JP4754153B2 - Vehicle motion control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle motion control device that controls the motion of the vehicle by controlling the braking force applied to the front and rear wheels of the vehicle.
[0002]
[Prior art]
Conventionally, it is required to improve the turning ability of the vehicle (increase the change in the angle of the vehicle body at the start of turning) when the vehicle travels at a relatively low speed. For this reason, for example, the braking force control device for a vehicle disclosed in Japanese Patent Application Laid-Open No. 9-2235 applies a braking force to the rear wheel of the vehicle when the rotational speed of the steering wheel that steers the steering wheel is larger than a predetermined value. It is supposed to be. According to this, for example, when the driver tries to make a sudden turn of the vehicle and rotates the steering at a rotational speed greater than the predetermined value, the cornering force of the rear wheel of the vehicle decreases. Therefore, the yaw rate in the turning direction of the vehicle is increased, and the turning ability of the vehicle is improved.
[0003]
[Problems to be solved by the invention]
By the way, when the vehicle is traveling at a relatively high speed, improving the turning performance of the vehicle tends to make the vehicle's motion state unstable. Therefore, it is required to improve the stability of the vehicle.
[0004]
However, according to the device described in the above publication, the braking force is applied to the rear wheels of the vehicle when the rotational speed of the steering is greater than a predetermined value regardless of the vehicle body speed. Even when the vehicle is running, the turning ability of the vehicle may be improved. Therefore, there is a problem that the control in the direction opposite to the above request may be performed during high speed traveling.
[0005]
In order to solve such a problem, for example, a gear ratio variable mechanism that can vary a ratio of a change amount of a steering rotation angle to a change amount of a steering angle of a steered wheel (hereinafter referred to as “gear ratio”). And the gear ratio variable mechanism may be configured such that the gear ratio decreases during low-speed traveling and the gear ratio increases during high-speed traveling. However, in this case, since the variable gear ratio mechanism requires a complicated configuration, its manufacturing cost increases, and as a result, the manufacturing cost of the entire apparatus also increases.
[0006]
Accordingly, it is an object of the present invention to provide a vehicle motion control device that can improve both the turning performance of a vehicle at low speed traveling and the stability of the vehicle at high speed traveling with a simple configuration.
[0007]
SUMMARY OF THE INVENTION
  A feature of the present invention is that a vehicle motion control device acquires a vehicle body speed acquisition unit that acquires a vehicle body speed of the vehicle, and a steering operation amount acquisition that acquires a steering operation amount that changes a turning angle of a steering wheel of the vehicle. Means, and an actual yaw rate related amount acquisition means for acquiring an actual amount of the yaw rate related amount indicating the degree of turning of the vehicle as an actual yaw rate related amount;When the absolute value of the acquired steering operation amount is not less than a first predetermined value and the acquired vehicle body speed is not less than a second predetermined value,The absolute value of the target yaw rate related amount, which is the target amount of the yaw rate related amount, isIt is a reference amount for the yaw rate related amountTo reduce the absolute value of the reference yaw rate related amountAcquiredWhile calculating the target yaw rate related amount according to the vehicle speed,When the absolute value of the acquired steering operation amount is not less than the first predetermined value and the acquired vehicle body speed is less than the second predetermined value,The absolute value of the target yaw rate related amount is larger than the absolute value of the reference yaw rate related amount.AcquiredTarget yaw rate related amount calculating means for calculating the target yaw rate related amount according to the vehicle body speed, and the actual yaw rate related amount are given to the front and rear wheels of the vehicle so as to approach the target yaw rate related amount. And a braking force control means for controlling the braking force. Here, the “yaw rate related amount” is an amount indicating the degree of turning of the vehicle, and is, for example, a yaw rate or a component of the acceleration acting on the vehicle in the left-right direction (lateral acceleration).
[0008]
  Here, the reference yaw rate related amount is a yaw rate theoretical formula derived from a vehicle motion model that calculates a theoretical value of the yaw rate when the vehicle turns while the vehicle body speed and the steering operation amount are both constant. The vehicle body speed is Vso, the steering operation amount is θs, and the steering gear ratio that is the actual specification value of the vehicle isn0, When the wheelbase that is the actual specification value of the vehicle is l, and the stability factor that is the actual specification value of the vehicle is expressed as Kh ((Vso · θs) / (n0・ L)) ・ (1 / (1 + Kh ・ Vso²)) Is determined by using the acquired vehicle body speed as Vso and the acquired steering operation amount as θs. And the target yaw rate related amount calculating means is:In the yaw rate theory,The actual steering gear ration0Instead of the acquired vehicle body speed, the acquired steering operation amount, the vehicle body speed and the steering operation amount.AndControl steering gear ratio obtained from a predetermined relationship with the tearing gear rationIt was used,((Vso ・ θs) / (n ・ l)) ・ (1 / (1 + Kh ・ Vso ² )) Theoretical formula for control yaw rateThe reference yaw rate related amount determined based on the target yaw rate related amount is calculated. In the predetermined relationship, when the absolute value of the acquired steering operation amount is not less than the first predetermined value and the acquired vehicle body speed is not less than the second predetermined value, the control steering Gear rationIs the actual steering gear ration0When the absolute value of the acquired steering operation amount is not less than the first predetermined value and the acquired vehicle body speed is less than the second predetermined value, the control steering gear is set to a larger value. rationIs the actual steering gear ration0Set to a smaller value.
[0009]
  The target yaw rate related amount calculating means calculates a target yaw rate related amount that is shifted from the reference yaw rate related amount in accordance with the vehicle body speed acquired by the vehicle body speed acquiring means. In particular,The steering operation amount is large andWhen the vehicle speed is high, the target yaw rate related amount is calculated according to the vehicle speed so that the target yaw rate related amount (absolute value thereof) is smaller than the reference yaw rate related amount (absolute value),The steering operation amount is large andWhen the vehicle body speed is low, the target yaw rate related amount can be calculated in accordance with the vehicle body speed so that the target yaw rate related amount (absolute value thereof) becomes larger than the reference yaw rate related amount (absolute value thereof).
[0010]
  The braking force control means is applied to each wheel of the front and rear wheels of the vehicle so that the actual yaw rate related quantity acquired by the actual yaw rate related quantity acquisition means approaches the target yaw rate related quantity that can be calculated as described above. Control braking force. Therefore, when the vehicle is turning or starting to turn,The steering operation amount is large andWhen the vehicle body speed is high, the braking force of each wheel is controlled so that a yaw rate related amount smaller than the reference yaw rate related amount is generated in the vehicle. Therefore, each wheel is controlled so that the reference yaw rate related amount is generated in the vehicle. As compared with the case where the braking force of the vehicle is controlled, the turning ability of the vehicle is reduced and the stability of the vehicle can be improved. on the other hand,The steering operation amount is large andWhen the vehicle body speed is low, the braking force of each wheel is controlled so that a yaw rate related amount larger than the reference yaw rate related amount is generated in the vehicle. Therefore, each wheel is controlled so that the reference yaw rate related amount is generated in the vehicle. As compared with the case where the braking force of the vehicle is controlled, the turning ability of the vehicle can be improved.
[0011]
  From the above, according to the above configuration, with a simple configurationThe steering operation amount is large andThe turning ability of the vehicle during low-speed drivingThe steering operation amount is large andBoth the stability of the vehicle during high speed traveling can be improved.
