JP4759978B2 - Control device for electric power steering device - Google Patents

Description

  The present invention includes a steering torque detection means for detecting a steering torque input to a steering system, an amplification circuit for amplifying the steering torque detected by the steering torque detection means, and an amplified steering torque amplified by the amplification circuit. And a steering assist control means for controlling an electric motor that applies a steering assist force to the steering system based on the control system.

As a control device for this type of electric power steering apparatus, for example, a torque detection means for outputting a signal corresponding to the steering torque, an amplification means for amplifying the output signal of the torque detection means, and an amplification output by the amplification means Control means for controlling drive current by inputting voltage, abnormality detection means for detecting abnormality of the amplification means from a deviation between the output signal of the torque detection means and the amplification signal, and abnormality detected by the abnormality detection means Timer means for measuring the duration of the state, time change rate detecting means for detecting when the time change rate of the amplified signal exceeds a predetermined value, and counting the number of detections of the time change detection means A counting means and an electric motor driven by an output current output from the control means and providing an auxiliary torque to the steering device, and an abnormal state measured by the timer means. When the duration exceeds a first predetermined time, the control means cuts off the drive current of the motor, and when the count number of the count means exceeds a predetermined number, the control means drives the motor. There is known an electric power steering control device that cuts off a current for a second predetermined time (see, for example, Patent Document 1).
JP 2001-171538 A (2nd page, FIG. 9, FIG. 10)

  However, in the conventional example described in Patent Document 1 above, in order to improve the controllability of the electric power steering device, the range used for the control of the steering torque signal detected by the steering torque sensor is determined by a hardware configuration amplifier circuit. In a normal control state, the steering assist control is performed using only the steering torque signal amplified by the amplifier circuit, and the deviation between the output signal of the torque detection means and the amplified signal is performed. When an abnormality in the amplifier circuit is detected, the drive current of the motor is cut off and the steering assist control is immediately stopped so that the manual steering state is established. Especially when the vehicle is large, the steering gear ratio, etc. As a result, manual steering requires a large steering torque, and there is an unsolved problem that the burden on the driver increases.

  Further, as shown in FIG. 10A, when the steering torque signal output from the steering torque sensor indicated by the broken line is amplified by the amplification circuit as shown in FIG. When the steering torque signal is negative, the negative maximum value is maintained, and when the steering torque signal is positive, the positive maximum value is maintained. In some cases, the output state is the same as that of the comparator that takes the maximum value of. In this case, the theoretical calculation value obtained by calculating the amplified output when the steering torque signal detected by the steering torque sensor is amplified by an amplifier circuit is as shown by a one-dot chain line. This theoretical calculation value is compared with the amplified output of the actual amplifier circuit, and when the deviation between the two is small, it is reset to “0”, which is normal. When the amplification circuit abnormality flag is set, the amplification circuit abnormality flag is normal in the vicinity of the positive and negative peak values of the theoretical calculation value where the deviation between the theoretical calculation value and the amplified output is small, as shown in FIG. Is also reset to “0”, and when the theoretical calculation value crosses “0”, the deviation between the theoretical calculation value and the amplified output becomes small and is reset to “0” indicating normality. On the contrary, the amplifier circuit malfunctions between the theoretical calculation value where the deviation between the theoretical calculation value and the amplified output becomes large until “0” before reaching the positive / negative peak and between when it exceeds the positive / negative peak and reaches “0”. The flag is set to “1” indicating abnormality. At this time, in the above conventional example, when the number of times that the rate of change of the output signal of the amplification circuit exceeds the predetermined value reaches the predetermined number, the driving current of the motor is cut off for the predetermined time. Until the current is cut off, the steering assist control is continued based on the amplified output of the amplifier circuit, which may give the steering system an unintended steering assist force to the driver. There is also an unsolved problem of giving.

  Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and when an abnormality occurs in the amplifier circuit, the steering assist control can be continued without causing the driver to feel uncomfortable. An object of the present invention is to provide a control device for an electric power steering device that can be used.

In order to achieve the above object, a control device for an electric power steering apparatus according to claim 1 detects a steering torque input to a steering system and outputs a steering torque detection signal; An amplifying circuit for amplifying a steering torque detection signal output from the steering torque detecting means, and a steering for controlling a motor for applying a steering assist force to the steering system based on the amplified steering torque signal amplified by the amplifying circuit. When the steering torque detected by the steering torque detecting means is normal, the amplified torque signal and the steering torque detection signal output from the amplifier circuit when the steering torque detected by the steering torque detecting means is normal. An abnormality of the amplifier circuit is detected by comparing with an amplified steering torque comparison value multiplied by a coefficient corresponding to the gain of the amplifier circuit. It includes a width circuit fault detecting means, before Kimisao steering assisting control means to the steering torque detection signal instead of amplifying the steering torque signal of the amplifier circuit upon detection of an abnormality in the amplifier circuit in the amplifier circuit abnormality detecting means The steering assist control is continued based on the amplified torque alternative value multiplied by a coefficient corresponding to the gain of the amplifier circuit.

