JP2018199397A - Rotation monitoring circuit - Google Patents

Abstract

To provide a rotation monitoring circuit making it possible to utilize a highly reliable result of calculation of a rotational quantity.SOLUTION: When an IG signal represents an off state, a rotation monitoring circuit 32 monitors rotation of a rotating shaft 26a of an electric motor 26 on the basis of a first reference signal sin outputted from a first reference sensor 52 and a second reference signal cos outputted from a second reference sensor 54. Specifically, the rotation monitoring circuit 32 performs sampling of the first reference signal sin and second reference signal cos plural times. When sampling values thereof include one that provides a result of calculation of a rotational quantity which is different from the other results, a result of calculation based on a majority of sampling values that provides the same result of calculation of the rotational quantity is adopted.SELECTED DRAWING: Figure 1

Description

  The present invention provides a control unit that operates an operation target device of the steered device with the steered device that steers the steered wheel as a control target, and the rotation of the rotating shaft that steers the steered wheel by rotating. A rotation monitoring circuit that monitors when the power of the unit is in an off state and outputs the rotation monitoring result to the control unit on condition that the power of the control unit is switched on. The present invention relates to the rotation monitoring circuit mounted on the apparatus.

  For example, Patent Literature 1 describes a steering control device in which an evaluation unit configured to detect a rotation amount of a steering angle is configured by an ASIC during a period in which an ignition switch of a vehicle is in an off state. Here, the evaluation unit includes a state automatic unit (SM1, SM2) that specifies the rotation direction of the steering angle, an analog unit (AFE1, AFE2) that uses the output of the MR sensor as a signal that can be input to the state automatic unit, and the rotation direction. The redundant design is provided with two sets of counters (CNT1, CNT2) for counting the specific results.

European Patent No. 2050658

  By the way, in the case of the above device, when noise is superimposed on one of the two sets of circuits, the values indicated by the two sets of counters are different from each other. When the value is used, there is a possibility that a rotation amount with low reliability is used. Further, if the detection result is not used when the two sets of counters do not match, there is a possibility that the rotation amount calculation result cannot be used.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
1. The control unit that operates the operation target device of the steered device with the steered device that steers the steered wheel as a control target, and the rotation of the rotating shaft that steers the steered wheel is in an off state. A rotation monitoring circuit for monitoring the rotation control circuit for outputting the rotation monitoring result to the control unit on the condition that the power of the control unit is switched to an ON state. In the circuit, a circuit for outputting a detection result of a rotation angle sensor for detecting a rotation angle of the rotation shaft as an electric signal, wherein detection of power supply and interruption is repeated when the power supply of the control unit is off The amount of rotation of the rotating shaft is calculated based on the output signal of the detection circuit when power is supplied to the detection circuit and the detection circuit, and the control unit is turned on. Subject to the above An arithmetic circuit that outputs a calculation result to the control unit, and the arithmetic circuit includes a plurality of samplings that are output in time series of the output signal of the detection circuit within a predetermined period when the power source is off. The calculation result of the rotation amount based on the sampling value having a large number of the same calculation result of the rotation amount is provided on the condition that the value includes a value that gives the calculation result of the rotation amount different from the others. Output target to the control unit.

  In the above configuration, when a value that gives a calculation result of a rotation amount different from the others is included in a plurality of sampling values, a calculation result based on a sampling value having a large number of the same calculation results is output to the control unit And Here, a sampling value with a large number of the same calculation results is more reliable than a sampling value with a small number. For this reason, a calculation result based on a sampling value having a large number of identical ones is used as an output target, so that a highly reliable calculation result of the rotation amount can be used.

  2. 2. The rotation monitoring circuit according to claim 1, wherein the minimum unit of the rotation amount by the arithmetic circuit is larger than the minimum unit of the rotation amount of the rotating shaft used by the control unit when the power is on.

  When the rotating shaft rotates, there is a possibility that a plurality of sampling values that move back and forth in time series may give a calculation result of the amount of rotation different from the others due to the rotation of the rotating shaft. However, in the above configuration, since the minimum unit of the rotation amount by the arithmetic circuit is larger than the minimum unit of the rotation amount of the rotating shaft used by the control unit when the power is on, it is compared with the rotation amount by the control unit. Then, the minute amount of rotation is not required for the amount of rotation by the arithmetic circuit. For this reason, compared with the case where identification of a minute amount of rotation is required, some sampling values that move back and forth in time series due to rotation of the rotating shaft include those that give different rotation amount calculation results. As a result, it is possible to increase the effectiveness of the process of evaluating the reliability of the calculation result of the rotation amount by comparing a plurality of sampling values moving back and forth in time series.

  3. 3. The rotation monitoring circuit according to 1 or 2, wherein the arithmetic circuit includes a first rotation calculation circuit and a second rotation calculation circuit as circuits for calculating a rotation amount of the rotation shaft, and a calculation result by the first rotation calculation circuit. And an output circuit for outputting the matched calculation result to the control unit on condition that the calculation results by the second rotation calculation circuit match, and the first rotation calculation circuit is within the predetermined period. Sampling with a large number of samples with the same rotation amount calculation result, provided that a plurality of sampling values of the output signal of the detection circuit include a value that gives a different calculation result of the rotation amount. The calculation result of the rotation amount based on the value is output to the output circuit, and the second rotation calculation circuit outputs a plurality of sampling values of the output signal of the detection circuit within the predetermined period. The output circuit calculates the calculation result of the rotation amount based on the sampling value having a large number of the same calculation result of the rotation amount, on the condition that the value giving the calculation result of the rotation amount different from the others is included in the output circuit. Output to.

  In the above embodiment, the first rotation calculation circuit and the second rotation calculation circuit are output to the control unit on condition that the calculation result by the first rotation calculation circuit and the calculation result by the second rotation calculation circuit match. When calculating the rotation amount based on one sampling value, there is a high possibility that the condition for outputting the calculation result to the control unit is not satisfied due to noise. For this reason, the utility value of the process that employs the calculation result of the rotation amount based on the sampling value having a large number of the same calculation results of the rotation amount is particularly great.

  4). 4. The rotation monitoring circuit according to any one of 1 to 3, wherein the arithmetic circuit determines that the rotating shaft is not rotating based on the calculation result, compared with a case where it is determined that the rotating shaft is rotating. Then, the length of the predetermined period is increased.