[0012]
In this case, it is preferable that the target yaw rate related amount calculating means is configured to change an amount by which the target yaw rate related amount shifts with respect to the reference yaw rate related amount according to the steering operation amount. In general, the degree to which the turning ability of the vehicle decreases during low-speed driving is determined by the amount of steering operation (the steering angle from the steering reference position corresponding to the turning angle of the steering wheel of the vehicle becomes the reference angle at which the vehicle goes straight). It increases when the operation amount (rotation angle) is large. In addition, the degree to which the stability of the vehicle is reduced during high-speed traveling also increases when the steering operation amount is large.
[0013]
Therefore, if the shift amount of the target yaw rate related amount is changed from the reference yaw rate related amount not only according to the vehicle body speed but also the steering operation amount as described above, for example, as the steering operation amount increases. The deviation amount (absolute value thereof) can be set large, and as a result, the same vehicle according to the degree to which the turning performance of the vehicle is lowered during low speed running and the degree of stability of the vehicle is lowered during high speed running. The degree of improving the turnability of the vehicle and the degree of improving the stability of the vehicle are set without excess or deficiency, and the motion state (turning state) of the vehicle can be made closer to an ideal state.
[0014]
  Further, in the vehicle motion control apparatus described above, the target yaw rate related amount calculating means includes theActual steering gear ratioInstead, the larger the amount of deviation of the acquired steering operation amount from the first predetermined value in the increasing direction, and the larger the amount of deviation of the acquired vehicle body speed from the second predetermined value. The aboveActual steering gear ratioThe amount of deviation fromSteering gear ratio for controlPreferably, the reference yaw rate related amount determined based on the yaw rate theoretical formula is calculated as the target yaw rate related amount..
[0015]
  In the vehicle motion control device described above, the target yaw rate related amount from the reference yaw rate related amount to be set according to the vehicle body speed and the steering operation amount at the stage of design and development of the device before using the device. Need to be determined in advance. In this case, as above,Actual steering gear ratioInstead of the aboveSteering gear ratio for controlIf the above-mentioned deviation amount is determined by calculating a reference yaw rate related amount determined based on the yaw rate theoretical formula as a target yaw rate related amount using Thus, the deviation amount can be determined only by predetermining the control specification value according to the vehicle body speed or the vehicle body speed and the steering operation amount.
[0016]
Here, it is relatively easy to predict and estimate in advance the degree of change in vehicle motion characteristics (turning characteristics) when a specification value (for example, gear ratio) of a specific vehicle is changed. Therefore, according to the above configuration, it is possible to relatively shorten the time required for tuning and determining the control specification values through various vehicle experiments, vehicle simulations, etc. Work man-hours at the development stage can be reduced.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a vehicle motion control apparatus according to the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a vehicle equipped with a vehicle motion control apparatus 10 according to an embodiment of the present invention. This vehicle has two front wheels (left front wheel FL and right front wheel FR) that are steering wheels and non-drive wheels, and two rear wheels (left rear wheel RL and right rear wheel RR) that are drive wheels. This is a wheel drive type four-wheel vehicle.
[0018]
The vehicle motion control device 10 includes a front wheel steering mechanism 20 for steering the steering wheels FL and FR, and a driving force transmission mechanism that generates driving force and transmits the driving force to the driving wheels RL and RR. Part 30, a brake fluid pressure control device 40 for generating brake force by brake fluid pressure on each wheel, a sensor unit 50 composed of various sensors, and an electric control device 60. .
[0019]
The front wheel steering mechanism 20 includes a steering wheel 21, a column 22 that can rotate integrally with the steering wheel 21, a steering actuator 23 connected to the column 22, and the steering actuator 23 in the left-right direction of the vehicle body. A link mechanism portion 24 including a tie rod to be moved and a link capable of turning the steered wheels FL and FR by the movement of the tie rod. As a result, the steering angle of the steered wheels FL, FR is changed from the reference angle at which the vehicle goes straight by rotating the steering 21 from the neutral position (reference position). Further, the gear ratio as an actual specification value in the front wheel steering mechanism section 20 is set to a constant value “20”.
[0020]
The steered actuator 23 includes a so-called known hydraulic power steering device, and generates an assisting force for moving the tie rod in accordance with the rotational torque of the steering wheel 21, that is, the column 22. The tie rod is displaced from the neutral position in the left-right direction of the vehicle body by the same assisting force in proportion to the steering angle θs from the vehicle. In addition, since the structure and operation | movement of this steering actuator 23 are known, the detailed description is abbreviate | omitted here.
[0021]
The driving force transmission mechanism unit 30 is disposed in the intake pipe 31a of the engine 31 that generates the driving force, and controls the opening degree of the throttle valve TH that makes the opening cross-sectional area of the intake passage variable. A throttle valve actuator 32 composed of a motor, a fuel injection device 33 including an injector for injecting fuel near an intake port (not shown) of the engine 31, a transmission 34 connected to the output shaft of the engine 31, and transmission from the transmission 34 And a differential gear 35 for appropriately distributing the driving force to be transmitted to the rear wheels RR and RL.
[0022]
As shown in FIG. 2 showing the schematic configuration, the brake fluid pressure control device 40 includes a high pressure generator 41, a brake fluid pressure generator 42 that generates brake fluid pressure according to the operating force of the brake pedal BP, FR brake fluid pressure adjusting unit 43, FL brake fluid pressure adjusting unit 44, RR capable of adjusting brake fluid pressure supplied to wheel cylinders Wfr, Wfl, Wrr, Wrl respectively arranged on wheels FR, FL, RR, RL The brake fluid pressure adjusting unit 45 and the RL brake fluid pressure adjusting unit 46 are included.
[0023]
The high pressure generator 41 is connected to the electric motor M, the hydraulic pump HP driven by the electric motor M and boosting the brake fluid in the reservoir RS, and the discharge side of the hydraulic pump HP via a check valve CVH. And an accumulator Acc that stores brake fluid boosted by the hydraulic pump HP.
[0024]
The electric motor M is driven when the hydraulic pressure in the accumulator Acc falls below a predetermined lower limit value, and is stopped when the hydraulic pressure in the accumulator Acc exceeds a predetermined upper limit value. The hydraulic pressure in the accumulator Acc is always maintained at a high pressure within a predetermined range.
[0025]
Further, a relief valve RV is disposed between the accumulator Acc and the reservoir RS, and when the hydraulic pressure in the accumulator Acc becomes abnormally higher than the high pressure, the brake fluid in the accumulator Acc is stored in the reservoir RS. It is supposed to be returned to. As a result, the hydraulic circuit of the high pressure generator 41 is protected.
[0026]
The brake fluid pressure generating unit 42 includes a hydro booster HB that responds by the operation of the brake pedal BP, and a master cylinder MC that is connected to the hydro booster HB. The hydro booster HB uses the high pressure supplied from the hydraulic high pressure generator 41 to assist the operating force of the brake pedal BP at a predetermined rate and transmit the assisted operating force to the master cylinder MC. ing.
[0027]
The master cylinder MC generates a master cylinder hydraulic pressure corresponding to the assisted operating force. Further, the hydro booster HB generates a regulator hydraulic pressure corresponding to the assisted operating force, which is substantially the same hydraulic pressure as the master cylinder hydraulic pressure, by inputting the master cylinder hydraulic pressure. Since the configurations and operations of the master cylinder MC and the hydro booster HB are well known, a detailed description thereof will be omitted here. In this way, the master cylinder MC and the hydro booster HB generate the master cylinder hydraulic pressure and the regulator hydraulic pressure according to the operating force of the brake pedal BP, respectively.
