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.

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.

This paper focuses on the recent advancements made in hydraulic motor. Various parameters of hydraulic motors are studied and their performance with respect to the parameters is studied. nonlinear dynamics model, Gear motor, swash plate motor, radial piston hydraulic motor etc have been examined. Fault diagnosis, dynamic vibration, frictional analysis and speed variation are some of the issues which are being discussed in the paper. The performance results showed that the amplitude of vibration increased with the increase of output torque of the water hydraulic motor and the hydraulic motor with planetary gear train has the advantages of large unit volume displacement and small flow rate fluctuation ratio. Some measures were proposed to improve the low-speed stability of the hydraulic motor. Keywords-hydraulic motor, nonlinear dynamics, hydraulic spring

Nowadays with the high fuel costs, the stress for energy saving and green emission of construction machineries, while not sacrifice of the operating performance, safety and dependableness, particularly for hydraulic excavators (HYEXs), are extremely exaggerated. As a result, electro-hydraulic actuators (EHA), that is promoted and with success applied to industry, is recently introduced to HYEXs. The aim of this paper is to propose a new style of excavator - electrical excavator (ELEX) - with energy saving capability using the EHAs. Each of the hybrid actuators is driven by an electrical motor/generator for retrieving a potential energy or a kinetic energy at the time of lowering or slewing stoppage of the excavator. An excavator having a hybrid boom system (HBS) is analyzed. Finally, operating efficiency and energy consumption of the projected excavator area unit are clearly studied. Keywords: Hydraulic excavator; electric excavator; electro-hydraulic actuator; control

The hydrostatic transmission energy-saving system is proposed in this paper. The efficiency of the primary power source improves by system. The system is energy regenerative, highly efficient even under partial load conditions. It can work in either a flow or pressure coupling configuration allowing it to avoid the disadvantages of each configuration. The displacement variation in the secondary unit was reduced, increasing the uses of several types of hydraulic pump/motors. The proposed system was modeled based on its physical attributes. A hierarchal control system was implemented and focused on the design of an adaptive fuzzy sliding mode control for speed control of the secondary unit. The energy utilization and the influences on the energy-recovery potential of the system were analyzed.Keywords-Hydrostatic drive, energy saving system, Regenerative systems