JP5976609B2 - Electric gripper device and origin return method of electric gripper - Google Patents

Description

  The present invention relates to, for example, an electric gripper in which a gripping member that grips a workpiece is opened and closed by a motor, and is suitable for application in a case where the gripping member is returned to the origin accurately and in a short time at power-on timing. It is.

  In the past, the global competitiveness of domestic production facilities has been intensifying, and the global EMS (Electronics Manufacturing Service) has emerged in mobile terminals, and there is an urgent need to avoid the causes of fluctuations in intensive manual operations. . In the electrification of automation, line design, shortening of start-up time and reliability are demanded.

  In the automated manufacturing field, an electric gripper that becomes a hand of a robot is mounted on the shaft tip of an articulated robot or an X, Y, Z axis electric table, and is used for assembling or conveying a workpiece. In such an electric gripper, a workpiece may be abutted during line operation, or a workpiece mounting abnormality may occur.

  For this reason, the electric gripper is required to return the gripping member such as a claw for gripping the workpiece to the origin position when the power is turned on, for example, because the motor encoder outputs a Z-phase signal every rotation of the motor. A geared motor that returns the motor shaft of a motor connected to a gripping member to the origin position of the gripping member based on the Z-phase signal has been proposed (for example, see Patent Document 1).

  Generally, an electric gripper is provided with a controller for controlling opening and closing of a gripping member, and the controller grips based on a Z-phase signal representing a mechanical origin detected once for each motor rotation by a rotary encoder. There are an origin return method in which the member is returned to the origin position, and an origin return method in which the controller returns the gripping member to the origin position without using a Z-phase signal. Here, an origin return method for returning the gripping member to the origin position based on the Z-phase signal will be described below.

  Note that in the origin return method based on the Z-phase signal, the Z-phase signal is detected only once during the entire stroke of the gripping member, and the Z-phase signal is detected multiple times during the entire stroke of the gripping member. There is. 6 and 7, when the Z-phase signal is detected only once during the entire stroke of the gripping member (in this case, the gripping member of one claw on one side) (the motor is 1 in the entire stroke of the gripping member). An origin return method that rotates and detects the Z-phase signal only once (for example, in the case of a single cam method) will be described.

  In FIG. 6, the stop position of the gripping member when the power of the electric gripper is turned off is set as the origin return start position S1, and the controller starts the origin return operation when the power of the electric gripper is turned on. At this time, after the power is turned on, the controller moves the gripping member to a position where the excitation currents of the A phase 0% and the B phase 100% exist in the vicinity of the origin return start position S1, and the counter value of the rotary encoder is set to “ Reset to “0”.

  (1) As a first step, the controller moves the gripping member from the gripper closing direction to the gripper opening direction by reversing the excitation order of the A-phase coil and B-phase coil of the motor. Stop after hitting the stroke end StEND.

  (2) As the second stage, the controller sequentially applies the excitation current of the excitation pattern shown in the figure to the A-phase coil and B-phase coil of the motor. As a result, the controller moves the gripping member of the electric gripper from the stroke end StEND to the gripper closing direction to move the Z-phase signal, which is the mechanical origin, to the Z-phase position SZ detected by the rotary encoder, and from the stroke end StEND to the Z-phase. The counter value (number of pulses) of the rotary encoder corresponding to the Z-phase moving distance Lmp when the gripping member moves to the position SZ is actually measured.

  Here, a position that is separated from the stroke end StEND by a predetermined set distance Lop (predetermined value) is preset as a target origin position TG1, and from the target origin position TG1 toward the gripper opening direction, the A phase 0 is initially set. %, The position where the B phase is 100% is set as the final origin position G1 of the gripping member.

  By the way, between the Z-phase signal detected once in one motor rotation and the next Z-phase signal detected in the next one rotation, the position where the excitation current of the A phase is 0% and the B phase is 100%. In this case, for example, the position where the excitation current of the A phase 0% and the B phase 100% is first set in the gripper opening direction from the target origin position TG1 is set as the origin position G1. It is.

  (3) As a third step, the controller returns the target origin return distance Lz2p (= Lmp) for moving from the Z phase position SZ to the target origin position TG1 by reversing the excitation order for the A phase coil and B phase coil of the motor. -Lop) is calculated, and the number of pulses corresponding to the target home position return distance Lz2p is output to the motor as a command value, so that the motor rotates backward by the number of pulses of the command value and the gripping member reaches the target home position TG1. Move.

  After that, (4) As the fourth stage, the controller moves the gripping member from the target origin position TG1 in the gripper opening direction, and stops excitation at the position where the excitation current of the A phase is 0% and the B phase is 100% first. As a result, the gripping member is moved from the target origin position TG1 to the final origin position G1 to return to the origin. The origin position G1 is a position with a moving distance of 0 mm where the gripping member has not started moving because of the setting.

  By the way, in the electric gripper shown in FIG. 7 different from the electric gripper shown in FIG. 6, the A phase is 0% due to individual differences such as variation in the mounting position of the motor shaft and the cam member of the gripping member. The position where the excitation current of the B phase is 100%, that is, the origin position G1 of the gripping member is different. For this reason, even when the origin return operation is performed in the procedure from the first stage to the fourth stage as described above, the origin position G1 is shifted for each electric gripper.

  In this way, in the electric gripper, since the origin position G1 of the gripping member and the gripping effective range differ for each individual electric gripper due to individual differences, when a plurality of electric grippers are newly attached or the electric grippers are replaced, It took a lot of time to start operation, such as making individual adjustments with actual machines during operation and changing the design of the shape of the claws attached to the gripping members of the individual electric grippers.

  Next, when the Z-phase signal is detected multiple times during the entire stroke of the gripping member (the motor rotates multiple times during the entire stroke of the gripping member and there are multiple detections of the Z-phase signal, for example, in the case of a double cam system or ball screw) ) Will be described.

  When the Z-phase signal is detected twice or more during the entire stroke of the gripping member, the Z-phase position SZ and the Z-phase detection start position ZSS1 (described later) are separated, and the Z-phase position SZ There are cases where the Z-phase detection start position ZSS1 is close to each other, and each will be described.

  In FIG. 8, when the Z-phase position SZ and the Z-phase detection start position ZSS1 (described later) are separated, the controller turns on the A phase 0% and B-phase existing in the vicinity of the origin return start position S1 after the power is turned on. The gripping member is moved to a position where the excitation current is 100%, and the counter value of the rotary encoder is reset to “0” at that time.

