JP5023500B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device, and more particularly, to an electric power steering device including a control device capable of appropriately controlling a steering assist torque even if a torque detection value shows an abnormal value due to a failure of a torque sensor for detecting a steering torque. Relates to the device.

  An electric power steering device for a vehicle detects a steering torque generated in a steering shaft that connects a steering handle and a steering mechanism, controls a motor output based on the detected steering torque, and generates a driving force of the motor. Generally, a steering assist torque is applied to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt to appropriately assist the steering torque of the steering handle.

  FIG. 8 is a diagram for explaining an example of the configuration of such an electric power steering apparatus. A steering shaft 102 of the steering handle 101 is connected to a tie rod 106 of a steering wheel via a reduction gear 103, universal joints 104a and 104b, and a pinion / rack mechanism 105. The steering shaft 102 is provided with a torque sensor 107 that detects a steering torque generated in the steering shaft, and a motor 108 that assists the steering torque is connected via a reduction gear 103.

  The control device 109 controls the output of the motor 108 and inputs the steering torque detected by the torque sensor 107, the vehicle speed detected by a vehicle speed sensor (not shown), the angular velocity of the motor detected by the hall sensor 110, and the like. The current command value is calculated as follows, and the motor is controlled based on the calculated current command value. The control device 109 is constituted by a CPU, and controls a motor by a control program inside the CPU to generate an appropriate steering assist torque.

  FIG. 9 is a diagram illustrating an example of a block diagram illustrating the control function of the control device 109 described above. The detected torque value T detected by the torque sensor 107 is input to the current command value calculation unit 120, and the current command value Ir is calculated and output to the adder 121. The adder 121 calculates a current control value E that is a difference (Ir−im) between the current command value Ir and the motor current detection value im detected by the current detector 124, and outputs it to the current control unit 122.

  The current control unit 122 calculates a duty ratio D based on the current control value E, and outputs a PWM signal (pulse width signal) corresponding to the duty ratio D to the motor driving unit 123. In response to the PWM signal, the motor driving unit 123 operates an H bridge circuit composed of a semiconductor element (not shown) to drive the motor 108. The motor current flowing through the motor 108 is detected by the motor current detector 124, and the detected motor current detection value im is fed back to the adder 121 for feedback control.

  In the electric power steering apparatus as described above, the motor is controlled on the assumption that the torque sensor operates normally and the steering torque is accurately detected. However, in actuality, the torque sensor may also fail, and if it fails, an abnormal torque detection value is input to the control device, which may cause an abnormal operation unintended by the driver. Has been.

  For example, FIG. 10 is a block diagram illustrating a control function of an example of a control device configured to solve the above problem. The calculator 201 of the control device includes a steering torque calculator 202, a response compensation calculator 203, a current calculator 204 that calculates a motor current, a torque sensor operation determiner 205, an adder 206, a current control calculator 207, and a selector. 208, and an interrupter 209 for supplying or cutting off power from the power source 8 to the motor.

  The detected torque value T is input to the steering torque calculator 202, the response compensation calculator 203, and the torque sensor operation determiner 205. On the other hand, a motor current detection value I is input to the current calculator 204, and a current calculation value Ie is calculated based on the motor current detection value I.

  A steering torque calculator 202 calculates a steering assist torque corresponding to the detected torque value T, and outputs a basic steering torque value T0. The response compensation calculator 203 calculates a compensation force necessary for response compensation during steering, and outputs a response compensation value T1. The adder 206 adds the basic steering torque value T 0 and the response compensation value T 1 to calculate the steering command value T 2 and outputs it to the current control calculator 207. The current control calculator 207 feeds back the current flowing through the motor based on the steering command value T2 and the current calculation value Ie output from the current calculator 204, and calculates the steering assist command value TA (same as the current command value). To the selector 208.

  Further, in the torque sensor operation determination unit 205, the abnormality determination of the torque sensor is always executed by a predetermined calculation process, and the selector switching signal S1 and the interrupter switching signal S2 are output according to the determination result.

  Next, the operation will be briefly described. The torque sensor operation determination unit 205 constantly monitors the signal level of the torque detection value T. When the signal level of the torque detection value T is out of the predetermined normal value range, the elapsed time from the detection time point. When the state outside the range of the normal value continues for a predetermined time ta, the selector switch signal S1 is output to the selector 208, the steering assist command value TA is cut off, and the motor drive is stopped. Is done.

  Further, when the time tb elapses from the time when the steering assist command value TA is interrupted, the interrupter switching signal S2 is output to the interrupter 209, and the motor power supply is interrupted (see Patent Document 1).

  In the above-described control method, the steering assist command calculated based on the abnormal torque detection value T until a predetermined time ta elapses after the state where the torque detection value T is out of the normal value range is detected. The motor is driven by the PWM signal having the duty ratio D determined by the value TA, and an abnormal steering assist torque unintended by the driver is generated, which may cause the driver to feel uncomfortable.

  In addition, when a predetermined time ta elapses after the state outside the normal value range is detected, the current command value Ir is cut off and the steering assist force suddenly becomes zero, so that the driver operates the steering handle. When a large torque is applied, the driver suddenly changes the torque suddenly and feels that the steering wheel is heavy.

