Compliant motion control of manipulators with flexible joints
Abstract
Qualitative data suggests most industrial manipulators are inherently flexible. Flexibilities in the manipulator structure not only limits its ability to perform high precision positioning, but also fine force manipulation. The effect of compliance in the manipulator structure is readily observable, but has been virtually ignored when considering the synthesis of robot control strategies. In the past, these control schemes have been formulated for robots whose dynamics are modeled by rigid bodies. Control algorithms obtained under this assumption can be severely deficient in achieving the desired results when absolute rigidity is not satisfied. The principal sources of mechanical compliance are distributed between flexibilities in the leakage members and the transmission unit. For a wide class of robots, however, experimental results reveal the joint flexibility rather than the linkage compliance is the dominating source contributing to the overall robot flexibility. The objective of the research presented in this thesis is to analyze the influence of a finite joint stiffness on the development of a hybrid position/force control architecture. The proposed controller scheme provides adequate control in a dynamically changing work environment. The suggested procedure is then applied to a position controlled robot and a force controlled robot in order to specifically quantify the different control issues that are involved with flexible joint robots for these types of control problems. The proposed controller scheme actively compensates for the joint compliance. The torsional stiffness of the joint can be compensated by using adequate feed-forward control. The theoretical analysis was verified using simulations and experimental built hardware.
Degree
Ph.D.
Advisors
Ahmad, Purdue University.
Subject Area
Electrical engineering
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