Autonomous Water Sampling Research Articles

A motion control framework for autonomous water sampling and swing‐free transportation of a multirotor UAV with a cable‐suspended mechanism

AbstractIn this work, we present an end‐to‐end solution for autonomous water sampling by utilizing an unmanned aerial vehicle (UAV) with a cable‐suspended mechanism. Towards this direction, a sampling mechanism is initially designed in such a manner that the water sampling success ratio is maximized. However, the disturbances, acting on the submerged mechanism due to the water flow during the sampling procedure, impede the stabilization of the vehicle above the desired sampling position. Consequently, to achieve the precise hovering of the UAV, the vehicle's sensor suite is further augmented with a load cell, a depth sensor, an ultrasonic sensor, and a camera. The respective measurements are appropriately fused by employing an extended Kalman filter (EKF). Hence, an estimate of the disturbances is available in real‐time and is incorporated into a Model Predictive Control scheme which compensates for the aforementioned disturbances and stabilizes the vehicle above the sampling location. Finally, a complete water sampling mission entails the safe and swing‐free transportation of the mechanism towards the sampling location and, then, to a position where the collected samples are postprocessed by human operators. Consequently, a model predictive controller is employed which ensures the navigation of the vehicle to the desired waypoints while minimizing the swinging motion of the mechanism. The state of the mechanism is obtained by fusing measurements provided by the load cell and the camera with an EKF. The performance of the proposed framework, which aims to address all the aspects of a water sampling mission, is demonstrated through real experiments with an octorotor.

Robotic environmental DNA bio-surveillance of freshwater health

Autonomous water sampling technologies may help to overcome the human resource challenges of monitoring biological threats to rivers over long time periods and across large geographic areas. The Monterey Bay Aquarium Research Institute has pioneered a robotic Environmental Sample Processor (ESP) that overcomes some of the constraints associated with traditional sampling since it can automate water sample filtration and preservation of the captured material. The ESP was originally developed for marine environment applications. Here we evaluated whether the ESP can provide reliable, timely information on environmental (e)DNA detections of human and fish pathogens and introduced fishes at U.S. Geological Survey streamgage sites in freshwater rivers. We compared eDNA collected via ESP at high frequency (e.g., every 3 h) with manual eDNA collections collected at lower frequency (e.g., weekly). We found that water samples filtered and preserved by ESPs successfully detected the DNA of human pathogens, fish pathogens and introduced fishes. Both ESP and manually collected samples provided similar information about target DNA presence. We suggest that the greatest current benefit of the ESP is the cost savings of high frequency, bio-surveillance at remote or hard to access sites. The full potential of robotic technologies like the ESP will be realized when they can more easily execute in situ analyses of water samples and rapidly transmit results to decision-makers.

Autonomous Water Sampling Payload Design

Ideally, water sampling process is conducted due to the need for physical, chemical and bacteriological analysis. Difficult access of water bodies, excessive need for personnel, time, and costs are factors that contribute to the complexity of the sampling process. In order to overcome these challenges, a water sampling payload unit is developed and mounted on Lockheed Martin’s multirotor Unmanned Aerial Vehicle (Indago UAV) for autonomous water sampling. In this work, the allowable requirements of the sampling unit in terms of weight, size, and dimensions have been given by the Lockheed Martin due to the limitations of Indago UAV. The developed unit is an integrated system that includes winch system, cup, sterilized sponge, spherical weight, and software. The winch system is used to lower and lift the cup and its components. The cup is well-sealed in order to prevent the sample from any dust, water or air when the winch is lifting the sample, however it is designed where allowing a water to flow in when the cup is reaching the water. It contains a sterilized sponge that absorbs the inflow water. A trapezoidal weight below the cup connected to the winch via a fisher line is used to lower the cup contents into the water and to seal the cup contents when the winch lifts the sample. The unit also includes height sensor and release mechanism. The height sensor detects the UAV’s height above the water. Once the required height is reached, the winch will start lowering the cup. When the required sample has been taken, the cup will move back up by the winch and will be sealed by the trapezoidal weight in order to avoid any spillage of water. The advantage of developed water sampling payload unit is to get the water sample without the need for an individual diver or boat and to provide a safer way to prevent contact with dangerous fluids. Moreover, it can be used to take a sample from a body of water that is difficult to access, possibly off a major road in sand or forest and spill dams of a mine site could be analyzed.

Adaptive Water Sampling Device for Aerial Robots

Water quality monitoring and predicting the changes in water characteristics require the collection of water samples in a timely manner. Water sample collection based on in situ measurable water quality indicators can increase the efficiency and precision of data collection while reducing the cost of laboratory analyses. The objective of this research was to develop an adaptive water sampling device for an aerial robot and demonstrate the accuracy of its functions in laboratory and field conditions. The prototype device consisted of a sensor node with dissolved oxygen, pH, electrical conductivity, temperature, turbidity, and depth sensors, a microcontroller, and a sampler with three cartridges. Activation of water capturing cartridges was based on in situ measurements from the sensor node. The activation mechanism of the prototype device was tested with standard solutions in the laboratory and with autonomous water sampling flights over the 11-ha section of a lake. A total of seven sampling locations were selected based on a grid system. Each cartridge collected 130 mL of water samples at a 3.5 m depth. Mean water quality parameters were measured as 8.47 mg/L of dissolved oxygen, pH of 5.34, 7 µS/cm of electrical conductivity, temperature of 18 °C, and 37 Formazin Nephelometric Unit (FNU) of turbidity. The dissolved oxygen was within allowable limits that were pre-set in the self-activation computer program while the pH, electrical conductivity, and temperature were outside of allowable limits that were specified by Environmental Protection Agency (EPA). Therefore, the activation mechanism of the device was triggered and water samples were collected from all the sampling locations successfully. The adaptive water sampling with Unmanned Aerial Vehicle-assisted water sampling device was proved to be a successful method for water quality evaluation.