  Then, (1) as the first stage, when the controller starts the home return operation by turning on the electric gripper, the controller moves the gripping member from the gripper closing direction to the gripper opening direction, and moves the gripping member to the stroke end StEND. Stop after hitting.

  (2) As the second stage, the controller sequentially applies an excitation current to the A phase coil and B phase coil of the motor in the same manner as the excitation pattern shown in FIG. In this case, the gripping member is moved to the Z-phase detection start position ZSS1 beyond the origin position EG1. That is, the gripping member is quickly moved to the Z-phase detection start position ZSS1 without performing the Z-phase detection operation. Here, the Z-phase detection start position ZSS1 is the same as the target origin position TG1, and is a position away from the stroke end StEND by a predetermined set distance Lop (default value).

  The reason for moving the gripping member to the Z-phase detection start position ZSS1 beyond the origin position EG1 is that the Z-phase signal is detected multiple times during the entire stroke of the gripping member, so the stroke end StEND to the final origin position EG1 If a Z-phase signal is detected during this period and the Z-phase signal is detected, the original origin position EG1 cannot be found with this method, and the gripping member is returned to the origin at the origin position EG1. It is because it becomes impossible.

  (3) As a third stage, the controller moves the gripping member while performing the Z-phase detection operation from the Z-phase detection start position ZSS1 (target origin position TG1) to the Z-phase position SZ where the Z-phase signal is detected by the rotary encoder. As a result, the controller can detect the first Z-phase signal that exists beyond the origin position EG1 from the stroke end StEND side. At this time, the gripping member has moved from the stroke end StEND to the Z-phase position SZ. Measure the counter value (number of pulses) of the rotary encoder corresponding to the distance Lmp.

  (4) As the fourth stage, the controller reverses the excitation order for the A-phase coil and B-phase coil of the motor and moves from the Z-phase position SZ to the Z-phase detection start position ZSS1 (target origin position TG1). By calculating the target home position return distance Lz2p (= Lmp-Lop) and outputting the number of pulses corresponding to the target home position return distance Lz2p as a command value to the motor, the motor rotates backward by the number of pulses of the command value. The gripping member is moved to the target origin position TG1.

  After that, (5) As the fifth stage, the controller moves the gripping member from the target origin position TG1 in the gripper opening direction, and stops the excitation at the position where the excitation current of the A phase is 0% and the B phase is 100% first. As a result, the gripping member can be moved from the target origin position TG1 to the final origin position EG1 to return to the origin.

  On the other hand, referring to FIG. 9, the origin return operation when the first Z-phase position SZ1 beyond the origin position EG1 and the Z-phase detection start position ZSS1 are close to each other will be described. In this case, as shown in FIG. 8, the Z-phase position SZ and the Z-phase detection start position ZSS1 are similar to each other, and the controller exists in the vicinity of the origin return start position S1 after the power is turned on. The gripping member is moved to a position where the excitation current of the A phase is 0% and the B phase is 100%. At that time, the counter value of the rotary encoder is reset to “0”.

  (1) As the first stage, when the controller starts the home position return operation from the home position return start position S1, the gripping member is moved from the gripper closing direction to the gripper opening direction, and the gripping member is abutted against the stroke end StEND. Stop after.

  (2) As the second step, the controller moves the gripping member from the stroke end StEND by a predetermined set distance Lop1 (default value) to the Z-phase detection start position ZSS1 (target origin position TG1) beyond the origin position EG1. The gripping member is moved.

  (3) As a third stage, the controller moves from the Z-phase detection start position ZSS1 (target origin position TG1) to the first Z-phase position SZ1 where the first Z-phase signal is detected by the rotary encoder. At this time, the interval between the Z phase detection start position ZSS1 (target origin position TG1) and the first Z phase position SZ1 is very close.

  The controller measures the counter value (number of pulses) of the rotary encoder corresponding to the Z-phase moving distance Lmp1 when the gripping member moves from the stroke end StEND to the first Z-phase position SZ1.

  (4) As the fourth stage, the controller reverses the excitation order for the A-phase coil and B-phase coil of the motor and moves from the first Z-phase position SZ1 to the target origin position TG1 (Z-phase detection start position ZSS1). Output the number of pulses corresponding to the target home position return distance Lz2p (= Lmp1-Lop1) to the motor as a command value, so that the motor rotates backward by the number of pulses of the command value and grips to the target home position TG1 Move the member.

  After that, (5) As the fifth stage, the controller moves the gripping member from the target origin position TG1 in the gripper opening direction, and stops the excitation at the position where the excitation current of the A phase is 0% and the B phase is 100% first. As a result, the gripping member is moved from the target origin position TG1 to the final origin position EG1 to return to the origin.

  However, in the second home position return operation, (6) as the sixth stage, the controller moves the gripping member from the home position return start position S1 in the gripper opening direction and hits the gripping member against the stroke end StEND. When a foreign object is caught between StEND and the gripping member, (7) As a seventh step, the distance Lop1 ′ (Lop1 = Lop1) from the erroneous stroke end b to the Z-phase detection start position ZSS1 (target origin position TG1) If only ') is moved, the gripping member moves to an erroneous erroneous Z-phase detection start position ZX1 different from the initially assumed Z-phase detection start position ZSS1 (target origin position TG1).

  (8) As the eighth stage, when the Z-phase signal detection operation is started from the erroneous Z-phase detection start position ZX1, the controller sets the second Z-phase position SZ2 different from the Z-phase position SZ1 detected in the first time. Thus, the Z-phase moving distance Lmp2 from the stroke end b to the second Z-phase position SZ2 is actually measured. Based on this Z-phase movement distance Lmp2, even if the target origin return distance Lz2p (= Lmp2-Lop1 ') for moving from the Z-phase position SZ2 to the Z-phase detection start position ZSS1 (target origin position TG1) is calculated, The first Z-phase detection start position ZSS1 (target origin position TG1) could not be reached, and accurate origin return could not be performed.

JP 2006-271189 A

  As described above, in the conventional method, the origin position of the gripping member cannot be aligned due to individual differences of the electric grippers (FIGS. 6 and 7), or the gripping is caused by the influence of foreign matter between the stroke end StEND and the gripping member. The member cannot be accurately returned to the origin (FIG. 9), and the origin return operation is complicated, so that many production line start-up times and line restart times are required.

  The present invention has been made to solve such a problem. An electric gripper device and an electric motor capable of accurately returning the gripping member to the origin and reducing the production line start-up time and the line reactivation time. It is intended to propose a gripper origin return method.

