JP2005156496A - Speed detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent noise generation, resulting from quantization errors, without causing lowering of responsiveness during speed control of a servomotor. <P>SOLUTION: The speed detector has a rotating substrate 27 fixed to the rotating shaft of a servomotor, on which two acceleration sensors 21 and 22 are arranged to detect acceleration in the circumferential direction. The acceleration sensors 21 and 22 are placed point symmetrically with respect to the center of turning substrate 27. Both the acceleration sensors 21 and 22 have a piezoelectric member 28, which output positive signals, when the rotating substrate 27 rotates in the CW direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a speed detection device used for speed control of a servo motor.

Servo motors are widely used as drive sources when high responsiveness such as frequent changes in speed and rotation direction is required. As a control method of such a servo motor, it is known to feedback control the speed of the rotation shaft of the servo motor. When controlling the servo motor at speed, the speed command value created by the controller is input to the driver to rotate the servo motor, and the rotation speed of the rotor at this time is detected by the encoder and fed back to the controller ( For example, see Patent Document 1).
JP 2002-6961 A

However, if an encoder is used to detect the rotation speed of a servo motor, pulse-like noise may occur due to an error accompanying quantization when the analog signal output from the encoder is digitally processed. It was one of the causes.
As a means for preventing the quantization error of the encoder, it is possible to increase the resolution of the encoder, but an encoder having a high resolution is expensive. Also, if the speed control cycle is lengthened in order to prevent quantization errors of the encoder, the response performance of the servo motor is degraded.
The present invention has been made in view of such a problem, and an object of the present invention is to prevent the generation of noise based on a quantization error without reducing the response when performing speed control of a servo motor. .

The invention according to claim 1 of the present invention for solving the above-mentioned problems is arranged such that the substrate attached to the rotation shaft of the servo motor and the substrate are distributed along the rotation direction of the substrate, and the rotation speed of the rotation shaft is detected. The speed detection device includes an acceleration sensor used to perform the calculation and a calculation circuit that calculates the speed of the rotation axis from the acceleration detected by the acceleration sensor.
According to this speed detection apparatus, since the acceleration sensor is arranged on the substrate attached to the rotation shaft of the servo motor, when the rotation shaft is rotated, the acceleration generated due to this can be detected. If this acceleration is calculated by an arithmetic circuit, for example, an integration process, the speed of the rotation axis can be obtained.

According to a second aspect of the present invention, in the speed detection device according to the first aspect, the acceleration sensor is a piezoelectric element that detects an acceleration in the rotation direction of the substrate, and the arithmetic circuit includes an integration circuit. And
According to this speed detection device, when the substrate rotates, the piezoelectric element is deformed in the direction opposite to the rotation direction, so that the acceleration of the substrate can be obtained from the deformation amount of the piezoelectric element. Then, when the obtained acceleration is integrated by an integration circuit, the speed of the substrate (rotating axis) can be obtained.

The invention according to claim 3 is the speed detection device according to claim 1 or 2, wherein the acceleration sensor is a piezoelectric element that detects a force acting in a direction orthogonal to a rotation direction of the substrate. The arithmetic circuit includes a square root circuit.
According to this speed detection device, when the substrate rotates, a centrifugal force acts on the piezoelectric element, and the piezoelectric element is deformed toward the outer peripheral side of the substrate. Therefore, by performing a predetermined calculation based on the deformation amount, the speed of the substrate Can be requested.

According to a fourth aspect of the present invention, in the speed detection device according to any one of the first to third aspects, the acceleration sensor is disposed at a point-symmetrical position with respect to the rotation center of the substrate. It is characterized by that.
According to this speed detection device, since the acceleration sensor is arranged at a point-symmetrical position with respect to the rotation axis of the substrate, the same signal is output for the rotation of the substrate, but the substrate vibrates. In this case, a signal in which the sign is reversed is output. Therefore, when the signals of the two acceleration sensors arranged at the target positions are added, the vibration component of the substrate can be removed.

