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Research Papers

Two Degree of Freedom Control Synthesis With Applications to Agricultural Systems

[+] Author and Article Information
Yangmin Xie

Department of Mechanical
Science and Engineering,
University of Illinois at
Urbana-Champaign,
1206 W. Green Street MC-244,
Urbana, IL 61801
e-mail: xie3@illinois.edu

Andrew Alleyne

Department of Mechanical
Science and Engineering,
University of Illinois at
Urbana-Champaign,
1206 W. Green Street MC-244,
Urbana, IL 61801
e-mail: alleyne@illinois.edu

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received December 3, 2012; final manuscript received March 7, 2014; published online May 28, 2014. Assoc. Editor: Hashem Ashrafiuon.

J. Dyn. Sys., Meas., Control 136(5), 051006 (May 28, 2014) (11 pages) Paper No: DS-12-1399; doi: 10.1115/1.4027157 History: Received December 03, 2012; Revised March 07, 2014

This paper presents a two degree of freedom (DOF) controller for combine harvester header height control (HHC). Fundamental limitations to the tracking and disturbance rejection bandwidth for feedback control designs exist in the HHC system due to the considerable actuator delay and underactuated and noncollocated mechanical design. In this work, we utilize H optimal control design to ensure closed-loop stability and robust performance, and augment the feedback loop with a feedforward control structure based on readily available global positioning system (GPS) information. The GPS provides anticipatory information of the field map elevation; albeit with noise, resolution limits, and latency. The elevation changes result in disturbances to the header height control problem and the feedforward controller uses the knowledge of the field to increase the overall disturbance rejection bandwidth. Simulation and experimental results illustrate the performance improvements resulting from the 2-DOF design over the stand alone feedback controller, which removes a long standing obstacle in increasing the harvesting productivity. Additionally, an error analysis examines the effect of uncertainties from system modeling and field map measurements on the system performance.

Copyright © 2014 by ASME
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References

Figures

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Fig. 2

IMC feedback and feedforward control

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Fig. 3

General feedback and feedforward control

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Fig. 4

Equivalent feedback for robust performance analysis

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Fig. 5

Uncertainty disk for feedback control

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Fig. 6

Optimal design for Q(s)

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Fig. 7

Closed-loop frequency response comparisons between experimental results and simulations

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Fig. 8

Performance limitations: (a) performance limitation by model uncertainty, (b) performance limitation by delay, and (c) performance limitation by combined effect

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Fig. 9

Block diagram of system with controller

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Fig. 10

Modified feedback loop with Smith predictor

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Fig. 11

Equivalent setup for H synthesis

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Fig. 12

Formulation of standard H problem

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Fig. 13

Magnitude plot of the sensitivity functions and inverse of the weighting functions

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Fig. 14

Comparison between magnitude plots form the ground profile to error with and without feedforward compensator

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Fig. 15

Deere S690 combine used in experiments

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Fig. 16

Performance comparison between feedback controller and 2-DOF controllers at 0.4 mph (0.64 km/h)

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Fig. 17

Performance of 2-DOF controllers at 4 mph (6.4 km/h)

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Fig. 18

Standard deviation of error of sandlot tests

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