针对玻璃成形抛光中玻璃与抛光轮接触点相对线速度持续减小从而影响加工效率的问题,以控制相对线速度基本恒定、保证加工效率和精度为目标,提出基于三次NURBS曲线的速度控制算法。基于线性加减速方案,确定速度特性曲线控制点。结合Preston公式,以相对线速度基本恒定为约束条件,求解抛光轮中心末速度。以加加速度连续为约束条件,求取与控制点对应的权因子,确定抛光轮中心速度变化时的控制方程。采用四阶龙格-库塔数值方法确定插补初始点,再由米勒一汉明数值方法进行迭代校正,实现参数式曲线插补控制算法。试验结果表明,该速度控制方法能够有效保持玻璃与抛光轮接触点相对线速度基本恒定,加工效率较传统方法有较大提高。
To deal with low machining productivity and quality due to continuous decreasing of rel- ative velocity at touch point between glass and polishing wheel,a velocity control algorithm based on cubic NURBS was proposed to keep the limited relative velocity fluctuation. Based on linear accelera- tion/deceleration,the control points for proposed velocity control curve were confirmed. Using the Preston equation,the final velocity of polishing wheel center for velocity control curve was solved un- der the conditions of limited relative velocity fluctuation. Based on jerk continuity,the weighting fac- tors were obtained and control equations for velocity smoothly changing were confirmed. Using fourth Runge--Kutta formula to obtain the initial points and Milne--Hamming equation to predict and cor- rect the next points, the interpolation algorithm for parametric trajectory was accomplished. Experi- mental results show that the proposed approach guarantees limited fluctuation of relative velocity at touch point and improves the efficiency of glass polishing compared with traditional method.