Constrained mechanical systems modeling and control: A free-floating space manipulator case as a multi-constrained system

This paper presents a novel, robust, adaptive trajectory-tracking control scheme for the free-floating space robot system in Cartesian space. The dynamic equation of the free-floating space robot system in Cartesian space is derived from the augmented variable method. The proposed basic robust adaptive controller is able to deal with parametric and non-parametric uncertainties simultaneously. Another advantage of the control scheme is that the known and unknown external disturbance bounds can be considered using a modification of the parameter-estimation law. In addition, three cases are certified to achieve robustness for both parametric uncertainties and external disturbances. The simulation results show that the control scheme can ensure stable tracking of the desired trajectory of the end-effector.

https://journals.sagepub.com/doi/pdf/10.5772/61743

Robust Adaptive Control of a Free-floating Space Robot System in Cartesian Space

This paper deals with the problem of robust trajectory tracking control for free-floating manipulator systems subject to plant uncertainties and external disturbances. The system model is described through the Dynamically Equivalent Manipulator approach and the tracking problem is formulated directly in task space. Two adaptive techniques are developed considering nonlinear ℋ ∞ controllers and artificial neural networks. Experimental results are obtained from an underactuated three-link fixed-base planar manipulator dynamically equivalent to a two-link free-floating planar space manipulator.

http://www.dcsc.tudelft.nl/~bdeschutter/private_20100705_acc_2010/data/papers/1719.pdf

Neural network robust controllers applied to free-floating space manipulators in task space

Space robots are featured by a dynamic coupling which causes the rotation of the main body with the coordinated motions of the arm. A number of dynamic and control problems are unique to this area due to the distinctive and complex dynamics found in many applications. In-space operations such as assembly, inspection and maintenance of satellites or space stations have been receiving considerable research efforts. Considering the hostile environment where a space robot operates, which can deteriorate its structure and physical characteristics, and also considering the difficulty of taking the system back to reformulate its dynamic model due to these uncertainties, the proposal of intelligent adaptive robust controllers to this kind of system becomes very interesting. One of the representative types of space robotic systems identified by [Dubowsky & Papadopoulos (1993)], free-floating space manipulators are systems that allows the spacecraft to move freely in response to the manipulator motions in order to conserve fuel and electrical power, [Papadopoulos & Dubowsky (1991)]. Trajectory planning algorithms have been developed in order to minimize the reaction motion of the free-floating base while executing the manipulator task, [Huang & Xu (2006); Liu et al. (2009); Papadopoulos et al. (2005); Torres & Dubowsky (1992); Tortopidis & Papadopoulos (2006)]. In case of redundant manipulators, coordinated spacecraft/manipulator motion control has been addressed in [Caccavale & Siciliano (2001); Dubowsky & Torres (1991)]. Solving control problems in joint space is an inconvenient task for a space robot with a freefloating base. When the base is free-floating, the kinematic mapping from task space to joint space, where the control is executed, becomes non-unique because of non-integrable angular momentum conservation. This may cause non-existence of the reference trajectory in joint space. Also, parametric uncertainties appear not only in the dynamic equation, but also in kinematic mapping from the joint space to the task space due to the absence of a fixed base. The model inaccuracies lead to the deviation of operational space trajectory provided by the kinematic mapping. [Parlaktuna & Ozkan (2004)] and [Abiko & Hirzinger (2009)] applied on-line adaptive techniques to deal with parametric uncertainties in controlling free-floating 1

/pdf/adaptive-robust-controller-designs-applied-to-free-floating-56ul46ywol.pdf

Adaptive Robust Controller Designs Applied to Free-Floating Space Manipulators in Task Space

This paper proposes an adaptive controller for a free-floating space robot (FFSR) in the presence of kinematic and dynamic model uncertainties. Because of high dynamical coupling between the actively operated manipulator and the free-floating base, two inherent difficulties exist, such as non-linear parameterization of the dynamic equation and both kinematic and dynamic parameter uncertainties. In order to compensate these uncertainties, we use the fuzzy logic system (FLS) that has the capability to approximate any nonlinear function. The proposed adaptive controller does not involve complex calculations, but it is still possible for the system to generate a suitable input torque and a compensator to overcome the uncertainties. Then, the stability is proved and the structure of the control method is given. To verify the validity of the proposed method, a computer simulation of a two-link planar FFSR is carried out.

Robust adaptive control of free-floating space robot based on fuzzy compensation

A dynamic control approach in task space is proposed for trajectory tracking problem of free-floating space manipulator without controlling the pose of the spacecraft. Based on the extended manipulator model, the dynamic equation of the system is derived. The dynamic parameters needed by the dynamic control in task space could be estimated by the off-line adaptive identification method. The presented control scheme guarantees asymptotic tracking of the desired end-effector trajectory and does not require measurement of the joint accelerations. Simulation results given show the feasibility and effectiveness of the proposed method.

Zhongying Chi

Papers

A dynamic control method for free-floating space manipulator in task space