JP2004130903A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device that does not perform unnecessary fade-in control in turning-on a system having an adjustable fade means. <P>SOLUTION: The electric power steering device comprises a motor 110 for applying auxiliary torque to a steering system, a steering torque detecting section 112 for detecting the steering torque of the steering system, a target current determining means 115 for determining a target current to be supplied to the motor based on at least a steering torque signal, a current detecting section 120 for detecting current flowing through the motor, a motor operation control section 118 for outputting a motor drive control signal for controlling the motor, and a gradual decrease section 30 for gradually decreasing the motor drive control signal. When an assist to the steering system is not required in turning on an ignition switch, initial multiplication coefficient of the gradual decrease section 30 is increased. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device, and more particularly to an electric power steering device that reduces the steering force of a driver by applying the power of a motor to a steering system.
[0002]
[Prior art]
The electric power steering device includes a motor in a steering system, and controls the power supplied from the motor by using a control device to reduce the steering force of the driver.
[0003]
FIG. 5 is a schematic structural diagram of the electric power steering device. In the electric power steering apparatus 100, a steering shaft 102 provided integrally with a steering wheel (handle) 101 is connected to a pinion 105a of a rack and pinion mechanism 105 via a connection shaft 103 having universal joints 103a and 103b. Thus, the manual steering torque generating mechanism 106 is configured.
[0004]
The rack shaft 107 which has rack teeth 107a meshing with the pinion 105a and is reciprocated by being axially converted by the meshing is connected to the left and right front wheels 109 as rolling shafts at both ends via tie rods 108. I have. By operating the steering wheel 101, the driver can change the direction of the vehicle by swinging the front wheels via the manual steering torque generating mechanism 106 and a normal rack and pinion type steering device.
[0005]
In order to reduce the steering torque generated by the manual steering torque generating mechanism 106, a motor 110 for supplying an assist torque (steering assist torque) is disposed coaxially with the rack shaft 107, for example, and is substantially parallel to the rack shaft 107. The assist torque supplied by the rotational movement from the motor 110 via the provided ball screw mechanism 111 is converted into a force for the linear movement and acts on the rack shaft 107.
[0006]
The rotor of the motor 110 is integrally provided with a drive-side helical gear 110a. The helical gear 110a meshes with a helical gear 111b provided integrally with the shaft end of the screw shaft 111a of the ball screw mechanism 111. The nut of the ball screw mechanism 111 is connected to the rack shaft 107.
[0007]
FIG. 6 is a diagram illustrating a control device of the electric power steering device. In FIG. 5, a manual steering torque detector 112 for detecting a manual steering torque T acting on the pinion 105a is provided in a steering gear box (not shown). The manual steering torque detector 112 converts the detected manual steering torque T into a manual steering torque detection signal Td, and inputs the converted manual steering torque detection signal Td to the control device 114. The control device 114 operates the motor 110 using the manual steering torque detection signal Td as a main signal, and controls the power (steering assist torque) output by the motor 110.
[0008]
The control device 114 includes a target current determination unit 115 and a control unit 116. The target current determination unit 115 determines a target assist torque based on the manual steering torque detection signal Td, and outputs a target current signal IT required to supply the target assist torque from the motor 110.
[0009]
FIG. 7 is a block diagram of the control device 114. The control device 114 includes a target current determination unit 115 and a control unit 116, and the control unit 116 includes a deviation calculation unit 117, a motor operation control unit 118, a motor drive unit 119, and a current detection unit 120. The deviation calculator 117 obtains a deviation between the target current signal IT output from the target current determiner 115 and the motor current signal IM from the current detector 120, and outputs the value as a deviation signal 117a.
[0010]
The motor operation control unit 118 includes a deviation current control unit 121, a gradual increase unit 130, and a PWM signal generation unit 122. The deviation current control unit 121 performs processing such as proportionality, integration, and differentiation on the input deviation signal 117a to control the motor current supplied to the motor 110 so that the value of the deviation signal 117a approaches zero. Of the drive current signal 121a is generated and output.
[0011]
The gradual increase unit 130 is a device configured to gradually increase the drive current signal 121a as time passes when the ignition switch is turned on. That is, the device is a device that performs a process of multiplying the input drive current signal by a multiplication coefficient k and outputs the multiplication coefficient k. At this time, the multiplication coefficient k is gradually increased with time.