  In order to solve this problem, in the first aspect of the present invention, an encoder that outputs an A-phase signal, a B-phase signal, and a Z-phase signal as the motor shaft of the motor rotates, and the motor shaft are mechanically connected and fixed A gripping member that is movably supported within a stroke range, and a control unit that returns the gripping member to the origin based on the Z-phase signal output from the encoder, and the control unit includes a gripper in the gripping member. A position that is a predetermined set distance away from the stroke end in the opening direction is set as the origin position, and after turning on the power, when the origin return command is given, the current position of the gripping member is set as the origin return start position. Moves to the stroke end and detects the Z-phase movement distance when the gripping member is moved from the stroke end to the Z-phase position where the Z-phase signal is detected , Determine the homing travel by subtracting the set distance from the Z-phase moving distance, so as to homing to the original position by moving the gripping member in accordance with the homing travel distance.

  In this invention of Claim 2, the said control part is in the whole stroke of the said holding member, when the whole stroke which the said holding member can move is smaller than the moving amount | distance of the said holding member per motor rotation of the said motor. It is determined that the Z-phase signal is a model that is detected only once.

  In the invention of claim 3, in order to assemble so that the Z-phase position is the center of the entire stroke of the gripping member, the motor shaft of the motor is fixed in advance to a position that is the center of the entire stroke of the gripping member. The encoder in a state adjusted to the Z-phase position is attached to the motor.

  In the invention according to claim 4, the control unit includes a movement distance from the stroke end of the gripping member to the Z-phase position where the Z-phase signal is detected in a constant central range in the entire stroke of the gripping member. It is confirmed that the Z-phase position is in the center range of the entire stroke of the gripping member by determining whether or not it is determined.

  According to a fifth aspect of the invention, an encoder that outputs an A-phase signal, a B-phase signal, and a Z-phase signal as the motor shaft of the motor rotates, is mechanically connected to the motor shaft, and is movable within a certain stroke range. A gripping member that is supported, and a control unit that returns the gripping member to the origin based on the Z-phase signal output from the encoder, the control unit being fixed from a stroke end of the gripping member in the gripper opening direction. A position separated by the set distance is set as the origin position, and after turning on the power, when the origin return command is given, the current position of the gripping member is set as the origin return start position, and the gripping member is moved from there to the stroke end. Move from the stroke end to the first Z-phase detection start position beyond the origin position, and start detecting the Z-phase signal from the first Z-phase detection start position , Detecting the Z-phase movement distance from the stroke end to the Z-phase position when the Z-phase signal is detected, and subtracting the set distance from the Z-phase movement distance to obtain the origin return movement distance, The origin is returned to the origin position by moving the gripping member according to the origin return movement distance.

  In the invention of claim 6, in the second and subsequent home-return operations, the control unit is closer to the gripper closing direction than the first Z-phase detection start position, and the stroke end side is a fixed amount from the Z-phase position. When the gripping member is moved from the stroke end to the second Z-phase detection start position that has returned to, the detection of the Z-phase signal is started from the second Z-phase detection start position, and the Z-phase signal is detected Detecting the Z-phase movement distance from the stroke end to the Z-phase position, subtracting the set distance from the Z-phase movement distance to obtain an origin return movement distance, and according to the origin return movement distance, the gripping member Is moved back to the origin position.

  In the invention according to claim 7, when the total movable stroke of the gripping member is equal to or greater than the moving amount of the gripping member per one motor rotation of the motor, the control unit performs the Z during the full stroke of the gripping member. It is determined that the model is a model in which the phase signal is detected multiple times.

  In the invention of claim 8, an encoder that outputs an A-phase signal, a B-phase signal, and a Z-phase signal as the motor shaft of the motor rotates, and is mechanically connected to the motor shaft so as to be movable within a certain stroke range. In the origin return method of the electric gripper device, comprising: a supported grip member; and a control unit for returning the grip member to the origin based on the Z-phase signal output from the encoder. The origin position setting step for setting the position away from the stroke end in the gripper opening direction as the origin position at the origin position, the current position of the gripping member as the origin return start position at the time of origin return command after power-on, A stroke end moving step for moving the gripping member from there to the stroke end, and the Z-phase signal is detected from the stroke end. A Z-phase movement distance detection step for detecting a Z-phase movement distance when the gripping member is moved to the Z-phase position, and an origin for obtaining an origin return movement distance by subtracting the origin setting distance from the Z-phase movement distance A return movement distance calculating step and an origin return step of returning the origin to the origin position by moving the gripping member according to the origin return movement distance.

  According to the ninth aspect of the present invention, an encoder that outputs an A-phase signal, a B-phase signal, and a Z-phase signal as the motor shaft of the motor rotates, and mechanically connected to the motor shaft and movable within a certain stroke range. In the origin return method of the electric gripper device, comprising: a supported grip member; and a control unit for returning the grip member to the origin based on the Z-phase signal output from the encoder. The origin position setting step for setting the position away from the stroke end in the gripper opening direction as the origin position at the origin position, the current position of the gripping member as the origin return start position at the time of origin return command after power-on, A stroke end moving step for moving the gripping member from there to the stroke end, and 1 exceeding the origin position from the stroke end. The first Z-phase detection start position moving step for moving to the first Z-phase detection start position, and the detection of the Z-phase signal from the first Z-phase detection start position, and when the Z-phase signal is detected A Z-phase movement distance detection step for detecting a Z-phase movement distance from the stroke end to the Z-phase position, and an origin return movement distance calculation for obtaining an origin return movement distance by subtracting the origin setting distance from the Z-phase movement distance. And an origin return step for returning the origin to the origin position by moving the gripping member according to the origin return movement distance.

  According to the first aspect of the present invention, a position that is a fixed set distance away from the stroke end in the gripper opening direction of the gripping member is set as the origin position, and the set distance is determined from the Z-phase moving distance from the stroke end to the Z-phase position. Since the gripping member is returned to the home position according to the home position return movement distance obtained by subtraction, the gripping member can be returned to the home position at which the individual difference between the plurality of electric grippers is eliminated while shortening the time to return to the home position. it can.

  According to the second aspect of the present invention, when the entire stroke of the gripping member that can be moved is smaller than the movement amount of the gripping member per one rotation of the motor, the control unit generates a Z-phase signal during the entire stroke of the gripping member. It can be determined that the model is detected only once.

  According to the third aspect of the invention, since the motor shaft of the motor is fixed in advance at a position that becomes the center of the entire stroke of the gripping member and the encoder in the state adjusted to the Z-phase position is attached to the motor, Z The phase position is positioned at the center of the full stroke of the gripping member.

