Development of Unmanned Surface Vehicles System for Water

Quality Inspection

Wenxuan Guo

, Yusen Tang

and Jianjun Wang

1,*

School of Naval Architecture and Ocean Engineering, Huazhong University of Science and Technology, Wuhan, China

Faculty of Arts, McGill University, Montreal, Canada

Keywords: Unmanned Surface Vehicles, Water Quality Inspection, Internet of Things, Mobile Terminal, MQTT.

Abstract: In recent years, the problem of water pollution has attracted wide attention all over the world. To strengthen

water quality monitoring, a water quality inspection system for Unmanned Surface Vehicles (USV) based on

the Internet of Things (IoT) was designed. The system uses the Message Queuing Telemetry Transport

(MQTT) protocol to construct the boat-cloud-shore communication link. Design the terminal system of the

USV to realize state perception, motion control, and data sharing. The mobile client is developed based on

the Android platform, which supports real-time monitoring and remote control of the USV. Automatic control

of USV movement and real-time monitoring of water quality is realized. After the actual water surface trial,

the communication of the system is stable, with manual remote control, fixed-point inspection, independent

cruise, and other functions, which verify the feasibility of the system design.

1 INTRODUCTION

In recent years, people pay more and more attention

to the exploration, development, and protection of

water resources. The traditional water quality

inspection is to organize personnel to the scene area,

points for sampling, and then sent to the laboratory

for data analysis and water quality inspection. It is

time-consuming and laborious, easy to cause

secondary pollution, and can't guarantee the

timeliness of monitoring (Kondle R et al., 2020).

Unmanned Surface Vehicles (USV) is a multi-

purpose small surface carrying platform that can sail

by remote control or autonomous way. It has broad

prospects in the fields of marine transportation,

marine environment investigation, and marine

resources exploration. With the rapid development of

the Internet of Things (IoT), Big Data and cloud

computing, and other emerging technologies, the use

of USV for water quality inspection has become a

trend (Steimle E T and Hall M L, 2006). Therefore, it

has certain research significance and engineering

value to design and develop a set of USV water

quality inspection systems based on IoT

communication technology, which uses mobile

terminals to monitor USV to perform water quality

inspection tasks.

In actual projects, the water quality inspection

system not only needs to receive remote sensing data

in real-time, including water quality monitoring data

and sampling positioning data, etc., for data

processing and interactive display. In the USV water

quality inspection system, the data acquisition unit is

the core of the whole system. When designing the

data acquisition unit, this paper focuses on the design

of sensors for three indicators of water temperature,

carbon dioxide concentration (CO

), and Hydrogen

ion concentration (pH). Use sensors and Internet of

Things technology to collect and send data. At the

same time, it is necessary to be flexible and

compatible with various inspection modes, such as

random inspection, fixed-point inspection, and roving

inspection (Madeo D et al., 2020). To meet the needs

of water quality inspection operations, this paper

designed a water quality inspection system for USV

based on IoT technology. In this system, the USV

completes autonomous control, data acquisition and

analysis. And the mobile client is responsible for state

monitoring and command decision. In addition, a

remote monitoring program and mobile phone

application software was developed, and the IoT

communication technology was adopted to realize

remote information sharing and control instruction

issuance. Through the system, a user can remotely

control USV anytime and anywhere by using a

Guo, W., Tang, Y. and Wang, J.

Development of Unmanned Surface Vehicles System for Water Quality Inspection.

DOI: 10.5220/0011887000003536

In Proceedings of the 3rd International Symposium on Water, Ecology and Environment (ISWEE 2022), pages 21-28

ISBN: 978-989-758-639-2; ISSN: 2975-9439

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

mobile phone, water quality data collected at the USV

terminal can be quickly obtained, and the

performance of the traditional water quality

inspection system is greatly improved.

2 DESIGN OF USV WATER

QUALITY INSPECTION

SYSTEM

As shown in Fig. 1, the overall architecture of the

system is mainly divided into three parts, which are

the USV subsystem, mobile client, and cloud server.

