Research On Trajectory Planning Technology Based On Motion Stability

At present,the method of approximating curve trajectory by continuous small line segments is often used in CNC system to overcome the difficulties in the process of parametric curve machining.However,because of the tangential discontinuity at the junction of adjacent segments,the feed system needs to reduce the feedrate to zero at these corner points.Such frequent start and stop will reduce the machining efficiency and surface quality.Therefore,a local smoothing method based on clothoid curves is proposed,it can achieve the G~2 continuous machining path,controllable approximation error and non-zero smoothing feedrate.This paper mainly carries out the following research:Firstly,according to the linear relationship between arc length and curvature of clothoid curve,the analytical relationship between arc length,curvature extremum,maximum approximation error and smooth length is established.Combined with geometric constraints such as line length,trajectory angle and maximum approximation error,the geometric smoothing of continuous linear instructions is accomplished.Meanwhile,The analytical expression of trajectory length and the curvature extremum of smoothing curve are obtained.Secondly,according to the geometric characteristics of the blended tool path and the kinematics constraints of the feed system,the bidirectional scanning strategy is adopted in lookahead phase to obtain the feedrate allowable value of the feedrate sensitive point.In the phase of feedrate planning,continuous and stable motion is achieved by using S-shaped acceleration and deceleration feedrate planning with 7 interval.Finally,in the interpolation phase,the corresponding interpolation algorithm is applied to the linear and curve segments of the blended machining trajectory.It effectively allocates the displacement at the junction of linear segment and curve segment reasonably,and overcomes the possible impact when cross-segment interpolation.The experimental results show that the clothoid smoothing algorithm based on analytic arc length in this paper can achieve G~2 continuity in the machining process and effectively shorten the machining time.Moreover,it can greatly improve the computational efficiency of lookahead phase and help to realize the online interpolation of smoothing algorithm.Figures 50,Tables 2,References 53.