JP3268705B2 - Robot home search method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for finding the origin of a movable portion of a robot, such as a hand finger or an arm.

[0002]

2. Description of the Related Art Conventionally, the origin of a robot has been determined only by a positioning command by a control device as shown in FIG. That is, when the command position 1 is given, the current position indicated by the current position counter 204 is subtracted from the command position by the adder 2, multiplied by a predetermined gain by the position loop gain multiplier 3, and input to the adder 4. . In the adder 4, the current speed obtained by the differentiator 9 is subtracted from the output of the multiplier 3, and this subtracted value is passed through a speed loop gain multiplier 5 via a feedback system including an adder 7 and a torque amplifier 8. Output to the servo motor 101. The rotation of the servomotor 101 drives the SCARA robot S-axis unit 104. The movement of the servo motor 101 is
2 to the current value counter 204 to form a loop.

FIG. 11 is a diagram showing an S-axis portion of a conventional SCARA robot. The following describes the conventional home search operation with reference to the home search flowchart shown in FIG. First, when an origin search command is given, the S-axis portion of the SCARA robot starts rotating at a low speed in a certain direction (step S21). This rotation is based on the origin sensor 112
The process is continued until the output is turned ON by the origin dog 110A (step S22). When the origin sensor 112 is turned on, the S-axis section shifts to a slight movement operation (step S2).
3). This minute movement continues the minute movement until the encoder 102 detects the Z phase (step S24). When the Z-phase is detected, the current value counter is cleared and the origin search operation is completed (step S25).

The above is a description of the conventional control procedure, mechanism, and control circuit for finding the origin.

[0005]

However, in the above-mentioned conventional example, since the origin sensor 112 is used, the wiring of the origin sensor is required, and a stable base and space for mounting are required. Was. Therefore, it costs extra, and it takes time to find the origin by the position command.

[0006]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, a movable part of the robot, an electric motor for moving the movable part along a predetermined movement path, and an end of the movable part which is provided at one end of the predetermined movement path, and moves the movable part by contacting the movable part. And a position detector provided on the rotating shaft of the electric motor, and the origin of the movable part of the robot is determined by controlling the moving position, moving speed, and drive current of the electric motor. A method for locating the origin of a robot, wherein a first movement is performed by applying a first command torque to the movable part in a stopper direction, and it is determined that the speed of the movable part has become zero during the first movement. In this case, it is determined that the movable portion has come into contact with the stopper, and a second command torque is further applied to the movable portion in the stopper direction to perform the second movement. Part speed Is determined to be zero again, it is determined that the movable portion has reliably contacted the stopper by the second command torque, and the movable portion is moved in a direction opposite to the stopper by a constant value. At the end, it is determined that the movable portion has reached the origin position.

[0007] Further, in the method of locating the origin of a robot according to the present invention, a movable part of the robot, an electric motor for moving the movable part along a predetermined moving path, and one end of the predetermined moving path of the movable part are provided. A stopper that abuts on the movable part to prevent the movement of the movable part, and a position detector provided on a rotating shaft of the electric motor, and determines a moving position, a moving speed, and a driving current of the electric motor. A robot origin finding method for performing origin finding of a movable part of the robot by controlling, wherein a target position is set in a command position register for storing a target position, and an output of the electric motor is used for the electric motor based on an output from the position detector. A current position is calculated by a current position counter that calculates a current position, and a position deviation of the electric motor is calculated from an output of the current position counter and an output of the command position register. The position deviation is obtained by a first adder to be calculated, and the target movement speed is calculated by a position loop gain multiplier that calculates a target movement speed by multiplying the position deviation by a predetermined control gain. The current speed is obtained by a differentiator that obtains the current speed from the output of the position counter, and the speed deviation is obtained by a second adder that obtains the speed deviation between the target moving speed and the current speed. A speed loop gain multiplier that calculates a target command current by multiplying by a control gain, calculates the target command current, and obtains a current deviation between the target command current and the current command current currently output to the electric motor. By the adder of the above, the current deviation is obtained, the current deviation is amplified, and the torque amplifier outputs the first command current to the electric motor, Outputs the first command current to the electric motor, the speed monitoring device for monitoring the current speed, to monitor the current speed, by a first command torque current register and the second command torque current register, said third
The command value is output directly as a second command current to the adder of the above, and the first command torque current register and the second command torque current register are switched by a torque switch,
In order to switch the command current and drive the electric motor by the circuit switch for switching between the first command current and the second command current, the first command torque is directly supplied to the third adder. By supplying the movable portion, the movable portion is caused to perform the first movement in the stopper direction, and during the first movement, when a speed monitor that monitors the speed of the movable portion determines that the speed of the movable portion is zero, When it is determined that the movable portion has come into contact with the stopper, the torque changeover switch is switched to the second command torque, and the movable portion is caused to move in the stopper direction by the second command torque. During the movement, when the speed monitor determines that the speed of the movable portion is zero again, it is determined that the movable portion has reliably contacted the stopper by the second command torque, and the second command is issued by the circuit changeover switch. The first command power from the current The switching, the stopper causes the movable portion in an opposite direction to move a predetermined value, when the predetermined value movement end, the movable part is characterized in that the discrimination is affirmative home search position.

