A Spiral-Propulsion Amphibious Intelligent Robot for Land Garbage Cleaning and Sea Garbage Cleaning

Abstract

To address the issue of current garbage cleanup vessels being limited to performing garbage cleaning operations in the ocean, without the capability of transferring the garbage from the ocean to the land, this paper presents a spiral-propulsion amphibious intelligent robot for land garbage cleaning and sea garbage cleaning. The design solution is as follows. A mechanical structure based on a spiral drum is proposed. The interior of the spiral drum is hollow, providing buoyancy, allowing the robot to travel both on marshy, tidal flats and on the water surface, in conjunction with underwater thrusters. Additionally, a mechanical-arm shovel is designed, which achieves two-degrees-of-freedom movement through a spiral spline guide and servo, facilitating garbage collection. Our experimental results demonstrated that the robot exhibits excellent maneuverability in marine environments and on beach, marsh, and tidal flat areas, and that it collects garbage effectively.

1. Introduction

Marine litter pollution has emerged as a critical economic, political, and environmental concern, garnering significant international attention [1,2]. According to the National Academy of Sciences’ 1997 estimates, approximately 6.4 million tons of garbage enters the oceans every year. A report by the National Oceanic and Atmospheric Administration (NOAA) in 2018 highlighted a concerning trend in the Arctic marine environment, with floating debris increasing almost twentyfold over the past decade [3]. These figures unequivocally demonstrate the worsening magnitude of the global marine litter pollution issue.

Multiple studies have shown that plastic waste constitutes a significant portion of marine and coastal litter [4,5]. Plastic products alone account for 80% of anthropogenic marine debris (AMD) resulting from human activities. Notably, beaches are particularly prone to AMD accumulation [6]. Research conducted on beach and riverside litter in the southeastern part of the Black Sea revealed that plastic products comprised over 75% of the litter [7]. As of 2017, it was estimated that around 150 million metric tons (MMT) of plastic were present in the marine environment [8]. The global oceans are estimated to contain at least 5.25 trillion plastic particles, with a combined weight of approximately 268,940 tons [9]. In a study conducted by Flores-Ocampo et al. in 2022, it was found that sediment samples collected at Tampico Beach in southern Mexico contained between 256 and 283 microplastic particles per 20 g of sediment, equating to roughly 13,392 microplastic particles per kilogram of sediment [10].

Plastic waste has had a significant impact on marine ecosystems [11]. According to Gall et al.’s study, marine debris affects a minimum of 690 distinct species, with 92% of the debris being composed of plastic [12]. It not only hinders navigation and maritime activities [13,14] but also disrupts habitats’ structure and functioning [5], leading to issues such as biological invasions [15]. Plastic waste negatively affects biodiversity [12,16], and it poses threats to the survival and reproduction of marine animals [15,17,18]. Moreover, ingestion of plastic debris by marine animals exposes them to toxic substances present in microplastics, including reproductive toxins, carcinogens, and mutagens. These toxic substances can propagate through the food chain, impacting higher trophic levels, and causing severe harm to marine ecosystems and human health [19,20]. Therefore, there is an urgent need to clean up marine and shoreline litter [21]. However, traditional methods of floating cleaning and shoreline litter cleaning rely primarily on manual labor [22]. Manual collection of waste on the water surface poses risks of accidental drowning and ingestion of toxic pollutants. Additionally, relying solely on manual labor results in low efficiency [23]. Most current garbage-cleaning vessels utilize the conveyor belt method for garbage collection. For example, A. Jayawant et al. proposed a water-surface garbage-cleaning robot equipped with a conveyor belt, which automatically cleans the water surface by collecting floating garbage [24]. J. Shalini Priya et al. developed a beach-cleaning robot with a conveyor belt mechanism for removing waste from sandy surfaces [25]. Shreya Phirke designed a garbage-cleaning robot that uses a conveyor belt mechanism to collect and remove marine debris [26]. Z. Wang et al. designed a robot that uses a conveyor belt mechanism to collect floating garbage [27]. However, the conveyor belt method presents several issues: firstly, garbage easily gets stuck during the conveyor belt transportation process; secondly, the conveyor belt’s collection accuracy is not high, making it difficult to collect all the garbage; thirdly, the conveyor belt collection structure is only suitable for the water surface—it cannot be used for collecting garbage in intertidal zones. Furthermore, most marine litter cleaning vessels lack the ability to transfer waste ashore, and they are not suitable for complex aquatic environments, limiting their application. These collection systems can also cause secondary pollution. Additionally, the equipment is costly, energy-intensive, labor-intensive, and inefficient. To address these issues, this study proposes a spiral-propulsion-based amphibious intelligent robot for marine litter cleaning and shoreline litter cleaning.

