JP2014100981A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device of which failure can be securely detected and which can prevent decline in steering feeling caused by wrong failure determination and has good steering feeling.SOLUTION: An electric power steering device includes: abnormality detection means for detecting whether the electric power steering device is normal or abnormal; and failure determination means for incrementing a value of an abnormal counter every time the abnormality detection means detects an abnormality and determining that the electric power steering device is broken when the value of the abnormal counter reaches a failure determination value. The abnormality detection means includes random sampling period generation means for generating a random sampling period. By comparing predetermined data sampled in the random sampling period generated by the random sampling period generation means with a predetermined threshold value, the abnormality detection means detects whether the electric power steering device is normal or abnormal.

Description

  The present invention relates to an electric power steering apparatus.

  Conventionally, an abnormality detection method for an electric power steering apparatus adds an abnormality counter each time an abnormality is detected, and determines that the electric power steering apparatus is out of order when the failure determination value is reached. Is turned off. If an abnormality cannot be detected before the abnormality counter reaches the failure determination value, it is immediately determined that the abnormality is normal, and the abnormality counter is returned to zero.

  However, in such a control method, when the data in which an abnormality is detected causes chattering, the failure determination is immediately reset and regarded as normal. Therefore, for example, in the control device for the electric power steering mechanism described in Patent Document 1, when the abnormality counter reaches the failure determination value, it is determined that the electric power steering mechanism has failed, and the abnormality detection unit temporarily detects an abnormality. If the abnormality detecting means detects normality continuously for a predetermined number of sampling times, the failure determining means returns the abnormality counter being held to zero.

JP 2002-178945 A

  However, even in the above method, when the sampling period for detecting an abnormality is constant, the period of disturbance from the road surface (for example, a concave / convex groove for preventing dozing or preventing protrusion) is the same as the sampling period for detecting the abnormality. In such a case, although the data is a normal value, the failure determination means determines that there is a failure and stops the assist, which may cause a decrease in steering feeling.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electric power steering device that can detect a failure of an electric power steering device reliably and prevent a steering feeling from being lowered due to an erroneous failure determination, and has a good steering feeling. is there.

  In order to solve the above-described problems, the invention according to claim 1 is directed to a steering force assisting device provided to apply an assist force for assisting a steering operation to a steering system by a motor, and a steering torque detection for detecting a steering torque. Means, vehicle speed detecting means for detecting the vehicle speed, actual current detecting means for detecting the actual current flowing through the motor, steering torque detected from the steering torque detecting means, and assist force from the vehicle speed detected from the vehicle speed detecting means. Based on the command value generated from the assist force generation unit and the actual current detected from the actual current detection unit, the motor is driven as the drive source of the steering force assisting device. Control means for controlling the operation of the steering force assisting device by supplying electric power; and an electric power steering apparatus comprising: , An abnormality detection means for detecting whether the electric power steering device is normal or abnormal, and an abnormality counter is added each time the abnormality detection means detects an abnormality, and the abnormality counter Failure determination means for determining that the electric power steering apparatus has failed when the value is reached, the abnormality detection means includes random sampling period generation means for generating a random sampling period, and the random detection period The gist is to detect whether the electric power steering apparatus is normal or abnormal by comparing predetermined data generated by the sampling period generating means and sampled at random sampling periods with a predetermined threshold.

  In the electric power steering apparatus according to the present invention, an abnormality detection means for detecting whether the electric power steering apparatus is normal or abnormal, and an abnormality counter is added each time the abnormality detection means detects an abnormality. When the abnormality counter reaches the failure determination value, failure determination means for determining that the electric power steering device has failed is provided. The abnormality detection means has a random sampling period generation means for generating a random sampling period, and compares predetermined data generated by the random sampling period generation means and sampled at a random sampling period with a predetermined threshold value. By doing so, it is configured to detect whether the electric power steering device is normal or abnormal.

  That is, when the data detected at a random sampling period is normal, the assist is continued as it is. On the other hand, if the data detected in the random sampling period is abnormal, the abnormality counter is added and at the same time, the data is detected again in the random sampling period. Therefore, the period of disturbance from the road surface is continuously synchronized with the sampling period, and no abnormality is detected.

  As a result, it is possible to reliably detect a failure of the electric power steering device and prevent the steering feeling from being lowered due to an erroneous failure determination, and to provide an electric power steering device with good steering feeling.

  In the invention according to claim 2, when the predetermined data sampled at a random sampling period is an abnormal value, the abnormality detecting means adds a random sampling period at that time to the data abnormality counter. The gist of the invention is that when the data abnormality counter is equal to or greater than the failure determination value, the failure determination means sets the failure determination flag and stops the assist.

