JP5585423B2 - Electric power steering apparatus and vehicle - Google Patents

Description

  The present invention relates to an electric power steering apparatus that applies a steering assist force by an electric motor to a steering system of a vehicle, and in particular, detects a torque by detecting a rotation angle difference between an input shaft and an output shaft connected by a torsion bar. The present invention relates to an electric power steering apparatus provided with torque detecting means.

An electric power steering device that applies a steering assist force to a steering device of an automobile by the rotational force of an electric motor applies a steering assist force generated by the electric motor to a steering system such as a steering shaft or a rack shaft via a reduction gear. I am doing so.
In such an electric power steering device, the steering torque of the steering system is detected by a torque sensor, a steering assist current command value is calculated based on the detected value of the torque sensor, and the steering assist current command value and the motor current detection value are calculated. The electric motor is driven by feedback control based on the above.

  Here, if an abnormality occurs in the torque sensor, an accurate steering assist command value cannot be obtained. Therefore, when an abnormality is detected in the torque detection system, an alternative control torque is calculated based on the motor rotation angle and the steering wheel rotation angle. An electric power steering apparatus has been proposed in which a current command value for controlling a motor is determined using an alternative control torque instead of a steering torque detected by a torque sensor (see, for example, Patent Document 1). .

JP 2009-12511 A

  However, in the conventional example described in Patent Document 1, since the motor rotation angle is used when the torque sensor is abnormal, it is generated by a reduction mechanism existing between the motor rotation angle and the output shaft angle. Due to the influence of nonlinear distortion components such as backlash, there is an unsolved problem that a certain error must be allowed in the detected alternative steering torque.

  Therefore, the present invention has been made paying attention to the unsolved problems of the above conventional example, and a sensor abnormality has occurred by multiplexing the torque detection means with a plurality of input shaft rotation angle sensors and output shaft rotation angle sensors. In this case, an object of the present invention is to provide an electric power steering apparatus capable of calculating a torque detection value using the remaining input shaft rotation angle sensor and output shaft rotation angle sensor.

  In order to achieve the above object, an electric power steering apparatus according to the present invention includes an input shaft rotation angle sensor that individually detects a rotation angle of an input shaft and an output shaft connected by a torsion bar provided in a vehicle steering system, and An electric power steering apparatus comprising: torque detection means having an output shaft rotation angle sensor; and an electric motor that is controlled based on a torque detection value detected by the torque detection means and generates a steering assist force for the steering system. And a steering angle detection means for detecting a rotation angle of the input shaft to detect a steering angle of the steering system, and a resolver for detecting a motor rotation angle of the electric motor, wherein the torque detection means comprises: Sensor abnormality detecting means having a plurality of sets of input shaft rotation angle sensors and output shaft rotation angle sensors and detecting an abnormality in each of the input shaft rotation angle sensors and each of the output shaft rotation angle sensors And when the sensor abnormality detecting means detects at least one abnormality of the input shaft rotation angle sensor and the output shaft rotation angle sensor, the presence / absence of the replacement rotation angle sensor is determined, and the replacement rotation angle sensor When there is a substitute rotation angle sensor, the substitute rotation angle sensor substitutes for a detection signal, and when there is no substitute rotation angle sensor, the steering angle detection means and the substitute control means for replacing with one of the resolvers are provided.

  According to this configuration, a plurality of sets of input shaft rotation angle sensors and output shaft rotation angle sensors for detecting torque are configured and multiplexed, and any one or more of the input shaft rotation angle sensor and the output shaft rotation angle sensor. When an abnormality occurs, if the remaining sensor is present, torque detection is performed using the remaining sensor, and if the remaining sensor is not present, it is based on the detected rotation angle value of the steering angle detection means or resolver. To detect torque.

Also, in the electric power steering apparatus according to the present invention, the torque detection means includes two sets of the input shaft rotation angle sensor and the output shaft rotation angle sensor, and the rotation angle detection values of the two sets of input shaft rotation angle sensors. The torque detection value is calculated by multiplying the absolute value of the deviation between the addition value of the two and the addition value of the rotation angle detection values of the two sets of output shaft rotation angle sensors by the spring coefficient of the torsion bar. It is characterized by being.
According to this configuration, when one of the input shaft rotation angle sensor or the output shaft rotation angle sensor becomes abnormal, the detected rotation angle value of the abnormal sensor is converted into a normal input shaft rotation angle sensor or output shaft rotation angle sensor. The detected value can be substituted, and an accurate torque detection value can be calculated.

