 decreases as the vehicle speed V increases.
- the vehicle speed is “low speed” and “high speed” are described. In this case, for example, “low speed” is set as appropriate within a range of 0 km / h to less than 30 km / h, and “high speed” is set within a range of 30 km / h or higher.
- an assist map may be created for three or more types of vehicle speeds V.
- “low speed” is in a range from 0 km / h to less than 10 km / h
- “medium speed 1” is from 10 km / h to less than 30 km
- “medium speed 2” is from 30 km / h to less than 60 km / h
- “high speed” "Is appropriately set so as to be in a range of 60 km / h or more.
- the range for dividing the vehicle speed may be a constant interval or may vary.
- the steering torque Thdl input to the assist map is subjected to phase compensation processing to ensure the stability of the control system of the steering control device.
- the technique for ensuring the stability of the control system by applying the current command value 1 is not limited to a simple phase compensation process, and the stability may be ensured by a known technique.
- step S3 the differentiator 12 calculates the differential value of the steering torque.
- the calculation may be performed from the difference from the previous value, or the pseudo-differentiation calculation by high-pass filter processing may be performed.
- the cut-off frequency of the high-pass filter is set to be higher than the mechanical resonance frequency (about 10 Hz) of the steering control device and higher than the frequency of road vibration that is not desired to be transmitted to the driver.
- step S4 the notch filter processing unit 13 filters the steering torque differential value with a notch filter.
- a filter represented by the following expression (11) is used as the notch filter.
- ⁇ 1 is the notch frequency
- ⁇ 1 is the numerator-side damping ratio (numerator-side damping ratio)
- ⁇ 2 is the denominator-side damping ratio (denominator-side damping ratio).
- s is a Laplace operator.
- the notch depth is adjusted from the value of ⁇ 2 / ⁇ 1
- the width of the notch is adjusted from the value of ⁇ 1 .
- the notch frequency ⁇ 1 is set to be higher than the mechanical resonance frequency (about 10 Hz) of the steering control device and lower than the crossing frequency of the open loop characteristic of the steering control device.
- ⁇ 1 is set to 0.1 and ⁇ 2 is set to 1. That is, the depth of the notch is 10.
- this is not restrictive, and ⁇ 1 and ⁇ 2 are adjusted according to the open loop characteristics.
- step S5 the current command value 2 calculation unit 14 calculates the current command value 2 that is directly proportional to the differential value of the steering torque, using the filtered differential value of the steering torque.
- the vehicle speed detected by the vehicle speed sensor 7 is also used for the calculation of the current command value 2. That is, a torque differential control gain based on the vehicle speed is obtained, and a current command value 2 is calculated based on the torque differential control gain and the filtered steering torque differential value.
- a method for calculating the current command value 2 will be described. For example, as shown in FIG. 5, a torque differential control gain map that defines the relationship between the vehicle speed V and the torque differential control gain is created in advance. In the example of FIG.
- step S5 in the region where the vehicle speed is low (range from 0 to a preset speed), the torque differential control gain increases in direct proportion to the increase in vehicle speed, but the vehicle speed is faster than that. In the high speed region (speed range faster than the preset speed), the torque differential control gain is a constant value.
- step S5 first, a torque differential control gain corresponding to the vehicle speed V is read from the torque differential control gain map. The torque differential control gain is multiplied by the read torque differential control gain by the differential value of the steering torque after the notch filter processing to obtain a current command value of 2. In this way, by changing the torque differential control gain according to the vehicle speed, it is possible to suppress the road surface vibration from being transmitted to the driver with respect to the road surface vibration whose ease of transmission changes according to the vehicle speed. Further, the upper limit value and the lower limit value of the calculated current command value 2 may be limited by preset values.
- step S6 the adder 15 adds the current command value 1 and the current command value 2 to obtain a current command value.
- step S7 the current drive unit 10 drives the current so that the current of the motor 5 matches the current command value. As a result, the motor 5 generates assist torque corresponding to the current command value.
