Research On Smooth Transition And Velocity Look-ahead Control Of NC Machining Micro Segments

The high-speed and high-precision CNC system is a key tool for the equipment manufacturing industry,and plays an important role in improving the overall level of the manufacturing industry.In NC area,machining parts with complex profiles are widely represented by continuous micro segments.Aiming at the problem of the geometrical discontinuity of the continuous micro segment toolpath,which causes sudden changes in the machine’s feedrate and acceleration during machining.Based on the existing technology,this paper focuses on acceleration/deceleration control algorithms,smooth transition algorithms between micro segments,and velocity look-ahead control.The thesis first studies the principles and functions of several common acceleration and deceleration control algorithms(linear acceleration/deceleration control algorithms,exponential acceleration/deceleration control algorithms,trigonometric function acceleration/deceleration control algorithms,cubic polynomial acceleration/decelera-tion control algorithms,and S-shape acceleration/deceleration control algorithms).In addition,their advantages and disadvantages are compared,and how to choose the appropriate acceleration/deceleration control algorithm according to the requirements is discussed.Second,the implementation principles of the direct transition algorithm,line segment transition algorithm,arc transition algorithm,and cubic Bezier curve transition algorithm are studied.In view of the shortcomings of these transition algorithms,a axis velocity adjustment transition algorithm is proposed.The velocity,acceleration,and jerk of each axis are limited within the system constraints to achieve a high-speed smooth transition between small line segments.Third,in order to obtain the global optimal corner velocity and achieve the overall optimization of velocity,an adaptive velocity look-ahead control algorithm is proposed,which adopts the form of non-fixed look-ahead segments to ensure better adaptability in the face of complex and variable processing paths.Then adjust the corner velocity through the forward and backward revision to ensure the attainment of the velocity at both ends of each processing line segment.Finally,the proposed axis velocity adjustment transition algorithm and adaptive look-ahead control algorithm are verified by simulation and experiment.The results show that the algorithm proposed in this paper can achieve smooth transition between small line segments while satisfying the axis motion constraints,and ensure continuous changes in feedrate and acceleration To achieve the purpose of smooth and high-speed processing.