The cyclic and often linear torque-angle
relationship of locomotion presents the opportunity to innovate
on the design of traditional series-elastic actuators (SEAs). In
this paper, a novel modification to the SEA architecture was
proposed by adding a clutch in parallel with the motor within
the SEA—denoted as a CSEA. This addition permits bimodal
dynamics where the system is characterized by an SEA when
the clutch is disengaged and a passive spring when the clutch is
engaged. The purpose of the parallel clutch was to provide the
ability to store energy in a tuned series spring, while requiring
only reactionary torque from the clutch. Thus, when the clutch
is engaged, a tuned elastic relationship can be achieved with
minimal electrical energy consumption. The state-based model
of the CSEA is introduced and the implementation of the
CSEA mechanism in a powered knee prosthesis is detailed. The
series elasticity was optimized to fit the spring-like torqueangle
relationship of early stance phase knee flexion and
extension during level ground walking. In simulation, the
CSEA knee required 70% less electrical energy than a
traditional SEA. Future work will focus on the mechanical
implementation of the CSEA knee and an empirical
demonstration of reduced electrical energy consumption
during walking.United States. Dept. of Defense (National Defense Science and Engineering Graduate Fellowship Award 1122374
