JP4449488B2 - Control device for electric power steering device - Google Patents

Description

  The present invention relates to a control device for an electric power steering device, and more particularly to a control device for an electric power steering device capable of continuing control even when a torque sensor for detecting a steering force acting on a handle becomes abnormal.

  An electric power steering device that applies a steering assist force to a steering device of an automobile by the rotational force of a motor is a steering assist force applied to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer. Is supposed to be granted. A simple configuration of such an electric power steering apparatus will be described with reference to FIG. A 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 shaft 102 is provided with a torque sensor 107 that detects the steering torque of the steering handle 101, and a motor 108 that assists the steering force of the steering handle 101 is connected to the shaft 102 via the reduction gear 103. . The motor control of the electric power steering device is controlled by the control unit 109 using the torque value detected by the torque sensor 107, the vehicle speed detected by a vehicle speed sensor (not shown), the rotation angle of the motor detected by the hall sensor 110, etc. as input values. Is done. The control unit 109 is mainly a CPU, and motor control is executed by a program inside.

  FIG. 9 shows an example of a control block diagram of a motor for controlling the motor 108 of the electric power steering apparatus having such a configuration. In FIG. 9, the torque value detected by the torque sensor 107 is input, the current command value calculation unit 120 calculates the current command value Iref, the difference from the detected motor current value is calculated by the subtraction unit 121, and current control is performed. The duty ratio is determined by the unit 122, and the motor driving unit 123 drives the motor 108 by executing PWM control according to the duty ratio.

  In such an electric power steering apparatus, control of the electric power steering apparatus is executed on the assumption that the torque value detected by the torque sensor 107 is correctly detected. However, in actuality, when the torque sensor 107 also fails and an abnormal torque detection value is input, there is a risk of causing an abnormal operation with respect to the handle operation. Has been applied.

  For example, in Patent Document 1, a control method as shown in FIG. 10 is adopted to deal with an abnormality in the torque value output from the torque sensor. When the torque value output from the torque sensor becomes abnormal, if the abnormality continues for a certain time (tA), the auxiliary steering force command value that is the output value of the current control calculation based on the torque value is cut off. This is a control method in which the motor drive power supply is shut off when the abnormality continues for a longer period of time (tB). FIG. 11 shows the relationship between the torque value and the motor current when such a control method causes a ground fault in the torque sensor and the torque value, which is the output of the torque sensor, becomes zero. In the case of this control method, since the calculation is performed based on the output value of the abnormal torque sensor during the determination time tA, the torque generated by the motor also becomes abnormal, and the steering wheel moves unintended by the driver. Furthermore, if the abnormality continues for the determination time (tB) or longer, the motor power supply is shut off. Therefore, if a large torque is applied to the handle, the torque changes suddenly, which is not preferable.

  As another countermeasure, there is a control method as in Patent Document 2. In Patent Document 2, when a serious abnormality such as a voltage drop or a momentary interruption of the torque sensor power supply occurs, the fail switch is opened, and the torque value that is the torque sensor output before the fail switch is opened is held. The auxiliary steering force command value is obtained by multiplying the held value by the output gain. Further, since the subsequent auxiliary steering force is controlled to gradually attenuate, the auxiliary steering force does not change suddenly. FIG. 12 shows the relationship between the torque value, which is the output of the torque sensor at the time of a torque sensor ground fault, and the motor current when the control method of Patent Document 2 is used. The maximum negative current flows through the motor from the occurrence of the failure to the detection of the failure. However, since the motor current is gradually decreased from the torque immediately before the occurrence of the failure after the failure is detected, a sudden torque change as in Patent Document 1 occurs. do not do.

  However, when a ground fault occurs while the torque value as shown in FIG. 13 causes chattering, a value such as a black circle may be sampled when the output value of the torque sensor is sampled by the AD converter. If these values do not fall below the ground fault detection threshold, it cannot be detected that a ground fault has occurred, and the control is continued as it is. After the ground fault is detected, the motor current is gradually decreased from the torque value immediately before the occurrence of the failure, but chattering is caused to gradually decrease the motor current from the unstable torque value. Since the decrease starts from the reverse torque, it is not preferable.

