DEVELOPMENT OF AN UNCREWED SEDIMENT SAMPLING SYSTEM
thesisposted on 2021-12-18, 19:46 authored by Jun han BaeJun han Bae
Sediment has a significant impact on social, economic, and environmental systems. With the need for an effective sediment management and monitoring system growing more important,
a method for precisely and reproducibly obtaining sediment samples that represent the actual environment is essential for water resource management and researchers across aquatic domains (such as lakes, rivers, reservoirs, mine drainage ponds, and wastewater lagoons).
Sediment sampling is usually carried out less frequently than water sampling because of the cost and labor involved. However, more frequent sediment sampling and an increase in the
range of the sampling area are necessary to more effectively monitor the ecosystem and water quality.
To fill this gap, robotic approaches for sediment sampling have been introduced. However, they are not tailored to a sediment sampling method and do not focus on the quality of
the sediment sample. Moreover, there are many challenges involved in developing such a sediment sampling system for the surface water of rivers, streams, lakes, ponds reservoirs, and lagoons. Thus, this study can be conducted to investigate to design and develop an uncrewed sediment sampling system for surface-water environments based on marine robot platforms that are capable of collecting intact sediment samples from a range of sediment types. As part of this study, an unmanned surface vehicle (USV) was used to deploy the underwater sediment sampler (USS) at the sampling locations. The USS adopted a core sampling method to collect the sediment samples. The specific requirements were integrated, taking into consideration the challenges posed by surface water and underwater environments, to design and develop an unmanned sediment sampling system.
The USV has two missions - deploying and positioning. Users can deploy the USV with the USS to the desired sampling area. Once the USV arrives, it has to maintain its position while launching the USS and during the sampling process. The USS also has two missions — launching and sampling. The USS must be a negative-buoyancy platform so it can reach the bottom and maintain its stability during sampling. To sample the sediment, the USS has to generate a sampling pattern. We defined and formulated challenges based on the missions of each platform.
The USV consists of three sub-systems; propulsion, launching, and monitoring system to accomplish missions. The propulsion system and launching system are necessary to accomplish deploying and positioning missions. The propulsion system is consists of two thrusters to navigate the USV. The launching system is to launch anchors for positioning and the USS for sampling. The monitoring system is to monitor and control other systems on-board via online video. The USS can generate sampling patterns based on three motions; linear, rotational, and hammering motion. We integrated servos, sensors, and mechanical components to generate three motions. The main system of the USS is completely waterproof, even for linear and rotational motion with enclosures, O-rings, and rubber bellows. Since the USS operates underwater, the water pressure causes the pressure difference between inside and outside the enclosure. We designed a pressure-equalizing system to compensate for the volume change because of sampling motions and pressure differences. Extensive field experiments were conducted to evaluate the proposed system. Users can monitor and control the system from the base station based on all data and images from each platform. The evaluation of the system is based on the data from sensors installed on each platform. Deploying and positioning missions of the USV can be shown based on the trajectory data. Launching and sampling missions of the USS can be validated based on depth, orientation, and reaction force data.
Contributions of the proposed unmanned sediment sampling system are, 1) It is the first unmanned system with a novel design to collect the less disturbed sediment samples even
from the inaccessible area and remove the potential risks of human-based sampling tasks, 2) We proposed and integrated a new sediment sampling pattern based on the sediment
sampling pattern analysis to increase the quality of sediment samples by minimizing disturbances, and 3) The proposed unmanned sediment sampling system is the first step toward the autonomous environmental monitoring system for more effective environmental monitoring.
This proposed system has many potential elements that can be a total solution for robotic environmental monitoring in addition to other features such as water sampling system, and various types of sensing system.