Control unit

Control units are used to achieve a certain output variable despite disturbances and interferences in the input variable. Control units and factors are a constant part of our lives, whereas they appear in nature or are employed by humans. Already in ancient times people used irrigation systems with drains and inflows to ensure a constant water level. The use of a steam engine with a centrifugal governor by James Watt appears to be the origin of control system theory as part of engineering science. This centrifugal governor was connected to the drive of the steam engine (output) and the faster the engine was operating the more the governor closed a valve that was feeding the machine (input). Therefore, the output of the engine could be kept on a constant level without outside assistance.

Our active vibration isolators use control units as well. The to be achieved output is the total absence of vibration. On the simplified operation chart of the active vibration isolator the control unit is marked with a 2 and also includes an amplifier for the electric signal (see chart). Upstream is a sensor (1) and downstream is an actuator (3). The sensor detects vibration and the control unit puts an according signal through to the actuators. The control units of our active vibration isolators operate partially on an analog and partially on a digital basis. Analog control units (like the centrifugal governor by James Watt) check the input continuously, whereas digital control units just do a discrete time check, meaning the input is only measured at specific points in time. When choosing control units for active vibration isolation an analog control unit or a digital unit with a high rate of input checks is preferable to isolate against high frequency vibration reliably.

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