A novel hydromechatronics system towards: micro-independent metering.

Abstract

This thesis presents the outcome of an investigation into the development of an existing hydraulic control system known as Independent Metering towards Micro-Independent Metering (MIM). The Independent Metering system uses a different configuration of the connection between the main elements of the hydraulic systems when compared to a traditional hydraulic circuit arrangement. These elements are pump, tank, and actuator. In a conventional control valve, meter-in connects pump flow to one side of the actuator, while meter-out connects the other side of the actuator back to the tank, these metering features are physically linked. With Independent Metering, these metering features are separated such that they can be independently controlled with a potential resultant reduction of energy losses, improved controllability, but with the increased complexity of the control system. In a conventional Independent Metering system, a spool, poppet or cartridge valve is generally utilised. However, in this research, a new stepped rotary flow control valve is used for the development of a novel configuration that also meets the rules of Independent Metering. The use of this valve alongside the electronic driving technique micro-stepping, commonly used in electronically controlled electrical drives, improved the system controllability by introducing a smoothing operation in the hydraulic system. This resulted in the new Micro-Independent Metering algorithm which is one of the main contributions to knowledge in this research. To develop the MIM system, the Model-Based Design technique including the system analysis, modelling and simulation, software-in-the-Loop (SIL) simulation, and the hardware-in-the- Loop (HIL) test, are used. Mathematical model and performance analysis of the valve were conducted in this research. The multi-step response analysis was used to evaluate the dynamical performance of the valve. This indicated that the micro-step driving technique is more suitable for driving the valve as it reduces the effect of the transient response due to friction, while increasing the resolution. Root Locus Analysis (RLA) was used to study valve stability and the performance limitations. The RLA demonstrated the effect of key parameters on the valve operation. For example, the study show that the valve starts losing stability when the applied pressure drop exceeds 35 MPa. A new algorithm was developed to formulate and apply the rules of the MIM system. The algorithm includes an operational modes selection procedure, valve conductance calculation procedure, anti-cavitation procedure, and close value detection (CVD) procedure. The proposed CVD determines the stepper motor position based on a predetermined vector selection.