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Resolved Resolved by DJ Sures!

All Servos Jerk When First Used After A Release (Not Power Up)

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I haven't seen this one before but there's a lot I haven't seen. lol.

I'm using EZ Robot HDD servos for my first time. I've always mostly used analog servos. Here's my problem:

*When I power up the EZ HDD servos I get no jerk. *However the first time I send a signal to move (either with a script or a servo control) they will jerk quickly opposite of the way I want it to go then proceed in the wanted direction. *If I do not release the servos they will move smoothly the next time I send a command with no jerk. *However if I release them then the next I send a command to move the the servo the jerk is back.

Is this normal behavior or is there something I can do to keep this from happening? I guess I could just not release the servos but I don't like to keep the strain on them when not in use.

Related Hardware EZ-B v4
Related Control Horizontal Servo

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#1   — Edited

You’d have to contact ezrobot at www.ez-robot.com. They have a Contact Us page if you think it’s an issue with their hardware, but...

I don’t know what their servos are Iike these days or if they have different versions or bugs. Best to contact them and verify expected behavior with their hardware. However, keep reading...

I would not recommend releasing pwm servos. There’s no need to release because they don’t use much or any current when holding a position. Because servos use a pwm signal, they can react strange when the new signal is sent. This is primarily due to how a servo works. Lots of information in the support section on this website about how a servo works. Click the word servo on any forum post since the beginning of time. Or click here: https://synthiam.com/Support/Advanced-Fundamentals/servo-motor

but if the pwm is detected part way because you’re turning it on and off, any pwm servo will react poorly. It’s pretty mean thing to do is shut off the pwm and turn it back on repeatedly to a servo :)

#2   — Edited

Thanks @DJ. As usual that sounds like good advice that makes sense.

I don't think it's a "issue" with the servos unless like you say EZ-Robot made changes across the board. I have three servos that act exactly the same. I feel it's most likely either in my wiring or my coding.

LOL, I never considered myself being "mean" to my servos. Maybe I need to look into my abuse issues.xD . I do have a habit of pushing my hardware to it's limits and I want it all to stand up to the worst of treatments for a long time.

I think I remember fighting this issue a few years ago when I built my first B9 robot. I'll have to go back and look at my old notes and scripts to see what I ended up doing.

More to come.......................

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#3  

Haha mean in the sense that they’re being teased with pwm signals. A comical mean - they get a pwm signal and taken away LOL

#4  

Well, I guess there is no work around that I can fund.

I did find the script I used years ago that worked to reset my analog servos to keep them from jumping after they were released. It does nothing to fix the jump on these EZ Robot HDD servos when sending a move signal after a release command.

Here is that old script I would run before commanding a released servo to move:

#Reset released servo before a move to keep it from jumping 
ServoUp(D14,1 ) 
ServoSpeed(D14,0 )

I'll contact EZ Robot on this but I have my doubts they will have an answer.

I will follow DJ's advice and not release the servos. From what I've seen these EZ Robot servos can take being held in place. The best part is that is no servo whine when being pushed out of the dead zone. As I remembered that was the real reason I didn't like digital servos.

Thanks DJ for the help and insight.

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