JP3451912B2 - Drive control device for electric vehicles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive controller mounted on an electric vehicle having a motor for each drive wheel and controlling these motors.

[0002]

2. Description of the Related Art An electric vehicle is a general term for vehicles propelled by a motor. When classifying by focusing on the form of power distribution from the motor to the drive wheels, electric vehicles are divided into a type in which the output of a certain common motor is distributed to multiple drive wheels and a type in which a motor is provided for each drive wheel. To be A typical example of the former is a one-motor type in which the output of a single motor is distributed to two or four drive wheels on the left and right via a differential gear. A typical example of the latter is a wheel-in motor type in which each motor is incorporated (or integrated) in a drive wheel corresponding to the motor. Compared to the former, the latter does not require a distribution mechanism such as a differential gear, resulting in low transmission loss and low energy consumption, and since it is only necessary to drive the corresponding drive wheels, the motor can be downsized and transmission loss is small. Since the motor is small, the battery that is the power source of the motor can be downsized, and since the motor is built in the drive wheels, the integration is high and the vehicle interior space is widened.

Including the wheel-in motor type,
In an electric vehicle of a type in which a motor is provided for each drive wheel (left-right drive wheel independent drive type electric vehicle), the vehicle travels by further adjusting or controlling distribution of output (torque) to the left and right drive wheels as needed. There is also an advantage that safety can be improved. For example, in a wheel-in motor type electric vehicle disclosed in Japanese Patent Laid-Open No. 5-91607, a yaw rate model predicted value is calculated based on both detected values of a steering angle and a vehicle speed, and a yaw rate sensor is calculated for the calculated model predicted value. The output distribution to each motor is determined so that the difference that the actual measurement value obtained in step 1, that is, the yaw rate noise, is reduced. The yaw rate noise referred to in this publication is a deviation that cannot be predicted from the detected values of the steering angle and the vehicle speed, for example, the left / right difference in the tire radius of movement, the left / right difference in the wheel load,
It indicates the deviation due to the slope / roughness of the road and the wind direction. Therefore, if the method described in this publication can be realized, the straightness of the vehicle can be improved among the constituent elements of the traveling safety of the vehicle.

[0004]

However, in order to realize the method described in the above publication, the model predicted value of the yaw rate must be obtained accurately and in real time. Actually, since the rotation speed and torque of the electric vehicle traveling motor dynamically change, it is difficult to obtain the model predicted value of the yaw rate accurately and in real time, and thus the method described in the above publication is difficult to realize. Further, in the method described in the above publication, since the cornering power that changes according to the vehicle speed and the like is actually treated as a constant, it is possible in principle to improve the running stability among the components of the running safety of the vehicle. Absent.

The applicant of the present application has already proposed several control methods for improving the running stability of the vehicle. For example, in Japanese Patent Application No. 8-238961, the steer characteristic of the vehicle is detected, and if the detected steer characteristic is oversteer, the torque command for the inner drive wheel is increased (or the torque command for the outer drive wheel is decreased) to cause the understeer. If so, a control method is proposed in which the torque command for the outer drive wheels is increased (or the torque command for the inner drive wheels is decreased). According to this method, the ability to smoothly execute acceleration / deceleration, turning, lane change, etc.
Unlike (four-wheel steering), it can be realized without a mechanism having a complicated structure, an electronic control system, and a hydraulic control system. However, this method still has room for improvement. That is, in this method, the torque command to each of the left and right driving wheels is determined so that the steer characteristic becomes a neutral steer, so that the turning locus of the vehicle becomes a locus of steady circular turning. Therefore, if you want to make a small turn when traveling at low speed,
In principle, I cannot answer.

The present invention has been made to solve the above problems, and in an electric vehicle with left and right drive wheels independently driven, steer characteristics to be realized can be set for each range division such as vehicle speed. By doing so, a first object is to be able to meet a request for turning with a small radius when traveling at a low speed, for example. A second object of the present invention is to make it possible to variably set the above-mentioned range division so as to meet a more precise request.

[0007]

In order to achieve such an object, the present invention provides a plurality of motors for individually driving the left and right drive wheels of an electric vehicle with a command relating to the output thereof (for example, In the drive control device for controlling the traveling of the vehicle by giving a command regarding the output torque), a command temporary confirmation means for temporarily confirming the command according to a request from the vehicle operator (for example, the depression amount of the accelerator pedal), A steer characteristic control setting means for setting a target steer characteristic in each range in which the vehicle can take a speed, a yaw rate or a lateral acceleration, and a steer characteristic of the vehicle is set with respect to the vehicle speed, yaw rate or lateral acceleration at the present time. So that the target steer characteristics are changed to
Steer characteristic control means for correcting the temporarily determined command according to the steering angle or the turning state of the vehicle to generate an output difference between the drive wheels.

In the present invention, the target steer characteristic is set by the steer characteristic control setting means. The target steer characteristic is set for each range in which the vehicle can adopt a speed, a yaw rate, or a lateral acceleration (the setting here includes not only manual setting but also automatic setting). For example, understeer is set at a low speed, and neutral steer is set at a high speed. The command provisionally determined by the command provisional determination means is corrected by the steer characteristic control setting means and given to the corresponding motor. The correction in the steering characteristic control means is performed by generating an output difference between the driving wheels,
This is a correction for changing the steer characteristic of the vehicle to the target steer characteristic that is set regarding the vehicle speed, yaw rate, or lateral acceleration at the present time. Therefore, according to the present invention, it is possible to meet the detailed request that the vehicle should turn with a smaller radius only when the vehicle speed is low. Further, when the correction in the steering characteristic control means is performed according to the steering angle, the advantage of the target yaw rate adaptive control proposed by the applicant of the present application in Japanese Patent Application No. 9-8693, for example, it can be more appropriately dealt with by the rotation of the vehicle. You can also enjoy the advantages such as. Further, the correction in the steering characteristic control means is performed by correcting the turning state of the vehicle (lateral acceleration,
When performed according to the slip angle, the yaw rate, or the combination thereof, the advantages of the state feedback control proposed by the applicant of the present application in Japanese Patent Application No. 9-68571, for example, excessive or small steering angle, disturbance or control received after steering, You can also enjoy the advantages of being less susceptible to system delays.

Further, it is preferable to provide a reference value setting means for variably setting the reference value for dividing the above range (the setting here includes not only manual setting but also automatic setting).
In such a case, the range classification for switching the target steer characteristic can be variably set, so that a more precise request can be met.

More preferably, one of the means for determining whether or not the vehicle is slipping, and the means for determining whether or not the vehicle is turning based on the result of detecting the steering angle is provided. When it is determined that the drive wheels are slipping, the TRC / ABS equivalent control means is used. When it is determined that neither drive wheel is slipping and the vehicle is turning, the steer characteristic control means is used. When it is determined that neither of the driving wheels is slipping and the vehicle is not turning, the means for giving the temporarily determined command to the corresponding motor without correction and determining that at least the vehicle is slipping TRC / ABS for time-varying the above-mentioned command relating to the driven wheel according to a predetermined rule
And corresponding control means. That is, when it can be considered that neither of the driving wheels is slipping and the vehicle is not turning, the tentatively determined command is set, and when any of the driving wheels is slipping, the TRC / ABS equivalent control (JP-A-8- No. 182119, Japanese Patent Application No. 9-8693, etc.), the command corrected by the steer characteristic control means when none of the driving wheels slip and the vehicle is turning, Given to the corresponding motor.
As a result, a vehicle that is strong on low μ roads and has excellent running stability can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the following description, the principles and effects of the target yaw rate adaptation control and the state feedback control are omitted, but regarding these, Japanese Patent Application Nos. 9-8693 and 9-68571
See the description in the issue. Further, although an embodiment relating to a four-wheel drive type pure electric vehicle will be described, the present invention can be applied to, for example, a two-wheel drive type vehicle, a so-called hybrid vehicle and the like. Further, the present invention is applicable not only to the wheel-in motor type, but also to all left and right drive wheel independent drive type electric vehicles. Furthermore, the present invention can be implemented in either hardware or software.

(1) System Configuration FIG. 1 shows the system configuration of an electric vehicle suitable for implementing the present invention. This electric vehicle is a wheel-in motor type four-wheel drive vehicle, and all of the driving wheels are right front wheel 10FR, left front wheel 10FL, right rear wheel 10RR, and left rear wheel 10RL.
R, 12FL, 12RR or 12RL are incorporated. In the reference numerals used in the following description, those suffixed with FR or fr are members, numerical values or characteristics related to or corresponding to the right front wheel 10FR, and those suffixed with FL or fl are left. A member, numerical value, or characteristic associated with or corresponding to the front wheel 10FL and having RR or rr at the end is a member, numerical value, or characteristic associated with or corresponding to the right rear wheel 10RR, having RL or rl at the end. The parts shown in the figure represent members, numerical values or characteristics associated with or corresponding to the left rear wheel 10RL. Similarly, a suffix F or f indicates a numerical value or characteristic associated with the front wheels 10FR and 10FL, and a suffix R or r indicates a rear wheel 1.
Numerical values or characteristics associated with 0RR and 10RL are shown, respectively. Further, for simplification of description, subscripts indicating front, rear, left, and right of wheels are omitted, and "drive wheels 10FR, 10FL, 10FL
The place that should be described as "RR and 10RL" is simply "driving wheel 1"
Sometimes referred to as "0". Regarding this omission, the same applies to other member names. Further, with respect to the reference numeral 10, depending on the context, it is also referred to as a drive wheel or a wheel.