  In response to such a problem, when a serious abnormality such as a decrease in the power voltage of the torque sensor or a momentary power failure occurs, the fail switch is activated, and the gain is added to the torque detection value T immediately before the occurrence of the abnormality. Control of the control device that calculates the current command value Ir using the value multiplied by, continues control, and then gradually attenuates the current command value Ir so that the steering assist torque does not change suddenly There is a method (see Patent Document 2).

According to this control method, when the torque detection value T is out of the normal value range, the motor is driven by the current command value Ir calculated based on the immediately preceding torque detection value T, and then the current command value Ir is A control that gradually attenuates is performed, whereby the motor current is also gradually reduced, so that a sudden torque change does not occur.
JP 2000-318633 A. JP 2000-329628 A.

  As described above, in the control method of the conventional control device, when an abnormality occurs in the torque sensor, the current command value Ir is calculated based on the torque detection value T immediately before the abnormality occurs, and then the current command value Ir is calculated. By performing control that gradually attenuates, a sudden change in the auxiliary steering torque is suppressed. Hereinafter, in this application, control that gradually attenuates the current command value Ir after occurrence of an abnormality will be referred to as “gradual change processing”.

  However, when the “gradual change process” is performed when the rotation speed of the motor is high, the driver may feel uncomfortable. For example, when the driver steers suddenly in a short time, the motor angular velocity increases due to sudden steering, and a region where the motor current necessary to generate the steering assist torque cannot be generated, and the steering assist torque is insufficient. There is a case.

  At this time, the driver operates the steering handle with a steering torque that is larger by the insufficient steering assist torque, so the torque sensor outputs an excessive torque detection value. In such a situation, when a failure occurs in the torque sensor and an abnormality is detected in the torque detection value, the torque detection value T immediately before the occurrence of the abnormality is an excessive torque, and therefore, based on the excessive torque detection value. When the steering assist torque is generated, the steering assist torque is generated more than necessary, which may cause the driver to feel uncomfortable.

  In addition, if the driver steers abruptly in a short time, the rotation of the motor cannot follow, and there is a time in which the motor rotates in the direction opposite to the steering direction intended by the driver for a short time. For this reason, the torque detection value T input to the control device is a value in the direction opposite to the direction intended by the driver, excessive torque is generated, and the torque detection value T indicates an abnormal value. Further, after this, the motor rotates in the reverse direction in the direction intended by the driver. However, when the motor is reversed, the angular acceleration of the motor becomes high, and there is an inconvenience that an abnormal value is indicated.

SUMMARY OF THE INVENTION The present invention solves the above problems, and an electric power steering device according to a first aspect of the present invention is a motor for applying a steering assist force to a steering system of a vehicle and a torque sensor for detecting a steering torque acting on a steering handle. A control device that controls the motor output based on the torque detection value of the torque sensor sampled at a predetermined timing, a torque value abnormality detection means that detects abnormality of the torque detection value, a motor angular velocity output means, or a motor angle In the electric power steering apparatus including the acceleration output means , the control device includes a storage means for storing an alternative torque value, and calculates the alternative torque value by a parameter corresponding to the detected torque value and the motor angular velocity or motor angular acceleration. The alternative torque value is constantly updated and stored in the storage means, and the torque value abnormality detection means After the abnormality of the torque detection value is detected is an electric power steering apparatus characterized by controlling the motor output based on the substitute torque values in place of the torque detection value.

According to a second aspect of the present invention, there is provided an electric power steering apparatus comprising: a motor that applies a steering assist force to a vehicle steering system; a torque sensor that detects a steering torque that acts on a steering handle; and the torque sampled at a predetermined timing. An electric power steering apparatus comprising: a control device that controls a motor output based on a torque detection value of a sensor; a torque value abnormality detection unit that detects abnormality of the torque detection value; and a motor angular velocity output unit or a motor angular acceleration output unit. The control device comprises storage means for storing a value necessary for the calculation of the alternative torque value, and constantly updates the value required for the calculation of the alternative torque value and stores the value in the storage means so that the torque value abnormality occurs. After the abnormality of the torque detection value is detected by the detection means, the value necessary for the calculation of the alternative torque value and the motor angular velocity or motor angle addition Parameter by calculating the substitute torque value corresponding to the time, an electric power steering apparatus characterized by controlling the motor output based on the substitute torque values in place of the torque detection value.

An electric power steering apparatus according to a third aspect of the present invention is the electric power steering apparatus according to any one of the first and second aspects, wherein the control device includes a gradual change processing means for gradually decreasing the output of the motor. The dynamic power steering apparatus is characterized in that after the abnormality of the torque detection value is detected by the torque value abnormality detection means, the gradual change processing means is operated to control to gradually reduce the motor output. .

An electric power steering apparatus according to a fourth aspect of the invention is the electric power steering apparatus according to any one of the first to third aspects, wherein a corrected torque value obtained by multiplying the previous torque detection value just before the abnormality detection by the parameter is substituted. An electric power steering apparatus characterized by having a torque value.

