Stabilization of Contactor Servos by using Coulomb Friction

On the Compensation of Hysteresis Effects in Relay Control Systems by using Positive Hysteresis

Abstract: In this paper a technique for the compensation of the hysteresis effects in relay control systems using positive hysteresis non-linearity has been suggested. The instrumentation of these positive hysteresis characteristics with simple analogue computer components has been shown. An alternative compensation principle for relay control systems has also been proposed. The effectiveness of these compensation schemes has been observed with relay control systems set up in an analogue computer.

Analysis of Relay Servomechanisms

Abstract: Methods are developed for the transient and steady-state analysis of relay-type servomechanisms, with intermittently applied torque, inertia, viscous friction, dry friction, finite spacing of the controlling contacts, constant delay time in torque change, and stabilization by "flip-flop/' "front-lash," and anticipatory circuits. Solutions are obtained through representation of the motion of the servomechanism in the position-velocity or "phase" plane. In this plane, the discontinuous character of the driving torques, dry friction, delay time, finite contact spacing, and certain types of stabilizers, defines boundaries that are frequently straight lines. The boundaries divide the phase plane into a number of regions, within each of which the motion of the servomechanism is determinable by elementary means. Theorems and semigraphical constructions are developed for the rapid representation of the transient and steady-state motion in the phase plane, and simple constructions are demonstrated for converting the phase-plane plots to conventional time plots. Guided by phase-plane representations, exact mathematical solutions are obtained for a number of cases of interest. A method is developed for testing the physical significance of the tnathematically derived steady-state solutions. Finally, the techniques developed are applied to the comparative examination of several methods for suppressing "hunt ing" of the servo. The analysis indicates an anticipatory signal to be the most promising for control of torque application in a high performance relay servomechanism.

An Analysis of Relay Servomechanisms

Abstract: THE METHODS of analysis and synthesis of linear servomechanism loops have been developed to the point where they have become a common and useful tool. Comparable advances have not been made in the case of relay-type control although the latter is of great importance in many engineering fields. The reason for this failure is that the differential equations governing a relay-controlled system are nonlinear in nature and cannot be solved by conventional means. Nevertheless, it is possible to analyze such a system by accepting something less than a finite analytic expression for the solution of the governing differential equation. Application of Laplace transform theory to this problem yields the response expressed as a series of terms from which the system behavior may be found. The information obtainable in this manner indicates whether the system under consideration is stable or unstable and gives relations among the circuit parameters which must hold if the response of the system is periodic. This method is not restricted to cases of intermittently applied constant torque as in previous treatments but is applicable to any controlled object whose unilateral transfer function can be written, as for example a motor, a vacuum-tube circuit, or a complete servomechanism loop.