According to a fifth aspect of the present invention, in the speed detection device according to any one of the first to third aspects, the substrate is provided with a plurality of light reflecting portions along a circumferential direction, and the housing of the servo motor is provided. An optical pickup for irradiating light to the light reflecting portion and receiving reflected light is fixed on the body side.
According to this speed detection device, when the substrate rotates together with the rotation shaft of the servo motor, the light reflecting portion passes on the optical path of the optical pickup. Since the interval at which the light reflecting portion passes on the optical path changes according to the rotation speed of the substrate, the rotation speed of the substrate can be detected by examining the light receiving period of the reflected light. The light reflecting portion and the optical pickup constitute a light reflecting encoder. Such an encoder is used, for example, to compensate information of an acceleration sensor or to detect the rotation direction of the substrate.

According to a sixth aspect of the present invention, in the speed detection device according to any one of the first to fourth aspects, a high-pass filter that removes a low-frequency component from a signal based on an output of the acceleration sensor, and the rotating shaft An encoder used to detect the rotational speed of the encoder, a low-pass filter that removes high-frequency components from a signal based on the output of the encoder, and an adder that adds the low-pass filter and the signal that has passed through the high-pass filter. It is characterized by.
In this speed detection device, the acceleration sensor information is compensated by the information obtained by cutting the low frequency component with a filter and the cut portion information from the encoder. When calculating the speed by integrating the acceleration, it is possible to accurately detect the speed of the servo motor by cutting a low frequency component that is likely to cause an error.

According to the first aspect of the present invention, the substrate is attached to the rotation shaft of the servo motor, and the acceleration sensors are distributed and arranged along the rotation direction of the substrate, so that the speed of the rotation shaft can be reliably detected with a simple configuration. can do. Since the speed information obtained in this way is obtained by integrating the acceleration, for example, it does not have a conventional differential error (quantization error). Therefore, the generation of noise based on the differential error can be prevented. Further, in such a speed detection device, the speed control cycle can be shortened, so that responsiveness can be improved.
According to the second aspect of the present invention, the acceleration of the substrate can be easily obtained by using the piezoelectric element that detects the acceleration in the rotation direction of the substrate. For this reason, since the cycle of speed control can be shortened, responsiveness can be further improved.
According to the third aspect of the present invention, the piezoelectric element is deformed in the direction orthogonal to the rotation direction of the substrate, the centrifugal force is measured, and the speed of the rotation shaft is calculated therefrom. The generation of noise can be prevented.
According to the invention described in claim 4, since it is arranged point-symmetrically with respect to the rotation center of the substrate, when the rotation shaft vibrates, a signal resulting from such vibration is superimposed on the output of the acceleration sensor. However, since it can be easily removed, the speed of the rotating shaft can be accurately detected.
According to the fifth aspect of the present invention, when the speed detection using the acceleration sensor and the speed detection using the encoder are used in combination, the part that reflects the light of the encoder is arranged on the substrate used for the arrangement of the acceleration sensor. Since it is used as a member to be used, the number of parts can be reduced. Therefore, the speed detection device can be manufactured at low cost. Moreover, the speed detection device can be made compact by sharing the parts.
According to the sixth aspect of the invention, the low-frequency component of the acceleration sensor information is cut by the high-pass filter, and thus the insufficient information is compensated by the information from the encoder. It can be detected accurately. The information from the encoder is not affected by the differential error because the high frequency component is cut by the low pass filter.

The best mode for carrying out the invention will be described in detail with reference to the drawings.
First, the servo motor system will be described with reference to FIG.
The servo motor system 1 has a subtracter 2 that subtracts an actually measured speed signal (speed feedback signal) from a speed command signal created by an external device. The output of the subtracter 2 is connected to the input of the speed controller 3. The speed controller 3 is a device that calculates a current command value for driving the servo motor 4 in accordance with the speed deviation, and its output is connected to the driver 5. The driver 5 is a drive circuit including a switching element that rotates the servo motor 4 based on a current command value. Further, the servo motor 4 includes a first speed detection device 6 that detects the rotational speed of the servo motor 4 using a piezoelectric accelerometer described later, and a second speed detector that detects the rotational speed of the servo motor 4 using an encoder described later. A speed detection device 7 is linked. The output of the first speed detection device 6 is connected to an adder 9 through a high pass filter 8. The output of the second speed detection device 7 is connected to the adder 9 via the low-pass filter 10. The adder 9 creates the speed feedback signal, and its output is connected to the subtractor 2 described above.