An electric power steering apparatus according to a fifth aspect is the electric power steering apparatus according to any one of the first to fourth aspects, wherein the parameter is inversely proportional to an increase in the motor angular velocity or the motor angular acceleration. This is an electric power steering device characterized in that it decreases.

An electric power steering apparatus according to a sixth aspect of the present invention is the electric power steering apparatus according to any one of the first to fifth aspects, wherein the parameter is constant when the motor angular velocity or the motor angular acceleration is a predetermined value or less. When the motor angular velocity or the motor angular acceleration exceeds a predetermined value, the electric power steering device decreases as the motor angular velocity or the motor angular acceleration increases.

An electric power steering device according to a seventh aspect of the invention is the electric power steering device according to any one of the first to third aspects, wherein the corrected torque value obtained by subtracting the parameter from the past torque detection value immediately before the abnormality detection is substituted. An electric power steering apparatus characterized by having a torque value.

An electric power steering apparatus according to an eighth aspect of the present invention is the electric power steering apparatus according to any one of the first to third and seventh aspects, wherein the parameter is proportional to an increase in the motor angular velocity or the motor angular acceleration. Thus, the electric power steering apparatus increases in number.

An electric power steering apparatus according to a ninth aspect of the present invention is the electric power steering apparatus according to any one of the first to third, and 7 to 8, wherein the parameter is such that the motor angular velocity or the motor angular acceleration is a predetermined value or less. In this case, the electric power steering apparatus has a constant value, and increases when the motor angular velocity or the motor angular acceleration exceeds a predetermined value.

  As described above, according to the electric power steering device of the present invention, the control device quickly detects an abnormality when a failure occurs in the torque sensor and an abnormality occurs in the torque detection value output from the torque sensor. The motor output is controlled based on an appropriate alternative torque value instead of the torque value.

  As a result, it is possible to provide a highly safe electric power steering apparatus that can operate the steering handle with an appropriate steering torque without causing the driver to feel uncomfortable even if a torque sensor failure occurs.

  Embodiments of the present invention will be described below. Since the schematic configuration of the entire electric power steering apparatus according to the embodiment of the present invention is the same as the conventional configuration described above with reference to FIG. 8, the description thereof will be omitted here and the configuration of the control apparatus will be described.

[First Embodiment]
FIG. 1 is a block diagram illustrating a control function of a control device for an electric power steering apparatus according to a first embodiment of the present invention. The control device 10 includes a torque value abnormality detection unit 23 that is a torque value abnormality detection unit, a torque calculation unit 24 that is an alternative torque value output unit, a motor angular velocity estimation unit 25 that is a motor angular velocity output unit, and a storage device 26 that is a storage unit. , A current command value calculation unit 27, a gradual change processing unit 28 which is a gradual change means, an adder 29, a current control unit 31, and a motor drive unit 32. The control device 10 is connected to a torque sensor 21 that detects a steering torque and outputs a detected torque value, a motor 33 that supplies a steering assist force, and a motor current detector 34 that detects a motor current. In the following description, the motor angular speed estimation unit 25 is shown as the motor angular speed output means, but it may be a motor angular speed output means that directly detects the motor angular speed.

  Further, instead of the motor angular velocity output means, motor angular acceleration output means may be used. In this case, the motor angular velocity estimation unit 25 is replaced with the motor angular acceleration estimation unit 25. The motor angular acceleration can be obtained by differentiating the motor angular velocity.

  Further, in a plurality of embodiments for calculating a corrected torque value to be described later, there are shown an embodiment for calculating a corrected torque value using a motor angular velocity and an embodiment for calculating a corrected torque value using motor angular acceleration. .

  The torque value abnormality detection unit 23 determines whether or not the detected torque detection value T is abnormal, and determines a torque value abnormality by a known torque diagnosis means. When it is determined that the detected torque detection value T is abnormal, an abnormality detection signal G is output to the torque calculation unit 24 and the gradual change processing unit 28 to execute abnormality processing.

  The motor angular velocity estimation unit 25 estimates the motor angular velocity Ve by a known method. The torque calculation unit 24 outputs a steering torque value Ta used for driving control of the motor 33 to the current command value calculation unit 27. The torque calculation value T sampled from the torque sensor 21 at predetermined time intervals, and The motor angular speed Ve estimated by the motor angular speed estimation unit 25 is input.

  When the abnormality detection signal G is not input from the torque value abnormality detection unit 23, that is, when the abnormality of the torque detection value T is not detected, the torque calculation unit 24 receives the torque detection value input from the torque sensor 21. T is output as it is to the current command value calculation unit 27 as the steering torque value Ta, and the corrected torque value Te is calculated based on the detected torque value T input from the torque sensor 21 and the motor angular velocity Ve estimated by the motor angular velocity estimation unit 25. Calculate and store in the storage device 26.

  Here, since the corrected torque value Te calculated and output at a predetermined time interval is overwritten and stored every time in the storage device 26, the stored corrected torque value Te is constantly updated. A method for calculating the corrected torque value Te will be described later.

