Because of the throttling loss of the control valves and the overflow loss in the frequently accelerating and decelerating motion with a large inertia, the swing system of a hydraulic excavator has a high energy consumption; also, it has a poor controllability. To solve these problems, this paper proposes flow matching with combined control of the pump and the valves and an independent metering method for the swing system of the hydraulic excavator. The inlet pressure and the outlet pressure of the hydraulic motor can be controlled independently. With combined control of the pump and the valves, the flow rate can match the rotational speed of the hydraulic motor so that the overflow loss is avoided. Furthermore, we also develop a simulation model consisting of the mechanical structure of the hydraulic excavator with multi-body dynamics and an electrohydraulic system for analysing the feasibility of this swing system, and the simulation results demonstrate that this system works smoothly. After using the presented control strategies, the results of experiments show that the energy efficiency is improved and that the system can reduce the throttling loss and can obviously suppress the swing vibrations.
A first step is presented toward a simulation tool for shared space zones, including all three prevailing individual modes of transport: cars, bicycles, and walking. Unlike on conventional roads, the behavior in shared spaces cannot be modeled by following a predefined path and strictly obeying traffic rules because the architectural design allows for many more degrees of freedom. Therefore, the research focused on two main aspects: finding a path for each individual and handling potential conflicts with other individuals. A simulation tool is needed because many urban planners see shared space as a modern design concept for busy urban roads. A growing number of cities are interested in experimenting with shared space zones but are uncertain about safety issues and the effectiveness of the design. Although mature simulation tools exist for conventional road designs, no such tool is available for shared space designs because of the added degrees of freedom in movement and more-complex social interactions. To tackle these problems, an infrastructure model was created to help all agents find a path to their destinations. A separate system for handling conflict detects when two agents, following their individual paths, might collide. Game theory is used to resolve these conflicts by maximizing a utility function for different strategies. First results give a preliminary assessment of the functionality of the proposed simulation model for shared space zones and its calibration that uses real trajectories from an existing shared space.
Hydraulic axial piston motor is one of the fundamental components in hydraulic systems; it is widely used in engineered machine, especially in high-power drive or reciprocating motion, such as hydraulic excavator. For hydraulic axial piston motor efficient planning, in addition designing and controlling are required for system operating safety and efficiency. Simulation delivers an advantage over analytical approaches and allows better understanding of the motor performance. For multi-piston hydraulic motor, one of the simulation methods, distributed parameter model, could analyze the detailed performance in each piston chamber. Therefore, in this study, we investigate the characteristics of hydraulic axial piston motor by setting up a distributed parameter model based on physical prototype, which includes mechanical–hydraulics coupling process. The effects of the dynamic pressure inside the piston chamber, the fluidic compressibility and other related parameters are considered in the coupling process. At the same time, the distributed parameter model of hydraulic axial piston motor was used in the simulation model of hydraulic excavator. The results indicate that in two-way hydraulic axial piston motor, the valve plane should adopt symmetrical structure, and silencing groove set should be put on both ends of the valve plane slots, which could reduce pressure ripple and overshoot in the piston chamber. Furthermore, the torque characteristics are highly affected by the clearance between the piston and the cylinder bore. Through this research, we may have a better understanding about the mechanism of output torque fluctuation in hydraulic axial piston motor, and the pressure ripple and overshoot in the piston chamber due to through-flow area discontinuity between the silencing groove and the ends of the valve plane slots. The model is verified using a nine-piston hydraulic motor in hydraulic excavator.
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