Adaptive Trajectory Tracking Control for Nonholonomic Wheeled Mobile Robots:A Barrier Function Sliding Mode Approach

The trajectory tracking control performance of nonholonomic wheeled mobile robots(NWMRs)is subject to nonholonomic constraints,system uncertainties,and external disturbances.This paper proposes a barrier function-based adaptive sliding mode control(BFASMC)method to provide high-precision,fast-response performance and robustness for NWMRs.Compared with the conventional adaptive sliding mode control,the proposed control strategy can guarantee that the sliding mode variables converge to a predefined neighborhood of origin with a predefined reaching time independent of the prior knowledge of the uncertainties and disturbances bounds.Another advantage of the proposed algorithm is that the control gains can be adaptively adjusted to follow the disturbances amplitudes thanks to the barrier function.The benefit is that the overestimation of control gain can be eliminated,resulting in chattering reduction.Moreover,a modified barrier function-like control gain is employed to prevent the input saturation problem due to the physical limit of the actuator.The stability analysis and comparative experiments demonstrate that the proposed BFASMC can ensure the prespecified convergence performance of the NWMR system output variables and strong robustness against uncertainties/disturbances.

Analytical modeling and multi-objective optimization(MOO) of slippage for wheeled mobile robot(WMR) in rough terrain

Good understanding of relationship between parameters of vehicle,terrain and interaction at the interface is required to develop effective navigation and motion control algorithms for autonomous wheeled mobile robots(AWMR) in rough terrain.A model and analysis of relationship among wheel slippage(S),rotation angle(θ),sinkage(z) and wheel radius(r) are presented.It is found that wheel rotation angle,sinkage and radius have some influence on wheel slippage.A multi-objective optimization problem with slippage as utility function was formulated and solved in MATLAB.The results reveal the optimal values of wheel-terrain parameters required to achieve optimum slippage on dry sandy terrain.A method of slippage estimation for a five-wheeled mobile robot was presented through comparing the odometric measurements of the powered wheels with those of the fifth non-powered wheel.The experimental result shows that this method is feasible and can be used for online slippage estimation in a sandy terrain.

Robust simultaneous tracking and stabilization of wheeled mobile robots not satisfying nonholonomic constraint

A robust unified controller was proposed for wheeled mobile robots that do not satisfy the ideal rolling without slipping constraint.Practical trajectory tracking and posture stabilization were achieved in a unified framework.The design procedure was based on the transverse function method and Lyapunov redesign technique.The Lie group was also introduced in the design.The left-invariance property of the nominal model was firstly explored with respect to the standard group operation of the Lie group SE(2).Then,a bounded transverse function was constructed,by which a corresponding smooth embedded submanifold was defined.With the aid of the group operation,a smooth control law was designed,which fulfills practical tracking/stabilization of the nominal system.An additional component was finally constructed to robustify the nominal control law with respect to the slipping disturbance by using the Lyapunov redesign technique.The design procedure can be easily extended to the robot system suffered from general unknown but bounded disturbances.Simulations were provided to demonstrate the effectiveness of the robust unified controller.

Sensor-less Terrain Estimation and Torque Control of a Wheeled Mobile Robot

As unmanned electric wheeled mobile robots have been increasingly applied to high-speed operations in unknown environments,the wheel slip becomes a problem when the robot is either accelerating,decelerating,or turning at high speed.Ignoring the effect of wheel slip may cause the mobile robot to deviate from the desired path.In this paper a recently proposed method is implemented to estimate the surface conditions encountered by an unmanned wheeled mobile robot,without using extra sensors.The method is simple,economical and needs less processing power than for other methods.A reaction torque observer is used to obtain the rolling resistance torque and it is applied to a wheeled mobile robot to obtain the surface condition in real-time for each wheel.The slip information is observed by comparing the reaction torque of each wheel.The obtained slip information is then used to control the torque of both wheels using a torque controller.Wheel slip is minimized by controlling the torque of each wheel.Minimizing the slip improves the ability of the unmanned electric wheeled mobile robot to navigate in the desired path in an unknown environment,regardless of the nature of the surface.