Further, FIG. 2 shows a configuration of the first speed detection device 6.
As shown in FIG. 2, the first speed detection device 6 includes two acceleration sensors 21 and 22, each of which is connected to sensor amplifiers 23 and 24. The outputs of the sensor amplifiers 23 and 24 are connected to an adder 25, and the added signal is input to an integration circuit 26 which is an arithmetic circuit. The output of the integrating circuit 26 is connected to the low pass filter 8 shown in FIG.

Next, a specific configuration of the first speed detection device will be described with reference to FIGS. 3 and 4.
The first speed detection device 6 has a rotating substrate 27 on which acceleration sensors 21 and 22 are mounted. The rotating substrate 27 is fixed to the other end of the rotating shaft 41 of the servo motor 4. Note that one end of the rotating shaft 41 of the servo motor 4 is linked to a load (not shown).

  As shown in FIG. 3, two acceleration sensors 21 and 22 are attached to the rotary substrate 27 at positions that are 180 degrees out of phase with respect to the center (rotary axis) of the rotary substrate 27 along the circumferential direction. Yes. The acceleration sensors 21 and 22 include a piezoelectric member 28 that generates a voltage by being deformed according to the magnitude of acceleration, and electrodes 29 and 30 that extract the voltage as an electrical signal at both ends of the piezoelectric member 28. The electrode 30 has a long side that is in close contact with the piezoelectric member 28, and is disposed along the circumferential direction of the rotating substrate 27 and perpendicular to the radial direction of the rotating substrate 27. Further, the electrode 29 is disposed in parallel with the electrode 30 on the outer edge side of the rotating substrate 27. The electrodes 29 and 30 are attached to the rotating substrate 27 with silver paste or solder.

The ends of the piezoelectric member 28 are fixed to the electrodes 29 and 30 arranged as described above, and can be deformed mainly along the rotation direction of the rotating substrate. In this embodiment, the acceleration sensor 21 is configured to output a positive value as the acceleration when the piezoelectric member 28 is deformed in the direction indicated by the arrow A. The acceleration sensor 22 is configured to output a positive value as the acceleration when the piezoelectric member 28 is deformed in the direction indicated by the arrow B. That is, the acceleration sensors 21 and 22 are arranged symmetrically with respect to the center of the rotating board 27, and when the rotating board 27 rotates clockwise (CW), both the acceleration sensor 21 and the acceleration sensor 22 output positive signals. When output and rotate counterclockwise (CCW), both output negative signals.
Further, as schematically shown in FIG. 3, sensor amplifiers 23 and 24 that amplify electric signals of the acceleration sensors 21 and 22, an adder 25, and an integration circuit 26 are mounted on the rotating substrate 27. These components are lightweight, but are preferably arranged symmetrically with respect to the center of the rotating substrate 27 in consideration of the balance during rotation.
The acceleration sensors 21 and 22, the sensor amplifiers 23 and 24, the adder 25, and the integration circuit 26 are mounted on the surface of the rotary substrate 27 that faces the servo motor 4.

