JP2005067290A - Control device for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively converge a steering wheel to the straight-ahead position of a vehicle while giving no feel of hitch of the steering wheel to a driver. <P>SOLUTION: A basic assist torque Tab is computed in accordance with steering torque Ts and a vehicle speed V so that it gets greater as the steering torque Ts gets greater and it gets smaller as the vehicle speed V gets higher (S20-40), damping control torque Tdp is computed in accordance with a steering angle speed θd, the vehicle speed V and the steering torque Ts for improving the converging performance of the steering wheel 14 to the straight-ahead position (S50-80), and assist torque is controlled in accordance with target assist torque Ta as the sum of the basic assist toque Tab and the damping control torque Tdp (S90, 100). However, the damping control torque Tdp is computed to be greater as the vehicle speed V gets higher and to be smaller as the steering torque Ts gets greater (S60, 70). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electric power steering device for a vehicle, and more particularly to a control device for an electric power steering device.

  In a vehicle such as an automobile, as one of control devices for an electric power steering device that reduces a steering burden on a driver by applying a steering assist torque, for example, as described in Patent Document 1 below, 2. Description of the Related Art Conventionally, a control device for an electric power steering device that performs damping control for converging a steering wheel to a straight traveling position of a vehicle is known.

According to such a control device for an electric power steering device, the target assist torque is calculated as the sum of at least the basic assist torque based on the steering torque and the damping control torque based on, for example, the steering angular velocity, and the electric assist is performed based on the target assist torque. Since the power steering apparatus is controlled, the convergence of the steering wheel to the straight traveling position of the vehicle can be improved as compared with the case where the damping control is not performed.
Japanese Patent No. 2568817

  However, in the conventional control device for an electric power steering apparatus that performs the damping control as described above, the damping control torque acts on the direction opposite to the steering angular velocity based on the steering angular velocity or the steering angular velocity and the vehicle speed. Therefore, if the damping control torque is set high in order to improve the convergence of the steering wheel, the steering reaction force increases when the driver steers relatively quickly, and the driver gets caught in the steering wheel. In contrast, if the damping control torque is set low to prevent the steering wheel from getting caught, the steering wheel cannot be effectively converged to the straight traveling position of the vehicle.

  The present invention has been made in view of the above-described problems in a conventional control device for an electric power steering apparatus configured to perform damping control. The main problem of the present invention is that it depends on the steering torque. By increasing or decreasing the damping control torque, the steering wheel is effectively converged to the straight traveling position of the vehicle while preventing the driver from feeling that the steering wheel is caught.

  According to the present invention, the above-mentioned main problem is that, according to the present invention, the basic assist torque is calculated based on at least the steering torque, the steering system convergence torque is calculated based on at least the steering speed, and at least the basic A target assist torque is calculated based on the assist torque and the steering system convergence torque, and a control device for the electric power steering device that controls the electric power steering device based on the target assist torque is used. This is achieved by a control device for an electric power steering apparatus, in which the magnitude of the steering system convergence torque is made smaller when the magnitude is larger than when the magnitude of the steering torque is small.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1, the magnitude of the steering system convergence torque is determined when the vehicle speed is low and the vehicle speed is low. It is comprised so that it may be large compared with (Structure of Claim 2).

  According to the configuration of the first aspect, the target assist torque is calculated based on at least the basic assist torque and the steering system convergence torque, and the electric power steering apparatus is controlled based on the target assist torque. When the steering torque is large, the steering system convergence torque is small compared to when the steering torque is small. Therefore, when the driver steers relatively quickly, the steering torque increases when the steering torque is large. The system convergence torque is reduced, which prevents the driver from feeling that the steering wheel is caught, and when the steering torque is small, such as when the steering wheel is turned back or released. A sufficiently large steering system convergence torque is generated. The ring wheel can be effectively converged into the straight-ahead position of the vehicle.

