Dynamics Of Mobile Robot Research Articles

Formulations about Dynamics of Mobile Robots

In this paper the dynamics equations for a mobile robot, named PatrolBot, will be developed, using new concepts in advanced mechanics, based on important scientific researches of the main author, concerning the kinetic energy. In keeping the fact that the mathematical models of the mobile platforms are different besides the other robots types, due to nonholonomic constraints, these dynamic control functions, will be computed, according to these restrictions for robot motion.

Dynamics and stability of a hybrid serial-parallel mobile robot

Kinematics, dynamics, and stability analysis of a hybrid serial-parallel wheeled mobile robot is detailed in this paper. Privileging the advantages of both serial and parallel robots, the suggested structure will provide higher stability for heavy object manipulation by a mobile robotic system. The proposed system is made of a differentially-driven wheeled platform, a planar parallel manipulator, which is called here as star-triangle (ST) mechanism, and a serial Puma-type manipulator arm. In order to develop a comprehensive kinematics model of the robot; first it is divided into three modules, i.e. a mobile platform, a parallel ST mechanism, and a serial robot. Next, a closed-form dynamics model is derived for the whole hybrid system based on a combined Newton–Euler and Lagrange formulation. Then, a careful validation procedure is presented to verify the obtained dynamics model. Finally, using the new postural stability metric named as moment-height stability (MHS), the important role of the parallel ST mechanism for stabilizing the mobile robotic system is demonstrated. The obtained results show that the proposed hybrid serial–parallel arrangement effectively enhances the tip-over stability of the overall mobile robotic system. Hence, it can be successfully exploited to prevent tip-over instability particularly during heavy object manipulation tasks.

Design of a sliding mode controller for an automatic guided vehicle and its implementation

In this paper, a control scheme that combines a kinematic controller and a sliding mode dynamic controller with external disturbances is proposed for an automatic guided vehicle to track a desired trajectory with a specified constant velocity. It provides a method of taking into account specific mobile robot dynamics to convert desired velocity control inputs into torques for the actual mobile robot. First, velocity control inputs are designed for the kinematic controller to make the tracking error vector asymptotically stable. Then, a sliding mode dynamic controller is designed such that the mobile robot’s velocities converge to the velocity control inputs. The control law is obtained based on the backstepping technique. System stability is proved using the Lyapunov stability theory. In addition, a scheme for measuring the errors using a USB camera is described. The simulation and experimental results are presented to illustrate the effectiveness of the proposed controller.

The influence of friction forces on the dynamics of a two-link mobile robot

Abstract Controlled periodic motions of a planar two-link robot in a horizontal plane when there is dry friction are considered. The two-link is controlled by means of an internal torque applied to the joint connecting the links. The dynamics of the two-link, taking into account the influence of friction forces and the constrained nature of the control torque, is analysed assuming that the angle between the links is small. The conventional locomotion algorithm of a two-link is modified to ensure rectilinear displacement of the two-link. The influence of various geometrical and mechanical parameters of the system on the average rate of locomotion and on the power consumption during the motion of the two-link robot in a plane is investigated.

Improving the stability level for on-line planning of mobile manipulators

SUMMARYThis paper presents a quadratic programming (QP) form algorithm to realize on-line planning of mobile manipulators with consideration for improving the stability level. With Lie group and screw tools, the general tree topology structure mobile robot dynamics and dynamic stability attributes were analysed. The stable support condition for a mobile robot is constructed not only in a polygonal support region, but also in a polyhedral support region. For a planar supporting region, the tip-over avoiding requirement is formulated as the tip-over prevent constraints with the reciprocal products of the resultant support wrench and the imaginary tip-over twists, which are constructed with the boundaries of the convex support polygon. At velocity level, the optimized resolution algorithm with standard QP form is designed to resolve the inverse redundant kinematics of the Omni-directional Mobile ManipulatorS (OMMS) with stability considerations. Numerical simulation results show that the presented methods successfully improve the stability level of the robot within an on-line planning process.

