JP3666244B2 - Control device for electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an electric power steering device that applies a steering assist force by a motor to a steering system of an automobile or a vehicle, and particularly when the vehicle is running even if it is stalled during steering. The present invention relates to a control device for an electric power steering apparatus provided with means for continuing an assist function.
[0002]
[Prior art]
An electric power steering device for energizing an automobile or vehicle steering device with an auxiliary load by the rotational force of a motor is an auxiliary load applied to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer. It comes to be energized. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist torque (steering assist torque). The feedback control adjusts the motor applied voltage so that the difference between the current control value and the motor current detection value becomes small. The adjustment of the motor applied voltage is generally performed by a PWM (pulse width modulation) control duty. This is done by adjusting the tee ratio.
[0003]
Here, the general configuration of the electric power steering apparatus will be described with reference to FIG. 6. The shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering handle 1. A motor 20 that assists the steering force of the steering handle 1 is coupled to the shaft 2 via the clutch 21 and the reduction gear 3. Has been. The control unit 30 that controls the power steering device is supplied with electric power from the battery 14 via the ignition key 11 and the relay 13, and the control unit 30 is detected by the steering torque T detected by the torque sensor 10 and the vehicle speed sensor 12. The steering assist command value I of the assist command is calculated based on the vehicle speed V, and the current supplied to the motor 20 is controlled based on the calculated steering assist command value I. The clutch 21 is ON / OFF controlled by the control unit 30 and is ON (coupled) in a normal operation state. The clutch 21 is turned off (disconnected) when the control unit 30 determines that the power steering device is out of order and when the power of the battery 14 is turned off by the ignition key 11 and the relay 13.
[0004]
The control unit 30 is mainly composed of a CPU, and FIG. 5 shows general functions executed by a program inside the CPU. For example, the phase compensator 31 does not indicate a phase compensator as independent hardware, but indicates a phase compensation function executed by the CPU. The function and operation of the control unit 30 will be described. The steering torque T detected and input by the torque sensor 10 is phase-compensated by the phase compensator 31 in order to improve the stability of the steering system, and the phase-compensated steering torque. TA is input to the steering assist command value calculator 32. The vehicle speed V detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 32. The steering assist command value calculator 32 determines a steering assist command value I that is a control target value of the current supplied to the motor 20 based on the input steering torque TA and vehicle speed V. The steering assist command value I is input to the subtractor 30A, and is also input to the feedforward differential compensator 34 for increasing the response speed. The deviation (Ii) of the subtractor 30A is input to the proportional calculator 35. The proportional output is input to the adder 30B and to the integration calculator 36 for improving the characteristics of the feedback system. The outputs of the differential compensator 34 and the integral compensator 36 are also added to the adder 30B, and the current control value E, which is the addition result of the adder 30B, is input to the motor drive circuit 37 as a motor drive signal. The motor current value i of the motor 20 is detected by the motor current detection circuit 38, and the motor current value i is input to the subtractor 30A and fed back.
[0005]
A configuration example of the motor drive circuit 37 will be described with reference to FIG. 6. The motor drive circuit 37 is a FET gate that drives the gates of the field effect transistors (FETs) FET1 to FET4 based on the current control value E from the adder 30B. A drive circuit 371, an H bridge circuit composed of FET1 to FET4, a boost power source 372 for driving the high side of FET1 and FET2, and the like. The FET1 and FET2 are turned on / off by a PWM (pulse width modulation) signal having a duty ratio D1 determined based on the current control value E, and the magnitude of the current Ir that actually flows through the motor is controlled. FET3 and FET4 are driven by a PWM signal having a duty ratio D2 defined by a predetermined linear function equation (D2 = a · D1 + b, where a and b are constants) in a region where the duty ratio D1 is small, and a region where the duty ratio D1 is large. Then, it is turned ON / OFF according to the rotation direction of the motor determined by the sign of the PWM signal. For example, when the FET 3 is in a conductive state, the current flows through the FET 1, the motor 20, the FET 3, and the resistor R 1, and a positive current flows through the motor 20. When the FET 4 is in a conductive state, the current flows through the FET 2, the motor 20, the FET 4, and the resistor R 2, and a negative current flows through the motor 20. Therefore, the current control value E from the adder 30B is also a PWM output. The motor current detection circuit 38 detects the magnitude of the positive current based on the voltage drop across the resistor R1, and detects the magnitude of the negative current based on the voltage drop across the resistor R2. The motor current value i detected by the motor current detection circuit 38 is input to the subtracter 30A and fed back.