Also, in the electric power steering apparatus according to the present invention, the substitute control means is one of the two sets of the input shaft rotation angle sensor and the output shaft rotation angle sensor, the input shaft rotation angle sensor or the output shaft rotation angle sensor. When an abnormality is detected, the other input shaft rotation angle sensor or output shaft rotation angle sensor is selected as a substitute sensor.
According to this configuration, when an abnormality occurs in one of the two sets of the input shaft rotation angle sensor or the output shaft rotation angle sensor, the rotation angle detection value of the other input shaft rotation angle sensor or output shaft rotation angle sensor is set to the normal value. Based on this, an accurate torque detection value can be calculated.

Also, in the electric power steering apparatus according to the present invention, the substitute control means includes either the input shaft rotation angle sensor or the output shaft rotation angle sensor of the two sets of the input shaft rotation angle sensor and the output shaft rotation angle sensor. When an abnormality is detected, the steering angle sensor or the resolver is selected as an alternative sensor.
According to this configuration, when the input shaft rotation angle sensor or the output shaft rotation angle sensor of the two sets of the input shaft rotation angle sensor and the output shaft rotation angle sensor becomes abnormal, the other steering angle detection means or resolver is not used for the first time. The detected steering angle value can be used to continue the steering assist control state.

Further, in the electric power steering apparatus according to the present invention, the sensor abnormality detecting means is configured such that a deviation between a rotation angle detection value detected by two sets of input shaft rotation angle sensors and a steering angle detected by the steering angle sensor is an allowable value. When it is above, it detects as sensor abnormality.
According to this configuration, the abnormality of the input shaft rotation angle sensor can be detected immediately by comparing it with the steering angle detected by the steering angle detection means.

Further, in the electric power steering apparatus according to the present invention, the sensor abnormality detection means outputs an output shaft estimated based on a rotation angle detection value detected by two sets of output shaft rotation angle sensors and a motor rotation angle detected by the resolver. A sensor abnormality is detected when the deviation from the rotation angle is greater than or equal to an allowable value.
According to this configuration, the abnormality of the output shaft rotation angle sensor can be detected immediately by comparing it with the output shaft rotation angle estimated based on the motor rotation angle detected by the resolver.

  According to the present invention, when an input shaft rotation angle sensor and an output shaft rotation angle sensor for detecting a steering torque are multiplexed and an abnormality of one or more input shaft rotation angle sensors or output shaft rotation angle sensors is detected. In addition, there is an effect that an accurate torque detection value can be calculated based on a rotation angle detection value of a normal input shaft rotation angle sensor or output shaft rotation angle sensor.

It is a block diagram which shows the electric power steering apparatus by this invention. It is a block diagram which shows the torque detection value calculating circuit of a steering assistance control apparatus. It is a flowchart which shows an example of the sensor abnormality detection process procedure performed with the sensor abnormality detection circuit of a steering assist control apparatus. It is a flowchart which shows an example of the alternative control processing procedure performed with the alternative control circuit of a steering assistance control apparatus. It is a flowchart which shows an example of the steering assistance control processing procedure performed with a steering assistance control apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing an embodiment of an electric power steering apparatus according to the present invention. In the figure, 1 is a steering wheel, and the steering wheel 1 is attached to a vehicle rear side tip of a steering shaft 2. It has been. The steering shaft 2 includes an input shaft 2a to which a steering force applied from a driver is transmitted via the steering wheel 1, and an output shaft 2c connected to the input shaft 2a via a torsion bar 2b. Yes.

The steering force transmitted to the output shaft 2 c is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear mechanism 8 to steer a steered wheel (not shown). Here, the steering gear mechanism 8 is configured in a rack and pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is transmitted by the rack 8b. It has been converted to straight movement.
A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2c is connected to the output shaft 2c of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear mechanism 11 connected to the output shaft 2c, an electric motor 12 including a brushless electric motor connected to the reduction gear mechanism 11 and generating a steering assist force, and a brushless electric motor. It has.

  A steering angle sensor 13 including a rotary encoder, for example, is provided as a steering angle detection means for detecting the steering angle θs of the steering wheel 2 by detecting the rotation angle of the input shaft 2 a of the steering shaft 2. In addition, a torque sensor 14 is provided as torque detecting means for detecting a steering torque by detecting a torsional angular displacement of a torsion bar 2b disposed between the input shaft 2a and the output shaft 2c.