FIG. 2 shows an example of how to install the right rear wheel 10RR as an example. In this figure, the rotor 18 is fixed to the inside of the wheel 16 so that it can rotate integrally with the tire 14, while the stator 2 is attached to the rear axle 22 via the motor shaft 20.
4 is fixed, and the stator 24 is joined to the rotor 18 via a bearing or the like. Further, a rotor magnet (permanent magnet) 26 is fixed to the inner wall surface of the rotor 18 so as to face the stator 24 with a small gap, while the stator 24
A stator winding 28 is wound around the
A cable 30 for passing a current through the motor 8 is connected to the stator winding 28 through the inside of the motor shaft 20. In such a structure, by supplying an alternating current to the stator winding 28 via the cable 30, the rotor 18 rotates and produces a propulsive force of the vehicle. In implementing the present invention, other types of structures may be used.

A battery 32 shown in FIG. 1 is a drive power supply source for each motor 12, and its discharge output is an inverter 34FR, 34FL, 34 which is a kind of power converter.
It is supplied to each motor 12 corresponding to the inverter 34 via RR and 34RL. Each inverter 34
Are motor control units 36FR, 36FL, 36RR and 3
Under control of the corresponding one of the 6RL, the battery 32
Is converted into a predetermined electric power format (three-phase alternating current in this figure) and supplied to the corresponding motor 12. The motor control unit 36 controls the inverter 34 corresponding to the corresponding one of the torque commands Tfr, Tfl, Trr, and Trl supplied from the vehicle control unit 38, thereby supplying the supplied torque command (Tfr, Tfl). , Trr
And corresponding to Tr1) is output from the corresponding motor 12. Motor control unit 36
In addition, the corresponding inverter 34 and vehicle control unit 38
It also has the function of insulating and separating between and. Further, the control of the inverter 34 by the motor control unit 36 is based on the detected value of each phase current of the corresponding motor 12 obtained from a current sensor (not shown), or the estimation of each phase current of the corresponding motor 12 obtained from the rotor angular position or the like. Based on the value.

The vehicle controller 38 controls the output torque of each motor 12, monitors and controls the state of each on-vehicle component,
It is a control member for informing the vehicle occupant of the vehicle state and other functions, and can be realized mainly by software modification of an electronic control unit (ECU) conventionally used. The vehicle control unit 38 uses outputs of sensors provided in each unit of the vehicle for motor output control and vehicle state monitoring.

For example, the wheel of each wheel 10 (1 in FIG. 2)
6) wheel speed sensors (for example, resolvers) 40
FR, 40FL, 40RR or 40RL are provided. These wheel speed sensors 40 generate signals indicating the wheel speeds Vfr, Vfl, Vrr, and Vrl of the corresponding wheels 10 (for example, pulse signals for each minute angular position displacement). Further, the accelerator sensor 42 outputs a signal indicating the depression amount of an accelerator pedal (not shown), that is, the accelerator opening VA,
The brake sensor 44 outputs a signal indicating the stepping amount of the brake pedal 56, that is, the braking force (stepping force) FB, and the shift position switch 46 uses the shift lever (not shown) closing range (and engine braking range, etc.) within the range. Of the shift lever position), that is, a signal indicating the shift position. Further, the steering angle sensor 48
Generates a signal indicating a steering angle δ that changes according to the operation of a steering wheel (not shown). Vehicle control unit 3
8, the yaw rate sensor 49a that generates a signal indicating the detected value γ of the yaw rate around the center of gravity of the vehicle, and the lateral acceleration sensor 49b that generates a signal indicating the detected value Gy of the lateral acceleration applied to the vehicle body. May be provided. In the figure, the symbol (•) means that it can be omitted depending on the control law or control procedure. The outputs of these sensors are converted into data in a format that can be processed by the vehicle control unit 38 upon being input to the vehicle control unit 38. The vehicle control unit 38 uses the converted data to determine the torque commands Tfr, Tfl, Trr, and Trl, execute control switching, and the like.

Further, in this embodiment, a reference speed setting switch 50 and a steering characteristic control setting switch 52 are provided. The reference speed setting switch 50 is, for example, as shown in FIG.
It is a switch for setting the vehicle speed, that is, the reference speed V ^* , which has the appearance as shown in FIG. In addition, the steering characteristic control setting switch 52
Is composed of a low speed range steering characteristic control setting switch 52a having an appearance as shown in FIG. 3 (b) and a high speed range steering characteristic control setting switch 52b having an appearance as shown in FIG. 3 (c). ing. The low speed steer characteristic control setting switch 52a is the reference speed setting switch 5
It is a switch for setting the target steer characteristic on the lower speed side than the reference speed V ^* set by the operation of 0, and the high speed steer characteristic control setting switch 52b is the reference speed V ^*.
* A switch for setting the target steer characteristic on the higher speed side. Low speed steering characteristic control setting switch 5
2a and the high speed region steer characteristic control setting switch 52b are
Both have understeer, neutral steer, and oversteer positions.
Any of these steer characteristics can be selected. The reference speed setting switch 50 and the steer characteristic control setting switch 52 are set when the manufactured vehicle is shipped or when the vehicle user maintains the vehicle. Further, the reference speed setting switch 50 and the steer characteristic control setting switch 52 can be configured so that the target steer characteristic can be set for each of three or more speed range divisions (in the following description, for simplification). , Two speed ranges, low speed and high speed are assumed).

Further, the vehicle shown in FIG. 1 uses both hydraulic braking and regenerative braking. That is, the brake pedal 56
When is depressed, the hydraulic pressure generated in the master cylinder 58 is correspondingly transmitted by the proportioning valve 59 to the front wheels 10FR and 10FL and the rear wheels 10RR and 10RL.
Wheel cylinder 60 of each wheel 10
It is transmitted to FR, 60FL, 60RR and 60RL.
The transmitted hydraulic pressure corresponds to brake wheels 62FR, 62FL, 62RR and 62R corresponding to the wheel cylinder 60.
It acts on L and a braking torque by hydraulic pressure is applied to each wheel 10. On the other hand, the braking force detected by using the brake sensor 44 (for example, the hydraulic pressure of the master cylinder 58) FB
In response to the torque command T belonging to the regeneration region
It outputs fr, Tfl, Trr and Trl. Therefore,
As shown in FIG. 4, the braking force distribution in the vehicle of FIG. 1 is such that the front wheels (front) 10FR and 10FL and the rear wheels (rear) 10RR and 10RL are increased with an increase in the braking force FB (“brake pedal depression force” on the horizontal axis). Therefore, the hydraulic regeneration is increased. As described above, since the hydraulic system and the regenerative system are separated after the brake sensor 44, even if one of the hydraulic pressure and the regenerative power fails, the other can evacuate the vehicle. Moreover, since the hydraulic system has almost no hydraulic shutoff / control mechanism such as valves and pumps and an electric system for driving and controlling the hydraulic shutoff / control mechanism, for example, a system that shuts off hydraulic pressure during regenerative power generation or a conventional engine. The system configuration is simpler than that of a system equipped with the same TRC / ABS function as a car. One of the reasons why it is not necessary to provide the hydraulic system with a mechanism such as a valve or a pump or an electric system for driving and controlling the same is that the output torque of each motor 12 is individually controlled as described later to stabilize traveling. The characteristic configuration of this embodiment is that sex control is performed.

(2) Operation of Vehicle Control Section (2.1) Overall Operation FIG. 5 shows an outline of the operation of the vehicle control section 38 in this embodiment. As shown in this figure, the vehicle control unit 38 first receives signals from various parts of the vehicle, such as the accelerator opening degree VA, the braking force FB, the shift position, the wheel speeds Vfr, Vfl, and the like.
Input signals indicating Vrr and Vrl, steering angle δ, etc. (1
00). The vehicle control unit 38 receives the input signal, particularly the wheel speed V.
A vehicle speed V is obtained by using fr, Vfl, Vrr, and Vrl.
Is calculated (200). The vehicle control unit 38 controls the accelerator opening degree VA, the braking force FB, the shift position, and the vehicle body speed V.
Torque command Tfr, Tfl, Trr and T
The rl is provisionally confirmed (300). The vehicle control unit 38 uses the information such as the steering angle δ and also determines the reference speed setting switch 5
The torque commands Tfr, Tfl, Trr, and Trl are determined by referring to 0 or the setting of the steering characteristic control setting switch 52 (400). The vehicle control unit 38 stores the determined torque commands Tfr, Tfl, Trr, and Trl and supplies them to the corresponding motor control unit (500). The vehicle control unit 38 repeatedly executes the above procedure at a predetermined frequency.

