A 3D dynamic model of a spherical wheeled self-balancing robot

Mobility through balancing on spherical wheels has recently received some attention in the robotics literature. Unlike traditional wheeled platforms, the operation of such platforms depends heavily on understanding and working with system dynamics, which have so far been approximated with simple planar models and their decoupled extension to three dimensions. Unfortunately, such models cannot capture inherently spatial aspects of motion such as yaw motion arising from the wheel rolling motion or coupled inertial effects for fast maneuvers. In this paper, we describe a novel, fully-coupled 3D model for such spherical wheeled platforms and show that it not only captures relevant spatial aspects of motion, but also provides a basis for controllers better informed by system dynamics. We focus our evaluations to simulations with this model and use circular paths to reveal advantages of this model in dynamically rich situations. © 2012 IEEE

Self-propelled Bouncing Spherical Robot

25th Annual Denman Undergraduate Research Forum Finalist Second PlaceMost robots that can travel on the ground are either traditional wheeled robots or legged robots. Exploring non-traditional novel robots may provide new solutions for locomotion not previously examined. Currently, self-rolling spherical robots have been designed and manufactured for hobbies, entertainment, or military uses. Similarly, various researchers have built legged robots that walk and run. Our objective in this research project was to design, build, and control a self-propelled bouncing and rolling spherical robot. While some self-bouncing wheeled robots have been built as toys, the self-bouncing spherical robot (one that looks like a ball) remains largely not explored. No one has produced a robot that can bounce continuously and can be steered without any external device to assist its movement. To achieve this goal, we plan to prototype up to three different mechanisms for bouncing. Each prototype would go through brainstorming, computer-aided design and simulation (of the bouncing), initial build, redesign, second build, and final analysis. We follow the classic design cycle: observe, ideation, prototype, and testing. We will also perform dynamic analyses of the robot to improve the design. This thesis reports on current progress towards these goals: we have designed and fabricated (and iterated) on a simple prototype bouncing ball, based on a spinning internal mass; we have performed some 2D and 3D simulations of the spinning mechanism that shows promise for the mechanism to produce persistent bouncing. Future work will consist of improving the current prototype, matching the computer simulations quantitatively to the prototype, performing design optimization and trajectory optimizations for optimal control, exploring other designs closer to hopping robots, and finally, building the ability to control and steer the robot.The Ohio State University Second-year Transformational Experience ProgramThe Ohio State University College of EngineeringNo embargoAcademic Major: Mechanical Engineerin

Robust balancing and position control of a single spherical wheeled mobile platform

Self-balancing mobile platforms with single spherical wheel, generally called ballbots, are suitable example of underactuated systems. Balancing control of a ballbot platform, which aims to maintain the upright orientation by rejecting external disturbances, is important during station keeping or trajectory tracking. In this paper, acceleration based balancing and position control of a single spherical wheeled mobile platform that has three single-row omniwheel drive mechanism is examined. Robustness of the balancing controller is achieved by employing cascaded position, velocity and current control loops enhanced with acceleration feedback (AFB) to provide higher stiffness to the platform. The effectiveness of the proposed balancing controller is compared with commonly used optimal state feedback method. Additionally, the position controller is designed by utilizing the dynamic conversion of desired torques on the ball that are calculated from virtual control inputs generated in the inertial coordinates. Dynamical model of a ballbot platform is investigated by considering highly nonlinear couplings. Performance of the controllers are presented via simulation results where the external torques were applied on the body in order to test disturbance rejection capabilities

Locomotion system for ground mobile robots in uneven and unstructured environments

