A 'smart' series-elastic actuator that integrate a brushless motor, geartrain, spring, encoders, and control electronics into a compact package. The actuators run on standard DC voltages and communicate using 10/100Mbps Ethernet. These actuators are designed to function as full-featured robotic components and enable the simultaneous control of position, velocity, and torque. Each actuator also has a wide range of other sensors, all of which can be easily accessed in the the various APIs. The act