1. Introduction
In recent years, autonomous underwater vehicles (AUVs) have been becoming increasingly popular in wide range of marine applications [
1,
2]. With widespread applications across civilian, military, and commercial sectors, AUVs are playing a crucial role in various domains such as underwater exploration and maritime surveillance [
3,
4]. The increasing enhancements of AUV performance, functionalities, and intelligence significantly extend the operational capabilities of surface and underwater tasks [
5,
6]. However, single AUVs still have the obvious limitations of energy supply and payload capacity during complex tasks [
7,
8]. Collaboration of multiple AUVs has become a significant research direction to address these limitations [
9,
10].
Within collaborative systems of multiple AUVs, collaborative path planning emerges as a highly significant issue to guide a group of AUVs to reach designated target locations along collision-free paths of coordinated collaboration among the AUVs [
11]. Collaborative operations of multiple AUVs not only need to consider the shortest path, minimum time cost, and energy consumption of individual AUV, but also involve multi-objective optimization of multiple AUVs considering internal collision avoidance and external risk control [
12,
13]. Collaborative path planning of multiple AUVs is challenging due to the dynamic environments and complex tasks, which require coordinating the movements of AUVs to avoid collisions and simultaneously optimize overall task [
14].
To consider both local avoidance and global optimization, Zeng et al. [
15] and Youakim et al. [
16] conducted comparisons and categorizations of various path-planning methods, such as artificial potential field (APF) methods, sampling-based methods, and search-based methods. The multi-point potential field method (MPPF), as a variant of APF, shares the efficient and rapid characteristics of APF, but it is susceptible to convergent local optimization [
17]. Rapidly-exploring random trees (RRTs), as a classic sampling-based method, has an impact on the effectiveness of cost reduction and performance optimization in high-dimensional and time-constrained path-planning scenarios [
18]. Genetic algorithm (GA), as a classic search-based method, is capable of generating optimal and robust paths via a heuristic approach [
19]. However, there is the limitation of computational efficiency when GA deals with complex problems. Hermand et al. [
20] employed an explicit reference governor (ERG) framework to control drones within a geo-fenced area, ensuring accurate control within a limited range and improving safety. However, the performance may be affected in highly dynamic or chaotic environments. Ru et al. [
21] used an approach that included an O-AUV sensing model. This model allowed the AUV to sense omnidirectional areas, which significantly enhanced underwater information acquisition. They also made improvements to the NSGA-II algorithm to develop a trajectory optimization strategy for the accelerated optimization and identification of Pareto optimal solutions. However, the complexity of the omnidirectional sensing model may pose computational challenges. Liu et al. [
22] employed model predictive control (MPC) to address intricate path planning issues in dynamic environments. The approach considered vehicle dynamics constraints and the presence of other vehicles. However, the approach might be computationally intensive due to the nonlinear and non-convex nature of the MPC problems. Evolutionary algorithms still demonstrate remarkable performance in addressing path optimality issues, especially when high-dimensional, complex problems are considered [
23,
24]. Among existing evolutionary algorithms, Zeng et al. [
15] highlighted that particle swarm optimization (PSO) exhibits notable robustness and efficiency in addressing high-dimensional path planning problems. The related works studying modification PSO are summarized in
Table 1. Panda et al. [
25] compared various algorithms’ AUV path optimization strategies based on PSO to clarify their advantages and limitations. The practical application of path optimization algorithms based on PSO strongly relies on appropriate cost functions and different types of constraints. To ensure path smoothness, feasibility, and collision avoidance for AUVs, it is essential to integrate multiple conflicting criteria to achieve optimal control decisions [
26]. These criteria involve the following objectives: (i) Avoid collisions by maintaining a safe distance from obstacles; (ii) ensure the path has an adequate number of control points to generate a complete trajectory; and (iii) satisfy AUV minimum turning radius and pitch control limitations.
In this study, we introduce the adaptive multi-population particle swarm optimization (AMP-PSO) algorithm, a novel approach in the field of autonomous underwater vehicle (AUV) path planning. AMP-PSO employs an innovative grouping strategy and a dynamic exchanging mechanism of particles which are not found in traditional PSO algorithms. The novel combination of proposed AMP-PSO can enhance global search capability, accelerate convergence speed, and improve solution adaptability, particularly in complex and dynamic underwater environments. AMP-PSO overcomes specific limitations which are inherent in existing methods, such as susceptibility to local optimization and difficulty in navigating intricate terrains. AMP-PSO represents a significant advancement in efficient and effective AUV path planning. These advancements directly address the research gaps identified earlier, offering a robust solution to the challenges in current AUV path planning methodologies. Through comparative analysis in simulation experiments, this paper successfully verifies that AMP-PSO achieves the best performance than classic PSO and other improved PSO methods in terms of solving collaborative path planning problem with multiple AUVs. AMP-PSO not only has a relatively low computational cost, but also provides high-quality path-planning solutions. The main contributions of this study are as follows. (i) AMP-PSO includes a distributed strategy of multi-population for the collaborative path planning of multiple AUVs. In AMP-PSO, the leader population can learn from follower populations to improve the search ability in global optimization, while follower populations learn only by themselves to keep local solution exploring as a priority. (ii) AMP-PSO adopts an adaptive configuration of parameter updating to enhance the benefits of multi-population so that adaptive updating rules can increase diversity in the leader population and accelerate convergence in follower populations.
The remaining parts of this paper are organized into four sections.
Section 2 provides a detailed description and constraint analysis of collaborative issues concerning multiple AUVs.
Section 3 introduces the methodology of AMP-PSO and its application of collaborative path planning for multiple AUVs.
Section 4 presents the numerical experiments and simulation results.
Section 5 concludes the paper with a summary.
5. Conclusions
To solve the problem of collaborative path planning of multiple AUVs, AMP-PSO was proposed in this paper. This paper first introduced the rapid development and wide application of AUVs, and emphasized the importance of multiple AUV systems in overcoming the energy and load capacity limitations of a single AUV. Then, the challenges and constraints of collaborative path planning with multiple AUVs were analyzed, and the existing AUV path planning techniques were reviewed. On this basis, the AMP-PSO algorithm was proposed, which uses a clustering strategy and adaptive parameter configuration to achieve a balance between global search and convergence speed. Through simulation evaluation, the performance of the algorithm was verified and compared with the traditional PSO algorithm. The results show that the proposed AMP-PSO algorithm can generate feasible and optimal path planning, so that multiple AUVs can effectively avoid obstacles and meet various constraints. Compared with traditional PSO algorithms, AMP-PSO has more advantages in terms of path quality and environment adaptability, and also achieved significant improvements in both procedure running time and path adaptation across all three scenarios. In Scenario I, AMP-PSO achieved a maximum improvement of approximately 126% in procedure running time and 80% in path adaptation. In Scenario II, AMP-PSO achieved a maximum improvement of approximately 92% in procedure running time and 96% in path adaptation. Finally, in Scenario III, AMP-PSO achieved a maximum improvement of approximately 96% in program running time and 41% in path adaptation. This research is of great significance for promoting the application of multiple AUVs in the fields of underwater exploration, monitoring, and reconnaissance, and provides an innovative solution to the collaborative path planning problem of multiple AUVs, with wide application prospects and practical value. However, there are several limitations of the current research, and we plan to improve them in future work. First, we plan to improve environmental modeling and simulations by including more shapes of obstacles (e.g., pipes) and moving obstacles with dynamic characteristics. Secondly, we plan to extend experimental comparisons including other classic evolutionary computation algorithms and deep reinforcement learning methods.