(2.2) Vehicle speed calculation In the routine 200 for calculating the vehicle speed V (see FIG. 6), the vehicle control unit 38 first

[Formula 1] Nslip0 ← Nslip Nslip ← 0 is processed (202). The variable Nslip is a variable for counting the number of the four drive wheels 10 that can be regarded as slipping (slip wheels), and Step 2
By executing 02, the numerical value previously stored in the variable Nslip, that is, the number of slip wheels when the routine 200 is executed last time is stored in the variable Nslip0, and at the same time, the variable Nslip is reset for the subsequent processing. .

Next, the vehicle control unit 38 determines whether or not each drive wheel 10 is slipping (204, 214) (206). As a slip determination method, here, the angular acceleration dω / dt (or acceleration) of each drive wheel 10 is calculated, and the calculated angular acceleration dω / dt (or acceleration) is calculated.
The driving wheel 10 that exceeds a predetermined threshold is regarded as slipping is used. The angular acceleration dω / dt is obtained by detecting how much the corresponding one of the wheel speeds Vfr, Vfl, Vrr, and Vrl input in step 100 has changed from the previous time, and the angular acceleration dω / dt is calculated from the speed change dimension to the angular acceleration dimension. Obtained by converting to units. Note that the slip-related determination may be performed by another method. The vehicle control unit 38 stores the wheel speed of the drive wheel 10 (non-slip wheel) when it is determined that the vehicle is not slipping (208), and specifies the drive wheel 10 (slip wheel) when it is determined that the vehicle is slipping. The information is stored (212) and the variable Nslip is incremented by 1 (210).

When the processes up to step 214 are completed, the vehicle control unit 38 determines whether the number Nslip of slip wheels corresponds to 0, 1 to 3, or 4 (21).
6). When the number Nslip of slip wheels is 0, the vehicle control unit 38 uses the information stored in step 208,

## EQU2 ## The calculation of V = (Vfr + Vfl + Vrr + Vrl) / 4 is performed (218). Number of slip wheels Nslip
Is 1 to 3, the vehicle control unit 38 uses the information stored in steps 210 and 212,

## EQU00003 ## V = sum (Vfr, Vfl, Vrr, Vr
l) / (4-Nslip) where sum (•): sum of wheel speeds of non-slip wheels among the wheel speeds as arguments is calculated (220). And the number of slip wheels N
When the slip is 4, the vehicle control unit 38 has the drive wheel 10 that finally reaches the condition of dω / dt> threshold just before the condition of dω / dt> threshold. The wheel speed is set to the vehicle speed V (224). Step 22
The value of the vehicle body speed V at 4 is maintained while the condition of Nslip = 4 is satisfied (222, 226).

The vehicle controller 38 then

[Equation 4] N ← V · 60 / (2πR) where R (m): radius of driving wheel V is (m / sec) and N is (rpm). V is converted to the number of revolutions N (228). The rotation speed N obtained here is not an actual rotation speed of the drive wheels 10 and the motor 12, but a so-called virtual rotation speed corresponding to the vehicle body speed V.

(2.3) The rotational speed N determined by the torque command provisionally determined vehicle speed calculation routine 200 is
It is used in the routine 300 (FIG. 7) for temporarily determining the torque commands Tfr, Tfl, Trr, and Trl. That is, in the torque command temporary confirmation routine 300, the vehicle control unit 38 uses one of the powering time map 1000 (FIG. 8A) and the regeneration time map 1002 (FIG. 8B) to calculate the vehicle speed calculation routine 200. The rotation speed N obtained in step 1 is referred to as a key, and thereby the torque commands Tfr, Tfl, Trr, and Trl for each drive wheel 10 are provisionally determined.
The powering time map 1000 is a map that associates the rotation speed N with the maximum torque Tmax of the motor, and the regeneration map 1002 is a map that associates the rotation speed N with the minimum torque Tmin of the motor. Maximum torque Tma here
x is the maximum power running torque that each motor 12 can output, and the minimum torque Tmin is the maximum absolute value regenerative torque that each motor 12 can output. Since both are values determined by the performance of the motor 12, when the performance of each motor 12 with respect to the rotation speed N (not the performance of the motor 12 with respect to the rotation speed of the motor 12) is different from each other, each of the motors 12 has a different value. These maps 1000 and 1002 are provided individually. Here, for simplicity of explanation,
It is assumed that the four motors 12 have the same performance with respect to the rotation speed N.

The vehicle control unit 38 uses the maps 1000 and 1
In order to determine which of 002 is to be referred to, it is determined based on the output of the accelerator sensor 42 whether or not the accelerator pedal is currently depressed (whether or not the accelerator is on) (302). The vehicle control unit 38 displays the powering time map 1000 (304) when the accelerator is on and, conversely, displays the regeneration time map 1002 (30) when the accelerator is off.
6), refer to. As a result, the maximum torque Tmax or the minimum torque Tmin associated with the current rotational speed N on the powering time map 1000 or the regeneration time map 1002 is obtained. The vehicle control unit 38 tentatively determines the torque commands Tfr, Tfl, Trr, and Trl for each motor 12 with a certain common torque value by apportioning the obtained torque.

For example, in step 304, the vehicle control unit 38 multiplies the maximum torque Tmax obtained by referring to the power running map 1000 by the proportion ratio a (%) obtained from the accelerator opening degree VA. Torque command Tfr,
Tfl, Trr, and Trl are provisionally determined. Further, in step 306, the torque command Tf is obtained by multiplying the minimum torque Tmin obtained by referring to the regenerative map 1002 by the proportion ratio b (%) obtained from the braking force FB.
R, Tfl, Trr, and Trl are provisionally determined.

As is apparent from FIGS. 8 (a) and 8 (b), at the stage of provisional confirmation, if the accelerator is on, only the power running region (the region where the rotation speed> 0 and the torque> 0) is off. If there is a regeneration area (revolutions> 0 and torque ≤ 0)
Note that only one is used. TRC described later
In the equivalent control, the ABS equivalent control, and the steer characteristic control, the torque commands Tfr, Tfl, Trr, and Trl may take the value of the regenerative region even when the accelerator is on, and the torque commands of the powering region even when the accelerator is off. May take a value. Further, at the stage of temporary confirmation, the torque commands Tfr, Tf
l, Trr, and Trl are equal to each other, but TR
Note that this is not always the case when the C equivalent control, the ABS equivalent control, and the steer characteristic control are executed.
Further, although only the maximum torque Tmax and the minimum torque Tmin are mapped, a large number of torque curves may be mapped using the accelerator opening degree VA or the braking force FB as parameters. If such mapping is performed, the torque command T can be obtained by referring to the map with the pair of the accelerator opening degree VA or the braking force FB and the rotation speed N.
Since fr, Tfl, Trr, and Trl are obtained, it is not necessary to execute the pro rata processing. On the other hand, mapping only the rotational speed vs. maximum (or minimum) torque characteristics saves storage space for map retention.

(2.4) Torque Command Confirmation The torque command temporarily confirmed in the torque command temporary confirmation routine 300 determines the torque commands Tfr, Tfl, Trr, and Trl except when a specific condition is satisfied. In (Fig. 9), it is confirmed as it is (40
2), in step 500, each motor controller 36 is supplied. Torque commands Tfr, Tfl, Tr
When r and Trl are settled, the output of each motor 12, and thus the drive wheel 10, becomes a value according to the pedal operation or shift operation of the vehicle operator. On the contrary, when the following conditions are satisfied, the temporarily determined torque commands Tfr, Tfl,
Trr and Trl are corrected, and with the corrected torque commands Tfr, Tfl, Trr, and Trl,
Torque command T for each motor 12 and thus drive wheel 10
fr, Tfl, Trr and Trl are established.

Torque commands Tfr, Tfl, Trr and T
One of the cases in which rl is corrected is when the TRC equivalent control (600) or the ABS equivalent control (700) is executed. The TRC-equivalent control referred to here has a function corresponding to TRC (truction control) in a conventional engine vehicle, and has torque commands Tfr, Tfl, and T related to each motor 12.
This is a control method that is realized by adjusting and correcting rr and Trl, and thus without operating and controlling hydraulic pressure and fuel injection (see Japanese Patent Application Laid-Open No. 8-182119, Japanese Patent Application No. 9-8693, etc.). Further, the ABS-equivalent control referred to here has a function corresponding to an ABS (anti-lock break system) in a conventional engine vehicle, and a torque command Tfr related to each motor 12,
This is a control method realized by adjusting / correcting Tfl, Trr, and Trl, and thus without operating / controlling the hydraulic pressure (see Japanese Patent Application No. 9-8693). All of these controls are executed on condition that the number Nslip of slip wheels is not 0 (404). The TRC equivalent control is executed when the accelerator is on, and the ABS equivalent control is executed when the accelerator is off (406).

