JPS62174806A - Industrial robot controller - Google Patents

Abstract

PURPOSE:To prevent the mistaken execution of calibration due to the existence of a hindrance by providing an encoder, a mechanical stopper, a measuring means, a memory means, a comparison means and a signalling means. CONSTITUTION:A CPU 13 reads out a value counting said output pulses and a permissible value previously stored in a ROM 14, and compares them. If the counted value of the output pulse stands at a value within the prescribed permissible range, it is judged that a rotating shaft in a joint part correctly abuts on the mechanical stopper. Then the CPU 13 decides whether rotating shafts in all joint parts abut on the mechanical stopper or not. Whereas the said counted value is beyond the permissible range, the CPU 12 causes a display part 5 in a teaching box 3 to display characters showing that the rotating shaft hits hindrances apart from the mechanical stopper, and informs a robot operator.

Description

[Detailed Description of the Invention] <Technical Field of the Invention> The present invention is directed to the control of an industrial robot in which an incremental rotary encoder (hereinafter simply referred to as an "encoder") is used, for example, to detect the position of a robot joint. In relation to the apparatus, in particular, the present invention proposes an improved method of calibration (origin position alignment) at the joints of this type of industrial robot.

<Background of the Invention> In conventional industrial robots, mechanical stoppers are provided corresponding to each end position of the rotation axis in the positive and negative rotation directions to define the range of movement of the arm at each joint. . When calibrating each joint of an industrial robot with this type of structure, first rotate the arm (rotation axis) in either the positive or negative direction, bring it into contact with a mechanical stopper, and then is rotated in the opposite direction, and when the encoder outputs the first Z-phase output,
A method was developed for setting and adjusting the origin position using this as a reference. However, with this type of method, if there is an obstacle during rotation and the arm collides with it, there is a risk that the obstacle will be mistakenly recognized as a mechanical stopper and an incorrect calibration will be performed. . In addition, when performing calibration on multiple joints at the same time, the state in which each joint presses against the mechanical stopper is maintained until contact with the mechanical stopper is detected in all joints. However, in this case, if the object the arm contacts is not a mechanical stopper but an obstacle, the pushing force may cause deformation or destruction of the obstacle, and if the obstacle is a human being. In some cases, there are problems such as serious danger that may result in personal injury.

<Purpose of the Invention> The present invention provides a novel industrial robot control device that can prevent incorrect calibration due to the presence of obstacles, etc., and can also prevent damage to obstacles and accidents resulting in injury or death. The purpose is to

<Structure and Effects of the Invention> In order to achieve the above object, the industrial robot control device of the present invention provides an output pulse and a rotation reference position that are connected to the rotation axis of the robot joint and that correspond to the rotation angle of the rotation axis. an encoder that outputs a basic signal that gives a basic signal, a mechanical stopper disposed at the robot joint for defining the rotation angle range of the rotary shaft, and a calibration operation that rotates the rotary shaft in a direction that hits the mechanical stopper. Measuring means that is cleared every time a 1 m signal is input from the encoder and counts the number of output pulses output by the encoder between a predetermined reference signal input position and a contact position of the mechanical stopper; a storage means for presetting an allowable value for the output pulse count; and a comparison means for comparing the output pulse count by the measuring means with the allowable value set in the storage means. , and a notification means for notifying the comparison results obtained by the comparison means.

According to this invention, when the count value of output pulses by the measuring means deviates from a predetermined tolerance value during calibration, it can be determined that the joint has hit an obstacle other than the mechanical stopper. This makes it possible to prevent erroneous calibration due to the presence of obstacles with a high probability. Also, even when calibrating multiple joints at the same time,
Since it can be immediately determined that any of the joints has hit an obstacle, there is no risk that the pressing force will act on the obstacle for a long period of time, leading to deformation or destruction of the obstacle. Furthermore, in the event of a collision with a human being, the occurrence of an accident resulting in injury or death will be prevented, and the safety of the robot will be greatly improved, achieving the remarkable effect of achieving the purpose of the invention.

<Description of Embodiments> FIG. 2 shows an example of the overall configuration of an industrial robot according to one embodiment of the present invention. The illustrated industrial robot is composed of a robot body 1, a controller 2 that controls the operation of the robot body 1, and a teaching box 3 that performs input and output to the controller 2. In addition to a key operation section 4 operated by an operator, a display section 5 on which characters related to input and output are displayed is provided.