Navegación de Robots Móviles en Entornos no Estructurados utilizando Álgebra Lineal

Este trabajo presenta un enfoque basado en la teoria del algebra lineal, los metodos numericos y una modificacion al metodo de fuerza ficticia, para la navegacion de robots moviles en entornos dinamicos. Para el diseno del controlador se utiliza el modelo dinamico de un robot movil no holonomico tipo uniciclo. Trabajos anteriores a menudo ignoran la dinamica del robot, por lo que sufren de singularidades en sus algoritmos. Los resultados de simulacion y experimentacion confirman la factibilidad y efectividad del controlador propuesto, logrando que el robot sea capaz de adaptar su comportamiento al nivel del conocimiento disponible y navegar de manera segura en entornos no estructurados, mientras se minimiza el error de seguimiento.

Trajectory tracking of mobile robots in dynamic environments—a linear algebra approach

SUMMARYA new approach for navigation of mobile robots in dynamic environments by using Linear Algebra Theory, Numerical Methods, and a modification of the Force Field Method is presented in this paper. The controller design is based on the dynamic model of a unicycle-like nonholonomic mobile robot. Previous studies very often ignore the dynamics of mobile robots and suffer from algorithmic singularities. Simulation and experimentation results confirm the feasibility and the effectiveness of the proposed controller and the advantages of the dynamic model use. By using this new strategy, the robot is able to adapt its behavior at the available knowing level and it can navigate in a safe way, minimizing the tracking error.

마그네틱 콤파스 기반의 전 방향 로봇의 방위각 제어

In this paper, control of an omni-directional mobile robot is presented. Relying on encoder measurements to define the azimuth angle yields the dead-reckoned situation which the robot fails in localization. The azimuth angle error due to dead-reckoning is compensated and corrected by the magnetic compass sensor. Noise from the magnetic compass sensor has been filtered out. Kinematics and dynamics of the omni-directional mobile robot are derived based on the global coordinates and used for simulation studies. Experimental studies are also conducted to show the correction by the magnetic compass sensor.

Real-Time Trajectory Tracking Of Mobile Robots Based On Sliding Mode Control Using Irbfnns

Abstract A control scheme for dynamic tracking of mobile robots is presented, which integrates a velocity controller based on backstepping techniques and a torque controller based on improved RBF neural networks. The proposed torque control strategy derived from sliding modes depends on the dynamics of mobile robots. Because of the uncertainties in robot dynamics, the robustness of the system cannot be guaranteed In order to decrease the impact of the uncertainties and improve the robustness of the system, improved RBF neural networks are designed online by the integrated resource allocating network method, which is used to model the dynamics of the mobile robots online in the torque controller. Thus the proposed torque controller is composed of a neural network controller and a robust compensator. Simulation studies show that the proposed system is competent for robust tracking control of mobile robots and the tracking performance is improved effectively.

Dynamic Performance of Mobile Haptic Interfaces

The increasing demand for virtual reality applications in several scientific disciplines feeds new research perspectives dealing with robotics, automation, and computer science. In this context, one of the topics is the design of advanced force-feedback devices allowing not only kinesthetic interaction with virtual objects but also locomotion and navigation inside virtual worlds. This has the main advantage to stimulate human vestibular apparatus, thus increasing the overall realism of simulation. Particularly, this paper deals with mobile haptic interfaces (MHIs), built by combining standard force-feedback devices with mobile platforms. We investigated which factors may affect the transparency of this kind of devices, identifying in mobile robot dynamics a possible cause of loss of transparency. Hence, in this paper, we present a method to analyze dynamic performance of an MHI and some basic guidelines to design controller in order to meet desired specifications. Experimental validation of the theoretical results is reported.

Neurocontrollers for Trajectory Tracking Problem of a Nonholonomic Mobile Robot

In this paper, a trajectory tracking control for a nonholonomic mobile robot by the integration of a kinematic controller and a torque controller is investigated. The proposed torque controllers (PTCs) are based on a Gaussian radial basis function neural network (RBFNN) modeling technique, which are used to compensate the mobile robot dynamics, significant uncertainties and disturbances. Also, the PTCs are not dependent of the robot dynamics neither requires the off-line training process. The stability analysis and the convergence of tracking errors to zero, as well as the learning algorithms (for weights, centers, and widths) are guaranteed with basis on Lyapunov's theory. In addition, the simulation results shows the efficiency of the PTCs.

