JP2005193752A - Right-to-left independent drive type vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a right-to-left independent drive type vehicle to independently control the driving force of right and left wheels which is capable of obtaining the target yaw angle acceleration even when the required difference in the driving force of the right and left wheels is not realized because the possible range of the driving force difference of the right and left wheels is reduced. <P>SOLUTION: For the condition to achieve the target longitudinal acceleration A, driving devices 3FL and 3FR output the total target driving force Fa to right and left wheels 2FL and 2FR. Next, under this condition, in Step S10, the possible yaw angle acceleration Mm is operated by the driving force difference between the right and left wheels 2Fl and 2FR. In Step S13, the possible yaw angle acceleration Mm is subtracted from the target yaw angle acceleration to operate the shortage ΔM for the target yaw angle acceleration. In Step S14, the turning angle δm required for generating the shortage ΔM is operated. In Step S19, a turning angle control device 6 turns the right and left wheels 2FL and 2FR so as to obtain the target turning angle δ* which is the sum of the present actual steering angle δ and the required turning angle δm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for realizing a target yaw angular acceleration for a left and right independent drive type vehicle such as a left and right independent drive type electric vehicle in which left and right wheels are independently driven by drive sources such as individual motors. .

Conventionally, as an invention of an independently driven vehicle that controls the yaw angle of a vehicle body by independently driving left and right wheels with a drive source such as a drive motor and controlling the difference in driving force between the left and right wheels, for example, Patent Literature Those described in 1 are known. In the wheel independent drive type vehicle described in Patent Document 1, when the driver inputs a steering angle to the steering wheel with the intention of turning, the left and right drive wheels are steered based on the input steering angle. The target yaw rate is calculated from the turning angle and the vehicle speed, and if there is a difference (yaw rate noise) between the detected yaw rate and the target yaw rate, the difference in driving force between the left and right wheels is controlled so as to reduce the yaw rate noise. .
JP-A-5-91607

By the way, in a general vehicle, it is usual to increase or decrease the longitudinal acceleration of the vehicle body by the driver's accelerator pedal operation amount, and the same applies to the wheel independent drive type vehicle described in Patent Document 1.
However, in the conventional left and right independent drive type vehicle, when the driver increases the accelerator pedal, the target longitudinal acceleration increases, and the output of the drive motor approaches the upper limit value. Causes problems as described below. That is, since the driving force of the left and right wheels increases and approaches the upper limit value, it becomes impossible to control the motor output of one of the left and right drive motors beyond the upper limit value. Furthermore, since there must be no obstacle to achieving the target longitudinal acceleration, the total driving force of the left and right wheels must be secured, and the output of the other of the left and right drive motors can be greatly reduced. Disappear. As a result, the feasible range of left and right wheel driving force difference is reduced. This means that the controllable range of the yaw angle of the vehicle body is reduced, and there is a case where the target yaw angular acceleration is insufficient.

  Even if the required driving force difference between the left and right wheels cannot be realized because the output of the drive motor has reached the upper limit due to an increase in the amount of depression of the accelerator pedal or for other reasons, the present invention The purpose is to make it possible to achieve yaw angular acceleration.

For this purpose, the vehicle according to the present invention comprises a steering wheel that is steered based on a steering operation and at least one pair of left and right drive wheels, as described in claim 1, and the left and right drive so as to achieve a target longitudinal acceleration. Means for controlling the sum of the driving forces of the wheels and calculating a difference between the driving forces of the left and right driving wheels necessary to achieve the target yaw angular acceleration, and driving the left and right driving wheels based on the calculated driving force difference The basic premise is to control the force independently.
Further, wheel steering means for controlling the steering angle of the steered wheels separately from the steering operation is provided, and drive force control based on the drive force difference between the left and right drive wheels is insufficient with respect to the target yaw angular acceleration. In this case, the target yaw angular acceleration is realized by turning the steered wheels by turning angle control of the wheel turning means.

