Abstract
The paper is focused to design a robust and a simple fixed structure H ∞ control synthesis for an Electrohydraulic Servo System (EHSS) and comparing its performance with the conventional H ∞ controller and the classical proportional integral derivative (PID) controller. The precise position tracking of the piston load of EHSS system using classical PID controller is a difficult task due to some non-linear properties of EHSS and the dynamic behaviour of its parameters. The conventional H ∞ controllers also have constraints on gain ( H ∞ norm) for typical design requirement such as the speed of response, higher order, complex structure, control bandwidth, and robust stability. To overcome the above limitations, the proposed synthesis is formulated in the MATLAB. The proposed synthesis has fixed order and fixed structure and is also a linear robust controller. The control parameters of proposed synthesis are tuned using Genetic Algorithm optimization in MATLAB. Another advantage of this design is to use higher order complex shaping fillers to shape the close loop sensitivity S s and complementary sensitivity T s for the desired robust performance, without effecting the structure fixed of proposed synthesis. The order of the proposed controller is not affected by using the higher order complex weights transfer functions W s s and W T s on sensitivity and complementary sensitivity, respectively, whereas the structure of the conventional H ∞ controller becomes more complex due to higher order shaping weights. Model of the Electrohydraulic Servo System is validated experimentally, and results of proposed robust synthesis are compared with conventional H ∞ controller and the classical PID.
Highlights
Electrohydraulic Servo System (EHSS) are extensively used in industrial automation applications because of their small size to power ratios, fast response to input, reliability, ability to handle large force or torque and their continuous, intermittent, reversing, and stalled operation without damage
A non-linear adaptive control [7] and the design of indirect adaptive fuzzy control of EHSS [8] hold the valuable performance in position and velocity tracking. e normal practice is to use non-linear techniques to synthesize controllers for EHSS, whereas linear time invariant (LTI) model-based controllers are more practical because they have fewer complications
No work on fixed structure intelligent robust H∞ control of EHSS is presented yet. Another contribution shows that the objective function is optimized intelligently using Genetic Algorithm, where linear fraction transformation (LFT) objective function is formulated in MATLAB
Summary
Electrohydraulic Servo System (EHSS) are extensively used in industrial automation applications because of their small size to power ratios, fast response to input, reliability, ability to handle large force or torque and their continuous, intermittent, reversing, and stalled operation without damage. In case where system contains nonlinearity and system’s parameters have dynamic behaviour due to load conditions, the design of suitable controller is an issue To overcome these difficulties and for precise control of EHSS, various non-linear control strategies are proposed in literature. Ese frequency domain-based techniques were used for optimal and robust performance These conventional techniques have slowed their adoption in practical word because of many constraints, such as complex design, speed of response, control bandwidth, disturbance rejection, and robust stability [19], where controllers with fixed order and fixed structure are more practical. Since the design of the proposed controller is based on intelligent H∞ optimization and has all abovementioned advantages, the researchers have focused on the design of fixed structure-based robust control systems for many practical applications.
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