As shown in FIG. 1, the torque sensor 14 detects, for example, two sets of input shaft rotation angle sensors 15a and 15b that include a rotary encoder that detects the rotation angle of the input shaft 2a, and the rotation angle of the output shaft 2c. For example, two sets of output shaft rotation angle sensors 16a and 16b configured to include a rotary encoder for detection are provided. Each of the input shaft rotation angle sensors 15a and 15b individually detects the rotation angle of the input shaft 2a and outputs detected input shaft rotation angle values θ1a and θ1b. Similarly, the output shaft rotation angle sensors 16a and 16b also detect the rotation angle of the output shaft 2c and output output shaft rotation angle detection values θ2a and θ2b.
Further, the resolver 17 detects the motor rotation angle of the electric motor 12 connected to the output shaft 2 c via the reduction gear mechanism 11.

The steering angle detection value θs detected by the steering angle sensor 13, the input shaft rotation angle detection values θ1a and θ1b detected by the input shaft rotation angle sensors 15a and 15b constituting the torque sensor 14, and the output shaft rotation angle sensors 16a and 16b. The output shaft rotation angle detection values θ2a and θ2b detected in step S2 and the motor rotation angle detection value θm detected by the resolver 17 are supplied to the steering assist control device 20.
The steering assist control device 20 also receives a vehicle speed detection value Vs detected by the vehicle speed sensor 18.

  The steering assist control device 20 includes sensor abnormality detection means 20a for detecting abnormality of the input shaft rotation angle sensors 15a and 15b and the output shaft rotation angle sensors 16a and 16b constituting the torque sensor 14, and sensor abnormality detection means 20a. Is detected, and if there is an alternative rotation angle sensor, the detection signal of the alternative rotation angle sensor is substituted, and if there is no alternative rotation angle sensor, the steering angle sensor 13 and the resolver 17 are detected. Substitution control means 20b that substitutes for one of the values, and steering assistance control means 20c that performs steering assistance control processing based on torque detection value T and vehicle speed detection value Vs are provided.

Further, as shown in FIG. 2, the steering assist control device 20 includes the input shaft rotation angle detection values θ1a and θ1b detected by the input shaft rotation angle sensors 15a and 15b constituting the torque sensor 14, and the output shaft rotation angle sensor 16a, A torque detection value calculation circuit 30 that calculates a torque detection value T based on the output shaft rotation angle detection values θ2a and θ2b detected in 16b is provided.
This torque detection value calculation circuit 30 includes selection switch circuits 33a and 33b in which input shaft rotation angle detection values θ1a and θ1b output from the input shaft rotation angle sensors 15a and 15b are individually input to the normally closed contact tnc, and outputs There are provided selection switch circuits 34a and 34b in which the output shaft rotation angles θ2a and θ2b output from the shaft rotation angle sensors 16a and 16b are individually input to the normally closed contact tnc.

The selection signal output from the movable contact tc of the selection switch circuit 33b is input to the normally open contact tno of the selection switch circuit 33a, and the movable contact tc of the selection switch circuit 33a is input to the normally open contact tno of the selection switch circuit 33b. The selection signal output from is input.
Similarly, the selection signal output from the movable contact tc of the selection switch circuit 34b is input to the normally open contact tno of the selection switch circuit 34a, and the selection switch circuit 34b receives the selection signal output from the movable contact tc. A selection signal output from the movable contact tc is input.

Further, the torque detection value calculation circuit 30 includes selection switch circuits 35a and 35b in which selection signals output from the movable contacts tc of the selection switch circuits 33a and 33b are individually input to the normally closed contacts tnc, and selection switch circuits 34a and 34a, Selection switch circuits 36a and 36b for individually selecting selection signals output from the movable contact tc of 34b to the normally closed contact tnc.
Here, the steering angle θs detected by the steering angle sensor 13 is input to the normally open contact tno of the selection switch circuits 35a and 35b, respectively, and the motor detected by the resolver 17 is input to the normally open contact tno of the selection switch circuits 36a and 36b. An output rotation angle θ2m estimated based on the rotation angle θm and the gear ratio of the reduction gear mechanism 11 is input.

  Further, the torque detection value calculation circuit 30 adds the selection signal output from the movable contact tc of the selection switch circuits 35a and 35b, and the selection signal output from the movable contact tc of the selection switch circuits 36a and 36b. , A subtractor 39 that subtracts the addition output of the adder 38 from the addition output of the adder 37, and a torsion output from the torsion bar spring coefficient setting unit 40 to the subtraction output of the subtractor 39 A multiplier 41 that multiplies the spring coefficient K of the bar 2b to calculate the torque detection value T.

  The selection switch circuits 33a, 33b, 34a, 34b, 35a, 35b and 36a, 36b are selected and controlled by an alternative control circuit 43 serving as alternative control means. The substitution control circuit 43 receives sensor abnormality detection signals from a sensor abnormality detection circuit 44 as sensor abnormality detection means for detecting abnormality of the input shaft rotation angle sensors 15a and 15b and the output shaft rotation angle sensors 16a and 16b. ing.

