JP4676348B2 - Rotation angle detection device, abnormality detection device, and electric power steering device - Google Patents

Description

  The present invention relates to a rotation angle detection device including a resolver provided in a motor shaft or an engine connected to the shaft, an abnormality detection device thereof, an electric power steering device using the rotation detection device, and the like.

  In servo system control, a rotation angle sensor is required to detect the rotation angle and realize feedback control. Further, in brushless motor control, since it is necessary to energize the motor coil in accordance with the rotation angle of the motor, a rotation angle sensor is required in addition to the servo control system.

  As a rotation angle sensor, a resolver has been widely used because of its environmental resistance resulting from its simple configuration.

  Further, in a servo control system applied to electric power steering or the like, safety and reliability are required, so a failure detection function of the rotation angle detection device is required.

  A resolver digital converter has been developed in order to convert it into a rotation angle based on a signal from a resolver and input it as digital data to a microcomputer or the like.

  Patent Document 1 discloses that a SIN signal and a COS signal that are output signals of a resolver are captured at a pair of symmetrical timings before and after their peak positions.

  With this method, sampling is performed at the timing between the peaks and evenly spaced on both sides of the peak, so that two output signals (SIN signal and COS signal) are both sampled at timing close to the peak position. . Further, an error from the voltage value at the peak position of the sampling value is suppressed and equalized.

  Also, assuming that the detected rotation angle is θ, the sum of squares of detected sin θ and con θ is calculated, and a fluctuation that causes the sum of squares to fall below a predetermined threshold value causes an abnormality such as the resolver output signal harness being disconnected. It is also disclosed to detect.

JP 2000-39337 A (Overall)

  However, in the above technique, an error component is included in the SIN signal and the COS signal of the resolver output signal, and the angle cannot be accurately detected.

  As is clear from FIG. 2C of Patent Document 1, it is ideal that the SIN signal and COS signal of the resolver are taken at the same time at the peak positions, and the signal is shifted at a position shifted from the peak. By taking in, an error component is included.

  In addition, in a control target that requires high reliability, such as an electric power steering system, it is necessary to be able to determine the abnormality of the resolver digital converter used in the main system.

  Furthermore, when an abnormality such as a failure of the resolver digital converter occurs, it is necessary to detect an angle with a level of accuracy that enables a safe backup at a minimum.

  An object of the present invention is to provide a rotation angle detection device capable of highly accurate angle detection from an output signal of a resolver.

  Another object of the present invention is to enable safe backup in a rotation angle detection device having a slave system that performs second angle detection in addition to a master system that performs first angle detection from an output signal of a resolver. It is to realize a subordinate angle detection with accuracy.

  Still another object of the present invention is to back up by a secondary rotation angle detection device that performs the second angle detection when the angle detection of the main system is abnormal, and to extend the life of the target system.

  In a preferred embodiment of the present invention, an excitation signal generation unit that generates an AC excitation signal and a rotation shaft are attached, and the excitation signal is input, amplitude-modulated according to the rotation angle of the rotation shaft, and output. A resolver, an AD conversion unit that converts an analog output signal of the resolver into a digital signal, and a main system that inputs the digital output signal of the AD conversion unit and outputs a first rotation angle signal to a control device to be controlled In a rotation angle detection apparatus comprising a calculation unit and a second calculation unit that inputs an analog output signal of the resolver and the excitation signal and outputs a second rotation angle signal, the second calculation unit includes the second calculation unit, A period measurement unit that sequentially measures the period of the excitation signal, and an AD conversion timing signal that generates an AD conversion timing signal that AD converts the analog output signal of the resolver based on the period measurement result. It provided with a command unit.

  Further, in a preferred embodiment of the present invention, in the abnormality detection device of the rotation angle detection device provided with an abnormality detection unit for detecting an abnormality of the output signal of the resolver, the second calculation unit includes a period of the excitation signal. A period measurement unit that sequentially measures, an AD conversion command unit that generates an AD conversion timing signal based on the period measurement result, and a sample holder that samples and holds the output signal of the resolver according to the AD conversion timing signal .

  Further, in a preferred embodiment of the present invention, an offset amount calculation unit that calculates an offset amount of the period of the output signal of the resolver based on a period measurement result of the period measurement unit, and the period measurement based on the offset amount A correction unit for correcting the result is provided, and the AD conversion command unit is configured to generate an AD conversion timing signal based on the corrected period measurement result.

  A desirable control target of the present invention is an electric power steering or a motor control system called a by-wire system by electrically transmitting a signal.