Further, in the method of finding the origin of a robot according to the present invention, a movable part of the robot, an electric motor for moving the movable part along a predetermined moving path, and one end of the movable part of the movable part are provided. A stopper that abuts on the movable part to prevent the movement of the movable part, and a position detector provided on a rotating shaft of the electric motor, and determines a moving position, a moving speed, and a driving current of the electric motor. A robot origin finding method for performing origin finding of a movable part of the robot by controlling, wherein a target position is set in a command position register for storing a target position, and an output of the electric motor is used for the electric motor based on an output from the position detector. The current position is calculated by a current position counter that calculates the current position, and the position of the electric motor is calculated from the output of the current position counter and the output of the command position register. The first adder for calculating the difference,
The position deviation is obtained, the target position speed is calculated by a position loop gain multiplier that calculates a target moving speed by multiplying the position deviation by a predetermined control gain, and the current speed is obtained from the output of the current position counter. By a differentiator, the current speed is obtained, and a second adder for obtaining a speed deviation between a target moving speed and a current speed is obtained, the speed deviation is obtained, the speed deviation is multiplied by a predetermined control gain, and a target command current is obtained. The target command current is calculated by a speed loop gain multiplier to be calculated, and the current deviation is obtained by a third adder that obtains a current deviation between the target command current and the current command current currently output to the electric motor. Amplifying the current deviation and outputting the first command current to the electric motor by a torque amplifier that outputs the first command current to the electric motor as a first command current. The speed monitoring device for monitoring the speed,
The current speed is monitored, and a first command torque current register and a second command torque current register are used to directly output a command value to the third adder as a second command current. A command current is switched by a circuit changeover switch that switches between a first command current register and a second command current register, and switches between the first command current and the second command current, and drives the electric motor. In order to achieve this, the first command torque is directly supplied to the third adder to cause the movable section to make a first movement in the stopper direction, and monitor the speed of the movable section during the first movement. When the speed monitor determines that the speed of the movable portion is zero, it determines that the movable portion has come into contact with the stopper,
The torque changeover switch is switched to a second command torque, and the second command torque causes the movable portion to move in the stopper direction in the second direction.
During the second movement, when the speed monitor determines that the speed of the movable portion is zero again, it is determined that the movable portion has reliably contacted the stopper by the second command torque. The first command current from the second command current
And the movable part is moved in the third direction in the direction opposite to the stopper. During the third movement, when the origin detector outputs an origin pulse, the movable part returns to the origin. It is characterized that it is determined that the position has been reached.

[0009]

【Example】

<First Embodiment> FIG. 2 is an overall external view of a SCARA robot according to a first embodiment, and FIG. 3 is a view showing only the S-axis portion of the SCARA robot. In FIG. 2, reference numeral 1 denotes a SCARA-type robot, and reference numeral 2 denotes an S-axis mechanism of the SCARA-type robot for rotating and positioning a robot hand mechanism.

