JP2008006997A - Control method and device for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method and a device for an electric power steering device not giving an incompatible sense to a driver on the operation of a steering wheel by performing the gradual increase processing of assist torque according to a traveling state when an assist restriction state is generated and an assist restriction state is released. <P>SOLUTION: In the control method for the electric power steering device, a current instruction value of a motor for giving the assist torque to a steering mechanism based on steering torque and a vehicle speed and the motor is drive-controlled by the duty of PWM control. When assist restriction is released, the assist torque is subjected to gradual increase processing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control method and apparatus for an electric power steering apparatus that assists by applying assist torque by a motor to a steering system of a vehicle, and particularly relates to an assist restriction state based on occurrence of an abnormality or the like. The present invention relates to a control method and apparatus for an electric power steering apparatus in which an assist torque is gradually increased to prevent a sense of incongruity when canceling the control.

  An electric power steering apparatus that assists a steering apparatus of a vehicle with the rotational force of a motor is configured to bias the driving force of the motor to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer. It has become. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist torque (steering assist force). 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.

  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. It is connected 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 connected to the column shaft 2 via the reduction gear 3. ing. The control unit 30 that controls the power steering apparatus is supplied with electric power from the battery 14 and also receives an ignition key signal from the ignition key 11. The control unit 30 detects the steering torque T detected by the torque sensor 10 and the vehicle speed. Based on the vehicle speed V detected by the sensor 12, the current command value I of the assist command is calculated using an assist map or the like, and the current supplied to the motor 20 is controlled based on the calculated current command value I. .

  A general configuration example of the control system of the electric power steering apparatus is as shown in FIG. 10. The steering torque T detected by the torque sensor 10 and the vehicle speed detected by the vehicle speed sensor are supplied to the current command value calculation unit 31. The current command value I1 input and calculated by the current command value calculation unit 31 is added to the subtraction unit 32, and the deviation (I1-Im) obtained by the subtraction unit 32 is a duty for calculating a duty for PWM control. Input to the calculation unit 33. The duty D1 calculated by the duty calculator 33 is input to the motor drive circuit 34 to drive the motor 20. The motor current Im of the motor 20 is detected by the motor current detection circuit 35 and fed back to the subtraction unit 32.

  Such an electric power steering device is used when the ignition key 11 is turned off from the on state, or when a stop signal is generated from an abnormality detection means (not shown) for detecting an abnormality or failure of the control device. Stops the motor control and stops the assist. Thus, when the ignition key 11 is turned off, or when the motor control is stopped when a stop signal is generated from the abnormality detection means, the steering torque increases rapidly and the steering handle 1 suddenly becomes heavy. In addition to impairing the sense of quality of steering, the steering feeling is significantly reduced particularly during steering.

  As an apparatus for solving such a problem, there is an apparatus disclosed in Japanese Patent Laid-Open No. 2003-182608 (Patent Document 1). The device disclosed in Patent Literature 1 includes a control unit that calculates an assist current command value based on at least the steering torque of the steering wheel and assists the motor so as to output an assist force based on the assist current command value. In the electric power steering control device, when an abnormality of the circuit related to the assist control is detected, a suppression means for suppressing the assist control of the control means, and a circuit abnormality is detected within a period during which the assist control of the suppression means is suppressed. When continued, the circuit returned to normal within a period during which the assist control of the motor power supply stop means for opening the power supply means for opening the power supply to the motor drive unit for driving the motor and the suppression means was suppressed. In this case, a suppression release unit that releases the suppression of the suppression unit is provided.

According to the apparatus disclosed in Patent Document 1, the assist control is suppressed when a circuit abnormality related to the assist control is detected, and the circuit abnormality determination time is obtained during the suppression period. This makes it possible to lengthen the determination time and prevent erroneous determination. In addition, when a circuit related to the assist control becomes normal during the assist control suppression period, it is possible to return to the assist control.
JP 2003-182608 A

  However, in the device described in Patent Literature 1, the assist gradual increase time at the time of normal recovery after the occurrence of an abnormality is always a constant value, and depending on the state of the vehicle at the time of normal recovery, the driver feels uncomfortable when operating the steering wheel. There is a case.

  In addition, motor overheat protection (recoverable due to temperature drop if temporarily restricted), controller (ECU) overheat protection (recoverable due to temperature drop if temporarily restricted), power supply voltage abnormality (requires temporary restriction) However, it is possible to return by charging due to driving), etc., an assist limiting state occurs such as a state of waiting for return by adding a limitation to the assist, and a gradual reduction process of lowering the steering torque or current command value to the limiting value. It is requested that the driver not feel uncomfortable even when the restriction is released.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to perform an assist torque gradual increase process according to the running state when the assist limited state occurs and the assist limited state is released. Accordingly, it is an object of the present invention to provide a control method and apparatus for an electric power steering apparatus that does not give the driver a sense of incongruity when operating the steering wheel.