[0028]
Between the master cylinder MC and each of the upstream side of the FR brake hydraulic pressure adjusting unit 43 and the upstream side of the FL brake hydraulic pressure adjusting unit 44, a control valve SA1 which is a three-port two-position switching type electromagnetic valve is interposed. Has been. Similarly, between the hydro booster HB and the upstream side of the RR brake hydraulic pressure adjusting unit 45 and the upstream side of the RL brake hydraulic pressure adjusting unit 46, a control valve SA2 which is a three-port two-position switching type electromagnetic valve is provided. Is intervening. Further, a switching valve STR, which is a 2-port 2-position switching type normally closed electromagnetic on-off valve, is interposed between the high-pressure generator 41 and each of the control valve SA1 and the control valve SA2.
[0029]
When the control valve SA1 is in the first position shown in FIG. 2 (the position in the non-excited state), each of the master cylinder MC, the upstream portion of the FR brake fluid pressure adjusting portion 43, and the upstream portion of the FL brake fluid pressure adjusting portion 44. And the communication between the master cylinder MC and each of the upstream part of the FR brake fluid pressure adjusting part 43 and the upstream part of the FL brake fluid pressure adjusting part 44 when in the second position (position in the excited state). The switching valve STR and the upstream portion of the FR brake fluid pressure adjusting unit 43 and the upstream portion of the FL brake fluid pressure adjusting unit 44 are communicated with each other.
[0030]
When the control valve SA2 is in the first position shown in FIG. 2 (the position in the non-excited state), each of the upstream portion of the hydro booster HB and the RR brake hydraulic pressure adjusting portion 45 and the upstream portion of the RL brake hydraulic pressure adjusting portion 46. And the hydro booster HB and the upstream portion of the RR brake hydraulic pressure adjusting unit 45 and the upstream portion of the RL brake hydraulic pressure adjusting unit 46 when in the second position (position in the excited state). The switching valve STR and the upstream portion of the RR brake fluid pressure adjusting unit 45 and the upstream portion of the RL brake fluid pressure adjusting unit 46 are communicated with each other by being shut off.
[0031]
Thus, the master cylinder hydraulic pressure is supplied to each of the upstream portion of the FR brake hydraulic pressure adjusting unit 43 and the upstream portion of the FL brake hydraulic pressure adjusting unit 44 when the control valve SA1 is in the first position, When the control valve SA1 is in the second position and the switching valve STR is in the second position (position in the excited state), the high pressure generated by the high pressure generator 41 is supplied.
[0032]
Similarly, the regulator hydraulic pressure is supplied to the upstream portion of the RR brake hydraulic pressure adjusting unit 45 and the upstream portion of the RL brake hydraulic pressure adjusting unit 46 when the control valve SA2 is in the first position, and the control is performed. The high pressure generated by the high pressure generator 41 is supplied when the valve SA2 is in the second position and the switching valve STR is in the second position.
[0033]
The FR brake fluid pressure adjusting unit 43 includes a pressure increasing valve PUfr which is a 2-port 2-position switching type normally open electromagnetic switching valve and a pressure reducing valve PDfr which is a 2-port 2-position switching type normally closing electromagnetic switching valve. The pressure increasing valve PUfr communicates the upstream portion of the FR brake fluid pressure adjusting unit 43 and the wheel cylinder Wfr when in the first position (position in the non-excited state) shown in FIG. When in the excited state), the communication between the upstream portion of the FR brake fluid pressure adjusting portion 43 and the wheel cylinder Wfr is cut off. When the pressure reducing valve PDfr is in the first position shown in FIG. 2 (the position in the non-excited state), the communication between the wheel cylinder Wfr and the reservoir RS is blocked, and when the pressure reducing valve PDfr is in the second position (the position in the excited state). The wheel cylinder Wfr and the reservoir RS are communicated with each other.
[0034]
As a result, the brake fluid pressure in the wheel cylinder Wfr is supplied from the upstream portion of the FR brake fluid pressure adjusting unit 43 to the wheel cylinder Wfr when both the pressure increasing valve PUfr and the pressure reducing valve PDfr are in the first position. When the pressure-increasing valve PUfr is in the second position and the pressure-reducing valve PDfr is in the first position, the fluid pressure at that time is irrespective of the fluid pressure upstream of the FR brake fluid pressure adjusting unit 43. When the pressure increasing valve PUfr and the pressure reducing valve PDfr are both in the second position, the brake fluid in the wheel cylinder Wfr is returned to the reservoir RS to reduce the pressure.
[0035]
In addition, a check valve CV1 that allows only one-way flow of brake fluid from the wheel cylinder Wfr side to the upstream portion of the FR brake fluid pressure adjusting unit 43 is disposed in parallel with the pressure increasing valve PUfr. When the brake pedal BP operated with the control valve SA1 in the first position is released, the brake fluid pressure in the wheel cylinder Wfr is quickly reduced.
[0036]
Similarly, the FL brake fluid pressure adjusting unit 44, the RR brake fluid pressure adjusting unit 45, and the RL brake fluid pressure adjusting unit 46 are respectively a pressure increasing valve PUfl and a pressure reducing valve PDfl, a pressure increasing valve PUrr and a pressure reducing valve PDrr, a pressure increasing valve PUrl, and The pressure reducing valve PDrl is configured, and by controlling the position of each pressure increasing valve and each pressure reducing valve, the brake fluid pressure in the wheel cylinder Wfl, the wheel cylinder Wrr, and the wheel cylinder Wrl is increased and held, respectively. The pressure can be reduced. In addition, check valves CV2, CV3, and CV4 that can achieve the same function as the check valve CV1 are arranged in parallel on the pressure increasing valves PUfl, PUrr, and PUrl, respectively.
[0037]
Further, the control valve SA1 is provided with a check valve CV5 that allows only one-way flow of the brake fluid from the upstream side to the downstream side in parallel. The control valve SA1 is in the second position and is the master valve. The brakes in the wheel cylinders Wfr and Wfl are operated by operating the brake pedal BP when the communication between the cylinder MC and each of the FR brake fluid pressure adjusting unit 43 and the FL brake fluid pressure adjusting unit 44 is cut off. The hydraulic pressure can be increased. In addition, a check valve CV6 that can achieve the same function as the check valve CV5 is arranged in parallel in the control valve SA2.
[0038]
With the configuration described above, the brake fluid pressure control device 40 can supply brake fluid pressure corresponding to the operating force of the brake pedal BP to each wheel cylinder when all the solenoid valves are in the first position. Yes. In this state, for example, by controlling the pressure increasing valve PUrr and the pressure reducing valve PDrr, for example, only the brake fluid pressure in the wheel cylinder Wrr can be reduced by a predetermined amount.
[0039]
Further, the brake hydraulic pressure control device 40 switches, for example, the control valve SA1, the switching valve STR, and the pressure increasing valve PUfl to the second position when the brake pedal BP is not operated (opened state). In addition, by controlling each of the pressure increasing valve PUfr and the pressure reducing valve PDfr, only the brake fluid pressure in the wheel cylinder Wfr is obtained by using the high pressure generated by the high pressure generator 41 while maintaining the brake fluid pressure in the wheel cylinder Wfl. The pressure can be increased by a predetermined amount. In this manner, the brake fluid pressure control device 40 independently controls the brake fluid pressure in the wheel cylinder of each wheel regardless of the operation of the brake pedal BP, and independently performs a predetermined brake for each wheel. Power can be given.
