基于3-SPR型并联机构机器人曲面制孔末端执行器动力学与控制

发布时间：2019-02-20 20:42

【摘要】：利用3-SPR并联机构设计了一种新型机器人曲面制孔末端执行器。根据3-SPR型并联机构的特点,结合曲面制孔末端执行器的设计要求,将该并联机构作为曲面制孔末端执行器的调姿压紧机构。在该调姿压紧机构运动学分析的基础上,给出了本文研究的并联制孔末端执行器刀具姿态调整算法。在末端执行器刀具四周均布的四个距离传感器测得曲面上制孔点周围四点数据的基础上,计算获得该四点在同一坐标系下的坐标,结合已知的制孔点坐标,给出了一种基于矢量加权求和的新曲面法向测量算法。并对该算法与球面拟合的法向测量算法进行了仿真对比,可知本文设计的新算法在法向测量时有更高的精度。对制孔末端执行器并联调姿机构,采用拉格朗日方程建立了该机构的动力学模型,得到了驱动力的显示解,为进一步分析末端执行器调姿机构动力学控制提供数学模型。基于该数学模型对末端执行器并联调姿机构动力学特性进行了仿真分析,根据驱动力的显示解,模拟动平台姿态变化时驱动力的变化曲线,得到姿态调整中各驱动力的变化情况。同时对动平台加载与不加载时,驱动力的变化情况进行对比,给出了各支链可以忽略质量的条件。分析驱动力变化与机构结构参数之间的关系,为机构动力学特性的深入分析及其用于制孔执行器的优化设计提供了参考。以所设计调姿机构动力学方程为模型,设计了基于该模型的修正PD控制策略及滑模变结构控制策略。通过仿真说明对于该动力学模型,基于趋近律的滑模变结构控制器比PD控制器具有更好的鲁棒性,更适合于该末端执行器并联调姿机构。对所建立末端执行器制孔单元的进给系统数学模型,采用传统的PID控制器与有自适应特点的模糊PID控制器。通过仿真分析得出模糊PID策略更适合用于制孔单元进给系统。
[Abstract]:Using 3-SPR parallel mechanism, a new type of robot curved hole end actuator is designed. According to the characteristics of the 3-SPR parallel mechanism and the design requirements of the curved hole making end actuator, the parallel mechanism is used as the adjusting and compacting mechanism of the curved hole making end actuator. On the basis of kinematics analysis of the attitude adjusting and compacting mechanism, a tool attitude adjustment algorithm of parallel hole end actuator is presented in this paper. On the basis of the data of four points around the hole making point on the curved surface measured by four distance sensors distributed evenly around the end actuator tool, the coordinates of the four points in the same coordinate system are calculated and combined with the known coordinates of the hole making point. A new surface normal measurement algorithm based on vector weighted summation is presented. Compared with the normal measurement algorithm of spherical surface fitting, the new algorithm designed in this paper has higher accuracy in normal measurement. The dynamic model of the mechanism is established by Lagrangian equation, and the display solution of driving force is obtained, which provides a mathematical model for the further analysis of the dynamic control of the end-actuator attitude adjusting mechanism. Based on the mathematical model, the dynamic characteristics of the parallel attitude adjusting mechanism of the end actuator are simulated. According to the display solution of the driving force, the change curve of the driving force during the attitude change of the moving platform is simulated. The change of driving force in attitude adjustment is obtained. At the same time, the change of driving force is compared between dynamic platform loading and non-loading, and the condition that the quality of each branch chain can be neglected is given. The relationship between the change of driving force and the structural parameters of the mechanism is analyzed, which provides a reference for the in-depth analysis of the dynamic characteristics of the mechanism and its application in the optimization design of the hole making actuator. The modified PD control strategy and sliding mode variable structure control strategy are designed based on the dynamic equation of the designed attitude adjusting mechanism. The simulation results show that the sliding mode variable structure controller based on approach law is more robust than the PD controller and is more suitable for the parallel attitude adjustment mechanism of the end actuator. The traditional PID controller and the fuzzy PID controller with adaptive characteristics are used for the mathematical model of the feed system of the end actuator hole making unit. Simulation results show that fuzzy PID strategy is more suitable for feed system of hole making unit.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP242

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