A new CPG model for the generation of modular trajectories for hexapod robots

Legged robots are often used in a large variety of tasks, in different environments. Nevertheless, due to the large number of degrees-of-freedom to be controlled, online generation of trajectories in these robots is very complex. In this paper, we consider a modular approach to online generation of trajectories, based on biological concepts, namely Central Pattern Generators (CPGs). We introduce a new CPG model for hexapod robots’ rhythms, based in the work of Golubitsky et al (1998). Each neuron/oscillator in the CPG consists of two modules/primitives: rhythmic and discrete. We study the effect on the robots’ gaits of superimposing the two motor primitives, considering two distinct types of coupling.We conclude, from the simulation results, that the amplitude and frequency of periodic solutions, identified with hexapods’ tripod and metachronal gaits, remain constant for the two couplings, after insertion of the discrete part.CP was supported by Research funded by the European Regional Development Fund through the programme COMPETE and by the Portuguese Government through the FCT Fundacao para a Ciencia e a Tecnologia under the project PEst-C/MAT/UI0144/2011. This work was also funded by FEDER Funding supported by the Operational Program Competitive Factors COMPETE and National Funding supported by the FCT - Portuguese Science Foundation through project PTDC/EEACRO/100655/2008

Impact of discrete corrections in a modular approach for trajectory generation in quadruped robots

Online generation of trajectories in robots is a very complex task that involves the combination of different types of movements, i.e., distinct motor primitives. The later are used to model complex behaviors in robots, such as locomotion in irregular terrain and obstacle avoidance. In this paper, we consider two motor primitives: rhythmic and discrete. We study the effect on the robots’ gaits of superimposing the two motor primitives, considering two distinct types of coupling. Additionally, we simulate two scenarios, where the discrete primitive is inserted in all of the four limbs, or is inserted in ipsilateral pairs of limbs. Numerical results show that amplitude and frequency of the periodic solutions, corresponding to the gaits trot and pace, are almost constant for diffusive and synaptic couplings.CP was supported by Research funded by the European Regional Development Fund through the programme COMPETE and by the Portuguese Government through the FCT Fundacao para a Ciencia e a Tecnologia under the project PEst-C/MAT/UI0144/2011. This work was also funded by FEDER Funding supported by the Operational Program Competitive Factors COMPETE and National Funding supported by the FCT - Portuguese Science Foundation through project PTDC/EEACRO/100655/2008

A modular approach for trajectory generation in biped robots

Robot locomotion has been a major research issue in the last decades. In particular, humanoid robotics has had a major breakthrough. The motivation for this study is that bipedal locomotion is superior to wheeled approaches on real terrain and situations where robots accompany or replace humans. Some examples are, on the development of human assisting device, such as prosthetics, orthotics, and devices for rehabilitation, rescue of wounded troops, help at the office, help as maidens, accompany and assist elderly people, amongst others. Generating trajectories online for these robots is a hard process, that includes different types of movements, i.e., distinct motor primitives. In this paper, we consider two motor primitives: rhythmic and discrete.We study the effect on a bipeds robots’ gaits of inserting the discrete part as an offset of the rhythmic primitive, in synaptic and diffusive couplings. Numerical results show that amplitude and frequency of the periodic solution, corresponding to the gait run are almost constant in all cases studied here.(undefined

Dört bacaklı robotlar için önizlemeli kontrol ile sıfır moment noktası tabanlı yürüme yörüngesi sentezi

Bacakları üzerinde hareket eden robotların engel aşma konusunda önemli avantajları söz konusudur. Özellikle dört bacaklı robotların değişken arazi yapıları üzerinde birçok uygulamaları düşünülmektedir. Bu çalışmada, dört bacaklı bir robotun düz zemin üzerinde hızlı yol almasına yönelik tırıs türü ilerleme üzerinde durulmaktadır. Sıfır Moment Noktası (SMN) karalılık kriterine ve Doğrusal Ters Sarkaç Modeli’ne (DTSM) dayalı bir yürüme referansı sentez yöntemi sunulmaktadır. Tırıs ilerleme için bir SMN referans yörüngesi önerilmiş, bu yörüngeden, önizlemeli kontrol yaklaşımı ile Robot Ağırlık Merkezi (RAM) için bir referans yörünge elde edilmiştir. Oluşturulan ağırlık merkezi yörüngesi ters kinematik yöntemi ile bacak eklemlerinin konum referanslarının hesaplanmasında kullanılmıştır. Önerilen referans sentezi yöntemi, 16 serbestlik dereceli bir robot modeli ile üç boyutlu ve tam dinamikli bir simülasyon ortamında denenmiştir. Simülasyon sonuçları sunulan yaklaşımın başarılı olduğunu göstermektedir