  According to a preferred embodiment of the present invention, it is possible to provide a rotation angle detection device capable of highly accurate angle detection from an output signal of a resolver.

  In addition, according to a preferred embodiment of the present invention, in a rotation angle detection device including a slave system that performs second angle detection in addition to a master system that performs first angle detection from an output signal of a resolver, It is possible to realize a secondary angle detection with accuracy capable of backup.

  Furthermore, according to a preferred embodiment of the present invention, when the angle detection of the main system is abnormal, it can be backed up by the secondary rotation angle detecting device that performs the second angle detection, and the life extension of the target system can be achieved.

  Other objects and features of the present invention will be clarified in the embodiments described below.

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

  FIG. 1 is an overall functional block diagram of a rotation angle detection device according to an embodiment of the present invention.

  The resolver 1 is attached to a rotating shaft of an electric power steering (EPS) motor, for example, and detects the rotational angle position of the motor. The resolver 1 receives the excitation signal 2a from the excitation signal generator 2 as a bias, and the resolver digital converter 3 receives the sin θm signal 1a and the cos θm signal 1b obtained by integrating the excitation signal component 2a and the rotation angle θm information of the rotation shaft. Entered. The resolver digital converter 3 calculates the motor shaft angle θm based on the sin θm signal 1a, the cos θm signal 1b, and the excitation signal 2a. The angle information θm is transmitted to the CPU 4 through the signal lines 3a and 3b, and the CPU 4 controls the motor based on the angle information θm.

  The above is the main system basic method for detecting the motor shaft angle. However, when the resolver digital conversion unit 3 calculates the abnormal angle, the CPU 4 performs wrong motor control. In addition, when motor control is applied particularly to electric power steering, safety and reliability are required. Therefore, a safe steering operation can be performed simultaneously with a failure detection function, even when the resolver digital conversion unit 3 fails. A backup (life extension) means that can be continued is required.

  Therefore, a comparison reference value for determining an abnormality in angle detection in the main system including the resolver digital conversion unit 3 and a redundant detection unit 5 for improving the accuracy of the detection angle used as a backup (life extension) in an emergency are provided.

  The zero-cross detector 6 is configured with a differential output, and detects a portion where the differential component of the excitation signal 2a is zero. The edge discriminating unit 7 detects whether the zero cross edge of the excitation signal 2a is rising or falling. The counter 8 is a digital counter and is a so-called time counter that counts up by free run using the zero-cross detection signal 6a as a reset signal. The counter 8 sequentially stores and updates the interval (cycle) of the reset signal based on the zero-cross detection signal 6a, and sequentially measures the frequency of the excitation signal 2a as its reciprocal. For this reason, even if the excitation signal 2a fluctuates temporarily due to disturbances such as temperature and voltage, the redundancy detection unit 5 has a self-correcting function.

  Further, the reference signal 8 a is output from the counter 8 to the one-shot generation unit 9 only when the rising edge signal 7 a is input by the edge determination unit 7. The reference signal 8a operates with a default of 1/2 of the interval of the zero cross detection signal 6a that is sequentially measured by the counter 8. Further, the output timing of the reference signal 8a can be moved in the front-rear direction by a command value from the offset addition / subtraction unit 10.

  The phase delay / advance amount by the resolver 1 is stored in the ROM of the CPU 4 in advance. Thereby, even if the resolver 1 has a phase lag / advance, the redundancy detector 5 can be employed with versatility.

  The SPI unit 11 is a serial peripheral interface (Serial Peripheral Interface). The SPI unit 11 transmits the phase lag / advance amount generated by the resolver 1 stored in advance in the ROM of the CPU 4 to the offset addition / subtraction unit 10 in the redundancy detection unit 5 when the CPU 4 is activated.

  The counter 8 outputs the reference signal 8 a to the one-shot generation unit 9 based on ½ of the reset interval measured by the previous counter and the offset amount from the offset addition / subtraction unit 10.

  The sin θm signal 1 a and the cos θm signal 1 b are input to the sample holder 12 in the redundancy detection unit 5 and sampled and held by a hold command signal 9 a from the one-shot generation unit 9.

  In the one-shot generation unit 9, the sample holder 12 outputs a signal 9 a for holding the sin θm / cos θm signal, and simultaneously outputs an AD conversion command signal 9 b to the CPU 4. The CPU 4 generates an interrupt process by the AD conversion command signal 9b, and AD converts the sample hold value 12a of the sin θm signal 1a and the sample hold value 12b of the cos θm signal 1b.

