| With the development of thin and crimpable flat panel display,flexible display has gradually become the trend of display industry.Ultra-thin stainless steel substrate is the ideal materials for next generation flexible display substrate.Chemical Mechanical Polishing(CMP)has been widely used in surface planarization of display substrates for its high quality and low damage.The rotary swing gravity polishing machine has the characteristics of simple structure,high precision and the like,and the polishing pressure can be stably and uniformly applied on the surface of a workpiece through gravity pressurization,and a complex polishing track can be obtained.However,the automatic loading and continuous loading of pressure in polishing process can not be realized by gravity pressurization,which affects the processing efficiency and quality of workpiece.With the development of pneumatic technology,pneumatic technology has been widely used in the field of industrial control for its advantages of simple structure,reliable operation and no pollution.However,the compressible and the non-linearity of gas and the environmental disturbance for the system parameters and the like,increase the difficulty of aerodynamic control system and make it difficult to obtain satisfactory performance.In order to solve the above problems,based on the rotary swing gravity polishing machine,a polishing pressure automatic loading system based on embedded arm microprocessor and Linux operating system is designed by using pneumatic proportional control technology.The polishing pressure auto-loading system takes ARM controller as the control core,and develops the control interface at the PC end to realize the display and on-line control of polishing parameters in the polishing process.Secondly,the mathematical model of the polishing pressure automatic loading system is established and the fuzzy PID controller is designed.Finally,on the basis of ZPY200 gravity rotary swing polishing machine,a pressure loading system experimental platform was built,and the function modules of the automatic loading system were debugged.the closed-loop polishing pressure loading experiment and ultra-thin stainless steel substrate polishing experiment were designed.The surface quality of polished stainless steel was tested,and the effective performance of the loading system was verified.The main research methods and conclusions are as follows:(1)The pressure control requirements of CMP equipment for ultra-thin stainless steel substrate CMP process are analyzed.Based on the pneumatic proportional force control system,an automatic pressure loading system for CMP machine polishing head is designed.The pneumatic control loop and system controller of automatic loading system are designed.For pneumatic control circuit,the models of electric proportional valve,double acting cylinder and air source are analyzed and selected.For the automatic loading system controller,the controller microprocessor,pressure sensor,ultrasonic sensor,A/D converter,D/A converter,serial port and so on are analyzed and selected.(2)The mathematical model of the automatic pressure loading system is established.The differential equation of cylinder pressure,the pressure-flow equation of proportional valve and the force balance equation of cylinder piston are analyzed,and the transfer function of the system is obtained.The response characteristics of the pressure-loaded system are analyzed.The response curves show that the system is stable,but the response is slow.According to the characteristics of pneumatic system,the advantages and disadvantages of classical PID control and modern intelligent control theory are analyzed,and a fuzzy PID controller for pneumatic proportional force control system is designed.(3)According to the functional requirements of the controller system,the system controller software is designed.Based on the ARM-Linux platform,a cross-compiling environment is built,and the embedded BootLoader and Linux operating system are cut and transplanted for the ARM S5PV210 microprocessor.On this basis,the design and debugging of the program of each part of the measurement and control software are completed,mainly including temperature detection,ultrasonic distance detection,D/A?A/D conversion,fuzzy PID algorithm,filtering algorithm and other functional modules,and the overall program flow of pressure control is designed.In order to facilitate monitoring,the host computer monitoring and control interface is developed based on Qt platform,and the online debugging and monitoring of the control process is realized.(4)Based on the existing gravity polishing machine,an automatic loading system experiment platform is built,and the controller software and hardware are debugged online,including serial transmission,A/D module and D/A module.The pressure response curve is obtained through pressure loading closed-loop experiment,the system loading steady-state error is within 10N,and the control requirement of CMP polishing machine is met;At the same time,a polishing experiment was designed for 0.1mm 304 stainless steel substrate,and the surface morphology and surface roughness of the polished stainless steel substrate were tested.the test results show that the surface morphology of the polished stainless steel substrate is effectively improved,and the surface roughness R_a<5nm,which meets the design requirements of CMP polishing machine,and verifies the effectiveness of the pressure automatic loading system. |
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