Electric power steering device

Abstract

To provide an electric power steering device in which a steering torque is detected by first and second torque sensors, a rotation angle of a motor that applies a steering assist force is detected by first and second rotation angle sensors, the first torque sensor and the first rotation angle sensor share a common power source and the second torque sensor and the second rotation angle sensor share the common power source, the electric power steering device being designed to achieve smooth sensor switching for controlling the motor when any anomaly is detected in these sensors.SOLUTION: When an anomaly in a first torque sensor 10a or a first rotation angle sensor 12a is detected, a switching control unit (26, 32, 35, 36, 44, 45) turns off a first power supply 20 after a motor control unit 25 switches a selected steering torque Th and a selected rotation angle θm, which are to be used for controlling drive of a motor 11, from a first steering torque Th1 and a first rotation angle θm1 to a second steering torque Th2 and a second rotation angle θm2, respectively.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric power steering device. [Background technology]

[0002] The electric power steering device described in Patent Document 1 has a redundant configuration in which a first torque sensor and a second torque sensor each detect a steering torque applied to a steering shaft of a vehicle, and a redundant configuration in which a first rotation angle sensor and a second rotation angle sensor each detect a motor rotation angle of a motor that applies a steering assist force to a steering mechanism of the vehicle. When an abnormality is detected in the first torque sensor, the sensor for detecting the steering torque used for controlling the motor is switched from the first torque sensor to the second torque sensor, and when an abnormality is detected in the first rotation angle sensor, the sensor for detecting the motor rotation angle used for controlling the motor is switched from the first rotation angle sensor to the second rotation angle sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-22801 Summary of the Invention [Problem to be solved by the invention]

[0004] In the redundant configuration of Patent Document 1, when an abnormality is detected in the first torque sensor, the power supply that supplies power to the first torque sensor is turned off, thereby preventing further damage caused by power supply to the failed sensor. The same applies when an abnormality is detected in the first rotation angle sensor. On the other hand, by having the first torque sensor and the first rotation angle sensor share a common first power supply and the second torque sensor and the second rotation angle sensor share a common second power supply, the number of required power supply circuits can be reduced, thereby reducing costs.

[0005] However, if the first torque sensor and the first rotation angle sensor share a common first power supply, turning off the first power supply in response to an abnormality in the first torque sensor will prevent a normal motor rotation angle signal from being obtained from the first rotation angle sensor.Similarly, turning off the first power supply in response to an abnormality in the first rotation angle sensor will prevent a normal steering torque signal from being obtained from the first torque sensor.

[0006] The present invention has been made in light of the above-mentioned problems, and has an object to smoothly switch the sensor used to control the motor when an abnormality is detected in an electric power steering device in which a first torque sensor and a second torque sensor detect steering torque, a first rotational angle sensor and a second rotational angle sensor detect the rotational angle of a motor that provides steering assist force, the first torque sensor and the first rotational angle sensor share a common power supply, and the second torque sensor and the second rotational angle sensor share a common power supply. [Means for solving the problem]

[0007] In order to achieve the above object, an electric power steering device according to one aspect of the present invention includes a first torque sensor and a second torque sensor each detecting a steering torque applied to a steering shaft of a vehicle, a motor that applies a steering assist force to a steering mechanism of the vehicle, a first rotation angle sensor and a second rotation angle sensor each detecting a rotation angle of a motor rotating shaft of the motor, and a selected steering torque that is a selected one of the first steering torque detected by the first torque sensor and the second steering torque detected by the second torque sensor, and a first rotation angle detected by the first rotation angle sensor and a second rotation angle detected by the second rotation angle sensor. the first power source supplying power to the first torque sensor and the first rotation angle sensor; a second power source supplying power to the second torque sensor and the second rotation angle sensor; and a switching control unit which, when an abnormality is detected in the first torque sensor or the first rotation angle sensor, switches the selected steering torque and selected rotation angle used by the motor control unit to control the drive of the motor from the first steering torque and the first rotation angle to the second steering torque and the second rotation angle, respectively, and then turns off the first power source. Effect of the Invention

[0008] According to the present invention, in an electric power steering device in which a first torque sensor and a second torque sensor each detect steering torque, a first rotational angle sensor and a second rotational angle sensor each detect the rotational angle of a motor that provides steering assist force, the first torque sensor and the first rotational angle sensor share a common power supply, and the second torque sensor and the second rotational angle sensor share a common power supply, if an abnormality is detected in any of these sensors, the sensor used to control the motor can be smoothly switched. [Brief description of the drawings]

[0009] [Figure 1] 1 is a configuration diagram showing an overview of an example of an electric power steering device according to an embodiment; [Diagram 2] 2 is a block diagram showing an example of a functional configuration of a torque sensor signal processing unit in FIG. 1. [Diagram 3]2 is a block diagram showing an example of a functional configuration of a rotation angle sensor signal processing unit in FIG. 1. [Figure 4] 4 is an explanatory diagram of an example of a method for determining a motor rotation angle by the abnormality determination unit in FIG. 3. [Diagram 5] 6(a) to 6(h) are diagrams illustrating an example of an FOP process when an abnormality occurring in the first torque sensor is detected. [Figure 6] 13(a) to 13(h) are diagrams illustrating an example of an FOP process when an abnormality occurring in the first rotation angle sensor is detected. [Figure 7] 13(a) to 13(h) are diagrams illustrating an example of an FOP process when an abnormality occurs in the first power supply IC. [Figure 8] 2 is a block diagram showing an example of a functional configuration of a motor control unit in FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. The embodiments of the present invention described below are merely examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the configuration, arrangement, etc. of the components to those described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims.

[0011] (composition) 1 is a configuration diagram showing an outline of an example of an electric power steering device according to an embodiment. The electric power steering device 1 according to the embodiment is an EPS (Electric Power Steering) device that controls a motor 11 to apply torque (i.e., steering assist force) to a steering shaft 3. In an electric power steering device 1 according to this embodiment, as shown in FIG. 1, a steering shaft 3 of a steering wheel 2 is connected to steered wheels 9L, 9R via a reduction gear 4, universal joints 5a and 5b, a rack and pinion mechanism 6, tie rods 7a, 7b, and further via hub units 8a, 8b.

[0012] A torque sensor unit 10 for detecting steering torque Th of the steering wheel 2 is attached to the steering shaft 3 on the steering wheel 2 side, and a motor 11 for generating an assist torque (i.e., steering assist force) that assists steering is connected to the rack and pinion mechanism 6 side of the steering shaft 3 via a reduction gear 4. A rotation angle sensor unit 12 for detecting a motor rotation angle θm, which is a rotation angle of a motor rotating shaft 11a of the motor 11, is attached to the motor 11. Output signals of the torque sensor unit 10 and the rotation angle sensor unit 12 are output to a controller 13 (ECU: Electronic Control Unit) for controlling the electric power steering device 1.

[0013] The torque sensor unit 10 includes a first torque sensor 10a and a second torque sensor 10b. The first torque sensor 10a and the second torque sensor 10b may be, for example, individual sensor integrated circuits (ICs). The steering shaft 3 has a structure in which a first member 3a on the steering wheel 2 side and a second member 3b on the rack and pinion mechanism 6 side are connected via a torsion bar 3c. A multi-pole magnet 10c, in which N poles and S poles are arranged alternately in the circumferential direction, is attached to the outer circumferential surface on the lower end side of the first member 3a.

[0014] The first torque sensor 10a and the second torque sensor 10b are disposed around the multi-pole magnet 10c so that the strength of the magnetic field applied to the first torque sensor 10a and the second torque sensor 10b by the multi-pole magnet 10c changes when the steering torque Th is input to the first member 3a and the torsion bar 3c is twisted. The first torque sensor 10a and the second torque sensor 10b each output a signal corresponding to the strength of the magnetic field applied by the multi-pole magnet 10c. That is, the first torque sensor 10a and the second torque sensor 10b each output a signal corresponding to the magnetic flux density that changes according to the steering torque Th input to the first member 3a. The output signals of the first torque sensor 10a and the second torque sensor 10b are output to the controller 13.

[0015] The rotation angle sensor unit 12 includes a first rotation angle sensor 12a, a second rotation angle sensor 12b, and a third rotation angle sensor 12c. A multi-pole magnet 12d is attached to the tip of the motor shaft 11a of the motor 11. The first rotation angle sensor 12a, the second rotation angle sensor 12b, and the third rotation angle sensor 12c are arranged around the multi-pole magnet 12d so that when the motor 11 is driven and the motor shaft 11a is rotated, the strength of the magnetic field applied to the first rotation angle sensor 12a, the second rotation angle sensor 12b, and the third rotation angle sensor 12c by the multi-pole magnet 12d changes.

