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Research Papers

Simulation and Experimentation of a Precise Nonlinear Tracking Control Algorithm for a Rotary Servo-Hydraulic System With Minimum Sensors

[+] Author and Article Information
M. H. Toufighi

e-mail: toufighi@alborz.kntu.ac.ir

S. H. Sadati

e-mail: sadati@kntu.ac.ir

F. Najafi

e-mail: fnajafi@guilan.ac.ir

A. A. Jafari

e-mail: ajafari@kntu.ac.ir
K. N. Toosi University of Technology,
Faculty of Mechanical Engineering,
Vanak Square, Mollasadra Street,
Tehran 19991, Iran

Contributed by the Dynamic Systems Division of ASME for publication in the Journal of Dynamic Systems, Measurement, and Control. Manuscript received May 23, 2011; final manuscript received April 3, 2013; published online August 23, 2013. Assoc. Editor: Robert Landers.

J. Dyn. Sys., Meas., Control 135(6), 061004 (Aug 23, 2013) (14 pages) Paper No: DS-11-1161; doi: 10.1115/1.4024799 History: Received May 23, 2011; Revised April 03, 2013

The dynamics of hydraulic systems involves slow and fast modes. These modes are associated with the mechanical components and those involving fluid flow, respectively. As such, controllers for electro-hydraulic servo systems (EHSS) can be designed and analyzed using singular perturbation theory. In this paper, a singular perturbation control (SPC) algorithm is proposed and investigated on a rotary EHSS modeled based on a two-time-scale behavior of the system. For modeling, the components of the hydraulic system, specifically the nonlinear model of the orifice in servo valve, are modeled. A mathematical modeling and nonlinear control analysis that validated by experiment is presented. The controlled system with the SPC algorithm tracks a fairly smooth trajectory with very small error. As well, the control algorithm is successfully verified by experiment as the main contribution of the paper. In addition, this is robust to variations in the hydraulic fluid bulk modulus such that only its nominal value is sufficient. Furthermore, the proposed control design will not require derivatives of the control pressures and any output acceleration feedback. Hence, it can be implemented easier in the real system setup. The controller design approach addresses the nonlinearities of the rotary EHSS. The parameters of the real system model are experimentally identified using the continuous recursive least square method.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Circuit diagram of the electro-hydraulic servo-actuation system

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Fig. 2

Experimental setup of the electro-servo- hydraulic system

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Fig. 3

Physical diagram of the two-stage electro-hydraulic servo-valve (Pc1 and Pc2 are measured values)

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Fig. 5

Inputs to valve and outputs from the real system in experimental setup for parameter identification

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Fig. 4

Simulation plan and system identification algorithm

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Fig. 12

Real angular position responses to the sine reference with 1 rad amplitude and 2π rad/s frequency with SPC controller

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Fig. 13

Real angular position responses to the sine reference with 1 rad amplitude and 3π rad/s frequency with SPC controller

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Fig. 14

Real angular velocity responses to the displacement sine reference with 1 rad amplitude and π rad/s frequency with SPC

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Fig. 9

Block diagram of the SPC control design

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Fig. 8

Diagram of actual angular velocity and that obtained from identification and modeling, (a) for input frequency 2π (rad/s), (b) for input frequency 3π (rad/s)

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Fig. 7

Convergence of some parameters identification, (a) w1, (b) p1

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Fig. 6

Effect of input noise on valve area opening parameter

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Fig. 10

Experimental model of SPC algorithm in MATLAB

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Fig. 11

Real angular position responses to the sine reference with 1 rad amplitude and π rad/s frequency with SPC controller

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Fig. 15

Real angular velocity responses to the displacement sine reference with 1 rad amplitude and 2π rad/s frequency with SPC

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Fig. 16

Real angular velocity responses to the displacement sine reference with 1 rad amplitude and 3π rad/s frequency with SPC

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Fig. 17

Real valve input for the displacement sine reference with 1 rad amplitude and 3π rad/s frequency with SPC controller

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Fig. 18

Real load pressure for the displacement sine reference with 1 rad amplitude and 3π rad/s frequency with SPC controller

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Fig. 19

Real angular position responses to the sine reference with 1 rad amplitude and π rad/s frequency, comparing PID and SPC

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Fig. 20

Real angular position responses to the sine reference with 1 rad amplitude and 3π rad/s frequency, comparing PID and SPC

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Fig. 21

Real angular position responses to the sine reference using various amplitudes and frequencies with SPC controller

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Fig. 22

Real control input signal to the valve for the sine reference based on position reference of Fig. 21 with SPC controller

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Fig. 23

Real angular velocity responses for the sine reference based on position reference of Fig. 21 with SPC controller

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Fig. 24

Real load pressure for the sine reference based on position reference of Fig. 21 with SPC controller

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Fig. 25

Angular position error to the sine reference with 1 rad amplitude and 3π rad/s frequency for the SPC controller b = β/βnom = 0.1

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Fig. 26

Angular position maximum errors to the sine reference with 1 rad amplitude and 3π rad/s frequency for the SPC controller with respect to b = β/βnom

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