  According to the above configuration, when the predetermined data sampled at a random sampling cycle is an abnormal value, the random sampling cycle at that time is added to the data abnormal counter, and the data abnormal counter is equal to or greater than the failure determination value. In this case, the failure determination means sets a failure confirmation flag and stops the assist. As a result, even when predetermined data is sampled at a random sampling period, a failure determination can always be made with the same failure determination time, so that a failure can be reliably detected.

  The gist of the invention described in claim 3 is that the abnormality detecting means detects abnormality of the steering torque detecting means, the vehicle speed detecting means, and the actual current detecting means.

According to the above configuration, it is possible to reliably detect an abnormality in the steering torque, the vehicle speed, and the actual current necessary for improving the steering feeling of the electric power steering apparatus.

  According to the present invention, it is possible to reliably detect a failure of the electric power steering device and prevent the steering feeling from being lowered due to an erroneous failure determination, and to provide an electric power steering device with good steering feeling. it can.

The schematic block diagram of an electric power steering device (EPS). The control block diagram of EPS. The flowchart figure which shows the process sequence of an abnormality detection part, a random sampling period generation part, and a failure determination part. The schematic explanatory drawing of output data when a fixed sampling period and the period of the disturbance from a road surface become the same. The schematic explanatory drawing of the abnormality output data in case the sampling period which detects abnormality in a prior art is constant.

Hereinafter, an embodiment of the present invention embodied in a column-type electric power steering apparatus (hereinafter referred to as EPS) will be described with reference to the drawings.
As shown in FIG. 1, in the EPS 1 of the present embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. The rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 of this embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. The reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 11 connected to both ends of the rack shaft 5, whereby the steered angle of the steered wheels 12. Has been changed.

  The EPS 1 controls the EPS actuator 24 (steering force assisting device) as a steering force assisting device that applies assisting force for assisting the steering operation to the steering system using the motor 21 as a driving source, and the operation of the EPS actuator 24. ECU27 which performs.

  The EPS actuator 24 of the present embodiment is a column type EPS actuator, and the motor 21 that is a drive source thereof is drivingly connected to the column shaft 8 via a speed reduction mechanism 23. The rotation of the motor 21 is decelerated by the speed reduction mechanism 23 and transmitted to the column shaft 8 so that the motor torque is applied to the steering system as an assist force.

  On the other hand, a vehicle speed sensor 25 (vehicle speed detection means), a torque sensor 26 (steering torque detection means), and a motor rotation angle sensor 22 are connected to the ECU 27. The ECU 27 is based on the output signals of these sensors. The vehicle speed V, the steering torque τ, and the motor rotation angle θm are detected.

Next, an electrical configuration in the EPS 1 of the present embodiment will be described.
FIG. 2 is a control block diagram of the EPS 1 of the present embodiment. As shown in the figure, the ECU 27 supplies three-phase drive power to a motor 21 that is a drive source of the EPS actuator 24 based on a microcomputer 29 (control means) that outputs a motor control signal and the motor control signal. Current sensors (actual current detection means) 30u, 30v, and 30w for detecting the U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw that are supplied to the motor 40 and the motor 21; It has.

  The drive circuit 40 is a known PWM inverter (not shown) formed by connecting three arms corresponding to each phase in parallel with a pair of switching elements connected in series as a basic unit (arm). Further, the motor control signal output from the microcomputer 29 defines the on-duty ratio of each switching element constituting the motor drive circuit 40. A motor control signal is applied to the gate terminal of each switching element, and in response to the motor control signal, each switching element is turned on / off to generate three-phase motor driving power based on the power supply voltage of the battery 28. The motor 21 is configured to output.

  A motor rotation angle sensor 22 for detecting the motor rotation angle θm of the motor 21 is connected to the ECU 27. The microcomputer 29 is driven based on the phase current values Iu, Iv, Iw of the motor 21 and the motor rotation angle θm detected based on the output signals of these sensors, the steering torque τ, and the vehicle speed V. A motor control signal is output to the circuit 40.

  Each control block shown below is realized by a computer program executed by the microcomputer 29. The microcomputer 29 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks every predetermined period.

  As shown in FIG. 2, the microcomputer 29 inputs external phase signals Iu, Iv, Iw, motor rotation angle θm, steering torque τ, and vehicle speed V, which are external signals, via the interface unit 33. Are taken into the microcomputer 29 at a sampling cycle of. In detail, the interface unit 33 includes an I / O port that takes in a digital signal and an A / D converter that converts an analog value into a digital value.

