A novel hydromechatronics system towards: micro-independent metering.

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

Numerical and experimental investigation of the metering characteristic and pressure losses of the rotary tubular spool valve.

This paper presents the results of numerical and experimental performance evaluation of the rotary tubular spool valve. The aim of this work is to develop further the novel design of the tubular spool valve by confirming experimentally the validity of the simulation model and its results, thereby proving the valve's potential to represent a feasible and more efficient alternative to conventionally used translation spool valves avoiding the use of two stage valve configurations. In this research the valve performance is assessed through numerical modelling and experimental studies of its metering characteristic and pressure losses. This paper demonstrates that the used valve model yields the results, which agree well with the conducted experimental study. Therefore, validation of the numerical model and the modelling results in the form of theoretical valve characteristics was accomplished. Firstly, the paper presents details of a numerical approach employed to evaluate valve performance and then analyzes the simulation results. Next, the valve performance is experimentally validated by testing a prototype valve on a hydraulic test rig capable of measuring the volume flow rate, pressure levels in up- and downstream lines of the valve across the entire spool angular stroke. Initially, average discrepancies between modelling and test results were 52.46% for the metering and 82.78% for the pressure loss characteristics. Correcting the model geometry aimed at eliminating differences between the valve model and the practically used prototype-test rig system enabled reduction of the error between experiment and modelling by 47.75% for the pressure loss function. This confirmed validity of the simulated characteristics of the valve. The benchmark comparison of pressure losses confirmed average 71.66% energy dissipation reduction compared to the industry-available analogue valve

A dynamic model and performance analysis of a stepped rotary flow control valve

The hydraulic independent metering (IM) is an advanced actuator driving technique that allows the implementation of advanced control algorithms or methods. The main concept of IM is to control hydraulic actuators ports, which are the meterin and meter-out, separately. In this paper, a novel stepped rotary type valve has been developed for embedding in hydraulic independent metering systems, instead of conventional types such as poppet and spool. The insertion leads to developing different and novel control techniques, which require a software in loop and hardware in loop simulation of the proposed system. The paper explores the dynamic representation of this valve and defines its own performance limitations. This includes the development of a linear model comprising its two main sub-parts which are the stepper motor and the rotary orifice. Consequently, the linear timeinvariant methods are used to explore the performance of the valve by considering the effect of different parameters namely the pressure drop, friction coefficient, damping coefficient and bristle coefficient