APP

Aliyun

MQTT

Mobile Client

Cloud Server

Industrial

Computer

PLC GPS

Propulsion

Controller

Electric Propeller

Modbus

USV

Electrochemical

workstation

Figure 1: USV water quality inspection system structure.

The USV subsystem mainly consists of an

onboard industrial computer, programmable logic

controller (PLC), GPS receiver, propulsion

controller, electric propeller, electrochemical

workstation, and other equipment. The USV has a

certain degree of autonomy, focusing on the functions

of state perception, motion control, and data sharing,

and can realize multi-source information fusion

processing and drive control (T. H. Yang et al., 2018).

Moreover, its modular design is easy to flexibly

expand the subsequent functions.

The mobile client completes the remote

monitoring function of the system. This paper

specially designs the application software based on

the Android system, which is based on the Android

Studio program development environment and is

developed using JAVA. Based on the cellular mobile

network, users can obtain the status information of the

USV in real-time at the mobile terminal and send

various control commands.

Cloud server currently uses Alibaba Cloud server

that supports free small-scale data transmission.

Relying on the cloud platform of Aliyun Internet of

Things, using Message Queuing Telemetry Transport

(MQTT) for network communication, the USV

terminal interacts with the mobile terminal through

the cloud. To realize the remote monitoring of USV,

a boat-cloud-shore communication link is constructed

to complete the cloud flow of data in the cloud server.

According to the requirements of different

projects, we can expand the related functional

modules based on this architecture, such as video

transmission unit, pollution source detection unit (G.

Zhang and Y. Hao, 2020), etc. This paper, the design

and application of the monitoring system are mainly

focused on motion control in the water quality

inspection task of USV.

2.1 Design of IoT Communication

MQTT is a lightweight IoT transport protocol based

on message publish/subscribe mode, which has the

advantages of low bandwidth and easy

implementation. In this protocol, the publisher, server

and subscriber are involved, i.e. each part in the

corresponding boat-cloud-shore communication link.

In this system, both the USV terminal and the shore

mobile terminal serve as clients and simultaneously

serve as a publisher and a subscriber of messages. The

IoT cloud platform is used as a message cloud flow

server. It completes the authentication of client

devices by logging in and obtaining authentication

information such as server address and port number

and realizes the initialization and connection of

MQTT communication.

When using the MQTT protocol to communicate

with the cloud flow server, the transmitted message is

divided into two parts, Topic and Payload. Where, the

topic is the type of message, such as speed, mode, etc.

If one terminal publishes a message about a topic, the

other terminal will receive the content of the

corresponding message after subscribing to the topic,

that is, the payload (A. Eleyan and J. Fallon, 2020).

In this monitoring system, the payload data adopts the

ICA standard format Alink JSON data format and

transmits the specific speed value and model number,

etc. To distinguish messages under different topics,

the topic communication identifier needs to be

customized in the Internet of Things platform, and

some customized topics are shown in Table 1.

Table 1: Custom Topic (Part).

Mobile Client

Directive Title

Topic

Identifier

USV

State Title

Topic

Identifier

Mode Switch MODE Latitude Lat

Target Position TGT Longitude Lon

ISWEE 2022 - International Symposium on Water, Ecology and Environment

Set Speed RPM Speed Spd

Manual WSAD Heading HDG

Testing ANAL Quality WAQ

2.2 Design of USV Subsystem

2.2.1 Control Module

The control module is the core of the USV subsystem,

and it consists of an Advantech ARK-3500 embedded

industrial computer and a SIMATIC S7-1200PLC

controller. Among them, the onboard industrial

control computer is the control center of the USV

subsystem. Equip and run the terminal monitor

program, which can bidirectionally transmit real-time

parameter information and control instructions.

Responsible for the calculation of control logic and

algorithms, with information interaction and

processing functions.

S7-1200 controller has the advantages of compact

structure, many interfaces, and modularization.

Mainly through the accurate control of the thruster

controller and the electrochemical workstation, the

navigation control and water quality inspection

functions of the USV are realized. At the same time,

the internal logic program can also process double

GPS signals and water quality inspection data, and

carry out multi-source information fusion and

processing to obtain USV sensing data. And the real-

time data is packaged according to a specified

interactive format and then sent to the onboard

industrial personal computer.