  According to the above configuration, the detection circuit is turned off by making the length of the predetermined period longer than when rotating when not rotating, compared to the case where both are set to the same length. The time during which the state can be achieved can be made as long as possible.

  5. 5. The rotation monitoring circuit according to any one of 1 to 4, wherein the first predetermined number is a plurality, the second predetermined number is one or more, and the arithmetic circuit is configured to detect the detection within the predetermined period. On the condition that the first predetermined number of sampling values of the output signal of the circuit for use include a value that gives a calculation result of the rotation amount different from the other, the second predetermined number of sampling values within the predetermined period The sampling value is further acquired, and the rotation based on the sampling value having a large number of the same calculation result of the rotation amount among the first predetermined number and the second predetermined number of total sampling values. The amount calculation result is set as an output target to the control unit.

  Compared with the case where the first predetermined number of sampling values give calculation results of the same rotation amount, the reliability of the calculation results based on those sampling values is included when there are those that give different calculation results. It is considered low. Therefore, in the above configuration, when the first predetermined number of sampling values include those that give different calculation results, the second predetermined number of sampling values are added, and the first predetermined number and the second predetermined value are added. The reliability of the output target to the control unit by setting the calculation result based on the sampling value with a large number of the same rotation amount calculation results among several total sampling values as the output target to the control unit Can be increased.

The figure which shows the steering control apparatus and steering apparatus concerning 1st Embodiment. The figure which shows the process regarding control of the controlled variable of the electric motor concerning the embodiment. The figure which shows the structure of the rotation monitoring circuit concerning the embodiment. The time chart which shows the quadrant calculation process concerning the embodiment. The flowchart which shows the procedure of the calculation process of the rotation amount concerning the embodiment. (A) And (b) is a time chart which shows the calculation process of the rotation amount concerning the embodiment. The flowchart which shows the setting process of the ON / OFF period of the detection side power supply concerning 2nd Embodiment.

<First Embodiment>
Hereinafter, a first embodiment according to the rotation monitoring circuit will be described with reference to the drawings.
As shown in FIG. 1, the steering wheel (steering 10) can transmit power to the steered wheels 12 via the steered device 20. The steered device 20 includes a steering shaft 22 connected to the steering 10. The steering shaft 22 is configured by connecting a column shaft 22a, an intermediate shaft 22b, and a pinion shaft 22c in order from the steering 10 side.

  The rack shaft 24 and the pinion shaft 22c are arranged with a predetermined crossing angle, and the rack and pinion mechanism is formed by meshing the rack teeth formed on the rack shaft 24 and the pinion teeth formed on the pinion shaft 22c. Is configured. The steered wheels 12 are connected to both ends of the rack shaft 24 via tie rods and knuckles. Therefore, the rotation of the steering shaft 22 accompanying the operation of the steering wheel 10 is converted into the axial movement of the rack shaft 24 by the rack and pinion mechanism, and this axial movement is transmitted to the knuckle via the tie rod, thereby turning the steered wheels 12. The steering angle, that is, the traveling direction of the vehicle is changed.

  The steering shaft 22 is connected to a rotating shaft 26a of an electric motor 26 via a speed reduction mechanism 25 such as a worm and wheel. In the vicinity of the rotation shaft 26a, a first reference sensor 52 and a second reference sensor 54, which are two rotation angle sensors, are provided. In the present embodiment, MR sensors are exemplified as the first reference sensor 52 and the second reference sensor 54.

  The first reference sensor 52 detects the rotation angle of the rotation shaft 26a with reference to the first angle, and the second reference sensor 54 detects the rotation angle of the rotation shaft 26a different from the first angle. The detection is based on the second angle. Here, in the present embodiment, the first angle and the second angle are shifted by “90 °”. The first reference signal sin output from the first reference sensor 52 is regarded as a sine wave signal, and the second reference signal cos output from the second reference sensor 54 is regarded as a cosine wave signal.

  The first reference signal sin and the second reference signal cos are taken into the rotation monitoring circuit 32. The rotation monitoring circuit 32 operates using the battery 50 as a power source. In the present embodiment, the rotation monitoring circuit 32 is configured by a dedicated integrated circuit (ASIC).

  The microcomputer 34 controls the control amount (torque) of the electric motor 26 by operating the inverter 28 connected to the electric motor 26. At this time, the microcomputer 34 detects the steering torque Trq applied to the steering shaft 22 based on the torsion bar torsion provided on the steering shaft 22 and the first reference sensor 52 and the second reference sensor 54 via the rotation monitoring circuit 32. The detected values of the torque sensor 56 that detects the vehicle speed and the vehicle speed sensor 58 that detects the vehicle speed V are referred to.

The microcomputer 34 includes a CPU 36, a ROM 38, and an electrically rewritable nonvolatile memory 40.
FIG. 2 shows a part of processing realized by the CPU 36 executing the program stored in the ROM 38. Specifically, the part surrounded by the alternate long and short dash line in FIG. 2 indicates the above processing, and the other parts describe some of the components of the microcomputer 34 for convenience of explanation.

  The base value setting processing unit M10 sets a base value Ta1 * of assist torque generated by the electric motor 26 based on the vehicle speed V and the steering torque Trq. On the other hand, the A / D converter 42 converts the sine wave signal SIN corresponding to the first reference signal sin into digital data and outputs it, and the A / D converter 44 cosine wave corresponding to the second reference signal cos. The signal COS is converted into digital data and output. The turning angle calculation processing unit M12 calculates and outputs the turning angle θp of the steered wheels 12 based on the output values of the A / D converters 42 and 44.

  Here, from only one of the sine wave signal SIN and the cosine wave signal COS, the rotation angle within one rotation of the rotation shaft 26a cannot be uniquely determined. That is, for example, the sine wave signal SIN cannot distinguish between 0 ° and 180 °. On the other hand, since the sine wave signal SIN and the cosine wave signal COS are signals having a phase difference from each other, according to the sine wave signal SIN and the cosine wave signal COS, the rotation angle within one rotation of the rotary shaft 26a is determined. It can be defined uniquely. In the turning angle calculation processing unit M12, the rotation angle within one rotation of the rotating shaft 26a is calculated from the sine wave signal SIN and the cosine wave signal COS, and the turning angle θp is calculated together with the rotation history of the rotating shaft 26a. . That is, the rotation of the rotating shaft 26 a rotates the rack shaft 24 via the speed reduction mechanism 25 and the steering shaft 22, and the turning angle θp of the steered wheels 12 changes as the rack shaft 24 rotates. In particular, the rotation shaft 26a rotates a plurality of times until the absolute value of the turning angle θp changes from zero to the maximum rotation angle. For this reason, there is no one-to-one correspondence between the rotation angle of the rotating shaft 26a and the turning angle θp, and it is necessary to use the rotation history of the rotating shaft 26a to determine the turning angle θp.

