A sliding mode control algorithm has been designed for control of a balance beam on two symmetric magnetic bearings. A state space model of the system is developed and the controller is separated into a linear and non-linear component. A reaching condition to bring the system to the sliding surface is developed and a continuous function boundary layer approach is evaluated to avoid chattering. Previous works have discussed theoretical and experimental sliding mode control with physical sensors. This paper represents the first use of a simple envelope filter for sliding mode self sensing. The system simulation demonstrates arrival at the hyperplane surface within 0.003 sec and converges to the zero angular displacement value within 0.008 sec. Experimental results produced system convergence to zero angular displacement within approximately 0.35 sec both for the case when an eddy current position sensor was used and the case when system self sensing was employed. Some small scale chatter was observed in the experimental results with a peak to peak magnitude of approximately 3 times larger in the self-sensing case as compared to the case with a physical sensor.

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