need help on electronic driven robotic control system


Thread Starter


I am working on a small amateur project. I intend to control a light beam using electronic control system. My main constraints are:

1. Since I am working on a scaled down model initially, torque requirements can be neglected. Load to be carried is negligible.
1. The motion of the light beam(a torch on the robotic arm end effector) cannot be more than 45 degrees on the spherical work volume i.e. a 46 degree of the sector of sphere only. Hence my motor (servo/stepper shall never cross 45 degrees)

2. Also the motion has to be smooth. Hence can I use a stepper motor?(jerkiness of light beam if not percieved by human eye can be accepted). Here I am confused on stepper or servo motor?

3. Since my unit has to be portable in nature and no computer facility shall be available, I am going to use an electronic circuit which shall be preprogrammed for a specific function preferably a random number.

4. The The polarity of the motor at any particular instant shall be changed by a random number generated by electronic circuit.

5. No feed back is required. Only the constraint is that the end effector can operate in the 45 degrees work volume.

Kindly help me on the feasibility of the project.
Please express

what motors DC/AC Stepper/servo should I use?
Do I need anything more than the electronic circuit? ie. encoder etc.??


Joshua Schultz


What you need is some sort of quantitative spec on what "smooth" means. There is some angle variation (call it "delta"), at which the light beam will become visible. This variation will corrospond to some displacement of the end effector, which will corrospond to some rotary displacement of your actuator. Since torque is not a factor and you are not necessarily looking at good control (as far as a dynamic response), I would say choose a stepper motor with sufficient steps per rev such that you achieve the "delta" required from your light beam. Remember to take your gear train into account. Often times the backlash can have more effect on your accuracy than the actuator resolution itself.