JPS6263303A - Position correcting method for mechanical origin of articulated robot - Google Patents

Abstract

PURPOSE:To execute a palletizing function, etc., with high accuracy, by measuring the discrepancy between a detected position of a mechanical origin and its designed position and correcting the discrepancy in accordance with the measured results. CONSTITUTION:Pins 43 and 44 are respectively fitted to the 1st and 2nd horizontal arms 2 and 4 and a robot arm is returned to the position of its mechanical origin, and then, the 2nd arm 4 is rotated in the (+) direction until the pins 43 and 44 are respectively put in the through holes 41 and 42 of an arm angle measuring jig 40. Under this condition the relative angle formed by the 1st and 2nd horizontal arms 2 and 4 becomes 90 deg.. When the moving quantity of the 2nd arm 4 per one pulse of a motor, theoretical pulse value when the relative angle formed by the 1st and 2nd arms 2 and 4 is 90 deg., and measured pulse value when the relative angle formed by the 1st and 2nd arms 2 and 4 is 90 deg. are represented by phi2, theta2, and theta'2, respectively, an offset value DELTAtheta2 can be found from the following formula: DELTAtheta2=(theta'2-theta2)Xphi2, and correction of the position of the mechanical origin is performed in accordance with this offset value DELTAtheta2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for correcting the mechanical origin position of an articulated robot.

(Prior Art) In order to accurately position the working arm, hand, etc. of an articulated robot, it is necessary to have the control device that controls the robot accurately recognize the mechanical origin position (home position) of the robot. be.

First, a method for detecting the mechanical origin position of an articulated robot will be explained. FIG. 6 is a schematic diagram showing the external appearance of the horizontally articulated robot, and FIG. 7 is a diagram of the same mouth and throat viewed from above. In these figures, 1 is the robot body. A first horizontal arm 2 is rotatably attached to the robot body 1 by a first rotating shaft 3 provided at one end thereof. A second horizontal arm 4 is rotatably attached to the other end of the first horizontal arm 2 by a second rotating shaft 5 provided at one end thereof. A vertical arm 6 that moves in the vertical direction is attached to the other end of the second horizontal arm 4, and a support member 7 that supports a hand (not shown) of the robot is rotated by a third rotation shaft 8 on this vertical arm 6. installed as possible. 1st to 3rd
The rotating shafts 3 and 5.8 are oscillatingly driven by correspondingly provided motors (not shown), and the vertical arm 6 is also movable in the vertical direction by a drive mechanism (not shown). As shown in FIG. 7, an x-y orthogonal coordinate system is set to pass through the center of the first rotation axis 3, and the angle between the X axis and the first horizontal arm 2 is 01, and the angle of the first horizontal arm 2 is 01. The angle between the longitudinal direction and the longitudinal direction of the second horizontal arm 4 is θ2, and the clockwise direction is the positive direction. And θl200, θ2=4
When the angle is 5°, that is, the state shown in FIG. 8 is the machine origin position.

Conventionally, the mechanical origin position of such robots was detected using deceleration switches installed in correspondence with the rotational axes of each robot arm and rotary encoders built into the motors that drive each rotational axis. . More specifically, a dog is provided on the rotating shaft, and on the fixed side of the rotating shaft there is a deceleration switch that detects the dog and performs a deceleration operation, and a deceleration switch that detects the dog and prohibits the robot arm from moving out of the operating area. ←) Provide a limit switch. In this case, both switches are arranged so that the origin position is located between both switches. First, move the robot arm in the (→ direction) from the position where the dog is on the positive side of the deceleration switch. When the deceleration switch detects the dog, it will start decelerating, and once it has decelerated to a predetermined speed, the arm will move at a slow speed. After that, when the origin detection signal pulse (described later) is first detected from the rotary encoder, the arm is stopped and that position is set as the machine origin position.

Here, the position detection principle of the rotary encoder will be explained using FIG. 9. FIG. 9 is a diagram simply showing the position detection structure of a rotary encoder. In the same figure, 2
Reference numeral 1 denotes a rotating shaft of a motor that rotates the arm. On this motor rotating shaft 21, a slit disk 23 in which a plurality of through holes 22 arranged in an annular manner are formed, as shown in the figure, rotates together with the motor rotating shaft 21. installed to do so.

Light emitting diodes 24 are placed on both sides of the slit disk 23.
and a light receiving element 25 are installed. Motor rotation shaft 21
When the slit disk 23 rotates, the slit disk 23 also rotates at the same time, and the light emitted from the light emitting diode 24 is intermittently divided by the slit disk 23 body and the through hole 22. Through hole 2
The light passing through 2 is received by the light receiving element 25. As a result, a pulse signal corresponding to the rotation of the motor rotation shaft 21 is obtained, and based on this pulse signal, the motor rotation shaft 21 is
An origin detection signal is created that indicates one revolution of 1 and is used for origin detection. One of the pulses of this origin detection signal
One corresponds to the machine origin position.

However, in such a conventional method for detecting the mechanical origin position, there is a limit to the starting position of the return-to-origin operation, so the applicant has proposed the following method for detecting the mechanical origin position.

