Design And Research Of Hydraulic Control System For Constant Force Grinder

In the context of the transformation and upgrading of the world’s equipment manufacturing industry,as well as the clustering and intelligence of the mechanical industry,the high-quality and diversified development of the manufacturing industry has become the current main focus.Grinding technology,as an important processing method in the mechanical manufacturing industry,has always been developing towards high-speed,high-precision,and efficient directions.Nowadays,low roughness grinding,intelligent automatic grinding,and other grinding methods have been developed.In order to improve the machining accuracy of a constant force grinder,a constant force grinder equipment with a required working output force of 19300 N is designed and studied.Due to the structure of the equipment,it is not possible to use force sensors at the grinding head to monitor the output force in real time.Therefore,the constant force output of the grinder is achieved by controlling the constant pressure output of the hydraulic system.Now,the working output force of 19300 N is equivalent to the hydraulic system output pressure of 49.147 bar.The hydraulic control system was studied,and the steady-state accuracy of the system output pressure is required to be ± 1% F.S.,besides,it can still ensure stable output of the system pressure within the accuracy range in the face of positional deviation interference during the machining process.By consulting domestic,foreign pressure control equipment materials and relevant literature on constant force control technology,we combined with the actual processing process,working principles,and other aspects of the grinder,the main research objectives and content of this article have been determined.Based on the project technical indicators provided by Party A,the hydraulic system control plan was finally determined,and a hydraulic control schematic diagram of the constant force grinding machine was drawn.Parameter calculations and selection work was carried out on the proportional relief valve,oil pump motor group,and accumulator components of the hydraulic system.A mathematical model for the pressure closed-loop control system of a constant force grinder has been Established,the derivation of the system transfer function has been completed,the open loop system transfer function Bode has been drawn based on Amesim.Analyzing and studying the system stability through the Bode criterion to verify the system stability.In order to deeply study the control performance of the pressure closed-loop control system,based on the sample data of the selected hydraulic components,a simulation model of hydraulic components such as proportional relief valve and floating oil cylinder was built in Amesim software.Finally,the Amesim simulation model of the constant force grinder closed-loop pressure control system was established,the correctness of the system modeling and system stability could be verified through the simulation results.Analyzing the simulation results of the uncorrected control system,it was found that the response time is too long and the output pressure cannot reach the target pressure value;After introducing the traditional PID correction scheme on this basis,the output pressure of the system could reach the target pressure value and have a certain steady-state accuracy,but the response speed was still slow.When facing position deviation interference during the machining process,the system output pressure fluctuates violently;Based on various control schemes,a composite PID control strategy of feedforward compensation and pressure feedback was attempted.Simulation was conducted on the position interference signal with a sinusoidal waveform input at the grinding head end,and the results showed that the pressure control system has certain anti-interference ability,it can ensure that the grinding machine can still meet the indicator requirements when facing positional interference.On the basis of achieving the control objectives,further in-depth research was conducted on the factors that affect the performance of other pressure control systems.The results showed that adding an accumulator with appropriate capacity to the system,using the shortest possible sampling time,and reducing the internal friction of the floating cylinder can improve the pressure control performance.Based on the above research content,a physical control system for a constant force grinding machine was designed and manufactured.After the installation of the equipment,the test data showed that the pressure error was ± 0.341 bar,and the pressure control accuracy was ± 0.7%,meeting the technical indicators of grinding machine pressure control.The successful development of the hydraulic control system for the constant force grinding machine provides valuable theoretical basis and practical experience for the design and research of machine tools with the same working principle.