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In the subject area of control theory, an internal model is a process that simulates the response of the system in order to estimate the outcome of a system disturbance. The internal model principle was first articulated in 1976 by B. A. Francis and W. M. Wonham [1] as an explicit formulation of the Conant and Ashby good regulator theorem. [2]
Digital model railway control systems are an alternative to control a layout and simplify the wiring and add more flexibility in operations. A number of control systems are available to operate locomotives on model railways. Analog systems where the speed and the direction of a train is controlled by adjusting the voltage on the track are still ...
The actuator is then controlled with a servo controller to control the torque or current of the motor. An outer-loop control then controls the torque provided to the pilot using a control loop around a force sensor. The control loading system must take in inputs from the simulator and pilot and provide outputs for the pilot and simulator.
Its name comes from the information path in the system: process inputs (e.g., voltage applied to an electric motor) have an effect on the process outputs (e.g., speed or torque of the motor), which is measured with sensors and processed by the controller; the result (the control signal) is "fed back" as input to the process, closing the loop.
The definition of a closed loop control system according to the British Standards Institution is "a control system possessing monitoring feedback, the deviation signal formed as a result of this feedback being used to control the action of a final control element in such a way as to tend to reduce the deviation to zero." [2]
A control loop is the fundamental building block of control systems in general and industrial control systems in particular. It consists of the process sensor, the controller function, and the final control element (FCE) which controls the process necessary to automatically adjust the value of a measured process variable (PV) to equal the value of a desired set-point (SP).
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The key feature of the Ward Leonard control system is the ability to smoothly vary the speed of a DC motor, including reversing it, by controlling the field and hence the output voltage of a DC generator, as well as the field of the motor itself. As the speed of a DC motor is dictated by the supplied voltage, this gives simple speed control.