Vehicle control device, vehicle control method, and vehicle control system

Abstract

When the vehicle is decelerated on the basis of the total brake torque, in a state in which friction braking force is being generated, a control command that is output in order to generate driving force by the rear motor is corrected on the basis of the reliability of the calculation result caused by the state of the vehicle.

Description

Technical Field

[0001] The invention relates to a vehicle control device, a vehicle control method and a vehicle control system. Background Art

[0002] Patent document 1 discloses the following technology: with the goal of suppressing pitch changes when a vehicle is about to stop, a physical quantity related to the vehicle speed and a physical quantity related to the required braking force required to decelerate the vehicle are obtained, and when the vehicle is decelerated based on the physical quantity related to the required braking force, a driving force is generated by a driving device while a friction braking force is being generated.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-056583 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, in the above-mentioned conventional vehicle control device, the driving force is increased based on the command value of the friction braking force, but an error occurs between the estimated friction braking force and the braking force actually generated in the vehicle due to changes in the friction coefficient due to temperature changes of the brake pad, etc., and due to the influence of this error, there is a concern that smooth parking cannot be effectively achieved.

[0008] One of the objects of the present invention is to provide a vehicle control device, a vehicle control method, and a vehicle control system that can effectively suppress pitch fluctuations when a vehicle is parked.

[0009] Means for solving problems

[0010] When a vehicle control device in one embodiment of the present invention decelerates a vehicle based on a physical quantity related to the total braking force, while a friction braking force is being generated, the control instruction for generating a driving force based on a driving device is corrected and output according to the reliability of the calculation result caused by the state of the vehicle.

[0011] According to one embodiment of the present invention, it is possible to effectively suppress the pitch fluctuation when the vehicle is stopped. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of an electric vehicle 1 including the vehicle control system according to the first embodiment.

[0013] Figure 2 This is a control block diagram of the rear motor 7 according to the first embodiment.

[0014] Figure 3 This is a control block diagram of the total braking torque calculation unit 34 according to the first embodiment.

[0015] Figure 4 This is a control block diagram of the control gain calculation unit 35 according to the first embodiment.

[0016] Figure 5 This is a control block diagram of the addition torque calculation unit 37 according to the first embodiment.

[0017] Figure 6 This is a control block diagram of the estimated friction braking force correction gain calculation unit 33 according to the first embodiment.

[0018] Figure 7 This is a control block diagram of the reliability evaluation filter unit 73 according to the first embodiment.

[0019] Figure 8 It is a cutoff frequency map based on the magnitude of the friction braking force.

[0020] Fig. 9 It is a cutoff frequency mapping based on the speed of change of the friction braking force.

[0021] Fig.10 is a cutoff frequency map based on vehicle speed.

[0022] Fig.11 3 is a control block diagram of the gain conversion section of the variable cutoff filter 85 .

[0023] Fig.12 This is a control block diagram of the reliability evaluation gain calculation unit 74 according to the first embodiment.

[0024] Fig.13 It is a reliability evaluation gain map based on the magnitude of the friction braking force.

[0025] Fig.14 It is a reliability evaluation gain map based on the friction braking force change speed.

[0026] Fig.15 It is a reliability evaluation gain map based on the pad temperature change.

[0027] Fig.16 1 is a time chart of the vehicle speed, the G sensor value, the brake fluid pressure, and the pad μ, showing an operation example of the reliability evaluation filter unit 73 according to the first embodiment.

[0028] Fig.17 1 is a timing chart of the vehicle speed, the G sensor value, the brake fluid pressure, the pad μ, and the motor torque, showing an example of the operation of the reliability evaluation gain calculation unit 74 according to the first embodiment. DETAILED DESCRIPTION

[0029] [Implementation method 1]

[0030] Figure 1 This is a schematic diagram of an electric vehicle 1 including the vehicle control system according to the first embodiment.

[0031] The electric vehicle 1 includes front wheels 2FL, 2FR and rear wheels 2RL, 2RR, and friction brakes (friction brake devices) 3FL, 3FR, 3RL, 3RR provided on each wheel to generate friction braking force on the wheel (hereinafter, the friction brakes of each wheel are collectively referred to as friction brakes 3).

[0032] The electric vehicle 1 has a rear motor (drive device) 7 that outputs torque to the rear wheels 2RL and 2RR. The rear wheels 2RL and 2RR are also collectively referred to as drive wheels 2. Power is transmitted between the rear motor 7 and the rear wheels 2RL and 2RR via a speed reducer 8, a differential 10, and rear axles 6RL and 6RR.

[0033] Each wheel 2FL, 2FR, 2RL, 2RR has a wheel speed sensor 11FR, 11FL, 11RL, 11RR for detecting the wheel speed. The rear motor 7 has a rear wheel resolver 13 for detecting the motor speed (motor rotation speed). In addition, the electric vehicle 1 has a G sensor 5 for detecting the acceleration of the vehicle in the front-rear direction (hereinafter, also referred to as acceleration).

[0034] The friction brake 3 presses the brake pad in the direction of the rotation axis of each wheel relative to the brake rotor that rotates integrally with each wheel, and generates a braking force by friction. The friction brake 3 of the first embodiment presses the brake pad by a wheel cylinder that works by using brake fluid pressure, but it can also be set to a structure that presses the brake pad via a ball screw mechanism driven by an electric motor, etc., without special limitation.

[0035] The electric vehicle 1 includes a low voltage power supply (battery) 14 and a high voltage power supply 15 . The low voltage power supply 14 is, for example, a lead acid battery. The high voltage power supply 15 is, for example, a lithium ion battery or a nickel metal hydride battery. The high voltage power supply 15 is charged by power boosted by a DC-DC converter 16 .