  The present invention calculates a current command value of a motor for applying assist torque to a steering mechanism based on a steering torque and a vehicle speed, and controls the drive of the motor with a duty of PWM control. Regarding the method, the above object of the present invention is achieved by gradually increasing the assist torque when releasing the assist restriction.

  The object of the present invention is to perform the gradual increase process of the assist torque by gradually increasing the steering torque, or to perform the gradual increase process of the assist torque by gradually increasing the current command value, or to gradually increase the assist torque. By gradually increasing the duty, determining the time of the gradually increasing process based on the steering torque, determining the time of the gradually increasing process based on the vehicle speed, or determining that the vehicle speed is abnormal In this case, the time for the gradual increase processing is set to a predetermined default value, which is more effectively achieved.

  The present invention also provides a current command value calculation unit that calculates a current command value of a motor that applies assist torque to the steering mechanism based on the steering torque and the vehicle speed, and the motor with a duty of PWM control based on the current command value. The above-mentioned object of the present invention is to provide an assist limit / return detection unit for detecting an assist limit state and a return, and the assist limit / return detection unit. Is achieved by providing a time setting unit for setting a set time when it is detected that the vehicle has returned from the assist limit state, and a gradually increasing means for gradually increasing the assist torque based on the set time.

  The object of the present invention is that the gradually increasing means gradually increases the steering torque, or that the gradually increasing means gradually increases the current command value, or that the gradually increasing means gradually increases the duty, or The time setting unit sets the set time based on the steering torque, or the time setting unit sets the set time based on the vehicle speed, or sets the time for the gradual increase process to a predetermined default value. This is achieved more effectively.

  According to the present invention, the assist torque is gradually increased by gradually increasing the steering torque, the current command value or the duty even when the limit is released from the assist limit state caused by motor overheat protection, controller overheat protection, power supply voltage abnormality, etc. In addition, since the gradual increase process is performed in a set time corresponding to the traveling state such as the steering torque or the vehicle speed, an electric power steering that does not give the driver a sense of incongruity can be realized.

  The present invention gradually increases the assist torque in order to prevent the assist from suddenly changing when the limit is released from the assist limit state when the assist limit state occurs for motor overheat protection or controller overheat protection. . The gradual increase of the assist torque is performed by gradually increasing the steering torque, gradually increasing the current command value, or gradually increasing the duty, and the gradual increase processing is performed at a set time corresponding to the steering torque and the vehicle speed.

  When the assist restriction state is released, the assist torque is gradually increased according to the traveling state, so that the steering feeling can be improved without giving the driver an uncomfortable feeling of steering operation.

  The assist limit state is for protecting the motor from overheating, protecting the controller (ECU) overheating, the case where the power supply voltage becomes abnormal, etc. When such assist limitation state is detected, the assist torque is gradually reduced. Processing is performed.

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

  In the present embodiment, the return from the abnormality occurrence state will be described, but the present invention can be similarly applied to the case where the assist restriction is canceled from the assist restriction state caused by motor overheat protection, controller overheat protection, or the like.

  First, a case where the steering torque is gradually decreased / increased will be described as a first example.

  FIG. 1 shows an embodiment of the present invention corresponding to FIG. 10, and the steering torque T1 from the torque sensor 10 is input to the gradual decrease / gradual increase unit 38 and the time setting for setting the gradual decrease time / gradual increase time is shown. The vehicle speed V from the vehicle speed sensor 12 is input to the current command value calculation unit 31 and is also input to the time setting unit 37 for setting the gradual decrease time / gradual increase time. Each sensor signal SS from the sensors 40 and each detection signal ES from the ECU circuit 50 are input to the abnormality / return detection unit 36. The abnormality / recovery detection unit 36 detects an abnormality (including a failure) based on each sensor signal SS and each detection signal ES, detects a return from the failure, and outputs an abnormality / recovery signal AR. The abnormality / return signal AR output from the abnormality / recovery detection unit 36 is input to the time setting unit 37 and the gradual decrease / gradual increase unit 38, and the set time TS set by the time setting unit 37 is gradually decreased to the gradual decrease / gradual increase unit 38. / Entered as incremental time.

