Control techniques of bonnet polishing for free-form optical lenses with precession

Control techniques of bonnet polishing free-form optical lenses with 'precession' is studied, according to the processing characters of free-form optical lenses, to figure out the rotating angles of two virtual axes of bonnet tool, which lead to the controllability of spin axis of bonnet tool. The spin axis of bonnet tool is taken as the object, due to the difference of the local normal of each polishing point and the angle between the spin axis of bonnet tool and local normal is keeping constant in polishing process, a method about how to set up basic coordinate and corresponding coordinate of polishing point is proposed, aiming to get the positions of spin axis of bonnet tool in polishing process, by which a movement model can be obtained by combining with rotating coordinate transformation; Then control algorithm is added to the movement model, and rotating angles of two virtual axes of bonnet tool when polishing each point on free-form optical lenses are calculated. At the end, simulations in polishing different directions of free-form optical lens in Matlab are carried out, to get the curves of precession control and the simulated precession angles, the results reveal that the movement model and control algorithm presented are both correct.