Artificial Knee Joints Actuators with Energy Recovery Capabilities: A Comparison of Performance

The human knee absorbs more energy than it expends in level ground walking. for this reason it would be useful if the actuation system of a wearable robot for lower limbs was able to recover energy thus improving portability. presently,we recognize three promising technologies with energy recovery capabilities already available in the literature: the series elastic actuator (sea),the clutchable series elastic actuator (c-sea),and the flywheel infinitely variable transmission (f-ivt) actuator. in this paper,a simulation model based comparison of the performance of these actuators is presented. the focus is on two performance indexes: the energy consumed by the electric motor per gait and the peak torque/power requested to the electric motor. both quantities are related to the portability of the device: the former affects the size of the batteries for a given desired range; the latter affects the size and the weight of the electric motor. the results show that,besides some well-explained limitations of the presented methodology,the c-sea is the most energy efficient whereas the f-ivt allows cutting down the motor torque/peak power strongly. the analysis also leads to defining how it is possible to improve the f-ivt to achieve a reduction of the energy consumption. © 2016 roberta alò et al.