[0036] The electric vehicle 1 includes a vehicle control device (control unit) 17 , a brake control device 18 , a rear motor control device 20 , and a power supply control device 19 . The control devices 17 , 18 , and 20 share information with each other via a CAN bus 21 .

[0037] The vehicle control device 17 obtains information from various sensors such as the rear wheel rotary transformer 13, the accelerator pedal sensor 22 for detecting the accelerator operation amount, the brake sensor 23 for detecting the brake operation amount, and the gear position sensor 24, and performs comprehensive control of the vehicle. The vehicle control device 17 distributes the torque according to the driver's accelerator operation, brake operation, etc., and outputs the driver's required torque to be output by the rear motor 7.

[0038] The brake control device 18 obtains information from various sensors such as the brake sensor 23 and sets a torque conversion value of the target braking force of the vehicle, namely a target braking torque, generates brake hydraulic pressure required for each wheel according to the target braking torque, and outputs it to the friction brake 3 through the hydraulic piping 18a.

[0039] The power supply control device 19 monitors the charge and discharge state of the high voltage power supply 15 and the single battery cells constituting the high voltage power supply 15. The power supply control device 19 calculates the power supply required torque limit value based on the charge and discharge state of the high voltage power supply 15, etc. The power supply required torque limit value is the maximum torque allowed in the rear motor 7. For example, when the charge amount of the high voltage power supply 15 decreases, the power supply required torque limit value is set to a value smaller than usual.

[0040] The rear motor control device 20 controls the electric power supplied to the rear motor 7 based on the rear required torque.

[0041] In the electric vehicle 1 of the first embodiment, in order to suppress the uncomfortable shaking of the vehicle when parking and reduce the fatigue of the passengers, the following anti-jerk control is implemented when the vehicle is stopped: the rear motor 7 outputs a driving torque equivalent to the total braking torque estimated from the braking torque actually generated in the vehicle. As a result, the front-rear jerk (acceleration) generated when parking at a fixed brake operation amount can be reduced by about 68% compared to the case without anti-jerk control. That is, even without skillful brake operation, smooth parking can be achieved.

[0042] Figure 2 This is a control block diagram of the rear motor 7 according to the first embodiment.

[0043] The driver required torque calculation unit 31 calculates the driver required torque based on the accelerator operation amount and the vehicle speed. The wheel speed is obtained by any appropriate method based on the wheel speeds detected by the wheel speed sensors 11FR, 11FL, 11RL, and 11RR, but at low speeds, it is obtained by referring to the motor speed detected by the rear wheel resolver 13.

[0044] The slope resistance calculation unit 32 calculates the resistance acting on the vehicle due to the road surface slope, i.e., the slope resistance, based on the vehicle speed, the G sensor value, and the vehicle weight. Specifically, the estimated slope acceleration caused by the slope is obtained based on the deviation between the differential value of the vehicle speed and the G sensor value, and the slope resistance is calculated based on the estimated slope acceleration caused by the slope and the vehicle weight.

[0045] The estimated friction braking force correction gain calculation unit 33 calculates a final correction gain for correcting an estimated error in the estimated friction braking force accompanying a change in the pad μ (friction coefficient) based on the G sensor value, vehicle speed, estimated friction braking force, running resistance, vehicle weight, motor torque, and brake pad temperature. If the pad μ changes due to temperature change, humidity change, etc., a deviation occurs in the estimated friction braking force relative to the braking force actually generated by the brake on the vehicle. Therefore, the estimated pad μ calculates a gain for correcting the estimated friction braking force (torque conversion value) in order to offset the error of the estimated pad μ relative to the nominal value of the pad μ.

[0046] The estimated friction braking force is obtained as the sum of the estimated friction braking forces of the wheels. The estimated friction braking force Bi of each wheel is calculated using the following formula (1).

[0047] Estimated friction braking force of each wheel Bi = brake fluid pressure × hydraulic cylinder area × brake effective radius × pad μ (nominal value)… (1)

[0048] Here, once the nominal value of the pad μ is set, it will not be changed during driving. For the nominal value, the temperature-μ characteristic of the brake pad is obtained in advance as a map, and the map is referred to for setting. The temperature of the brake pad when calculating the nominal value can be the outside air temperature at the start of driving, or a predetermined temperature (for example, 20°C) can be used.

[0049] The running resistance may be calculated based on changes in the running resistance with respect to changes in the vehicle weight or the vehicle speed, or may be estimated.

[0050] The estimated friction braking force may be estimated not based on the brake fluid pressure but based on the amount of stroke of the driver's brake pedal.

[0051] The estimated friction braking force correction gain calculation unit 33 will be described in detail later.

[0052] The total braking torque calculation section 34 calculates the total braking torque based on the running resistance, the estimated friction braking force, the gradient resistance, and the final correction gain. Figure 31 is a control block diagram of the total braking torque calculation unit 34 of the first embodiment. The braking force torque conversion unit 41 converts the estimated friction braking force into the estimated friction braking torque. The multiplier 42 multiplies the estimated friction braking torque by the final correction gain to calculate the corrected estimated friction braking torque that corrects the estimation error accompanying the change in μ of the brake pad. The first adder 43 and the second adder 44 add the torque equivalent to the slope resistance and the torque equivalent to the running resistance to the corrected estimated friction braking torque. The limiter 45 compares the value obtained by adding the torque equivalent to the slope resistance and the torque equivalent to the running resistance to the corrected estimated friction braking torque with 0, and outputs the larger value as the total braking torque.