- FIG. 6 shows the control open loop characteristics when notch filter processing is not performed.
- the control open loop of FIG. 6 is a control open loop from the current command value input to the current driver 10 to the current command value 1 output by the adder 15. Since FIG. 6 shows a case where notch filter processing is not performed, the configuration of the steering control device is a configuration in which the notch filter processing unit 13 is deleted from the configuration of FIG. Accordingly, the current command value 2 calculation unit 14 calculates the current command value 2 using the steering torque differential value output from the differentiator 12 instead of the filtered steering torque differential value. Other operations are the same as described above.
- the upper diagram in FIG. 6 shows the relationship between frequency and gain.
- the lower diagram of FIG. 6 shows the relationship between frequency and phase. In FIG.
- broken lines 62 and 63 indicate the control open loop characteristics when the current command value 2 that does not perform the notch filter processing is added. Hereinafter, this case will be referred to as “when current command value 2 not performing the notch filter processing is added (b)”.
- dotted lines 60 and 61 are control open loop characteristics when the current command value 2 is not used. Hereinafter, this case will be referred to as “when the current command value 2 is not used (a)”. This shows the control open-loop characteristic when the current driving unit 10 drives the motor 5 using only the current command value 1 output from the current command value 1 calculation unit 11 of FIG.
- the configuration of the steering control device in this case is a configuration in which the differentiator 12, the notch filter processing unit 13, and the current command value 2 calculation unit 14 are deleted from the configuration of FIG. Further, in FIG. 6, 64 is a cross frequency of the control open loop characteristic of “when current command value 2 not performing notch filter processing is added (b)”. The crossing frequency is a frequency value when the gain becomes zero. 65 is the crossover frequency of the control open loop characteristic of “when the current command value 2 is not used (a)”.
- FIG. 7 shows a control open loop characteristic when notch filter processing is performed according to the present embodiment having the configuration shown in FIG.
- the control open loop of FIG. 7 is a control open loop from the current command value input to the current driver 10 to the current command value 1 output by the adder 15.
- the upper diagram in FIG. 7 shows the relationship between frequency and gain.
- the lower diagram in FIG. 7 shows the relationship between frequency and phase.
- dotted lines 60 and 61 indicate the control open loop characteristics of “when the current command value 2 is not used (a)”, as in FIG.
- Solid lines 72 and 73 indicate control open loop characteristics when the current command value 2 subjected to the notch filter processing according to the present embodiment is added.
- FIG. 8 shows the mechanical resonance frequency of the steering control device.
- the solid line 80 is the mechanical resonance frequency of the steering control device.
- the frequency is referred to as “mechanical resonance frequency (80) of the steering control device”.
- the mechanical resonance frequency indicates a resonance mode frequency generated from the torsional rigidity of the torque sensor 4, the inertia moment of the steering wheel 1, and the inertia moment of the motor 5.
- This resonance frequency is also indicated by a solid line 80 in FIGS.
- the gain peak corresponds to “mechanical resonance frequency (80) of the steering control device”.
- the “mechanical resonance frequency (80) of the steering control device” is about 10 Hz.
- FIG. 9 shows the frequency characteristics of the notch filter according to this embodiment.
- a solid line 90 indicates the notch filter frequency.
- the notch filter frequency 90 is referred to as “notch frequency (90)”.
- notch frequency (90) is larger than “mechanical resonance frequency (80) of the steering control device”, and “current command value 2 not performing notch filter processing is added.
- (b) a range smaller than the cross frequency (solid line 64) of the control open loop characteristic is set.
- (1) is not used, it is smaller than the phase margin of (a) "and the stability of the control is poor, so that it becomes easy to transmit road surface vibration near the crossing frequency.
- the “notch frequency (90)” of the notch filter is larger than the “mechanical resonance frequency (80) of the steering control device”, and the “current command value not performing the notch filter processing”.
