JP3929998B2 - Reaction force control device - Google Patents

Description

  The present invention relates to a reaction force control device for controlling a reaction force component to be applied to an operator in a vehicle steering system.

  An electric power steering device is known as a vehicle steering device. In the electric power steering apparatus, a steering shaft coupled to a steering wheel and a steering mechanism for steering the steered wheels are mechanically coupled, and an electric motor for assisting a steering force is linked to the steering mechanism. In general, the drive torque command value (drive current value) of the electric motor is controlled such that the auxiliary steering force increases as the steering torque acting on the steering shaft increases.

  Further, in this electric power steering device, in order to suppress the irregular behavior of the vehicle due to disturbance, the vehicle behavior (for example, the yaw rate) is detected by the detecting means, and the driving torque correction value in the direction to cancel the vehicle behavior is calculated. In some cases, the motor is controlled by subtracting the drive torque correction value from a base drive torque command value set according to the steering torque to obtain a drive torque command value (see, for example, Patent Document 1). When configured in this way, even when a yaw rate is generated during normal turning, the driving torque correction value is generated in a direction to suppress these, that is, in a direction to return the vehicle to a straight traveling state. Therefore, it can be said that the drive torque correction value is a reaction force component with respect to the assist force.

When the reaction force component is controlled based on the yaw rate information, conventionally, the reaction force component (drive torque correction value) is generally controlled to increase as the yaw rate increases. In other words, the drive torque control of the electric motor is performed so that the auxiliary steering force by the electric motor decreases as the yaw rate increases. Thereby, the stability of steering when the yaw rate is large is maintained.
Japanese Patent No. 3229074

However, when the reaction force component is controlled in this way, in a region where the steering torque is high, such as during turning at a high lateral acceleration (hereinafter abbreviated as high G), the yaw rate is large, so the reaction force component is controlled to be a large reaction force component. Therefore, there is a problem that a large manual steering force is required (in other words, the steering wheel is felt heavy) and the steering feeling is deteriorated.
Therefore, the present invention provides a reaction force control device that can obtain a good steering feeling by preventing the steering force from being increased more than necessary during high-G turning.

In order to solve the above-mentioned problems, the invention according to claim 1 is a method for controlling a reaction force component to be applied to an operator (for example, a steering wheel 3 in an embodiment described later) operated by a vehicle driver. In the force control device, a steering torque detecting means (for example, a steering torque sensor 16 in an embodiment described later) for detecting a steering torque acting on the operation element, and a vehicle behavior detecting means (for example, a behavior of the vehicle) The reaction force component is set to be larger as the detection value of the yaw rate sensor 18) and the vehicle behavior detection means is larger, and the reaction force component is set to be smaller as the detection value of the steering torque detection means is larger. Reaction force component control means (for example, a reaction force correction unit 33 in an embodiment described later).
With this configuration, basically, the greater the vehicle behavior, the larger the reaction force component that acts on the operating element, and the greater the steering torque (for example, the greater the lateral acceleration in the vehicle). ), The reaction force component acting on the operation element can be set small.

The invention according to claim 2 is the invention according to claim 1, wherein the reaction force component control means has a steering torque region that does not affect the setting of the reaction force component, and the steering torque region has a vehicle speed. The larger the size, the larger.
With this configuration, it is possible to set the reaction force component to a small value when the steering torque is relatively small at a high vehicle speed, and to increase the reaction force component until the steering torque is relatively large at a low vehicle speed. It becomes possible to set.

According to the first aspect of the present invention, it is possible to prevent the steering force from becoming too heavy when the steering torque is high, such as during turning with a large lateral acceleration, and the steering feeling is improved.
According to the second aspect of the present invention, the reaction force component can be set according to the vehicle speed, so that the steering feeling is further improved.

Embodiments of the reaction force control apparatus according to the present invention will be described below with reference to the drawings of FIGS. In the following embodiments, the present invention will be described in an aspect applied to an electric power steering device.
First, the configuration of the electric power steering apparatus will be described with reference to FIG. The electric power steering apparatus includes a manual steering force generating mechanism 1, and the manual steering force generating mechanism 1 includes a connecting shaft 5 in which a steering shaft 4 integrally coupled to a steering wheel (operator) 3 has a universal joint. And is connected to the pinion 6 of the rack and pinion mechanism. The pinion 6 meshes with a rack 7a of a rack shaft 7 that can reciprocate in the vehicle width direction, and left and right front wheels 9, 9 as steered wheels are connected to both ends of the rack shaft 7 via tie rods 8, 8. ing. With this configuration, a normal rack and pinion type steering operation can be performed when the steering wheel 3 is steered, and the direction of the vehicle can be changed by turning the front wheels 9 and 9. The rack shaft 7 and the tie rods 8 and 8 constitute a steering mechanism.