Real-time Non-linear Target Tracking Control of Wheeled Mobile Robots

A control strategy for real-time target tracking for wheeled mobile robots is presented.Using a modified Kalman filter for environment perception,a novel tracking control law derived from Lyapunov stability theory is introduced.Tuning of linear velocity and angular velocity with mechanical constraints is applied.The proposed control system can simultaneously solve the target trajectory prediction,real-time tracking,and posture regulation problems of a wheeled mobile robot.Experimental results illustrate the effectiveness of the proposed tracking control laws.

Mathematical modeling and simulation application for a wheeled mobile robot applied on pipe welding

A geometric model was built to represent the position relation of a wheeled mobile robot relative to a pipe. The relationship between the deviation of falling off for the robot and the curvature of the pipe was formulated quantitatively. Based on the relationship, a mathematical model was derived and a fuzzy control algorithm for the robot was developed. Simulations were carried out to confirm the dynamic index and the validity of the mathematical model of the fuzzy control algorithm for seam tracking of pipe welding. Experiments for pipe welding with the mobile robot were also carried out to verify the algorithm, and the results showed that the seam has a good quality with a preferable appearance of weld.

A Real Time Self-Tuning Motion Controller for Mobile Robot Systems

This paper proposes an intelligent controller for motion control of robotic systems to obtain high precision tracking without the need for a real-time trial and error method.In addition, a new self-tuning algorithm has been developed based on both the ant colony algorithm and a fuzzy system for real-time tuning of controller parameters. Simulations and experiments using a real robot have been addressed to demonstrate the success of the proposed controller and validate the theoretical analysis. Obtained results confirm that the proposed controller ensures robust performance in the presence of disturbances and parametric uncertainties without the need for adjustment of control law parameters by a trial and error method.

Design of dead reckoning system for mobile robot

A dead reckoning system for a wheeled mobile robot was designed, and the method for robot’s pose estimation in the 3D environments was presented on the basis of its rigid-body kinematic equations. After analyzing the locomotion architecture of mobile robot and the principle of proprioceptive sensors, the kinematics model of mobile robot was built to realize the relative localization. Considering that the research on dead reckoning of mobile robot was confined to the 2 dimensional planes, the locomotion of mobile robot in the 3 coordinate axis direction was thought over in order to estimate its pose on uneven terrain. Because the computing method in a plane is rather mature, the calculation in height direction is emphatically represented as a key issue. With experimental results obtained by simulation program and robot platform, the position of mobile robot can be reliably estimated and the localization precision can be effectively improved, so the effectiveness of this dead reckoning system is demonstrated.

PRINCIPLE, CONSTRUCTION AND KINEMATIC ANALYSIS FOR THE OMNIDIRECTIONAL MOBILE ROBOT——ICE-SKATER ROBOT

Three main basic types of locomotion for a mobile robot were introduced and the advantages and disadvantages of a legged mobile robot, a wheeled mobile robot and an articulated mobile robot were also discussed. A new type of leg wheeled mobile robot was introduced which combines the adaptability of legged robot with the stability of wheeled robot. On the basis of the structure of the wheels, the paper described the principle of the ice skater robot developed from Roller walker and ALDURO and its construction. The paper also established an inertia coordinate system and a wheel coordinate system, and analyzed the configuration or the posture and the related kinematic constraints of the robot according to some assumptions. Based on the motion principle, a logic based coordinated control system and corresponded flowchart were designed. At last, taking the ice skater robot as an example the paper expounded its application and the actual experiment proved its feasibility.