In FIG. 3, reference numeral 101 denotes a servo motor, 1
02 is a position detection pulse encoder, 103 is a timing pulley attached to the rotation output shaft of the servomotor,
104 is a timing belt, 105 is a timing pulley located on the opposite side of the pulley 103, and 106 is (for S axis)
Rotation axis, 107 is a base attached to the SCARA robot body, 108 is a robot hand mechanism, 109 is a stopper attached to the base, 110 is a dog for originating the S axis attached to a joint, 111 is an S axis And a robot hand mechanism 108.

The operation of the S-axis part of this SCARA type robot is as follows.
The rotation output of the servo motor 101 is output to the timing pulley 10
3, timing belt 104 and timing pulley 105
To rotate the S-axis rotation shaft 106. Thereby, the attitude of the hand mechanism 108 is determined. Further, the position of the hand mechanism can be detected by the pulse encoder 102 attached to the servomotor 101.

The robot hand mechanism 108 performs origin search by pressing the two by means of an origin search stopper 109 and a dog 110. FIG. 4 shows an example of a hardware configuration diagram of a control device for realizing the first embodiment. 201 is a central processing unit (CPU) for realizing control
Numeral 202 is bus-coupled to the CPU 201 and includes a nonvolatile memory (RO) including a series of control processing algorithm programs and a man-machine interface program.
M), and 203 is a memory (RAM) backed up by a power supply capable of storing teaching data. Also, 204
Is a pulse encoder 1 connected to the servo motor 101
02 is a current value counter which is capable of counting the current position of the servomotor. Reference numeral 205 denotes a D / A converter connected to the servo motor through the torque amplifier 8. The D / A converter 205 can output an analog current instruction to the torque amplifier 8 according to an instruction from the CPU 201. Also,
A communication interface 206 connects the external teaching device 207 and the CPU. ROM 202, RAM 20
3, counter 204, D / A 205, interface 2
06 are all connected to the CPU 201 by the bus 208.

FIG. 1 is a block diagram of the control device of the first embodiment, and is a block diagram of a control circuit relating to a method of controlling the origin of the S-axis portion of the SCARA robot. The control circuit of FIG.
It consists of two loops: a positioning control loop (shown by a solid frame in the figure) and a torque control loop 400 (shown by a broken frame in the figure). The positioning control loop 300 is a loop for positioning control used during the operation of the S-axis part of the normal SCARA robot, and the torque control loop is a control loop used at the time of finding the origin of the S-axis part of the SCARA robot.
Next, each control loop will be described.

[Positioning Control Loop] In FIG. 1, a target positioning position of the S-axis portion of the SCARA robot is set to a command position 1. The target command position 1 is output to the adder 2. The adder 2 obtains a positional deviation between the target command position 1 and the current position of the robot arm 100, which is the S-axis part of the SCARA robot, and outputs it to the position loop gain multiplier 3. The position loop gain multiplier 3 calculates a target moving speed by multiplying the position deviation by a predetermined control gain, and outputs the target moving speed to the adder 4. The adder 4 obtains a speed deviation between the input target moving speed and the current moving speed of the robot arm 100, and outputs the result to the speed loop gain multiplier 5. The speed loop gain multiplier 5 multiplies the input speed deviation by a predetermined control gain, and outputs a target command current to the adder 7. The adder 7 obtains a current deviation between the input target command current and the current command current currently being output to the servo motor 101, and outputs this to the torque amplifier 8.
The torque amplifier 8 amplifies the input current deviation,
It is output to the servo motor 101 as a command current. The servo motor 101 is driven by the input command current, generates a torque, moves and drives the SCARA robot S-axis unit 100 to the target command position 1, and performs positioning. The encoder 102 outputs a signal corresponding to the rotation of the servo motor 101 to the current position counter 204 to detect the current position of the SCARA robot S-axis unit 100, and the current position counter 204 outputs the signal based on the signal from the encoder 102. The position is calculated and used as the current position. The output of the current position counter 204 is set to the current speed through the differentiator 9. These are conventional positioning control loops.

