Motor rotation control device, motor rotation control method, and distance measurement apparatus

Abstract

To rotate a motor at a target rotation speed stably.SOLUTION: A motor rotation control device includes: a rotation monitoring circuit that outputs a measurement rotation speed which is a measurement result of a rotation speed of a motor; a disturbance injection circuit that outputs a disturbance signal which alternately becomes a prescribed upper limit and a prescribed lower limit in a fixed cycle; a rotation control circuit that outputs a signal formed by combining an operation amount based on a deviation between the measurement rotation speed output from the rotation monitoring circuit and a target rotation speed which is a target rotation speed of the motor with the disturbance signal; and a motor driver circuit that applies current or voltage based on the signal output from the rotation control circuit to the motor.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a motor rotation control device, a motor rotation control method, and a distance measurement device.

Background Art

[0002] A rotation control device that controls the rotation of a motor using an encoder is known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the rotation speed of the motor can be changed by controlling the current or voltage applied to the motor, it is difficult to stably rotate the motor at a target rotation speed.

[0005] An object of the present disclosure is to provide a technique for stably rotating a motor at a target rotation speed.

Means for Solving the Problems

[0006] A motor rotation control device according to an aspect of the present disclosure includes a rotation monitoring circuit that outputs a measured rotation speed that is a measurement result of the rotation speed of the motor, a disturbance injection circuit that outputs a disturbance signal that repeats a predetermined upper limit value and a lower limit value at a constant period, and a rotation control circuit that outputs a signal obtained by synthesizing the disturbance signal with an operation amount based on a deviation between the measured rotation speed output from the rotation monitoring circuit and a target rotation speed that is a target rotation speed of the motor, and a motor driver circuit that applies a current or voltage based on the signal output from the rotation control circuit to the motor.

[0007] The motor rotation control method according to one aspect of the present disclosure monitors a measured rotation speed which is a measurement result of the rotation speed of a motor, outputs a disturbance signal that repeats a predetermined upper limit value and a lower limit value at a constant period, calculates an operation amount based on a deviation between the measured rotation speed and a target rotation speed which is the target rotation speed of the motor, outputs a signal obtained by synthesizing the disturbance signal with the operation amount, and applies a current or a voltage based on the signal output from the rotation control circuit to the motor.

[0008] A distance measuring device according to one aspect of the present disclosure is a distance measuring device that measures the distance to an object, and includes the above-described motor rotation control device.

Effects of the Invention

[0009] According to the present disclosure, the motor can be stably rotated at a target rotation speed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with appropriate reference to the drawings. However, a more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate the understanding of those skilled in the art. Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims thereby.

[0012] (Embodiment 1) FIG. 1 is a block diagram showing a configuration example of a motor rotation control device 500 according to Embodiment 1.

[0013] The motor rotation control device 500 is a device for controlling the rotational speed of the motor 402. The motor rotation control device 500 includes a rotation control circuit 501, a motor driver circuit 502, a rotation monitoring circuit 503, and a disturbance injection circuit 504. Note that these circuits may be separate integrated circuits or a single integrated circuit. Also, the functions of these circuits may be realized by a predetermined processor (not shown) cooperating with a memory (not shown) to execute a predetermined computer program.

[0014] The rotation monitoring circuit 503 measures the rotation speed of the motor 402 and outputs the measured rotation speed (hereinafter referred to as the measured rotation speed). In the present embodiment, the rotation speed of the motor 402 is set as the number of rotations per minute (rpm). The rotation monitoring circuit 503 may measure the rotation speed by counting the encoder attached to the motor 402 with a photocoupler. Alternatively, the rotation monitoring circuit 503 may measure the rotation speed by counting the change in magnetism using a Hall element (Hall IC) or the like attached to the motor 402. Alternatively, the rotation monitoring circuit 503 may measure the rotation speed by measuring the back electromotive voltage generated in the motor 402.

[0015] The rotation control circuit 501 performs control to stably rotate the motor 402 at a target rotation speed (hereinafter referred to as the target rotation speed). The target rotation speed may be predetermined or input from the user. The rotation control circuit 501 includes a deviation calculation unit 511, a servo filter 512, a disturbance synthesis unit 513, and a PWM conversion unit 514. PWM is an abbreviation for Pulse Width Modulation. The servo filter 512 may be read as a PID filter.