On the other hand, as shown in FIG. 3, in the center of the surface opposite to the surface on which the acceleration sensors 21 and 22 are mounted on the rotary substrate 27, the speed signal output from the integrating circuit 26 is taken out to the outside. A light emitting element 31 to be used is attached. A light receiving element 32 is provided at a position facing the light emitting element 31. The light receiving element 32 is attached to a fixing member 33 provided outside the rotating substrate 27. The fixing member 33 is fixed to a cover 34 fixed to the housing 4 a of the servo motor 4.
Further, a transformer core 42 having an annular groove is attached around the light emitting element 31. A transformer core 43 is attached around the light receiving element 32. These transformer cores 42 and 43 are made of a magnetic material. The annular grooves are provided so as to face each other, and coils 35 and 36 are provided in each of the annular grooves. The secondary coil 35 on the rotary substrate 27 side is disposed in the annular groove of the transformer core 42 and is connected to the sensor amplifiers 23 and 24, the adder 25, the integrating circuit 26, the light emitting element 31, and the like. The primary coil 36 on the fixing member 33 side is disposed in the annular groove of the transformer core 43 and is connected to a power source (not shown). Therefore, when the primary side coil 36 is energized, a magnetic path is formed by electromagnetic induction, and power is supplied to the sensor amplifier 23 and the like via the secondary side coil 35.

  The second speed detection device 7 includes an encoder 37 disposed on the housing side of the servo motor 4 with respect to the rotating substrate 27, and an electric circuit (not shown) connected to the encoder 37. The encoder 37 is a rotary encoder that detects the rotation of the rotary shaft using magnetism or light. FIG. 3 shows a configuration example of a transmissive optical rotary encoder. That is, the encoder 37 has slits (not shown) at substantially equal intervals along the circumferential direction of the disk 38 fixed to the rotating shaft 41, and the light emitting element 39 and the light receiving element 40 are sandwiched between the slits. It has the structure fixed to the cover 34 side.

Next, rotation control of the servo motor 4 in the servo motor system 1 will be described. It is assumed that power is stably supplied to the circuit mounted on the rotating substrate 27 through the coils 35 and 36.
When the servo motor 4 starts to rotate by the speed controller 3 shown in FIG. 1 or the like, the rotating shaft 41 as shown in FIG. 3 rotates, and the rotating substrate 27 rotates accordingly. For example, when the rotary substrate 27 starts to rotate clockwise (CW), the piezoelectric member 28 of the acceleration sensor 21 is deformed in the direction opposite to the rotation direction, and the electrode 29 and 30 have a size corresponding to the deformation amount. A positive voltage is generated. A sensor amplifier 23 connected to the acceleration sensor 21 amplifies this voltage and takes it out as an acceleration signal. Similarly, since a positive voltage corresponding to the magnitude of acceleration is also generated in the acceleration sensor 22 at a position that is 180 degrees out of phase with the acceleration sensor 21, the acceleration signal is amplified by the sensor amplifier 24 and extracted.

  The acceleration signals output from the sensor amplifiers 25 and 26 are added by the adder 25 and then input to the integration circuit 26. Here, the rotary substrate 27 may vibrate in the radial direction as indicated by an arrow X due to the vibration of the rotation shaft 41 of the servo motor 4. In such a case, the acceleration sensors 21 and 22 may also be deformed by vibration, and noise based on vibration may be included in the acceleration signals output from the sensor amplifiers 23 and 24. However, in this embodiment, such noise is removed by adding the acceleration signals from the acceleration sensors 21 and 22 at positions shifted by 180 degrees by the adder 25. That is, for example, when the rotating substrate 27 is rotating while moving at a predetermined acceleration in the X direction at a certain time interval, the acceleration sensor 21 is moving the rotating substrate 27 in the direction opposite to the detection direction. Therefore, an acceleration signal reduced by the amount of movement in the X direction is output. On the other hand, the acceleration sensor 22 outputs the acceleration signal increased by the amount of movement in the X direction because the rotary substrate 27 is moving in the same direction as the detection direction. As a result, when the two acceleration signals are added, the increase / decrease in the acceleration signal due to the movement in the X direction is canceled, and an electric signal obtained by doubling the rotation acceleration signal is obtained.

The acceleration signal added by the adder 25 is input to the integration circuit 26, and the speed signal is calculated in the integration circuit 26.
The speed signal output from the first speed detection device 6 in this way is input to the light emitting element 31 attached to the center of the rotating substrate 27 toward the fixed member 33. The light emitting element 31 emits light according to the profile of the speed signal, and the light receiving element 32 arranged oppositely outputs an electric signal according to the light emission. This electrical signal is input to the high-pass filter 8 (see FIG. 1) as a speed signal detected by the first speed detector 6.
The high pass filter 8 removes low frequency components from the speed signal. The reason why the high-pass filter 8 is provided is that an integration error when integrating the speed from the acceleration is likely to appear in the low frequency band, so that such an integration error is eliminated and the speed control of the servo motor 4 is performed with high accuracy. is there.