[Torque Control Loop] Hereinafter, the operation of locating the origin of the S-axis portion of the SCARA robot will be described. In the control block diagram of FIG. 1, before performing the home search operation, the loop changeover switch 6 is connected to the position A and connected to the positioning control loop.

Therefore, when the home search operation shown in the home search operation flowchart of FIG.
In step S1, the first command torque value 11 is set in the torque control loop of FIG.
Is set to the C position, and the loop changeover switch 6 is connected to the B position so that the output of the loop changeover switch 6 becomes a torque control loop.

Next, in steps S3 and S4, the first command torque is output while the speed monitor 14 continues to output the first command torque until the speed becomes zero. In the operations of steps S3 and S4, the dog 110 moves toward the stopper 109 of the SCARA robot S-axis portion as shown in FIG. The movement operation according to the first command torque is performed by the dog 110.
Is continued until it collides with the stopper 109. The speed monitor 14 monitors the moving speed of the arm, and the moving speed =
By “zero”, it is detected that the dog collides with the stopper 109.

When this collision is detected, the second command torque value 12 is set in step S5, the torque switch 13 is switched from the C position to the D position in step S6, and the second command torque value is servo-controlled in steps S7 and S8. Output control to motor. This second command torque value is larger than the first command torque value. The second command torque value is completely transmitted to the SCARA robot S-axis unit (step S8), and the process proceeds to the next step when the current speed becomes zero in step S9.

At the end of the steps S7, S8, and S9, the SCARA robot S-axis is
It is in a state of hitting with a constant load without variation from 09. Further, in step S10, the loop changeover switch 6 shown in FIG. 1 is connected to the position A to switch to the positioning control loop. At this time, the value of the current position from the current position counter 204 is substituted for the command position 1.

In step S11, the target command position 1
, A small moving amount that is opposite to the previous moving direction is continuously added, and the servo motor 101 is set to be opposite to the previous moving direction.
To rotate. In step S12, an origin pulse signal (servo motor 1) from the pulse encoder 102 connected to the rotating servo motor 101 is output.
Until a signal of one pulse per rotation) is detected, the servo motor 101 instructed in step S11 is moved. When the home pulse signal is detected, step S is immediately executed.
In step 13, the current value counter 204 shown in FIG. 1 is cleared, the movement of the servo motor 101 is stopped, and the origin search operation is completed.

The first embodiment is an example in which a constant value is set as the first command torque value from the beginning, and control is performed to move the robot arm. As described above, according to the first embodiment, by outputting the first and second command torque values and performing the origin finding operation of the S-axis portion of the SCARA type robot, the SCARA type robot can be accurately loaded. Is pressed against the stopper 109, the reproducibility of the amount of deformation of the transmission unit is improved, and the origin sensor is eliminated, which has the effect of reducing costs.

<Second Embodiment> The second embodiment is for performing accurate home search using a pulse encoder that does not output a home pulse. Some small-sized servomotors having a small capacity do not output an origin pulse (Z-phase). FIG.
Is a flowchart of the second embodiment, in which step S1
Steps S10 to S10 are the same as in the first embodiment.

In FIG. 6, in step S11 ', the servo motor 101 is rotated by a certain amount so as to be opposite to the moving direction in the torque control in steps S3 and S7. The certain amount is the amount of rotation applied to both the S-axis portion of the SCARA type robot and the stopper 109 before the servo motor 101 is rotated, but the amount is enough to release the load.

Next, when the servo motor 101 completes the rotation of the set amount in step S12 ', the current value counter 204 is cleared immediately in step S13', and the origin search operation ends. With the above control, A
Even with an inexpensive pulse encoder having only the phase and B phases and no origin pulse, accurate origin search operation is possible.

<Third Embodiment> The first embodiment described in the first embodiment
The third embodiment is an embodiment in which the command torque control is further improved in reliability. Hereinafter, description will be made with reference to the flowchart of FIG. Note that the flowchart of FIG.
7 is a detailed flowchart corresponding to step S3 in the flowchart of FIG.

