JP5585403B2 - 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 capable of easily detecting an abnormality of a 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 apparatus, in the electric power steering apparatus including a twin resolver type torque sensor including a torsion bar, an input shaft side rotation angle sensor, and an output shaft side rotation angle sensor, the input shaft side rotation angle sensor The electrical angle calculation result by either one of the output shaft side rotation angle sensor and the output shaft side rotation angle sensor is included in a first predetermined angle range including 45 ° for a certain period of time, and the input shaft side rotation angle sensor and the output shaft side rotation When the electric angle calculation result by the other of the angle sensors is included outside the second predetermined angle range including 45 ° for a certain period of time, it is determined that an inter-circuit short has occurred in one of the sensors. A power steering device is known (see, for example, Patent Document 1).

JP-A-2005-43071

However, in the conventional example described in Patent Document 1, it is possible to detect the occurrence of a short-circuit between one of the input shaft side rotation angle sensor and the output shaft side rotation angle sensor. However, there is an unsolved problem that an abnormality cannot be detected unless a certain period of time elapses because it is included in a predetermined angle range in order to detect an abnormality.
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and an electric power steering device capable of immediately detecting an abnormality in the input shaft side rotation angle sensor and the output shaft side rotation angle sensor. The purpose is to provide.

  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. The steering angle detecting means for detecting the rotation angle of the input shaft to detect the steering angle of the steering system, the resolver for detecting the motor rotation angle of the electric motor, the input shaft rotation angle sensor, and the Abnormality of the output shaft rotation angle steering angle detection means is detected based on the steering angle detection value detected by the steering angle detection means and the motor rotation angle detection value detected by the resolver. It is characterized in that it comprises a capacitors abnormality detecting means.

  According to this configuration, the abnormality of the input shaft rotation angle sensor and the output shaft rotation angle sensor for detecting torque is detected based on the steering angle detection value detected by the steering angle detection means and the motor rotation angle detection value detected by the resolver. Therefore, the abnormality detection can be performed accurately in a short time by performing the abnormality determination based on the rotation signals correlated with each other.

The electric power steering apparatus according to the present invention is characterized in that the sensor abnormality detection means detects a sensor abnormality when a rotation angle deviation between the detected rotation angle values having a correlation with each other becomes a predetermined value or more. It is said.
According to this configuration, accurate abnormality detection can be performed by comparing the rotation angle detection values having a correlation with each other.

The electric power steering device according to the present invention is configured such that each of the input shaft rotation angle sensor and the output shaft rotation angle sensor calculates and outputs an angle value corresponding to the rotation angle. It is a feature.
According to this configuration, since both the input shaft rotation angle sensor and the output shaft rotation sensor are configured to calculate and output an angle value, the rotation angles of the input shaft and the output shaft are calculated from the output signal of the rotation sensor. There is no need to do.

Further, in the electric power steering apparatus according to the present invention, the sensor abnormality detection means calculates an angle deviation between the angle value output from the input shaft rotation angle sensor and the steering angle detection value detected by the steering angle detection means. It is calculated, and when the calculated angle deviation becomes a predetermined value or more, it is determined that the angle value is abnormal.
According to this configuration, both the input shaft rotation angle sensor and the steering angle detection means detect the angle value of the rotation angle of the input shaft and have a correlation with each other, so that when the angle deviation between the two exceeds a predetermined value, Can immediately detect an abnormality in the angle value output from the input shaft rotation angle sensor.

  In the electric power steering apparatus according to the present invention, the sensor abnormality detection means calculates an angle deviation between the angle value output from the output shaft rotation angle sensor and the motor rotation angle detection value detected by the resolver. When the calculated angle deviation is equal to or greater than a predetermined value, it is determined that the angle value is abnormal.

Furthermore, in the electric power steering apparatus according to the present invention, the sensor abnormality detection means calculates an angle deviation between the angle value output from the output shaft rotation angle sensor and the motor rotation angle detection value detected by the resolver. When the calculated angle deviation is equal to or greater than a predetermined value, it is determined that the angle value is abnormal.
According to these configurations, the output shaft rotation angle sensor and the resolver are both connected to the output shaft and have a correlation with each other. Therefore, when the angular deviation between the two exceeds a predetermined value, the output shaft rotation angle sensor immediately Abnormality of the output angle value can be detected.

