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

Abstract

This motor rotation control device includes: a rotation monitoring circuit that outputs a measured rotation speed that is a measurement result of a rotation speed of a motor; a disturbance injection circuit that outputs a disturbance signal which indicates a predetermined upper limit value and a lower limit value repeatedly at fixed intervals; a rotation control circuit that outputs a signal obtained by combining the disturbance signal with an operation amount based on the deviation between the measured rotation speed output from the rotation monitoring circuit and a target rotation speed which is a rotation speed set as a target for the motor; and a motor driver circuit that applies, to the motor, a current or a voltage based on the signal output from the rotation control circuit.

Description

Motor rotation control device, motor rotation control method, and distance measuring device

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

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

[0003] Japanese Patent Publication No. 1-132967

[0004] Although the rotation speed of a 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.

[0006] A motor rotation control device according to one aspect of the present disclosure includes a rotation monitoring circuit that outputs a measured rotation speed, which is a measurement result of the rotation speed of a motor; a disturbance injection circuit that outputs a disturbance signal that repeats predetermined upper and lower limit values ​​at a constant period; a rotation control circuit that outputs a signal that combines the disturbance signal with an operation amount based on the deviation between the measured rotation speed output from the rotation monitoring circuit and a target rotation speed, which 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] A 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 predetermined upper and lower limit values ​​at a constant period, calculates a manipulated variable based on the deviation between the measured rotation speed and a target rotation speed, which is a target rotation speed of the motor, outputs a signal that combines the disturbance signal with the manipulated variable, and applies a current or voltage to the motor based on the signal output from the rotation control circuit.

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

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

[0010] Graph showing an example of the loop characteristics of motor rotation control; Diagram for explaining an input PWM signal and an input carrier signal, and an output PWM signal and an output carrier signal in a conventional motor driver circuit; Diagram for explaining the relationship between the input duty ratio and the output duty ratio in a conventional motor driver circuit; Graph showing an example of the change over time between the conventional output duty ratio and the rotation speed of the motor; Diagram for explaining the relationship between the output duty ratio and the average output duty ratio in the motor driver circuit according to this embodiment; Diagram showing an example of the frequency band of a disturbance signal according to this embodiment; Graph showing an example of the change over time between the output duty ratio and the rotation speed of the motor according to this embodiment; External perspective view of the distance measurement device according to embodiment 1; Longitudinal cross-sectional view of the distance measurement device according to embodiment 1

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

[0012] First Embodiment FIG. 1 is a block diagram showing an example of the configuration of a motor rotation control device 500 according to a first embodiment.

[0013] The motor rotation control device 500 is a device for controlling the rotation 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. These circuits may be separate integrated circuits or may be a single integrated circuit. The functions of these circuits may be realized by a predetermined processor (not shown) working in cooperation 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 this embodiment, the rotation speed of the motor 402 is defined as the number of rotations per minute (rpm). The rotation monitoring circuit 503 may measure the rotation speed by counting an encoder attached to the motor 402 using a photocoupler. Alternatively, the rotation monitoring circuit 503 may measure the rotation speed by counting magnetic changes 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 force 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 determined in advance or may be input by 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 interpreted 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. In other words, the deviation calculation unit 511 calculates "deviation = (target rotation speed - measured rotation speed)".

[0017] The servo filter 512 calculates and outputs a manipulated variable 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 by the disturbance injection circuit 504 with the manipulated variable output from the servo filter 512, and outputs the manipulated variable resulting from the synthesis of the disturbance signal (hereinafter referred to as a disturbance-added manipulated variable). The disturbance injection circuit 504 generates and outputs the 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 disturbance-added manipulated variable as input, and outputs a PWM signal corresponding to the disturbance-added manipulated variable (hereinafter referred to as a disturbance-added PWM signal).

[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 to the motor an output current or output voltage corresponding to the duty ratio (input duty ratio) of the input PWM signal. As shown in the graph of solid line 601A in FIG. 2, the motor driver circuit 502 has a characteristic of applying an output current or output voltage of 0 to 100% in response to an input duty ratio of 0 to 100%. Alternatively, as shown in the graph of dashed dotted line 601B in FIG. 2, the motor driver circuit 502 may have a characteristic of applying an output current or output voltage of 0 to 100% in response to an input duty ratio of 50% to 100%. Alternatively, although not shown, the motor driver circuit 502 may have a characteristic of applying an output current or output voltage in the range of −100 to 100% in accordance with an input duty ratio of 0% to 100%.

