I don't know what the proper technical term is, so I will call it "jiggle" for now. I am making a puppet that is using industrial servo motors. However, the motion is not as smooth as I would like. Rather, when the arm moves, it tends to sway back and forth when it stops. It does this at around 11 Hz, and settles down after 4 or 5 sways.
I have set the motion velocity to ramp up and down in speed as it starts and stops. This does help the situation, but there is obviously a pendulum type of motion that must be planned and compensated for.
In my case, the motions will all be programmed in advance. So it may be viable to simply monitor the motion, and then make some sort of adjustment to try to compensate, and then try again, until the motion is satisfactory. But, of course, it would be ideal for the robot to manage this problem in an unplanned performance. Also, since this is for an entertainment robot that does not have to walk, I think the position control itself does not require high precision compared to most industrial robots.
I can observe the motion from the current and position data collected in the servo system. Although, the data seems to show very little straying from ideal, when I see the magnitude of the jiggle itself. I am sure that this is because the mechanism itself has some spring to it. So, the jiggle is behaving like a weight at the end of a length of spring wire.
Here are a few more details. Rather than a DC motor, the motor itself is a stepper motor, and is driven using a Elmo DC Bell. I am using the Elmo Motion Control system software, which includes some automatic tuning. This tuning includes a routine that can sense the mechanical system and apply notch filters at various frequencies. However, the automatic system does not seem to be able to sense and compensate for the 11hz jiggle I am seeing.
Any suggestions about the search terms I should use on the Internet search engine?
Any other advice?
Thank you in advance for the replies,
Joe Dunfee