VEHICLE CONTROL DEVICE, VEHICLE CONTROL METHOD AND VEHICLE CONTROL SYSTEM

Abstract

A vehicle control device corrects a control command for generating a driving force by a rear motor according to a reliability degree of a calculation result associated with a state of a vehicle in a state where a friction braking force is generated at the time of deceleration of the vehicle based on a total braking force.

Description

TECHNICAL FIELD

[0001] The present invention relates to a vehicle control device, a vehicle control method and a vehicle control system. TECHNICAL BACKGROUND

[0002] PTL 1 discloses a technique that detects a physical quantity related to a speed of a vehicle and a physical quantity related to a requested braking force required to decelerate the vehicle, and generates a driving force by a driving device in a state where a friction braking force is generated when the vehicle is to be decelerated based on the physical quantity related to the requested braking force, with the aim of suppressing a pitch fluctuation that occurs just before the vehicle stops. LIST OF REFERENCES PATENT LITERATURE

[0003] PTL 1: Japanese Patent Laid-Open No. 2022-056583 PRESENTATION OF THE INVENTIONTECHNICAL PROBLEM

[0004] However, although the above-described prior art vehicle control device increases the driving force based on a command value of the frictional braking force, an error may arise between the estimated frictional braking force and a braking force actually generated on the vehicle due to, for example, a change in the friction coefficient depending on, for example, a change in the temperature of the brake pad, resulting in a smooth stop of the vehicle not being effectively realized under the influence of this error.

[0005] One of the objects of the present invention is to provide a vehicle control apparatus, a vehicle control method and a vehicle control system capable of effectively suppressing a pitch fluctuation when holding a vehicle. SOLUTION TO THE PROBLEM

[0006] According to one aspect of the present invention, a vehicle control device corrects a control instruction for generating a driving force by a driving device according to a reliability degree of a calculation result associated with a state of a vehicle, and outputs the control instruction in a state where a friction braking force is generated at the time of deceleration of the vehicle based on a physical quantity related to a total braking force.

[0007] According to one aspect of the present invention, a pitch fluctuation when holding a vehicle can be effectively suppressed. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 schematically shows an electric vehicle 1 with a vehicle control system according to a first embodiment. Fig. 2 is a control block diagram of a rear engine 7 according to the first embodiment. Fig. 3 is a control block diagram of a total braking torque calculating section 34 according to the first embodiment. Fig. 4 is a control block diagram of a control gain calculation section 35 according to the first embodiment. Fig. 5 is a control block diagram of an additional torque calculating section 37 according to the first embodiment. Fig. 6 is a control block diagram of an estimated friction braking force correction gain calculation section 33 according to the first embodiment. Fig. 7 is a control block diagram of a reliability evaluation filter section 73 according to the first embodiment. Fig. 8 is a cutoff frequency map based on the magnitude of a friction braking force. Fig. 9 is a cut-off frequency map based on the rate of change of the friction braking force. Fig. 10 is a map of the cutoff frequency as a function of the vehicle speed. Fig. 11 is a control block diagram of a gain conversion section of a variable cutoff filter 85. Fig. 12 is a control block diagram of a reliability evaluation calculation section 74 according to the first embodiment. Fig. 13 is a reliability evaluation map based on the magnitude of the friction braking force. Fig. 14 is a reliability evaluation map based on the rate of change of friction braking force. Fig. 15 is a reliability evaluation map based on a change in pad temperature. Fig. 16 shows time charts of vehicle speed, a G-sensor value, a hydraulic brake pressure, and a pad µ, illustrating an example of the operation of the reliability evaluation filter section 73 according to the first embodiment. Fig. 17 shows time charts of the vehicle speed, the G-sensor value, the hydraulic brake pressure, the pad µ, and an engine torque, illustrating an example of the operation of the reliability evaluation calculating section 74 according to the first embodiment. DESCRIPTION OF EMBODIMENTS

[0008] [First embodiment] Fig. 1 schematically shows an electric vehicle 1 with a vehicle control system according to a first embodiment.

[0009] The electric vehicle 1 includes front wheels 2FL and 2FR and rear wheels 2RL and 2RR, and friction brakes (friction brake devices) 3FL, 3FR, 3RL, and 3RR attached to the respective wheels and configured to generate friction braking forces at the respective wheels (hereinafter, the friction brakes of the respective wheels are also collectively referred to as friction brake 3).

[0010] The electric vehicle 1 includes a rear motor (drive device) 7 that delivers torque to the rear wheels 2RL and 2RR. The rear wheels 2RL and 2RR are also referred to below as drive wheel 2. Power is transmitted between the rear motor 7 and the rear wheels 2RL and 2RR via a reduction gear 8, a differential 10, and the rear axles 6RL and 6RR.

[0011] The wheels 2FL, 2FR, 2RL, and 2RR contain wheel speed sensors 11FR, 11FL, 11RL, and 11RR, each of which detects the wheel speed. The rear motor 7 includes a rear wheel resolver 13 that detects the motor speed. Furthermore, the electric vehicle 1 includes a G-sensor 5 that detects the longitudinal acceleration (hereinafter also referred to simply as acceleration) of the vehicle.

[0012] The friction brake 3 generates braking force based on frictional force by pressing the brake pads against a brake rotor that rotates with each wheel in a direction along the rotational axis of each wheel. The friction brake 3 according to the first embodiment is described as pressing the brake pads using a wheel cylinder actuated by hydraulic brake pressure, but it may also be configured to press the brake pads, for example, via a ball screw mechanism driven by an electric motor, and is not specifically limited.

[0013] The electric vehicle 1 comprises a low-voltage battery 14 and a high-voltage battery 15. The low-voltage battery 14 is, for example, a lead-acid battery. The high-voltage battery 15 is, for example, a lithium-ion battery or a nickel-hydrogen battery. The high-voltage battery 15 is charged with electric current, the voltage of which is increased by a DC-DC converter 16.