JP 2000-318633 A JP 2000-329628 A

  When the torque value, which is the output of the torque sensor, becomes abnormal, in the conventional control method, the output torque of the motor becomes abnormal because control is performed based on the abnormal torque value until the torque sensor detects failure. . Further, even when a substitute value is used instead of an abnormal torque value, there is a problem that an appropriate substitute value is not calculated. As a result, when the output of the torque sensor becomes abnormal, the steering wheel moves unintended by the driver, and there is a problem that the driver feels uncomfortable with the steering wheel operation. In addition, during the period when the torque value is abnormal, an abnormal current flows through the motor. Therefore, when the abnormal state continues for a predetermined time, the predetermined time (failure detection time) for determining a failure cannot be made long. There has been a problem that causes false detection with respect to failure confirmation detection. In particular, the chattering phenomenon that occurs when the wiring that transmits the torque value detected by the torque sensor is likely to break, and if the torque value alternates between the maximum and minimum values at high speed, the correctness of the electric power steering device There was a problem that torque control became difficult.

  The present invention has been made in the circumstances as described above, and the object of the present invention is to use an alternative value instead of the output value of the torque sensor even when the output value of the torque sensor becomes abnormal. It is a control device for an electric power steering device that ensures a safe handle operation without giving a sense of incongruity to the handle operation while ensuring a failure detection period long enough to prevent erroneous detection of a failure confirmation detection such as a torque sensor. In particular, it is an object of the present invention to provide a control device for an electric power steering apparatus that can accurately estimate an alternative value used for control during an abnormal period.

The present invention includes a motor that applies a steering assist force to a steering system of a vehicle, and a torque sensor that detects a steering force acting on a steering wheel, and controls the motor based on a torque detection value of the torque sensor. The present invention relates to a control device for an electric power steering device, and the object of the present invention is to provide a main torque detection means for detecting a main torque detection value Tm based on the output of the torque sensor, and a sub-control based on the output of the torque sensor. Sub-torque detection means for detecting a torque detection value Ts, torque abnormality detection means for detecting an abnormality of the main torque detection value Tm or the sub-torque detection value Ts, and the main torque detection value Tm or the sub-torque detection value Ts The past normal main torque detection value Tm and the main torque detection value Tm or the sub torque detection value Ts before the abnormality becomes abnormal. A substitute value calculating means for calculating the substitute value Ta based on the click detection value Ts, the determination that the main torque detection value Tm and the status sub torque detection value Ts is abnormal is faulty when continued for a predetermined time A torque failure determination means for determining, and when the main torque detection value Tm or the sub-torque detection value Ts is detected to be abnormal, before the determination that the torque failure determination means is a failure is also made. This is achieved by controlling the motor based on the alternative value Ta instead of the main torque detection value Tm, and controlling the motor by a gradual reduction process when a failure is determined by the torque failure determination means .

Further, the object is to take a difference between the main torque detection value Tm and the sub-torque detection value Ts at the past simultaneous point before the main torque detection value Tm or the sub-torque detection value Ts becomes abnormal, and the difference amount A combination (Tm, Ts) of the main torque detection value Tm and the sub-torque detection value Ts at the same time in the past that minimizes is selected, and any one of the combinations (Tm, Ts) is set as the substitute value Ta. Can be achieved more effectively.

Moreover, the said objective is achieved more effectively by selecting the newest combination (Tm, Ts), when there exist two or more said combinations (Tm, Ts) .

Further, the object is more effectively achieved by setting the detected torque value closer to the torque neutral value at which the steering wheel indicates the neutral point in the combination (Tm, Ts) as the substitute value Ta. .

Further, the object is that the torque abnormality detection means detects the abnormality of the torque sensor based on the main torque detection value Tm, the sub torque detection value Ts, or the main torque detection Tm and the sub torque detection value Ts. Can be achieved more effectively by detecting .