In this method, the deceleration switch in the above conventional method and ←
) The machine origin position is detected using a magnetic sensor that has the function of two limit switches and the aforementioned rotary encoder. FIG. 10 is an external view showing the mounting positions of the magnetic sensor and the dog, and FIG. 11 is a diagram showing the relationship between the mounting positions of both. In these figures, 30 is (
→Side dog, 31 is a magnetic sensor, 32 is a stopper, 33
is ←) side dog. The detection operation will be explained with reference to FIG. 12. First, when the dog 30 is on the (+) side of the mounting position of the magnetic sensor 31-, the arm is rotated in the () direction from that position. and magnetic sensor 31
When it detects the dog 30, it decelerates and stops.

After that, the direction is reversed and the arm is moved at a slow speed in the → direction. After the limit is released, the arm is stopped when the origin detection signal from the rotary encoder is first detected, and the position is set to the machine origin. position.

In this way, the restrictions on the starting position of the return-to-origin operation are greatly reduced.

(Problems to be Solved by the Invention) However, in the above mechanical origin position detection method, due to variations in the mounting position of the magnetic sensor when assembling the robot body, variations in the rotary encoder o origin signal detection position, etc., the design value For example, as shown in Figure 12, the rotary encoder's origin detection signal may vary as shown in ■, ■, and ■ due to variations in motor installation. As a result, the recognized origin position deviates as follows: ■, ■, ■.

However, in an articulated robot to which the mechanical origin position detection method described above is applied, if there is a discrepancy between the mechanical origin position and the designed origin position, it is difficult to move between predetermined points. Since this deviation has nothing to do with the movement of the cut arm, the actual situation was that no special measures were taken to correct this deviation. Furthermore, when using a function that requires precision, such as linear interpolation, it is extremely difficult to make adjustments on the mechanical side to correct the mechanical origin position and the designed origin position.

However, in order to accurately position the robot, it is desired to correct the above-mentioned deviation using a simple method and to recognize the accurate machine origin position.

The present invention provides an articulated robot that can easily compensate for variations in the mechanical origin position caused by variations in the mounting positions of magnetic sensors, etc. during assembly of the oyyite body as described above, and variations in the origin signal detection position of the rotary encoder. The purpose of this invention is to provide a method for correcting the mechanical origin position.

(Means for Solving the Problems) The present invention provides a detection means (for example, ) limit sensor and deceleration switch; magnetic sensor) and motor rotation information detection means that is provided on the motor that rotationally drives the robot arm and detects rotation information of the motor (for example, a function that detects the mechanical origin position based on a rotary encoder). This is aimed at articulated robots that have
In order to solve the problems of the prior art, the deviation between the detected mechanical origin position and the designed mechanical origin position is measured, and the deviation is corrected based on the measurement results.

In the method of the present invention, it is preferable to measure the deviation using an arm angle measuring jig.

(Operation) In the present invention, the deviation (offset amount) between the machine origin position detected based on the output of the detection means and motor rotation information and the designed (theoretical) machine origin position is determined by measuring in advance. This measurement is performed with high precision using, for example, an arm angle measuring jig. Specifically, the deviation is determined based on the measured value and theoretical value of the motor that drives the robot arm, and the amount of arm movement per 1. By storing the obtained deviation in the memory of the control mechanism that controls the robot, this deviation is automatically taken into account in subsequent program operations of the robot. Therefore, the above-mentioned problems of the prior art can be solved by making it possible to accurately detect the machine origin position.

(Example) A method for correcting the mechanical origin position of an articulated robot according to the present invention will be described in detail below.

In the method of the present invention, the deviation (offset amount) between the mechanical origin position of the robot arm and the designed (ideal) mechanical origin position is measured, and the value is stored in the control device that controls the robot. Used to detect the machine origin position.

By doing this, it is not necessary to program the onset amount condition every time when programming the robot operation, and the machine origin position can be easily corrected.

The specific steps of the method of the present invention are shown in the operation 20-chart in FIG.
The offset amount of the machine origin position and the jig used to determine the offset amount will be explained with reference to FIGS.

FIG. 2 shows the first horizontal arm 2 and the second horizontal arm 4 (see FIG. 6) at the machine home position.

In design, the relative angle between both arms is 45° (imaginary line)
However, suppose that due to the reasons mentioned above, a deviation occurs as shown by the solid line. Here, the offset amount is calculated in the longitudinal direction PtQ of the second horizontal arm in the two states.
It is expressed as Δθ2.

In this case, the measurement of the offset amount Δθ2 is obtained from the measured base las value and the theoretical base las value of the motor of the second horizontal arm 4 at an arbitrary position. This measurement is performed using, for example, an arm angle measuring jig 40 as shown in FIG. The angle formed by both arms of the arm angle measuring jig 40 is 90
°, and both arms are provided with through holes 41 and 42, respectively. On the other hand, holes (not shown) are provided in the first horizontal arm 2 and the second horizontal arm 4, and pins 43 and 44 shown in FIG. 3(b) are inserted into these holes during measurement. It has become. When the relative angle between the first horizontal arm 2 and the second horizontal arm 4 reaches 90°, the pin 43
．． 44 fits into the through holes 41 and 42 of the arm angle measuring jig 40 (FIG. 4). Note that the angle formed by both arms of the jig 40 is not necessarily limited to 90°, and may be set to any other angle.