Autonomous In Situ Measurements of Noncontaminant Water Quality Indicators and Sample Collection with a UAV

The objective of this research was to conduct in situ measurements of electrical conductivity (EC), pH, dissolved oxygen (DO), and temperature, and collect water samples simultaneously at different depths using an unmanned aerial vehicle (UAV). The UAV system consists of a hexacopter, water sampling cartridges (WSC), and a sensor node. Payload capacity and endurance of the UAV were determined using an indoor test station. The UAV was able to produce 106 N of thrust for 10 min with 6.3 kg of total takeoff weight. The thrust-to-weight ratio of the UAV was 2.5 at 50% throttle. The decision for activating the water sampling cartridges and sensor node was made autonomously from an onboard microcontroller. System functions were verified at 0.5 m and 3.0 m depths in 6 locations over a 1.1 ha agricultural pond. Average measurements of EC, pH, DO, and temperature at 0.5 m depth were 42 µS/cm, 5.6, 8.2 mg/L, and 31 °C, while the measurements at 3 m depth were 80 µS/cm, 5.3, 5.34 mg/L, and 24 °C, respectively. The UAV-assisted autonomous water sampling system (UASS) successfully activated the WSC at each sampling location. The UASS would reduce the duration of water quality assessment and help practitioners and researchers to conduct observations with lower operational costs. The developed system would be useful for sampling and monitoring of water reservoirs, lakes, rivers, and ponds periodically or after natural disasters.

Evaluation of a UAV-Assisted Autonomous Water Sampling

Water quality assessment programs for the management of water resources require the collection of water samples for physical, chemical, and biological analyses. Lack of personnel, accessibility of water bodies, and time constraints, especially after natural disasters and emergencies, are some of the challenges of water sampling. To overcome these challenges, a custom-made thief-style water sampling mechanism was developed and mounted on a multirotor unmanned aerial vehicle (UAV) for autonomous water sampling. The payload capacity and endurance of the UAV were determined using an indoor test station. The UAV was equipped with floatation, and electronic components were coated to prevent water damage in the event of a forced landing or for sample collection. Water samples from a 1.1 ha pond were collected with the developed UAV-assisted water sampling system and traditional manual methods. Dissolved oxygen (DO), electrical conductivity (EC), pH, temperature and chloride measurements were made on samples collected with both UAV-assisted and manual methods and compared. Percent differences between the two sampling methods for DO, EC, pH, and temperature were minimal except for chloride level. Percent differences between the two sampling methods for DO, EC, pH, and temperature measurements were 3.6%, 2.3%, 0.76%, and 0.03%, respectively. Measured chloride levels for the manual and UAV-assisted sampling methods were 3.97 and 5.46 mg/L. UAV-assisted water sampling may prove faster and safer than manual water sampling from large surface waters and from difficult to access water bodies.

A novel mesocosm setup for benthic‐pelagic coupling experiments

AbstractA new mesocosm setup containing both water column and sediment suitable for benthic‐pelagic coupling experiments is described. The presence of a large volume of water (>1.5 m3) with sufficient depth (4 m) on the top of the sediment, combined with a large volume of sediment on the bottom (30 cm height, 80 L volume) offers new opportunities for benthic‐pelagic experiments on the mesocosm scale. The experimental setup includes a mesocosm bag, a securing ring with a cap on the top, a sediment container on the bottom, sediment traps, an autonomous water sampling system at specific depths, and a newly developed sediment sampler for collecting samples without disturbing the system. The mesocosm setup was successfully deployed in the context of a benthic‐pelagic coupling eutrophication experiment in the CRETACOSMOS mesocosm facilities of the Hellenic Centre for Marine Research in Crete. A number of variables related to the technical aspects and proper ecosystem functions of the mesocosm setup were monitored throughout the duration of the experiment (58 d), which proved that the proposed setup is suitable for benthic‐pelagic coupling experiments, providing an intermediate experimental tool between small‐scale micro/benthocosm experiments and large scale in situ sea experiments.

Autonomous Water Sampling for Long-Term Monitoring of Trace Metals in Remote Environments

A remotely controlled autonomous method for long-term high-frequency sampling of environmental waters in remote locations is described. The method which preserves sample integrity of dissolved trace metals and major ions for month-long periods employs a gravitational filtration system (GFS) that separates dissolved and particulate phases as samples are collected. The key elements of GFS are (1) a modified "air-outlet" filter holder to maximize filtration rate and thus minimize filtration artifacts; and (2) the direct delivery of filtrate to dedicated bottle sets for specific analytes. Depth and screen filter types were evaluated with depth filters showing best performance. GFS performance is validated using ground, stream, and estuary waters. Over 30 days of storage, samples with GFS treatment had average recoveries of 95 ± 19% and 105 ± 7% of Fe and Mn, respectively; without GFS treatment, average recoveries were only 16% and 18%. Dissolved major cations K, Mg, and Na were stable independent of collection methodology, whereas Ca in some groundwater samples decreased up to 42% without GFS due to CaCO(3) precipitation. In-field performance of GFS equipped autosamplers is demonstrated using ground and streamwater samples collected at the Angelo Coast Range Reserve, California from October 3 to November 4 2011.