  According to the present invention, when the torque sensor for detecting the torque value indicated by the steering handle or the torque detecting means becomes abnormal, the torque used in place of the abnormal torque detected value detected by the torque sensor and the torque detecting means. Since the substitute value Ta, which is an estimated value of the detected value, is calculated based on the normal past main torque detected value Tm and the sub torque detected value Ts before the torque sensor or the torque detecting means becomes abnormal, it is estimated. Until the torque sensor and torque detecting means become abnormal and it is determined that there is a malfunction, the correct torque output can be ensured, and the steering operation without giving a sense of incongruity can be ensured. In particular, in the case of a chattering phenomenon that occurs when the wiring that transmits the torque value detected by the torque sensor is likely to break, both the main torque value Tm and the sub torque value Ts are less likely to cause chattering simultaneously. Thus, there is an effect that a torque output by an alternative value including information on the correct torque value of either the main torque value Tm or the sub torque value Ts can be secured.

  Also, when the torque sensor or torque detection means becomes abnormal, the electric power steering device is controlled using an alternative value that is predicted correctly based on the past detected torque value instead of the abnormal torque value immediately. Because the torque failure determination means can control the substitute value for a long period of time that can correctly determine that the torque sensor is faulty, even when the torque sensor is abnormal, handle operation that does not give a sense of incongruity and safe handle operation can be ensured A control device for an electric power steering device can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a control block diagram showing an embodiment of the present invention. The sensor signal Tr detected by the torque sensor 107 is input to a main torque detection unit 107A that is a main torque detection unit and a sub torque detection unit 107B that is a sub torque detection unit. The main torque detection unit 107A and the sub torque detection unit 107B are for detecting the torque value of the steering handle 101 from the sensor signal Tr output from the torque sensor 107. From an electronic circuit such as an operational amplifier or software processing, etc. Composed. The main torque detection unit 107A outputs a main torque detection value Tm, and the sub torque detection unit 107B outputs a sub torque detection value Ts. The main torque detection unit 107A and the sub torque detection unit 107B constitute a double system related to torque detection. In this embodiment, one torque sensor 107 is commonly used. However, two torque sensors for main torque detection value and sub torque detection are prepared, and a dual system configuration is made from the torque sensor stage. Also good.

  The main torque detection value Tm output from the main torque detection unit 107A and the sub torque detection value Ts output from the sub torque detection unit 107B are input to the torque input processing unit 10. Since the details of the torque input processing unit 10 will be described later in detail, the part related to motor control after the torque input processing unit 10 will be described first. The torque value T that is the output of the torque input processing unit 10 is input to the current command value calculation unit 120, and the current command value calculation unit 120 calculates the current command value Iref. Next, the current command value Iref is input to the subtraction unit 121 via the limiter 11 controlled by the torque input processing unit 10. In the subtraction unit 121, a deviation between the current command value Iref and the detected value Im of the motor current is calculated. The deviation is input to a current control unit 122 configured by proportional integration and the like, and the current control unit 121 outputs a duty ratio of PWM control of an inverter which is an example of the motor driving unit 123. The motor driving unit 123 supplies a motor current by PWM control according to the duty ratio to the motor 108, and the motor 108 outputs a torque corresponding to the torque value instructed by the steering handle 101.

  The above is the description of the basic part of the motor control of the electric power steering apparatus of the present embodiment. Hereinafter, the torque input processing unit 10 which is a main part of the present invention will be described in detail.

  The main torque detection value Tm from the main torque detection unit 107A and the sub torque detection value Ts from the sub torque detection unit 107B are input to the torque input processing unit 10. The torque input processing unit 10 includes a torque abnormality detection unit 10-1 and an alternative value calculation unit 10-2 that receive the main torque detection value Tm and the sub torque detection value Ts as inputs. The torque abnormality detection means 10-1 has a function of detecting an abnormality in the torque sensor 107, the main torque detection unit 107A, or the sub torque detection unit 107B. The substitute value calculation means 10-2 uses the main torque detection value Tm and the sub torque detection value Ts to detect the main torque detection value Tm when the torque sensor 107, the main torque detection unit 107A or the sub torque detection unit 107B is abnormal. An alternative value Ta of torque to be used instead of is calculated.

