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Friction Characteristics of a Cylinder Based on a Bridge-Type Pneumatic Energy-saving Circuit
Hongwang Du,Wei Xiong,Zhong’ai Jiang,Qiu Li,Lu Wang 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.1
A bridge-type energy-saving circuit is a new type of pneumatic system that uses four on-off valves tocontrol the inlet and exhaust of two cylinder chambers. It saves energy through the open-and-close sequence of thefour control valves. Cylinder friction is the key factor in accuracy and stability of the bridge-type pneumatic energysavingcircuit. This paper focuses on research of the circuit’s friction characteristics. Based on friction theory andthe classic Stribeck model, a composite dynamic friction model of a cylinder in a circuit system is established, anda cylinder friction test platform is constructed. The Nelder-Mead algorithm is used to identify static parametersof the model through the relationship between friction and velocity while the piston is moving. Friction modelverification with error analysis is achieved by comparison with the traditional friction model. Experiments withthe energy-saving circuit under certain conditions are carried out to illustrate the effectiveness of the compositedynamic friction model. Finally, compared with existing friction model, the validity of the model is proved to beapplicable to different working conditions.
A Nonlinear Dynamic Optimization Algorithm of a Novel Energy Efficient Pneumatic Drive System
Hongwang Du,Wei Xiong,Wei Liu 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.5
A standard pneumatic system is usually controlled by a 5/2 directional control valve in which compressed-air utilization rate is low. To solve the problem, scholars have proposed a bridge pneumatic circuit controlled by four switch valves that uses expansion energy of compressed air to do work. The key to this bridge circuit lies in the accuracy and speed of on-off sequence of the valves. To realize this goal, we study dynamic optimization control of the circuit and establish an optimal valve opening and closing time-sequence control model with a continuous-discrete time differential algebraic equation on the base of the dynamic characteristics of the pneumatic drive system. We use the direct method in modern optimal control theory to solve the problem. Because the model has the characteristics of more equality constraints, lower freedom of variables, and a sparse structure, we use the simplified space sequential quadratic programming algorithm and interior-point methods for computation and analysis so that the process optimization and partial-differential equations are solved simultaneously. To improve the precision and the speed of solving the derivative during the solution-optimization process, the derivative information is obtained with a combination of symbol and numerical automatic differentiation. By analyzing the efficiency of the two algorithms, the interior-point method was proved to be more suitable for use in obtaining the sequence. Finally, the experimental results were realized and showed that our contribution builds a good foundation for the energy-saving research of pneumatic systems.
Hongwang Du,Hancong Xu,Jialong Li,Zhanpeng Zhou 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11
The thermal load in the piston head is becoming heavy with the application of supercharging technology. This makes the piston cooling become more challenging to ensure the reliability of the piston. In this study, an oil-injection cooling process in a medium-speed Vtype diesel engine is numerically investigated. The simulations are performed for the direct coupling of the piston head structure and the two-phase flow in the cooling gallery. The effect of the flow pattern on heat transfer characteristics during the whole process is discussed. The results reveal a series of the flow characteristics including thrown flow, interrupted flow, wall impingement, oil oscillating and sedimentation during the reciprocating movement of the piston and the flow characteristics become more obvious with the increase of the engine speed, but the cooling oil is more widely distributed in the oil gallery due to more intense oscillation. After multi-cycle calculations, the flow characteristics of the cooling oil and the heat transfer characteristics of the piston both have a certain periodicity.
A Novel Globally Adaptive Load-Balanced Routing Algorithm for Torus Interconnection Networks
Hong Wang,Du Xu,Lemin Li 한국전자통신연구원 2007 ETRI Journal Vol.29 No.3
A globally adaptive load-balanced routing algorithm for torus interconnection networks is proposed. Unlike previously published algorithms, this algorithm employs a new scheme based on collision detection to handle deadlock, and has higher routing adaptability than previous algorithms. Simulation results show that our algorithm outperforms previous algorithms by 16% on benign traffic patterns, and by 10% to 21% on adversarial traffic patterns.