Research On The Motion Control Method Of Deformable Wheel Propeller Robot Facing The Littoral Environment

The littoral environment is a transitional zone where land and sea interact,and the terrain is complex.In recent years,the exploration of the environment of the littoral zone and the demand for resource exploitation have increased,and the research on amphibious robots capable of operating in the littoral zone has received wide attention.In this paper,we study the motion control problem of a deformable propeller robot to meet its operational capability in the coastal environment.The kinetic and kinematic models of the crawling and swimming modes are developed based on the motion requirements of the deformable propeller robot in the coastal environment and its structural characteristics in the swimming and crawling modes,respectively.For the motion requirements of the deformable propeller robot in the crawling mode,the mechanical characteristics of the sand are fully considered,the shear characteristics and pressure-bearing characteristics of the sand medium are analyzed,and the traction force model of the propeller and the sand environment is established.By sensing the motion state of the robot during the sand maneuver,the traction force control system is designed to dynamically adjust the desired slip rate of the robot.Considering the uncertainty of external disturbance,the torque control algorithm based on the extended state observer is proposed to control the rotational speed of the wheel propeller so that the slip rate of the wheel propeller and the sand can reach the desired slip rate.The simulation results prove the effectiveness of the algorithm.For the motion requirements of the swimming mode of the deformable propeller robot,we focus on the problems of head-on surface change,depth control force change,interference from the coastal environment and thrust derating caused by the speed during the swimming process,and propose a disturbance observer with estimation compensation based on the neural network algorithm to estimate the force and thrust derating caused by the head-on surface change and thrust derating through the acceleration information when the speed information is not observable.moment by the acceleration information.Based on the disturbance observer,an integral sliding mode controller with position and velocity loops is proposed to control the bow,pitch and depth during navigation,which reduces the influence of unknown speed on the controller performance and improves the overall control system anti-disturbance capability.To address the thrust saturation problem caused by large pitch angle swimming under high speed navigation,a dynamic weight assignment algorithm based on control error is proposed to improve the stability of the control system.A test system of deformable wheel-propeller robot is built,and the test verification of underwater direct navigation and hovering motion is carried out in the pool.The experimental results show that the proposed control method is able to achieve a good control of constant depth steerage with different pitch angles of 35 and 50 degrees,and can track the continuously changing desired bow and desired depth well.