- the frequency is set to be smaller than the crossing frequency (solid line 64) of (b) ". Accordingly, as shown in the lower diagram of FIG. 7, the phase margin of (c) is made larger than the phase margin of “when the current command value 2 without executing the notch filter processing (b)” in FIG. 6 is used. Can do.
- the gain in the frequency band in which the road surface vibration generated when traveling on a rough road or the like is easily transmitted is increased as compared with “when the current command value 2 is not used (a)”.
- the phase margin can be increased, and the stability of the control system is improved as compared with “when the current command value 2 not performing the notch filter processing is used (b)”.
- the crossing frequency after applying the notch filter processing is lowered by the effect of sharply reducing the gain at the notch frequency which is a characteristic of the notch filter characteristics.
- the phase per cross frequency after applying the notch filter processing is advanced by the effect of advancing the phase at a frequency higher than the notch frequency, which is a characteristic of the notch filter characteristics.
- the “mechanical resonance frequency (80) of the steering control device” to which the notch filter is generally applied is set as the notch frequency (90) of the notch filter, the “notch filter processing is indicated by a solid line 64.
- the current command value 2 not to be applied is added, the effect of advancing the phase cannot be obtained because the control open loop characteristic of (b) "is separated from the crossing frequency. As a result, control stability cannot be improved. Furthermore, since the gain of the frequency band in which road surface vibration generated when traveling on a rough road or the like is easily transmitted is lowered, road surface vibration is easily transmitted.
- a phase advance filter is generally used as a filter process for advancing the phase.
- the high frequency gain is increased, so that it is easily affected by noise from a torque sensor or the like, and a problem such as noise may occur.
- the notch filter so as not to increase the high frequency gain, the high frequency gain of the control open loop characteristic is not changed. As a result, the influence of noise such as a torque sensor can be reduced.
- the damping ratios ⁇ 1 and ⁇ 2 in the equation (1) may be changed according to the vehicle speed V, and the depth or width of the notch filter may be changed with respect to the vehicle speed V.
- the characteristics of the notch filter become steep, and the frequency characteristics can be corrected in a more limited frequency region.
- the notch frequency 90 is smaller than the cross frequency of the control open loop characteristic of “when the current command value 2 not performing the notch filter processing is added (b)” indicated by the solid line 64, and The effect of realizing higher stability can be obtained by setting the frequency within ⁇ 5 Hz of the crossover frequency of the control open loop characteristic of “when the current command value 2 is not used (a)” indicated by the solid line 65. .
- the present embodiment is configured to improve the stability by performing notch filter processing that is easy to apply to the current command value 2, the current command value 1 is equal to the current command value 2. And the adjustment when the current command value 2 is applied can be reduced.
- the steering control device includes a torque sensor 4 (steering torque detector) that detects the steering torque of the steering wheel 1, a vehicle speed sensor 7 (vehicle speed detector) that detects the vehicle speed of the vehicle, and the steering wheel 1. Based on the motor 5 for applying the steering assist force, the steering torque detected by the torque sensor 4 and the vehicle speed detected by the vehicle speed sensor 7, a current command value 1 (first current command value) for the motor 5 is calculated.
- a torque sensor 4 steering torque detector
- vehicle speed detector 7 vehicle speed detector
- a current command value 1 calculation unit 11 (first current command value calculation unit), a differentiator 12 (steering torque differentiation unit) that calculates a differential value of steering torque detected by the torque sensor 4, and a notch filter
- a notch filter processing unit 13 for filtering a steering torque differential value using a notch filter, and based on the filtered steering torque differential value
- a current command value 2 calculation unit 14 (second current command value calculation unit) that calculates a current command value 2 (second current command value) for the motor 5, and a sum of the current command value 1 and the current command value 2
- a current driving unit 10 for driving the motor 5 so that the values of the currents flowing through the motor 5 coincide with each other, and the current command value 2 calculation unit 14 uses a filter instead of the filtered steering torque differential value.
