Research On The Drive System And Control Method For Nano-table With Six Degrees Of Freedom

Micro-displacement technology is one of the key technologies in precision machinery and precision instruments fields.With the rapid development of micro-nano manufacturing technology,there are more and more fields need nano-driven control technology.The dissertation is based on the project sponsored by the National Natural Science Foundation of "Nano-CMM key technology research",Focus on the driving technology and systems of a six degrees of freedom nano-table which is the key components of the whole field parallel confocal microscope used for measuring surface topography of small devices,to realization the rapid adjustment,high-precision positioning and miniaturization of the micro-platform.Six degrees of freedom nano-table with single-layer structure is driven by the eight parallel PZT,therefore it's necessary to establish the relationship between the table displacement and the driving volume of every PZT.The PZT actuator demonstrates superior characteristics of high displacement resolution,miniature size,high-frequency response,strong power,no generate heat etc.But the inherent hysteresis and creep effect the application of PZT badly.The quality of PZT power supply will impact the positioning accuracy of table directly.At present,the PZT power supply in market for sale,not only the number of output channels,but also the volume and output voltage stability are difficult to meet the demands of the parallel driving of six degrees of freedom nano-table.In this dissertation,carried out a systematic study in depth about the high-precision driving control technology around the six degrees of freedom nano-table.The main works and its originality of this dissertation are as follows:(1)The establishment of six degrees of freedom nano-table- parallel control modelIn accordance with the structure parameters of six degrees of freedom nano-table,the mathematical relationship between three mobile workstations parameters and three rotation parameters with the driving capacity of eight PZT have been established.(2) The research on high-precision open-loop control method of PZTBecause the requirements of miniaturization,there is no space for the installation of displacement sensor on the six degrees of freedom nano-table,only the open-loop control could be adopted.But the hysteresis and creep of PZT impact the open-loop control accuracy badly.From the deformation mechanism of the PZT,the hysteresis and creep characteristics of PZT have been studied deeply.The high-precision open-loop control method of PZT "anti-lag" and "anti-creep" also have been made.The experimental results show that:the hysteresis error of the PZT has been reduced about 90%,the creep error also be reduced of an order of magnitude,and the location time has been greatly shortened,It makes the adoption of open-loop control to achieve high-precision positioning of six degrees of freedom become possible.The above-mentioned methods have applied for two national invention patents,which have been granted one.(3) The development of miniaturized multi-channel high-precision PZT power supplyGood performance of driving power supply is the key to achieve high-precision positioning of the piezoelectric ceramic.In this paper,mainly from the expansion of power-channel-count,lower ripple and interference,reducing the volume and temperature control of amplifier such as aspects,developed own micro-low ripple of the multi-channel PZT power supply,and completed the corresponding experiments of the calibration characteristics.By testing,the output voltage of eight channels shows good linearity,the nonlinear error is less than 0.05%.the resolution is 6mv,the static ripple voltage is less than 9mV,the power bandwidth could be 5kHz,the continuous output current could be 1.5A,the voltage variation is less than 0.01%after eight hours continuous working.The volume of power supply is only 280~*260~*120mm(The volume of three-channel PZT power supply of BOSHI is 385~*150~*340mm),the power could satisfy the requirements of PZT driving.(4) The research on driving experiments of six degrees of freedom nano-tableThere are differences between the actual parameter values with the theoretical values of the table,and the characteristics of the PZT is not exactly the same,so the displacement calibration experiments on six degrees of freedom nano- table have been made,the driving characteristics of various degrees of freedom have been determined,and established a revised six degree of freedom parallel-driven control model,then the final campaign precision of the nano-table has been calibrated,the preliminary research results have been verified by experiments.The largest repeatability error of six degrees of freedom nano-table is less than 28nm,could meet the needs of the sample interpolation for whole confocal microscope in parallel.