Further, even if the number Nslip of slip wheels is 0, if the steering angle δ is equal to or more than a predetermined threshold value, that is, if turning steering is in progress (408), the vehicle control unit 38 controls the steer characteristic. Is executed (800). Steer characteristic control is
The torque commands Tfr and Tf are set according to the settings of the reference speed setting switch 50 and the steering characteristic control setting switch 52.
This is a control method that corrects l, Trr, and Trl, and performs target control of the steer characteristic of the vehicle for each speed range (more generally, for each vehicle state), which is one of the features of the present invention.

These TRC equivalent control, ABS equivalent control and steer characteristic control have the characteristic of the left and right wheel independent drive type electric vehicle in which the torque commands Tfr, Tfl, Trr and Trl are individually applied to the respective motors 12. To obtain different output torque for each motor 12,
Have the common points. Therefore, any of these control methods can be applied not only to the wheel-in motor type, but also to left and right wheel independent drive type electric vehicles in general. Next, these procedures will be described.

(2.4.1) TRC equivalent control In the TRC equivalent control routine 600 (FIG. 10),
The vehicle control unit 38 (60
2, 626) The following processing is performed.

The vehicle control unit 38 first determines the wheel speed Vfr,
Vfl, Vrr, and Vrl are set to the rotational speeds Nfr and N, respectively.
Convert to fl, Nrr and Nrl (604). The conversion from the wheel speeds Vfr, Vfl, Vrr and Vrl (m / sec) to the rotational speeds Nfr, Nfl, Nrr and Nrl (rpm) is performed by multiplying the former by 60 / (2πR). The vehicle control unit 38 determines the rotation speed Nf obtained as a result.
Base rotation speed NB of r, Nfl, Nrr and Nrl
It is determined that those falling below the constant torque region on the torque characteristics are included, and those exceeding the above are determined to belong to the constant power region (606). The constant torque region is a region where the maximum torque Tmax and the minimum torque Tmin of the motor 12 are constant, and the constant power region is the maximum power running power (= Tmax × rotation speed) and the maximum regenerative power (= Tmin ×) of the motor 12. This is a region where the rotation speed) is constant. Further, the base rotation speed NB is the rotation speed at the boundary between the constant torque region and the constant power region.

The vehicle control unit 38 refers to different data on the coefficient determination map (powering) 1004 according to the result of the determination, thereby individually determining the constant group used for the subsequent processing for each drive wheel 10. (608, 610). As shown in FIG. 11, a coefficient determination map (powering) 1004
Is a constant group (1) in the power running side of the constant torque region.
, And the constant group (2) is associated with the power running side portion of the constant power region.
Rotational speed Nf corresponding to fr, Vfl, Vrr, and Vrl
Different constant groups are selected and determined depending on whether r, Nfl, Nrr, and Nrl belong to the constant torque region or the constant power region. The constant group mentioned here includes constants a1 to a3, b1 to b3, c1 to c3 and d1 to determine the thresholds THω1 to THω3.
d3 and constants A1, A2, B1, B2, C1, C2, D1 for determining the feedback gains G1 and G2.
And D2 and correction terms S1 and S2. The correction terms S1 and S2 may have the same value in the constant torque region and the constant power region.

The vehicle controller 38 uses the determined constant group to calculate the threshold values THω1 to THω3 and the feedback gains G1 and G2 for each drive wheel 10 (61).
2). The calculation formula is, for example,

[Equation 5] THω1 ← a1 × exp (b1 × VA + c1 ×
Wheel speed + d1 × VA × wheel speed) THω2 ← a2 × exp (b2 × VA + c2 × wheel speed +
d2 × VA × wheel speed) THω3 ← a3 × exp (b3 × VA + c3 × wheel speed +
d3 × VA × wheel speed) G1 ← A1 × exp (B1 × VA + C1 × wheel speed +
D1 × VA × wheel speed) G2 ← A2 × exp (B2 × VA + C2 × wheel speed +
D2 × VA × wheel speed). The wheel speeds Vfr, Vfl, Vrr and Vr
Instead of 1, the rotational speeds Nfr, Nfl, Nrr and Nrl may be used. Also, THω1>THω2>0> THω3
So that is always satisfied, the coefficient determination map (powering) 100
The contents of 4 are set.

The vehicle control unit 38 has an angular acceleration dω / dt (using the value obtained in step 206 or calculating again) for each drive wheel 10 that exceeds THω1, THω1 and below THω2, and THω2 and below THω3. , And THω3 or less, it is determined to which one of the four ranges it belongs (614). The vehicle control unit 38 executes any one of steps 616 to 622 according to the result. The processing executed in steps 616 to 622 is calculated by the following equation.

[Equation 6] Step 616: ΔT ← G1 · (dω / dt-S1) Step 618: ΔT ← 0 Step 620: ΔT ← G2 · (dω / dt-S2) Step 622: ΔT ← 0 Is an operation represented by.

The vehicle controller 38 proceeds to steps 616-62.
The torque commands Tfr, Tfl, Trr, and Trl are determined by subtracting the feedback torque ΔT determined for each drive wheel 10 in the process of 2 from the provisionally determined value (6
24). Thus, the angular acceleration dω / dt and the rotation speed N
Since the correction is performed by the feedback torque ΔT determined for each drive wheel 10 according to fr, Nfl, Nrr, and Nrl, the fixed torque commands Tfr, Tfl, Tr are determined.
The range that the values of r and Trl can take is the range shown by the diagonal lines in FIG. 12, that is, the range extending over both the power running region and the regeneration region.

The state where one of the drive wheels 10 is slipping (dω / dt exceeds the threshold value) usually continues for a certain period of time. During that period, the torque commands Tfr, Tfl, Trr according to the procedure described above are used.
And when Trl is corrected and confirmed, each motor 12
Output torque fluctuates over time with a predetermined regularity, and in the same way as TRC in a conventional vehicle,
All the driving wheels 10 are in a state of gripping the road surface. At that time, control of hydraulic pressure and fuel injection amount is unnecessary.

(2.4.2) ABS-equivalent control Next, ABS-equivalent control can be realized by substantially the same procedure as TRC-equivalent control. FIG. 13 shows a part of the ABS equivalent control routine 700 which is different from the TRC equivalent control routine 600. In FIG. 13, the vehicle control unit 38
For each drive wheel 10 (702) its wheel speed Vf
r, Vfl, Vrr, and Vrl are rotation speeds Nfr, Nf
The values are converted into l, Nrr, and Nrl (704), and the result belongs to the constant torque region for the driving wheel 10 whose base rotational speed NB is lower, and to the constant power region for the driving wheel 10 higher than the base rotational speed NB. It is judged that there is (706).
The vehicle control unit 38 refers to the coefficient determination map (regeneration) 1006 based on the result of this determination to determine the constant group used in the subsequent processing (708, 710). As shown in FIG. 14, the coefficient determination map (regeneration) 10
06 associates the constant group (3) with the part on the regeneration side in the constant torque region and the constant group (4) with the part on the regeneration side in the constant power region. Therefore, the wheel speed Vfr, Revolutions N corresponding to Vfl, Vrr and Vrl
Different constant groups are selected and determined depending on whether fr, Nfl, Nrr, and Nrl belong to the constant torque region or the constant power region. The constant group determined here is the same as the constant group determined in step 608 or 610 described above. However, the value is generally different from the value at the time of power running.

The vehicle control unit 38 uses the determined constant group to set thresholds THω1 to THω for each drive wheel 10.
3 and feedback gains G1 and G2 are calculated (712). The calculation formula is the accelerator opening V in the above-mentioned equation 5.
A formula in which A is replaced by the braking force FB may be used. The process executed by the vehicle control unit 38 thereafter is the same as the steps 614 to 626 in the TRC equivalent control routine 600. Therefore, the torque commands Tfr, Tfl, Trr, and Trl determined in the ABS-equivalent control are also TRC.
Torque commands Tfr, Tf determined in the equivalent control
Similar to l, Trr, and Trl, values in the range indicated by the diagonal lines in FIG. 12 can be taken. Further, since the time variation similarly occurs, by executing the ABS equivalent control, it is possible to recover the state in which all the driving wheels 10 grip the road surface in the same manner as the ABS in the conventional vehicle.

(2.4.3) Steer characteristic control In the steer characteristic control routine 800 (FIG. 15),
The vehicle control unit 38 first reads the reference speed V ^* set by the reference speed setting switch 50 and the target steer characteristic set by the steer characteristic control setting switch 52 (802), and calculates the vehicle speed calculation routine. The vehicle body speed V obtained at 200 is compared with the reference speed V ^* (804). When the vehicle body speed V is equal to or higher than the reference speed V ^* , the vehicle control unit 38 adopts the target steer characteristic set by the high speed range steer characteristic control setting switch 52b as the target steer characteristic (8
06), conversely, if the vehicle speed V is less than the reference speed V ^* ,
The target steer characteristic set by the low speed region steer characteristic control setting switch 52a is adopted as the target steer characteristic (808). As an example of setting the target steer characteristic,
As shown in the upper half of Table 1 below, there are oversteer settings in the low speed range and neutral steer settings in the high speed range.

