Control for the Therapeutic Arm Neural Prosthesis

  • Popovic, Mirjana (Project Participant)
  • Popovic, Dejan (Project Participant)
  • Iftime, Simona Denisia (Project Participant)
  • Sinkjær, Thomas (Project Participant)

Project Details


Results of the application of the Functional Electrical Therapy indicate that the stimulation of distal sensory-motor system in the paretic arm of hemiplegics works to the satisfaction of users only if the patients have some control of the wrist and some control of the arm (shoulder, elbow). In order to broaden the indication range it is necessary to develop new technology that can stimulate proximal sensory-motor systems in hemiplegics with greater disability in the arm. The main issue in the new technology is control that mimics able-bodied control in order to provide timing that reinforce brain training. A coordination control of a neural prosthesis comprises pre-programmed time sequencing and pre-programmed spatial synergies (Popovic, 2003). Two properties of reach/grasp/release (RGR) control that are instrumental are: 1) temporal synchrony, and 2) spatial synergies. The temporal synchrony model decomposes the RGR process into the phases (e.g., the hand transport to the object post - reaching, hand orientation and opening - prehension, hand closing - grasping; using the object; returning the object and releasing it at the object post; and finally returning the hand to the initial position) that are characterized by spatial synergies in the state space formed by joint trajectories. The spatial synergies are general relations among the state variables (e.g., joint angular velocities, angular accelerations) being characteristic for a specific phase of the RGR process. The study includes able-bodied volunteers. The subjects will perform self-paced functional tasks. The RGR tasks are selected to include palmar, lateral, and precision grips of objects with three different sizes, three different weights, and positioned at six different positions within the workspace. The data will be recorded in all subjects during at least three independent sessions, and the order of tasks will be randomly changed. The experimental data will be processed using the newly developed software. The processing results with the tabulated data for all movement of interest in a form suitable for automatic analysis. The task of analysis will be to determine the minimal number of unique couplings between joint angular velocities that characterize the task, hand position, objects size, or their combination. Two forms of couplings are of interest: 1) the spatial mapping, and 2) the time synchrony. Computerized matching based on radial basis functions will be performed to determine the spatial synergies. The correlation will be analysed, and the best mappings selected as the candidates for the rule-base control of a neural prosthesis to be used in hemiplegic patients with impact on the shoulder and whole arm.
Effective start/end date31/12/200431/12/2004


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