Research On Position-pressure Cooperative Control Strategy For Full-hydraulic Leveler

The characteristics of electro-hydraulic servo system of full-hydraulic leveler are high speed,large inertia,high frequency and multiple degrees freedom.In the process of straightening of the plate,the traditional control method mainly focuses on the position closed loop which can guarantee the control and tracking of the output displacement of the hydraulic cylinder well,but can not realize the online change of the pressure and ensure the stable output of the straightening force.The electromagnetic spill valve is used to operate pressure in the pump source of traditional hydraulic systems,which will cause overflow loss as well as energy loss in the process of straightening the steel plate and resulted in energy loss meanwhile result to the low degree of automation.With the continuous development of science and technology and the improvement of requirements for the degree of automation and control accuracy,the simple position closed loop has been unable to meet the needs of modern straightening process.Focusing on the above-mentioned problems,this paper proposes a position-pressure cooperative control strategy for full hydraulic straightening machine.The core idea of the position-pressure cooperative control strategy proposed in this paper is that,during the process of straightening roll downward and straightening,the pressure-position conversion gain will turn the dynamic working pressure signal of the hydraulic cylinder into a real-time position signal which then will be compensated into the position close-loop in order to improve the response speed of the system meanwhile the pressure signal of the rear cavity is fed back to the input of proportional relief valve at the source of pump which can realize the change of working pressure of the system according to the different thickness and then improve the automation degree of the whole machine.In this paper,the single-cylinder mathematical model of position-pressure cooperative control strategy for full hydraulic straightening machine is constructed through detailed analysis,theoretical derivation and calculation in terms of the working principle and electro-hydraulic servo system,meanwhile,made comparison with the control effect of simple position closed loop.Firstly,the cooperative control simulation for single cylinder and four-cylinder synchronous are simulated in AMESim software to prove pressure signal,which is compensated into position closed loop is tested by the small-scale valve-controlled cylinder test bench of the laboratory and finally the feasibility and practicality of coordination control for four-cylinder synchronization is proved by 11-roll straightening machine in the field.The position-pressure coordination control strategy of the hydraulic straightening machine not only improves the response speed of the hydraulic system of the straightening machine,but also realizes the rapid change of the pressure of hydraulic system and improves the automation degree of the whole machine.The realization of the position-pressure coordination control strategy of the hydraulic straightening machine provides a reliable theoretical basis and technical support for China's independent innovation in large-scale metallurgical equipment and the development of independent intellectual property rights.