基于改进三次B样条的灌木修剪运动轨迹光顺算法研究

Trajectory Fairing Algorithm for Shrub Pruning Based on Improved Cubic B-spline

针对复杂造型灌木修剪过程中机器人末端运动平稳性差的问题,提出了一种基于双切矢连续的改进三次B样条轨迹光顺算法。首先建立了线性轨迹拐角过渡模型,利用B样条曲线局部性质构造衔接点切矢约束,使初始不平滑的修剪轨迹经光顺处理后可达到G;连续;其次构建平面多段轨迹在不同光顺算法下的过渡曲线,经对比分析,本算法所构造的过渡曲线在相同逼近误差下,相比传统圆弧过渡算法曲率极值降低40.5%,相比传统三次B样条过渡算法在衔接点处曲率更加连续,整体光顺效果更优;最后为验证算法对空间修剪轨迹的光顺效果,建立了5轴关节机器人模型进行鸭形轨迹修剪仿真,结果表明本算法可使机器人末端速度极值提升13.5%,加速度极值降低86.9%,机器人各关节运动更平稳,验证了本算法在复杂修剪轨迹光顺方面的可行性与有效性。

Aiming at the problem of poor stationarity of robot end motion in the process of complex shape shrub pruning,an improved cubic B-spline trajectory fairing algorithm based on double tangent vector continuity was proposed.Firstly,the transition model of linear trajectory corner was established.The tangent vector constraint of connecting point was constructed by using the local properties of B-spline curve,so that the initial unsmooth pruning trajectory can be G;continuous after fairing.Secondly,the transition curves of planar multi-segment trajectories under different fairing algorithms were constructed.Through comparison and analysis,under the same approximation error,the curvature extreme value of the transition curve constructed by this algorithm was 40.5%lower than that of the traditional arc transition algorithm.Compared with the traditional cubic B-spline transition algorithm,the curvature of the transition curve constructed by this algorithm was more continuous and the overall fairing effect was better than that of the traditional cubic B-spline transition algorithm under the same approximation error.Finally,in order to verify the fairing effect of the algorithm on spatial pruning trajectory,a 5-axis joint robot model was established for duck-shaped trajectory pruning simulation experiment.The results showed that the algorithm can increase the extreme velocity at the end of the robot by 13.5%,reduce the extreme acceleration by 86.9%,and make the joints of the robot move more smoothly.The results verified the feasibility and effectiveness of the algorithm in the fairing of complex pruning trajectories.