[0014] The electric vehicle 1 includes a vehicle control device (a control section) 17, a brake control device 18, a rear motor control device 20, and a battery control device 19. These control devices 17, 18, and 20 exchange information with each other via a CAN bus 21.

[0015] The vehicle control device 17 acquires information from various types of sensors, such as the rear wheel resolver 13, an accelerator pedal sensor 22 that detects an accelerator pedal operation amount, a brake sensor 23 that detects a brake operation amount, and a gear position sensor 24, and comprehensively controls the vehicle. The vehicle control device 17 outputs a driver-requested torque that the rear motor 7 should output according to a requested distribution torque in response to a driver's accelerator pedal operation, brake operation, or the like.

[0016] The brake control device 18 acquires information from various types of sensors such as the brake sensor 23 to set a target braking torque, which is a value of a target braking force of the vehicle converted into a torque, to generate the hydraulic braking pressure required for each wheel according to the target braking torque, and output it to the friction brake 3 via a hydraulic line 18a.

[0017] The battery control device 19 monitors a charge / discharge state of the high-voltage battery 15 and a cell constituting the high-voltage battery 15. The battery control device 19 calculates a battery request torque limit based on the charge / discharge state of the high-voltage battery 15 or the like. The battery request torque limit is the maximum allowable torque for the rear motor 7. For example, when the charged capacity of the high-voltage battery 15 decreases, the battery request torque limit is set to a smaller value than normal.

[0018] The rear motor control device 20 controls electric power to be supplied to the rear motor 7 based on a requested rear torque.

[0019] The electric vehicle 1 according to the first embodiment performs anti-jerk control, which causes the rear motor 7 to output a drive torque corresponding to a total braking torque determined by estimating a braking torque actually generated on the vehicle when the vehicle is stopped, with the aim of suppressing unpleasant vibration of the vehicle when the vehicle is stopped and thus reducing passenger fatigue. As a result, a longitudinal jerk (jerk) that occurs when the vehicle is stopped with a predetermined braking operation amount can be reduced by about 68% compared with the case where the anti-jerk control is not provided. In other words, the vehicle can stop smoothly even without a skillful braking operation.

[0020] Fig. 2 is a control block diagram of the rear engine 7 according to the first embodiment.

[0021] A driver request torque calculation section 31 calculates the driver request torque based on the accelerator pedal depression amount and vehicle speed. The wheel speed is determined by an arbitrary method based on each wheel speed detected by each of the wheel speed sensors 11FR, 11FL, 11RL, and 11RR, but it is determined by referring to the engine speed detected by the rear wheel resolver 13 at a low speed.

[0022] A gradient resistance calculation section 32 calculates gradient resistance, which is a resistance acting on the vehicle due to a slope of a road surface, based on the vehicle speed, the G-sensor value, and a vehicle weight. Specifically, the gradient resistance calculation section 32 determines an estimated gradient acceleration generated due to the gradient based on a deviation between a difference value of the vehicle speed and the G-sensor value, and calculates the gradient resistance based on the estimated gradient acceleration generated due to the gradient and the vehicle weight.

[0023] An estimated friction braking force correction gain calculation section 33 calculates a final correction gain for correcting an estimation error of an estimated friction braking force that occurs along with a change in a pad µ (a friction coefficient) based on the G-sensor value, the vehicle speed, the estimated friction braking force, driving resistance, the vehicle weight, an engine torque, and a brake pad temperature. When the pad µ changes due to, for example, a change in temperature or humidity, the estimated friction braking force deviates from the braking force actually generated by the brake on the vehicle. Therefore, the pad µ is estimated, and a gain for correcting the estimated friction braking force (a value converted to a torque) is calculated to compensate for an error in an estimated pad µ from a nominal value of the pad µ.

[0024] The estimated friction braking force is calculated as the sum of the respective estimated friction braking forces of the wheels. The estimated friction braking force Bi of the individual wheels is calculated using the following equation (1). Estimated friction braking force Bi of each wheel = hydraulic brake pressure × cylinder area × effective braking radius × lining μ (nominal value)

[0025] In this case, the nominal value of the pad µ is kept constant while the vehicle is driving once it is adjusted. The nominal value is adjusted by pre-determining a temperature-µ characteristic of the brake pad as a map and relating it to the map. The brake pad temperature used to calculate the nominal value can be the outside temperature at the start of the vehicle's journey, or a predefined temperature (for example, 20 °C) can be used.

[0026] The driving resistance can be determined by pre-detecting a change in the driving resistance with respect to a change in the vehicle weight or the vehicle speed and calculating the driving resistance on this basis, or by estimating the driving resistance.

[0027] The estimated friction braking force can be estimated based on the driver's brake pedal stroke instead of the hydraulic brake pressure.

[0028] The details of the section for calculating the correction gain of the estimated friction braking force 33 are described below.

[0029] A total braking torque calculation section 34 calculates the total braking torque based on the driving resistance, the estimated friction braking force, the gradient resistance and the final correction gain. Fig. 3 is a control block diagram of the total braking torque calculation section 34 according to the first embodiment. A braking force-to-torque conversion section 41 converts the estimated friction braking force into an estimated friction braking torque. A multiplier 42 calculates an estimated post-correction friction braking torque, which results from correcting the estimation error that occurs along with the change in μ of the brake pad, by multiplying the estimated friction braking torque by the final correction gain. A first adder 43 and a second adder 44 add a torque corresponding to the gradient resistance and a torque corresponding to the road resistance to the post-correction estimated friction braking torque.A limiter 45 compares a value resulting from the addition of the torque corresponding to the gradient resistance and the torque corresponding to the running resistance with the friction braking torque estimated after the correction with zero and outputs one of them having a larger value as the total braking torque.

