JP2005067414A - Control device for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an electric power steering device capable of performing smooth and safe assist restriction by providing assist reduction characteristic corresponding to power source voltage. <P>SOLUTION: In the control device for the electric power steering device, assist force by a motor is imparted to a steering system. The control device has function for reducing assist upon reduction or increase of the power source voltage and is constituted so that the reduction characteristic is variably performed in multi-stages of at least two stages or more by the power source voltage, or the reduction characteristic is variably performed in multi stages of at least two stages or more and variable gain is expressed as a voltage function of the power source voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for an electric power steering apparatus that applies a steering assist force by a motor to a steering system of an automobile or a vehicle.

  An electric power steering device that biases an automobile or a vehicle steering device with an auxiliary load by the rotational force of a motor assists the steering shaft or rack shaft with a transmission mechanism such as a gear or a belt via a reduction gear. The load is energized. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist torque (steering assist torque). In the feedback control, the motor applied voltage is adjusted so that the difference between the current command value and the motor current detection value becomes small. Generally, the adjustment of the motor applied voltage is a duty of PWM (pulse width modulation) control. This is done by adjusting the tee ratio.

  Here, the general configuration of the electric power steering apparatus will be described with reference to FIG. 9. The column shaft 2 of the steering handle 1 is connected to the steering wheel via the reduction gear 3, the universal joints 4 a and 4 b, and the pinion rack mechanism 5. Coupled to the tie rod 6. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering handle 1, and a motor 20 that assists the steering force of the steering handle 1 is coupled to the column shaft 2 via the reduction gear 3. ing. 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 control unit 30 is mainly composed of a CPU (including an MPU), and FIG. 10 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. At the same time, it is input to an integration calculator 36 for improving the characteristics of the feedback system. Together with the output of the differential compensator 34, the outputs of the proportional calculator 35 and the integral calculator 36 are also added to the adder 30B, and the current control value E, which is the addition result of the adder 30B, is used as a motor drive signal as a motor drive circuit. 37. The current i of the motor 20 is detected by the motor current detection circuit 38 and fed back to the subtractor 30A.

  In such an electric power steering device, there is a problem that the assist is suddenly lost when the conventional control device is stopped, the steering feeling is lowered, and the driver feels uncomfortable. The assist force is gradually reduced and then stopped. I was able to eliminate the sense of incongruity.

11 Such conventional shows a state of the assist operation, and reaches the operation limit voltage V ₁₀ of the power source voltage is set in advance, so that immediately stops the assist.
Japanese Patent No. 3328595

  Conventionally, in order to prevent a sense of incongruity that occurs when the electric power steering is stopped and the steering wheel becomes heavier and the steering wheel becomes heavier, the assist is gradually limited with time. In addition, even when processing for preventing such a sense of incongruity due to a decrease in feeling is performed, if the power supply voltage of the vehicle fluctuates extremely, normal control cannot be performed (a high voltage that destroys the control device). Therefore, when the power supply voltage is extremely lowered or increased, the control device must be stopped.

  As a solution to these two problems, a first determination value is set outside the normal assist operation range, and when the power supply voltage exceeds this determination value, a process of gradually limiting the assist is first performed. Then, a second determination value is further set on the outside, and when the power supply voltage exceeds the first determination value and further exceeds the second determination value, the assist system control device is stopped. (Patent Document 1).

  FIG. 12 shows an example of the configuration. The detection signal of the steering torque detection means 40 is input to the steering torque input correction means 41, the corrected steering torque signal is input to the motor control signal generation means 42, and the power source (battery ) A detection signal of the battery voltage detecting means 44 for detecting the voltage is inputted to the assist reduction start voltage range detecting means 45 and the assist stop voltage range detecting means 47. The output of the assist reduction start voltage range detection means 45 is input to the steering torque input correction means 41 via the assist reduction gain setting detection means 46, and the stop signal of the assist stop voltage range detection means 47 is input to the motor control signal generation means 42. The motor is driven via motor driving means 43.

