I want to be able to slowly raise and lower a weight vertically against gravity. The raising part is easy, but I cant get my mind around the lowering part. I need the weight to be lowered slowly (constant speed, no need to control velocity) and I also need to be able to stop at certain points along the way. I am thinking electric brake, but I am afraid that that is a more of an all on or all off thing and will help me stop but wont help me lower the weight.
The best method is to use an AC motor that is fitted with an encoder and a variable speed drive that can operate as a vescor drive. This combination will give you precise contol up and down and you will be able to stop at predetermined points....just like a lift or elevator control. Contact Control Techniques plc or Seimens or SSD Parker or Hitachi or any self respecting drives company...they will help you Good luck
Regenerative braking might be your answer. Essentially, the motor becomes a generator driving a load. The work done to generate power is obtained from the potential energy in the weight.