This paper introduces the design of an amphibious robot featuring a spiral drum and a mechanical-arm shovel as its primary mechanical structure. This design enables the robot to fulfill dual functionality: marine-surface garbage cleanup and tidal-flat garbage transportation. The robot can carry out various operations, including garbage collection and continuous execution of cleanup tasks, while possessing the ability to operate in both aquatic and terrestrial environments. By addressing the drawbacks of current marine-garbage-cleanup robots—such as high cost, inadequate automation, and low efficiency—this design offers an effective solution. The unique design features and innovations include:

• A mechanical structure based on a spiral drum that provides buoyancy, enabling the robot to traverse both marshy tidal flats and the water surface. This innovative design allows the robot to operate in a variety of environments, overcoming the limitations of traditional garbage cleanup vessels.
• The integration of underwater thrusters that work in conjunction with the spiral drum, further enhancing the robot’s mobility in marine environments.
• A specially designed mechanical-arm shovel that achieves two-degrees-of-freedom movement through a spiral spline guide and servo. This unique design feature facilitates efficient garbage collection in challenging environments.

Our experimental results demonstrate that the robot exhibits excellent maneuverability in marine environments and on beach, marsh, and tidal flat areas, and that it collects garbage effectively. The inclusion of these novel design elements sets this work apart from existing approaches, making a significant contribution to the field of garbage-cleanup robotics.

2. Related Work

Currently, water-surface- and nearshore-beach-garbage-cleaning robots can be categorized into four main types: cruising-type water-surface-garbage-cleaning robots; interception-type water-surface-garbage-cleaning robots; fixed-type water-surface-garbage-cleaning robots; and beach-garbage-cleaning robots [28].

2.1. Cruising Surface-Garbage-Cleaning Robot

The WasteShark, developed by South African entrepreneur Richard Hardiman, is a cruising surface-garbage-cleaning robot capable of navigating and collecting garbage on the water surface. However, it has limitations, such as its inability to automatically dump garbage and to close its garbage bin during the collection process, which may lead to garbage overflow [29]. Yicha Liang et al. proposed an innovative design of the forearm drainage and retraction device, based on deep-sea cage farming technology. However, this equipment is expensive, and it lacks universality [30]. Kong Shihan et al. developed an intelligent water-surface-cleaner robot system called IWSCR, which can autonomously perform tasks such as cruising, detection, tracking, grasping, and collection. Nevertheless, the collection system of this robot has certain limitations, and the operational costs are high, making it inefficient for long-term garbage collection [31]. Chidambaram Vigneswaran et al. designed a garbage-cleaning robot capable of autonomously moving in rivers and collecting garbage, which possesses certain visual detection capabilities, to identify and capture different types of garbage. However, due to its structural limitations, this robot faces difficulties in handling large and heavy garbage [32]. While cruising surface-garbage-cleaning robots have many advantages, they are limited in terms of application scenarios, the size and type of garbage they can handle, and their inability to achieve on-land transportation of garbage.

2.2. Barrier-Type Water-Body-Garbage-Cleaning Robot

Edgar Tovar proposed an innovative design solution called the “CSC (Catamaran Sargassum Cleaning) Integrated System” for seaweed cleaning and garbage cleaning using a catamaran. The system utilizes a trawl net to collect brown algae and garbage, which is then transported and stored on the boat for further processing. The system features detachable equipment, providing it with strong environmental adaptability. However, the automation level of this system is relatively low [33]. Overall, the barrier-type water-body-garbage-cleaning robot device is relatively large and expensive. The operation process requires manual removal of the filled garbage from the vessel, increasing the complexity and labor cost. Additionally, the placement of the barrier may impact navigation, limiting its applicability to specific scenarios.

