Currently, there are many simultaneous localization and mapping (SLAM) algorithms for 3-D light detection and ranging (lidar) relying on features such as planes and edges. However, if a robot needs to work in a rubber forest, these simple features can be unstable due to the complexity of the environment. To address this problem, in this article, we propose the first SLAM system to make a deep adaptive adjustment for the particularity of the rubber-tapping robot and the rubber forest environment. In our article, tree trunks are used to construct a set of sparse maps called trunk atlas, which contain environmental information for localization and trunk position for rubber tapping. To ensure the quality of feature extraction, density field correction and multicriteria trunk detection are proposed. Due to the sparsity and stability of the trunk atlas, our SLAM system can ensure real-time performance. Experiments show that our lidar-only SLAM system can achieve nearly the same performance as state-of-the-art inertial-measurement-unit-aided algorithms in terms of runtime and localization accuracy. In addition, our trunk atlas also takes up less memory for storage than other algorithms. More specifically, it takes less than 50 kB to store a map of an area of approximately 5000 m $^2$ .

In the case of a single scene feature, the positioning of an indoor service robot takes a long time, and localization errors are likely to occur. A new method for a hybrid indoor localization system according to multi-sensor fusion is proposed to solve these problems. The localization process is divided in two stages: rough positioning and precise positioning. By virtue of the K nearest neighbors based on possibility (KNNBP) algorithm first created in the present study, the rough position of a robot is determined according to the received signal strength indicator (RSSI) of Wi-Fi. Then, the hybrid particle filter localization (HPFL) algorithm improved on the basis of adaptive Monte Carlo localization (AMCL) is adopted to get the precise localization, which integrates various information, including the rough position and information from Lidar, a compass, an occupancy grid map, and encoders. The experiments indicated that the positioning error was 0.05 m; the success rate of localization was 96% with even 3000 particles, and the global positioning time was 1.9 s. However, under the same conditions, the success rate of AMCL was approximately 40%, the required time was approximately 25.6 s, and the positioning accuracy was the same. This indicates that the hybrid indoor location system is efficient and accurate.

A globally consistent map is the basis of indoor robot localization and navigation. However, map built by Rao-Blackwellized Particle Filter (RBPF) doesn’t have high global consistency which is not suitable for long-term application in large scene. To address the problem, we present an improved RBPF Lidar SLAM system with loop detection and correction named LCPF. The efficiency and accuracy of loop detection depend on the segmentation of submaps. Instead of dividing the submap at fixed number of laser scan like existing method, Dynamic Submap Segmentation is proposed in LCPF. This segmentation algorithm decreases the error inside the submap by splitting the submap where there is high scan match error and later rectifies the error by an improved pose graph optimization between submaps. In order to segment the submap at appropriate point, when to create a new submap is determined by both the accumulation of scan match error and the particle distribution. Furthermore, LCPF uses branch and bound algorithm as basic detector for loop detection and multiple criteria to judge the reliability of a loop. In the criteria, a novel parameter called usable ratio was proposed to measure the useful information that a laser scan containing. Finally, comparisons to existing 2D-Lidar mapping algorithm are performed with a series of open dataset simulations and real robot experiments to demonstrate the effectiveness of LCPF.

Path planning under two-dimensional (2D) maps is a fundamental problem in mobile robotics and other real-world applications (unmanned vehicles, navigation apps for mobile phones, and so forth). However, traditional algorithms (graph searching, artificial potential field, genetic, and so forth) rely on grid-by-grid searching. Thus, these methods generally do not find the global optimal path, and as the map scale increases, their time cost sharply increases, except artificial potential field. A few algorithms that do not rely on grid-by-grid searching (RRT, visibility graph, and tangent graph) have special requirements for maps. Considering that the shortest path is often composed of tangents between obstacles, in this paper, we propose a method called ReinforcedRimJump (RRJ) that does not rely on point-by-point traversal but rather obtains the shortest path by finding the tangent multiple times between obstacles. The first improvement of this method is the precomputation of tangents, which causes the method to have a lower time cost than traditional methods. The second improvement of RRJ is edge segmentation, which allows RRJ to be used when the target is in the depression of the obstacle. To verify the theoretical advantages of RRJ, some comparative experiments under various maps are performed. The experimental results show that RRJ can always find the shortest path in the shortest time. Furthermore, the time cost of RRJ is insensitive compared to other methods. The experimental results presented herein demonstrate that RRJ meets the theoretical expectations.

Localization is one of the most fundamental problems for a mobile robot. Aiming at the phenomenon that robot is prone to be lost in navigation under severe occlusion, a robust localization system combining vision and lidar is proposed in this paper. The system is split into off-line stage and online stage. In the off-line stage, a method of actively detecting and recording visual landmarks is introduced, and an off-line visual bag-of-words is generated from the recorded landmarks training. In the online stage, the prediction and update phase of Adaptive Monte Carlo Localization (AMCL) are improved respectively to enhance the performance of localization. The prediction phase generates the proposal distribution according to the prior information obtained through retrieving visual landmarks, and the newly proposed measurement model that selects reliable beams of lidar as the observation is to update the prediction. Experiments are carried out under strict conditions, that is 60% of the lidar is occluded, 1/12 of the beams are regarded as observation, and only 300 particles were adopted at most, it is shown that, no matter in the global localization or pose tracking, the localization system proposed in this paper performs much better than AMCL that is the state of art lidar-based localization algorithm.