Mine rescues often utilize rescue robots instead of humans to protect workers from the mine's high levels of flammable gas and dust. Designing an effective robotic system is therefore crucial.
Image Credit: Parilov/Shutterstock.com
Rescuers are unable to approach the confined space due to the complex environment, therefore they must rely on robots to seek and rescue. Furthermore, the robot can calculate its own location using the map it has created and help trapped people to safety after the accident.
Although a corresponding positioning system is installed beneath the mine, the positioning equipment is destroyed, and the exact positioning functionality cannot be accomplished when the mine collapses. As a result, robots’ simultaneous localization and mapping (SLAM) plays an important part in mine recovery.
The SLAM concept is presented as a solution to the difficulty of robot positioning and mapping at the same time. The Kalman filterbased EKFSLAM and particle filterbased FastSLAM algorithms are examples of traditional SLAM algorithms that are based on filtering theory.
This study, published in the MDPI journal Sensors, uses the FastSLAM2.0 algorithm to divide the robot positioning and mapping into a moving part and a conditional map part to decrease the sample space to solve the problem of low efficiency of mine rescue robot positioning and mapping.
Methodology
SLAM means that the robot decides its trajectory in a location environment using its own sensors while also creating an environmental map. The SLAM challenge for robots can be thought of as a probability issue. Figure 1 depicts the SLAM problem as a dynamic Bayesian network.
Figure 1. Dynamic Bayesian networks for SLAM. Image Credit: Zhu, et al., 2022
The Lion Swarm Optimization Algorithm (LSO) is a new technique for solving the objective function’s global optimal control problem. To tackle the challenge, this technique completely matches the lion’s foraging behavior, migration, and population change.
Various options for improvement were presented by the researchers. One option was to alter the particle set using the global optimal value technique to prevent slipping into the local optimal. The other is to increase the algorithm’s filtering performance by optimizing or replacing the particle resampling technique, which will reduce particle weight degradation and diversity loss.
Simultaneously, the lion swarm algorithm’s survival strategies for all types of individuals were refined and optimized. The capacity of particles to optimize was greatly boosted when the Lion King position updating and the cub following method were improved.
A genetic algorithm was used to optimize the lioness hunting process to prevent the improved algorithm’s local ideal scenario. Moreover, the loss of particle variety and deterioration of particle weight has been shown to increase the robot’s positioning accuracy. Figure 2 illustrates the modified algorithm flow chart.
Figure 2. Flowchart of improved algorithm. Image Credit: Zhu, et al., 2022
Results and Discussion
Table 1 shows the mobile robot’s motion characteristics and noise parameters. The robot’s control noise and the observation noise are both threedimensional. The speed noise of the robot is demonstrated in the following table as noise in the direction of the movement process of the robot, which is made up of xaxis noise and yaxis noise.
Table 1. Motion parameters and noise parameters of mobile robots. Source: Zhu, et al., 2022
Parameter 
Numerical Value 
Noise Parameters 
Numerical Value 
Robot speed 
3 m/s 
Motion noise 
0.3 m/s
1.5° 
Max steering angle 
10° 
Maxi steering angular speed 
15°/s 
Observation noise 
0.1 m/s
1° 
Wheel spacing 
4 m 
Sampling time interval 
0.025 s 


Next, simulate robot mapping and localization by setting up the working environment as shown in Figure 3, which includes 17 heading points, 35 road marking points, and a mobile robot movement range of 100 m × 80 m. The mobile robot moves counterclockwise, starting at the origin of the coordinates (red point in Figure 3).
Figure 3. Simulation Environment. Image Credit: Zhu, et al., 2022
When there are 20, 50, 80, or 100 particles, the RMSE of the robot position estimate and the road sign estimation were calculated using the GFAFastSLAM2.0 algorithm, FastSLAM2.0 algorithm, and LSOFastSLAM2.0 algorithm in 20 experiments, and the average value was determined. Table 2 shows the results of the experiments.