  The target turning angle setting processing unit M14 sets the target turning angle θp * based on the sum of the steering torque Trq detected by the torque sensor 56 and the base value Ta1 *. Here, the target turning angle θp * is set using the following model.

Trq + Ta1 * = K · θp * + C · θp * '+ J · θp *''
In the above formula, the viscosity coefficient C is obtained by modeling the friction of the steering mechanism including the steering shaft 22 and the rack shaft 24, and the inertia coefficient J is obtained by modeling the inertia of the steering mechanism. is there. On the other hand, the spring coefficient K is a model of the influence of the vehicle, and is determined by specifications such as a suspension and a hole alignment.

  The feedback processing unit M16 calculates and outputs a correction amount of the base value Ta1 * as an operation amount for performing feedback control of the turning angle θp to the target turning angle θp *. The correction processing unit M18 corrects the base value Ta1 * by adding the correction amount of the feedback processing unit M16 to the base value Ta1 *, and sets this as the torque command value Ta * of the electric motor 26. In the operation processing unit M20, the inverter 28 is operated in order to control the torque of the electric motor 26 to the torque command value Ta *.

  As shown in FIG. 1, a travel permission signal (IG signal) is input to the rotation monitoring circuit 32 when the ignition switch is turned on. The microcomputer 34 detects this when the IG signal is switched from the on state to the off state via the rotation monitoring circuit 32. And the microcomputer 34 interrupts | blocks electric power supply on condition that an IG signal is an OFF state. That is, the microcomputer 34 performs necessary post-processing when the IG signal is turned off. The post-processing here includes storage processing of the turning angle θp in the nonvolatile memory 40 shown in FIG. When the post-processing is completed, the microcomputer 34 instructs the rotation monitoring circuit 32 to cut off the power supply. Thereby, the power supply of the microcomputer 34 is interrupted.

  The microcomputer 34 is activated when the IG signal is turned on. That is, the rotation monitoring circuit 32 resumes the power supply to the microcomputer 34 when the IG signal is turned on. When the microcomputer 34 is activated in this way, the microcomputer 34 acquires the rotation amount Δθ of the rotating shaft 26a from the rotation monitoring circuit 32 when the IG signal is in the OFF state. And the microcomputer 34 correct | amends the turning angle (theta) p just before interruption | blocking of the electric power supply of the microcomputer 34 memorize | stored in the non-volatile memory 40 in the turning angle calculation process part M12 based on acquired rotation amount (DELTA) (theta). The turning angle θp is grasped.

FIG. 3 shows the configuration of the rotation monitoring circuit 32.
The first reference operational amplifier 60 amplifies the first reference signal sin and outputs a sine wave signal SIN to the first reference comparators 64 and 68. The first reference comparator 64 determines whether or not the sine wave signal SIN is equal to or higher than the rising threshold value V + having a positive value. The first reference comparator 68 determines whether the sine wave signal SIN is a negative value. It is determined whether or not it is equal to or less than the lower-side threshold value V−. Note that the rising threshold value V + is generated by the rising threshold value generation circuit 62, and the decreasing threshold value V− is generated by the decreasing threshold value generation circuit 66. Here, the rising-side threshold value generating circuit 62 and the decreasing-side threshold value generating circuit 66 are configured by a series connection body of a pair of resistors, for example, and their output terminals may be connection points of the pair of resistors. .

  The second reference operational amplifier 70 amplifies the second reference signal cos and outputs a cosine wave signal COS to the second reference comparators 74 and 78. The second reference comparator 74 determines whether or not the cosine wave signal COS is equal to or higher than the rising threshold value V + having a positive value. The second reference comparator 78 determines that the cosine wave signal COS is a negative value. It is determined whether or not it is equal to or less than the lower-side threshold value V−. Note that the rising threshold value V + is generated by the rising threshold value generation circuit 72, and the decreasing threshold value V− is generated by the decreasing threshold value generation circuit 76.

  The detection-side power supply 80 is a power supply for the detection circuit DSC and the first reference sensor 52 and the second reference sensor 54. The detection circuit DSC includes a first reference operational amplifier 60, a second reference operational amplifier 70, first reference comparators 64 and 68, second reference comparators 74 and 78, rising threshold generation circuits 62 and 72, decreasing threshold generation circuit 66, 76 and a power supply 80 on the detection side. The detection circuit DSC is an analog circuit.

  Output signals from the first reference comparators 64 and 68 and the second reference comparators 74 and 78 are output to both the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92. The first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 have the same function. The redundant design provided with two circuits having the same function is aimed at improving the reliability of the circuit. In this embodiment, in order to identify these two circuits, “first”, “ 2nd ". Therefore, the description of “first” and “second” for identifying two circuits provided with the aim of improving reliability is the above-mentioned “first reference” and “second reference”. Is not relevant.

  The first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 are configured so that the rotation angle of the rotation shaft 26a is changed from the first quadrant based on the output signals of the first reference comparators 64 and 68 and the second reference comparators 74 and 78. A quadrant calculation process for calculating which of the four quadrants is performed is executed.

  FIG. 4 shows quadrant calculation processing. As shown in FIG. 4, the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 cause the sine wave signal SIN to decrease after the sine wave signal SIN increases to the rising threshold value V + or higher. A period until the lower side threshold value V− is less than or equal to the lower threshold value V− is a period in which the first expression signal Dsin representing the sign of the first reference signal sin is positive. In addition, the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 cause the cosine wave signal COS to rise to the rising threshold value V + or higher, and then the cosine wave signal COS decreases to decrease the lower threshold value V−. The period until the following is a period in which the second expression signal Dcos representing the sign of the second reference signal cos is positive. The first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 are configured so that the rotation angle of the rotation shaft 26a is between the first quadrant and the fourth quadrant based on the signs of the first representation signal Dsin and the second representation signal Dcos. Calculate where it is.