Further, the controller of an electric power steering apparatus according to claim 2, in the invention according to claim 1, before Kimisao steering assisting control means continues the state of the steering assist control based on the steering torque detection signal is a predetermined time or more When the operation is continued, the steering assist control is configured to stop.

Furthermore, the control apparatus for an electric power steering apparatus according to claim 3 is the invention according to claim 2, before Kimisao steering assisting control means, when stopping the steering rudder auxiliary control, steering rudder that occur in the electric motor It is characterized by stop control so that the assist force gradually decreases.

Furthermore, in the control device for the electric power steering apparatus according to claim 4, in the invention according to any one of claims 1 to 3 , the amplification circuit abnormality detection means continuously detects abnormality of the amplification circuit and detects the predetermined number of times. It is configured to determine an abnormality of the amplifier circuit when you are characterized Rukoto.

The control device for an electric power steering apparatus according to claim 5, in any one invention of claims 1 to 4, before Kimisao steering assisting control means, an abnormality of the amplifier circuit in the amplifier circuit abnormality detecting means after detecting, at the return to a state of not detecting the abnormality of the amplifier circuit, that is configured to return to the state in which the steering rudder auxiliary control based on the amplification steering torque signal outputted from the amplifier circuit It is characterized by.

According to the first aspect of the present invention, when the abnormality of the amplification circuit that amplifies the steering torque detection signal is detected by the amplification circuit abnormality detection means, the amplified steering torque signal output from the amplification circuit is used by the auxiliary control means. since continued steering assist control based on the amplification torque alternative value without, amplified steering torque signal an abnormality has occurred is reliably prevented Shinano that affect the steering control to continue RaMisao steering assist control Thus, it is possible to reliably prevent the shift to the manual steering state and increase the driver's steering load or give a sense of incongruity.

Further, according to the invention of claim 2, when an abnormality is detected in the amplifier circuit in amplification circuit fault detecting means, in the steering control means, based on the steering torque detection signal outputted from the steering torque detection means steering When the control is continued and the steering continuation state continues for a predetermined time or longer, the steering assist control is stopped. Therefore, when the abnormal state of the amplification circuit continues for a long time, the steering assist control is stopped and the abnormal state The effect that the driver can be surely notified of the occurrence is obtained.

Furthermore, according to the invention according to claim 3, when stopping the steering rudder auxiliary control, because gradually decreasing the steering rudder assist force that occur in the electric motor, the operation to prevent a large change in the steering assist force Ru effect is obtained that it is possible to return to manual steering state without giving an uncomfortable feeling to the person.

According to the fifth aspect of the present invention, when the amplification circuit abnormality detecting means detects the abnormality of the amplified steering torque signal output from the amplification circuit a predetermined number of times, it is determined that the amplification circuit is abnormal. It is possible to immediately detect an abnormality in the amplifier circuit by setting the number to one, and to accurately detect an abnormality excluding the abnormality due to noise or the like by setting the predetermined number of times to a plurality of times. An effect is obtained.

According to the sixth aspect of the invention, the amplified steering torque output from the amplifier circuit when the amplifier circuit abnormality detecting means detects abnormality of the amplifier circuit and then returns to a state in which the normality of the amplifier circuit is detected. since return to the state of performing a steering assist control based on the signal, when a temporary abnormality in the amplifier circuit is restored to the normal state is generated, it is possible to immediately return to the normal steering steering assisting control state, exactly The effect that it is possible to perform proper steering control is obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In the figure, 1 is a steering wheel, and a steering force applied to the steering wheel 1 from a driver is an input shaft 2a and an output shaft. And 2b to the steering shaft 2. The steering shaft 2 has one end of an input shaft 2a connected to the steering wheel 1 and the other end connected to one end of an output shaft 2b via a steering torque sensor 3 serving as a steering torque detecting means.

The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured in a rack and pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is linearly moved by the rack 8b. It has been converted to movement.
The output shaft 2b of the steering shaft 2 are coupled deceleration gear 10 for transmitting the output shaft 2b of the steering rudder assist force, to the reduction gear 10, the output shaft of the electric motor 12 for generating a steering rudder assist force Are connected.

The steering torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the steering torque sensor 3 is a torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b. It is configured to convert to a torsional angular displacement and detect the torsional angular displacement with a potentiometer. The steering torque sensor 3, as shown in FIG. 2, when the steering torque input is zero, a predetermined neutral voltage V ₀ becomes, when the right turn from this state, the neutral voltage V ₀ in accordance with the increase of the steering torque When the steering torque is turned to the left from the state where the steering torque is zero, the steering torque detection signal T that is a voltage that decreases from the neutral voltage V ₀ according to the increase of the steering torque is output.

A steering torque detection signal T output from the steering torque sensor 3 is input to the controller 13. In addition to the torque detection value T, the controller 13 is also supplied with a vehicle speed detection value V detected by the vehicle speed sensor 14 and a drive current detection value _IMD flowing through the electric motor 12, and an input steering torque detection signal T and vehicle speed detection. A steering assist command value I _M ^* generated by the electric motor 12 with a steering assist force corresponding to the value V is calculated, and supplied to the electric motor 12 based on the calculated steering assist command value I _M ^* and the motor current detection value I _MD. The drive current to be fed back is controlled.

