OpenServo.com

[whiptrackercracker]

I am sorry if this is answered already in the forums, but I am new to the open servo project. I am currently trying set up robotic arms for a controls algorithm. I thought about using lynxmotion arms, however I am running into a problem when it comes to servos. As you all know, the servos are local loop controlled. However, I am trying to develop a system that can take outer loop control. That is, I control the velocity input into the servo and take back position feedback from the servo to fine tune the control. Sorry, control theory for all those who did not already know. Is the open servo project for me?? Can I easily for example take out control inside the servo, sort of like a continous rotation servo, yet still pull off position information so that I can control the servos properly externally. Anyone who could help, I would be extremely pleased. I'm just trying to find or figure out the best situation, but I know traditional servos will not get me there without serious hacking. Thanks a bunch!!!

[ginge]

Hi and welcome

You pose an interesting question, and one which the answer is yes, you could.

The simplest way to do it would be to change the OpenServo code to allow control over the PWM directly. It would be a fairly simple change which you would comment out the PID control, adc controls and define 2 registers to handle pwm and direction.

You would still read the position out in the normal way, but your PID and control algo would be running on the master device. Once you calculate your PWM value, send it out over I2C for the change.

The only thing that would concern me is the speed in which you need to send commands. For a full PID commanded slowdown you would be sending hundreds of data packets. in a short amount of time.

Good luck

Barry
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http://www.robotfuzz.co.uk/

[whiptrackercracker]

Thank you so much for the reply. I'm still not sure if this will work for me or not. Each robotic arm will probably have 6 or so servos on it. Therefore, I have yet to figure out how best to talk to and listen back if I use the openservo stuff. It seems as if the servos are addressable, so I can use one i2c/usb per robot arm and tax the servos. I'm a little unsure myself of whether the time delay would be too great for the servos, however I think from experience that it may work. Looks like y'all might have a new convert joining the group soon. Thanks !!!!