In step S31, a preset command lower limit is set as an initial value. In step S32, the servo motor 10
Apply current to 1. In step S33, the servo motor 1
It is checked whether 01 has not moved due to friction between the rotating shaft and the base or the transmission system (that is, whether the speed was 0). If it is moving, the current continues to flow to the servo motor with the same command value in step S36.

If it is determined in step S33 that the motor has not moved, it is checked in step S34 whether the current command value has exceeded a preset command upper limit value. If the upper limit is exceeded, the control procedure ends, and the process proceeds to step S4 in FIG. Step S3
If it is determined in step 4 that the current value does not exceed the upper limit value, the process proceeds to step S35, where a preset increase value is added to the current command value, and the process returns to step S36 to execute the above-described contents again.

Here, the first command torque value according to the third embodiment for finding the origin will be described. A rotation transmission system such as an arm has an inherent sliding resistance. Due to this resistance or the like, when the command torque value is small, the S-axis portion of the SCARA robot may not operate. This is to prevent the erroneous recognition that the rotation system does not rotate due to the resistance and that the dog collides with the stopper and does not rotate. Therefore, a value equal to or greater than the torque value at which the S-axis portion of the SCARA robot can actually operate is determined as the command torque value by overcoming the sliding resistance. Usually, this resistance has an upper limit. If the command value exceeds the upper limit in step S34,
With the torque at that value, the arm should always move depending on the normal frictional resistance. In other words, when the speed value exceeds the upper limit and the speed value is 0, the dog must always collide with the stopper. It is.

According to the first command torque value, the S-axis portion of the SCARA type robot moves in the direction of origin search with respect to the base, and when the stopper 109 and the dog 110 actually contact,
Set the command torque value changeover switch 13 to the second command torque value (D
Position) (step S6). The timing of switching the torque changeover switch 13 from the position C to the position D is the time when the rotation speed of the motor becomes zero after the loop changeover switch 6 is switched from the positioning control loop side A to the torque control side B. This speed monitor is a speed monitor 1
When the current speed becomes 0, it is determined that the dog 110 has come into contact with the stopper 109, and the second
The command torque switch 13 is switched to the command torque side D.

When the switch is switched to the second command torque side D, the second command torque 12 is output to the adder 7 through the loop switch 6 as a command value. Therefore, a torque control is performed by the torque control loop to generate a constant torque in the servo motor 101 to operate the S-axis portion of the SCARA robot, so that the dog 110 and the stopper 109 are pushed with a constant load without variation. Has been applied.

Here, in order to find the origin of the S-axis portion of the SCARA type robot, the first and second command torque values are set to two.
The reason for controlling in stages is that if the command torque value of only one rotation is used, the reproducibility of the amount of deformation of the transmission unit is low depending on the moving distance.
This is because it is desired to minimize the impact applied to the dog 110 and the stopper 109 as soon as possible in the event of a collision between the dog 110 and the stopper 109 (= the minimum torque value at which the S-axis can rotate). Dog 11
From the state where 0 and the stopper 109 are in contact, a torque value larger than the first command torque value is given as the second command value. By doing so, a stable contact state (deformation amount) can be obtained.

FIG. 8 is a diagram showing the generated load when the command torque is applied only once. FIG. 9 is a diagram showing an example of a command torque value according to the present invention and a load generated at the time of a collision.
As shown in FIG. 9, the method according to the present embodiment has a smaller load generated at the time of contact and a smaller fluctuation range.

[0033]

As described above, according to the home search method of the present invention, the home sensor is eliminated, cost can be reduced while maintaining accurate home search accuracy, and the time required for home search operation can be reduced. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device according to an embodiment of the present invention.

FIG. 2 is an overall external view of a SCARA robot embodying the present invention.

FIG. 3 is a diagram in which only the S-axis portion of the SCARA robot embodying the present invention is exposed.

FIG. 4 is an example of a hardware configuration diagram of a control device for realizing the present invention.

FIG. 5 is a flowchart of an origin finding operation in the first embodiment of the present invention.

FIG. 6 is a flowchart of an origin finding operation according to the second embodiment of the present invention.

FIG. 7 is a flowchart of an origin finding operation according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a generated load when a command torque is given only once.

FIG. 9 is a diagram showing a command torque value according to the present invention and a load generated at the time of a collision.

FIG. 10 is a block diagram of a conventional control device.

FIG. 11 is a diagram in which an S-axis portion of a SCARA type robot using a conventional origin finding method is exposed.

FIG. 12 is a flowchart of a conventional origin finding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Command position 2, 4, 7 Adder 3 Position loop gain multiplier 5 Speed loop gain multiplier 6 Loop switch 8 Torque amplifier 9 Differentiator 11 First command torque 12 Second command torque 13 Torque switch 14 Speed monitor 15 (Speed = 0) Detector 100 Scalar Robot Shaft 101 Servo Motor 102 Pulse Encoder 103, 105 Timing Pulley 104 Timing Belt 106 Rotary Axis 107 Base 108 Robot Hand Mechanism 109 Stopper 110 Dog 111 Joint 201 CPU 202 ROM 203 RAM 204 Current position counter 205 D / A converter 206 Communication interface 207 Teaching device 300 Positioning control loop 400 Torque control loop

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G05B 19/18-19/46 B23Q 15/00-15/28 B25J 3/00-3/10 B25J 9 / 10-9/22 B25J 13/00-13/08 B25J 19/02-19/06 G05D 3/00-3/12

Claims (6)