  According to the second aspect of the present invention, since the magnitude of the steering system convergence torque is larger when the vehicle speed is higher than when the vehicle speed is low, it is more effective as the vehicle speed increases and the steering reaction force decreases. Steering system convergence torque can be generated, which can effectively improve the convergence of the steering wheel when the vehicle is running at medium and high speeds, and can effectively reduce the fluctuation of the steering wheel. Thus, it is possible to effectively prevent the driver from feeling that the steering wheel is caught when the vehicle is traveling at a low speed.

[Preferred embodiment of problem solving means]
According to one preferable aspect of the present invention, in the configuration of the first or second aspect, the target assist torque is calculated based on at least the sum of the basic assist torque and the steering system convergence torque (preferably). Aspect 1).

  According to another preferred aspect of the present invention, in the configuration of claim 1 or 2, the steering system convergence torque is calculated based on at least the steering angular velocity (preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration according to claim 1 or 2, the correction coefficient is calculated so as to decrease as the magnitude of the steering torque increases, and the convergence of the steering system is calculated based on the correction coefficient. It is comprised so that a torque may be correct | amended (Preferable aspect 3).

  According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 3, the correction coefficient is 1 when the magnitude of the steering torque is equal to or less than the first reference value, and the magnitude of the steering torque. When the value exceeds the first reference value, the larger the steering torque, the more gradually decreases (preferred aspect 4).

  According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 4, the correction coefficient is configured to be 0 when the magnitude of the steering torque is equal to or greater than the second reference value (preferably Aspect 5).

  The present invention will now be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing one embodiment of a control device for an electric power steering apparatus according to the present invention.

  In FIG. 1, 10 FL and 10 FR respectively indicate left and right front wheels that are driven wheels of the vehicle 12, and 10 RL and 10 RR respectively indicate left and right rear wheels that are drive wheels of the vehicle 12. The left and right front wheels 10FL and 10FR, which are also steered wheels, are steered via tie rods 18L and 18R by a rack-and-pinion type electric power steering device 16 driven in response to steering of the steering wheel 14 by the driver. The

  In the illustrated embodiment, the electric power steering device 16 is a rack coaxial type electric power steering device and is controlled by the electronic control unit 20. The electric power steering device 16 includes an electric motor 22 and a conversion mechanism 26 of, for example, a ball screw type that converts the rotational torque of the electric motor 22 into a force in the reciprocating direction of the rack bar 24. By generating an auxiliary turning force that drives the bar 24, a steering assist torque that reduces the steering burden on the driver is generated.

  The braking force of each wheel is controlled by controlling the braking pressure of the wheel cylinders 34FR, 34FL, 34RR, 34RL by the hydraulic circuit 32 of the braking device 30. Although not shown in the drawing, the hydraulic circuit 32 includes a reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven in accordance with the depression operation of the brake pedal 36 by the driver. It is controlled by the master cylinder 38 and is controlled by the electronic control unit 40 as necessary. When the behavior of the vehicle deteriorates, the electronic control device 40 cooperates with the electronic control device 20 to control the braking force of a predetermined wheel in a manner known in the art, thereby causing the behavior of the vehicle. Control the behavior to stabilize.

  The steering shaft 42 is provided with a steering angle sensor 44 for detecting the steering angle θ and a torque sensor 46 for detecting the steering torque Ts, and the vehicle 12 is provided with a vehicle speed sensor 48 for detecting the vehicle speed V. The steering angle sensor 44 and the torque sensor 46 detect the steering angle θ and the steering torque Ts, respectively, with the vehicle turning right as positive.

  As shown in the figure, a signal indicating the steering angle θ detected by the steering angle sensor 44, a signal indicating the steering torque Ts detected by the torque sensor 46, and a signal indicating the vehicle speed V detected by the vehicle speed sensor 48 are the electronic control unit 20. Is input. Although not shown in detail in the figure, the electronic control devices 20 and 40 have, for example, a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus. Includes component microcomputer.