As shown in FIG. 3, the controller 13 controls the microcomputer 15 that executes control processing of the electric motor 12 and the drive current supplied to the electric motor 12 based on the motor drive current I _M output from the microcomputer 15. the motor driving circuit 17, a motor current detecting circuit 18 for detecting a drive current supplied by the motor driving circuit 16 to the electric motor 12, a drive voltage V _M supplied to the electric motor 12 from the motor current and the motor drive circuit 17 And a motor angular velocity estimation circuit 19 for estimating the motor angular velocity ω based on the above.

Then, the vehicle speed detection value V detected by the vehicle speed sensor 14 is directly input to the microcomputer 15, while the steering torque detection signal T detected by the steering torque sensor 3 is amplified, for example, three times by the amplifier circuit 20. The A / D converter 21 converts the digital signal into a digital signal and inputs it, and the steering torque detection signal T detected by the steering torque sensor 3 is directly converted into a digital signal by the A / D converter 22 and input. The motor current detection value _IMD detected by the current detection circuit 18 and the motor angular velocity ω estimated by the motor angular velocity estimation circuit 19 are converted into digital signals by the A / D converters 23 and 24, and inputted.

The microcomputer 15 includes an input interface circuit 15a to which the steering torque detection signal T, the amplified steering torque signal AT amplified by the amplifier circuit 20, the vehicle speed detection value V, the motor current detection value _IMD, and the motor angular velocity ω are input. Based on the steering torque detection signal T, the amplified steering torque signal AT, the motor current detection value _IMD, and the motor angular velocity ω, the steering assist control process is executed to control the drive of the electric motor 12 and generate the steering assist force according to the steering torque. And a central processing unit 15b that executes an amplification circuit abnormality detection process for detecting an abnormality in the amplification circuit 20, a ROM (read only memory) 15c that stores a steering assist control processing program executed by the central processing unit 15b, and the like. steering torque detection signal T, amplified steering torque signal, the motor current detection value I _MD and detection data such as the motor angular speed ω Has a RAM (Random Access Memory) 15d for storing data and processing results required during processing of the drive control process to be executed by the central processing unit 15b, and an output interface circuit 15e.

Here, the amplification circuit abnormality detection process executed by the central processing unit 15b is executed as a timer interruption process every predetermined time (for example, 10 msec). First, as shown in FIG. From the steering torque detection signal T output from the amplifier circuit 20 and the amplified steering torque signal AT output from the amplifier circuit 20, and then the process proceeds to step S2 where the steering torque detection signal T is a coefficient Kg corresponding to the gain of the amplifier circuit 20. After multiplying (= 3) to calculate the amplified steering torque comparison value ATc, the routine proceeds to step S3.

  In this step S3, it is determined whether or not the absolute value | AT-ATc | of the value obtained by subtracting the amplified steering torque comparison value ATc from the amplified steering torque signal AT is greater than or equal to a preset threshold value ΔT for abnormality determination in the amplifier circuit 20. If it is determined that | AT−ATc | <ΔT, it is determined that the amplifier circuit 20 is normal, the process proceeds to step S4, the amplifier circuit abnormality flag FA is reset to “0”, and timer interrupt processing is performed. When | AT−ATc | ≧ ΔT, it is determined that the amplifier circuit 20 is abnormal, the process proceeds to step S5, the amplifier circuit abnormality flag FA is set to “1”, and the timer interrupt process is performed. Exit.

Further, the steering assist control process executed by the central processing unit 15b is executed as a timer interrupt process every predetermined time (for example, 10 msec), and as shown in FIG. 5, first, detected by the steering torque sensor 3 in step S11. Whether or not the steering torque sensor 3 is abnormal is read by reading the steering torque detection signal T and then proceeding to step S12 to determine whether or not the steering detection signal is a value within a preset normal range. If the steering torque detection signal T exceeds a value within the normal range, it is determined that an abnormality due to disconnection or short circuit of the steering torque sensor 3 has occurred, and the process proceeds to step S13, where the motor The steering control process is terminated after the output of the motor drive current I _M to the drive circuit 17 is stopped.

On the other hand, when the determination result of step S12 is that the steering torque detection signal T is within the normal range and the steering torque sensor 3 is normal, the process proceeds to step S14 and the amplified steering amplified by the amplifier circuit 20 is performed. The torque signal AT is read, and then the process proceeds to step S15 to determine whether or not the amplification circuit abnormality flag FA set in the above-described amplification circuit abnormality detection processing is set to “1” indicating abnormality, and the amplification circuit When the abnormality flag FA is reset to “0”, it is determined that the amplifier circuit 20 is normal and the process proceeds to step S16.
In this step S16, it is determined whether or not the amplifier circuit abnormality flag FA was set to “1” during the previous timer interrupt process. If the amplifier circuit abnormality flag FA was set to “1”, the amplifier circuit abnormality was determined. It is determined that the state of the flag FA has changed, and the process proceeds to step S17.

