NSF Award
0854498
0854498<br/>Zhang<br/><br/><br/>Virtually all functional movements require coordination among multiple joints. Neurological disorders such as stroke affect multiple joints simultaneously with considerable motor impairment. However, there is a lack of quantitative methods and apparatus to evaluate neuromechanical changes at the multiple joints simultaneously and individually, especially for complex systems with three or more joints involved. This project will develop a rehabilitation robot to control the shoulder, elbow and wrist individually. In general, the approach can be similarly applied to even more complex systems involving more joints and/or more degrees of freedom (DOF). <br/><br/>Intellectual Merit: The project will develop a novel method and associated whole-arm rehabilitation robot to characterize multi-joint/multi-DOF arm dynamics with dynamic and static terms to characterize the relevant contributions, including both properties local to the individual joints and cross-coupling terms between joints. Such characterization has been impractical when 3 or more joints (and/or DOFs) are involved. A systematic multi-step method will be developed to characterize such complex system by controlling the joints individually and identify the system dynamics with a divide-and-conquer approach. Scientifically, it will help us investigate motor control of multi-joint movements with the ability to control/perturb each joint individually and multiple joints simultaneously. Clinically, it will help us understand the mechanisms underlying the abnormal couplings between joints and dynamic and static changes associated with spastic hypertonia in patients with hemiparesis. Furthermore, in addition to the above characterization of system dynamics, ability of controlling individual joints and loss of individuation post stroke will also be characterized systematically using the proposed measures of an inter-joint torque-coupling matrix and an inter-joint movement-coupling matrix, which provide complete characterization of biomechanical couplings among the joints during voluntary movements. <br/><br/>Broader Impacts: The proposed activity will develop a new method to characterize multi-joint neuro-dynamics with complete dynamic and static terms in the stiffness and viscosity matrices, including both components local to each individual joint and coupling terms between the joints, under both passive (by the robot) and active (by the subject) conditions. In general, the method can be used to investigate complex systems not practical to evaluate with existing methods. Complex systems with any number of joints can be reduced to the single-joint level, making investigations of very complex system dynamics systematic and practical. Furthermore, a similar approach can be used to examine the cross-couplings between different DOFs at a single joint or at different joints, such as between shoulder flexion and shoulder abduction and between wrist flexion and forearm pronation. Lower limb as well as upper limb can be similarly evaluated. Considering that many joints are involved in the upper and lower limbs (with multiple DOFs at each joint), the potential impact of the proposed method will be broad. Finally, a systematic method has also been proposed to characterize couplings among joints and loss of individuation during voluntary movements, which are directly related to functional movements. <br/><br/>Scientifically, the proposed activity will facilitate the investigation of multi-joint and multi-DOF limb dynamics in general and provide a foundation for better understanding of the complex system behaviors. Clinically, the proposed activity will provide us a practical and quantitative tool to investigate impaired motor control of multi-joint movements, which often involve excessive inter-joint/inter-DOF couplings. The proposed activity will deepen our understanding of hemiparetic hypertonia in patients with stroke by characterizing the complete stiffness and viscosity matrices including dynamic and static changes and abnormal couplings between joints/DOFs. Furthermore, the comprehensive diagnosis can potentially be used to guide rehabilitation treatments of the impaired arms by conducting impairment-specific treatment based on the diagnosis, including both multi-joint passive stretching and voluntary movement training based on the multi-joint diagnosis. <br/><br/>The proposed activity will be incorporated into classroom teaching and disseminated through Internet, publications, and presentations at scientific/clinical conferences for broader impact.
