JP2015120230A - Robot hand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a robot hand which estimates an absolute position of a fingertip without turning the fingertip to a turnable end, in a robot hand having an encoder for detecting rotation state of a motor for turning the fingertip.SOLUTION: A robot hand includes a motor for turning a fingertip, an encoder for detecting rotation state of a motor, and a control device (hereafter, "ECU"). The encoder has a disc rotated integrally with the motor. At least three origin point slits which indicate an origin point are arrayed at different intervals along the rotation direction of the disc, on the disc. An ECU rotates the motor in a fingertip-opening direction upon the estimation of an absolute position of the fingertip, and, when the first origin slit is detected, the rotation direction of the motor is inverted and, based on a rotation amount of the motor after the rotation direction of the motor is inverted until another origin slit is subsequently detected, the absolute position of the fingertip is estimated.

Description

  The present invention relates to a robot hand, and more particularly to a robot hand having an encoder in a movable part.

  Japanese Patent Application Laid-Open No. 1-253610 (Patent Document 1) discloses an encoder device that detects the rotational state of a movable part of an industrial robot. This encoder apparatus includes a disk that rotates integrally with the movable part, an optical sensor provided in the vicinity of the disk, and a controller. In the disk, two phases extending along the rotation direction of the disk are arranged side by side in the radial direction. In the phase on the outer diameter side, a plurality of first slits detected by the optical sensor are arranged at equal intervals. In the phase on the inner diameter side, a plurality of second slits detected by the optical sensor are arranged at different intervals.

  The control unit calculates the amount of rotation of the movable unit based on the number of detected first slits. If a power failure occurs during the work, and then the power failure is restored, the control unit rotates the movable unit in a fixed direction, and another second slit is detected after any one of the plurality of second slits is first detected. The absolute position of the movable part is estimated based on the amount of rotation of the movable part until the next slit is detected (the number of detections of the first slit).

JP-A-1-253610

  In order to estimate the absolute position of the movable part after power failure recovery using the technique disclosed in Patent Document 1, the motor must continue to rotate in a certain direction until at least two second slits are detected. .

  However, in a robot hand in which the movable range of the movable portion is physically limited, the movable portion rotates before the second second slit is detected depending on the posture of the movable portion during a power failure. There is a possibility that the absolute position of the movable part cannot be estimated due to the rotation to the movable end.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to rotate a movable portion in a robot hand having an encoder that detects a rotation state of a motor for rotating the movable portion. It is possible to estimate the absolute position of the movable part without rotating it to the possible end.

  (1) A robot hand according to the present invention is a robot hand having a rotatable movable part, and rotates integrally with a motor having a rotation shaft for rotating the movable part and the rotation axis of the motor. An encoder having a disk part and capable of optically detecting the amount of rotation of the disk part, and a control device for controlling the motor based on the output of the encoder. In the disk part, at least three or more origin slits indicating the origin position are arranged at different intervals along the rotation direction of the disk part. When the absolute position of the movable part is estimated, the control device rotates the motor in a predetermined direction. When any of the origin slits is detected for the first time, the control device reverses the motor rotation direction and reverses the motor rotation direction. The absolute position of the movable part is estimated based on the amount of rotation of the disk part until one of the other origin slits is detected next.

  According to such a configuration, the control device first detects one of three or more origin slits arranged at different intervals in the disk portion, and then detects one of the other origin slits. The absolute position of the movable part is estimated on the basis of the amount of rotation of the disk part until. At this time, the control device rotates the motor in a predetermined direction until the origin slit is first detected, and reverses the rotation direction of the motor after the origin slit is first detected. Thereby, compared with the case where the motor continues to rotate in a predetermined direction until two origin slits are detected, the amount by which the movable part is rotated in the same direction can be reduced. Therefore, when estimating the absolute position of the movable part, it is possible to prevent the movable part from rotating to the rotatable end.

  (2) Preferably, the rotatable range of the motor is limited to a range between the first restriction position and the second restriction position as the rotation of the movable portion is physically restricted. When controlling the motor during normal control of the movable part, the control device uses a control range between the first control position inside the first restriction position and the second control position inside the second restriction position. And when controlling a motor at the time of absolute position estimation of a movable part, the rotatable range between the 1st regulation position and the 2nd regulation position is used. At least two of the origin slits are respectively disposed in a range between the first restriction position and the first control position and in a range between the second restriction position and the second control position.

  According to such a configuration, the absolute position of the movable part can be estimated without rotating the motor to the first restriction position or the second restriction position. Therefore, when the absolute position of the movable part is estimated, it is possible to accurately suppress the movable part from rotating to the rotatable end.