  According to this embodiment, the values of the sin θm signal 1a and the cos θm signal 1b can be simultaneously held outside the CPU, and the signals 1a and 1b can be AD-converted during the processing free time of the CPU 4. Therefore, the CPU 4 can calculate the motor shaft angle θm on the basis of the sin θm signal 1a and the cos θm signal 1b with no time error.

  Therefore, the redundancy detection unit 5 can calculate the motor shaft angle θm with high accuracy, and can obtain a reference value for comparison for abnormality determination of the resolver digital conversion unit 3. In addition, even if an abnormality occurs in the resolver digital conversion unit 3, by using the detected value of the motor shaft angle θm by the redundancy detection unit 5 as a backup, the safe steering operation can be continued (prolonged) at the minimum. Can do.

  As a further abnormality detection means, the sky / earth fault detection unit 13 can perform self-diagnosis of the sky / ground fault by monitoring the voltages of the sin θm signal 1a and the cos θm signal 1b.

  According to the present embodiment, it is possible to prevent abnormality of the signal line itself and to calculate an incorrect motor shaft angle, thereby realizing high reliability.

  The diagnosis result of the top / bottom detection unit 13 is transmitted to the CPU 4 via the SPI unit 11, and the CPU 4 can immediately detect an abnormality.

  FIG. 2 is a diagram showing operation waveforms of respective parts in the embodiment of FIG. 1 of the present invention.

The excitation signal 2 a is generated as a differential signal and is composed of a signal 21 and a signal 22. As the angle signals, there are a sin θm signal 1a and a cos θm signal 1b, but only the cos θm signal 1b is described in this figure. cosθm
The signal 1b is formed of a differential signal like the excitation signal 2a, and includes signals 23 and 24. This is because the common-mode noise component is removed by the differential signal, and noise resistance can be improved.

  The zero-cross detection COMP signal 25 is a signal component in the zero-cross detection unit 6 and detects a cross point of the excitation signals 21 and 22. When the excitation signal 22 changes from a state larger than the excitation signal 21 to a smaller state, the state changes from HIGH to LOW. When the excitation signal 21 changes from a state larger than the excitation signal 22 to a smaller state, the signal is switched from LOW to HIGH. The zero-cross detection signal 6 a is an output signal from the zero-cross detection unit 6 and is output when the zero-cross detection COMP signal 25 rises and falls. The rising edge detection signal 7 a is output at the falling edge of the zero cross detection COMP signal 25. That is, it is output when the excitation signal 22 changes from a state larger than the excitation signal 21 to a smaller state.

  The counter signal 26 is a counter that operates in the counter 8 and clocks the clock using the zero cross detection signal 6a as a reset signal. It also operates as a frequency measurement reference signal.

  Further, the count-up operation after the rising edge detection signal 7a is output is set as an effective value, and the AD conversion command signal 9b is output based on 1/2 of the period measurement result by the previous counter operation and the offset signal from the CPU 4. To do. At the same time, the output of the sample holder 12, that is, the AD input 12b is calculated from the differential values of the signals 23 and 24 of the cos θm signal 1b and sample-held.

  In this waveform diagram, only the cos θm signal 1b is described, but the same operation is performed for the sin θm signal 1a.

  FIG. 3 is an internal block diagram of the top / bottom detector 13 in the embodiment of the present invention shown in FIG.

  The earth-and-earth fault detector 13 monitors the voltages of the sin θm signal 1a and the cos θm signal 1b, and determines whether the voltages are within the reference voltages 33 and 34 by a window comparator constituted by the comparators 31 and 32 and the OR gate 35. judge. When normal, the sin θm signal 1a and the cos θm signal 1b are within the reference voltages 33 and 34. If the sin θm signal 1 a or the cos θm signal 1 b has a power fault, it becomes larger than the reference voltage 33 and an abnormality detection signal is output from the comparator 31. When the sin θm signal 1 a or the cos θm signal 1 b is grounded, the reference voltage 34 is lower, and an abnormality detection signal is output from the comparator 32. Abnormal signals from the comparators 31 and 32 are collected by an OR gate 35. The filter 36 is set to prevent erroneous detection due to noise. The signal 13a from the top / bottom detection unit 13 that has passed through the filter 36 is input to the SPI unit 11, and the CPU 4 can detect the presence / absence of the top / bottom fault of the signal line.

  FIG. 4 is an overall functional block diagram of an electric power steering system using a rotation angle detection device according to an embodiment of the present invention.

