JPH0591607A - Controller for wheel drive motor - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to improve the straightness of the vehicle by controlling the wheel drive motor so as to reduce the yaw rate noise. A wheel drive motor for driving left and right wheels respectively, a steering angle detection means for detecting a steering angle of the wheels, a vehicle speed detection means for detecting a vehicle speed, and a yaw rate detection means for detecting a yaw angular velocity of the vehicle, A yaw rate calculating means for calculating a model yaw rate value of the vehicle based on signals from the steering angle detecting means and the vehicle speed detecting means, and a yaw rate noise calculating means for making a difference between the model yaw rate value and the detected value of the yaw rate detecting means a yaw rate noise. And a control means for controlling the left and right wheel drive motors so as to reduce the yaw rate noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle wheel drive motor control device for driving left and right wheels by separate wheel drive motors.

[0002]

2. Description of the Related Art Conventionally, as a control device for a wheel drive motor of this type, there is one described in, for example, Japanese Patent Laid-Open No. 62-138002.

This conventional device drives a wheel drive motor for driving each of the left and right wheels, a vehicle speed sensor for detecting a vehicle speed, a sensor for detecting a steering angle of a steering wheel, and a wheel drive for the left and right wheels in response to outputs of the respective sensors. A control means for controlling the rotation speed of the motor is provided, and the rotation of the left and right wheel drive motors is changed according to the rotation angle of the steering wheel to perform straight traveling and curve traveling.

[0004]

However, in such a conventional apparatus, if the turning angle of the steering wheel is 0, the vehicle should run straight, but the left and right differences in tire radius of movement, left and right. There is a possibility that straightness may not always be obtained due to the difference in wheel load of the wheels, the inclination and unevenness of the road, and the influence of the wind direction.

Therefore, an object of the present invention is to provide a control device for a wheel drive motor which controls the vehicle drive motor so as to reduce the yaw rate noise so as to improve the straightness of the vehicle.

[0006]

In order to solve the above problems, the present invention is directed to a wheel drive motor 7 or 9 for driving left and right wheels, respectively, as shown in FIG. 1, and a steering angle for detecting the steering angle of the vehicle. Detecting means CL3, vehicle speed detecting means CL2 for detecting the vehicle speed, yaw rate detecting means CL5 for detecting the yaw angular velocity of the vehicle, and the model yaw rate value of the vehicle by signals from the steering angle detecting means CL3 and the vehicle speed detecting means CL2. Yaw rate calculation means CL4 and a yaw rate noise calculation means CL that makes the difference between the model yaw rate value and the detection value of the yaw rate detection means the yaw rate noise.
6 and control means CL1 for controlling the left and right wheel drive motors so as to reduce the yaw rate noise.

[0007]

In the present invention, the yaw rate calculating means CL4 calculates the model yaw rate value of the vehicle based on the signals from the steering angle detecting means CL3 and the vehicle speed detecting means CL2, and the yaw rate noise calculating means CL6 calculates the model yaw rate value and the yaw rate detecting means CL5. The yaw rate noise is calculated from the detected value. Control means C is provided to reduce this yaw rate noise.
L1 controls the left and right wheel drive motors 7 and 9.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic block diagram of a vehicle having a wheel drive motor control device according to one embodiment.

The vehicle 1 according to this embodiment has left and right front wheels 3, 5
Is configured as a drive wheel and a steering wheel, and includes wheel drive motors 7 and 9 for driving the left and right front wheels 3 and 5, respectively, and a steering wheel 11 and a steering device 13 for steering the left and right front wheels 3 and 5. There is. Further, a microcomputer 15 is provided as control means CL1 for controlling the wheel drive motors 7 and 9.

The microcomputer 15 in this embodiment includes a yaw rate calculating means CL4 and a yaw rate noise calculating means CL6. The yaw rate calculating means CL4 is a vehicle speed sensor 17 as a vehicle speed detecting means CL2 for detecting a vehicle speed and a steering angle detecting means CL for detecting a steering angle.
A model yaw rate value of the vehicle is calculated by a signal from the steering angle sensor 19 as No. 3. The yaw rate noise calculating means CL6 detects the yaw rate noise from the detected value of the yaw rate sensor 21 as the yaw rate detecting means CL5 for detecting the actual yaw rate of the vehicle and the model yaw rate value (the reason other than the steering angle, for example, disturbance, vehicle variation, etc.). Yaw rate generated by) is calculated.

