| Modern times, membrane material is widely used as it is less dense, lighter, longer lifespan, vibrate resistant and convenient to execute. Especially, it is widely used in construction, aeronautics and astronautics areas. However, membrane material is one kind of composite material with nonlinear property and anisotropy. The mechanical property is so complicated that it is hard to find a suitable model during the calculation. Only the coefficients are used during the calculation, crafting and engineering design. So, it is quite beneficial and useful to get the property coefficients using suitable methods.Recently, the main coefficients for membrane materials are tested under single axis loading experiment. Using the single axis test results only will usually lead to unexpected dangerous. As a result, bi-axial loading experiment is beneficial and necessary for membrane materials.Focusing on the bi-axial loading system for membrane materials, the bi-axial electro-hydraulic loading system has been developed. Also, the control strategy with Wavelet Neuran Network(WNN) PID algorithm and position compensation has been proposed to fit the bi-axial experiment requirements, and the prototype has been built to analyze the experimental results. This paper has coved the tasks including properties and requirements discussion for bi-axial loading experiment, system design for bi-axial loading machine, modeling and simulation for the loading system, control strategy analysis and design, hardware and software design, building the prototype and experiment at last.In more detail, five parts are included in this research.Firstly, the properties of membrane materials and the requirements for bi-axial loading experiment have been discussed, which are the basic for bi-axis electro-hydraulic loading system for membrane materials.Secondly, the bi-axial electro-hydraulic loading system for membrane materials has been designed on the basic of the properties of membrane materials and the requirements for bi-axial loading experiment. Especially, the schematic diagram for hydraulic loading system has been proposed and the relevant components used in this hydraulic loading system have been designed and selected. Besides, the test platform has been designed and its 3D model has been developed in Solidworks software. Also, specific control system for bi-axial loading system has been designed, which will be used to realized force close-loop control, position close-loop control and speed close-loop control.Thirdly, with the help of AMESim software, the simulation model for bi-axial hydraulic loading system has been built. On the basic of simulation model, the stability of the bi-axial loading system, as well as the force tracking property, position tracking property and speed tracking property, have been analyzed and verified.Besides, according to the simulation results, the control strategy with WNN PID algorithm and position compensation has been proposed, which is also based on the properties of membrane materials and the requirements for bi-axial loading experiment. Moreover, the control strategy has also been discussed and verified by using the co-simulation of AMESim software and Simulation software.Last but not the least, the hardware and the software for the control system have been designed and realized. Also, the prototype has been built and the experiments have been carried out. The experimental results have also been compared with the simulation results.The experimental results and simulation results show that, the bi-axial electro-hydraulic loading system and the relative control strategy proposed in this paper fulfill the requirements for bi-axial loading experiment for membrane materials. The bi-axial loading system has good performance in force tracking, position tracking and speed tracking. The strategy with WNN PID algorithm and position compensation is more adaptable, which makes it fit the bi-axial loading system well. The bi-axial electro-hydraulic loading system with WNN PID algorithm and position compensation does well in force tracking as well as position tracking. |
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