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

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

[0023] The rotation control of the motor 402 may be designed to have a gain crossover frequency of about several Hz. For example, as shown in Figure 3, the rotation control of the motor 402 may be designed with a phase margin of 60 degrees or more at the gain crossover and a gain margin of about 20 dB at the phase crossover. In this way, by ensuring sufficient phase margin and gain margin, stable rotation control can be achieved.

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

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

[0026] The duty ratio D of the PWM signal is calculated as follows: D=n / (n+m)×100(%), where n indicates the time during which the voltage is high, m indicates the time during which the voltage is low, and (n+m) indicates the period of the PWM signal.

[0027] As shown in Figure 4(a), the resolution of n1 and m1 of the PWM signal (input PWM signal) input to the motor driver circuit 502 is based on the frequency (input carrier frequency) f1 of the input carrier signal to the motor driver circuit 502. In other words, 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 a base frequency for determining the duty ratio of the PWM signal, and the carrier signal is a signal having this carrier frequency.

[0028] 4(b), the resolution 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 is based on the frequency (output carrier frequency) f2 of the output carrier signal from the motor driver circuit 502. In other words, 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 lower 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. In other words, 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] Because the resolution on the input side and the resolution on the output side differ in this way, the motor driver circuit 502 cannot necessarily 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). In other words, even if the input duty ratio D1 is set precisely, the output duty ratio D2 is limited by the resolution on the output side.

[0031] For example, even if the input duty ratio D1 is set to 49.8%, as shown by the dashed line 604 in Figure 5, the output duty ratio D2 will be 49.6%, as shown by the solid line 605 in Figure 5. Therefore, even if the target rotation speed of the motor 402 is set to 1200 rpm and the optimal input duty ratio D1 is set to 1200 rpm, the motor driver circuit 502 may not be able to generate the optimal output duty ratio D2 for 1200 rpm due to limitations on the output resolution. In this case, for example, as shown by the thin line 607 in Figure 6, the output duty ratio D2 may repeatedly increase and decrease (oscillate), and as a result, the rotation speed of the motor 402 may also repeatedly increase and decrease (oscillate) between approximately 1190 rpm and 1205 rpm, as shown by the thick line 606 in Figure 6. That is, even though the rotation control of the motor 402 is stable as shown in FIG. 3, the rotation speed of the motor 402 may become unstable as shown in FIG.

[0032] In order to solve this problem, the present embodiment provides a motor rotation control device 500 with a disturbance injection circuit 504 and a disturbance synthesis unit 513. The present embodiment will be described in detail below.

[0033] <Configuration of this embodiment> Next, the operation and effect of the motor rotation control device 500 according to this embodiment, which includes the disturbance synthesis unit 513 and the disturbance injection circuit 504, will be described with reference to FIGS.

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

[0035] 7, the disturbance injection circuit 504 outputs a disturbance signal that repeats predetermined upper and lower limit values ​​at a constant cycle. The magnitude between the upper and lower limit values ​​(i.e., the difference between the upper and lower limit values) 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 and lower limit values ​​of the disturbance signal is greater than the resolution of the output duty ratio.

[0036] As shown in FIG. 8 , the frequency band of the disturbance signal may be greater than the frequency band (gain crossover) related to the control of the motor 402, but 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 , assume that 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. In other words, 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, but shorter than the period related to the control of the motor 402.

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

[0038] The PWM converter 514 generates a PWM signal according to the disturbance-added manipulated variable and outputs the disturbance-added PWM signal, which is a signal whose duty ratio fluctuates at a constant cycle.

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

[0040] As a result, as shown in FIG. 7 , the motor driver circuit 502 can apply to the motor 402 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). While the increasing and decreasing output duty ratio (thick dotted line 610) is limited by the resolution of the output side of the motor driver circuit 502, the average output duty ratio (solid line 611) is not limited by the resolution of 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 more finely than the resolution of the output side. In other words, the motor rotation control device 500 can adjust the rotation speed of the motor 402 more finely.

