RC servo smoothing for robotic arm

Aamir · Joined: 11 Apr 2010 Posts: 13

Hi, I am making a robotic arm in which I have installed 6 servos. I have written the code for my system and the servos are working accordingly. The only problem is that all the servos are moving very fast and thus the overall system seems as if it would break apart at any moment. I am directly giving signal to all servos from PIC 16f877a.

I am using TOWER PRO SERVOS which give around 180 DEG rotation. I have written the program myself but the program is just for generating the PWM for servos and I am using CCS compiler for it. I am not sure how to control the speed of RC SERVOs through programming and due to this when the servo receives signal it immediately turns in the corresponding direction.

I have to provide different signals to 5 motors in parallel. That is, I have to provide 80 degrees to base, 40 to base joint, 30 to above joint, 20 to wrist and 70 to gripper.

All angles should be provided simultaneously such that all motors get the signal in parallel. I am using port C of PIC16f877A for motors.
Can you help me out a little, actually I am stuck currently and have no choice and chance in such a short notice.

bungee- · Joined: 27 Jun 2007 Posts: 206

How do you control your servos?

I wrote a sample program where I used timer interrupt for controlling several servos. You can then ramp servos slowly. Search the forum for my post about this topic. Sample was written for 18f4550 but it will give you general idea how to do that.

Aamir · Joined: 11 Apr 2010 Posts: 13

currently i m controling them through a very poor approch (as people use to say it) just a high pulse, delay, low pulse and delay
well i saw your code but it did'nt helped me exactly. i am not a professional so quiet weak in timers and intrupts
if u help me out in PIC16f877A about how to control these motors in parallel it would be helpful

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

It sounds like you have two pieces of code. One determines where the motor should be. That code sets the TARGET. You also have code that starts with a NUMBER and generates pulses to control the motor.

Right now the TARGET instantly becomes the NUMBER and the motor jerks from one TARGET to the next. You need some middle code that looks at the old NUMBER and the new TARGET and generates a set of new NUMBERs that slowly change from the old NUMBER to the TARGET. Something like: