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Abstract-This paper presents the design of the lightweight BioRob manipulator with spring-loaded tendon-driven actuation developed for safe physical human-robot interaction. The safety of the manipulator is analyzed by an analytical worstcase estimation of impact and clamping forces in the absence of collision detection. As intrinsic joint compliance can pose a threat by storing energy, a safety evaluation method is proposed taking the potential energy stored in the elastic actuation into account. The evaluation shows that the robot arm design constrains the worst case clamping forces to only 25 N, while being able to handle loads up to 2 kg, and inherits extremely low impact properties, such as an effective mass of less than 0.4 kg in non near-singular configurations, enabling safe operation even in case of high velocities. The results are validated in simulation and experiments.

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In this paper, multibody system dynamics simulation for manipulators and legged robots with high joint elasticities, particularly with focus on collision modeling, is addressed. We present the architecture of a newly developed toolbox in conjunction with a detailed discussion of a realistic contact, friction and stiction model, which is validated with real measurement data of a bouncing ball. The work presented is driven and inspired by two concrete robot developments in the authors' group: the manipulator BioRob and the biped BioBiped. The libraries are used to develop kinematic and kinetic models of these bio-inspired and highly elastic robots. Models and simulation of both robots are discussed, as well as occurring forces during collisions of the BioRob-X4 arm with the ground. We are also able to demonstrate good agreement of ground contact forces measured during slow jogging motion of a human subject with simulation results obtained with BioBiped1.

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