2.2.2 Sensing Module

The sensing module is composed of GPS and an

electrochemical workstation, which provides

information such as the position, speed, heading, and

water quality of the USV for inspection control. The

USV is equipped with a TimeNav-H positioning and

direction-finding receiver and two GPS antennas.

Where the main antenna is located at the stern and the

slave antenna is located at the bow, the current motion

state can be calculated.

The electrochemical workstation realizes the

water quality inspection function. The pump,

solenoid valve, and analyzer work together to

complete the integrated water sampling-water quality

testing-visual analysis-water sample elimination, and

other inspection processes (L. S. Bratchenko et al.,

2022). Automatic collection, analysis, and treatment

of water samples are realized.

There are three types of sensors used in

monitoring purposes embarked on workstation.

Water temperature, carbon dioxide concentration

(CO

) and Hydrogen ion concentration (pH), as

follows:

a. Temperature transducer

Temperature is the basic information of water quality.

When collecting temperature information, the sensor

used by USV water quality inspection system is the

temperature and humidity sensor of OMEGA

Company. This sensor can realize the digital signal

output function, and has the advantages of

debugging-free and simple peripheral circuit. It still

has high temperature detection accuracy under harsh

water conditions.

b. Carbon dioxide concentration sensor

The concentration of carbon dioxide is the main

measure of water quality. If the concentration of

carbon dioxide is too high, the water area may be

polluted. In the USV water quality inspection system,

NDIR carbon dioxide concentration sensor is used.

This sensor has the function of automatic calibration,

and the accuracy of signal acquisition is high.

c. pH sensor

For the pH data of water area, the USV water quality

inspection system adopts a composite pH electrode,

which includes a glass electrode and a test electrode,

and converts the pH value into an electrical signal.

2.2.3 Driver Module

The propulsion module of the USV subsystem adopts

an electric propulsion mode with fast response and

wide speed regulation range. It is equipped with two

propeller propellers and two matched electric

propulsion controllers (Rybin, V. G. et al., 2020).

When the USV moves, the PLC inputs the

corresponding digital signal and analog signal to the

propulsion controller according to the received

control command to realize the positive and negative

rotation of the propeller as well as the speed

regulation function. The steering motion of the USV

can also be realized by using the rotation speed

difference between the two propeller propellers.

3 SOFTWARE DEVELOPMENT

AND REALIZATION

3.1 Mobile Client Application Software

Design

In the mainstream mobile terminal operating system,

Android is characterized by its Linux-based open-

source operating system, which is highly applicable

to portable intelligent terminal devices and has the

Development of Unmanned Surface Vehicles System for Water Quality Inspection

advantages of low development cost, small difficulty,

and large market share. Therefore, this paper will

design the mobile client application software based

on the Android operating system, as shown in Figure

2, which covers the functions of status display, target

positioning, mode switching, speed regulation, and

manual direction control.

User Interface

Target Location

Target Velocity

Direction Control

Mode Switch

Latitude

Heading

Speed

Longitude

Status Display

Operation

Instruction

Fixed-point Inspection

Manual Control

Autonomous Cruise

Expand Functions Live Picture

Water Quality Inspection

Selective USV

Figure 2: Mobile terminal application framework.

The key to developing mobile application

software with Android Studio is to establish a

communication connection with the IoT cloud

platform (M. K. Madisa and M. K. Joseph, 2018).

Considering the issue and subscription of topic

content based on the MQTT communication protocol,

the Handler message transfer mechanism is

introduced in the design and development, which is

used to send, receive and process messages, and

realize the update of interface state data.

Figure 3: Mobile client application software interface.

As shown in Figure 3, on the mobile terminal

interface, different control functions correspond to

different topic information, triggering click events,

and the instruction data will be uploaded to the IoT

cloud platform in JSON format and sent to the USV

terminal via the cloud server so that the remote USV

can execute the control commands under the

corresponding topic.

