Manually JOG the robot during the robot debugging process is an indispensable job, but does the robot really understand you during JOG? (Or do you really know robots?) Is there a lot of situations when you let the robot go east, but the robot goes west? In linear motion mode, it’s okay to say, anyway, it only controls one coordinate direction. If the positive direction is wrong, change The negative direction is fine. But when it comes to the repositioning motion mode, many friends have to try it randomly. Because they don’t know whether the result of the next robot motion is what they want, it’s already a little bit calibrated, in order to prevent the wrong direction from crashing things. I had to shake the robot away from the target point, first adjust the TCP posture accurately through the relocation mode, and then slowly approach the target point through the linear motion mode. If there is still a problem with your posture, you have to repeat the above process, which is actually a waste of time. In fact, most of this phenomenon is caused by the fact that the friends do not really understand the effects of the different coordinate system combinations of the robot. So this time, let's take a look at the principle of action of different coordinate systems in robot motion, and then learn to really control the robot. Let the robot go north when it goes north, and when repositioning, let the robot go wherever it goes.
Let's first look at the several coordinate systems we can use in ABB robots. In the manual operation interface of the robot, we can see that there are four types of coordinate systems of the robot. They are geodetic coordinates, base mark, tool coordinates, and workpiece coordinates.
Base mark
The base coordinate system is located at the bottom of the robot base and does not need to be defined separately. The direction of the base marking of each robot is uniform. If you are used to programming directly with the base mark (of course, this habit is not a good habit), even if you are facing a new robot, when the coordinate system mode of the new robot is also the base mark, you will find all JOG operations Time so familiar.
The definition rules of the robot base logo are shown in the figure below:
Workpiece coordinate system
The position of the workpiece coordinate system is related to the actual position of the workpiece in the field application. The coordinate system obtained by using different workpiece coordinate system definition methods for the same workpiece may also be different. The workpiece coordinate system can define the position of the workpiece relative to the earth coordinate system (or other coordinate system). A robot can define multiple workpiece coordinate systems, so that it is convenient to represent different workpieces or several copies of the same workpiece at different positions. There are many advantages for programming using the workpiece coordinate system established according to the actual situation of the site. For example, there is no specific relationship between the working surface of the existing workpiece and the robot base mark, so it will be more difficult to perform JOG operations along the workpiece surface or use Offset if the base mark is used for programming. And if the workpiece coordinates suitable for the characteristics of the workpiece are established according to the workpiece before the programming operation, then some subsequent operations on the position will become much simpler.
The definition effect of workpiece coordinates is shown in the figure below:
A: Geodetic coordinates (or base mark)
B: Workpiece coordinate 1
C: Workpiece coordinate 2
Geodetic coordinates
The geodetic coordinate system can define the positional relationship between multiple robot units or multiple other coordinate systems. Generally used in multi-robot or multi-axis robot work cell. The position of the geodetic coordinate system coincides with the position of the robot's base mark by default.
As shown in the figure above, the two robots each have a base mark, and the directions of base mark A and base mark C are different, which makes it very difficult to control. But if the geodetic coordinate system B is used for control at the same time, then the motion control mode of the two robots is the same.
Tool coordinates
The tool coordinate system sets the tool center point as the origin of the coordinate system. The tool coordinate system can define the position and direction of the tool. When executing the program, the robot moves the TCP to the programmed position. Therefore, if the tool (or tool coordinate system) is changed, the actual movement position of the robot will change accordingly. All robots have a predefined tool coordinate system (tool0) on the wrist. The position of the new tool coordinate system is obtained based on the tool0 offset. The tool coordinate system definition requirements of different application scenarios may be different. For example, the definition results of the tool coordinate system of the two common welding guns are different, as shown in the following figure:
The meaning of the four coordinate systems is simply understood. Next, let’s take a look at how to flexibly and correctly select the above-mentioned coordinate systems in the JOG process, and judge the teach pendant according to the direction of the coordinate system and the direction we want the robot to run. The direction of use of the rod.
First understand a few concepts:
The coordinate system mode we selected will automatically reset to the default value after the robot restarts;
The default coordinate system of linear motion is the base mark, of course we can switch to other coordinates;
The default coordinate system of the repositioning movement is to use tool coordinates, of course we can switch to other coordinates;
The linear motion is to make the TCP move along the coordinate axis of the selected coordinate system, the position of the TCP changes but the posture remains unchanged. The X axis plus TCP position moves towards the positive direction of the X axis, and the X axis minus TCP position moves towards the negative direction of the X axis. The same is true for other coordinate system axes.
The repositioning movement is to make the TCP move around the coordinate axis of the selected coordinate system, the position of the TCP does not change but the posture changes. The X axis plus TCP rotates clockwise around the X axis in the positive direction of the X axis, and the X axis minus TCP rotates counterclockwise around the X axis in the positive direction of the X axis. The same is true for other coordinate system axes;
Here are a few animated pictures to get a feel. Pay attention to the direction of the coordinate system in the animation diagram. Regardless of the base mark, workpiece coordinates, and tool coordinates, red represents the X axis, green represents the Y axis, and purple represents the Z axis. The direction of the arrow (the direction away from the origin) represents the positive direction of the corresponding coordinate system axis.
Use the base to mark linear motion
Use tool coordinates to move linearly
Use tool coordinates to reposition the movement
Use the base mark to reposition the movement
The repositioning movement does not necessarily have to use tool coordinates. If you are more familiar with the base mark or workpiece coordinates, it will be more efficient to use the latter for repositioning movement; the same linear movement can also use tool coordinates. Which coordinate to use depends on your familiarity and actual process requirements.
Well, this sharing is over here. If this article is helpful or inspiring for you, then move your cute little hand to read it or forward it to the circle of friends, let it help inspire more people.
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