Bioinspired Control Method Based on Spiking Neural Networks and SMA Actuator Wires for LASER Spot Tracking

This chapter presents a new biologically inspired technique for automatically compensating the light spot deviation from the normal position for laser spot trackers. The method is based on hardware implementation of the spiking neural networks which provides fast response due to real time operation and ability to learn unsupervised when they are stimulated by concurrent events. For increasing the biological plausibility of the method, the spiking neural network controls the contraction of shape memory alloy (SMA) actuator wires that operates as the muscular fibres. These SMA wires are the most suitable actuators for being controlled by the electronic spiking neurons because the contraction force increases naturally with the spiking frequency. From our knowledge the laser spot tracking using spiking neural networks was not performed previously. Moreover, other original ideas represent the use of analogue implementation of the spiking neural networks for real time operation as well as the SMA actuator wires for more biological plausibility. To validate this method we implemented in hardware a spiking neural network structure that processes the input from a one dimensional photodiode array and controls a positioning system based on SMA actuator wires. The results show that the spiking neural network is able to detect the one-dimensional spot motion and to adapt the response time by Hebbian learning mechanisms to the spot wandering amplitude. Moreover, by driving two antagonistic SMA actuator wires the system is able to track the laser spot with low response time and acceptable precision. These results are encouraging to develop bio-inspired low power spot tracking system for enhancing the receiving accuracy in free space optical communications or for enhancing the efficacy of the photovoltaic systems. Moreover, the light tracking principle based on spiking neural networks and SMA wires can be successfully used in implementation of the light tracking mechanism of an artificial eye.