One of the technology domains with the greatest growth rates nowadays is service robots. The extensive use of ground mobile robots in environments that are unstructured or structured for humans is a promising challenge for the coming years, even though Automated Guided Vehicles (AGV) moving on flat and compact grounds are already commercially available and widely utilized to move components and products inside indoor industrial buildings. Agriculture, planetary exploration, military operations, demining, intervention in case of terrorist attacks, surveillance, and reconnaissance in hazardous conditions are important application domains. Due to the fact that it integrates the disciplines of locomotion, vision, cognition, and navigation, the design of a ground mobile robot is extremely interdisciplinary. In terms of mechanics, ground mobile robots, with the exception of those designed for particular surroundings and surfaces (such as slithering or sticky robots), can move on wheels (W), legs (L), tracks (T), or hybrids of these concepts (LW, LT, WT, LWT). In terms of maximum speed, obstacle crossing ability, step/stair climbing ability, slope climbing ability, walking capability on soft terrain, walking capability on uneven terrain, energy efficiency, mechanical complexity, control complexity, and technology readiness, a systematic comparison of these locomotion systems is provided in [1]. Based on the above-mentioned classification, in this thesis, we first introduce a small-scale hybrid locomotion robot for surveillance and inspection, WheTLHLoc, with two tracks, two revolving legs, two active wheels, and two passive omni wheels. The robot can move in several different ways, including using wheels on the flat, compact ground,[1] tracks on soft, yielding terrain, and a combination of tracks, legs, and wheels to navigate obstacles. In particular, static stability and non-slipping characteristics are considered while analyzing the process of climbing steps and stairs. The experimental test on the first prototype has proven the planned climbing maneuver’s efficacy and the WheTLHLoc robot's operational flexibility. Later we present another development of WheTLHLoc and introduce WheTLHLoc 2.0 with newly designed legs, enabling the robot to deal with bigger obstacles. Subsequently, a single-track bio-inspired ground mobile robot's conceptual and embodiment designs are presented. This robot is called SnakeTrack. It is designed for surveillance and inspection activities in unstructured environments with constrained areas. The vertebral column has two end modules and a variable number of vertebrae linked by compliant joints, and the surrounding track is its essential component. Four motors drive the robot: two control the track motion and two regulate the lateral flexion of the vertebral column for steering. The compliant joints enable limited passive torsion and retroflection of the vertebral column, which the robot can use to adapt to uneven terrain and increase traction. Eventually, the new version of SnakeTrack, called 'Porcospino', is introduced with the aim of allowing the robot to move in a wider variety of terrains. The novelty of this thesis lies in the development and presentation of three novel designs of small-scale mobile robots for surveillance and inspection in unstructured environments, and they employ hybrid locomotion systems that allow them to traverse a variety of terrains, including soft, yielding terrain and high obstacles. This thesis contributes to the field of mobile robotics by introducing new design concepts for hybrid locomotion systems that enable robots to navigate challenging environments. The robots presented in this thesis employ modular designs that allow their lengths to be adapted to suit specific tasks, and they are capable of restoring their correct position after falling over, making them highly adaptable and versatile. Furthermore, this thesis presents a detailed analysis of the robots' capabilities, including their step-climbing and motion planning abilities. In this thesis we also discuss possible refinements for the robots' designs to improve their performance and reliability. Overall, this thesis's contributions lie in the design and development of innovative mobile robots that address the challenges of surveillance and inspection in unstructured environments, and the analysis and evaluation of these robots' capabilities. The research presented in this thesis provides a foundation for further work in this field, and it may be of interest to researchers and practitioners in the areas of robotics, automation, and inspection. As a general note, the first robot, WheTLHLoc, is a hybrid locomotion robot capable of combining tracked locomotion on soft terrains, wheeled locomotion on flat and compact grounds, and high obstacle crossing capability. The second robot, SnakeTrack, is a small-size mono-track robot with a modular structure composed of a vertebral column and a single peripherical track revolving around it. The third robot, Porcospino, is an evolution of SnakeTrack and includes flexible spines on the track modules for improved traction on uneven but firm terrains, and refinements of the shape of the track guidance system. This thesis provides detailed descriptions of the design and prototyping of these robots and presents analytical and experimental results to verify their capabilities