  The torque input processing unit 10 further includes torque failure determination means 10-3 and a selection switch 10-4. The selection switch 10-4 selects either the alternative value Ta, which is the output of the alternative value calculation means 10-2, or the main torque detection value Tm, which is the output of the main torque detection unit 107A, from the torque abnormality detection means 10-1. Select based on output. Further, the torque failure determination means 10-3 uses the output that the abnormality of the torque abnormality detection means 10-1 is abnormal, and if the abnormal condition is maintained for a long time, specifically, the predetermined time T1, the torque is determined. The sensor 107, the main torque detection unit 107A, or the sub torque detection unit 107B has a function of determining a failure, and when the failure is determined, the limit value of the limiter 11 is controlled.

  The operation of the torque input processing unit 10 will be described in more detail with reference to the flowchart of FIG. An abnormality of the main torque detection value Tm, for example, a normal value output by the main torque detection value Tm is 0.5 V or more and 4.5 V or less, and therefore it is abnormal to output 0 V or 5 V. If the abnormal state continues for a set time, for example, 30 ms, the failure is determined. The flowchart of FIG. 2 is an embodiment showing substitution value control, torque abnormality detection, and torque failure determination in the case of the above-described torque abnormality and torque failure determination.

  First, the main torque detection value Tm and the sub torque detection value Ts are read from the main torque detection unit 107A and the sub torque detection unit 107B, respectively (S1). It is determined whether the main torque detection value Tm is 0.5V or less, or 4.5V or more. If the value is between 0.5V and 4.5V, it is determined as normal (YES) and 0.5V or less. Or, if it is 4.5 V or more, it is determined as abnormal (NO) (S2). If the main torque detection value Tm is normal, the detection counter is cleared (S3). This counter measures the duration of the abnormality used to determine that the torque sensor 107 that outputs the main torque detection value Tm or the main torque detection unit 107A is out of order. In this embodiment, When the abnormality of the main torque detection value Tm continues for 30 ms, the failure is determined.

  Next, if the main torque detection value Tm is normal, the past main torque value Tm and the past sub torque detection value Ts are updated and stored (S4). A flowchart of details of the past torque value update is shown in FIG. 3 and will be described in detail later. Next, the main torque detection value Tm is used as the torque value T used for motor control (S5). In other words, it means that the selection switch 10-4 has selected the main torque detection value Tm.

  On the other hand, when it is determined that the main torque detection value Tm is abnormal (S2), the detection counter starts counting (S6). The counter determines whether or not the torque sensor 107 for calculating the main torque detection value Tm and the main torque detection unit 107A are equal to or greater than a predetermined value (30 ms) indicating the time for determining that the failure has occurred (S7).

  First, while the abnormality duration is 30 ms or less (NO), alternative value control is executed without determining that the torque sensor or the like is out of order (S7). In the alternative value control, the motor 108 is controlled using the alternative value Ta instead of the abnormal main torque detection value Tm detected by the torque sensor, and it is necessary to calculate the alternative value Ta so that the motor control does not become abnormal. (S8). A method of calculating the substitute value Ta will be described later in detail using the flowchart of FIG. When the alternative value Ta is set, the alternative value Ta is input to the torque value T as the output of the input processing unit 10 (S9), and the alternative value Ta is output as the torque value T (S5). If the abnormality continues for 30 ms or longer (YES), it is determined that there is a failure, and a reduction process for narrowing down the torque value using the limiter 11 is performed (S10).

  Next, update of the past main torque detection value Tm and the sub torque detection value Ts, which is Step 4 (S4) described above, will be described with reference to FIG. The embodiment of FIG. 3 is an embodiment in the case of calculating an alternative value using five past torque values. First, the past main torque value Tm2 and sub torque detection value Ts2 new by one step are respectively substituted into the main torque detection value Tm1 and the sub torque detection value Ts1 (S14). Similarly, the past main torque value Tm3 and auxiliary torque detection value Ts3 new by one step are respectively substituted into the main torque detection value Tm2 and the sub torque detection value Ts2 (S15). The past main torque value Tm4 and sub torque detection value Ts4 new by one step are respectively substituted into the main torque detection value Tm3 and the sub torque detection value Ts3 (S16). The past main torque value Tm5 and sub torque detection value Ts5 new by one step are respectively substituted into the main torque detection value Tm4 and the sub torque detection value Ts4 (S17). The current main torque value Tm and sub torque detection value Ts new by one step are respectively substituted into the main torque detection value Tm5 and sub torque detection value Ts5 (S18).