[0030] A control gain calculation section 35 calculates a control gain based on the vehicle speed and the total braking torque. Fig. 4 is a control block diagram of the control gain calculation section 35 according to the first embodiment. An acceleration estimation value calculation section 51 calculates acceleration by differentiating the vehicle speed. An acceleration-based control gain map 52 sets an acceleration-based control gain according to the acceleration. The acceleration-based control gain map 52 sets the acceleration-based control gain to 1 (100%) when a deceleration smaller than a predefined value x2 (G) in magnitude is generated, while the acceleration-based control gain is gradually decreased as the magnitude of the deceleration increases when a deceleration equal to or greater than the predefined value x2 (G) in magnitude is generated. The minimum value of the acceleration-dependent control gain is set to zero (0%).This setting prevents torque from being added during sudden braking. It is clear that it is more desirable to ensure braking force than to prevent vibration in the pitch direction during sudden braking.

[0031] A speed-based control gain map 53 sets a speed-based control gain based on a three-dimensional map according to the vehicle speed and the total braking torque. The speed-based control gain has the characteristic of decreasing linearly as the total braking torque decreases only in a predetermined range where the total braking torque is approximately zero, and of remaining at a maximum value of 1 in most ranges beyond the predetermined range. The maximum value can be set to a positive value other than 1. Furthermore, the speed-based control gain is set to increase linearly as the vehicle speed decreases.In addition, the speed-based control gain is set such that the vehicle speed at which the value increases from zero (a starting speed for the gain increase) increases with increasing total braking torque. In other words, the speed-based control gain has a characteristic such that the vehicle speed at which an anti-jerk control command intervenes (the vehicle speed at which the generation of driving force by the anti-jerk control is started) increases as the total braking torque increases.

[0032] A vehicle stop determination section 54 inputs the vehicle speed, the total braking torque, the vehicle weight, and the estimated friction braking force, and clears a vehicle stop determination flag (= 0) unless a vehicle stop time is zero, and sets the vehicle stop determination flag (= 1) when the vehicle stop time becomes zero.

[0033] A control gain rate limiting section 55 limits the speed of change of the speed-based control gain on an increase side and a decrease side. When the vehicle stop determination flag is set (= 1), the control gain rate limiting section 55 changes the speed change limit on the decrease side that has been used up to that point.

[0034] A multiplier 56 outputs as the final control gain a value resulting from multiplying the acceleration-based control gain by the velocity-based control gain.

[0035] With further reference to Fig. 2, a multiplier 36 calculates a total braking torque multiplied by the control gain by multiplying the total braking torque by the control gain.

[0036] An additional torque calculation section 37 calculates additional torque as anti-jerk control torque based on the driver requested torque and the total braking torque multiplied by the control gain. Fig. 5 is a control block diagram of the additional torque calculation section 37 according to the first embodiment. A limiter 61 compares the driver-requested torque with zero and outputs one of the two values that has a larger value. A comparator 62 subtracts the output of the limiter 61 from the total braking torque multiplied by the control gain. A limiter 63 compares the output of the comparator 62 with zero and outputs one of the two values that has a larger value than the added torque.

[0037] An adder 38 sets the torque resulting from the addition of the added torque to the torque requested by the driver as the request rear torque.

[0038] Fig. 6 is a control block diagram of the estimated friction braking force correction gain calculation section 33 according to the first embodiment.

[0039] A correction gain reference value calculating section 71 calculates a correction gain reference value with reference to the following equation (2) based on the estimated friction braking force, the engine torque, the G-sensor value, the running resistance, and the vehicle weight. Correction gain reference value = (G sensor value × vehicle weight − braking / driving force corresponding to the engine torque − driving resistance) / estimated friction braking force

[0040] A final torque command value of the vehicle control device or a final torque command value of the inverter can be used as the motor torque.

[0041] The vehicle speed differential value can be used instead of the G-sensor value. Since the vehicle speed differential value also includes the influence of gradient resistance in this case, the numerator part on the right side of equation (2) is modified as follows. (Difference value of vehicle speed × vehicle weight − braking / driving force corresponding to engine torque − driving resistance − gradient resistance)

[0042] Furthermore, the tilt angle of the vehicle affects the value of the longitudinal acceleration sensor, and therefore the vehicle control device 17 may be configured to detect or estimate the tilt angle of the vehicle and take it into account when calculating the correction gain reference value or the gradient resistance.

[0043] An estimated friction braking force change rate calculation section 72 calculates a change rate of the estimated friction braking force by differentiating the estimated friction braking force.

[0044] A reliability evaluation filter section 73 evaluates the reliability (calculates a reliability degree) of the correction gain reference value based on the vehicle speed, the estimated frictional braking force, and the rate of change of the estimated frictional braking force, and corrects the correction gain reference value according to the evaluation result. The reliability degree indicates how high the reliability of the correction gain target value is (a dispersion of the estimation accuracy or the expected estimation accuracy). Fig. Fig. 7 is a control block diagram of the reliability evaluation filter section 73 according to the first embodiment. The reliability evaluation filter section 73 uses, for example, a variable cutoff filter 85 whose response characteristic is variable, as shown in Fig. 11, to realize evaluation in which, in a section where the correction gain reference value has high reliability, the current correction gain reference value is weighted, and in a section where the correction gain reference value has low reliability, an output value (a correction gain) of the reliability evaluation filter is weighted instead of the current correction gain reference value. In this case, the smallest of the respective output values of the frequency maps 81 to 83 in a previous stage is used as the response characteristic of the variable cutoff filter 85. Fig. 11 is a control block diagram of a gain conversion section of a variable cutoff filter 85. The gain conversion section 851 converts the cutoff frequency determined by these frequency maps 81 to 83 into a corresponding gain. A first multiplier 852 multiplies the reference value of the correction gain by the gain. A comparator 853 subtracts the gain from 1. A second multiplier 854 multiplies the output of the comparator 853 by a previous output value (correction gain) of the variable cutoff filter 85. A storage section 855 stores the previous output value of the variable cutoff filter 85. An adder 856 outputs a correction gain resulting from the multiplication of the output value of the first multiplier 852 and the output value of the second multiplier 854.In the present example, the variable cutoff filter 85 has similar characteristics to a low-pass filter (LPF), and may further have a filter configuration that stores the previous output value of the variable cutoff filter 85 by outputting zero as the output value of the gain conversion section when the cutoff frequency is set to zero, and can therefore calculate the correction gain while appropriately changing the response characteristic to the correction gain reference value estimated in the present control cycle according to the reliability.