[0016] The first rotation angle sensor 12a outputs a first sine signal SIN1 and a first cosine signal COS1 according to the strength of the magnetic field applied by the multi-pole magnet 12d. Similarly, the second rotation angle sensor 12b outputs a second sine signal SIN2 and a second cosine signal COS2 according to the strength of the magnetic field applied by the multi-pole magnet 12d. The third rotation angle sensor 12c outputs a third sine signal SIN3 and a third cosine signal COS3 according to the strength of the magnetic field applied by the multi-pole magnet 12d. That is, each of the first rotation angle sensor 12a, the second rotation angle sensor 12b, and the third rotation angle sensor 12c outputs a signal according to the magnetic flux density that changes according to the motor rotation angle θm. The output signals of the first rotation angle sensor 12a, the second rotation angle sensor 12b, and the third rotation angle sensor 12c are output to the controller 13.

[0017] Motor 11 is a three-phase brushless motor having a stator, a rotor, and a shaft. The rotor is housed inside the stator and rotatably supported by the shaft. The rotor has a permanent magnet attached to its surface and has magnetic poles. The stator has protruding portions that protrude radially inward at predetermined angles, and a U-phase coil, a V-phase coil, and a W-phase coil are wound around these protruding portions. Motor 11 may be a dual three-phase brushless motor having two winding sets, or a three-phase brushless motor having three or more winding sets.

[0018] The controller 13 is an electronic control unit (ECU) that calculates a current command value corresponding to an assist torque that assists steering based on the output signal of the torque sensor unit 10, the output signal of the rotation angle sensor unit 12, and the vehicle speed Vh detected by the vehicle speed sensor 14, and controls the current supplied to the motor 11 based on the calculated current command value.

[0019] The controller 13 includes, for example, a computer including a processor and a storage device, a power supply that supplies power to the torque sensor unit 10 and the rotation angle sensor unit 12, and a drive circuit for the motor 11 (for example, an inverter circuit). The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The storage device may include any one of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may include a register, a cache memory, a ROM (Read Only Memory) used as a main storage device, and a RAM (Random Access Memory), etc.

[0020] The functions of the controller 13 described below are realized, for example, by the processor of the controller 13 executing a computer program stored in a storage device. The controller 13 may be formed of dedicated hardware for executing each information processing described below. For example, the controller 13 may include a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the controller 13 may have a programmable logic device (PLD) such as a field programmable gate array (FPGA).

[0021] The controller 13 includes a first power supply IC 20, a second power supply IC 21, a third power supply IC 22, a torque sensor signal processing unit 23, a rotation angle sensor signal processing unit 24, a motor control unit 25, and a safety control manager . The first power supply IC20 supplies power to the first torque sensor 10a and the first rotation angle sensor 12a. That is, the first torque sensor 10a and the first rotation angle sensor 12a share a common first power supply IC20. The second power supply IC21 supplies power to the second torque sensor 10b and the second rotation angle sensor 12b. That is, the second torque sensor 10b and the second rotation angle sensor 12b share a common second power supply IC21. The third power supply IC22 supplies power to the third rotation angle sensor 12c.

[0022] The torque sensor signal processing unit 23 calculates the detection value of the steering torque Th input to the steering wheel 2 (i.e., the steering torque input to the steering shaft 3) as a first steering torque Th1 based on the output signal of the first torque sensor 10a. Also, the torque sensor signal processing unit 23 calculates the detection value of the steering torque Th input to the steering wheel 2 as a second steering torque Th2 based on the output signal of the second torque sensor 10b. The torque sensor signal processor 23 selects either the first steering torque Th1 or the second steering torque Th2, and outputs it as a selected steering torque Th to the motor control unit 25. The torque sensor signal processor 23 will be described in detail later.

[0023] The rotation angle sensor signal processing unit 24 calculates the detection value of the motor rotation angle θm as a first rotation angle θm1 based on the output signal of the first rotation angle sensor 12a. Also, the detection value of the motor rotation angle θm is calculated as a second rotation angle θm2 based on the output signal of the second rotation angle sensor 12b. The rotation angle sensor signal processing unit 24 selects one of the first rotation angle θm1 and the second rotation angle θm2, and outputs it to the motor control unit 25 as the selected rotation angle θm. The rotation angle sensor signal processing unit 24 will be described in detail later. The output signal of the third rotation angle sensor 12c is used to detect abnormalities in the first rotation angle sensor 12a and the second rotation angle sensor 12.

[0024] The motor control unit 25 calculates a current command value corresponding to an assist torque that assists steering based on the vehicle speed Vh detected by the vehicle speed sensor 14, the selected steering torque Th, and the selected rotation angle θm, and controls the current supplied to the motor 11 based on the calculated current command value. The motor control unit 25 will be described in detail later.

[0025] The safety control manager 26 performs a fail operation (FOP) in which a device in which an abnormality has occurred is prohibited from operating and a normal device continues to function in a redundant configuration formed by a combination of the first torque sensor 10a, the first rotation angle sensor 12a, and the first power supply IC 20 and a combination of the second torque sensor 10b, the second rotation angle sensor 12b, and the first power supply IC 21.

[0026] When the torque sensor signal processing unit 23 detects an abnormality occurring in the first torque sensor 10a, it outputs a torque sensor diagnosis signal Sdt notifying the detection of the abnormality occurring in the first torque sensor 10a to the safety control manager 26. Upon receiving the torque sensor diagnosis signal Sdt, the safety control manager 26 outputs a switch request signal Ssr requesting to switch the selected rotation angle θm from the first rotation angle θm1 to the second rotation angle θm2 to the rotation angle sensor signal processing unit 24, and then turns off the first power supply IC 20.

[0027] Furthermore, when the torque sensor signal processing unit 23 detects an abnormality occurring in the second torque sensor 10b, it outputs a torque sensor diagnosis signal Sdt notifying the detection of the abnormality occurring in the second torque sensor 10b to the safety control manager 26. Upon receiving the torque sensor diagnosis signal Sdt, the safety control manager 26 outputs a switch request signal Ssr requesting to switch the selected rotation angle θm from the second rotation angle θm2 to the first rotation angle θm1 to the rotation angle sensor signal processing unit 24, and then turns off the second power supply IC 21.

[0028] When the rotation angle sensor signal processing unit 24 detects an abnormality occurring in the first rotation angle sensor 12a, it outputs a rotation angle sensor diagnosis signal Sdr notifying that an abnormality occurring in the first rotation angle sensor 12a has been detected to the safety control manager 26. Upon receiving the rotation angle sensor diagnosis signal Sdr, the safety control manager 26 outputs a switch request signal Sst requesting that the selected steering torque Th be switched from the first steering torque Th1 to the second steering torque Th2 to the torque sensor signal processing unit 23, and then turns off the first power supply IC 20.

[0029] Furthermore, when the rotation angle sensor signal processing unit 24 detects an abnormality occurring in the second rotation angle sensor 12b, it outputs a rotation angle sensor diagnosis signal Sdr notifying the detection of the abnormality occurring in the second rotation angle sensor 12b to the safety control manager 26. Upon receiving the rotation angle sensor diagnosis signal Sdr, the safety control manager 26 outputs a switch request signal Sst requesting to switch the selected steering torque Th from the second steering torque Th2 to the first steering torque Th1 to the torque sensor signal processing unit 23, and then turns off the second power supply IC 21.

[0030] Next, an example of the functional configuration of the torque sensor signal processing unit 23 will be described with reference to Fig. 2. As shown in Fig. 2, the first torque sensor 10a includes a first magnetic detection element 10aa and a second magnetic detection element 10ab for detecting the magnetic field applied by the multi-pole magnet 10c. The second torque sensor 10b includes a third magnetic detection element 10ba and a fourth magnetic detection element 10bb for detecting the magnetic field applied by the multi-pole magnet 10c.

[0031] The first magnetic detection element 10aa, the second magnetic detection element 10ab, the third magnetic detection element 10ba, and the fourth magnetic detection element 10bb are arranged around the multi-pole magnet 10c so that when a steering torque Th is input to the first member 3a and a twist occurs in the torsion bar 3c, the strength of the magnetic field applied to the first magnetic detection element 10aa, the second magnetic detection element 10ab, the third magnetic detection element 10ba, and the fourth magnetic detection element 10bb by the multi-pole magnet 10c changes. The first magnetic detection element 10aa, the second magnetic detection element 10ab, the third magnetic detection element 10ba, and the fourth magnetic detection element 10bb output torsion angle signals St1a, St1b, St2a, and St2b, respectively, according to the strength of the applied magnetic field.

[0032] The torque sensor signal processing unit 23 includes conversion units 30a, 30b, 33a and 33b, average value calculation units (Avr) 30c and 33c, a first torque sensor abnormality judgment unit 31, signal holding units 32 and 35, a second torque sensor abnormality judgment unit 34, a steering torque switching unit 36, and a diagnosis processing unit 37. The conversion units 30a and 30b convert the torsion angles represented by the torsion angle signals St1a and St1b into steering torques Th1a and Th1b, respectively. The average value calculation unit 30c calculates the average value of the steering torques Th1a and Th1b as a first steering torque Th1 and outputs it to the signal holding unit 32.

