The Study Of Fast Tool Servo Driven By Maxwell Normal Stress Motor And Its Techniques

The demands of more complex optical freeform surfaces are increasing invarious areas, such as imaging, illumination and concetration. Optical freeformsurfaces can be fabricated using the ultraprecision machining techniques, amongwhich the single-point diamond turning technique based on fast tool servo has theadvantages of high effiency and high accuracy when processing complex freeformsurfaces. However the lack of fast tool servos with moderate stroke and highbandwidth has limited the development of optical freeform surfaces machining. Thefast tool servo driven by Maxwell normalstress motor (MNM-FTS) which is studiedin this thesis has the characteristics of moderate stroke and high bandwidth.Experimental verification based on fast tool servo is also studied.The studies in theis thesis can be summarized as follows:1. The full-bandwidth magnetic circuit and driving formula of the Maxwellnormalstress motor are analyzed, the mechanical stress is analyzed, the kinematicmodel is built, and then the electromagnetic-mechnical-kinematic model is built aswell, characterizing the relationship between the driving force and the driving currentwith differenet amplitudes and frequencies.2. A multi-objective optimization model is built and reformulated based on themotor’s model solving through sequential quadratic programming algorithm. Themotor is designed with the optimized parameters which are verified through finiteelement analysis.3. A dual-loop feedback power amplifier is proposed to drive the motor and acontroller with DSP as the core. The adaptive feedforward cancelling-PID algorithmis developed as the controlling method.4. The tool path generation of fast tool servos is studied, including scattered datainterpolation algorithm to regulate the data, surface decomposition with smooth toenlarge the sagittal height of the machining surface, smoothing method of the edge toeliminate the error of the acceleration contravariant point.5. The interpolation in the toolpath-generation-controller is studied. The fast toolservo driven by Maxwell normalstress motor is tested on an ultraprecsion lathe. Theexperiments on flat cutting and freeform surfaces cutting are conducted.The optimized fast tool servo driven by Maxwell normalstress motor has characteristics of reaching the acceleration of6295.598m/s2, the resonance frequencyof3.2kHz, the closed-loop bandwith of3kHz, the stroke of50μm. The developpedfast tool servo is capable of fabricating flat specimens to a surface roughness of17nmin Ra and a freeform profile accuracy of0.5μm in peak-to-valley.