[0042]

[Table 1] The vehicle control unit 38 then detects (or estimates) the current steer characteristic (900). The steer characteristic is detected by, for example, as shown in FIG. 16, a target yaw rate γ ^* or a target lateral acceleration G that is a target value of the yaw rate or the lateral acceleration.
y ^* is calculated (902), and the difference Eγ of the detected yaw rate value γ with respect to the target yaw rate γ ^* or the difference EGy of the detected lateral acceleration value Gy with respect to the target lateral acceleration Gy ^* is calculated (90).
4) If the calculated difference is sufficiently small (906), it is determined to be neutral steer (914). If the calculated difference is not so small and the product of the steering angle δ and the calculated difference is positive, oversteer is performed. It is determined to be present (910), and if not, it is determined to be understeer (912). Note that the left turning direction is positive with respect to the steering angle and the yaw rate.

After detecting (or estimating) the steer characteristic, the vehicle control unit 38 proceeds to step 8 as shown in FIG.
The target steer characteristic adopted in 06 or 808 is compared with the detected (or estimated) actual steer characteristic (81
0). If they match, the vehicle control unit 38 determines the torque commands Tfr, Tfl, Trr, and Trl using the temporarily determined values (812). If they do not match, the vehicle control unit 38 determines that the mode determination table 1008 has been set.
The steering mode change mode is determined with reference to (81
4).

As shown in FIG. 17, the mode decision table 1008 gives six possible ways of transition between the three types of steer characteristics of neutral steer, oversteer and understeer. For example, the change mode a in the figure is a mode in which the steer characteristic of the vehicle transits from oversteer to neutral steer, and the change mode c is a mode in which the steer characteristic of the vehicle transits from neutral steer to understeer. The process executed by the vehicle control unit 38 in step 814 is specifically based on the detected or estimated actual steer characteristic (for example, oversteer) and the adopted target steer characteristic (for example, neutral steer). This is a process of deciding a change mode (for example, a) necessary for changing the steer characteristic to the target steer characteristic. In addition, these three types of steering characteristics are expressed by the following equations.

## EQU7 ## Oversteer: δ × (γ−γ ^* )> 0, δ × (Gy−Gy ^* )> 0 Neutral steer: δ × (γ−γ ^* ) = 0, δ × (Gy−Gy ^* ) = 0 understeer: δ × (γ−γ ^* ) <0, δ × (Gy−Gy ^* ) <0, as shown in the actual yaw rate γ or the actual lateral acceleration Gy.
Is the standard value (value at neutral steer) γ ^* or G
It can be defined by whether or not the difference that it has with respect to y ^* has the same sign as the steering angle δ.

Before and after the above processing, the vehicle control unit 38 calculates and determines the friction coefficient μ of the road surface for each drive wheel 10 (900). For example, as shown in FIG. 18, a process of determining the friction coefficient μ by referring to the μ determination map 1010 using the angular acceleration dω / dt of each drive wheel 10 as a key (95
4), execute for all drive wheels 10 (952, 95)
6). The μ determination map 1010 is a map that associates the angular acceleration dω / dt with the friction coefficient μ, and has the content shown in FIG. 19, for example. Below, right front wheel 10F
R, left front wheel 10FL, right rear wheel 10RR and left rear wheel 10R
The friction coefficient μ of the road surface at L is μfr and μ
Represented by fl, μrr and μrl.

After that, the vehicle control unit 38 thereafter controls the torque command T.
A constant group used for correcting fr, Tfl, Trr, and Trl is determined by referring to the constant group table 1012 (8
16). As shown in the following Table 2, the constant group table 1012 is a combination of the accelerator on / off, the sign of the steering angle δ, that is, the turning steering direction, and the combination of the change mode determined in step 814 and the torque command Tfr, Constants Pfr, pf used to correct Tfl, Trr and Trl
r, qfr, Pfl, pfl, qfl, Prr, pr
r, qrr, Prl, prl and qrl in combination,
It is a table to be associated.

[0047]

[Table 2] The vehicle control unit 38 uses the following equation defined by the constant group determined in step 816.

## EQU8 ## kfr ← 1-Pfr × exp (pfr × | δ |
+ Qfr × μfr) kfl ← 1-Pfl × exp (pfl × | δ | + qfl
× μfl) krr ← 1-Prr × exp (prr × | δ | + qrr
× μrr) krl ← 1-Prl × exp (prl × | δ | + qrl
Xμrl), the steering angle δ and the friction coefficients μfr, μfl, μr
Correction factors kfr, kfl, krr based on r and μrl
And krl, and further

[Equation 9] Tfr ← Tfr × kfr Tfl ← Tfl × kfl Trr ← Trr × krr Trl ← Trl × krl By the torque commands Tfr, Tfl, Trr, and Trl,
Is corrected (818). The right side of Expression 8 is a function that gives the curved surface shown in FIG. 20, and using the correction coefficients kfr, kfl, krr, and krl determined according to this function, Expression 9 is used.
By executing the correction process shown in Fig. 21, the range of the values of the torque commands Tfr, Tfl, Trr, and Trl becomes the range of both the power running and the regeneration as shown by the shaded area in Fig. 21. Note that other types of functions may be used. That is, the correction coefficient calculation method shown in the equation 8 and FIG. 20 uses the torque commands Tfr and Tf according to the steering angle δ.
l, Trr, and Trl are different from each other, and a method of generating a moment M around the center of gravity of the vehicle, in other words, a method of applying target yaw rate matching control, is applied to the present invention by applying state feedback control as described later. In order to realize, for example, yaw rate γ,
Detection of lateral acceleration Gy, slip angle β and other vehicle state quantities
The correction coefficients kfr, kfl, krr, and krl are determined by a function using the feedback value as an independent variable.

The torque commands Tfr, Tfl, Trr, and Trl corrected in step 818 are fixed as they are (83) unless they include ones exceeding the maximum torque Tmax and ones below the minimum torque Tmin.
2. (See also FIG. 31 and Table 4). However, according to the equation (9), if the maximum torque Tmax is exceeded (820), the upper limit is limited by the maximum torque Tmax (822). The torque that cannot be realized due to this restriction, that is, the torque obtained by subtracting the maximum torque Tmax from the value immediately after the correction, is added to the torque command for the drive wheels on the same left and right sides (82).
4. (See also FIG. 32 and Table 5). Similarly, according to the equation (9), if the torque is lower than the minimum torque Tmin (826), the lower limit is limited by the minimum torque Tmin (828. See also FIG. 31 and Table 4). The torque that cannot be realized due to this restriction, that is, the torque obtained by subtracting the minimum torque Tmin from the value immediately after the correction, is added to the torque command related to the drive wheels on the left and right sides (830). (See also FIG. 32 and Table 5).

For example, if the torque command Tfr relating to the right front wheel 10FR exceeds the maximum torque Tmax, at step 822.

[Equation 10] δT ← Tfr−Tmax Tfr ← Tmax is processed. Since the driving wheel on the right side like the right front wheel 10FR is the right rear wheel 10RR, at step 824

## EQU11 ## The processing of Trr ← Trr + δT is performed. Note that the torque command Tr is
When the value of r exceeds the maximum torque Tmax, the limiting process relating to step 822 is performed on the torque command Trr this time. In this case, step 824 is omitted (not shown) to prevent endless repetition.

When such steer characteristic control is executed, the steer characteristic of the vehicle is controlled to the target steer characteristic set by the high speed range steer characteristic control setting switch 52b in the high speed range equal to or higher than the reference speed V ^* , In the low speed range below the reference speed V ^*, the low speed range steer characteristic control setting switch 52
The target steer characteristic set by a is controlled.
For example, when the settings shown in the upper half of Table 1 are made, the steer characteristic change mode is selected and decided as shown in the lower half of the table, and the steer characteristic change mode is selected according to the decided change mode. Torque commands Tfr, Tfl, Trr and Tr
Correction and confirmation of 1 are performed. Therefore, according to the present embodiment, it is possible to turn with the target steer characteristic set by the manufacturer or the user in each of the low speed region and the high speed region. In particular, if the target steer characteristic in the low speed range is oversteered as shown in Table 1, the turning radius of the vehicle in the low speed range can be reduced, and therefore, the turning stability can be improved without impairing the running stability of the vehicle. A vehicle can be realized.

(2.4.4) Principle of steer characteristic control Such an effect can be obtained as described below.
This is because the cornering powers Kf and Kr can be changed by appropriately correcting and determining the torques Tfr, Tfl, Trr, and Trl related to the drive wheels 10, and thereby the steer characteristics can be changed. For variables and constants that appear in the following description, see FIG. 22 showing the behavior of the vehicle body in the plane in which the vehicle turns, FIG. 23 showing the rotational movement of the wheels, and Table 3 that is a list of variables and constants. I want to be done.

[0052]

[Table 3] First, for a moving vehicle,

## EQU12 ## A lateral force represented by mGy = mV (dβ / dt + γ) acts. When the vehicle is turning, centrifugal force is applied to the vehicle.

Fc = m · V ² / ρ where ρ: turning radius acts. Therefore, when the vehicle is turning, the following relation derived from Eqs.

(14) dβ / dt + γ = V / ρ Holds.