In such a configuration, the assistance reducing firing voltage range detection unit 45 is set to reduce starting voltage V ₁₁ as the first determination value shown in FIG. 13 (A), the assist decreasing gain setting detection means 46 Figure 13 (B) in inclined shown (gain) is set, the operation limit voltage V ₁₂ as a second determination value shown in FIG. 13 (a) to assist stop voltage range detection unit 47 is set . Supply voltage is always detected by the battery voltage detection unit 44, when the power supply voltage as shown in FIG. 13 (A) becomes reduced starting voltage V ₁₁ decreases (time T _1), the assistance reducing firing voltage range detection means 45 detects this, and inputs the detection signal to the assist reduction gain setting detection means 46. As a result, the assist reduction gain setting detection means 46 performs gain correction by the steering torque input correction means 41 at the time points T _{1 to} T _{2 in} FIG. 13B, and the corrected steering torque signal is sent to the motor control signal generation means 42. Entered. Further, when the power supply voltage subsequently becomes the operation limit voltage V ₁₂ (time point T ₂ ), this is detected by the assist stop voltage range detection unit 47, and the stop signal is input to the motor control signal generation unit 42, thereby the time point T _2. Thereafter, the assist is stopped.

However, since the power source of the automobile has a large fluctuation range and is unspecified, it is difficult to optimize the operation limit voltage V ₁₂ (second determination value), and the processing of the operation limit voltage V ₁₂ (stop of the control device) is difficult. For this reason, there may be a situation in which the effect of the process of the reduction start voltage V ₁₁ (first determination value) (the assist is gradually limited) cannot be obtained. On the contrary, if priority is given to the first process, the effect of the second process cannot be obtained, and a situation may occur in which the control device is destroyed.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to provide a smooth and safe assist limit without deteriorating steering feeling by providing an assist reduction characteristic according to the power supply voltage. It is an object of the present invention to provide a control device for an electric power steering device capable of performing the above.

  The present invention relates to a control device for an electric power steering apparatus configured to apply an assist force by a motor to a steering system, and the above object of the present invention has a function of reducing assist when a power supply voltage is lowered or increased. This is achieved by varying the reduction characteristic according to the power supply voltage.

  Further, the object of the present invention is to perform the reduction characteristic in a multi-stage variable of at least two stages or to perform the reduction characteristic in a multi-stage variable of at least two stages and to provide a variable gain to the power source. This is achieved more effectively by using a voltage function of the voltage.

  According to the present invention, since the gain is gradually reduced until the power supply voltage reaches the operation limit voltage, smooth assist can always be performed without lowering the steering feeling, and the driver feels uncomfortable. Never give.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows the operating principle of the present invention, and three determination values V1, V2, and V3 are set for the power supply voltage. The determination value V1 is the assist reduction start voltage, the determination value V2 is the assist reduction characteristic change voltage, and the determination value V3 is the assist operation limit voltage. As shown in FIG. 1A, when the power supply voltage from the time point t0 reaches the determination value V1 (time point t1), the assist reduction (inclination L1) is started as shown in FIG. When the power supply voltage further reaches the determination value V2 (time point t2), the reduction characteristic L2 is changed so that the assist can be stopped before the operation limit, and when the power supply voltage reaches the determination value V3 ( At time 3), the assist is stopped. By making the slope of the characteristic L2 steeper than the slope of the characteristic L1, a smooth assist stop can be realized. It is also possible to make the slopes of the characteristics L1 and L2 a function of the power supply voltage. In FIG. 1, the range from time t0 to t1 is the assist normal operation region, the range from time t1 to t3 is the assist reduction region, and the time after time t3 is the assist stop region.