[0040]
Referring to FIG. 1 again, the sensor unit 50 is a wheel speed sensor 51fl, 51fr, 51rl composed of a rotary encoder that outputs a signal having a pulse each time the wheels FL, FR, RL, and RR rotate by a predetermined angle. And 51rr, a steering angle sensor 52 as a steering operation amount acquisition means for detecting a rotation angle from the neutral position of the steering wheel 21 and outputting a signal indicating the steering angle θs, and an operation of an accelerator pedal AP operated by a driver An accelerator opening sensor 53 that detects the amount and outputs a signal indicating the operation amount Accp of the accelerator pedal AP, and a yaw rate that is a change speed of the vehicle rotation angle about the vertical axis that passes through the center of gravity of the vehicle. A yaw rate sensor 54 as an actual yaw rate related amount acquisition means for outputting a signal indicating The brake switch 55 detects whether or not the key pedal BP is operated and outputs a signal indicating the presence or absence of the brake operation.
[0041]
The steering angle θs is “0” when the steering 21 is in the neutral position, and is a positive value when the steering 21 is rotated counterclockwise (as viewed from the driver) from the neutral position. The steering wheel 21 is set to a negative value when the steering wheel 21 is rotated clockwise. Further, the yaw rate Yr is set to be a positive value when the vehicle is turning leftward and to a negative value when the vehicle is turning rightward.
[0042]
The electric control device 60 is connected to each other via a bus 61, a routine (program) executed by the CPU 61, a table (look-up table, map), a ROM 62 in which constants are stored in advance, and the CPU 61 temporarily stores data as necessary. This is a microcomputer comprising a RAM 63 for storing data, a backup RAM 64 for storing data while the power is on, and retaining the stored data while the power is shut off, an interface 65 including an AD converter, and the like. . The interface 65 is connected to the sensors 51 to 55 and supplies signals from the sensors 51 to 55 to the CPU 61, and the electromagnetic valves, the motor M, and the throttle valve of the brake fluid pressure control device 40 according to instructions from the CPU 61. Drive signals are sent to the actuator 32 and the fuel injection device 33.
[0043]
Thus, the throttle valve actuator 32 drives the throttle valve TH so that the opening degree of the throttle valve TH becomes an opening degree corresponding to the operation amount Accp of the accelerator pedal AP, and the fuel injection device 33 The fuel is injected in an amount necessary to obtain a predetermined target air-fuel ratio (theoretical air-fuel ratio) with respect to the intake air amount corresponding to the opening degree.
[0044]
(Outline of vehicle motion control according to the present invention)
The vehicle motion control apparatus 10 according to the present invention first calculates a target yaw rate Yrt (deg / sec) based on the following formula 1 based on a theoretical formula as a predetermined rule derived from a vehicle motion model. This target yaw rate Yrt is a positive value when the vehicle is turning left (when the steering angle θs (deg) is a positive value), and when the vehicle is turning right (the steering angle θs is It is set to be a negative value when the value is negative. This theoretical formula is a formula for calculating the theoretical value of the yaw rate when the vehicle turns with the steering angle and the vehicle body speed being constant (at the time of steady circle turning).
[0045]
[Expression 1]
Yrt = (Vso ・ θs) / (n ・ l) ・ (1 / (1 + Kh ・ Vso²))
[0046]
In Equation 1, Vso is an estimated vehicle speed (km / h) calculated as described later. Also, l is a vehicle wheelbase (km) that is a constant value determined by the vehicle body, and Kh is a stability factor (h²/ km²) And the wheel base l and the stability factor Kh are actual specification values of the vehicle.
[0047]
In the above equation 1, n is a control gear ratio. The gear ratio as the actual specification value of the vehicle is the constant value “20” as described above. However, when the target yaw rate Yrt is calculated in the above equation 1, the apparatus sets the actual gear ratio “20”. Instead, the control gear ratio n is used as a specification value for control that changes in accordance with the estimated vehicle body speed Vso and the steering angle θs.
[0048]
More specifically, as shown in FIG. 3 showing an example of the relationship between the control gear ratio n, the steering angle θs, and the estimated vehicle body speed Vso, the absolute value of the steering angle θs is predetermined for the control gear ratio n. When the angle is smaller than 90 °, the constant value “20”, which is the same value as the actual gear ratio, is set regardless of the estimated vehicle body speed Vso. In this case, only the actual specification value of the vehicle is used (using the actual gear ratio “20” instead of the control gear ratio n), and the reference is the theoretical value of the yaw rate calculated from the above equation (1). The yaw rate and the target yaw rate Yrt have the same value.
[0049]
On the other hand, when the absolute value of the steering angle θs is equal to or greater than the predetermined angle 90 °, the estimated vehicle speed Vso is equal to or greater than the predetermined value (for example, 45 km / h) (for example, when Vso = 80 km / h shown in FIG. 3). The control gear ratio n is set such that the greater the absolute value of the steering angle θs, the greater the actual gear ratio “20” according to the estimated vehicle body speed Vso. In this case, as apparent from the above equation 1, the absolute value of the target yaw rate Yrt is a value equal to or smaller than the absolute value of the reference yaw rate.
[0050]
When the absolute value of the steering angle θs is equal to or greater than the predetermined angle 90 ° and the estimated vehicle body speed Vso is less than the predetermined value (for example, when Vso = 20 km / h shown in FIG. 3), the control gear The ratio n is set such that the greater the absolute value of the steering angle θs, the smaller the actual gear ratio “20” or less according to the estimated vehicle body speed Vso. In this case, as is apparent from reference to Equation 1, the absolute value of the target yaw rate Yrt is equal to or greater than the absolute value of the reference yaw rate.
[0051]
In this way, the present apparatus uses the control gear ratio n set as described above instead of the actual gear ratio “20” as the target yaw rate Yrt. calculate.
[0052]
Next, this apparatus is a deviation between the absolute value of the target yaw rate Yrt calculated as described above and the absolute value of the actual yaw rate Yr (deg / sec) obtained by the yaw rate sensor 54 based on the following formula 2. The yaw rate deviation ΔYr (deg / sec) is calculated.
[0053]
[Expression 2]
ΔYr = | Yrt |-| Yr |
[0054]
When the yaw rate deviation ΔYr is a positive value, the vehicle is in a state where the turning radius is larger than the turning radius when the target yaw rate Yrt is assumed to be generated in the vehicle (hereinafter referred to as “understeer”). Therefore, the present apparatus executes understeer suppression control for suppressing the understeer state. Specifically, this device forcibly generates a yawing moment in the same direction as the turning direction to the vehicle by generating a predetermined braking force according to the value of the yaw rate deviation ΔYr on the rear wheel inside the turning direction. Let Thereby, the absolute value of the actual yaw rate Yr is increased, and the actual yaw rate Yr is controlled to approach the target yaw rate Yrt.
[0055]
Further, when the value of the yaw rate deviation ΔYr is a negative value, the vehicle is in a state where the turning radius becomes smaller than the turning radius when the target yaw rate Yrt is assumed to be generated in the vehicle (hereinafter referred to as “oversteer”). Therefore, the present apparatus executes oversteer suppression control for suppressing the oversteer state. Specifically, this device forcibly generates a yawing moment in a direction opposite to the turning direction with respect to the vehicle by generating a predetermined braking force according to the value of the yaw rate deviation ΔYr on the front wheel outside the turning direction. . Thereby, the absolute value of the actual yaw rate Yr is reduced, and the actual yaw rate Yr is controlled so as to approach the target yaw rate Yrt.
