Modeling And Control Of Spray Boom Suspension System With Double Pendulum Of Plant Protection Machinery

As the dramatic development of technology and agriculture,the plant protection machinery is larger-sized and more intelligentized.However,with the increase of spray boom length,when the plant protection machinery travelling on the field with undulations or obliquity,its movements would be enlarged at both ends of the spray boom,and this may cause overdose spray and underdose spray easily,which can not only pollute the soil and environment we rely on but also threaten our health.Thus,it is extremely significant to control the of spray boom to make it steady.Currently,aiming at the problem that the control of the height of boom on the large-sized plant protection machinery has not always satisfied to tracking the designated value under the condition of the ground undulations or obliquity,a model of the spray boom suspension with double pendulum is built,and two kinds of controllers are designed by applying position tracking strategy and robust control strategy.The exact studies in detail are stated as following:First,the working principle of suspension system with double-pendulum is analyzed in this thesis,and the second Lagrange kinematics equation is applied to build double-pendulum spray boom suspension model,then a non-linearity mathematical model is gained.Under the operating point of the spray boom,it is obvious to assume that the angles are small enough,then the system is linearized at the operating point,a state space model is established for satisfying the demands of controller designing.Additionally,based on the above state space model,a quadratic performance index is selected.In addition,a tracking controller is designed by optimal control theory to make the output error of the system converge to zero.The results of simulation show that the controller designed in this thesis has excellent advantages of feasibility and validity.Considering that the linearization process may cause errors on the model,thus,to make the controller designed based on the model to satisfy the control accuracy of practice spray boom,the uncertainty of parameters are introduced into the model.Then a robust position tracking controller is designed to keep the spray boom parallel to the slope of field or canopy height,and the stability of the closed-loop are proved.And then several sets of uncertainty areselected in the simulation to test how it influence the pendulum rod,the results of the simulation show that the controller designed has an excellent performance of adjusting the spray boom to parallel to the ground and also have a great performance of tracking the ground undulations or obliquity to realize an excellent performance of tracer control.