立体石雕弱刚度部位的机器人柔性磨削加工方法研究

Industrial robot machining systems has prominent advantages of high efficiency, wide processing range and strong flexibility for the stone stereo-lithography grinding process. However, the machining chatter is serious during the process of robot maching three-dimensional stone-carving products the due to the hard brittle and natural crystal defects. Especially, when the robot machining system during the weak-rigidity position of three-dimensional stone-carving products grinding process, the time-varying grinding force and the inappropriate machining pose will cause the phenomenon of stone fracture or even discarded. Aiming at this problem, the robot end effector will be added the flexible joint in this project. The robot will control the machining pose, and the external forces will be complied by the flexible effector, thus the controlled flexible contact between grinding tool and workpiece. The coupling dynamic model of robot, tool and three-dimensional stone-carving products will be built by the means of numerical calculation and parameter identification. The influence on flutter stability of weak-rigidity position of robotic machining pose and grinding force will be revealed. Based on the above results, the robotic flexible grinding method will be developed, in which maximizing the material removal under the condition that stable grinding process is a constrain condition. The research results can provide the new system scheme for increasing the machining quality of robot, reducing processing risk, thus increasing promotion and application of robot in stone carving industry.

采用工业机器人进行石材立体雕刻的磨削加工具有灵活性强、加工范围大等突出优势。然而，由于石材的硬脆性和天然结晶缺陷，机器人在进行石材立体雕刻时，极易发生加工颤振现象。特别是在加工其弱刚度部位时，在不适当加工位姿与瞬态时变强磨削力的作用下，加工颤振将直接导致石材坯料发生折断，造成工件报废。针对此问题，本项目在机器人末端增加一个柔性执行器，通过机器人实现加工位姿的控制，通过柔性执行器对外部作用力产生自然顺从，从而实现磨削刀具与工件的柔性可控接触。采用数值计算与参数辨识的方法，建立机器人-刀具-立体石雕耦合系统动力学模型，进而揭示机器人加工位姿与磨削力对弱刚度部位颤振稳定性的影响规律。根据以上结果，制定以稳定磨削条件下最大材料去除率为约束目标的机器人磨削力柔性调控方法。研究成果可为提升机器人立体石雕加工系统的加工能力，降低加工风险，提供新的系统解决方案，从而促进机器人在石雕产业中的推广与应用。

采用工业机器人进行立体石雕的磨削加工具有灵活性强、加工范围大等突出优势。然而，由于石材的硬脆性和天然结晶缺陷，机器人在磨削立体石雕弱刚度部位时，极易发生加工颤振现象，从而导致石材坯料的折断。针对此问题，项目组以实现工业机器人对立体石雕弱刚度部位的稳定高效加工为目标，综合考虑机器人端动态特性与立体石雕弱刚度部位的动态特性，建立了耦合系统的动力学模型，在此基础上，提出了针对立体石雕弱刚度部位的机器人柔性加工工艺与控制方法，具体进展如下：(1) 提出了立体石雕机器人加工系统关节刚度的高精度辨识方法, 从而建立了耦合系统的动力学模型，实现了工业机器人磨削石雕弱刚度部位时加工稳定性的精准预报与加工误差的准确预测；(2) 采用曲面分区加工方法，建立了工业机器人加工立体石雕弱刚度部位的工艺参数与路径轨迹生成策略，表面粗糙度降低了25%；(3) 研究了机器人加工立体石雕弱刚度部位时振动冲击抑制的控制方法，所提出的滑模控制器，使得无颤振加工效率提升37%；(4) 研发了机器人加工立体石雕工艺数据库与加工装备，在相关企业得到成功应用。在机械制造与机器人领域重要主流期刊发表学术论文11篇（其中SCI收录8篇，EI收录1篇），申请发明专利21项（授权9项），作大会邀请报告3次，软件著作权4项，培养博硕士研究生10名。