Dynamic Modelling and Adaptive Traction Control for Mobile Robots

Mobile robots have received a great deal of research in recent years. A significant amount of research has been published in many aspects related to mobile robots. Most of the research is devoted to design and develop some control techniques for robot motion and path planning. A large number of researchers have used kinematic models to develop motion control strategy for mobile robots. Their argument and assumption that these models are valid if the robot has low speed, low acceleration and light load. However, dynamic modelling of mobile robots is very important as they are designed to travel at higher speed and perform heavy duty work. This paper presents and discusses a new approach to develop a dynamic model and control strategy for wheeled mobile robot which I modelled as a rigid body that roles on two wheels and a castor. The motion control strategy consists of two levels. The first level is dealing with the dynamic of the system and denoted as Low level controller. The second level is developed to take care of path planning and trajectory generation

Collaborative Nonlinear Model-Predictive Motion Planning and Control of Mobile Transport Robots for a Highly Flexible Production System

This study is based on a new approach for an advanced microproduction system or highly flexible production systems where all necessary production and assembly processes are connected in a very flexible way using autonomous mobile transport and handling robots. Each robot has to follow its planned paths while avoiding collisions with other robots. In addition, problem-specific constraints for a defined microproduction system, such as limitations of the velocity and accelerations of the robots, have to be fulfilled. This paper focuses on a two-level model predictive optimizing approach. On a global long-term level, simple dynamic models of the robots are used to compute optimal paths under differential constraints where a safety distance between all robots is achieved. Since many uncertainties and unforeseen events could occur, all robots also use a nonlinear model predictive control approach on a local real-time level. This control approach solves the path following and the collision avoidance problems in parallel, while also taking into account differential constraints of the single robots

Diseño e implementación de un sistema de generación de trayectorias para un robot móvil utilizando control odométrico

La generación de trayectorias es uno de los aspectos básicos del desarrollo de robots móviles. Permite al móvil poder desplazarse de un lugar a otro de manera óptima y segura, a partir de un modelo de obstáculos que lo rodean y a un camino ya calculado. Los estudios en generación de trayectorias son importantes debido a que son la base del desplazamiento de un robot móvil. El movimiento debe de ser seguro, esquivando los obstáculos, y eficiente, que se traslade de un lugar a otro en el menor tiempo posible, o con el menor consumo de potencia. Para esto, en primer lugar, se debe de calcular una trayectoria. Ésta puede ser calculada por distintos métodos dependiendo del algoritmo utilizado. Una vez calculada la trayectoria, debe ser realizada por el robot real, lo que lleva a un problema de incertidumbre en su ejecución. Esto se debe a la inexactitud de la ejecución de las órdenes de velocidad y a la inexactitud en la localización del robot mediante los cálculos odométricos. Esta incertidumbre es acumulativa, es decir, mientras más larga sea la trayectoria, se generan errores mayores. La implementación de un sistema de generación de trayectorias servirá para que luego existan estudios sobre mejoras en la automatización de robots móviles, y que lleve a su vez a un impulso al desarrollo de la robótica en general. La presente investigación aplicada propone un sistema de generación de trayectorias que permitirá a un usuario aplicar parámetros iniciales a un algoritmo generador de trayectorias para luego ser enviado al robot móvil que recorrerá el camino planteado y llegar al lugar de destino. El objetivo es el diseño y construcción de un robot móvil para pruebas de generación de trayectorias óptimas, usando distintos algoritmos para este propósito, con la finalidad de poder realizar estudios posteriores sobre el tema.Tesi

Control Oriented System Modelling and Instrumentation of Intelligent Walker-Human Systems