3.2 USV Terminal Program Design

3.2.1 Onboard Industrial Computer

Program

The remote monitoring program for the USV terminal

is designed and developed based on LabVIEW. The

program block diagram replaces the traditional code

language and adopts data flow programming. The

program is intuitive and easy to understand and

convenient to run. As shown in Figure 4, the software

design of the onboard industrial computer mainly

includes two parts: the cloud dialogue part and the

communication cycle with PLC, so the parallel cycle

design mode can be adopted.

Figure 4:

Parallel Loops.

The onboard industrial control computer can be

regarded as a hub for data exchange at the USV

terminal. Its data communication is divided into two

parts, namely, communication with the cloud server

of the IoT and communication with the underlying

PLC controller, to collect, process, and transfer

various data inputs and outputs.

In the circular structure of communication with

the onboard PLC, the Modbus library encapsulated by

LabVIEW is introduced to establish the Modbus

communication connection. By reading the data in the

PLC holding register, each state information of the

USV is obtained and then used for cloud interaction

after data processing. At the same time, various

parameters of the USV terminal in operation will also

be recorded by the monitoring program to the local

file in real time for subsequent data analysis.

Based on the communication technology of the

IoT, the USV terminal uses MQTT communication to

publish and subscribe to topics with the cloud server.

The monitoring program at the terminal of the USV

obtains the data such as water quality information and

USV posture collected and processed by PLC.

Packaging the sensing information of the USV

terminal into a plurality of topics to be released to the

ISWEE 2022 - International Symposium on Water, Ecology and Environment

cloud. At the same time, subscribe to the remote

instruction topic in the cloud server, and obtain the

mode number, expected speed, target latitude,

longitude, etc. according to the flag bit. In addition,

as the control module of the USV subsystem, the

terminal monitoring program, after obtaining the

remote command information, converts each

operation command into a data form through the

built-in mode algorithm and sends the data form to

the PLC controller (W. Wei et al., 2019), to finally

realize the autonomous navigation of the USV and

water quality inspection according to the command of

the mobile client. It should be noted that the control

algorithms in different modes can be independently

designed and developed in the software, which

facilitates the subsequent function expansion and

greatly improves the flexibility of the system.

3.2.2 PLC Control Program

The main function is to collect, process and transmit

GPS information and water quality information from

the sensing module. At the same time, each control

instruction transmitted by the onboard industrial

control computer is received, and corresponding

digital or analog signals are input to the propeller

controller and the electrochemical workstation after

logic processing. And finally, the navigation control

and water quality inspection functions of the USV are

completed.

In the main program of the PLC, the Modbus TCP

communication connection with the USV terminal

monitoring program is established first. Next, the

perception information is extracted and analyzed to

obtain the current longitude, latitude, speed, heading,

and water quality. The data sent and received are

formatted and stored into Data Blocks for program

calls and data transmission. Finally, based on the

received mode command, a function block for

executing navigation control or water quality analysis

is selected. In the motion control subprogram, the

incremental PID controller is designed to calculate

the rotation speed difference increment of the motor

and correspondingly input the left and right motors to

realize the navigation control of the USV.

3.3 Application of USV Water Quality

Inspection System

As a platform for users to analyze and operate, the

mobile terminal in the USV water quality inspection

system plays the role of state monitoring and

command decision-making, while the USV terminal

has a certain degree of autonomy and can realize state

perception, motion control, etc.

When the water quality inspection system works

normally, the state parameters of the USV on the

mobile user interface will be updated in real-time.

Users can view the position, posture, and speed

information of the real-time USV at the mobile client

anytime and anywhere, and click the "position" icon

to pop up the built-in Baidu map. As shown in Figure

5, calibrate the position and heading of the current

USV on the electronic map.

Figure 5: Monitoring interface and electronic map.

Figure 6: Control interface and virtual joystick.