  When the steering 401 is rotated, the rotational driving force is decelerated by the manual steering gear 403 via the rod 402 and transmitted to the left and right wheels 406 and 407 via the left and right tie rods 404 and 405. Steer.

  The EPS motor 408 according to this embodiment is attached to the vicinity of the rod 402 of the steering 401 and transmits the driving force to the rod 402 via the gear 409. A torque sensor 410 is attached to the rod 402 and detects a rotational driving force (torque) applied to the steering 401.

  The control device 411 includes the CPU 4 in FIG. 1 and first inputs the output of the torque sensor 410. Further, the rotational angle θm signal of the EPS motor 408 detected through the resolver digital conversion unit 3 and the redundancy detection unit 5 is input from the resolver 1 described in FIG. Then, the energization current of the motor 408 is controlled so that the rotation angle θm of the EPS motor 408, that is, the steering angle becomes the operation angle of the steering 401.

  Here, the rotation angle θm of the EPS motor 408 is transmitted from the resolver 1 to the control device 411 via the resolver digital conversion unit 3 which is the main system. Further, the rotation angle θm signal of the EPS motor 408 from the redundant system detected through the redundancy detection unit 5 described in FIG. 1 is determined so that the controller 411 can determine whether there is an error in the rotation angle θm signal. Enter also. In addition, as described above, the redundancy detection unit 5 realizes high-precision detection and reliability as compared with the conventional case. Even if the main system fails, the minimum backup (life extension) control is realized. Can continue.

  FIG. 5 is a functional block diagram of a steering drive control device 500 that drives and controls the EPS motor 408 in the control device 411 in the embodiment of FIG. The steering drive control device 500 includes a power module 501 that constitutes an inverter main circuit (conversion circuit), and a control module 502 that controls an on / off operation (switching operation) of a power semiconductor switching element of the power module 501. . The inverter main circuit of the power module 501 is composed of a three-phase bridge circuit configured by bridge-connecting six power semiconductor switching elements. The battery 503 is electrically connected to the input side (DC side) of the inverter main circuit of the power module 501, and the stator coil 504 of the EPS motor 408 is electrically connected to the output side (AC side). The control module 502 controls switching of each of the six power semiconductor switching elements of the power module 501. Thus, the DC power output from the battery 503 is converted into three-phase AC power in the inverter main circuit of the power module 501 and supplied to the stator coil 504 of the EPS motor 408.

  The control module 502 generates a control signal for controlling the on / off operation (switching operation) of the power semiconductor switching element, and configures a control unit that outputs the control signal to a driver circuit (not shown) of the power module 501. is doing. In the control module 502, the torque detection value Tf of the steering wheel 401 detected by the torque sensor 410, the rotation speed detection value ωf of the rotor 506 detected by the encoder 505, and the rotor 506 detected by the resolver 1 are input parameters. The detected magnetic pole position value θm is input. As described with reference to FIGS. 1 and 4, the rotational angle θm of the EPS motor 408 is transmitted from the resolver 1 to the control device 411 via the resolver digital conversion unit 3 which is the main system. Further, the rotation angle θm signal of the EPS motor 408 from the redundant system is obtained via the redundancy detector 5 described in detail in FIG. 1 so that the controller 411 can determine whether the rotation angle θm signal is correct. Enter also. The redundancy detection unit 5 realizes high-precision detection and reliability, and even if the main system fails, the minimum backup (life extension) control can be continued.

  The torque detection value Tf is input to the torque control circuit 507 together with the torque command value Ts. The torque control circuit 507 calculates the torque target value Te based on the torque detection value Tf and the torque command value Ts, and outputs the current command value Is and the rotation angle θ1 by proportional integration of the calculated torque target value Te. . The rotation angle θ1 is input to the phase shift circuit 508 together with the rotation speed detection value ωf. The phase shift circuit 508 calculates the rotation angle θa of the rotor 506 based on the detected rotation speed value ωf, and outputs the calculated rotation angle θa after phase shifting based on the rotation angle θ1. The rotation angle θa is input to the sine wave / cosine wave generation circuit 509 together with the magnetic pole position detection value θm. The sine wave / cosine wave generation circuit 509 is a sine wave basic waveform (drive current waveform) obtained by phase-shifting the induced voltage of each winding (here, three phases) of the stator coil 506 based on the rotation angle θa and the magnetic pole position detection value θm. ) Generate and output the value Iav. Note that the amount of the phase shift may be zero.