Stability analysis of non-holonomic inverted pendulum system

The inverted pendulum is doubtlessly one of the most famous control problems found in most control text books and laboratories worldwide. This popularity comes from the fact that the inverted pendulum exhibits nonlinear, unstable and non-minimum phase dynamics. The basic control objective of the study is to design a controller in order to maintain the upright position of the pendulum while also controlling the position of the cart. In our study we explored the relationship that the tuning parameters (weight on the position of the car and the angle that the pendulum makes with the vertical) of a classical inverted pendulum on a cart has on the pole placement and hence on the stability of the system. We then present a family of curves showing the local root-locus and develop relationships between the weight changes and the system performance. We describe how these locus trends provide insight that is useful to the control designer during the effort to optimize the system performance. Finally, we use our general results to design an effective feedback controller for a new system with a longer pendulum, and present experiment results that demonstrate the effectiveness of our analysis. We then designed a simulation-based study to determine the stability characteristics of a holonomic inverted pendulum system. Here we decoupled the system using geometry as two independent one dimensional inverted pendulum and observed that the system can be stabilized using this method successfully with and without noise added to the system. Next, we designed a linear system for the highly complex inverted pendulum on a non-holonomic cart system. Overall, the findings will provide valuable input to the controller designers for a wide range of applications including tuning of the controller parameters to design of a linear controller for nonlinear systems

3D dynamic modeling of spherical wheeled self-balancing mobile robot

Ankara : The Department of Electrical and Electronics Engineering and the Graduate School of Engineering and Science of Bilkent University, 2012.Thesis (Master's) -- Bilkent University, 2012.Includes bibliographical references.In recent years, dynamically stable platforms that move on spherical wheels, also known as BallBots, gained popularity in the robotics literature as an alternative locomotion method to statically stable wheeled mobile robots. In contrast to wheeled platforms which do not have to explicitly be concerned about their balance, BallBot platforms must be informed about their dynamics and actively try to maintain balance. Up until now, such platforms have been approximated by simple planar models, with extensions to three dimensions through the combination of decoupled models in orthogonal sagittal planes. However, even though capturing certain aspects of the robot’s motion is possible with such decoupled models, they cannot represent inherently spatial aspects of motion such as yaw rotation or coupled inertial effects due to the motion of the rigid body. In this thesis, we introduce a novel, fully-coupled 3D model for such spherical wheeled balancing platforms. We show that our novel model captures important spatial aspects of motion that have previously not been captured by planar models. Moreover, our new model provides a better basis for controllers that are informed by more expressive system dynamics. In order to establish the expressivity and accuracy of this new model, we present simulation studies in dynamically rich situations. We use circular paths to reveal the advantages of the new model for fast maneuvers. Additionally, we introduce new inverse-dynamics controllers for a better attitude control and investigate within simulations the capability of sustaining dynamic behaviors. We study the relation between circular motions in attitude angles and associated motions in positional variables for BallBot locomotion.İnal, Ali NailM.S

Wheeled Mobile Robots: State of the Art Overview and Kinematic Comparison Among Three Omnidirectional Locomotion Strategies

In the last decades, mobile robotics has become a very interesting research topic in the feld of robotics, mainly because of population ageing and the recent pandemic emergency caused by Covid-19. Against this context, the paper presents an overview on wheeled mobile robot (WMR), which have a central role in nowadays scenario. In particular, the paper describes the most commonly adopted locomotion strategies, perception systems, control architectures and navigation approaches. After having analyzed the state of the art, this paper focuses on the kinematics of three omnidirectional platforms: a four mecanum wheels robot (4WD), a three omni wheel platform (3WD) and a two swerve-drive system (2SWD). Through a dimensionless approach, these three platforms are compared to understand how their mobility is afected by the wheel speed limitations that are present in every practical application. This original comparison has not been already presented by the literature and it can be used to improve our understanding of the kinematics of these mobile robots and to guide the selection of the most appropriate locomotion system according to the specifc application