  Next, the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 assume that the unit rotation amount (90 °) is rotated every time the quadrant where the rotation angle exists changes to the adjacent quadrant. The rotation direction is specified from the relationship between the quadrant existing before the change and the quadrant existing after the change. As described above, the minimum unit of the rotation amount handled by the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 is “90 °”, which is the output signal of the A / D converters 42 and 44. The value is larger than the minimum unit of the rotation amount calculated by the turning angle calculation processing unit M12.

  When the unit rotation amount is rotated, the first rotation direction detection circuit 90 outputs a signal to that effect and a signal indicating the rotation direction to the first counter 94 shown in FIG. On the other hand, when the unit rotation amount is rotated, the second rotation direction detection circuit 92 outputs a signal to that effect and a signal indicating the rotation direction to the second counter 96.

  Based on the output signal of the first rotation direction detection circuit 90, the first counter 94 treats the unit rotation amount of the rotating shaft 26a as a vector amount, and integrates them. That is, for example, when the unit rotation amount is rotated twice on the positive side, the counter value is “2”, and when the unit rotation amount on the positive side and the negative side is rotated once, the counter value is , “0”.

  The second counter 96 has the same configuration as that of the first counter 94. Based on the output signal of the second rotation direction detection circuit 92, the second counter 96 treats the unit rotation amount of the rotating shaft 26a as a vector amount, and integrates them.

  The determination circuit 98 outputs the counter value of the first counter 94 or the second counter 96 to the microcomputer 34 via the interface 100 on condition that the values of the first counter 94 and the second counter 96 match. This counter value is the rotation amount Δθ shown in FIG. On the other hand, if the values of the first counter 94 and the second counter 96 do not match, the determination circuit 98 assumes that the counter values are abnormal and outputs a signal indicating that there is an abnormality without outputting the counter values. Is output to the microcomputer 34 via the interface 100. Incidentally, when a signal indicating that there is an abnormality is output, the microcomputer 34, for example, operates the electric motor 26 by substituting the base value Ta1 * into the torque command value Ta * instead of the processing shown in FIG. On the condition that the steering torque Trq is “0”, a process for learning that the turning angle θp of the steered wheel 12 at that time is the neutral position may be executed.

  The intermittent processing circuit 102 executes a process of repeatedly turning on / off the detection-side power supply 80 when the IG signal is in an off state. As a result, when the IG signal is off, the detection circuit DSC is intermittently turned on.

  The clock circuit 104 generates an operation clock for the first rotation direction detection circuit 90, the second rotation direction detection circuit 92, the first counter 94, the second counter 96, the determination circuit 98, the interface 100, and the intermittent processing circuit 102. It is.

  The calculation-side power source 106 is a power source that generates power for the calculation circuit PSC based on the power of the battery 50. The arithmetic circuit PSC includes a first rotation direction detection circuit 90, a second rotation direction detection circuit 92, a first counter 94, a second counter 96, a determination circuit 98, an interface 100, an intermittent processing circuit 102, a clock circuit 104, and a calculation side. A power source 106 is provided. The arithmetic circuit PSC is a digital circuit, and consumes less power than the detection circuit DSC when the arithmetic circuit PSC and the detection circuit DSC are turned on for the same time.

  Here, the processing of the first rotation direction detection circuit 90 when the IG signal is in the OFF state will be described in detail. Note that the processing of the second rotation direction detection circuit 92 when the IG signal is in the OFF state is the same as the processing of the first rotation direction detection circuit 90, and thus description thereof is omitted.

FIG. 5 shows a procedure of processing executed by the first rotation direction detection circuit 90. This process is repeatedly performed every time the detection circuit DSC is turned on by the intermittent processing circuit 102.
In the series of processes shown in FIG. 5, the first rotation direction detection circuit 90 first executes the quadrant calculation process described above once (S10). That is, the first rotation direction detection circuit 90 samples the output signals of the first reference comparators 64 and 68 and the output signals of the second reference comparators 74 and 78 once, and based on these sampling values, the first expression signal Dsin and the first reference signal Dsin. 2 The expression signal Dcos is calculated, and a quadrant is calculated based on the two expression signals Dcos.

  Next, the first rotation direction detection circuit 90 substitutes the quadrant calculation result for the calculation result SM (n) (S12). Here, the variable n is set to “1” when the series of processing shown in FIG. 5 starts when the detection circuit DSC is turned on by the intermittent processing circuit 102 for the processing of S22 described later. It has become.

  Next, the first rotation direction detection circuit 90 determines whether or not the variable n is “3” (S14). This process is a process for determining whether or not the number of samples of the calculation result SM (n) is sufficient to output the calculation result to the first counter 94. When determining that the variable n is less than “3” (S14: NO), the first rotation direction detection circuit 90 increments the variable n by “1” (S16), and returns to the process of S10. Thereby, the first rotation direction detection circuit 90 newly samples the output signals of the first reference comparators 64 and 68 and the output signals of the second reference comparators 74 and 78 once, and based on these sampling values, the first expression signal Dsin and the second expression signal Dcos are calculated, and a quadrant is calculated based on them.

  On the other hand, when the first rotation direction detection circuit 90 determines that the variable n is “3” (S14: YES), the calculation results SM (1), SM (2), SM (3) match. It is determined whether or not (S18). In this process, the sampling values of the output signals of the first reference comparators 64 and 68 and the output signals of the second reference comparators 74 and 78 sampled in the process of S10 and the calculation results SM (1), SM (2), SM This is a process for evaluating the reliability of (3). If the first rotation direction detection circuit 90 determines that they match (S18: YES), it outputs the calculation result SM (1) to the first counter 94 (S20). Then, the first rotation direction detection circuit 90 substitutes “1” for the variable n (S22), and once ends the series of processes shown in FIG.