  On the other hand, when the abnormality detection signal G is input from the torque value abnormality detection unit 23, that is, when abnormality of the torque detection value T is detected, the torque calculation unit 24 sets the torque detection value T determined to be an abnormal value. Instead, the corrected torque value Te stored in the storage device 26 is output to the current command value calculation unit 27 as an alternative torque value for the steering torque value Ta. At this time, the correction torque value Te is not calculated, and the correction torque value Te stored in the storage device 26 is not updated.

  Based on the alternative torque value output from the torque calculation unit 24, the current command value calculation unit 27 calculates a current command value Ir for performing motor drive control by a known method, and outputs it to the gradual change processing unit 28.

  When the abnormality detection signal G is input from the torque value abnormality detection unit 23, that is, when an abnormality in the torque detection value T is detected, the gradual change processing unit 28 outputs the current output from the current command value calculation unit 27. A gradual change process for gradually attenuating the command value Ir is performed, and the current command value Ir subjected to the gradual change process is output to the adder 29.

  Further, when the abnormality detection signal G is not input from the torque value abnormality detection unit 23, that is, when the abnormality of the torque detection value T is not detected, the gradual change process is not performed and the current command value Ir is added as it is. Output to the unit 29.

  The adder 29 subtracts the current command value Ir (including the current command value Ir subjected to the gradual change process) output from the current command value calculation unit 27 and the motor current im detected by the motor current detector 34. The current control value E is output to the current control unit 31.

  The current control unit 31 calculates a duty ratio of a PWM signal that drives the semiconductor switching element of the motor drive unit 32 based on the current control value E, and outputs the calculated duty ratio to the motor drive unit 32. The motor drive unit 32 drives the motor 33 by operating an H bridge circuit composed of semiconductor switching elements based on the duty ratio.

  A motor current im flowing through the motor 33 is detected by a motor current detector 34, and input to an adder 29 for feedback.

  As described above, when no abnormality is detected in the detected torque value T, the detected torque value T is output as the steering torque value Ta, and the motor 33 is driven. If an abnormality is detected in the detected torque value T, the motor 33 is prevented from being driven based on the detected torque value T, which is an abnormal value, and the corrected torque value Te stored in the storage device 26 is set to the steering torque value Ta. As a substitute torque value, the motor 33 is driven, and the gradual change processing unit 28 performs a gradual change process gradual change process in which the current command value Ir is gradually attenuated.

  Next, calculation of the corrected torque value Te used as an alternative torque value when an abnormality in the detected torque value is detected will be described. Since there are a plurality of embodiments of the calculation method of the corrected torque value Te, description will be made sequentially below.

[First Embodiment of Corrected Torque Value Calculation]
In the first embodiment of the corrected torque value calculation, the corrected torque value Te is calculated based on the detected torque value T and the motor angular velocity Ve, and the corrected torque value Te is converted to the detected torque value T as will be described later. It is calculated by the following equation (1a) which multiplies the parameter p1 of the value corresponding to the motor angular velocity Ve.

Te = T × p1 (1a)
Here, as the torque detection value T, the past torque T0 which is the torque detection value detected in the previous sampling is used.

  An example of the parameter p1 is shown in (1) of FIG. When the motor angular velocity Ve is equal to or less than Vea, the parameter p1 is set to a constant value (for example, p1 = 1.0). When the motor angular velocity Ve exceeds Vea, the parameter p1 is decreased in inverse proportion to the increase of the motor angular velocity. Is set by a linear function. Note that the linear function and the threshold value Vea vary depending on the vehicle, the motor to be used, and other factors. At this time, in the first embodiment, an example is shown in which the parameter p decreases in accordance with the linear function in inverse proportion to the increase in the motor angular velocity, but a function other than the linear function may be used.

[Second Example of Corrected Torque Value Calculation]
In the second embodiment of the corrected torque value calculation, the corrected torque value Te is calculated based on the torque detection value T and the motor angular velocity Ve or the motor angular acceleration Ae. Are multiplied by a plurality of preset parameters (for example, p1, p2, p3, .about.pn) to calculate a plurality of calculated torque values Te1, Te2, Te3, .about.Ten, and calculated torque values Te1, Te2, Te3. , .About.Ten, if the minimum value, for example, the minimum value is Ten, Ten is set as the corrected torque value Te. Here, as the torque detection value T, the past torque T0 which is the torque detection value detected in the previous sampling is used.

[Third Example of Corrected Torque Value Calculation]
In the third embodiment of the correction torque value calculation, the motor angular acceleration Ae is used in place of the motor angular velocity Ve used in the first embodiment. That is, the corrected torque value Te is calculated based on the detected torque value T and the motor angular acceleration Ae estimated and calculated based on the motor angular velocity Ve. In this case, the corrected torque value Te is calculated as the torque detected value T, which will be described later. The following equation (1b) is used to multiply the parameter p2 of the value corresponding to the motor angular acceleration Ae to be calculated.

Te = T × p2 (1b)
Here, as the torque detection value T, the past torque T0 which is the torque detection value detected in the previous sampling is used.

