Analysis of guidance and control laws for orbiting multibody manipulators

Paper number

IAC-08.C1.1.7

Author

Ms. Chiara Toglia, University of Rome "La Sapienza", Italy

Coauthor

Mr. Marco Sabatini, University of Rome "La Sapienza", Italy

Coauthor

Prof. Paolo Gasbarri, Università di Roma "La Sapienza", Italy

Coauthor

Dr. Giovanni B. Palmerini, Universita' di Roma 'La Sapienza', Italy

Year

2008

Abstract

The increasing interest in automatic missions, due to high risk and cost of manned missions, calls for a renovated interest in space robotics. The analysis of the guidance and the control of space manipulators needs an intensive campaign of numerical simulations carried out on a suitable mathematical model, taking into account different forces such as gravity and gravity gradient, elastic forces, possibly the air drag and of course the inertial forces. The model should allow for an efficient solution of the inverse kinematics, exploited to attain a desired final state. At the same time, the model should preserve the correctness of the solution which is seriously affected in the specific case by numerical problems, due to the different scales of the phenomena occurring: gravity, related to the orbital radius; gravity gradient, related to the manipulator overall dimensions; and flexibility, related to the characteristics of each link.

The paper, after a short recall of a proper dynamic model of a multibody system solving these numerical issues, will investigate in detail the GNC loop architecture. The working scheme is based on a path planning optimization algorithm for the evaluation of the reference motion of the manipulator arm, and a set of possible control laws, including the classical proportional derivative controller and the feedback linearization technique, to follow the reference trajectory. The performances of the GNC loop are assessed in terms of the accuracy of the final state achieved, of the time required to complete the manoeuvre and of the power consumption needed by the actuators. The attitude of the spacecraft, which the manipulator is linked to, can either keep a steady condition or follow a predefined pointing.

Several simulations are presented in the paper for different cases, all of them supposing a Low Earth Orbit manoeuvre. Finally, in order to test and validate the proposed techniques for guidance and control, the results obtained with a simple, limited scale experimental test-bed purposely setup in the labs of AeroAstro Dept of Università di Roma La Sapienza are reported.

Abstract document

IAC-08.C1.1.7.pdf

Manuscript document

IAC-08.C1.1.7.pdf (🔒 authorized access only).

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