  On the other hand, the first rotation direction detection circuit 90 determines that they do not match (S18: NO), that is, the calculation results SM (1), SM (2), SM (3) are different from others. If included, the variable n is incremented by “1” (S24). Next, the first rotation direction detection circuit 90 adds and executes quadrant calculation processing (S26). That is, the first rotation direction detection circuit 90 newly samples the output signals of the first reference comparators 64 and 68 and the output signals of the second reference comparators 74 and 78 once, and based on these sampling values, the first expression signal Dsin. The second expression signal Dcos is calculated, and the quadrant is calculated based on the second expression signal Dcos. Next, the first rotation direction detection circuit 90 substitutes the calculation result of the process of S26 for the calculation result SM (n) (S28). Then, the first rotation direction detection circuit 90 determines whether or not the variable n is “7” (S30). This process is a process for determining whether or not the number of samples of the calculation result SM (n) is sufficient to output the calculation result to the first counter 94 in the situation where a negative determination is made in the process of S18. is there. When determining that the variable n is less than “7” (S30: NO), the first rotation direction detection circuit 90 returns to the process of S24.

  On the other hand, when the first rotation direction detection circuit 90 determines that it is “7” (S30: YES), the seven rotation results SM (1) to SM (7) have the same value. A majority process for determining the largest number is executed (S32). Then, the first rotation direction detection circuit 90 outputs the value determined by the majority process to the first counter 94 (S34), and proceeds to the process of S22.

Here, the operation of the present embodiment will be described.
FIG. 6A illustrates a period in which the detection-side power supply 80 is turned on and a period in which the detection-side power supply 80 is turned off when the IG signal is in an off state, and FIG. 6B illustrates a period in which the detection-side power supply 80 is turned on. Is shown enlarged.

  As shown in FIG. 6, the detection circuit DSC is turned on / off at a cycle of a predetermined period TL. Here, the ON period TS of the detection circuit DSC is shorter than the period “TL-TS” in which the detection circuit DSC is OFF in the predetermined period TL. The on period TS is preferably a length of “1/10” or less of the period “TL-TS” that is turned off in the predetermined period TL, and more preferably a length of “1/20” or less. . It should be noted that the OFF period is set to be equal to or less than the minimum value assumed as the time required for the rotation shaft 26a to rotate 90 °.

  In the on period TS, the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 sample the output signals of the first reference comparators 64 and 68 and the output signals of the second reference comparators 74 and 78 a plurality of times, A quadrant calculation process is executed based on each sampling value. Here, the time interval Tn between the sampling timings is set to a time longer than a cycle that is the reciprocal of the frequency of the noise when the assumed noise is superimposed.

  In the example shown in FIG. 6, in the on period TS starting from time t1, t3, the case where the calculation results SM (1), SM (2), SM (3) match is illustrated, and the on period TS starting from time t2 Shows a case where the calculation results SM (1), SM (2), and SM (3) are different from others. The first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 calculate seven when the calculation results SM (1), SM (2), SM (3) are different from others. A calculation result to be output to the first counter 94 and the second counter 96 is selected by majority processing of the results SM (1) to SM (7). Here, there is a high possibility that the majority-processed value is a correct value. Therefore, for example, even when noise is superimposed only on the calculation result obtained by the first rotation direction detection circuit 90, the calculation results output from the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92 are mutually different. Different values are suppressed. Therefore, as compared with the case where the quadrant calculation process is performed only once and the calculation result is output, the determination circuit 98 determines that the counter value of the first counter 94 and the counter value of the second counter 96 do not match. The possibility of determination is suppressed. For this reason, when the IG signal is switched to the ON state, the possibility that the rotation amount Δθ cannot be output to the microcomputer 34 can be suppressed, and the reliability of the output rotation amount Δθ can be maintained high.

According to the embodiment described above, the following effects can be obtained.
(1) The minimum unit of the rotation amount Δθ calculated by the arithmetic circuit PSC is set to “90 °” which is larger than the minimum unit of the rotation amount of the rotary shaft 26a used by the microcomputer 34 when the IG signal is in the ON state. . For this reason, it is not required to identify a minute rotation amount as the rotation amount Δθ by the arithmetic circuit PSC. For this reason, in comparison with a case where identification of a minute rotation amount is required, the rotation amount calculation result SM (i) “i = 1 to 7” based on each of a plurality of sampling values that move back and forth in time series is included. The possibility of including different parts due to the rotation of the rotating shaft 26a is suppressed. Therefore, it is possible to increase the effectiveness of the process of evaluating the reliability of the calculation result by comparing the rotation amount calculation results SM (i) based on each of the plurality of sampling values.

  (2) A circuit for calculating the rotation amount Δθ in the rotation monitoring circuit 32 when the IG signal is in the OFF state is a first rotation direction detection circuit 90, a first counter 94, a second rotation direction detection circuit 92, and a second counter. The number of rotations Δθ is output to the microcomputer 34 on condition that the calculation results of the amounts of rotation Δθ by them match. In this case, when the rotation amount Δθ is updated based on one sampling value in each of the two sets, there is a risk that the update results of the two sets will be inconsistent due to noise, which causes the microcomputer 34 to have the rotation amount Δθ. The calculation result may not be output. For this reason, the utility value of the majority process of the calculation result by the quadrant calculation process by each of a plurality of sampling values is particularly great.

  (3) When the calculation results SM (1), SM (2), and SM (3) include those that do not match each other, the majority processing of the calculation results SM (1) to SM (7) is executed. For this reason, the reliability of the final rotation amount Δθ can be improved as compared with the case where the majority process based on only the calculation results SM (1), SM (2), and SM (3) is executed.

<Second Embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, the length of the period in which the detection circuit DSC is turned off in the period in which the IG signal is off is longer than that in the case where the rotation of the rotating shaft 26a is not detected. To do.

FIG. 7 shows a processing procedure of the intermittent processing circuit 102 according to the present embodiment. This process is executed every predetermined period TL, which is a cycle for turning on / off the detection circuit DSC.
In the series of processing shown in FIG. 7, the intermittent processing circuit 102 first increases the length of the period during which the detection circuit DSC is turned off due to the rotation shaft 26a being stopped (when stopped). It is determined whether or not the process is being executed (S40). Next, when it is determined that the intermittent processing circuit 102 is executing the process at the time of stop (S40: YES), it is determined whether or not the counter value of the first counter 94 is changed (S42). . If the intermittent processing circuit 102 determines that there is no change (S42: NO), the intermittent processing circuit 102 substitutes the stop time TLS for the predetermined period TL, assuming that the rotating shaft 26a continues to be stopped (S44). The stop time TLS is set to be equal to or less than a minimum value assumed as a time required for the rotation shaft 26a to rotate 90 ° when the rotation shaft 26a starts to rotate.