Kinematic modeling of wheeled mobile robots with slip

This work presents a kinematic modeling method for wheeled mobile robots with slip based on physical principles. First, we present the kinematic modeling of a mobile robot with no-slip considering four types of wheels: fixed, centered orientable, off-centered orientable (castor) and Swedish (also called Mecanum, Ilon or universal). Then, the dynamics of a wheeled mobile robot based on Lagrange formulation are derived and discussed. Next, a quasi-static motion is considered to obtain the kinematic conditions that provide the slip modeling equations. Several types of traction models for the slip between the wheel and the floor are indicated. In particular, for a frictional force linearly dependent on the sliding velocity, the no-slip kinematic equation of the wheeled mobile robot is related, through the weighted least-squares algorithm, with the slip modeling equations. To illustrate the applications of the proposed approach a tricycle vehicle is considered in a real situation. The experimental results obtained for the slip kinematic model are compared with the ones obtained for the well-known Kalman filter.

Neural Torque Controllers For Trajectory Tracking Problem Of A Nonholonomic Mobile Robot

In this paper, a trajectory tracking control for a nonholonomic mobile robot by the integration of a kinematic controller and torque controllers is investigated. The proposed neural torque controllers (PNTCs) are based on a Gaussian radial basis function neural network (RBFNN) modeling technique, which are used to compensate the mobile robot dynamics, and bounded unknown disturbances. Also, the PNTCs are not dependent of the robot dynamics neither requires the off-line training process. The stability analysis and the convergence of tracking errors, as well as the learning algorithm for weights are guaranteed with basis on Lyapunov theory. In addition, the simulations results shows the efficiency of the PNTCs.

Study of the internal dynamics of an autonomous mobile robot

The requirement of ideal rolling without sideways slipping for wheels imposes nonholonomic (non-integrable) constraints on the motion of the wheels and consequently on the motion of wheeled mobile robots. From the control point of view, the dynamics of nonholonomic systems can be divided in two parts: external and internal dynamics. The dimension of the external dynamics of nonholonomic systems depends on the number of inputs to the system and the dimension of the internal dynamics depends on the number of independent nonholonomic constraints. For different motion control problems of nonholonomic systems, a smooth (model based) state feedback control law only deals with the system external dynamics; therefore, the system internal dynamics must be examined separately and its stability has to be analyzed and proved. In this paper, the internal dynamics of a three-wheel mobile robot with front wheel steering and driving is investigated. In particular, its internal dynamics stability is analyzed for two different situations, when the mobile robot is moving and when it is stationary.

Analytical framework for the smooth manoeuvre of wheeled mobile robots traversing obstacles

The aims of this paper are twofold. The first aim is to employ a vectorial approach to model the dynamics of wheeled mobile robots (WMRs), which need to travel over localized surface irregularities. This approach results in compact vectorial equations which are more easily programmable using a symbolic programming software tool. The second aim is to apply the model in conjunction with temporal trajectory functions to compute the traction–force requirements of WMRs traversing obstacles of specified profiles. This model–based approach provides a more robust framework for the development of active control of the motion of WMRs traversing obstacles. It is demonstrated that, during obstacle traversing, a compromise can be achieved between the minimal times of manoeuvre on the one hand and traction force, inertia load and geometrical properties of WMRs and obstacles on the other. The traction force needed to complete the manoeuvre may change sign, necessitating a switch to a braking action. This shift between the traction mode and braking mode of the actuators can be avoided by an appropriate choice of a minimum time of manoeuvre. This study also provides a basis for the selection of an appropriate manoeuvre time based on prior knowledge of the friction characteristics of a traction surface.

