The article directs to improve the accuracy of output quantities of complex managed objects, including cochlear feeders in the mining-ore industry. The aim of this work is developing of adaptive minimax criterion that provides virtually unchanged accuracy determination of ratio of solid/liquid under the conditions of action of complex and prolonged disturbances. The goal is solved by solving the problems managed object analysis, theoretical description of minimax criterion, substantiation and analysis changes the parameter defining criterion, development the algorithm of realization of criterion and valuation of output parameter of object. The problems were solved by methods of analysis, theory of automatic control, physical modeling the theory of error, the theory of sensitivity. It was got analytical dependence for determining the optimal duration averaging the output value (Minimax),it was substantiated decisive criterion setting, it was found the connection velocity of change of the output value (vacuum) with the duration of the transitional process, it was obtained accordance the duration of intervals averaging ranges of variation the output value in transitional process, it was appreciated obtained minimax, it was elaborated the algorithm of discovering the ratio of solid / liquid using adaptive minimax criterion, it was made valuing of determining the initial value. Minimax criterion includes 14 cycles of working cochlear feeder with length of 1.56 sec. The best results of formation the output value correspond to the minimum initial duration of averaging 1.56 with a further increasing it of the same quantity accordingly velocity of change of the pulp dilution, reaching minimax 21,84 sec. Then increase the duration averaging is not necessary. The discovered conditions of realization minimax criterion provide high accuracy of the output value in the most complicated exploitation conditions. The adaptive minimax criterion realizes automatically by controller. This can significantly to increase the accuracy and effectiveness of functioning of the systems automatic control of technological process.