Fri. Jan 30
Speakers: Reva Johnson and Lauren Smith
Title1: Sensorimotor Adaptation with Powered Upper-Limb Prosthesis Control
Abstract1: Powered upper limb prostheses offer hope in restoring the abilities lost to amputation; however, the current lack of kinesthetic feedback requires users to devote constant visual attention. Providing additional sensory feedback is an intuitive solution, and many groups are working towards clinical implementation. However, we do not understand how amputees rely on sensory feedback during movements with a prosthesis, and how this use of feedback differs from movements with intact limbs. To help answer these questions, we studied how amputees and able-bodied subjects relied on feedback during trial-by-trial adaptation using different control signals: joint angle, joint torque, and EMG. Our results suggest that adaptation was not significantly affected by control signal or limb used, but depended primarily on mean error. Thus we can apply models of sensorimotor adaptation to powered prosthesis control and use them to clarify the most effective sensory feedback information.
Title2: Intramuscular EMG for the Simultaneous Control of Multiple Degrees of Freedom in Upper-Limb Myoelectric Prostheses
Clinically available myoelectric prostheses use surface EMG signals to control prosthetic joint movement, and have limited ability to provide simultaneous control of multiple degrees of freedom (DOFs). Instead, most patients are required to operate each DOF sequentially, unlike the coordinated multi-joint movements produced by intact limbs. Recent advances in implantable EMG recording devices have the potential to provide intramuscular EMG signals for clinical applications, which may allow for the use of simultaneous control approaches that have not been successfully implemented using surface EMG. Using fine wire EMG recordings from the forearm, we investigated the potential for using intramuscular EMG for the simultaneous control of a three-DOF wrist/hand system. We evaluated different methods for predicting intended wrist/hand movement from intramuscular EMG, how subjects used the simultaneous myoelectric control in a virtual task, and the potential for providing improved controllability compared to sequential control methods.
Fri Jan 23
Speaker: Tommaso Lenzi, PhD
Title: User-Adaptive Control of Powered Transfemoral Prostheses: Leveraging Robotics to Meet the Clinical Needs of the Amputee Population
Abstract: Robotic leg prostheses can actively regulate joint torque to emulate the full biomechanical functionality of the healthy limb, possibly restoring physiological gait efficiency and stability. However, proper emulation of the healthy limb depends on how well the prosthesis controller synchronizes the movement of the leg with the movement of the user. To this end, available control strategies rely on experimental, user-specific tuning that optimizes the leg behavior for the user’s preferred speed and cadence. Outside the tuned speed and cadence the prosthesis does not properly synchronize with the movement of the user, thus impairing walking ability. In addition, the tuning process is time consuming and requires expertise in robotics, which considerably limits the clinical viability of powered robotic legs. We have developed a new controller that automatically adapts to the user’s speed and cadence, providing physiological gait symmetry and joint energetics without need for tuning. The talk will describe the design, implementation, and preliminary validation of the new controller on transfemoral amputee patients.
Tue Jan 6
Speaker: Mingbo Cai
Title: Time perception - impact of expectation and duration cue combination
Abstract: Our perception of duration can be biased by many factors, including both stimulus history and stimulus properties. In this talk, I am going to present results from psychophysical experiments and modeling work to answer two questions: (1) is the influence of stimulus history on perceived duration due to the expectation of a stimulus or purely because of stimulus repetition? (2) How does the brain form a representation of duration when simultaneously presented stimuli provide conflicting cues of duration?
Host: Dr. Kording