Active intelligent walkers (i-walkers) are promising to provide stable and efficient motion to people with walking disabilities. There are three focuses in this thesis: system modelling, controller design, and instrumentation of an active type i-walker system considering interaction with human user as well. Two different control oriented system models and one high-fidelity model are proposed. All system models are designed as having two-body kinematics and consider the physical human-walker interaction (pHWI) based on the user gait dynamics and characteristics. The two-body kinematics of the systems define the relative motion of the user body with the i-walker. The dynamic models of control oriented systems are developed as single-body i-walker dynamics with human effect. These single-body models are classified as symmetric vs. asymmetric, and designed considering the vertical force components of pHWI on the i-walker. The symmetric model is developed for the center of gravity (CG) displacement of the i-walker human system only along the symmetric axis. The asymmetric model is more comprehensive than the symmetric one including the lateral CG displacement as well. The high-fidelity model considers the effect of human user as a separate dynamic body and covers the horizontal and vertical force components of pHWI during walking. Different control schemes are designed for each of the models with single-body dynamics, demonstrating the characteristics and efficiency of each model. All of these control designs are based on the same inverse kinematic controller, which utilizes two-body kinematic model and provides the desired i-walker velocities regarding the user motion intention. Each of the aforementioned dynamic controllers is designed to generate the torques required to track these desired velocities. Two different dynamic control schemes are proposed for dynamic controller: Proportional-integral-derivative (PID) and sliding mode controllers. The designed controllers are simulation tested in MATLAB/Simulink for the control oriented models. The asymmetric model parameters are also set for two different type of users with symmetric and asymmetric gait patterns, respectively. Finally, instrumentation of i-walkers for implementing the designed controllers is discussed, including presentation of a new human motion detection technique involving laser range finder (LRF) and encoders, and instrumentation is performed regarding the designed controllers

Guidance and search algorithms for mobile robots: application and analysis within the context of urban search and rescue

Urban Search and Rescue is a dangerous task for rescue workers and for this reason the use of mobile robots to carry out the search of the environment is becoming common place. These robots are remotely operated and the search is carried out by the robot operator. This work proposes that common search algorithms can be used to guide a single autonomous mobile robot in a search of an environment and locate survivors within the environment. This work then goes on to propose that multiple robots, guided by the same search algorithms, will carry out this task in a quicker time. The work presented is split into three distinct parts. The first is the development of a nonlinear mathematical model for a mobile robot. The model developed is validated against a physical system. A suitable navigation and control system is required to direct the robot to a target point within an environment. This is the second part of this work. The final part of this work presents the search algorithms used. The search algorithms generate the target points which allow the robot to search the environment. These algorithms are based on traditional and modern search algorithms that will enable a single mobile robot to search an area autonomously. The best performing algorithms from the single robot case are then adapted to a multi robot case. The mathematical model presented in the thesis describes the dynamics and kinematics of a four wheeled mobile ground based robot. The model is developed to allow the design and testing of control algorithms offline. With the model and accompanying simulation the search algorithms can be quickly and repeatedly tested without practical installation. The mathematical model is used as the basis of design for the manoeuvring control algorithm and the search algorithms. This design process is based on simulation studies. In the first instance the control methods investigated are Proportional-Integral-Derivative, Pole Placement and Sliding Mode. Each method is compared using the tracking error, the steady state error, the rise time, the charge drawn from the battery and the ability to control the robot through a simple motion. Obstacle avoidance is also covered as part of the manoeuvring control algorithm. The final aspect investigated is the search algorithms. The following search algorithms are investigated, Lawnmower, Random, HillClimbing, Simulated Annealing and Genetic Algorithms. Variations on these algorithms are also investigated. The variations are based on Tabu Search. Each of the algorithms is investigated in a single robot case with the best performing investigated within a multi robot case. A comparison between the different methods is made based on the percentage of the area covered within the time available, the number of targets located and the time taken to locate targets. It is shown that in the single robot case the best performing algorithms have high random elements and some structure to selecting points. Within the multi robot case it is shown that some algorithms work well and others do not. It is also shown that the useable number of robots is dependent on the size of the environment. This thesis concludes with a discussion on the best control and search algorithms, as indicated by the results, for guiding single and multiple autonomous mobile robots. The advantages of the methods are presented, as are the issues with using the methods stated. Suggestions for further work are also presented

Dynamic Modelling and Adaptive Traction Control for Mobile robots

Mobile robots have been used in many application such as moving material between work stations. They can also be found in many areas such as industrial, medical, environmental and even domestic machines. Research on mobile robots has mounted and attracted s

Dynamic Modelling and Adaptive Traction Control for Mobile Robots

Abstract: Mobile robots have received a great deal of research in recent years. A significant amount of research has been published in many aspects related to mobile robots. Most of the research is devoted to design and develop some control techniques for robot motion and path planning. A large number of researchers have used kinematic models to develop motion control strategy for mobile robots. Their argument and assumption that these models are valid if the robot has low speed, low acceleration and light load. However, dynamic modelling of mobile robots is very important as they are designed to travel at higher speed and perform heavy duty work. This paper presents and discusses a new approach to develop a dynamic model and control strategy for wheeled mobile robot which I modelled as a rigid body that roles on two wheels and a castor. The motion control strategy consists of two levels. The first level is dealing with the dynamic of the system and denoted as ‘Low ’ level controller. The second level is developed to take care of path planning and trajectory generation