## 2 Grinding Robot Process Introduction and Kinematics Model  
### Grinding Robot Process Introduction  
Finishing is the last process of quality control of special steel products, and it is unimportant means to ensure the quality of steel products, improve the grade of products and create fine products. It is through the special steel products shot blasting, straightening, chamfering, flaw detection, grinding, labeling, baling, weighing, heat treatment, surface peeling and other processing, to eliminate surface and internal defects of the special steel bar, so that special steel products can meet the factory standards and user requirements, but also can greatly improve the added value of products. The finishing process includes online finishing and offline finishing. The online finishing process is shown in Figure 2.  
Online finishing generally refers to the product in the rolling line completing the relevant finishing process. The offline finishing is independent of the rolling production line, which is a process route for the advanced finishing treatment of steel. There are different offline processing processes according to different steel products. As an important part of the finishing process, grinding is paid more and more attention by scientific and technical workers. Grinding robots are mainly used for polishing sanitary porcelain, tables, chairs, and body and deburring castings, these are floating flexible polish. Special steel bar grinding belongs to rigid grinding, grinding material is hard, compared with manual grinding existing problems of uncontrollable depth, and surface quality is not high, it is necessary to realize the special steel bar grinding robotization. Therefore, it is necessary to efficiently predict the kinematic solution of the grinding robot before the online grinding of the special steel bar. Before the grinding robot is used to grind the defects of the special steel bar, the robot grinding system needs to recognize the bar defect data provided by the crack detection device, then the program in the robot database is called to command the grinding robot to realize the grinding of bar defects. According to the actual working conditions provided parameters, the parameters of bar defect are depth greater than 0.2 mm and length greater than 0.5 mm. The defect location and sample diagram of the bar are shown in Figure 3. According to the requirements of the grinding compliance rate of the production line, the compliance rate of the bar after the robot grinding should be greater than or equal to 95%. The actual transfer speed of the special steel bar production line is 1-2 m per s.  
Special steel bar grinding belongs to rigid grinding, grinding material is hard, compared with the traditional manual grinding, there are problems of uncontrollable depth, and surface quality is not high. The kinematics control of the robot must be considered to realize the robotic operation of the grinding process. The efficiency and accuracy of the robot grinding steel bar depend on whether the robot can accurately reach the target grinding point. The motion trajectory and drive control of the robot have a great influence on the grinding, so it is necessary to effectively predict the robot's kinematic solution in  
Figure 3: The defect location and sample diagram of the bar. Figure 2: Online finishing process of the steel bar. advance. In the process of robot grinding, there will be kinematic problems such as rotation of each joint, trajectory planning, position, and attitude of the end-effector. Considering the timeliness of robot motion control by the robot grinding strategy program, it is necessary and effective to predict the robot kinematic solution to improve the grinding efficiency and precision. In order to accurately control the robot to reach the grinding target point, it must be able to accurately predict the actual state displacement of the robot in the moving space.