[0053] The control gain calculation unit 35 calculates a control gain based on the vehicle speed and the total braking torque. Figure 4 This is a control block diagram of the control gain calculation unit 35 of the first embodiment. The acceleration estimation value calculation unit 51 calculates the acceleration by differentiating the vehicle speed. The acceleration-based control gain map 52 sets the acceleration-based control gain corresponding to the acceleration. In the acceleration-based control gain map 52, in the case of a deceleration that is less than the default value x2 (G) in absolute value, the acceleration-based control gain is set to 1 (100%). On the other hand, in the case of a deceleration that is greater than the default value x2 (G) in absolute value, the acceleration-based control gain is gradually reduced as the absolute value of the deceleration increases. The minimum value of the acceleration-based control gain is set to 0 (0%). In this way, it is possible to avoid adding torque during emergency braking. In addition, during emergency braking, it is of course preferable to ensure the braking force rather than suppress vibration in the pitch direction.

[0054] The speed-based control gain map 53 sets the speed-based control gain based on the three-dimensional map corresponding to the vehicle speed and the total braking torque. The speed-based control gain has the following characteristics: only in the specified area near the total braking torque of 0, it linearly decreases as the total braking torque decreases, and in most areas exceeding the specified area, it becomes a maximum value of 1. In addition, the maximum value can also be set to a positive value other than 1. In addition, the speed-based control gain is set to increase linearly as the vehicle speed decreases. Further, the speed-based control gain is set so that as the total braking torque increases, the vehicle speed at which the value rises from 0 (the gain increase start speed) increases. That is, the speed-based control gain has the following characteristics: as the total braking torque increases, the vehicle speed at which the anti-bumping control instruction intervenes (the vehicle speed at which the generation of the driving force based on the anti-bumping control begins) increases.

[0055] The parking determination unit 54 inputs the vehicle speed, total braking torque, vehicle weight, and estimated friction braking force, and clears a parking determination flag (=0) when the parking time is other than 0, and sets the parking determination flag (=1) when the parking time becomes 0.

[0056] The control gain rate limiting unit 55 limits the change speed on the increasing side and the decreasing side of the speed-based control gain. If the parking determination flag is set (=1), the previously used change speed limit value on the decreasing side is changed.

[0057] The multiplier 56 outputs a value obtained by multiplying the control gain based on acceleration by the control gain based on speed as a final control gain.

[0058] return Figure 2 The multiplier 36 multiplies the total braking torque by the control gain to calculate the total braking torque after the control gain multiplication.

[0059] The additional torque calculation unit 37 calculates the additional torque as the anti-bumping control torque based on the driver request torque and the total braking torque after multiplication by the control gain. Figure 5 1 is a control block diagram of the addition torque calculation unit 37 of the first embodiment. The limiter 61 compares the driver's request torque with 0 and outputs the larger value. The comparator 62 subtracts the output of the limiter 61 from the total braking torque after multiplication of the control gain. The limiter 63 compares the output of the comparator 62 with 0 and outputs the larger value as the addition torque.

[0060] The adder 38 adds the addition torque to the driver requested torque, and sets the added torque to be the post-requested torque.

[0061] Figure 6 This is a control block diagram of the estimated friction braking force correction gain calculation unit 33 according to the first embodiment.

[0062] The correction gain reference value calculation unit 71 calculates the correction gain reference value based on the estimated friction braking force, the motor torque, the G sensor value, the running resistance, and the vehicle weight, referring to the following equation (2).

[0063] Correction gain reference value = (G sensor value × vehicle weight - braking force equivalent to motor torque - driving resistance) / estimated friction braking force... (2)

[0064] The motor torque can use a final torque command value of the vehicle control device or a final torque command value of the inverter.

[0065] Alternatively, the differential value of the vehicle speed may be used instead of the G sensor value. In this case, since the differential value of the vehicle speed also includes the influence of the slope resistance, the numerator on the right side of the equation (2) is changed as follows:

[0066] (Vehicle speed differential × vehicle weight - braking force equivalent to motor torque - driving resistance - slope resistance).

[0067] Furthermore, since the pitch angle of the vehicle affects the longitudinal acceleration sensor values, the pitch angle of the vehicle may be detected or estimated and taken into consideration when calculating the correction gain reference value or the slope resistance.

[0068] The estimated friction braking force change speed calculation unit 72 calculates the change speed of the estimated friction braking force by differentiating the estimated friction braking force.

[0069] The reliability evaluation filter unit 73 evaluates the reliability of the correction gain reference value (obtains the reliability) based on the vehicle speed, the estimated friction braking force, and the estimated friction braking force change speed, and corrects the correction gain reference value according to the evaluation result. The reliability is the degree of reliability of the correction gain reference value (the variance of the estimation accuracy, the expectation of the estimation accuracy). Figure 7 : is a control block diagram of the reliability evaluation filter unit 73 of the first embodiment. In order to focus on the current correction gain reference value in the interval where the reliability of the correction gain reference value is high, and to focus on the output value (correction gain) of the reliability evaluation filter instead of the current correction gain reference value in the interval where the reliability of the correction gain reference value is low, the reliability evaluation filter unit 73 uses, for example, Fig.11 The variable cutoff filter 85 whose responsiveness is made variable as shown. Here, the responsiveness of the variable cutoff filter 85 uses the minimum value among the output values ​​of the frequency maps 81 to 83 in the previous stage. Fig.1185 is a control block diagram of the gain conversion unit of the variable cutoff filter 85. The gain conversion unit 851 converts the cutoff frequency determined by each frequency map 81 to 83 into a gain corresponding thereto. The first multiplier 852 multiplies the correction gain reference value by the gain. The comparator 853 subtracts the gain from 1. The second multiplier 854 multiplies the output of the comparator 853 by the output value (correction gain) of the previous variable cutoff filter 85. The previous value holding unit 855 holds the output value of the previous variable cutoff filter 85. The adder 856 outputs the correction gain obtained by multiplying the output value of the first multiplier 852 by the output value of the second multiplier 854. Here, the characteristic of the variable cutoff filter 85 is the same as that of an LPF (Low Pass Filter), and further, when the cutoff frequency is set to 0, by setting the output value of the gain conversion unit to 0, it is possible to set the filter structure so as to maintain the output value of the last variable cutoff filter 85. Therefore, the responsiveness to the correction gain reference value estimated in the current control cycle can be appropriately changed according to the reliability, and the correction gain can be calculated.

