Investigations of the operation of the automatic load stabilization system of the unit which controls the excavator section of the Yurkovskii conveyer bridge have shown that the load regulator is not operating satisfactorily. The coefficient of demand efficiency (the ratio of the maximum value to the mean) of the power expended in the motor, the forces in the guy rope suspension cables and in the metal structures of the rotor arm arehigher during automatic operation than when controlled manuaIly ( Figs. 1 and 2). This means that the regulator is causing oscillations in the system, which are dangerous because they might cause fatigue phenomena in the structure. 510

'blat UDC [622.2 ~ 622.6]:621.879 In determining the optimum level of automation of rotor excavators it is of great value to assess the mechanical constructions of these machines from the viewpoint of suitabiIity for automation. This may be done by analyzing their "controllability."By the controllability of a system we mean its ability to process input control signals to the required degree of accuracy; in other words, controllability is the ability of the controlled system to minimize deviations of its output parameter due to the action of disturbances.Quantitatively, controllability can be represented by a coefficient r given by the formulas proposed in [1, 2]:where r is the coefficient of controllability, x is the mean value of the equivalent disturbance, and ~ is the mean deviation of the output parameter from its set value.From (1) and Fig. 1 it follows that in any conditions the coefficient of controllability must lie between 0 and 1:0 < r < 1. The value r = 1 means that the system is completely controlled, i.e., it can reduce to zero the effects of disturbances in the output parameter y (t); the value r = 0 means that the system is completely uncontrolled, i.e., the energy of deviation is equal to the energy of disturbance. In practice the achievable effectiveness of control will always be less than the value given by (1).The controllability of a system characterizes its property of filtering out random disturbances x (t) in such a way that the mean deviation of the output parameter of the system e(t) will be as small as possible. We can calculate the parameters of such a filter by using a theory developed by Wiener. For minimum error, we havewhere 0xy is the pulse characteristic of a Wiener filter.Knowing the transfer function of the controlled system, we can express 0xy in the form of simplified formulas.Thus the coefficient of controllability r depends on the inertia, variability, pure delay time, and other factors governed by the structural features of the machine, regarded as controlled systems. Therefore, before constructing ) mCt} Fig. 1. Structural scheme of controlled system. an automatic control system for any machine, we must study the machine for controllability in order to determine the degree of applicability of automation.To illustrate the above considerations, we will give the results of an investigation of the controllability of the RS-1200 rotor excavator of the Zvenigorod open-cut coal mine.A rotor excavator, regarded as a controlled system, is a complex electromechanical system consisting of the rotor drives and slewing drives, which mutually interact via the excavated rock, together with the hoisting drives and the UkrNIIProekt, Kiev.

A. A Preobrazhenskiiand I. S. Mandel'blat UDC 622.232As automatic control of mining machinery becomes more and more sophisticated, the automatic systems are getting more and more complex, their structure is becoming more and more varied, and the number of control operations executed by a system and the number of elements in a system are increasing. We therefore have to take steps to increase the working reliability of the apparatus (by providing complete or partial reserve systems, using high-reliability elements, etc.).In assessing various automat/on schemes from the viewpoint of efficiency, together with other indices (rapidity and accuracy of action, cost, etc), we need a combined index which will provide an objective estimate of the constructional complexity of the apparatus, its structure, and its reliability, i.e., an index which will reflect the convenience of the apparatus in use. Naturally, multifunctional automation systems can reasonably be more complex than very simple systems which process a small number of control signals.