  According to the present invention, the steering detected by the steering angle detection sensor for detecting the rotation angle of the input shaft correlated with the input shaft rotation angle sensor and the output shaft rotation angle sensor for detecting the steering torque is detected. Since the detection is based on the detected angle and the rotation angle detection value of the resolver that detects the motor rotation angle of the electric motor connected to the output shaft, the abnormality of the input shaft rotation angle sensor and the output shaft rotation angle sensor is detected immediately. The effect that it can be obtained.

It is a block diagram which shows the electric power steering apparatus by this invention. It is a flowchart which shows an example of the steering torque detection process procedure performed with a steering assist control apparatus. It is a flowchart which shows an example of the sensor abnormality detection process procedure performed with a steering assistance control apparatus. It is a flowchart which shows the input shaft rotation angle of FIG. 3, and an output shaft rotation angle calculation process. 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 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 2a of the steering shaft 2, and the input shaft 2a and the output shaft 2c. A torque sensor 14 is provided as a torque detecting means for detecting a steering torque by detecting a torsional angular displacement of a torsion bar 2b disposed therebetween.

  As shown in FIG. 1, the torque sensor 14 is configured to include, for example, a double rotary encoder that detects the rotation angle of the input shaft 2a, calculates an angle value, and outputs an output value. An output shaft rotation angle sensor 16 that includes, for example, a double rotary encoder that detects the rotation angle of the shaft 2c and calculates and outputs an angle value is provided. The input shaft rotation angle sensor 15 detects the rotation angle of the input shaft 2a and outputs two sets of input shaft rotation angle detection values θ1a and θ1b. Similarly, the output shaft rotation angle sensor 16 detects the rotation angle of the output shaft 2c and outputs two sets of output shaft rotation angle detection values θ2a and θ2b. The input shaft rotation angle detection value θ1a output from the input shaft rotation angle sensor 15 and the output shaft rotation angle detection value θ2a output from the output shaft rotation angle sensor 16 are supplied to a multiplexer (MUX) 19A, and this multiplexer 19A Is time-division multiplexed and transmitted. Similarly, the input shaft rotation angle detection value θ1b output from the input shaft rotation angle sensor 15 and the output shaft rotation angle detection value θ2b output from the output shaft rotation angle sensor 16 are supplied to the multiplexer (MUX) 19B, and this The data is multiplexed in a time division manner by the multiplexer 19B.

The motor rotation angle θm of the electric motor 12 connected to the output shaft 2c via the reduction gear mechanism 11 is detected by the resolver 17, and the sine wave signal Vsin and the cosine wave signal Vcos are output from the resolver 17.
The steering angle detection value θs detected by the steering angle sensor 13, the input shaft rotation angle detection values θ 1 a and θ 1 b detected by the input shaft rotation angle sensor 15 and the output shaft rotation angle sensor 16 constituting the torque sensor 14, and the output shaft rotation. The detected angle values θ2a and θ2b and the sine wave signal Vsin and the cosine wave signal Vcos output from 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 input shaft rotation angle detection values θ1a and θ1b detected by the input shaft rotation angle sensor 15 constituting the torque sensor 14, and an output shaft rotation angle detection value θ2a detected by the output shaft rotation angle sensor 16. Torque detection value calculation means 20a that calculates a torque detection value T based on θ2b, sensor abnormality detection means 20b that detects abnormality of the input shaft rotation angle sensor 15 and output shaft rotation angle sensor 16 that constitute the torque sensor 14, and torque A steering assist control means 20c that performs steering assist control processing based on the detected value T and the vehicle speed detected value Vs is provided.

In this steering assist control device 20, input shaft rotation angle detection values θ 1 a and θ 1 b detected by the input shaft rotation angle sensor 15 constituting the torque sensor 14 and output shaft rotation angle detection signals θ 2 a and θ 2 b detected by the output shaft rotation sensor 16. Torque detection value calculation processing corresponding to the torque detection value calculation means 20a for calculating the torque detection value T based on the above is executed.
As shown in FIG. 2, this torque detection value calculation process is executed as a timer interrupt process at predetermined time intervals (for example, 10 msec). First, in step S1, an input shaft formed in a storage device such as a RAM, which will be described later. After the input shaft rotation angle θ1 and the output shaft rotation angle θ2 updated and stored in the rotation angle storage area and the output shaft rotation angle storage area are read, the process proceeds to step S2.