[0070] The cutoff frequency mapping 81 based on the magnitude of the friction braking force is a mapping used to estimate by focusing on the value estimated in the interval where the influence of interference, etc., which is not fully considered in the mathematical formula, may be small. The smaller the friction braking force, the greater the influence of the acceleration caused by the interference, which is not taken into account in the mathematical formula, relative to the acceleration caused by the friction braking force included in the G sensor value. As a result, the error between the true value that should actually be corrected and the correction gain reference value estimated by formula (2) may become larger. Therefore, the larger the estimated friction braking force, the higher the first cutoff frequency Y is made by the cutoff frequency mapping 81 based on the magnitude of the friction braking force. As shown in FIG. Figure 8 As shown, the first cut-off frequency Y is set to take the minimum value Y1 when the estimated friction braking force is lower than X1, take the maximum value Y2 when the estimated friction braking force exceeds X2, and take the maximum value Y2 when the estimated friction braking force is greater than X1 and less than X2. In addition, as mentioned above, when the estimated friction braking force is small, there is a concern that the estimation error of the correction gain reference value will increase due to the influence of interference that is not fully considered in the mathematical formula. Therefore, when it becomes less than the specified estimated friction braking force, the cut-off frequency is reduced. Here, Y1 is set to a non-zero value, but it can also be set to 0.

[0071] The cutoff frequency map 82 based on the friction braking force change speed is a map for making an estimate with emphasis on the value estimated in the interval where the influence of the response delay of the G sensor 5 is likely to be small. The G sensor 5 is mounted on the spring of the vehicle, so even if the friction braking force is actually generated, there is a time lag before the G sensor value is detected. Therefore, when the friction braking force changes quickly, even if the denominator of the formula (2) increases due to the increase in the friction braking force, the increase in the G sensor value in the numerator is slow, so the estimation error of the correction gain reference value becomes larger. Therefore, in the case where such a response delay is assumed, the estimation is made with emphasis on the output value of the last variable cutoff filter. In addition, when pseudo differential is used for the differentiation of the vehicle speed, when the sensor noise is removed, there are also elements such as filters with delay, so there is a response delay relative to the increase in the friction braking force. As mentioned above, the larger the friction braking force change speed, the larger the response delay of the sensor, and the higher the possibility that the error with the true value becomes larger. Therefore, the smaller the estimated friction braking force change speed, the higher the second cutoff frequency W is made by the cutoff frequency map 82 based on the friction braking force change speed.

[0072] like Fig. 9 As shown, the second cutoff frequency W is set to take the minimum value W1 when the absolute value of the estimated friction braking force change speed exceeds |Z2|, take the maximum value W2 when the absolute value of the estimated friction braking force change speed is less than |Z1|, and the larger the absolute value of the estimated friction braking force change speed is when the absolute value of the estimated friction braking force change speed is greater than |Z1| and less than |Z2|. When the estimated friction braking force change speed is fast, there is a concern that the output value of the G sensor 5 mounted on the spring of the vehicle will produce a response delay relative to the change of the estimated friction braking force due to the influence of the spring mass damper system of the suspension. Therefore, when the estimated friction braking force changes quickly, in order to increase the weight of the output value of the previous variable cutoff filter, the cutoff frequency is set to a lower characteristic. Here, W1 is set to a non-zero value, but it can also be 0. Further, it is set to be a characteristic that is symmetrical with respect to 0, but it can also be set to an asymmetric characteristic.

[0073] When the vehicle speed decreases, the cutoff frequency map 83 based on the vehicle speed is estimated with emphasis on the output value of the last variable cutoff filter. This is because the brake changes kinetic energy into thermal energy, so it is assumed that when the vehicle speed decreases, the state of the brake pad is difficult to change even if the braking force is applied. The greater the vehicle speed, the higher the third cutoff frequency R is made by the cutoff frequency map 83 based on the vehicle speed. Fig.10As shown, the third cutoff frequency R is set to take the minimum value R1 when the vehicle speed is lower than V1, the maximum value R2 when the vehicle speed exceeds V2, and the higher the vehicle speed is when the vehicle speed is greater than V1 and less than V2. When the vehicle speed is low, the state of the brake pad is difficult to change. Furthermore, if the anti-bumping control intervenes with the decrease in vehicle speed and the motor torque increases, the response of the G sensor value is delayed relative to the change in the motor torque, as in the case where the change speed of the friction braking force is fast, and there is a concern that the estimation error of the correction gain reference value will increase. Therefore, as the speed decreases, the cutoff frequency is reduced so that the output value of the last variable cutoff filter can be focused on for estimation. Here, V1 can be set to the fastest vehicle speed at which the anti-bumping control begins to intervene, which is specified in the gain characteristics of the anti-bumping control determined by the total braking force and speed, or it can be a speed other than this. In addition, R1 can also be 0.