  According to the invention of claim 4, the control unit determines whether or not the Z-phase moving distance from the stroke end of the gripping member to the Z-phase position is included in a certain central range in the entire stroke of the gripping member. It can be confirmed that the Z-phase position is in the center range of the entire stroke of the gripping member.

  According to the fifth aspect of the present invention, a position that is a predetermined set distance away from the stroke end in the gripper opening direction of the gripping member is set as the origin position, and from the stroke end to the first Z-phase detection start position that exceeds the origin position. The gripping member is returned to the origin according to the origin return movement distance obtained by subtracting the set distance from the Z-phase movement distance from the first Z-phase detection start position to the Z-phase position. Even when the Z-phase signal is detected a plurality of times, it is possible to return the gripping member to the origin at the origin position that eliminates the individual difference between the plurality of electric grippers while shortening the time until the origin return.

  According to the sixth aspect of the present invention, in the second and subsequent home-return operations, the second Z that is in the gripper closing direction from the first Z-phase detection start position and returns to the stroke end side by a certain amount from the Z-phase position. Obtained by moving the gripping member from the stroke end to the phase detection start position, detecting the Z phase movement distance from the second Z phase detection start position to the Z phase position, and subtracting the set distance from the Z phase movement distance Since the gripping member is returned to the origin according to the origin return movement distance, the time until the origin return after the second time can be further shortened.

  According to the seventh aspect of the present invention, when the total movable stroke of the gripping member is equal to or greater than the movement amount of the gripping member per one rotation of the motor, the Z-phase signal is detected a plurality of times during the entire stroke of the gripping member. It can be determined that it is a model.

  According to the invention of claim 8, a position that is a fixed set distance away from the stroke end in the gripper opening direction of the gripping member is set as the origin position, and the set distance is determined from the Z-phase moving distance from the stroke end to the Z-phase position. Since the gripping member is returned to the home position according to the home position return movement distance obtained by subtraction, the gripping member can be returned to the home position at which the individual difference between the plurality of electric grippers is eliminated while shortening the time to return to the home position. it can.

  According to the ninth aspect of the present invention, a position that is a predetermined set distance away from the stroke end in the gripper opening direction of the gripping member is set as the origin position, and from the stroke end to the first Z-phase detection start position that exceeds the origin position. The gripping member is returned to the origin according to the origin return movement distance obtained by subtracting the set distance from the Z-phase movement distance from the first Z-phase detection start position to the Z-phase position. Even when the Z-phase signal is detected a plurality of times, it is possible to return the gripping member to the origin at the origin position that eliminates the individual difference between the plurality of electric grippers while shortening the time until the origin return.

It is a block diagram which shows the whole structure of an electric gripper apparatus. It is a block diagram which shows the structure of the control apparatus for electric grippers, and a gripper part. It is a sequence chart which shows the process sequence of an origin return operation | movement when a Z phase signal is detected only once during the whole stroke of a holding member. It is a flowchart which detects that a Z phase position is in the center range of a stroke. It is a sequence chart which shows the process sequence of an origin return operation | movement when Z phase signal is detected in multiple times during the whole stroke of a holding member. It is a sequence chart which shows the process sequence (1) of an origin return operation | movement in case the Z phase signal is detected only once during the whole stroke of the conventional holding member. It is a sequence chart which shows the process sequence (2) of the origin return operation | movement in case the Z phase signal is detected only once during the whole stroke of the conventional holding member. FIG. 7 is a sequence chart showing a procedure for returning to the origin when the Z-phase position and the Z-phase detection operation start position are separated when a Z-phase signal is detected a plurality of times during the entire stroke of the gripping member. . Conventionally, a sequence chart showing the processing procedure of the origin return operation when the Z-phase position is close to the Z-phase detection operation start position when the Z-phase signal is detected multiple times during the entire stroke of the gripping member. is there.

  Next, an embodiment of the present invention will be described with reference to the drawings.

<Overall configuration of electric gripper device>
FIG. 1 shows an electric gripper device 100 according to the present invention, which is constituted by an electric gripper 101 and an electric gripper control device 104 for controlling the electric gripper 101.

  The electric gripper 101 includes an electric actuator 102 and a gripper unit 103. The electric gripper control device 104 is connected to a control device power source 106, an electric actuator power source 107, and a PLC (programmable logic controller) or a personal computer 108.

  The electric gripper control device 104 operates by receiving power supply from the control device power source 106, and drives the electric actuator 102 by supplying electric power from the electric actuator power source 107 to the electric actuator 102.

<Configuration of Electric Gripper Control Device and Gripper Unit>
As shown in FIG. 2, the electric gripper controller 104 has a CPU (Central Processing Unit) 110 as a control unit that performs overall control. The CPU 110 includes a ROM (Read Only Memory) 111, a RAM (Random Access). A PLC or personal computer 108 is connected via an interface 119 and a driver 114 that operates an EEPROM (Electrically Erasable Programmable Read-Only Memory) 113 and a stepping motor 116 which are nonvolatile memories.

  The CPU 110 develops application programs such as a basic program and an origin return program stored in a ROM (Read Only Memory) 111 on a RAM (Random Access Memory) 112 used as a work area, and performs an origin return operation of the present invention described later. Etc.

  The electric actuator 102 of the electric gripper 101 includes a stepping motor 116 as a motor and a rotary encoder 115 as an encoder incorporated in the stepping motor 116. The rotary encoder 115 outputs an A-phase signal and a B-phase signal whose phases are different by 90 degrees as the motor shaft 116a of the stepping motor 116 rotates, to the CPU 110 of the electric gripper control device 104, and 1 for each rotation of the motor. A Z-phase signal representing the mechanical origin detected once is output to the CPU 110.

  The gripper unit 103 is mechanically connected to the motor shaft 116 a of the stepping motor 116 and rotates forward and backward, and mechanically connected to the cam member 117, and sandwiches the workpiece via the cam member 117. And a gripping member for opening and closing the gripper (in this case, a gripping member for one claw on one side) 118.

  The CPU 110 of the electric gripper control device 104 controls the stepping motor 116 of the electric actuator 102 of the electric gripper 101 according to the origin return program, thereby returning the origin to the gripping member of the gripper portion 103 via the motor shaft 116a of the stepping motor 116. It is configured to execute an operation and an opening / closing operation.

<Home return operation for models in which the Z-phase signal is detected only once during the entire stroke of the gripping member>
In the electric gripper device 100, before starting the return to origin operation, it is first determined whether the Z-phase signal is detected only once during the entire stroke of the gripping member 118 or is detected more than once. It is necessary to determine.