  On the other hand, when it is determined that there is a change (S42: YES), the intermittent processing circuit 102 assumes that the rotating shaft 26a starts to rotate, and the rotation time TLR shorter than the stop time TLS during the predetermined period TL. Is substituted (S46). The rotation time TLR is set to be equal to or less than the minimum value assumed as the time required for the rotation shaft 26a to rotate 90 ° when the rotation shaft 26a is rotating.

  On the other hand, when determining that the predetermined period TL is set to the rotation time TLR (S40: NO), the intermittent processing circuit 102 determines whether or not the counter value has changed (S48). When determining that there is a change (S48: NO), the intermittent processing circuit 102 proceeds to the process of S46. On the other hand, if it is determined that there is no change (S48: YES), the intermittent processing circuit 102 increments a counter Cn that counts the duration after the change is lost (S50). Next, the intermittent processing circuit 102 determines whether or not the counter Cn is greater than or equal to the threshold value Cth (S52). When the intermittent processing circuit 102 determines that the threshold value is less than the threshold Cth (S52: NO), the process proceeds to S46, and when it is determined that the threshold value Cth is greater than or equal to the threshold Cth (S52: YES), the counter Cn is initialized. The process proceeds to S44.

The intermittent processing circuit 102 once ends the series of processes shown in FIG. 7 when the processes of S44 and S46 are completed.
Here, the operation of the present embodiment will be described.

  When the IG signal is in the off state, the detection circuit DSC is normally turned on / off at the cycle of the stop time TLS. When the rotation of the rotating shaft 26a is detected by the change of the count value of the first counter 94, the detection circuit DSC is turned on / off at the period of the rotation time TLR. For this reason, suitable coexistence with suppressing the power consumption by the circuit DSC for detection as much as possible and monitoring the rotation of the rotating shaft 26a with high accuracy can be achieved.

<Correspondence>
The correspondence relationship between the items in the above embodiment and the items described in the column “Means for Solving the Problems” is as follows. In the following, the correspondence relationship is shown for each number of solution means described in the “means for solving the problem” column. [1] The operation target device corresponds to the inverter 28, the rotation shaft corresponds to the rotation shaft 26a, and the control unit corresponds to the microcomputer 34. [2] The minimum unit of the rotation amount by the arithmetic circuit is 90 °, and the minimum unit of the rotation amount of the rotating shaft used by the control unit is the minimum of the turning angle θp calculated by the turning angle calculation processing unit M12. Corresponds to the unit. [3] The first rotation calculation circuit corresponds to the first rotation direction detection circuit 90 and the first counter 94, and the second rotation calculation circuit corresponds to the second rotation direction detection circuit 92 and the second counter 96. The output circuit corresponds to the determination circuit 98 and the interface 100. [4] Corresponds to the processing of FIG. [5] The first predetermined number corresponds to three, and the second predetermined number corresponds to four.

<Other embodiments>
In addition, you may change at least 1 of each matter of the said embodiment as follows.
・ About the detection circuit
The member that quantizes the sensor output value includes a first reference comparator 64 and a second reference comparator 74 that determine whether the sensor output value is equal to or greater than a predetermined positive value, and whether the sensor output value is equal to or less than a negative predetermined value. It is not limited to the first reference comparator 68 and the second reference comparator 78 that determine whether or not. For example, each of the first reference comparator and the second reference comparator may be a circuit that determines whether the sensor output value is greater than or equal to zero or less than zero. Also, for example, whether each of the first reference comparator and the second reference comparator is less than a value corresponding to −45 degrees and a circuit that determines whether or not the sensor output value is equal to or more than a value corresponding to 45 degrees. It is good also as a circuit which judges.

  In the above embodiment, the output signals of the first reference comparators 64 and 68 are input to both the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92. However, the present invention is not limited to this. For example, a first reference comparator that inputs an output signal to the first rotation direction detection circuit 90 and a first reference comparator that inputs an output signal to the second rotation direction detection circuit 92 may be separate circuits.

  In the above embodiment, the output signals of the second reference comparators 74 and 78 are input to both the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92, but the present invention is not limited to this. For example, the second reference comparator that inputs an output signal to the first rotation direction detection circuit 90 and the second reference comparator that inputs an output signal to the second rotation direction detection circuit 92 may be separate circuits.

  Although the first reference operational amplifier 60 that converts the first reference signal sin into the sine wave signal SIN is shared by the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92, it is not limited thereto. For example, the first reference operational amplifier for the first rotation direction detection circuit 90 and the first reference operational amplifier for the second rotation direction detection circuit 92 may be different operational amplifiers. However, in this case, the first reference comparator that inputs the output signal to the first rotation direction detection circuit 90 and the first reference comparator that inputs the output signal to the second rotation direction detection circuit 92 are different circuits. Is desirable.

  Although the second reference operational amplifier 70 that converts the second reference signal cos into the cosine wave signal COS is shared by the first rotation direction detection circuit 90 and the second rotation direction detection circuit 92, the present invention is not limited to this. For example, the second reference operational amplifier for the first rotation direction detection circuit 90 and the second reference operational amplifier for the second rotation direction detection circuit 92 may be different operational amplifiers. However, in this case, the second reference comparator that inputs the output signal to the first rotation direction detection circuit 90 and the second reference comparator that inputs the output signal to the second rotation direction detection circuit 92 are different circuits. Is desirable.

As described in the section “Rotation angle sensor” below, when the rotation angle sensor is a resolver, the detection circuit includes a circuit that outputs an excitation current to the resolver.
・ "On period of detection circuit"
In the above-described embodiment, the on period is increased between the case where the sampling number is increased because a sampling value giving a different calculation result is included and the case where the sampling number is not increased because a plurality of sampling values give the same calculation result. Although the same, it is not limited to this. For example, the ON period may be extended when the number of samplings is increased because sampling values that give different calculation results are included. In this case, since a sampling value that gives a different calculation result is included, the power consumption can be further reduced as compared with the case where the ON period is the same when the number of samplings is increased and when the number of samplings is not increased. .

  In the above-described embodiment, the ON period within the predetermined period TL is a single period, but the present invention is not limited to this. For example, an off period may be provided between a pair of sampling timings adjacent in time series.