  According to such a configuration of the present invention, the output of the left and right wheel drive motors approaches the upper limit as the driver depresses the accelerator pedal, so the target yaw angular acceleration is achieved simply by controlling the difference in driving force between the left and right wheels. Even if this is not possible, in order to increase the turning angle of the left and right wheels to achieve the shortage to the target yaw angular acceleration, the difference in driving force between the left and right wheels and the increase in the turning angle of the left and right wheels As a result, the target yaw angular acceleration can be realized.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 is a plan view of an essential part showing a left and right independent drive type vehicle according to an embodiment of the present invention together with its drive system and steering system.
The vehicle 1 has four wheels, a left front wheel 2FL, a right front wheel 2FR, a left rear wheel 2RL, and a right rear wheel 2RR. Of these, the front wheels 2FL and 2FR are steered by a steering device described below. To do. That is, the steering wheel 4 that is rotated by the driver's operation is connected to the turning angle control device 6 via the steering shaft 5. The turning angle control device 6 includes a variable mechanism such as a planetary gear train or a lever, and can change the ratio between the operation amount input to the steering wheel 4 and the turning angles of the front wheels 2FL and 2FR to the rack and pinion 7. Output.
The turning angle control device 6 does not mechanically connect the steering shaft 5 and the rack and pinion 7, detects the operation amount input to the steering wheel with a sensor, and a numerical value obtained by multiplying the detected value by a variable coefficient. May be a so-called steering-by-wire in which the electric motor or the like operates the rack and pinion 7.

  The rack and pinion 7 is connected to an axle member (not shown) that supports the front wheels 2FL and 2FR via side rods 8FL and 8FR on the left and right sides. The front wheels 2FL and 2FR are steered in response to the movement of the rack and pinion 7 in the left-right direction.

The left and right front wheels 2FL and 2FR are individually driven by the driving devices 3FL and 3FR, which are individual driving sources, and the driving forces of the front wheels 2FL and 2FR are individually controlled via these driving devices 3FL and 3FR. Make it possible.
The driving devices 3FL and 3FR are left and right independent driving motors disclosed in, for example, Japanese Patent Laid-Open No. 5-91607. Alternatively, the driving force output from one driving source may be distributed to the left and right, and the driving force of the left and right front wheels 2FL and 2FR may be variably controlled by a multi-plate clutch mechanism or the like.

First, when the driver depresses the accelerator pedal 9, the driving devices 3FL and 3FR output a driving force corresponding to the accelerator operation amount to the front wheels 2FL and 2FR.
Further, when the driver operates the steering wheel 4, the target yaw angular acceleration is calculated according to the steering wheel operation amount, and the driving devices 3FL and 3FR drive the driving force between the front wheels 2FL and 2FR so as to achieve the target yaw angular acceleration. A driving force difference is generated.

A control program executed by the driving devices 3FL and 3FR at regular intervals for controlling the driving force of the left and right front wheels 2FL and 2FR will be described below with reference to FIG.
First, in step S1, the accelerator operation amount a of the accelerator pedal 9 is read, and in the next step S2, the target driving force total Fa of the left and right wheels 2FL and 2FR that achieves the target longitudinal acceleration A according to the accelerator operation amount a is a function. Or it calculates by map search.

In the subsequent step S3, the steering wheel operation amount h input to the steering wheel 4 is read.
In the next step S4, the target driving force difference Fh between the left and right wheels 2FL and 2FR necessary to achieve the target yaw angular acceleration M corresponding to the steering wheel operation amount h is calculated by a function or map search.
In the present embodiment, the target yaw angular acceleration M is determined based on the steering wheel operation amount h. In addition to this, for example, the wheels 2FL, 2FR, 2RL, 2RR detected by various sensors. Speed, yaw rate of the vehicle 1, longitudinal acceleration of the vehicle 1, numerical values calculated based on these various detection values, numerical values given by using external signals such as GPS, etc. Alternatively, the target yaw angular acceleration M may be obtained based on a combination thereof.

When the target driving force total Fa and the target driving force difference Fh are obtained, the driving forces of the left and right wheels 2FL and 2FR are controlled so as to realize these values. Therefore, in the next step S5, the target driving force Fr of the right front wheel 2FR is calculated based on the following equation.
Fr = (Fa + Fh) / 2 (when the right target driving force Fr is increased) (1)
In the next step S6, the maximum value Frmax that can be output by the driving device 3FR is compared with the target driving force Fr, and whether or not the target driving force Fr is equal to or less than the maximum value Frmax, that is, whether or not the target driving force Fr can be realized. Determine whether. If it cannot be realized (No), the process proceeds to step S10 described later.

On the other hand, if feasible (Yes), the process proceeds to step S7, and the target driving force Fl of the left front wheel 2FL is calculated based on the following equation.
Fl = (Fa−Fh) / 2 (when the left target driving force Fl is decreased) (2)
In the opposite case, that is, when the right target driving force Fr is decreased and the left target driving force Fl is increased, the plus sign in equation (1) is changed to the minus sign, and the minus sign in equation (2). To + sign.
In the next step S8, the maximum value Flmax that can be output by the driving device 3FL is compared with the target driving force Fl, and whether or not the target driving force Fl is less than or equal to the maximum value Flmax, that is, whether or not the target driving force Fl can be realized. Determine whether. If it cannot be realized (No), the process proceeds to step S10 described later.
On the other hand, if feasible (Yes), the process proceeds to step S9, and the driving devices 3FL, 3FR output the target driving forces Fr and Fl to the left and right front wheels 2FL, 2FR. And step S10-S19 are skipped and this control is complete | finished.