  The CPU 110 of the electric gripper control device 104 determines the first relational expression St <that the stroke St at which the gripping member 118 is movable is smaller than the movement amount Ld of the gripping member 118 per one rotation of the stepping motor 116 according to the origin return program. It is determined whether or not Ld is satisfied, and when the first relational expression St <Ld is satisfied, it is automatically determined that the Z-phase signal is detected only once during the entire stroke of the gripping member 118. To do.

  In this case, as shown in FIG. 3, the CPU 110 of the electric gripper control device 104 starts the origin return operation of the gripping member 118 from the origin return start position S1 according to the origin return program.

  At this time, after the power is turned on, the CPU 110 moves the gripping member to a position where the excitation currents of the A phase 0% and the B phase 100% exist in the vicinity of the origin return start position S1, and the counter value of the rotary encoder 115 is set to “ Reset to “0”.

  (1) As a first step, based on a command from the PLC or personal computer 108, the CPU 110 reverses the excitation order for the A-phase coil and B-phase coil of the stepping motor 116, and the excitation current of the excitation pattern shown in the figure. Is passed through the A-phase coil and B-phase coil to move the gripping member 118 from the gripper closing direction to the gripper opening direction via the motor shaft 116a and the cam member 117 of the stepping motor 116, and the gripping member 118 is moved to the stroke end StEND. Stop after hitting.

  (2) As a second stage, the CPU 110 causes the excitation current of the excitation pattern shown in the figure to flow in the order of the A phase coil and the B phase coil with respect to the A phase coil and B phase coil of the stepping motor 116. Thereby, the CPU 110 moves the gripping member 118 of the electric gripper 101 from the stroke end StEND to move to the Z-phase position SZ where the Z-phase signal is detected by the rotary encoder 115, and from the stroke end StEND to the Z-phase position SZ. The counter value (number of pulses) of the rotary encoder 115 corresponding to the Z-phase movement distance Lmp moved is measured, and the Z-phase movement distance Lmp (number of pulses) is stored in the EEPROM 113 in which various parameters are initialized.

  Here, a position that is separated from the stroke end StEND by a predetermined set distance Lop (default value) is set as the final origin position EG1. This origin position EG1 is the same as the conventional target origin position TG1 (FIG. 6). In the present invention, the conventional target origin position TG1 is set as the final origin position EG1. The origin position EG1 is a predetermined set distance Lop (predetermined value) from the stroke end StEND, and is a position having no individual difference common to each of the plurality of electric grippers 101.

  (3) As a third stage, the CPU 110 reverses the excitation order of the A-phase coil and B-phase coil of the stepping motor 116 and moves the gripping member 118 from the Z-phase position SZ to the final origin position EG1. The origin return movement distance Lz2p (= Lmp−Lop) is calculated, and the number of pulses corresponding to the origin return movement distance Lz2p is output as a command value from the driver 114 to the stepping motor 116, whereby the gripping member 118 is obtained from the Z phase position SZ. Is returned to the final origin position EG1.

  In this way, the CPU 110 sets the conventional target origin position TG1 separated from the stroke end StEND by a predetermined set distance Lop (default value) as the final origin position EG1 of the present invention, and the origin position EG1 from the Z phase position SZ. Since the home position can be returned by moving the gripping member 118, it is not necessary to move to the position where the excitation current of the A phase is 0% and the B phase is 100% with individual differences compared to the conventional home position return operation. The home return operation time can be shortened by the amount of.

  In addition, since there is no individual difference for each electric gripper 101 in the final origin position EG1 that is separated from the stroke end StEND by a predetermined set distance Lop (default value), the origin positions of the gripping members 118 of the plurality of electric grippers 101 are determined. All can be prepared.

  Subsequently, in the second and subsequent home-return operations, the Z-phase movement distance Lmp from the stroke end StEND to the Z-phase position SZ stored in the EEPROM 113 during the first home-return operation and the second home-return operation The measured Z-phase movement distance Lmp from the stroke end StEND to the Z-phase position SZ is compared.

  As a result, if the first Z-phase movement distance Lmp matches the second Z-phase movement distance Lmp, or if the difference is equal to or less than a predetermined threshold, no mechanical deviation has occurred. In addition, the second home position return operation is recognized as being performed normally, and the second home position return operation is performed using the Z-phase moving distance Lmp (or the second moving distance Lmp) stored in the first time. After the movement distance Lz2p is calculated, the origin return is performed by moving the gripping member 118 to the final origin position EG1 according to the origin return movement distance Lz2p, as in the first origin return operation.

  On the other hand, when the comparison result between the first Z-phase movement distance Lmp and the second Z-phase movement distance Lmp is not less than a predetermined threshold, the CPU 110, for example, a foreign object between the stroke end StEND and the gripping member. Recognize that a failure such as is caught.

  In this case, the CPU 110 calculates the origin return movement distance Lz2p using the Z phase movement distance Lmp stored in the first time without using the second Z phase movement distance Lmp, and the origin return movement distance. The origin return is performed by moving the gripping member 118 from the Z-phase position SZ to the final origin position EG1 based on Lz2p.

  As a result, even when a failure such as a foreign object is caught between the stroke end StEND and the gripping member 118, the CPU 110 can reliably return the gripping member 118 to the origin.

  The CPU 110, when the comparison result between the Z-phase movement distance Lmp stored during the first home position return operation and the Z-phase movement distance Lmp2 measured during the second home position return operation is not less than a predetermined threshold value, Warning by an alarm or the like allows the user to recognize an abnormality such as a foreign object inserted between the stroke end SeEND and the gripping member.

  Further, the CPU 110 stores the counter value Ce0 of the rotary encoder 115 at the origin position EG1, and measures the counter value Ce of the rotary encoder 115 at the current position Cp when the gripping member 118 is moved from the origin position EG1. Thereby, the CPU 110 can calculate the current position Cp (= Ce−Ce0) of the gripping member 118 from the origin position EG1, and can present the value of the current position Cp to the user.

<Attaching method so that the Z-phase position is near the center of the stroke of the gripping member>
In the model of the electric gripper 101 in which the Z-phase signal is detected only once during the entire stroke of the gripping member 118, a jig for assembling so that the Z-phase position SZ is the center of the entire stroke of the gripping member 118 is created. In order to position the Z-phase position SZ at the center of the entire stroke of the gripping member 118, the motor shaft of the stepping motor 116 assembled previously is fixed at a position that is the center of the entire stroke of the gripping member 118. The rotary encoder 115 in a state matched to the Z phase position SZ may be attached to the stepping motor 116.