  In addition, an electric motor 10 that supplies auxiliary steering force for reducing the steering force generated by the manual steering force generation mechanism 1 is disposed coaxially with the rack shaft 7. The auxiliary steering force supplied by the electric motor 10 is converted into thrust via a ball screw mechanism 12 provided substantially parallel to the rack shaft 7 and is applied to the rack shaft 7. For this purpose, a drive-side helical gear 11 is integrally provided on the rotor of the electric motor 10 through which the rack shaft 7 is inserted, and a driven-side helical gear 13 that meshes with the drive-side helical gear 11 is provided at one end of the screw shaft 12 a of the ball screw mechanism 12. The nut 14 of the ball screw mechanism 12 is fixed to the rack 7.

The steering shaft 4 is provided with a steering speed sensor 15 for detecting the steering speed (angular speed) of the steering shaft 4, and is provided in a steering gear box (not shown) that houses the rack and pinion mechanism (6, 7a). Is provided with a steering torque sensor (steering torque detecting means) 16 for detecting a steering torque acting on the pinion 6. The steering speed sensor 15 outputs an electrical signal corresponding to the detected steering speed, and the steering torque sensor 16 outputs an electrical signal corresponding to the detected steering torque to the steering control device 20, respectively.
Further, a yaw rate sensor (yaw rate detecting means, vehicle behavior detecting means) 18 for detecting the yaw rate (vehicle behavior) of the vehicle and a vehicle speed sensor 19 for outputting an electric signal corresponding to the vehicle speed are attached to appropriate positions of the vehicle body. It has been. The yaw rate sensor 18 outputs an electric signal corresponding to the detected yaw rate, and the vehicle speed sensor 19 outputs an electric signal corresponding to the vehicle speed to the steering control device 20, respectively.

  The steering control device 20 determines a target current to be supplied to the electric motor 10 based on a control signal obtained by processing input signals from the sensors 15, 16, 18, and 19, and the electric motor 10 through the drive circuit 21. , The output torque of the electric motor 10 is controlled, and the auxiliary steering force in the steering operation is controlled.

Next, with reference to the control block diagram of FIG. 2, the current control for the electric motor 10 in this embodiment will be described.
The steering control device 20 includes a base current determination unit 31, an inertia correction unit 32, and a reaction force correction unit (reaction force component control means) 33.
The base current determination unit 31 determines a base current value corresponding to the steering torque and the vehicle speed with reference to a base current table (not shown) based on the output signals of the steering torque sensor 16 and the vehicle speed sensor 19. Here, the base current table is set so that the base current increases as the steering torque increases, and the base current decreases as the vehicle speed increases.
In the inertia correction unit 32, inertia mass compensation of the electric motor 10 is performed on the base current determined by the base current determination unit 31.

The reaction force correction unit 33 subtracts a correction current corresponding to the reaction force component from the current after inertia mass compensation, calculates a target current for the electric motor 10, and outputs the target current to the drive circuit 21. The drive circuit 21 controls the supply current to the electric motor 10 to be a target current, supplies the electric current to the electric motor 10, and controls the output torque of the electric motor 10.
Therefore, in the electric power steering apparatus of this embodiment, the correction current set in the reaction force correction unit 33 can be referred to as a reaction force component for the steering assist force, and the base current set in the base current determination unit 31 is this It can be said that the steering assist force before canceling the reaction force component.
The reaction force correction unit 33 includes a damper correction unit 34 and a yaw rate reaction force correction unit 35.
The damper correction unit 34 calculates a first reaction force correction current based on the steering speed, and subtracts the first reaction force correction current from the current after the inertial mass compensation.

The yaw rate reaction force correction unit 35 calculates the second reaction force correction current Im2 based on the yaw rate, and subtracts the second reaction force correction current Im2 from the current output from the damper correction unit 34 to calculate the target current. .
The calculation of the second reaction force correction current Im2 in the yaw rate reaction force correction unit 35 will be described in detail. The yaw rate correction current calculation unit 36 calculates a reference yaw rate correction current Imb with reference to a yaw rate correction current table (not shown) based on the output signal of the yaw rate sensor 18. Here, the yaw rate correction current table is set such that the reference yaw rate correction current Imb increases as the yaw rate increases (in other words, the reaction force component increases).

On the other hand, based on the output signal from the vehicle speed sensor 19, the offset torque corresponding to the vehicle speed is calculated with reference to the offset table 37. In the offset table 37, the offset torque is constant and sufficiently large in the region where the vehicle speed is low. When the vehicle speed exceeds a predetermined vehicle speed, the offset torque gradually decreases as the vehicle speed increases. Is set to be.
Then, the offset torque is subtracted from the steering torque detected by the steering torque sensor 16 to obtain a steering torque for ratio calculation (hereinafter referred to as offset steering torque), and the offset torque is obtained by referring to the steering torque ratio table 38. The corresponding ratio R is calculated. If the value obtained by subtracting the offset torque from the steering torque (ie, the offset steering torque) is negative, the offset steering torque is set to “0”.
In the steering torque ratio table 38, the ratio R is constant at 1.0 when the offset steering torque is smaller than T1, and the ratio R gradually increases as the offset steering torque increases when the offset steering torque is T1 or more and T2 or less. The ratio R is set to be constant at the lower limit value RL (1.0>RL> 0) when the offset steering torque becomes T2 or more.
A product obtained by multiplying the reference yaw rate correction current Imb calculated by the reference yaw rate correction current calculation unit 36 by the ratio R calculated from the steering torque ratio table 38 is defined as a second reaction force correction current Im2 (Im2 = Imb · R).