[0016] The deviation calculation unit 511 calculates and outputs the deviation between the target rotation speed and the measured rotation speed output from the rotation monitoring circuit 503. That is, the deviation calculation unit 511 calculates "deviation = (target rotation speed - measured rotation speed)".

[0017] The servo filter 512 calculates and outputs an operation amount corresponding to the deviation calculated by the deviation calculation unit 511 using at least one of a proportional term, a differential term, and an integral term and a predetermined gain.

[0018] The disturbance synthesis unit 513 synthesizes the disturbance signal output from the disturbance injection circuit 504 with the operation amount output from the servo filter 512 and outputs the operation amount with the disturbance signal synthesized (hereinafter referred to as the operation amount with disturbance). The disturbance injection circuit 504 generates and outputs a disturbance signal. Details of the disturbance synthesis unit 513 and the disturbance injection circuit 504 will be described later.

[0019] The PWM conversion unit 514 receives the manipulated variable with disturbance and outputs a PWM signal (hereinafter referred to as the PWM signal with disturbance) corresponding to the manipulated variable with disturbance.

[0020] The motor driver circuit 502 is a circuit for controlling the rotational drive of the motor 402. FIG. 2 is a graph showing an example of the correspondence between the input duty ratio and the output current (IM) or output voltage (VM). In the graph shown in FIG. 2, the horizontal axis represents the input duty ratio, and the vertical axis represents the output current or output voltage. For example, as shown in FIG. 2, the motor driver circuit 502 applies an output current or output voltage corresponding to the duty ratio of the input PWM signal (input duty ratio) to the motor. The motor driver circuit 502 has a characteristic of applying the output current or output voltage at 0 to 100% according to the input duty ratio of 0 to 100% as shown in the solid line 601A graph of FIG. 2. Alternatively, the motor driver circuit 502 may have a characteristic of applying the output current or output voltage at 0 to 100% according to the input duty ratio of 50% to 100% as shown in the dashed-dotted line 601B graph of FIG. 2. Alternatively, although not shown, the motor driver circuit 502 may have a characteristic of applying the output current or output voltage at -100 to 100% according to the input duty ratio of 0% to 100%.

[0021] The motor 402 is rotationally driven at a rotational speed corresponding to the output current or output voltage applied from the motor driver circuit 502. Examples of the motor 402 include a DC motor or a three-phase brushless motor.

[0022] FIG. 3 is a graph showing an example of the loop characteristics of the rotational control of the motor 402. In FIG. 3, the horizontal axis represents the frequency, the left vertical axis represents the gain [dB], and the right vertical axis represents the phase [deg]. In FIG. 3, the solid line 602 graph represents the gain and corresponds to the left vertical axis of the graph. The dashed-dotted line 603 graph represents the phase and corresponds to the right vertical axis of the graph.

[0023] The rotational control of the motor 402 may be designed such that the gain crossover is on the order of several Hz. For example, as shown in FIG. 3, the rotational control of the motor 402 may be designed such that the phase margin at the gain crossover is 60 deg or more and the gain margin at the phase crossover is about 20 dB. In this way, by ensuring sufficient phase margin and gain margin, stable rotational control can be achieved.

[0024] <Conventional Configuration> Next, problems in a conventional motor rotational control device that does not include the disturbance synthesizing unit 513 and the disturbance injection circuit 504 will be described with reference to FIGS. 4 to 6.

[0025] FIG. 4 is a diagram for explaining the input PWM signal and the input carrier signal, and the output PWM signal and the output carrier signal in the conventional motor driver circuit 502. FIG. 5 is a diagram for explaining the relationship between the input duty ratio and the output duty ratio in the conventional motor driver circuit 502. In the graph shown in FIG. 5, the horizontal axis represents time, and the vertical axis represents the resolution (duty ratio). FIG. 6 is a graph showing an example of the time change of the conventional output duty ratio and the rotational speed of the motor 402. In the graph shown in FIG. 6, the horizontal axis represents time, the left vertical axis represents the rotational speed (rpm), and the right vertical axis represents the output duty ratio. Also, in the graph shown in FIG. 6, the thick line 606 represents the graph of the rotational speed, and the thin line 607 represents the graph of the output duty ratio.