  When the current main torque value Tm and the sub torque detection value Ts are also used to calculate a substitute value when the torque detection value becomes abnormal in the next step, the past torque one step before It is a detected value. If the performance of the CPU, memory, etc. is good, high-speed processing is possible, and the memory capacity is sufficient, an alternative value may be calculated using a large number of past torque values of five or more. Conversely, an alternative value may be calculated using five or less past torque values. What is necessary is just to determine the number of past torque values to be used in relation to the accuracy of the substitute value, the performance of the CPU, and the memory capacity.

  Next, the contents of the substitute value setting step (S8) for calculating the substitute value, which is the main part of the present invention, will be described in detail with reference to the flowcharts of FIGS. 4 (A) and 4 (B).

  First, in FIG. 4A, a difference amount ΔTi = | Tmi−Tsi | in the combination of the main torque detection value Tmi and the sub torque detection value Tsi of the past torque is calculated. For example, ΔT1 = | Tm1−Ts1 | and ΔT2 = | Tm2−Ts2 |. (S21). Next, a combination (Tmk, Tsk) that minimizes the difference amount ΔTi is selected (S22). If there are a plurality of combinations (Tmk, Tsk) that minimize the difference amount ΔTi, the latest combination is selected (S23). Next, if the difference amount ΔTi is equal to or smaller than the predetermined value ΔTlimit using the combination (Tmk, Tsk) that minimizes the difference amount ΔTi and using the latest combination (Tmk, Tsk), the main value is the substitute value Ta. The torque detection value Tmk or the sub torque detection value Tsk is selected (S24). The reason why the main torque detection value Tmk or the sub torque detection value Tsk of the combination (Tmk, Tsk) is selected as the alternative value Ta is that if the difference amount ΔTi is not more than the predetermined value ΔTlimit, the main torque detection value Tmk This means that both the torque detection values are correct and both torque detection values are used as substitute values.

  An example in which the selection method of the alternative value Ta is different will be described with reference to FIG. In FIG. 4B, the difference amount ΔTi = | Tmi−Tsi | in the combination of the main torque detection value Tmi and the sub torque detection value Tsi of the past torque is calculated. For example, ΔT1 = | Tm1−Ts1 | and ΔT2 = | Tm2−Ts2 |. (S21). Next, a combination (Tmk, Tsk) that minimizes the difference amount ΔTi is selected (S22). If there are a plurality of combinations (Tmk, Tsk) that minimize the difference amount ΔTi, the latest combination is selected (S23). Next, whether the main torque detection value Tmk in the latest combination (Tmk, Tsk) with the smallest difference amount ΔTi is used as the alternative value Ta or whether the sub torque detection value Tsk is selected is determined by the operation handle 101. The torque detection value closer to the torque value Tn indicating the intermediate value is selected (S25). In the case of FIG. 4B as well, it may not be as small as the predetermined value as in FIG. 4A, but it is safer to add a condition that the difference amount ΔTi is equal to or smaller than the predetermined value.

  The reason for executing such substitution value calculation is that if the torque detection value is normal, the main torque detection value Tm and the sub-torque detection value Ts should originally show the same value, so that the difference amount is small. Preferred as value. If the difference amount is the same, it is obvious that it is preferable to select the latest torque detection value closer to the present time as the substitute value used for the current control. Further, whether the main torque detection value Tm or the sub-torque detection value Ts is selected from the selected torque detection values is determined as an abnormal torque detection value. In many cases, such as hunting, 0V and 5V are alternately output at high speed. Considering the fact of such a failure phenomenon, a value closer to 2.5V, which is an intermediate value between 0V and 5V, is preferable as an alternative value. The reason why the value closer to the intermediate value is selected is that the value closer to the intermediate value is often safer because the motor current value is smaller.

  Note that the method of calculating the substitute value Ta by using both torque detection values of the combination (Tmk, Tsk) is not limited to the method of FIG. 4A or 4B described above.