  Here, the sensor abnormality detection circuit 44 executes a sensor abnormality detection process shown in FIG. This sensor abnormality detection process is executed as a timer interruption process every predetermined time (for example, 10 msec). First, in step S1, the steering angle detection value θs detected by the steering angle sensor 13 and the input shaft rotation angle sensors 15a and 15b. After reading the input shaft rotation angle detection values θ1a and θ1b detected in Step 1, the output shaft rotation angle detection values θ2a and θ2b detected by the output shaft rotation angle sensors 16a and 16b, and the motor rotation angle θm detected by the resolver 17, the process proceeds to Step S2. Transition.

  In this step S12, whether or not the angle deviation Δθ1a (= | θ1a−θs |), which is the absolute value of the value obtained by subtracting the steering angle θs from the detected input shaft rotation angle θ1a, is equal to or larger than a preset allowable angle difference Δθp1. When Δθ1a <Δθp1, it is determined that the input shaft rotation angle sensor 15a is normal, and the process proceeds to step S3, where the abnormality flag F1a is set to “0” indicating normality of the input shaft rotation angle sensor 15a. After resetting, the process proceeds to step S5. When Δθ1a ≧ Δθp1, it is determined that the input shaft rotation angle sensor 15a is abnormal, and the process proceeds to step S4, where the abnormality flag F1a indicates an abnormality of the input shaft rotation angle sensor 15a. After setting to “1”, the process proceeds to step S5.

  In step S5, whether or not an angle deviation Δθ1b (= | θ1b−θs |), which is an absolute value of a value obtained by subtracting the steering angle θs from the input shaft rotation angle detection value θ1b, is equal to or larger than a preset allowable angle difference Δθp1. When Δθ1b <Δθp1, it is determined that the input shaft rotation angle sensor 15b is normal, and the process proceeds to step S6. The abnormality flag F1b is “0” indicating that the input shaft rotation angle sensor 15b is normal. Then, the process proceeds to step S8, and when Δθ1a ≧ Δθp1, it is determined that the input shaft rotation angle sensor 15b is abnormal, the process proceeds to step S7, and the abnormality flag F1b is set to indicate an abnormality in the input shaft rotation angle sensor 15b. After setting to “1”, the process proceeds to step S8.

  In step S8, an angular deviation Δθ2a that is an absolute value of a value obtained by subtracting the output shaft rotation angle θ2m estimated in consideration of the gear ratio of the reduction gear mechanism 11 based on the motor rotation angle θm from the detected output shaft rotation angle θ2a. It is determined whether (= | θ2a−θ2m |) is greater than or equal to a preset allowable angle difference Δθp2. If Δθ2a <Δθp2, it is determined that the output shaft rotation angle sensor 16a is normal, and the process proceeds to step S9. The process proceeds to step S11 after the abnormality flag F2a is reset to “0” indicating that the output shaft rotation angle sensor 16a is normal. When Δθ2a ≧ Δθp2, the output shaft rotation angle sensor 16a is abnormal. If it is determined that there is an error, the process proceeds to step S10, and the abnormality flag F2a is set to “1” indicating an abnormality of the output shaft rotation angle sensor 16a, and then the process proceeds to step S11.

  In step S11, an angle deviation Δθ2b (= | θ2b−θ2m |) that is an absolute value of a value obtained by subtracting the output shaft rotation angle θ2m calculated based on the motor rotation angle θm from the output shaft rotation angle detection value θ2b is set in advance. It is determined whether or not the permissible angle difference Δθp2 is greater than or equal to Δθ2b. If Δθ2b <Δθp2, it is determined that the output shaft rotation angle sensor 16b is normal, the process proceeds to step S12, and the abnormality flag F2b is set to the output shaft rotation angle. After resetting to “0” indicating that the sensor 16b is normal, the timer interrupt process is terminated and the program returns to a predetermined main program. When Δθ2b ≧ Δθp2, the output shaft rotation angle sensor 16b is abnormal. The process proceeds to step S13 and sets the abnormality flag F2b to “1” indicating the abnormality of the output shaft rotation angle sensor 16b, and then ends the timer interruption process. To return to the constant of the main program.

