I am working on my final year university project, designing and building a machine to act as a training partner when lifting weights.
It will work using two support arms which will track the barbell's movement during the exercise, staying relatively close (~5cm). When the user reaches failure and can no longer keep the weight moving upwards, the support arms will gradually apply an increasing amount of pressure to allow the upwards motion to continue to complete the repetition.
I am struggling to find suitable ways of making the support arms move up and down to my requirments. They need to be able to move at 2m/s (max unloaded) and be capable of lifting upto 400kg at 0.04 m/s. It will need to be a precise method of movement (to 5mm) and should preferably be as quiet as possble.
I have considered using a scissor lifting mechanism, and also considered hydraulic cylinders, however these seem noisy, expensive to maintain and not very precise.
Any suggestions appreciated!
You will have to monitor the carrier's distance from the barbell bar, the barbell's motion, and the vertical position and speed of your carrier. You also have to respond to unexpected conditions like dropping the bar, stopping the motion, or other events. For that kind of feedback-controlled operation you are probably going to end up with a stepper or servo driven electronic linear actuator controlling a carriage mounted on linear bearings and rails.
How about a couple of linked hydraulic actuators that offers no resistance to extension however one can set the rate of retraction?
The rate of retraction would be the safety mechanism.
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