Multibody model of the collaborative human-inspired robot charmie

With the worldwide ageing of population, domestic robots can provide important aid by assisting elderly persons with mobility limitations, increasing their autonomy, while reducing caretaker fatigue. Currently, a human-like mobile system, called CHARMIE, is being assembled, which can be applied for those situations. For this purpose, a full multibody model has been developed, which allows for the assessment of the robot’s performance as well as its structural analysis and actuators’ selection. The robot multibody model consists of 40 rigid bodies, interconnected by 34 ideal revolute joints, 10 translational joints, and three rigid joints, resulting in a total of 21 degrees of freedom, namely three for the locomotion, two for the hip, seven for each arm and two for the neck. The system is driven by four linear actuators and 17 motors. The multibody dynamic simulations use an in-house software structured around two approaches: a recursive forward kinematics algorithm based on Euler angles, and a recursive Newton-Euler formulation for solving inverse dynamics. For implementing these approaches, the robot has been modelled as three serial kinematic chains, all starting from its base and finishing in the left end-effector, right end-effector, and head respectively. This work focuses on the model developed for the motion simulation of CHARMIE. The proposed methodology includes seven main steps: (i) identify the main bodies and kinematic chains; (ii) convert the body properties into the required software inputs; (iii) analyze the geometry of the indirectly actuated joints; (iv) model the kinematics of the main bodies with the first recursive algorithm; (v) determine the kinematics of additional bodies; (vi) solve the inverse dynamics of the main bodies with the second recursive algorithm; (vii) manually compute the dynamics of the closed and overconstrained loops. The overall outcomes produced have been validated against those obtained by a commercial software

Farming system change under different climate scenarios and its impact on food security : an analytical framework to inform adaptation policy in developing countries

Os países em desenvolvimento são considerados extremamente vulneráveis às alterações climáticas, devido ao seu contexto socioeconómico (elevados níveis de pobreza) e à elevada dependência dos seus meios de subsistência dos recursos naturais. As zonas rurais destes países concentram a maior parte das pessoas mais pobres e com insegurança alimentar do mundo, estando os agricultores entre os mais vulneráveis às alterações climáticas. Prevê-se que os impactos das alterações climáticas sejam espacialmente heterogéneos. Neste sentido, este artigo visa explorar o efeito directo e marginal das alterações climáticas na escolha do sistema agrícola e as suas implicações para a segurança alimentar em Moçambique, utilizando uma abordagem espaço-por-tempo. Os nossos resultados sugerem que são esperadas grandes mudanças na escolha do sistema agrícola e na sua distribuição espacial devido às alterações climáticas, o que terá potencialmente impacto nos meios de subsistência e no estado de segurança alimentar dos pequenos agricultores. Os sistemas agrícolas, incluindo culturas alimentares/de rendimento e/ou pecuária, que estão entre os mais seguros em termos alimentares, tenderão a ser substituídos por outros sistemas em todos os cenários climáticos. Os sistemas agrícolas mistos (incluindo alimentação e pecuária) e os sistemas orientados para a pecuária, na sua maioria inseguros em termos alimentares, predominantes em zonas áridas, deverão expandir-se com as alterações climáticas. Os mapas de stress da segurança alimentar e da inovação foram esboçados a partir dos resultados da modelização, identificando áreas prioritárias para intervenção pública. Destacamos também como a nossa abordagem pode ser um quadro eficaz e facilmente replicável para abordar este tipo de questões noutras regiões em desenvolvimento que enfrentam problemas semelhantes.Developing countries are considered extremely vulnerable to climate change, due to their socioeconomic context (high levels of poverty) and high dependence of their livelihoods on natural resources. Rural areas in these countries concentrate most of the poorest and food-insecure people in the world, with farmers being among the most vulnerable to climate change. The impacts of climate change are expected to be spatially heterogeneous. In this sense, this paper aims at exploring the direct, marginal effect of climate change on farming system choice and its implications to food security in Mozambique, using a space-for-time approach. Our results suggest that major changes are to be expected in farming system choice and their spatial distribution due to climate change, which will potentially impact the livelihoods and food security status of smallholder farmers. Farming systems including food/cash crops and/or livestock, which are among the most food secure, will tend to be replaced by other systems in all climate scenarios. Mixed farming systems (including food and livestock) and livestock-oriented systems, mostly food insecure, predominant in arid areas are expected to expand with climate change. Food security and innovation stress maps were sketched out from the modelling results, identifying priority areas for public intervention. We also highlight how our approach can be an effective and easily replicable framework to address this type of issues in other developing regions facing similar problems.info:eu-repo/semantics/publishedVersio

