The priority valve is considered to be one of the critical parts of the hydraulic system used in mining equipment. This article analyzes the dynamic performance of a hydro-motor drive system using priority valve through system modeling and simulation. A typical hydraulic system of a mining equipment is considered for the analysis, where a stable source of flow is supplied to two hydro-motors through priority flow divider valve. Bondgraph simulation technique is used for the modeling of the complete system, which is validated experimentally. The influences of some key parameters on the transient response of the system have been studied through simulation. The work presented in this article forms the basis idea for the design and optimization of the priority flow control valve for a given application.

In this article, an improved fault isolation in the model-based fault detection and isolation (FDI) method is presented using parallely computed bond graph models. All component faults in a system may not be uniquely isolable. However, some faulty parameters' subspaces may be identified. One of the possible solutions as proposed in this article is to estimate parameters from the actual performance of the plant assuming a single fault hypothesis. Then incorporating the estimated values, all the parallel models are run on a single-core processor and their responses are compared with the healthy plant to identify the actual fault. In this respect, a typical hydro-motor drive system is considered for the FDI analysis, where a stable source of flow is supplied through a priority flow divider valve to two hydro-motors. A methodology for parametric fault isolation under single fault assumption with minimum measurements is discussed. Such method is capable to estimate the remaining useful life (RUL) of the faulty components of a system. The proposed methodology used for identifying the fault and estimating the RUL is simple enough to adopt it in industrial practices. Keywords Priority valve • Bond graph • Hydro-motor • Priority flow • Bypass flow • Fault detection and isolation (FDI) • Analytical redundancy relation (ARR) • Diagnostic bond graph (DBG) • Fault signature matrix (FSM) • Remaining useful life (RUL) List of symbols A sp Area of the valve spindle toward the main port A bp Area of the valve spindle toward the bypass port A pr Area of the valve spindle toward the priority port β f Generalized bulk modulus of the fluid D m1 Motor displacement rate of hydro-motor HM 1 D m2 Motor displacement rate of hydro-motor HM 2 D p Volume displacement rate of loading pump C Single-port energy storage capacitive elements d bp Diameter of the bypass port d pr Diameter of the priority port F sp Stopper reaction force on the valve spindle F ff Flow force on the valve spindle I Single-port energy storage inertial element J ld1 Load inertia connected with hydro-motor HM 1 J ld2 Load inertia connected with hydro-motor HM 2 K stf Stiffness of the fluid at the respective plenum K sp Valve spring stiffness K s Bulk stiffness of the fluid at the pump plenum K vp Bulk stiffness of the fluid at the valve plenum K bp Bulk stiffness of the fluid at the plenum of the bypass port K pr Bulk stiffness of the fluid at the plenum of the priority port K m1 Bulk stiffness of the fluid at the plenum of the hydro-motor HM1 K m2 Bulk stiffness of the fluid at the plenum of the hydro-motor HM2 K a Generalized bulk stiffness of the fluid M ld1 Angular momentum of the load connected with hydro-motor HM 1 M ld2 Angular momentum of the load connected with hydro-motor HM 2 P s Supply pressure P vp

It is well known that simple proportional, integral, and derivative control yields poor tracking performance due to the friction-and flow-related nonlinearities in electrohydraulic servo-systems. Nonlinear effects are more significant in proportional valve having deadband and non-matched ports with potential application in systems with complex ground friction in off-road vehicles or complex inertia loads in simulators meant for pilot training. A feedforwardbased controller has been designed here by performing a number of characterization experiments for achieving good tracking performance overcoming severe nonlinearities. An algebraic model of friction has been developed for including hysteresis beyond the static friction zone in a double-rod piston-cylinder arrangement. A proportional valve with nonmatched ports and large deadband has been characterized in terms of command signal to flow gains for each metered port and a leakage coefficient. Also, a dynamic model for the valve with embedded control has been constructed. All these models have been integrated together to predict the piston-motion dynamics. A simple theoretical analysis with a fixed command excitation revealed that following the initial transients a sustained oscillation over a constant mean piston velocity could exist for low pump pressure and valve damping due to the flow-motion coupling. The bandwidth and damping coefficient of the valve flow have been estimated through a comparison between the predicted and experimentally measured piston displacement variation with time. Besides evaluating the feedforward using the algebraic friction model along with assuming incompressible flow and negligible valve leakage, the predictions of the complete model were used to ascertain the proportional, integral, and derivative gains to be implemented in real-time control. Up to 0.5 Hz sinusoidal excitation, the proposed control revealed excellent tracking performance. Controls with only proportional, integral, and derivative and proportional, integral, and derivative together with feedforward exhibited noticeable phase shifts, respectively, from frequencies 0.0625 Hz and 0.6 Hz. Hence, the proposed controller can be useful in low-cost, low-power, precision applications up to 0.5 Hz input excitations.

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Directional control valves start, stop or change the direction of flow in compressed air applications. To understand the different applications of compressed air and how valves are used, one must first have knowledge of the kinds and types of valves used by industries. This paper studies local valve control of the electro-hydraulic system. The slow response of hydraulic control valve usually becomes the hold-up of whole system performance. Although fast valves (e.g. high-bandwidth servo-valves) are available, they are far more expensive than slow valves (e.g. proportional directional control valves). To improve the performance of proportional directional control valves, three different types of controllers are synthesized. Firstly, based on the pole zero cancellation technique, an open loop compensator is designed which requires the accurate valve dynamic model information; Secondly, a full state feedback adaptive robust controller (ARC) is synthesized, which effectively takes into account the effect of parametric uncertainties and uncertain nonlinearities such as friction force and flow force. Finally, an output feedback ARC controller is synthesized to address the problem of un measurable states. Keywords: valve, hydraulic device, Simulink.