The compensation of friction nonlinearities for servo motor control has received much attention due to undesirable and disturbing effects that the friction often has on conventional control systems. Compensation methods have generally involved selecting a friction model and then using model parameters to cancel the effects of the nonlinearity. In this paper, a method using fuzzy logic for the compensation of nonlinear friction is developed for the control of a dc motor. The method is unique in that a single fuzzy rule is used to compensate directly for the nonlinearity of the physical system. As a result, the method introduces fewer adjustable parameters than a typical fuzzy logic approach while still incorporating many advantages of using fuzzy logic such as the incorporation of heuristic knowledge, ease of implementation and the lack of a need for an accurate mathematical model. The general approach, analysis and experimental results obtained for an actual dc motor system with nonlinear friction characteristics are presented and the effectiveness of the fuzzy friction compensation control technique is discussed. The smoothness of response, response times and disturbance rejection of a PI control system with and without the proposed fuzzy compensator are analyzed and discussed to illustrate the effectiveness of the proposed method.

Comparative effects of anticonvulsant drugs on the thalamocortical system were analyzed quantitatively. Paired stimuli were delivered to the ventrolateral thalamus with evoked responses recorded from the ipsilateral sensorimotor cortex in the cat. Threshold and excitability profiles were developed with an on-line computer. Effects of phenytoin and diazepam were generally similar, with depression of excitability and slight elevation of thresholds. Ethosuximide produced a pronounced pair-interval dependent effect of unchanged or increased excitability and lowered threshold at shorter intervals, with depressed excitability and raised threshold at longer intervals. These data demonstrate a marked difference in effect of the petit mal and grand mal agents tested and suggest a basis for the effectiveness of ethosuximide in controlling 3-per-second repetitive activity.

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A patient with cystic fibrosis and cirrhosis developed a progressive neurological syndrome associated with ataxia, proximal weakness, and ophthalmoplegia. Profound deficiencies of vitamins A, D, and E were present. Visual acuity and results of retinal funduscopy were normal. The pattern reversal visual evoked potential was initially abnormal (P100 latency, 136 and 130 ms from left and right eyes, respectively) but became normal (less than 3 standard deviations from mean control P100 latency) over a two-month period when vitamin E was administered. This case documents a potentially reversible visual evoked potential abnormality in a visually asymptomatic patient with vitamin E deficiency.

Regional effects of electrical stimulation of the cerebellar surface were quantitatively analyzed. Computer controlled stimulus sequences were delivered to ventrolateral thalamus and evoked responses recorded from ipsilateral sensorimotor cortex in the cat. Threshold and excitability profiles were produced with an on-line computer, and their modification by cerebellar stimulation was determined. The results of electrical stimulation of the cerebellar surface were: (1) depressed excitability from paramedian lobule and lobulus simplex; (2) uniquely elevated thresholds from paramedian lobule; and (3) a profound and long-lasting depression of excitability following termination of lobulus simplex stimulation. In comparison with our anticonvulsant drug studies, these data suggest that cerebellar surface stimulation has a far greater capacity to control excitability and threshold responsiveness of thalamocortical systems. Cerebellar electrode placement and temporal pattern of stimulation appear to be important factors in the production of antiepileptic effects.