  Furthermore, the microcomputer 29 calculates an Iq * current command value calculation unit 31 (assist force generation means) that calculates a q-axis current command value Iq * for controlling the motor 21, and a failure determination unit 32 (determines whether the assist is continued or interrupted. A failure determination means, an abnormality detection means, a random sampling period generation means, including an abnormality detection section and a random sampling period generation section), and a motor control signal generation section 44 that generates a motor control signal for controlling the drive circuit 40. I have.

  The microcomputer 29 performs current feedback control in the d / q coordinate system by mapping the phase current values Iud, Ivd, and Iwd input from the interface unit 33 to the d / q coordinate system (d / q conversion). Run. Then, the PWM output unit 38 generates a DUTY command value for determining the on / off timing of the FET constituting the drive circuit 40, and outputs a gate on / off signal based on the DUTY command value.

The steering torque τd detected by the torque sensor 26 and the vehicle speed Vg detected by the vehicle speed sensor 25 are input to the current command value calculation unit 31. Based on the steering torque τd and the vehicle speed Vg, the current command value calculation unit 31 determines a q-axis current command value Iq * that is a control target of the assist torque from a steering torque / q-axis current command value map.
The steering torque / q-axis current command value map is configured to determine a larger q-axis current command value Iq * as the vehicle speed Vg is smaller for the same steering torque.

  The failure determination unit 32 includes a steering torque τd detected by the torque sensor 26, a vehicle speed Vg detected by the vehicle speed sensor 25, a motor rotation angle θmd detected by the motor rotation angle sensor 22, and current sensors 30u, 30v, 30w. The phase current values Iud, Ivd, and Iwd of the motor 21 detected by the above are input. The state quantities of these vehicles are individually sampled at random periods by the abnormality detection unit included in the failure determination unit 32, and an abnormality is detected by comparing with the abnormality threshold.

When the failure determination unit 32 determines a failure, the failure determination flag FLG1 is set, and the failure determination flag FLG1 is input to the current command value calculation unit 31 and the motor control signal generation unit 44. Thus, the assist is interrupted.
Further, the failure determination unit 32 includes a random sampling period generation unit that generates a random sampling period. The random sampling period generation unit generates a random sampling period by generating a random number using the microcomputer 29.

  The motor control signal generation unit 44 includes a d / q conversion calculation unit 34, a q-axis PID control unit 35, a d-axis PID control unit 36, a d / q reverse conversion calculation unit 37, and a PWM output unit 38.

  The U-phase current value Iud, the V-phase current value Ivd, and the W-phase current value Iwd input to the d / q conversion calculation unit 34 are d / q-converted to obtain a q-axis current value Iq and a d-axis current value Id. Become. The q-axis current value Iq is input to the subtractor 53. The subtractor 53 inputs the q-axis deviation current value ΔIq obtained by subtracting the q-axis current value Iq from the q-axis current command value Iq * output from the Iq * current command value calculation unit 31 to the q-axis PID control unit 35. . The q-axis voltage command value Vq * calculated by the q-axis PID control unit 35 is input to the d / q inverse conversion calculation unit 37.

  On the other hand, the d-axis current value Id converted by the d / q conversion calculation unit 34 is input to the subtractor 54. The subtractor 54 inputs a d-axis deviation current value ΔId obtained by subtracting the d-axis current value Id from the d-axis current command value Id * (Id * = 0) to the d-axis PID control unit 36. The d-axis voltage command value Vd * calculated by the d-axis PID control unit 36 is input to the d / q inverse conversion calculation unit 37.

  The q-axis voltage command value Vq * and the d-axis voltage command value Vd * input to the d / q reverse conversion calculation unit 37 are converted by the d / q reverse conversion calculation unit 37 into the U-phase voltage command value Vu * and V-phase. The voltage command value Vv * and the W-phase voltage command value Vw * are converted and input to the PWM output unit 38.

Next, an abnormality detection method when the sampling period for detecting an abnormality in the prior art is constant will be described with reference to a schematic explanatory diagram of abnormality output data in FIG. The horizontal axis of FIG. 5 is a time axis (ms), and the vertical axis is output data of a predetermined detector.
When the output data becomes larger than the abnormality threshold (L11) and becomes abnormal (L22), the state is measured a predetermined number of times. More specifically, the microcomputer 29 samples abnormal output data several times (three times: t1, t2, t3) at a constant sampling period (T1s: 6 ms), and the output data is abnormal while sampling. The failure determination unit 32 determines that there is a failure, sets the failure determination flag FLG1, and interrupts the assist.