As described above, since the second reaction force correction current Im2 is determined by the yaw rate reaction force correction unit 35, the reaction force component based on the yaw rate is basically controlled to increase as the yaw rate increases. However, since the ratio R, which varies depending on the magnitude of the steering torque (more precisely, the offset steering torque), is multiplied, the steering torque is larger when the steering torque is larger than when the magnitude of the yaw rate is the same. The reaction force component is set smaller than when it is small. Here, the steering torque and the lateral acceleration in the vehicle have a substantially linear relationship, and the larger the steering torque, the larger the lateral acceleration, and the smaller the steering torque, the smaller the lateral acceleration. Therefore, when the steering torque is large, the reaction force component is set smaller than when the steering torque is small. In other words, when the lateral acceleration is large, the reaction force component is set smaller than when the lateral acceleration is small. Will be. That is, when the lateral acceleration is large, the reaction force component (second reaction force correction current Im2) based on the yaw rate is set to be smaller than that at normal time (when the lateral acceleration is small), so the target current of the motor 10 is increased, and the motor The output torque of 10 is increased, and the auxiliary steering force is increased. As a result, it is possible to prevent the steering wheel from becoming heavier than necessary during high-G turning and the like, and it becomes possible to operate with an appropriate steering force from normal steering to high-G turning, and a good steering fee. A ring can be realized.
In particular, in this embodiment, paying attention to the correlation between the steering torque and the lateral acceleration, the steering torque is used instead of the lateral acceleration, so that it is not necessary to use the lateral acceleration sensor, and the device configuration can be simplified. .

The reason why the ratio R is calculated based on the offset steering torque obtained by subtracting the offset torque from the steering torque detected by the steering torque sensor 16 is as follows.
In the steering torque ratio table 38, the ratio R is set to “1.0” in the region where the offset steering torque is T1 or less. Therefore, the steering torque corresponding to this region affects the setting of the reaction force component based on the yaw rate. Does not reach. In other words, the offset steering torque region below T1 is a dead zone.
On the other hand, since the offset torque is a variable set according to the vehicle speed, the offset steering torque changes according to the vehicle speed even if the steering torque is the same. FIGS. 3A and 3B are ratio characteristic diagrams in which the horizontal axis indicates the steering torque. FIG. 3A shows a case where the vehicle speed is high, and FIG. 3B shows a case where the vehicle speed is low. By using the offset steering torque in this way, the dead zone can be made variable according to the vehicle speed. That is, the dead zone at low vehicle speed (see FIG. 3B) can be made larger than the dead zone at high vehicle speed (see FIG. 3A).
As a result, a reduction effect on the reaction force component based on the yaw rate is exhibited from a relatively small steering torque at a high vehicle speed, and a reaction force based on the yaw rate until the steering torque becomes relatively large at a low vehicle speed. It is possible to make it difficult to reduce the components. In this way, for example, when turning an intersection at a low speed, the auxiliary steering force by the electric motor 10 can be reduced, and the steering wheel 3 can be easily returned.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, the reaction force control device according to the present invention is not limited to the application to the electric power steering device of the above-described embodiment, but is a steering device for a vehicle (SBW) of a steering-by-wire system, an active steering device, The present invention can also be applied to a vehicle steering device for a system and a vehicle steering device (VGS) for a variable gear ratio steering system.
Note that the steering-by-wire system means that the operating element and the steering mechanism are mechanically separated, a reaction force motor that applies a reaction force to the operating element, and a steering wheel provided in the steering mechanism. The steering system includes a steering motor that generates a force for turning the vehicle.
The active steering system is a steering system that controls the front wheel steering angle and the rear wheel steering angle in accordance with the steering operation of the driver and the motion state of the vehicle.
The variable gear ratio steering system is a steering system in which the steering gear ratio can be changed according to the magnitude of the steering angle.

It is a lineblock diagram of an electric power steering device provided with a reaction force control device concerning this invention. It is a block diagram of the current control with respect to the electric motor of the said electric power steering device. It is a ratio characteristic figure at the time of high vehicle speed and low vehicle speed.

Explanation of symbols

3 Steering wheel (operator)
16 Steering torque sensor (steering torque detection means)
18 Yaw rate sensor (yaw rate detection means, vehicle behavior detection means)
33 reaction force correction unit (reaction force component control means)

Claims (2)

In a reaction force control device that controls a reaction force component to be applied to an operator operated by a driver of a vehicle,
Steering torque detecting means for detecting steering torque acting on the operating element;
Vehicle behavior detecting means for detecting the behavior of the vehicle;
Reaction force component control means for setting the reaction force component to be larger as the detection value of the vehicle behavior detection means is larger, and setting the reaction force component to be smaller as the detection value of the steering torque detection means is larger;
A reaction force control device comprising: 2. The reaction force control according to claim 1, wherein the reaction force component control means has a steering torque region that does not affect the setting of the reaction force component, and the steering torque region increases as the vehicle speed increases. apparatus.

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