[0041] For example, the motor driver circuit 502 sets the target rotation speed of the motor to 1200 rpm and combines the disturbance signal with the manipulated variable as described above. As a result, as shown in Fig. 9 , the motor driver circuit 502 applies to the motor 402 an output current (or output voltage) corresponding to the average output duty ratio from the output PWM signal with the increasing and decreasing output duty ratio (thin line 613). As a result, the motor rotation control device 500 according to this embodiment applies to the motor 402 an output current (or output voltage) corresponding to the average output duty ratio that cannot be obtained with the resolution of conventional configurations, and as shown in Fig. 9 , the rotation speed (thick line 612) can be stabilized around 1200 rpm without significant fluctuations.

[0042] <Distance Measuring Device> Next, a case where the above-described motor rotation control device is applied to a 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 vertical cross-sectional view of the distance measuring device 1 according to embodiment 1. Fig. 11 corresponds to the A-A cross-sectional view of the distance measuring device 1 shown in Fig. 10.

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

[0044] The fixed unit 100 has a substantially rectangular parallelepiped shape. The rotating unit 300 is connected to the upper surface of the fixed unit 100 and has a cylindrical shape that rotates around a rotation axis C that is perpendicular to the upper surface. The outer cover unit 10 has a substantially cylindrical shape and covers the rotating unit 300 from above. The outer cover unit 10 has a wavelength window 11 formed using a wavelength selection member on at least a portion 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 range. The wavelength selection member has the role of blocking ambient light, such as natural light and electric light.

[0045] For ease of explanation, as shown in FIG. 10 , the axis perpendicular to the top surface (or bottom surface) of the fixed unit 100 is referred to as the Z axis. The axis perpendicular to the Z axis is referred to as the X axis. The axis perpendicular to the Z axis and the X axis is referred to as the Y axis. For ease of explanation, the positive direction of the Z axis may be referred to as "up," the negative direction of the Z axis as "down," and the direction away from the Z axis in the X axis direction or the Y axis direction as "sideways." Note that these directional expressions are used for ease of explanation and are not intended to limit the orientation of the structure during actual use. For example, the distance measurement device 1 shown in FIG. 10 may be used upside down. The A-A cross-sectional view shown in FIG. 11 corresponds to a cross-sectional view in 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 the surface of a housing of a predetermined device).

[0047] The rotating unit 300 rotates around a rotation axis C, which is the central axis in the height direction (Z axis) of the cylinder. As the rotating unit 300 rotates, the optical axis of the projection light (hereinafter referred to as projection light 3A) projected laterally from a portion of the side surface of the rotating unit 300 rotates around the rotation axis C. Accordingly, the projection light 3A and the area where distance measurement can be performed using the projection light 3A (hereinafter referred to as the distance measurement area) also rotate. As described below, the distance measurement device 1 measures the distance to an object 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 reflected from the projection light 3A by an object in the distance measurement area (hereinafter referred to as reflected light 3B) is received. As the rotating unit 300 rotates around the rotation axis C, the distance measurement device 1 can measure the distance to an object in the distance measurement area 360 degrees around it in the horizontal 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 photointerrupter 107. The rotating part 300 includes a rotating member 301, a magnet 302, and a reflecting mirror 303.

[0049] The coil 106 of the fixed part 100 and the magnet 302 of the rotating part 300 form a hollow motor 402, and when driven by this motor 402, the rotating part 300 rotates around the rotation axis C.

[0050] The substrate 101 is, for example, a printed circuit board (PCB). The motor rotation control device 500 described above 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 to be approximately parallel light and outputs it upward.

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

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

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

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

[0057] The rotating member 301 has a plurality of ribs 311 spaced at regular intervals. The photointerrupter 107 is positioned so as to detect the passage of one rib 311. By using the photointerrupter 107 to detect and count the passage of one rib 311, the rotation monitoring circuit 503 can detect the rotation position (rotation angle) of the rotating member 301 (i.e., the rotating part 300). Therefore, the photointerrupter 107 and the ribs 311 can constitute the rotation monitoring circuit 503 shown in FIG. 1 .