  The sensors 40 include a torque sensor 10, a vehicle speed sensor 12, a steering angle sensor, a motor angle sensor, a motor angular velocity sensor, a yaw rate sensor, a temperature sensor, and the like. The ECU circuit 50 includes a motor drive circuit 34, a motor current detection. A circuit 35, a power supply circuit, a sensor signal input circuit, a motor terminal voltage detection circuit, and the like are included. Further, the vehicle speed V and the like may be acquired from a CAN (Controller Area Network).

  The gradual decrease / gradual increase unit 38 switches the gradual decrease / gradual increase process based on the abnormality / return signal AR, and outputs the steering torque T2 gradually decreased / gradually increased only during the set time TS set using the steering torque T1 and the vehicle speed V as parameters. To do. In the normal operation where the gradual decrease / gradual increase process is not required, the gradual decrease / gradual increase unit 38 outputs the steering torque T1 as it is as the steering torque T2.

  FIG. 2 shows a configuration example of the gradual decrease / gradual increase unit 38. The steering torque T1 is input to the switching unit 381 that is switched based on the abnormality / return signal AR, and the steering torque T1 output from the switching unit 381 is the gradual decrease unit. 382, the gradually increasing unit 383, or the OR circuit 384. The switching unit 381 has contacts a, b, and c. The contact a is detected when an abnormality is detected based on the abnormality / recovery signal AR, the contact b is detected when a return is detected, and the contact c is detected during other normal operations. Connected. The set time TS is input to the gradually decreasing unit 382 and the gradually increasing unit 383, the gradually decreasing unit 382 gradually decreases the steering torque T1 only during the set time TS, and the gradually increasing unit 383 gradually increases the steering torque T1 only during the set time TS. The outputs of the gradual decrease unit 382 and the gradual increase unit 383 are input to the OR circuit 384, and the output of the contact point c is also input to the OR circuit 384. The steering torque gradually decreased / gradually increased from the OR circuit 384 as the steering torque T2. Alternatively, the steering torque T1 is output as it is as the steering torque T2.

  In such a configuration, an abnormality is detected by the abnormality / return detection unit 36, a return from the abnormal state is detected, and an operation example when gradually decreasing / gradually increasing the steering torque T1 will be described with reference to the flowchart of FIG. To do.

  When the abnormality / return detection unit 36 does not detect any abnormality and does not detect the return, the switching unit 381 is connected to the contact c based on the abnormality / return signal AR, and the steering torque T1 remains as it is. T2 is input to the current command value calculation unit 31, and the same operation as described in FIG. 10 is performed. Abnormality / recovery detection unit 36 detects whether it is abnormal, return, or normal based on each sensor signal SS and each detection signal ES (step S20). The signal AR is output to switch the contact of the switching unit 381 from “c” to “a”. The time setting unit 37 sets a set time TS for gradual decrease based on the abnormality / return signal AR. The steering torque T1 is gradually reduced only for the set time TS, the steering torque T2 is output from the OR circuit 384, the assist gradually decreasing process is performed, the assist is stopped, and the process returns (step S21). Thereby, smooth steering is possible even if a failure occurs.

If it is determined in step S20 that the operation is normal, the abnormality / recovery detection unit 36 determines whether or not the operation has returned from the abnormal state (step S22). Then, when it is determined that the recovery from the abnormality is made, the contact of the switching unit 381 is switched from “c” to “b” based on the abnormality / recovery signal AR, and the time setting unit 37 is based on the abnormality / return signal AR. To set a set time TS for gradual increase processing. In this case, the set time TS is varied based on the magnitude of the steering torque T1. That is, the steering torque T1 is longer than the standard time set time TS in the case of more than the predetermined value _{T 0} (step S23, S25), when the steering torque T1 is smaller than a predetermined value _{T 0} is the standard set time TS Time is set (steps S23 and S24). In accordance with the set time TS set in this way, the gradually increasing unit 383 gradually increases the steering torque T1 (step S26). As a result, even when the vehicle recovers from the failure, smooth steering is possible.

  As shown in FIG. 4, the gradual decrease unit 382 that performs the gradual decrease process of the assist torque by the occurrence of the abnormal state performs the gradual decrease process by multiplying the steering torque T1 by a gain value that decreases with time. That is, the steering torque T2 gradually decreased by the gradually decreasing unit 382 is input to the current command value calculating unit 31, and the current command value I1 based on the gradually decreased steering torque T2 is calculated. Further, the gradual increase unit 383 that detects the return from the abnormal state and performs the gradual increase process of the assist torque performs the gradual increase process by multiplying the steering torque T1 by a gain value that increases with time as shown in FIG. Do. That is, the steering torque T2 gradually increased by the gradually increasing unit 383 is input to the current command value calculating unit 31, and the current command value I1 based on the gradually increased steering torque T2 is calculated.