[0006]
In such a configuration, when the engine speed is stopped, the power supply from the alternator to the battery 14 is stopped. At this time, if the current output to the motor 20 is continued for a long time, the battery 14 is overdischarged and the engine cannot be started. For this reason, conventionally, when the engine is stopped or when the engine speed becomes a predetermined value or less, the current output to the motor 20 is stopped. Similarly, when the engine is started, the assist of the electric power steering is stopped until the engine speed reaches a predetermined value.
[0007]
[Problems to be solved by the invention]
If the engine speed is stopped or lower than a predetermined value at the time of steering and if the assist is suddenly lost while the vehicle is running due to inertia, the steering force changes suddenly, which is dangerous when the driver steers. In particular, if the engine stalls during low-speed steering or low-speed steering and the steering is suddenly returned by the reaction force from the tires, the driver will feel anxious and dangerous. End up. However, if the motor is assisted regardless of the operation / stop of the engine rotation, depending on the driving situation of the driver, the battery may be over-discharged by steering for a long time in the stopped state, and the engine cannot be started. . For this reason, the motor could not be assisted regardless of the engine speed.
[0008]
In addition, as disclosed in Japanese Patent Laid-Open No. 5-77749, an electric power steering device has been proposed that assists the vehicle speed until the vehicle speed becomes a predetermined speed or less when the engine stops. However, when turning at an intersection, etc., when the engine speed is stopped and the vehicle speed is, when steering while decelerating, depending on the setting, the assist is stopped despite being steered, It is conceivable that the purpose of the sudden steering change at the time of the engine stall cannot be achieved.
[0009]
The present invention has been made under the circumstances as described above, and an object of the present invention is to provide means for continuing the assist function when the vehicle is running and steering even if it is stalled. It is an object of the present invention to provide a control device for an electric power steering apparatus that is provided to improve stability.
[0010]
[Means for Solving the Problems]
The present invention, the motor giving a steering assist command value calculated by have groups Dzu on a steering torque generated in a steering shaft, a steering assist force to a steering mechanism have groups Dzu the current control value calculated from the motor current value of the motor The above-described object of the present invention is to provide an engine speed sensor for detecting the engine speed, and the engine speed when the engine is started. An engine start detection means for determining whether or not the rotation speed has become a predetermined value or more by inputting a rotation speed signal from the number sensor, and when the engine start detection means determines that the rotation speed has become the predetermined value or more In response to the engine start detection flag set to, allow the steering assist force to be applied to the motor A cyst permission determining means, a torque sensor for detecting the steering torque, a neutral determining means for determining whether or not the torque signal of the torque sensor is in a neutral state, a vehicle speed sensor for detecting a vehicle speed, and an output of the vehicle speed sensor Stop assisting means for determining whether or not it is equal to or less than a predetermined value, and the assist permission determining means is configured such that the engine speed is equal to or lower than a predetermined value and the engine start detection flag is set. The condition is achieved by stopping the application of the steering assist force to the motor when the vehicle speed is equal to or lower than a predetermined value and the torque signal is in a neutral state .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In order to solve the above-described problem, in the present invention, at the time of starting, motor assist is prohibited until the engine speed reaches a predetermined value or more. When the engine speed is detected to be equal to or higher than a predetermined value after starting, the fact that the engine has started is stored, and then motor assist is permitted. If the engine speed becomes less than the predetermined value after the engine starts, the motor assist is continued when the vehicle speed signal is greater than the predetermined value and the torque signal is in the steering state. When neutral, motor assist is prohibited. As a result, when steering at a stationary or low speed state, if the engine stops or falls below a predetermined value, the vehicle is almost stopped, and the assist is continued until the steering torque becomes neutral. The assist can be stopped without suddenly changing the steering force.
[0012]
Embodiments of the present invention will be described below with reference to the drawings.
[0013]
FIG. 1 shows an embodiment of the present invention corresponding to FIG. 5. In the present invention, an engine speed sensor 16 for measuring the engine speed of a vehicle is provided, and a speed signal RS from the engine speed sensor 16 is provided. Is input to the engine start detection means 301 and the assist permission determination means 302. Further, the steering torque T from the torque sensor 10 is input to the assist permission determination unit 302 via the neutral determination unit 303 and the gate circuit 305, and the vehicle speed V from the vehicle speed sensor 12 passes through the stop determination unit 304 and the gate circuit 305. The information is input to the assist permission determination unit 302. Then, the permission / prohibition signal PR determined by the assist permission determination unit 302 is input to the motor drive circuit 37.