  On the other hand, in the second speed detection device 7, a pulse signal is output from the encoder 37 as the rotation shaft 41 of the servo motor 4 rotates. As for the pulse signal, for example, when the slit of the disk 38 that rotates together with the rotating shaft 41 passes on the optical path of the light emitting element 39, the amount of light received by the light receiving element 40 continuously changes from zero to the maximum value. Quantized analog information can be obtained.

  The pulse signal output from the encoder 37 is input to an electric circuit (not shown) and converted into a speed signal. Here, the speed signal generated in the second speed detecting device 7 is input to the adder 9 after the high frequency component is removed by the low-pass filter 10. The reason why the low-pass filter 10 is provided is that noise due to the quantization error is likely to appear in a high frequency band, so that such a quantization error is eliminated. Since the speed signal of the second speed detection device 7 is sufficient if the speed signal of the first speed detection device 6 can be compensated, a filter having characteristics that compensate the high-pass filter 8 is used.

  In the adder 9, the speed signal detected by the first speed detection device 6 and the speed signal detected by the second speed detection device 7 are added. The added speed signal becomes a speed feedback signal. As described above, the two detection signals are composed of frequency domain signals that can output signals with high accuracy for the respective speed detection devices 6 and 7, and signals in all frequency bands are compensated by the adder 9. Therefore, the speed feedback signal is a signal with less noise and accurately detecting the rotation speed of the servo motor 4.

  The speed feedback signal is input to the subtracter 2 and used for calculating a deviation from the speed command signal, that is, fed back to the servo control of the servo motor. Thereby, the speed of the servo motor 4 is controlled so as to quickly reach the commanded speed.

According to this embodiment, since the acceleration sensors 21 and 22 for detecting the acceleration in the rotation direction of the rotation shaft 41 of the servo motor 4 are arranged separately and the speed of the servo motor 4 is detected, quantization is performed. A speed signal without the accompanying differential error can be obtained. Therefore, noise generated by the differential error can be prevented. Further, since the generation of noise can be prevented, the proportional gain of the current supplied to the servo motor 4 can be increased, so that the response of the servo motor 4 can be improved.
Moreover, since the acceleration sensors 21 and 22 are composed of piezoelectric elements, the first speed detection device 6 can be manufactured at low cost. Furthermore, since two acceleration sensors 21 and 22 are arranged and the sum of their output signals is taken, the sensitivity can be improved by a factor of two compared to a single case. Since the acceleration sensors 21 and 22 are arranged at positions that are 180 degrees out of phase so that they are in the same direction in the circumferential direction and the sum of the two output signals is taken, the servo motor 4 vibrates. Even in this case, noise due to vibration can be removed. Therefore, the speed of the servo motor 4 can be detected with high accuracy.

  Furthermore, since the second speed detection device 7 including the encoder 37 is provided as a device for detecting the speed of the servo motor 4 and the second speed detection device 7 is used for speed detection in the low frequency region, the low frequency is used. A speed signal can be generated with high accuracy up to a high frequency. It is possible to detect the speed of the servo motor only by the first speed detection device 6 without providing the second speed detection device 7. This is because the first speed detection device 6 can improve the responsiveness of the servo motor 4 because an accurate speed signal can be obtained in a high frequency region.

Next, a second embodiment of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment. Moreover, the description which overlaps with 1st Embodiment is abbreviate | omitted.
This embodiment is characterized in that the acceleration sensor is arranged so that the radial acceleration (centrifugal force) of the rotary substrate 27 can be detected.