[0033] The first torque sensor abnormality determination unit 31 determines whether or not an abnormality has occurred in the first torque sensor 10a based on the torsion angle signals St1a and St1b. For example, the first torque sensor abnormality determination unit 31 may determine that an abnormality has occurred in the first torque sensor 10a when a communication abnormality occurs between the first torque sensor 10a and the torque sensor signal processing unit 23. For example, when the first torque sensor 10a transmits the torsion angle signals St1a and St1b to the torque sensor signal processing unit 23 by SENT (Single Edge Nibble Transmission) communication, the first torque sensor abnormality determination unit 31 may determine that an abnormality has occurred in the first torque sensor 10a when an abnormality occurs in the SENT protocol.

[0034] For example, the first torque sensor abnormality determination unit 31 may determine whether or not an abnormality has occurred in the first torque sensor 10a based on the correlation between the torsion angle signal St1a and the torsion angle signal St1b. For example, the first torque sensor abnormality determination unit 31 may determine that an abnormality has occurred in the first torque sensor 10a when the absolute value |St1a-St1b| of the difference between the torsion angle signal St1a and the torsion angle signal St1b exceeds a threshold value.

[0035] The first torque sensor abnormality determination unit 31 outputs an abnormality determination signal Sat1 to the signal holding unit 32, the steering torque switching unit 36, and the diagnosis processing unit 37 when it determines that an abnormality has occurred in the first torque sensor 10a. When the signal holding unit 32 does not receive the abnormality determination signal Sat1, the signal holding unit 32 outputs the first steering torque Th1 received from the average value calculation unit 30c to the steering torque switching unit 36 ​​as is.

[0036] Upon receiving the abnormality determination signal Sat1, the signal holding unit 32 holds the first steering torque Th1 received from the average value calculation unit 30c immediately before receiving the abnormality determination signal Sat1 for a first predetermined time T1. The signal holding unit 32 outputs the held first steering torque Th1 to the steering torque switching unit 36 ​​for the first predetermined time T1 from time t10 when the abnormality determination signal Sat1 is received. That is, the signal holding unit 32 outputs the first steering torque Th1 detected before the detection of the abnormality to the steering torque switching unit 36 ​​for the first predetermined time T1 from time t10 when the abnormality occurring in the first torque sensor 10a is detected. For example, the first predetermined time T1 may be 8 [msec].

[0037] On the other hand, the conversion units 33a and 33b convert the torsion angles represented by the torsion angle signals St2a and St2b into steering torques Th2a and Th2b, respectively. The average value calculation unit 33c calculates the average value of the steering torques Th2a and Th2b as a second steering torque Th2 and outputs it to the signal holding unit 32. The second torque sensor abnormality determination unit 34 determines whether or not an abnormality has occurred in the second torque sensor 10b based on the torsion angle signals St2a and St2b. The method of abnormality determination by the second torque sensor abnormality determination unit 34 may be similar to the method of abnormality determination by the first torque sensor abnormality determination unit 31 based on the torsion angle signals St1a and St1b.

[0038] The second torque sensor abnormality determination unit 34 outputs an abnormality determination signal Sat2 to the signal holding unit 35, the steering torque switching unit 36, and the diagnosis processing unit 37 when it determines that an abnormality has occurred in the second torque sensor 10b. When the signal holding unit 35 does not receive the abnormality determination signal Sat2, the signal holding unit 35 outputs the second steering torque Th2 received from the average value calculation unit 33c to the steering torque switching unit 36 ​​as is.

[0039] Upon receiving the abnormality determination signal Sat2, the signal holding unit 35 holds the second steering torque Th2 received from the average value calculation unit 33c immediately before receiving the abnormality determination signal Sat2 for a first predetermined time T1. The signal holding unit 35 outputs the held second steering torque Th2 to the steering torque switching unit 36 ​​for the first predetermined time T1 from time t20 when the abnormality determination signal Sat2 is received. That is, the signal holding unit 35 outputs the second steering torque Th2 detected before the detection of the abnormality to the steering torque switching unit 36 ​​for the first predetermined time T1 from time t20 when the abnormality occurring in the second torque sensor 10b is detected.

[0040] The steering torque switching unit 36 ​​selects either the first steering torque Th1 output from the signal holding unit 32 or the second steering torque Th2 output from the signal holding unit 35, and outputs it to the motor control unit 25 as a selected steering torque Th. When the steering torque switching unit 36 ​​receives an abnormality determination signal Sat1 indicating that it has been determined that an abnormality has occurred in the first torque sensor 10a while the first steering torque Th1 is being output to the motor control unit 25 as the selected steering torque Th, the steering torque switching unit 36 ​​outputs the first steering torque Th1 held in the signal holding unit 32 as the selected steering torque Th for a first predetermined time T1 from the time t10 at which the abnormality determination signal Sat1 is received (i.e., the time at which the abnormality occurring in the first torque sensor 10a is detected). In other words, the steering torque switching unit 36 ​​outputs the first steering torque Th1 detected before the detection of the abnormality as the selected steering torque Th. If the first torque sensor 10a does not recover to normal even after the first predetermined time T1 has elapsed since the time t10 when the abnormality judgment signal Sat1 was received, and an abnormality in the first torque sensor 10a is confirmed, the steering torque switching unit 36 ​​switches the selected steering torque Th to be output to the motor control unit 25 from the first steering torque Th1 to the second steering torque Th2 at the time t11 when the first predetermined time T1 has elapsed since the time t10.

[0041] If the first torque sensor 10a recovers to normal before the first predetermined time T1 has elapsed from time t10 when the abnormality occurring in the first torque sensor 10a was detected, the signal holding unit 32 stops holding the first steering torque Th1 received before the abnormality was detected in the first torque sensor 10a, and outputs the first steering torque Th1 currently received from the average value calculation unit 30c as is to the steering torque switching unit 36. The steering torque switching unit 36 ​​does not switch the selected steering torque Th to be output to the motor control unit 25 from the first steering torque Th1 to the second steering torque Th2.

[0042] When the steering torque switching unit 36 ​​receives an abnormality determination signal Sat2 indicating that it has been determined that an abnormality has occurred in the second torque sensor 10b while the second steering torque Th2 is being output to the motor control unit 25 as the selected steering torque Th, the steering torque switching unit 36 ​​outputs the second steering torque Th2 held in the signal holding unit 35 as the selected steering torque Th for a first predetermined time T1 from the time t20 when the abnormality determination signal Sat2 is received (i.e., the time when the abnormality occurring in the second torque sensor 10b is detected). In other words, the steering torque switching unit 36 ​​outputs the second steering torque Th2 detected before the detection of the abnormality as the selected steering torque Th. If the second torque sensor 10b does not recover to normal even after the first predetermined time T1 has elapsed from the time t20 when the abnormality judgment signal Sat2 was received, and an abnormality in the second torque sensor 10b is confirmed, the steering torque switching unit 36 ​​switches the selected steering torque Th to be output to the motor control unit 25 from the second steering torque Th2 to the first steering torque Th1 at the time t21 when the first predetermined time T1 has elapsed from the time t20.

[0043] If the second torque sensor 10b recovers to normal before the first predetermined time T1 has elapsed from time t20 when the abnormality occurring in the second torque sensor 10b was detected, the signal holding unit 35 stops holding the second steering torque Th2 received before the abnormality was detected in the second torque sensor 10b, and outputs the second steering torque Th2 currently received from the average value calculation unit 33c as is to the steering torque switching unit 36. The steering torque switching unit 36 ​​does not switch the selected steering torque Th to be output to the motor control unit 25 from the second steering torque Th2 to the first steering torque Th1.

[0044] In addition, when an abnormality is detected in the first rotation angle sensor 12a while the first rotation angle θm1 is being output to the motor control unit 25 as the selected rotation angle θm, the safety control manager 26 outputs a switching request signal Sst to the steering torque switching unit 36 ​​requesting that the selected steering torque Th be switched from the first steering torque Th1 to the second steering torque Th2.

[0045] The steering torque switching unit 36, which has received the switching request signal Sst, switches the selected steering torque Th to be output to the motor control unit 25 from the first steering torque Th1 to the second steering torque Th2 at time t31 when the second predetermined time T2 has elapsed from time t30 when the abnormality occurring in the first rotation angle sensor 12a is detected. The second predetermined time T2 is set to a time longer than the first predetermined time T1. For example, the second predetermined time T2 may be 50 [msec]. For example, the safety control manager 26 may transmit a switching request signal Sst to the steering torque switching unit 36 ​​at a time t31 which is a second predetermined time T2 after a time t30 when an abnormality occurring in the first rotation angle sensor 12a is detected, and the steering torque switching unit 36 ​​may switch the selected steering torque Th immediately after receiving the switching request signal Sst.