[0014]
In such a configuration, after the ignition key 11 is turned on, the initial setting and initial diagnosis in the control unit 30A are performed, and thereafter the assist of the motor 20 is prohibited until the engine speed becomes a predetermined value or more. When the engine speed exceeds a predetermined value, an engine start detection flag is set and assist of the motor 20 is permitted. If the engine speed becomes a predetermined value or less after the engine is started, an engine start flag for recognizing whether the engine has already been started is checked. If the engine is stopped after starting, check the vehicle speed V. If the vehicle speed V is equal to or lower than a predetermined value, the steering torque T is checked next to determine whether or not the vehicle is in a neutral state. If the vehicle speed V is equal to or higher than the predetermined value or the steering torque T is in the steering state, the assist of the motor 20 is continued even if the engine is stopped. On the other hand, when the vehicle speed V becomes equal to or lower than the predetermined value and the torque becomes neutral, the assist of the motor 20 is stopped.
[0015]
The flowchart of FIG. 2 shows an operation example at the time of engine start, and it is always determined whether or not the ignition key 11 is ON (step S1). The motor assist by the motor drive circuit 37 is prohibited by prohibiting the / prohibition signal PR (step S2). Then, the engine start detection means 301 reads the rotational speed signal RS (step S3), determines whether or not the engine rotational speed has become a predetermined value or more (step S4), and assist permission determination when it has exceeded the predetermined value. An engine start detection flag is set for the means 302 (step S5). As a result, the assist permission determination means 302 permits the permission / prohibition signal PR and permits motor assist (step S6).
[0016]
On the other hand, FIG. 3 shows an operation example at the time of engine stall. The engine start detection means 301 reads the rotation speed signal RS (step S10) and determines whether the rotation speed is equal to or less than a predetermined value (step S11). . When the vehicle speed V is less than the predetermined value, the vehicle speed V is read through the stop determination means 304 and the gate circuit 305 (step S12), and it is determined whether or not the vehicle speed V is less than the predetermined value (step S13). When the vehicle speed V is equal to or lower than the predetermined value, the steering torque T is read through the neutral determination means 303 and the gate circuit 305 (step S14), and it is determined whether or not the vehicle is in the neutral state (step S15). When it is determined that the vehicle is in the neutral state, the assist permission determination unit 302 permits the permission / prohibition signal PR and prohibits the motor assist (step S16). On the other hand, when it determines with NO in said step S11, S13, and S15, normal control is implemented (step S17) and it returns to said step S10.
[0017]
In the above description, the neutral state is determined after it is determined that the vehicle speed is equal to or lower than the predetermined value. However, the determination may be performed in parallel or the order may be changed.
[0018]
【The invention's effect】
As described above, according to the control device for the electric power steering apparatus of the present invention, since the means for continuing the assist function is provided when the vehicle is running even if the vehicle is stalled during steering, It is possible to ensure extremely high safety even in
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of a control unit in an electric power steering apparatus according to the present invention.
FIG. 2 is a flowchart showing an operation example at start-up according to the present invention.
FIG. 3 is a flowchart showing an operation example at the time of stall according to the present invention.
FIG. 4 is a block diagram showing an example of an electric power steering device.
FIG. 5 is a block diagram showing a general internal configuration of a control unit.
FIG. 6 is a connection diagram illustrating an example of a motor drive circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steering handle 5 Pinion rack mechanism 10 Torque sensor 12 Vehicle speed sensor 16 Engine speed sensor 20 Motor 30, 30A Control unit 31 Phase compensator 37 Motor drive circuit 38 Motor current detection circuit 301 Engine start detection means 302 Assist permission determination means

Claims (1)

Control for controlling the motor to provide a steering assist command value calculated by have groups Dzu on a steering torque generated in a steering shaft, a steering assist force to a steering mechanism have groups Dzu the current control value calculated from the motor current value of the motor In the control device for the electric power steering apparatus provided with the unit, the control unit includes:
An engine speed sensor for detecting the engine speed;
Engine start detection means for inputting a rotation speed signal from the engine rotation speed sensor at the time of engine start and determining whether or not the rotation speed is equal to or higher than a predetermined value;
An assist permission determination means for allowing an engine start detection flag to be set when the engine start detection means determines that the rotational speed has reached a predetermined value or more, and allowing a steering assist force to be applied to the motor;
A torque sensor for detecting the steering torque;
Neutral determination means for determining whether the torque signal of the torque sensor is in a neutral state;
A vehicle speed sensor for detecting the vehicle speed;
Stop determination means for determining whether an output of the vehicle speed sensor is equal to or less than a predetermined value;
With
The assist permission determining means is provided on the condition that the engine speed is not more than a predetermined value and the engine start detection flag is set, and the vehicle speed is not more than a predetermined value and the torque signal is in a neutral state. Sometimes, the control device for the electric power steering device stops applying the steering assist force to the motor.

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