JPS6351282B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for controlling an industrial robot,
For details, see manual operation CP teaching, CP
The present invention relates to a motion control method for a teaching playback robot that performs playback control.

As a conventional example, Japanese Patent Publication No. 55-37768 is mentioned. The gist of this prior art is that ``During a teaching operation in which the robot memorizes operating procedures in advance prior to actual work, a roller attached to a displacement pulse generator detachably attached to the tip of the arm rotates a fixed distance along a trajectory. A pulse is generated each time the robot moves, and the position information is memorized at each fixed distance.In the playback operation for performing actual work, the displacement pulse generator and the actual work machine are replaced, and the robot is A speed control method for an industrial robot, characterized in that speed control is performed in addition to position control by commanding the stored position information for each time as a target value at fixed time intervals, which is variably set regardless of teaching time. .”
It is.

However, the displacement pulse generator (hereinafter referred to as "teaching roller"), which is an essential component in this prior art, is expensive and has been a factor in increasing costs.

Therefore, the main object of the present invention is to provide a motion control method that does not require teaching rollers, and particularly to improve a sampling method during teaching.

In order to achieve the above object, the gist of the present invention is to provide a method for controlling a teaching playback robot that performs CP teaching and CP playback control by manual operation, in which sampling is performed at fixed time intervals Ts during teaching. In some cases, the position data is captured, subjected to arithmetic processing, and then stored in the main storage means.
During playback, the distance between the two points is calculated from the position data of the two points Pi and Pi ₊₁ obtained in the CP teaching above, and the distance between the two points determined by the calculation is moved at a predetermined constant speed. Calculate the required time Ti, and set the period between the above two points Tc
The number of positioning points required for linear interpolation n
is determined by the value of Ti/Tc, and the determined score n
The industrial robot is characterized in that interpolated data is obtained every fixed distance determined by the above-mentioned fixed distance, and positioning control is performed using the interpolated data as a target value, thereby controlling the speed during playback to the above-mentioned fixed speed. This is a control method.

Hereinafter, the present invention will be explained based on examples.

The robot to which this embodiment is applied is a welding robot with a multi-joint structure (5 degrees of freedom), and the control means includes an arithmetic function section, and the main functions of the control means are configured to be executed by a computer, preferably a microcomputer. ing. Furthermore, since the teaching operation is performed directly by a person, it is assumed that a gravity balance device is provided so that each axis can be easily moved by human power.

During teaching, the control device is activated, the robot is put into operation, and the operator holds a grip provided near the welding torch and moves the arm along a preset welding trajectory. The control device is for a certain period of time
A sampling command is issued every Ts, and each joint angle data of the robot arm (θ ₁ ~
θ ₅ ). This joint angle data is stored in the buffer memory and read out at the appropriate time.
After performing calculation processing to convert to values in the XYZ coordinate system,
Stored in main memory. Note that the coordinate transformation is performed based on a formula programmed in advance by the CPU of the microcomputer. These formulas are already well known. In addition, the sampling period
T _s is, for example, 40 ms. In this case, starting point P ₁
Since it is only sampled every Ts from to the end point Pn, the point Pi and the next point Pi ₊₁ (i = 1, 2, ...,
The distance li between n-1) is not a constant distance. That is, the speed during teaching is not constant.
However, during playback, the welding speed must be controlled constant in order to obtain a good weld.

During playback, the control device performs feedback control based on the difference between the current position data from the position detector and previously stored position data. now,
The control between two points Pi and Pi ₊₁ will be described as an example.

P _i (x _i , y _i , z _i ) is the current position, P _i+1 (x _i+1 ,
y _i+1 , z _i+1 ) is the next target position. Before proceeding with the welding operation from Pi to P _i+1 , the position data of Pi and P _i+1 are first read from the main memory, and the distance li between them is
is calculated as follows:

l _i =√( _i+1 − _i ) ² + ( _i+1 − _i ) ² + ( _i+1
− _i ) ² Torch movement speed Vi (constant) between Pi and P _i+1
is preset as the welding speed or air cut speed. From these two parameters, the current position Pi
Time required to reach the next target position P _i+1
T _i is determined as Ti=li/Vi. This time T _i
is calculated for each teaching point.

On the other hand, during playback, positioning control is performed every playback control period _Tc (for example, 20 ms).
Therefore, interpolation calculation between the two points P _i and P _i+1 is performed before movement. This is linear interpolation. This is to ensure accurate positioning accuracy (for example, ±0.2 mm) and constant speed accuracy. The reason is as follows. That is, since the teaching speed is actually higher than the welding speed, the above-mentioned time T _i increases, which adversely affects the positioning accuracy. for example,
When teaching at a teaching speed of 30 m/min = 0.5 m/s and a sampling period of 40 ms, li = 500 mm x 40/1000 = 20 mm, and if this is welded at a speed of 60 cm/min = 10 mm/s, This is because T _i =20/10=2s, and if playback control is performed every T _i , it will be difficult to reproduce accurate positional accuracy (±0.2 mm).

If positioning control is performed every playback control period T _c , after determining the time T _i , T _i /
Perform the operation T _c =n to find n (positive integer). For example, in the above example, n=2/0.02=100. Next, the coordinates P _i (x _i , y _i , z _i ), P _i+1 (x _i+1 , y _i+1 ,
A linear interpolation operation is performed to equally divide z _i+1 ) into n parts. The result of this calculation is the inverse coordinate transformation (XYZ system →
After converting to the joint angle θ system), all interpolated data is stored in buffer memory. Next, target data is retrieved one by one from the buffer memory every playback control period _Tc , and the welding work is proceeded at a constant speed _Vi while controlling the positioning.

To summarize the above embodiments, sampling is performed for a fixed time during teaching, and reproduction is performed at a fixed control cycle during playback, but in order to ensure positioning accuracy and constant speed accuracy, playback is performed between two points. The moving time T _i between the two points is determined from the distance li between the two points and the welding speed V _i given in advance, and the number n of interpolations between the two points is determined from this T _i and the playback control period T _c , and the interpolation is performed. After performing the calculation, the interpolated data is used as target data to actually perform the reproduction operation.

As described above, according to the present invention, fixed-time sampling is performed based on commands from the control device during teaching, which has the effect of eliminating the need for teaching rollers, which were indispensable for fixed-distance sampling as in the past. Yes, it is possible to achieve cost reduction.

Another advantage is that during teaching, it is possible to teach corners, etc., which cannot be taught sufficiently with the teaching roller due to physical limitations.

Furthermore, since the CP method performs teaching while visually checking the welded part, there are fewer cases of teaching failures, and the loss of time spent on re-teaching can be reduced, which has the advantage of allowing the advantages of CP teaching to be utilized as is. be.

Claims (1)

[Claims] 1 Perform CP teaching using manual operation
A method of controlling a teaching playback robot that performs playback control, in which position data is captured by sampling at fixed time intervals Ts during teaching, and is stored in a main memory after being subjected to arithmetic processing. When playing back, use the two points obtained from the CP teaching above.
Calculate the distance between two points from the position data of Pi, Pi ₊₁ , and calculate the time Ti required to move the calculated distance between the two points at a predetermined constant speed. The number n of positioning points required for linear interpolation with a constant period Tc is Ti/Tc
By determining the interpolated data at every fixed distance determined by the determined number of points n, and performing positioning control using this interpolated data as a target value, the speed during playback is controlled to the above-mentioned constant speed. A method for controlling an industrial robot, characterized in that: