A study on motion analysis and control of mechanical systems connected by a cable

Abstract

Cables connected to mechanical systems enable efficiently power supply to the system and also enable high speed communication even in a poor communication environment. But it is not easy to control position and attitude of such mechanical systems with cables or tethers, because tension and inertia of the cables become disturbances, which greatly affect the behavior of the mechanical system. However, there is not enough studies on the control of such a mechanical system with cable. In this study, the cable is expressed by absolute nodal coordinate formulation (ANCF) which is one of the nonlinear finite element methods. The control system design method using the ANCF model has not been established and there are few research examples. Control law is derived by the use of the special feature of obtained model, that is inertia matrix of the system is constant. By applying coordinate transformation utilizing the feature, a controller design problem for mechanical system with cable is converted to that for mechanical system which consists of only rigid body, and the derive controller achieves low calculation cost. The proposed method controls the mechanical system so that the influence of the tether is compensated. Furthermore, in order to achieve the proposed control law, state variables of the cable are estimated by Kalman filter. Numerical analyses are carried out for evaluation of the proposed method.

Keywords

• absolute nodal coordinate formulation
• cable
• flexible multibody system
• motion control
• state estimation
• unscented kalman filter