  In this step S17, a period determination flag FB indicating whether or not the amplifier circuit 20 is in the determination period for determining whether or not it has truly returned to the normal state is set to “1” indicating that it is in the determination period. Next, the process proceeds to step S18, where the variable N for counting the predetermined period is incremented by “1”, and then the process proceeds to step S19 to determine whether or not the variable N has reached or exceeded the predetermined number Ns set in advance. When N <Ns, the process jumps to step S27 described later, and when N ≧ Ns, the process proceeds to step S20. Here, an arbitrary value can be set as the predetermined number Ns, but at least the amplified steering torque signal described in the section of the problem to be solved by the invention crosses “0” with the amplified steering torque comparison value. It is preferable to set the deviation so that the duration exceeding the time when the amplifier circuit abnormality flag FA is “0” can be secured.

In this step S20, the variable N is cleared to “0”, the period determination flag FB is reset to “0”, then the process proceeds to step S21, and based on the amplified steering torque signal AT read in step S14. Then, the amplified steering torque signal ATo is calculated by performing the calculation of the following equation (1) and performing the offset removal correction.
ATo = AT−V ₀ (1)

Next, the process proceeds to step S22, the calculated amplified steering torque signal ATo is set as the normal steering torque signal Ts, and then the process proceeds to step S27 described later.
If the determination result in step S15 indicates that the amplifier circuit abnormality flag FA is set to “1”, it is determined that the amplifier circuit 20 is abnormal, and the process proceeds to step S24, where the variable N is cleared to “0”. Then, the process proceeds to step S25, where the amplified steering torque substitute value ATa is calculated by performing the following equation (2) based on the steering torque detection signal T read in step S11.
ATa = 3 (T−V ₀ ) (2)

Next, the process proceeds to step S26, where the calculated amplified steering torque substitute value ATa is set as the normal steering torque signal Ts, and then the process proceeds to step S27.
In step S27, the vehicle speed detection value V detected by the vehicle speed sensor 14 is read, and then the process proceeds to step S28, where the steering shown in FIG. 6 is performed based on the steering torque signal Ts and the vehicle speed detection value V set in step S22 or S26. Referring to the auxiliary command value calculation map, a steering auxiliary command value I _M ^* that is a motor current command value is calculated.

Here, as shown in FIG. 6, the steering assist command value calculation map is a characteristic in which the horizontal axis represents the steering torque signal Ts, the vertical axis represents the steering assist command value I _M ^* , and the vehicle speed detection value V is a parameter. A straight line portion L1 that is configured by a diagram and extends with a relatively gentle gradient regardless of the vehicle speed detection value V until the steering torque signal Ts increases in the positive direction from “0” and reaches the first set value Ts1. When the steering torque signal Ts increases from the first set value Ts1, the linear portions L2 and L3 extending with a relatively gentle slope and the steering torque detection value Ts are obtained when the vehicle speed detection value V is relatively fast. Linear portions L4 and L5 that are parallel to the horizontal axis in the vicinity of the second set value Ts2 that is greater than the first set value Ts1, and in the state where the vehicle speed detection value V is slow, the linear portions L6 and L7 that have a relatively large gradient, , Gradient from these straight line parts L6 and L7 Four characteristics composed of straight line portions L8 and L9 having a large slope, a straight line portion L10 having a larger gradient than the straight line portion L8, and straight line portions L11 and L12 extending in parallel with the horizontal axis from the ends of the straight line portions L9 and L10. Similarly, when the steering torque signal Ts increases in the negative direction, four characteristic lines to be pointed are formed with the above and the origin in between.

Next, the processing proceeds to step S29, reads the motor acceleration omega estimated by the motor angular speed estimating circuit 19, and then proceeds to step S30, by multiplying the inertia gain K _i to the motor angular velocity omega, is the motor inertia acceleration The inertia compensation value I _i (= K _i · ω) for inertia compensation control for eliminating the torque from the steering torque Ts and obtaining a steering feeling without inertia is calculated, and the absolute value of the steering assist command value I _M ^* is calculated. Friction compensation value I _f (= K _f · I _M ^* ) for friction compensation control in order to eliminate the influence of the friction of the power transmission unit and the electric motor on the steering force by multiplying the value by the friction coefficient gain K _f Is calculated. Here, the sign of the friction compensation value _If is determined on the basis of the sign of the steering torque Ts and the steering direction signal for determining whether the steering is increased / returned based on the steering torque Ts.

Next, the process proceeds to step S31, where a differential operation process is performed on the steering torque signal Ts to calculate a center responsiveness improvement command value Ir for ensuring stability in the assist characteristic dead zone and compensating for static friction, and then the process proceeds to step S32. The calculated inertia compensation value I _i , friction compensation value _If and center response improvement command value Ir are added to the steering assist command value I _M ^* to obtain the steering assist compensation value I _M ^* ′ (= I _M ^* + I _i + I _f + Ir) is calculated, and then the process proceeds to step S33, the motor current detection value _IMD is read, and then the process proceeds to step S34.

