Society of Robots - Robot Forum

General Misc => Misc => Topic started by: matt liao on August 13, 2009, 01:47:22 AM

Title: How to reduce the self-vibration of a servo?
Post by: matt liao on August 13, 2009, 01:47:22 AM
I have some servos like the pics, I want to use these servos to build a humanoid robot, but the  precision of the servo gears is not high, so these is always a gap between too linked gears, because of this, if I electrify the servo, the servo maybe self-vibrate frequently. so if I run a humanoid robot which is made of these servos, the robot maybe tremble fast.
So, my question is how to reduce the self-vibration of a servo?
Title: Re: How to reduce the self-vibration of a servo?
Post by: Joker94 on August 13, 2009, 05:44:18 AM
depending on how big it is and what materials you make it out of you may be ok
Title: Re: How to reduce the self-vibration of a servo?
Post by: wil.hamilton on August 13, 2009, 08:58:34 AM
i've build structures to lift weights using a standard servo, i've seen the tremble you're talking about, it seems to depend on how much abuse the servo has taken over time and how good your controller is.  plus, having a heavy structure helps reduce it.
Title: Re: How to reduce the self-vibration of a servo?
Post by: Admin on August 14, 2009, 08:51:01 AM
A few tips:

- use digital servos
- buy more expensive high quality servos
- optimize the delay between pulses (too low or too high and you get too much vibration)

The actual optimal pulse depends on the servo, but I find its between 20ms and 50ms for a typical analog servo.
Title: Re: How to reduce the self-vibration of a servo?
Post by: Ro-Bot-X on August 15, 2009, 12:06:10 AM
I wanted to build a biped using cheap servos from TowerPro. Before I went ahead and buy 20 servos, I searched the forums to see if anybody else succeded using them for a biped, but I found they are of a less quality and they vibrate a lot around the hold position. After I got a couple servos to do some tests, I found that the electronics are the weak point. I replaced the electronics with ones found in GWS servos and that greatly improved the servo performance.

Conclusion: for a hexapod, biped or any robot like that, high quality servos are desirable, or your robot will perform poorly. You don't have to buy the most expensive servos, but get at least GWS, where Futaba and Hitech are the top quality. I think there are other brands for digital servos that might work, but I didn't get info on them yet.