  (3) Preferably, the control range of the motor includes a high usage area where the usage frequency is higher than a predetermined value and a low usage area where the usage frequency is lower than the predetermined value. The number or density of origin slits in the high use area is greater than the number or density of origin slits in the low use area.

  According to such a configuration, it is possible to reduce the amount of rotation of the motor required to estimate the absolute position of the movable part in the frequently used region.

  According to this invention, the absolute position of the movable part can be estimated without rotating the movable part to the rotatable end.

It is a figure which shows the structure of a robot hand typically. It is a figure which shows typically the internal structure of an encoder. It is the figure which looked at the disk from the rotating shaft side. It is a flowchart which shows the flow of a process of ECU. FIG. 3 is a diagram (part 1) illustrating an exemplary calibration operation by an ECU. FIG. 6 is a diagram (part 2) illustrating an exemplary calibration operation by an ECU. It is a figure which shows the disk by this modification example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 is a diagram schematically showing a configuration of a robot hand 1 according to the present embodiment. Note that the configuration of the robot hand 1 shown in FIG. 1 is merely an example, and the present invention is not limited to this.

  The robot hand 1 includes a hand unit 10 for gripping an object and an electronic control unit (Electronic Control Unit, hereinafter referred to as “ECU”) 100 that controls the movement of the hand unit 10.

  The hand part 10 includes two finger parts 20 and a base part 30 on which the two finger parts 20 are supported at a predetermined distance. In the present embodiment, an example in which the number of finger portions 20 is two is described. However, the number of finger portions is not limited to two, and may be three or more. It may be.

  Each finger portion 20 includes a fingertip portion 21, a joint portion 22, and a finger base portion 23. One end of the finger base part 23 is connected to the base part 30, and the other end of the finger base part 23 is connected to the fingertip part 21 via the joint part 22. In the present embodiment, the number of joints of the finger part 20 (the number of joint parts 22) is one, but the number of joints of the finger part is not limited to one and may be two or more. .

  The joint portion 22 is provided between the fingertip portion 21 and the fingertip portion 23, and supports the fingertip portion 21 so as to be rotatable in the movable direction α with respect to the fingertip portion 23. In the following, the direction in which the fingertip 21 holds the object is also referred to as “closing direction α1”, and the direction in which the fingertip 21 releases the object is also referred to as “opening direction α2.”

  The joint portion 22 includes a motor (for example, an ultrasonic motor) 50 for rotating the fingertip portion 21 in the movable direction α and an incremental encoder (hereinafter simply referred to as “encoder”) 40 for detecting the rotation state of the motor 50. Consists of including.

  The ECU 100 controls the motor 50 of each finger unit 20 to grip the target object by rotating each fingertip part 21 in the closing direction α <b> 1 when it is desired to grip the target object using the finger unit 20. In addition, when it is desired to release the object gripped by the finger part 20, the ECU 100 controls the motor 50 of each finger part 20 to release the object by rotating each fingertip part 21 in the opening direction α2.

  ECU 100 grasps the rotation state of motor 50 based on the detection result of encoder 40 and generates a command signal for motor 50 using the grasp result.

  FIG. 2 is a diagram schematically showing the internal configuration of the encoder 40. FIG. 2 illustrates the case where the encoder 40 is a transmissive encoder, but the encoder 40 is not limited to the transmissive encoder and may be a reflective encoder.

  The encoder 40 includes a disk-shaped wheel disk 42 (hereinafter simply referred to as “disk 42”) connected to the rotating shaft 41 of the motor 50, and an optical sensor (light emitting elements 44A, 44B) disposed at a position close to the disk 42. 44C and light receiving elements 45A, 45B, 45C).

  Since the disk 42 is connected to the rotating shaft 41 of the motor 50, it rotates integrally with the motor 50.

  As shown in FIG. 2, the light emitting elements 44A, 44B, and 44C are arranged at positions facing the light receiving elements 45A, 45B, and 45C, respectively, with the disk 42 interposed therebetween.

  As shown in FIG. 3 to be described later, on the disk 42, three phases (A phase, B phase, and Z phase) extending along the rotation direction of the disk 42 are arranged side by side in the radial direction. A plurality of A-phase slits 43A, which are detection targets of the light receiving element 45A, are arranged at equal intervals in the A-phase on the outermost diameter side. In the B phase on the inner diameter side of the A phase, a plurality of B phase slits 43B, which are detection targets of the light receiving element 45B, are arranged at equal intervals.