In the so-called neutral steer state,

[Mathematical formula-see original document] Since dβ / dt = 0 dγ / dt = 0, if the vehicle body speed V is constant, the turning radius ρ appearing in equation 14 becomes a constant (hereinafter referred to as ρ0), and the following equation

[Mathematical formula-see original document] [rho] 0 = V / [gamma] 0 where [gamma] 0 is a value represented by the yaw rate during neutral steering. That is, at this time, the vehicle turns with a constant radius ρ0 (steady circle turn).

On the other hand, in this embodiment, the torque commands Tfr, Tfl, and Tfl are individually supplied to the motors 12 associated with the drive wheels 10.
Trr and Trl are applied to generate a moment M around the vehicle body weight center G (see FIG. 24). Therefore, assuming that there is no difference in the cornering forces acting on the left and right wheels, the motion around the center of gravity G of the vehicle body is expressed by the following equation including the moment M:

[Expression 17] I · dγ / dt = 2 · (Lf · F′yf + Lr · F′yr) + M where F′yf = F′yfr + F′yfl = −Kf · {β + (Lf / V) · γ−δ } F′yr = F′yrr + F′yrl = −Kr · {β + (Lr / V) · γ} The following equations obtained by modifying the equations 12 and 17

[Expression 18] dβ / dt = K11 · β + K12 · γ + K1
3 ・ δ + K14 ・ M dγ / dt = K21 ・ β + K22 ・ γ + K23 ・ δ + K
24 · M However, K11 = −2 · (Kf + Kr) / (m · V) K12 = −1-2 · (Lf · Kf−Lr · Kr) / (m
^{· V 2) K13 = 2 ·} Kf / (m · V) K14 = 0 K21 = -2 · (Lf · Kf-Lr · Kr) / I K22 = -2 · (Lf 2 · Kf-Lr 2 · Kr) / (I
V) K23 = 2 · Lf · Kf / I K24 = 1 / I gives the torque commands Tfr, Tfl, Trr, and Trl to the motor 12 of each drive wheel 10 individually, thereby generating the moment M. It is an equation showing the behavior of the vehicle body when.

When the steer characteristic is set to the neutral steer without generating the moment M, the following equation is obtained from the equations (15) and (18).

[Formula 19] K11 ・ β + K12 ・ γ + K13 ・ δ = 0 K21 ・ β + K22 ・ γ + K23 ・ δ = 0 Is obtained. Solving this equation for yaw rate γ,

[Formula 20] γ = 1 / (1 + A · V ² ) · (V / L) · δ where A: Stability factor = −m / V ² · (Lf
-Kf-Lr-Kr) / (Kf-Kr). From this equation and Equation 16 already derived, the turning radius ρ0 during steady circle turning is

It can be seen that ρ0 = (1 + A · V ² ) · L / δ. In particular, it should be noted that the stability factor A appears on the right side of Expression 21, and the sign of the stability factor A depends on the index values Lf · Kf−Lr · Kr. That is, the steering angle δ is constant (= δ
0 = 1 / ρ0),

Lf · Kf−Lr · Kr <0 ... Understeer Lf · Kf−Lr · Kr = 0 ... Neutral steer Lf · Kf−Lr · Kr> 0 ... Oversteer (see FIG. 25). The turning radius ρ when the steering is not in neutral steering depends on the vehicle speed V (see FIG. 26). The characteristics of the suspension are ignored here.

Thus, the index value L that influences the steering characteristic
f · Kf−Lr · Kr is determined by the wheel bases Lf and Lr and the cornering powers Kf and Kr. Since the wheel bases Lf and Lr are constant, if the cornering powers Kf and Kr can be changed as desired, the steer characteristic of the vehicle can be controlled. The steer characteristic control according to the present embodiment is performed according to whether the vehicle speed V is high or low (more generally, according to the magnitude of the physical quantity indicating the running state of the vehicle or the height thereof), and the current steer characteristic and the target steer characteristic. This is a method of controlling the steer characteristic so as to obtain the target steer characteristic by changing the cornering powers Kf and Kr according to the difference.

First, the moment M about the vehicle body weight center G is
The following formula

(23) M = Td / 2 · (Fxfr−Fxfl + Fx
rr-Fxrl), the longitudinal force Fxfr acting on each drive wheel 10,
Determined by Fxfl, Fxrr and Fxrl. Further, as is clear from this equation, the longitudinal force Fxfr acting on the right front wheel 10FR and the longitudinal force Fxfl acting on the left front wheel 10FL.
Is equal and the front-rear force Fxrr acting on the right rear wheel 10RR and the front-rear force Fxrl acting on the left rear wheel 10RL are equal, the moment M becomes zero. Furthermore,

(24) It · dωfr / dt = Tfr−Fxfr ·
R = Tfr-μ · mt · R It · dωfl / dt = Tfl-Fxfl · R = Tfl
−μ · mt · R It · dωrr / dt = Trr −Fxrr · R = Trr
−μ · mt · R It · dωrl / dt = Trl−Fxrl · R = Trl
Since −μ · mt · R,

## EQU25 ## dωfr / dt = 0 dωfl / dt = 0 dωrr / dt = 0 dωrl / dt = 0 If

[Equation 26] M = (Tfr-Tfl + Trr-Trl)
It is Td / (2 · R).

Therefore, as shown in FIG. 27, torque commands Tfr and Tf that are equal to each other for each drive wheel 10 are obtained.
When 1, l, Trr, and Trl are given, each drive wheel 10
Are equal to each other in the longitudinal force Fxfr, Fxfl, Fxrr
And Fxrl work, the moment M becomes zero. 27 (and FIG. 28), F is the propulsive force of the vehicle, βr
And βf are the slip angles of the rear wheel and the front wheel, respectively. Further, in the description of the present application, the torque commands Tfr, Tfl, T
It is assumed that rr and Trl are realized exactly.

On the contrary, as shown in FIG. 28, the torque commands Tfr and Tf which are not equal to each other for each drive wheel 10 are provided.
When 1, l, Trr, and Trl are given, each drive wheel 10
Longitudinal force Fxfr, Fxfl, Fxrr and Fxr
Moments M are generated because l are generally not equal to each other. When the longitudinal forces Fxfr, Fxfl, Fxrr, and Fxrl change, the lateral forces Fyfr, Fyfl, Fy.
rr and Fyrl also occur or change, so their magnitude is

F'y = Fy · cos β−Fx · sin β where Fx: longitudinal force Fy: lateral force β: cornering force F'yfr, F'y given by slip angle
fl, F'yrr and F'yrl (if no slip occurs, the direction is orthogonal to the direction (travel direction) of each wheel), and the slip angle β appearing in this equation
(Difference between the traveling direction of each wheel and the traveling direction of the vehicle) also changes.

That is, the slip angle β, longitudinal force Fx, lateral force Fy
29 and the cornering force F'y.
Where there is a relationship as shown in, for example, a drive wheel 1
With respect to 0, when the longitudinal force Fx is increased (change from the "longitudinal force" of the solid line in Fig. 30 to the "longitudinal force (control)" of the broken line, the characteristics of the lateral force Fy and the cornering force F'y are correspondingly increased. Changes from a solid line to a broken line, the operating point indicated by a white circle in the figure changes as shown by ← in the figure, and as a result, the slip angle β also decreases.

As shown in FIG. 28, when the torque command for the outer (right side when turning left, left side when turning right) drive torque 10 is set smaller than the torque command for the inner drive wheel 10, it is shown in FIG. As described above, the cornering force F'y decreases, and the cornering power also decreases accordingly. For example, when Trr> Trl, the cornering power Kr of the rear wheels decreases,
Lf · Kf−Lr · Kr, which is the amount that determines the steer characteristic
Also decreases. That is, switching from understeer to neutral steer or oversteer or from neutral steer to oversteer is realized. On the contrary, when the torque command for the inner drive wheel 10 is set smaller than the torque command for the outer drive wheel 10, FIG.
Contrary to this, the cornering force F'y increases, and the cornering power also increases accordingly. For example, Trr
When <Trl is set, the cornering power Kr increases and Lf · Kf−Lr · Kr also increases. That is, switching from oversteer to neutral steer or understeer or from neutral steer to understeer is realized.

In the present embodiment, since the cornering powers Kf and Kr are changed, the steering angles δ are assigned to the torque commands Tfr, Tfl, Trr, and Trl for each drive wheel 10.
To generate different torques,
As a result, a moment M corresponding to the steering angle δ is generated,
Is adopted. This is an application of the target yaw rate adaptive control proposed by the applicant of the present application in Japanese Patent Application No. 9-8693. That is, the torque commands Tfr, Tfl, Trr, and Trl relating to each drive wheel 10 are subjected to increase / decrease correction according to the logics shown in Tables 4 and 5, thereby generating the moment M around the vehicle body weight center G, and the steer characteristic. Target control is performed (FIG. 31). Further, in the present embodiment, when the torque command for a certain drive wheel is about to exceed the limit value of the maximum value Tmax or the minimum value Tmin due to the increase / decrease correction, the drive wheel on the left and right sides of the certain drive wheel are The torque command increase / decrease correction is performed so that the target control of the steer characteristic is not hindered by the limit value of the output torque (FIG. 32. FIG. 15).
, Steps 820-830). By such control, in the present embodiment, improvement of energy efficiency at the time of turning, securing of traveling stability, and facilitation of maneuver (reduction of frequency of operation of accelerator and brake) are realized. In addition, it is economical because the number of sensors used at that time is small.