In step S2, the input shaft rotation angle θ1 and the output shaft rotation angle θ2 set in the sensor abnormality detection process described later are read, and the torque detection value T is calculated by performing the calculation of the following equation (1) based on these. To do.
T = K (θ1-θ2) (1)
Here, K is a spring coefficient of the torsion bar 2b.

Next, the process proceeds to step S3, where the calculated torque detection value T is updated and stored in a torque detection value storage area formed in a memory such as a RAM, and then the timer interruption process is terminated and the process returns to a predetermined main program.
Further, the steering assist control device 20 detects the input shaft rotation angle detection values θ1a and θ1b input from the input shaft rotation angle sensor 15 constituting the torque sensor 14 and the output shaft rotation angle detection input from the output shaft rotation angle sensor 16. A sensor abnormality detection process corresponding to the sensor abnormality detection means 20b for detecting an abnormality in the values θ2a and θ2b is executed.

  As shown in FIG. 3, this sensor abnormality detection process is executed as a timer interruption process at predetermined time intervals (for example, 10 msec). First, in step S11, the steering angle detection value θs detected by the steering angle sensor 13 is input. After reading the input shaft rotation angle detection values θ1a and θ1b detected by the shaft rotation angle sensor 15, the θ2a and θ2b detected by the output shaft rotation angle sensor 16 and the resolver signals Vsin and Vcos output from the resolver 17, the process proceeds to step S12. To do.

In this step S12, it is determined whether or not the resolver 17 is normal. Whether or not the resolver 17 is normal is determined by, for example, reading the sine wave signal Vsin and the cosine wave signal Vcos output from the resolver 17 and determining whether the sum of squares of both signals falls within the predetermined ranges V1 and V2. To determine whether the resolver 17 is normal. That is, whether the resolver 17 is normal or not is determined depending on whether V1 ≦ Vsin ² + Vcos ² ≦ V2.
The determination of the resolver 17 is not limited to the above, and whether or not the sum of squares of the sine wave signal Vsin and the cosine wave signal Vcos falls within a predetermined range and the added value of the sine wave signal Vsin and the cosine wave signal Vcos. Whether or not the absolute value is less than the predetermined value V3 may be added, and various other known resolver abnormality detection methods can be applied.

If the result of determination in step S12 is that the resolver 17 is normal, the process proceeds to step S14. If the resolver 17 is abnormal, the process proceeds to step S13, and a steering assist control process described later is stopped before the timer allocation. Finish the process.
In step S14, the motor rotation angle θm is calculated based on the resolver signals Vsin and Vcos, and then the process proceeds to step S15 to determine whether or not the steering angle sensor 13 is normal. Whether the steering angle sensor 13 is normal or not is determined by, for example, reducing the motor rotation angle detection value θm calculated from the steering angle θs based on the sine wave signal Vsin and the cosine wave signal Vcos of the resolver 17 to the reduction gear mechanism 11. This is performed by determining whether or not the absolute value of the value obtained by subtracting the estimated steering angle θse calculated by multiplying the gear ratio exceeds the set value Δθs (| θs−θse |> Δθs). The correctness determination of the steering angle sensor 13 is not limited to the above, and various known steering angle abnormality detection methods can be applied.

If the result of determination in step S15 is that the steering angle sensor 13 is normal, the process proceeds to step S16, and if the steering angle sensor 13 is abnormal, the process proceeds to step S13.
In step S16, whether or not an angle deviation Δθ1a (= | θ1a−θs |), which is an absolute value of a value obtained by subtracting the steering angle θs from the input shaft rotation angle detection value θ1a, is equal to or larger than a preset allowable angle difference Δθp1. If Δθ1a <Δθp1, the input shaft rotation angle detection value θ1a is determined to be normal, and the process directly proceeds to step S18. If Δθ1a ≧ Δθp1, the input shaft rotation angle detection value θ1a is abnormal. The process proceeds to step S17, and an abnormality flag F1a indicating an abnormality in the input shaft rotation angle detection value θ1a is set to “1”. Then, the process proceeds to step S18.