In this step S34, the steering assist compensation value I _M ^* ′ is differentiated to calculate a feed forward control differential value Id, and then the process proceeds to step S35, where the motor current detection value _IMD is subtracted to obtain a current deviation ΔI. Then, the process proceeds to step S36, where the current deviation ΔI is proportionally calculated to calculate the proportional value ΔIp for proportional compensation control, and then the process proceeds to step S37, where the current deviation ΔI is integrated and calculated. The integral value ΔIi for integral compensation control is calculated, then the process proceeds to step S38, and the motor drive current I _M (= Id + ΔIp + ΔIi) is calculated by adding the differential value Id, the proportional value ΔIp and the integral value ΔIi, and then step In S39, the calculated motor drive current I _M is output to the motor drive circuit 17, and then the timer interrupt process is terminated and the process returns to the predetermined main program.
The processing in FIG. 4 corresponds to the amplification circuit abnormality detection means, and the processing in FIG. 5 corresponds to the steering control means.

Next, the operation of the above embodiment will be described.
Now, assuming that the steering torque sensor 3 is normal and the amplifier circuit 20 is also normal. In this state, for example, when the key switch is turned on to turn on the controller 13, the central processing of the microcomputer 15 is performed. The apparatus 15b starts executing the amplification circuit abnormality detection process shown in FIG. 4 and the steering control process shown in FIG.

  At this time, since the amplification circuit 20 is normal, as shown in FIG. 7A, the amplification steering torque signal AT and the steering torque detection signal T shown by the solid line output from the amplification circuit 20 are used as the gain of the amplification circuit 20. The amplified steering torque comparison value ATc indicated by the broken line multiplied by the corresponding coefficient Kg becomes substantially equal, and the absolute value | AT−ATc | of the deviation between the two is less than the threshold value ΔT, so that the amplification circuit abnormality detection processing of FIG. Thus, the process proceeds from step S3 to step S4, and the amplifier circuit abnormality flag FA is continuously reset to “0” representing normal as shown in FIG. At this time, the period determination flag FB is reset to “0” in the initialization process.

For this reason, in the amplification circuit abnormality detection process of FIG. 5, the steering torque detection signal T is read in step S11, and the steering torque detection signal T is normal. Therefore, the process proceeds from step S12 to step S14 and is output from the amplification circuit 20. After reading the amplified steering torque signal AT, the process proceeds to step S15.
At this time, as described above, in the amplification circuit abnormality detection process of FIG. 4, the state where the amplification circuit abnormality flag FA is reset to “0” is continued, and the period determination flag FB is also reset to “0”. Therefore, the process proceeds from step S15 through step S23 to step S21, and by subtracting the neutral voltage V ₀ from the amplified steering torque signal AT, a correction for removing the offset is performed, for example, right-handed positive, left-handed A correction amplification steering torque signal ATo that becomes negative is calculated.

Next, the process proceeds to step S22, where the corrected amplified steering torque signal ATo is set as the normal steering torque signal Ts, then the vehicle speed detection value V is read from the vehicle speed sensor 14 (step S27), and the steering torque Ts and the vehicle speed detection value V are read. Based on the above, the steering assist command value I _M ^* is calculated with reference to the steering assist command value calculation map shown in FIG. 7 (step S28).
On the other hand, the motor angular velocity ω estimated by the motor angular velocity estimation circuit 19 is read (step S29), the inertia compensation value I _i for inertia compensation control is calculated based on the motor angular velocity ω, and the friction compensation value for friction compensation control is calculated. calculating the I _f (step S30), further the steering torque Ts differential operation to calculate a center response improving command value I _r (step S31), these inertia compensation value I _i, friction compensation value I _f and the center response The steering assist compensation value I _M ^* ′ is calculated by adding the performance improvement compensation value I _r to the steering assist command value I _M ^* (step S32).

Then, read the motor current detection value I _MD detected by the motor current detecting circuit 18 (step S33), then the steering assist compensation value I _M ^* 'a by differentiating processing differentiated value Id for differential compensation control in feed forward control Is calculated by subtracting the motor current detection value _IMD from the steering assist compensation value I _M ^* ′ (step S35), and the calculated current deviation ΔI is proportionally processed. Thus, a proportional value ΔIp for proportional compensation control is calculated.

Further, the current deviation ΔI is subjected to integral calculation processing to calculate an integral value ΔIi for integral compensation control (steps S36 and S37), and then the differential value Id, the proportional value ΔIp and the integral value ΔIi are added to obtain the motor drive current I. _M is calculated (step S38), and the calculated motor drive current I _M is output to the motor drive circuit 17 (step S39), so that the drive current is supplied from the motor drive circuit 17 to the electric motor 12, and this electric motor is supplied. 12, a steering assist force corresponding to the steering torque applied to the steering wheel 1 is generated as shown in FIG. 7B, and this is transmitted to the output shaft 2 b via the reduction gear 10.

