Electrohydraulic servoniechanisms are used in control systems requiring a rapid response

Chapter 0, Problem P9.8

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Electrohydraulic servoniechanisms are used in control systems requiring a rapid response for a large mass. An electrohydraulic servomechanism can provide an output of 100 kW or greater [17]. A photo of a servovalve and actuator is shown in Figure P9.8(a). The output sensor yields a measurement of actuator position, which is compared with Vm. The error is amplified and controls the hydraulic valve position, thus controlling the hydraulic fluid flow to the actuator. The block diagram of a closed-loop electrohydraulic servomechanism using pressure feedback to obtain damping is shown in Figure P9.8(b) [17, 18]. Typical values for this system are T = 0.02 s; for the hydraulic system they are w2 = 7(2-n-) and 2 = 0.05. The structural resonance coy is equal to 10(27r), and the damping is Ci = 0.05. The loop gain is KAKXK2 = 1.0. (a) Sketch the Bode diagram and determine the phase margin of the system, (b) The damping of the system can be increased by drilling a small hole in the piston so that 2 = 0.25. Sketch the Bode diagram and determine the phase margin of this system.