In this paper,four novel evaluation indices and corresponding hierarchical optimization strategies are proposed for a deployable solar array system considering panel flexibility and joint clearance.The deployable sola...In this paper,four novel evaluation indices and corresponding hierarchical optimization strategies are proposed for a deployable solar array system considering panel flexibility and joint clearance.The deployable solar array model consists of a rigid main-body,two panels and four key mechanisms,containing torsion spring mechanism,closed cable loop mechanism,latch mechanism and attitude adjustment mechanism.Rigid and flexible components are established by Nodal Coordinate Formulation and Absolute Nodal Coordinate Formulation,respectively.The clearance joint model is described by nonlinear contact force model and amendatory Coulomb friction model.The latch time,stabilization time,maximum contact force and impulse sum of the contact force of the solar array system are selected as the four novel evaluation indices to represent the complex dynamic responses of a deployable solar array with clearance joints instead of the lock torque widely used in conventional works.To eliminate the gross errors caused by the nonlinear and nonsmooth mechanical properties,a hierarchical optimization strategy based on an adaptive simulated annealing algorithm and a nondominated sorting genetic algorithm is adopted for the solar array system with clearance joints.Results indicate that the effects of panel flexibility on the evaluation index responses and design optimization of the solar array system cannot be neglected.Besides,increasing the weight factor of the stabilization time index of the rigid system may compensate for the differences in optimal results of the rigid–flexible coupling system.That may provide some references for optimization design of deployable space mechanisms considering clearance joints.展开更多
In South China,the tropical weather and climate result in severe sugarcane lodging problems which greatly hinders sugarcane mechanical harvesting.The main function of the crop divider is to lift lodged canes and facil...In South China,the tropical weather and climate result in severe sugarcane lodging problems which greatly hinders sugarcane mechanical harvesting.The main function of the crop divider is to lift lodged canes and facilitate base-cut cane feeding.In this study,a series of field tests were conducted on crop dividers of Liugong 4GQ-180 sugarcane chopper harvester.The tests were designed to identify the relationships of the performance index(maximum lifting height of sugarcane)and the main influencing factors(machine forward speed,rotational speed of inside scrolls,and ground clearance of crop divider toes).The single factor test was conducted to determine optimum range of these test factors:the forward speed(FS)was 2.0-4.0 km/h,the rotational speed of inside scrolls(RS)was 100-140 r/min,and the toe ground clearance(GC)was 0-5 cm.The orthogonal test(three factors and three levels)was carried out to determine the optimal combination of operating parameters:FS was 2.0 km/h,RS was 115 r/min,and GC was 0 cm.In addition,the range analysis of orthogonal test results revealed that the order of each test factor affecting crop divider performance was RS,FS,GC.This study was expected to provide valuable references for the optimal operation of sugarcane harvester crop dividers.展开更多
基金supported by the National Natural Science Foundation of China(No.U1637207)Beijing Natural Science Foundation of China(No.1204040)。
文摘In this paper,four novel evaluation indices and corresponding hierarchical optimization strategies are proposed for a deployable solar array system considering panel flexibility and joint clearance.The deployable solar array model consists of a rigid main-body,two panels and four key mechanisms,containing torsion spring mechanism,closed cable loop mechanism,latch mechanism and attitude adjustment mechanism.Rigid and flexible components are established by Nodal Coordinate Formulation and Absolute Nodal Coordinate Formulation,respectively.The clearance joint model is described by nonlinear contact force model and amendatory Coulomb friction model.The latch time,stabilization time,maximum contact force and impulse sum of the contact force of the solar array system are selected as the four novel evaluation indices to represent the complex dynamic responses of a deployable solar array with clearance joints instead of the lock torque widely used in conventional works.To eliminate the gross errors caused by the nonlinear and nonsmooth mechanical properties,a hierarchical optimization strategy based on an adaptive simulated annealing algorithm and a nondominated sorting genetic algorithm is adopted for the solar array system with clearance joints.Results indicate that the effects of panel flexibility on the evaluation index responses and design optimization of the solar array system cannot be neglected.Besides,increasing the weight factor of the stabilization time index of the rigid system may compensate for the differences in optimal results of the rigid–flexible coupling system.That may provide some references for optimization design of deployable space mechanisms considering clearance joints.
基金The research presented in this work was partially supported by the Major Program of the National Natural Science Foundation of China(Grant No.32071916)the Major State Research Development Program of China(Grant No.2016YFD0701200)+1 种基金and China Agricultural University,Institute for New Rural Development Guangxi Fusui Professor Workstation Grant(No.201805510710115)Any opinions,findings,and conclusions expressed in this work are those of the authors and do not necessarily reflect the views of China Agricultural University.The authors acknowledge Mr.Xiangwei Li,Mr.Xiaobin Huang,Mr.Yuanmin Gan and Mr.Pingang Wu for their help in the harvesting test.
文摘In South China,the tropical weather and climate result in severe sugarcane lodging problems which greatly hinders sugarcane mechanical harvesting.The main function of the crop divider is to lift lodged canes and facilitate base-cut cane feeding.In this study,a series of field tests were conducted on crop dividers of Liugong 4GQ-180 sugarcane chopper harvester.The tests were designed to identify the relationships of the performance index(maximum lifting height of sugarcane)and the main influencing factors(machine forward speed,rotational speed of inside scrolls,and ground clearance of crop divider toes).The single factor test was conducted to determine optimum range of these test factors:the forward speed(FS)was 2.0-4.0 km/h,the rotational speed of inside scrolls(RS)was 100-140 r/min,and the toe ground clearance(GC)was 0-5 cm.The orthogonal test(three factors and three levels)was carried out to determine the optimal combination of operating parameters:FS was 2.0 km/h,RS was 115 r/min,and GC was 0 cm.In addition,the range analysis of orthogonal test results revealed that the order of each test factor affecting crop divider performance was RS,FS,GC.This study was expected to provide valuable references for the optimal operation of sugarcane harvester crop dividers.