[0074] The limiter 84 outputs the smallest value among the first cutoff frequency Y, the second cutoff frequency W, or the third cutoff frequency R as the cutoff frequency.

[0075] The variable cutoff filter 85 performs filtering processing on the correction gain reference value according to the cutoff frequency output from the limiter 84 .

[0076] return Figure 6 The reliability evaluation gain calculation unit 74 calculates the reliability evaluation gain for correcting the output value of the reliability evaluation filter unit 73 based on the estimated friction braking force, the estimated friction braking force change speed, and the brake pad temperature. The reliability evaluation gain is a gain used to reduce the final correction result when the output of the reliability evaluation filter unit 73 is not so reliable and when the anti-bumping control does not intervene strongly. In addition, it is also possible to set a structure that maintains the previously calculated reliability evaluation gain when traveling at a low speed (for example, below 1 km / h). Fig.12 This is a control block diagram of the reliability evaluation gain calculation unit 74 according to the first embodiment.

[0077] The larger the estimated friction braking force is, the higher the first reliability evaluation gain M is in the reliability evaluation gain map 91 based on the magnitude of the friction braking force. Fig.13As shown, the first reliability evaluation gain M is set to take the minimum value M3 when the estimated friction braking force is lower than X1, take the maximum value 1 when the estimated friction braking force exceeds X2, and the higher the estimated friction braking force is when the estimated friction braking force is greater than X1 and less than X2. When the estimated friction braking force is small, the creep torque is likely to be close to the braking force generated by the vehicle, and the pitch of the vehicle is small, so it is assumed that even if the anti-bumping control does not intervene, it will not have a significant impact on the ride quality. However, the correction gain is more likely to have a larger estimation error due to the influence of interference, so the gain is reduced to avoid a significant increase in the braking distance by mistake.

[0078] The smaller the friction braking force change speed, the higher the second reliability evaluation gain N is according to the reliability evaluation gain map 92 based on the friction braking force change speed. Fig.14 As shown, the second reliability evaluation gain N is set to take the minimum value N3 when the estimated friction braking force change speed exceeds Z2, take the maximum value 1 when the estimated friction braking force change speed is less than Z1, and take the higher value when the estimated friction braking force change speed is greater than Z1 and less than Z2. When the friction braking force changes rapidly, there is a concern that the update in the reliability evaluation filter unit 73 will be stopped so that the estimation will not deteriorate, so when the pedaling is increased, an error may occur between the previous estimated value and the previous estimated value. Therefore, when the estimated friction braking force increases at a speed greater than a predetermined speed, there is a concern that the previous estimated result will change significantly, so the second reliability evaluation gain N is reduced. In addition, for the release of the pedaling, it is assumed that the increase in the brake pad temperature, etc., will not change significantly from the previous estimated result (the output value of the previous reliability evaluation filter), so in this embodiment, the second reliability evaluation gain is set to 1, but it may also be set to a mapping having a characteristic of reducing the second reliability evaluation gain when the estimated friction braking force change speed caused by the release of the pedaling is rapid. In the present embodiment, the gain is determined with reference to only the estimated friction braking force change rate, but a three-dimensional mapping may be used with reference to the friction braking force change rate and the vehicle speed, where the gain is reduced when the vehicle speed is above a predetermined value and the friction braking force change rate is fast.

[0079] The smaller the pad temperature change relative to the brake pad temperature during the last friction braking, the higher the third reliability evaluation gain Q is in the reliability evaluation gain map 93 based on the pad temperature change. Fig.15As shown, the third reliability evaluation gain Q is set to take the minimum value Q1 when the pad temperature change exceeds P2, take the maximum value 1 when the pad temperature change is less than P1, and take the higher value when the pad temperature change is greater than P1 and less than P2. When the pad temperature change is small, the reliability of the correction gain estimated at the last braking is high, so the gain is increased. When the pad temperature change is large, the reliability of the last value is reduced, so the gain is reduced. The pad temperature can be obtained by a sensor or an estimated value can be used. In addition, the brake pad temperature at the last friction braking can use the final pad temperature at the last friction braking.

[0080] The limiter 94 outputs the second reliability evaluation gain N and the third reliability evaluation gain Q, whichever has a larger value.

[0081] The multiplier 95 outputs a value obtained by multiplying the first reliability evaluation gain M by the output value of the limiter 94 as the reliability evaluation gain.

[0082] return Figure 6 The multiplier 75 outputs a value obtained by multiplying the output value of the reliability evaluation filter unit 73 by the reliability evaluation gain as a final correction gain.

[0083] Next, the effects of the first embodiment will be described.

[0084] Fig.16 1 is a time chart of the vehicle speed, the G sensor value, the brake fluid pressure, and the pad μ, showing an operation example of the reliability evaluation filter unit 73 according to the first embodiment.

[0085] In the interval from time t1 to t2, the hydraulic pressure changes rapidly, and there is a concern that the error in estimating the pad μ may increase due to the influence of the delay of the G sensor value, so the weight of the output value of the last variable cutoff filter is increased and updated compared to the current gain reference value. Fig.16 In this case, the cutoff frequency is set to 0 and the last value is saved.

[0086] In the interval from time t3 to t4, the brake fluid pressure is small and the friction braking force is weak. Therefore, the influence of interference and sensor error that are not fully considered becomes relatively large relative to the influence of the friction braking force included in the vehicle deceleration, and there is a concern that the estimation error becomes large. Therefore, in this case, the weight of the output value of the previous variable cutoff filter is also increased and updated.

[0087] Fig.17 1 is a timing chart of the vehicle speed, the G sensor value, the brake fluid pressure, the pad μ, and the motor torque, showing an example of the operation of the reliability evaluation gain calculation unit 74 according to the first embodiment.

