| Hydraulic excavator is a widely used construction machinery with typical function and complex structure. As the advances in computer control and communication technologies keep emerging, the excavator is also becoming more intelligent and energy efficient. Intelligent excavator improves the operation accuracy and efficiency on one hand, and makes itself applicable in some hazardous environment on the other. Independent Metering (IM) control technologies separately control meter in and meter out orifice with two direction valves, and successively control the velocity of actuator. The application of IM control technologies in excavators as well as making full use of the increased control degree of freedom to improve energy saving and control performance of excavator hydraulic system, are among the research focus of IM control technology.This thesis focuses on intelligent excavator control system and IM valve controller. First, software and hardware plans of each node are given, along with the design and implementation of datalink. Second, kinematics model of operation device is established and the method of trajectory planning is discussed. Excavator 3D simulation environment being built, the skeletal animation is adopted for accurate control. Finally, the functional requirements of IM valve controller is given, and both software and hardware are designed. The simulation load testing loop is built and the experiment of displacement closed-loop control of main spool has been carried out.The layout of this thesis is described as follow:In Chapter one, the aim and significance of this thesis are pointed out. Besides, the state of art at home and abroad on intelligent excavator control system and independent metering control system are reviewed. And the main research subjects are also presented.In Chapter two, based on the function of each system device and control process, datalink’s information process is put forward. The hardware selection and software function architecture of each node are discussed. In this datalink, Redis database service, data transmission service based on the TCP, data transmission service based on CANBus and the design and implementation of the Server/Client network communication service are studied extensively and thoroughly. Approaches to enhance data transmission timeliness and the reliability of wireless device connection are also presented and discussed.In Chapter three, the kinematics model of operation device (including rotary) is established on the basis of D-H coordinate system. The transformation and inverse transformation between cylinder driving space and cartesian space are derived. By means of trajectory planning program, the planning of bucket-end’s straight trajectory and single joint’s trajectory under continuous acceleration is presented and studied.In Chapter four, based on OGRE graphics engine and skeletal animation,3D entity simulation environment of excavator kinematics is established to realize accurate parametric control and feedback of movement. The deviation and the corresponding causes are analyzed through the representation of the results of trajectory planning in this simulation environment.In Chapter five, in view of the design requirements of IM valve controller, the controller’s core and sensors are selected, in an attempt to figure out the related circuit principle and produce PCBs. Based on DSP TMS320F28335 and SYS/BIOS embedded operation system, the architecture of real-time multitasking control software is studied. Simulation testing loop based on relief valve and throttle valve is built correspondingly. Through the displacement’s step response experiment and sine signal tracking experiment, control problems of main spool are discussed and the optimization scheme is put forward. Meanwhile several modified PID algorithms to improve the control performance are also explored in this chapter.In Chapter six, a brief summary of the present thesis and some practical suggestions for future research are provided. |
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