Table 2. Improved algorithm validity proof. Source: Zhu, et al., 2022
Number of Particles 
Algorithm 
Mean Localization Accuracy Error/M 
RMSE of Road Sign Estimation (m) 
20 
FastSLAM2.0 
3.0535 
4.1399 
GFAFastSLAM2.0 
2.9060 
3.3545 
LSOFastSLAM2.0 
2.3025 
2.2837 
50 
FastSLAM2.0 
2.7718 
3.2106 
GFAFastSLAM2.0 
2.3629 
2.5990 
LSOFastSLAM2.0 
2.0470 
2.2837 
80 
FastSLAM2.0 
2.6843 
2.9199 
GFAFastSLAM2.0 
1.7504 
1.9072 
LSOFastSLAM2.0 
1.2745 
1.3762 
100 
FastSLAM2.0 
2.5907 
2.8538 
GFAFastSLAM2.0 
1.3693 
1.6422 
LSOFastSLAM2.0 
1.1745 
1.3279 
The effective particle number of the algorithm suggested in this paper is higher than the other two algorithms, as seen in Figure 4.
Figure 4. Effective particle number comparison. Image Credit: Zhu, et al., 2022
The green and red triangles in Figure 5 depict the robot’s actual and expected positions, while the yellow lines indicate the robot’s perception of the road markers. The improved algorithm suggested in this paper has the best degree of coincidence with the real trajectory, followed by the GFAFastSlam2.0 algorithm, and the FastSlam2.0 algorithm has the worst impact, as shown in Figure 5.
Figure 5. The algorithm real trajectory: (a) FastSLAM2.0 Simulation Result; (b) GFAFastSLAM2.0 Simulation Result; (c) LSOFastSLAM2.0 Simulation Result. Image Credit: Zhu, et al., 2022
Figure 6 shows that the algorithm proposed in this paper has the lowest error and is reasonably constant, whereas the positioning accuracy error of the classic FastSLAM2.0 algorithm keeps increasing as the running time rises, while the positioning accuracy error of the classic FastSLAM2.0 algorithm increases as the running time intensifies.
The cause of this issue is that as the iterative method progresses, the particles get substantially damaged and their diversity is destroyed, resulting in poorer robot placement accuracy.
Figure 6. Comparison Chart of Robot Localization Accuracy Error. Image Credit: Zhu, et al., 2022
When comparing the average error and variance of the three algorithms’ positioning accuracy, it is clear that the modified algorithm has enhanced the robot positioning performance, as shown in Table 3 below.
Table 3. Comparison of mean error and variance of localization accuracy of three algorithms. Source: Zhu, et al., 2022
Algorithm 
Mean Localization Accuracy Error/m 
Variance of Localization Accuracy Error 
FastSLAM2.0 
2.7718 
1.6403 
GFAFastSLAM2.0 
1.4036 
0.9059 
LSOFastSLAM2.0 
1.1867 
0.2519 
Researchers examined the RMSE of the xaxis, yaxis, and road signs, respectively, to validate the modest improvement in robot localization and mapping accuracy, as shown in Table 4.
Table 4. Comparison of RMSE of three algorithms: xaxis, yaxis and road sign estimation. Source: Zhu, et al., 2022
Algorithm 
RMSE of xAxis (m) 
RMSE of yAxis (m) 
RMSE of Road Sign Estimation (m) 
FastSLAM2.0 
2.0447 
2.2676 
2.9871 
GFAFastSLAM2.0 
1.6015 
1.1018 
1.5841 
LSOFastSLAM2.0 
0.6932 
1.0518 
1.3383 
In the xaxis, yaxis, and road sign estimation, the improved algorithm suggested in this paper outperforms FastSLAM2.0 and GFAFastSLAM2.0 algorithms, as shown in Table 4.
Conclusion
This research provides an improved FastSLAM method based on the lion swarm optimization technique to enhance the precision of mine rescue robot positioning and mapping.
The lion swarm optimization algorithm improves the accuracy of robot positioning and mapping by optimizing the particle distribution after sampling. This solves particle weight degradation and loss of particle diversity in the FastSLAM algorithm.
The revised algorithm will be used to test the practicality of the method on mine rescue robots in the coming years.
Journal Reference:
Zhu, D., Ma, Y., Wang, M., Yang, J., Yin, Y., Liu, S. (2022) LSOFastSLAM: A New Algorithm to Improve the Accuracy of Localization and Mapping for Rescue Robots. Sensors, 22(3), p. 1297. Available Online: https://www.mdpi.com/14248220/22/3/1297/htm.
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