Design of a hybrid spherical manipulator for lower limb exoskeleton applications

An estimated (7.1%) of North American residents suffered from an ambulatory disability and mobility disablements in 2013. These disabilities cost an estimated annual equivalent of $375 billion in family caregiver support. One emergent technology that aims to address this health problem and improve the quality of life for sufferers is a lower-body exoskeleton which is a wearable robotic system that completely or partially supports users weight and provide controlled guidance of legs movements, thereby allowing them to stand and walk. One major shortcoming of current exoskeleton technologies is their limited range of motion about the hip joint. Such joints are capable of three rotational degrees of-freedom (DOFs). Current technologies only provide a single DOF hip-centered movements. The other two DOFs are either fully constrained or only available with passive motion. This design scheme generally results in a serial joint structure within the exoskeleton device, which has an inherently lower payload to-weight ratio than a parallel structure counterpart. Therefore, this characteristic leads to bulkier than necessary devices. The objective of this thesis is studying the feasibility and later on design compact three DOF robotic joints to replace the single DOF of the hip actuator of the commercially available exoskeletons. In this thesis a three degree-of-freedom (DOF) hip exoskeleton system that is capable of providing decoupled or combined 3-DOF rotational motion to a separate and passive target joint (i.e. the hip joint) is proposed.