[0045] The cutoff frequency map 81, based on the magnitude of the friction braking force, is a map for estimating the correction gain, giving weight to a value estimated in a section where a disturbance or the like that cannot be sufficiently reflected in the equation is expected to be less influential. As the friction braking force decreases, an acceleration generated due to an error that cannot be accounted for in the equation becomes relatively more influential compared to an acceleration generated due to the friction braking force included in the G sensor value. As a result, an error between an actual value that should actually be corrected and the reference value of the correction gain estimated using equation (2) may increase.Against this background, the friction braking force magnitude-based cutoff frequency map 81 increases a first cutoff frequency Y as the estimated friction braking force increases. As shown in . Fig. 8, the first cutoff frequency Y is set to a minimum value Y1 when the estimated friction braking force is less than X1 and to a maximum value Y2 when the estimated friction braking force exceeds X2, and is set to increase with increasing estimated friction braking force when the estimated friction braking force is equal to or greater than X1 and equal to or less than X2. Furthermore, as described above, an error in estimating the correction gain reference value may increase under the influence of a disturbance that cannot be sufficiently accounted for in the equation when the estimated friction braking force is small. Therefore, the cutoff frequency decreases when the estimated friction braking force reaches or falls below a predetermined estimated friction braking force. Y1 is assumed to be a non-zero value in this example, but it may also be zero.

[0046] The cutoff frequency map 82 based on the rate of change of the friction braking force is a map for estimating the correction gain, giving weight to a value estimated in a section where a response delay of the G sensor 5 is less likely to have an influence. Since the G sensor 5 is mounted on the sprung side of the vehicle, a time delay occurs until the G sensor value is detected even when the friction braking force is actually generated. When the rate of change of the friction braking force is high, an increase in the friction braking force causes an increase in the denominator term in equation (2), but an increase in the G sensor value component in the numerator proceeds slowly, and therefore an error in estimating the correction gain reference value increases.Therefore, when such a response delay is expected, the correction gain is estimated with a weighting of the previous output value of the variable cutoff filter. The use of a pseudo-differential for differentiating the vehicle speed or removing sensor noise, etc., also involves a delay-causing element, such as a filter, and is thus subject to a response delay behind the increase in the frictional braking force. As described above, as the rate of change of the frictional braking force increases, the response delay of the sensor is very likely to increase and an error from the true value increases. Therefore, the cutoff frequency map 82 based on the rate of change of the frictional braking force increases a second cutoff frequency W as the rate of change of the estimated frictional braking force decreases.

[0047] As in Fig. As shown in Figure 9, the second cutoff frequency W is set to a minimum value W1 when the rate of change of the estimated frictional braking force exceeds |Z2|, and to a maximum value W2 when the rate of change of the estimated frictional braking force is less than |Z1|, and is set to decrease as the rate of change of the estimated frictional braking force increases when the rate of change of the estimated frictional braking force is equal to or greater than |Z1| and equal to or less than |Z2|. When the rate of change of the estimated frictional braking force is high, a response delay may occur in the output value of the G sensor 5, which is mounted on the sprung side of the vehicle behind the change of the estimated frictional braking force under the influence of a spring-mass damper system of the suspension.Given this, the second cutoff frequency W is set such that the cutoff frequency decreases to further weight the previous output value of the variable cutoff filter when the estimated friction braking force changes rapidly. W1 is assumed to be a non-zero value in this example, but may also be zero. Furthermore, the second cutoff frequency W is set to have a horizontally symmetrical characteristic about zero, but may also be set to have an asymmetrical characteristic.

[0048] The vehicle speed-based cutoff frequency map 83 estimates the correction gain, weighting the previous output value of the variable cutoff filter at low vehicle speeds. This is because the brake converts kinetic energy into thermal energy, and therefore the condition of the brake pad is less likely to change even with a braking force applied at low vehicle speeds. The vehicle speed-based cutoff frequency map 83 increases a third cutoff frequency R as the vehicle speed increases. As shown in Fig. As shown in Figure 10, the third cutoff frequency R is set to a minimum value R1 when the vehicle speed is lower than V1 and to a maximum value R2 when the vehicle speed exceeds V2, and is set to increase with increasing vehicle speed when the vehicle speed is equal to or higher than V1 and equal to or lower than V2. When the vehicle speed is low, the condition of the brake pad is less likely to change, and further, the anti-jerk control intervenes according to the reduction in vehicle speed. As the engine torque increases, the response of the G sensor value lags behind the change in the engine torque, similar to a high change rate of the friction braking force, and an error may increase in estimating the correction gain reference value.Therefore, the cutoff frequency is lowered to estimate the correction gain, with the previous output value of the variable cutoff filter being weighted according to the reduction in speed. In this case, V1 can be, for example, the highest vehicle speed at which the anti-jerk control begins to intervene, which is specified in the anti-jerk control gain characteristics, which are determined depending on the total braking force and speed, or a different speed. Furthermore, R1 can be zero.

