# Path Planning Based on NURBS for Hyper-Redundant Manipulator Used in Narrow Space
## 4 The Tip-Following B-Spline Path Planning
The hyper-redundant robot designed in this paper can complete some complex, dangerous and boring tasks. In particular, the generator blades of the nuclear power plant need to be overhauled every year, and the nuclear power plant can not avoid radiation, which is generally harmful to the human body, so it is necessary to use robots to replace human beings to complete dangerous work. As shown in Figure 17, the hyper-redundant robot designed in this paper can travel freely between narrow blades to complete the maintenance and maintenance of engine blades. Figure 16: Schematic diagram of manipulator for tube obstacle avoidance. Figure 17: _Cont_. ## 6 Conclusions

In this paper, a hyper-redundant robot composed of four pairs of double UCR (Universal-Cylindrical-Revolute) parallel mechanisms (2R1T, 2 Rotational DOFs and 1 Translation DOF) in series to realize flexible obstacle avoidance motion in narrow spaces is designed. Then, a method combining cubic B-spline algorithm with A * Algorithm is proposed to plan the trajectory of obstacle avoidance for hyper-redundant robot in constrained space. The experimental results show that the robot can move smoothly in a plane or inclined plane, it can also travel freely in the narrow space between engine blades. The proposed algorithm reduces the computational complexity of the obstacle avoidance process of hyper-redundant robots and, at the same time, the robot can avoid obstacles flexibly in the complex narrow space. By setting various simulation test environments, it can be seen that the algorithm proposed in this paper can make the hyper-redundant manipulator pass through many restricted spaces, laying a theoretical foundation and experimental method for the detection of narrow spaces. However, the redundant arm designed in this paper still has certain limitations. For example, the existing mechanical arm has a small load, and a larger motor can be used to improve the load capacity in the future. Methodology, J.D., B.W. ; validation and data curation, B.W., J.D. ; writing--original draft preparation, J.D., B.W., K.C. ; writing--review and editing, J.D., K.C., B.W. ; visualization, J.D. ; supervision, Z.D. ; project administration, Z.D. ; funding acquisition, Z.D. All authors have read and agreed to the published version of the manuscript. This research was funded by National Key Research and Development Plan under grant number 2018 YFB1305601. and Open Project Program of the Key Laboratory of Measurement and Control of Complex Systems of Engineering, Ministry of Education, Southeast University under grant number MCCSE2021A04. and the Fundamental Research Funds for the Central Universities under grant number MCCSE2021A04. The authors declare no conflict of interest. ## References

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