Trajectory solutions for a game-playing robot using nonprehensile manipulation methods and machine vision

The need for autonomous systems designed to play games, both strategy-based and physical, comes from the quest to model human behaviour under tough and competitive environments that require human skill at its best. In the last two decades, and especially after the 1996 defeat of the world chess champion by a chess-playing computer, physical games have been receiving greater attention. Robocup TM, i.e. robotic football, is a well-known example, with the participation of thousands of researchers all over the world. The robots created to play snooker/pool/billiards are placed in this context. Snooker, as well as being a game of strategy, also requires accurate physical manipulation skills from the player, and these two aspects qualify snooker as a potential game for autonomous system development research. Although research into playing strategy in snooker has made considerable progress using various artificial intelligence methods, the physical manipulation part of the game is not fully addressed by the robots created so far. This thesis looks at the different ball manipulation options snooker players use, like the shots that impart spin to the ball in order to accurately position the balls on the table, by trying to predict the ball trajectories under the action of various dynamic phenomena, such as impacts. A 3-degree of freedom robot, which can manipulate the snooker cue on a par with humans, at high velocities, using a servomotor, and position the snooker cue on the ball accurately with the help of a stepper drive, is designed and fabricated. [Continues.

A comprehensive survey of the analytical, numerical and experimental methodologies for dynamics of multibody mechanical systems with clearance or imperfect joints

"Available online 19 December 2017"A comprehensive survey of the literature of the most relevant analytical, numerical, and experimental approaches for the kinematic and dynamic analyses of multibody mechanical systems with clearance joints is presented in this review. Both dry and lubricated clearance joints are addressed here, and an effort is made to include a large number of research works in this particular field, which have been published since the 1960′s. First, the most frequently utilized methods for modeling planar and spatial multibody mechanical systems with clearance joints are analyzed, and compared. Other important phenomena commonly associated with clearance joint models, such as wear, non-smooth behavior, optimization and control, chaos, and uncertainty and links’ flexibility, are then discussed. The main assumptions procedures and conclusions for the different methodologies are also examined and compared. Finally, future developments and new applications of clearance joint modeling and analysis are highlighted.This research was supported in part by the China 111 Project (B16003) and the National Natural Science Foundation of China under Grants 11290151, 11472042 and 11221202. The work was also supported by the Portuguese Foundation for Science and Technology with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941.info:eu-repo/semantics/publishedVersio

歩行メカニズムにおける粘弾性着地の効果および動力学解析のための計算論的手法に関する研究

Since animal bodies are highly complex to be organized biologically, it is not easy to evaluate the advantage of flexibility in the muscularskeletal system in comparison with mechanical rigid bodies. For the reason, a simplification had been implemented in traditional scheme of the reduced degree of freedom mechanisms with well-designed fixed limb trajectory for real world applications, and the best mechanical structure was explored to minimize its energy consumption known in walking linkage mechanisms. As the possible hypothesis, the advantage of high energy conservation effect can be maximized according to a smooth grounding at the touching moment of the toe on the ground. The smooth trajectory itself can be reproduced by closed-linkage walking models, while the effect of the interaction between the toe and ground is unclear and viscoelastic contact may enhance the effect. For the clarification of the hypothesis, a fine computational framework is needed to be established to provide less computational cost and enough accuracy and stability in the analysis. Traditionally, the rigid-body mechanics and contact force analysis were separately studied and developed. In the present study, multibody dynamics approach based on the analytical mechanics was newly integrated with the viscoelastic contact force model, which is able to implement a hysteresis damping phenomenon simply. By using the linkage mechanisms, the elasticity of the grounding was analyzed through the inverse dynamics based on the proposed computational framework involving the multibody dynamics and contact force model implementation. The proposed method was located in an intermediate position between the discrete contact model for a less frequency attachment of bodies and the continuous model for stable attachment phenomenon. In the sense, the method was appropriate for analyses of walking mechanisms with a consistent frequency of the attachment with the ground, which requires a fine reaction force analysis. In the computer experiment as the comparison of typical and simplified walking linkage mechanisms, the proposed method applied to Chebyshev and Theo-Jansen walking mechanisms and demonstrated the required torque in the driving input when those mechanisms were walking on the ground. In an energy analysis, which is defined as the required input-torque integration in a cycle of the leg motion, the perfectly elastic ground contact commonly reduced the energy consumption significantly in the comparison of the coefficient of restitution in the damping factor model by Lankarani and Nikravesh. The result proved the hypothesis of the positive effect of the smooth grounding in the range of the proposed computational approach. It may contribute to providing an criterion not only for a real walking robot design but also assistive devise configurations to absorb unnecessary ground reaction force to prevent the damage to the leg mechanism and enhance a smooth walking pattern.九州工業大学博士学位論文 学位記番号：生工博甲第407号 学位授与年月日：令和3年3月25日1 Introduction|2 Mathematical formulations in multibody system dynamics|3 Foot-ground contact model|4 An integrated computational framework for the energy analysis of rigid closed-loop walking mechanisms|5 Comparison between the proposed method and the other methods|6 Dynamic modelling of the horse locomotion|7 Discussion and Conclusion九州工業大学令和2年

Microgravity Particle Research on the Space Station

Science questions that could be addressed by a Space Station Microgravity Particle Research Facility for studying small suspended particles were discussed. Characteristics of such a facility were determined. Disciplines covered include astrophysics and the solar nebula, planetary science, atmospheric science, exobiology and life science, and physics and chemistry