At this time, in a so-called stationary state in which the steering wheel 1 is steered while the vehicle is stopped, a large steering angle with a small steering torque Ts is obtained due to the large gradient of the characteristic line of the steering assist command value calculation map shown in FIG. Since the auxiliary command value I _M ^* is calculated, a large steering assist force can be generated by the electric motor 12 to perform light steering.
On the other hand, when the vehicle starts and exceeds the predetermined vehicle speed, the gradient of the characteristic line of the steering assist command value calculation map shown in FIG. 6 is reduced, so that a small steering assist command value I _M ^* is calculated even with a large steering torque Ts. Therefore, the steering assist force generated by the electric motor 12 is reduced, and the steering of the steering wheel 1 can be suppressed from becoming too light and optimal steering can be performed.

  However, when the steering torque sensor 3 and the amplifier circuit 20 are maintained in a normal state, an abnormality occurs due to, for example, a short circuit to the positive power source side at the time t1 in FIG. As shown in FIG. 7A, the amplified steering torque signal AT output from the amplifier circuit 20 rapidly rises to a predetermined power supply voltage exceeding the threshold value ΔT with respect to the amplified steering torque comparison value ATc. Occurs in step S3 in the process of FIG. 4 and | AT−ATc | ≧ ΔT, and it is determined that the amplifier circuit 20 is abnormal, and the process proceeds to step S5. Then, the amplification circuit abnormality flag FA is set to “1” as shown in FIG.

Therefore, in the steering assist control process of FIG. 5, since the amplification circuit abnormality flag FA is set to “1”, the variable N is cleared to “0” from step S15 to step S24, and then the process proceeds to step S25. Then, the amplified steering torque substitute value ATa is calculated based on the steering torque detection signal T to calculate the amplified steering torque substitute value ATa, and the calculated amplified steering torque substitute value ATa is set as the normal steering torque Ts (step S26). ), By referring to the control map of FIG. 6 based on the steering torque Ts and the vehicle speed detection value V, the steering assist command value I for generating a steering assist torque substantially equal to the corrected amplified steering torque ATo immediately before the abnormality occurs. _M ^* is calculated.

Then, a steering assist compensation value I _M ^* ′ is calculated based on the steering assist command value I _M ^* calculated based on the steering torque alternative value ATa, and the motor drive is performed based on the steering assist compensation value I _M ^* ′. Even if the current I _M is calculated and this motor drive current I _M is output to the motor drive circuit 17 and the electric motor 12 is driven and controlled, and the amplifier circuit 20 becomes in an abnormal state, the electric motor 12 can operate as shown in FIG. ), The steering assist control for generating the steering assist force according to the steering torque is continued, and it is prevented that the drive current to the electric motor is cut off and the manual steering state is prevented as in the conventional example. Steering state can be maintained.

  Incidentally, in the above-described conventional example, as shown in FIG. 8, when the amplification circuit becomes abnormal at time t1 and the amplified steering torque signal AT shown in the solid line increases rapidly to the power supply voltage, the amplified steering torque signal AT is broken. The counter is counted up when it is larger than the amplification steering torque comparison value ATc shown in the figure by a threshold value ΔT or more, and the motor control circuit is turned off when the count value of the counter reaches a set value. Is interrupted and a manual steering state is entered, so that steering assistance is performed based on the amplified steering torque signal of the amplifier circuit that becomes abnormal until the count value of the counter reaches the set value. In addition, when the count value of the counter reaches the set value, the drive current to the electric motor is cut off. When the gear ratio is large, the driver's steering load increases rapidly. In the above embodiment, however, the amplified steering torque substitute value ATa is used instead of the corrected amplified steering torque signal ATo immediately when the amplification circuit 20 becomes abnormal. Since the steering assist control is continued, the burden on the driver does not increase, and the amplified steering torque substitute value ATa is calculated based on the steering torque detection signal T, so that the steering following the change in the steering torque is performed. Auxiliary control can be continued.

Further, as shown in FIG. 9, the abnormal state of the amplifier circuit 20 is a temporary abnormality due to a contact failure or the like at time t1, which continues until time t2 after the required time, and becomes normal at time t2. When returning, when the deviation between the amplified steering torque signal AT output from the amplifier circuit 20 and the amplified steering torque comparison value ATc becomes equal to or larger than the threshold value ΔT at time t1, the process of FIG. 4 performs step S3. From step S5, the amplifier circuit flag FA is set to “1”. Therefore, in the steering assist control process of FIG. 5, the step shifts from step S15 to step S24 to step S25 to replace the amplified steering torque. value ATa is calculated, which by being re-set as the steering torque Ts of the normal, to immediately shift to the amplification steering torque alternative value ATa to based KuMisao steering assisting control state . Thereafter, when the deviation between the amplified steering torque signal AT output from the amplifier circuit 20 and the amplified steering torque comparison value ATc becomes less than the threshold value ΔT at time t2, the process proceeds from step S3 to step S4 in the process of FIG. Then, since the amplification circuit abnormality flag FA is reset to “0”, the process proceeds from step S15 to step S16 in the steering assist control process of FIG. 5, but the amplification circuit abnormality flag FA is “1” during the previous processing. Therefore, the process proceeds to step S17, the period determination flag FB is set to “1”, then the process proceeds to step S18, and the variable N is incremented to “1”. At this time, since the variable N is still smaller than the predetermined value Ns, the state of the amplified steering torque alternative value ATa is continued as the normal steering torque Ts by jumping from step S19 to step S27.