  The sine wave basic waveform (drive current waveform) value Iav is input to the two-phase / three-phase conversion circuit 510 together with the current command value Is. The two-phase / three-phase conversion circuit 510 outputs current commands Isa, Isb, Isc corresponding to each phase based on the sine wave basic waveform (drive current waveform) value Iav and the current command Is. The control module 502 includes current control systems 511 to 513 for each phase. The current control systems 511 to 513 for each phase are input with current commands Isa, Isb, Isc for the corresponding phases and current detection values Ifa, Ifb, Ifc for the corresponding phases. The detected current values Ifa, Ifb and Ifc are detected by the current detector 514 and are phase currents supplied from the conversion circuit of the power module 501 to the stator coils 504 of the respective phases. The current control systems 511 to 513 of each phase switch the power semiconductor switching elements of the corresponding phase based on the current commands Isa, Isb, Isc of the corresponding phase and the detected current values Ifa, Ifb, Ifc of the corresponding phase. A control signal for controlling the operation is output. The control signal for each phase is input to a driver circuit (not shown) for the corresponding phase of the power module 501.

  A driver circuit (not shown) for each phase of the power module 501 outputs a drive signal for switching the power semiconductor switching element of the corresponding phase based on the control signal of the corresponding phase. The drive signal for each phase is input to the power semiconductor switching element for the corresponding phase. When the power semiconductor switching element performs a switching operation, DC power supplied from the battery 503 is converted into AC power and supplied to the stator coil 504 of the EPS motor 408. At this time, the combined current of the phase currents supplied to the stator coil 504 is always formed at a position that is orthogonal to or phase shifted from the field magnetic flux. Thereby, the EPS motor 408 generates a rotating magnetic field corresponding to the rotational position of the rotor 506, and the rotor 506 rotates.

  In such an electric power steering system, when the steering wheel is cut without permission is called self-steering, which is an abnormality that should never occur. Due to the presence of the redundancy detection unit 5 having excellent accuracy and reliability in the above-described embodiment, it is possible to realize a highly reliable electric power steering system without such a situation.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various changes can be made in the design without departing from the spirit of the invention described in the claims. Is.

1 is an overall functional block diagram of a rotation angle detection device according to an embodiment of the present invention. The operation | movement waveform diagram of each part in one Example of FIG. The internal structural example figure of the top-and-bottom detection part 13 in one Example of FIG. 1 is an overall functional block diagram of an electric power steering system using a rotation angle detection device according to an embodiment of the present invention. FIG. 5 is a functional block diagram illustrating an example of a steering drive control device in the embodiment of FIG. 4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Resolver, 2 ... Excitation signal production | generation part, 3 ... Resolver digital conversion part, 4 ... CPU, 5 ... Redundancy detection part, 6 ... Zero cross detection part, 7 ... Edge determination part, 8 ... Counter, 9 ... One shot production | generation part DESCRIPTION OF SYMBOLS 10 ... Offset addition / subtraction part, 11 ... SPI, 12 ... Sample holder, 13 ... Top-and-bottom detection part.

Claims (11)

