1. Introduction
The drone market has witnessed a notable trend toward the miniaturization of Unmanned Aerial Vehicles (UAVs or drones), with smaller drones emerging as the prevalent models in commercial sectors. Nevertheless, the constraints of these drones become evident when faced with large-scale operations. This scenario unveils a fresh avenue for cooperation between drones and ground vehicles (considered trucks in this paper).
Table 1 illustrates that both the truck and the drone have their respective advantages and limitations. However, their complementary functional characteristics offer clear collaborative benefits. Firstly, the truck acts as a mobile base station for the drone, enhancing its operational scope. Owing to its excellent endurance, the truck can be equipped with mechanisms for drone launch and landing. Secondly, the truck can carry multiple spare batteries or be fitted with charging equipment, enhancing the drone’s continuous operational capacity enabling swift battery replacement or recharging. Furthermore, leveraging its substantial payload capacity, the truck can serve as a mobile warehouse, and pre-load necessary materials or packages for the drone’s subsequent work. Lastly, the drone’s versatility, unconstrained by road conditions, enables it to swiftly and directly access challenging environments or high-risk areas.
Acknowledging the significant advantages of cooperated trucks and drones, scholars have intensively explored this field, especially following the introduction of the Flying Sidekick Traveling Salesman Problem (
FSTSP) by Murry and Chu in 2015 [
1].
In order to carry out a comprehensive investigation, we employed the keywords “truck drone” and “route planning” on the Web of Science (WOS) platform, searching for publications from 2015 to 2024. Among the 256 articles retrieved, 225 were directly related to the routing challenges with the truck-drone cooperation. The distribution of these studies over the years is depicted in the
Figure 1. As can be seen, there has been a notable surge in publications within this domain, with over 120 new papers emerging in 2022 and 2023 alone, constituting half of the total number of articles.
In this survey, we first categorize the problem context into three main application areas: logistics and delivery, intelligence surveillance and data collection, as well as area monitoring and patrol. This classification helps to clarify the various scenarios where truck-drone teamwork can be utilized.
Considering the variety of application scenarios, the functions performed by trucks and drones in these tasks differ considerably. Based on the unique roles these two vehicles play in the collaboration, the truck-drone cooperation mode can be categorized into four primary types: synchronous operation of truck and drone, independent operation of truck and drone, the truck serving as auxiliary support to the drone, and the drone serving as auxiliary support to the truck. We not only provide a detailed description of these modes, but also conduct an in-depth analysis of the challenges that such collaboration introduces to route planning in each mode.
With the growing exploration of cooperation between trucks and drones, contemporary research extends beyond the analysis of individual vehicles. To assess the impact of vehicle quantity on route planning, we further explore the complexities of route planning across diverse vehicle counts. Specifically, drawing from research conducted over the past two years, we concentrate on three situations in multiple trucks and multiple drones: multiple combinations of single truck and single drone, multiple combinations of single truck and multiple drones, and multiple trucks and multiple drones without predetermined pairings.
Furthermore, current research gives greater consideration to the optimization challenges in real-world scenarios. We therefore perform a thorough analysis of objective functions and constraints, categorizing them as time-related factors, drone performance limits, and operational constraints. By addressing these constraints, we attain a broader understanding of the issues investigated in the majority of the existing literature. Moreover, we have conducted a supplementary review that focuses on dynamic issues, which have received increased attention in the past two years. To our knowledge, this is the inaugural instance where dynamic issues have been included in such a review.
Lastly, we provide an overview of the solution methodologies employed, categorizing them into four types: the exact algorithms, the heuristic algorithms, the metaheuristic algorithms, and other algorithms. For each category, we undertake a systematic analysis and summation, contributing to a deeper understanding of the methodologies available to address these challenges.
In the context of prior research, several reviews have indeed delved into the collaboration between trucks and drones from various perspectives. Nonetheless, it bears mentioning that a substantial number of novel studies have surfaced in the last two years. This review provides a thorough examination of existing literature across three key aspects: cooperation modes, problem constraints, and solution methodologies. The distinctions between this review and existing reviews can be summarized as follows:
Khoufi et al. [
2] examined the role of drones in assisting trucks through an extension of the
TSP-D and
VRP-D problems. However, as drone technology has advanced, there have been some studies highlighting drones’ capability to undertake tasks independently.
Chung et al. [
3] focused on the drone route planning problem, categorizing it into drone operations (
DO) and combined drone-truck operations (
DTCO). In this process, the challenges and constraints encountered in real-world truck-drone collaboration have not been fully explored.
Macrina et al. [
4] also discussed the application and challenges of drones in the commercial field, specifically from the angle of drone assistance.
Li et al. [
5] summarized the collaborative route planning between trucks and drones from a two-echelon perspective, where the truck route constitutes the first echelon and the drone route the second.
Jazemi et al. [
6] focused on the scenario where unmanned devices (robots or drones) aid truck deliveries in last-mile delivery.
It is apparent that the current reviews have neglected a significant portion of research conducted over the past five years, particularly those studies from the last two years, and have not provided a comprehensive summary analysis including more than 200 articles. Furthermore, existing reviews are inadequate in terms of depth and comprehensiveness when it comes to addressing the problem constraints and challenges associated with collaborative route planning for trucks and drones.
To rectify this gap, the present paper embarks on a detailed examination of all literature on truck-drone cooperated route planning in the following sections.
The paper is structured as follows:
Section 2 provides a summary of the current background of the application.
Section 3 presents the classification of the truck-drone cooperation mode. In
Section 4, an analysis of the configurations of trucks and drones involved in the current literature is provided.
Section 5 offers an analysis of the problem objectives and constraints considered so far. The algorithms and solution methodologies applied in the literature are presented in
Section 6. Finally, some possible existing problems and future research directions are given in
Section 7.
7. Conclusions
This paper systematically analyzes and reviews over 200 research articles pertaining to the routing problem involving collaborated trucks and drones from 2015 to 2024. We categorize the application background, specify four categories for the truck-drone collaboration modes, summarize the existing configurations of trucks and drones utilized in current literature, classify the involved problems and provide a summary of existing solution methodologies.
Despite progress, there are still some limitations: firstly, existing research insufficiently addresses customer time window and truck-drone collaboration constraints, hindering practical application. Secondly, overlooking drone performance constraints complicates real-world implementation. Lastly, advancing research necessitates more precise models and algorithms for effective solutions in complex scenarios.
Additionally, we propose several potential directions for further research: Firstly, from the perspective of model construction and algorithm design, developing flexible and practical mathematical models is crucial for improving and innovating existing algorithms, thus enhancing the coordination efficiency between trucks and drones in complex environments. Meanwhile, considering multiple optimization objectives such as truck and drone routing distance, energy consumption, and task completion time, finding the optimal solution can be achieved through multi-objective optimization algorithms. Furthermore, future research should focus on exploring realistic solutions under time window constraints, as time windows are critical factors in delivery services. Besides, researchers can delve into the actual performance limitations of drones and develop more feasible methods, such as considering multiple visiting nodes and the impact of payload on energy consumption during delivery. Secondly, attention should be given to dynamic environment adaptability, studying how to achieve efficient collaborative route planning in dynamic environments. This includes developing algorithms that can update routes in real-time to respond to dynamic obstacles and unforeseen events in the environment, as well as researching adaptive planning strategies that allow trucks and drones to dynamically adjust their routes based on environmental changes. Lastly, from an environmental perspective, future research can expand the collaboration modes between drones and engine-fueled vehicles, including electric vehicles, to reduce pollution emissions.