Next, the abnormality detection method of the present embodiment will be described with reference to the schematic explanatory diagram of output data in the case where the constant sampling period and the period of disturbance from the road surface are the same in FIG.
The horizontal axis in FIG. 4 is the time axis (ms) as in FIG. 5, and the vertical axis is the output data of a predetermined detector. The difference from FIG. 5 is that in FIG. 4, the output data (L2) may be continuous and not larger than the abnormal threshold value (L1). As is clear from the figure, the output data is larger than the abnormal threshold value (E1, E2, E3 points: t1, t2, t3) only at a fixed sampling period (T1s: 6 ms). This is because a certain sampling period for detecting an abnormality is synchronized with a period of disturbance from the road surface.

  In such a case, if the constant sampling period (T1s: 6 ms) is changed to a random sampling period (Trs1: 3 ms, Trs2: 5 ms, Trs3: 6 ms), the synchronization with the period of disturbance from the road surface is shifted. The output data becomes normal values (N1, N2, N3 points: t4, t5, t6). It should be noted that the output data becomes an abnormal value (N4 point, t7). Coincidentally, the random sampling period (Trs4: 4 ms) is synchronized with the period of disturbance from the road surface as with the constant sampling period (T1s). Only when.

Next, the processing procedure of the abnormality detection unit, random sampling period generation unit, and failure determination unit by the microcomputer 29 of this embodiment will be described with reference to FIG.
First, the microcomputer 29 determines whether or not the random sampling period Trs has elapsed (step S101). When the random sampling period Trs has elapsed (step S101: YES), the microcomputer 29 reads the data D1 sampled at the random sampling period Trs of the predetermined device at the random sampling period Trs (step S102).

  Next, the microcomputer 29 determines whether or not the data D1 sampled at the random sampling period Trs of the predetermined device is abnormal (step S103). When the data D1 sampled at the random sampling period Trs of the predetermined device is abnormal (step S103: YES), the microcomputer 29 adds the random sampling period Trs to the data abnormality counter 1CTR1 (CTR1 = CTR1 + Trs, step S104). Note that steps S101 to S104 and step S108 are abnormality detection means.

  Next, the microcomputer 29 determines whether or not the data abnormality counter 1CTR1 is equal to or greater than the failure determination value CTR1s of the data abnormality counter 1 (step S105). If the data abnormality counter 1CTR1 is greater than or equal to the failure determination value CTR1s of the data abnormality counter 1 (CTR1 ≧ CTR1s, step S105: YES), the microcomputer 29 sets the failure confirmation flag FLG1 (FLG1 = “1”, Step S106). Further, the microcomputer 29 determines the next random sampling period Trs in the random sampling period generation unit (step S107), and ends the process. Steps S105 and S106 are failure determination means, and step S107 is random sampling period generation means.

  If the data abnormality counter 1CTR1 is not equal to or greater than the failure determination value CTR1s of the data abnormality counter 1 (CTR1 <CTR1s, step S105: NO), the microcomputer 29 causes the random sampling period generator to generate the next random sampling period Trs. Is determined (step S107), and the process ends.

  Next, the microcomputer 29 resets the data abnormality counter 1CTR1 (CTR1 = "0", step S108) when the data D1 sampled at the random sampling period Trs of the predetermined device is not abnormal (step S103: NO). The process proceeds to step S105. If the random sampling period Trs has not elapsed (step S101: NO), the microcomputer 29 ends the process without doing anything.

Next, the operation and effect of the EPS 1 of the present embodiment configured as described above will be described.
In the present embodiment, an abnormality detection unit that detects whether the electric power steering apparatus is normal or abnormal, and an abnormality counter is added each time the abnormality detection unit detects an abnormality, and the abnormality counter fails. When the determination value is reached, a failure determination means for determining that the electric power steering apparatus has failed is provided. The abnormality detection means has a random sampling period generation means for generating a random sampling period, and compares predetermined data generated by the random sampling period generation means and sampled at a random sampling period with a predetermined threshold value. By doing so, it is configured to detect whether the electric power steering apparatus is normal or abnormal.

  That is, when the data detected at a random sampling period is normal, the assist is continued as it is. On the other hand, if the data detected in the random sampling period is abnormal, the abnormality counter is added and at the same time, the data is detected again in the random sampling period. Therefore, the period of disturbance from the road surface is continuously synchronized with the sampling period, and no abnormality is detected.

  As a result, it is possible to reliably detect a failure of the electric power steering apparatus and to prevent the steering feeling from being lowered due to an erroneous failure determination, thereby improving the steering feeling.

