Nonlinear inverse dynamic models can be utilized in various parts of advanced model-based control system design: reference trajectory optimization, feedforward control and feedback linearization [35]. In this paper, a new synthesis approach for nonlinear inverse dynamic models of satellites with flexible structures is presented. For satellite configurations with unstable zero dynamics, a stable inverse model approximation is proposed which has been successfully applied to robots with flexible bodies. This inverse modeling approach is part of the newly developed DLR Space Systems Library for objectoriented modeling and simulation of satellites and launchers in a detailed space environment. For satellites with flexible structures, the library provides models for normal simulation mode and the necessary tools to directly generate approximate inverse models. In this paper, trajectory optimization is shown to be an important use case for inverse dynamic models. By inversion based reformulation of the trajectory optimization problem, the optimal reference motion of the control system can be determined in a reliable and efficient way.

Abstract:In this article tracking control of nonlinear plants using a two degree of freedom controller structure is considered. The work described herein focuses on the design of feedforward controllers based on automatic generation of inverse plant models. The method is applied to the problem of vibration control of elastic joint robots and is demonstrated with simulations and experimental results.

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We consider the global tracking control problem of robots with elastic joints. Even if joint elasticity introduces beneficial features for modern applications which require physically resilient and safer robots that can interact with the environment or humans, it challenges the achievable control performance. We propose a novel controller which combines the benefits of two approaches: the intrinsic robustness to model uncertainty from passivity-based control and the implementation efficiency of inverse-dynamics control schemes using a modern recursive algorithm. The novel controller is applied to an elastic-joint reconfigurable robotic arm using a recently proposed framework for on-the-fly control design. Simulation and experimental results validate our proposed approach.

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