As shown in FIG. 5, the first speed detection device 46 includes two acceleration sensors 51 and 52, to which sensor amplifiers 23 and 24 are connected, respectively. Further, the outputs of the sensor amplifiers 23 and 24 are connected to an adder 25, and the signal after the addition is input to a square root circuit (square root circuit) 53 which is an arithmetic circuit.
Further, as shown in FIG. 6, the first speed detection device 46 has a rotating board 27 that rotates together with the rotating shaft 41 of the servo motor 4, and two acceleration sensors 51 and 52 are mounted on the rotating board 27. Yes. The acceleration sensors 51 and 52 have a configuration in which the electrodes 29 and 30 are provided at both ends of the piezoelectric member 28, and are rotated 90 degrees counterclockwise (CCW) from the direction of the first embodiment. It is attached. That is, the piezoelectric member 28 is disposed so as to generate a voltage by deforming a change in centrifugal force generated when the rotating substrate 27 rotates according to detection.

  The acceleration sensor 51 is configured to output a positive value as an acceleration when the piezoelectric member 28 is deformed radially outward as indicated by an arrow B. The acceleration sensor 22 is configured to output a positive value as the acceleration when the piezoelectric member 28 is deformed in the direction indicated by the arrow D. That is, the acceleration sensors 51 and 52 are arranged symmetrically with respect to the center of the rotating board 27 so that when the rotating board 27 rotates, the acceleration sensor 51 and the acceleration sensor 52 output signals having the same sign. It has become.

Processing for detecting the rotation speed of the servo motor 4 using the first speed detection device 46 will be described.
When the rotating substrate 27 starts to rotate together with the rotating shaft 41, centrifugal force acts on the acceleration sensors 51 and 52, and the piezoelectric member 28 is deformed outward in the radial direction of the rotating substrate 27. A voltage is generated between the electrodes 29 and 30 in accordance with the magnitude of the centrifugal force, and this voltage is amplified by the sensor amplifiers 23 and 24, respectively, to obtain a centrifugal force signal. The centrifugal force signals are added by the adder 25, and after the vibration component is removed, the centrifugal force signals are input to the square root circuit 53. Since the centrifugal force is proportional to the square of the circumferential speed, the square root circuit 53 calculates the circumferential speed from the centrifugal force. The speed signal obtained as the calculation result is transmitted from the light emitting element 31 on the rotating substrate 27 side to the light receiving element 32 on the fixed member 33 side and input to the high pass filter 8.
The speed signal of the first speed detection device 46 thus obtained is compensated with the speed signal simultaneously detected by the second speed detection device 7 to generate a speed feedback signal.

  Here, the rotating substrate 27 may vibrate in the radial direction as indicated by an arrow Y, for example, due to the rotating shaft 41 of the servo motor 4 vibrating. In such a case, the acceleration sensors 51 and 52 may also be deformed by vibration, and noise based on vibration may be included in the acceleration signals output from the sensor amplifiers 23 and 24. However, in this embodiment, such noise is removed by adding the acceleration signals from the acceleration sensors 51 and 52 at the positions shifted by 180 degrees by the adder 25. That is, for example, when the rotary substrate 27 is rotating while moving at a predetermined acceleration in the Y direction at a certain time interval, the acceleration sensor 51 is subjected to acceleration in the same direction as the centrifugal force, and thus parallel. A signal increased by the movement acceleration is output. On the other hand, the acceleration sensor 52 outputs the acceleration signal reduced by the amount of movement in the Y direction because the rotary substrate 27 is moving in the direction opposite to the detection direction. As a result, when the two acceleration signals are added, the increase / decrease in the acceleration signal due to the movement in the Y direction is canceled, and an electric signal obtained by doubling the signal due to the centrifugal force is obtained.

According to this embodiment, as in the first embodiment described above, it is possible to obtain a speed signal without a differential error associated with quantization and to prevent noise. In addition, the response of the servo motor 4 can be improved.
Furthermore, since the two acceleration sensors 51 and 52 are arranged, the sensitivity can be improved by a factor of two. Further, even when the servo motor 4 vibrates, noise due to vibration can be removed, so that the speed of the servo motor 4 can be detected with high accuracy.
And by using together the 2nd speed detection apparatus 7 containing the encoder 37, a speed signal can be accurately generated from a low frequency to a high frequency. At this time, since the first speed detection device 46 does not perform integration processing, the high-pass filter 8 can use a filter that passes a speed signal on a lower frequency side than the first embodiment. Therefore, since only the information on the lower frequency side is sufficient for the information of the encoder 37, an encoder with a low resolution can be used.