Next, the operating procedure of the method of the present invention will be explained with reference to FIG.

First, the pins 43, 44 are respectively attached to the first horizontal arm 2. It is attached to the second horizontal arm 4 (step 101). Next, return the robot arm to the mechanical home position (Stella 7°1
02), then the pins 43 and 44 are connected to the arm angle measuring jig 4.
0 through hole 41. ．． 42 (steps 103 to 1o).
5). This position is the first horizontal arm 2 and the second horizontal arm 4.
This is the position where the relative angle formed by is 90°. By using this jig 4o, anyone can easily measure the arm angle of 900', and the pins 43 and 44 will not fit into the jig 40 when the arm angle is at a position other than 90', making it accurate. The arm angle can be measured.

Next, according to steps 106 to 109, the offset value Δ
Find θ2. Here, the motor l- of the second horizontal person 4
Theoretical angle value θ when the amount of movement of the contact point is φ2, and the relative angle between the first horizontal arm 2 and the second horizontal arm 4 is 90'.
2. Let θ'2 be the measurement/crux value when the relative angle between the first horizontal arm 2 and the second horizontal arm 4 is 90'. The offset value Δθ2 is determined by Δθ2=(θ'2-02)×φ2.

The offset value Δθ2 obtained as described above is stored in the memory of the control device that controls the operation of the robot (Stella 7'11O), and the mechanical origin position is corrected based on the value.

Incidentally, FIG. 5 shows the configuration of the control mechanism for robot operation.

In the figure, 5o is the central control unit (
The offset value is stored in this memory by the CPU (CPU). Further, 51 is a memory, 52 is an operation box interface, 53-1 to 53-N are external interfaces, 54 is a serve interface, 55 is a calculation processor, 56;
'! , I10 processor, 57 is an interpolation calculation unit, 58-1
58-4 is a servo control section, and 59 is a magnetic sensor.

Here, the magnetic sensor 59 corresponds to the magnetic sensor 31 in FIG. Also, servo control sections 58-1 to 58-4
controls the movement of the rotation axis of each robot arm, and controls the counter, tightening converter, and server. Amplifier, motor, (M
), tacho generator (TG) and hipulse encoder (P
E) It is constructed well.

In the figure, 2 is the amount of vertical movement of the vertical arm, and θ3 is the amount of rotation from the reference position of the support member that supports the hand of the mouthpiece.

(Effects of the Invention) As described above in detail, according to the present invention, it is possible to easily find and correct the deviation between the mechanical origin position detected in the articulated robot and the design value. Using the method of the present invention, once the amount of offset is measured when assembling the robot and once stored in the memory of the control device, the offset can be completely ignored when performing the programmed operation of the cut. As a result, it becomes possible to perform linear interpolation with high precision, allowing for highly accurate functions such as ``Gredai Song''.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for explaining the method of correcting the mechanical origin position of an articulated robot according to the present invention, and FIG. 2 shows the deviation of the detected mechanical origin position from the design value.
3rd Q (a) and (b) are perspective views of the arm angle measurement jig;
Fig. 4 is an explanatory diagram of arm angle measurement using an arm angle measurement jig, Fig. 5 is a block diagram showing the configuration of the control mechanism for robot motion, Fig. 6 is an external view of the horizontal articulated robot, and Fig. 7 is a diagram of the robot in Figure 6 viewed from above, Figure 8 is a diagram showing the mechanical origin position of the robot, Figure 9 is an explanatory diagram of the operating principle of the rotary encoder, and Figure 10 is the installation of the magnetic sensor and dog. FIG. 11 is a schematic diagram showing the relationship between the mounting positions of the magnetic sensor and the dog, and FIGS. 1-2 are explanatory diagrams of the origin detection operation and the variation in the detected origin position. 1... Robot body, 2... First horizontal arm, 3...
...First rotation axis, 4...Second horizontal arm, 5...Second rotation axis, 6...Vertical arm, 30...Dog, 31
...Magnetic sensor, 40...Arm angle measurement jig, 43
．． 44...pin. Figure 2 (a) (b) Figure 3 Figure 4 Figure 8

Claims (2)

[Claims] (1) A detection means for detecting the rotational state of the robot arm and decelerating and stopping the robot when the robot arm reaches a predetermined position; and a detection means provided in the motor that rotationally drives the robot arm;
a motor rotation information detection means for detecting rotation information of the motor, and a mechanical origin position correction method in an articulated robot having a function of detecting a mechanical origin position based on the outputs of the detection means and the motor rotation information detection means. A method for correcting a mechanical origin position of an articulated robot, comprising: measuring a deviation between a detected mechanical origin position and a designed mechanical origin position, and correcting the deviation based on the measurement result. (2) The method according to claim 1, wherein the measurement of the deviation is performed using an arm angle measuring jig in which the angle formed by both arms is 90°.