The insertion task had been implemented before using an industrial robot and a compliant force-torque sensor [lo]. This experiment in addition focused on the auto- matic tracking of the motor block by image processing. Despite a well tuned Cartesian force controller, the insertion process had to be performed much slowlier, because of the well known control problems which oc- cur in case of hard contacts with conventional robots. In this context, the advantage of a compliant manip ulator became clear. Thus it is our strong belief that torque controlled light-weight robots may bring significant advantages, not only in applications which demand mobility, and hence low masses, but also for applications requiring manipulation in contact with unknown environments. Conclusions Three different approaches for implementing com- pliant manipulation were analyzed: impedance, stiff- ness and admittance control. A new controller struc- ture was proposed, which consists of an impedance controller enhanced by local stiffness control. The presented methods were implemented and compared on DLR’s light-weight robots. The proposed con- troller shows up a better performance than classical impedance and stiffness control. Compared to admit- tance control, it has lower geometric accuracy, but higher bandwidth and impedance range. As an ap- plication for the new controller, the insertion of pis- tons into a motor block was described; programming times (by directly guiding the robot), and execution times were drastically reduced compared to conven- tional techniques. References [l] D. Abadia. Comparative analysis development of con- trol systems for the DLR light weight robot. Master’s thesis, DLR, University of Zaragossa, 2000. State feedback controller for flexible joint robots:
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