  Since the acceleration sensors 51 and 52 cannot detect the rotation direction of the rotation board 27, the rotation direction of the rotation board 27 is specified based on the output of the encoder 37. Further, at least one acceleration sensor 21, 22 as shown in FIG. 4 may be arranged to detect the rotation direction of the rotating substrate 27.

Next, a third embodiment of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the component same as 1st, 2nd embodiment. Moreover, the description which overlaps with 1st, 2nd embodiment is abbreviate | omitted.
This embodiment is characterized in that the first speed detection device and the second speed detection device in each of the above-described embodiments are integrally configured.

  As shown in FIG. 7, the speed detection device 61 includes a rotating board 62 attached to the rotating shaft 41, and two acceleration sensors 21 and 22 are arranged in a distributed manner in the circumferential direction of the rotating board 62. In addition, sensor amplifiers 23 and 24, an adder 25, and an integration circuit 26 (see FIG. 1) are mounted on the rotating substrate 62. In addition, a light emitting element 31 is attached to the surface of the rotating substrate 62 opposite to the acceleration sensors 21 and 22 and the like, and a secondary coil 35 is disposed so as to surround the light emitting element 31. . Further, as shown in FIG. 8, a light reflecting portion in which a material having a high light reflectance is printed in a substantially square shape at equal intervals along the circumferential direction on the outer peripheral portion of the surface to which the light emitting element 31 is attached. 63.

  In the speed detection device 61, the fixed plate 33 fixed to the housing 4a side of the servo motor 4 is provided with a light receiving element 32 facing the light emitting element 31 at the center, and a primary side coil 36 is disposed around the light receiving element 32. Has been. Further, the light reflecting portion 63 is irradiated with light at a position facing the one light reflecting portion 63 of the plurality of light reflecting portions 63 of the rotating substrate 62 on the outer periphery of the fixed plate 33, and the reflected light is received. A reflective pickup 64 is attached. The reflection type pickup 64 and the light reflection portion 63 constitute an optical encoder having the same function as the encoder 37 in the first embodiment. Reference numeral 65 denotes a terminal for taking out a signal from the light reflection type pickup 64, and reference numeral 66 denotes a cable for connecting the terminal 65 to an external device.

  In the speed detection device 61, when the servo motor 4 rotates, the rotating substrate 62 rotates together with the rotating shaft 41. At this time, as described above, the acceleration sensors 21 and 22 are deformed to detect circumferential acceleration. At the same time, when the light reflecting pickup 64 emits light, the light reflecting portion 63 that rotates together with the rotating substrate 62 sequentially passes through the light path of the light reflecting pip-up 64. Since the light is reflected when the light reflecting portion 63 passes on the optical path, the reflected light is received by the light reflecting pickup. As the rotation speed of the rotating substrate 62 gradually increases, the time interval for receiving the reflected light gradually decreases. On the other hand, as the rotational speed decreases, the time interval for receiving the reflected light increases. Then, the analog signal generated by the light reflection type pickup 64 with light reception is differentiated and converted into a digital signal, and the rotation speed of the rotary substrate 62, that is, the rotary shaft 41 is obtained. Subsequent processing is the same as in the first embodiment.

According to this embodiment, since the rotary substrate 62 on which the acceleration sensors 21 and 22 are arranged is shared as a component part of the encoder, the number of parts can be reduced, and the speed detection device can be manufactured at low cost. can do. Further, by sharing the rotating substrate 62, the length direction of the speed detection device (the length direction of the rotating shaft 41) can be made compact. Other effects are the same as those of the first embodiment.
Here, instead of the acceleration sensors 21 and 22, acceleration sensors 51 and 52 as shown in an arrangement example in FIG. 6 may be used.

