Equal coded digital hydraulics in low temperatures using water-glycol solution

• Main Author: Grönholm, Joni
• Other Authors: Automaatio ja hydrauliikka – Automation and Hydraulic Engineering, Teknisten tieteiden tiedekunta - Faculty of Engineering Sciences, Tampere University of Technology, Linjama, Matti, Siivonen, Lauri
• Format: Master Thesis
• Language: English
• Published: 2018
• Subjects: Automaatiotekniikka; Arctic
• Online Access: https://trepo.tuni.fi//handle/123456789/26664

In this thesis work, effects of arctic temperatures for digital hydraulic system was researched. Hydraulic medium was environmentally friendly and additive free 50 wt% water-glycol solution. Dynamics of on/off valves, steady-state properties of on/off valves and system’s hydraulic natural frequency were qualities under inspection. These qualities were chosen as they are key qualities for digital hydraulics. On the other hand, this research was conducted to determine usability of commercially avail-able on/off valves, when controller applying multi-valve pulse modulation and multi-valve pulse frequency modulation is used. Another objective was to find out, which method might be preferable to compensate the changing properties of system to accuracy of control. Research was conducted as simulation and experimental study. Simulations were minor part of the research and were performed to validate the implemented controller. Experimental study was done using a hydraulic system that composed of equal coded digital valve system and a hydraulic cylinder that was used to move a mass in horizontal direction. Experimental research can be separated to two different parts. In first part, changes in system properties were investigated in temperature interval of ˗20°C…30°C. Second part of the experimental research was testing the controller in different temperatures. Controller was tested with three different cylinder strokes (15 mm, 150 mm and 300 mm) in three different temperatures (˗20°C, 0°C and 30°C). Results of this research indicate that dynamics of on/off valves slows down and volume flow in steady-state conditions decrease in low temperatures. Hydraulic natural frequency of the system increased in low temperatures. Results attained using the controller were comparable to results achieved in reference study. This indicates that commercially available valves are usable in multi-valve modulation control. In addition, results attained in low temperature using the controller suggest that correct way to increase control ...