[0026] The duty ratio D of the PWM signal is calculated as follows. D = n / (n + m)×100 (%) Here, n represents the time when the voltage is High, m represents the time when the voltage is Low, and (n + m) represents the period of the PWM signal.

[0027] As shown in Fig. 4(a), the resolutions of n1 and m1 of the PWM signal (input PWM signal) input to the motor driver circuit 502 are based on the frequency of the input carrier signal (input carrier frequency) f1 of the motor driver circuit 502. That is, the input PWM signal is chopped at the input carrier frequency f1. In this case, n1 is the number of pulses of the input carrier signal included in the time when the voltage is High, and m1 is the number of pulses of the input carrier signal included in the time when the voltage is Low. Note that the carrier frequency is the base frequency for determining the duty ratio of the PWM signal, and the carrier signal is a signal having the carrier frequency.

[0028] As shown in Fig. 4(b), the resolutions of n2 and m2 of the PWM signal (hereinafter referred to as the output PWM signal) corresponding to the output current (or output voltage) output from the motor driver circuit 502 are based on the frequency of the output carrier signal (output carrier frequency) f2 of the motor driver circuit 502. That is, the output PWM signal is chopped at the output carrier frequency f2. In this case, n2 is the number of pulses of the output carrier signal included in the time when the voltage is High, and m2 is the number of pulses of the output carrier signal included in the time when the voltage is Low.

[0029] The output carrier frequency f2 is smaller than the input carrier frequency f1. For example, the output carrier frequency f2 is several hundred Hz, and the input carrier frequency f1 is several hundred kHz. That is, the resolution on the output side of the motor driver circuit 502 is lower than the resolution on the input side of the motor driver circuit 502.

[0030] Since the resolution on the input side and the resolution on the output side are different in this way, the motor driver circuit 502 cannot always generate the output duty ratio D2 (= n2 / (n2 + m2) × 100) at exactly the same ratio as the input duty ratio D1 (= n1 / (n1 + m1) × 100). That is, even if the input duty ratio D1 is set finely, the output duty ratio D2 is limited by the resolution on the output side.

[0031] For example, as shown by the dashed line 604 in FIG. 5, even if the input duty ratio D1 is set to 49.8%, as shown by the solid line 605 in FIG. 5, the output duty ratio D2 will be 49.6%. Therefore, for example, if the target rotational speed of the motor 402 is 1200 rpm and an input duty ratio D1 that is optimal for setting it to 1200 rpm is set, due to the limitation of the resolution on the output side, the motor driver circuit 502 may not be able to generate an output duty ratio D2 that is optimal for setting it to 1200 rpm. In this case, for example, as shown by the graph of the thin line 607 in FIG. 6, the output duty ratio D2 repeats increasing and decreasing oscillations (fluctuations), and as a result, as shown by the graph of the thick line 606 in FIG. 6, a phenomenon may occur in which the rotational speed of the motor 402 also repeats increasing and decreasing oscillations (fluctuations) between around 1190 rpm and 1205 rpm. That is, a phenomenon may occur in which, although the rotational control of the motor 402 is stable as shown in FIG. 3, the rotational speed of the motor 402 becomes unstable as shown in FIG. 6.

[0032] In order to solve such problems, in the present embodiment, a disturbance injection circuit 504 and a disturbance synthesis unit 513 are provided in the motor rotation control device 500. Hereinafter, the present embodiment will be described in detail.

[0033] <Configuration of the Present Embodiment> Next, the operation and effects of the motor rotation control device 500 according to the present embodiment including the disturbance synthesis unit 513 and the disturbance injection circuit 504 will be described with reference to FIGS. 7 to 9.

