Rookie looking for advice, simple reciprocating motor

Robotics
1

Hello-

I need to design a motor and control system that simply moves (snaps may be a better description) a light weight arm back and forth between two positions (A ->B, B->A) quickly, traversing from A to B in less than 10ms (pretty fast I realize). Think of the arm as being something like a hand of a clock, where the hand is being snapped back and forth between 1 o’clock and three o’clock. There will be mechanical stops at 1 & 3 o’clock which will stop the motion of the arm at that position.

The angle between A and B is fairly flexible, but should be somewhere between 30 and 90 degrees. It would be preferable that while the motor is at each position (A or B), that it maintain some torque, pressing the hand of the clock up against the mechanical stop. I’ll be using one of the stops to open and close another circuit.

I also need the system to stay at each position for two seconds or so and then have it return, again quickly, to the other position. The pause between motions is not that critical. I’m a software developer, so I am very familiar with coding, however I know very little about hardware, motor controllers etc.

I’ve looked around at the various controllers but due to my inexperience in this sort of thing I was hoping that someone could point me in the right direction.

I greatly appreciate any suggestions!

Thanks,

Jim H

2

With the caveat that I’m NOT a Mechanical Engineer, off hand, if your load is pretty light (like a clock hand), you might consider using a solenoid to move it. You’d probably have to rig a “spring return”. (I have seem some true bidirectional push-pull solenoids on the surplus market, but never tinkered with them. I don’t think they were rated for continuous operation though – if memory serves, they had been originally intended to operate the door locks on cars.)

Another alternative would be a servo motor, though I’m not sure you could attain the 10mS transition time.

I do know that the mass, and “rotational moment” (the amount of torque required to move it) are important considerations, especially with tight time requirements. Maybe a Mechanical Engineer on the forum could comment? (I have seen one guy who said he is.)

3

a light weight arm

Tells us nothing.

However, a rotation of 60 degrees from a dead stop in 10 ms requires the driving shaft to rotate at an average angular velocity of 1000 RPM, and the peak will be well over that. A mid range hobby servo like the MG995 takes about 200 ms to rotate 60 degrees.