[0046] When an abnormality is detected in the second rotation angle sensor 12b while the second rotation angle θm2 is being output to the motor control unit 25 as the selected rotation angle θm, the safety control manager 26 outputs a switching request signal Sst to the steering torque switching unit 36 ​​requesting that the selected steering torque Th be switched from the second steering torque Th2 to the first steering torque Th1.

[0047] The steering torque switching unit 36, which has received the switching request signal Sst, switches the selected steering torque Th to be output to the motor control unit 25 from the second steering torque Th2 to the first steering torque Th1 at time t41 when the second predetermined time T2 has elapsed from time t40 when the abnormality occurred in the second rotation angle sensor 12b was detected. For example, the safety control manager 26 may transmit the switching request signal Sst to the steering torque switching unit 36 ​​at time t41 when the second predetermined time T2 has elapsed from time t40 when the abnormality occurred in the second rotation angle sensor 12b was detected, and the steering torque switching unit 36 ​​may switch the selected steering torque Th immediately after receiving the switching request signal Sst.

[0048] In addition, when the steering torque switching unit 36 ​​is outputting the first steering torque Th1 as the selected steering torque Th and receives a switching request signal Sst requesting to switch the selected steering torque Th from the second steering torque Th2 to the first steering torque Th1, the steering torque switching unit 36 ​​continues the state of outputting the first steering torque Th1 as the selected steering torque Th. Similarly, when the second steering torque Th2 is being output as the selected steering torque Th, if a switching request signal Sst is received requesting that the selected steering torque Th be switched from the first steering torque Th1 to the second steering torque Th2, the state of outputting the second steering torque Th2 as the selected steering torque Th is continued.

[0049] The diagnostic processing unit 37 determines whether the abnormality occurring in the first torque sensor 10a continues based on the abnormality judgment signal Sat1, and if the first torque sensor 10a does not recover to normal even after a second predetermined time T2 has elapsed from the time t10 when the abnormality occurring in the first torque sensor 10a was detected, outputs a torque sensor diagnosis signal Sdt to the safety control manager 26 at a time t12 when the second predetermined time T2 has elapsed from the time t10, notifying that an abnormality occurring in the first torque sensor 10a has been detected. The safety control manager 26, which has received the torque sensor diagnosis signal Sdt, outputs a switching request signal Ssr requesting that the selected rotation angle θm output by the rotation angle sensor signal processing unit 24 be switched from the first rotation angle θm1 to the second rotation angle θm2 at time t12 when the torque sensor diagnosis signal Sdt is received. Also, at time t13 after time t12 when the torque sensor diagnosis signal Sdt is received, the safety control manager 26 turns off the first power supply IC 20.

[0050] In addition, if the first torque sensor 10a recovers to normal before the second predetermined time T2 has elapsed since the time t10 when the abnormality occurring in the first torque sensor 10a is detected and the selected steering torque Th is switched from the first steering torque Th1 to the second steering torque Th2, the diagnosis processing unit 37 does not output the torque sensor diagnosis signal Sdt notifying the detection of the abnormality occurring in the first torque sensor 10a to the safety control manager 26. As a result, the selected rotation angle θm is not switched from the first rotation angle θm1 to the second rotation angle θm2, and the first power supply IC 20 is also maintained on. In this case, the steering torque switching unit 36 ​​does not need to switch the selected steering torque Th to the first steering torque Th1 (i.e., it may continue to output the second steering torque Th2 as the selected steering torque Th).

[0051] In addition, the diagnostic processing unit 37 determines whether the abnormality occurring in the second torque sensor 10b is continuing based on the abnormality judgment signal Sat2, and if the second torque sensor 10b does not recover to normal even after the second predetermined time T2 has elapsed from the time t20 when the abnormality occurring in the second torque sensor 10b was detected, outputs a torque sensor diagnosis signal Sdt to the safety control manager 26 at the time t22 when the second predetermined time T2 has elapsed from the time t20, notifying that an abnormality occurring in the second torque sensor 10b has been detected. The safety control manager 26, which has received the torque sensor diagnosis signal Sdt, outputs a switching request signal Ssr requesting that the selected rotation angle θm output by the rotation angle sensor signal processing unit 24 be switched from the second rotation angle θm2 to the first rotation angle θm1 at time t22 when the torque sensor diagnosis signal Sdt is received. Also, at time t23 after time t22 when the torque sensor diagnosis signal Sdt is received, the safety control manager 26 turns off the second power supply IC 21.

[0052] Furthermore, if the first torque sensor 10a or the second torque sensor 10b does not recover to normal even after a third predetermined time T3 longer than the second predetermined time T2 has elapsed since the time t10 when the abnormality occurred in the first torque sensor 10a or the time t20 when the abnormality occurred in the second torque sensor 10b was detected, the diagnosis processor 37 outputs a warning to the occupant or stores the occurrence of the abnormality in a storage device. For example, the third predetermined time T3 may be 100 [msec].

[0053] Next, an example of the functional configuration of the rotation angle sensor signal processing unit 24 will be described with reference to Fig. 3. As shown in Fig. 3, the first rotation angle sensor 12a, the second rotation angle sensor 12b, and the third rotation angle sensor 12c each include a fifth magnetic detection element 40a, a sixth magnetic detection element 41a, and a seventh magnetic detection element 42a for detecting a magnetic field applied by the multi-pole magnet 12d, respectively. The fifth magnetic detection element 40a, the sixth magnetic detection element 41a, and the seventh magnetic detection element 42a are arranged around the multi-pole magnet 12d so that when the motor 11 is driven and the motor rotating shaft 11a is rotated, the strength of the magnetic field applied to the fifth magnetic detection element 40a, the sixth magnetic detection element 41a, and the seventh magnetic detection element 42a by the multi-pole magnet 12d changes.

[0054] The fifth magnetic detection element 40a outputs a first sine signal SIN1 and a first cosine signal COS1 according to the strength of the magnetic field applied by the multi-pole magnet 12d. Similarly, the sixth magnetic detection element 41a outputs a second sine signal SIN2 and a second cosine signal COS2 according to the strength of the magnetic field applied by the multi-pole magnet 12d. The seventh magnetic detection element 42a outputs a third sine signal SIN3 and a third cosine signal COS3 according to the strength of the magnetic field applied by the multi-pole magnet 12d.

[0055] The rotation angle sensor signal processing unit 24 includes diagnostic mechanical angle calculation units 40b, 41b, and 42b, sensor signal abnormality determination units 40c, 41c, and 42c, an abnormality determination unit 43, a mechanical angle calculation unit 44, an angle estimation unit 45, an angle conversion unit 46, and a diagnostic processing unit 47. The signal holding units 32 and 35 and the steering torque switching unit 36 ​​of the torque sensor signal processing unit 23, the mechanical angle calculation unit 44 and the angle estimation unit 45 of the rotational angle sensor signal processing unit 24, and the safety control manager 26 are examples of a "switching control unit" as defined in the claims.

[0056] The diagnostic mechanical angle calculator 40b calculates a diagnostic mechanical angle θdm1 of the motor rotating shaft 11a based on the first sine signal SIN1 and the first cosine signal COS1. Similarly, the diagnostic mechanical angle calculation units 41b and 42b calculate diagnostic mechanical angles θdm2 and θdm3 of the motor rotating shaft 11a, respectively, based on the second sine signal SIN2 and the second cosine signal COS2 and the third sine signal SIN3 and the third cosine signal COS3. The diagnostic mechanical angles θdm1, θdm2, and θdm3 are output to the abnormality determination unit 43 and are used to detect abnormalities occurring in the first rotation angle sensor 12a, the second rotation angle sensor 12b, and the third rotation angle sensor 12c.

[0057] The sensor signal abnormality determination unit 40c determines whether the first sine signal SIN1 and the first cosine signal COS1 are abnormal. For example, the sensor signal abnormality determination unit 40c may determine whether the first sine signal SIN1 and the first cosine signal COS1 are abnormal by two types of abnormality determination processing. In the first abnormality judgment process, it is determined whether the amplitudes of the first sine signal SIN1 and the first cosine signal COS1 are within a predetermined range, and if the amplitudes of both the first sine signal SIN1 and the first cosine signal COS1 are within the predetermined range, it is determined that the first sine signal SIN1 and the first cosine signal COS1 are normal, and if the amplitude of either one is outside the predetermined range, it is determined that the first sine signal SIN1 and the first cosine signal COS1 are abnormal.

[0058] In the second abnormality judgment process, it is determined whether the sum of squares of the first sine signal SIN1 and the first cosine signal COS1 is within a predetermined range (for example, a range obtained by adding a predetermined margin to the square of the amplitude), and if the sum of squares is within the predetermined range, it is determined that the first sine signal SIN1 and the first cosine signal COS1 are normal, and if the sum of squares is outside the predetermined range, it is determined that the first sine signal SIN1 and the first cosine signal COS1 are abnormal. The sensor signal abnormality determination unit 40c outputs a determination result Sas1 of the abnormality determination of the first sine signal SIN1 and the first cosine signal COS1 to the abnormality determination unit 43 and the diagnosis processing unit 47.

[0059] The sensor signal abnormality determination units 41c and 42c respectively determine whether the second sine signal SIN2 and the second cosine signal COS2, and the third sine signal SIN3 and the third cosine signal COS3 are abnormal or not. The abnormality determination method by the sensor signal abnormality determination units 41c and 42c is similar to the determination method by the sensor signal abnormality determination unit 40c. The sensor signal abnormality judgment units 41c and 42c output the abnormality judgment result Sas2 of the second sine signal SIN2 and the second cosine signal COS2 and the abnormality judgment result Sas3 of the third sine signal SIN3 and the third cosine signal COS3 to the abnormality judgment unit 43 and the diagnostic processing unit 47, respectively.

[0060] The abnormality determination unit 43 determines whether or not an abnormality has occurred in the first rotation angle sensor 12a and the second rotation angle sensor 12b, based on the diagnostic mechanical angles θdm1 to θdm3 and the determination results Sas1 to Sas3. Specifically, the abnormality determination unit 43 determines whether or not the first rotation angle sensor 12a and the second rotation angle sensor 12b are abnormal, based on the difference between the diagnostic mechanical angles θdm1 to θdm3.

[0061] For example, the abnormality determination unit 43 may determine whether the difference between the diagnostic mechanical angles θdm1 and θdm2 is greater than or equal to a predetermined value, whether the difference between the diagnostic mechanical angles θdm2 and θdm3 is greater than or equal to a predetermined value, or whether the difference between the diagnostic mechanical angles θdm1 and θdm3 is greater than or equal to a predetermined value, and may determine whether the first rotation angle sensor 12a, the second rotation angle sensor 12b, and the third rotation angle sensor 12c are abnormal by referring to the table of FIG. 4 which shows the correspondence between these determination results and the states of the first rotation angle sensor 12a, the second rotation angle sensor 12b, and the third rotation angle sensor 12c.

[0062] 3, the abnormality determination unit 43 determines that the first rotation angle sensor 12a is normal when it is determined that the first rotation angle sensor 12a is normal based on the diagnostic mechanical angles θdm1 to θdm3 and the determination result Sas1 of the sensor signal abnormality determination unit 40c is normal. When it is determined that the first rotation angle sensor 12a is abnormal based on the diagnostic mechanical angles θdm1 to θdm3 or the determination result Sas1 of the sensor signal abnormality determination unit 40c is abnormal, an abnormality that has occurred in the first rotation angle sensor 12a is detected. The abnormality determination unit 43 outputs a status signal Saa1 indicating whether the first rotation angle sensor 12a is normal or abnormal to the mechanical angle calculation unit 44, the angle estimation unit 45, and the diagnosis processing unit 47.

[0063] In addition, the abnormality judgment unit 43 judges that the second rotation angle sensor 12b is normal when the second rotation angle sensor 12b is judged to be normal based on the diagnostic mechanical angles θdm1 to θdm3 and the judgment result Sas2 of the sensor signal abnormality judgment unit 41c is normal, and detects an abnormality that has occurred in the second rotation angle sensor 12b when the second rotation angle sensor 12b is judged to be abnormal based on the diagnostic mechanical angles θdm1 to θdm3 or the judgment result Sas2 of the sensor signal abnormality judgment unit 41c is abnormal. The abnormality determination unit 43 outputs a status signal Saa2 indicating whether the second rotation angle sensor 12b is normal or abnormal to the mechanical angle calculation unit 44, the angle estimation unit 45, and the diagnosis processing unit 47.

[0064] The mechanical angle calculation unit 44 calculates a first mechanical angle θmm1, which is the mechanical angle of the motor rotating shaft 11a, based on the first sine signal SIN1 and the first cosine signal COS1. Also, the mechanical angle calculation unit 44 calculates a second mechanical angle θmm2, which is the mechanical angle of the motor rotating shaft 11a, based on the second sine signal SIN2 and the second cosine signal COS2. The angle conversion unit 46 converts the mechanical angle calculated by the mechanical angle calculation unit 44 into an electrical angle and outputs it as a selected rotation angle θm. The first rotation angle θm1 is an electrical angle converted from the first mechanical angle θmm1, and the second rotation angle θm2 is an electrical angle converted from the second mechanical angle θmm2.

[0065] For example, in a state in which the first rotation angle θm1 is output as the selected rotation angle θm, while the status signal Saa1 indicates that the first rotation angle sensor 12a is normal, the mechanical angle calculation unit 44 calculates the first mechanical angle θmm1 based on the first sine signal SIN1 and the first cosine signal COS1, and the angle estimation unit 45 outputs the first mechanical angle θmm1 calculated by the mechanical angle calculation unit 44 as is to the angle conversion unit 46. The angle conversion unit 46 converts the first mechanical angle θmm1 into the first rotation angle θm1, which is an electrical angle, and outputs it as the selected rotation angle θm.

[0066] From this state, when an abnormality occurring in the first rotation angle sensor 12a is detected at time t30 (i.e., when the status signal Saa1 indicates an abnormality in the first rotation angle sensor 12a), the mechanical angle calculation unit 44 continues calculating the first mechanical angle θmm1 and calculates the second mechanical angle θmm2 for angle estimation processing by the subsequent angle estimation unit 45 based on the second sine signal SIN2 and the second cosine signal COS2.

[0067] If the first rotation angle sensor 12a does not recover to normal even after the second predetermined time T2 has elapsed since time t30 and an abnormality in the first rotation angle sensor 12a is confirmed, the mechanical angle calculation unit 44 calculates a second mechanical angle θmm2 based on the second sine signal SIN2 and the second cosine signal COS2 at time t31 when the second predetermined time T2 has elapsed from time t30. The angle estimation unit 45 outputs the second mechanical angle θmm2 calculated by the mechanical angle calculation unit 44 directly to the angle conversion unit 46. The angle conversion unit 46 converts the second mechanical angle θmm2 into a second rotation angle θm2, which is an electrical angle, and outputs it as a selected rotation angle θm.

[0068] The angle estimation unit 45 executes an angle estimation process to estimate the mechanical angle of the motor rotating shaft 11a during the period from time t30 to time t31 when the second predetermined time T2 has elapsed (or, if the first rotation angle sensor 12a has recovered to normal before time t31, during the period from time t30 to when the first rotation angle sensor 12a recovers).

[0069] In the angle estimation process, the first mechanical angle θmm1 calculated by the mechanical angle calculation unit 44 before the abnormality of the first rotation angle sensor 12a is detected is set as an initial value θint, and the amount of change in the second mechanical angle θmm2 from time t30 when the abnormality of the first rotation angle sensor 12a is detected to the present time is added to the initial value θint to calculate an estimated value θest. The angle conversion unit 46 converts the estimated value θest into an electrical angle and outputs it as the selected rotation angle θm. If the first rotation angle sensor 12a recovers to normal before the second predetermined time T2 has elapsed from time t30, the angle estimation unit 45 terminates the angle estimation process and outputs the first mechanical angle θmm1 calculated by the mechanical angle calculation unit 44 as is to the angle conversion unit 46.

[0070] Similarly, in a state in which the second rotation angle θm2 is output as the selected rotation angle θm, while the status signal Saa2 indicates that the second rotation angle sensor 12b is normal, the mechanical angle calculation unit 44 calculates the second mechanical angle θmm2 based on the second sine signal SIN2 and the second cosine signal COS2, and the angle estimation unit 45 outputs the second mechanical angle θmm2 calculated by the mechanical angle calculation unit 44 as is to the angle conversion unit 46. The angle conversion unit 46 converts the second mechanical angle θmm2 into the second rotation angle θm2, which is an electrical angle, and outputs it as the selected rotation angle θm.

[0071] From this state, when an abnormality occurring in the second rotation angle sensor 12b is detected at time t40 (i.e., when the status signal Saa2 indicates an abnormality in the second rotation angle sensor 12b), the mechanical angle calculation unit 44 continues calculating the second mechanical angle θmm2 and calculates the first mechanical angle θmm1 for angle estimation processing by the subsequent angle estimation unit 45 based on the first sine signal SIN1 and the first cosine signal COS1.