[0012]
The PWM signal generation unit 122 generates a PWM (pulse width modulation) signal for performing the PWM operation of the motor 110 based on the drive current signal 121a, and outputs the generated PWM signal as a motor drive control signal 122a. When the drive current signal is gradually increased with the passage of time by the gradually increasing section 130, the PWM signal generation section 122 outputs a gradually increasing motor drive control signal.
[0013]
The motor drive section 119 includes a gate drive circuit section 123 and a motor drive circuit 124 in which four power field effect transistors are connected in an H-bridge circuit configuration. The gate drive circuit unit 123 selects two field effect transistors according to the steering direction of the steering wheel 101 based on the motor drive control signal (PWM signal) 122a, and drives the gates of the selected two field effect transistors. These field effect transistors are switched.
[0014]
The current detection unit 120 detects a motor current (armature current) flowing through the motor 110 and outputs a motor current signal IM.
[0015]
As described above, the control device 114 PWM-controls the current supplied from the battery power source 126 to the motor 110 based on the manual steering torque T detected by the manual steering torque detection unit 112, and outputs the power (the steering assist torque) ) Control.
[0016]
As shown in FIG. 7, the control device 114 detects the motor current actually flowing to the motor 110 as a motor current signal IM in the control unit 116 and performs feedback control based on the motor current signal IM, thereby controlling the motor 110. The control characteristics have been improved.
[0017]
As described above, the manual steering torque T of the driver is detected by the manual steering torque detecting unit 112 of the manual steering torque generating mechanism 106, and the output of the motor 110 is controlled by the control device 114 to drive the steering gear box. Assists the force for the rack shaft 107 to move straight. Several such electric power steering devices have been disclosed (for example, see Patent Document 1).
[0018]
[Patent Document 1]
JP-A-11-263239
[Problems to be solved by the invention]
The control device has a microcomputer that controls the electric power steering device, and the microcomputer performs current feedback so that the motor current matches the target current signal IT corresponding to the manual steering torque. At the beginning and end of the control, there is known a function of fading in / out the assist amount so as not to give a sense of incongruity (abrupt force change or the like) to the steering. In particular, the fade-in is performed in order that the driver may turn on the ignition while applying torque to the steering wheel. At that time, if the assist gain is set to 100%, the steering wheel suddenly comes off to give an uncomfortable feeling. there were. However, when no torque is applied when the ignition is turned on, that is, when assist is not required, fade-in control is not necessary.
[0020]
An object of the present invention is to provide an electric power steering apparatus that does not perform unnecessary fade-in control when the system is turned on in a system including variable fade means in order to solve the above problem.
[0021]
Means and action for solving the problem
The electric power steering apparatus according to the present invention is configured as follows to achieve the above object.
[0022]
An electric power steering apparatus according to the present invention (corresponding to claim 1) includes a motor for applying an auxiliary torque to a steering system, a steering torque detecting unit for detecting a steering torque of the steering system, and a motor based on at least a steering torque signal. A target current determining unit that determines a target current to be supplied to the motor, a current detecting unit that detects a current flowing through the motor, a motor operation control unit that outputs a motor drive control signal for driving the motor, and gradually outputs the motor drive control signal. Fade-in processing for outputting a no-fade-in command signal to the gradually increasing portion when the target current signal output from the target current determining portion when the ignition switch is turned on is less than or equal to a predetermined value in the electric power steering apparatus having the gradually increasing portion Unit, which receives the non-fade-in command signal by the fade-in processing unit. Characterized by increasing the initial multiplication coefficients to be multiplied to the signal.