  An example of the parameter p2 is shown in FIG. When the motor angular acceleration Ae is less than Aea, the parameter p2 is a constant value (for example, p2 = 1.0). When the motor angular acceleration Ae exceeds Aea, the parameter p2 is inversely proportional to the increase of the motor angular velocity. The linear function is set so as to decrease.

[Fourth Example of Corrected Torque Value Calculation]
The fourth embodiment of the corrected torque value calculation is a modification of the first to third embodiments, and the torque detection value T and the motor are the same as in the first to third embodiments of the corrected torque value calculation. The corrected torque value Te is calculated based on the angular velocity Ve or the motor angular acceleration Ae. The corrected torque value Te is calculated by the following equation (1c) that multiplies the torque detection value T by a parameter p3 described later. To do. Here, as the torque detection value T, the past torque T0 which is the torque detection value detected in the previous sampling is used.

Te = T × p3 (1c)
As the parameter p3, the smaller one of the two parameters p1 and p2 is used.

Alternatively, the parameter p4 calculated by the following equation (1d) for weighting the two parameters p1 and p2
p4 = (p1 × w1 + p2 × w2) (1d)
However, w1 and w2 can also be used to calculate the corrected torque value Te using weighted values.

  The correction torque value Te may be calculated using the torque detection value T and one or both of the motor angular velocity Ve and the motor angular acceleration Ae.

[Fifth Example of Corrected Torque Value Calculation]
In the fifth embodiment of the corrected torque value calculation, the corrected torque value Te is calculated by the following equation (3) in which the parameter s is subtracted from the past torque detected value T that is the previously detected torque detected value.

          Te = T−s (3).

  An example of the parameter s is shown in (3) of FIG. The parameter s is set to increase in proportion to the increase of the motor angular velocity Ve. When the motor angular velocity Ve is equal to or less than Veb, the parameter s may be a constant value (for example, s = 1.0), and may be increased after the motor angular velocity Ve exceeds Veb. Note that Veb, which is the proportionality constant and the threshold value, is determined by examining vehicle-mounted data and the like since the optimum value varies depending on the vehicle, the motor used, and other factors. At this time, in the fourth embodiment, the example in which the parameter s increases in proportion to the increase in the motor angular velocity is shown, but it may be increased in a relationship other than the proportion.

  As shown in the third embodiment for calculating the corrected torque value, when the motor angular acceleration Ae is used instead of the motor angular velocity Ve, the parameter s is increased in proportion to the increase of the motor angular acceleration Ae. It is good to set to.

[Sixth Example of Corrected Torque Value Calculation]
In the sixth embodiment of the corrected torque value calculation, as shown in FIG. 3, when the motor angular velocity Ve exceeds Vec, the corrected torque value Te is fixed to a predetermined limit value Toff, and when the motor angular velocity Ve is less than Vec. The torque detection value T is directly used as the corrected torque value Te. The threshold value Vec differs depending on the vehicle, the motor to be used, and other factors, and is determined by examining vehicle-mounted data and the like at the time of implementation. Further, the motor angular acceleration Ae can be used in place of the motor angular velocity Ve.

  In the first embodiment, as described in the second to sixth embodiments, the motor angular velocity Ve estimated by the motor angular velocity estimating unit or the motor angular acceleration Ae obtained by differentiating the motor angular velocity Ve is calculated. Is used to calculate the corrected torque value Te, but the motor angular speed Ve can be determined from the motor rotational speed N that is proportional to the motor angular speed. At that time, the motor rotational speed N is measured by a known motor rotational speed detection means such as a motor rotational speed detector using a Hall sensor, a motor rotational speed detector using a resolver, or a motor rotational speed detector using an angle sensor. What is necessary is just to detect. In addition, the motor angular velocity may be directly detected.

  Further, the motor angular acceleration Ae can be obtained by an operation for differentiating the motor angular velocity Ve obtained by the above method.

  Furthermore, in the first embodiment, each time the detected torque value T is sampled, the corrected torque value Te is calculated and overwritten and stored in the storage device 26, but the torque detection necessary for calculating the corrected torque value Te is detected. The value T and the motor angular velocity Ve or the motor angular acceleration Ae are overwritten and updated in the storage device 26 every time sampling is performed, and stored only when an abnormality in the torque detection value T is detected by the torque value abnormality detection unit 23. The corrected torque value Te may be calculated from the detected torque value T and the motor angular velocity Ve stored in the device 26 or the motor angular acceleration Ae.

[Second Embodiment]
A second embodiment of the present invention will be described. In the first embodiment, when an abnormality is detected in the torque detection value T by the torque value abnormality detection unit 23, the motor is used with the corrected torque value immediately before the torque detection value T is determined to be abnormal as an alternative torque value. In the second embodiment, in order to make the corrected torque value Te a more appropriate value, n (n before the torque detection value T is determined to be abnormal) (n The drive control of the motor 33 is performed using an alternative torque value calculated based on the corrected torque values Te1 to Ten of natural numbers.

