JP2505251B2 - Vehicle auxiliary steering system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an auxiliary steering device for a multi-axle vehicle such as a large truck.

(Prior Art) A multi-axle vehicle has two rear axles, and in assisting steering, two sets of rear wheels of these rear axles are assisted to steer according to the steering angle of the front wheels that are mainly steered by the steering wheel.

Then, when the two sets of rear wheels are assisted to be steered, it is proposed in Japanese Patent Laid-Open No. 62-258867 to control the auxiliary steering angles of these rear wheels by a transfer function such that the side slip angle of the center of gravity of the vehicle becomes zero. Has been done.

(Problems to be Solved by the Invention) When discussing the motion of a vehicle only from the standpoint of minimizing the kinetic energy of the vehicle, it is best that the sideslip angle of the center of gravity of the vehicle is zero. However, the driver does not drive at the center of gravity of the vehicle, and the driver is not aware of where the center of gravity of the vehicle is. Therefore, when discussing the movement of the vehicle from the viewpoint of the driver's driving feeling,
A zero side slip angle of the center of gravity of the vehicle is not preferable for the driver. In other words, whether or not the side slip angle of the center of gravity of the vehicle is zero is something that the driver does not know.
It is important for the driver to know where the skid angle is zero relative to his / her sitting position.

However, the conventional auxiliary steering system cannot perform control such that the sideslip angle is zero except at the center of gravity of the vehicle, and this cannot always be said to provide suitable vehicle dynamic performance.

Further, in the above-described auxiliary steering device, the steady-state yaw rate gain (the ratio of the yaw rate to the front wheel main steering angle when the steering frequency is zero) is uniquely determined, and the degree of freedom in design is reduced.

Furthermore, the yaw rate gain (response) to the front wheel main steering angle
The characteristics are uniquely determined, and only the first-order lag characteristics are obtained.

It is an object of the present invention to provide a device for performing auxiliary steering with respect to main steering with a transfer function that can solve such problems.

(Means for Solving the Problem) For this purpose, the auxiliary steering apparatus of the present invention has the other two auxiliary steering wheels δ ₂ and δ ₃ , respectively, according to the steering angle δ ₁ of the main steering wheel by the steering wheel. In a device designed for auxiliary steering, the auxiliary steering angles δ ₂ and δ ₃ are However, M: vehicle mass I: yaw moment of inertia S: Laplace operator a: center of gravity and main steering wheel axle distance b: center of gravity and first auxiliary steering wheel axle distance c: center of gravity and second auxiliary steering wheel axle distance c ₁ : Total tire cornering power of the main steering wheel c ₂ : Total tire cornering power of the first auxiliary steering wheel c ₃ : Total tire cornering power of the second auxiliary steering wheel l ₃ : Distance from the center of gravity of the point where you want to set the vehicle body side slip angle to 0 V: Vehicle speed: It is configured to be controlled by the transfer function of yaw rate.

(Operation) When steering the main steering wheel with the steering wheel,
The two sets of auxiliary steering wheels are given the auxiliary steering angles obtained by the above transfer function.

By the way, in the above equation, the position (distance
l ₃ ) can be freely determined as desired, so that the position with a sideslip angle of zero can be brought to a desired position, for example, the driver's seat. Further, in the above equation, the ratio of the yaw rate to the main steering angle, that is, the yaw rate gain characteristic / δ ₁ can also be freely determined according to the desired characteristic, and the degree of freedom in design is high. It can be a characteristic or a flat characteristic.

(Example) Hereinafter, the Example of this invention is described in detail based on drawing.

FIG. 1 shows an embodiment of the auxiliary steering device of the present invention. In this embodiment, as shown in FIG. 4 (a), a pair of rear wheels 1 as a first auxiliary steering wheel and a second auxiliary steering wheel are provided. It is assumed that the rear wheels 2 of the set are assisted to be steered according to the main steering angle of the front two wheels 4 by the steering wheel 3.

Actuators 5 and 6 for controlling the auxiliary steering of the rear wheels 1 and 2 are provided. The actuators 5 can be stroked simultaneously in the same steering direction at the same speed by hydraulic control valves 7, and the actuators 6 are controlled at the same time by hydraulic control valves 8. It is possible to stroke in the same steering direction at speed.

