This thesis presents an optoelectronic stand-off sensor and actuation system developed for robotic applications. The measuring principle is based on an on-axis method of detecting variation in a beam reflected from a surface. The sensor utilizes two photodiodes to measure the difference in beam power falling through two pinholes, to estimate the distance between the workpiece surface and incident focused beam waist. The output voltage from the differential stage is normalized to negate the effects of surface reflectivity, colour, and texture. Two mathematical models are presented which simulate the device. The first depends only on the theory of propagation of gaussian beams, whilst the second relies upon simulating the reflected beam using geometrical optics to calculate the radiometric distribution at the detecting pinholes. A set of experiments were performed to analyze and optimize the performance of a number of sensor configurations. The experimental results are bounded between gaussian and radiometric model results. A comparison of the results of the three models, conclusions regarding sensor performance and principles for optimally designing such systems are given. A proportional control circuit for one sensor servo combination was designed and tested using a solenoid as an actuator. The predicted performance of the complete servo system was modelled utilizing the ACSL language. While an experimental rig was built and experiments designed to analyze the output of the system in response to a step input. The results of this show that the stand-off system gives varying response to different materials indicating that the electronic method of normalizing the sensor output is insufficient. The results also show that the device is sensitive to controller gain and behaves in a non-linear fashion as predicted. The actual response is generally faster than the predicted response. Conclusions and recommendations for further work and development are given