The vehicle speed sensor 17, the steering angle sensor 19 and the yaw rate sensor 21 are connected to the input side port of the microcomputer 15. Vehicle speed sensor 17
Detects the vehicle speed by, for example, taking in a signal from a speedometer. The steering angle sensor 19 is composed of, for example, a potentiometer, a slit-photocoupler, or the like provided in the steering wheel 11, and detects the steering angle by detecting the rotation angle of the steering wheel 11. Further, the yaw rate sensor 21 detects the yaw angular velocity by taking in a signal from, for example, an encoder provided on the vehicle body.

Wheel drive motors 7 and 9 are connected to the output port of the microcomputer 15 through a drive circuit (not shown).

FIG. 3 shows a block diagram for calculating the yaw rate noise.

The advance model 31 compensates for the steering angle detection delay of the steering angle sensor 19. That is, the steering angle sensor 1
If 7 is an analog type such as a potentiometer, there is almost no detection delay, so there is no need to compensate, but slit-
In the case of a digital type such as a photocoupler, a detection delay occurs, which is compensated for.

The vehicle model 33 defines the vehicle motion that outputs the yaw rate r (S) of the vehicle when the steering angle δ (S) is input. In the simplest two-degree-of-freedom model, the transfer function of the steering response is defined. The following will be displayed.

[0017]

[Equation 1]

Here, S: Laplace operator ω _n : Natural frequency of vehicle response to steering ζ: Damping ratio of vehicle response to steering A: Stability factor V: Vehicle speed 1: Wheelbase 1 / T _r : _{= 2lK r / ml f V K} r: rear wheel cornering force l _f: distance from the front wheel to the vehicle center of gravity _m: response of r for δ as vehicle mass (1) is given in the form of a Laplace transform For example, the response of r to a given δ can be specifically obtained by inverse Laplace transforming it, so that the yaw angular velocity r when the actual steering angle δ is given to the vehicle traveling straight now. If you ask for the response,

[0019]

[Equation 2]

The yaw angular velocity when the actual steering angle is given can be obtained by the equation (2). However, £ ⁻¹ indicates the inverse Laplace transform, and the actual steering angle δ can be regarded as an impulse input if Δt is sufficiently small compared to the motion of the vehicle. Therefore, the Laplace transform δ (S) is δ ₀ Δt.

Then, the delay model 35 performs compensation corresponding to the yaw rate detection delay by the yaw rate sensor 21 to calculate the model yaw rate r (bar).

On the other hand, the actual yaw rate r is detected after the actual vehicle response 37 and the delay 39 of the yaw rate sensor.

Here, the response of the yaw angular velocity r to the actual steering angle δ of the vehicle will be specifically described.

Now, as shown in FIG. 4, the coordinate system fixed on the ground in the horizontal plane is XY, the center of gravity P of the vehicle projected on the moving surface is the origin, and the longitudinal direction of the vehicle is x, The direction perpendicular to this is set to y, the coordinate system fixed to the vehicle is set to xy, and all angles around the vertical axis are positive in the counterclockwise direction.

The angles formed by the front left and right wheels with respect to the vehicle front-rear direction, that is, the actual steering angle is δ, and the side slip angles of the front and rear wheel tires are β _f1 , β _f2 , β _r1 , and β _r2, and these tires work. If the cornering forces are C _f1 , C _f2 , C _r1 , and C _r2 ,

[0026]

[Equation 3]

Since the cornering force acts as a yawing moment around the center of gravity, the yawing motion around the center of gravity of the vehicle can be described by the following equation.

[0028]

[Equation 4]

Here, I is the yaw moment of inertia of the vehicle, l _f and l _r are the distances between the center of gravity of the vehicle and the front and rear axles, and the force applied by the cornering force is on the front and rear axles.

The expressions (3) and (4) are basic expressions that represent the motion of the vehicle in the horizontal plane when the vehicle travels at a constant speed, ignoring the rolling of the vehicle body.