[0063]

[Table 4]

[Table 5] (3) Modifications The above-described embodiment can be modified in various ways.
First, in the above embodiment, the reference speed V ^* for dividing the low speed region / high speed region was given by the reference speed setting switch 50, but as shown in FIG.
Instead of 0, a reference yaw rate setting switch 50A may be provided to give the reference yaw rate γs ^* . In such a case, the steps 802 to 808 in the steering characteristic control routine 800 are modified as steps 802A to 808A shown in FIG. 34, and the comparison judgment of the yaw rate γ with the reference yaw rate γs ^* and the result thereof are performed. The target steer characteristic is set based on. In addition, the steering characteristic control setting switch 52 is set in a region where the yaw rate γ is small /
Used to set the target steer characteristic for each large area. Similarly, as shown in FIG. 35, the reference lateral acceleration setting switch 5 is used instead of the reference speed setting switch 50.
0B may be provided to provide the reference lateral acceleration Gys ^* . In this case, the steering characteristic control routine 8
The steps 802 to 808 in 00 are modified as steps 802B to 808B shown in FIG. 36 so that the lateral acceleration Gy is compared with the reference lateral acceleration Gys ^* and the target steer characteristic is set based on the result. To do. Also,
The steer characteristic control setting switch 52 is used to set the target steer characteristic for each of the region where the lateral acceleration Gy is small and the region where the lateral acceleration Gy is large.

Further, as shown in FIG. 37, the reference speed setting switch 50 and the reference yaw rate setting switch 50
A, the reference lateral acceleration setting switch 50B and the steer characteristic control setting switch 52 can be eliminated. That is, as shown in FIG. 38, the steering characteristic control routine 800
Steps 802-808 in steps 801 and 80
Replace with 2C-808C. In steps 801 and 802C, the detection value (V, γ or Gy) corresponding to the previous reference value (V ^* , γs ^* or Gys ^* ) on the travel history / reference value memory 1014 provided in the vehicle control unit 38 is set. Use and update sequentially. In step 802C, the target steer characteristics above and below the reference value are displayed as the running history / reference value memory 10
It is determined from the traveling history (history of the vehicle body speed V, the yaw rate γ, the lateral acceleration Gy, etc.) that is separately written on the controller 14. In steps 804C to 808C, the same processing as that of the above-described embodiment or its modification is executed by using the updated reference value. In this way, by automatically setting the target steer characteristic and its setting range or reference value, the above-mentioned reference value for switching the target of the steer characteristic can be adapted to the habit of the vehicle operator.

Further, the steering characteristic detection routine 900 is
If it is modified as shown in FIG. 39, the yaw rate sensor 49a and the lateral acceleration sensor 49b can be omitted. In FIG. 39, the vehicle control unit 38 obtains the time derivative dδ / dt of the steering angle δ obtained by the steering angle sensor 48 (916), and if this time derivative dδ / dt is sufficiently small, the current steer characteristic is obtained. Is almost in line with the operator's wishes (91
8). On the contrary, when the time derivative dδ / dt is not sufficiently small (918), if the steering angle δ and the time derivative dδ / dt have the same sign (920), there is a tendency to understeer the driver's wish (for example, oversteer). It is determined that the steering characteristic is a neutral steering characteristic (neutral steering or understeering) (922), and if the sign is different, it is determined that the steering characteristic is oversteering (922). Vehicle control unit 3
8 uses the result of the above processing to perform the above step 81.
Execute 0.

Further, instead of the constant group table 1012 described above, a correction coefficient k relating to different combinations of P, p and q is associated with the absolute value of steering angle | δ | and the road surface friction coefficient μ.
Number of constant group maps 1016-1 to 1016-n (n: 2
The above natural number) may be provided. In that case, the steering characteristic control routine 800 is modified according to FIG. 40, and instead of step 816, the constant group maps 1016-1 to 1016-1.
Step 816A of selectively referencing 1016-n is provided.

Further, the above-mentioned embodiment is an embodiment to which the target yaw rate matching control is applied, but the present invention is applied to the state feedback control proposed by the applicant of the present application in Japanese Patent Application No. 9-68571. It can be carried out. For example, the yaw rate sensor 49a and the lateral acceleration sensor 49b
Yaw rate detection value γ and lateral acceleration detection value Gy
According to the torque commands Tfr, Tfl,
Trr and Trl are corrected to generate different torques for each drive wheel 10, thereby generating a moment M about the center of gravity G of the vehicle, and cornering powers Kf and Kr.
It is also possible to adopt a control law of changing the. Alternatively, the yaw rate detection value γ and the following equation

[Equation 28] In accordance with β = ∫ (Gy / V−γ) dt, the yaw rate detection value γ, the lateral acceleration detection value Gy, and the slip angle β obtained from the vehicle speed V
The torque commands Tfr, Tfl, Trr, and Trl according to the above are corrected to generate different torques for each drive wheel 10,
As a result, a control law of generating a moment M around the vehicle body weight center G and changing the cornering powers Kf and Kr can also be adopted.

[0068]

As described above, according to the present invention,
Targets are set for each range of speed, yaw rate, or lateral acceleration that can be taken by the vehicle by generating an output difference between the drive wheels by correcting the temporarily determined command in response to the request from the vehicle operator. Since the steer characteristic of the vehicle is changed to the steer characteristic, various vehicle behaviors can be realized by setting the target steer characteristic to be realized. For example, at a low speed, it is possible to meet a small request such as turning with a smaller radius. Further, since the above-described correction is performed according to the steering angle or the turning state of the vehicle, the advantages of the target yaw rate matching control or the state feedback control can be enjoyed together. In addition, when the reference value setting means is provided, the range division for switching the target steer characteristic can be variably set, so that a more precise request can be met. Furthermore, TR
C / ABS equivalent control means is provided, and when any of the drive wheels slips, the torque command corrected by the TRC / ABS equivalent control means does not slip on any of the drive wheels and the vehicle is turning. When the control is switched such that the torque command corrected by the steer characteristic control means at a certain time, a vehicle that is strong on a low μ road and has excellent running stability regardless of whether the vehicle is going straight or turning is obtained. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration in the case where the present invention is applied to a four-wheel drive wheel-in motor type electric vehicle and a steer characteristic control target can be switched according to a vehicle speed range range. .

FIG. 2 is a cross-sectional view showing an example structure of a wheel-in motor.

FIG. 3 (a) shows an external view of a reference speed setting switch.
(B) shows the appearance of the low speed steering characteristic control setting switch.
(C) is a figure which shows the external appearance of a high speed area steer characteristic control setting switch, respectively.

FIG. 4 is a characteristic diagram showing braking force distribution between front wheels (front) and rear wheels (rear), braking force distribution between hydraulic pressure and regeneration, and changes in various braking forces with respect to brake pedal depression force.

FIG. 5 is a flowchart showing the overall flow of the operation of the vehicle control unit.

FIG. 6 is a flowchart showing a flow of a vehicle body speed calculation routine.

FIG. 7 is a flowchart showing a flow of a torque command temporary confirmation routine.

FIG. 8 is a diagram conceptually showing a map used in a torque command temporary confirmation routine, in which (a) is a power running map,
(B) is a figure which respectively shows the map at the time of regeneration.

FIG. 9 is a flowchart showing the flow of a torque command determination routine.

FIG. 10 is a flowchart showing a flow of a TRC equivalent control routine.

FIG. 11 is a diagram conceptually showing a coefficient determination map used in a TRC equivalent control routine.

FIG. 12 is a rotational speed vs. torque characteristic diagram in which a range in which a torque command output when the TRC equivalent control or the ABS equivalent control is executed can be taken is indicated by diagonal lines.

FIG. 13 is a flowchart showing the flow of an ABS equivalent control routine.

FIG. 14 is a diagram conceptually showing a coefficient determination map used in the ABS equivalent control routine.

FIG. 15 is a flowchart showing a flow of a steer characteristic control routine in which different control targets can be set for each range range of the vehicle speed regarding the steer characteristic and target yaw rate adaptive control is applied.

FIG. 16 is a flowchart showing a flow of a steer characteristic detection routine using a detected value of a yaw rate or a lateral acceleration.

FIG. 17 is a diagram conceptually showing a mode determination table used in a steering characteristic control routine.

FIG. 18 is a flow chart showing a flow of a road surface friction coefficient calculation routine using a detected value of wheel angular acceleration.

FIG. 19 is a diagram conceptually showing a μ determination map used in a road surface friction coefficient calculation routine.

FIG. 20 is a graph showing a characteristic that a correction coefficient obtained by the steering characteristic control routine has with respect to the absolute value of the steering angle and the road surface friction coefficient when the steering characteristic control is performed by applying the target yaw rate adaptive control. It is a figure which shows notionally the constant group map used in a steering characteristic control routine.