・ About "predetermined period"
The setting of the time interval of the predetermined period TL is not limited to that exemplified in the above embodiments. For example, the rotation time TLR is set to be equal to or less than a minimum value assumed as the time required for the rotation shaft 26a to rotate 270 ° when the rotation shaft 26a is rotating, and the stop time TLS is set. When the rotation shaft 26a starts to rotate, the rotation shaft 26a may be set to be equal to or less than a minimum value assumed as the time required for the rotation shaft 26a to rotate 270 °. However, even in this case, the time interval between the beginning and the end of the sampling timing that goes back and forth in time series within the predetermined period TL is such that the rotating shaft 26a rotates 90 ° when the rotating shaft 26a rotates. It is desirable to set it below the time required for

  In the above embodiment, when the sampling number is increased for the predetermined period TL because a sampling value that gives a calculation result different from the others is included, and when the sampling number is not increased because a plurality of sampling values give the same calculation result However, the present invention is not limited to this. For example, as described in the column “On period of detection circuit”, the sampling period that includes a different calculation result is included. The length of the off period between the on period and the on period may be constant depending on whether the period is extended or not. In this case, the predetermined period that is the sum of the on period and the off period is longer when the on period is not expanded than when the on period is not expanded.

・ About the number of sampling
In the above-described embodiment, the number of samplings within the predetermined period TL is set to three as long as sampling values that give different calculation results are not included, but the number is not limited to this. For example, the number may be three or more, such as five, or two.

  In the above-described embodiment, the number of samplings in the predetermined period TL is 7 when the sampling value that includes a different calculation result is included. However, the present invention is not limited to this. For example, five may be sufficient and nine may be sufficient. It is not limited to an odd number. However, in the case of an even number, it is determined that an abnormality has occurred in the rotation amount calculation result when there are a plurality of rotation amount calculation results that have the same number of identical values.

  In the above-described embodiment, the number of samplings is increased in one step on condition that sampling values that give different calculation results are included, but the present invention is not limited to this. For example, when the number of samplings is increased, the number of samplings may be increased again on condition that the increased sampling values include those that give different calculation results. However, it is not essential to increase the number of samplings on the condition that sampling values giving different calculation results are included. For example, when a negative determination is made in the process of S18 of FIG. 5, the majority process may be executed only by the calculation results SM (1), SM (2), SM (3).

・ "About the first rotation calculation circuit"
In the above embodiment, the first rotation direction detection circuit 90 determines whether or not the calculation results SM (1), SM (2),... Of the quadrant calculation processing match, but this is not restrictive. For example, on the condition that the first counter 94 executes a process of temporarily updating the counter value based on the calculation result based on the sampling value for each of the plurality of sampling values, and those different from others are included in them. The majority counter value may be determined to be the final value.

  The first rotation calculation circuit is not limited to the one provided with the first rotation direction detection circuit 90 and the first counter 94. For example, the minimum rotation amount with a lower resolution than that of the A / D converters 42 and 44 and which can be handled. You may provide the A / D converter below "90 degrees", and the circuit which calculates rotation amount based on the output value of these A / D converters. In this case, however, an analog signal such as signals output from the first reference operational amplifier 60 and the second reference operational amplifier 70 is input to the first rotation calculation circuit.

・ About the second rotation calculation circuit
In the above-described embodiment, the second rotation direction detection circuit 92 determines whether the quadrant calculation processing results SM (1), SM (2),... Match or not. For example, on the condition that the second counter 96 performs a process of temporarily updating the counter value based on the calculation result based on the sampling value for each of the plurality of sampling values, and those different from others are included in them. The majority counter value may be determined to be the final value.

  The second rotation calculation circuit is not limited to the one provided with the second rotation direction detection circuit 92 and the second counter 96. For example, the minimum rotation amount that can be handled with lower resolution than the A / D converters 42 and 44 is provided. You may provide the A / D converter below "90 degrees", and the circuit which calculates rotation amount based on the output value of these A / D converters. In this case, however, analog signals such as signals output from the first reference operational amplifier 60 and the second reference operational amplifier 70 are input to the second rotation calculation circuit.

・ About the arithmetic circuit
In the above embodiment, the second rotation direction detection circuit 92, the second counter 96, and the determination circuit 98 may be deleted. Even in this case, in order to improve the reliability of the rotation amount Δθ output to the microcomputer 34, it is effective to execute quadrant calculation processing based on each of a plurality of sampling values.

  In addition to the rotation calculation circuit including the first rotation direction detection circuit 90 and the first counter 94, and the rotation calculation circuit including the second rotation direction detection circuit 92 and the second counter 96, a third rotation calculation circuit may be included. Good. In this case, for example, the determination circuit may output the calculation result to the microcomputer 34 when the calculation results of the three rotation calculation circuits are the same.

  The arithmetic circuit is not limited to an ASIC. For example, a CPU having a processing capability lower than that of the CPU 36 and a ROM that stores a program executed by the CPU may be provided.

・ "Rotation monitoring circuit"
In the above embodiment, the process of monitoring the rotation of the rotating shaft 26a is performed when the microcomputer 34 is in the off state. However, the present invention is not limited to this, and the rotation of the rotating shaft 26a is performed even when the microcomputer 34 is in the on state. May be constantly monitored. As a result, when the power supply voltage of the microcomputer 34 recovers after temporarily decreasing for some reason, the microcomputer 34 cannot execute the process of calculating the rotation angle of the rotary shaft 26a due to the temporary decrease of the power supply voltage. Even if the period occurs, the rotation angle of the rotation shaft 26a can be calculated with high accuracy based on the rotation amount Δθ monitored by the rotation monitoring circuit after the supply voltage is restored.

・ "About vehicle control using the turning angle θp"
Control of the vehicle using the turning angle θp is not limited to steering assist control. For example, vehicle side slip prevention control may be used. In this case, for example, an external electronic device different from the microcomputer 34 may execute the skid prevention control. In this case, when the IG signal is switched to the on state, the microcomputer 34 stores the rotation amount Δθ from the rotation monitoring circuit 32 and then stored in the nonvolatile memory 40 when the IG signal is switched to the on state. What is necessary is just to correct | amend steering angle (theta) p and to transmit to an external electronic device.