Chaotic dynamics of a behavior-based miniature mobile robot: effects of environment and control structure

To study the regularity and complexity of autonomous behavior, the flow of sensory information obtained in autonomous mobile robots under various conditions was analyzed as a complex system. Sensory information time series X n was collected from a miniature mobile robot during free navigation, and plotted on the return map, the graph of X n+τ vs. X n . The plot exhibited a characteristic trajectory, representing the regularity of the time series. Correlation integral and Lyapunov exponent analysis also showed properties of deterministic chaos; the presence of fractal dimension and positive Lyapunov exponent. Analysis of sensory information obtained in the robot with three different neural controllers revealed that the autonomous robot behaves in such a way that the flow of sensory information is governed by a deterministic rule, and this pattern is unique to each controller. Furthermore, the analysis in various environments exhibited that transitions from one trajectory to another on the return map occur during the course of autonomous behavior. The fractal and Lyapunov dimensions calculated in various conditions indicate that these dimension could be utilized to quantify the complexity of autonomous behavior and the relative difficulty of tasks. Analyses at different evolutionary stage revealed that behavioral performance correlates with fractal dimension. These studies using a miniature mobile robot that allowed to idealize the experimental conditions demonstrated firmly that the complex analysis could be utilized in evaluation and optimization of autonomous systems and the behavior.

Realization of a ball passing strategy for a robot soccer game: a case study of integrated planning and control

Ball passing is an elementary and frequently employed human soccer skill. This paper examines the realization and visualization of ball passing, a low level move-to-ball behavior of a soccer robot, in a robot soccer game. A case study of three mechanically identical mobile robots with a formation ready to pass a ball cyclically in a zigzag pattern is examined. We build a control command driven mobile robot motion simulator with a controller and dynamics of mobile robots, not only nonholonomic kinematic constraints to simulate the motion of a soccer robot driven by wheels torques to generate wheels accelerations, to update the robot position and orientation at successive time instants. Kick motion follows a physical law, and a simplified collision check and response model is utilized for the efficient detection of the hitting a robot with the ball or other robots. The realization of specific ball passing strategy to drive each soccer robot in a position to receive a pass includes three levels of organization, coordination, and execution: careful integrated design of a dynamic formation and role change scheme, ball position estimation, and coordinated trajectory (i.e. path and velocity) planning and tracking control. Simulations are performed to illustrate the feasibility of the realization of ball passing among three robots, implemented by a software program for coordinated trajectory planning and tracking control in the developed simulator.

장님 이동 로봇의 힘 제어 : 분석, 시뮬레이션 및 실험

We propose a blind mobile robot force control algorithm that uses force information as a guidance toward to the goal position. Based on the mobile robot dynamics, the control law is formed from explicit force errors. Simulation studies are conducted based on the kinematics and the dynamics of the mobile robot. Simulation results show that good force tracking can be achieved. In order to confirm simulation results, experiments are performed. The robot is commanded to follow unknown environment with maintaining a certain desired force. Experimental results show that the blind mobile robot successfully maintains contact with a regulated desired force and arrives at the goal position.

Motion planning for anguilliform locomotion

We investigate issues of control and motion planning for a biomimetic robotic system. Previous work has shown that a successful approach to solving the motion planning problem is to decouple it into the two subproblems of trajectory generation (feedforward controls) and feedback regulation. In this paper, we investigate basic issues of momentum generation for a class of dynamic mobile robots, focusing on eel-like swimming robots. We develop theoretical justification for a forward gait that has been observed in nature, and for a turning gait, used in our control laws, that has not been extensively studied in the biological literature. We also explore theoretical predictions for novel gaits for turning and sideways swimming. Finally, we present results from experiments in motion planning for a biomimetic robotic system. We show good agreement with theory for both open and closed-loop control of our modular, five-link, underwater swimming robot using image-based position sensing in an aquatic environment.

Full-state tracking and internal dynamics of nonholonomic wheeled mobile robots

In the paper, the stable full-state tracking problem is investigated for nonholonomic wheeled mobile robots under output-tracking control laws. Dynamics of such wheeled mobile robots are nonholonomic and pose challenging problems for control design and stability analysis. The dynamics formulated in terms of full-state tracking errors offer some properties that allow better understanding of the internal and zero dynamics of the tracking-error system and more insights to the trajectory tracking stability. Output functions are chosen as virtual reference points for various types of wheeled mobile robots in aid of output controller designs. Sufficient conditions are derived to ensure the stable full-state trajectory tracking under output-tracking control laws. A type (1,1) mobile robot of car-like configuration is studied in detail and further numerical analysis provides more results which are beyond the reach of analytical means. An example and simulation results are presented to confirm the theory and observations.