Research On Motion Control Of A Underwater Robot

There are certain difficulties in detection,development and transportation resources under the sea compared with the land.Underwater robot,an important tool for exploring and exploiting marine resources,can be used to develop marine resources efficiently.With the development of science and technology,underwater robot is moving to miniaturization and intellectualization.Its ability to resist external disturbances declines due to reduced volume and weight of the underwater robot,which makes it difficult to be controlled.This dissertation is focused on anti-disturbance research of small-scale underwater robot,aiming to improve the robot stability by designing the self-balanced control system.The main tasks of this research are:1)Designing the actuating layout and driving circuit according to robot motion characteristics to provide hardware for algorithm research;2)Implementing robot dynamics modeling and finishing the control method research to provide the basis for the control algorithm design;3)Designing the self-balanced control algorithm and verifying it by experiments.The contents of this dissertation are as follows:Firstly,underwater robot has multiple spatial degrees of freedom and the strong coupling between them.To reduce the difficulty of control,the space motion of the underwater robot is separated into horizontal movement and vertical movement.Robot actuating layout is designed by the concept of horizontal control and vertical control decomposition.Circuit which satisfies the control requirements of the underwater robot is designed based on the three elements of the motion control system.Secondly,modeling and simulation of the underwater robot are performed.The PID motion controller is established according to the state equation,which is analyzed under the net forces of underwater robot through the establishment of a motion coordinate system.According to the simulation under ideal conditions,it is verified that PID controller can get a good control effect in the underwater robot control.Thirdly,the motion control algorithm is deployed on the actuating layout and driving circuit.The outputs of the sensor are used as the inputs and state feedback of the motion control algorithm.The underwater robot is driven by the outputs of the propellers which are determined by the PID controller outputs.The motion control is mainly to improve the motion stability of underwater robot.Finally,the effect of underwater robot control algorithm is verified through experiments.Static and dynamic tests both conducted to verify the underwater robot's ability to resist external disturbance during the operation.It is proved that the motion control algorithm can improve the underwater robot's motion stability,which can provide reference for the design to improve the stability of other small underwater robots in similar type.