  By executing the substitute value control using the past main torque detection value and the past sub torque detection value described above, the substitute calculated from the past torque detection value compared to the case where there is only one torque detection value. This is because the accuracy of the value is further improved. In the case of an abnormality that causes chattering, both the main torque detection value Tm and the sub-torque detection value Ts rarely cause chattering, and either of them is a correct torque detection value. Using the two torque detection values of the main torque detection value Tm and the sub torque detection value Ts is effective in calculating a correct substitute value.

  FIG. 5 is a diagram showing the relationship between the torque value that is the output of the torque sensor and the motor current when the output value of the torque sensor suddenly becomes zero, using the torque input processing unit 10 of the present embodiment. . Even if the torque value suddenly becomes zero, the substitute value is immediately used instead of the abnormal torque value, so that the motor current maintains the value immediately before the torque value becomes abnormal. The motor current maintains the previous value until it is determined that the torque sensor has failed, and the motor current gradually attenuates after it is determined that the torque sensor has failed. Compared with FIG. 11 and FIG. 12 of the result by the conventional control method, the motor current does not reverse the polarity immediately before the torque value becomes abnormal, and the steering wheel operation does not feel uncomfortable.

  FIG. 6 shows the torque value (worst case) that is the output of the torque sensor when the output value of the torque sensor malfunctions due to chattering using the torque input processing unit 10 of this embodiment, and the motor current. The figure showing the relationship is shown. If the torque value causes chattering and it is determined that the torque value is abnormal, a substitute value is calculated using a past normal torque value, and the motor current is controlled based on the substitute value. Therefore, the motor current is output that is not significantly different from the motor current immediately before the chattering is generated. Furthermore, the motor current is gradually attenuated after the failure is detected. This result is compared with FIG. 13 of the result of control by the conventional control method. In the case of the conventional control method, a motor current having a polarity opposite to that before the motor current becomes an abnormality in the torque sensor output is generated, and then the result is unfavorable for the driver. Although it is preferable to gradually attenuate the motor current after the failure is detected, it is not preferable because the motor current immediately before the attenuation is attenuated from the current having the opposite polarity. Obviously, the control method of this embodiment is more preferable for steering the steering wheel even in the worst case.

  As described above, according to the present invention, until the torque sensor and the torque detection unit are determined to be in failure, the motor uses the substitute value calculated with high accuracy instead of the abnormal torque detection value. Even if the torque sensor or the torque detector becomes abnormal, even if the predetermined time until the torque sensor or the torque detector is determined to be faulty is taken long enough not to be erroneously detected, It is possible to provide a control device for an electric power steering device capable of operating the steering wheel without a sense of incongruity.

  In the first embodiment, the main torque detection value Tm is outside the normal range (0.5 V or more and 4.5 V or less) as an example of determining that the torque sensor or the torque detection unit is abnormal or malfunctioning. Although a case is assumed, there are a plurality of abnormality detection and failure determination methods in which the torque sensor and the torque detection unit are abnormal or faulty. Such an embodiment will be described with reference to FIG.

  The difference from the first embodiment is that the torque abnormality detecting means 10-1 has a plurality of torque failure abnormality detecting means 10-1A, 10-1B, 10-1C having different detection principles, and therefore the selection switch 10- The switching judgment of 4 is as follows. If any one of the torque abnormality detection means 10-1A, 10-1B, 10-1C is abnormal (the output of each torque abnormality detection means in the case of abnormality is "1"), the torque abnormality detection means Based on the output of the OR unit 10-5 that receives the outputs of 10-1A, 10-1B, and 10-1C, the alternative value Ta that is the output of the alternative value selection unit 10-2 is selected. On the other hand, when all of the torque abnormality detection means 10-1A, 10-1B, 10-1C are not abnormal, that is, all are normal (the output of each torque abnormality detection means when normal is set to “0”). , Based on the AND section 10-7 that receives the outputs of the NOT sections 10-6A, 10-6B, and 10-6C that receive the outputs of the torque abnormality detection means 10-1A, 10-1B, and 10-1C, respectively. The selection switch 10-4 selects the main torque detection value Tm that is the output of the main torque detection unit 107A.