- the notch frequency was set to be higher than the mechanical resonance frequency (80) of the steering control device and lower than the first crossing frequency (64). Thereby, it is possible to suppress a decrease in stability in the vicinity of the cross frequency 74 due to the addition of the current command value 2, and to suppress deterioration of disturbance vibration in the vicinity of the cross frequency 74.
- a phase lead compensator is used instead of the notch characteristic, the high-frequency gain becomes high and is susceptible to noise, but the notch characteristic does not increase the gain at frequencies above the notch frequency. Can be suppressed. Since the current command value 2 is processed to improve the stability, the current command value 1 can be easily applied, and adjustment and rework can be reduced.
- the order of the notch filter is second order, the stability decrease near the crossing frequency due to the addition of the current command value 2 is suppressed, and the deterioration of the disturbance vibration near the crossing frequency is suppressed. Can do.
- a phase lead compensator is used instead of the notch characteristic, the high-frequency gain becomes high and is susceptible to noise, but the notch characteristic does not increase the gain at frequencies above the notch frequency. Can be suppressed. Since the current command value 2 is processed to improve the stability, the current command value 1 can be easily applied, and adjustment and rework can be reduced.
- the current command value 2 calculation unit 14 calculates the current command value 2 using the vehicle speed detected by the vehicle speed sensor 7 in addition to the differential value of the filtered steering torque.
- the disturbance suppression characteristic can be adjusted according to the vehicle speed.
- Embodiment 2 Since the overall configuration and operation of the steering control device according to the second embodiment are the same as those of the first embodiment, description thereof is omitted here. In addition, the same reference numerals are used for configurations common to those in the first embodiment.
- the operation of the current command value 2 calculation unit 14 which is different from the first embodiment will be mainly described. The operation of the current command value 2 calculation unit 14 will be described with reference to the flowchart shown in FIG.
- steps S1 to S5 and S6 to S7 are the same as those in FIG.
- steps S52 to S54 are added between step S5 and step S6.
- Steps S52 to S54 constitute correction means for obtaining a correction gain for correcting the current command value 2 and correcting the current command value 2 using the correction gain.
- step S ⁇ b> 52 the steering torque from the torque sensor 4 is input to the current command value 2 calculation unit 14.
- the current command value 2 calculation unit 14 calculates a second torque differential control gain from the magnitude of the steering torque.
- the second torque differential control gain is set to be smaller as the steering torque is larger. That is, the second torque differential control gain map that defines the relationship between the magnitude of the steering torque and the second torque differential control gain so that the second torque differential control gain decreases as the magnitude of the steering torque increases. Is prepared in advance, and the second torque differential control gain corresponding to the magnitude of the steering torque is read from the second torque differential control gain map.
- an arithmetic expression in which the second torque differential control gain decreases as the steering torque increases is prepared in advance, and is obtained from the arithmetic expression.
- the magnitude of the steering torque is x
- the second torque differential control gain is y
- step S53 the current command value 2 calculator 14 calculates a third torque differential control gain from the magnitude of the steering speed.
- the third torque differential control gain is set to be smaller as the steering speed increases. That is, the third torque differential control gain map that defines the relationship between the magnitude of the steering speed and the third torque differential control gain so that the third torque differential control gain decreases as the magnitude of the steering speed increases. Is prepared in advance, and a third torque differential control gain corresponding to the magnitude of the steering speed is read from the third torque differential control gain map.
- an arithmetic expression in which the third torque differential control gain decreases as the steering speed increases is prepared in advance, and is obtained from the arithmetic expression.
- examples of the arithmetic expression include the following.
- Y a 2 x 2 + b 2 x + c 2 (a 2 ⁇ 0) (quadratic function)
- ⁇ Y k 3 x (k 3 ⁇ 0) (Directly proportional)
- Y k 4 / x (k 4 > 0) (inverse proportion)
- a detection method which detects a steering speed
- the steering speed may be estimated from the current or voltage.