[0088] In the period from time t1 to time t2 , the change speed of the hydraulic pressure is high and there is a possibility that the updating in the reliability evaluation filter unit 73 stops, so the corrected estimated friction braking force is reduced.

[0089] In the interval from time t3 to t4, the friction braking force is small, so even if the anti-bumping control does not intervene strongly, the ride quality is unlikely to deteriorate. Therefore, the estimated pad μ may contain errors, and the corrected estimated friction braking force is reduced.

[0090] As described above, the vehicle control device 17 of the first embodiment corrects the control command (the final correction gain when calculating the total braking torque for determining the additive torque) outputted to generate the driving force based on the rear motor 7 in the state where the friction braking force is being generated when the vehicle is decelerated based on the total braking torque, according to the reliability of the calculation result caused by the state of the vehicle. As a result, in the anti-bumping control, the additive torque can be outputted to suppress the influence of the estimated error of the friction braking force on the actual braking force, and the pitch change when the vehicle is stopped can be effectively suppressed.

[0091] The vehicle control device 17 corrects the control command based on the reliability of the calculation result caused by the state of the vehicle including at least the vehicle speed, the physical quantity related to the friction braking force, and the temperature of the friction brake 3. In the anti-bump control, the error between the true value to be corrected and the correction gain reference value varies greatly depending on the vehicle speed, the friction braking force, and the temperature of the friction brake 3. Therefore, by correcting the control command based on the reliability of these, the influence of the estimation error of the friction braking force can be more effectively suppressed in the anti-bump control.

[0092] The vehicle control device 17 obtains a final correction gain by multiplying the output value of the reliability evaluation filter unit 73 by a reliability evaluation gain, and corrects the control command based on the final correction gain, wherein the output value of the reliability evaluation filter unit 73 is obtained by correcting a predetermined correction gain reference value based on the reliability of the calculation result caused by the vehicle speed and the reliability of the calculation result caused by the physical quantity related to the friction braking force, and the reliability evaluation gain is calculated by the reliability evaluation gain calculation unit 74 based on the reliability evaluation gain set according to the reliability of the calculation result caused by the physical quantity related to the friction braking force and the reliability evaluation gain set according to the reliability of the calculation result caused by the physical quantity related to the temperature of the friction brake 3. As a result, it is possible to estimate the current correction gain reference value in a high reliability interval and the previous variable cutoff filter output value in a low reliability interval, and it is possible to more effectively suppress the influence of the estimation error. In addition, when the reliability of the output of the reliability evaluation filter unit 73 is low and it is not necessary to strongly intervene in the anti-bumping control, by reducing the final correction gain, it is possible to suppress the braking distance from increasing significantly by mistake.

[0093] The vehicle control device 17 obtains a final correction gain by multiplying the output value obtained by passing a predetermined correction gain reference value through a variable cutoff filter 85, the variable cutoff filter 85 being a variable cutoff filter having a cutoff frequency set based on a third cutoff frequency R according to the vehicle speed and the reliability of a calculation result caused by a physical quantity related to the friction braking force. By using the variable cutoff filter 85, the cutoff frequency is increased in a high reliability interval and the cutoff frequency is decreased in a low reliability interval, so that the output value of the variable cutoff filter can be estimated with emphasis on the current correction gain reference value in a high reliability interval and with emphasis on the previous output value in a low reliability interval.

[0094] The cutoff frequency set according to the reliability of the calculation result caused by the physical quantity related to the friction braking force includes: a first cutoff frequency Y, which is set according to the reliability of the calculation result caused by the magnitude of the friction braking force; and a second cutoff frequency W, which is set according to the reliability of the calculation result caused by the change speed of the friction braking force. The smaller the friction braking force, the higher the possibility that the error with the true value will become larger. When the friction braking force changes quickly, the error becomes larger due to the response delay of the G sensor 5. Therefore, by setting the cutoff frequency according to the magnitude of the friction braking force and the change speed of the friction braking force, the increase of the estimation error of the friction braking force can be suppressed.

[0095] The third cutoff frequency R based on the vehicle speed is set to be higher as the speed is higher, the first cutoff frequency Y based on the magnitude of the friction braking force is set to be higher as the friction braking force is higher, and the second cutoff frequency W based on the friction braking force change speed is set to be higher as the change speed is lower. Thus, during the period of reduced reliability, the estimation of the output value of the variable cutoff filter last time is emphasized, so that an increase in the estimation error of the friction braking force can be suppressed.

[0096] The cutoff frequency of the variable cutoff filter 85 is set by selecting low from the cutoff frequency based on the vehicle speed, the cutoff frequency based on the friction braking force, and the cutoff frequency based on the friction braking force change speed. By selecting the cutoff frequency by selecting low, it is possible to suppress an increase in the estimation error caused by focusing on the current correction gain reference value for estimation even in a low reliability interval.

[0097] The physical quantity related to the temperature of the friction brake 3 is the temperature of the brake pad. The pad μ depends on the pad temperature. When the pad temperature changes little since the last friction brake, it is assumed that the error is small when the output value of the reliability evaluation filter estimated in the past is used forcibly. On the other hand, when the pad temperature changes greatly, it is assumed that the error between the true value and the output value of the reliability evaluation filter estimated in the past is large. Therefore, by changing the reliability gain according to the pad temperature change, it is possible to suppress the increase in the braking distance caused by the error between the estimated correction gain and the true value.