  Here, an example of the detection principle of the torque abnormality detection means 10-1A, 10-1B, 10-1C will be described. The torque abnormality detection unit 10-1A is the same as the torque abnormality detection unit used in the first embodiment, and is a torque abnormality detection unit that determines that an abnormality occurs when the main torque detection value Tm is not in the normal range. The torque abnormality detection unit 10-1B is a torque abnormality detection unit that determines that the sub torque detection value Ts is not in the normal range (0.5 V or more and 4.5 V or less) as abnormal. In the torque abnormality detection means 10-1C, the main torque detection value Ts and the sub-torque detection value Ts should originally take the same value, so that the difference between the main torque detection value Ts and the sub-torque detection value Ts is not in the normal range. It is a torque abnormality detection means for determining an abnormality.

  Next, the difference between the torque failure determination means 10-3 and the first embodiment is that the torque abnormality detection means 10-1 has a plurality of torque abnormality detection means, and a plurality of delay units (hereinafter, referred to as the torque abnormality detection means 10-1). 10-3, 10-3B, and 10-3C). That is, the TD unit 10-3A determines that the torque sensor 107 and the main torque detection unit 107A are out of order if the output of the torque abnormality detection unit 10-1 is abnormal for a predetermined time T1 (for example, 30 ms). To do. Similarly, if the state where the output of the torque abnormality detecting means 10-2 is abnormal continues for a predetermined time T1 (30 ms as an example), the TD unit 10-3B indicates that the torque sensor 107 and the sub torque detecting unit 107B are out of order. It will be confirmed. If the output of the torque abnormality detection means 10-3 is abnormal for a predetermined time T1 (for example, 30 ms), the TD unit 10-3C has failed in the torque sensor 107, the main torque detection unit 107A, or the sub torque detection unit 107B. It is decided that it is.

  Based on the output of the OR unit 10-3D that receives the output of the torque failure determination means 10-1A, 10-1B, 10-1C (“1” for failure), the torque sensor and torque detection unit When it is determined that there is a failure, the limiter 11 is controlled, and a temporary reduction process for narrowing down the current command value Iref is performed.

  The second embodiment differs from the first embodiment in that it has a plurality of torque abnormality detection means, and therefore the reason for switching the selection switch 10-4 is abnormal even in one of the plurality of torque abnormality detection means. Upon detection, the selection switch 10-4 selects an alternative value Ta instead of the main torque detection value Tm. On the other hand, when a detection result indicating that the plurality of torque abnormality detection means are all normal is obtained, the selection switch 10-4 selects the main torque detection value Tm.

  On the other hand, the calculation principle of the alternative value calculation means 10-2 of the second embodiment is the same as that of the first embodiment, and specifically, is calculated based on the alternative value calculation step shown in the flowchart of FIG.

  In the case of a double system that detects the main torque detection value Tm and the sub torque detection value Ts, it is natural that a plurality of abnormality detection means and failure determination means exist corresponding to the double system as in the second embodiment. is there. As described above, even if there are a plurality of abnormality detection means and failure determination means, if the torque sensor or the torque detection unit is abnormal, an alternative value using the past main torque detection value Tm and the sub torque detection value Ts is used. Thus, it is possible to provide a control device for an electric power steering device that does not give a sense of incongruity to the steering wheel operation until the torque sensor or the torque detector becomes abnormal and the failure is determined.

  As described above, when the present invention is used, the alternative value using the past main torque detection value Tm and the sub torque detection value Ts can detect the correct torque even if an abnormality occurs in the torque detection. Since the substitute value is calculated using the correct past torque detection value that is correct, the torque sensor and the torque detection are compared with the substitute value that can only use the main torque detection value Tm. It is possible to provide a control device for an electric power steering apparatus capable of operating the steering wheel without causing a sense of incongruity until the part becomes abnormal and the failure is determined. In particular, in the case of chattering abnormality that occurs when wiring relating to torque detection is disconnected, both main torque detection value Tm and sub torque detection value Ts are particularly effective because there is little possibility of chattering.

