The Optimization Of On-line Measurement Based On Efficient Machining Of Aeronautics Thin-walled Parts

Aeronautics manufacturing is one of the most important components of manufacturing industry.Its technological level and capacity are the comprehensive embodiment of the national manufacturing and the contemporary level of national defense technology.With the further development of the Aeronautics industry,the processing demand of thin-walled parts is getting higher and higher.In manufacturing,the requirements of the aeronautical thin-walled parts include the accuracy of thickness,the precision of surface and the precision of contour.Thickness is an important index for aeronautical thin-walled parts.The consistency of wall thickness is very important for aerodynamic performance.In addition,the bearing capacity of aerocraft can be improved by reducing the thickness of the thin-walled parts.Therefore,the accuracy of thickness should be strictly guaranteed in the processing of thin-walled parts.In order to ensure the thickness of thin-walled parts,it is necessary to measure the thickness.The efficiency of the traditional off-line measurement is low and the precision is low.In order to improve the manufacturing efficiency of aeronautical thin-walled parts,the method of on-line measurement is used for the thickness of thin-walled parts.Through the on-line measurement of the thickness of the thin-walled parts,the efficient machining of the aeronautical thin-walled parts is realized.In order to realize the on-line measurement of wall thickness,ultrasonic sensor can be used in the detection process.The thickness of the thin-walled parts is measured by ultrasonic sensor.The accuracy of the measurement results is higher and the reliability of the measurement is greater.The non-contact ultrasonic measurement is adopted,the cavity of the thickness measuring device must be filled with liquid,so the hydraulic closed-loopcontrol system is needed to make the hydraulic constant in the cavity of thickness measuring device.We need dynamic thickness measurement on thin-walled parts,we should prevent the pressure too large to scratch on the surface of the thin-walled parts and the pressure is too small to cause the instability of the thickness measurement.So we introduce the pressure closed-loop control to stabilize the pressure between the thickness measuring device and the surface of thin-walled parts.And then the thickness data of thin-walled parts are stable.The ultrasonic thickness measurement is realized through the hydraulic closed-loop control and the pressure closed-loop control.The main work of this paper is as follows:1.The hydraulic closed-loop control system is one of the important subsystem of thickness on-line measurement.The angle of the thickness measuring device,the location of the thickness measuring device and the location of the water pipe line are often changed in the hydraulic closed-loop control system,and the experimental environment are greatly disturbed by the outside world.The effect of PID control is also very different at different times.PID control is particularly sensitive to this situation.The system can not achieved better and more efficient control if we use the traditional PID control.In this paper,the type of P closed-loop iterative learning algorithm is applied to optimize the closed-loop control of hydraulic,and the convergence of the type of P closed-loop iterative learning control is proved theoretically.It is verified that the iterative learning control is better than the PID control in the hydraulic closed-loop control system by experiment,and the thickness of thin-walled parts is stable.2.The pressure closed-loop control system is one of the important subsystem of thickness on-line measurement.The pressure closed-loop control system is different from the hydraulic closed-loop control system.The pressure closed-loop control system is not easy affected by the outside world.The thin-walled parts in different height correspond the different pressure control because of the poor inflexibility of thin-walled parts.The calibration of pressure sensor is a difficulty.The tuning of traditional PID parameters is not suitable for this pressure closed-loop control system.Using thedirectly engineering parameter tuning method of PID control is not effective and especially wastes time.This method often depends on the experience of people and it is not necessarily achieve the best results.In this paper,the pressure closed-loop control is optimized through cuckoo search algorithm to get the best PID parameters in different parts of thin-walled part.Then,after engineering tuning,the engineering application is given.By the experiments,it is proved that the PID parameters are obtained through the cuckoo search algorithm are better than direct engineering setting,and the thickness of the thin-walled parts is stable.The pressure closed-loop control is introduced and the speed of on-line measurement is 1000mm/min.3.The speed of thickness on-line measurement should be improved.When the speed of on-line measurement is raised to 3000mm/min,the effect of hydraulic control and pressure control is bad,and the thickness data fluctuates greatly.The main reason for the poor control is that the control speed is not fast enough.The speed of control can not keep up with the moving speed of the processing.In order to improve the speed of measurement,the SIEMENS ET200 M is optimized into the SIEMENS high speed module ET200 S.After using ET200 S,the transmission speed is 12 Mbps,while the transmission speed of ET200 M is only 1.5Mbps,and the time of a cycle is shortened a lot.After using ET200 S,the hydraulic control and pressure control are reached the control requirement under the speed of 3000mm/min.When finishing all the above optimization,it can reach the thickness of aeronautics thin-wall parts of on-line measurement.So the aeronautics thin-walled parts were processed efficiently.Processing and measuring are conducted at the same time.And then it reach the exact requirement of aeronautics thin-walled parts.