I'm working on creating a robotic device capable of oscillating an adult human leg using the knee as pivot, being able to constrain the amplitude of oscillation by controlling the mechanism with a microcontroller and some other electronic components.
The only idea I have to do this is by placing a pair of servomotors and some gears that will rotate the structure that holds the leg and then control the PWM, however I don't think I will be able to find servos strong enough to lift both the structure and the leg, so it would be very useful to hear some suggested mechanism and motors to accomplish this device.