By the way, the vehicle as a rigid body makes a translational motion while having a velocity component of Vβ in the x direction, that is, the longitudinal direction of the vehicle, and a V direction in the y direction, that is, the lateral direction of the vehicle, and has an angular velocity of r around the center of gravity. Therefore, each tire of the vehicle has a velocity component at the center of gravity and a velocity component due to rotation around the center of gravity.
The velocity components in the direction and the y direction are as shown in FIG. On the other hand, the rotation surface of the front wheels, that is, the direction in which the tires face, has an actual steering angle δ with respect to the vehicle front-rear direction (x direction), and the direction in which the rear wheels face indicates the vehicle front-rear direction (x direction). ) Matches.

Therefore, the sideslip angle β _f1 ,
β _f2 , β _r1 , and β _r2 can be expressed as follows.

[0033]

[Equation 5]

Here, β is an angle formed between the traveling direction of the vehicle and the front-rear direction, d _f and d _r are treads in the front and rear of the vehicle, and | β |,
| L _f r / V |, | l _r r / v |, | d _f r / 2v |,
| D _r r / 2v | << 1 and these terms of the second or higher order are neglected as minute. In other words, equal respectively sideslip angles of the left and right tires both the front and rear wheels, which β _f · β _r
Then,

[0035]

[Equation 6]

[0036]

[Equation 7]

[0037]

As described above, considering the range in which the sideslip angles of the left and right tires are equal, the values thereof are small, and the actual steering angle is also small, it means that rolling of the vehicle body is ignored and the vehicle is traveling at a constant speed. When considering the yawing motion in the horizontal plane of the vehicle, as shown in FIG. 6, the treads d _f and d _r of the vehicle are ignored, and the front and rear left and right wheels are equivalent to the intersection of the front and rear axles of the vehicle and the axle. This is equivalent to considering the movement of concentrated vehicles, that is, equivalent movements of two front and rear wheels. In this way, if there is no characteristic of the left and right tires themselves, there is no difference in the cornering force acting on the left and right tires.
_{As f}・ C _r

[0039]

[Equation 8]

It can be expressed as Since this force can be regarded as acting in the y direction, equations (3) and (4) describing the motion of the vehicle are

[0041]

[Equation 9]

It becomes Here, assuming that the cornering powers of the front and rear tires are K _f and K _r , respectively, if the side slip angle is small, the cornering force C _f and C _r is proportional to the side slip angle β _f and β _r , and as shown in FIG. If the y coordinate is taken and all angles are positive in the counterclockwise direction, they work in the negative direction when the sideslip angle is positive, and therefore can be expressed as follows.

[0043]

[Equation 10]

As described above, the cornering forces C _f and C _r acting on the vehicle are not affected by the position or stability of the vehicle with respect to the coordinates fixed on the ground, and the motion state β,
It will be determined only by r and the actual steering angle δ.

By substituting the equations (8) and (9) into the equation (6),

[0046]

[Equation 11]

To obtain By rearranging this formula,

[0048]

[Equation 12]

Then, a basic equation of motion describing the motion of the horizontal plane is obtained. The left side of the equations (13) and (14) indicates the motion of the vehicle, and the vehicle moves according to the uniqueness of the actual steering angle δ of the front wheels that can be arbitrarily given on the right side.

If both sides of the above equations of motion (11) and (12) are Laplace transformed,

[0051]

[Equation 13]

Can be obtained. However, β (S),
r (S) and δ (S) are the Laplace transforms of β, r, and δ.

Mechanically solving this algebraic equation for r (S),

[0054]

[Equation 14]

It becomes

By rearranging this equation (17) using the vehicle's natural drive number ω _n for steering and the damping ratio ζ of the vehicle's response to steering, the above equation (1) is obtained, and the equation (1) is reversed. Equation (2) is obtained by performing the Laplace transform.

As described above, the equation (1) expresses the response of the yaw angular velocity r to the actual steering angle δ of the vehicle as a transfer function.

By applying the Laplace transform formula to the equation (2), r (t) becomes as follows. However, the initial value of r is 0.

When the vehicle exhibits a non-oscillating response with ζ> 1,

[0060]

[Equation 15]

When the vehicle exhibits a non-oscillating response with ζ = 1,

[0062]

[Equation 16]

When the vehicle exhibits a vibrational response with ζ <1,

[0064]

[Equation 17]

The solutions of the equations (18), (19), and (20) specifically show the response of the yaw angular velocity r to the actual steering angle δ of the vehicle.