- step S54 the current command value 2 calculating unit 14 corrects the current command value 2 by multiplying the current command value 2 by the second torque differential control gain and the third torque differential control gain.
- step S6 the adder 15 adds the current command value 1 and the corrected current command value 2 to obtain a current command value.
- the second torque differential control gain may be set from the ratio of the change amount of the current command value 1 to the change amount of the steering torque. That is, in a region where the ratio is larger than a preset value, the second torque differential control gain can be set so as to decrease the current command value 2, and the stability of the control system can be further ensured.
- the present invention is not limited to this.
- the current command value 2 may be corrected using only the torque differential control gain, or the current command value 2 may be corrected using only the third torque differential control gain.
- the same effect as in the first embodiment can be obtained. Further, in the present embodiment, the following effects can be obtained.
- a correction gain set according to the steering torque detected by the torque sensor 4 is obtained, and a current command calculated based on the differential value of the filtered steering torque using the correction gain. Since the correction unit (S52, S54) for correcting the value 2 is provided, the disturbance suppression characteristic can be adjusted according to the assist gain. In a region where the disturbance suppression characteristic by the current command value 1 can be ensured, the current command value 2 is reduced to ensure stability.
- a correction gain set according to the ratio of the change amount of the current command value 1 to the change amount of the steering torque detected by the torque sensor 4 is obtained, and the filter is obtained using the correction gain. Since the correction unit that corrects the current command value 2 calculated based on the differential value of the processed steering torque is provided, the disturbance suppression characteristic can be adjusted according to the assist gain. In a region where the disturbance suppression characteristic by the current command value 1 can be ensured, the current command value 2 is reduced to ensure stability.