The hydraulic control valves 7 and 8 have a common oil pump 9, and the discharge oil from this is distributed at a predetermined ratio by the flow dividing valve 10 and supplied to the inflow circuits 11 and 12 of the hydraulic control valves 7 and 8. Note that 13 is a drain circuit of the hydraulic control valves 7 and 8.

The hydraulic control valves 7 and 8 are electronically controlled by the microcomputer 14, but in the normal state, all the chambers of the actuators 5 and 6 are in a non-pressure state, and the rear wheels 1 and 2 are in the non-steering neutral position. When the hydraulic control valves 7 and 8 are operated to a certain state by the computer 14, one of the chambers of the actuators 5 and 6 is connected to the circuit 1
Pressurized with oil from 1, 12 and drain circuit the other chamber
It is assumed that the rear wheels 1 and 2 are assisted in one direction via the actuators 5 and 6 through the actuator 13. Further, when the hydraulic control valves 7 and 8 are operated to other states by the computer 14, the actuators 5 and 6 are stroked in the reverse direction to assist the rear wheels 1 and 2 in the reverse direction.

The microcomputer 14 outputs a signal from a vehicle speed sensor 15 which emits a pulse signal having a frequency corresponding to the vehicle speed V, a signal from a steering angle sensor 16 which detects a turning angle θ of the steering wheel 3 (see FIG. 4) and a vehicle body load L. A signal from the load sensor 17 for detection is input, and the control program of FIG. 2 is executed based on these input information to assist steering of the rear wheels 1 and 2.

Here, in order to obtain the transfer function that determines the auxiliary steering angles of the rear wheels 1 and 2, FIG. 3 shows an analytical model for obtaining this transfer function as an x, y coordinate system in the horizontal plane including the vehicle center of gravity 0. It was In FIG. 3, portions similar to those in FIGS. 1 and 4 (a) are designated by the same reference numerals, a is the distance from the vehicle center of gravity 0 to the axle of the front wheel 4 which is the main steering wheel, and b is the vehicle center of gravity 0. From first
The distance to the axle of the rear wheel 1 which is the auxiliary steering wheel, and c is the distance from the vehicle center of gravity 0 to the axle of the rear wheel 2 which is the second auxiliary steering wheel. Further, δ ₁ is the main steering angle of the front wheel 4 by the steering wheel 3, δ ₂ , δ ₃ are the auxiliary steering angles of the rear wheels 1 and 2, respectively, and β ₁ ,
β ₂ and β ₃ are the slip angles of the front wheels 4 and the rear wheels 1 and 2, respectively, F ₁ , F ₂ and F ₃ are the total tire cornering forces related to the axles of the front wheels 4 and the rear wheels 1 and 2, and the yaw rate is the yaw rate. Angular acceleration), l ₃ is the distance from the center of gravity 0 at the point where the vehicle side slip angle is zero, v ₃ is the lateral movement speed at the same point, y
Indicates a lateral movement distance of the center of gravity 0 (is its changing speed, is acceleration) V is a vehicle speed.

In FIG. 3, when the vehicle mass is M and its yaw moment of inertia is I, the equation of motion of the vehicle is M (+ V) = F ₁ + F ₂ + F ₃ (1) I () = aF ₁ −bF ₂ −cF ₃ …… It is expressed by (2). Here, assuming that the total tire cornering powers related to the axles of the front wheels 4 and the rear wheels 1 and 2 are c ₁ , c ₂ and c ₃ , respectively, F ₁ , F ₂ and F _{3 in the} above formula are respectively When these are Laplace-transformed and put together, they are represented by ι [] = ι [] =, and therefore, when the Laplace operator is S in the above equations (1) and (2), respectively, Becomes

On the other hand, the lateral movement speed v ₃ locations to be the slip angle to zero is represented by v ₃ = -l _3, because preconditions are v ₃ = 0, the following relation is obtained.

= L ₃ Substituting this into equations (3) and (4), Is obtained, and these are summarized for δ ₂ / δ ₁ and δ ₃ / δ ₁ , The following two equations are obtained, and finally Is established. Then, these are δ ₂ / δ ₁ and δ ₃
By solving for / δ ₁ Is obtained.

