Omnidirectional Control of the Hexapod Robot TigerBug

TigerBug is a six legged, hexapod robot built and designed by students in the Rochester Institute of Technology\u27s (RIT) Multi Agent Bio-Robotics Laboratory (MABL). TigerBug is comprised of 18 servo motors, 3 degrees of freedom (DOF) per leg, supported by carbon fiber wrapped foam legs placed in a circular pattern around its hexagon shaped body. In order to control such a complex system, much research has been done in the field of kinematics. There exist two derivations of kinematic solutions, forward and inverse. The forward kinematic (FK) solution tends to be much simpler than its inverse kinematic (IK) counterpart. There has been many methods developed to quickly, and efficiently solve the IK in order to control the position and orientation of a robot. This thesis details the process of developing the IK solution and two gait algorithms for TigerBug. The IK solution was developed by first solving for the FK solution of TigerBug using Denavit-Hartenberg (DH) Parameters. After the FK solution was solved, differentials were applied to each equation in order to solve for the IK solution. Once the IK solution was tested, a fixed gait algorithm was developed in order to understand basic motion control of hexapod locomotion. Once the fixed gait was implemented successfully a rule-based free gait algorithm was developed. The rule-based free gait was accomplished using the rule set governed by restrictiveness to determine when leg state transitions were to occur, as described in the literature. Once implemented, the different combinations of gait parameters were tested for quickness of convergence and efficiency to determine the most optimal set of walking parameters for TigerBug

SWheg: A Wheel-Leg Transformable Robot With Minimalist Actuator Realization

This article presents the design, implementation, and performance evaluation of SWheg, a novel modular wheel-leg transformable robot family with minimalist actuator realization. SWheg takes advantage of both wheeled and legged locomotion by seamlessly integrating them on a single platform. In contrast to other designs that use multiple actuators, SWheg uses only one actuator to drive the transformation of all the wheel-leg modules in sync. This means an N-legged SWheg robot requires only N+1 actuators, which can significantly reduce the cost and malfunction rate of the platform. The tendon-driven wheel-leg transformation mechanism based on a four-bar linkage can perform fast morphology transitions between wheels and legs. We validated the design principle with two SWheg robots with four and six wheel-leg modules separately, namely Quadrupedal SWheg and Hexapod SWheg. The design process, mechatronics infrastructure, and the gait behavioral development of both platforms were discussed. The performance of the robot was evaluated in various scenarios, including driving and turning in wheeled mode, step crossing, irregular terrain passing, and stair climbing in legged mode. The comparison between these two platforms was also discussed

Locomotion performance of hexapod robots on rough substrates and the influence of leg compliance

ABSTRACT OF THE THESISLocomotion performance of hexapod robots on rough substrates and the influence of leg compliancebyAmartya Bhattacharyya Master of Science in Engineering Sciences (Mechanical Engineering)University of California San Diego, 2019Professor Nicholas Gravish, ChairHexapod Robots are a complex system where six legs are connected to the main body which acts as a support frame. A lot of research has been performed in this field from the study of six legged insects to present day implementations where the robot uses its own decision making network. The motivation for this field are the various advantages that hexapedal robots provide like; Obstacle climbing capability, omnidirectional motion, variable geometry, stability, access to uneven terrain etc. At the same time they also have many disadvantages like low energy efficiency, low speeds, complexity of operation and design and especially a lot of attention has to be given to path and gait planning. Therefore, in this paper wexiiuse an open loop platform for our robot and test the performance on simulated rough substrates. Using the results we propose a compliant leg design which will improve the performance while maintaining the stability. We compare the new design with solid legs to quantify the gain. And also test for the shear force limits to make sure the design is ready to be tested on a robot for full length runs. With a goal to utilize the new design and simplify the requirements of complicated neural networks for gait planning

On the Controlling of Multi-Legged Walking Robots on Stable and Unstable Ground

In this chapter, we developed and investigated numerically a general kinematic model of a multi-legged hybrid robot equipped with a crab-like and/or mammal-like legs. To drive the robot’s limbs, a novel generator of gait was employed and tested. The simulation model developed in Mathematica is suitable for virtual study and visualization of the locomotion process. In contrast to our previous papers, in this study we focused especially on precise control of the position of the robot during walking in different directions. In our study we were able to simultaneously control all six spatial degrees of freedom of the robot’s body, as well as all the robot’s legs. Therefore, the investigated robot can be considered and used as a fully controlled walking Stewart platform. What is more, the used algorithm can also be successfully employed to coordinate and control all limbs of the robot on unstable or vibrating ground. As an example, it can be used to stabilize spatial position of the robot when the supporting ground becomes vibrating or unstable, and it will keep the robot stable and prevent it from falling over. Eventually, the developed simulation algorithms can be relatively simply adopted to control real constructions of different multi-legged robots