[0056]
In this way, by executing understeer suppression control or oversteer suppression control (hereinafter collectively referred to as “brake steering control”), the present apparatus controls the braking force to be applied to each wheel. Then, a predetermined yawing moment is generated for the vehicle in a direction in which the actual yaw rate Yr approaches the target yaw rate Yrt calculated as described above. Further, when executing braking steering control, when any one of anti-skid control, front / rear braking force distribution control, and traction control, which will be described later, needs to be executed together, In consideration of the braking force to be applied to each wheel in order to execute one control, the braking force to be applied to each wheel is finally determined. The above is the outline of the vehicle motion control according to the present invention.
[0057]
(Actual operation)
Next, the actual operation of the vehicle motion control device 10 according to the present invention configured as described above will be described with reference to FIGS. 4 to 8, which are flowcharts showing routines executed by the CPU 61 of the electric control device 60. explain. In addition, “**” appended to the end of various variables / flags / signs, etc., indicates the variable / flag / flag / sign etc. -Comprehensive notation such as "fl", "fr", etc. appended to the end of the code etc., for example, wheel speed Vw ** is left front wheel speed Vwfl, right front wheel speed Vwfr, left rear wheel speed Vwrl, right The rear wheel speed Vwrr is shown comprehensively.
[0058]
The CPU 61 repeatedly executes a routine for calculating the wheel speed Vw ** and the like shown in FIG. 4 every elapse of a predetermined time. Accordingly, when the predetermined timing is reached, the CPU 61 starts the process from step 400, proceeds to step 405, and calculates the wheel speed (the outer peripheral speed of each wheel) Vw ** of each wheel FR and the like. Specifically, the CPU 61 calculates the wheel speed Vw ** of each wheel FR and the like based on the time interval of the pulse included in the signal output from each wheel speed sensor 51 **.
[0059]
Next, the CPU 61 proceeds to step 410 and calculates the maximum value of the wheel speeds Vw ** of the wheels FR and the like as the estimated vehicle body speed Vso. Note that an average value of the wheel speeds Vw ** of the respective wheels FR and the like may be calculated as the estimated vehicle body speed Vso. Here, step 410 corresponds to the vehicle body speed acquisition means.
[0060]
Next, the CPU 61 proceeds to step 415, where the value of the estimated vehicle speed Vso calculated in step 410, the value of the wheel speed Vw ** of each wheel FR calculated in step 405, and the like are described in step 415. The actual slip ratio Sa ** for each wheel is calculated based on the formula. This actual slip ratio Sa ** is used when calculating the braking force to be applied to each wheel, as will be described later. Then, the CPU 61 proceeds to step 495 to end this routine once.
[0061]
Next, calculation of yaw rate deviation will be described. The CPU 61 repeatedly executes the routine shown in FIG. 5 every elapse of a predetermined time. Therefore, when the predetermined timing is reached, the CPU 61 starts processing from step 500 and proceeds to step 505, where the absolute value of the steering angle θs obtained by the steering angle sensor 52 and the estimated vehicle body calculated in step 410 of FIG. Based on the value of the speed Vso and the table described in step 505, the control gear ratio n is calculated.
[0062]
Thus, when the absolute value of the steering angle θs is smaller than 90 °, the control gear ratio n is set to a constant value “20” that is the same value as the actual gear ratio regardless of the estimated vehicle speed Vso. Is set. When the absolute value of the steering angle θs is 90 ° or more and the estimated vehicle speed Vso is 45 (km / h) or more, the control gear ratio n is the actual gear ratio “20” or more and the steering The angle θs is set so as to increase as the absolute value of the angle θs increases and as the estimated vehicle body speed Vso increases. When the absolute value of the steering angle θs is 90 ° or more and the estimated vehicle speed Vso is less than 45 (km / h), the control gear ratio n is a value equal to or less than the actual gear ratio “20” and the steering The angle θs is set so as to decrease as the absolute value of the angle θs increases and as the value of the estimated vehicle body speed Vso decreases.
[0063]
Next, the CPU 61 proceeds to step 510 where the value of the control gear ratio n calculated in step 505, the value of the steering angle θs obtained by the steering angle sensor 52, and the estimated vehicle body calculated in step 410 of FIG. The target yaw rate Yrt is calculated based on the value of the velocity Vso and the formula described in step 510 corresponding to the right side of the above equation 1. Here, step 510 corresponds to a target yaw rate related amount calculation means.
[0064]
Next, the CPU 61 proceeds to step 515, where the target yaw rate Yrt value calculated in step 510, the actual yaw rate Yr value obtained by the yaw rate sensor 54, and the step 515 corresponding to the right side of the above equation 2 are described. The yaw rate deviation ΔYr is calculated based on the above equation. Then, the CPU 61 proceeds to step 595 to end this routine once.
[0065]
Next, calculation of the target slip ratio of each wheel necessary for determining the braking force to be applied to each wheel when only the above-described braking steering control is executed will be described. The CPU 61 performs the routine shown in FIG. Is repeatedly executed every elapse of a predetermined time. Therefore, when the predetermined timing is reached, the CPU 61 starts processing from step 600 and proceeds to step 605 to determine whether or not the actual yaw rate Yr value obtained by the yaw rate sensor 54 is equal to or greater than “0”. If the actual yaw rate Yr is “0” or more, “Yes” is determined in Step 605 and the process proceeds to Step 610 to set the turning direction display flag L to “1”. If the actual yaw rate Yr is a negative value, “No” is determined in step 605 and the process proceeds to step 615 to set the turning direction display flag L to “0”.
[0066]
Here, the turning direction display flag L is a flag indicating whether the vehicle is turning left or right, and when the value is “1”, the vehicle is turning left. When the value is “0”, it indicates that the vehicle is turning right. Therefore, the turning direction of the vehicle is specified by the value of the turning direction display flag L.
[0067]
Next, the CPU 61 proceeds to step 620, and the magnitude of the yawing moment to be generated in the vehicle by the brake steering control based on the absolute value of the yaw rate deviation ΔYr calculated in step 515 of FIG. 5 and the table described in step 620. A control amount G corresponding to the above is calculated. As shown in the table described in step 620, the control amount G is set to be “0” when the absolute value of the yaw rate deviation ΔYr is less than or equal to the value Yr1, and the absolute value of the yaw rate deviation ΔYr is greater than or equal to the value Yr1. When the value is less than Yr2, the absolute value of the yaw rate deviation ΔYr is set to linearly change from “0” to a positive constant value G1 as the absolute value of the yaw rate deviation ΔYr changes from the value Yr1 to the value Yr2. Is set to be maintained at a positive constant value G1 when is equal to or greater than the value Yr2. In other words, the brake steering control is not executed when the absolute value of the yaw rate deviation ΔYr is equal to or less than the value Yr1, while when the absolute value of the yaw rate deviation ΔYr is equal to or greater than the value Yr1, the control amount G is based on the table described in step 620. Is determined according to the absolute value of the yaw rate deviation ΔYr.