[0072] If the second rotation angle sensor 12b does not recover to normal even after the second predetermined time T2 has elapsed since time t40 and an abnormality in the second rotation angle sensor 12b is confirmed, the mechanical angle calculation unit 44 calculates a first mechanical angle θmm1 based on the first sine signal SIN1 and the first cosine signal COS1 at time t41 when the second predetermined time T2 has elapsed from time t40. The angle estimation unit 45 outputs the first mechanical angle θmm1 calculated by the mechanical angle calculation unit 44 directly to the angle conversion unit 46. The angle conversion unit 46 converts the first mechanical angle θmm1 into a first rotation angle θm1, which is an electrical angle, and outputs it as a selected rotation angle θm.

[0073] The angle estimation unit 45 executes an angle estimation process to estimate the mechanical angle of the motor rotating shaft 11a during the period from time t40 to time t41 when the second predetermined time T2 has elapsed (or, if the second rotation angle sensor 12b has recovered to normal before time t41, during the period from time t40 to when the second rotation angle sensor 12b recovers).

[0074] In the angle estimation process, the second mechanical angle θmm2 calculated by the mechanical angle calculation unit 44 before the abnormality of the second rotation angle sensor 12b is detected is set as an initial value θint, and an estimated value θest obtained by adding the amount of change in the first mechanical angle θmm1 from time t40 when the abnormality of the second rotation angle sensor 12b is detected to the current time to the initial value θint is output to the angle conversion unit 46. The angle conversion unit 46 converts the estimated value θest into an electrical angle and outputs it as the selected rotation angle θm. If the second rotation angle sensor 12b recovers to normal before the second predetermined time T2 has elapsed from time t40, the angle estimation unit 45 terminates the angle estimation process and outputs the second mechanical angle θmm2 calculated by the mechanical angle calculation unit 44 as is to the angle conversion unit 46.

[0075] Furthermore, in a state where the first rotation angle θm1 is output as the selected rotation angle θm, when the mechanical angle calculation unit 44 receives a switching request signal Ssr from the safety control manager 26 requesting to switch the selected rotation angle θm from the first rotation angle θm1 to the second rotation angle θm2, the mechanical angle calculation unit 44 calculates the second mechanical angle θmm2 based on the second sine signal SIN2 and the second cosine signal COS2, and the angle estimation unit 45 outputs the second mechanical angle θmm2 calculated by the mechanical angle calculation unit 44 as is to the angle conversion unit 46. The angle conversion unit 46 converts the second mechanical angle θmm2 into the second rotation angle θm2 which is an electrical angle, and outputs it as the selected rotation angle θm.

[0076] Similarly, when the mechanical angle calculation unit 44 receives a switching request signal Ssr from the safety control manager 26 requesting to switch the selected rotation angle θm from the second rotation angle θm2 to the first rotation angle θm1 while the second rotation angle θm2 is being output as the selected rotation angle θm, the mechanical angle calculation unit 44 calculates the first mechanical angle θmm1 based on the first sine signal SIN1 and the first cosine signal COS1, and the angle estimation unit 45 outputs the first mechanical angle θmm1 calculated by the mechanical angle calculation unit 44 as is to the angle conversion unit 46. The angle conversion unit 46 converts the first mechanical angle θmm1 into the first rotation angle θm1, which is an electrical angle, and outputs it as the selected rotation angle θm.

[0077] The diagnostic processing unit 47 determines whether the abnormality occurring in the first rotation angle sensor 12a continues based on the status signal Saa1, and if the first rotation angle sensor 12a does not recover to normal even after a second predetermined time T2 has elapsed from time t30 when the abnormality occurring in the first rotation angle sensor 12a was detected, outputs a rotation angle sensor diagnostic signal Sdr notifying the safety control manager 26 that an abnormality occurring in the first rotation angle sensor 12a has been detected at time t31 when the second predetermined time T2 has elapsed from time t30. The safety control manager 26, which has received the rotation angle sensor diagnosis signal Sdr, outputs a switching request signal Sst requesting switching of the selected steering torque Th from the first steering torque Th1 to the second steering torque Th2 to the steering torque switching unit 36 ​​at time t31 when the rotation angle sensor diagnosis signal Sdr is received. In addition, at time t32 after time t31 when the rotation angle sensor diagnosis signal Sdr is received, the first power supply IC 20 is turned off.

[0078] In addition, the diagnostic processing unit 47 determines whether the abnormality occurring in the second rotation angle sensor 12b continues based on the status signal Saa2, and if the second rotation angle sensor 12b does not recover to normal even after a second predetermined time T2 has elapsed from time t40 when the abnormality occurring in the second rotation angle sensor 12b was detected, outputs a rotation angle sensor diagnostic signal Sdr notifying the safety control manager 26 that an abnormality occurring in the second rotation angle sensor 12b has been detected at time t41 when the second predetermined time T2 has elapsed from time t40. The safety control manager 26, which has received the rotation angle sensor diagnosis signal Sdr, outputs a switching request signal Sst requesting switching of the selected steering torque Th from the second steering torque Th2 to the first steering torque Th1 to the steering torque switching unit 36 ​​at time t41 when the rotation angle sensor diagnosis signal Sdr is received. In addition, at time t42 after time t41 when the rotation angle sensor diagnosis signal Sdr is received, the safety control manager 26 turns off the second power supply IC 21.

[0079] Furthermore, if the first rotation angle sensor 12a or the second rotation angle sensor 12b does not recover to normal even after a third predetermined time T3 longer than the second predetermined time T2 has elapsed since the time t30 when the abnormality occurred in the first rotation angle sensor 12a or the time t40 when the abnormality occurred in the second rotation angle sensor 12b was detected, the diagnosis processing unit 47 outputs a warning to the occupant or stores the occurrence of the abnormality in a storage device. For example, the third predetermined time T3 may be 100 [msec].

[0080] (operation) Below, we will explain the operation when an abnormality occurs in any of the first torque sensor 10a, the first rotation angle sensor 12a, or the first power supply IC 20 while the first steering torque Th1 and the first rotation angle θm1 are selected as the selected steering torque Th and the selected rotation angle θm, respectively, and the motor control unit 25 is controlling the motor 11. 5(a) to 5(h) are diagrams illustrating an example of the FOP process when an abnormality occurring in the first torque sensor 10a is detected.

[0081] Figures 5(a) and 5(b) show the states of the first torque sensor 10a and the second torque sensor 10b. Figure 5(c) shows the value of the steering torque output from the torque sensor signal processing unit 23 as the selected steering torque Th. Figures 5(d) and 5(e) show the states of the first rotation angle sensor 12a and the second rotation angle sensor 12b. Figure 5(f) shows the value of the motor rotation angle output from the rotation angle sensor signal processing unit 24 as the selected rotation angle θm. Figures 5(g) and 5(h) show the states of the first power supply IC 20 and the second power supply 21.

[0082] When an abnormality occurring in the first torque sensor 10a is detected at time t10 in a state in which the first steering torque Th1 is output as the selected steering torque Th, the signal holding unit 32 holds the previous value of the first steering torque Th1 detected before the detection of the abnormality in the first torque sensor 10a from time t10 to time t11 at which a first predetermined time T1 has elapsed. The steering torque switching unit 36 ​​outputs the previous value of the first steering torque Th1 held in the signal holding unit 32 as the selected steering torque Th. At time t11, the steering torque switching unit 36 ​​switches the selected steering torque Th from the first steering torque Th1 to the second steering torque Th2.

[0083] If the first torque sensor 10a does not recover to normal even after the second predetermined time T2 has elapsed from time t10, the diagnostic processing unit 37 outputs a torque sensor diagnostic signal Sdt to the safety control manager 26 at time t12, which is the time when the second predetermined time T2 has elapsed from time t10, to notify that an abnormality has occurred in the first torque sensor 10a. The safety control manager 26 outputs a switch request signal Ssr that requests the selected rotation angle θm output by the rotation angle sensor signal processing unit 24 to be switched from the first rotation angle θm1 to the second rotation angle θm2.

[0084] The mechanical angle calculation unit 44 of the rotational angle sensor signal processing unit 24 calculates a second mechanical angle θmm2 based on the second sine signal SIN2 and the second cosine signal COS2, and the angle conversion unit 46 converts the second mechanical angle θmm2 into a second rotational angle θm2, which is an electrical angle, and outputs it as the selected rotational angle θm. The safety control manager 26 turns off the first power supply IC 20 at time t13, which is after time t12.

[0085] 6(a) to 6(h) are explanatory diagrams of an example of FOP processing when an abnormality occurring in the first rotation angle sensor 12a is detected. FIG. 6(a) and FIG. 6(b) show the states of the first torque sensor 10a and the second torque sensor 10b. FIG. 6(c) shows the value of the steering torque output from the torque sensor signal processing unit 23 as the selected steering torque Th. FIG. 6(d) and FIG. 6(e) show the states of the first rotation angle sensor 12a and the second rotation angle sensor 12b. FIG. 6(f) shows the value of the motor rotation angle output from the rotation angle sensor signal processing unit 24 as the selected rotation angle θm. FIG. 6(g) and FIG. 6(h) show the states of the first power supply IC 20 and the second power supply 21.

