A fundamental requirement for the success of a manipulation task is the capability to handle the physical contact between a robot and the environment. Pure motion control turns out to be inadequate because the unavoidable modeling errors and uncertainties may cause a rise of the contact force, ultimately leading to an unstable behavior during the interaction, especially in the presence of rigid environments. Force feedback and force control becomes mandatory to achieve a robust and versatile behavior of a robotic system in poorly structured environments as well as safe and dependable operation in the presence of humans. This chapter starts from the analysis of indirect force control strategies, conceived to keep the contact forces limited by ensuring a suitable compliant behavior to the end effector, without requiring an accurate model of the environment. Then the problem of interaction tasks modeling is analyzed, considering both the case of a rigid environment and the case of a compliant environment. For the specification of an interaction task, natural constraints set by the task geometry and artificial constraints set by the control strategy are established, with respect to suitable task frames. This formulation is the essential premise to the synthesis of hybrid force/motion control schemes.
COMRADE: Compliant motion research and development environment
Author Joris De Schutter, Herman Bruyninckx, Hendrik Van Brussel et al.
Video ID : 691
The video collects works on force control developed in the 1970s-1980s and 1990s at the Department of Mechanical Engineering of the Katholieke Universiteit Leuven, Belgium. The tasks were programmed and simulated using the task-frame-based software package COMRADE (compliant motion research and development environment). The video was recorded in the mid-1990s.
The main references for the video are:
1. H. Van Brussel, J. Simons: The adaptable compliance concept and its use for automatic assembly by active force feedback accommodations, Proc. 9th Int. Symposium Indust. Robot., Washington (1979), pp.167-181
2. J. Simons, H. Van Brussel, J. De Schutter, J. Verhaert: A self-learning automaton with variable resolution for high precision assembly by industrial robots, IEEE Trans. Autom. Control 27(5), 1109-1113 (1982)
3. J. De Schutter, H. Van Brussel: Compliant robot motion II. A control approach based on external control loops, Int. J. Robot. Res. 7(4), 18-33 (1988)
3.J. De Schutter, H. Van Brussel: Compliant robot motion I. A formalism for specifying compliant motion tasks, Int. J. Robot. Res. 7(4), 3-17 (1988)
4. W. Witvrouw, P. Van de Poel, H. Bruyninckx, J. De Schutter: ROSI: A task specification and simulation tool for force-sensor-based robot control, Proc. 24th Int. Symp. Indust. Robot., Tokyo (1993), pp. 385-392
5. W. Witvrouw, P. Van de Poel, J. De Schutter: COMRADE: Compliant motion research and development environment, Proc. 3rd IFAC/IFIP Workshop on Algorithms and Architecture for Real-Time Control. Ostend (1995), pp. 81-87
6. H. Bruyninckx, S. Dutre, J. De Schutter: Peg-on-hole, a model-based solution to peg and hole alignment, Proc. IEEE Int. Conf. Robot. Autom. (ICRA), Nagoya (1995), pp. 1919-1924
7. M. Nuttin, H. Van Brussel: Learning the peg-into-hole assembly operation with a connectionist reinforcement technique, Comput. Ind. 33(1), 101-109 (1997)