  Further, as shown in FIG. 3 described later, three Z-phase slits 43Z, which are detection targets of the light receiving element 45Z, are arranged at different intervals in the Z-phase inner diameter side than the B-phase. Since the Z-phase slit 43Z is a slit for generating a signal indicating the origin position, it is also referred to as “origin slit” below. The A phase, the B phase, and the Z phase are not necessarily limited to being formed separately in the radial direction. For example, the A phase, the B phase, and the Z phase may be integrated.

  When light generated by the light emitting elements 44A, 44B, and 44Z passes through the phase slits 43A, 43B, and 43Z and is received by the light receiving elements 45A, 45B, and 45Z, the light receiving elements 45A, 45B, and 45Z receive electric signals. Occur. Therefore, when the disk 42 rotates about the rotation shaft 41, the light receiving element 45A has the same number of electric pulse signals (hereinafter referred to as “A phase pulse”) as the number of A phase slits 43A passing between the light emitting element 44A and the light receiving element 45A. Signal "). Similarly, the light receiving element 45B generates the same number of electric pulse signals as the number of B phase slits 43B passing between the light emitting element 44B and the light receiving element 45B (hereinafter also referred to as “B phase pulse signal”). The light receiving element 45Z generates the same number of electrical pulse signals as the number of Z phase slits 43Z passing between the light emitting element 44Z and the light receiving element 45Z (hereinafter also referred to as “Z phase pulse signal” or “origin signal”).

  FIG. 3 is a view of the disk 42 as viewed from the rotating shaft 41 side. The A-phase slit 43A and the B-phase slit 43B are arranged at equal intervals over the entire circumference of the disk 42 in the rotation direction. Therefore, the relative rotation amount of the disk 42 can be detected by detecting the number of A-phase pulse signals or the number of B-phase pulse signals.

  The width and number of the A-phase slits 43A are the same as the width and number of the B-phase slits 43B. The A-phase slit 43A and the B-phase slit 43B are arranged so as to be shifted so that the rotation angles overlap each other by a predetermined amount (for example, 90 degrees in electrical angle). By detecting the output patterns of the A-phase pulse signal and the B-phase pulse signal, it is possible to detect whether the rotation direction of the disk 42 is the closing direction α1 or the opening direction α2.

  The width of the Z-phase slit 43Z is the same as the width of the A-phase slit 43A and the B-phase slit 43B. The number of Z-phase slits 43Z (three in the present embodiment) is smaller than the number of A-phase slits 43A and B-phase slits 43B.

  The arrangement of the three Z-phase slits 43 </ b> Z is determined in consideration of the rotatable range and control range of the motor 50.

  The rotation of the fingertip portion 21 in the present embodiment is regulated by a first stopper and a second stopper (so-called “stopping”) not shown. That is, the rotatable range of the fingertip portion 21 is physically limited to a range between the first stopper and the second stopper. Accordingly, the rotatable range of the motor 50 is physically limited to a range between the first restriction position L1 corresponding to the first stopper and the second restriction position L2 corresponding to the second stopper.

  When the ECU 100 controls the motor 50 during the normal control of gripping an object using the finger unit 20 (fingertip unit 21), the ECU 100 controls the first control position C1 inside the first regulation position L1 and the second regulation position L1. The range between the second control position C2 and the inner side is used. In other words, during normal control of the fingertip portion 21 (non-power failure), the control range of the motor 50 is a range between the first control position C1 and the second control position C2.

  In the present embodiment, the Z-phase slit 43Z includes a first origin slit 43Z1, a second origin slit 43Z2, and a third origin slit 43Z3.

  The first origin slit 43Z1 is disposed slightly outside the first control position C1 (on the first restriction position L1 side). The position of the first origin slit 43Z1 is not limited to the position shown in FIG. 3 as long as it is within the range between the first restriction position L1 and the first control position C1.

  The second origin slit 43Z2 is disposed slightly outside (the second restriction position L2 side) from the second control position C2. Note that the position of the second origin slit 43Z2 is not limited to the position shown in FIG. 3 as long as it is within the range between the second restriction position L2 and the second control position C2.

  The third origin slit 43Z3 is disposed between the first origin slit 43Z1 and the second origin slit 43Z2 and at a position where the distance to the first origin slit 43Z1 is larger than the distance to the second origin slit 43Z2. Is done. The position of the third origin slit 43Z3 is not limited to the position shown in FIG. 3 as long as the distance to the first origin slit 43Z1 is different from the distance to the second origin slit 43Z2.