[0098] The reliability evaluation gain set according to the reliability of the calculation result caused by the physical quantity related to the friction braking force includes: a first reliability evaluation gain M based on the size of the friction braking force, and a second reliability evaluation gain N based on the speed of change of the friction braking force. When the friction braking force is small, even if the anti-bumping control does not intervene, it will not have a big impact on the ride experience, and due to the influence of interference, the estimation error is likely to become larger. In addition, when the speed of change of the friction braking force is large, there is a concern that the error between the estimated correction gain and the true value will become larger due to the cessation of the update in the reliability evaluation filter unit 73. Therefore, by setting the reliability evaluation gain according to the size of the friction braking force and the speed of change of the friction braking force, it is possible to suppress the increase in braking distance due to the error between the estimated correction gain and the true value.

[0099] The first reliability evaluation gain M based on the magnitude of the friction braking force is set to be higher as the friction braking force is larger, the second reliability evaluation gain N based on the friction braking force change speed is set to be higher as the friction braking force change speed is smaller, and the third reliability evaluation gain Q based on the pad temperature change is set to be higher as the pad temperature change since the last friction braking. Thus, the reliability evaluation gain becomes smaller during the period of reduced reliability, so that the increase in braking distance due to the error between the estimated correction gain and the true value can be suppressed.

[0100] The reliability evaluation gain is set to multiply the first reliability evaluation gain M based on the magnitude of the friction braking force by the following gain: a gain obtained by selecting high the second reliability evaluation gain N based on the speed of change of the friction braking force and the third reliability evaluation gain Q based on the change of the pad temperature. For example, when the brake is pressed from a low speed, the increase in the pad temperature is small, so it is assumed that the friction coefficient of the brake does not change much, but since the speed of change of the friction braking force is large, the second reliability evaluation gain N will become the minimum value. Therefore, by setting the second reliability evaluation gain N and the third reliability evaluation gain Q to high, the third reliability evaluation gain Q is selected when the brake is pressed from a low speed, so that even in the interval where the reliability of the output value of the reliability evaluation filter is high, the reliability evaluation gain can be suppressed from becoming too small.

[0101] [Other implementation methods]

[0102] Although the embodiments for carrying out the present invention have been described above, the specific configuration of the present invention is not limited to the configuration of the embodiments, and design changes and the like that do not depart from the gist of the invention are also included in the present invention.

[0103] In the embodiment, an example of applying the present invention to a rear-wheel drive electric vehicle is shown, but it may also be a front-wheel drive electric vehicle or a four-wheel drive electric vehicle. In addition, it is not limited to electric vehicles, and it may also be a vehicle having an engine as an internal combustion engine, or a hybrid vehicle that can use both an engine and a motor to travel. That is, as long as it is a structure that can impart torque from the drive source side or a structure that can reduce friction braking within the range where the vehicle can stop or within the range where the braking force acts between the drive wheel and the road surface when the vehicle stops using the friction brake.

[0104] In the reliability evaluation filter unit 73 of the first embodiment, the cutoff frequency is set by selecting the lower of the output values ​​of the frequency maps 81 to 83 . However, the cutoff frequency may be calculated by multiplying the output values ​​of the frequency maps 81 to 83 .

[0105] In addition, for example, due to the speed of change of the motor torque, the response delay of the G sensor value may sometimes occur, so the frequency mapping for changing the cutoff frequency may be added with reference to the speed of change of the motor torque. Furthermore, when the road surface is considered to be a dangerous road, there is a concern that the noise in the G sensor value increases and the estimation accuracy of the correction gain reference value deteriorates, so the frequency mapping for changing the cutoff frequency according to the road surface disturbance may be added (in the estimation of the road surface disturbance, the noise generated in the G sensor value can be detected by a high-pass filter or the like, or it can be detected based on the information of the stereo camera or the like.).

[0106] In the reliability evaluation gain calculation unit 74 of the first embodiment, the upper limits of the three reliability evaluation gains M, N, and Q are preferably set to 1, but may be set to values ​​other than 1, and the lower limits (M3, N3, and Q1) may be set to 0. In addition, in the first embodiment, a configuration is used in which the reliability evaluation gain maps 91 to 93 are used, but since it is assumed that the humidity of the pad surface also affects the braking force, a map that calculates the gain based on the elapsed time from the last braking, the braking start speed, and the humidity may be used.

[0107] In addition, in the embodiment, X1 and X2 of the cutoff frequency map (MAP) 81 based on the magnitude of the friction braking force and the reliability evaluation gain map (MAP) 91 based on the magnitude of the friction braking force, and Z1 and Z2 of the cutoff frequency map (MAP) 82 based on the friction braking force change speed and the reliability evaluation gain map (MAP) 92 based on the friction braking force change speed are marked with the same variables, but different values ​​can also be used respectively.

[0108] In addition, the present invention is not limited to the above-mentioned embodiments, and includes various modified examples. For example, the above-mentioned embodiments are described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to having all the structures described. In addition, a part of the structure of a certain embodiment can be replaced with the structure of other embodiments, and in addition, the structure of other embodiments can be added to the structure of a certain embodiment. In addition, for a part of the structure of each embodiment, other structures can be added / deleted / replaced.

[0109] This application claims the priority based on Japanese Patent Application No. 2022-138913 filed on September 1, 2022. The entire disclosure of Japanese Patent Application No. 2022-138913 filed on September 1, 2022 including the specification, claims, drawings, and abstract is incorporated herein by reference in its entirety.

[0110] Description of Reference Numerals

[0111] 1 Electric vehicle (vehicle); 3 Friction brake (friction brake device); 7 Rear motor (drive device); 17 Vehicle control device (control unit).

