Toolpath smoothing is an important approach to improve robots’ operational stability and machining quality. Nowadays, the corner rounding smoothing and curve fitting smoothing algorithms are usually adopted to process the linear toolpath segments to improve its continuity. But the high order continuity between the fitted curve and its adjacent curves is difficult to be guaranteed. For parallel machining robots (PMRs), the tangential, curvature and curvature derivative discontinuities at the junction may lead to the self-excited vibration of mechanical structure, consequently the machining efficiency and quality are decreased. Under this consideration, a global G³ continuity toolpath smoothing method for five degrees of freedom (5-DoF) PMRs is proposed. The linear segments toolpath generated by the Computer-Aided Manufacturing (CAM) system is first divided into long linear segments (LLSs) and short linear segments groups (SLSGs) through breakpoint searching. At the junction point, a B-spline transition curve is inserted to blend adjacent toolpaths. For the SLSG, the quintic B-spline is adopted to fit the discrete data points, constraint equations about the derivatives at the start and end points are established to achieve G³ continuity with the adjacent transition curves. Based on the proposed method, the smoothing for two test toolpaths is carried out, and experiments on a 5-DoF PMR are conducted to show the validity of the method in motion smoothness.

刀具路径平滑是提高机器人操作稳定性和加工质量的重要方法。如今，通常采用圆角倒圆平滑和曲线拟合平滑算法来处理线性刀具路径段以提高其连续性。但是，很难保证拟合曲线与其相邻曲线之间的高阶连续性。对于并行加工机器人（PMR），结点处的切线，曲率和曲率导数间断可能会导致机械结构的自激振动，从而降低加工效率和质量。在这种考虑下，全球G ³提出了一种用于五自由度（5-DoF）PMR的连续性刀具路径平滑方法。首先，通过断点搜索将计算机辅助制造（CAM）系统生成的线性段工具路径分为长线性段（LLS）和短线性段组（SLSG）。在接合点处，插入B样条过渡曲线以混合相邻的刀具路径。对于SLSG，采用五次B样条拟合离散数据点，建立关于起点和终点导数的约束方程，以实现与相邻过渡曲线的G ³连续性。基于所提出的方法，对两个测试刀具路径进行了平滑处理，并在5-DoF PMR上进行了实验，以证明该方法在运动平滑度方面的有效性。