圆—长方形复合孔件机器人装配技术研究

发布时间：2018-09-02 09:59

【摘要】：在产品生产过程中,装配作业占据重要地位,直接决定产品生产周期和生产效率。装配工艺作业劳动量大、任务重,如何高效开展装配作业是生产管理、设备技术等领域研究的重点。随着工业自动化技术的应用,一系列搬运、焊接、喷涂、装配等机器人出现在产品生产的各个环节中。装配的特殊之处在于工件形状各异并且需要接触环境,孔件配合间隙小,这对机器人力位控制技术和检测技术都提出了严格的要求。目前机器人装配生产线上的零件多是形状规则、完全对称,对复杂形状的装配对象研究较少,因此机器人装配仍是一个需要深入研究的领域。本文利用模块化组合式机械臂,引入力位控制策略,对圆—长方形复合孔件进行装配技术的研究。为实现圆—长方形复合孔件的自动装配,首先对零件进行了几何形状分析,拟定装配策略,得出复合件需要沿三轴进行位姿调整来控制工件与孔的相对位置角度偏差。采用设计的三种系列关节模块根据装配需要组合成六自由度机械臂,并得出正逆运动学关系;其次对装配过程进行接触静力学分析,对孔件沿各平面的接触分布进行了归类。复合件装配接触状态复杂,尤其是孔内位姿调整阶段,采用空间的柔顺装配模型来推导装配力与装配深度的数学模型,得出一点、两点、三点等接触状态的受力特征。通过对阻碍装配的“卡阻”和“楔紧”现象进行了探究,分析了入孔深度和表面质量对装配的影响,得到成功装配的满足条件。提出了圆—长方形复合孔件的装配策略,分为接近孔、接触、孔内位姿调整三个阶段。接近孔属于非接触状态,为特定轨迹规划粗定位孔,由最底层关节位置控制实现;接触后先搜长方孔、再搜圆孔使工件入孔;孔内根据运动是否受阻,建立复合件位置姿态与接触力的对应关系,实现主动接触力控制。装配过程中的接触力过大会阻碍装配进行,严重还会损坏工件和机器人,采用调整侧向位姿减少侧向力和力矩的方式来保证装配顺利进行,即阻抗控制。建立与环境接触的弹簧模型,结合阻抗模型分析了阻抗参数对力控制偏差的影响。对装配过程的各个阶段进行控制器设计并在Matlab/Simulink进行了搭建。以圆—长方形复合孔件作为装配对象,在Adams建立机械臂模型,进行了联合仿真来验证装配策略;仿真结果表明,在保证装配成功的同时,能够将接触力控制一定范围内,验证了装配策略的可行性。
[Abstract]:In the process of product production, assembly plays an important role, which directly determines product production cycle and production efficiency. The assembly process has a large amount of labor and heavy tasks. How to carry out assembly work efficiently is the focus of research in the fields of production management, equipment technology and so on. With the application of industrial automation technology, a series of robots, such as handling, welding, spraying and assembling, appear in every step of product production. The special feature of assembly is that the workpiece has different shapes and needs contact environment, and the hole fitting clearance is small, which puts forward strict requirements for robot force position control technology and detection technology. At present, most of the parts in the robot assembly line are regular shape, complete symmetry, and less research on the assembly object of complex shape, so the robot assembly is still a field that needs further research. In this paper, the assembly technology of circular and rectangular composite holes is studied by using modular combined manipulator and force position control strategy. In order to realize the automatic assembly of circular and rectangular composite holes, the geometric shape of the parts is analyzed, and the assembly strategy is drawn up. It is concluded that the compound parts need to adjust the position and orientation along the three axes to control the relative position deviation between the workpiece and the hole. The three series of joint modules designed are combined into six degrees of freedom manipulator according to the assembly requirements, and the forward and inverse kinematics relations are obtained. Secondly, the contact statics analysis of the assembly process is carried out, and the contact distribution of the holes along each plane is classified. The assembly contact state of composite parts is complex, especially in the adjustment stage of position and pose in the hole. The mathematical model of assembly force and assembly depth is derived by using the spatial compliant assembly model, and the mechanical characteristics of the contact state of one point, two points and three points are obtained. This paper probes into the phenomenon of "blocking" and "wedge tightening" which hinders the assembly, analyzes the influence of the depth of the hole and the quality of the surface on the assembly, and obtains the conditions for the successful assembly. The assembly strategy of circular-rectangular composite hole parts is put forward, which is divided into three stages: close hole, contact and adjustment of position and orientation inside hole. The approach hole is in a non-contact state, and the coarse positioning hole is planned for a particular trajectory, which is controlled by the position of the lowest joint; after contact, the long square hole is searched first, then the round hole is searched to make the workpiece enter the hole, and the hole is blocked according to the motion or not. The corresponding relation between the position and the contact force of the composite is established, and the active contact force control is realized. The contact force in the assembly process hinders the assembly and seriously damages the workpiece and robot. The method of adjusting the lateral position and reducing the lateral force and torque is adopted to ensure the assembly to proceed smoothly namely impedance control. The spring model of contact with environment was established, and the influence of impedance parameters on force control deviation was analyzed with impedance model. The controller of each stage of assembly process is designed and built in Matlab/Simulink. Taking the circular and rectangular composite holes as the assembly object, the manipulator model is established in Adams and the joint simulation is carried out to verify the assembly strategy. The simulation results show that the contact force can be controlled within a certain range while the assembly is successful. The feasibility of assembly strategy is verified.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP242

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