  As a result, the electric gripper device 100 can be assembled so that the Z-phase position SZ is at the center of the entire stroke of the gripping member 118, so that the Z-phase position SZ is controlled within a certain angular range of the motor rotation angle of the stepping motor 116. be able to. Thus, the Z-phase signal is always detected at the center of the stroke of the gripping member 118, and the origin return operation can be executed reliably.

<Checking operation of Z phase position>
In this way, the gripping member 118 is fixed to the motor shaft 116a of the stepping motor 116. The processing procedure for confirming whether the Z-phase position SZ is actually in the center range of the entire stroke of the gripping member 118 is as follows. explain.

  As shown in FIG. 4, the CPU 110 of the electric gripper control device 104 enters from the start step of the routine RT1, moves to the next step SP1, and detects the Z-phase signal from the stroke end StEND of the gripping member 118 as described above. The Z-phase movement distance Lmp to the Z-phase position SZ is actually measured, the counter value of the rotary encoder 115 at that time is acquired, and then the process proceeds to the next step SP2.

  In step SP2, the CPU 110 stores the counter value of the Z-phase moving distance Lmp acquired in step SP1 in the EEPROM 113, and proceeds to the next step SP3. In step SP3, the CPU 110 determines whether or not the counter value of the Z-phase moving distance Lmp is included in the center range (for example, counter values L to M) of the entire stroke of the gripping member 118.

  If an affirmative result is obtained in step SP3, this indicates that the Z-phase position SZ is in the center range of the entire stroke of the gripping member 118. At this time, the CPU 110 moves to the next step SP4, where the PLC or personal computer "Shipment OK" is displayed on the monitor 108, and the process proceeds to the next step SP6 to end the process.

  On the other hand, if a negative result is obtained in step SP3, this indicates that the Z-phase position SZ does not exist in the center range of the entire stroke of the gripping member 118. At this time, the CPU 110 proceeds to the next step SP5. Then, “Shipment NG” is displayed on the monitor of the PLC or the personal computer 108, and the process proceeds to the next step SP6 to end the process.

<Home return operation for models in which the Z-phase signal is detected multiple times during the entire stroke of the gripping member>
In this case, the electric gripper device 100 is also a model in which the Z-phase signal is detected only once during the entire stroke of the gripping member 118 or a model in which multiple detections are made before starting the return to origin operation. Is determined first.

  Does the CPU 110 of the electric gripper controller 104 satisfy the second relational expression St ≧ Ld that the movable stroke St of the gripping member 118 is equal to or greater than the moving amount Ld of the gripping member 118 per one rotation of the stepping motor 116? If the second relational expression St ≧ Ld is satisfied, it is automatically determined that the Z-phase signal is detected multiple times during the entire stroke of the gripping member 118.

  In this case, as shown in FIG. 5, the CPU 110 of the electric gripper control device 104 starts the origin return operation of the gripping member 118 from the origin return start position S1 according to the origin return program.

  At this time, after the power is turned on, the CPU 110 moves the gripping member to a position where the excitation currents of the A phase 0% and the B phase 100% exist in the vicinity of the origin return start position S1, and the counter value of the rotary encoder 115 is set to “ Reset to “0”.

  (1) As a first step, based on a command from the PLC or the personal computer 108, the CPU 110 reverses the excitation order for the A-phase coil and B-phase coil of the stepping motor 116, thereby moving the gripping member 118 in the gripper closing direction. The gripper 118 is moved in the gripper opening direction, and the gripping member 118 is brought into contact with the stroke end StEND and then stopped.

  Also in this case, a position that is separated from the stroke end StEND by a predetermined set distance Lop (default value) is set as the final origin position EG1. This origin position EG1 is the same as the conventional target origin position TG1 (FIG. 6). In the present invention, the conventional target origin position TG1 is set as the final origin position EG1. The origin position EG1 is separated from the stroke end StEND by a predetermined set distance Lop (predetermined value), and is a position having no individual difference common to each of the plurality of electric grippers 101.

  (2) As the second stage, the CPU 110 causes the excitation current similar to the excitation pattern shown in FIG. 6 to flow in the order of the A phase coil and the B phase coil for the A phase coil and B phase coil of the stepping motor 116. The gripping member 118 of the electric gripper 101 is moved. In this case, the gripping member 118 is moved to the first Z-phase detection start position ZSS1 beyond the origin position EG1.

  Here, the first Z-phase detection start position ZSS1 is an arbitrary position that always exceeds the origin position EG1 from the stroke end StEND, and is set as the movement distance Lzs1 (= Lop + En / 2) from the stroke end StEND. .

  Here, En is a distance for one rotation of the rotary encoder 115. If the first Z-phase detection start position ZSS1 can be set at an arbitrary position beyond the origin position EG1 from the stroke end StEND, the stroke end The addition distance En / 2 to be added to the set distance Lop (predetermined value) from StEND to the origin position EG1 may be other addition distances such as En / 3 and 3En / 4. However, in the model of the electric gripper 101 in which the Z-phase signal is detected a plurality of times during the entire stroke of the gripping member 118, the entire stroke St of the gripping member 118 needs to satisfy the third relational expression St> Lop + (addition distance) + En. There is. This is because if the third relational expression is not satisfied, the Z-phase signal may not be detected.

  The first Z-phase detection start position ZSS1 in this case is a position that exceeds the Z-phase position SZ1 of the first Z-phase signal that is closest to the origin position EG1, but it may even exceed the origin position EG1. For example, the first Z-phase detection start position ZSS1 may be set between the origin position EG1 and the Z-phase position SZ1 of the first Z-phase signal.

  Thus, the reason why the first Z-phase detection start position ZSS1 is set beyond the origin position EG1 is that the Z-phase signal is detected a plurality of times during the entire stroke of the gripping member 118. This is because when the Z-phase signal existing between EG1 and EG1 is detected, the origin return method cannot find the origin position EG1 set at a position separated by the set distance Lop from the stroke end StEND.

  (3) As a third stage, the CPU 110 starts the Z-phase signal detection operation from the first Z-phase detection start position ZSS1, and holds the gripping member up to the Z-phase position SZ2 where the second Z-phase signal is detected by the rotary encoder 115. 118 is moved.

  As a result, the CPU 110 can detect the second Z-phase signal existing beyond the origin position G1 from the stroke end StEND side. At this time, the gripping member 118 moves from the stroke end StEND to the second Z-phase position SZ2. The counter value (number of pulses) of the rotary encoder 115 corresponding to the moved Z movement distance Lmp1 is measured, and this Z-phase movement distance Lmp1 (pulse number) is stored in the EPPROM 113 in which various parameters are initialized.