[0034] FIG. 7 is a diagram for explaining the relationship between the output duty ratio and the average output duty ratio in the motor driver circuit 502 according to the present embodiment. In the graph shown in FIG. 7, the horizontal axis represents time, and the vertical axis represents the resolution (duty ratio). Also, in the graph shown in FIG. 7, the pulsed dotted line 608 represents the disturbance signal, the thick dashed line 609 represents the input duty ratio, the thick dotted line 610 that increases and decreases represents the output duty ratio when the disturbance signal is synthesized, and the solid line 611 represents the average output duty ratio. FIG. 8 is a diagram showing an example of the frequency band of the disturbance signal according to the present embodiment. In FIG. 8, the horizontal axis represents the frequency [Hz]. FIG. 9 is a graph showing an example of the time change of the output duty ratio and the rotational speed of the motor 402 according to the present embodiment. In the graph shown in FIG. 6, the horizontal axis represents time, the left vertical axis represents the rotational speed (rpm), and the right vertical axis represents the output duty ratio. Also, in the graph shown in FIG. 9, the thick line 612 represents the graph of the rotational speed, and the thin line 613 represents the graph of the output duty ratio.

[0035] As shown in FIG. 7, the disturbance injection circuit 504 outputs a disturbance signal that repeats a predetermined upper limit value and a lower limit value at a constant period. The magnitude between the upper limit value and the lower limit value (that is, the difference between the upper limit value and the lower limit value) may be determined based on the resolution of the output duty ratio of the motor driver circuit 502. For example, the magnitude between the upper limit value and the lower limit value of the disturbance signal is larger than the magnitude of the resolution of the output duty ratio.

[0036] As shown in FIG. 8, the frequency band of the disturbance signal may be in a range that is larger than the frequency band (gain crossover point) related to the control of the motor 402 and smaller than the frequency band (output control band) of the output carrier signal of the motor driver circuit 502. For example, as shown in FIG. 8, if the frequency band related to the control of the motor 402 is 0.1 Hz to 10 Hz, the frequency band of the output carrier signal of the motor driver circuit 502 is 100 Hz to 1 kHz, and the frequency band of the input carrier signal of the motor driver circuit 502 is 1 kHz to 10 kHz. In this case, the frequency band of the disturbance signal may be 10 Hz to 100 Hz. That is, the period of the disturbance signal may be 0.01 seconds to 0.1 seconds. In other words, the period of the disturbance signal may be longer than the period of the output carrier signal of the motor driver circuit 502 and shorter than the period related to the control of the motor 402.

[0037] The disturbance synthesizing unit 513 synthesizes the above-described disturbance signal output from the disturbance injection circuit 504 with the operation amount output from the servo filter 512, and generates and outputs an operation amount with disturbance. The operation amount with disturbance becomes a signal that repeatedly alternates between an amount larger than the original operation amount and an amount smaller than the original operation amount at a constant period due to the synthesis of the disturbance signal.

[0038] The PWM conversion unit 514 generates a PWM signal corresponding to the operation amount with disturbance and outputs a PWM signal with disturbance. The PWM signal with disturbance becomes a signal whose duty ratio varies at a constant period.

[0039] The motor driver circuit 502 receives the PWM signal with disturbance as an input PWM signal, and generates and outputs an output PWM signal corresponding to the input PMW signal. Since the input PWM signal is a signal whose input duty ratio varies at a constant period, the output PWM signal is also a signal whose output duty ratio varies at a constant period.

[0040] As a result, as shown in FIG. 7, the motor driver circuit 502 can apply an output current (or output voltage) corresponding to an average output duty ratio (solid line 611), which is the average of the increasing and decreasing output duty ratios (thick dotted line 610), to the motor 402. Although the increasing and decreasing output duty ratios (thick dotted line 610) are limited by the resolution on the output side of the motor driver circuit 502, the average output duty ratio (solid line 611) is not limited by the resolution on the output side of the motor driver circuit 502. Therefore, by using the average output duty ratio (solid line 611), the motor driver circuit 502 can adjust the output current (or output voltage) applied to the motor 402 in finer steps than the resolution on the output side. That is, the motor rotation control device 500 can adjust the rotation speed of the motor 402 in finer steps.

[0041] For example, assuming that the target rotation speed of the motor is 1200 rpm and a disturbance signal is synthesized with the operation amount as described above, as shown in FIG. 9, the motor driver circuit 502 causes the motor 402 to be applied with an output current (or output voltage) corresponding to the average output duty ratio from the output PWM signal having an increasing and decreasing output duty ratio (thin line 613). As a result, the motor rotation control device 500 according to the present embodiment applies an output current (or output voltage) corresponding to an average output duty ratio that cannot be obtained with the resolution of the conventional configuration to the motor 402, and as shown in FIG. 9, the rotation speed (thick line 612) can be stabilized near 1200 rpm without large increasing and decreasing vibrations.