  Further, the substitution control circuit 43 executes the substitution control process shown in FIG. In this alternative control process, first, in step S20, it is determined whether or not the abnormality flag F1a is set to “1”. When F1a = “0”, the process proceeds to step S21, and the movable contact tc is normally set. The switch control signal Sc1a having the logical value “0” for the closed contact tnc side is output to the selection switch circuit 33a and then the process proceeds to step S23. When F1a = “1”, the process proceeds to step S22 and the movable contact tc. Is switched to the normally open contact tno side, and a switching control signal Sc1a having a logical value “1” is output to the selection switch circuit 33a, and then the process proceeds to step S23.

  In step S23, it is determined whether or not the abnormality flag F1b is set to “1”. When F1b = “0”, the process proceeds to step S24, and the logical value that sets the movable contact tc to the normally closed contact tnc side. After the switching control signal Sc1b of “0” is output to the selection switch circuit 33b, the process proceeds to step S26. When F1b = “1”, the process proceeds to step S25, and the movable contact tc is switched to the normally open contact tno side. After the switching control signal Sc1b having the logical value “1” is output to the selection switch circuit 33b, the process proceeds to step S26.

  In step S26, it is determined whether or not the abnormality flag F2a is set to “1”. When F2a = “0”, the process proceeds to step S27 to set the movable contact tc to the normally closed contact tnc side. After the switching control signal Sc2a of “0” is output to the selection switch circuit 34a, the process proceeds to step S29. When F2a = “1”, the process proceeds to step S28, and the movable contact tc is switched to the normally open contact tno side. After the switching control signal Sc2a having the logical value “1” is output to the selection switch circuit 34a, the process proceeds to step S29.

  In step S29, it is determined whether or not the abnormality flag F2b is set to “1”. When F2b = “0”, the process proceeds to step S30 to set the movable contact tc to the normally closed contact tnc side. After the switching control signal Sc2b of “0” is output to the selection switch circuit 34b, the process proceeds to step S32, and when F2b = “1”, the process proceeds to step S31, and the movable contact tc is switched to the normally open contact tno side. After the switching control signal Sc2b having the logical value “1” is output to the selection switch circuit 34b, the process proceeds to step S32.

  In step S32, it is determined whether or not both of the abnormality flags F1a and F1b are set to “1”. When both of the abnormality flags F1a and F1b are not set to “1”, the process proceeds to step S33 to move the movable contact. A switching control signal Sc3 having a logical value “0” with tc as the normally closed contact tnc side is output to the selection switch circuits 35a and 35b, and then the process proceeds to step S35, where both the abnormality flags F1a and F1b are set to “1”. If YES in step S34, the flow shifts to step S34 to output a switching control signal Sc3 having a logical value "1" for switching the movable contact tc to the normally open contact tno side to the selection switch circuits 35a and 35b, and then shifts to step S35.

  In step S35, it is determined whether or not both of the abnormality flags F2a and F2b are set to “1”. When both of the abnormality flags F2a and F2b are not set to “1”, the process proceeds to step S36 to move the movable contact. A switching control signal Sc4 having a logical value “0” with tc as the normally closed contact tnc side is output to the selection switch circuits 36a and 36b, and then the timer interrupt process is terminated to return to a predetermined main program, and the abnormality flag F2a When F1 and F2b are both set to "1", the process proceeds to step S37, and a switching control signal Sc4 having a logical value "1" for switching the movable contact tc to the normally open contact tno is output to the selection switch circuits 36a and 36b. Then, the timer interrupt process is terminated and the process returns to a predetermined main program.

  Further, the steering assist control device 20 executes a steering assist control process shown in FIG. This steering assist control process is executed as a main program. First, in step S41, the torque detection value T calculated in the torque detection process described above and stored in the torque detection value storage area of the memory is read, and then in step S42. Transition is made to read the vehicle speed detection value Vs, and then the routine proceeds to step S43, where the relationship between the torque detection value and the steering assist command value using the vehicle speed detection value V (not shown) as a parameter based on the torque detection value T and vehicle speed detection value V. After calculating the steering assist current command value Iref with reference to the steering assist command value calculation map representing the above, the process proceeds to step S44.

In step S44, the motor current detection value Imd detected by the motor current detection circuit 21 is read, and then the process proceeds to step S45 where the motor current detection value Imd is subtracted from the steering assist current command value Iref to calculate the current deviation ΔI. Then, the process proceeds to step S46.
In step S46, a PI control process is performed based on the calculated current deviation ΔI to calculate a voltage command value Vmt, and then the process proceeds to step S47 to perform a pulse width modulation process based on the voltage command value Vmt. A switching signal is formed, and then the process proceeds to step S48, where the switching signal is output to the motor drive circuit 22 composed of an H bridge circuit having a switching element, an inverter, etc., and then returns to step S41.

