Research On Spray Boom Motion Control Technology Based On Variable Damping

The medium and small-sized boom sprayer with a spray range of 10-20 m is one of the main agricultural machinery for field crop protection operations in China.The medium and small-sized boom sprayer has high operating efficiency and uniform distribution of liquid spraying volume,which is suitable for largescale spraying of various pesticides,chemical fertilizers and other liquid preparations,and is widely used in pesticide and chemical fertilizer spraying.However,during the process of pesticide application and fertilization in the field,the unevenness of the ground can easily cause vibration of the spray boom,which seriously affects the uniformity of pesticide application and directly reduces the effectiveness of pesticide application.In view of the above problems,this paper takes the medium and small-sized boom sprayer with rod shaped spray boom as the research object,starting with the factors that may cause the vibration of the spray boom,and fully considers the influence of the flexible sprayer body and the suspension of the spray boom on the elastic vibration of the spray boom.First,based on the Euler Bernoulli beam theory,the sprayer body and the suspension of the spray boom are equivalent to a spring damping system,A geometric continuous model of rod structure spray boom vibration based on multi body vibration has been established.The SWAN3WP-500 self-propelled spray boom sprayer of Essen Agricultural Machinery Changzhou Co.,Ltd.was used as the test model to obtain the tire stiffness and damping,as well as the equivalent stiffness and damping of the trapezoidal suspension and lifting mechanism of the spray boom.Then,the vibration of the spray boom of the spray boom sprayer under step excitation was simulated in MATLAB software,and the geometric continuous model of the vibration of the rod structure spray boom based on multi-body vibration was experimentally verified.In response to the emergency stop oscillation of the current spray boom under the constraint of a fixed length steel cable,the force exerted by the steel cable on the spray boom is equivalent to a spring damping system.Segmental motion analysis is conducted on the spray boom and spring damping system,and dynamic response models of the spray boom at different motion stages under the constraint of a fixed length steel cable are established.Based on SWAN3WP-500 self-propelled spray boom sprayer parameters,a spray boom vibration test system under cable constraint was built,and the correctness of the dynamic response model of the spray boom under cable constraint was verified.In view of the vibration characteristics of the rod structure spray boom of the medium and small-sized spray boom sprayer,the concept of soft stop control for spray boom vibration is proposed,and a vibration model of the spray boom with changes in steel cable tension and length is constructed.On the basis of constructing the current torque model of the magnetic powder brake,a vibration control scheme for the spray boom based on fuzzy PID control was established.A simulation model for the vibration control of the spray boom was constructed in MATLAB/Simulink environment,and simulation and result analysis were conducted to verify the accuracy of the proposed soft stop control scheme for the spray boom vibration.A vibration control mechanism for the spray boom based on a magnetic particle brake was designed,and the field excitation spectrum of the research model during operation in the working area was obtained using a dual GPS assisted inertial attitude measurement system.Then,according to the performance requirements of the designed spray boom vibration control mechanism,the high-performance TMS320C28 x series 32-bit floating point DSP processor TMS320F28335 produced by Texas Instruments(TI)was selected.The TMS320F28335 processor,crystal oscillator,JTAG interface for chip internal testing,power adapter module,and control button for reset circuit were printed and welded together to form the minimum system.The built-in A/D conversion circuit of the DSP chip has been expanded,and the D/A conversion circuit including the DAC7724 chip has been expanded.Then,a user interface for monitoring software was developed based on Lab Windows/CVI(National Instruments),and a real-time control system for spray arm vibration was developed based on Microsoft Visual Studio 10.0 and Interval Zero’s real-time Windows RTX 8.0 demo.Finally,the dynamic characteristics of the developed spray boom vibration control system were tested and analyzed using a six degree of freedom experimental platform for spray boom vibration control.The results show that under step input,the developed real-time control system for the vibration of the spray rod arm enables the spray rod arm to enter a steady state in about 0.9 seconds.The maximum amplitude of the upward vibration of the spray rod arm decreases by69.59%,and the maximum amplitude of the downward vibration of the spray rod arm decreases by88.06%.Meet the design requirements.The above research results provide a theoretical basis and a new method for the research of the spray boom vibration control of medium and small-sized boom sprayer.