- a steering speed detector that detects the steering speed of the steering wheel, and a correction gain that is set according to the magnitude of the steering speed that is detected by the steering speed detector are obtained. Since the correction unit for correcting the current command value 2 calculated based on the filtered steering torque differential value is provided, the disturbance suppression characteristic can be adjusted in accordance with the steering speed. By reducing the current command value 2 in a region where the steering speed is high, it is possible to suppress changes in the steering torque when fast steering is performed.
- the first correction gain that is set according to the steering torque detected by the torque sensor 4 and the magnitude of the steering speed that is detected by the steering speed detector are set.
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Abstract
Description
・制御系の安定性を悪化させる。
・自励振動が発生する。
・交差周波数付近の路面振動を伝えやすくなる。
図1は本発明の実施の形態1による操舵制御装置を示す構成図である。図1に示すように、ステアリングホイール1に、ステアリング軸2が連結されている。ステアリング軸2には、タイロッドを介して、一対の転舵輪3が連結されている。運転者がステアリングホイール1を操作すると、ステアリングホイール1に連結したステアリング軸2の回転に応じて左右の転舵輪3が転舵される。ステアリング軸2には、トルクセンサ4が配置され、ステアリング軸2に作用する操舵トルクを検出する。モータ5は減速機構6を介してステアリング軸2に連結しており、モータ5が発生する操舵補助トルクをステアリング軸2に付与することができる。また、車両の車速は車速センサ7で検出する。モータ5に流れる電流は電流センサ8で検出する。
なお、本実施の形態においても、特許文献1と同様に、アシストマップに入力する操舵トルクThdlには、位相補償処理を行い、操舵制御装置の制御系の安定性を確保する。ただし、電流指令値1を付与することによる制御系の安定性を確保する技術として、単純な位相補償処理に限定するものではなく、公知の技術で安定性を確保すれば良い。
なお、ζ2/ζ1の値からノッチ深さを調整し、また、ζ1の大きさからノッチの幅を調整する。
ここで、ノッチ周波数ω1は、操舵制御装置の機械共振周波数(約10Hz)より大きく、かつ、操舵制御装置の開ループ特性の交差周波数より小さく設定する。
また、例えば、ζ1は0.1に設定し、ζ2は1に設定する。すなわち、ノッチの深さは10となる。ただし、この限りではなく、開ループ特性に応じて、ζ1とζ2は調整する。
また、図6において、点線60、61は、電流指令値2を使用しない場合の制御開ループ特性である。以下では、当該場合を、「電流指令値2を使用しない場合(a)」と呼ぶこととする。これは、電流駆動部10が、図2の電流指令値1演算部11から出力される電流指令値1のみを用いて、モータ5を駆動した場合の制御開ループ特性を示している。この場合の操舵制御装置の構成としては、図2の構成から、微分器12、ノッチフィルタ処理部13、および、電流指令値2演算部14を削除した構成となる。
さらに、図6において、64は、「ノッチフィルタ処理を実施しない電流指令値2を加えた場合(b)」の制御開ループ特性の交差周波数である。交差周波数とは、ゲインが0になるときの周波数値のことである。65は、「電流指令値2を使用しない場合(a)」の制御開ループ特性の交差周波数である。
図7において、点線60、61は、図6と同様に、「電流指令値2を使用しない場合(a)」の制御開ループ特性を示す。
実線72、73は、本実施の形態によるノッチフィルタ処理を実施した電流指令値2を加えた場合の制御開ループ特性を示す。以下では、当該場合を、「ノッチフィルタ処理を実施した電流指令値2を加えた場合(c)」と呼ぶこととする。
図7において、74は、「ノッチフィルタ処理を実施した電流指令値2を加えた場合(c)」の制御開ループ特性の交差周波数である。
(1)ノッチフィルタ特性の特徴であるノッチ周波数で急峻にゲインを小さくする効果により、ノッチフィルタ処理適用後の交差周波数を下げたこと。
(2)ノッチフィルタ特性の特徴であるノッチ周波数より高い周波数で、位相を進ませる効果により、ノッチフィルタ処理適用後の交差周波数あたりの位相を進ませたこと。