The robot main body 1 of this embodiment has rotational degrees of freedom of θ and ~θ at three joints, and each of the first to third arms 6.7.8 has a rotation axis 9.10.11. The third arm 8 rotates forward and backward around the center, and also moves linearly back and forth with one degree of freedom in the Z direction. The rotating shafts 9, 10.11 are independently driven by servo motors M+-M3 (shown in FIG. 3) as a drive mechanism.

FIG. 3 shows a schematic configuration of the control device of the industrial robot. In the figure, the circuit configuration indicated by the chain line 12 is
It is incorporated into the controller 2 shown in the figure.

In the illustrated example, CPUL3 is connected to ROMI4 and RAM1.
5 constitutes a microcomputer, and executes various calculations and processes such as command analysis, command value calculation, and position control calculation. Further, the ROM 14 stores programs for controlling the robot, and the RAM 15 stores calculation results and other data.

The output of the CPU 13 is the servo amplifier A, ~A.

These servo amplifiers A.

~A amplifies each output value (current command value) from the CPU 13 and supplies it to each of the servo motors M1~M. The encoder E t "" Ex is an incremental rotary encoder attached to each of the servo motors M1 to M3, and detects the rotation angle of each motor and provides it to the CPU 13. Each of the incremental encoders E1 to E3 outputs output pulses (for example, 1000 pulses per rotation) according to the rotation angle as A-phase and B-phase outputs, and also outputs a reference signal that provides a reference position of rotation as a Z-phase output. (For example, 1 pulse per revolution) is output.

Mechanical stoppers (not shown) for defining the rotation angle range of the rotation shafts 9, 10, and 11 are provided at each joint, corresponding to each end position of the rotation shafts in the positive and negative rotation directions. .

FIG. 4 illustrates the rotation angle range α1 of the rotation shaft 9 and the locations S+ and SZ of the mechanical stoppers at both ends thereof. Origin P1 is set (same for other joints)
. Note that in the figure, Z and ~Z indicate the angular position at which the encoder E1 outputs the Z-phase output (reference signal) when the rotating shaft 9 rotates.

The above positioning (calibration) of the origin Pi (where i = 1.2.3) is performed after the power is turned on using the A-phase or B-phase output and Z-phase output of encoders E1 to E□. The specific procedure is as shown in Figure 1.

Note that in this calibration, the CPU
3 functions as a measurement means for counting the number of output pulses of each encoder E, ~E, and a comparison means for comparing the counted value of the output pulses with a tolerance value described later, as well as various functions related to calibration. Perform calculations and processing. In addition, the ROM 14 is used to store the tolerance value as well as a program for executing calibration.
Further, the RAM 15 stores various data such as the count value of the output pulses, and is also used as a work area.

In step 1 of FIG. 1 (indicated by rsTIJ in the figure), the CPU 13 in the controller 2 first drives all the motors M1 to M3 at the same time to rotate the rotating shafts 9 to 11 in the forward rotation direction (see FIG. 4). Rotate to This operation is carried out as shown in FIG.
U13 executes calculations for the servo system for position control, and sends the current command value, which is the calculation result, to each servo amplifier A + "
A While counting by adding up the numbers (Step 2), each time a reference signal (Z-phase output) of one pulse per rotation is input from each encoder (Step 3).
is "YES"), the process proceeds to step 4 and the count value is cleared.

Thus, each of the first to third arms 6 to 8 (rotating shafts 9 to 1
0) is rotated by an appropriate angle and comes into contact with a mechanical stopper at any of the joints, the CPU 13 detects this and the determination of "Did it hit the mechanical stopper?" in step 5 becomes YES. Contact with the mechanical stopper can be detected from the fact that the output pulses from the encoder are no longer input to the CPU 13. At this time, the CPU 3 stores the counted value of the output pulses at this point in the RAM.
15 in the designated area. In Fig. 4, the count value of this output pulse is determined by the angular position Z1 where the encoder finally outputs the reference signal and the mechanical stopper position S.
1 corresponds to the number of output pulses output by the encoder.

Next, in step 6, the CPU 3 reads out the count value of the output pulse and a tolerance value stored in advance in the ROM 14, and compares the magnitude of the two. This tolerance value is for specifying an appropriate count value to prevent incorrect calibration due to the presence of obstacles, etc., and is related to the assembly accuracy of the motor and encoder. the last reference signal output position Zl
The angle between and the position SL of the mechanical stopper is usually set at an angle corresponding to half a revolution of the motor, so for example, in the case of an encoder that outputs 1000 pulses per revolution, the allowable value is 450~ Set to a range of about 550 pulses.