In the present invention, the rear wheels 1, 2 are assisted by steering (δ ₂ , δ ₃ ) according to the steering angle δ ₁ of the front wheels 4 by the transfer functions of the equations (5), (6) to obtain a predetermined motion performance. According to such auxiliary steering,
The position at which the sideslip angle is zero can be arbitrarily set, and the yaw rate gain characteristic / δ ₁ can be freely set, so that the degree of freedom in control can be extremely increased. For example, a yaw rate gain flat characteristic (characteristic that the yaw rate gain / δ ₁ is kept constant even if the steering frequency becomes high) that is ideal for control is secured, and a portion where the sideslip angle is zero (center of gravity 0 From the distance l ₃ ) can be freely changed according to changes in loading conditions.

In order to achieve such auxiliary steering, the computer 14 in FIG. 1 executes the control program in FIG. That is, first, the load applied to each wheel is calculated from the signal from the sensor 17, and then the vehicle mass M, the yaw inertia moment I, the position of the center of gravity O, and the tire cornering powers c ₁ , c ₂ , c ₃ are calculated.
Then, the distance l ₃ from the center of gravity position 0 to the point where the side slip angle is desired to be zero is calculated, and then the vehicle speed V is calculated based on the signal from the vehicle speed sensor 15. In addition to calculating the front wheel steering angle δ ₁ based on the signal from the steering angle sensor 16, various necessary data are calculated and then the control parameters are calculated. Finally, the auxiliary steering angles δ ₂ and δ ₃ are calculated from the equations (5) and (6) based on the various information obtained as described above, and the control signals corresponding to these calculation results are sent to the hydraulic control valves 7, 8 Output to the rear wheels to assist steering the rear wheels 1 and 2 to the calculated steering angles δ ₂ and δ ₃ , respectively.

With such assisted steering, steering stability at high speed and responsiveness at transition can be improved, and not only lateral acceleration characteristics but also yaw rate characteristics can be improved. As described above, the location where the sideslip angle is zero and the yaw rate gain characteristic can be freely changed, and the degree of freedom in control is significantly improved.

Although the above-mentioned example has been described on the premise of the rear-wheel biaxial vehicle as shown in FIG. 4 (a), in the front-wheel biaxial vehicle as shown in FIG. The above-mentioned idea of the present invention can be applied to the case where the auxiliary steering is also performed. In this case, it goes without saying that it is necessary to replace c with -c in the above formula.

(Advantages of the Invention) Thus, the auxiliary steering apparatus of the present invention is configured to perform auxiliary steering of the two sets of wheels other than the main steering wheel with the peculiar transfer function, so that the position with zero sideslip angle and the yaw rate gain characteristic can be freely set. It can be changed, and the degree of freedom of control can be greatly improved.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of an auxiliary steering device of the present invention, FIG. 2 is a flowchart of a control program executed by a computer of the same example, FIG. 3 is an analytical model diagram of a transfer function in the same example, and FIG. 1A and 1B are schematic plan views illustrating a multi-axle vehicle to be controlled according to the present invention. 1 ... 1st auxiliary steering wheel, 2 ... 2nd auxiliary steering wheel 3 ... Steering wheel 4 ... Front wheel (main steering wheel) 5,6 ... Auxiliary steering actuator 7,8 ... Hydraulic control valve, 9 ... … Oil pump 10 …… Shunt valve 14 …… Microcomputer 15 …… Vehicle speed sensor, 16 …… Steering angle sensor 17 …… Load sensor, 18 …… Auxiliary steering front wheel

Claims (1)

(57) [Claims] 1. A depending on the steering angle [delta] ₁ of the primary steering wheels according to the steering wheel, respectively [delta] ₂ of the other two sets of auxiliary steering wheel, in the apparatus so as to assist steering by [delta] _3, the auxiliary steering angle [delta] _2, δ ₃ is However, M: vehicle mass I: yaw moment of inertia S: Laplace operator a: center of gravity and main steering wheel axle distance b: center of gravity and first auxiliary steering wheel axle distance c: center of gravity and second auxiliary steering wheel axle distance c ₁ : Total tire cornering power of the main steering wheel c ₂ : Total tire cornering power of the first auxiliary steering wheel c ₃ : Total tire cornering power of the second auxiliary steering wheel l ₃ : Distance from the center of gravity of the point where you want to set the vehicle body side slip angle to 0 V: Vehicle speed: An auxiliary steering device for vehicles, which is configured to be controlled by the transfer function of yaw rate.