Motor selection question: Automating Manual Single crank hospital bed

[therealsana]

I am working on a personal project to Automate Manual Single crank hospital bed by using a DC Stepper Motor and Arduino. I wish to use a DC stepper motor coupled to the crank shaft and use push buttons/coupling and Arduino to control the motor, AC/DC converter and an external power supply as per requirement of motor.

Based on my calculations of required torque, ~50NM rated motor is required with slow speed.

I want to know what would be the best motor & associated accessories for this application.

I have looked up online and most automated hospital beds use a linear motor. Im not sure how it can be assembled onto my system. I feel incorporating a rotary motor would reduce the amount of hardware changes needed. Please suggest best possible approach to materialize this project soon.

Thanks.

 

[betwixt]

A stepper motor isn't a good solution here because it would have to be permanently powered to stop the lifted part dropping again. It would also need to be geared to achieve enough torque unless a big motor was used and consider that the weight of the patient may have to lifted as well as the bed itself.

Where a small movement with high pressure is needed it would be better to use a linear screw mechanism. A DC motor turns a long screw and a captive nut is forced to move along it. The nut is coupled to the part to be lifted so the motor turns the screw thread, the nut moves back and forth and lifts the bed section.

You can still use an MCU to operate the motor if that's your idea but have it monitor end sensor switches (limit switches) or if you need more precise angle control, a rotary encoder.

Brian.