JP2005254983A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of realizing vehicle behavior in response to steering force input of a driver at high speed traveling and obtaining natural steering feeling. <P>SOLUTION: The electric power steering device has a torque sensor for detecting steering torque applied to a steering 1; a motor 5 for applying steering auxiliary force to a steering mechanism 2; and a control unit 13 for driving/controlling the motor 5 so as to generate the steering auxiliary force corresponding to the steering torque and vehicle speed. In the device, a vehicle speed sensor 14 for detecting traveling speed of the vehicle; a target yaw rate setting part 13d for setting a target yaw rate of the vehicle based on the steering torque and the vehicle speed; and a yaw rate sensor 16 for detecting an actual yaw rate are provided. The control unit 13 controls/drives the motor based on the steering torque and the deviation of the target yaw rate from the actual yaw rate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention belongs to the technical field of an electric power steering device that reduces the steering force of a driver.

The conventional electric power steering device gives the driver the optimum steering reaction force according to the steering angle by controlling the steering assist force based on the deviation between the target yaw rate calculated from the steering angle and the actual yaw rate. (For example, refer to Patent Document 1).
JP-A-9-142331

  Usually, the driver performs steering by inputting a steering angle when traveling at a low speed and by inputting a steering torque when traveling at a high speed. However, since the vehicle behavior is always defined from the steering angle in the above-described prior art, there is a problem that the vehicle behavior corresponding to the steering force input cannot be obtained during high-speed traveling, and the driver feels uncomfortable.

  The present invention has been made paying attention to the above-mentioned problem, and an object of the present invention is to provide an electric motor that can realize a vehicle behavior in accordance with a driver's steering force input during high-speed driving and obtain a natural steering feeling. The object is to provide a power steering device.

In order to achieve the above object, according to the present invention, a torque detection means for detecting a steering torque applied to the steering steering means, a motor for applying a steering assist force to the steering mechanism, and at least a detection torque according to the torque detection means. In an electric power steering apparatus having steering assist force control means for driving and controlling the motor so as to generate a steering assist force,
Vehicle speed detecting means for detecting the traveling speed of the vehicle;
A target motion state quantity setting means for setting a target motion state quantity of the vehicle based on the steering torque and the vehicle speed;
An actual motion state amount detecting means for detecting a motion state amount actually generated in the vehicle;
Deviation calculation means for obtaining a deviation between the target motion state and the actual motion state;
Provided,
The steering assist force control means controls and drives the motor based on the steering torque and the output of the deviation calculation means.

  In the present invention, the target motion state quantity of the vehicle is defined based on the steering torque, and the motor is driven and controlled based on the deviation between the target motion state quantity and the actual motion state quantity. The vehicle behavior according to the driver's steering force input can be realized, and a natural steering feeling can be obtained.

  Below, the best form for implementing the electric power steering device of the present invention is explained based on Examples 1-3.

First, the configuration will be described.
FIG. 1 is a block diagram illustrating a vehicle steering system to which the electric power steering apparatus according to the first embodiment is applied.

  A torque sensor (torque detection means) 4 for detecting a steering torque applied to the handle 1 and a steering assist to a steering shaft 3 that couples a steering operation handle (steering operation means) 1 and a steering mechanism 2 that performs a steering operation. A motor 5 is disposed.

  The handle 1 is fixed so as to be rotatable around an axis so as to face the driver in a vehicle interior (not shown). The steering mechanism 2 is constituted by a rack and pinion type steering device including a pinion 6 integrally formed at the lower end of the steering shaft 3 and a rack shaft 7 meshing with the pinion 6. The rack shaft 7 is fixed to a vehicle front portion (not shown) so as to be slidable in the left-right direction, and both ends of the rack shaft 7 are connected to steering wheels 10, 11 via left and right tie rods 8, 9. Has been.

  The motor 5 that assists the steering is coupled to the steering shaft 3 via a speed reducer 12 that converts the torque generated by the motor 5 into the rotational torque of the steering shaft 3. The motor current supplied to the motor 5 is controlled by the control unit 13.

Next, the control system of the first embodiment will be described with reference to the control block diagram of FIG.
When the steering wheel 1 is operated by the driver, the wheels 10 and 11 are steered by mechanical connection. At this time, the torsional load input to the torque sensor 4 is input to the control unit 13 as a steering torque. Further, the control unit 13 includes signals from a vehicle speed sensor 14 that detects the traveling speed of the vehicle, a yaw rate sensor (actual motion state amount detection means) 16 that detects a yaw rate that is a motion state amount actually generated in the vehicle, and the like. Is given.

  The control unit 13 has a built-in motor terminal voltage sensor 13 a for estimating the rotation speed of the motor 5 and a motor current sensor 13 b for detecting the actual current value of the motor 5.