  The electronic control unit 20 calculates the basic assist torque Tab for reducing the driver's steering burden based on the steering torque Ts and the vehicle speed V according to the flowchart shown in FIG. 2, and the steering angular velocity θd, vehicle speed V, steering Based on the torque Ts, a damping control torque Tdp for improving the convergence of the steering wheel 14 to the straight traveling position is calculated, and the electric power steering is based on the target assist torque Ta which is the sum of the basic assist torque Tab and the damping control torque Tdp. The assist torque by the device 16 is controlled.

  In this case, the electronic control unit 20 calculates the basic damping control torque Tdp ′ as a torque in a direction opposite to the steering angular velocity θd so that the basic damping control torque Tdp ′ increases as the steering angular velocity θd increases. The vehicle speed coefficient Kvdp is calculated so that the vehicle speed coefficient Kvdp increases as the vehicle speed V increases, the correction coefficient Ktdp is calculated so that the correction coefficient Ktdp decreases as the steering torque Ts increases, and the vehicle speed coefficient Kvdp and the correction coefficient Ktdp are calculated. By calculating the damping control torque Tdp as the product of the basic damping control torque Tdp ′, the higher the vehicle speed V, the higher the damping effect and the steering wheel while preventing the driver from feeling the steering wheel 14 being caught. 14 is effectively converged to the straight position of the vehicle.

  Next, steering assist torque control in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals until the ignition switch is opened.

  First, at step 10, a signal indicating the steering angle θ is read, and at step 20, the basic assist torque Tab ′ increases as the steering torque Ts increases, based on the steering torque Ts. Based on the vehicle speed V, the basic assist torque Tab ′ is calculated from the map corresponding to the graph shown in FIG. 3 so that the vehicle speed coefficient Kv decreases as the vehicle speed V increases in step 30. The vehicle speed coefficient Kv is calculated from the map corresponding to the graph, and in step 40, the corrected basic assist torque Tab is calculated as the product of the vehicle speed coefficient Kv and the basic assist torque Tab ′.

  In step 50, the steering angular velocity θd is calculated as a time differential value of the steering angle θ, and the basic damping control torque Tdp ′ increases in the opposite direction to the steering angular velocity as the magnitude of the steering angular velocity θd increases. Thus, the basic damping control torque Tdp ′ is calculated from the map corresponding to the graph shown in FIG. 5 based on the steering angular velocity θd, and in step 60, the vehicle speed coefficient Kvdp is gradually increased as the vehicle speed V increases. Based on V, a vehicle speed coefficient Kvdp is calculated from a map corresponding to the graph shown in FIG.

  In step 70, the steering torque is calculated from the map corresponding to the graph shown in FIG. 7 based on the absolute value of the steering torque Ts so that the correction coefficient Ktdp based on the steering torque decreases as the absolute value of the steering torque Ts increases. Based on the correction coefficient Ktdp, the damping control torque Tdp is calculated in step 80 as the product of the vehicle speed coefficient Kvdp, the correction coefficient Ktdp, and the basic damping control torque Tdp ′.

  In step 90, the target assist torque Ta is calculated as the sum of the basic assist torque Tab and the damping control torque Tdp. In step 100, a control signal corresponding to the target assist torque Ta is output to the motor 22, thereby Steering assist torque control for reducing the steering force required for the driver is executed.

  Thus, according to the illustrated embodiment, in steps 20 to 40, the steering torque Ts and the vehicle speed V are set such that the magnitude increases as the steering torque Ts increases and the magnitude decreases as the vehicle speed V increases. Based on the basic assist torque Tab, the damping control torque Tdp for improving the convergence of the steering wheel 14 to the straight traveling position is calculated based on the steering angular velocity θd, the vehicle speed V, and the steering torque Ts in steps 50 to 80. In steps 90 and 100, the assist torque by the electric power steering device 16 is controlled based on the target assist torque Ta which is the sum of the basic assist torque Tab and the damping control torque Tdp.

