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TOPIC: Jerky motion

Jerky motion 4 years 3 months ago #2266

  • Processman
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OK, let me start by saying I'm new to this product. I have an SM2337 motor, Version 4.15b,Serial Number E14336, MFG Date 3/20/02. It's on a testing device someone made in 2002. It is quite simple really. All it does is find a home prox, then depending on what information you put into a Red Lion controller that talks to the servo, the shaft will move 90, or 180 degrees from home and back again to home continuously for a specified amount of times at whatever speed it's told to go. Well recently it was decided to put a 10 inch plastic plate on the shaft with a dial on it instead of the much smaller original one. This new one has a sticker with the degrees on it and the changes has been basically done for the looks of it. I've been told that it has always had a little jerking motion and at higher speeds it is really bad but ever since they put this larger wheel on it, it's more apparent. So they want the jerk taken out. I have played with the tuning and after looking at the manual, felt confident in doing so. I adjusted and watched the graph and got things looking a lot better. But it seems that every time I power it down the tuning parameters revert back to what they were. I Clicked Save Values and Clicked Load Saved Values. But it keeps going back to what it was.

Also I uploaded the program from it because I had a print out of what looked like was put in it in 2002. I saved that to a file so if something happened I could load it back in. How would you go bout loading that file back to the servo? Just curious, for future reference.
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Re: Jerky motion 4 years 3 months ago #2268

  • csearcy
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The jerky motion is being caused by inertia mismatch. Adding to the load has most likely made the load inertia greater than 10 times the motor's rotor inertia. The best fix is to add a planetary gearhead to give the motor a better advantage. If this is not possible, changing some tuning values may help. The KD on that motor is 550 by default. Try increasing the KD to about 1500 for starters.

'Put the following line somewhere in the top of your SmartMotor program.
KD=1500 F

Note: These tuning values MUST be in a downloaded SmartMotor program. They can be modified with the Tuner tool or in the Terminal window, but they are only valid until power is cycled. If they are not in the SmartMotor program, the default values will be used.

You can try increasing this value again by a factor of 1.5 or 2. If it gets too high, the motor will begin to "growl". The hopeful result will be less jerking during movement.

You can modify the program that you uploaded from the motor. It will have a .sms extension when you save it to your hard disk. You can modify this file, then download it to the motor by either pressing F5 (with the program opened up and "on top"... or right clicking on the program which brings up a popup menu that gives you a download option. It will allow you to select the communications port and motor that you want to download to. It will give you a few warnings about ENDing the program and taking it out of SERVO.

Note: Before you compile the program with the suggested changes, be sure you go to the compile menu... select "Default compiler firmware version"... and select 415... so it will compile knowing that you are using a Class4 motor (which has different instructions than the Class5 and Class6 motors).
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