2.3. Fixed-Type Water-Surface-Garbage-Cleaning Robot

The fixed-type water-surface-garbage-cleaning robot uses a device fixed on the shore and it utilizes a water pump’s suction action to create a height difference between the inner and outer liquid levels, pulling the garbage into the collection device. This robot is typically fixed in a specific area, limiting its mobility and working radius. It is suitable for locations such as coastlines, docks, and ports, where fixed-type devices are required for garbage cleaning, but it is not applicable to vast water bodies. Furthermore, compared to other types of garbage-cleaning robots, fixed-type robots have lower work efficiency. Due to the need for fixed devices and water pumps, the cost of fixed-type water-surface-garbage-cleaning robots is higher. For example, the Seabin, developed by the Australian company Seabin Pty Ltd., Mullumbimby, NSW, Australia, is a “trash skimmer”, used to clean floating garbage and contaminated organic matter in calm, sheltered environments, such as docks, ports, and yacht clubs. The Seabin uses a submersible pump to continuously draw water inward, and it filters the water through a triangular mesh bag, leaving the garbage in the collection bag. Although the Seabin is effective in capturing different types of floating garbage around marinas, assessments have found that its garbage capture rate is lower than manual cleaning and that its cost is higher than manual cleaning [34]. In conclusion, fixed-type water-surface-garbage-cleaning robots have application advantages in specific situations, and can provide continuous garbage cleaning services. However, they have low work efficiency, limited applicability, and higher costs, making them unable to flexibly address water-surface garbage collection issues.

2.4. Beach-Garbage-Cleaning Robot

In addition to water-surface-garbage-cleaning robots, beach-garbage-cleaning robots are also a research focus, and have achieved some relevant results. For instance, Amit Kumar Yadav et al. developed a robot that can travel laterally along the beach and can clear up tiny fragments of garbage. The robot is equipped with a rake, conveyor belt, and solar panels. However, the automation level of this robot is relatively low [35]. Nasreen Bano et al. designed and built a prototype of a remote-controlled beach-cleaning robot, which includes a filtration mechanism and a drive mechanism. The robot’s movement is remotely controlled through a Bluetooth module, and a vibration mechanism is used to separate sand from small debris, such as plastic fragments, glass shards, cans, and cigarette butts [36]. Tomoyasu Ichimura et al. developed a small beach-cleaning robot called Hirottaro, which mimics the use of a broom and dustpan to clean the floor. It is equipped with a scanning rangefinder that uses sensor information to calculate the robot’s position and direction, enabling precise collection and processing of beach garbage [37]. Overall, beach-garbage-cleaning robots tend to have larger dimensions, limited flexibility in narrow or crowded beach environments, higher energy consumption, poor continuous operation capabilities, and relatively low automation levels. They typically require manual remote control or operation. Additionally, these robots can only clean the garbage on the beach, and are unable to effectively collect garbage from the water surface.

2.5. Summary

Current research primarily focuses on developing robots and devices capable of collecting and cleaning floating debris on the ocean surface. These devices employ technologies such as mechanical retrieval, adsorption, sieving nets, and sensors, to effectively collect floating garbage. However, their application scenarios in the marine environment are limited, and they may not cope with complex and variable marine conditions or large-scale floating debris. Another key challenge is transferring the collected garbage to land, for processing and recycling. The transportation process between ocean and land needs to consider different environmental conditions and facilities, to ensure safe transfer and effective treatment of the garbage. Similarly, the structure of beach-garbage-cleaning robots is not suitable for water environments, rendering them incapable of addressing surface garbage cleaning on the ocean. Additionally, the collection and cleaning of floating debris on the ocean surface presents challenges, in terms of cost and energy consumption. The development and maintenance of these devices requires significant financial and resource investment, resulting in high costs in practical applications. Therefore, future research needs to address these challenges and to develop comprehensive, efficient, and sustainable marine- and land-garbage-cleaning robot systems. This paper presents the design of a robot with a primary mechanical structure consisting of a spiral drum and a mechanical arm-shaped bucket. The robot effectively addresses the aforementioned issues, and achieves the dual functionality of cleaning surface garbage and transferring beach litter, thereby enhancing the efficiency and automation level of water surface and beach garbage cleaning.