[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 unit 300 at a constant rotation speed. As a result, the distance measurement device 1 incorporating the motor rotation control device 500 can more stably and accurately measure the positions and distances of surrounding objects.

[0059] (Summary of First Embodiment) The above description of the first embodiment discloses the following techniques.

[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 predetermined upper and lower limit values ​​at a constant period; a rotation control circuit (501) that outputs a signal that combines the disturbance signal with a manipulated variable based on the 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 (502) that applies a current or voltage based on the signal output from the rotation control circuit to the motor. This allows the motor driver circuit to apply a current or voltage based on the signal that combines the disturbance signal to the motor, thereby achieving a finer resolution than the resolution of a current or voltage based on a signal that does not combine the disturbance signal. This allows the motor to stably rotate 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 to the motor by the motor driver circuit is based on the duty ratio of the PWM signal. This allows the motor driver circuit to apply to the motor a current or voltage based on the duty ratio of the PWM signal.

[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. This makes it possible to stably rotate the motor at a target rotation speed even if the resolution of the duty ratio on the output side is lower than the resolution of the duty ratio on the input side.

[0063] <Technology 4> In the motor rotation control device described in Technology 3, the magnitude between the predetermined upper and lower limit values ​​of the disturbance signal is greater than the resolution of the duty ratio on the output side of the motor driver circuit. This makes it possible to stably rotate the motor at a target rotation speed even if the resolution of the duty ratio on the output side is lower than the resolution of the duty ratio on the input side.

[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 a period corresponding to a control band of the motor and longer than a period of the PWM signal output by the motor driver circuit, thereby enabling the motor to rotate stably at a 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 predetermined upper and lower limit values ​​at a constant cycle, calculates a manipulated variable based on the deviation between the measured rotation speed and a target rotation speed, which is a target rotation speed of the motor, outputs a signal that combines the disturbance signal with the manipulated variable, and applies a current or voltage based on the output signal that combines the disturbance signal to the motor. This allows the current or voltage based on the signal that combines the disturbance signal to be applied to the motor, achieving a finer resolution than the resolution of a current or voltage based on a signal that does not combine a disturbance signal. This allows the motor to rotate stably 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. This makes it possible to realize a distance measurement device in which the motor rotates stably at a target rotation speed.

[0067] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, alterations, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the components in the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0068] This application is based on a Japanese patent application (Patent Application No. 2023-213178) filed on December 18, 2023, the contents of which are incorporated herein by reference.

[0069] The technology of the present disclosure is useful for stabilizing the rotation speed of a motor.

[0070] REFERENCE SIGNS LIST 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 Condenser lens 105 Collimator lens 106 Coil 107 Photointerrupter 300 Rotating part 301 Rotating member 302 Magnet 303 Reflecting 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 part 512 Servo filter 514 PWM conversion part 513 Disturbance synthesis part

Claims

1. A motor rotation control device comprising: a rotation monitoring circuit which outputs a measured rotation speed which is a measurement result of the rotation speed of a motor; a disturbance injection circuit which outputs a disturbance signal which repeats predetermined upper and lower limit values ​​at a constant period; a rotation control circuit which outputs a signal which combines the disturbance signal with an operation amount based on the deviation between the measured rotation speed output from the rotation monitoring circuit and a target rotation speed which is a target rotation speed of the motor; and a motor driver circuit which applies a current or voltage based on the signal output from the rotation control circuit to the motor.

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

3. The motor rotation control device according to claim 2, wherein 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.

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

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

6. A motor rotation control method comprising: monitoring a measured rotation speed, which is a measurement result of the rotation speed of a motor; outputting a disturbance signal which repeats predetermined upper and lower limit values ​​at a constant cycle; calculating a manipulated variable based on the deviation between the measured rotation speed and a target rotation speed which is a target rotation speed of the motor; outputting a signal obtained by synthesizing the disturbance signal with the manipulated variable; and applying a current or voltage based on the output signal obtained by synthesizing the disturbance signal to the motor.

7. A distance measuring device for measuring a distance to an object, comprising the motor rotation control device according to claim 1.

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