[0049] A limiter 84 outputs a cutoff frequency having the smallest value among the first cutoff frequency Y, the second cutoff frequency W and the third cutoff frequency R as the cutoff frequency.

[0050] The variable cutoff filter 85 performs filter processing of the correction gain command value according to the cutoff frequency output from the limiter 84.

[0051] With further reference to Fig. 6, a reliability evaluation calculation section 74 calculates a reliability evaluation gain for correcting the output value of the reliability evaluation filtering section 73 based on the estimated frictional braking force, the rate of change of the estimated frictional braking force, and the brake pad temperature. The reliability evaluation gain is a gain for decreasing the final correction result when the output of the reliability evaluation filtering section 73 is not as reliable or when strong intervention by the anti-jerk control is unnecessary. The vehicle control device 17 may be configured to store the calculated reliability evaluation gain until the vehicle travels at a low speed (for example, 1 km / h or less). Fig. 12 is a control block diagram of the reliability evaluation calculation section 74 according to the first embodiment.

[0052] A reliability evaluation gain map 91, which is based on the magnitude of the friction braking force, increases a first reliability evaluation gain M as the estimated friction braking force increases. As shown in Fig. As shown in Figure 13, the first reliability evaluation gain M is set to a minimum value M3 when the estimated friction braking force is less than X1, and to a maximum value of 1 when the estimated friction braking force exceeds X2, and is set to increase with increasing estimated friction braking force when the estimated friction braking force is equal to or greater than X1 and equal to or less than X2. When the estimated friction braking force is small, creep torque and braking force generated on the vehicle are very likely to be close to each other, and pitching or the like of the vehicle is small. Therefore, it is expected that ride comfort will not be significantly affected even without the intervention of the anti-jerk control.However, it is very likely that an error in estimating the correction gain will increase under the influence of a disturbance or the like, and therefore the gain is reduced to avoid an unintentional significant increase in the braking distance.

[0053] A reliability evaluation map 92 based on the rate of change of the friction braking force increases a second reliability evaluation gain N as the rate of change of the friction braking force decreases. As shown in Fig. As shown in Figure 14, the second reliability evaluation gain N is set to a minimum value N3 when the change rate of the estimated frictional braking force exceeds Z2, and to a maximum value of 1 when the change rate of the estimated frictional braking force is lower than Z1, and is set to increase as the change rate of the estimated frictional braking force decreases when the change rate of the estimated frictional braking force is equal to or higher than Z1 and equal to or lower than Z2. When the frictional braking force changes rapidly, the update by the reliability evaluation filtering section 73 may be stopped so as not to degrade the estimation, and therefore, an error may be generated from the estimated value resulting until the brake pedal is further increasingly depressed.Therefore, when the estimated friction braking force increases at a predetermined speed or higher, the second reliability evaluation gain N is lowered due to the possibility of a significant change in the estimation result obtained up to that point. When the depressed brake pedal is returned, it can be expected that, for example, an increase in brake pad temperature will not occur, and it can be assumed that the estimated value will not change significantly from the estimation result obtained up to that point (the previous output value of the reliability evaluation filter). Therefore, the second reliability evaluation gain is set to 1 in the present embodiment.However, the map may be modified to have a characteristic of decreasing the second reliability evaluation gain when the rate of change of the estimated friction braking force due to the return of the pressed brake pad is high. Furthermore, the gain is determined by referring only to the rate of change of the friction braking force in the present embodiment, but the map may be modified into a three-dimensional map that relates to the rate of change of the friction braking force and the vehicle speed, and decreases the gain when the vehicle speed is a predetermined value or higher and the rate of change of the friction braking force is high.

[0054] A reliability evaluation map 93 based on the pad temperature change increases a third reliability evaluation gain Q when the amount of pad temperature change decreases compared to the brake pad temperature detected at the time of the previous friction braking. As shown in Fig. As shown in Figure 15, the third reliability evaluation gain Q is set to a minimum value Q1 when the pad temperature change exceeds P2, and to a maximum value of 1 when the pad temperature change is less than P1, and is set to increase as the pad temperature change decreases when the pad temperature change is equal to or greater than P1 and equal to or less than P2. When the pad temperature change is small, the correction gain estimated at the time of the last braking operation is very reliable and is therefore increased. When the pad temperature change is large, the previous value is less reliable, and the gain is therefore decreased. The pad temperature may be detected with a sensor, or an estimated value may be used as the pad temperature.In addition, a final pad temperature at the previous friction braking application can be used as the brake pad temperature determined at the time of the previous friction braking application.

[0055] A limiter 94 outputs either the second reliability evaluation gain N or the third reliability evaluation gain Q which has a larger value.

[0056] A multiplier 95 outputs a value resulting from multiplying the first reliability evaluation gain M by the output value of the limiter 94 as the reliability evaluation gain.

[0057] As in Fig. 6, a multiplier 75 outputs a value resulting from multiplying the output value of the reliability evaluation filter section 73 by the reliability evaluation gain as the final correction gain.

[0058] The advantageous effects of the first embodiment are described below.

[0059] Fig. 16 shows time charts of the vehicle speed, the G-sensor value, the hydraulic brake pressure, and the brake pad µ, which illustrate an example of the operation of the reliability evaluation filter section 73 according to the first embodiment.

[0060] In a period from t1 to t2, the hydraulic pressure changes rapidly, and an error in the estimated pad µ may increase, for example, under the influence of a delay in the G-sensor value. Therefore, the correction gain is updated, with the previous output value of the variable cut-off filter being given greater weight than the current reference value of the correction gain. In the case of Fig. 16 the cutoff frequency is set to zero to save the previous value.

[0061] In a period from t3 to t4, the brake hydraulic pressure is low and the friction braking force is small. Therefore, the estimation error may increase due to a relative increase in the influence of disturbances, sensor errors, and the like, which cannot be adequately considered compared to the influence of the friction braking force included in the vehicle deceleration. Therefore, the correction gain is updated, giving greater weight to the previous output value of the variable cutoff filter in this case as well.

