To verify all robotic tasks involving a space robot interacting with environment, such as the special purpose dexterous manipulator, one should appeal to a simulation technique because the space robot cannot operate in an 1-g environment. However, to simulate dynamical behavior of a robot interacting with environment possess many difficulties due to complexity of the physical phenomenon involved during the interaction. In this work we develop an hardware-in-loop simulation technique, where a simulation of the space robot dynamics is combined with emulation of the contact dynamics by using a rigid robot prototype performing the contact task. The rigid robot is not dynamically or kinematically equivalent to the space robot, but it is controlled so that its endpoint dynamics replicates that of the space robot. Experimental results given from implementation of a single axis arm are presented.

To verify the tasks of one of the Space Station manipulator, the Canadian Space Agency is developing a hardware-in-the-loop simulation system. A hydraulic robot manipulating mockup of the space payload reproduces the contact forces occurring during insertion and extraction. The control law allowing a good performance requires a very accurate torque tracking for the hydraulic robot. With good force sensing in the hydraulic cylinder the torque control can be achieved in constraint motion but not in free motion. A controller using a feedforward term to compensate the velocity related effect is presented and tested experimentally. It is shown that this controller achieves very good results both in free motion and in a constrained task.

This paper presents six methods to model a flexible beam rotating in the vertical plane. The first three methods, Hamilton's principle, Lagrange's equations for quasi-coordinates and Newton-Euler equations, give a continuous model. The last three methods, Lagrange's equations, Jourdain's principle and Newton-Euler equations, give a discrete model. The paper discusses how the different methods apply. It also shows how to derive the discrete model directly from the continuous one. The main conclusion of the paper is that if the foreshortening of the flexible link is neglected, then starting from the same assumptions, different methods give different models.

Analyses the performance and stability of a force/moment accommodation (FMA) loop closed around a joint rate controller. A synthesis methodology is given to select the gains of the accommodation controller. The bandwidth and coupling limitations of the FMA control architecture are discussed. It is shown that the closed-loop FMA exhibits natural decoupling when FMA acts on the "transpose Jacobian rate" controller. The theoretical developments in the paper are supported by simulation and experimental results.

Hardware-in-the-loop simulation is an attractive tool to validate the functionality of space robots. It is the purpose of the hardware-in-the-loop simulation to make a rigid robot prototype behave, in contact/noncontact phases, as closely as possible to a given robot reference model that would be encountered in the real-world. We introduce a method for the hardware-in-the-loop simulation that is based on the projection of the generalized coordinates of the robot model into two subspaces representing independent and dependent coordinates. The independent coordinate is obtained via simulation by making use of its acceleration model expressed in a closed form. While, the dependent coordinate is obtained from the generalized coordinated of the linearized robot prototype acting as a double integrator on the input dependent-coordinate acceleration. It is followed by investigating the effect of external disturbance on the performance of the hardware-in-the-loop simulation, by the method of Lagrangian multiplier. Finally experimental results obtained from implementation of a single axis arm is presented.

As a partner in the International Space Station, Canada is responsible for the verification of all tasks involving the special purpose dextrous manipulator (SPDM). In this paper, the concept of an SPDM task verification facility (STVF) is described. The verification process involves three complementary stages. First, a real-time software simulator is used to verify the complete nominal and malfunction procedures. Next, the feasibility of a task involving contact is verified with the help of a hardware-in-the-loop simulator. Finally, a non real-time simulator is used to perform detailed parametric studies given the known tolerances on the components. The paper describes all three stages but emphasizes on the hardware-in-the-loop simulator, the only new facility within the STVF.

Addition of viscoelastic layers on flexible beam improves the behavior of flexible robots. However, the time domain simulation of such multilayer flexible beams is usually done through finite elements which makes it very time consuming. This paper proposes to build an equivalent homogenous flexible beam such that the flexible manipulator can be simulated using the variety of efficient methods developed in robotics. We propose a method to develop the equivalent Voigt-Kelvin model based on the frequency response obtained from the finite-element model. Then, we evaluate the performance of the model by simulating an experimental slewing beam covered with constrained viscoelastic material. The results are very satisfactory and the simulation is one hundred times faster than with the finite element method.