Accession Number : ADA329618

Title :   Experiments in Neural-Network Control of a Free-Flying Space Robot.

Descriptive Note : Final rept. 1 Jun 92-31 Oct 95,

Corporate Author : STANFORD UNIV CA AEROSPACE ROBOTICS LAB

Personal Author(s) : Wilson, Edward

PDF Url : ADA329618

Report Date : MAR 1995

Pagination or Media Count : 154

Abstract : Four important generic issues are identified and addressed in some depth in this thesis as part of the development of an adaptive neural network based control system for an experimental free flying space robot prototype. The first issue concerns the importance of true system level design of the control system. A new hybrid strategy is developed here, in depth, for the beneficial integration of neural networks into the total control system. A second important issue in neural network control concerns incorporating a priori knowledge into the neural network. In many applications, it is possible to get a reasonably accurate controller using conventional means. If this prior information is used purposefully to provide a starting point for the optimizing capabilities of the neural network, it can provide much faster initial learning. In a step towards addressing this issue, a new generic Fully Connected Architecture (FCA) is developed for use with backpropagation. A third issue is that neural networks are commonly trained using a gradient based optimization method such as backpropagation; but many real world systems have discrete valued functions (DVFs) that do not permit gradient based optimization. One example is the on-off thrusters that are common on spacecraft. A new technique is developed here that now extends backpropagation learning for use with DVFs. The fourth issue is that the speed of adaptation is often a limiting factor in the implementation of a neural network control system. This issue has been strongly resolved in the research by drawing on the above new contributions.

Descriptors :   *ROBOTICS, *NEURAL NETS, *ROBOTS, *UNMANNED SPACECRAFT, ALGORITHMS, ADAPTIVE CONTROL SYSTEMS, COMPUTER LOGIC, COMPUTER ARCHITECTURE, HYBRID SYSTEMS, CONTROL THEORY, THRUST CONTROL, THRUSTERS, REMOTE CONTROL, FREE FLIGHT.

Subject Categories : Cybernetics
      Unmanned Spacecraft

Distribution Statement : APPROVED FOR PUBLIC RELEASE