What If Your Robot Moves Unexpectedly?

Manipulator Model: Yaskawa Motoman GP180

Controller Model: YRC1000

Application: Handling and Palletizing

This morning I faced an annoying problem, which was related to robot movement through the programmed steps during the playback. For solving this problem, I tried some solutions and as a result, I am thinking that I solved this problem. Therefore, I decided to create a post for problem definition and solving of this problem. Shortly explaining my problem, when robot goes from one point to the another point robot tool is turning 360 degree at around itself to reach same coordinate. It may causes major problems such as collide with something at the cell, destroying cables of sensors onto the tool. On the other hand, this type of movement had no sense to move like that. (Who wants extra paths and movements at the robot?). To reach the solution, I tried three steps, which are listed below:

1. Change the orientation degrees of the point data. (Sending away Rx, Ry and Rz from 0 and +-180 degree). Actually, this approach couldn’t solve my problem for all path movement.
2. I changed the motion types Joint movement to Linear Movement. I was thinking that If I choose Linear Movement it could give me more precious and strict path movement. As I described before in my Robot Movement Principles & Motion Types post, robot moves more freely in the Joint Movement. Again, this solution was not my unique solution.
3. Lastly, I made a search on Yaskawa documents and I found an important information about this topic.  According to this document, I added more points between the start and the end point to solve my problem. For smoothing the movement along the path I prefer to use SPLINE Interpolation. Finally, it seems like I found the proper solution for my problem. I will update if I face any other problem with this topic.

“Teach points in the way that the distances between the three points are roughly equal. If there are any significant differences, an error will occur during playback and the robot may perform an unexpected and dangerous movement. Ensure that the ratio of distances between steps m:n is within the range of 0.25 to 0.75.”

Fig: Ratio Between The Points

Friendly Reminder:  You need to consider cycle time and movement when adding some extra points from the initial point through the end point. As a simple way of looking, if you add some extra points, this condition affects the cycle time of the robot. But the main goal of the robotic automation system must be "doing some tasks in the proper cycle time correctly". You should use robot movement commands' configuration to decrease cycle time.

Thanks For Reading...

Okan Okumuş

27.10.2020