(57) [Claims] 1. A movable part of a robot, an electric motor for moving the movable part along a predetermined movement path, and an electric motor provided at one end of the predetermined movement path of the movable part, wherein the movable part comes into contact with the movable part. A stopper for preventing the movement of the robot, and a position detector provided on the rotating shaft of the electric motor, and by controlling the moving position, the moving speed, and the driving current of the electric motor, the origin of the movable part of the robot is controlled. A method of locating the origin of a robot that performs a first movement by applying a first command torque to the movable part in a stopper direction, wherein during the first movement, the speed of the movable part becomes zero. If it is determined that the movable portion has come into contact with the stopper, it is determined that the movable portion has come into contact with the stopper, and a second command torque is further applied to the movable portion in the direction of the stopper to perform a second movement. , Possible When it is determined that the speed of the moving part has become zero again, it is determined that the movable part has reliably contacted the stopper by the second command torque, and the movable part is moved by a fixed value in the direction opposite to the stopper, At the end of the constant value movement, it is determined that the movable section has reached the home position. 2. A movable section of a robot, an electric motor for moving the movable section along a predetermined movement path, and an electric motor provided at one end of the predetermined movement path of the movable section, the movable section being in contact with the movable section and being movable. A stopper for preventing the movement of the robot, and a position detector provided on the rotating shaft of the electric motor, and by controlling the moving position, the moving speed, and the driving current of the electric motor, the origin of the movable part of the robot is controlled. A method of locating the origin of a robot that performs locating, wherein a target position is set in a command position register that stores the target position, and a current position counter that calculates a current position of the electric motor based on an output from the position detector. A first adder for calculating a position, and calculating a position deviation of the electric motor from an output of the current position counter and an output of the command position register; Is calculated by a position loop gain multiplier that calculates a target moving speed by multiplying the position deviation by a predetermined control gain.
The target moving speed is calculated, the current speed is obtained by a differentiator that obtains a current speed from the output of the current position counter, and the speed is obtained by a second adder that obtains a speed deviation between the target moving speed and the current speed. Determine the deviation, by a speed loop gain multiplier that calculates the target command current by multiplying the speed deviation by a predetermined control gain,
A third adder that calculates the target command current and obtains a current deviation between the target command current and the current command current that is currently being output to the electric motor; obtains the current deviation; amplifies the current deviation; The first command current is output to the electric motor by a torque amplifier that outputs the first command current to the electric motor, and the current speed is monitored by a speed monitor that monitors the current speed. A command value is directly supplied to the third adder by a second register and a second command torque current register.
The first command torque current register and the second command torque current register are switched by a torque switch, and the circuit switch is configured to switch between the first command current and the second command current. Switching the command current, and supplying the first command torque directly to the third adder in order to drive the electric motor, thereby causing the movable portion to make a first movement in the stopper direction, During the first movement, when the speed monitor that monitors the speed of the movable portion determines that the speed of the movable portion is zero, it determines that the movable portion has come into contact with the stopper, and sets the torque switch to the second position. Switching to the command torque, causing the movable portion to make a second movement in the stopper direction by the second command torque. During the second movement, the speed monitor determines that the speed of the movable portion is again zero. Then, it is determined that the movable portion has securely contacted the stopper by the second command torque, and the second command current is switched from the second command current to the first command current by the circuit changeover switch, and the movable portion is moved in the opposite direction to the stopper. A method of locating an origin of a robot, comprising: moving a fixed value, and determining that the movable portion has reached an origin locating position at the end of the constant value movement. 3. A movable part of the robot, an electric motor for moving the movable part along a predetermined movement path, and one end of the movable part provided at one end of the predetermined movement path, the movable part being in contact with the movable part and being movable. A stopper for preventing the movement of the robot, and a position detector provided on the rotating shaft of the electric motor, and by controlling the moving position, the moving speed, and the driving current of the electric motor, the origin of the movable part of the robot is controlled. A method of locating the origin of a robot that performs a locating operation, comprising: setting a target position in a command position register storing a target position; and calculating a current position of the electric motor by an output from the position detector. A first adder for calculating a current position, and calculating a position deviation of the electric motor from an output of the current position counter and an output of the command position register; A position loop gain multiplier that calculates a deviation and calculates a target moving speed by multiplying the position deviation by a predetermined control gain,
The target position speed is calculated. The current speed is obtained by a differentiator that obtains the current speed from the output of the current position counter. The speed is obtained by a second adder that obtains a speed deviation between the target moving speed and the current speed. A deviation is obtained, the speed deviation is multiplied by a predetermined control gain, and the target command current is calculated by a speed loop gain multiplier that calculates a target command current.The target command current and the current command currently output to the electric motor are calculated. A third adder for calculating a current deviation from a current obtains the current deviation, amplifies the current deviation, and outputs the first command current to an electric motor by a torque amplifier that outputs the first command current to the electric motor as a first command current. The current speed is monitored by a speed monitor that outputs to the motor and monitors the current speed, and is stored in a first command torque current register and a second command torque current register. Thus, the command value is directly sent to the third adder in the second adder.
A first command current register and a second command current register by a torque switch, and a circuit switch for switching between the first command current and the second command current. In order to switch the command current and directly supply the first command torque to the third adder in order to drive the electric motor, the movable portion is caused to perform the first movement in the stopper direction, When the speed monitor that monitors the speed of the movable unit determines that the speed of the movable unit is zero during the movement of the first unit, it is determined that the movable unit has come into contact with the stopper, and the torque switch is set to the second command. When the speed monitor determines that the speed of the movable portion is again zero during the second movement, the speed is switched to torque, and the movable portion is caused to perform a second movement in the stopper direction by the second command torque. The movable portion is determined to have reliably contacted the stopper by the second command torque, and the second command current is switched from the second command current to the first command current by the circuit changeover switch. 3. The method of claim 3, further comprising: determining that the movable section has reached the origin search position when an origin pulse is output from the position detector during the third movement. . Wherein said second command torque, claims 1 to 3 Neu and greater than the first command torque
The method of finding the origin of the robot according to any one of the first to third aspects . When wherein movement of the movable portion is not recognized even by applying a first command torque value, claims 1 to 4 noise, wherein the gradually increasing the first command torque value
7. The method for finding the origin of a robot according to item 1 . 6. The method according to claim 5, wherein in the step of gradually increasing the first command torque, the increase is stopped when an upper limit value is reached.