  FIG. 2 shows a first embodiment of the present invention, in which the output of the steering torque detection means 50 is input to the steering torque input correction means 51, and the detection signal of the battery voltage detection means 54 for detecting the power supply voltage starts assist reduction. The voltage is input to the voltage range detection unit 61 and the assist reduction characteristic change voltage range detection unit 62. The detection signals from the assist reduction start voltage range detection unit 61 and the assist reduction characteristic change voltage range detection unit 62 are input to the assist reduction gain setting detection unit 55, and the reduction signal from the assist reduction gain setting detection unit 55 is the steering torque. The steering torque corrected and input to the input correcting means 51 is input to the motor control signal generating means 52, and the motor is further driven via the motor driving means 53.

  The assist reduction start voltage range detection means 61 is set with the determination value V1 described in FIG. 1, and the assist reduction characteristic change voltage range detection means 62 is set with the determination value V2. Further, in the assist reduction gain setting detection means 55, inclinations L1 and L2 shown in FIG. 1B are set as correction gains.

  In such a configuration, the operation will be described with reference to the flowchart of FIG.

  First, the circuit system is initialized (step S1), the steering torque detection signal is input from the steering torque detection means 50 (step S2), the current detection signal is input (step S3), and further the battery voltage detection means. The battery voltage is input from 54 (step S4). Then, the assist reduction start voltage range detection unit 61 determines whether or not the battery voltage is outside the determination value V1 (step S5). If the battery voltage is within the determination value V1, the assist reduction gain setting detection unit 55 outputs a gain. The steering torque input correcting means 51 and the motor control signal generating means 52 calculate the motor control signal in order to perform normal assist (step S6), and the motor control signal generating means 52 outputs the motor control signal. Perform (step S7), and return to step S2.

  If it is determined in step S5 that the value is outside the determination value V1, the steering torque reduction rate is set to A (inclination L1 in FIG. 1B) (step S10), and the assist reduction characteristic change voltage range. The detection means 62 then determines whether or not the battery voltage is outside the determination value V2 (step S11). If the battery voltage is within the determination value V2, the assist reduction gain setting detection unit 55 decreases the steering torque detection signal via the steering torque input correction unit 51 (step S13), and is outside the determination value V2. The steering torque decrease rate is set to B (inclination L2 in FIG. 1B), and then the steering torque detection signal is decreased (step S12). Then, the assist reduction characteristic changing voltage range detecting means 62 determines whether or not the steering torque detection signal is 0 (step S14), and if not, the process proceeds to step S6. If the steering torque detection signal is 0, the assist of the electric power steering is stopped via the assist reduction gain setting detection means 55 and finished (step S15).

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 corresponds to FIG. 2, and the same devices are denoted by the same reference numerals and description thereof is omitted. In this example, the output of the battery voltage detection means 54 is input to the assist reduction start voltage range detection means 61, the assist reduction characteristic # 1 change voltage range detection means 621, and the assist reduction characteristic # 2 change voltage range detection means 622.

  In such a configuration, the operation will be described with reference to the flowchart of FIG. 5 and the time chart of FIG. The assist reduction start voltage range detection means 61 is set with a determination value V1, the assist reduction characteristic # 1 change voltage range detection means 621 is set with determination values V2 to V3, and the assist reduction characteristic # 2 is set. Determination values V <b> 3 to V <b> 4 are set in the changed voltage range detection unit 622.

  First, a circuit system is initialized (step S20), a steering torque detection signal is input (step S21), a current detection signal is input (step S22), and a battery voltage is input (step S23). Then, it is determined whether or not the battery voltage is outside the determination value V1 (step S24). If the battery voltage is within the determination value V1, a motor control signal is calculated to perform normal assist (step S25). A motor control signal is output (step S26), and the process returns to step S21.

  If it is determined in step S24 that the value is outside the determination value V1, the steering torque reduction rate is set to A (inclination L1 in FIG. 6A) (step S30), and then the battery voltage is determined to be the determination value. It is determined whether or not it is outside V2 (step S31). If it is outside the determination value V2, the rate of decrease in steering torque is set to B (inclination L2 in FIG. 6B) (step S32), and thereafter or above If it is determined in step S31 that the battery voltage is inside, it is further determined whether or not the battery voltage is outside the determination value V3 (step S33). In the case of the inner side, the steering torque detection signal is decreased (step S35). In the case of the outer side, the rate of decrease in the steering torque is set to C (inclination L3 in FIG. 6B) and the steering torque detection signal is decreased later. (Step S35). Thereafter, it is determined whether or not the steering torque detection signal is 0 (step S36). If not, the process proceeds to step S25. If the steering torque detection signal is 0, the electric power steering assist is stopped and terminated (step S37).