  In the second embodiment, when there are a plurality of correction torque values Te (Te1 to Ten) stored in the storage device 26 and when the torque value abnormality detection unit 23 detects an abnormality in the torque detection value T, In the first embodiment, the corrected torque value Te is used as an alternative torque value as it is, but in the second embodiment, the alternative torque value is calculated from a plurality of corrected torque values Te (Te1 to Ten). Is different.

  Others are the same as in the first embodiment, and the block diagram for explaining the control function of the control device of the second embodiment is the same as that of the control device of the electric power steering device of the first embodiment shown in FIG. Since the block diagram for explaining the control function is the same as the block diagram for explaining the control function of the control device according to the second embodiment, the block diagram shown in FIG. A description of the characteristic part will be omitted.

  In normal times, when there is no abnormality in the torque detection value T, that is, when the abnormality signal G is not output from the torque value abnormality detection unit 23, the torque calculation unit 24 uses the torque detection value T input from the torque sensor 21. The steering torque value Ta is output to the current command value calculation unit 27 as it is, and the torque calculation unit 24 corrects it based on the detected torque value T input from the torque sensor 21 and the motor angular velocity Ve estimated and calculated by the motor angular velocity estimation unit 25. The torque value Te is calculated and stored in the storage device 26.

  Here, each time the corrected torque value Te is calculated, the storage device 26 sequentially stores the corrected torque values Te1, Te2, Te3,. When the corrected torque value Te is calculated more than n times and the corrected torque value Te (n + 1) is calculated, Te2 is overwritten and stored on Te1 and Te3 is stored on Te2. In the same way, Te (n + 1) is overwritten and stored on Ten. In this way, the latest n corrected torque values Te are stored by sequentially updating and storing the storage contents of the storage device 26.

  On the other hand, when an abnormality is detected in the torque detection value T, that is, when an abnormality signal G is output from the torque value abnormality detection unit 23, the torque calculation unit 24 replaces the torque detection value T determined as an abnormal value. The alternative torque value is obtained by calculation from the corrected torque value Te (Te1 to Ten) stored in the storage device 26, and the alternative torque value obtained by the calculation is output to the current command value calculation unit 27 as the steering torque value Ta. At this time, the correction torque value Te (n + 1) is not calculated, and the correction torque value Te (Te1 to Ten) stored in the storage device 26 is not updated.

  Next, an alternative torque value calculation method used for drive control of the motor 33 when the torque value abnormality detection unit 23 determines that the torque detection value T is abnormal will be described. There are a plurality of embodiments for calculating the alternative torque value. Hereinafter, description will be made sequentially.

[First embodiment of alternative torque value calculation]
In the first embodiment of the alternative torque value calculation, the alternative torque value is the most neutral torque among the n (n is a natural number) corrected torque values Te1 to Tenn immediately before it is determined that the torque detection value T is abnormal. A value close to (0 Nm) is obtained and set as an alternative torque value.

[Second Example of Alternative Torque Value Calculation]
In the second embodiment of the alternative torque value calculation, the alternative torque value is calculated by the following equation (2a) for calculating the arithmetic average of n corrected torque values Te (Te1 to Ten).

    Alternative torque value = {Te 1 + Te 2 + Te 3 to + Ten} / n (2a).

[Third embodiment of alternative torque value calculation]
In the third embodiment of the alternative torque value calculation, the alternative torque value is calculated by a weighted average method of n corrected torque values Te (Te1 to Ten). For example, when the number n of the corrected torque values Te is n = 5, the alternative torque value is calculated by the following equation (2b-1).

Alternative torque value = (aTe1 + bTe2 + cTe3 + dTe4 + eTe5)
/ (A + b + c + d + e) (2b-1)
Here, a, b, c, d, and e are weights, and the weights a, b, c, d, and e have the relationship of the following expression (2b-2). It is.

                a <b <c <d <e (2b-2).

[Fourth Embodiment of Alternative Torque Value Calculation]
In the fourth embodiment of the alternative torque value calculation, the alternative torque value is calculated from the n corrected torque values Te (Te1 to Ten) by the least square method.

  In this method, a linear expression is created from the corrected torque value Te (Te1 to Ten), and the corrected torque value Te (n + 1) is estimated to be used as an alternative torque value. Here, the corrected torque value Te (n + 1) is obtained by estimating from the latest n corrected torque values although the corrected torque value is not calculated because the detected torque value T is actually determined to be abnormal. If the detected torque value T is not determined to be abnormal, it is a corrected torque value that is estimated to have been calculated.

  The linear expression for estimating the corrected torque value Te (n + 1) is expressed by the following expression (2c-1), and the coefficients a and b are obtained from the simultaneous equations expressed by the following expression (2c-2). .

  For example, as shown in FIG. 4, when the corrected torque values at the past time points t1, t2, and t3 are three samples of Te1, Te2, and Te3, the current value Te4 of the corrected torque is expressed by the equation (2c− It becomes like 3).

  In actual calculation, the inverse matrix can be calculated in advance, and Expression (2c-3) is expressed as Expression (2c-4).

  Here, the corrected torque value Te4 obtained by the estimation is used as an alternative torque value.

