The paper analyses the possibility to replace the hydraulic and mechanical
parts of a hydraulic position servo with a real-time simulation model. The
aim is to test the controller hardware against the simulation model that in
cludes the dynamics of the servo system as well as the feedback sensors and
amplifier card. The requirements caused by this hardware-in-the-loop (HIL)
approach are analyzed. A special attention is paid to the correct modeling
of incremental encoders that are widely used as a feedback sensor. Experim
ental results show that there is no remarkable difference between the respo
nses of the real system and HIL model and so the HIL model can replace the
real system. (C) 2000 Elsevier Science B.V. All rights reserved.