・ About the rotation angle sensor
In the above embodiment, each of the first reference sensor 52 and the second reference sensor 54 is a single sensor, and two sets of circuits for calculating the rotation amount from the output values thereof are used. However, the present invention is not limited to this. For example, the first reference sensor and the second reference sensor for the first rotation direction detection circuit 90 and the first reference sensor and the second reference sensor for the second rotation direction detection circuit 92 in FIG. 3 are different from each other. Also good.

The rotation angle sensor is not limited to the MR sensor, and may be a resolver, for example.
・ About the rotation axis and rotation angle sensor
A rotating shaft that turns the steered wheel 12 by rotating and whose rotation angle is a detection target of the rotation angle sensor is not limited to the rotating shaft 26a of the electric motor 26, and may be, for example, a pinion shaft 22c. .

・ About the steering device
The operation target device of the steering device is not limited to the inverter 28. For example, in a hydraulic power steering apparatus, a pump that adjusts the flow rate of hydraulic oil supplied to the power cylinder may be used as the operation target device, and the discharge flow rate may be used as the operation amount.

  As illustrated in FIG. 1, the steered device is not limited to the one provided with a rack and pinion mechanism. Further, for example, a steering angle ratio variable mechanism that can variably control the ratio between the steering angle that is the rotation angle of the steering wheel 10 and the turning angle θp may be mounted. Even in this case, for example, when the IG signal is provided with a lock mechanism that fixes the steering angle ratio when the IG signal is off, the user operates the steering 10 when the IG signal is off. As a result, the turning angle θp may change, so that the rotation monitoring circuit 32 is useful. Furthermore, a steer-by-wire system in which the steering 10 and the rack shaft 24 are separated may be used. Even in this case, for example, when an IG signal is in an off state, and provided with a fastening member such as a clutch that mechanically connects the steering wheel 10 and the steered wheels 12, the IG signal is in an off state. Since the turning angle θp may change when the user operates the steering wheel 10 at times, there is a utility value of the rotation monitoring circuit 32. However, the need to monitor the change of the turning angle θp when the IG signal is in the off state is not limited to the case where the turning angle θp may change due to the operation of the steering 10.

  DESCRIPTION OF SYMBOLS 10 ... Steering, 12 ... Steering wheel, 20 ... Steering device, 22 ... Steering shaft, 22a ... Column shaft, 22b ... Intermediate shaft, 22c ... Pinion shaft, 24 ... Rack shaft, 25 ... Deceleration mechanism, 26 ... Electric motor, 26a Rotating shaft 28 Inverter 32 Rotation monitoring circuit 34 Microcomputer 36 CPU 38 ROM 40 Non-volatile memory 42, 44 A / D converter 50 Battery 52 First Reference sensor 54 ... second reference sensor 56 ... torque sensor 58 ... vehicle speed sensor 60 ... first reference operational amplifier 62 ... rising side threshold value generating circuit 64 ... first reference comparator 66 ... decreasing side threshold value generating circuit 68: first reference comparator, 70: second reference operational amplifier, 72: rising threshold generation circuit, 74: second reference comparator, 76: decreasing threshold generation circuit, 78 Second reference comparator, 80 ... detection-side power supply, 90 ... first rotation direction detection circuit, 92 ... second rotation direction detection circuit, 94 ... first counter, 96 ... second counter, 98 ... determination circuit, 100 ... interface, 102: Intermittent processing circuit, 104: Clock circuit, 106: Operation side power supply

Claims (5)

The control unit that operates the operation target device of the steered device with the steered device that steers the steered wheel as a control target, and the rotation of the rotating shaft that steers the steered wheel is in an off state. A rotation monitoring circuit for monitoring the rotation control circuit for outputting the rotation monitoring result to the control unit on the condition that the power of the control unit is switched to an ON state. In the circuit
A circuit for outputting a detection result of a rotation angle sensor for detecting a rotation angle of the rotation shaft as an electric signal, and a detection circuit in which power supply and interruption is repeated when the power supply of the control unit is in an off state; ,
Based on the output signal of the detection circuit when power is supplied to the detection circuit, the rotation amount of the rotation shaft is calculated, and the control unit is turned on. An arithmetic circuit that outputs a calculation result to the control unit,
The arithmetic circuit gives a calculation result of the amount of rotation different from the others among a plurality of sampling values that move back and forth in time series of the output signal of the detection circuit within a predetermined period when the power source is in an off state. A rotation monitoring circuit that sets the rotation amount calculation result based on a sampling value having a large number of the same rotation amount calculation results on the condition that a value is included as an output target to the control unit.   The rotation monitoring circuit according to claim 1, wherein a minimum unit of the rotation amount by the arithmetic circuit is larger than a minimum unit of the rotation amount of the rotating shaft used by the control unit when the power is on. The arithmetic circuit includes a first rotation calculation circuit and a second rotation calculation circuit as circuits for calculating a rotation amount of the rotation shaft, and a calculation result by the first rotation calculation circuit and a calculation result by the second rotation calculation circuit. An output circuit that outputs the matched calculation result to the control unit on the condition that they match,
The first rotation calculation circuit is configured on the condition that a plurality of sampling values of the output signal of the detection circuit within the predetermined period include a value that gives a calculation result of the rotation amount different from others. The calculation result of the rotation amount based on the sampling value having a large number of the same calculation result of the amount is output to the output circuit,
The second rotation calculation circuit, on the condition that a value giving a calculation result of the rotation amount different from the others is included in a plurality of sampling values of the output signal of the detection circuit within the predetermined period. The rotation monitoring circuit according to claim 1, wherein the rotation amount calculation result based on a sampling value having a large number of the same amount calculation results is output to the output circuit.   The said arithmetic circuit lengthens the length of the said predetermined period, when it determines with the said rotating shaft not rotating based on the said calculation result compared with the case where it determines with rotating. The rotation monitoring circuit according to any one of the above. The first predetermined number is a plurality, the second predetermined number is one or more,
The arithmetic circuit, on the condition that the first predetermined number of sampling values of the output signal of the detection circuit within the predetermined period includes a value that gives a calculation result of the rotation amount different from others. The second predetermined number of the sampling values are further acquired within the predetermined period, and the calculation result of the rotation amount is the same among the first predetermined number and the second predetermined number of total sampling values. The rotation monitoring circuit according to any one of claims 1 to 4, wherein a calculation result of the rotation amount based on a sampling value having a large number of objects is an output target to the control unit.