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Novel fine positioning method for hydraulic drives utilizing on/off-valves

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Original languageEnglish
Title of host publicationProceedings of the BATH/ASME 2018 Symposium on Fluid Power and Motion Control FPMC2018
Subtitle of host publicationBath, UK, September 12-14, 2018
Number of pages10
ISBN (Electronic)978-0-7918-5196-8
Publication statusPublished - 14 Sep 2018
Publication typeA4 Article in a conference publication
EventBATH/ASME Symposium on Fluid Power and Motion Control - Bath, United Kingdom
Duration: 12 Sep 201814 Sep 2018


ConferenceBATH/ASME Symposium on Fluid Power and Motion Control
CountryUnited Kingdom


This paper studies a novel on/off-valve-based fine positioning method for hydraulic drives. The method proposed utilizes four on/off-valves in independent metering configuration to reach good positioning accuracy and low power losses. Previously, servo valves have been used in precise position control of hydraulic double acting cylinders. Another approach uses on/off-valves, which are typically driven by using pulse width modulation (PWM) or, if there are parallel connected valves, pulse code modulation (PCM). Typically, both cylinder sides are modulated simultaneously. The new concept proposed uses a cylinder model to calculate a correct opening sequence for the on/off-valves, such that the target piston position is reached. The method proposed modulates single cylinder side at a time in order to achieve small piston position step sizes. Despite relying on the modelled compressibility of the fluid, the method presented requires no knowledge about the bulk modulus of the fluid. It is enough that the bulk modulus of the fluid in both cylinder chambers can be assumed equal. The paper includes the design of the control method, a simulation study proving the validity of the method, and an experimental part investigating the performance in practice. The experimental results show a positioning accuracy of +/- 1 μm with an on/off-valve-based hydraulic drive, the maximum velocity of which is 0.7 m/s.

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