New Methods in Modeling and Control of Modern Electrohydraulic Systems
thesisposted on 29.10.2016 by Sameh N. Alkam
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
The concept of the independent metering valve (IMV) is a new technology that allows more flexibility in terms of control and energy saving compared to traditional valves, because each inlet or outlet from the hydraulic cylinder to the pump or to the tank is independently opened or closed. In this work, the IMVs are modeled, and analyzed, and its digital control is discussed. Valve control is studied in terms of sensitivity, physical limitations, work port pressure, and the cavitation condition. This work introduced the sixth mode which is the High Side Regeneration Retraction that was not addressed by previous work, besides introducing a more systematic way of calculating the equivalent pressure and the pressure supply set point. Continuously variable modes is then introduced and analyzed. The idea behind it is using three valves instead of two to control the system, and this will solve many of the problems inherent by the discontinuity of flow when only two valves are used. The three modes are: powered high side regeneration extension (PHSRE), the powered low side regeneration retraction (PLSRR), and the powered low side regeneration extension (PLSRE). The contribution of this paper to this field was introducing a fourth CVM which is the powered high side regeneration retraction mode ( PHSRR), and deriving all the equation related to it. Control of the IMV systems require highly sophisticated algorithms, and currently some sort of relation is found among the valves openings in order to send a command signal. This work uses the simple PID controller for each valve without any coupling among them. Finally, an experimental approach is proposed and tested for modeling hydraulic systems without the need to know the complicated dynamics of the system.