An excitation signal generator for generating an alternating excitation signal;
A resolver that is connected to a rotating shaft and that receives the excitation signal and modulates the amplitude according to the rotation angle of the rotating shaft;
And the AD conversion unit of the main system for converting an analog output signal of the resolver to digital rotation angle signal,
A main system arithmetic CPU for inputting the main system digital rotation angle signal and outputting it to the control device to be controlled;
A redundant detection unit that inputs the analog output signal of the resolver and the excitation signal, and outputs a secondary rotation angle signal ;
A slave AD conversion unit that AD converts the analog rotation angle signal of the resolver obtained through the redundancy detection unit,
The redundant detection unit is a zero cross detection unit that detects rising and falling of a zero cross edge of the excitation signal;
A period measurement unit that is reset by a detection signal of the zero cross detection unit and updates an interval of the detection signal for each period of the excitation signal;
An AD conversion command unit that generates an AD conversion timing signal based on the previous measurement result of the period measurement unit, and
The slave AD conversion unit AD-converts the analog rotation angle signal of the resolver based on the AD conversion timing signal to obtain a reference value for determining abnormality of the main system including the AD conversion unit, A rotation angle detection apparatus characterized by obtaining a slave digital rotation angle signal used as a backup when an abnormality of the main system is determined . An excitation signal generator for generating an alternating excitation signal;
A resolver that is connected to a rotating shaft, inputs the excitation signal, modulates the amplitude according to the rotation angle of the rotating shaft, and outputs it;
And the AD conversion unit of the main system for converting an analog output signal of the resolver to digital rotation angle signal,
A main system arithmetic CPU for inputting the main system digital rotation angle signal and outputting it to the control device to be controlled;
A redundant detection unit that inputs the analog output signal of the resolver and the excitation signal, and outputs a secondary rotation angle signal ;
An abnormality detector that compares the digital rotation angle signals of the main system and the sub system and detects an abnormality of the output signal of the resolver ;
A slave AD conversion unit that AD converts the analog rotation angle signal of the resolver obtained through the redundancy detection unit,
The redundant detection unit is a zero cross detection unit that detects rising and falling of a zero cross edge of the excitation signal;
A period measurement unit that is reset by a detection signal of the zero cross detection unit and updates an interval of the detection signal for each period of the excitation signal;
An AD conversion command unit that generates an AD conversion timing signal based on the previous measurement result of the period measurement unit, and
The slave AD conversion unit AD-converts the analog rotation angle signal of the resolver based on the AD conversion timing signal, and obtains a reference value for determining abnormality of the main system including the AD conversion unit. rotation angle detecting equipment which is characterized in <br/> to obtain a digital rotational angle signal of the slave to be used as a backup when it is determined the abnormality of the main system. 3. The offset amount calculation unit that calculates an offset amount of the period of the output signal of the resolver based on the cycle measurement result of the cycle measurement unit, and a correction unit that corrects the cycle measurement result based on the offset amount wherein the AD conversion command unit, the rotation angle detecting equipment which is characterized by being configured to generate an AD conversion timing signal on the basis of the corrected period measurement results. 4. The sample holder according to claim 2, further comprising: a sample holder that samples and holds the output signal of the resolver according to the AD conversion timing signal and outputs the analog output signal to the CPU outside the main operation CPU . rotation angle detecting equipment, characterized in that. 5. The rotation angle detection according to claim 2, wherein the AD conversion command unit is configured to generate the AD conversion timing signal on the basis of 1/2 of the previous period measurement result. equipment. 4. The rotation according to claim 3, wherein the AD conversion command unit is configured to generate the AD conversion timing signal based on half of the previous period measurement result and the offset amount. corner detection equipment. The rotation angle detection according to claim 3 or 6, wherein the AD conversion command unit includes a counter that measures a time based on 1/2 of the previous period measurement result and / or the offset amount. equipment. The redundant detection according to any one of claims 2 to 7, wherein the frequency is measured for each period from the reciprocal of the interval (period) of the detection signal measured by the period measurement unit, and the excitation signal fluctuates temporarily. A rotation angle detection device characterized by self-correction within a unit. 9. A voltage detection unit for detecting a voltage of a resolver output signal according to claim 2, and a ground fault abnormality detection unit for detecting a ground fault abnormality when the detected voltage is equal to or lower than a predetermined voltage. rotation angle detection equipment to. The voltage detection unit for detecting a voltage of a resolver output signal according to any one of claims 2 to 9, and a power fault abnormality detection unit for detecting a power fault abnormality when the detection voltage is equal to or higher than a predetermined voltage. rotation angle detection equipment to. In an electric power steering apparatus provided with a motor for assisting / driving a wheel according to a steering operation by a driver,
An excitation signal generator for generating an alternating excitation signal;
A resolver that is connected to the rotating shaft of the motor, inputs the excitation signal, and modulates and outputs the amplitude according to the rotation angle of the rotating shaft;
And the AD conversion unit of the main system for converting an analog output signal of the resolver to digital rotation angle signal,
A main rotation angle calculation CPU that inputs a digital rotation angle signal of the main AD converter and outputs the digital rotation angle signal to the motor control device;
A redundant detection unit that inputs the analog output signal of the resolver and the excitation signal, and outputs a secondary rotation angle signal ;
A slave AD conversion unit that AD converts the analog rotation angle signal of the resolver obtained through the redundancy detection unit,
The redundant detection unit is a zero cross detection unit that detects rising and falling of a zero cross edge of the excitation signal;
A period measurement unit that is reset by a detection signal of the zero cross detection unit and updates an interval of the detection signal for each period of the excitation signal;
An AD conversion command unit that generates an AD conversion timing signal based on the previous measurement result of the period measurement unit, and
The slave AD conversion unit AD-converts the analog rotation angle signal of the resolver based on the AD conversion timing signal to obtain a reference value for determining abnormality of the main system including the AD conversion unit, An electric power steering apparatus characterized by obtaining a secondary digital rotation angle signal used as a backup when an abnormality of the main system is determined .

Images