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

Design Issues for Hexapod Walking Robots

Hexapod walking robots have attracted considerable attention for several decades. Many studies have been carried out in research centers, universities and industries. However, only in the recent past have efficient walking machines been conceived, designed and built with performances that can be suitable for practical applications. This paper gives an overview of the state of the art on hexapod walking robots by referring both to the early design solutions and the most recent achievements. Careful attention is given to the main design issues and constraints that influence the technical feasibility and operation performance. A design procedure is outlined in order to systematically design a hexapod walking robot. In particular, the proposed design procedure takes into account the main features, such as mechanical structure and leg configuration, actuating and driving systems, payload, motion conditions, and walking gait. A case study is described in order to show the effectiveness and feasibility of the proposed design procedure

Learning to stop: a unifying principle for legged locomotion in varying environments.

Evolutionary studies have unequivocally proven the transition of living organisms from water to land. Consequently, it can be deduced that locomotion strategies must have evolved from one environment to the other. However, the mechanism by which this transition happened and its implications on bio-mechanical studies and robotics research have not been explored in detail. This paper presents a unifying control strategy for locomotion in varying environments based on the principle of 'learning to stop'. Using a common reinforcement learning framework, deep deterministic policy gradient, we show that our proposed learning strategy facilitates a fast and safe methodology for transferring learned controllers from the facile water environment to the harsh land environment. Our results not only propose a plausible mechanism for safe and quick transition of locomotion strategies from a water to land environment but also provide a novel alternative for safer and faster training of robots

Research Trends and Future Perspectives in Marine Biomimicking Robotics

Mechatronic and soft robotics are taking inspiration from the animal kingdom to create new high-performance robots. Here, we focused on marine biomimetic research and used innovative bibliographic statistics tools, to highlight established and emerging knowledge domains. A total of 6980 scientific publications retrieved from the Scopus database (1950–2020), evidencing a sharp research increase in 2003–2004. Clustering analysis of countries collaborations showed two major Asian-North America and European clusters. Three significant areas appeared: (i) energy provision, whose advancement mainly relies on microbial fuel cells, (ii) biomaterials for not yet fully operational soft-robotic solutions; and finally (iii), design and control, chiefly oriented to locomotor designs. In this scenario, marine biomimicking robotics still lacks solutions for the long-lasting energy provision, which presently hinders operation autonomy. In the research environment, identifying natural processes by which living organisms obtain energy is thus urgent to sustain energy-demanding tasks while, at the same time, the natural designs must increasingly inform to optimize energy consumption

Investigation of energy efficiency of hexapod robot locomotion

Disertacijoje nagrinėjamos vaikščiojančių robotų energijos sąnaudų problemos jiems judant lygiu ir nelygiu paviršiumi. Pagrindinis tyrimo objektas yra vaikščiojančio roboto valdymo, aplinkos atpažinimo bei kliūčių išvengimo žinomoje aplinkoje metodas. Energijos sąnaudų minimizavimas leistų praplėsti vaikščiojančių robotų pritaikymą ir veikimo laiką. Pagrindinis darbo tikslas – sukurti energijos sąnaudų minimizavimo metodus vaikščiojantiems robotams ir sukurti aplinkos atpažinimo ir klasifikavimo metodus bei ištirti šešiakojo roboto energijos sąnaudas jiems judant žinomoje aplinkoje. Šie metodai gali būti taikomi vaikščiojantiems daugiakojams robotams. Darbe sprendžiami šie uždaviniai: šešiakojo roboto eisenos parinkimas atsižvelgiant į energijos sąnaudas, paviršiaus kliūčių aptikimo ir perlipimo metodų sudarymas ir jų efektyvumo palyginimas. Taip pat sprendžiami uždaviniai, kurie siejasi su pėdų trajektorijos generavimo metodo kūrimu bei kliūčių dydžio ir tankio įtaka roboto energijos sąnaudoms. Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvade aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmasis skyrius skirtas literatūros apžvalgai. Jame pateikta mobiliųjų robotų energetinio efektyvumo bei energijos sąnaudų matavimo, skaičiavimo ir optimizavimo metodų analizė. Antrajame skyriuje pateiktas energetiškai efektyvaus judėjimo metodikos sudarymas vaikščiojantiems robotams. Šiame skyriuje pateiktas šešiakojo roboto matematinio ir fizinio modelių sudarymas, nelygaus paviršiaus klasifikavimo modelio sudarymas bei taktilinio kliūčių aptikimo bei perlipimo metodų sudarymas. Skyriaus gale pateikiamos išvados. Trečiajame skyriuje tiriamos energijos sąnaudų priklausomybės nuo roboto eisenos bei judėjimo parametrų, kliūčių aptikimo ir perlipimo tikslumas priklausomai nuo kliūčių skaičiaus roboto kelyje, taip pat kliūčių dydžio ir tankio įtaka roboto energijos sąnaudoms. Disertacijos tema paskelbti 9 straipsniai: keturi – Clarivate Analytics Web of Science duomenų bazės leidiniuose, turinčiuose citavimo rodiklį, trys – Clarivate Analytics Web of Science duomenų bazės „Conference Proceedings“ leidiniuose ir du – kituose recenzuojamuose mokslo leidiniuose. Disertacijos tema perskaityti 7 pranešimai konferencijose Lietuvoje bei kitose šalyse

