Design of a Hip Exoskeleton With Actuation in Frontal and Sagittal Planes

One third of older adults and one half of people with a lower limb amputation fall each year. A hip exoskeleton capable of rapidly delivering high torques in frontal and sagittal planes could assist with fall recovery. Here we describe the design and testing of a hip exoskeleton emulator with actuation to adjust foot placement or center-of-mass state. The emulator was designed to be lightweight and comfortable while exceeding the torque and range of motion requirements of the hip joint during walking and fall recovery. We conducted tests to determine step response time, bandwidth, and torque tracking error. The emulator has a peak torque of 75 Nm in frontal and sagittal planes and has a worn mass of 10.9 kg. Benchtop tests demonstrated rise times in frontal and sagittal planes of 44 and 32 ms, respectively, and bandwidths of 14 and 17 Hz, respectively. During walking trials, the emulator demonstrated an average of 1.6 Nm of RMS torque tracking error (7.86% of commanded torque range) across three exoskeleton behaviors. Experiments conducted using this emulator could identify control behaviors and mechanical performance requirements of untethered devices designed for improving mobility and quality of life of populations prone to falling.