[0062] Fig. 17 shows time charts of the vehicle speed, the G-sensor value, the brake hydraulic pressure, the pad µ, and the engine torque, illustrating an example of the operation of the reliability evaluation calculating section 74 according to the first embodiment.

[0063] In the section between t1 and t2, the hydraulic pressure changes rapidly, and the reliability evaluation filter section 73 may stop updating. Therefore, the estimated friction braking force after the correction is lowered.

[0064] In the period from t3 to t4, the friction braking force is low, so ride comfort is less likely to be affected even without significant anti-jerk control intervention. Therefore, the estimated friction braking force after the correction is reduced, also considering the possibility that an error may be present in the estimated brake pad µ.

[0065] In this way, the vehicle control device 17 according to the first embodiment corrects the control command to be output for generating the driving force by the rear motor 7 (the final correction gain in the calculation of the total braking torque for determining the added torque) according to the degree of reliability of the calculation result associated with the state of the vehicle in a state where the friction braking force is generated at the time of deceleration of the vehicle based on the total braking torque. This enables the vehicle control device 17 to output the added torque that is less affected by the estimation error in the friction braking force from the actual braking force in the anti-jerk control, thereby effectively realizing, for example, suppression of pitch fluctuation when the vehicle is stopped.

[0066] The vehicle control device 17 corrects the control command according to the reliability level of the calculation result associated with the state of the vehicle, which includes at least the vehicle speed, the physical quantity related to the friction braking force, and the temperature of the friction brake 3. The error between the true value to be corrected and the correction gain reference value largely changes depending on the vehicle speed, the friction braking force, and the temperature of the friction brake 3 in the anti-jerk control, and therefore, the influence of the estimation error in the friction braking force in the anti-jerk control can be further effectively suppressed by correcting the control command according to the reliability level determined by considering these factors.

[0067] The vehicle control device 17 determines the final correction gain by multiplying the output value of the reliability evaluation filtering section 73, which results from the correction of the predetermined correction gain reference value according to the reliability degree of the calculation result associated with the speed of the vehicle and the reliability degree of the calculation result associated with the physical quantity related to the frictional braking force, by the reliability evaluation gain calculated by the reliability evaluation calculating section 74 based on the reliability evaluation gain assigned according to the reliability degree of the calculation result associated with the physical quantity related to the frictional braking force and the reliability evaluation gain calculated according to the reliability degree of the calculation result associated with the physical quantity3, which relates to the temperature of the friction brake, and corrects the control command based on the final correction gain. This allows the vehicle control device 17 to implement the estimation with a weight applied to the current correction gain reference value in the section where reliability is high and to the previous output value of the variable cutoff filter in the section where reliability is low, thereby further effectively suppressing the influence of the estimation error. Furthermore, when the output of the reliability evaluation filter section 73 is less reliable or when strong intervention of the anti-jerk control is unnecessary, an unintended significant increase in the braking distance can be prevented by reducing the final correction gain.

[0068] The vehicle control device 17 determines the final correction gain by multiplying the output value resulting from filtering the predetermined correction gain reference value by the variable cutoff filter 85 based on the third cutoff frequency R based on the vehicle speed and the cutoff frequency determined according to the degree of reliability of the calculation result associated with the physical quantity related to the friction braking force by the evaluation gain.In this way, the vehicle control device 17 can perform the estimation with a weighting of the current reference value of the correction gain in the section where the reliability is high and the previous output value of the variable cutoff filter in the section where the reliability is low by increasing the cutoff frequency in the section where the reliability is high and decreasing the cutoff frequency in the section where the reliability is low using the variable cutoff filter 85.

[0069] The cutoff frequency, which is set according to the degree of reliability of the calculation result associated with the physical quantity related to the friction braking force, includes the first cutoff frequency Y, which is set according to the degree of reliability of the calculation result associated with the magnitude of the friction braking force, and the second cutoff frequency W, which is set according to the degree of reliability of the calculation result associated with the rate of change of the friction braking force. The error from the true value is likely to increase as the friction braking force decreases, and the error increases due to a delay in the response of the G-sensor 5 when the rate of change of the friction braking force is high.Therefore, the increase of the estimation error of the friction braking force can be suppressed by adjusting the cutoff frequency depending on the magnitude of the friction braking force and the change rate of the friction braking force.

[0070] The third cutoff frequency R, which is based on the vehicle speed, is set to increase with increasing speed. The first cutoff frequency Y, which is based on the magnitude of the frictional braking force, is set to increase with increasing frictional braking force. The second cutoff frequency W, which is based on the rate of change of the frictional braking force, is set to increase as the rate of change decreases. This allows the brake control device 17 to realize the estimation with a weight placed on the previous output value of the variable cutoff filter during the period where reliability is low, thereby suppressing the increase in the estimation error of the frictional braking force.

[0071] The cutoff frequency of the variable cutoff filter 85 is adjusted by selecting the lowest cutoff frequency based on the vehicle speed, the cutoff frequency based on the friction braking force, and the cutoff frequency based on the rate of change of the friction braking force. Selecting the cutoff frequency according to the "select-low" principle can prevent an increase in the estimation error due to estimation with weighting of the current correction gain reference value, despite the section where reliability is low.

[0072] The physical quantity related to the temperature of the friction brake 3 is the brake pad temperature. The pad µ depends on the pad temperature. When the pad temperature changes less than when the friction brake was previously applied, it is expected that extensive use of the previously estimated output value of the reliability evaluation filter will also keep the error small. On the other hand, when the pad temperature changes significantly, the error between the true value and the previously estimated output value of the reliability evaluation filter is expected to increase. Therefore, an increase in the braking distance due to the error between the estimated correction gain and the true value can be suppressed by changing the reliability gain according to the change in the pad temperature.