It is a control block diagram of the electric power steering device according to the present invention. It is a flowchart which shows operation | movement of a torque input process part. It is a flowchart of the update operation | movement of the past main torque detection value Tm and the past subtorque detection value Ts. It is a flowchart which calculates an alternative value from the past main torque detection value Tm and the past subtorque detection value Ts. It is a figure which shows the output result of the motor current at the time of the torque sensor ground fault at the time of using this invention. It is a figure which shows the output result of the motor current at the time of the failure where the torque sensor at the time of using this invention caused the chattering phenomenon. It is an Example of the torque input process part in the case of having a some torque abnormality detection means. It is a figure which shows the structure of an electric power steering apparatus. It is a control block diagram of the conventional electric power steering device. It is a control block diagram of the conventional electric power steering device corresponding to a torque sensor ground fault It is a figure which shows the output result of the motor current by the conventional control at the time of a torque sensor ground fault failure. It is a figure which shows the output result of the motor current by the conventional improved control at the time of a torque sensor ground fault failure. It is a figure which shows the output result of the motor current by the conventional control at the time of a torque sensor chattering failure.

Explanation of symbols

107 Torque Sensor 107A Main Torque Detection Unit 107B Sub Torque Detection Unit 10 Torque Input Processing Unit 10-1 Torque Abnormality Detection Unit 10-1A, 10-1B, 10-1C Torque Abnormality Detection Unit 10-2 Alternative Value Calculation Unit 10-3 Torque failure determination means 10-4 selection switch 10-3, 10-5 OR section 10-6A, 10-6B, 10-6C NOT section 10-7 AND section 10-3A, 10-3B, 10-3C delay section ( TD)
DESCRIPTION OF SYMBOLS 11 Limiter 108 Motor 120 Current command value calculation part 121 Subtraction part 122 Current control part 123 Motor drive part

Claims (5)

An electric power steering apparatus comprising: a motor that applies a steering assist force to a steering system of a vehicle; and a torque sensor that detects a steering force acting on a steering wheel, and controls the motor based on a torque detection value of the torque sensor. In the control device of
Main torque detection means for detecting a main torque detection value Tm based on the output of the torque sensor, sub torque detection means for detecting a sub torque detection value Ts based on the output of the torque sensor, and the main torque detection value Tm Or torque abnormality detection means for detecting an abnormality in the auxiliary torque detection value Ts, and the main torque detection value Tm or the previous normal main torque detection value Tm and the main torque before the auxiliary torque detection value Ts becomes abnormal. An alternative value calculation means for calculating an alternative value Ta based on a past normal auxiliary torque detection value Ts before the detection value Tm or the auxiliary torque detection value Ts becomes abnormal, and the main torque detection value Tm or the auxiliary torque detection Torque failure determination means for determining determination of failure when a state in which the value Ts is abnormal continues for a predetermined time ;
When it is detected that the main torque detection value Tm or the sub torque detection value Ts is abnormal, the main torque detection value Tm is used instead of the main torque detection value Tm even before the determination that the torque failure determination means is in failure. A control device for an electric power steering apparatus, wherein the motor is controlled based on the substitute value Ta, and the motor is controlled by a gradual reduction process when a failure is determined by the torque failure determination means . The difference between the main torque detection value Tm and the sub torque detection value Ts at the same time in the past before the main torque detection value Tm or the sub torque detection value Ts becomes abnormal is taken, and the difference amount is minimized. The combination (Tm, Ts) of the main torque detection value Tm and the sub torque detection value Ts at the same time is selected, and one of the combinations (Tm, Ts) is set as the substitute value Ta . Control device for electric power steering device. The control device for an electric power steering apparatus according to claim 2 , wherein when there are a plurality of combinations (Tm, Ts), the latest combination (Tm, Ts) is selected . 4. The control device for an electric power steering apparatus according to claim 2, wherein, in the combination (Tm, Ts), a torque detection value closer to a torque neutral value at which the steering wheel indicates a neutral point is set as the alternative value Ta. 5. . The torque failure detection means, said main torque detection value Tm, or the sub torque detection value Ts, or claim 1 for detecting an abnormality of the torque sensor based on said main torque detection Tm and the sub torque detection value Ts The control device for the electric power steering device according to any one of No.4 .

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