The present invention can be widely applied without being limited to the above embodiments.
For example, the acceleration sensors 21, 22, 51, 52 are not limited to sensors using the piezoelectric member 28, and may be any type of acceleration sensor.
Further, the number of acceleration sensors is not limited to two but may be three or more. When three acceleration sensors are arranged, it is desirable that the phases are shifted by 120 degrees. The adder 25 in this case removes the acceleration component caused by the vibration of the servo motor 4 from the output signal of the acceleration sensor arranged in this way, and performs data processing that triples the rotational speed detection sensitivity. It becomes the arithmetic circuit which performs. Further, when four acceleration sensors are arranged, it is desirable to arrange two acceleration sensors at positions symmetrical with respect to the center of the rotating substrate 27. In this case, the rotational speed detection sensitivity is quadrupled. That is, when n acceleration sensors are arranged (n is a positive integer), the detection sensitivity of the rotational speed can be increased by n times.

  Furthermore, four acceleration sensors are arranged, and a set of acceleration sensors 21 and 22 arranged at positions symmetrical with respect to the center of the rotating substrate 27, that is, at positions shifted by 180 degrees, You may arrange | position in the direction to detect and arrange | position the remaining one set of acceleration sensors 51 and 52 so that the acceleration of a radial direction may be detected. Since such a speed detection device has a biaxial acceleration sensor in a pseudo manner, it becomes possible to simultaneously measure the tangential acceleration and the radial acceleration of the rotating substrate 27, and the rotational speed. Detection accuracy can be improved.

1 is a block diagram of a servo motor system in an embodiment of the present invention. It is a block diagram of a 1st speed detection apparatus. It is a figure which shows the structure of a 1st speed detection apparatus and a 2nd speed detection apparatus. It is a figure which shows the example of arrangement | positioning of an acceleration sensor. It is a block diagram of a 1st speed detection apparatus. It is a figure which shows the example of arrangement | positioning of an acceleration sensor. It is a figure which shows the structure of a speed detection apparatus. It is a figure which shows a rotation board | substrate.

Explanation of symbols

4 Servo motor 8 High pass filter (HPF)
9 Adder 10 Low-pass filter (LPF)
21, 22 Acceleration sensor 26 Integration circuit (arithmetic circuit)
27, 62 Rotating substrate (substrate)
28 Piezoelectric member
33 fixed member 37 encoder 41 rotating shaft 51, 52 acceleration sensor 53 square root circuit (arithmetic circuit)
63 Light Reflector 64 Light Reflective Pickup

Claims (6)

  From a substrate attached to the rotation shaft of the servo motor, an acceleration sensor that is distributed and arranged along the rotation direction of the substrate, and that is used to detect the rotation speed of the rotation shaft, and the acceleration detected by the acceleration sensor A speed detection device comprising: an arithmetic circuit for calculating the speed of the rotating shaft.   The speed detection apparatus according to claim 1, wherein the acceleration sensor includes a piezoelectric element that detects acceleration in a rotation direction of the substrate, and the arithmetic circuit includes an integration circuit.   3. The speed according to claim 1, wherein the acceleration sensor is a piezoelectric element that detects a force acting in a direction orthogonal to a rotation direction of the substrate, and the arithmetic circuit includes a square root circuit. Detection device.   4. The speed detection apparatus according to claim 1, wherein the acceleration sensor is disposed at a point-symmetrical position with respect to the rotation center of the substrate. 5.   The substrate is provided with a plurality of light reflecting portions along a circumferential direction, and an optical pickup for irradiating light and receiving reflected light is fixed to the light reflecting portion on the housing side of the servo motor. The speed detection apparatus as described in any one of Claims 1-3. A high-pass filter that removes low-frequency components from the signal based on the output of the acceleration sensor, an encoder that is used to detect the rotational speed of the rotating shaft, and a low-pass filter that removes high-frequency components from the signal based on the output of the encoder And an adder that adds the low-pass filter and the signal that has passed through the high-pass filter.

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