[0073] The reliability evaluation gain, which is set according to the degree of reliability of the calculation result assigned to the physical quantity related to the friction braking force, includes the first reliability evaluation gain M based on the magnitude of the friction braking force and the second reliability evaluation gain N based on the rate of change of the friction braking force. When the friction braking force is small, ride comfort is not so significantly affected even without the intervention of the anti-jerk control, and the estimation error is likely to increase under the influence of a disturbance. When the rate of change of the friction braking force is high, the error between the estimated correction gain and the true value may increase due to a stop of the update by the reliability evaluation filtering section 73.Therefore, an increase in the braking distance due to the error between the estimated correction gain and the true value can be suppressed by adjusting the reliability evaluation gain according to the magnitude of the friction braking force and the changing speed of the friction braking force.

[0074] The first reliability evaluation gain M, based on the magnitude of the friction braking force, is set to increase as the friction braking force increases. The second reliability evaluation gain N, based on the rate of change of the friction braking force, is set to increase as the rate of change of the friction braking force decreases. The third reliability evaluation gain Q, based on the change in pad temperature, is set to increase as the pad temperature changes less since the previous friction braking. This results in a decrease in the reliability evaluation gain during the period when reliability is low, thus helping to prevent an increase in the braking distance due to the error between the estimated correction gain and the true value.

[0075] The reliability evaluation gain is determined by multiplying the first reliability evaluation gain M, which is based on the magnitude of the frictional braking force, by the gain obtained by selecting the higher of the second reliability evaluation gain N, which is based on the rate of change of the frictional braking force, and the third reliability evaluation gain Q, which is based on the change in the pad temperature. For example, when the brake pedal is depressed while the vehicle is traveling at a low speed, the friction coefficient of the brake is expected to not change significantly because, for example, the pad temperature increases less, but the second reliability evaluation gain N, in contrast, is minimized due to an increase in the rate of change of the frictional braking force.In view of this, selecting the higher of the second reliability evaluation gain N and the third reliability evaluation gain Q causes the third reliability evaluation gain Q to be selected when the brake pedal is depressed while the vehicle is traveling at a low speed, thereby contributing to preventing the reliability evaluation gain from being underestimated despite the section in which the output value of the reliability evaluation filter maintains high reliability.

[0076] (Other Embodiments) Having described the embodiment for implementing the present invention, the specific configuration of the present invention is not limited to the configuration of the embodiment, and the present invention also includes a design change and the like within a range that does not deviate from the gist of the present invention.

[0077] The embodiment was described with reference to the example in which the present invention is applied to the rear-wheel drive electric vehicle, but the present invention can also be applied to a front-wheel drive electric vehicle or a four-wheel drive electric vehicle. Furthermore, without being limited to the electric vehicle, the present invention can also be applied to a vehicle equipped with an internal combustion engine or a hybrid vehicle that can be powered by both an internal combustion engine and a motor.In other words, the present invention can be applied to any configuration capable of providing torque from a drive source side, or to any configuration capable of reducing the friction brake in a range where the vehicle can stop, or in a range where a braking force acts between a drive wheel and a road surface when the vehicle stops using the friction brake.

[0078] The reliability evaluation filter section 73 according to the first embodiment sets the cutoff frequency by selecting the lowest of the respective output values of the frequency maps 81 to 83, but may calculate the cutoff frequency by multiplying the respective output values of the frequency maps 81 to 83 with each other.

[0079] Furthermore, the response of the G-sensor value may be delayed due to, for example, the rate of change of the engine torque, and therefore, a frequency map may be added to change the cutoff frequency with reference to the rate of change of the engine torque. Furthermore, if noise is added to the G-sensor value, the estimation accuracy of the correction gain reference value may be degraded, and therefore, a frequency map may be added to change the cutoff frequency according to a disturbance in the road surface (a disturbance in the road surface can be estimated by detecting the noise contained in the G-sensor value using a high-pass filter or the like, or can be detected by referring to information such as a stereo camera).

[0080] The upper limit values of the three reliability evaluation gains M, N, and Q are preferably set to 1 in the reliability evaluation calculation section 74 according to the first embodiment, but may be set to a value other than 1, and the lower limit values (M3, N3, and Q1) may also be set to zero. Furthermore, the vehicle control device 17 is configured to use each of the reliability evaluation gain maps 91 to 93 in the first embodiment, but may use a map for calculating the gain based on the time elapsed since the vehicle was previously braked, a braking start speed, and humidity, since the moisture of the pad surface is expected to also affect the braking force.

[0081] Further, X1 and X2 in the cutoff frequency map 81 based on the magnitude of the friction braking force and the reliability evaluation gain map 91 based on the magnitude of the friction braking force, and Z1 and Z2 in the cutoff frequency map 82 based on the change rate of the friction braking force and the reliability evaluation gain map 92 based on the change rate of the friction braking force are displayed using the same variables in the embodiment, but may be displayed by using different values.

[0082] The present invention is not limited to the above-described embodiment and includes various modifications. For example, the above-described embodiment has been described in detail in order to facilitate a better understanding of the present invention, and the present invention is not necessarily limited to the configuration having all of the described features. Furthermore, part of the configuration of one embodiment may be replaced with the configuration of another embodiment. In addition, one embodiment may also be implemented with a configuration of another embodiment added to the configuration of this embodiment. Furthermore, each embodiment may also be implemented with another configuration added, deleted, or replaced with respect to part of the configuration of this embodiment.