  (4) As a fourth step, the CPU 110 reverses the excitation order for the A-phase coil and B-phase coil of the stepping motor 116 and moves the origin return movement distance from the second Z-phase position SZ2 to the origin position EG1. By calculating Lz2p (= Lmp-Lop) and outputting the number of pulses corresponding to the home return movement distance Lz2p as a command value to the stepping motor 116, the stepping motor 116 reversely rotates by the number of pulses of the command value. Then, the origin return is performed by moving the gripping member 118 to the final origin position EG1.

  Subsequently, in the second and subsequent home-return operations, (5) as a fifth step, the CPU 110 reverses the excitation order for the A-phase coil and B-phase coil of the stepping motor 116 as in the first step. The gripping member 118 is moved from the gripper closing direction to the gripper opening direction, and the gripping member 118 is abutted against the stroke end StEND and then stopped.

  Thereafter, (6) as a sixth stage, the CPU 110 moves the gripping member 118 of the electric gripper 101 to the second Z-phase detection start position ZSS2 beyond the origin position. Here, the second Z-phase detection start position ZSS2 is closer to the gripper than the first Z-phase detection start position ZSS1, and the stroke end StEND side is a fixed distance En / 4 from the second Z-phase detection SZ2. That is, the second Z-phase detection start position ZSS2 is a position away from the stroke end StEND by a distance Lzs2 (= Lmp−En / 4). The CPU 110 starts detection of the second Z-phase signal from the second Z-phase detection start position ZSS2 in the second and subsequent origin return operations.

  This is because the Z-phase position SZ2 of the second Z-phase signal to be detected is already known at the first stage, so detection of the second Z-phase signal is started from the first Z-phase detection start position ZSS1. In this case, since it takes time to detect the Z-phase position SZ2, when the second Z-phase position SZ2 is detected, the position slightly returned from the second Z-phase position SZ2 by the subtraction distance En / 4. This is to start the Z-phase signal detection operation from the beginning. Incidentally, the magnitude relationship between the addition distance En / 2 set at the first Z-phase detection start position ZSS1 and the subtraction distance En / 4 set at the second Z-phase detection start position ZSS2 is the following third relational expression: It is necessary to satisfy En / 2> En / 4 ((addition distance)> (subtraction distance)).

  Here, as the subtraction distance En / 4 is reduced, the detection time until the second Z-phase position SZ2 is detected can be shortened, but if it is reduced too much, (1) the first stage If a foreign object is caught between the stroke end StEND and the gripping member 118 and the stroke end is displaced in the gripper opening direction, the second Z-phase detection start position ZSS2 (Lzs2 = Lmp-En / 4) is the second. The Z-phase position SZ2 is exceeded, and the home return operation cannot be performed accurately.

  Therefore, this subtraction distance En / 4 can be set arbitrarily according to the trade-off between giving priority to shortening the Z-phase position detection time or prioritizing the accuracy of return to origin, and reducing the Z-phase position detection time. If priority is given, it can be set to a subtraction distance En / 5 or the like shorter than the subtraction distance En / 4, and if priority is given to the accuracy of return to origin, a subtraction distance En longer than the subtraction distance En / 4. Can be set to / 3 etc.

  (7) As the seventh stage, the CPU 110 starts the detection operation of the second Z-phase signal from the second Z-phase detection start position ZSS2, and the Z-phase position SZ2 where the second Z-phase signal is detected by the rotary encoder 115. Until the gripping member 118 is moved. Thus, the CPU 110 can detect the second Z-phase signal from the second Z-phase detection start position ZSS2 in a short time, and at this time, the gripping member 118 from the stroke end StEND to the second Z-phase position SZ2. The counter value (number of pulses) of the rotary encoder 115 corresponding to the Z-phase moving distance Lmp2 that has moved is actually measured, and this Z-phase moving distance Lmp2 (number of pulses) is stored in the EPPROM 113.

  The CPU 110 stores the Z-phase movement distance Lmp1 from the stroke end StEND stored in the first home return operation to the second Z-phase position SZ2, and the second stroke end StEND measured in the second home return operation. The Z-phase movement distance Lmp2 to the Z-phase position SZ2 is compared.

  If the difference between the comparison results is equal to or less than a predetermined threshold value, the CPU 110 recognizes that no mechanical deviation has occurred and that the second home position return operation is normally performed, and stores it for the first time. After calculating the second home position return travel distance Lz2p (= Lmp1 or Lmp2-Lop) using the Z phase travel distance Lmp1 (or second Z phase travel distance Lmp2), the first home position return operation is performed. In the same manner as described above, the gripping member 118 is moved to the final origin position EG1 according to the origin return movement distance Lz2p to return to the origin.

  On the other hand, when the comparison result between the first Z-phase movement distance Lmp1 and the second Z-phase movement distance Lmp2 is not less than a predetermined threshold, the CPU 110, for example, has a foreign object between the stroke end StEND and the gripping member 118. It is recognized that a trouble such as pinching has occurred, so the return movement distance Lz2p using the Z phase movement distance Lmp1 memorized for the first time without using the second Z phase movement distance Lmp2 The origin return is performed by moving the gripping member 118 from the second Z-phase position SZ2 to the final origin position EG1 based on the origin return movement distance Lz2p. Thus, even when a failure such as a foreign object is caught between the stroke end StEND and the gripping member 118, the CPU 110 can reliably return the gripping member 118 to the origin.

<Other embodiments>
In the above-described embodiment, the physical position separated from the stroke end StEND by the set distance Lop at the time of home return operation of the model in which the Z-phase signal is detected only once during the entire stroke of the gripping member 118 is finally set. However, the present invention is not limited to this, and the position is a predetermined distance from the stroke end StEND, and there is an individual difference between the plurality of electric grippers 101. Another physical position that does not exist may be set as the final origin position EG1.

  In the above-described embodiment, the first Z-phase detection is started so that the second Z-phase signal is detected during the origin return operation of the model in which the Z-phase signal is detected a plurality of times during the entire stroke of the gripping member 118. Although the case where the position ZSS1 and the second Z-phase detection start position ZSS2 are set has been described, the present invention is not limited to this, and the first Z-phase signal and the third Z-phase signal are detected. The first Z-phase detection start position ZSS1 and the second Z-phase detection start position ZSS2 may be set.