  In step S18, 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 detection value θ1b is normal, and the process directly proceeds to step S20. When Δθ1b ≧ Δθp1, the input shaft rotation angle detection value θ1b is abnormal. The process proceeds to step S19, and an abnormality flag F1b indicating an abnormality in the input shaft rotation angle detection value θ1b is set to “1”, and then the process proceeds to step S20.

  In step S20, an angle deviation Δθ2a that is an absolute value of a value obtained by subtracting the output shaft rotation angle θ2m calculated in consideration of the gear ratio of the reduction gear mechanism 11 based on the motor rotation angle θm from the output shaft rotation angle detection value θ2a. It is determined whether (= | θ2a−θ2m |) is greater than or equal to a preset allowable angle difference Δθp2, and if Δθ2a <Δθp2, it is determined that the output shaft rotation angle detection value θ2a is normal and the direct step is performed. The process proceeds to S22, and when Δθ2a ≧ Δθp2, it is determined that the output shaft rotation angle detection value θ2a is abnormal, and the process proceeds to step S21, where the abnormality flag F2a indicating the abnormality of the output shaft rotation angle detection value θ2b is set to “1”. Then, the process proceeds to step S22.

In step S22, an angle deviation Δθ2b (= | θ2b−θ2m |), which 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 allowable angle difference Δθp2 or more is satisfied. If Δθ2b <Δθp2, it is determined that the output shaft rotation detection value θ2b is normal, and the process directly proceeds to step S24, and if Δθ2b ≧ Δθp2, the output is performed. It is determined that the detected shaft rotation angle value θ2b is abnormal, and the process proceeds to step S23. After the abnormality flag F2b indicating the abnormality of the detected output shaft rotation angle value θ2b is set to “1”, the process proceeds to step S24.
In step S24, a rotation angle calculation process for calculating the input shaft rotation angle θ1 and the output shaft rotation angle θ2 based on the normal rotation angle is executed, and then the timer interrupt process is terminated and the process returns to the predetermined main program.

In this rotation angle calculation process, as shown in FIG. 4, first, in step S31, it is determined whether both of the abnormality flags F1a and F1b are reset to “0”, and F1a = 0 and F1b = 0. Sometimes, it is determined that both the detected input shaft rotation angle values θ1a and θ1b are normal, and the process proceeds to step S32. In step S32, the average value calculation of the following equation (2) is performed to calculate the input shaft rotation angle θ1, and the calculated input shaft rotation angle θ1 is updated to an input shaft rotation angle storage area formed in a storage device such as a RAM. After storing, the process proceeds to step S38.
θ1 = (θ1a + θ1b) / 2 (2)

If the determination result in step S31 is not F1a = 0 and F1b = 0, the process proceeds to step S33, where it is determined whether the abnormality flag F1a = 0 and F1b = 1, and the input shaft rotation angle is detected. When the value θ1a is reset to “0” and the input shaft rotation angle detection value θ1b is set to “1”, it is determined that only the input shaft rotation angle detection value θ1a is normal, and the process proceeds to step S34.
In this step S34, the detected normal input shaft rotation angle value θa is determined as the input shaft rotation angle θ1, and the determined input shaft rotation angle θ1 is updated and stored in the aforementioned input shaft rotation angle storage area, and then the process proceeds to step S38. To do.

If the determination result in step S33 is not the abnormality flag F1a = 0 and the abnormality flag F1b = 1, the process proceeds to step S35, where it is determined whether the abnormality flag F1a = 1 and F1b = 0. When only the flag F1a is set to “1” and the abnormality flag F1b is reset to “0”, it is determined that only the detected input shaft rotation angle value θ1a is normal, and the process proceeds to step S36.
In this step S36, the normal input shaft rotation angle detected value θ1b is determined as the input shaft rotation angle θ1, and the determined input shaft rotation angle θ1 is updated and stored in the above-described input shaft rotation angle storage area, and will be described later in step S38. Migrate to

  Further, when the determination result in step S35 is not the abnormality flag F1a = 1 and the abnormality flag F1b = 0, it is determined that both the input shaft rotation angle detection values θ1a and θ1b are abnormal, and the process proceeds to step S37, where the steering angle θs is determined as the input shaft rotation angle θ1, the determined input shaft rotation angle θ1 is updated and stored in the input shaft storage area described above, and then the process proceeds to step S38 described later.

