外文翻译An adaptive dynamic controller for autonomous mobile robot rajectory trackingabstractThis paper proposes an adaptive controller to guide an unicycle-like mobile robotduring trajectory tracking.Initially,the desired values of the linear and angularvelocities are generated,considering only the kinematic model of the robot.Next,suchvalues are processed to compensate for the robot dynamics,thus generating thecommands of linear and angular velocities delivered to the robot actuators.Theparameters characterizing the robot dynamics are updated on-line,thus providingsmaller errors and better performance in applications in which these parameters canvary,such as load transportation.The stability of the whole system is analyzed usingLyapunov theory,and the control errors are proved to be ultimately bounded.Simulation and experimental results are also presented,which demonstrate the goodperformance of the proposed controller for trajectory tracking under different loadconditions.1.IntroductionAmong different mobile robot structures,unicycle-like platforms are frequentlyadopted to accomplish different tasks,due to their good mobility and simpleconfiguration.Nonlinear control for this type of robot has been studied for severalyears and such robot structure has been used in various applications,such as surveillance and floor cleaning.Other applications,like industrial load transportationusing automated guided vehicles (AGVs)automatic highway maintenance andconstruction,and autonomous wheelchairs,also make use of the unicycle-like structure.Some authors have addressed the problem of trajectory tracking,a quiteimportant functionality that allows a mobile robot to describe a desired trajectorywhen accomplishing a task.An important issue in the nonlinear control of AGVs is that most controllersdesigned so far are based only on the kinematics of the mobile robot.However,when high-speed movements and/or heavy load transportation arerequired,it becomes essential to consider the robot dynamics,in addition to itskinematics.Thus,some controllers that compensate for the robot dynamics have beenproposed.As an example,Fierro and Lewis (1995)proposed a combined kinematic/torquecontrol law for nonholonomic mobile robots taking into account the modeled vehicledynamics.The control commands they used were torques,which are hard to deal withwhen regarding most commercial robots.Moreover,only simulation results werereported.Fierro and Lewis (1997)also proposed a robust-adaptive controller based onneural networks to deal with disturbances and non-modeled dynamics,althoughnot reporting experimental results.Das and Kar(2006)showed an adaptive fuzzylogic-based controller in which the uncertainty is estimated by a fuzzy logic systemand its parameters were tuned on-line.The dynamic model included the actuatordynamics,and the commands generated by the controller were voltages for the robotmotors.The Neural Networks were used for identification and control,and the controlsignals were linear and angular velocities,but the realtime implementation of their solution required a high -performance computer architecture based on a multiprocessorsystem.On the other hand,De La Cruz and Carelli(2006)proposed a dynamic modelusing linear and velocities as inputs,and showed the design of a trajectory trackingcontroller based on their model.One advantage of their controller is that itsparameters are directly related to the robot parameters.However,if the parameters are not correctly identified or if they change withtime,for example,due to load variation,the performance of their controller will beseverely affected.To reduce performance degradation,on-line parameter adaptationbecomes quite important in applications in which the robot dynamic parameters mayvary,such as load transportation.It is also useful when the knowledge of the dynamic parameters is limited ordoes not exist at all.In this paper,an adaptive trajectory-tracking controller based onthe robot dynamics is proposed,and its stability property is proved using theLyapunov theory.The design of the controller was divided in two parts,each part being acontroller itself.The first one is a kinematic controller,which is based on the robotkinematics,and the second one is a dynamic controller,which is based on the robotdynamics.The dynamic controller is capable of updating the estimated parameters,which are directly related to physical parameters of the robot.Both controllersworking together form a complete trajectory-tracking controller for the mobile robot.The controller shave been designed based on the model of a unicycle-like mobilerobot proposed by De La Cruz and Carelli A s-modification term is applied to theparameter-updating law to prevent possible parameter drift.The asymptotic stability of both the kinematic and the dynamic controllers isproven.Simulation results show that parameter drift does not arise even when thesystem works for a long period of time.Experimental results regarding such acontroller are also presented and show that the proposed controller is capable ofupdating its parameters in order to reduce the tracking error.An experiment dealingwith the case of load transportation is also presented,and the results show that theproposed controller is capable of guiding the robot to follow a desired trajectory witha quite small error even when its dynamic parameters change.The main contributions of the paper are:(I)the use of a dynamic model whose input commands are velocities,which is usual in commercial mobile obots,while mostof the works in the literature deals with torque commands;(2)the design of anadaptive controller with a s-modification term,which makes it robust,with thecorresponding stability study for the whole adaptive control system;and (3)thepresentation of experimental results showing the good performance of the controllerin a typical industrial application,namely load transportation.2.Dynamic modelIn this section,the dynamic model of the unicycle-like mobile robot proposed byDe La Cruz and Carelli (2006)is reviewed.Fig.Idepicts the mobile robot,itsparameters and variables of interest.u and o are the linear and angular velocitiesdeveloped by the robot,respectively,G is the center of mass of the robot,C is theposition of the castor wheel,E is the location of a tool on board the robot,h is thepoint of interest with coordinates x and y in the XY plane,c is the robotorientation,and a is the distance between the point of interest and the central point ofthe virtual axis linking the traction wheels(point B).The complete mathematicalmodel is written as.000010where ng and o are the desired values of the linear and angularvelocities,respectively,and represent the input signals of the system.A vector ofidentified parameters and a vector of parametric uncertainties are associated with theabove model of the mobile robot,which are,respectively.where dx and dy are functions of the slip velocities and the robot orientation,duand do are