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Ch60-I044963.fm Page 297 Thursday, July 27, 2006 9:00 AM
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Thursday, July 27, 2006
Ch60-I044963.fm
9:00 AM
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WIRELESS DATA TRANSFER APPLIED ON
HYDRAULIC SERVO

1
1
O. I. Karhu , T. K. Virvalo , and M. A. Kivikoski 2
'institute of Hydraulics and Automation, Tampere University of
Technology, P. O. Box 589, 33101 Tampere, Finland
institute of Electronics, Tampere University of Technology,
P. O. Box 692, 33101 Tampere, Finland

ABSTRACT
In hydraulic servo systems, especially in mobile applications, there might be great advantages if there
was no need for wiring between actuators and users and/or a main controller. Most of the wires in
hydraulic servo systems carry measurement and control signals. Therefore, wireless transfer of
feedback signals and output of the controller is studied. Experimental results are shown and the
performance and possibilities of wireless data transfer in these kinds of control applications are
discussed.

KEYWORDS
wireless, data transfer, latency, closed-loop, control, hydraulic servo

INTRODUCTION

Wireless closed-loop control has been studied by a couple of different groups in recent years. These
projects are discussed by Horjel (2001), Ploplys & Alleyne (2003), Ploplys (2003), and Kawka &
Alleyne (2004). The majority of research has been carried out using PC hardware, which is not an
optimal solution for most applications. Many standards for wireless communication are designed for
fast file transfer instead of low latency. In this research the objective is to find a solution that makes it
possible to achieve a minimal sampling and control interval.

EQUIPMENT

The equipment used in the experiments is shown in Figure 1. It consists of two units, the controller
unit and the hydraulic unit. Everything in the hydraulic unit is either mounted to the hydraulic test rig
or located very near it. The controller unit is located a couple of meters away from the hydraulic unit.