How to accurately control the pressure fluctuation of the hydraulic system in hydraulic processing of automatic cover?
Release Time : 2025-10-15
In the hydraulic processing of automotive covers, pressure fluctuations in the hydraulic system directly impact part molding accuracy and surface quality. Automotive covers often feature complex curved surfaces, requiring the hydraulic system to drive the mold for high-precision mold closing and pressure maintenance. If pressure fluctuations exceed the allowable range, this can easily lead to wrinkling, cracking, or excessive springback in the part. Therefore, precise control of pressure fluctuations requires a comprehensive approach encompassing hydraulic system design, component selection, control strategy, and dynamic compensation.
As a pressure source, the stability of the hydraulic pump is fundamental to controlling fluctuations. Hydraulic processing of automotive covers typically utilizes variable displacement piston pumps, which dynamically match flow and pressure by adjusting the swash plate angle. If the pump's regulating mechanism experiences sticking or delayed response, the output pressure can fluctuate around the desired value and cause high-frequency oscillations. For example, when the pump's regulating frequency resonates with the system's natural frequency, the amplitude of pressure fluctuations can significantly increase. Therefore, regular inspections of the pump's servo valve, feedback linkage, and other components are necessary to ensure smooth and unobstructed movement. Furthermore, the pump's suction line design should be optimized to prevent cavitation caused by poor suction.
The performance of hydraulic valves directly impacts the accuracy of pressure control. Relief valves are key components for controlling system pressure. If the valve core becomes stuck with impurities or the spring becomes fatigued, the valve core will frequently switch between open and closed states, causing pressure chatter. Furthermore, if the proportional pressure valve's control signal contains high-frequency noise or delayed response from the feedback sensor within the valve, the output pressure can overshoot and retract following the command signal, resulting in periodic fluctuations. Therefore, high-precision, contamination-resistant hydraulic valves should be selected. The valve core and seat should be cleaned regularly, and the spring condition should be checked to ensure stable and reliable valve regulation.
The layout and damping design of hydraulic pipelines can amplify or dampen pressure fluctuations. Right-angle elbows and reducers in complex pipelines can increase oil flow turbulence, causing localized pressure pulsations. Pipeline pressure fluctuations are particularly pronounced under high-flow conditions, such as those encountered in hydraulic processing or automation. To address this, pipeline routing should be optimized, the number of elbows and joints should be reduced, and hydraulic dampers or orifice plates should be installed at key locations to absorb pressure pulsations. Furthermore, the proper configuration of accumulators can effectively buffer pressure fluctuations generated by pumps or valves. Accumulator capacity and charge pressure must be precisely calculated based on system operating conditions.
Oil condition has a hidden impact on pressure stability. At low temperatures, oil viscosity increases dramatically, increasing flow resistance and causing periodic, stuttering fluctuations in the pump's output pressure. At high temperatures, oil viscosity decreases, increasing leakage and foaming, leading to pressure instability. Therefore, it is important to select hydraulic oil with an appropriate viscosity based on the ambient temperature and configure an oil temperature control system to ensure the oil operates within the optimal viscosity range. Furthermore, hydraulic oil should be regularly filtered to remove impurities such as metal particles and water to prevent oil contamination from exacerbating component wear and impairing dynamic control performance.
Dynamic compensation technology is key to improving pressure control accuracy. By installing a pressure sensor on the output side of the hydraulic cylinder to monitor pressure changes in real time and feed the signal back to the controller, closed-loop pressure control can be achieved. For example, a backstepping integral adaptive control algorithm can be used to incorporate pressure errors into the desired speed, enabling pressure-speed compound control of valve-controlled cylinder systems. This strategy effectively suppresses pressure overshoot and fluctuation by compensating for uncertainties such as oil viscosity variations and external load disturbances. Furthermore, compensating for hydraulic cylinder friction based on the LuGre friction model further improves the controller's modeling accuracy.
In the practical application of hydraulic processing of autom covers, a comprehensive control solution must be developed based on specific working conditions. For example, in deep drawing of large panels, a multi-stage pressure regulation circuit can achieve stepped pressure control to ensure pressure requirements at different forming stages. For hot forming of high-strength steel plates, fast-response proportional valves and high-performance sensors are required to achieve millisecond-level pressure adjustment. By continuously optimizing control parameters and algorithms, pressure control accuracy in hydraulic processing of autom covers can be significantly improved, ensuring consistent part quality.