[0086] When an abnormality occurring in the first rotation angle sensor 12a is detected at time t30 while the first rotation angle θm1 is being output as the selected rotation angle θm, the angle estimator 45 executes an angle estimation process from time t30 to time t31 when the second predetermined time T2 has elapsed. In the angle estimation process, the first mechanical angle θmm1 calculated by the mechanical angle calculator 44 before the abnormality in the first rotation angle sensor 12a is detected is set as an initial value θint, and an estimated value θest is calculated by adding the amount of change in the second mechanical angle θmm2 from time t30, when the abnormality in the first rotation angle sensor 12a is detected, to the initial value θint. The angle converter 46 converts the estimated value θest into an electrical angle and outputs it as the selected rotation angle θm.

[0087] If the first rotation angle sensor 12a does not recover to normal even after a second predetermined time T2 has elapsed since time t30, the mechanical angle calculation unit 44 calculates a second mechanical angle θmm2 based on the second sine signal SIN2 and the second cosine signal COS2 at time t31. The angle conversion unit 46 converts the second mechanical angle θmm2 into a second rotation angle θm2, which is an electrical angle, and outputs it as a selected rotation angle θm. The diagnosis processing unit 47 outputs a rotation angle sensor diagnosis signal Sdr to the safety control manager 26, notifying that an abnormality has occurred in the first rotation angle sensor 12a has been detected. The safety control manager 26, which has received the rotation angle sensor diagnosis signal Sdr, outputs to the steering torque switching unit 36 ​​a switching request signal Sst requesting that the selected steering torque Th be switched from the first steering torque Th1 to the second steering torque Th2.

[0088] The steering torque switching unit 36 ​​of the torque sensor signal processing unit 23 switches the selected steering torque Th from the first steering torque Th1 to the second steering torque Th2. The safety control manager 26 turns off the first power supply IC 20 at time t32 after time t31 when the safety control manager 26 receives the rotation angle sensor diagnosis signal Sdr.

[0089] 7(a) to 7(h) are explanatory diagrams of an example of FOP processing when an abnormality occurs in the first power supply IC 20. FIGS. 7(a) and 7(b) show the states of the first torque sensor 10a and the second torque sensor 10b. FIG. 7(c) shows the value of the steering torque output from the torque sensor signal processor 23 as the selected steering torque Th. FIGS. 7(d) and 7(e) show the states of the first rotation angle sensor 12a and the second rotation angle sensor 12b. FIG. 7(f) shows the value of the motor rotation angle output from the rotation angle sensor signal processor 24 as the selected rotation angle θm. FIGS. 7(g) and 7(h) show the states of the first power supply IC 20 and the second power supply 21.

[0090] When the first steering torque Th1 is output as the selected steering torque Th and the first rotation angle θm1 is output as the selected rotation angle θm, if an abnormality occurs in the first power supply IC 20 at time t50, normal power will no longer be supplied to the first torque sensor 10a and the first rotation angle sensor 12a, and the abnormality occurring in the first torque sensor 10a and the abnormality occurring in the first rotation angle sensor 12a will be detected.

[0091] From time t50 to time t51 when the first predetermined time T1 has elapsed, the signal holding unit 32 holds the previous value of the first steering torque Th1 detected before the abnormality of the first torque sensor 10a is detected. The steering torque switching unit 36 ​​outputs the previous value of the first steering torque Th1 held in the signal holding unit 32 as the selected steering torque Th. At time t51, the steering torque switching unit 36 ​​switches the selected steering torque Th from the first steering torque Th1 to the second steering torque Th2.

[0092] If the first torque sensor 10a does not recover to normal even after the second predetermined time T2 has elapsed from time t50, the diagnostic processing unit 37 outputs a torque sensor diagnostic signal Sdt to the safety control manager 26 at time t52, which is the time when the second predetermined time T2 has elapsed from time t50, to notify that an abnormality has occurred in the first torque sensor 10a.

[0093] On the other hand, from time t50 to time t52, the angle estimator 45 executes an angle estimation process. In the angle estimation process, the first mechanical angle θmm1 calculated by the mechanical angle calculator 44 before the abnormality of the first rotation angle sensor 12a is detected is set as an initial value θint, and an estimated value θest is calculated by adding the amount of change in the second mechanical angle θmm2 from time t30, when the abnormality of the first rotation angle sensor 12a is detected, to the current time to the initial value θint. The angle converter 46 converts the estimated value θest into an electrical angle and outputs it as the selected rotation angle θm.

[0094] If the first rotation angle sensor 12a does not recover to normal even after a second predetermined time T2 has elapsed since time t50, the mechanical angle calculation unit 44 calculates a second mechanical angle θmm2 based on the second sine signal SIN2 and the second cosine signal COS2 at time t52. The angle conversion unit 46 converts the second mechanical angle θmm2 into a second rotation angle θm2, which is an electrical angle, and outputs it as a selected rotation angle θm. The diagnosis processing unit 47 outputs a rotation angle sensor diagnosis signal Sdr to the safety control manager 26, notifying that an abnormality has occurred in the first rotation angle sensor 12a has been detected. The safety control manager 26 turns off the first power supply IC 20 at time t53 after time t52 when the torque sensor diagnosis signal Sdt and the rotation angle sensor diagnosis signal Sdr are received.

[0095] 8 is a block diagram showing an example of a functional configuration of the motor control unit 25. The motor control unit 25 includes a current command value calculation unit 50, subtractors 51 and 52, a proportional-integral (PI) control unit 53, a two-phase / three-phase conversion unit 54, a command value correction unit 55, a PWM control unit 56, an inverter 57, a three-phase / two-phase conversion unit 58, and an angular velocity conversion unit 59, and drives the motor 11 by vector control. In the attached drawings, the inverter is denoted as "INV."

[0096] The current command value calculation unit 50 calculates a q-axis current command value Iq0 and a d-axis current command value Id0 to be applied to the motor 11 based on the selected steering torque Th, the vehicle speed Vh, the selected rotation angle θm, and the rotation angular velocity ω of the selected rotation angle θm. On the other hand, motor currents i, ib, and ic of the motor 11 are detected by current sensors 60, 61, and 62, respectively. These detected motor currents i, ib, and ic are converted by a three-phase / two-phase converter 58 into currents id, iq of the d-q two axes.

[0097] Subtractors 51 and 52 calculate the q-axis deviation current Δq and the d-axis deviation current Δd by subtracting the fed-back currents iq and id from the q-axis current command value Iq0 and the d-axis current command value Id0, respectively. The q-axis deviation current Δq and the d-axis deviation current Δd are input to a PI control unit 53. The PI control unit 53 calculates voltage command values ​​vq and vd that make the q-axis deviation current Δq and the d-axis deviation current Δd zero, respectively.

[0098] The two-phase / three-phase conversion unit 54 converts the voltage command values ​​vd, vq into an A-phase voltage command value va0, a B-phase voltage command value vb0, and a C-phase voltage command value vc0 for the motor 11, respectively. Hereinafter, the A-phase voltage command value, the B-phase voltage command value, and the C-phase voltage command value are collectively referred to as "three-phase voltage command values." The command value correction unit 55 corrects the three-phase voltage command values ​​va0, vb0, and vc0 to improve the voltage utilization rate, and outputs the corrected three-phase voltage command values ​​va1, vb1, and vc1.

[0099] The PWM control unit 56 generates PWM-controlled gate signals based on the corrected three-phase voltage command values ​​va1, vb1, and vc1. The inverter 57 is driven by the gate signals generated by the PWM control unit 56. The motor 11 is supplied with currents such that the q-axis deviation current Δq and the d-axis deviation current Δd become zero.

[0100] The angular velocity conversion unit 59 calculates the rotational angular velocity ω of the motor rotating shaft 11a of the motor 11 based on the change over time of the selected rotational angle θm. The selected rotational angle θm and the rotational angular velocity ω are input to the current command value calculation unit 50 and used for vector control.