In step S38, it is determined whether or not the abnormality flags F2a and F2b are both reset to “0”. When F2a = 0 and F2b = 0, both output shaft rotation angle detection values θ2a and θ2b are normal. Determination is made and the process proceeds to step S39. In step S39, the average value calculation of the following equation (3) is performed to calculate the output shaft rotation angle θ2, and the calculated output shaft rotation angle θ2 is updated to an output shaft rotation angle storage area formed in a storage device such as a RAM. After the storage, the subroutine process is terminated and the process returns to the process of FIG. 3, the timer interrupt process is terminated and the process returns to the predetermined main program.
θ2 = (θ2a + θ2b) / 2 (3)

If the determination result of step S38 is not F2a = 0 and F2b = 0, the process proceeds to step S40 to determine whether or not the abnormality flag F2a = 0 and F2b = 1, and the abnormality flag F2a is “ When the flag is reset to 0 and the abnormality flag F2b is set to “1”, it is determined that only the output shaft rotation angle detection value θ2 is normal, and the process proceeds to step S41.
In this step S41, the normal output shaft rotation angle detected value θ2a is determined as the output shaft rotation angle θ2, the determined output shaft rotation angle θ2 is updated and stored in the input shaft rotation angle storage area, and the subroutine processing is terminated. Then, the process returns to the process shown in FIG. 3, the timer interrupt process is terminated, and the process returns to the predetermined main program.

If the determination result in step S40 is not the abnormality flag F2a = 0 and the abnormality flag F2b = 1, the process proceeds to step S35, where it is determined whether the abnormality flag F2a = 1 and F2b = 0. When the flag F2a is set to “1” and the abnormality flag F2b is reset to “0”, it is determined that only the detected output shaft rotation angle value θ2b is normal, and the process proceeds to step S42.
In this step S42, the detected normal output shaft rotation angle value θ2b is determined as the output shaft rotation angle θ2, the determined output shaft rotation angle θ2 is updated and stored in the output shaft rotation angle storage area, and the subroutine processing is terminated. Then, the process returns to the process shown in FIG. 3, the timer interrupt process is terminated, and the process returns to the predetermined main program.

  Further, when the determination result in step S42 is not the abnormality flag F2a = 1 and the abnormality flag F2b = 0, it is determined that both the output shaft rotation angle detection values θ2a and θ2b are abnormal, and the process proceeds to step S44, where the motor rotation A value θm * Gr obtained by multiplying the angle θm by the gear ratio Gr of the reduction gear mechanism 11 is determined as an output shaft rotation angle θ2, and the determined output shaft rotation angle θ2 is updated and stored in the output shaft storage area described above, and then subroutine processing is performed. 3 is finished and the process returns to the process of FIG.

  Further, the steering assist control device executes a steering assist control process shown in FIG. 5 corresponding to the steering assist control means 20c. This steering assist control process is executed as a main program. First, in step S51, 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 S52. It shifts and the vehicle speed detection value Vs is read. Next, the process proceeds to step S53, and a steering assist command value calculation map that represents 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 the vehicle speed detection value V. After referring to the calculation of the steering assist current command value Iref, the process proceeds to step S54.

In this step S54, the motor current detection value Imd detected by the motor current detection circuit 21 is read, and then the process proceeds to step S55, where the current deviation ΔI is calculated by subtracting the motor current detection value Imd from the steering assist current command value Iref. Then, the process proceeds to step S56.
In step S56, 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 S57 where a pulse width modulation process is performed based on the voltage command value Vmt. A switching signal is formed, and then the process proceeds to step S58, 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 S51.