3. Design of Amphibious Robot Structure

The spiral-propulsion-based amphibious intelligent robot for garbage cleaning proposed in this paper aims to automatically collect floating debris on the water surface and debris in areas such as coastal regions, lakes, and mudflats. Conventional garbage collection vessels are ineffective in these regions, due to their shallow depths, low water disturbance, and sandy terrain. To address these challenges, a structural design is proposed, consisting of a hollow spiral-propulsion drum, a chain drive structure, a mechanical-arm shovel for garbage collection, a waterproof box, and the main hull (Figure 1).

Figure 2 illustrates the overall working schematic of the spiral-propulsion-based amphibious intelligent robot. It can be remotely controlled through a PC host or a mobile app, to clean garbage on the sea surface. The rotation speed and direction of the spiral roller can be adjusted to control its movement, while the mechanical bucket arm collects the garbage. By combining the spiral roller and the mechanical bucket arm, the robot can transport litter from the water surface to the shoreline. The robot can collect garbage from the sea surface and shoreline areas, transport it to a designated collection area, and continue executing instructions for garbage collection. Figure 3 presents the working schematic of the litter collection process, showing the movement of the bucket and the feeding motion of the garbage into the robot’s garbage bin. Figure 4 displays the overall operational schematic, where an operator controls the robot via a PC terminal, for garbage collection from the sea surface and for onshore transportation. The cleaned garbage includes plastic waste, such as bottles, cans, and floating debris.

3.1. Spiral Propulsion System

The spiral drum has a historical background in coal mining, and it has undergone improvements by countries such as the United Kingdom, Germany, France, and the former Soviet Union. Initially used in coal cutting machines, the rotating spiral drum effectively excavates coal and transports it through internal conveyors or pipelines, significantly enhancing mining efficiency and reducing manual labor [38]. However, the spiral drum’s applicability is limited in complex environments. To address this, the spiral drum has been modified in this study, to provide excellent maneuverability in nearshore and beach areas, enabling the robot to operate in both aquatic and terrestrial environments. The outer part of the spiral drum incorporates spiral blades based on the Archimedean spiral principle, while the interior is hollow. By carefully designing the dimensions of the spiral drum, the robot obtains sufficient buoyancy, allowing it to perform well on water surfaces and land. The drive structure of the spiral drum primarily consists of a DC motor and a chain drive mechanism. This chain drive includes a pair of gear wheels with matching tooth counts and a corresponding chain. The DC motor is positioned inside the main body of the robot, at the rear ends on both sides, while the spiral drum is situated externally. The rotation of the spiral drum is achieved by the chain drive mechanism. One end of the outer casing of the float forms a rotational pair with the supporting shaft fixed on the motor housing end face, while the other end forms a rotational pair with the motor’s output shaft. The supporting shaft is secured to the robot frame, and the two rotational pairs are connected by the chain, enabling the rotation of the spiral drum. Power is supplied to the motor via a generator and an umbilical cable, with control signals transmitted from the main control board through the same cable. Sealing elements are incorporated between the supporting shaft fixed on the motor housing end face and the robot frame, and between the motor’s output shaft and the frame, to effectively seal the gaps between the motor and the propulsion casing. The spiral drum of the robot is constructed from stainless steel, providing exceptional corrosion resistance. Its high hardness allows it to withstand seawater erosion and collision damage. Additionally, the large surface area of the spiral drum ensures extensive contact with the ground, when traversing areas like beaches, thus enhancing buoyancy and traction. The movement posture of the robot is controlled by adjusting the direction and speed of the two spiral propulsion motors. Similar to tracked vehicles, it utilizes differential steering, to enable turning, through slipping. The control modes are as follows: a simultaneous left turn of both spiral drums results in lateral movement to the left, while a simultaneous right turn leads to lateral movement to the right. Inward rotation of both spiral drums propels the robot forward, while outward rotation enables backward movement. Unequal rotation speeds of the drums on both sides facilitates turning and maneuvering. These features greatly enhance the robot’s maneuverability and its ability to navigate challenging terrains, thereby ensuring outstanding amphibious performance. The entire spiral propulsion system operates on the principles of the Archimedean spiral, which combines uniform linear motion and uniform circular motion.