Thus, if the count value of the output pulse takes a value within the predetermined tolerance, step 7 is "YES", and the CP
UL3 determines that the rotating shaft has correctly contacted the mechanical stopper at that joint. And then CPUL3
In step 9, it is determined whether the rotation axes of all joints have hit the mechanical stopper.

On the other hand, if the above-mentioned count value takes a value outside the allowable range, the arm may have hit an obstacle other than the mechanical stopper and misidentified it as the mechanical stopper, or the mechanical stopper itself may have been damaged. In this case, the determination in step 7 is "NO" and the process proceeds to step 8, where the CPU 13 causes the display unit 5 of the teaching box 3 to display text indicating that the robot has hit an obstacle other than the mechanical stopper. , to notify the robot operator.

The flow of steps 2 to 8 is similarly executed for the other joints, and as a result, when the CPU 3 detects that all the rotation axes 9 to 10 have come into contact with their respective mechanical stoppers (determination in step 9 is "YES"), proceed to step 1o and set "1" to the counter section i in CPUL3.
” to specify execution of calibration for the first joint.

First, in step 11, the CPU 3 drives the motor ML to rotate the rotary shaft 9 at low speed in a negative rotation direction (opposite direction to the above). Along with this rotation operation, the CPU
Output pulses are sent from encoder E to 13, and CPU 3 counts the number of output pulses and
Wait for encoder E to send a reference signal (Z phase output) of one pulse per revolution. Thus encoder E
If the reference signal is received from step 1, step 12 is YES.
Then, CPUL3 writes information indicating the output position Z of the first reference signal with respect to the origin P1 (a value converted to the count value of the A-phase or B-phase output of encoder E) as current position information to a predetermined area of RAML5. At the same time, the rotation of the motor M1 is stopped (step 13).

Next, the CPU 13 at step 14.

Add 1 to the contents of the counter section i and proceed to the next step 1.
After confirming in Step 5 that the content of the counter part i has not reached "3", calibration for the second joint part is executed in Steps 11 to 14.

Also for the second and third joints, step 1
The flows below 1 are executed in the same way, and the ri of step 15
>3? At the stage when the determination of J becomes "YES", a series of calibration processing is completed.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a calibration operation according to an embodiment of the present invention, FIG. 2 is a diagram showing the overall schematic configuration of an industrial robot according to an embodiment of the invention, and FIG.
The figure is a block diagram showing an example of a circuit configuration of an industrial robot control device, and FIG. 4 is a diagram showing an example of a rotation angle range of a rotating shaft. 1...Robot body 2...Controller 5
... Display section 9 to 11 ... Rotating shaft 13
... CPU 14 ... ROM
15...RA M M1~M...Motor E1~E3...Encoder patent Applicant: Tateishi Electric Co., Ltd. Near 'F2+a Hayashi machine lj to fill in -~M3・・・Motor E, ～E, −・−Encoder 3 r'a + 0.7 IfA, t2

Claims (5)

[Claims] (1) An encoder that is connected to the rotation axis of the robot joint and outputs an output pulse according to the rotation angle of the rotation axis and a reference signal that provides a rotation reference position, and defines a rotation angle range of the rotation axis. During the calibration operation of rotating the rotary shaft in the direction in which it hits the mechanical stopper disposed at the robot joint, the reference signal is cleared each time the encoder inputs the reference signal, and the predetermined reference signal is cleared. a measuring means for counting the number of output pulses output by the encoder between a signal input position and a contact position of the mechanical stopper; a storage means for presetting an allowable value for the count value of the output pulses; An industrial device comprising comparing means for comparing the count value of output pulses by the measuring means and its tolerance value set in the storing means, and notifying means for notifying the comparison result by the comparing means. Robot control device. (2) The industrial use according to claim 1, wherein the encoder is an incremental rotary encoder that outputs the output pulse as an A-phase or B-phase output and also outputs the reference signal as a Z-phase output. Robot control device. (3) The industrial robot control device according to claim 1, wherein the mechanical stopper is disposed corresponding to each terminal position in the positive and negative rotational directions of the rotating shaft. (4) The industrial robot control device according to claim 1, wherein the measuring means and the comparing means are a CPU of a microcomputer. (5) The industrial robot control device according to claim 1, wherein the notification means is a display section provided on a teaching box.