[0083] This application claims priority under the Paris Convention to 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. LIST OF REFERENCE SYMBOLS 1 electric vehicle (vehicle) 3 Friction brake (friction brake device) 7 Rear engine (drive device) 17 Vehicle control device (control section) QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-056583

[0003] JP 2022-138913

[0083]

Claims

[1] A vehicle control device mounted on a vehicle, the vehicle having a friction braking device configured to generate a friction braking force on the vehicle and a driving device configured to generate a driving force on the vehicle, the vehicle control device comprising: a control section configured to output a result calculated based on input information, wherein the control section is configured to a physical quantity is recorded that relates to a total braking force for decelerating the vehicle, and in a state where the friction braking force is generated at the time of deceleration of the vehicle based on the physical quantity related to the total braking force, corrects a control command for generating the driving force by the driving device according to a reliability degree of a calculation result associated with a state of the vehicle, and outputs the control command. [2] The vehicle control device according to claim 1, wherein the control section corrects the control command according to the degree of reliability of the calculation result associated with the state of the vehicle, which includes 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 braking device. [3] A vehicle control device according to claim 2, wherein the control section a final correction gain is determined by multiplying an output value resulting from the correction of a predetermined correction gain reference value according to the degree of reliability of the calculation result associated with the physical quantity relating to the speed of the vehicle and the degree of reliability of the calculation result associated with the physical quantity relating to the target frictional force by an evaluation gain determined based on a gain set according to the degree of reliability of the calculation result associated with the physical quantity relating to the target frictional braking force and a gain set according to the degree of reliability of the calculation result associated with the physical quantity relating to the temperature of the frictional braking device, and corrects the control command based on the final correction gain. [4] The vehicle control device according to claim 3, wherein the control section determines the final correction gain by multiplying the output value resulting from filtering the predetermined correction gain reference value by a variable cutoff filter by the evaluation gain based on a cutoff frequency set according to the degree of reliability of the calculation result associated with the physical quantity related to the speed of the vehicle and a cutoff frequency set according to the degree of reliability of the calculation result associated with the physical quantity related to the target frictional braking force. [5] The vehicle control device according to claim 4, wherein the cutoff frequency set according to the degree of reliability of the calculation result associated with the physical quantity related to the target friction force includes a cutoff frequency set according to the degree of reliability of the calculation result associated with the magnitude of the target friction force, and a cutoff frequency set according to the degree of reliability of the calculation result associated with a rate of change of the target friction force. [6] A vehicle control device according to claim 5, wherein the cut-off frequency, which is set according to the degree of reliability of the calculation result associated with the physical quantity with respect to the speed of the vehicle, is increased with increasing speed, wherein the cut-off frequency, which is set according to the degree of reliability of the calculation result associated with the magnitude of the target friction force, is set to increase as the target friction force increases, and wherein the cut-off frequency, which is set according to the degree of reliability of the calculation result associated with the rate of change of the target friction braking force, is set to increase as the rate of change decreases. [7] The vehicle control device according to claim 6, wherein the cutoff frequency of the variable limit filter is set by selecting the lowest of the cutoff frequency set according to the degree of reliability of the calculation result associated with the physical quantity relating to the speed of the vehicle, the cutoff frequency set according to the degree of reliability of the calculation result associated with the magnitude of the target frictional braking force, and the cutoff frequency set according to the degree of reliability of the calculation result associated with the rate of change of the target frictional braking force. [8] The vehicle control device according to claim 3, wherein the physical quantity related to the temperature of the friction brake device is a temperature of a brake pad. [9] The vehicle control device according to claim 8, wherein the gain set according to the degree of reliability of the calculation result associated with the physical quantity with respect to the target frictional braking force includes a gain set according to the degree of reliability of the calculation result associated with the magnitude of the target frictional braking force, and a gain set according to the degree of reliability of the calculation result associated with the rate of change of the target frictional braking force. [10] A vehicle control device according to claim 9, wherein the gain set according to the degree of reliability of the calculation result associated with the magnitude of the target frictional braking force increases with increasing target frictional braking force, wherein the gain, which is set according to the degree of reliability of the calculation result associated with the rate of change of the target friction braking force, increases with decreasing rate of change, and wherein the gain, which is set according to the degree of reliability of the calculation result associated with the temperature of the brake pad, is set to increase as a change amount of the temperature decreases. [11] The vehicle control device according to claim 10, wherein the evaluation gain is set by multiplying the gain set according to the degree of reliability of the calculation result associated with the magnitude of the target friction force by a gain obtained by selecting the higher of the gain set according to the degree of reliability of the calculation result associated with the rate of change of the target friction force and the gain set according to the degree of reliability of the calculation result associated with the temperature of the brake pad. [12] The vehicle control device according to claim 3, wherein the control section determines the correction gain reference value based on the physical quantity related to the target frictional braking force, the driving force of the driving device, a longitudinal acceleration of the vehicle, the running resistance of the vehicle, and a weight of the vehicle. [13] A vehicle control method configured to be performed by a control unit mounted on a vehicle, the vehicle having a friction braking device configured to generate a friction braking force on the vehicle and a driving device configured to generate a driving force on the vehicle, the vehicle control method comprising: Initiate the control unit to record a physical quantity that relates to a total braking force for decelerating the vehicle, and in a state where the friction braking force is generated at the time of deceleration of the vehicle based on the physical quantity related to the total braking force, correct a control command for generating the driving force by the driving device according to a reliability degree of a calculation result associated with a state of the vehicle, and output the control command. [14] Vehicle control system comprising: a friction braking device configured to generate a friction braking force on a vehicle; a drive device configured to generate a driving force on the vehicle; and a control device configured to output a result calculated on the basis of input information, wherein the control device is configured to a physical quantity is recorded that relates to a total braking force for decelerating the vehicle, and in a state where the friction braking force is generated at the time of deceleration of the vehicle based on the physical quantity related to the total braking force, corrects a control command for generating the driving force by the driving device according to a reliability degree of a calculation result associated with a state of the vehicle, and outputs the control command.

Images