[0068]
Next, the CPU 61 proceeds to step 625 to determine whether or not the value of the yaw rate deviation ΔYr calculated in step 515 in FIG. 5 is “0” or more. Here, when the value of the yaw rate deviation ΔYr is “0” or more, the CPU 61 determines that the vehicle is in the understeer state as described above, and the target of each wheel when the understeer suppression control is executed. In order to calculate the slip ratio, the routine proceeds to step 630, where it is determined whether or not the value of the turning direction display flag L is “1”.
[0069]
When the turning direction display flag L is “1” in the determination in step 630, the CPU 61 proceeds to step 635 and multiplies the coefficient Kr, which is a positive constant value, by the value of the control amount G calculated in step 620. Is set as the target slip ratio Strl of the left rear wheel RL, and the target slip ratios Stfl, Stfr, Strr of the other wheels FL, FR, RR are all set to “0”, and the routine proceeds to step 695. Exit once. Thereby, the target slip ratio corresponding to the absolute value of the yaw rate deviation ΔYr is set only for the left rear wheel RL corresponding to the rear wheel in the turning direction when the vehicle is turning left.
[0070]
On the other hand, when the turning direction display flag L is “0” in the determination in step 630, the CPU 61 proceeds to step 640, and the value obtained by multiplying the coefficient Kr by the value of the control amount G calculated in step 620 is the right rear wheel. The target slip ratio Strr of RR is set and the target slip ratios Stfl, Stfr, Strl of the other wheels FL, FR, RL are all set to “0”, and the routine proceeds to step 695 and this routine is temporarily terminated. Thereby, the target slip ratio according to the absolute value of the yaw rate deviation ΔYr is set only for the right rear wheel RR corresponding to the rear wheel in the turning direction when the vehicle is turning right.
[0071]
On the other hand, if the yaw rate deviation ΔYr is negative in the determination in step 625, the CPU 61 determines that the vehicle is in an oversteer state as described above, and executes the oversteer suppression control. In order to calculate the target slip ratio of each wheel at the time, the routine proceeds to step 645, where it is determined whether or not the value of the turning direction display flag L is “1”.
[0072]
When the turning direction display flag L is “1” in the determination in step 645, the CPU 61 proceeds to step 650 and multiplies the coefficient Kf, which is a positive constant value, by the value of the control amount G calculated in step 620. Is set as the target slip ratio Stfr of the right front wheel FR, and the target slip ratios Stfl, Strl, Strr of the other wheels FL, RL, RR are all set to “0”, and the routine proceeds to step 695 to temporarily execute this routine. finish. Thus, the target slip ratio corresponding to the absolute value of the yaw rate deviation ΔYr is set only for the right front wheel FR corresponding to the front wheel outside the turning direction when the vehicle is turning left.
[0073]
On the other hand, when the turning direction display flag L is “0” in the determination of step 645, the CPU 61 proceeds to step 655, and multiplies the coefficient Kf by the value of the control amount G calculated in step 620 to the left front wheel FL. And the target slip ratios Stfr, Strl, Strr of the other wheels FR, RL, RR are all set to “0”, and the routine proceeds to step 695 to end the present routine tentatively. Thereby, the target slip ratio corresponding to the absolute value of the yaw rate deviation ΔYr is set only for the left front wheel FL corresponding to the front wheel on the outer side in the turning direction when the vehicle is turning right. As described above, the target slip ratio of each wheel necessary for determining the braking force to be applied to each wheel when only the brake steering control is executed is determined.
[0074]
Next, the setting of the vehicle control mode will be described. The CPU 61 repeatedly executes the routine shown in FIG. 7 every elapse of a predetermined time. Accordingly, when the predetermined timing is reached, the CPU 61 starts processing from step 700 and proceeds to step 705 to determine whether or not anti-skid control is necessary at the present time. The anti-skid control is a control for reducing the braking force of the specific wheel when the specific wheel is locked while the brake pedal BP is being operated. Since the details of the anti-skid control are well known, detailed description thereof is omitted here.
[0075]
Specifically, in step 705, the CPU 61 indicates that the brake switch BP is operated by the brake switch 55, and the actual wheel of the specific wheel calculated in step 415 of FIG. When the value of the slip rate Sa ** is equal to or greater than a predetermined positive value, it is determined that anti-skid control is necessary.
[0076]
When it is determined in step 705 that the anti-skid control is necessary, the CPU 61 proceeds to step 710 to set a variable Mode to “Variable Mode” in order to set a control mode in which the braking steering control and the anti-skid control are executed. 1 ”is set, and the process proceeds to the subsequent step 750.
[0077]
On the other hand, when it is determined in step 705 that the anti-skid control is not necessary, the CPU 61 proceeds to step 715 to determine whether the front / rear braking force distribution control is necessary at the present time. The front / rear braking force distribution control is a control that reduces the ratio (distribution) of the braking force of the rear wheel to the braking force of the front wheel in accordance with the magnitude of the deceleration in the front / rear direction of the vehicle when the brake pedal BP is operated. is there. Since the details of the front-rear braking force distribution control are well known, the detailed description thereof is omitted here.
[0078]
Specifically, in step 715, the CPU 61 indicates that the brake pedal BP is operated by the brake switch 55, and the time of the estimated vehicle body speed Vso calculated in step 410 of FIG. When the differential value is a negative value and the absolute value of the differential value is equal to or greater than a predetermined value, it is determined that the front / rear braking force distribution control is necessary.
[0079]
When it is determined in step 715 that the front / rear braking force distribution control is necessary, the CPU 61 proceeds to step 720 to set a control mode in which the braking steering control and the front / rear braking force distribution control are executed in a superimposed manner. The variable Mode is set to “2”, and the process proceeds to the next step 750.
[0080]
When it is determined in step 715 that the front / rear braking force distribution control is not necessary, the CPU 61 proceeds to step 725 to determine whether traction control is necessary at the present time. The traction control is a control or engine for increasing the braking force of a specific wheel when the specific wheel is spinning in a direction in which the driving force of the engine 31 is generated when the brake pedal BP is not operated. This is a control for reducing the driving force 31. Since details of the traction control are well known, a detailed description thereof is omitted here.
[0081]
Specifically, in step 725, the CPU 61 indicates that the brake switch BP indicates that the brake pedal BP is not operated, and the actual wheel of the specific wheel calculated in step 415 in FIG. If the slip ratio Sa ** is a negative value and the actual slip ratio Sa ** is equal to or greater than a predetermined value, it is determined that traction control is necessary.
[0082]
When it is determined in step 725 that traction control is necessary, the CPU 61 proceeds to step 730 and sets “3” in the variable Mode in order to set a control mode in which braking steering control and traction control are executed in a superimposed manner. And proceed to step 750.
[0083]
When it is determined in step 725 that traction control is not necessary, the CPU 61 proceeds to step 735 and determines whether or not the braking steering control is necessary at the present time. Specifically, the CPU 61 determines in step 735 that the absolute value of the yaw rate deviation ΔYr calculated in step 515 in FIG. 5 is equal to or larger than the value Yr1 in the table described in step 620 in FIG. Since there is a specific wheel whose target slip ratio St ** set at is not “0”, it is determined that the brake steering control is necessary.
[0084]
When it is determined in step 735 that braking steering control is necessary, the CPU 61 proceeds to step 740, sets “4” in the variable Mode to set a control mode for executing only braking steering control, and continues. Proceed to step 750. On the other hand, when it is determined in step 735 that braking steering control is not necessary, the CPU 61 proceeds to step 745 and sets “0” to the variable Mode to set a non-control mode in which vehicle motion control is not executed. Proceed to step 750 that follows. In this case, there is no specific wheel to be controlled.