Next, the operation of the above embodiment will be described.
Now, assuming that the input shaft rotation angle sensors 15a and 15b and the output shaft rotation angle sensors 16a and 16b constituting the torque sensor 14 are normal, the torque detection value calculation circuit 30 of the steering assist control device 20 performs the input shaft rotation angle. The input shaft rotation angle detection values θ1a and θ1b detected by the sensors 15a and 15b and the output shaft rotation angle detection values θ2a and θ2b detected by the output shaft rotation angle sensors 16a and 16b are read.

At this time, since the input shaft rotation angle sensors 15a, 15b and the output shaft rotation angle sensors 16a, 16b are normal, the abnormality flags F1a, F1b and F2a, F2b are all reset to “0”. For this reason, the switching control signals Sc1a, Sc1b, Sc2a, Sc2b, Sc3, and Sc4 become the logical value “0”, and the selection switch circuits 33a, 33b, 34a, 34b, 35a, 35b and 36a, 36b in FIG. As shown in FIG. 4, the movable contact tc is switched to the normally closed contact tnc side, and the torque detection value T is calculated by performing the calculation represented by the following equation (1), which is the torque detection value of a memory such as a RAM. It is updated and stored in the storage area.
T = {(θ1a + θ1b) − (θ2a + θ2b)} × K (1)

  On the other hand, the steering assist control device 20 executes the steering assist control process shown in FIG. 5, reads the torque detection value T updated and stored in the steering torque storage area of the memory, and detects the vehicle speed detected by the vehicle speed sensor 18. The value Vs is read (steps S41 and S42), the steering assist current command value Iref is calculated with reference to the steering assist current command value calculation map based on the torque detection value T and the vehicle speed detection value Vs (step S43), and then The motor current detection value Imd detected by the motor current detection circuit 21 is read (step S44), and the motor current detection value Imd is subtracted from the steering assist current command value Iref to calculate a current deviation ΔI (step S45).

  The calculated current deviation ΔI is subjected to PI control processing to calculate a voltage command value Vt (step S46). Based on the calculated voltage command value Vt, pulse width modulation processing is performed to form a switching signal (step S47). By outputting the switched signal to the motor drive circuit 22 (step S48), the motor drive circuit 22 rotationally drives the electric motor 12 to generate a steering assist force according to the torque detection value T. The steering assist force generated by the electric motor 12 is transmitted to the output shaft 2c of the steering shaft 2 via the reduction gear mechanism 11, and the output shaft 2c is auxiliary-steered. Therefore, the steering wheel 1 is steered with a light steering force. can do.

  As described above, the sensor abnormality detection process shown in FIG. 3 is executed as the timer interruption process in the state where the steering assist control device 20 performs the steering assist control based on the torque detection value T and the vehicle speed detection value Vs. The input shaft rotation angle detection values θ1a and θ1b detected by the input shaft rotation angle sensors 15a and 15b, the output shaft rotation angle detection values θ2a and θ2b detected by the output shaft rotation angle sensors 16a and 16b, and the steering angle sensor 13 The steering angle θs and the motor rotation angle θm detected by the resolver 17 are read.

  The input shaft rotation angle detection values θ1a and θ1b are compared with the steering angle θs detected by the steering angle sensor 13 that detects the rotation angle of the input shaft 2a in the same manner as the input shaft rotation angle sensors 15a and 15b. Abnormalities in the shaft rotation angle sensors 15a and 15b can be detected. That is, since the input shaft rotation angle sensors 15a and 15b and the steering angle sensor 13 detect the rotation angle of the same input shaft 2a and have a correlation with each other, the input shaft rotation angle detection values θ1a and θ12 and the steering angle θs The rotational angle difference between the two is within the range of the mounting error.

  Therefore, the absolute value | θ1a−θs | (or | θ1b−θs |) of the rotation angle difference obtained by subtracting the steering angle θs from the input shaft rotation angle θ1a (or rotation angle θ1b) is less than the preset allowable value Δθp1. Sometimes it can be determined that the input shaft rotation angle sensor 15a (or 15b) is normal. On the other hand, when the absolute value | θ1a−θs | (or | θ1b−θs |) is equal to or larger than a preset allowable value Δθp1, an abnormality such as an interphase short circuit occurs in the input shaft rotation angle sensor 15a (or 15b). Can be determined. When an abnormality of the input shaft rotation angle sensor 15a or 15b is detected, the abnormality flag F1a or F1b is set to “1”.

