Design and evaluation of a series-elastic gyroscopic actuator for balance assistance

Sensory-motor impairments due to age or neurological diseases can influence a person's ability to maintain balance, and increase the risk of falls. Recently, wearable Control Moment Gyroscopes (CMGs) have proven to provide effective balance support. Here, we show a new design of a Series-Elastic Control Moment Gyroscope (SECMG) enhanced by an additional passive degree of freedom, namely a second, orthogonal gimbal that is supported by a (visco)elastic element. The design mainly aims to reject disturbances originating from human movement and render a low remaining impedance, as well as to provide more accurate torque sensing, based on angular deflection of the compliant element. Evaluation of the torque tracking performance with regards to a classic rigid Single-Gimbal Control Moment Gyroscope (SGCMG) showed that the device equally exceeds the bandwidth requirements for its application in human augmentation. However, characterization of our current compliant construction also revealed some backlash occluding the torque-deflection relation. In the future, the SECMG could be evaluated in experiments with humans, to validate its predicted low remaining impedance.