Autonomous Locomotion Mode Transition Simulation of a Track-legged Quadruped Robot Step Negotiation

Multi-modal locomotion (e.g. terrestrial, aerial, and aquatic) is gaining increasing interest in robotics research as it improves the robots environmental adaptability, locomotion versatility, and operational flexibility. Within the terrestrial multiple locomotion robots, the advantage of hybrid robots stems from their multiple (two or more) locomotion modes, among which robots can select from depending on the encountering terrain conditions. However, there are many challenges in improving the autonomy of the locomotion mode transition between their multiple locomotion modes. This work proposed a method to realize an autonomous locomotion mode transition of a track-legged quadruped robot steps negotiation. The autonomy of the decision-making process was realized by the proposed criterion to comparing energy performances of the rolling and walking locomotion modes. Two climbing gaits were proposed to achieve smooth steps negotiation behaviours for energy evaluation purposes. Simulations showed autonomous locomotion mode transitions were realized for negotiations of steps with different height. The proposed method is generic enough to be utilized to other hybrid robots after some pre-studies of their locomotion energy performances

Dynamics and kinematics analysis and simulation of lower extremity power-assisted exoskeleton

According to the walking character of lower extremity power-assisted exoskeleton that was designed by our Robotics Laboratory, D-H convention was applied to the kinematics analysis of this exoskeleton model. Lagrangian dynamics was used to analyzing dynamics for the single-foot support model, double-feet support model and double-feet support with one redundancy model respectively. The kinematical equation was obtained and MATLAB was used to verify its validity. Meanwhile, the kinetic equations and torque of each joint were obtained by virtue of ADAMS. Our study provided a theoretical foundation for the control strategies, and optimization design of the mechanical structure and promoted the practical application of this lower extremity power-assisted exoskeleton in further research

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