Help us out with the mechanical setup.
It looks like you have a hinged point at the base of the leg. I labeled that point Point A in the attached photo for clarification. Does this point allow the leg to pivot on plane with the rest of the frame, but not pivot up and down providing any lift? Please confirm or correct. I cannot see a motor for this. How will it be connected to the motor?
It looks like you are using one motor to extend/retract a telescoping foot. I labeled that point Point B in the attached photo for clarification. Does this only extend and retract to provide lift?
How strong is the connection at Point A? It will need to be quite strong.
What is the distance from the center of the seat to point B?
What is the distance from Point A to Point B?
How much do you weigh?