Climbing and Walking Robots

Nowadays robotics is one of the most dynamic fields of scientific researches. The shift of robotics researches from manufacturing to services applications is clear. During the last decades interest in studying climbing and walking robots has been increased. This increasing interest has been in many areas that most important ones of them are: mechanics, electronics, medical engineering, cybernetics, controls, and computers. Today’s climbing and walking robots are a combination of manipulative, perceptive, communicative, and cognitive abilities and they are capable of performing many tasks in industrial and non- industrial environments. Surveillance, planetary exploration, emergence rescue operations, reconnaissance, petrochemical applications, construction, entertainment, personal services, intervention in severe environments, transportation, medical and etc are some applications from a very diverse application fields of climbing and walking robots. By great progress in this area of robotics it is anticipated that next generation climbing and walking robots will enhance lives and will change the way the human works, thinks and makes decisions. This book presents the state of the art achievments, recent developments, applications and future challenges of climbing and walking robots. These are presented in 24 chapters by authors throughtot the world The book serves as a reference especially for the researchers who are interested in mobile robots. It also is useful for industrial engineers and graduate students in advanced study

Legged Robots for Object Manipulation: A Review

Legged robots can have a unique role in manipulating objects in dynamic, human-centric, or otherwise inaccessible environments. Although most legged robotics research to date typically focuses on traversing these challenging environments, many legged platform demonstrations have also included "moving an object" as a way of doing tangible work. Legged robots can be designed to manipulate a particular type of object (e.g., a cardboard box, a soccer ball, or a larger piece of furniture), by themselves or collaboratively. The objective of this review is to collect and learn from these examples, to both organize the work done so far in the community and highlight interesting open avenues for future work. This review categorizes existing works into four main manipulation methods: object interactions without grasping, manipulation with walking legs, dedicated non-locomotive arms, and legged teams. Each method has different design and autonomy features, which are illustrated by available examples in the literature. Based on a few simplifying assumptions, we further provide quantitative comparisons for the range of possible relative sizes of the manipulated object with respect to the robot. Taken together, these examples suggest new directions for research in legged robot manipulation, such as multifunctional limbs, terrain modeling, or learning-based control, to support a number of new deployments in challenging indoor/outdoor scenarios in warehouses/construction sites, preserved natural areas, and especially for home robotics.Comment: Preprint of the paper submitted to Frontiers in Mechanical Engineerin

Mathematical Modelling and Control System Development of a Remote Controlled, IMU Stabilised Hexapod Robot

Walking robots are useful in search and rescue applications due to their ability to navigate uneven and complex terrain. A hexapod robot has been developed by the Robotics and Agents Research Lab at UCT, however multiple inadequacies have become evident. This work aims to produce a mathematical model of the hexapod and using this model, implement an effective control algorithm to achieve a smooth walking motion and overcome the original flaws. The mathematical model was integrated with the mechanical structure of the hexapod and controlled by a micro-controller. This micro-controller allows for a rapid start-up and low power consumption when compared to previous iterations of the hexapod. Using a path generation algorithm sets of foot positions and velocities are generated. Generating these points in real time allows for walking in any direction without any pre-defined foot positions. To enable attitude control of the hexapod body, an inertial measurement unit was added to the hexapod. By using a PID controller the IMU pitch and roll data was used to control a height offset of each foot of the hexapod, allowing for stabilisation of the hexapod body. An improved wireless remote control was developed to facilitate communication with a host computer. The remote system has a graphical user interface allowing for walking control and status information feedback, such as error information and current battery voltage. Walking tests have shown that the hexapod walks successfully with a smooth tripod gait using the path generation algorithm. Stabilisation tests have shown that the hexapod is capable of stabilising itself after a disturbance to its pitch and/or roll in ±2.5 seconds with a steady state error of ±0.001 radians. This proves that the hexapod robot can be controlled wirelessly while walking in any direction with a stabilised body. This is beneficial in search and rescue as the hexapod has a high degree of manoeuvrability to access areas too dangerous for rescuers to access. With cameras mounted on the stabilised body, it can be used to locate survivors in a disaster area and assist rescuers in recovering them with speed

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