Advice on balancing project

Other Hardware Motors, Mechanics, Power and CNC
1

Hi everyone,

I'm a totally new Arduino user, just on my way to starting a new project which involves balancing of a vertically rotating linear member (imagine a see-saw kind of thing), and more specifically positioning an object of around 2kg along a straight line path, like a counter-weight. For that I am considering using a motor with some positioning mechanism, however my lack of knowledge on the field leaves me puzzled as to which would be the best way to go. As such, I'd be thankful if someone pointed me to the right direction.

The specific requirements for this project are:

  1. Since the "see-saw" will be taking non-horizontal positions, the weight should stay in position without any action on the part of the motor/servo/etc.
  2. The movement should be rather fast, around 1m/sec., not less than 0.5m/sec definitely, but not necessarily very precise (i can deal with tolerances of a few mm).
  3. Ideally (although not very important) it shouldn't blow your ears off when the motor is active / moving the weight.

Here's what I've considered

  1. Stepper motor + belt and pulley, with one side of the belt clamped to the weight. Drawback: How do you keep the weight in position when idle? Possible solution: some sort of counterweight? Any examples perhaps?
  2. Geared motor + belt and pulley, with one side of the belt clamped to the weight. Do geared motors have some "detent torque"? Even still, is it enough to "hold" an object in the range of 2kg on a moderate/high slope?
  3. Model motor + lead screw / ball screw. Drawback: Slow / moderate speed?
  4. Some fluid transfer solution (although this sounds pretty exotic and perhaps not up to par with the above requirements...)

I'd be very much thankful if anyone could offer some advice on the matter.

Yannis

2

I would use a continuous rotation RC servo to move a belt in a similar fashion as an inkjet printer moves the printhead along the rails. Any type of geared motor would do fine but an RC servo already contains the drive electronics and is relatively cheaper.

A motor + lead screw combination would work but is pretty complex. You're not moving enough weight to warrant it.

If you only need to move the counterweight a few inches then you could just use a pushrod connected to an RC servo arm.

3

Hi chagrin,

Thanks a lot for the reply. I took a look at the servos at various sources (e.g. Servo Shop ), but they seemed a bit underpowered or too slow for the job (and the beefy ones too expensive :frowning: )...

The length of movement is not yet precisely known, but it would be in the range of 20-40cm (max)...
Following your advice, I was considering geared motors such as this http://www.technobotsonline.com/re-385-metal-gearbox-50-1.html , combined probably with a rather wide pulley (5-6 cm dia) and timing belt...
I thought of putting the whole thing together in a configuration similar to this: (see after 1:00) ServoBelt™: Amazing Belt Drive - YouTube but without the bottom belt of course (I dont care much about deformations anyway...)

Any ideas/suggestions on that perhaps?

Many thanks.