  Hereinafter, the position of the first origin slit 43Z1 is also referred to as “origin Z1”, the position of the second origin slit 43Z2 is also referred to as “origin Z2”, and the position of the third origin slit 43Z3 is also referred to as “origin Z3”.

  FIG. 4 is a flowchart showing a flow of processing performed when ECU 100 estimates the absolute position of motor 50 (that is, the absolute position of fingertip portion 21). Here, “when the absolute position of the motor 50 is estimated” means that, for example, after the power supply to the robot hand 1 is cut off due to a power failure and the absolute position of the motor 50 becomes unknown, the power failure is restored and the robot hand 1 is restored. This is when the power supply is resumed. Hereinafter, the operation in which the ECU 100 estimates the absolute position of the motor 50 is also referred to as “calibration operation”. When the ECU 100 controls the motor 50 during the calibration operation (when the absolute position of the fingertip portion 21 is estimated), the range between the first restriction position L1 and the second restriction position L2 (that is, the rotatable range of the motor 50). Is used.

  In step (hereinafter, step is abbreviated as “S”) 10, ECU 100 rotates motor 50 in opening direction α2 at a predetermined rotational speed.

  In S11, ECU 100 determines whether or not the first origin signal (Z-phase pulse signal) has been received.

  If the first origin signal has not been received (NO in S11), ECU 100 waits until the origin signal is received. During this standby, the rotation of the motor 50 in the opening direction α2 is continued.

  When the first origin signal is received (YES in S11), ECU 100 reverses the rotation direction of motor 50 in S12. That is, the ECU 100 stops the rotation of the motor 50 in the opening direction α2, and rotates the motor 50 in the closing direction α1.

  In S13, ECU 100 starts measuring the rotation amount of motor 50 (the rotation amount of disk 42). Specifically, ECU 100 starts counting the number of A-phase pulse signals or B-phase pulse signals.

In S14, ECU 100 determines whether or not the next origin signal has been received.
If the next origin signal has not been received (NO in S14), ECU 100 waits until the next origin signal is received. During this standby, the rotation of the motor 50 in the closing direction α1 is continued.

  When the next origin signal is received (YES in S14), ECU 100 measures the rotation amount of motor 50 (counting the number of A-phase pulse signals or B-phase pulse signals) started in S13 in S15. finish.

In S16, ECU 100 stops the rotation of motor 50.
In S17, ECU 100 estimates the absolute position of motor 50 based on the measured value of the rotation amount of motor 50 from when the first origin signal is received until the next origin signal is received. Note that the estimated absolute position of the motor 50 is stored in the memory of the ECU 100 and used for the subsequent control of the motor 50.

  FIG. 5 is a diagram exemplarily showing a calibration operation by the ECU 100. In the example shown in FIG. 5, the absolute position of the motor 50 exists in the area between the origin Z1 and the origin Z3 at the time t1 when the calibration operation is started.

  When the calibration operation is started at time t1, the motor 50 is rotated in the opening direction α2.

  When the first origin signal Z3 is detected at time t2, the rotation of the motor 50 in the opening direction α2 is temporarily stopped, and then the rotation of the motor 50 in the closing direction α1 is started at time t3.

  When the next origin signal Z1 is detected at time t4, the rotation of the motor 50 in the opening direction α2 is stopped. Since the rotation amount of the motor 50 from time t3 when the rotation direction of the motor 50 is reversed to time t4 when the next origin signal Z1 is detected corresponds to the distance D1 between the origin Z1 and the origin Z3, the ECU 100 The current absolute position of the motor 50 is estimated to be the origin Z1. If the amount of rotation of the motor 50 after reversal corresponds to the distance D2 between the origin Z2 and the origin Z3, the current absolute position of the motor 50 may be estimated as the origin Z3.

  As described above, the ECU 100 according to the present embodiment first detects one of the three origins Z1, Z2, and Z3 arranged at different intervals on the disk 42 and then detects another origin. The absolute position of the motor 50 (that is, the absolute position of the fingertip portion 21) is estimated on the basis of the rotation amount of the motor 50 until the end. At this time, the ECU 100 rotates the motor 50 in the opening direction α2 until the first origin is detected, and reverses the rotation direction of the motor 50 after the first origin is detected. Therefore, compared with the case where the motor 50 is continuously rotated in the same direction until the two origins are detected, the amount by which the fingertip portion 21 is rotated in the same direction can be reduced. Therefore, the absolute position of the motor 50 (i.e., the fingertip portion) without rotating the motor 50 to the first restriction position L1 or the second restriction position L2 (i.e., without causing the fingertip portion 21 to collide with the first stopper or the second stopper). 21 absolute position) can be estimated.

