Preface of the "Symposium on dynamical systems applied to robotics"

[Excerpt] Robotics has been evolving in last years, considering the different fields that can be tackled. This is an important and diversified domain, which is normally solved using bio-inspired or model-based approaches. In this symposia, we focus on the use of the dynamical systems theory to address any related problems in the robotics domain. Dynamical systems exhibit some properties which makes them well suited to real-time robotic applications, such as movement generation for legged; modular and wheeled platforms; balance control; grasping; reaching, etc. [...](undefined

A brainstem-like modulation approach for gait transition in a quadruped robot

The ability to traverse a wide variety of terrains while walking is basically a requirement for performing useful tasks in our human centric world. In this article, we propose a bio-inspired robotic controller able to generate locomotion and to easily switch between different type of gaits. In order to improve the robot stability and response while locomoting, we adjust both the duty factor and the interlimb phase relationships, according to the velocities. We extend previous work, by applying nonlinear oscillators to generate the rhythmic locomotor movements for a quadruped robot, similarly to the biological counterparts. The generated trajectories are modulated by a drive signal, that modifies the oscillator frequency, amplitude and the coupling parameters among the oscillators, proportionally to the drive signal strength. By increasing the drive signal, locomotion can be elicited and velocity increased while switching to the appropriate gaits. This drive signal can be specified according to sensory information or set a priori. The implementation of the central pattern generator network and the activity modulation layer is shown in simulation and in an AIBO robot

Double power law behavior in everyday phenomena

We study similar statistical properties observed in distinct real world data. In particular, we focus on the power law (PL) distribution. We nd that some data is well tted by a single PL distribution whereas other phenomena force the use of two distinct PLs. This behavior is similar in, a priori, unrelated phenomena, such as catastrophes (terrorism, earthquakes) and variables associated to man-made systems, such as distribution of the number of words in texts or of the number of hits received by websites.N/

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 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

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

Efficient Methods for Scheduling Jobs in a Simulation Model Using a Multicore Multicluster Architecture

Over the past decade, the fast advance of network technologies, hardware and middleware, as well as software resource sophistication has contributed to the emergence of new computational models. Consequently, there was a capacity increasing for efficient and effective use of resources distributed aiming to integrate them, in order to provide a widely distributed environment, which computational capacity could be used to solve complex computer problems. The two most challenging aspects of distributed systems are resource management and task scheduling. This work contributes to minimize such problems by i) aiming to reduce this problem through the use of migration techniques; ii) implementing a multicluster simulation environment with mechanisms for load balancing; iii) plus, the gang scheduling implementation algorithms will be analyzed through the use of metrics, in order to measure the schedulers performance in different situations. Thus, the results showed a better use of resources, implying operating costs reduction

Self-similarity in world economy

Self-similarity is a property of complex networks, commonly observed in many distinct areas of science. Many real networks are said to be ¸ Sscale-freeˇT since they show a power law behavior. In this paper, we focus in self-similarity of economical phenomena. For that purpose we analyze data and their corresponding statistical properties. We approximate data by trendlines, whose parameters are unequivocally related with each type of phenomenon.N/

Pareto and Zipf laws for city size distribution

Pareto and Zipf distributions have been used in the modeling of distinct phenomena, namely in biology, demography, computer science, economics, amongst others. In this paper, it is presented a short review of applications of these distributions in city sizes.N/

Analyzing the Implementation of Lean Methodologies and Practices in the Portuguese Industry: A Survey

The mass production paradigm on which much of the industry was based has changed. The market is increasingly demanding, requesting diversity and products that are more and more adapted to personal wishes and requirements. This implies producing a greater diversity of products in smaller quantities. Competitiveness is enormous, which forces most companies to be truly effective and efficient, taking care of product quality, delivery time, and final cost. Lean methodologies have been a valuable aid in this field. The diversity of Lean tools has been shown to have answers to the most diverse challenges, and companies are aware of this, increasingly adopting methodologies and processes that aim to progressively reduce waste and adapting their production paradigm to what the market requires. This work intends to provide a vision, as global as possible, of the pathway of Lean implementation in the Portuguese industry. For this purpose, a survey was carried out with a significant sample of Portuguese industrial companies from a wide range of activity sectors. The data collected through the survey were treated statistically, and then a SWOT analysis of the results was performed, which provided a collection of precious information on the evolution of industrial companies in Portugal.The author CP was partially supported by CMUP, which is financed by national funds through FCT—Fundação para a Ciência e a Tecnologia, I.P., under the project with reference UIDB/00144/2020. F.J.G.S. would like to thank INEGI Research Center due to its continuous support, namely to Jorge Seabra, as well as all remaining CETRIB/INEGI/LAETA teal.info:eu-repo/semantics/publishedVersio