  Furthermore, in the above-described embodiment, the case where the origin position EG1 is set in the gripper opening direction from the Z phase position SZ has been described. However, the present invention is not limited to this, and the Z phase position SZ is extended in the gripper closing direction. The origin position EG1 may be set.

  DESCRIPTION OF SYMBOLS 100 ... Electric gripper device, 101 ... Electric gripper, 102 ... Electric actuator, 103 ... Gripper part, 104 ... Electric gripper control device, 106 ... Power supply for control device, 107 ... Power supply for electric actuator power, 108 ... PLC or personal computer 110 ... CPU (control unit), 111 ... ROM, 112 ... RAM, 113 ... EEPROM, 114 ... driver, 115 ... rotary encoder (encoder), 116 ... stepping motor (motor), 117 ... cam member, 118 ... gripping member 119: Interface.

Claims (9)

An encoder that outputs an A-phase signal, a B-phase signal, and a Z-phase signal as the motor shaft of the motor rotates.
A gripping member mechanically connected to the motor shaft and supported so as to be movable within a certain stroke range;
A control unit for returning the gripping member to the origin based on the Z-phase signal output from the encoder,
The control unit sets a position that is a fixed distance away from the stroke end in the gripper opening direction of the gripping member as an origin position, and starts to return to the current position of the gripping member when an origin return command is issued after power-on. As the position, the gripping member is moved from there to the stroke end, and the Z-phase moving distance when the gripping member is moved from the stroke end to the Z-phase position where the Z-phase signal is detected is detected. An electric gripper device, wherein an origin return movement distance is obtained by subtracting the set distance from a Z-phase movement distance, and the origin is returned to the origin position by moving the gripping member according to the origin return movement distance. When the entire stroke of the gripping member that can be moved is smaller than the amount of movement of the gripping member per one rotation of the motor, the control unit outputs the Z-phase signal only once during the entire stroke of the gripping member. It discriminate | determines that it is a model detected. The electric gripper apparatus of Claim 1 characterized by the above-mentioned. In order to assemble so that the Z-phase position is at the center of the full stroke of the gripping member, the motor shaft of the motor is fixed in advance to the position at the center of the full stroke of the gripping member, and aligned with the Z-phase position. The electric gripper device according to claim 2, wherein the encoder in a state of being attached is attached to the motor. The control unit determines whether or not a Z-phase movement distance from the stroke end of the gripping member to the Z-phase position where the Z-phase signal is detected is included in a constant central range in the entire stroke of the gripping member. The electric gripper device according to claim 3, wherein the Z-phase position is confirmed to be within a center range of the entire stroke of the gripping member by determining. An encoder that outputs an A-phase signal, a B-phase signal, and a Z-phase signal as the motor shaft of the motor rotates.
A gripping member mechanically connected to the motor shaft and supported so as to be movable within a certain stroke range;
A control unit for returning the gripping member to the origin based on the Z-phase signal output from the encoder,
The control unit sets a position that is a fixed distance away from the stroke end in the gripper opening direction of the gripping member as an origin position, and starts to return to the current position of the gripping member when an origin return command is issued after power-on. As the position, the gripping member is moved from there to the stroke end, moved from the stroke end to the first Z-phase detection start position beyond the origin position, and from the first Z-phase detection start position to the Z-phase signal. Is detected, the Z-phase movement distance from the stroke end to the Z-phase position when the Z-phase signal is detected is detected, and the origin return is performed by subtracting the set distance from the Z-phase movement distance. An electric gripper characterized by obtaining a movement distance and returning the origin to the origin position by moving the gripping member according to the origin return movement distance. apparatus. In the second and subsequent home-return operations, the control unit is in the gripper closing direction from the first Z-phase detection start position, and returns to the stroke end side by a certain amount from the Z-phase position. The gripping member is moved from the stroke end to the detection start position, the detection of the Z-phase signal is started from the second Z-phase detection start position, and the Z-phase signal is detected from the stroke end when the Z-phase signal is detected. Detecting the Z-phase movement distance to the phase position, subtracting the set distance from the Z-phase movement distance to obtain an origin return movement distance, and moving the gripping member according to the origin return movement distance 6. The electric gripper device according to claim 5, wherein the origin is returned to the position. The control unit detects the Z-phase signal a plurality of times during the entire stroke of the gripping member when the total movable stroke of the gripping member is equal to or greater than the movement amount of the gripping member per one motor rotation of the motor. The electric gripper device according to claim 6, wherein the electric gripper device is determined to be a model. An encoder that outputs an A-phase signal, a B-phase signal, and a Z-phase signal as the motor shaft of the motor rotates, and a gripping member that is mechanically connected to the motor shaft and is movably supported within a certain stroke range; In the origin return method of the electric gripper device, comprising a control unit for returning the grip member to the origin based on the Z-phase signal output from the encoder,
The controller is
An origin position setting step for setting a position away from the stroke end of the gripper in the gripper opening direction by a predetermined set distance as an origin position;
After the power is turned on, a stroke end moving step for moving the gripping member to the stroke end from the current position of the gripping member as an origin return start position at the time of an origin return command;
A Z-phase movement distance detection step for detecting a Z-phase movement distance when the gripping member is moved from the stroke end to a Z-phase position where the Z-phase signal is detected;
Origin return movement distance calculation step for obtaining an origin return movement distance by subtracting the origin setting distance from the Z phase movement distance;
An origin return step of returning the origin to the origin position by moving the gripping member according to the origin return movement distance. An encoder that outputs an A-phase signal, a B-phase signal, and a Z-phase signal as the motor shaft of the motor rotates, and a gripping member that is mechanically connected to the motor shaft and is movably supported within a certain stroke range; In the origin return method of the electric gripper device, comprising a control unit for returning the grip member to the origin based on the Z-phase signal output from the encoder,
The controller is
An origin position setting step for setting a position away from the stroke end of the gripper in the gripper opening direction by a predetermined set distance as an origin position;
After the power is turned on, a stroke end moving step for moving the gripping member to the stroke end from the current position of the gripping member as an origin return start position at the time of an origin return command;
A first Z-phase detection start position moving step for moving from the stroke end to a first Z-phase detection start position exceeding the origin position;
The detection of the Z-phase signal is started from the first Z-phase detection start position, and the Z-phase movement distance is detected from the stroke end to the Z-phase position when the Z-phase signal is detected. A detection step;
Origin return movement distance calculation step for obtaining an origin return movement distance by subtracting the origin setting distance from the Z phase movement distance;
An origin return step of returning the origin to the origin position by moving the gripping member according to the origin return movement distance.

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