3.2. Mechanical Arm-Type Shovel

To address these challenges, this paper introduces a novel mechanical-arm-type shovel structure as a solution. The shovel structure comprises three main components: the shovel itself; a spiral mechanism; and guide rails. The design of the shovel incorporates a wide-bottom shape, enabling efficient collection of larger volumes of garbage. To prevent garbage from slipping off during collection, side plates are added to the shovel. Furthermore, the bottom of the shovel is tilted downward at a 100-degree angle, to facilitate rubbish collection. In intertidal areas, multiple drain holes are strategically placed at the bottom of the shovel, to automatically filter out interfering substances, such as dust and sediment. The proposed mechanical-arm-type shovel allows for movement in two degrees of freedom: the feeding degree of freedom along the guide rails, and the rotating degree of freedom around the servomotor axis. These two degrees of freedom work in tandem, enabling the shovel to move along the guide rails during garbage collection. By adjusting the tilt angle of the shovel, using the servomotor, the shovel can be rotated upwards by 120 degrees or more, allowing the garbage to be dumped into the robot’s garbage collection box. This mechanism effectively achieves the function of garbage collection. For a visual representation of the mechanical-arm-type shovel’s operation in garbage collection, refer to Figure 4, which illustrates the specific working schematic diagram.

3.3. Design of the Waterproof Box

Given the robot’s maritime and intertidal usage, waterproof performance is crucial. A waterproof box structure is adopted, consisting of a sealed waterproof garbage bin and a waterproof box for the main control board and chips. The box has two layers, with a hollow space for absorbent materials to provide protection in case of water leakage. The box is sealed with waterproof adhesive, to prevent water ingress, effectively protecting the robot’s circuitry (Figure 5).

4. The Design of the Control System

The amphibious garbage-cleaning robot, designed in this paper, incorporates two control schemes. The first scheme involves remote control, using an infrared remote controller, while the second scheme allows control through a mobile app. Both control schemes enable the manipulation of the robot’s movement, and they facilitate garbage collection in environments such as the sea and mudflats. Figure 6 illustrates the overall design diagram of the control system for the amphibious garbage-cleaning robot. The control system comprises a master and a slave. The master side refers to the mobile app, which can transmit control commands to the slave robot and receive video information from the slave. The slave unit encompasses the robot itself, consisting of components such as an ESP32-CAM wireless communication and camera module, a control board utilizing an STM32 microcontroller, a driving unit, a collection unit, and a power supply system. The driving unit is equipped with an underwater propeller and left-drum and right-drum motors, which can be controlled by the STM32 driver board, to output control signals, thereby facilitating the rotation of the drums and propeller for robot movement. The collection unit involves a bucket stepping motor and a bucket servomotor, which can also be driven by control signals output from the STM32 control board, to facilitate garbage collection by controlling the bucket. The implementation of the infrared remote control entails the transmission of wireless infrared signals from the remote controller. The integrated infrared receiver on the STM32 control board receives and decodes the signals, obtaining control commands. Based on these commands, the power system and collection system are controlled, to execute the corresponding movements.

Alternatively, the operator can control the robot using the mobile app. The ESP32-CAM module on the robot facilitates wireless communication with the master via WiFi. It receives commands transmitted by the master, and it forwards them to the STM32 control board, through a serial port. The STM32 control board then regulates the driving and collection systems, to perform the desired actions. Additionally, the ESP32-CAM module incorporates a camera that captures the road conditions ahead of the robot, transmitting the live video feed to the master. The mobile app allows real-time viewing of the video, facilitating adjustments to the robot’s motion, based on the camera feed, to optimize garbage collection. When garbage is detected ahead, the operator can control the robot to approach the garbage, provide instructions to the bucket for collection, and deposit the collected garbage into the collection bin.