Similarly, the output shaft rotation angle sensors 16 a and 16 b detect the rotation angle of the output shaft 2 c, and the motor rotation angle θm detected by the resolver 17 built in the electric motor 12 is output by the electric motor 12 via the reduction gear mechanism 11. Since it is connected to the shaft 2c, it can be converted into the output shaft rotation angle θ2m of the output shaft 2c by considering the gear ratio of the reduction gear mechanism 11 to the motor rotation angle θm.
Therefore, the output shaft rotation angle detection values θ2a and θ2b detected by the output shaft rotation angle sensors 16a and 16b and the motor rotation angle detection value θm output from the resolver 17 have a correlation with each other, and the motor rotation angle detection value θm. The rotation angle difference between the output shaft rotation angle θ2m and the output shaft rotation angles θ2a and θ2b estimated based on the above is within the range of the mounting error.

  For this reason, the absolute value | θ2a−θ2m | (or | θ2b−θ2m |) of the rotation angle difference obtained by subtracting the output shaft rotation angle θ2m from the output shaft rotation angle detection value θ2a (or θ2b) is less than the preset allowable value Δθp2. When it is, it can be determined that the output shaft rotation angle sensor 16a (or 16b) is normal. On the other hand, when the absolute value | θ2a−θ2m | (or | θ2b−θ2m |) is equal to or larger than a preset allowable value Δθp2, an abnormality such as an interphase short circuit occurs in the output shaft rotation angle sensor 16a (or 16b). Can be determined.

When an abnormality of the output shaft rotation angle sensor 16a or 16b is detected, the abnormality flag F2a or F2b is set to “1”.
Then, when an abnormality occurs in the input shaft rotation angle sensor 15a (or 15b) and the abnormality flag F1a (or F1b) is set to “1”, the replacement control shown in FIG. In the process, the switching control signal Sc1a (or Sc1b) becomes the logical value “1”, and the movable contact tc of the selection switch circuit 33a (or 33b) is switched from the normally closed contact tnc side to the normally open contact tno side accordingly. . Therefore, instead of the input shaft rotation angle detection value θ1a (or θ1b) of the input shaft rotation angle sensor 15a (or 15b) that has become abnormal in the selection switch circuit 33a (or 33b), a normal input shaft rotation angle is used as a substitute signal. The input shaft rotation angle detection value θ1b (or θ1a) of the sensor 15b (or 15a) is selected.

Accordingly, the torque detection value T is calculated based on the normal input shaft rotation angle detection value θ1a (or θ1b), and the accurate torque detection value T can be calculated, and normal steering assist control is continued. can do.
Similarly, when the output shaft rotation angle detection value θ2a (or θ2b) becomes abnormal, the torque detection value T is calculated on the basis of the normal output shaft rotation angle θ2b (or θ2a). The torque detection value T can be calculated, and normal steering assist control can be continued.

  However, when both the input shaft rotation angle sensors 15a and 15b (or the output shaft rotation angle sensors 16a and 16b) become abnormal, the accurate input shaft rotation angles θ1a and θ1b (or the output shaft rotation angles θ2a and θ2b) are detected. ) Cannot be calculated. In this case, when the switching control signal Sc3 (or Sc4) for the selection switch circuits 35a and 35b (or 36a and 36b) becomes a logical value “1”, the selection switch circuits 35a and 35b (or 36a and 36b) By selecting the steering angle θs (or the output shaft rotation angle θ2m estimated based on the motor rotation angle θm), the accuracy of the calculated torque detection value T is somewhat reduced, but the steering assist control is continued. Can do.

As described above, according to the above embodiment, the input shaft rotation angle sensors 15a and 15b and the output shaft rotation angle sensors 16a and 16b are duplicated, so that even if an abnormality is detected in one of the duplicated sensors, the accurate detection is possible. The torque detection value T can be calculated, accurate steering assist control can be continued, and if an abnormality is detected in both of the duplicated sensors, the steering angle θs and the motor are used as alternative rotation detection values. The torque detection value T can be calculated based on the output shaft rotation angle θ2m estimated based on the rotation angle θm, and the steering assist control can be continued with a slight decrease in accuracy.
In the above embodiment, the case where the input shaft rotation angle sensor and the output shaft rotation angle sensor are duplicated has been described. However, the present invention is not limited to this, and the input shaft rotation angle sensor and the output shaft rotation angle sensor are tripled. It is possible to multiplex more than the above.