Development of Unmanned Surface Vehicles System for Water Quality Inspection

As shown in Figure 6, users can select different

control modes according to the water quality

inspection requirements and issue decision

instructions at the mobile phone terminal, thus

realizing the remote control of the USV. During

manual control, the user operates the virtual rocker at

the mobile phone terminal to remotely control the

USV to advance, reverse, and right or left rudders. By

dragging the rotating speed lever, the speed of USV

can be controlled in real-time. To realize random

sampling inspection in the water area. When the user

presses the "TEST" button, the USV equipped with

the electrochemical workstation will independently

complete the integrated processes of water area

sampling, water quality inspection, visual analysis,

and water sample discharge, thereby helping the user

to quickly obtain water environment information.

When fixed-point inspection, the user selects the

navigation sampling point. The USV can get the

latitude and longitude of the target point, sail from the

current position to the target position automatically,

and finally stop there. And start the electrochemical

workstation for integrated water quality inspection

and analysis.

Using the autonomous cruise function can realize

the patrol inspection in the water area. The user needs

to import the path planning file in advance and switch

to autonomous cruise mode. The USV terminal reads

the local planning file, sequentially traverses the

longitude and latitude values of the path points, and

conducts independent patrol inspections along the

planned route.

4 COMMISSIONING AND

ANALYSIS

4.1 Native Debugging

To verify the feasibility of the water quality

inspection system proposed in this paper. Firstly, each

module of the system is configured and debugged

locally to test whether the communication,

positioning, power, software, and hardware functions

of the system are normal or not, to fully prepare for

the water surface trial. Figure 7 shows the actual

debugging situation.

Figure 7: Native debugging.

After testing, the IoT cloud platform has stable

communication with the mobile terminal and the

USV terminal and can carry out data flow in the

cloud. The mobile client can display the status of the

USV in real-time, and test the normal functions of the

system such as manual control, speed adjustment, and

mode switching by issuing instructions.

4.2 Trial Trip

Based on the motion control in the USV water quality

inspection task, the water surface navigation test was

carried out. After the trial voyage, the user can realize

the remote monitoring of the USV through the mobile

terminal, and the switching mode operation control

can meet the expected demand. The actual flight test

is shown in Figure 8.

Figure 8: Trial Trip.

Collect the navigation data of the USV under the

autonomous cruise mode (see Table 2) and analyze

the status data.

ISWEE 2022 - International Symposium on Water, Ecology and Environment

Table 2: Status data collected by USV (Part).

Longitude

(in deg.)

Latitude

(in deg.)

Heading

(in deg.)

Speed/

(in knot)

114.4245168 30.5225445 324.7 5.5

114.4245149 30.5225467 324.7 5.4

114.4245112 30.5225511 323.6 5.5

114.4245074 30.5225555 321.8 5.5

114.4245015 30.522562 316.7 5.4

114.4244971 30.522566 315.3 5.5

114.4244971 30.522566 313.1 5.4

114.4244902 30.5225715 314.0 5.4

114.4244807 30.5225786 314.8 5.3

114.4244807 30.5225786 315.8 5.3

First, the real-time longitude and latitude values

are extracted, and the navigation trace is drawn as

shown in Fig. 9. It can be seen that the USV can

automatically adjust its attitude to approach the path

node position after receiving the instruction, and it is

approximate to a straight line trajectory within the

allowable range of error.

Figure 9: Trajectory of USV

Extract and analyze the heading angle and speed

values of the USV during the trial voyage, and

generate the heading angle scatter diagram and speed

scatter diagram as shown in Figure 10 and Figure 11

according to the data acquisition frequency of 200ms.

It can be seen from the image that the heading angle

can be automatically adjusted during the trial voyage,

and the change of speed meets the real-time control

requirements.

Figure 10: Heading scatter plot.

Figure 11: Speed scatter plot.

Judging from the overall test results, the remote

monitoring system for USV based on the IoT

technology designed in this paper performs well in

water navigation. When the system is running, the

information such as target, pose, speed, and distance

displayed on the mobile terminal interactive interface

can be updated in real-time, the USV terminal state

information collection and storage function is normal,

and the action is flexible and smooth, and the target

instruction can be completed. From the above-

mentioned tests, it can be seen that the positioning

accuracy, communication quality, and operational

performance of the system all meet the requirements

of the water quality inspection system of the water

USV and ensures the smooth completion of the

follow-up water quality inspection, function

expansion, and other applications.