[0085]
In step 750, the CPU 61 sets “1” to the flag CONT ** corresponding to the control target wheel and sets “0” to the flag CONT ** corresponding to the non-control target wheel that is not the control target wheel. The wheel to be controlled in step 750 is a wheel that needs to control at least one of the corresponding pressure increasing valve PU ** and pressure reducing valve PD ** shown in FIG.
[0086]
Therefore, for example, when the brake pedal BP is not operated and the process proceeds to step 650 in FIG. 6 described above, when only the brake fluid pressure in the wheel cylinder Wfr of the right front wheel FR needs to be increased, The brake fluid pressure in the wheel cylinder Wfl is maintained by switching both the control valve SA1, the switching valve STR and the pressure increasing valve PUfl shown in FIG. 2 to the second position and controlling the pressure increasing valve PUfr and the pressure reducing valve PDfr, respectively. In this state, only the brake fluid pressure in the wheel cylinder Wfr is increased using the high pressure generated by the high pressure generator 41. Therefore, the control target wheels in this case include not only the right front wheel FR but also the left front wheel FL. Then, after executing step 750, the CPU 61 proceeds to step 795 to end the present routine tentatively. In this way, the control mode is specified and the control target wheel is specified.
[0087]
Next, the control of the braking force to be applied to each wheel will be described. The CPU 61 repeatedly executes the routine shown in FIG. 8 every elapse of a predetermined time. Therefore, when the predetermined timing is reached, the CPU 61 starts processing from step 800 and proceeds to step 805 to determine whether or not the variable Mode is “0”. If the variable Mode is “0”, the CPU 61 proceeds to step 805. Therefore, the process proceeds to step 810, and it is not necessary to execute the brake control for each wheel. Therefore, after all the solenoid valves in the brake hydraulic pressure control device 40 are turned off (non-excited state), Proceeding to step 895, the present routine is temporarily terminated. As a result, the brake fluid pressure corresponding to the operating force of the brake pedal BP by the driver is supplied to each wheel cylinder W **.
[0088]
On the other hand, if the variable Mode is not “0” in the determination in step 805, the CPU 61 determines “Yes” in step 805 and proceeds to step 815 to determine whether or not the variable Mode is “4”. When the variable Mode is not “4” (that is, when anti-skid control other than the brake steering control is necessary), the CPU 61 makes a “No” determination at step 815 to proceed to step 820, as shown in FIG. In step 750, the target slip ratio St of each wheel that is required when only the braking steering control already set in FIG. 6 is executed for the control target wheel whose flag CONT ** is set to “1”. After correcting **, the process proceeds to step 825. As a result, the target slip ratio St ** of each wheel already set in FIG. 6 is set by the target slip ratio of each wheel necessary for executing the control corresponding to the value of the variable Mode superimposed on the brake steering control. Is corrected for each wheel to be controlled.
[0089]
When the variable Mode is “4” in the determination in step 815, the CPU 61 determines “Yes” in step 815, and there is no need to correct the target slip ratio St ** of each wheel already set in FIG. Therefore, the process proceeds directly to step 825. When the CPU 61 proceeds to step 825, the value of the target slip ratio St ** and the step of FIG. 4 for the wheel to be controlled whose flag CONT ** value is set to “1” in step 750 of FIG. A slip ratio deviation ΔSt ** is calculated for each wheel to be controlled based on the actual slip ratio Sa ** calculated in 415 and the formula described in Step 825.
[0090]
Next, the CPU 61 proceeds to step 830 and sets the hydraulic pressure control mode for each wheel to be controlled with respect to the wheel to be controlled. Specifically, the CPU 61 determines the slip rate deviation ΔSt for each wheel to be controlled based on the value of the slip rate deviation ΔSt ** for each wheel to be controlled calculated in Step 825 and the table described in Step 830. When the value of ** exceeds a predetermined positive reference value, the hydraulic pressure control mode is set to “pressure increase”, and the value of the slip ratio deviation ΔSt ** is equal to or greater than a predetermined negative reference value and the predetermined value When the value is less than the positive reference value, the hydraulic pressure control mode is set to “hold”, and when the slip ratio deviation ΔSt ** falls below the predetermined negative reference value, the hydraulic pressure control mode is set to “reduced pressure”. Set.
[0091]
Next, the CPU 61 proceeds to step 835 and controls the control valves SA1 and SA2 and the switching valve STR shown in FIG. 2 on the basis of the hydraulic pressure control mode for each wheel to be controlled set in step 830 and the wheel to be controlled. Every time, the pressure increasing valve PU ** and the pressure reducing valve PD ** are controlled according to the same fluid pressure control mode.
[0092]
Specifically, the CPU 61 sets both the corresponding pressure-increasing valve PU ** and pressure-reducing valve PD ** to the first position (the position in the non-excited state) for the wheel whose hydraulic pressure control mode is “pressure-increasing”. ) And the corresponding pressure increasing valve PU ** is controlled to the second position (position in the excited state) and the corresponding pressure reducing valve PD * for the wheel whose hydraulic pressure control mode is “hold”. * Is controlled to the first position, and for the wheel whose hydraulic pressure control mode is “reduced pressure”, the corresponding pressure increasing valve PU ** and pressure reducing valve PD ** are both set to the second position (in the excited state). Position).
[0093]
As a result, the brake fluid pressure in the wheel cylinder W ** of the wheel to be controlled whose fluid pressure control mode is “increase” increases, and the control object whose fluid pressure control mode is “reduced pressure”. By reducing the brake fluid pressure in the wheel cylinder W ** of the wheel, the actual slip rate Sa ** of each control wheel is controlled so as to approach the target slip rate St **. As a result, as shown in FIG. Control corresponding to the set control mode is achieved. Here, step 835 corresponds to braking force control means.
[0094]
When the control mode set by executing the routine of FIG. 7 is the control mode for executing traction control (variable Mode = 3) or the control mode for executing only braking steering control (variable Mode = 4), the engine 31 is used. In order to reduce the driving force, the CPU 61 adjusts the throttle valve actuator 32 so that the opening of the throttle valve TH is smaller by a predetermined amount than the opening corresponding to the operation amount Accp of the accelerator pedal AP, if necessary. To control. Then, the CPU 61 proceeds to step 895 to end this routine once.
[0095]
As described above, according to the vehicle motion control apparatus of the present invention, when the estimated vehicle body speed Vso is equal to or greater than a predetermined value (45 km / h), the target yaw rate Yrt (absolute value) is calculated from the vehicle motion model. When the estimated vehicle speed Vso is less than the predetermined value, the target yaw rate Yrt (the absolute value thereof) is set to the above-mentioned reference yaw rate (the absolute value thereof) which is a theoretical value based on the derived theoretical formula. It is set to be equal to or higher than the reference yaw rate (the absolute value thereof). Then, the target slip rate St ** of each wheel of the vehicle is set so that the actual yaw rate Yr approaches the target yaw rate Yrt, and the actual slip rate Sa ** of each wheel becomes the same target slip rate St **. The brake force of each wheel is controlled. Therefore, when the vehicle is turning, or when turning is started, when the estimated vehicle speed Vso is equal to or higher than a predetermined value, the braking force of each wheel is controlled so that the reference yaw rate is generated in the vehicle. In comparison, the turning ability of the vehicle is reduced, and the stability of the vehicle is improved. On the other hand, when the estimated vehicle speed Vso is less than a predetermined value, the turning ability of the vehicle is improved as compared with the case where the braking force of each wheel is controlled so that the reference yaw rate is generated in the vehicle.