Next, the control operation of the above embodiment will be described with reference to the flow chart shown in FIG.

First, in step S ₁ , the steering angle δ from the steering angle sensor 19 and the vehicle speed V from the vehicle speed sensor 17 are read,
This calculates the model yaw rate r ▲ bar ▼ (t) from the steering angle δ and the vehicle speed V by the model yaw rate operation shown in FIG. 3 (step S2), the detection yaw rate r from the yaw rate sensor 21 in step S ₃ (t) Read.

Next, in step S ₄ , the yaw rate noise (error) e (t) is calculated from the model yaw rate r-bar (t) and the detected yaw rate r (t). In step S ₅ , as shown in FIG. 8, the yaw rate noise e (t)
Integrated value of Δt seconds

[0069]

[Equation 18]

Calculate This is because the motor has a mechanical time constant due to the moment of inertia of the rotor, and there is a time delay until the target rotational speed is reached. Therefore, direct feedback to make the yaw rate noise e (t) zero causes instability. This is a process performed because there is a risk of inviting it.

At step S ₆ , it is judged if the yaw rate noise integrated value E is close to zero. When the yaw rate noise integrated value E is a value close to 0, it is not necessary to measure the rotational speeds of the left and right wheel drive motors 3, 5, so step S ₁
To return, when the yaw rate noise integral value E is not close to 0 the process proceeds to step S _7. In step S ₇ , it is determined whether or not the yaw rate noise integrated value E exceeds 0. The process proceeds to step S ₈ when the yaw rate noise integral value E is greater than 0, the rotational speed of the left wheel drive motor _{3 ω L = ω L + kE} : increased by (k proportional constant). Further, when the yaw rate noise integral value E is below 0, the process proceeds to step S _9, the rotational speed of the right wheel drive motor _{5 ω R = ω R + kE} : increased by (k proportional constant).

Therefore, in order to control the rotational speeds of the left and right wheel drive motors 3 and 5 so that the yaw rate noise integrated value E is minimized, the left and right difference in tire radius of movement, the wheel load difference between the left and right wheels, and the road surface. Good straight running and curve running can be performed without being affected by inclination, unevenness, wind direction, and the like.

The present invention is not limited to the above embodiment, but the yaw rate of the vehicle may be controlled by controlling the torque of the left and right wheel drive motors. It is also possible to control the yaw rate of the vehicle by controlling the rear wheel steering angle.

[0074]

As is apparent from the above description, according to the present invention, since the left and right wheel drive motors are controlled so as to reduce the yaw rate noise, the straightness of the vehicle can be further improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a schematic configuration diagram of a vehicle including a wheel drive motor control device according to an embodiment.

FIG. 3 is a block diagram illustrating calculation of yaw rate noise.

FIG. 4 is an explanatory diagram showing movement of the vehicle.

FIG. 5 is an explanatory diagram showing a side slip angle of each tire of a vehicle.

FIG. 6 is an explanatory diagram showing a two-wheeled vehicle model equivalent to a four-wheeled vehicle.

FIG. 7 is a flowchart according to an embodiment.

FIG. 8 is an explanatory diagram showing an example of yaw rate noise calculation.

[Explanation of symbols]

1 vehicle 7 left wheel drive motor 9 right wheel drive motor CL1 control means (microcomputer 15) CL2 vehicle speed detection means (vehicle speed sensor 17) CL3 steering angle detection means (steering angle sensor 19) CL4 yaw rate calculation means (microcomputer 1)
5) CL5 yaw rate detecting means (yaw rate sensor 21) CL6 yaw rate noise calculating means (microcomputer 15)

Claims (1)

[Claims] 1. A wheel drive motor for driving left and right wheels, respectively, and a steering angle detection means for detecting a steering angle of the wheels,
A vehicle speed detecting means for detecting a vehicle speed, a yaw rate detecting means for detecting a yaw angular velocity of the vehicle, a yaw rate calculating means for calculating a model yaw rate value of the vehicle based on signals from the steering angle detecting means and the vehicle speed detecting means, and this model yaw rate. A yaw rate noise calculating means for setting a difference between the value and the detection value of the yaw rate detecting means as a yaw rate noise; and a control means for controlling the left and right wheel drive motors so as to reduce the yaw rate noise. Wheel drive motor controller.