FIG. 21 is a rotational speed vs. torque characteristic diagram in which a range in which a torque command output when the steer characteristic control is executed can be taken is indicated by diagonal lines.

FIG. 22 is a conceptual diagram showing various physical quantities relating to the longitudinal and lateral movements of the vehicle body on the plane in which the vehicle body turns.

FIG. 23 is a conceptual diagram showing various physical quantities related to rotational movement of a wheel on a plane in which the wheel rotates.

FIG. 24 is a conceptual diagram showing generation of a vehicle body center-of-gravity moment by outputting different torque commands for each drive wheel in a plane in which a vehicle body turns.

FIG. 25 is a conceptual diagram showing the relationship between the sign of the index values Lf · Kf−Lr · Kr and the steer characteristic and the change in the vehicle body turning radius due to the steer characteristic in the plane in which the vehicle body turns.

FIG. 26 is a diagram showing a change tendency of a vehicle body turning radius according to a change of a vehicle body speed, using the symbols of index values Lf · Kf−Lr · Kr as parameters.

FIG. 27 is a conceptual diagram showing the behavior of the vehicle body and the wheels when equal torques are generated for the respective drive wheels in the plane in which the vehicle body turns.

FIG. 28 is a conceptual diagram showing the behavior of the vehicle body and the wheels when unequal torques are generated for the respective drive wheels in the plane in which the vehicle body turns.

FIG. 29 is a diagram showing a relationship among a slip angle, a wheel longitudinal force, a wheel lateral force, and a cornering force.

FIG. 30 is an enlarged view of the horizontal axis of FIG.
In particular, the solid line shows the relationship between the slip angle, the wheel longitudinal force, the wheel lateral force and the cornering force when the same torque is generated for each drive wheel, and the broken line shows the outer drive wheel with a larger torque than the inner drive wheel. The relationship between the slip angle, the wheel longitudinal force, the wheel lateral force, and the cornering force when giving, the dashed-dotted line is a diagram showing the decrease in the slip angle and the cornering force when transitioning from the solid line state to the broken line state. is there.

FIG. 31 shows the behavior of the vehicle body when a torque larger than that of the inner drive wheel is applied to the outer drive wheel, and in particular, the behavior of the vehicle body when a torque command is increased / decreased only for each of the outer and inner wheels. It is a conceptual diagram shown in the plane which turns.

FIG. 32 shows the behavior of the vehicle body when a torque greater than that of the inner drive wheel is applied to the outer drive wheel, in particular, the behavior of the vehicle body when a torque command is increased / decreased for each of the outer and inner two wheels. It is a conceptual diagram shown in the plane which turns.

FIG. 33 is a block diagram showing a system configuration in a case where the present invention is applied to a four-wheel drive wheel-in motor type electric vehicle, and a steer characteristic control target can be switched according to a yaw rate range division.

FIG. 34 is a flowchart showing a flow of a steer characteristic control routine capable of setting different control targets for each yaw rate range division with respect to the steer characteristic, omitting an overlapping portion with FIG. 15.

FIG. 35 is a block diagram showing a system configuration in the case where the present invention is applied to a four-wheel drive wheel-in motor type electric vehicle and the control target of the steer characteristic can be switched according to the range division of the lateral acceleration. .

FIG. 36 is a flowchart showing a flow of a steer characteristic control routine capable of setting different control targets for respective lateral acceleration range divisions with respect to the steer characteristic, omitting an overlapping portion with FIG. 15.

FIG. 37 is a diagram showing a case where the present invention is applied to a four-wheel drive wheel-in motor type electric vehicle, and a steer characteristic control target can be switched according to a vehicle speed, yaw rate, or lateral acceleration range classification, and further steer characteristic control is performed. FIG. 3 is a block diagram showing a system configuration in the case where the boundaries of the range divisions for switching the target can be learned and updated.

FIG. 38 is a flow of a steer characteristic control routine in which different control targets can be set for each range category of vehicle speed, yaw rate, or lateral acceleration with respect to the steer characteristic, and the boundaries of the range categories for switching the control target of the steer characteristic can be learned and updated. FIG. 16 is a flowchart showing a part of FIG.

FIG. 39 is a flow chart showing the flow of a steer characteristic detection routine using the time derivative of the steering angle.

FIG. 40 is a flowchart showing a flow of a steer characteristic control routine to which target yaw rate adaptive control is applied, particularly a flow when a correction coefficient is mapped, omitting an overlapping part with FIG. 15.

[Explanation of symbols]

10FR, 10FL, 10RR, 10RL Drive wheels, 1
2FR, 12FL, 12RR, 12RL motor, 32
Battery, 34FR, 34FL, 34RR, 34RL
Inverter, 36FR, 36FL, 36RR, 36R
L motor control unit, 38 vehicle control unit, 40FR, 40
FL, 40RR, 40RL Wheel speed sensor, 42 Accelerator sensor, 44 Brake sensor, 46 Shift position switch, 48 Steering angle sensor, 49a Yaw rate sensor, 49b Lateral acceleration sensor, 50 Reference speed setting switch, 50A Reference yaw rate setting switch, 5
0B reference lateral acceleration setting switch, 52 steer characteristic control setting switch, 52a low speed steer characteristic control setting switch, 52b high speed steer characteristic control setting switch, 3
00 torque command temporary determination routine, 400 torque command determination routine, 600 TRC equivalent control routine, 70
0 ABS equivalent control routine, 800 steer characteristic control routine, 900 steer characteristic detection routine, 1008
Mode decision table, 1012 constant group table, 1
014 Running history / reference value memory 1016-1, 10
16-2, ..., 1016-n constant group map, Tfr, T
fl, Trr, Trl torque command, Tmax maximum torque, Tmin minimum torque, VA accelerator opening, F
B braking force, Vfr, Vfl, Vrr, Vrl wheel speed, V vehicle speed, V ^* reference speed, δ steering angle, γ yaw rate, γs ^* reference yaw rate, Gy lateral acceleration, G
ys ^* Reference lateral acceleration, P, p, q constant, k correction coefficient, G car body center of gravity, M moment, Fxfr, Fxf
l, Fxrr, Fxrl Wheel longitudinal force, Fyfr, Fy
fl, Fyrr, Fyrl Wheel lateral force, F'yfr,
F'yfl, F'yrr, F'yrl cornering force, β slip angle, Lf, Lr wheel base, K
f, Kr cornering power.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-176418 (JP, A) JP-A-2-262472 (JP, A) JP-A-7-298418 (JP, A) JP-A-6- 335115 (JP, A) JP 5-328542 (JP, A) JP 7-223526 (JP, A) JP 7-117645 (JP, A) JP 2-283555 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60L 15/00-15/38

Claims (7)

(57) [Claims] 1. A drive control device for controlling traveling of a vehicle by giving a command relating to the output to each of a plurality of motors for individually driving the left and right drive wheels of an electric vehicle, from a vehicle operator. Command temporary confirmation means for temporarily confirming the above command in accordance with the request of, and for each range in which the vehicle can adopt speed, yaw rate or lateral acceleration, steer characteristic control setting means for setting the target steer characteristic in that range, In order to change the steer characteristic of the vehicle to the target steer characteristic set for the vehicle speed, yaw rate, or lateral acceleration at the present time, each drive is performed by correcting the temporarily determined command according to the steering angle or the turning state of the vehicle. A drive control device, comprising: a steering characteristic control unit that generates an output difference between the wheels. 2. The drive control device according to claim 1, wherein
A drive control device comprising a reference value setting means for variably setting a reference value for dividing the range. 3. The drive control device according to claim 1 or 2.
The steer characteristic control setting means,
Characterized by being a means for manually setting a characteristic
Drive controller. 4. The drive control device according to claim 3,
The steer characteristic control setting means sets the target steer characteristic to
Characterized by means for manually setting each of the above ranges
Drive control device. 5. The drive control device according to any one of claims 1 to 4 , further comprising: a unit that determines whether or not a vehicle is slipping, and a steering angle that is detected based on a result of detecting a steering angle. Means for determining whether or not it is in the middle, and TRC /
When it is determined that the ABS equivalent control means has not slipped on any of the drive wheels and the vehicle is turning, the steering characteristic control means is operated so that none of the drive wheels slips. When it is determined that the vehicle is not turning, means for giving the temporarily determined command to the corresponding motor without correction, and at least the above command related to the drive wheel determined to be slipping are changed with time according to a predetermined rule. And a TRC / ABS-equivalent control means for controlling the drive control device. 6. The drive according to any one of claims 1 to 5.
In the control device, the steering characteristic control means is
In order to change the steer characteristic to the target steer characteristic,
Characterized by increasing or decreasing the above command according to the detection result of the steering angle
Drive control device. 7. The drive according to any one of claims 1 to 6.
In the control device, the electric vehicle is driven by a motor for each drive wheel.
It is a four-wheel drive vehicle equipped with a
Is given to the motor corresponding to the drive wheel
Drive control device.