In the above description but determined set time TS by comparing the magnitude of the steering torque T1 to a predetermined value T _0, it is also possible to set a plurality of setting time for the plurality of predetermined values, It is also possible to perform a gradual increase process with a value set according to the steering torque without using a threshold.

  Next, an example of operation when the set time TS is determined based on the vehicle speed V will be described with reference to FIG.

  The abnormality / recovery detection unit 36 detects whether it is abnormal, recovery, or normal (step S30). In the case of an abnormal state that is not normal, the abnormality / return signal AR is output and the contact of the switching unit 381 is set to “c”. Is switched from “a” to “a”, the time setting unit 37 sets the setting time TS for the gradual decrease processing based on the abnormality / return signal AR, and the gradual decrease unit 382 gradually decreases the steering torque T1 as described above, and OR circuit The steering torque T2 is output from 384, the assist gradually decreasing process is performed, the assist is stopped, and the process returns (step S31). Thereby, smooth steering is possible even if a failure occurs.

Further, when it is determined to be normal in step S30, the abnormality / recovery detection unit 36 determines whether or not it is a return from the abnormal state (step S32), and similarly returns if it is not a return from the abnormal state. . When the abnormality / return detection unit 36 determines that the vehicle is returning from the abnormal state, it is determined whether or not the vehicle speed V is normal (step S33). set the time TS to the default value (e.g., 2 seconds), returns to the gradual increase process, as described above (step S34), further the vehicle speed V when the vehicle speed V is normal whether a predetermined value greater than or equal _to V ₀ Is determined (step S35). The vehicle speed V is greater than the standard time set time TS for the assist gradual reduction in the case of more than a predetermined value V ₀ (e.g., 5.0 seconds) (step S37), when the vehicle speed V is smaller than the predetermined value V ₀ Sets the set time TS to a standard time (for example, 0.5 seconds) (step S36). In accordance with the set time TS set in this way, the gradually increasing portion 383 gradually increases the steering torque T1 (step S38). As a result, even when the vehicle recovers from the failure, smooth steering is possible.

In the above description, the set time TS is determined by comparing the magnitude of the vehicle speed V with the predetermined value V _0. However, a plurality of set times can be set for a plurality of predetermined values, and the threshold is set. It is also possible to carry out a gradual increase process at a value set according to the vehicle speed without using.

By the way, although the assist gradual increase time when the ignition key is turned on is set to a relatively short time (for example, 0.5 seconds), the gradual increase time of the assist torque in the case of normal recovery after the occurrence of abnormality is the normal recovery during steering. Is set to a relatively long time (for example, 5.0 seconds). If the ignition key is turned on and the engine is started while the battery is deteriorated, the battery voltage decreases during cranking, so that the assist is temporarily stopped. When the battery voltage returns to normal after the engine is started, the assist gradual increase time when the ignition key is turned on is originally 0.5 seconds, for example, but becomes 5.0 seconds as the battery voltage temporarily decreases. Therefore, the driver feels the start of assist. Therefore, in the present embodiment, the battery voltage assist increasing time upon normal return from the assist stop state when reduced (the set time TS) the vehicle speed sensitive, the vehicle speed V is when a predetermined value less than V ₀ a relatively short setting time When the vehicle speed V is equal to or higher than the predetermined value V ₀ , a relatively long set time TS is set. As a result, when the vehicle returns to the normal state while the vehicle is stopped, it is possible to eliminate the swaying feeling of starting or restarting the assist, and when the vehicle returns to the normal state while the vehicle is running, it is possible to prevent the assist torque from rapidly increasing.

  In the above example, the assist torque is gradually increased / decreased by gradually increasing / decreasing the steering torque T1, but the current command value or the duty may be gradually increased / decreased.

  FIG. 7 shows a configuration example in which the current command value I1 is gradually increased / decreased in correspondence with FIG. 1, and a gradually increasing / gradually decreasing unit 38 is interposed between the current command value calculating unit 31 and the subtracting unit 32. ing. The current command value I1 calculated by the current command value calculation unit 31 is gradually increased / gradually decreased by the gradual increase / gradual decrease unit 38, and the current command value I2 subjected to the gradual increase / gradual decrease processing is input to the subtraction unit 32 for processing. As a result, the assist torque is also gradually increased / decreased.