[Fifth Example of Alternative Torque Value Calculation]
In the fifth embodiment of the alternative torque value calculation, the alternative torque value is calculated from the n corrected torque values Te (Te1 to Ten) by the following equation (n-1) to estimate the corrected torque Te (n + 1). The calculated torque is used as an alternative torque value.

  A method of calculating an alternative torque value by creating the following equation (n-1) from n corrected torque values Te will be described. For example, as shown in FIG. 5, when the past corrected torque values are Te1, Te2, Te3, a quadratic expression is created from the three corrected torque values Te1, Te2, Te3 to predict the current value Tep. For this purpose, the following equation (2d-1) is used.

  The coefficients a, b, and c are calculated from the following simultaneous equations (2d-2).

  Therefore, the current value Te3 of the correction torque is expressed by the following equation (2d-3).

  In actual calculation, the inverse matrix can be calculated in advance. The inverse matrix in the case of the three corrected torque values Te1, Te2, and Te3 is as shown in Expression (2d-4).

  In the second embodiment described above, the n corrected torque values Te (Te1 to Ten) are overwritten and stored in the storage device 26, but the torque detection value T necessary for the calculation of the corrected torque value Te and Each of the n motor angular velocities Ve is updated and stored in the storage device 26, and the corrected torque value Te (Te1 to Ten) is obtained only when the torque value abnormality detection unit 23 determines that the torque detection value T is abnormal. An alternative torque value may be obtained by calculation.

[Third Embodiment]
In the third embodiment, when a failure or the like of the torque sensor occurs, the drive control of the motor 33 is controlled using the alternative torque value by avoiding the drive control of the motor 33 by the torque detection value T that is an abnormal value, Further, the alternative torque value is controlled to gradually approach an appropriate steering assist torque value Td set in advance.

  FIG. 6 is a block diagram for explaining the control function of the control device 60 of the electric power steering apparatus according to the third embodiment of the present invention, excluding the gradual change processing unit 28 from the first and second embodiments. A torque adjusting unit 35 is newly arranged after the torque calculating unit 24. Since other circuit elements and members have the same functions and operations as those of the first and second embodiments, the same circuit elements and members are denoted by the same reference numerals, and the description thereof is omitted. The configuration and operation of the characteristic part of the embodiment will be described.

  The torque adjustment unit 35 is provided with a storage device therein, and the appropriate steering assist torque value Td described above is preset and stored in the storage device of the torque adjustment unit 35. Since the appropriate steering assist torque value Td to be stored is required to be able to supply an appropriate steering assist torque for the vehicle type, it is determined by examining vehicle-mounted data and the like at the time of implementation.

  When the abnormality detection signal G is not input from the torque value abnormality detection unit 23 to the torque adjustment unit 35, that is, when the abnormality of the torque detection value T is not detected, the torque adjustment unit 35 performs the steering input from the torque calculation unit 24. The torque value Ta is output to the current command value calculation unit 27 as it is.

  On the other hand, when the abnormality detection signal G is input from the torque value abnormality detection unit 23 to the torque adjustment unit 35, that is, when abnormality of the torque detection value T is detected, the torque adjustment unit 35 is input from the torque calculation unit 24. The steering torque value Ta is adjusted to gradually approach the appropriate stored steering assist torque value Td, and then output to the current command value calculation unit 27.

[Fourth Embodiment]
FIG. 7 is a block diagram for explaining the control function of the control device 70 of the electric power steering apparatus according to the fourth embodiment of the present invention, excluding the gradual change processing unit 28 from the first and second embodiments. A current command value adjustment unit 36 that is newly provided with a storage device is arranged after the current command value calculation unit 27. Since other circuit elements and members have the same functions and operations as those of the first and second embodiments, the same circuit elements and members are denoted by the same reference numerals, and the description thereof is omitted. The configuration and operation of the characteristic part of the embodiment will be described.

  In the above-described third embodiment, the torque assist unit 35 adjusts the steering assist torque value after occurrence of a torque sensor failure to an appropriate value. However, instead of this, even in the configuration in which the current command value adjustment unit 36 stores an appropriate preset current command value, the steering assist torque value after the failure of the torque sensor is similarly adjusted to an appropriate value. be able to. That is, when the abnormality detection signal G is not input from the torque value abnormality detection unit 23 to the current command value adjustment unit 36, that is, when the abnormality of the torque detection value T is not detected, the current command value adjustment unit 36 is input. The current command value Ir is output to the adder 29 as it is.

  On the other hand, when the abnormality detection signal G is input from the torque value abnormality detection unit 23 to the current command value adjustment unit 36, that is, when an abnormality of the torque detection value T is detected, the current command value adjustment unit 36 determines the current command value. The current command value Ir corresponding to the steering torque value Ta input from the computing unit 27 is adjusted to gradually approach the appropriate stored current command value, and then output to the adder 29.

  In the embodiment of the present invention described above, the corrected torque value is calculated based on the detected torque value input from the torque sensor and the motor angular velocity, or the corrected torque value is calculated using the motor angular acceleration instead of the motor angular velocity. Arithmetic. When using motor angular acceleration, detect abnormal torque in the direction opposite to the steering direction temporarily generated by the inertia force of the motor when the driver suddenly operates the steering wheel in the opposite direction. You can also.