  If No in step S6 or S8, the driving devices 3FL and 3FR cannot achieve the target driving force difference Fh, and the target yaw angular acceleration M can be achieved only by the yaw angular acceleration due to the driving force difference between the left and right wheels 2FL and 2FR. In step S10, the target yaw angular acceleration M is achieved by the control described below.

In step S10, when the target driving force total Fa calculated in the previous step S2 is realized, the maximum yaw angular acceleration Mm that can be realized simultaneously is calculated.
For this calculation, first, the maximum driving force difference Fhmax that can be output by the driving devices 3FL and 3FR is calculated based on the following equation (3) or (4).
When performing yaw angular acceleration control that increases the driving force of the right wheel 2FR,
Fhmax = 2 (Frmax−Fa / 2) (3)
When performing yaw acceleration control that increases the driving force of the left wheel 2FL,
Fhmax = 2 (Flmax−Fa / 2) (4)
Second, the realizable yaw angular acceleration Mm is calculated based on the following equation.
Mm = k · Fhmax (5)
k is a numerical value based on the yaw moment of inertia determined by the characteristics of the vehicle 1.

In step S11, the target driving force Fr * of the right wheel 2FR is calculated based on the following equation.
Fr * = (Fa + Fhmax) / 2 (when the right target driving force Fr * is increased) (6)
In the next step S12, the calculation of the target driving force Fl * of the left wheel 2FL is performed based on the following equation.
Fl * = (Fa−Fhmax) / 2 (when the left target driving force Fl * is decreased) (7)
In the opposite case, that is, when the right target driving force Fr * is decreased and the left target driving force Fl * is increased, the plus sign in equation (6) is changed to the minus sign, and the equation (7) -Change the sign to a + sign.

In step S13, the shortage amount ΔM up to the target yaw angular acceleration M is calculated based on the following equation.
ΔM = M−Mm (8)
In step S14, a turning angle δm necessary for generating the deficient amount ΔM is calculated.
In step S15, the current actual steering angle δ of the left and right wheels 2FL, 2FR is read.
In step S16, the target turning angle δ * is calculated based on the following formula using the required turning angle δm and the actual turning angle δ obtained in steps S14 and S15.
δ * = δ + δm (9)

In step S17, the driving device 3FR outputs the right target driving force Fr * obtained in step S11 to the right front wheel 2FR.
In step S18, the driving device 3FL outputs the left target driving force Fl * obtained in step S12 to the left front wheel 2FL.
In step S19, the turning angle control device 6 changes the ratio between the steering wheel operation amount h and the actual steering angle δ of the front wheels 2FL, 2FR, so that the left and right wheels 2FL, 2FR become the target turning angle δ *. Steer so that.

  From the above, if the target yaw angular acceleration M is insufficient due to the control of the driving force difference between the left and right wheels 2FL and 2FR in Steps S1 to S9, the target of the left and right wheels 2FL and 2FR is determined in subsequent Steps S10 to 19. Control for increasing the turning angle δ * is further performed to achieve the target yaw angular acceleration M.

  Thereafter, when the driver depresses the accelerator pedal 9 and the accelerator operation amount a decreases, the target longitudinal acceleration A and the target driving force total Fa decrease accordingly, and the target driving force Fr becomes the target driving force Fr. It becomes the maximum value Frmax or less, and the target driving force Fl becomes the maximum value Flmax or less. In this case, Yes is selected in steps S6 and S8, the process proceeds to step S9, and the driving devices 3FL and 3FR output the target driving forces Fr and Fl to the left and right front wheels 2FL and 2FR. And step S10-S19 are skipped and this control is complete | finished.

  By the way, according to the above-described embodiment, the right and left wheels 2FL and 2FR are set so as to achieve the target longitudinal acceleration A corresponding to the accelerator operation amount a input to the accelerator pedal 9 in the normal control in steps S1 to S9. Is controlled by the target driving force total Fa. At the same time, the basic premise is that control is performed with a target driving force difference Fh between the left and right wheels 2FL and 2FR so as to achieve the target yaw angular acceleration M corresponding to the steering wheel operation amount h input to the steering wheel 4. .