Locomotion of Low-DoF Multi-legged Robots

Multi-legged robots inspired by insects and other arthropods have unique advantages when compared with bipedal and quadrupedal robots. Their sprawled posture provides stability, and allows them to utilize low-DoF legs which are easier to build and control. With low-DoF legs and multiple contacts with the environment, low-DoF multi-legged robots are usually over constrained if no slipping is allowed. This makes them intrinsically different from the classic bipedal and quadrupedal robots which have high-DoF legs and fewer contacts with the environment. Here we study the unique characteristics of low-DoF multi-legged robots, in terms of design, mobility and modeling. One key observation we prove is that 1-DoF multi-legged robots must slip to be able to steer in the plane. Slipping with multiple contacts makes it difficult to model these robots and their locomotion. Therefore, instead of relying on models, our primary strategy has been careful experimental study. We designed and built our own customized robots which are easily reconfigurable to accommodate a variety of research requirements. In this dissertation we present two robot platforms, BigAnt and Multipod, which demonstrate our design and fabrication methods for low-cost rapidly fabricated modular robotic platforms. BigAnt is a hexapedal robot with 1-DoF legs, whose chassis is constructed from foam board and fiber tape, and costs less than 20 USD in total; Multipod is a highly modular multi-legged robot that can be easily assembled to have different numbers of 2-DoF legs (4 to 12 legs discussed here). We conducted a detailed analysis of steering, including proposing a formal definition of steering gaits grounded in geometric mechanics, and demonstrated the intrinsic difference between legged steering and wheeled steering. We designed gaits for walking, steering, undulating, stair climbing, turning in place, and more, and experimentally tested all these gaits on our robot platforms with detailed motion tracking. Through the theoretical analyses and the experimental tests, we proved that allowing slipping is beneficial for improving the steering in our robots. Where conventional modeling strategies struggle due to multi-contact slipping, we made a significant scientific discovery: that multi-legged locomotion with slipping is often geometric in the sense known from the study of low Reynolds number swimmers and non-holonomic wheeled snake robots which have continuous contact with the environment. We noted that motion can be geometric ``on average'', i.e. stride to stride, and can be truly instantaneously geometric. For each of these we developed a data-driven modeling approach that allowed us to analyze the degree to which a motion is geometric, and applied the analysis to BigAnt and Multipod. These models can also be used for robot motion planning. To explore the mechanism behind the geometric motion characteristics of these robots, we proposed a spring supported multi-legged model. We tested the simulation based on this model against experimental data for all the systems we studied: BigAnt, Multipod, Mechapod (a variant of 6-legged Multipod) and cockroaches. The model prediction results captures many key features of system velocity profiles, but still showed some systematic errors (which can be alleviated ad-hoc). Our work shows the promise of low-DoF multi-legged robots as a class of robotic platforms that are easy to build and simulate, and have many of the mobility advantages of legged systems without the difficulties in stability and control that appear in robots with four or fewer legs.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/169985/1/danzhaoy_1.pd

Combining Sensors and Multibody Models for Applications in Vehicles, Machines, Robots and Humans

The combination of physical sensors and computational models to provide additional information about system states, inputs and/or parameters, in what is known as virtual sensing, is becoming increasingly popular in many sectors, such as the automotive, aeronautics, aerospatial, railway, machinery, robotics and human biomechanics sectors. While, in many cases, control-oriented models, which are generally simple, are the best choice, multibody models, which can be much more detailed, may be better suited to some applications, such as during the design stage of a new product