5 CONCLUSIONS

This paper designs and develops a water quality

inspection system for USV based on IoT technology,

114.4243 114.4244 114.4245 114.4246 114.4247

E/deg.

30.5219

30.522

30.5221

30.5222

30.5223

30.5224

30.5225

30.5226

30.5227

0 50 100 150 200 250 300 350 400 450

T/s

100

150

200

250

300

350

0 50 100 150 200 250 300 350 400 450

T/s

Development of Unmanned Surface Vehicles System for Water Quality Inspection

and introduces the design and application of a mobile

client and USV terminal system. From the

perspective of convenience, flexibility and

compatibility, the mobile client of the system

supports users to remotely monitor and issue tasks

anytime and anywhere, making it more convenient to

build a water quality inspection platform. The USV

subsystem has a certain degree of autonomy, and its

modular design is easy to flexibly expand the

subsequent functions. The system has been proved to

have stable remote monitoring capability for USV

through water surface trials and can realize real-time

synchronization of synchronous remote states. And

can complete various operations such as manual

control, fixed-point inspection, and autonomous

cruise. It has reliable communication and good real-

time performance. The next step will be to expand the

functions of the mobile client and USV. And continue

to improve the system on the existing hardware and

software architecture based on the actual water

quality inspection project requirements.

REFERENCES

A. Eleyan and J. Fallon, 2020. IoT-based Home

Automation Using Android Application. In

International Symposium on Networks, Computers and

Communications, pp. 1-4.

G. Zhang and Y. Hao, 2020. Design and Implementation of

a Home Intelligent Water Quality Inspection Device. In

IEEE International Conference on Information

Technology ,Big Data and Artificial Intelligence, pp.

628-631.

Kondle R, Dastagiri. S, Lakshmaiah M, 2020.

Implementation of IoT in Embedded Systems for Real

Time Water Quality Monitoring. In International

Journal of Innovative Technology and Exploring

Engineering

9(4S2):1-4.

L. S. Bratchenko, E. A. Rodionova, T. G. Shchetinina, G.

Y. Kolev and V. G. Rybin, 2022. Embedded Water

Analyzer for Unmanned Surface Vehicles. In

Conference of Russian Young Researchers in Electrical

and Electronic Engineering, pp. 119-122.

M. K. Madisa and M. K. Joseph, 2018. Android and Cloud

Based Traffic Control System. In International

Conference on Advances in Big Data, Computing and

Data Communication Systems, pp. 1-4.

Madeo D, Pozzebon A, Mocenni C, et al, 2020. A Low Cost

Unmanned Surface Vehicle for Pervasive Water

Quality Monitoring. In IEEE Transactions on

Instrumentation and Measurement, PP(99):1-1.

Rybin, V. G. , Kolev, G. Y. , Karimov, T. I. , Ostrovskii,

V. Y. , & Sigaeva, M. S., 2020. Estimating the

Autonomy Range of the Battery-Powered Small

Unmanned Surface Vehicle. In 2020 Ural Smart

Energy Conference.

Steimle E T , Hall M L, 2006. Unmanned Surface Vehicles

as Environmental Monitoring and Assessment Tools. In

Oceans. IEEE, 2006.

T. H. Yang et al. 2018. Development of unmanned surface

vehicle for water quality monitoring and measurement.

In 2018 IEEE International Conference on Applied

System Invention, pp. 566-569.

W. Wei, L. Shaohan and L. Kang, 2019. A Laboratory

Aquaponics System via PLC and LabVIEW. In 34rd

Youth Academic Annual Conference of Chinese

Association of Automation, pp. 547-551.

NOMENCLATURE

Create the following nomenclature for easy reading.

USV Unmanned Surface Vehicles

IoT Internet of Thin

APP Mobile Application

PLC Pro

rammable Lo

ic Controlle

GPS Global Positionin

ste

MQTT Message Queuing Telemetry

Transpor

ISWEE 2022 - International Symposium on Water, Ecology and Environment