Analysis of fault-tolerant neurocontrol architectures

The fault-tolerance of analog parallel distributed implementations of a multivariable aircraft neurocontroller is analyzed by simulating weight and neuron failures in a simplified scheme of analog processing based on the functional architecture of the electrically trainable analog neural network (ETANN) chip. The neural information processing is found to be only partially distributed throughout the set of weights of the neurocontroller synthesized with the backpropagation algorithm. Although the degree of distribution of the neural processing, and consequently the fault-tolerance of the neurocontroller, could be enhanced using locally distributed weight and neuron approaches, a satisfactory level of fault-tolerance could only be obtained by retraining the degraded VLSI neurocontroller. The possibility of maintaining neurocontrol performance and stability in the presence of single weight or neuron failures was demonstrated through an automated retraining procedure of the neurocontroller based on a pre-programmed choice and sequence of the training parameters