Technical session talks from ICRA 2012
TechTalks from event: Technical session talks from ICRA 2012
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Simplified Static Analysis of Large-Dimension Parallel Cable-Driven RobotsThis paper introduces a new simplified static analysis of parallel robots driven by inextensible cables of non-negligible mass. It is based on a known hefty cable static modeling which seems to have been overlooked in previous works on parallel cable-driven robots. This cable modeling is obtained from a well-known sagging cable modeling, known as the catenary, by assuming that cable sag is relatively small. The use of the catenary has been shown to lead to a non-linear set of equations describing the kinetostatic behavior of parallel robots driven by cables of non-negligible mass. On the contrary, the proposed simplified static analysis yields a linear relationship between (components of) the forces in the cables and the external wrench applied to the robot mobile platform. As a consequence, by means of the simplified static analysis, useful wrench-based analysis and design techniques devised for parallel robots driven by massless cables can now be extended to cases in which cable mass is to be accounted for.
Design Optimization for Parallel Mechanism Using on Human Hip Joint Power Assisting Based on Manipulability Inclusive PrincipleThis paper summarizes the design optimization of a parallel mechanism using on human hip joint power assisting. Manipulability Inclusive Principle (MIP) evaluation criterion for evaluating assisting mechanism's assisting feasibility and assisting effect is proposed. The design of parallel assisting mechanism and building kinematical Jacobian are discussed. Moreover, as an important part of this paper, in order to finding out a architecture, which can satisfy assisting feasibility and realize higher assisting efficiency, more assisting ability and better feature on assisting isotropy, design optimization MIP is shown in this paper.
The Kinematics of the Redundant $N-1$ Wire Driven Parallel RobotWe address the kinematics of the redundant N-1 wire-driven parallel robot, i.e. a robot with N > 3 wires connected at the same point on the platform. The redundancy allows one to increase the workspace size. But we show, both theoretically and experimentally that if the wires are not elastic, then the redundancy cannot be used to control the wire tensions. Indeed we show that whatever are the number of wires there will always be only at most 3 wires in tension, while the other N-3 wires will be slack. We then show that if the wires are elastic, then the platform positioning will be very sensitive to stiffness identification and wire lengths control. Hence classical redundant control schemes are difficult to use for such robot and alternate use of the geometry of redundant wires have to be considered.
Error Modeling and Accuracy Analysis of a Multi-Level Hybrid Support RobotAs for the multi-level hybrid feed support robot in the Five-hundred-meter Aperture Spherical radio Telescope (FAST), the cabin's time-varying barycenter and structural deformation are main factors causing the terminal receiversâ€™ pose error. In order to ensure tracking accuracy of astronomical observations, firstly the elasticity model of the cable-driven Stewart manipulator is deduced to analyze the terminal error caused by the gravity torque. Newton-Raphson method is adopted to acquire the terminal error range and propose compensation strategy. Then error model considering structural deformation is formulated and the terminal accuracy is analyzed with an improved set theory based method. Finally the sensitivity analysis is also carried out and accuracy synthesis is implemented. Error modeling and analysis method proposed for the support robot in this paper can also be used to other complex hybrid robots with either large dimension or heavy duty.
Point-To-Point Motion Planning of a Parallel 3-DOF Underactuated Cable-Suspended RobotThis paper presents a planar parallel three-degree-of-freedom underactuated cable-driven robot. The mechanism is first described and a dynamic model is derived. One of the advantages of the proposed mechanism is that it does not require any mechanical (e.g. pulleys) or electrical (e.g. actuators) hardware to be mounted on the end-effector. A trajectory planning approach is developed, which is based on the natural frequency of the pendulum-like free motion (unconstrained degree of freedom). Sine-like excitation functions are used and their frequency and phase delay are determined using simulation results. A prototype is then described and experimental results are provided together with a video clip of an example trajectory. The results confirm that the mechanism can be effectively used for point-to-point trajectories.