Robotic design and modelling of medical lower extremity exoskeletons

This study aims to explain the development of the robotic Lower Extremity Exoskeleton (LEE) systems between 1960 and 2019 in chronological order. The scans performed in the exoskeleton system’s design have shown that a modeling program, such as AnyBody, and OpenSim, should be used first to observe the design and software animation, followed by the mechanical development of the system using sensors and motors. Also, the use of OpenSim and AnyBody musculoskeletal system software has been proven to play an essential role in designing the human-exoskeleton by eliminating the high costs and risks of the mechanical designs. Furthermore, these modeling systems can enable rapid optimization of the LEE design by detecting the forces and torques falling on the human muscles

Determination Of Optimal Counter-Mass Location In Active Prostheses For Transfemoral Amputees To Replicate Normal Swing

Transfemoral amputees suffer the loss of the knee and ankle joints, as well as partial or complete loss of many of the lower extremity muscle groups involved in ambulation. Recent advances in lower limb prostheses have involved the design of active, powered prosthetic knee and ankle-foot components capable of generating knee and ankle torques similar to that of normal gait. The associated onboard motors, conditioning/processing, and battery units of these active components result in increased mass of the respective prosthesis. While not an issue during stance, this increased mass of the prosthesis affects swing. The goal of this study is to develop and validate mathematical models of the transfemoral residual limb and prosthesis, expand these models to include an active ankle-foot, and investigate counter-mass magnitude(s) and location(s) via model optimization that might improve kinematic symmetry during swing. Single- (thigh only, shank only) and multi-segment (combined thigh and shank) optimization of counter-mass magnitudes and locations indicated that a 2.0 kg counter-mass added 8 cm distal and 10 cm posterior to the distal end of knee unit within the shank segment approximated knee kinematics of able-bodied subjects. This location, however, induced artificial hip torques that reduced hip flexion during swing. While such a counter-mass location and magnitude demonstrated theoretical potential, this location is not clinically realistic; mass can only be added within the prosthesis, distal to the residual limb. Clinically realistic counter-masses must also keep the total prosthetic mass to less than 5 kg; greater mass requires supplemental prosthetic suspension, would likely increase energy expenditure during ambulation, and contribute to increased likelihood of fatigue even with active prosthetic components. The ability to simulate the effects of active prosthetic components inclusive of varying placement of battery and signal conditioning units may advance the design of active prostheses that will minimize kinematic asymmetry and result in greater patient acceptance

MyoSim:Fast and physiologically realistic MuJoCo models for musculoskeletal and exoskeletal studies

Owing to the restrictions of live experimentation, musculoskeletal simulation models play a key role in biological motor control studies and investigations. Successful results of which are then tried on live subjects to develop treatments as well as robot aided rehabilitation procedures for addressing neuromusculoskeletal anomalies ranging from limb loss, to tendinitis, from sarcopenia to brain and spinal injuries. Despite its significance, current musculoskeletal models are computationally expensive, and provide limited support for contact-rich interactions which are essential for studying motor behaviors in activities of daily living, during rehabilitation treatments, or in assistive robotic devices. To bridge this gap, this work proposes an automatic pipeline to generate physiologically accurate musculoskeletal, as well as hybrid musculoskeletal-exoskeletal models. Leveraging this pipeline we present MyoSim - a set of computationally efficient (over 2 orders of magnitude faster than state of the art) musculoskeletal models that support fully interactive contact rich simulation. We further extend MyoSim to support additional features that help simulate various real-life changes/diseases, such as muscle fatigue, and sarcopenia. To demonstrate the potential applications, several use cases, including interactive rehabilitation movements, tendon-reaffirmation, and the cosimulation with an exoskeleton, were developed and investigated for physiological correctness. Web-page: https://sites.google.com/view/myosuit

Design, control, and pilot study of a lightweight and modular robotic exoskeleton for walking assistance after spinal cord injury

Walking rehabilitation using exoskeletons is of high importance to maximize independence and improve the general well-being of spinal cord injured subjects. We present the design and control of a lightweight and modular robotic exoskeleton to assist walking in spinal cord injured subjects who can control hip flexion, but lack control of knee and ankle muscles. The developed prototype consists of two robotic orthoses, which are powered by a motor-harmonic drive actuation system that controls knee flexion–extension. This actuation module is assembled on standard passive orthoses. Regarding the control, the stance-to-swing transition is detected using two inertial measurement units mounted on the tibial supports, and then the corresponding motor performs a predefined flexion–extension cycle that is personalized to the specific patient’s motor function. The system is portable by means of a backpack that contains an embedded computer board, the motor drivers, and the battery. A preliminary biomechanical evaluation of the gait-assistive device used by a female patient with incomplete spinal cord injury at T11 is presented. Results show an increase of gait speed (+24.11%), stride length (+7.41%), and cadence (+15.56%) when wearing the robotic orthoses compared with the case with passive orthoses. Conversely, a decrease of lateral displacement of the center of mass (-19.31%) and step width (-13.37% right step, -8.81% left step) are also observed, indicating gain of balance. The biomechanical assessment also reports an overall increase of gait symmetry when wearing the developed assistive device.Peer ReviewedPostprint (published version