  This is an electric power steering device with high safety, and when an abnormality occurs in the detected torque value output from the torque sensor, the motor control is immediately executed using the alternative torque value instead of the abnormal torque detection value. An electric power steering device that generates an appropriate steering torque and can operate a steering handle without causing a sense of incongruity to the operation of the steering wheel is provided.

The block diagram explaining the control function of the control apparatus of the electric power steering apparatus of 1st and 2nd embodiment. The figure explaining the setting of the parameter used for calculation of correction torque. The figure explaining the relationship between the motor angular velocity and correction torque value in calculation of correction torque. The figure explaining the estimation of the present correction torque value from the past correction torque value (the 1). The figure explaining the estimation of the present correction torque value from the past correction torque value (the 2). The block diagram explaining the control function of the control apparatus of the electric power steering apparatus of 3rd Embodiment. The block diagram explaining the control function of the control apparatus of the electric power steering apparatus of 4th Embodiment. The figure explaining an example of a structure of an electric power steering apparatus. The block diagram explaining the control function of the conventional electric power steering apparatus (the 1). The block diagram explaining the control function of the conventional electric power steering apparatus (the 2).

Explanation of symbols

10, 60, 70 Control device 21 Torque sensor 23 Torque value abnormality detection unit 24 Torque calculation unit 25 Motor angular velocity estimation unit 26 Storage device 27 Current command value calculation unit 28 Gradual change processing unit 29 Adder 31 Current control unit 32 Motor drive unit 33 Motor 34 Motor current detector 35 Torque adjustment unit 36 Current command value adjustment unit

Claims (9)

A motor for applying a steering assist force to the vehicle steering system;
A torque sensor for detecting a steering torque acting on the steering handle;
A control device for controlling a motor output based on a torque detection value of the torque sensor sampled at a predetermined timing;
Torque value abnormality detection means for detecting abnormality of the torque detection value;
An electric power steering apparatus comprising motor angular velocity output means or motor angular acceleration output means ,
The control device includes storage means for storing an alternative torque value, calculates the alternative torque value based on a torque detection value and a parameter corresponding to the motor angular velocity or motor angular acceleration, and constantly updates and stores the alternative torque value. The motor output is controlled based on the alternative torque value instead of the torque detection value after the torque value abnormality detecting means detects the abnormality of the torque detection value. Electric power steering device. A motor for applying a steering assist force to the vehicle steering system;
A torque sensor for detecting a steering torque acting on the steering handle;
A control device for controlling a motor output based on a torque detection value of the torque sensor sampled at a predetermined timing;
Torque value abnormality detection means for detecting abnormality of the torque detection value;
Motor angular velocity output means or motor angular acceleration output means;
In the electric power steering apparatus with
The control device includes storage means for storing a value necessary for calculating the alternative torque value, constantly updating the value required for calculating the alternative torque value and storing the value in the storage means, thereby detecting the torque value abnormality detection means. After the abnormality of the torque detection value is detected by the above, the alternative torque value is calculated based on the value necessary for the calculation of the alternative torque value and the parameter corresponding to the motor angular velocity or the motor angular acceleration, and the torque detection value is replaced. An electric power steering apparatus, wherein a motor output is controlled based on the alternative torque value . The control device includes a gradual change processing means for gradually decreasing the output of the motor, and after detecting an abnormality in the torque detection value by the torque value abnormality detection means, operates the gradual change processing means to output the motor output. The electric power steering apparatus according to any one of claims 1 to 2, wherein a control for gradually decreasing the power is performed. The electric power steering apparatus according to any one of claims 1 to 3, wherein a corrected torque value obtained by multiplying the parameter by a past torque detection value immediately before abnormality detection is corrected as an alternative torque value. . The electric power steering apparatus according to any one of claims 1 to 4, wherein the parameter decreases in inverse proportion to an increase in the motor angular velocity or motor angular acceleration . The parameter is a constant value when the motor angular velocity or motor angular acceleration is less than or equal to a predetermined value, and decreases when the motor angular velocity or motor angular acceleration exceeds a predetermined value with respect to an increase in the motor angular velocity or motor angular acceleration. the electric power steering apparatus according to any one of claims 1 to 5, characterized in <br/> that. The electric power steering apparatus according to any one of claims 1 to 3 , wherein a corrected torque value obtained by subtracting the parameter from a past torque detection value immediately before abnormality detection is used as an alternative torque value. . The electric power steering apparatus according to any one of claims 1 to 3, wherein the parameter increases in proportion to an increase in the motor angular velocity or the motor angular acceleration . The parameter is a constant value when the motor angular velocity or motor angular acceleration is less than or equal to a predetermined value, and increases with an increase in the motor angular velocity or motor angular acceleration when the motor angular velocity or motor angular acceleration exceeds a predetermined value. claims 1 to 3, characterized in <br/> that, and, the electric power steering device according to any one of 7 to 8.

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