Shaking Forces Minimization of High-Speed Robots via an Optimal Motion Planning
This paper deals with the problem of shaking force balancing of high-speed robots based on a new optimal trajectory planning approach. The aim of the new approach is the optimal path planning of the robot links centre of masses, which allows a considerabl
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Institut de Recherches en Communications et Cybernétique de Nantes (IRCCyN), Nantes, FRANCE [email protected]
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Institut National des Sciences Appliquées (INSA), Rennes, FRANCE [email protected] [email protected] [email protected]
Abstract. This paper deals with the problem of shaking force balancing of high-speed robots based on a new optimal trajectory planning approach. The aim of the new approach is the optimal path planning of the robot links centre of masses, which allows a considerable reduction of the variable inertia forces transmitted to the robot frame. The efficiency of the suggested method is illustrated by a numerical simulation of a planar two links 2R serial robot, in which reductions in the shaking force of 63 % and in input torque of 84 % are achieved.
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Introduction
A primary objective of linkage balancing is to cancel or reduce the variable dynamic loads transmitted to the frame and surrounding structures. Different approaches and solutions devoted to this problem have been developed and documented for one degree of freedom mechanisms (Lowen et al., 1983), (Arakelian et al., 2000), (Arakelian and Smith, 2005). A new field for their applications is the design of mechanical systems for fast manipulation, which is a topical problem in advanced robotics. The balancing of a mechanism is generally carried out by two steps: (i) the cancellation (or reduction) of the shaking force and (ii) the cancellation (or reduction) of the shaking moment. Traditionally, the cancellation of the shaking force transmitted to the robot frame can be achieved via adding counterweights in order to keep the total centre of mass of moving links stationary (Lowen et al., 1983), (Arakelian et
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al., 2000). However, this approach leads to the increase in the total mass of the mechanical systems and consequently the increase in input torques. With regard to the shaking moment balancing of robots, the following approaches were developed: (i) balancing by counter-rotations (Berkof, 1973), (Dresig et al., 1994), (Arakelian and Smith, 1999), (Herder and Gosselin, 2004), (ii) balancing by adding four-bar linkages (Gosselin et al., 2004), (Ricard and Gosselin, 2000), (iii) balancing by optimal trajectory planning (Papadopoulos and Abu-Abed, 1994), (Fattah and Agrawal, 2006), (Arakelian and Briot, 2008) and (iv) balancing by adding an inertia flywheel rotating with a prescribed angular velocity (Arakelian and Smith, 2008). It should be noted that the complete dynamic balancing can only be reached by a considerably complicated design of initial robot mechanisms and by unavoidable increase in the total mass. This is the raison why we focused our research studies on the development of robot balancing methods via optimal motion planning approaches, i.e. without modification of the initial mechanical structure and without any adding masses. The paper is organized as follows. In the next part, the suggested optimal motion planning is described. Then, for
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