Design of a hexapod robotic system

The main purpose of this work was to design a prototype of an autonomous hexapod robot. This paper reports on an initial phase, where the basic geometry of the system was specified and improved through a kinematics and dynamic study, using a motion analysis software. This also allowed the design of all mechanical components and the definition of motion generation needs. In this paper the importance of legged robots on mobile research is emphasised. The capabilities of the computational programs specially dedicated to the analysis of mechanical systems are demonstrated. The mobility of the geometric model presented in this paper is a trade-off between natural idea and technical feasibility. Some results of the virtual simulation of the movement of this hexapod robotic system are presented

Dynamic modeling of a human-inspired robot based on a Newton-Euler approach

This work deals with the modeling process of a new three dimensional human-like robot for an inverse dynamic analysis. This robot intends to be utilized by caregivers to assist persons with reduced mobility (such as the elderly). The model under analysis is composed by 24 rigid bodies: 3 to represent the robot’s base and locomotion, 4 for the lower limbs and torso, 7 for each arm, and 3 for the head. The resulting multibody system has 19 degrees-of-freedom driven by 4 linear actuators and 15 revolute motors. The proposed approach was implemented using an in-house computational code, and validated against a commercial software for a general spatial motion. The outcomes achieved show that the proposed formulation is computationally effective both in terms of efficiency and accuracy. The general findings of this study are promising and useful for the mechanical design and construction of a real human-like robot prototype

Kinematics and dynamics study of a hexapod robotic system using computational packages’ capabilities

The main purpose of this work was to perform kinematics and dynamics analysis of a prototype of an autonomous hexapod robot. This paper reports on an initial phase, where the basic geometry of the system was specified and improved through a kinematics and dynamic study by using a motion analysis software. This study also allowed the design of all mechanical components and the definition of motion generation needs. In this paper the importance of legged robots on mobile research is emphasised. The capabilities of the computational programs specially dedicated to the analysis of mechanical systems are also discussed. The mobility of the geometric model presented in this paper is a trade-off between natural idea and technical feasibility. Some results of the computational simulations of the movement of the proposed hexapod robotic system are presented and discussed under the premises and assumptions adopted in this work

Trends in the control of hexapod robots: a survey

The static stability of hexapods motivates their design for tasks in which stable locomotion is required, such as navigation across complex environments. This task is of high interest due to the possibility of replacing human beings in exploration, surveillance and rescue missions. For this application, the control system must adapt the actuation of the limbs according to their surroundings to ensure that the hexapod does not tumble during locomotion. The most traditional approach considers their limbs as robotic manipulators and relies on mechanical models to actuate them. However, the increasing interest in model-free models for the control of these systems has led to the design of novel solutions. Through a systematic literature review, this paper intends to overview the trends in this field of research and determine in which stage the design of autonomous and adaptable controllers for hexapods is.The first author received funding through a doctoral scholarship from the Portuguese Foundation for Science and Technology (FCT) (Grant No. SFRH/BD/145818/2019), with funds from the Portuguese Ministry of Science, Technology and Higher Education and the European Social Fund through the Programa Operacional Regional Norte. This work has been supported by the FCT national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020

Hexapod posture control for navigation across complex environments

Hexapod locomotion in unstructured environments relies on an efficient posture adjustment with the terrain topology. This paper presents a strategy to adapt the hexapod torso orientation through ground plane estimation. With an Inertial Measurement Unit (IMU) and the robot kinematic model, the current supporting feet coordinates are calculated, and the relative inclination between the ground and the torso angular position can be obtained. This information is used to adjust the novel foothold positions, in order to ensure the hexapod posture remains stable. The torso height is also controlled to avoid collisions with the ground asperities and decrease its deviation during motion. The proposed method is evaluated in a complex terrain made of 0.1×0.1 m blocks with variable height, causing different slopes across the field. Through result analysis, a significant behavior improvement is observed, due to the reduction of the torso posture oscillation and the increase of its locomotion efficiency.The first author received funding through a doctoral scholarship from the Portuguese Foundation for Science and Technology (FCT) (Grant No. SFRH/BD/145818/2019), with funds from the Portuguese Ministry of Science, Technology and Higher Education and the European Social Fund through the Programa Operacional Regional Norte. This work has been supported by FCT within the R&D Units Project Scope: UIDB/00319/2020, UIDB/04436/2020 and UIDP/04436/2020