[0023]
According to the electric power steering apparatus according to the present invention, a motor that applies an auxiliary torque to a steering system, a steering torque detector that detects a steering torque of the steering system, and a target to be supplied to the motor based at least on the steering torque signal A target current determination unit for determining a current, a current detection unit for detecting a current flowing through the motor, a motor operation control unit for outputting a motor drive control signal for driving the motor, and a gradually increasing unit for gradually increasing the motor drive control signal An electric power steering device having a fade-in processing unit that outputs a no-fade-in command signal to a gradually increasing unit when a target current signal output from a target current determination unit when an ignition switch is turned on is equal to or smaller than a predetermined value; The gradually increasing section that receives the non-fade-in command signal by the When the driver suddenly steers the steering wheel immediately after the ignition switch is turned on, the system does not perform unnecessary fade-in control when the system is turned on to increase the initial multiplication coefficient to be calculated. In this case, appropriate assist can be performed instead of weak assist at the time of fade-in, and a good steering feel can be obtained.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0025]
The structure of the electric power steering device is basically the same as that shown in FIG. 5, and the structure and operation are as described above.
[0026]
FIG. 1 is a block diagram of a control device for an electric power steering device according to the present invention. The control device 1 shown in FIG. 1 is obtained by adding a fade-in processing unit 10 to the conventional control device 114 shown in FIGS. 6 and 7. Further, a function to be described later is added to the gradually increasing portion.
[0027]
In the gradual increase section 30, the fade-in processing section 10 performs a gradual increase processing of the multiplication coefficient k applied to the drive current signal when the steering torque is small and the target current IT is equal to or less than a very small torque input at which the target current IT becomes 0A. Is interrupted, and the multiplication coefficient k is set to 1 after a lapse of a specified time.
[0028]
FIG. 2 is a configuration diagram of the fade-in processing unit 10. The fade-in processing unit 10 includes a CPU 11 and a memory 12, and the memory 12 stores a fade-in processing program 14. Further, the fade-in processing unit 10 includes an input unit 15 and an output unit 16.
[0029]
The fade-in processing program 14 is a program for determining whether or not to perform the fade-in processing and outputting the fade-in command signal or the non-fade-in command signal, and its flowchart is shown in FIG. When the ignition switch is turned on and the target current IT is input from the target current determination unit 115 to the fade-in processing unit 10 (step ST10), the CPU 11 determines whether the target current IT is zero (step ST11). If the target current IT is not zero, a fade-in command signal is output to the gradually increasing section (step ST12). If the target current IT is zero, it is determined whether or not a specified time has elapsed by a timer (step ST13). If the specified time has not elapsed, the process returns. A fade-in command signal is output to the gradually increasing section (step ST14).
[0030]
Next, the gradually increasing section 30 will be described. The gradual increase unit 30 includes a CPU, a memory, an input unit, and an output unit (not shown). A processing program is stored in the memory. The flowchart of the processing program in the gradual increase unit 30 is as shown in FIG. When the ignition switch is turned on and an ON signal is input, the program starts, and first, it is determined whether the signal from the fade-in processing section is a fade-in command signal or a no-fade-in command signal (step ST20). If the signal is a fade-in command signal, a fade-in is executed (step ST21). That is, the multiplication coefficient k by which the drive current signal 121a output from the deviation current control unit 117 is multiplied by 0 until the preset time elapses from the supply of the fade-in command signal, and then the multiplication coefficient k by 0 The drive current is gradually increased from time to time 1 to generate a drive current gradually increasing signal. Then, it is determined whether or not the multiplication coefficient k has become 1 (step ST22). If the multiplication coefficient k becomes 1, normal control is performed with the multiplication coefficient k being 1 (step ST23). On the other hand, when the signal from the fade-in processing unit is a non-fade-in command signal, the multiplication coefficient k is set to 1 without performing fade-in, so that the signal is multiplied by the multiplication coefficient 1 without performing fade-in ( Step ST24). Then, the multiplication coefficient k is determined in step ST22 (step ST22), and since the multiplication coefficient k is 1, the multiplication coefficient k continues to be 1 immediately and normal control is performed (step ST23).
[0031]
Next, a control method in the control device 1 shown in FIG. 1 will be described.
[0032]
The gradually increasing unit 30 starts operating when an ON signal indicating that the ignition switch has been turned on is input. Otherwise, it does not operate, and the motor drive signal passes as it is. When receiving the ON signal indicating that the ignition switch has been turned on, the gradual increase unit 30 determines, when the fade-in command signal is supplied from the fade-in processing unit 10, the drive calculated by the current feedback control unit. The current signal is gradually increased from zero with the passage of time to generate a drive current incremental signal that is gradually increased so that the drive current signal finally becomes the target current, and the generated drive current incremental signal is converted into a PWM signal generation unit. 122.