  In this case, the damping control torque Tdp is calculated as the product of the vehicle speed coefficient Kvdp calculated in step 60, the correction coefficient Ktdp calculated in step 70, and the basic damping control torque Tdp 'calculated in step 50. Since the correction coefficient Ktdp is calculated so as to decrease as the steering torque Ts increases, a sufficient damping control torque is generated when the steering wheel 14 is released or when the driver is lightly steered. As a result, the steering wheel 14 can be effectively converged to the straight-ahead position of the vehicle, and the steering wheel 14 can be effectively prevented from wobbling, and the steering torque Ts can be increased when the driver performs relatively fast steering. As the vehicle speed increases, the damping control torque is reduced. It is possible to effectively prevent that feel caught feeling of the steering wheel 14.

  In particular, according to the illustrated embodiment, the vehicle speed coefficient Kvdp is calculated so as to increase as the vehicle speed V increases, so that it is possible to effectively improve the convergence of the steering wheel 14 when the vehicle is traveling at high speed. It is possible to effectively reduce the wobbling and effectively prevent the driver from feeling that the steering wheel 14 is caught when the vehicle travels at a low speed, which increases the steering burden on the driver.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the vehicle speed coefficient Kvdp is calculated to be 0 when the vehicle speed V is very low. For example, as shown by the broken line in FIG. Even when it is very small, it may be calculated to a value greater than 0. Also, as indicated by the one-dot chain line in FIG. This may be modified to improve the convergence of the steering wheel 14 when the vehicle is stopped.

  In the above-described embodiment, the correction coefficient Ktdp does not become zero even when the steering torque Ts is very large. For example, the correction coefficient Ktdp is indicated by a broken line in FIG. Thus, the steering torque Ts may be corrected to be 0 when the magnitude of the steering torque Ts is very large.

  In the above embodiment, the basic damping control torque Tdp ′ is calculated from the map corresponding to the graph shown in FIG. 5 based on the steering angular velocity θd in step 50, and the vehicle speed V is determined in step 60. On the basis of the map corresponding to the graph shown in FIG. 6, the vehicle speed coefficient Kvdp is calculated, and in step 70, the correction based on the steering torque is made based on the absolute value of the steering torque Ts based on the map corresponding to the graph shown in FIG. The coefficient Ktdp is calculated, and in step 80, the damping control torque Tdp is calculated as the product of the vehicle speed coefficient Kvdp, the correction coefficient Ktdp, and the basic damping control torque Tdp '. It may be modified to be calculated by a function having the angular velocity θd, the vehicle speed V, and the steering torque Ts as variables.

  Further, in the above-described embodiment, the vehicle is a rear wheel drive vehicle, but the vehicle to which the present invention is applied may be a front wheel drive vehicle or a four wheel drive vehicle, and the steering assist torque is arbitrarily controlled. As far as possible, the electric power steering device may be of any construction known in the art.

It is a schematic block diagram which shows one Embodiment of the control apparatus for electric power steering apparatuses by this invention. It is a flowchart which shows the steering assist torque control routine in an Example. It is a graph which shows the relationship between steering torque Ts and basic assist torque Tab '. It is a graph which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kv. It is a graph which shows the relationship between steering angular velocity (theta) d and basic damping control torque Tdp '. It is a graph which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kvdp. It is a graph which shows the relationship between the absolute value of steering torque Ts, and the correction coefficient Ktdp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 Steering wheel 16 Electric power steering device 20 Electronic control device 30 Braking device 40 Electronic control device 44 Steering angle sensor 46 Torque sensor 48 Vehicle speed sensor

Claims (2)

  Calculating a basic assist torque based on at least a steering torque; calculating a steering system convergence torque based on at least a steering speed; calculating a target assist torque based on at least the basic assist torque and the steering system convergence torque; A control device for an electric power steering apparatus that controls the electric power steering apparatus based on the assist torque. When the steering torque is large, the steering system convergence is larger than when the steering torque is small. A control device for an electric power steering apparatus, characterized by reducing the magnitude of torque.   The control device for an electric power steering apparatus according to claim 1, wherein the magnitude of the steering system convergence torque is larger when the vehicle speed is high than when the vehicle speed is low.

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