[0042] <Distance measuring device> Next, a case where the above-described motor rotation control device is applied to the distance measuring device 1 will be described. FIG. 10 is an external perspective view of the distance measuring device 1 according to Embodiment 1. FIG. 11 is a longitudinal sectional view of the distance measuring device 1 according to Embodiment 1. FIG. 11 corresponds to a cross-sectional view taken along line A-A in the distance measuring device 1 shown in FIG. 10.

[0043] As shown in FIGS. 10 and 11, the distance measuring device 1 includes a fixed portion 100, a rotating portion 300, and an outer cover portion 10.

[0044] The fixed part 100 has a substantially rectangular parallelepiped shape. The rotating part 300 is connected to the upper surface of the fixed part 100 and has a cylindrical shape that rotates about an axis perpendicular to the upper surface with the rotation axis C. The outer cover part 10 has a substantially cylindrical shape and covers the rotating part 300 from above. The outer cover part 10 has a wavelength window 11 formed using a wavelength selection member on at least a part of its side surface. The wavelength selection member is a material that transmits light of a predetermined wavelength (frequency) component used for distance measurement and blocks light of a wavelength (frequency) component in the visible region. The wavelength selection member has a role of blocking disturbing light such as natural light and electric lights, for example.

[0045] For convenience of explanation, as shown in FIG. 10, an axis perpendicular to the upper surface (or bottom surface) of the fixed part 100 is defined as the Z-axis. An axis perpendicular to the Z-axis is defined as the X-axis. An axis perpendicular to the Z-axis and the X-axis is defined as the Y-axis. Also, for convenience of explanation, the positive direction of the Z-axis may be referred to as "up", the negative direction of the Z-axis may be referred to as "down", and the direction away from the Z-axis in the X-axis direction or the Y-axis direction may be referred to as "sideways". Note that these expressions regarding directions are used for convenience of explanation and are not intended to limit the posture during actual use of the structure. For example, the distance measurement device 1 shown in FIG. 10 may be used with the top and bottom reversed. Also, the cross-sectional view A-A shown in FIG. 11 corresponds to a cross-sectional view of the YZ plane.

[0046] The bottom surface of the fixed part 100 may be fixedly installed on a predetermined plane (for example, a floor surface or a housing surface of a predetermined device, etc.).

[0047] The rotating part 300 rotates about the central axis in the height direction (Z-axis) of the cylinder as the rotation axis C. As the rotating part 300 rotates, the optical axis of the projection light (hereinafter referred to as projection light 3A) projected laterally from a part of the side surface of the rotating part 300 rotates about the rotation axis C. Accordingly, the projection light 3A and the area where distance measurement is possible with the projection light 3A (hereinafter referred to as the distance measurement area) also rotate. As will be described later, the distance measurement device 1 measures the distance to the object existing in the distance measurement area based on the time difference (Time of Flight (TOF)) between the timing when the projection light 3A is projected and the timing when the light (hereinafter referred to as reflected light 3B) reflected by the object in the distance measurement area is received. When the rotating part 300 makes one full rotation about the rotation axis C, the distance measurement device 1 can measure the distances to the objects existing in the distance measurement area of 360 degrees in the lateral circumferential direction.

[0048] The fixed part 100 includes a substrate 101, a light emitting element 102, a light receiving element 103, a condenser lens 104, a collimator lens 105, a coil 106, and a photo interrupter 107. The rotating part 300 includes a rotating member 301, a magnet 302, and a reflecting mirror 303.

[0049] A hollow motor 402 is formed by the coil 106 of the fixed part 100 and the magnet 302 of the rotating part 300. By driving this motor 402, the rotating part 300 rotates about the rotation axis C.

[0050] The substrate 101 is, for example, a Printed Circuit Board (PCB). The above-described motor rotation control device 500 may be mounted on the substrate 101.

[0051] The light emitting element 102 is arranged along the rotation axis C and projects the projection light 3A upward.

[0052] The collimator lens 105 corrects the projection light 3A projected from the light emitting element 102 into substantially parallel light and outputs it upward.

