To address the issue of chatter avoidance in robotic machining processes, a method was proposed to avoid chatters in industrial robot machining based on dynamics modal decoupling. Firstly, dynamics differential equations were established for the robot at various orientations within a specific location. Secondly, stability analyses were conducted separately for regenerative chatter and mode-coupling chatter, allowing the reachable robot orientations to be classified as either stable or chatter-prone. Thirdly, stability criteria for both regenerative chatter and mode-coupling chatter were derived to identify orientations where neither type of chatter occured. Based on these stability criteria, stable and chatter orientations were selected, and hammering experiments, as well as robotic machining chatter avoidance tests, were carried out.Experimental results validate the effectiveness of the proposed method.
式中:为加速度传感器所获得加速度向量与坐标系之间的方向余弦构成的对角矩阵,; V 为解耦坐标系中刀具接触动态反作用力与3个自由度振动方向的方向余弦构成的对角矩阵, V =diag(,,);为作业刀具振动位移向量;为加工宽度向量;、为加工产生的波纹面,其中T为加工周期;为单位加工宽度的刚度系数矩阵,解耦坐标系中的单位加工宽度的刚度系数矩阵,为了将解耦坐标系中3个自由度所对应运动方向的微分方程独立求解,忽略中的非对角线元素。
令rad、rad、rad,以()(10°)增量改变、的取值,当加工宽度系数、 V =diag(2/3,2/3,1/3)时,便可由式(26)计算出每个姿态下3个自由度所对应运动方向的极限加工宽度、、。假设3个自由度所对应运动方向的进给深度为、、,并将进给深度用矩阵形式表达,即。为了方便判断机器人系统是否发生再生型颤振,定义综合极限加工宽度b为极限加工宽度的二范数,即;综合进给深度h为3个自由度所对应运动方向的进给深度 H 的二范数,即,解耦坐标系中综合极限加工宽度的变化如图9所示。设定该机器人在实际加工过程中的综合进给深度为0.3 mm,根据上述分析可知,实际加工宽度小于综合极限加工宽度的加工姿态,视为不发生再生型颤振的姿态。对应不发生再生型颤振时机器人作业姿态所对应的的取值如图10所示,图10中红色矩形框内的空洞表示发生再生型颤振的机器人加工姿态所对应的的取值。
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