Human experiments with hip exoskeletons often depend on on-board sensing to obtain estimates of joint angle, which may be affected by relative motion between the exoskeleton and the wearer. This model adapts a musculoskeletal gait model to include a hip exoskeleton which can be tracked separately from the human wearer with marker-based motion capture. The modeled exoskeleton represents a hip exoskeleton developed at the Human Robot Systems Laboratory at UMass Amherst under the direction of Dr. Meghan Huber.

The modeled exoskeleton has two internal degrees of freedom common to many current hip exoskeletons: 1) The actuated motor angle, corresponding with hip flexion, and 2) A pin joint connecting the motor to the waist harness which passively allows hip ab/adduction. This model was defined so that the rigid body dynamics are generalizable to exoskeletons in use by other research groups.

We have also included a sample marker set used in our IROS 2022 and ICRA 2023 studies, which allows for the human kinematics and exoskeleton kinematics to be computed separately, as well as the relative motion between them.