| The non-cylindrical holes of a piston cann remarkably improve the inner stress concentration and prolong the service life of a piston.However,due to the particularity of non-cylindrical holes of a piston,traditional machining methods cannot be applied to the machining of the non-cylindrical holes.In order to improve the precision of non-cylindrical holes in high speed boring,the paper had proposed a technology of embedding the Giant Magnetostrictive Material in the boring bar,which realizes.the real time detection of radial micro displacement of boring cutter as well as the function of drive control,and results in building a piston non-cylindrical holes automatic boring NC system of high-precision.In chapter 1,firstly,the research background and significance were stated.Secondly,several research points were analyzed in details,such as the precision boring technology of piston non-cylindrical holes,the development and application of giant magnetostrictive mechanism(GMM),real time detection of boring cutter micro-displacement in the precision machining of non-cylindrical holes and error separation method,hysteresis nonlinearity modeling of GMM and its control strategy and so on.The subject and significance of the research can be seen from some extant problems about the research of embedded GMA precision boring of piston non-cylindrical holes,which were pointed out.Finally,major content of the research and the structure of the paper were stated.In chapter 2,the method of real time detection of two-point,based on two eddy current transducers and error separating technology was proposed to solve problem of real time detection of piston non-cylindrical holes radial micro-displacement in boring.According to geometrical relation between the displacements of detection position and the boring cutter blade,the placement of boring cutter blade can be transformed into the micro-displacement detection in a plane of boring bar at specific angle.The mathematical model of real time which is based on two eddy current transducers orthogonally assigned and spindle rotary encoder was established to obtain the data.Furthermore,some factors which affect the detection precision were analyzed.To separate and compensate the eccentricity error,deviation from circular form as well as the spindle radial rotation error,.error separation technology was reasonably adopted.The detector 's mechanical structure was designed,of which the rigidity,installation site and bias impact were analyzed and confirmed.Real time detection system of hardware and software was built based on NI Data Acquisition Card,DSP and Labview programming language.Experimental research of the micro-displacement real time detection method was tested in two cases,which are boring cutter feed constantly and elliptically.In chapter 3,two different control strategies of embedded GMA smart boring bar were designed based on the technology of real time detection of two-point.Emulation experiments of testing the precisions and interference immunity of open-loop inverse compensation control,feed forward PID control and closed-loop feedback control were carried to prove the efficiency of closed-loop control strategy.The mathematical model of processing trace of typical piston pinhole was analyzed and the clearance of processing control requirements of embedded GMA smart boring bar was made.The paper had constructed the GMA hysteresis nonlinearity model based on PI model,improved the operator structure,identified the parameters and performed numerical value inversion of the improved P-I model.The closed-loop control strategy of embedded GMA smart boring bar feed forward PID was established,based on which the incremental digital PID controller was designed and analyzed.And the parameters of PID controller are set by combining the attenuation curve method and empirical method.In order to improve the precision of non-cylindrical holes boring and enhance the immunity of closed-loop control system,the innovative idea of applying repetitive control strategy to control the embedded GMA smart boring bar was introduced;the smart boring bar repetitive control closed-loop system was established,the stability of which was also proven theoretically.The signal generating model of repetitive control of RC ring was designed and demonstrated to apply it to DSP programming.Finally,the emulation model of embedded GMA smart boring bar in Matlab was introduced.Emulation researches of tracking performance and immunity for typical signals under different control strategies were carried.And contrast experiments were made to analyze the emulation results.In chapter 4,to prove the performance of machining non-cylindrical pin hole,a CNC system based on closed loop feedback control technology of embedded GMA intelligent boring bar was structured.According to the design principle of generative system and the specific requirement of the precision machining system,a overall scheme of hardware and software was designed.On the hardware side,a upper and lower machine jointed structure of PC management and data processing and real-time control on DSP was used.A lot of modules including DSP control panel,interface circuit,hardware filter and date acquisition and transform and so on ware designed i and realized.The mechanical and electrical structure of precision spindle boring machine existing in the laboratory was modified.And two kinds of work mode of manual/automatic was set without affecting the original functions.DSP can control the machine digitally in automatic mode,guaranteeing the non-cylindrical pin hole boring accuracy is not affected by man-made factors.In terms of software,a control software of upper machine based on Labwindows was designed,which can simplify the complex process of the non-cylindrical pin hole boring In the "Wizard" human-computer interaction forms.And a test software based on mixed programming of Labview and Matlab was developed to diagnosis the experimental system and obtain and analyse the experimental data;Meanwhile,different control strategies of the software process ware analyzed,and a DSP real-time control program based on CC studio platform was written,the real-time of the DSP closed loop control was analyzed by calculating and testing.In chapter 5,in order to confirm the effectiveness of related theory,method,strategy and hardware and software system,the paper had performed comprehensive experiment and application research about piston non-cylindrical holes full closed-loop feedback control system on the embedded GMA smart boring bar component in the constructed comprehensive experiment platform.The control performance experiments include position tracking experiment of the open-loop inverse compensation control,feedforward + feedback composite PID closed-loop control and repetitive control,statically typical signal tracking experiments dynamically typical signal tracking experiments and anti-interference performance experiments,the tracking error was obtained by comparing the desired track and the actual machining track.The processing and application experiments include the taper pin hole machining experiments and the elliptic pin hole machining experiments by the open-loop inverse compensation control,feedforward + feedback composite PID closed-loop control and repetitive control.the machined pin hole profiles ware detected by using the precision noncircular pin hole detection device developed by the research group,so the pin hole profile error in different control strategies was got.The smart boring component working performances ware compared under the different working conditions,such as different signal excitation,different noncircular pin hole machining path and so on,and under the different control strategies such as open loop and closed loop control technology and Feedforward + feedback composite PID closed-loop control and repetitive control.The experimental results show that,compared with the open-loop control technology,the closed-loop control technology has a higher precision and a better anti-jamming performance.In chapter 6,the main conclusions of this dissertation are summarized and the future research work is put forward. |
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