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A new way of induction-motor position control for high-performance applications is developed in this paper using discrete-time sliding-mode (DSM) control. In addition to the main DSM position controller, the proposed control structure includes an active disturbance estimator (ADE), in which a passive filter is replaced by another DSM-controlled subsystem, in order to improve system robustness and accuracy. Furthermore, the application of an ADE makes possible the design of both controllers using the knowledge of the nominal system only. Experiments have verified high efficiency of the proposed servo system under the influence of large parameter perturbations and external disturbances in the presence of unmodeled dynamics. Index Terms--Discrete-time sliding-mode control (DSMC), disturbance estimator (DE), induction motors (IMs), position control, servo systems.

The paper presents experimental data of breakdown voltage as a function of voltage increase rate for nitrogen-filled tubes at pressures of 133 and 399 Pa. By fitting this data using polynomial approximation, static breakdown voltages for these tubes were estimated. The influence of voltage increase rate, voltage step, time interval between successive voltage step, and relaxation time on the static breakdown voltage was analyzed. The processes in gas advanced during breakdown were also analyzed, as well as their influence on the breakdown voltage. Index Terms--Breakdown voltage, nitrogen, relaxation time, static breakdown voltage, surface recombination, voltage increase rate, voltage step.

Variable structure systems (VSS), integrated with kinematic redundant robot control process, manipulate tasks with large decelerations or accelerations. A distributed positioning (DP) concept solves tactical control level. VS control algorithms combined with a PI controller evaluate executive control level. VS and PD controller tracking properties are comparatively analyzed on a SCARA robot with a pick-and-place movement.