Claims

1. A vehicle control device, the vehicle control device being provided in a vehicle, the vehicle having a friction braking device for generating a friction braking force in the vehicle and a driving device for generating a driving force in the vehicle, the vehicle control device comprising: The control unit outputs a result calculated based on the input information, The control unit obtains a physical quantity related to a total braking force for decelerating the vehicle, When the vehicle is decelerated based on a physical quantity related to the total braking force, while the friction braking force is being generated, the control unit corrects and outputs a control instruction for generating a driving force based on the driving device according to the reliability of a calculation result caused by the state of the vehicle.

2. The vehicle control device according to claim 1, wherein: The control unit corrects the control command based on reliability of a calculation result caused by a state of the vehicle including at least a physical quantity related to a speed of the vehicle, a physical quantity related to a target friction braking force of the vehicle, and a physical quantity related to a temperature of the friction brake device.

3. The vehicle control device according to claim 2, wherein: The control unit multiplies the output value by the evaluation gain to obtain a final correction gain, and corrects the control instruction based on the final correction gain, wherein: The output value is an output value obtained by correcting a predetermined correction gain reference value based on the reliability of a calculation result caused by a physical quantity related to the speed of the vehicle and the reliability of a calculation result caused by a physical quantity related to the target friction braking force. The evaluation gain is acquired based on a gain set according to reliability of a calculation result based on a physical quantity related to the target friction braking force and a gain set according to reliability of a calculation result based on a physical quantity related to a temperature of the friction brake device.

4. The vehicle control device according to claim 3, wherein: The control unit multiplies the output value by the evaluation gain to obtain the final correction gain, wherein: The output value is an output value obtained by passing the specified correction gain reference value through a variable cutoff filter, wherein the variable cutoff filter is a variable cutoff filter having a cutoff frequency set based on the reliability of a calculation result caused by a physical quantity related to the speed of the vehicle and a cutoff frequency set based on the reliability of a calculation result caused by a physical quantity related to the target friction braking force.

5. The vehicle control device according to claim 4, wherein: The cutoff frequency set according to the reliability of the calculation result caused by the physical quantity related to the target friction braking force includes: a cutoff frequency set according to the reliability of the calculation result caused by the size of the target friction braking force, and a cutoff frequency set according to the reliability of the calculation result caused by the change speed of the target friction braking force.

6. The vehicle control device according to claim 5, wherein: The cutoff frequency, which is set based on the reliability of the calculation result caused by the physical quantity related to the speed of the vehicle, is set to be higher as the speed is higher. The cut-off frequency set according to the reliability of the calculation result caused by the magnitude of the target friction braking force is set to be higher as the target friction braking force is larger. The cutoff frequency set according to the reliability of the calculation result caused by the change speed of the target friction braking force is set to be higher as the change speed is smaller.

7. The vehicle control device according to claim 6, wherein: The cutoff frequency of the variable cutoff filter is set by selecting the lower of the following cutoff frequencies: A cutoff frequency set according to the reliability of the calculation result caused by the physical quantity related to the speed of the vehicle, a cutoff frequency set according to the reliability of the calculation result caused by the magnitude of the target friction braking force, and a cutoff frequency set according to the reliability of the calculation result caused by the changing speed of the target friction braking force.

8. The vehicle control device according to claim 3, wherein: The physical quantity correlated with the temperature of the friction brake device is the temperature of the brake pad.

9. The vehicle control device according to claim 8, wherein: The gain set according to the reliability of the calculation result caused by the physical quantity related to the target friction braking force includes: a gain set according to the reliability of the calculation result caused by the magnitude of the target friction braking force, and a gain set according to the reliability of the calculation result caused by the change speed of the target friction braking force.

10. The vehicle control device according to claim 9, wherein: The gain set according to the reliability of the calculation result caused by the magnitude of the target friction braking force is set to be higher as the target friction braking force is larger. The gain set according to the reliability of the calculation result caused by the change speed of the target friction braking force is set to be higher as the change speed is smaller. The gain set according to the reliability of the calculation result due to the temperature of the brake pad is set to be higher as the amount of change in the temperature is smaller.

11. The vehicle control device according to claim 10, wherein: The evaluation gain is set by multiplying a gain set according to the reliability of the calculation result caused by the magnitude of the target friction braking force by the following gain: The gain is obtained by selecting a higher one of a gain set according to the reliability of a calculation result caused by a change speed of the target friction braking force and a gain set according to the reliability of a calculation result caused by a temperature of the brake pad.

12. The vehicle control device according to claim 3, wherein: The control unit obtains the correction gain reference value based on a physical quantity related to the target friction braking force, a driving force of the driving device, an acceleration in a front-rear direction of the vehicle, a running resistance of the vehicle, and a weight of the vehicle.

13. A vehicle control method, the vehicle control method being executed by a control unit mounted in a vehicle, the vehicle comprising a friction brake device for generating a friction brake force for the vehicle, and a drive device for generating a drive force for the vehicle, Through the control unit: obtaining a physical quantity related to a total braking force for decelerating the vehicle; and When the vehicle is decelerated based on a physical quantity related to the total braking force, while the friction braking force is being generated, a control command for generating a driving force based on the driving device is corrected and output according to the reliability of a calculation result caused by the state of the vehicle.

14. A vehicle control system comprising: The friction brake device generates friction braking force on the vehicle; a driving device for causing the vehicle to generate driving force; and The control device outputs the result of the operation based on the input information, The control device obtains a physical quantity related to a total braking force for decelerating the vehicle, When the vehicle is decelerated based on a physical quantity related to the total braking force, while the friction braking force is being generated, the control device corrects and outputs a control instruction for generating a driving force based on the driving device according to the reliability of a calculation result caused by the state of the vehicle.

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