Geometric Motion Planning for Inertial Systems

In order to enable better visualization and understanding of the effect of the robot's geometry and inertia on the robot's trajectories, this dissertation proposes to use geometric mechanics to bridge the gap between the physical motion of a robot and its mathematical structure. The main focus of this research is to investigate the system geometry and inertia and their relationship with the curves and acceleration that produce the most efficient trajectories or gaits. This dissertation ‘s approach has an advantage over the state-of-the-art method, which uses numerical forward dynamic simulations. Such numerical simulations are computationally expensive and dependent on starting parameters. The proposed geometric motion planning framework allows the user to design a trajectory with respect to the requirements without any need for forward simulation. Furthermore, the proposed framework enables the user to understand the system's movement from its mathematical model rather than computing the results and exploring the outputs. Unlike previous works that were focusing on the system geometry to gain insight about the system's movement, this dissertation uses the geometry and inertia to describe the system's movement. This is achieved using two tools to gain insight into the underlying locomotion: constructing geodesics and constructing metric fields. The geodesic illustrates the robots geometric structure of the natural dynamic path which is defined as the straightest path. The metric field in mechanical systems is obtained from the system's inertia which illustrates where it is easier to move in parameterized space. In this research we consider four classes of systems: (1) fixed base systems such as robotic arms, (2) crawling systems in an inertial based environment such as floating snakes, (3) flying object with an abrupt change in momentum such as casting manipulator, and (4) system with fast energy release such as jumping robots

Investigation of vibrational conveyor parameters for the transport of lunar regolith

Questa tesi si focalizza su una possibile applicazione pratica del concetto di In Situ Resource Utilization (ISRU) nell'ambito dell'esplorazione spaziale: il trasporto e la gestione della regolite lunare tramite l'utilizzo di trasportatori vibranti. I trasportatori vibranti, attuati tramite attuatori piezoelettrici, sono stati identificati come soluzione ideale per future operazioni logistiche sulla superficie lunare, grazie al loro basso consumo energetico e al ridotto numero di componenti mobili soggetti all'erosione causata dalla regolite. Al fine di comprendere le capacità di trasporto di tali strumenti, è stata condotta una campagna sperimentale su un modello in scala, studiando le variazioni del comportamento di trasporto del materiale in base all'ampiezza e alla frequenza di vibrazione, nonché all'inclinazione del trasportatore stesso. I test sono stati effettuati utilizzando un particolare materiale granulare composto da sfere di vetro di dimensioni uniformi e conosciute, al fine di limitare la variabilità sperimentale. I risultati hanno dimostrato una relazione non lineare tra la frequenza di vibrazione e il tempo totale di trasporto per una determinata quantità di materiale, evidenziando l'effetto positivo della risonanza meccanica tra l'attuatore e i giunti elastici sul flusso di scarico del trasportatore. Allo stesso tempo, è stato sviluppato un modello numerico basato sul Discrete Element Method (DEM) per simulare il comportamento del setup sperimentale. Il modello numerico è stato implementato utilizzando il linguaggio di programmazione scientifica ad alte prestazioni Julia e successivamente validato utilizzando sia risultati analitici che sperimentali, mostrando una buona corrispondenza con i risultati ottenuti dagli esperimenti. La simulazione è stata in grado di predire con un buon livello di precisione l'evoluzione del flusso di massa trasportato e della velocità di trasporto in base alla variazione della frequenza di vibrazione. Una volta calibrato e validato, il modello DEM è stato utilizzato per ottenere nuovi risultati sulle prestazioni di tali sistemi in ambienti a bassa gravità, come la superficie della Luna e di Marte. In generale, per tali ambienti, è stata osservata una previsione di flusso di massa molto più elevata rispetto a quella prevista in gravità terrestre, a causa delle diverse interazioni tra le particelle, le vibrazioni di attuazione e l'accelerazione di gravità locale. Questa tesi si propone di fornire una base per lo sviluppo ulteriore di simulazioni più avanzate, che possano fungere da strumenti di supporto nella progettazione di trasportatori vibranti specializzati per l'ISRU in ambienti extraterrestri.This thesis explores one possible application of the concept of In Situ Resource Utilization (ISRU) for space exploration: the transport and handling of regolith through the use of vibratory conveyors. A vibratory conveyor with piezoelectric actuators was identified as being the ideal setup for use on the surface of the Moon, due to its low-power requirements and low number of moving part. An experimental campaign was conducted on the model, investigating the effect of vibration amplitude, frequency, and trough inclination on the bulk material flow, constituted of monosized glass sphere. The results showed a more than linear relationship between frequency and transport time, highlighting the effect of resonance in the conveyor discharge flow. A Discrete Element Method (DEM) simulation was developed as a digital twin of the setup. The model was validated with both analytical and experimental results showing good accordance with real-life experiments, with the model being able to predict the evolution of mass flow and transport speed due to the variation of actuation frequency. The DEM model was then used to obtain new results in the low-gravity environments of the Moon and Mars, resulting in the observation of a much higher predicted mass flow than what observed under Earth's gravity. This thesis aims to provide a basis for the development of a more advanced simulation setups to help in the design of vibratory conveyors specialized for ISRU on extraterrestrial environments