In the next timer interrupt cycle, since the previous amplifier circuit abnormality flag FA is “0”, the process proceeds from step S16 to step S23. However, since the period determination flag FB is set to “1”, step S18 is performed. Then, the variable N is incremented.
Thereafter, the variable N is sequentially incremented every time the timer interruption period arrives. When the variable N reaches the predetermined value Ns at time t3, the process proceeds from step S29 to step S20, and the amplified steering torque signal ATo is calculated. This can return by being re-set, the normal steering steering assisting control state immediately based on the amplified steering torque signal ATo as the steering torque Ts of the normal.

Further, as described in the conventional example, as shown in FIG. 10A, the amplified steering torque signal ATo output from the amplifier circuit 20 is converted into the neutral torque V ₀ by the steering torque detection signal T shown in the broken line. As shown in the solid line, when an abnormality occurs that suddenly changes between the maximum value and the minimum value of the power supply voltage and becomes in the same state as the comparison output of the comparator, as shown by the solid line in FIG. As shown in (c), when the deviation between the amplified steering torque signal ATo and the amplified steering torque comparison value ATc is less than the threshold value ΔT, the amplification circuit abnormality flag FA is reset to “0”, and the amplified steering torque signal ATo and the amplified steering are reset. When the deviation from the torque comparison value ATc is greater than or equal to the threshold value ΔT, the amplification circuit abnormality flag FA is repeatedly set to “1”. However, in the steering assist control process of FIG. When A is reset from “1” to “0” and a state change occurs, the normal steering torque is reached when the amplification circuit abnormality flag FA can be reliably determined to be normal for a predetermined period of time. Since Ts is switched from the amplified steering torque substitute value ATa to the corrected amplified steering torque signal ATo, the absolute value of the deviation from the amplified steering torque comparison value ATc instantaneously becomes the threshold value ΔT when the amplified steering torque signal AT crosses “0”. When the amplification circuit abnormality flag FA is reset to “0” because the value is less than the value, the state of the amplified steering torque alternative value ATa is continued, and correction is performed only in the vicinity where the amplified steering torque comparison value ATc has a positive / negative peak. Since the amplified steering torque signal ATo is set as the normal steering torque Ts, the steering torque Ts is substantially the same as the steering system although the waveform is slightly broken as shown in FIG. Steering assist control according to the input steering torque can be continued.

In order to increase the continuation determination time when the amplifier circuit abnormality flag FA is reset from “1” to “0”, the step in FIG.
In this way, by setting the reset condition to provide a continuation determination time when the amplifier circuit abnormality flag FA is reset from “1” to “0”, it is determined that the normal time has passed sufficiently and is normally determined. Otherwise, it can be prevented from returning from the amplified torque substitute value ATa to the corrected amplified torque signal ATo, and the occurrence of the hunting phenomenon can be surely prevented and the uncomfortable feeling given to the driver can be surely prevented.

Further, when a disconnection or short circuit abnormality occurs in the steering torque sensor 3, the process proceeds to step S3 from step S2 in the process of FIG. 5, and the output of the motor drive current I _M to the motor drive circuit is stopped. At the same time, the steering assist control process of FIG. 5 is terminated, so that it is possible to reliably prevent malfunction due to an abnormality in the steering torque sensor 3.
In the above embodiment, the abnormality detection of the amplifier circuit 20 has been described for the case where it is determined whether or not the deviation between the amplified steering torque signal ATo and the amplified steering torque comparison value ATc is greater than or equal to the threshold value ΔT. It is not limited, and the absolute value of the deviation between the amplified steering torque signal ATo obtained by removing the offset from the amplified steering torque signal AT output from the amplifier circuit 20 and the amplified steering torque alternative value ATa is greater than or equal to the threshold value ΔT. Further, a value obtained by multiplying the amplified steering torque signal AT by a gain is compared with the steering torque detection signal T, and whether or not the absolute value of the deviation is equal to or greater than the threshold value ΔT1. You may make it determine.

In the above embodiment, the case where the steering assist control is continued using the amplified steering torque alternative value ATa when the abnormality of the amplifier circuit 20 is detected has been described. However, the present invention is not limited to this. the steering rudder assisting control processing to run by the central processing unit 15b of the microcomputer 15, as shown in FIG. 11, in which the decision result in the step S15 is, the amplifier circuit abnormality flag FA is set to "1" When the process proceeds to step S41 via step S24, it is determined whether or not the timer for measuring the duration is set. When the timer is not set, the process proceeds to step S42 and the timer is set. To step S43, and when the timer is set, the process proceeds directly to step S43, where the timer is It is determined whether or not the timer has expired. When the timer has not expired, the process proceeds to step S25. When the timer has expired, the process proceeds to step S13. When the FA is reset to “0”, the process proceeds to step S44, the timer is reset, and then the process proceeds to step S16, so that the abnormal state of the amplifier circuit 20 continues for the set time of the timer or more. May stop the driving of the electric motor 12. In this case, when the drive of the electric motor 12 is stopped, the motor drive current I _M at that time is gradually decreased by a predetermined value ΔI continuously or stepwise so that the motor drive current I _M is zero or in the vicinity thereof. It is preferable to perform a motor drive current gradual reduction process that stops the output of the motor drive current I _M when it becomes.

