IMPROVING THE OPERATION ACCURACY OF A POWER SHOVEL BY ADJUSTING ITS CONTROL SYSTEM

The authors propose a method of adjusting the working mechanism control system for the previously developed mathematical model of the working mechanism of a Chetra EGP-230 power shovel, supplemented by dynamic characteristics in operation, which allows to evaluate the accuracy of the work performed taking into account cutting forces. As a method of making adjustments, adaptive control methods have been chosen, since only they can allow to actively influence the process of digging, taking account of continuously changing working conditions. The control process is considered for a flat model of the working mechanism without any considerations of a turntable, since adaptive control is introduced only when digging, in order to prevent excessive burial of the working mechanism bucket. Among all the adaptive control methods, the authors have chosen control methods for the moving average, since they include information on the last few measured parameters, which provides for the most efficient corrections. Several formulas have been considered by which corrections in the working mechanism control system can be calculated, and an accuracy control factor has been proposed for evaluating the effectiveness of the control operations. For these formulas, the proposed method of making adjustments has been tested in a number of cases: with different laws of distribution of the measured value; with different permissible deviations of the measured value; with the introduction of a systematic error of the measured value; and with changed amounts of measurements. The authors have also evaluated the control effectiveness according to the quality management method described in the GOST R 50779 series. Basing on the experiments, the authors have shown that the proposed method of making adjustments in the working mechanism control system of a power shovel does not decrease the digging accuracy and a non-negative result can be obtained for any digging process. The introduction of control is most effective with a relatively small number of digging iterations (no more than 30); in this case, the selected control method, on the average, improves the adjusted position of the cutting edge by 15...25% as compared with the value obtained without introducing the control operations.