Preliminary assessment of the efficacy of supplementing knee extension capability in a lower limb exoskeleton with FES

Abstract

The authors describe a cooperative controller that combines the knee joint actuation of an externally powered lower limb exoskeleton with the torque and power contribution from the electrically stimulated quadriceps muscle group. The efficacy of combining these efforts is experimentally validated with a series of weighted leg lift maneuvers. Measurements from these experiments indicate that the control approach effectively combines the respective efforts of the motor and muscle, such that good control performance is achieved, with substantial torque and energy contributions from both the biological and non-biological actuators.

Figures

Figure 1

Block diagram of the motor controller supplemented with cooperative, adaptive control of FES.

Figure 2

Experimental setup for cooperative control of weighted leg lifts.

Figure 3

Knee joint tracking (top) and gain and phase parameter adaptation (bottom) during a series of weighted leg lifts with FES.

Figure 4

Top row: Series of 42 overlaid knee extension trajectories during leg lifts without FES, along with corresponding knee motor torque. Middle row: Series of 42 overlaid knee extension trajectories during leg lifts with FES, along with corresponding knee motor torque. Bottom row: Average trajectory tracking and average motor torque during a series of leg lifts, each bracketed by a standard deviation.