Bipedal Locomotion: A Fractional CPG for Generating Patterns

Proceedings of the 10th Conference on Dynamical Systems Theory and ApplicationsThere has been an increase interest in the study of animal locomotion. Many models for the generation of locomotion patterns of different animals, such as centipedes, millipedes, quadrupeds, hexapods, bipeds, have been proposed. The main goal is the understanding of the neural bases that are behind animal locomotion. In vertebrates, goal-directed locomotion is a complex task, involving the central pattern generators located somewhere in the spinal cord, the brainstem command systems for locomotion, the control systems for steering and control of body orientation, and the neural structures responsible for the selection of motor primitives. In this paper, we focus in the neural networks that send signals to the muscle groups in each joint, the so-called central pattern generators (CPGs). We consider a fractional version of a CPG model for locomotion in bipeds. A fractional derivative) Dα f (x), with α non-integer, is a generalization of the concept of an integer derivative, where α = 1 The integer CPG model has been proposed by Golubitsky, Stewart, Buono and Collins, and studied later by Pinto and Golubitsky. It is a four cells model, where each cell is modelled by a system of ordinary differential equations. The coupling between the cells allows two independent permutations, and, as so, the system has D2 symmetry. We consider 0 < α ≤ 1 and we compute, for each value of α, the amplitude and the period of the periodic solutions identified with two legs' patterns in bipeds. We find the amplitude and the period increase as α varies from zero up to one

The Multi-Chamber Electronic Nose—An Improved Olfaction Sensor for Mobile Robotics

One of the major disadvantages of the use of Metal Oxide Semiconductor (MOS) technology as a transducer for electronic gas sensing devices (e-noses) is the long recovery period needed after each gas exposure. This severely restricts its usage in applications where the gas concentrations may change rapidly, as in mobile robotic olfaction, where allowing for sensor recovery forces the robot to move at a very low speed, almost incompatible with any practical robot operation. This paper describes the design of a new e-nose which overcomes, to a great extent, such a limitation. The proposed e-nose, called Multi-Chamber Electronic Nose (MCE-nose), comprises several identical sets of MOS sensors accommodated in separate chambers (four in our current prototype), which alternate between sensing and recovery states, providing, as a whole, a device capable of sensing changes in chemical concentrations faster. The utility and performance of the MCE-nose in mobile robotic olfaction is shown through several experiments involving rapid sensing of gas concentration and mobile robot gas mapping

Dört bacaklı robotlar için önizleme kontrolü ve sıfır moment noktası esaslı yürüyüş yörüngesi üretimi

Robota verilen görevde engel aşımı gerektiğinde bacaklı robotların geri kalan mobil robotlara göre önemli avantajları bulunmaktadır. Bu makalede dört bacaklı robotların düz bir yüzeyde yürüyüşü için bir ölçümleme üretimi yöntemi sunuldu. Bu yaklaşım sıfır moment noktası (SMN) temelli kararlılık ve doğrusal ters sarkaç modeli (DTSM) üzerinedir. Yürüyüş için SMN referans gezingeleri ileri sürülüp oradan önizleme kontorü vasıtasıyla robotun ağırlık merkezi (RAM) referansı için referans gezingeleri elde edildi. Bacak eklemlerinin pozisyonları RAM referans gezingeleri üzerine ters kinematik uygulanarak hesaplandı. Öne sürülen referans gezinge üretimi sentezi, tamamen dinamik 3 boyutlu benzetimle test edildi. Benzetimde 16 serbestlik derecesine (SD) sahip dört bacaklı robot modeli kullanıldı. Benzetim sonuçları, yürüyüş için yapılan referans üretim tekniğinin başarıya ulaştığını gösteriyor