Study of the locomotion of a hexapod using CoppeliaSim and ROS

Generating adaptive locomotion has seen a growing interest for the design of hexapods due to improving the autonomy of these robots, allowing them to execute tasks in more demanding environments. Data from the robot’s surrounding must be acquired and processed to adjust the locomotion, and aid with the actuation of the six limbs. This paper aims at using force sensors placed on the feet of a hexapod to control the changes of the gait phase of each limb. These sensors also assist in the search of new footholds when no contact forces are established with the ground. The system is tested in a smooth irregular terrain with obstacles, steps, and ramps, using CoppeliaSim and ROS (Robot Operating System), to dynamically evaluate the behavior of the hexapod.(undefined

Reactive locomotion of a hexapod for navigation across irregular ground

In controlled environments, the hexapod limbs actuation can be controlled as a closed system. However, the increase of the terrain complexity implies an adaptation of their trajectory based on the robot interactions with the environment. Thus, the implementation of terrain data to the legs actuation potentially improves the hexapod quasi-static stability in these scenarios. This paper presents an adaptive control system based on the limbs reactive behavior for navigation across complex environments. Through force sensors placed on the foot-tips, the model detects the foot-ground interactions and adjusts the limbs trajectory accordingly. Furthermore, to ensure that the robot posture remains stable throughout locomotion, an impedance control is implemented in each limb. The proposed control architecture was tested in an irregular ground through dynamic simulations with five different configurations. Through result analysis, an optimized model was achieved which reduces the oscillations of the torso and slippage of the feet when walking across obstacles.The first author received funding through a doctoral scholarship from the Portuguese Foundation for Science and Technology (FCT) (Grant No. SFRH/BD/145818/2019), with funds from the Portuguese Ministry of Science, Technology and Higher Education and the European Social Fund through the Programa Operacional Regional Norte. This work has been supported by FCT within the R&D Units Project Scope: UIDB/00319/2020, UIDB/04436/2020 and UIDP/04436/2020

Incidência de fungos de armazenamento em função de nitrogênio em cobertura e variedades de milho

Maize is the main cereal grown in Brazil and is used mainly for animal feed and food consumption of its derivates. Under favorable environmental conditions, toxigenic fungi such as Fusarium, Aspergillus, and Penicillium spp. could produce mycotoxins in maize grain during plant growth or storage. This study aimed to evaluate the incidence of toxigenic fungi and its relationship with the grain weight of maize varieties grown under high and low topdressing nitrogen. The first factor consisted of 11 open-pollinated varieties, and the second factor of two topdressing nitrogen rates (60 and 180 kg ha-1). After harvesting the experimental units, the following variables were evaluated: 100-grain weight (HGW) and incidence of A. flavus, Penicillium spp., and Fusarium spp. There were differences (p<0.05) among maize varieties for all evaluated variables. There was a significant interaction between varieties and nitrogen for the percentage of seeds infected by A. flavus, Fusarium spp., and HGW. The incidence of fungi and HGW of maize depends on the variety and the topdressing nitrogen used.O milho é o principal cereal cultivado no Brasil e é utilizado principalmente para alimentação animal e consumo alimentar de seus derivados. Em condições ambientais favoráveis, fungos toxigênicos como Fusarium, Aspergillus e Penicillium spp. poderiam produzir micotoxinas nos grãos de milho durante o crescimento da planta ou no armazenamento. O objetivo deste trabalho foi avaliar a incidência de fungos toxigênicos e sua relação com o peso de grãos de variedades de milho cultivadas sob alta e baixa adubação de nitrogênio. O primeiro fator consistiu de 11 variedades de polinização aberta e o segundo fator de duas doses de nitrogênio em cobertura (60 e 180 kg ha-1). Após a colheita das unidades experimentais, foram avaliadas as seguintes variáveis: massa de cem grãos (MCG) e incidência de A. flavus, Penicillium spp. e Fusarium spp. Houve diferenças (p<0,05) entre as variedades de milho para todas as variáveis avaliadas. Houve interação significativa entre variedades x nitrogênio para a porcentagem de sementes infectadas por A. flavus, Fusarium spp. e MCG. A incidência de fungos e o MCG do milho dependem da variedade e do nitrogênio de cobertura usado