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 7 corresponds to FIG. 2, and the same devices are denoted by the same reference numerals and description thereof is omitted. In this example, assist reduction gain setting detection means (# 1) 551 with fixed reduction characteristics and assist reduction gain setting detection means (# 2) 552 with reduced characteristic voltage sensitivity are provided, and the output of battery voltage detection means 54 is The assist reduction start voltage range detection means 61, the assist reduction characteristic change voltage range detection means 62, and the assist reduction gain setting detection means 552 are input.

  In such a configuration, the operation will be described with reference to the flowchart of FIG.

  First, the circuit system is initialized (step S40), the steering torque detection signal is input (step S41), the current detection signal is input (step S42), and the battery voltage is input (step S43). Then, it is determined whether or not the battery voltage is outside the determination value V1 (step S44). If the battery voltage is within the determination value V1, a motor control signal is calculated to perform normal assist (step S45). A motor control signal is output (step S46), and the process returns to step S41.

  If it is determined in step S44 that the value is outside the determination value V1, the steering torque reduction rate is set to A (step S50), and it is determined whether or not the battery voltage is outside the determination value V2. (Step S51) If the value is outside the determination value V2, the rate of decrease in the steering torque is calculated as a function of the battery voltage (Step S52). Thereafter, or if it is determined that the value is inside in Step S51, the steering torque detection signal is calculated. Decrease (step S53), it is determined whether or not the steering torque detection signal is 0 (step S54), and if not 0, the process proceeds to step S45. If the steering torque detection signal is 0, the assist of the electric power steering is stopped and finished (step S55).

  In the above-described embodiment, the assist is stopped by reducing the number of steps in two and three steps, but it is also possible to make the number of steps more than four.

  According to the present invention, even when the power supply voltage drops, the assist is not stopped immediately, but the assist is adjusted by varying the gain according to the determination value in several steps. Applicable to power steering.

It is a figure for demonstrating the principle of operation of this invention. It is a block block diagram which shows 1st Example of this invention. It is a flowchart which shows the operation example of 1st Example of this invention. It is a block block diagram which shows 2nd Example of this invention. It is a flowchart which shows the operation example of 2nd Example of this invention. It is a figure for demonstrating 3rd Example. It is a block block diagram which shows 3rd Example of this invention. It is a flowchart which shows the operation example of 3rd Example of this invention. It is a block diagram of a general electric power steering. It is a block diagram of the conventional control apparatus. It is a time chart which shows the example of a conventional operation | movement. It is a block diagram which shows the structural example of a conventional apparatus. It is a time chart which shows the operation example of FIG.

Explanation of symbols

1 Steering handle 2 Column shaft 3 Reduction gear 10 Torque sensor 11 Ignition key 12 Vehicle speed sensor 20 Motor 30 Control unit 50 Steering torque detection means 51 Steering torque input correction means 52 Motor control signal generation means 53 Motor drive means 54 Battery voltage detection means 55 Assist reduction gain setting detection means 61 Assist reduction start voltage range detection means

Claims (3)

A control device for an electric power steering apparatus configured to apply an assist force by a motor to a steering system, and has a function of decreasing assist when a power supply voltage is lowered or increased, and the reduction characteristic is varied by the power supply voltage. A control device for an electric power steering device, characterized in that: 2. The control device for an electric power steering apparatus according to claim 1, wherein the reduction characteristic is made variable in multiple stages of at least two stages. 3. The control device for an electric power steering apparatus according to claim 2, wherein the reduction characteristic is performed in a multistage variable manner of at least two stages, and a variable gain is a voltage function of the power supply voltage.

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