Next, the operation of the above embodiment will be described.
The input shaft rotation angle detection values θ1a and θ1b detected by the input shaft rotation angle sensor 15 constituting the torque sensor 14 and the output shaft rotation angle detection values θ2a and θ2b detected by the output shaft rotation angle sensor 16 are normal. Then, in the sensor abnormality detection process of FIG. 3 executed by the steering assist control device 20, the abnormality flags F1a, F1b and F2a, F2b are all cleared to “0”. In the subroutine process of FIG. The average value of the input shaft rotation angle detected values θ1a and θ1b is calculated as the input shaft rotation angle θ1 by performing the calculation of equation (2), and the calculated input shaft rotation angle θ1 is updated and stored in the input shaft rotation angle storage area. . In step S39, the calculation of the expression (3) is performed to calculate the average value of the detected output shaft rotation angle values θ2a and θ2b as the output shaft rotation angle θ2, and the calculated lower output shaft rotation angle 2 is stored as the output shaft rotation angle. It is updated and stored in the area.

  Therefore, in the torque detection process of FIG. 2, the input shaft rotation angle θ1 stored in the input shaft rotation angle storage area and the output shaft rotation angle θ2 stored in the output shaft rotation angle storage area are read (step S1). Subsequently, based on the input shaft rotation angle θ1 and the output shaft rotation angle θ2, the calculation of the equation (1) is performed to calculate a torque detection value T (step S2), and the calculated steering torque T is stored in the steering torque of the memory. The update is stored in the area (step S3).

  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 S51 and S52), 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 S53), and then The motor current detection value Imd detected by the motor current detection circuit 21 is read (step S54), and the motor current detection value Imd is subtracted from the steering assist current command value Iref to calculate a current deviation ΔI (step S55).

  The calculated current deviation ΔI is subjected to PI control processing to calculate a voltage command value Vt (step S56). Based on the calculated voltage command value Vt, pulse width modulation processing is performed to form a switching signal (step S57). By outputting the switched signal to the motor drive circuit 22 (step S58), the motor drive circuit 22 rotates the electric motor 12 to generate a steering assist force corresponding to the detected torque 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 sensor 15 constituting the torque sensor 14 and the output shaft rotation angle detection values θ2a and θ2b detected by the output shaft rotation angle sensor 16 are read.

  The input shaft rotation angle detection values θ1a and θ1b detected by the input shaft rotation angle sensor 15 and the steering angle 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 sensor 15. By comparing with θs, it is possible to detect an abnormality in the input shaft rotation angle detection values θ1a and θ1b. That is, since the input shaft rotation angle sensor 15 and the steering angle sensor 13 detect the same rotation angle of the input shaft 2a and have a correlation with each other, the input shaft rotation angle detection values θ1a and θ12, the steering angle θs, and The rotation angle difference between 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 detection value θ1a (or the input shaft rotation angle detection value θ1b) is set in advance. When it is less than the allowable value Δθp1, it can be determined that the detected input shaft rotation angle value θ1a (or the detected input shaft rotation angle value θ1b) 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, the input shaft rotation angle detection value θ1a (or input shaft rotation angle detection value θ2a) is set. It can be determined that an abnormality such as a short circuit or disconnection has occurred. When an abnormality in the detected input shaft rotation angle value θ1a (or θ1b) is detected, the abnormality flag Fθ1a (or Fθ1b) is set to “1”.

  Similarly, the output shaft rotation angle sensor 16 detects the rotation angle of the output shaft 2c and is calculated based on the sine wave signal Vsin and the cosine wave signal Vcos output from the resolver 17 built in the electric motor 12. Since the electric motor 12 is connected to the output shaft 2c via the reduction gear mechanism 11, θm is the rotation of the output shaft of the output shaft 2c by considering the gear ratio Gr of the reduction gear mechanism 11 to the motor rotation angle θm. The angle can be converted into an estimated value θ2m (= θm * Gr).

Therefore, the output shaft rotation angle detection values θ2a and θ2b detected by the output shaft rotation angle sensor 16 and the motor rotation angle detection value θm output from the resolver 17 have a correlation with each other, and the output shaft rotation angle estimated value θ2m. And the rotation angle difference between the detected output shaft rotation angle values θ2a and θ2b output from the output shaft rotation angle sensor 16 are within the range of the mounting error.
Therefore, the absolute value | θ2a−θ2m | (or | θ2b−θ2m |) of the rotation angle difference obtained by subtracting the output shaft rotation angle estimated value θ2m from the output shaft rotation angle detection value θ2a (or θ2b) is a preset allowable value. When it is less than Δθp2, it can be determined that the detected output shaft rotation angle value θ2a (or θ2b) 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, the output shaft rotation angle detection value θ2a (or θ2b) is abnormal such as short circuit or disconnection. It can be determined that this has occurred.