  In particular, in the present embodiment, the origins Z1 and Z2 are disposed within the rotatable range of the motor 50 and on both outer sides of the control range during normal control. Specifically, the origin Z1 is disposed between the first restriction position L1 and the first control position C1, and the origin Z2 is disposed between the second restriction position L2 and the second control position C2. Therefore, when the calibration operation is started from a state where the absolute position of the motor 50 is within the control range during normal control (that is, when the power failure is restored after a power failure occurs during normal control), the motor 50 is opened in the opening direction. When rotating to α2, the origin Z2 is always detected before the motor 50 is rotated to the second restricting position L2, and when rotating the motor 50 in the closing direction α1, the motor 50 is rotated to the first restricting position L1. The origin Z1 is always detected before being performed. Therefore, the absolute position of the motor 50 can be estimated without rotating the motor 50 to the first restriction position L1 or the second restriction position L2.

<Modification>
The above-described embodiment can be modified as follows, for example.

  (1) Although the case where the number of origin slits is three has been described in the above-described embodiment, the number of origin slits may be four or more.

  FIG. 6 is a diagram exemplarily showing a calibration operation by the ECU 100 when there are five origin slits. In the example shown in FIG. 6, in addition to the origins Z1 to Z3 used in the above-described embodiment, an origin Z4 is added between the origin Z1 and the origin Z3, and further an origin Z5 between the origin Z2 and the origin Z3. Has been added.

  In this way, by increasing the origin slit, the amount of rotation of the motor 50 from the detection of the first origin to the detection of the next origin can be reduced, so the time required for the calibration operation can be shortened. .

  (2) Also, when there is a particularly frequently used area (a highly used area where the usage frequency exceeds a predetermined value) within the normal control range, the number or density of the origin slits in the frequently used area is You may make it increase more than the number or density of origin slits in other area | regions (low use area | region whose use frequency is less than predetermined value).

  FIG. 7 is a view exemplarily showing a disk 42 according to this modification. In the example shown in FIG. 7, there is a frequently used region within the normal control range. Then, in addition to the origins Z1 to Z3 used in the above-described embodiment, n origins 43Zn are added at different intervals in a frequently used region. As a result, the number or density of the origin slits in the frequently used region is larger than the number or density of the origin slits in the other regions.

  In this way, when the calibration operation is started from a state in which the absolute position of the motor 50 is in a frequently used region, the time required for the calibration operation can be further shortened.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 robot hand, 10 hand part, 20 finger part, 21 fingertip part, 22 joint part, 23 finger base part, 30 base part, 40 encoder, 41 rotating shaft, 42 disc, 43A A phase slit, 43B B phase slit, 43Z Z-phase slit (origin slit), 43Z1 first origin slit, 43Z2 second origin slit, 43Z3 third origin slit, 44A, 44B, 44Z light emitting element, 45A, 45B, 45Z light receiving element, 50 motor, C1 first control position , C2 second control position, L1 first restriction position, L1 second restriction position.

Claims (3)

A robot hand having a rotatable movable part,
A motor having a rotating shaft for rotating the movable part;
An encoder having a disk portion that rotates integrally with the rotating shaft of the motor and capable of optically detecting the amount of rotation of the disk portion;
A control device for controlling the motor based on the output of the encoder,
In the disk part, at least three or more origin slits indicating the origin position are arranged at different intervals along the rotation direction of the disk part,
The controller rotates the motor in a predetermined direction when the absolute position of the movable part is estimated, and reverses the rotation direction of the motor when any of the origin slits is detected first. A robot hand that estimates the absolute position of the movable part based on the amount of rotation of the disk part from when the rotation direction is reversed until another one of the origin slits is detected next. The rotatable range of the motor is limited to a range between the first restriction position and the second restriction position as the rotation of the movable portion is physically restricted.
When the control device controls the motor during normal control of the movable portion, the control device is configured to provide a position between a first control position inside the first restriction position and a second control position inside the second restriction position. When controlling the motor at the time of estimating the absolute position of the movable part, using a rotatable range between the first restriction position and the second restriction position,
The at least two of the origin slits are respectively disposed in a range between the first restriction position and the first control position and in a range between the second restriction position and the second control position. The robot hand according to 1. The control range of the motor includes a high usage area where the usage frequency is higher than a predetermined value and a low usage area where the usage frequency is lower than the predetermined value.
The robot hand according to claim 2, wherein the number or density of the origin slits in the high use area is greater than the number or density of the origin slits in the low use area.

Images