5. Experimental Results and Analysis

The robot conducted garbage collection experiments on both land and water surfaces, focusing on robot motion testing and floating garbage cleaning. On land, the robot primarily relies on helical drums for movement, while an underwater propeller enhances its speed on the water surface. The robot’s highly waterproof main body provides buoyancy during water operation, with the underwater propeller facilitating movement, while the helical drums contribute to steering. Figure 7 and Figure 8 depict the robot’s test runs on land and water, respectively. To ensure experimental accuracy, a 5 m test distance was selected, and each scenario was repeated three times, for reliable results.

The drum speed of the robot was set at approximately 0.5 r/s, resulting in an average speed of 0.53 r/s. On land, the robot achieved speeds of 0.27 m/s, 0.31 m/s, and 0.29 m/s, with an average speed of 0.29 m/s. On the water surface, speeds of 0.39 m/s, 0.25 m/s, and 0.34 m/s were obtained, averaging at 0.33 m/s. The experimental results indicated consistent movement speed on the water surface and drum speed on land, demonstrating excellent maneuverability in both environments.

Table 1. Experimental Results.

Test Parameter	Test 1	Test 2	Test 3	Test 4
Drum Speed	0.50 r/s	0.50 r/s	0.60 r/s	0.53 r/s
Land Movement Speed	0.27 m/s	0.31 m/s	0.29 m/s	0.34 m/s
Water Surface Movement Speed	0.39 m/s	0.25 m/s	0.34 m/s	0.33 m/s

summarizes the main tested parameters and experimental results of the prototype.

Based on the tests, the designed amphibious garbage-cleaning robot has an operational time of approximately 6–8 h. In unobstructed and interference-free environments, it can navigate with a maximum radius of 80 m, covering an area of 20,096 square meters. The garbage bin has a capacity of 0.5 m³, and the robot can handle a maximum garbage weight of 10 kg.

Table 2. Main Structural Dimensional Parameters of the Robot.

Parameter	Length	Width (Diameter)	Height
Main Body	0.50 m	0.53 m	0.33 m
Drum	0.50 m	0.11 m	-
Shovel	0.20 m	0.34 m	0.30 m
Guide Rail	0.30 m	-	-
Screw Mechanism	0.30 m/s	0.008 m/s	-

presents the main dimensional parameters of the robot’s outer appearance.

Figure 9 illustrates the control of the robot’s screen through a mobile app, while Figure 10 displays the real-time camera perspective. These figures showcase the intelligent capabilities of the robot, allowing the operator to monitor its field of view in real-time through the onboard camera, using a mobile app.

6. Conclusions

This paper introduces a spiral-propulsion-based amphibious intelligent robot designed for garbage cleaning, demonstrating its superior performance in marine debris removal through experiments. The results of the experiments validated the robot’s amphibious capabilities and consistent speeds in water and on land. The robot effectively collects marine debris and transports land-based waste, providing a significant advancement in marine garbage collection. The mechanical structures of the spiral roller and bucket enable smooth operations in diverse environments, addressing the challenges of garbage collection. The intelligent control system enhances efficiency, reduces human labor, and maintains low energy consumption for sustainable operation. Moreover, the robot’s manufacturing costs are relatively low, resulting in reduced investment for large-scale applications. In summary, this spiral-propulsion-based amphibious intelligent robot exhibits amphibious capabilities, high automation, low energy consumption, and affordable manufacturing costs, offering a practical and promising solution for marine garbage management. Future work will focus on enhancing the robot’s automation and intelligence, to further improve garbage collection and transportation efficiency. By reducing human intervention and costs, the robot’s performance will be enhanced, leading to more effective cleaning and to mitigation of the adverse impacts of garbage pollution on humans and on the environment.