Furthermore, in the above embodiment, the case where the motor drive current I _M is calculated by software processing executed by the central processing unit 15b has been described. However, the present invention is not limited to this, and the steering assist command value calculator, center response, Motor drive current I _M is calculated by hardware combining a performance improvement circuit, inertia compensator, friction compensator, differential compensator, subtractor, proportional calculator, integral calculator, adder, multiplier, comparator, etc. You may do it.

  Furthermore, in the above-described embodiment, the case where center response improvement compensation control, inertia compensation control, friction compensation control, differential compensation control, proportional / integral compensation control is applied as compensation control has been described. However, the present invention is not limited to this. Concentration compensation control for stabilizing the behavior of the vehicle described in JP 2003-170856 A, a motor loss that adds an auxiliary force equivalent to the loss torque to the direction in which the loss torque of the electric motor is generated Torque compensation control, robust compensation control that compensates for the phase shift of the resonance frequency that hinders the stability and responsiveness of the control system, and the output of the electric motor by adding a current that does not appear in the output of the electric motor even if the motor current flows In addition to the motor loss current compensation control that improves the rise from the torque “0”, the steering wheel is naturally returned to the neutral position. Various compensation control such as tearing wheel return compensation control may be incorporated in any combination.

It is a schematic structure figure showing one embodiment of the present invention. FIG. 6 is a characteristic diagram of a torque detection signal detected by a steering torque sensor. FIG. 2 is a block diagram illustrating a specific configuration of the controller in FIG. 1. It is a flowchart which shows an example of the amplification circuit abnormality detection process procedure performed with the central processing unit of a microcomputer. It is a flowchart which shows an example of the steering assistance control processing procedure performed with the central processing unit of a microcomputer. It is a characteristic diagram which shows a steering assistance command value calculation map. It is a time chart with which it uses for description of operation | movement of this invention. It is a time chart used for description of operation | movement of a prior art example. It is a time chart with which it uses for description of the operation | movement at the time of temporary abnormality of the amplifier circuit of this invention. It is a time chart with which it uses for description of operation | movement at the time of abnormality similar to the comparison output of a comparator in the amplifier circuit of this invention. It is a flowchart which shows an example of the steering assistance control processing procedure performed with the central processing unit of the microcomputer which shows other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Steering torque sensor, 8 ... Steering gear, 12 ... Electric motor, 13 ... Controller, 14 ... Vehicle speed sensor, 15 ... Microcomputer, 15a ... Input interface circuit, 15b ... Central processing 15c ... ROM, 15d ... RAM, 15e ... output interface circuit, 17 ... motor drive circuit, 18 ... motor current detection circuit, 19 ... motor angular velocity estimation circuit, 20 ... amplifier circuit, 21-24 ... A / D converter

Claims (5)

Steering torque detection means for detecting steering torque input to the steering system and outputting a steering torque detection signal, an amplification circuit for amplifying the steering torque detection signal output from the steering torque detection means, and the amplification circuit A control device for an electric power steering apparatus comprising: a steering assist control means for controlling an electric motor that applies a steering assist force to the steering system based on the amplified steering torque signal amplified in step
When the steering torque detected by the steering torque detecting means is normal, the amplified steering torque comparison obtained by multiplying the amplified torque signal output from the amplifier circuit and the steering torque detection signal by a coefficient corresponding to the gain of the amplifier circuit comprising an amplifier circuit abnormality detecting means for detecting an abnormality of the amplifier circuit by comparing the values before Kimisao steering assisting control means, the amplification when an abnormality is detected in the amplifier circuit in the amplifier circuit abnormality detecting means An electric power characterized in that steering assist control is continued based on an amplified torque alternative value obtained by multiplying the steering torque detection signal by a coefficient corresponding to the gain of the amplifier circuit instead of the amplified steering torque signal of the circuit. Control device for steering device. Before Kimisao rudder auxiliary control means, wherein the persistent state of the steering assist control based on the steering torque detection signal when a predetermined time or longer, characterized in that it is configured to stop the steering assist control Item 4. A control device for an electric power steering device according to Item 1. Before Kimisao rudder auxiliary control means, Misao when stopping the steering assist control, the electric according to claim 2, characterized in that the stop control as steering steering assist force that occur in the motor gradually decreases Control device for power steering device.   The amplifier circuit abnormality detecting means is configured to determine that the amplifier circuit is abnormal when the abnormality of the amplifier circuit is continuously detected a predetermined number of times. A control device for an electric power steering device. Before Kimisao rudder auxiliary control unit, after detecting an abnormality of the amplifier circuit in the amplifier circuit abnormality detecting means, at the return to a state of not detecting the abnormality of the amplifier circuit, amplification steering torque output from the amplifier circuit control device for an electric power steering apparatus according to any one of claims 1 to 4, characterized in that is configured to return to the state of performing the steering rudder auxiliary control based on the signal.

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