Mathematical modeling of orthosis for hand movement with loss of strength

Several factors that can lead to a loss or decrease of an individual’s motor and/or coordination abilities, such as spinal cord injury caused by an accident, a Cerebral Vascular Accident, Cerebral Palsy, and others alike. Since the hand is one of the members that most affect patient’s independence and quality of life, this study focus on the development of a solution for the condition of lost of motor skills in the hands, specifically, in the realization of the pinch movement. The solution proposed is the development a model of mechanical orthosis capable of assisting the basic movement of opposition between the index finger an the thumb (forceps), allowing the patient to perform daily actions that involve picking or lifting an object, as well as perform the writing movement, while keeping a low level of assembly complexity and cost of production. The development of the model began by identifying the needs of the patients considered, the formulation of a methodology for obtaining the optimal geometry for the mechanism components, and realizing preliminary and functional tests to verify the proposed ideas.By the end, we have a functional model of mechanical orthosis, that validates the methodology elaborated

Visual Odometry Based on Structural Matching of Local Invariant Features Using Stereo Camera Sensor

This paper describes a novel sensor system to estimate the motion of a stereo camera. Local invariant image features are matched between pairs of frames and linked into image trajectories at video rate, providing the so-called visual odometry, i.e., motion estimates from visual input alone. Our proposal conducts two matching sessions: the first one between sets of features associated to the images of the stereo pairs and the second one between sets of features associated to consecutive frames. With respect to previously proposed approaches, the main novelty of this proposal is that both matching algorithms are conducted by means of a fast matching algorithm which combines absolute and relative feature constraints. Finding the largest-valued set of mutually consistent matches is equivalent to finding the maximum-weighted clique on a graph. The stereo matching allows to represent the scene view as a graph which emerge from the features of the accepted clique. On the other hand, the frame-to-frame matching defines a graph whose vertices are features in 3D space. The efficiency of the approach is increased by minimizing the geometric and algebraic errors to estimate the final displacement of the stereo camera between consecutive acquired frames. The proposed approach has been tested for mobile robotics navigation purposes in real environments and using different features. Experimental results demonstrate the performance of the proposal, which could be applied in both industrial and service robot fields

Performance of UWB Wireless Telecommunication Positioning for Disaster Relief Communication Environment Securing

When an earthquake or a large fire has occurred, it is difficult to secure communication networks for rescue in the building due to the destruction of commercial communication networks. Although analog radio systems such as VHF (Very High Frequency) and UHF (Ultra-High Frequency) are used for rescue operation in general, communication failure occurs in closed spaces, causing difficulties in smooth rescue operations. When the communication infrastructures have been destroyed in a building in the disaster, an emergency wireless telecommunication environment should be constructed to secure a safer disaster response environment. In this study, along with comparison of the performances of diverse communication frequencies, UWB (Ultra-Wide Band) wireless telecommunication networks were evaluated under five building indoor environment conditions including open spaces. UWB communication modules were fabricated to satisfy the IEEE (The Institute of Electrical and Electronics Engineers) 802.15.4a standard performance to measure distances in which communications are possible according to the indoor environment for each of six channels with different UWB communication frequencies. The results indicated that the distances in which communications are possible for each the six channels were average 15.5 m, maximum 20 m in open spaces; average 17.33 m, maximum 20 m in corridors; average 15.3 m, maximum 20 m in indoor office environments with office fixtures; average 4.33 m, maximum 6 m in vertical spaces of stairs; and average 6.5 m, maximum 17 m in closed horizontal spaces with a fire door. In this case, the communication performance and distance performance were shown to be the most excellent at a frequency (Centre Frequency) of 6489.6 and a band of 5980.3–6998.9 MHz, which is UWB 7ch. In conclusion, it is judged that if UWB communication modules are installed in the disaster area at intervals of 20 m and multi-channels are used, communication environments can be constructed even in closed spaces