1、Tracking accuracy analysis of a planar flexible manipulator with lubricated joint and interval uncertainty 1 Tracking accuracy analysis of a planar flexible manipulator with lubricated joint and interval uncertaintyDongyang Sun 1 College of Aerospace Engineering Chongqing University Chongqing,China
2、Email: ABSTRACT A method for trajectory tracking accuracy analysis of a two-link flexible manipulator with lubricated revolute joint involving interval uncertainty is presented.In this method,firstly,fuzzy self-tuning PID control is applied to track the desired tip trajectory of the manipulator.The
3、absolute nodal coordinate formulation is employed for the finite element discretization of the flexible manipulator.And lubricated revolute joint is modeled based on the infinitely-short journal-bearing with Gmbel conditions.Secondly,uncertainty of clearance size is considered,and interval analysis
4、method is applied.Numerical simulation is posted to investigate the cushioning effect of lubricants on clearance and influence of uncertainty on control accuracy of the manipulator.The results show that the lubricants can improve the stability of motion and operation precision of the manipulator,how
5、ever,uncertainty of the manipulator may reduce the control accuracy of the manipulator.Keywords:Absolute nodal coordinate formulation;Flexible manipulator;Lubricated joint;Fuzzy self-tuning PID control;Interval uncertainty1 Corresponding author, Journal of Computational and Nonlinear Dynamics.Receiv
6、ed January 27,2016;Accepted manuscript posted May 12,2016.doi:10.1115/1.4033609 Copyright(c)2016 by ASMEAccepted Manuscript Not CopyeditedDownloaded From:http:/asmedigitalcollection.asme.org/on 05/29/2016 Terms of Use:http:/www.asme.org/about-asme/terms-of-useTracking accuracy analysis of a planar f
7、lexible manipulator with lubricated joint and interval uncertainty 2 1 Introduction For material and cost savings,the acquiring of the smaller actuator and larger working space,flexible manipulators have wide applications ranging from military,medical treatment to space exploration.However,the intri
8、nsic difficulties exist in modeling and control of flexible manipulators,especially for those with large deformations.In traditional methods,the kinematic joints are assumed as perfect joints,and all components are perfect.Actually,clearance and uncertainty always exist in manipulators due to design
9、 tolerance,imperfections,manufacturing tolerance and abrasion,which lead to pose error of end-effector and reduce reliability of control accuracy of the manipulator.Flores and his co-workers 1-3 systematically studied dynamics of rigid multibody systems with planar revolute clearance joints,spatial
10、revolute joints,spherical clearance joints and translational clearance joints,separately.They found that the joint clearance obviously affected the working performance of multibody systems and led to high frequency vibrations.Pereira et al.4 presented a novel approach to study the dynamic performanc
11、e of planar chain drives,in which the clearance between pin and bushing is considered.Machado et al.5,based on the comparison of several compliant contact force models,provided information on the range of application and accuracy in several contact scenarios.Then,Alves et al.6 compared the existing
12、viscoelastic contact force models.Erkaya et al.7 investigated the effects of clearance on partly compliant mechanisms via simulation and experiment.Zhang et al.8 used Kriging model to predict the dynamic response of a mechanical system with revolute joint clearance.Zhao and Bai 9 investigated the ef
13、fect of joint clearance on dynamic characteristic of a space robot manipulator,in which different clearance sizes were analyzed.Erkaya 10 studied the effect of joint clearance on a welding robot manipulator.The results showed that joint clearance obviously affected the control precision of the manip
14、ulator.The flexibility of manipulator induces many complications in the dynamic characteristic of manipulators with clearance.Based on the absolute nodal coordinate formulation(ANCF),proposed by Shabana 11,and the natural coordinate formulation(NCF),Liu et al.12 adopted the feedforward torque contro
15、l,which combined with a PID controller,to track the desired cylindrical joint trajectory for a rigid-flexible space robot system.In many mechanical systems,joints are designed to operate with some lubricant fluid to reduce friction,add damping,and extend the lifetime of the joints.By hydrodynamic th
16、eory,Flores et al.13,14 performed a series of studies on the dynamics of planar rigid multibody systems with lubricated revolute joints.They found that lubricants can eliminate the effects of clearance on dynamic characteristic.Flores et al.15 also studied dynamic behaviors of spatial rigid multibody systems with lubricated spherical joints.Daniel and Cavalca 16 used two models to analyze the dynamics of a slider-crank mechanism with hydrodynamic lubrication.Reis et al.17 presented a new hydrody
