The programmable spring research project is an attempt to create a general purpose electromagnetic actuator that can be programmed to emulate many mechanical systems. It incorporates a force controlled actuator with position sensing and a high level behaviour specification schema that allows you to control force and damping behaviour across all angles.

This high level ‘Programmable Spring’ system incorporates everything from the spring damping properties of the joint through to conditional behaviour switching, digital and analogue I/O and serial communications.  You can embed multiple behaviour profiles in an actuator and control when they come into action allowing you to construct quite complex behaviour systems.  With groups of actuators you can get them to communicate with each other to produce embedded reflex behaviour, for example you can make legs that automatically step when perturbed.

Force control is a central idea and allows the actuator to behave compliantly.  A normal servo system is designed to be stiff and resist any attempts to move it away from its current position but with a force control servo you can make joints that respond dynamically to forces – you can switch off torque in your robots joints making it go completely limp or you can map angles and velocities to torque to create springs and dampers.

Start with the control system overview to find out how it works then take a look at some videos of the early prototypes in action.