Catalyzing Clinically Driven Undergraduate Design Projects at the Nexus of Engineering, Medicine, and Business.

Design projects, particularly those related to assistive technology, offer unparalleled educational opportunities for undergraduate students to synthesize engineering knowledge with a clinically driven need to produce a product that can improve quality of life. Such projects are most effective when engineering, clinical, and business perspectives are considered throughout. However, the logistics of successfully implementing such interdisciplinary projects can be challenging. This paper presents an auto-ethnography of 12 undergraduate design team projects in assistive technology performed by 87 students from five majors (including engineering, business, and clinical students) over the course of 5 years. The overarching goal of our work was to establish an undergraduate integrated design experience at a university in the absence of a dedicated biomedical engineering major. The focus of this experience was to foster the creation of student-led prototypes to address real-world problems for people with disabilities while keeping commercialization potential at the forefront throughout. Student participation demonstrated a clear enthusiasm for completing biomedical engineering-themed projects. To encourage the implementation of similar approaches at universities where a biomedical engineering major does not exist, we identify common obstacles that can arise and present strategies for mitigating these challenges, as well as effective approaches for catalyzing cross-disciplinary collaborations. High impact practices include close involvement of end-users in the design process; cross-disciplinary team composition (e.g., engineering, business, and health sciences students); and choosing cross-disciplinary leads for project management. Teams experienced a high degree of success with all 12 teams producing functional prototypes. We conclude that at universities that do not offer a biomedical engineering major, health-focused integrated design experiences offer students important interdisciplinary perspectives, including a holistic approach to project implementation. Furthermore, for many students, these projects ultimately served as a gateway to subsequent careers and graduate study in biomedical engineering.

EMG control of a bionic knee prosthesis: exploiting muscle co-contractions for improved locomotor function.

This paper presents the development and experimental evaluation of a volitional control architecture for a powered-knee transfemoral prosthesis that affords the amputee user with direct control of knee impedance using measured electromyogram (EMG) potentials of antagonist muscles in the residual limb. The control methodology incorporates a calibration procedure performed with each donning of the prosthesis that characterizes the co-contraction levels as the user performs volitional phantom-knee flexor and extensor contractions. The performance envelope for EMG control of impedance is then automatically shaped based on the flexor and extensor calibration datasets. The result is a control architecture that is optimized to the user's current co-contraction activity, providing performance robustness to variation in sensor placement or physiological changes in the residual-limb musculature. Experimental results with a single unilateral transfemoral amputee user demonstrate consistent and repeatable control performance for level walking at self-selected speed over a multi-week, multi-session period of evaluation.

A configuration dependent muscle model for the myoelectric control of a transfemoral prosthesis.

This paper presents the development of a torque-based myoelectric impedance controller for an active-knee transfemoral prosthesis. An anthropomorphically inspired agonist-antagonist impedance controller studied in a myoelectric elbow prosthesis is adapted for the knee joint. To parameterize the controller, regression analysis was applied to a recently updated lower-extremity neuromuscular simulation model that provides estimates of knee torque as a function of knee angle and neural activation. Initial results using a constant moment arm suggest physically unreasonable parameters and poor model performance, but the inclusion of an angle-dependent moment arm in the reduced-order muscle model enables good correlation with the high-order neuromuscular model. The resulting limb controller is tested using a 1-DOF active knee prosthesis donned by a non-amputee subject with an able-bodied adapter. Initial treadmill walking tests demonstrate the potential of this controller to enable effective myoelectric control of the prosthetic limb.

Liquid-fueled actuation for an anthropomorphic upper extremity prosthesis.

This paper describes the design of a 21 degree-of-freedom, nine degree-of-actuation, gas-actuated arm prosthesis for transhumeral amputees. The arm incorporates a direct-drive elbow and three degree-of-freedom wrist, in addition to a 17 degree-of-freedom underactuated hand effected by five actuators. The anthropomorphic device includes full position and force sensing capability for each actuated degree of freedom and integrates a monopropellant-powered gas generator to provide on-board power for untethered operation. Design considerations addressed in this paper include the sizing of pneumatic actuators based on the requisite output energy at each joint; the development of small low-power servovalves for use with hot/cold gases; the design of compact joints with integrated position sensing; and the packaging of the actuators, on-board power, and skeletal structure within the volumetric envelope of a normal human forearm and elbow. The resulting arm prototype approaches the dexterous manipulation capabilities of its anatomical counterpart while delivering approximately 50% of the force and power output of an average human arm.