In addition, you may change this embodiment as follows.
In the present embodiment, the present invention is embodied in an electric power steering device, but the present invention may be applied to a transmission ratio variable device and a driving force distribution device.

In the present embodiment, the present invention is embodied in the column assist EPS, but the present invention may be applied to a rack assist EPS or a pinion assist EPS.

In the present embodiment, the present invention is embodied as a steering torque, a vehicle speed, a motor rotation angle, and an actual current as an abnormality detection state quantity, but may be applied to a power supply voltage and a motor terminal voltage.

1: Electric power steering device (EPS), 2: Steering,
3: Steering shaft, 4: Rack and pinion mechanism, 5: Rack shaft,
8: column shaft, 9: intermediate shaft, 10: pinion shaft, 11: tie rod, 12: steered wheel, 21: motor,
22: Motor rotation angle sensor, 23: Deceleration mechanism,
24: EPS actuator (steering force assist device),
25: vehicle speed sensor (vehicle speed detection means), 26: torque sensor (steering torque detection means), 27: ECU, 28: battery, 29: microcomputer (control means),
30u, 30v, 30w: current sensor (actual current detecting means),
31: Current command value calculation unit (assist force generation means),
32: Failure determination unit (including failure detection unit, abnormality detection unit, random sampling cycle generation unit, including abnormality detection unit and random sampling cycle generation unit),
33: Interface part,
34: d / q conversion calculation unit, 35: q-axis PID control unit, 36: d-axis PID control unit,
37: d / q inverse conversion calculation unit, 38: PWM output unit, 40: drive circuit,
44: Motor control signal generator, 53, 54: Subtractor,
V: vehicle speed, Vg: vehicle speed (vehicle speed after sampling),
τ: steering torque, τd: steering torque (steering torque after sampling),
θm: motor rotation angle, θmd: motor rotation angle (motor rotation angle after sampling),
Iu, Iv, Iw: current value of each phase,
Iud, Ivd, Iwd: each phase current value (each phase current value after sampling),
Iq *: q-axis current command value, Iq: q-axis current value, ΔIq: q-axis deviation current value,
Id *: d-axis current command value, Id: d-axis current value, ΔId: d-axis deviation current value,
Vq *: q-axis voltage command value, Vd *: d-axis voltage command value,
Vu *, Vv *, Vw *: Voltage command values for each phase,
Trs: random sampling period,
T1s: constant sampling period (one embodiment),
Trs1, Trs2, Trs3, Trs4: random sampling period (one embodiment),
D1: data sampled at a random sampling period of a predetermined device,
CTR1: data abnormality counter, CTR1s: failure judgment value of data abnormality counter,
FLG1: Failure confirmation flag,
L1, L11: Abnormal threshold value, L2, L22: Output data,
t1, t2, t3: sampling time of a fixed period,
t4, t5, t6, t7: random period sampling time,
E1, E2, E3: Output data sampled at a fixed sampling period,
N1, N2, N3, N4: Output data sampled at a random sampling period

Claims (3)

A steering force assisting device provided to apply an assisting force to assist the steering operation to the steering system by the motor;
Steering torque detection means for detecting steering torque;
Vehicle speed detection means for detecting the vehicle speed;
An actual current detecting means for detecting an actual current flowing through the motor;
An assist force generating means for generating an assist force from the steering torque detected from the steering torque detecting means and the vehicle speed detected from the vehicle speed detecting means;
Based on the command value generated from the assist force generating means and the actual current detected from the actual current detecting means, the driving force is supplied to the motor that is the driving source of the steering force assisting device, thereby providing the steering force. Control means for controlling the operation of the auxiliary device;
In the electric power steering apparatus with
The control means detects whether the electric power steering device is normal or abnormal, and an abnormality detection means;
A failure determination unit that increments an abnormality counter each time the abnormality detection unit detects an abnormality, and determines that the electric power steering device has failed when the abnormality counter reaches a failure determination value; ,
The abnormality detection means includes a random sampling period generation means for generating a random sampling period, and compares predetermined data generated by the random sampling period generation means and sampled at a random sampling period with a predetermined threshold value. Detecting whether the electric power steering device is normal or abnormal,
An electric power steering device. When the predetermined data sampled at the random sampling period is an abnormal value, the abnormality detection means adds a random sampling period at that time to the data abnormality counter, and the data abnormality counter fails. In the case of a determination value or more, the failure determination means sets a failure determination flag and stops the assist,
The electric power steering apparatus according to claim 1. The abnormality detection means detects an abnormality of the steering torque detection means, the vehicle speed detection means, and the actual current detection means;
The electric power steering apparatus according to claim 1 or 2, wherein

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