Modeling and Adaptive Control of an Omni-Mecanum-Wheeled Robot

The complete dynamics model of a four-Mecanum-wheeled robot considering mass eccentricity and friction uncertainty is derived using the Lagrange’s equation. Then based on the dynamics model, a nonlinear stable adaptive control law is derived using the backstepping method via Lyapunov stability theory. In order to compensate for the model uncertainty, a nonlinear damping term is included in the control law, and the parameter update law with σ-modification is considered for the uncertainty estimation. Computer simulations are conducted to illustrate the suggested control approach.

Adaptive trajectory tracking control of two-wheeled self-balance robot

Wheeled mobile robot is one of the well-known nonholonomic systems.A two-wheeled self-balancerobot is taken as the research objective.This paper carried out a detailed force analysis of the robot andestablished a non-linear dynamics model.An adaptive tracking controller for the kinematic model of anonholonomic mobile robot with unknown parameters is also proposed.Using control Lyapunov function(CLF),the controller's global asymptotic stability has been proven.The adaptive trajectory trackingcontroller decreases the disturbance in the course of tracking control and enhances the real-time controlcharacteristics.The simulation result indicated that the wheeled mobile robot tracking can be effectivelycontrolled.

Kinematics Modeling of an Omnidirectional Autonomous Mobile Robot with Castor Wheels

The kinematics model of an omnidirectional wheeled mobile robot （WMR） platform with 3 castor wheels was built, which includes the actuated inverse solution and the sensed forward solution. Motion simulations verify the consistency between the actuated inverse solution and the sensed forward solution. Analysis results show that the WMR possesses 3 degrees of freedom, and its motion trajectory is a straight line. The ＂pushing＂ and ＂pulling＂ motion patterns of the WMR can be generated by using different wheel orientations. It can be used in the places where the space is limited.

Novel Algorithm for Mobile Robot Path Planning in Constrained Environment

This paper presents a development of a novel path planning algorithm, called Generalized Laser simulator (GLS), for solving the mobilerobot path planning problem in a two-dimensional map with the presence ofconstraints. This approach gives the possibility to find the path for a wheelmobile robot considering some constraints during the robot movement inboth known and unknown environments. The feasible path is determinedbetween the start and goal positions by generating wave of points in alldirection towards the goal point with adhering to constraints. In simulation,the proposed method has been tested in several working environments withdifferent degrees of complexity. The results demonstrated that the proposedmethod is able to generate efficiently an optimal collision-free path. Moreover,the performance of the proposed method was compared with the A-star andlaser simulator (LS) algorithms in terms of path length, computational timeand path smoothness. The results revealed that the proposed method hasshortest path length, less computational time and the best smooth path. Asan average, GLS is faster than A∗ and LS by 7.8 and 5.5 times, respectivelyand presents a path shorter than A∗ and LS by 1.2 and 1.5 times. In orderto verify the performance of the developed method in dealing with constraints, an experimental study was carried out using a Wheeled Mobile Robot(WMR) platform in labs and roads. The experimental work investigates acomplete autonomous WMR path planning in the lab and road environmentsusing a live video streaming. Local maps were built using data from a live video streaming with real-time image processing to detect segments of theanalogous-road in lab or real-road environments. The study shows that theproposed method is able to generate shortest path and best smooth trajectoryfrom start to goal points in comparison with laser simulator.

Motion design of a hybrid wheeled/legged robot for lunar exploration

The robot consists of a quadruped mechanism and two active dual-wheel casters possesses the advan-tages of wheeled and legged mechanism, and can quickly move on the relatively plane ground with the wheeledmechanism, and can walk on the extremely uneven terrain with the legged mechanism. The effectiveness of themotion design of the hybrid robot is illustrated by simulation results.