[0053] The mirror 303 is provided on the rotating member 301 so as to reflect, in the lateral direction (direction along the XY plane), the parallel light projected upward from the light-emitting element 102 and corrected by the collimator lens 105. Since the mirror 303 rotates together with the rotating member 301, the projected light is projected (scanned) 360 degrees around in the direction orthogonal to the rotation axis C (lateral direction) with the rotation axis C as the center over time. The projected light 3A reflected by the mirror 303 passes through the wavelength window 11 of the outer cover portion 10 and is projected onto the distance measurement region.

[0054] The reflected light 3B obtained by reflecting the projected light 3A by the object passes through the wavelength window 11 of the outer cover portion 10 and is reflected downward by the mirror 303.

[0055] The condenser lens 104 condenses the reflected light 3B reflected downward by the mirror 303 and outputs it downward.

[0056] The light-receiving element 103 receives the reflected light 3B condensed by the condenser lens 104.

[0057] The rotating member 301 is provided with a plurality of ribs 311 at regular intervals. The photo interrupter 107 is arranged so as to be able to detect the passage of one rib 311. By detecting and counting the passage of one rib 311 using the photo interrupter 107, the rotation monitoring circuit 503 can detect the rotation position (rotation angle) of the rotating member 301 (that is, the rotating portion 300). Therefore, the rotation monitoring circuit 503 shown in FIG. 1 can be configured by the photo interrupter 107 and the rib 311.

[0058] By applying the above-described motor rotation control device 500 to the distance measurement device 1, the motor 402 can stably rotate the rotating portion 300 at a constant rotation speed. Thereby, the distance measurement device 1 to which the motor rotation control device 500 is applied can measure the surrounding object position and object distance more stably and accurately.

[0059] (Summary of Embodiment 1) According to the description of the above Embodiment 1, the following technology is disclosed.

[0060] <Technology 1> A motor rotation control device (500) according to one aspect includes a rotation monitoring circuit (503) that outputs a measured rotation speed which is a measurement result of the rotation speed of a motor (402), a disturbance injection circuit (504) that outputs a disturbance signal that repeats a predetermined upper limit value and a lower limit value at a constant period, and a rotation control circuit (501) that outputs a signal obtained by synthesizing the disturbance signal with an operation amount based on a deviation between the measured rotation speed output from the rotation monitoring circuit and a target rotation speed which is the target rotation speed of the motor, and a motor driver circuit (502) that applies a current or a voltage based on the signal output from the rotation control circuit to the motor. Thereby, since the motor driver circuit can apply a current or a voltage based on the signal obtained by synthesizing the disturbance signal to the motor, a resolution finer than the resolution of the current or voltage based on the signal without synthesizing the disturbance signal can be realized. Therefore, the motor can be stably rotated at the target rotation speed.

[0061] <Technology 2> In the motor rotation control device described in Technology 1, the signal output by the rotation control circuit is a Pulse Width Modulation (PWM) signal, and the current or voltage applied by the motor driver circuit to the motor is based on the duty ratio of the PWM signal. Thereby, the motor driver circuit can apply a current or a voltage based on the duty ratio of the PWM signal to the motor.

[0062] <Technology 3> In the motor rotation control device described in Technology 2, the resolution of the duty ratio on the output side of the motor driver circuit is lower than the resolution of the duty ratio on the input side of the motor driver circuit. Thereby, even when the resolution of the duty ratio on the output side is lower than the resolution of the duty ratio on the input side, the motor can be stably rotated at the target rotation speed.

[0063] <Technology 4> In the motor rotation control device described in Technology 3, the magnitude between the predetermined upper limit value and the lower limit value of the disturbance signal is larger than the magnitude of the resolution of the duty ratio on the output side of the motor driver circuit. Thereby, even when the resolution of the duty ratio on the output side is lower than the resolution of the duty ratio on the input side, the motor can be stably rotated at the target rotation speed.

[0064] <Technology 5> In the motor rotation control device according to any one of Technologies 2 to 4, the constant period of the disturbance signal is shorter than the period corresponding to the control band of the motor and longer than the period of the PWM signal output by the motor driver circuit. Thereby, the motor can be stably rotated at the target rotation speed.

