Developing active prostheses require robust design methodologies and smart controllers in order to appropriately provide net positive mechanical work to the user. Passive prostheses are limited in their ability to sustain walking for long periods of time as well as ambulating over different terrains/environmental conditions. In this paper we present a control architecture and validation results on three individuals with transfemoral amputation using our powered knee and ankle prosthetic device. A three stage controller structure is proposed: high-level control, mid-level control, and low-level control. The high-level controller is responsible for determining the locomotion mode. At the mid-level control, an impedance controller is paired with a state machine to coordinate the kinematics and kinetics of the device with the user during community ambulation tasks. At the low-level control, the device is paired in conjunction with a series elastic actuator (SEA) at each joint to enable closed-loop torque control (PID control). Our results indicate that our powered prosthetic device is capable of scaling to a range of speeds without having to tune many impedance parameters. Our approach shows that our device is a good platform for further testing robust controllers that can provide powered assistance to the user.

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