  In addition, the control unit 13 is provided with a target current setting unit 13c and a target yaw rate setting unit (target exercise state quantity setting means) 13d. The target current setting unit 13c sets a target current value based on the steering torque and the vehicle speed. The target yaw rate setting unit 13d sets the target yaw rate according to the steering torque and the vehicle speed.

  In the target yaw rate setting unit 13d, the target yaw rate corresponding to the vehicle speed is set to be smaller in proportion to the height of the vehicle speed. Further, the target yaw rate corresponding to the steering torque is set so as to increase in proportion to the steering torque, and the characteristic is composed of a linear term without delay.

  The control unit 13 takes a deviation between the actually measured yaw rate of the vehicle and the target yaw rate (corresponding to a deviation calculating means), and subtracts a correction amount corresponding to the deviation amount from the target current value, thereby obtaining a current command value for the motor 5. Is calculated. Then, the motor 5 is controlled and driven so that the actual current value of the motor 5 matches the current command value (corresponding to the steering assist force control means). Power supplied to the motor 5 is provided by a battery 15.

Next, the operation will be described.
In the first embodiment, in the target yaw rate setting unit 13d, the higher the vehicle speed, the lower the target yaw rate. Therefore, the deviation from the actual yaw rate increases and the reaction force increases. In addition, since the target yaw rate according to the steering torque is composed of a linear term without delay, when a vehicle behavior delay with respect to the steering angle occurs at the beginning of steering, the steering force becomes heavy and a more natural steering feeling. Can be realized.

Next, the effect will be described.
In the electric power steering apparatus according to the first embodiment, the effects listed below can be obtained.

  (1) The controller 13 sets a target yaw rate (target motion state quantity of the vehicle) based on the steering torque, and drives and controls the motor 5 based on a deviation between the target yaw rate and the actual yaw rate (actual motion state quantity). Therefore, the vehicle behavior according to the driver's steering force input during high-speed traveling can be realized, and a natural steering feeling can be obtained.

  (2) Since the yaw rate is used as the vehicle motion state quantity, the relationship with the turning direction of the vehicle can be optimized according to the input (steering angle, steering torque) selected by the driver.

First, the configuration will be described.
The electric power steering apparatus according to the second embodiment is different from the first embodiment in that a lateral acceleration (lateral G) is used instead of the steering torque as the actual motion state quantity. In addition, since the other structure is the same as Example 1, the same code | symbol is attached | subjected to the same component and description is abbreviate | omitted.

  FIG. 3 is a control block diagram of the electric power steering apparatus according to the second embodiment, in which the control unit 20 sets a target lateral G setting unit that sets a target lateral G based on the steering torque and the vehicle speed as target motion state amount setting means. 13e. In the target lateral G setting unit 13e, the target lateral G corresponding to the vehicle speed is set so as to decrease in proportion to the height of the vehicle speed. Further, the target lateral G corresponding to the steering torque is set so as to increase in proportion to the steering torque, and the characteristic is composed of a linear term without delay.

  The control unit 20 takes the deviation between the lateral G of the vehicle actually measured by the lateral G sensor 17 and the target lateral G, and subtracts a correction amount corresponding to the deviation amount from the target current value. Calculate the value.

Next, the effect will be described.
In the electric power steering apparatus according to the second embodiment, in addition to the effect (1) of the first embodiment, the following effects can be obtained.

  (3) Since the lateral G is used as the vehicle motion state quantity, the relationship with the lateral movement amount of the vehicle can be optimized according to the input (steering angle, steering torque) selected by the driver.

First, the configuration will be described.
The electric power steering apparatus according to the third embodiment is different from the first embodiment in that a steering amount in which a steering torque and a steering angle are combined is defined and a portion for setting a vehicle target exercise force with respect to the steering amount is provided. In addition, since the other structure is the same as Example 1, the same code | symbol is attached | subjected to the same component and description is abbreviate | omitted.

  FIG. 4 is a control block diagram of the electric power steering apparatus according to the third embodiment. The control unit 30 includes a steering amount setting unit 13f and a target yaw rate setting unit 13g. The steering amount setting unit 13f calculates the ratio of the steering torque and the steering angle to the steering amount based on the vehicle speed (weighs the steering torque and the steering angle according to the vehicle speed), and according to this ratio, The steering amount (sum of the steering torque and the steering angle) is set from the equation (1).

Steering amount = (steering angle × steering angle ratio) + (steering torque × steering torque ratio) (1)
However, the steering angle ratio + the steering torque ratio = 1, and the steering angle ratio is set to be larger as the vehicle speed is lower and the steering torque ratio is set to be larger as the vehicle speed is higher.

  Here, in the electric power steering apparatus, since the handle shaft and the motor shaft are mechanically connected via a speed reducer, in the first embodiment, the reduction ratio is added to the motor angle obtained by integrating the calculated motor speed. Thus, the steering angle is set (corresponding to the steering angle detecting means). The steering angle may be measured by adding a steering angle sensor that detects the angle to the handle shaft.