In the above embodiment, the case where the input shaft rotation angle sensors 15a and 15b and the output shaft rotation angle sensors 16a and 16b are formed by a rotary encoder has been described. However, the present invention is not limited to this, and a rotary lipometer or resolver is used. Other rotation angle sensors can be applied.
In the above embodiment, the case where the present invention is applied to a column-type electric power steering device has been described. However, the present invention is not limited to this, and the steering assist force is applied to the pinion shaft of the rack-and-pinion type steering gear mechanism. The present invention can also be applied to a pinion-type electric power steering device that transmits power and a rack-type electric power steering device that transmits steering assist force to the rack shaft. In these cases, the torque detection value T may be calculated from the rotational angle difference between the universal joint 6 and the pinion shaft 7 that sandwiches the torsion bar by placing the torsion bar between the universal joint 6 and the pinion shaft 7.

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 2a ... Input shaft, 2b ... Torsion bar, 2c ... Output shaft, 8 ... Steering gear mechanism, 10 ... Steering assist mechanism, 11 ... Reduction gear mechanism, 12 ... Electric motor, 13 ... Steering angle sensor, 14 ... torque sensor, 15a, 15b ... input shaft rotation angle sensor, 16a, 16b ... output shaft rotation angle sensor, 17 ... resolver, 18 ... vehicle speed sensor, 20 ... steering assist control device, 20a ... torque detection value Calculation means, 20b ... Sensor abnormality detection means, 20c ... Steering assist control means, 21 ... Motor current detection circuit, 22 ... Motor drive circuit, 30 ... Torque detection value calculation circuit, 31a, 31b, 32a, 32b ... RDC, 33a- 36b ... selection switch circuit, 37, 38 ... adder, 39 ... subtractor, 40 ... torsion bar spring constant setter, 41 ... Adder, 42 ... memory, 43 ... alternative control circuit, 44 ... sensor abnormality detecting circuit

Claims (5)

Torque detection means having an input shaft rotation angle sensor and an output shaft rotation angle sensor for individually detecting rotation angles of an input shaft and an output shaft connected by a torsion bar provided in a vehicle steering system, and detected by the torque detection means An electric power steering device including an electric motor that is controlled based on the detected torque value and generates a steering assist force for the steering system,
Steering angle detection means for detecting a rotation angle of the input shaft to detect a steering angle of the steering system;
A resolver for detecting a motor rotation angle of the electric motor,
The torque detection means has a plurality of sets of input shaft rotation angle sensors and output shaft rotation angle sensors,
Sensor abnormality detection means for detecting an abnormality of each input shaft rotation angle sensor and each output shaft rotation angle sensor;
When at least one abnormality of the input shaft rotation angle sensor and the output shaft rotation angle sensor is detected by the sensor abnormality detection means, the presence / absence of an alternative rotation angle sensor is determined. Substitute with a detection signal of the substitute rotation angle sensor, and when there is no substitute rotation angle sensor, the steering angle detection means and an alternative control means that substitutes one of the resolver ,
The substitute control means is configured to detect an abnormality in some of the input shaft rotation angle sensors among the plurality of input shaft rotation angle sensors constituting the plurality of sets of input shaft rotation angle sensors and output shaft rotation angle sensors. In addition, when a substitute sensor is selected from the remaining normal input shaft rotation angle sensors and an abnormality is detected in all of the plurality of input shaft rotation angle sensors, the steering angle sensor is changed to the input shaft rotation angle sensor. An abnormality was detected in some output shaft rotation angle sensors among the plurality of output shaft rotation angle sensors constituting the plurality of sets of input shaft rotation angle sensors and output shaft rotation angle sensors. When an alternative sensor is selected from the remaining normal output shaft rotation angle sensors and an abnormality is detected in all of the plurality of output shaft rotation angle sensors, the resolver is connected to the output shaft rotation angle sensor. It is configured to select as a substitute sensor
Electric power steering device comprising a call.   The torque detection means includes two sets of the input shaft rotation angle sensor and the output shaft rotation angle sensor, and an addition value of rotation angle detection values of the two sets of input shaft rotation angle sensors and the two sets of output shaft rotation angles. The torque detection value is calculated by multiplying the absolute value of the deviation from the addition value of the rotation angle detection value of the sensor by a spring coefficient of a torsion bar. Electric power steering device. The sensor abnormality detection means detects a sensor abnormality when a deviation between a rotation angle detection value detected by two sets of input shaft rotation angle sensors and a steering angle detected by the steering angle sensor is equal to or greater than an allowable value. The electric power steering apparatus according to claim 2 , wherein The sensor abnormality detection means is configured such that a deviation between a rotation angle detection value detected by two sets of output shaft rotation angle sensors and an output shaft rotation angle estimated based on a motor rotation angle detected by the resolver is equal to or greater than an allowable value. the electric power steering apparatus according to claim 2 or 3, characterized by detecting a sensor abnormality.   A vehicle comprising the electric power steering device according to any one of claims 1 to 4.

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