FLIMHILS: A Hardware-in-the-Loop Simulator of Flexible Links Mechanisms

Aerospace applications, fast industrial robots and large manipulators for construction belong to the growing number of robotic applications where the arms have to be lightweight compared to their size. These arms must have links of small inertia and small cross-section, but exhibit an undesirable flexibility that makes the control of the end-effector position extremely difficult. Therefore a great research efforts over the past years concentrated on modeling and controlling flexible structures. The dynamics of such structures is of very high order non-linear thus the control strategies are very complex. Moreover these control strategies, when they are implemented in the real control device, result hard to test since link flexibility is closely related to the mechanical fatigue, which is the main cause of arm fractures occurring when the control is not well tuned. This requires repeated replacement of the robot links. A Hardware-in-the-Loop-Simulation (HILS) refers to an increasingly popular engineering technique in which parts of a pure simulation have been replaced with actual physical components. In this manner a simulated control device as well as a simulated version of the plant could be inserted in the real loop. For flexible link manipulator, this allows to verify the effectiveness of a new control strategy on the real control device but using a simulated plant which is not affected by the arm fractures. Clearly the HILS requires an accurate model of the flexible manipulator. This paper proposes an architecture, named FLiMHILS, for applying HILS techniques to the design and testing of control strategies for flexible link manipulators. Potential benefits of this architecture include concurrent development of hardware and control system components. Moreover a reusable platform for define flexible link manipulators through a generic and modular structure is provided. An implementation for a simple flexible link is presented here to prove the effectiveness of the proposed architecture.