[0065] <Technology 6> A motor rotation control method according to one aspect monitors a measured rotation speed which is a measurement result of the rotation speed of a motor, outputs a disturbance signal that repeats a predetermined upper limit value and a lower limit value at a constant period, calculates an operation amount based on a deviation between the measured rotation speed and a target rotation speed which is the target rotation speed of the motor, outputs a signal obtained by synthesizing the disturbance signal with the operation amount, and applies a current or a voltage based on the signal obtained by synthesizing the output disturbance signal to the motor. Thereby, since a current or a voltage based on a signal obtained by synthesizing a disturbance signal can be applied to the motor, a finer resolution than the resolution of a current or a voltage based on a signal that does not synthesize a disturbance signal can be realized. Therefore, the motor can be stably rotated at the target rotation speed.

[0066] <Technology 7> A distance measurement device according to one aspect is a distance measurement device that measures the distance to an object, and includes the motor rotation control device according to any one of Technologies 1 to 4. Thereby, a distance measurement device in which the motor rotates stably at the target rotation speed can be realized.

[0067] The embodiments have been described above with reference to the accompanying drawings, but the present disclosure is not limited to such examples. It is obvious that those skilled in the art can conceive various modification examples, correction examples, substitution examples, addition examples, deletion examples, and equivalent examples within the scope described in the claims, and it is understood that these also belong to the technical scope of the present disclosure. Further, within the scope not departing from the gist of the invention, the components in the above-described embodiments may be arbitrarily combined.

Industrial Applicability

[0068] The technology of the present disclosure is useful for stabilizing the rotational speed of a motor.

Explanation of Signs

[0069] 1 Distance measuring device 3A Projected light 3B Reflected light 10 Outer cover part 11 Wavelength window 100 Fixed part 101 Substrate 102 Light emitting element 103 Light receiving element 104 Condensing lens 105 Collimator lens 106 Coil 107 Photointerrupter 300 Rotating part 301 Rotating member 302 Magnet 303 Mirror 311 Rib 402 Motor 500 Motor rotation control device 501 Rotation control circuit 502 Motor driver circuit 503 Rotation monitoring circuit 504 Disturbance injection circuit 511 Deviation calculation unit 512 Servo filter 514 PWM conversion unit 513 Disturbance synthesis unit

Claims

1. A rotation monitoring circuit that outputs a measured rotation speed which is the measurement result of the rotation speed of a motor, A disturbance injection circuit that outputs a disturbance signal that repeats a predetermined upper limit value and a lower limit value at a constant period, A rotation control circuit that outputs a signal obtained by synthesizing the disturbance signal with an operation amount based on the deviation between the measured rotation speed output from the rotation monitoring circuit and the target rotation speed which is the target rotation speed of the motor, A motor driver circuit that applies a current or voltage based on the signal output from the rotation control circuit to the motor, and comprises, A motor rotation control device.

2. The signal output by the rotation control circuit is a Pulse Width Modulation (PWM) signal, The current or voltage applied by the motor driver circuit to the motor is based on the duty ratio of the PWM signal, The motor rotation control device according to claim 1.

3. The resolution of the duty ratio on the output side of the motor driver circuit is lower than the resolution of the duty ratio on the input side of the motor driver circuit, The motor rotation control device according to claim 2.

4. The magnitude between the predetermined upper limit value and the lower limit value of the disturbance signal is larger than the magnitude of the resolution of the duty ratio on the output side of the motor driver circuit, The motor rotation control device according to claim 3.

5. The constant period of the disturbance signal is shorter than the period corresponding to the control band of the motor and longer than the period of the PWM signal output by the motor driver circuit, The motor rotation control device according to claim 2.

6. Monitoring the measured rotation speed which is the measurement result of the rotation speed of the motor, Outputting a disturbance signal that repeats a predetermined upper limit value and a lower limit value at a constant period, Calculating an operation amount based on the deviation between the measured rotation speed and the target rotation speed which is the target rotation speed of the motor, and outputting a signal obtained by synthesizing the disturbance signal with the operation amount, Applying a current or voltage based on the output signal obtained by synthesizing the disturbance signal to the motor, A motor rotation control method.

7. A distance measurement device that measures the distance to an object, Comprising the motor rotation control device according to claim 1, A distance measurement device.

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