[0096]
Further, since the deviation amount of the target yaw rate Yrt from the reference yaw rate is set to be larger as the absolute value of the steering angle θs becomes larger, the degree of turning of the vehicle at low speeds and the degree of turning of the vehicle at high speeds are reduced. The degree to which the turning ability of the vehicle is improved and the degree to which the stability of the vehicle is improved according to the degree to which the stability is reduced is set without excess or deficiency, and the vehicle motion state (turning state) is closer to ideal. became.
[0097]
Further, the yaw rate calculated based on the above theoretical formula using the control gear ratio n deviating from the actual gear ratio “20” instead of the actual gear ratio “20” of the vehicle is set as the target yaw rate Yrt. Calculated. Here, it is relatively easy to predict and estimate in advance the degree of change in the vehicle motion characteristics (turning characteristics) when the gear ratio is changed. Therefore, according to the vehicle motion control apparatus of the present invention, it is possible to relatively shorten the time required for tuning and determining the value of the control gear ratio n through various vehicle experiments, vehicle simulations, etc. The work man-hours in the design / development stage of the motion control device of the company were reduced.
[0098]
The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the slip ratio of each wheel of the vehicle is used as a control target for bringing the actual yaw rate Yr close to the target yaw rate Yrt. For example, the brake in the wheel cylinder W ** of each wheel is used. Any physical quantity may be used as the control target as long as it is a physical quantity that changes according to the braking force applied to each wheel, such as hydraulic pressure.
[0099]
In the above embodiment, the target yaw rate Yrt is calculated based on the above theoretical formula by using the control gear ratio n instead of the actual gear ratio “20”. Target yaw rate based on the above theoretical formula by setting and using a control stability factor that shifts from the actual stability factor Kh value according to the estimated vehicle speed Vso instead of the factor Kh (constant value) Yrt may be calculated. In addition, each specification value of the vehicle used in the above theoretical formula uses the actual specification value as it is, and by adding and setting a new parameter that changes according to the estimated vehicle body speed Vso in the above theoretical formula. The target yaw rate Yrt may be calculated.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a vehicle equipped with a vehicle motion control apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of the brake fluid pressure control device shown in FIG. 1;
FIG. 3 is a diagram showing an example of a relationship between a control gear ratio, a steering angle, and an estimated vehicle body speed used when the CPU shown in FIG. 1 calculates a target yaw rate.
4 is a flowchart showing a routine for calculating wheel speed and the like executed by a CPU shown in FIG. 1; FIG.
FIG. 5 is a flowchart showing a routine for calculating a yaw rate deviation executed by a CPU shown in FIG. 1;
FIG. 6 is a flowchart showing a routine for the CPU shown in FIG. 1 to calculate a target slip ratio.
FIG. 7 is a flowchart showing a routine for the CPU shown in FIG. 1 to set a control mode.
FIG. 8 is a flowchart showing a routine for controlling the braking force applied to each wheel by the CPU shown in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Vehicle motion control apparatus, 20 ... Front wheel steering mechanism part, 30 ... Driving force transmission mechanism part, 40 ... Brake hydraulic pressure control apparatus, 50 ... Sensor part, 51 ** ... Wheel speed sensor, 52 ... Steering Angle sensor, 54... Yaw rate sensor, 60... Electric control device, 61.

Claims (3)

Vehicle body speed acquisition means for acquiring a vehicle body speed;
Steering operation amount acquisition means for acquiring a steering operation amount for changing a turning angle of the steering wheel of the vehicle;
An actual yaw rate related amount acquisition means for acquiring an actual amount of a yaw rate related amount indicating the degree of turning of the vehicle as an actual yaw rate related amount;
A yaw rate theoretical formula derived from a vehicle motion model that calculates a theoretical value of yaw rate when the vehicle turns with both the vehicle body speed and the steering operation amount being constant, wherein the vehicle body speed is Vso, The steering operation amount is θs, the steering gear ratio that is the actual specification value of the vehicle is n0 , the wheel base that is the actual specification value of the vehicle is l, and the stability factor that is the actual specification value of the vehicle the based upon the ((Vso · θs) / ( n0 · l)) · (1 / (1 + Kh · Vso 2)) and the yaw rate theoretical formula represented expressed and Kh, which is the acquired as Vso The absolute value of the acquired steering operation amount when the reference yaw rate related amount that is the reference amount of the yaw rate related amount is determined by using the vehicle body speed and the acquired steering operation amount as θs. Is equal to or greater than a first predetermined value and the acquired vehicle body speed is equal to or greater than a second predetermined value, the absolute value of the target yaw rate related amount that is the target amount of the yaw rate related amount is the absolute value of the reference yaw rate related amount. The target yaw rate related amount is calculated according to the acquired vehicle body speed so as to be smaller than a value, and the absolute value of the acquired steering operation amount is equal to or greater than the first predetermined value and is acquired. When the vehicle body speed is less than the second predetermined value, the target yaw rate related amount is set according to the acquired vehicle body speed so that the absolute value of the target yaw rate related amount is larger than the absolute value of the reference yaw rate related amount. A target yaw rate related amount calculating means for calculating the amount;
Braking force control means for controlling the braking force applied to the front and rear wheels of the vehicle so that the actual yaw rate related amount approaches the target yaw rate related amount;
In a vehicle motion control apparatus comprising:
The target yaw rate related amount calculating means includes :
In the yaw rate theoretical formula, instead of the actual steering gear ratio n0, and the vehicle speed which the acquired, a steering operation amount the acquired previously and the vehicle speed and the steering operation amount and the scan Tearingugiya ratio Control represented by ((Vso ・ θs) / (n ・ l)) ・ (1 / (1 + Kh ・ Vso ² )) using the defined relationship and the control steering gear ratio n obtained from Calculating the reference yaw rate related amount determined based on the theoretical yaw rate theoretical formula as the target yaw rate related amount;
In the predetermined relationship,
When the absolute value of the acquired steering operation amount is not less than the first predetermined value and the acquired vehicle body speed is not less than the second predetermined value, the control steering gear ratio n is the actual steering Set to a value greater than gear ratio n0 ,
When the absolute value of the acquired steering operation amount is greater than or equal to the first predetermined value and the acquired vehicle body speed is less than the second predetermined value, the control steering gear ratio n is the actual steering A vehicle motion control device set to a value smaller than the gear ratio n0 . The vehicle motion control device according to claim 1,
The target yaw rate related amount calculation means is configured to change an amount by which the target yaw rate related amount shifts with respect to the reference yaw rate related amount according to the acquired steering operation amount. . The vehicle motion control device according to claim 2,
The target yaw rate related amount calculating means includes:
Instead of the actual steering gear ratio n0, the larger the amount of deviation of the acquired steering operation amount from the first predetermined value in the increasing direction, and the second predetermined value of the acquired vehicle body speed. The larger the deviation amount from the actual steering gear ratio n0 , the larger the deviation amount from the actual steering gear ratio n0 . The reference steering yaw rate related to the reference yaw rate is determined based on the control yaw rate theoretical formula using the control steering gear ratio n. A vehicle motion control device configured to calculate a quantity as the target yaw rate related quantity.

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