これにより、電流指令値2を加えたことによる交差周波数74付近の安定性低下を抑制し、交差周波数74付近の外乱振動の悪化を抑えることができる。
また、ノッチ特性でなく、位相進み補償器を用いると高周波ゲインが高くなり、ノイズの影響を受けやすくなるが、ノッチ特性は、ノッチ周波数以上の周波数でのゲインを増加させないため、ノイズの影響を抑制できる。
電流指令値2に処理して、安定性を改善する構成としているため、電流指令値1に付与しやすく、調整・手戻りを軽減できる。
また、ノッチ特性でなく、位相進み補償器を用いると高周波ゲインが高くなり、ノイズの影響を受けやすくなるが、ノッチ特性は、ノッチ周波数以上の周波数でのゲインを増加させないため、ノイズの影響を抑制できる。
電流指令値2に処理して、安定性を改善する構成としているため、電流指令値1に付与しやすく、調整・手戻りを軽減できる。
実施の形態2に係る操舵制御装置の全体の構成および動作については、上記の実施の形態1と同じであるため、ここでは、説明を省略する。また、上記の実施の形態1と共通する構成については、同一の符号を用いることとする。以下では、実施の形態1と異なる点である、電流指令値2演算部14の動作について主に説明する。電流指令値2演算部14の動作について、図10に示すフローチャートで説明する。
・y=a1x2+b1x+c1 (a1<0) (二次関数)
・y=k1x (k1<0) (正比例)
・y=k2/x (k2>0) (反比例)
・y=a2x2+b2x+c2 (a2<0) (二次関数)
・y=k3x (k3<0) (正比例)
・y=k4/x (k4>0) (反比例)
なお、操舵速度を検出する検出方法(操舵速度検出部)としては、ステアリングホイール1やモータ5に取り付けた角度センサの検出値を微分して操舵速度を演算する構成としても良いし、モータ5の電流や電圧から操舵速度を推定するようにしても良い。
Claims (7)
- 車両のステアリングホイールの運転者による操舵をアシストするための操舵制御装置であって、
前記ステアリングホイールの操舵トルクを検出する操舵トルク検出部と、
前記車両の車速を検出する車速検出部と、
前記ステアリングホイールに操舵補助力を付与するモータと、
前記操舵トルク検出部により検出される前記操舵トルク及び前記車速検出部により検出される前記車速に基づいて、前記モータに対する第1の電流指令値を演算する第1の電流指令値演算部と、
前記操舵トルク検出部により検出される前記操舵トルクの微分値を演算する操舵トルク微分部と、
ノッチフィルタを有し、前記ノッチフィルタを用いて前記操舵トルクの微分値をフィルタ処理するノッチフィルタ処理部と、
前記フィルタ処理された前記操舵トルクの微分値に基づいて、前記モータに対する第2の電流指令値を演算する第2の電流指令値演算部と、
前記第1の電流指令値と前記第2の電流指令値との和に前記モータに流れる電流の値が一致するように前記モータを駆動する電流駆動部と
を備え、
前記第2の電流指令値演算部が、前記フィルタ処理された前記操舵トルクの微分値の代わりに、前記フィルタ処理を実施しない前記操舵トルクの微分値を用いて、前記第2の電流指令値を求めた場合の前記操舵制御装置における制御開ループ特性の交差周波数を第1の交差周波数としたとき、
前記ノッチフィルタのノッチ周波数は、前記操舵制御装置の機械共振周波数より大きく、且つ、前記第1の交差周波数より小さくなるように設定される
操舵制御装置。 - 前記ノッチフィルタは、次数が2次である
請求項1記載の操舵制御装置。 - 前記操舵トルク検出部により検出される前記操舵トルクに応じて設定される補正ゲインを求め、当該補正ゲインを用いて、前記第2の電流指令値演算部が前記フィルタ処理された前記操舵トルクの微分値に基づいて演算した前記第2の電流指令値を補正する補正部をさらに備えた
請求項1または2に記載の操舵制御装置。 - 前記操舵トルク検出部により検出される前記操舵トルクの変化量に対する前記第1の電流指令値の変化量の比に応じて設定される補正ゲインを求め、当該補正ゲインを用いて、前記第2の電流指令値演算部が前記フィルタ処理された前記操舵トルクの微分値に基づいて演算した前記第2の電流指令値を補正する補正部をさらに備えた
請求項1または2に記載の操舵制御装置。 - 前記ステアリングホイールの操舵速度を検出する操舵速度検出部と、
前記操舵速度検出部で検出される前記操舵速度の大きさに応じて設定される補正ゲインを求め、当該補正ゲインを用いて、前記第2の電流指令値演算部が前記フィルタ処理された前記操舵トルクの微分値に基づいて演算した前記第2電流指令値を補正する補正部をさらに備えた
請求項1または2に記載の操舵制御装置。 - 前記ステアリングホイールの操舵速度を検出する操舵速度検出部と、
前記操舵トルク検出部により検出される前記操舵トルクに応じて設定される第1の補正ゲイン、および、前記操舵速度検出部で検出される前記操舵速度の大きさに応じて設定される第2の補正ゲインを求め、前記第1の補正ゲイン及び前記第2の補正ゲインを用いて、前記第2の電流指令値演算部が前記フィルタ処理された前記操舵トルクの微分値に基づいて演算した前記第2の電流指令値を補正する補正部と
をさらに備えた
請求項1または2に記載の操舵制御装置。 - 前記第2の電流指令値演算部は、前記フィルタ処理された前記操舵トルクの微分値に加え、前記車速検出部で検出された車速も用いて、前記第2の電流指令値を演算する
請求項1から6までのいずれか1項に記載の操舵制御装置。
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