[0101] (Effects of the embodiment) (1) The electric power steering device 1 includes a first torque sensor 10a and a second torque sensor 10b that respectively detect a steering torque applied to a steering shaft 3 of a vehicle, a motor 11 that applies a steering assist force to a steering mechanism of the vehicle, a first rotation angle sensor 12a and a second rotation angle sensor 12b that respectively detect a rotation angle of a motor rotating shaft of the motor 11, and a selected steering torque that is a selected one of the first steering torque detected by the first torque sensor 10a and the second steering torque detected by the second torque sensor 10b, and a selected one of the first rotation angle detected by the first rotation angle sensor 12a and the second rotation angle detected by the second rotation angle sensor 12b. the first torque sensor 10a and the first rotation angle sensor 12a; a second power source 21 that supplies power to the second torque sensor 10b and the second rotation angle sensor 12b; and a switching control unit that, when an abnormality is detected in the first torque sensor 10a or the first rotation angle sensor 12a, switches the selected steering torque and selected rotation angle used by the motor control unit 25 to control the drive of the motor 11 from the first steering torque and the first rotation angle to the second steering torque and the second rotation angle, respectively, and then turns off the first power source 20. As a result, when an abnormality is detected in the first torque sensor 10a or the first rotation angle sensor 12a, the sensor used for drive control of the motor 11 can be smoothly switched to the second torque sensor 10b or the second rotation angle sensor 12b.

[0102] (2) The switching control unit may include a signal holding unit 32 that, when an abnormality occurring in the first torque sensor 10a is detected, holds the first steering torque detected before the abnormality is detected from the time the abnormality is detected until a first predetermined time has elapsed; a steering torque switching unit 36 ​​that selects the first steering torque held in the signal holding unit from the time the abnormality is detected until the first predetermined time has elapsed as a selected steering torque and switches the selected steering torque to the second steering torque after the first predetermined time has elapsed; and a rotation angle calculation unit 44 that calculates the first rotation angle as the selected rotation angle from the time the abnormality is detected until a second predetermined time that is longer than the first predetermined time has elapsed, and calculates the second rotation angle as the selected rotation angle after the second predetermined time has elapsed. In this way, when an abnormality occurring in the first torque sensor 10a is detected, the sensor used for drive control of the motor 11 is switched after a predetermined time has elapsed, so that switching due to erroneous detection of an abnormality can be suppressed.

[0103] (3) When an abnormality occurring in the first rotation angle sensor 12a is detected, the steering torque switching unit 36 ​​switches the selected steering torque from the first steering torque to the second steering torque when a second predetermined time has elapsed since the abnormality was detected, and the rotation angle calculation unit 44 may use the first rotation angle detected before the abnormality was detected as an initial value and add the amount of change in the second rotation angle after the abnormality was detected to the initial value from the time the abnormality was detected until the second predetermined time has elapsed to calculate the selected rotation angle, and may calculate the second rotation angle as the selected rotation angle after the second predetermined time has elapsed. In this way, when an abnormality occurring in the first rotation angle sensor 12a is detected, the sensor used for drive control of the motor 11 is switched after a predetermined time has elapsed, so that switching due to erroneous detection of an abnormality can be suppressed.

[0104] (4) When an abnormality occurs in the first power source 20, the signal holding unit 32 holds the first steering torque detected before the abnormality is detected until a first predetermined time has elapsed from the time the abnormality is detected, the steering torque switching unit 36 ​​selects the first steering torque held in the signal holding unit from the time the abnormality is detected until the first predetermined time has elapsed as the selected steering torque and switches the selected steering torque to the second steering torque at the time the first predetermined time has elapsed, and the rotation angle calculation unit 44 may use the first rotation angle detected before the abnormality is detected as an initial value and calculate the selected rotation angle by adding the amount of change in the second rotation angle after the abnormality is detected to the initial value from the time the abnormality is detected until a second predetermined time has elapsed, and calculate the second rotation angle as the selected rotation angle after the second predetermined time has elapsed. As a result, if an abnormality occurs in the first power supply 20, the sensor used for driving control of the motor 11 can be smoothly switched to the second torque sensor 10b or the second rotation angle sensor 12b. [Explanation of symbols]

[0105] Reference Signs List 1...electric power steering device, 2...steering wheel, 3...steering shaft, 3a...first member, 3b...second member, 3c...torsion bar, 4...reduction gear, 5a, 5b...universal joint, 6...rack and pinion mechanism, 7a, 7b...tie rod, 8a, 8b...hub unit, 9L, 9R...steered wheels, 10...torque sensor unit, 10a...first torque sensor, 10aa...first magnetic detection element, 10ab...second Magnetic detection element, 10b...second torque sensor, 10ba...third magnetic detection element, 10bb...fourth magnetic detection element, 10c...multi-pole magnet, 11...motor, 11a...motor rotating shaft, 12...rotation angle sensor unit, 12a...first rotation angle sensor, 12b...second rotation angle sensor, 12c...third rotation angle sensor, 12d...multi-pole magnet, 13...controller, 14...vehicle speed sensor, 20...first power supply IC, 21...second power supply IC, 22...third power supply IC, 23...torque a torque sensor signal processing unit, 24...rotation angle sensor signal processing unit, 25...motor control unit, 26...safety control manager, 30a, 30b, 33a, 33b...conversion unit, 30c, 33c...average value calculation unit, 31...first torque sensor abnormality determination unit, 32, 35...signal holding unit, 34...second torque sensor abnormality determination unit, 36...steering torque switching unit, 37, 47...diagnosis processing unit, 40a...fifth magnetic detection element, 40b, 41b, 42b...diagnosis mechanical angle calculation unit, 40c , 41c, 42c...sensor signal abnormality determination unit, 41a...sixth magnetic detection element, 42a...seventh magnetic detection element, 43...abnormality determination unit, 44...mechanical angle calculation unit, 45...angle estimation unit, 46...angle conversion unit, 50...current command value calculation unit, 51, 52...subtractor, 53...PI control unit, 54...two-phase / three-phase conversion unit, 55...command value correction unit, 56...PWM control unit, 57...inverter, 58...three-phase / two-phase conversion unit, 59...angular velocity conversion unit, 60, 61, 62...current sensor

Claims

1. a first torque sensor and a second torque sensor each detecting a steering torque applied to a steering shaft of a vehicle; a motor that applies a steering assist force to a steering mechanism of the vehicle; a first rotation angle sensor and a second rotation angle sensor each detecting a rotation angle of a motor shaft of the motor; a motor control unit that drives and controls the motor on the basis of a selected steering torque that is a selected one of a first steering torque detected by the first torque sensor and a second steering torque detected by the second torque sensor, and a selected rotation angle that is a selected one of a first rotation angle detected by the first rotation angle sensor and a second rotation angle detected by the second rotation angle sensor; a first power source that supplies power to the first torque sensor and the first rotation angle sensor; a second power source that supplies power to the second torque sensor and the second rotation angle sensor; a switching control unit that switches the selected steering torque and the selected rotation angle used by the motor control unit for driving control of the motor from the first steering torque and the first rotation angle to the second steering torque and the second rotation angle, respectively, when an abnormality occurring in the first torque sensor or the first rotation angle sensor is detected, and then turns off the first power source; An electric power steering device comprising:

2. The switching control unit is a signal holding unit that holds, when the abnormality occurring in the first torque sensor is detected, the first steering torque detected before the abnormality is detected until a first predetermined time has elapsed from the time the abnormality is detected; a steering torque switching unit that selects the first steering torque held in the signal holding unit from the time when the abnormality is detected until the first predetermined time has elapsed as the selected steering torque, and switches the selected steering torque to the second steering torque when the first predetermined time has elapsed; a rotation angle calculation unit that calculates the first rotation angle as the selected rotation angle from a time point when the abnormality is detected until a second predetermined time period that is longer than the first predetermined time period has elapsed, and calculates the second rotation angle as the selected rotation angle after the second predetermined time period has elapsed; 2. The electric power steering device according to claim 1, further comprising:

3. When the abnormality occurring in the first rotation angle sensor is detected, the steering torque switching unit switches the selected steering torque from the first steering torque to the second steering torque when the second predetermined time has elapsed since the abnormality was detected, the rotation angle calculation unit calculates the selected rotation angle by setting the first rotation angle detected before the detection of the abnormality as an initial value, and adding an amount of change in the second rotation angle after the detection of the abnormality to the initial value from the time the abnormality is detected until the second predetermined time has elapsed, and calculates the second rotation angle as the selected rotation angle after the second predetermined time has elapsed.

3. The electric power steering device according to claim 2.

4. When an abnormality occurs in the first power source, The signal holding unit holds the first steering torque detected before the abnormality is detected, from a time point when the abnormality is detected until the first predetermined time has elapsed, the steering torque switching unit selects the first steering torque held in the signal holding unit from the time when the abnormality is detected until the first predetermined time has elapsed as the selected steering torque, and switches the selected steering torque to the second steering torque when the first predetermined time has elapsed; the rotation angle calculation unit calculates the selected rotation angle by setting the first rotation angle detected before the detection of the abnormality as an initial value, and adding an amount of change in the second rotation angle after the detection of the abnormality to the initial value from the time the abnormality is detected until the second predetermined time has elapsed, and calculates the second rotation angle as the selected rotation angle after the second predetermined time has elapsed.

4. The electric power steering device according to claim 2 or 3.

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