  The target yaw rate setting unit 13g sets the target yaw rate based on the set steering amount. In the target yaw rate setting unit 13g, the target yaw rate corresponding to the vehicle speed is set so as to decrease in proportion to the height of the vehicle speed. Further, the target yaw rate corresponding to the steering amount is set so as to increase in proportion to the steering amount, and its characteristic is composed of a linear term without delay.

Next, the operation will be described.
The driver selects the steering angle at low speed as the steering input and selects the steering torque at high speed. In the middle of this, it has been clarified by the present inventors' research that it is a combination of both.

  However, in the above-described conventional device described in Japanese Patent Laid-Open No. 9-142331, the vehicle behavior is always defined from the steering angle regardless of the vehicle speed, so that the vehicle behavior corresponding to the steering force input during high speed traveling cannot be obtained. The driver feels uncomfortable.

  On the other hand, in the electric power steering apparatus according to the third embodiment, the ratio of the steering angle to the steering amount is increased at a low speed (the ratio of the steering torque is decreased), and the ratio of the steering torque to the steering amount is increased as the speed increases. By setting a target yaw rate based on the calculated steering amount and correcting the motor current according to the deviation between the target yaw rate and the actual yaw rate, it is possible to generate a vehicle behavior according to the driver's input. And natural steering feeling can be realized.

Next, the effect will be described.
In the electric power steering apparatus according to the third embodiment, in addition to the effects (1) and (2) of the first embodiment, the following effects can be obtained.

  (4) The target yaw rate setting unit 13f changes the weighting of the steering torque and the steering angle with respect to the target motion state quantity according to the vehicle speed, and the weighting of the steering angle is larger than the weighting of the steering torque as the vehicle speed decreases, and as the vehicle speed increases. In order to make the weighting of the steering torque larger than the weighting of the steering angle, the target yaw rate according to the steering angle that is the driver's input when driving at low speed, the target yaw rate that is according to the steering torque that is the driver's input when driving at high speed, When traveling at a high speed, a natural steering feeling corresponding to the driver's input is obtained, such as a target yaw rate corresponding to a value obtained by distributing the steering torque and the steering angle.

1 is a block diagram showing a steering system of a vehicle to which an electric power steering device of Embodiment 1 is applied. FIG. 3 is a control block diagram of the electric power steering apparatus according to the first embodiment. FIG. 6 is a control block diagram of an electric power steering apparatus according to a second embodiment. FIG. 6 is a control block diagram of an electric power steering apparatus according to a third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Handle 2 Steering mechanism 3 Steering shaft 4 Torque sensor 5 Motor 6 Pinion 7 Rack 8, 9 Tie rod 10, 11 Front wheel 12 Reducer 13 Control unit 13a Voltage sensor 13b Current sensor 13c Target current setting part 13d Target yaw rate setting part 13e Target side G setting unit 13f Steering amount setting unit 13g Target yaw rate setting unit 14 Vehicle speed sensor 15 Battery 16 Yaw rate sensor 17 Lateral G sensor

Claims (5)

Torque detecting means for detecting steering torque applied to the steering means,
A motor that applies steering assist force to the steering mechanism;
Steering assist force control means for drivingly controlling the motor so as to generate at least steering assist force according to torque detected by the torque detection means;
In an electric power steering apparatus having
Vehicle speed detecting means for detecting the traveling speed of the vehicle;
A target motion state quantity setting means for setting a target motion state quantity of the vehicle based on the steering torque and the vehicle speed;
An actual motion state amount detecting means for detecting a motion state amount actually generated in the vehicle;
Deviation calculation means for obtaining a deviation between the target motion state and the actual motion state;
Provided,
The electric power steering apparatus characterized in that the steering assist force control means controls and drives the motor based on the steering torque and the output of the deviation calculation means. The electric power steering apparatus according to claim 1, wherein
A steering angle detecting means for detecting a steering angle of the steering operation means is provided;
The electric power steering apparatus, wherein the target motion state quantity setting means sets a target motion state quantity of the vehicle based on a steering torque, a vehicle speed, and a steering angle. The electric power steering apparatus according to claim 2,
The target motion state quantity setting means changes the weighting of the steering torque and the steering angle with respect to the target motion state quantity according to the vehicle speed,
The lower the vehicle speed, the larger the steering angle weight than the steering torque weight,
An electric power steering apparatus characterized in that the weighting of the steering torque is made larger than the weighting of the steering angle as the vehicle speed increases. In the electric power steering device according to any one of claims 1 to 3,
The electric power steering apparatus characterized in that the vehicle motion state quantity is a yaw rate. In the electric power steering device according to any one of claims 1 to 3,
The electric power steering apparatus characterized in that the vehicle motion state quantity is a lateral acceleration.

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