Adaptive impedance controller for prosthetic hand object grasping and manipulation
Esquivel-Ortiz, Jose D.
AdvisorYihun, Yimesker S.
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There are many complexities involving the human hand’s ability to perform stable grasping patterns. Human grasping is a complicated function to mimic in relation to prosthetic hands. Although there are various state-of-the-art-prosthetic mechanisms currently in the market that can perform different types of grasping patterns; these mechanisms still lack the ability to determine specific grasping stability properties. To improve prosthetic hand grasping, impedance control can be utilized. Impedance control provides the ability to adjust the dynamic relations between the robotic movements and the exterior forces in a continuous manner. In this study an impedance control algorithm is developed. The proposed impedance control algorithm will deal with uncertainties including object friction, physical properties, and contact points. The software known as SynGrasp will be utilized to model a hand to object grasping configuration. In addition, the scenario where an object is being perturbed while being grasped will be performed and analyzed. By utilizing grasping configuration properties, a grasp stability estimator function will determine if the final grasp (after the object is perturbed) is more stable or not. Quality measures for the initial grasp and final grasp will be calculated and analyzed. The data will then be used to determine if the stabilizing algorithm is needed or not. SynGrasp will also be used to provide all the data needed for the impedance stabilizing algorithm. The stability estimation function is the most crucial component in the impedance control algorithm. By utilizing SynGrasp a successful estimation function for an impedance control algorithm was created and tested. By incorporating this impedance control system to a prosthetic hand mechanism. The prosthesis will be one step closer in mimicking the dexterity of a human hand.
Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Mechanical Engineering