Research On The Dynamic Behavior And Adaptive Robust Control Method Of Large Spray Boom With Active And Passive Pendulum Suspension

With the intensification of land transfer and agricultural production in China,agricultural machinery is developing towards high efficiency,intellectualization,large scale,environmental protection,and economization.The traditional knapsack sprayer and small motorized sprayer can no longer meet the needs of grain yield increase and ecological environment protection.Large boom sprayer is widely used for spraying pesticide and fertilizer because of its high efficiency and uniform spraying.However,boom movement Seriously affected the spray distribution when sprayer working in the undulating field,Suspension system is the key device to change the dynamic behavior of the boom.Adding a suspension system between the spray boom and vehicle is an important way to improve the stability of the spray boom and control effect of pesticides.The design of boom suspension has always been a bottleneck for the development of large boom sprayer,which restricts the development of large boom sprayer in China.In this paper,the dynamic behavior modeling and parameters optimization of pendulum active and passive suspension system,the non-linear control strategy of boom motion and the stability evaluation of spray boom are studied around the dynamic behavior and control of large-scale spray boom.The main research contents are summarized below.Considering the coupling effect of chassis motion,the change of ground slope and friction of motion pair,etc.A mathematical model of sprayer chassis,pendulum suspension and boom system is established by using second kinds of Lagrange dynamics methods,and accurately describe the dynamic behavior of the of spray boom based on active and passive pendulum suspension.The mechanism of the influence of various parameters such as damping,friction,pendulum length,mass and moment of inertia on the motion behavior of the boom is revealed,then the motion state of the boom under different combination of control parameters(gain coefficient,time constant,suspension type parameters)is analyzed.The simulation results show that adding active actuator based on the passive suspension can significantly improve its low-frequency performance without losing the high-frequency vibration isolation performance of the passive suspension,and the power consumption of the active actuator is very low.In order to verify the accuracy of the suspension dynamics model,a 28 m boom is considered as the research object.According to the expected response characteristics,appropriate vibration absorbers are designed for pendulum passive suspension,the dynamic behavior of the spray boom under with passive suspension system is studied by using a sixdegree-of-freedom motion platform and a multi-channel dynamic test system.The timedomain and frequency-domain response characteristics of the roll motion and vertical motion of the boom under the action of the passive suspension system are tested,the influence of damping ratio and stiffness coefficient on the vibration characteristics of the boom is also analyzed,and the simulation results of the mathematical model of the pendulum passive suspension are verified.Because the large spray boom belongs to a kind of structure with large flexibility,weak damping and large inertia,and the chassis may resonate with pendulum suspension due to the random change of ground excitation in the field,so the parameters of passive suspension need to be further optimized.In the finite element software,Lansos method is used to treat the spray boom as a flexible body.The sprayer chassis,pendulum suspension and boom are taken as a multi-body dynamic system.The rigid flexible coupling model of the virtual prototype dynamics of the boom is established,and the accuracy of the model is verified by the suspension transient response test by the lifting method.The stiffness parameters and the damping parameters of the damper of the suspension are selected as design variables,and the root mean square of the boom roll angle and the root mean square of the vertical vibration displacement of the boom center are taken as optimization objectives.The optimal Latin hypercube design was used to obtain test samples.By using the sample data,neural network approximation model based on radial basis function was trained to replace simulation model,which improves the optimization speed.The NSGA-II multiobjective genetic algorithm is used to optimize the suspension parameters.The optimal values of suspension stiffness parameters and damping parameters are obtained by reasonably determining the weight coefficients.The suspension parameters are adjusted and reproduction test of field conditions are carried out on a six-degree-of-freedom motion platform.This study provides a theoretical basis and experimental method for optimizing the parameters of large-scale spray boom suspension.In order to improve the tracking accuracy of the boom for low frequency topographic changes,active suspension was studied on the basis of passive suspension research.During the operation of the boom sprayer,the boom is disturbed by the unevenness of the ground surface,the change of the liquid volume and the sloshing of the liquid,nd at the same time,there are many nonlinear problems in the electro-hydraulic active suspension itself,the active boom suspension belongs to a class of nonlinear uncertain systems.Therefore,the nonlinear model of servo valve controlled hydraulic cylinder,the relationship between displacement of hydraulic cylinder and roll angle of boom are established by combining the analytical modeling of system dynamics and parameter identification method.A nonlinear adaptive robust control algorithm based on model compensation is designed,the inherent nonlinearity,model deviation and unknown disturbance of the electro-hydraulic active suspension system are effectively stabilized.The rapid control prototyping(RCP)platform for electro-hydraulic active suspension with boom motion is built to ensure smooth connection between control algorithm and system hardware.The disturbance test and sinusoidal angle tracking experiment were carried out with the Stewart six-degree-offreedom motion platform,the performance of the adaptive robust controller was compared with that of PID controller under various working conditions.Theoretical analysis and experimental results show that the proposed nonlinear adaptive robust controller can guarantee the transient performance and steady-state tracking accuracy of the suspension system in the presence of parameters uncertainty and nonlinearity,the accurate tracking of ground slope change in a set frequency range is realized.Based on the development process of V-mode servo control system,the active suspension control terminal and human-machine interface with DSP chip as the core are developed.In order to eliminate the measurement noise of surface roughness and nonuniform canopy distribution noise,filtering,dynamic smoothing and limiting algorithm are designed to process the signal of the ultrasonic sensor.The data of the ultrasonic sensor and the inertial sensor are fused to obtain the inclination angle of the spray boom relative to the ground or the crop canopy and realize the active control of the roll angle of the boom.Through bench test and field test,the performance of the active control system of the spray boom is tested.The test results show that the low-frequency response characteristics of the passive suspension are significantly improved after adding the active suspension.The resonance peak of the original passive suspension is greatly reduced,and steady-state tracking error of roll angle of spray boom is less than 0.3 degree in the design frequency range.Finally,through the design of pendulum active and passive suspension,the optimal synthesis of chassis high frequency disturbance passive control and low frequency terrain fluctuation active control is achieved.At present,the field test and evaluation of boom suspension performance is influenced by many random factors,such as test terrain,soil properties,driving proficiency,etc.Therefore,a laboratory test system for boom suspension performance is established,including six-degree-of-freedom motion simulation platform,terrain fluctuation simulation platform and synchronous trigger measurement and control system.The revised Hockley index,standard deviation and coefficient of variation are used to describe the stability of the boom suspension system.The stability of 28 m boom under different installation modes such as non-suspension,passive suspension,active and passive suspension was tested successively by using spray boom suspension test system.The results of repeated tests show that the test system and evaluation index have better discrimination and applicability for different suspension systems.The research provides an important test and evaluation method for large-scale spray boom suspension.