Research On Walking Trajectory Tracking Control Of Tracked Hydraulic Excavator Based On Visual SLAM

As one of the most common,typical and complex machines in construction machinery,the excavator plays an extremely important role in engineering applications.In order to cope with increasingly operational requirements in terms of high efficiency and adapt to harsh environments,the development of autonomous operation and automated excavators has become a growing trend.Making the excavator track the planned trajectory is one of the foundations for realizing the autonomous operation and automation of the excavator.This thesis takes the tracking and control of the excavator's walking trajectory as the research goal.Firstly,the overall design of the track tracking control system of excavator and the development of test prototype are carried out;At the same time,the theoretical analysis and simulation research on the excavator walking system are carried out;Further the real-time perceptual positioning of the excavator based on Stereo visual SLAM(Simultaneous localization and mapping)is studied,a method to obtain the center position of excavator when the vehicle mechanism has rotation angle is proposed,and the rotation angle is estimated by visual SLAM;Finally,the trajectory tracking controller is designed,and the experimental research of trajectory tracking control is carried out for line,arc and arc plus line.The main contents of each chapter of this paper are as follows:Chapter 1,The chapter introduces the research background of the subject and the difficulties in the excavator's walking process,and analyzes the research status of the trajectory tracking control of excavators and other vehicles at home and abroad.The visual positioning applied to the excavator is analyzed,and introduce the feasibility of the visual SLAM positioning in walking control.The research content and purpose of the paper are clarified.Chapter 2,Software and hardware design of trajectory tracking control system for hydraulic excavator.The overall framework of the excavator's trajectory tracking control system is established,including the design and selection of the electro-hydraulic control components of the excavator,the design of the electronic control unit,the design of the remote controller,the selection of the camera and so on.The multi-threaded concurrent wireless data communication software is designed based on TCP/IP protocol,and experimental tests are carried out.The development of the excavator test prototype is completed.Chapter 3,Modeling analysis and simulation research on the walking system of tracked hydraulic excavator.The kinematics and dynamics of the excavator are analyzed,including the dynamics of the hydraulic walking system,the kinematics and dynamics of the tracked walking system.The analysis and modeling of track slippage provide theoretical basis for experimental research.The vehicle simulation model is built under Simulink,and the PID speed controller based on the tracked kinematics model was designed.The simulation results show that the speed controller is still controllable in the case of slippage.Chapter 4,Study on walking localization of excavator based on visual SLAM.The stereo camera Visual Odometry is established.The application features of visual SLAM in excavator's localization is studied.A visual SLAM localization scheme with back-end optimization is adopted,the software framework for SLAM positioning of excavator is built based on the ROS platform.The kinematic coordinate transformation when excavator has rotation angle is established.The SLAM is used to estimate the rotation angle,and the effectiveness of the method is verified.Chapter 5,Design and experiment of walking trajectory tracking controller for excavator.The framework of trajectory tracking controller is established.and a two-layer trajectory tracking controller including position loop and velocity loop is designed.The effectiveness of the control algorithm is verified by using the simulation model established in Chapter 3.The influence of slip parameters on trajectory tracking is analyzed.Experiments on speed control and trajectory tracking control are carried out.The trajectory tracking of the excavator is realized,and the accuracy and effectiveness of the trajectory tracking control method are verified.Chapter 6,Summary and prospect.The research contents are summarized and the future work is prospected.