Design And Research Of Underwater Robotics' Control System Based On Ardupilot

With the development of the global economy,land resources are facing a dilemma of scarcity.More and more countries have shifted their resource development goals to the ocean.At the 18 th National Congress of the Communist Party of China,it was also suggested that China should "improve the capacity of ocean resources development" as well as "building a strong country in terms of the ocean",the application prospects of underwater equipment,especially underwater vehicles,are becoming brighter and brighter.The remotely operated vehicles,is a kind of underwater vehicles,has the characteristics of flexibility and reliability,and has many applications in many fields such as resource development and pipeline inspection.In order to adapt to complex underwater environments and complete sophisticated underwater tasks,advanced underwater vehicle control systems are essential.Therefore,it is of great significance to develop an underwater vehicle and study the control system of the underwater vehicle.Under this background,this thesis develops a remotely operated vehicle.An underwater vehicle control system is designed based on Ardupilot,and the key technologies used in the control system are studied.Six-degree-of-freedom modeling of underwater vehicle,design of underwater vehicle hardware systems,design of underwater vehicle software systems,simulation and pool tests of underwater vehicle are accomplished.When designing the communication topology,the system discovery mechanism is used to enhance the flexibility and scalability of the communication system.When performing video stream processing,integrating different functions into one video pipeline saves the computing resources of the ground station computer.In the simulation test,the use of the ground station computer software and Gazebo model joint simulation can simultaneously verify the ground station computer software function and control algorithm implementation,and improve the efficiency of the pool test.First,the design goals of the remotely operated vehicle are proposed,the outline structure and thruster layout of the underwater vehicle are designed according to the design goals.Then,a six-degree-of-freedom model of the underwater vehicle is established based on Fossen's theory,and the added mass,damping coefficient,and thrust coefficient in the six-degree-of-freedom model of the underwater vehicle are given by empirical formulas,computational fluid dynamics techniques,and least squares methods.Secondly,based on the design goals and working methods of the underwater vehicle,the design and construction of the hardware system of the underwater vehicle are carried out.The mechanical design of the underwater vehicle including supporting structure and sealing structure are completed.The communication system is designed and the controller and sensors are selected.Then,the software system of the underwater vehicle is designed based on the hardware system of the underwater vehicle.Software requirements are analyzed,the overall design architecture of the software system is proposed based on the requirements analysis.The software architecture,software scheduling,message processing,and operation mode of the flight control software Ardupilot are studied.In order to meet the needs of this project,the message processing and operation mode of the Ardupilot is extended.The communication topology structure in the communication interface library,application layer communication protocol MAVLink,message processing and data storage modules,thread synchronization and mutual exclusion issues are described in detail.The design and implementation of the software interface,video stream and closed-loop control of the ground station software are described in detail.Finally,the control system of the designed underwater vehicle is tested by two methods: simulation test and pool test.Based on ROS and Gazebo,the simulation environment of the underwater vehicle is established.The six-degree-of-freedom model of the underwater vehicle and model parameters are used in simulation environment.The function and control performance of the control system were tested in the simulation environment.A single test and a comprehensive test of the underwater vehicle were performed in a pool environment.The two sets of tests show that the designed underwater vehicle control system can achieve the designed goals.After the pool test was completed,the results of the control test in the comprehensive test of the pool were compared with the results of the simulation control test,the gap between the two tests and the reasons for the gap were analyzed.