  If the control cannot be performed with the target driving force difference Fh, for example, as a result of controlling the driving force of the left and right wheels 2FL and 2FR with the target driving force total Fa, the right target driving force Fr becomes the upper limit value Frmax as described above. If the left target driving force Fl has reached the upper limit value Flmax and cannot be controlled with the target driving force difference Fh between the left and right wheels 2FL, 2FR, the process proceeds to the control in steps S10 to S19.

That is, in steps S17 and S18, the drive devices 3FL and 3FR output the left target drive force Fl * and the right target drive force Fr * to the left and right wheels 2FL and 2FR so as to realize the maximum drive force difference Fhmax that can be output. . At the same time, in step S19, the shortage ΔM between the realizable yaw angular acceleration Mm and the target yaw angular acceleration M achieved by the output possible driving force difference Fhmax is increased by the necessary turning angle δm for the left and right wheels 2FL and 2FR. To achieve.
Therefore, when the accelerator operation amount a is increased, the required left-right wheel driving force difference Fh cannot be realized. Therefore, the target yaw angular acceleration is obtained only by driving force control based on the driving force difference between the left and right wheels 2FR, 2FL. Even if it is insufficient for M, the target yaw angular acceleration can be achieved.

  Further, according to the present embodiment described above, when the required driving force difference Fh between the left and right wheels can be realized, such as when the accelerator operation amount a is subsequently reduced, the steering wheel operation amount and the front wheel The ratio of the 2FL and 2FR to the turning angle is returned to the normal control state, the turning angle is returned from δ * to δ, and the driving force between the left and right wheels 2FL and 2FR is controlled with the target driving force difference Fh. As a result, the control of the yaw angular acceleration by turning the left and right wheels 2FL and 2FR in steps S10 to S19 can be finished, and the normal control can be restored.

In this embodiment, the front wheels 2FL and 2FR are steered and these left and right driving forces are variably controlled independently. However, as shown in FIG. Even if the front wheels 2FL and 2FR are steered and the left and right driving forces of the rear wheels 2RL and 2RR are variably controlled independently by the driving devices 3RR and 3RL, the same effect can be obtained.
In addition, as shown in FIG. 4, the front wheels 2FL and 2FR are steered and these left and right driving forces are variably controlled independently, and the left and right driving forces of the rear wheels 2RL and 2RR are independently controlled by the driving devices 3RR and 3RL. The same effect can be obtained even if the configuration is variably controlled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a main part plan view showing a left and right independent drive type vehicle according to an embodiment of the present invention together with its steering system and drive system. It is a flowchart which shows the control program which the drive device of the left-right independent drive type vehicle performs. It is a principal part top view of the left-right independent drive type vehicle which becomes another Example. It is a principal part top view of the left-right independent drive type vehicle which becomes further another Example.

Explanation of symbols

1 Electric car (body)
2FL Left front wheel 2FR Right front wheel 2RL Left rear wheel 2RR Right rear wheel 3FL Left front wheel drive device 3FR Right front wheel drive device 4 Steering wheel 6 Steering angle control device 9 Accelerator pedal

Claims (5)

In order to achieve the target yaw angular acceleration while controlling the sum of the driving forces of the left and right driving wheels so as to achieve the target longitudinal acceleration, the steering wheel turning based on the steering operation and at least one pair of left and right driving wheels. Means for calculating the driving force difference between the left and right driving wheels necessary for the vehicle, and independently driving the left and right driving wheels independently based on the calculated driving force difference.
Wheel steering means for controlling the steering angle of the steered wheels separately from the steering operation,
When the driving force control based on the driving force difference between the left and right driving wheels is insufficient with respect to the target yaw angular acceleration, the steering wheel is steered by the turning angle control of the wheel turning means, and the target yaw angular acceleration is achieved. Left and right independent drive type vehicle characterized by being configured to realize   In the left and right independent drive type vehicle according to claim 2, when the driving force difference of the calculated driving force cannot be realized because the driving force of the left and right driving wheels has reached the upper limit value, the wheel steering means A left and right independently driven vehicle characterized in that a steered wheel is steered by turning angle control to realize a target yaw angular acceleration.   In the left and right independent drive type vehicle according to claim 1 or 2, when the calculated driving force difference can be realized during the turning angle control of the wheel turning means, the wheel turning means A left and right independent drive type vehicle configured to shift from turning angle control to driving force control based on the calculated driving force difference.   In the left and right independent drive type vehicle according to claim 3, since the driving force of the left and right driving wheels is reduced from the upper limit value, when the calculated driving force difference can be realized, the wheel steering means A left and right independent drive type vehicle configured to shift from turning angle control to driving force control based on the calculated driving force difference.   5. The left and right independent drive type vehicle according to claim 1, wherein the left and right drive wheels are configured to also serve as the steering wheels.

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