Research On Design And Control Of Precision Motion Stage Based On Voice Coil Actuator

The precision motion stages are the key component of the advanced precision manufacturing equipment,they are expected to achieve a multi-scale accurate and high bandwidth motion capability with the further development of the semiconductor technology,scanning probe microscope technology and micro/nano machining technology.The traditional piezoelectric actuator has the disadvantage of short motion range,the precision motion stage driven by voice coil actuator can overcome the disadvantage of piezoelectric actuator.The voice coil actuator with flexure guide can achieve nanometric motion accuracy in a motion range of millimeters.However,there are three design challenges for precision motion stage driven by voice coil actuator.The low driving capability which can hardly overcome the reaction force provided by the flexure guide.The high moving mass which decreases the response speed.The unmatched actuator and the flexure guide which restricts the global performance of the motion stage.Besides,the voice coil actuator is frequently applied in coarse-fine system,the fine stage driven by voice coil actuator with high precision and millimeters stroke can compensation the coarse stage,then,a high precision motion control in hundreds of millimeters is achieved.But the compensation performance is poor due to the lack of the high-performance fine stage control.Therefore,in order to improve the driving capability,improving the response speed,achieve the match of actuator and flexure guide,high performance of fine compensation,the research content is presented as following.The design,optimization and control of the voice coil actuator with Halbach array.The Halbach array was introduced in voice coil actuator,which effectively improved the air-gap flux density,the magnetic field characteristics and the advantages of the Halbach array were analyzed.For the complicated boundary conditions in magnetic field analysis,the magnetic resistance equivalence method was proposed based on the field-circuit combination ideology,which provides a substitution model with simplified boundary conditions.The scale of equations to be solved has reduced about 50%.The analytical models of air-gap flux density and thrust were obtained based on the variable separation method.Finally,the multi-object optimization was carried out.The prototype was fabricated,the magnetic resistance equivalence method and the analyzed models were verified,the motion stage was proved to be capable of achieving high precision motion,where the resolution reached40 nm and the repeatability accuracy reached 5 nm.The design and control of the self-damping magnetically controlled voice coil actuator.For the low mover thrust density problem,the magnetically controlled voice coil motor was proposed where the magnet was regarded as equivalent current.The working principle was intuitionally illustrated.The copper plate was added to the tooth surface and formed a novel self-damping structure,by which the dynamic characteristics was effective modulated and the control problems caused by low damping was avoided.The air-gap magnetic field was analyzed by sub-domain method,and further,the damping force model was obtained.For the hysteresis characteristics introduced by ferromagnetic materials,the modified rate-dependent hysteresis model was proposed.Based on which,the feedforward hysteresis compensation was obtained and the precision was improved.It was theoretically proved that the magnetically controlled voice coil motor can achieve thrust density up to 1300 N/kg,which is 60% high than the traditional one.The prototype was fabricated,the analytical models about thrust,damping coefficient etc.were verified.,and the hysteresis compensation performance was verified by trajectories with different frequencies and amplitudes where the tracking accuracy reached submicrometer.The research on actuator-guide integrated design.In the traditional voice coil actuator precision motion stage,the actuator and flexure guide are designed individually which restricted the global performance.Based on the analysis on the coupling between actuator,damper and flexure guide,the integrated model was established which was bridged by the open loop characteristics.Genetic algorithm was used to optimize the open-loop bandwidth,and the prototype was fabricated.The correctness of the integrated model,the open-loop bandwidth of the prototype reached71 Hz which is obviously higher than similar motion stage.The real-time precision compensation provided by the fine stage.There are coarse-fine coupling and time delay problems which restricts the compensation performance.The coupling net was transformed from input format to output format.Based on which the output decoupling method was proposed,which improved the decoupling effect.The Smith compensator was applied to move the time delay to the outer loop,and the predictor generates the time-leading trajectory to cancel the time delay of the outer loop.The fine stage trajectory prediction compensation method was obtained by the complementary of Smith compensator and position predictor.Experiments verify that the proposed methods can improve the real-time compensation performance,the tracking error was reduced to sub-micrometer.