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ABE 463 Electrohydraulic Systems. Feedforward-PID Controller. Basic Concept of FPID. The feedforward loop often create s basic control signals in terms of an inversed system transform function.
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ABE 463 Electrohydraulic Systems Feedforward-PID Controller
Basic Concept of FPID The feedforward loop often creates basic control signals in terms of an inversed system transform function. The feedback PID loop often used to correct the control signal in response to identified control error for improving tracking accuracy.
Dynamic Behaviors of E/H System • Noticeable timedelay • Deadzone and saturation • Asymmetric nonlinear flow gain • Hysteresis
The Need for FPID Controller • Design of FPID controller can be accomplished in three steps: • feedforward loop design, • PID loop design, and • FPID integration • In most cases, the inverse function of plant dynamics is selected as the transfer function for the feedforward loop. • The feedforward loop can also include an inverse function of the disturbances acting on the plant.
Modeling of Typical E/H System System model with incompressible fluid assumption for position control.
ZN Frequency Response Tuning Frequency response test is also called relay test: It starts tuning the proportional gain until the closed-loop controller becomes critically stable, and set this gain as the ultimate gain Ku, and the corresponding oscillation frequency is set as the ultimate time period Tu. ZN PID Frequency Response Tuning Parameters
Discussion • The frequency of input signal often have noticeable impact on tracking accuracy; • Nonlinear compensation can improve tracking accuracy; • Feedback signal often needs to be filtered. • The design of the FPID controller can be accomplished in three steps; feedforward loop design, PID loop design, and FPID integration