Collision avoidance and dynamic modeling for wheeled mobile robots and industrial manipulators

Collision Avoidance and Dynamic Modeling are key topics for researchers dealing with mobile and industrial robotics. A wide variety of algorithms, approaches and methodologies have been exploited, designed or adapted to tackle the problems of finding safe trajectories for mobile robots and industrial manipulators, and of calculating reliable dynamics models able to capture expected and possible also unexpected behaviors of robots. The knowledge of these two aspects and their potential is important to ensure the efficient and correct functioning of Industry 4.0 plants such as automated warehouses, autonomous surveillance systems and assembly lines. Collision avoidance is a crucial aspect to improve automation and safety, and to solve the problem of planning collision-free trajectories in systems composed of multiple autonomous agents such as unmanned mobile robots and manipulators with several degrees of freedom. A rigorous and accurate model explaining the dynamics of robots, is necessary to tackle tasks such as simulation, torque estimation, reduction of mechanical vibrations and design of control law

Design and control of a compact aerial manipulation system with a Delta-type parallel robot

This thesis presents the design, modeling, and control of a quadcopter equipped with a Delta-type parallel manipulator. Such systems present demanding challenges in both control theory and task planning, which are addressed with novel mechanical features, modern flight controllers, and optimal trajectory generation. They are primarily designed for versatile indoor pick-and-place tasks where the characteristics of the proposed solution introduce useful kinematic properties. We explore these traits to address critical deficiencies found in previous approaches. First, we introduce and discuss the mechanical design of the coupled system. Second, we derive the kinematics and dynamic relationships between all bodies. Third, we develop the flight controller, where baseline, feedforward, and adaptive components are combined and used in unison with an optimal trajectory generation algorithm. Finally, we present simulation results which reflect the feasibility of the concepts

Design of a planar cable-driven parallel robot for non-contact tasks

Cable-driven parallel robots offer significant advantages in terms of workspace dimensions and payload capability. Their mechanical structure and transmission system consist of light and extendable cables that can withstand high tensile loads. Cables are wound and unwound by a set of motorized winches, so that the robot workspace dimensions mainly depend on the amount of cable that each drum can store. For this reason, these manipulators are attractive for many industrial tasks to be performed on a large scale, such as handling, pick-and-place, and manufacturing, without a substantial increase in costs and mechanical complexity with respect to a small-scale application. This paper presents the design of a planar overconstrained cable-driven parallel robot for quasi-static non-contact operations on planar vertical surfaces, such as laser engraving, inspection and thermal treatment. The overall mechanical structure of the robot is shown, by focusing on the actuation and guidance systems. A novel concept of the cable guidance system is outlined, which allows for a simple kinematic model to control the manipulator. As an application example, a laser diode is mounted onto the end-effector of a prototype to perform laser engraving on a paper sheet. Observations on the experiments are reported and discussed

Stiffness modeling for perfect and non-perfect parallel manipulators under internal and external loadings

International audienceThe paper presents an advanced stiffness modeling technique for perfect and non-perfect parallel manipulators under internal and external loadings. Particular attention is paid to the manipulators composed of non-perfect serial chains, whose geometrical parameters differ from the nominal ones and do not allow to assemble manipulator without internal stresses that considerably affect the stiffness properties and also change the end-effector location. In contrast to other works, several types of loadings are considered simultaneously: an external force applied to the end-effector, internal loadings generated by the assembling of non-perfect serial chains and external loadings applied to the intermediate points (auxiliary loading due to the gravity forces and relevant compensator mechanisms, etc.). For this type of manipulators, a non-linear stiffness modeling technique is proposed that allows to take into account inaccuracy in the chains and to aggregate their stiffness models for the case of both small and large deflections. Advantages of the developed technique and its ability to compute and compensate the compliance errors caused by the considered factors are illustrated by an example that deals with parallel manipulators of the Orthoglide family

Static force capabilities and dynamic capabilities of parallel mechanisms equipped with safety clutches

Cette thèse étudie les forces potentielles des mécanismes parallèles plans à deux degrés de liberté équipés d'embrayages de sécurité (limiteur de couple). Les forces potentielles sont étudiées sur la base des matrices jacobienne. La force maximale qui peut être appliquée à l'effecteur en fonction des limiteurs de couple ainsi que la force maximale isotrope sont déterminées. Le rapport entre ces deux forces est appelé l'efficacité de la force et peut être considéré ; comme un indice de performance. Enfin, les résultats numériques proposés donnent un aperçu sur la conception de robots coopératifs reposant sur des architectures parallèles. En isolant chaque lien, les modèles dynamiques approximatifs sont obtenus à partir de l'approche Newton-Euler et des équations de Lagrange pour du tripteron et du quadrupteron. La plage de l'accélération de l'effecteur et de la force externe autorisée peut être trouvée pour une plage donnée de forces d'actionnement.This thesis investigates the force capabilities of two-degree-of-freedom planar parallel mechanisms that are equipped with safety clutches (torque limiters). The force capabilities are studied based on the Jacobian matrices. The maximum force that can be applied at the end-effector for given torque limits (safety index) is determined together with the maximum isotropic force that can be produced. The ratio between these two forces, referred to as the force effectiveness, can be considered as a performance index. Finally, some numerical results are proposed which can provide insight into the design of cooperation robots based on parallel architectures. Considering each link and slider system as a single body, approximate dynamic models are derived based on the Newton-Euler approach and Lagrange equations for the tripteron and the quadrupteron. The acceleration range or the external force range of the end-effector are determined and given as a safety consideration with the dynamic models

Novel Reconfigurable Delta Robot Dual-Functioning as Adaptive Landing Gear and Manipulator

In this work a novel dual-functioning rotorcraft undercarriage is developed. The design is a reconfigurable delta robot which allows for transformation between Adaptive Landing Gear for vertical take-off and landing and 3DOF Aerial Manipulation mode. To reconfigure between operation modes without reaching singularities, a guideline to find a singularity-free geometry is presented. An adaptive landing control was developed and validated on a test-stand. For the 3DOF manipulation of the delta-structure, a third-order smooth trajectory was presented and integrated. The prototype, also depicted in the accompanying video, is then presented in free flight experiments demonstrating the advantages of the dual-functioning system

A 3-DOF Stewart Platform for Trenchless Pipeline Rehabilitation

A major component of the infrastructure of any modern city is a network of underground pipes that transport drinking water, storm water and sewage. Most of the pipes currently being used are made out of concrete or various plastics. As with any material, they have an expected lifespan after which deterioration begins to occur. This can result in cracks, and in some cases, even large holes in the pipe which can cause a complete loss of function of the pipe. These defects invariably lead to water losses that necessitate the repair of the pipeline, which is an expensive undertaking. The purpose of this thesis is to give a detailed report of the development and testing of a robot with a spray head that is autonomously controlled. This spray head will deposit a liquid material onto the pipe that will then cure to form the new interior wall of the pipe. The design of the robot most suited to this task is a Stewart platform: a parallel manipulator that uses prismatic actuators to control a single end-effector. In contrast to the traditional Stewart platform design, which has six independently controlled legs that are used to control the position of the top platform, a novel design is used which has only three independently controlled legs. The advantages of this design are less weight, less complicated kinematics and a smaller design envelope. A circular trajectory was implemented in the microcontroller code and the accuracy of the Stewart platform was evaluated using videos and image processing techniques. An optimization algorithm is proposed which combines the controlled random search algorithm and the particle swarm optimization algorithm. The effectiveness of this algorithm is demonstrated by selecting the design parameters of a 3-DOF Stewart platform so that the radius of the circular spray path is maximized