When an abnormality of the detected output shaft rotation angle value θ2a (or θ2b) is detected, the abnormality flag Fθ2a (or Fθ2b) is set to “1”.
Then, when an abnormality occurs in any of the input shaft rotation angle detection values θ1a and θ1b detected by the input shaft rotation angle sensor 15 and the output shaft rotation angle detection values θ2a and θ2b detected by the output shaft rotation angle sensor 16, it corresponds. Since any one of the abnormality flags Fθ1a, Fθ1b, Fθ2a, and Fθ2b is set to “1”, it is possible to instantaneously determine which rotation angle detection value has occurred. Therefore, the input shaft rotation angle θ1 and the output shaft rotation angle θ2 can be calculated without using the rotation angle detection value in which an abnormality is detected, and these input shaft rotation angle θ1 and output shaft rotation angle θ2 are used. Since the torque detection value T is calculated, the normal torque detection value T can be calculated.

  As described above, according to the above embodiment, the abnormality in the output signals of the input shaft rotation angle sensor 15 and the output shaft rotation angle sensor 16 is incorporated in the steering angle θs detected by the steering sensor 13 having a correlation therewith and the electric motor 12. Output shaft rotation angle estimated value θ2m based on motor rotation angle θm detected by resolver 17, input shaft rotation angle detection values θ1a and θ1b detected by input shaft rotation angle sensor 15, and output shaft rotation angle sensor 16 By comparing the output shaft rotation angle detection values θ2a and θ2b, it is possible to detect immediately and accurately.

In the above embodiment, the case where the input shaft rotation angle θ1 and the output shaft rotation angle θ2 are calculated as average values of the input shaft rotation angle detection values θ1a and θ1b and the output shaft rotation angle detection values θ2a and θ2b, respectively, has been described. However, the present invention is not limited to this, and the input shaft rotation angle θ1 calculated in step S32 may be θ1 = θ1a + θ1b, and the output shaft rotation angle θ2 calculated in step S39 may be θ2 = θ2a + θ2b.
In the above-described embodiment, the case where the input shaft rotation angle sensor 15 and the output shaft rotation angle sensor 16 are configured to include a rotary encoder has been described. However, the present invention is not limited to this, and other devices such as a resolver, a potentiometer, etc. Any rotation angle sensor 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, 15 ... input shaft rotation angle sensor, 16 ... 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

Claims (6)

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 steering angle based on the steering angle detected value detected by the detection means detects an abnormality of the input shaft rotation angle sensor, detects the abnormality of the output shaft rotation angle sensor based on the motor rotation angle detection value detected by the resolver An electric power steering apparatus comprising a sensor abnormality detecting means for outputting.   2. The electric power steering apparatus according to claim 1, wherein the sensor abnormality detection unit detects a sensor abnormality when a rotation angle deviation between rotation angle detection values having a correlation with each other exceeds a predetermined value. .   The electric motor according to claim 1, wherein each of the input shaft rotation angle sensor and the output shaft rotation angle sensor is configured to calculate and output an angle value corresponding to a rotation angle. Power steering device.   The sensor abnormality detection means calculates an angle deviation between an angle value output from the input shaft rotation angle sensor and a steering angle detection value detected by the steering angle detection means, and the calculated angle deviation becomes a predetermined value or more. The electric power steering apparatus according to claim 3, wherein the angle value is determined to be abnormal when the operation is started.   The sensor abnormality detection means calculates an angle deviation between the angle value output from the output shaft rotation angle sensor and a motor rotation angle detection value detected by the resolver, and the calculated angle deviation becomes a predetermined value or more. 4. The electric power steering apparatus according to claim 3, wherein the angle value is sometimes determined to be abnormal.   A vehicle comprising the electric power steering device according to any one of claims 1 to 5.

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