[0033]
The gradual increase unit 30 sets the coefficient k by which the drive current signal calculated by the deviation current control unit is multiplied in accordance with the deviation to 0 until a preset time elapses from the time when the fade-in command signal is supplied, and thereafter, The drive current gradually increasing signal is generated by gradually increasing the multiplication coefficient k from 0 to 1 over time. Thereafter, when the multiplication coefficient k becomes 1, the drive current signal passes as it is.
[0034]
On the other hand, when the non-fade-in command signal is supplied from the fade-in processing unit 10, the multiplication coefficient k by which the signal is multiplied without fading is set to 1, and at the same time, the drive current signal is passed as it is.
[0035]
As described above, in this electric power steering apparatus, when the ignition switch is turned on in a small torque state, the instantaneous multiplication coefficient k becomes 1 and the drive current signal passes at the same time, so that appropriate assist is performed. Can be.
[0036]
In the present embodiment, the description has been given of the case where the gradual increase section is provided in the next stage of the deviation current control section. However, the gradual increase section is provided in the next stage of the target current determination section, thereby gradually increasing the target current signal. Alternatively, the motor drive control signal may be gradually increased, or the motor drive control signal may be gradually increased by inserting a gradually increasing unit next to the PWM signal generation unit. Further, in the present embodiment, the CPU of the fade-in processing unit and the CPU of the gradually increasing unit are described separately, but one CPU may be commonly used for the fade-in processing unit and the gradually increasing unit.
[0037]
【The invention's effect】
As apparent from the above description, the present invention has the following effects.
[0038]
A motor for providing an assist torque to the steering system, a steering torque detecting unit for detecting a steering torque of the steering system, a target current determining unit for determining a target current to be supplied to the motor based on at least the steering torque signal, In an electric power steering apparatus having a current detection unit that detects a flowing current, a motor drive control unit that outputs a motor drive control signal for driving a motor, and a gradually increasing unit that gradually gradually increases the motor drive control signal, when an ignition switch is turned on, When the target current signal output from the target current determining unit is zero, the gradually increasing unit includes a fade-in processing unit that outputs a non-fade-in command signal, and the gradually increasing unit that receives the non-fade-in command signal by the fade-in processing unit. Variable fade means to increase the initial multiplication coefficient by which the input signal is multiplied. Since the system does not perform unnecessary fade-in control when the system is turned on, immediately after the ignition switch is turned on, even if the driver steers the steering wheel suddenly, appropriate assist is provided instead of weak assist at the time of fade-in. And a good steering feel can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram of a control device of an electric power steering device according to the present invention.
FIG. 2 is a configuration diagram of a fade-in processing unit;
FIG. 3 is a flowchart of a fade-in process in a fade-in processing unit;
FIG. 4 is a processing flowchart in a gradually increasing unit.
FIG. 5 is a schematic structural view of an electric power steering device.
FIG. 6 is a diagram showing a control mechanism of a conventional electric power steering device.
FIG. 7 is a block diagram of a conventional control device.
[Explanation of symbols]
10 Fade-in processing unit 11 CPU
12 Memory 14 Fade-in processing program 15 Input unit 16 Output unit 30 Gradual increase unit 110 Motor 112 Manual steering torque detection unit 114 Control device 115 Target current determination unit 116 Control unit 117 Deviation calculation unit 118 Motor operation control unit 119 Motor drive unit 120 Current Detector 130 Gradual increase

Claims (1)

A motor for applying an assist torque to the steering system;
A steering torque detector that detects a steering torque of the steering system;
A target current determination unit that determines a target current to be supplied to the motor based on at least the steering torque signal;
A current detection unit that detects a current flowing through the motor,
A motor operation control unit that outputs a motor drive control signal for driving the motor,
In an electric power steering device having a gradually increasing portion that gradually increases the motor drive control signal,
When the target current signal output from the target current determination unit when the ignition switch is turned on is smaller than a predetermined value, the gradually increasing unit includes a fade-in processing unit that outputs a no-fade-in command signal. The electric power steering apparatus according to claim 1, wherein the gradual increase unit that receives the fade-in command signal increases an initial multiplication coefficient by which the input signal is multiplied.

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