  FIG. 8 shows a configuration example in which the duty D1 is gradually increased / decreased in correspondence to FIG. 1, and a gradually increasing / gradually decreasing unit 38 is interposed between the duty calculating unit 33 and the motor drive circuit 34. Yes. The duty D1 calculated by the duty calculation unit 33 is gradually increased / decreased by the gradual increase / decrease unit 38, and the duty D2 subjected to the gradual increase / decrease processing is input to the motor drive circuit 34 and the motor 20 is driven. The torque is also gradually increased / decreased.

  In the above description, the set time TS is set based on the steering torque T1 or the vehicle speed V. However, the set time TS may be set based on the steering torque T1 and the vehicle speed V. In the above description, the case of returning from a failure has been described. However, the present invention can also be applied to the case where the assist restriction state is canceled.

  Further, the present invention can be applied not only to column type and pinion type electric power steering apparatuses, but also to rack assist type electric power steering apparatuses.

It is a block diagram which shows the structural example (gradual reduction / gradual increase of steering torque) of the control apparatus which concerns on this invention. It is a block diagram which shows the structural example of a gradual reduction / gradual increase part. It is a flowchart which shows the operation example (gradual reduction / gradual increase of steering torque) of this invention. It is a figure which shows the operation example of a gradual reduction part. It is a figure which shows the operation example of a gradual increase part. It is a flowchart which shows the other operation example (gradual reduction / gradual increase of steering torque) of this invention. It is a block diagram which shows the other structural example (gradual reduction / gradual increase of an electric current command value) of the control apparatus which concerns on this invention. It is a block diagram which shows the other structural example (gradual reduction / gradual increase of a duty) of the control apparatus which concerns on this invention. It is a figure which shows the general structural example of an electric power steering apparatus. It is a block diagram which shows the structural example of the general control system of an electric power steering apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 2 Column shaft 3 Reduction gear 10 Torque sensor 12 Vehicle speed sensor 14 Battery 20 Motor 30 Control unit 31 Current command value calculation part 32 Subtraction part 33 Duty calculation part 34 Motor drive circuit 35 Motor current detection circuit 36 Abnormality / recovery detection Unit 37 time setting unit 38 gradual decrease / gradual increase unit 40 sensors 50 ECU circuit 381 switching unit 382 gradual decrease unit 383 gradual increase unit

Claims (14)

In a control method of an electric power steering apparatus, a current command value of a motor that applies assist torque to a steering mechanism is calculated based on steering torque and vehicle speed, and the motor is driven and controlled with a duty of PWM control. A control method for an electric power steering apparatus, wherein when the restriction is released, the assist torque is gradually increased. The method for controlling the electric power steering apparatus according to claim 1, wherein the process of gradually increasing the assist torque is performed by gradually increasing the steering torque. The method for controlling an electric power steering apparatus according to claim 1, wherein the assist torque gradually increasing process is performed by gradually increasing the current command value. The method of controlling an electric power steering apparatus according to claim 1, wherein the process of gradually increasing the assist torque is performed by gradually increasing the duty. The method of controlling an electric power steering apparatus according to any one of claims 1 to 4, wherein a time for the gradual increase processing is determined based on the steering torque. The method for controlling the electric power steering apparatus according to any one of claims 1 to 4, wherein a time for the gradual increase processing is determined based on the vehicle speed. The method for controlling the electric power steering apparatus according to claim 6, wherein when the vehicle speed is determined to be abnormal, the time for the gradual increase process is set to a predetermined default value. A current command value calculation unit that calculates a current command value of a motor that applies assist torque to the steering mechanism based on the steering torque and the vehicle speed, and a motor drive that controls the motor with a duty of PWM control based on the current command value An assist limit / return detector for detecting an assist limit state and return, and when the assist limit / return detector is detected to return from the assist limit state. A control device for an electric power steering apparatus, comprising: a time setting unit that sets a set time; and a gradually increasing means that gradually increases the assist torque based on the set time. 9. The control device for an electric power steering apparatus according to claim 8, wherein the gradually increasing means gradually increases the steering torque. The control device for an electric power steering apparatus according to claim 8, wherein the gradually increasing means gradually increases the current command value. The control device for an electric power steering apparatus according to claim 8, wherein the gradually increasing means gradually increases the duty. The control device for an electric power steering apparatus according to any one of claims 8 to 11, wherein the time setting unit sets the set time based on the steering torque. 12. The control device for an electric power steering apparatus according to claim 8, wherein the time setting unit sets the set time based on the vehicle speed. The method of controlling an electric power steering apparatus according to claim 13, wherein when the vehicle speed is determined to be abnormal, the time for the gradual increase process is set to a predetermined default value.

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