**Collision-Free Path Planning Method for Robots Based on an Improved Rapidly-Exploring Random Tree Algorithm**

#### **Xinda Wang 1, Xiao Luo 2,\*, Baoling Han 1, Yuhan Chen 1, Guanhao Liang 3 and Kailin Zheng 1**


Received: 20 January 2020; Accepted: 13 February 2020; Published: 19 February 2020

#### **Featured Application: The new method can be used to guide the path planning of robots with any number of degrees of freedom in complex environments.**

**Abstract:** Sampling-based methods are popular in the motion planning of robots, especially in high-dimensional spaces. Among the many such methods, the Rapidly-exploring Random Tree (RRT) algorithm has been widely used in multi-degree-of-freedom manipulators and has yielded good results. However, existing RRT planners have low exploration efficiency and slow convergence speed and have been unable to meet the requirements of the intelligence level in the Industry 4.0 mode. To solve these problems, a general autonomous path planning algorithm of Node Control (NC-RRT) is proposed in this paper based on the architecture of the RRT algorithm. Firstly, a method of gradually changing the sampling area is proposed to guide exploration, thereby effectively improving the search speed. In addition, the node control mechanism is introduced to constrain the extended nodes of the tree and thus reduce the extension of invalid nodes and extract boundary nodes (or near-boundary nodes). By changing the value of the node control factor, the random tree is prevented from falling into a so-called "local trap" phenomenon, and boundary nodes are selected as extended nodes. The proposed algorithm is simulated in different environments. Results reveal that the algorithm greatly reduces the invalid exploration in the configuration space and significantly improves planning efficiency. In addition, because this method can efficiently use boundary nodes, it has a stronger applicability to narrow environments compared with existing RRT algorithms and can effectively improve the success rate of exploration.

**Keywords:** Rapidly-exploring Random Tree (RRT); manipulator; motion planning; obstacle avoidance; complex environment