Optimum Design of Stair-Climbing Robots Using Taguchi Method

Environmental issues like pollution are major threats to human health.Many systems are developed to reduce pollution.In this paper,an optimal mobile robot design to reduce pollution in Green supply chain management system.Green supply chain management involves as similating environmentally and eco-nomically feasible solutions into the supply chain life-cycle.Smartness,advanced technologies,and advanced networks are becoming pillars of a sustainable supply chain management system.At the same time,there is much change happening in the logistics industry.They are moving towards a new logistics model.In the new model,robotic logistics has a vital role.The reasons for this change are the rapid growth of the e-commerce business and the shortage of workers.The advantages of using robotic logistics are reduction in human errors,faster delivery speed,better customer satisfaction,more safety for workers,and high workforce adaptability.A robot with rocker-bogie suspension is a six-wheeled mobile platform that has a distinctive potential to keep all wheels on the ground continuously.It has been designed to traverse rough and uneven terrain by distributing the load over its wheels equally.However,there is a limitation to achieving high-speed mobility against vertical barriers.In this research,an optimal design of product delivery wheeled robots for a sustainable supply chain system is proposed to ensure higher adaptability and maximum stability during climbing staircases.The design parameters of the proposed robot are optimized using Taguchi Method.The aim is to get a smooth trajectory of the robot’s center-of-mass.The proposed approach realizes a robot with much-improved stability which can climb over heights more than the size of the wheel(i.e.,3 times the radius of wheels).The results reveal that the modified rocker-bogie system not only increases the stair-climbing capability but also thwarts instability due to overturning of a wheel of the robot.

基于改进模糊PID果园双轮移动机器人运动控制

针对果园双轮机器人在果园路面移动时难平衡、易失稳的问题,提出了一种基于改进萤火虫算法优化的模糊比例-积分-微分(PID)控制策略。首先,根据机器人与果园不平整路面特点,建立其动力学状态空间模型;第二,阐述改进萤火虫算法原理并用其优化控制器模糊规则;第三,利用MatLab/Simulink软件对机器人运动控制进行仿真试验;最后,为检验所提出算法的可行性,建立对比试验。研究结果表明:改进萤火虫算法优化的模糊PID控制器实现了果园双轮移动机器人的稳定运动功能,到达稳定的时间与最大倾角较传统PID控制器分别减少了3.9s和20.4°。

B-2WMR系统模型及其欠驱动特性分析

平衡两轮移动机器人(B-2WMR)是自然不稳定体,是高阶次、不稳定、多变量、非线性、强耦合系统,其动力学系统比较复杂,它属于欠驱动系统。针对该系统,选用合适状态变量,采用Euler-Lagrange方法推导了系统的多输入多输出(MIMO)非线性动态模型,并采用该模型对平衡两轮移动机器人不同任务下的姿态和速度控制进行分析,探求了欠驱动系统的控制方法,对该模型系统在MATLAB中进行了SIMULINK仿真,得到了系统的响应曲线,为该欠驱动平衡两轮移动机器人的平衡运动控制器的设计提供一个完善的实验平台。

轮式移动机器人在卫勤保障中的应用综述

介绍了轮式移动机器人(wheeled mobile robot,WMR)的概念、发展路线及其在国内外卫勤保障中的应用现状,分析了各国WMR的优点和存在的不足,阐述了WMR的关键技术,指出了越障能力优化、战场感知信息交互能力提升、续航能力增强是WMR未来的发展方向。

一种轮腿式越障机器人的研究

针对移动机器人在复杂多变地形环境下实现高机动性、强越障等需求,提出了一种被动变形式的轮腿式越障机器人设计方案。该机器人的变形轮转换过程是由外力操作得到的,因此,不需要任何驱动器,减少了机构的复杂性。在完成机器人整体三维建模的基础上,对变形轮的结构、原理及受力情况进行了分析;以变形过程中的触发转矩和展开前后半径之比为指标进行结构优化;分析机器人变形阶段受力情况,并对机器人平台的相关参数进行调整以实现稳定越障;使用Adams软件对机器人变形、越障过程进行运动学仿真,并制作物理样机对整机结构设计的合理性进行了实验验证。