Nelson Luis Cappelli

Penetrógrafo eletrônico automático

This paper presents the development of an automatic recording penetrometer, which operates at the touch of a button. It incorporates a data acquisition system, which can store data of 187 tests and has a serial PC interface. The test characterization such as dates, location (latitude and longitude) can be recorded as well. The maximum working depth may be set and the load cell calibration can be verified through a keyboard with 2 lines display. A speed variation error of < 5% compared to ASAE standard was verified for cone indices between 500 and 5,684 kPa. The equipment is compact, easy to handle and can realize one test every minute.

Desenvolvimento e avaliação de um controlador eletrônico para equipamentos de aplicação de insumos

The objective of this research was the development and evaluation of a control system used to compensate variation on angular speed of dosers in an equipment for formulation, dosing and application of solid fertilizers in the furrow, at variable rates, by monitoring the hydraulic oil temperature changes. PID controllers were designed to guarantee the desired angular speed of the hydraulic motors dosing shaft. The equipment was tested in laboratory using standard signal tests procedure, being able to analyze the machine behavior as a function of the hydraulic oil temperature variations. The accomplished tests showed that the implemented control system was suitable and exhibited a steady behavior even during hydraulic oil temperature changes.

Development and simulation of an advanced system of ambient control in agricultural greenhouses.

Production in greenhouses is a technique that aims at protecting flowers and vegetable production against meteorological agents that affect production adversely, as well as allowing favorable environments throughout the year with productive and commercial advantages. One important issue regarding greenhouse systems is the control of the air temperature and relative humidity. The automatic environmental control allows the improvement of quality, and the efficient and rational use of resources. The aim of this work was to develop a system of temperature and humidity control for a greenhouse prototype in reduced scale, by using the concepts of Fuzzy Logic. The input variables were: air temperature and humidity, and the output variables were: changes in the environmental heating system and humidification. The environmental control was simulated and project parameters were adjusted. The results of the simulation showed that the air temperature and humidity adjustment based on the inference developed Fuzzy system, was satisfactory for the performance of the greenhouse environmental control.ABSTRACT Production in greenhouses is a technique that aims at protecting flowers and vegetable production against meteorologicalagents that affect production adversely, as well as allowing favorable environments throughout the year with productive andcommercial advantages. One important issue regarding greenhouse systems is the control of the air temperature and relativehumidity. The automatic environmental control allows the improvement of quality, and the efficient and rational use ofresources. The aim of this work was to develop a system of temperature and humidity control for a greenhouse prototype inreduced scale, by using the concepts of Fuzzy Logic. The input variables were: air temperature and humidity, and the outputvariables were: changes in the environmental heating system and humidification. The environmental control was simulatedand project parameters were adjusted. The results of the simulation showed that the air temperature and humidity adjustmentbased on the inference developed Fuzzy system, was satisfactory for the performance of the greenhouse environmental con-trol.

Push cone eletrônico de baixo custo para estudo da resistência mecânica ao desenvolvimento radicular das plantas

This work describes the construction, calibration and tests of a Low Cost Electronic Push Cone (LCPC) for the study of mechanical impedance to root growth and plant emergence. The LCPC may be used to determine Cone Index up to a 40 mm depth. The LCPC developed is made up of three parts: mechanical device, electronic circuit and software. The mechanical part is composed, basically, of an aluminium body that shelters a cone. The force for penetration in the soil is supplied by a spring of linear characteristic. The electronic part consists of a displacement sensor that is used to measure the springs displacement. An electronic circuit makes the interface of the signal with a microcomputer. The software has the function of controlling the acquisition, storage and processing of the data. The LCPC presented good results in the calibration and in the field tests.

Desenvolvimento e avaliação de uma servoválvula de baixo custo para a aplicação de insumos líquidos

The present work aimed the development of a low cost servo-valve that answers to an electronic control signal, for variable rates liquid inputs application. A literature research to define which valve type should be used was made. A mechanically activated proportional valve with an electronically controlled servo-engine was designed and evaluated. Since developed the servo-valve, the system was submited to a number of tests .The evaluation of its behavior was obtained in terms of repeatability, hystheresis and linearity. The test was accomplished in a bench, specially developed for this aim. As a result, were obtained three curves of opening percentage as function of flow rate, describing three opening and closing increments in two different work pressures. The servo-valve presented a good repeatability, reasonable hysteresis and a typically quadratic curve. This one maintained the low cost target. These results were very satisfied because the non-linearity and the hysteresis could be easily corrected by software.

Métodos probabilístico e determinístico para diagnóstico da necessidade de subsolagem de solos agrícolas

Este trabalho apresenta duas metodologias para avaliar os niveis de resistencia mecânica a penetracao e auxiliar na tomada de decisao quanto a necessidade de se proceder a operacao de subsolagem. A tomada de decisao baseia-se no volume de solo a ser mobilizado em funcao da resistencia mecânica a penetracao considerada critica para o caso. O primeiro metodo, denominado probabilistico, utiliza-se de tecnicas estatisticas para a definicao do volume de solo a ser mobilizado. O segundo metodo, denominado deterministico, utiliza-se do calculo da porcentagem do volume de solo a ser mobilizado e de sua distribuicao espacial. Em ambos, sao construidas curvas de porcentagem de pontos experimentais com niveis de resistencia mecânica a penetracao igual ou superior ao nivel estabelecido como critico, curvas de volume de solo a ser mobilizado em funcao do nivel e, finalmente, o metodo deterministico apresenta ainda uma distribuicao espacial dos pontos com resistencia a penetracao igual ou superior ao nivel critico. Uma comparacao entre as curvas de volume de solo a ser mobilizado em funcao do nivel critico, obtidas por cada um dos metodos, mostra que os metodos sao equivalentes. O metodo deterministico tem a vantagem de mostrar a distribuicao espacial dos pontos criticos.

Equipamento microprocessado para geração de sinal de correção diferencial, em tempo real, para GPS

This work presents the development of low cost microprocessor-based equipment for generation of differential GPS correction signal, in real time, and configuration and supervision of the GPS base. The developed equipment contains a dedicated microcontroller connected to the GPS receiver, alphanumeric display and multifunction keyboard for configuration and operation of the system and communication interfaces. The electronic circuit has the function of receiving the information from GPS base; interpret them, converting the sentence in the RTCM SC-104 protocol. The microcontroller software makes the conversion of the signal received by the GPS base from the specific format to RTCM SC-104 protocol. The processing main board has two serials RS-232C standard interfaces. One of them is used for configuration and receiving the information generated by the GPS base. The other operates as output, sending the differential correction signal for the transmission system. The development of microprocessor-based equipment showed that it is possible the construction of a low cost private station for real time generation of differential GPS correction signal.This work presents the development of low cost microprocessor-based equipment for generation of differential GPS correction signal, in real time, and configuration and supervision of the GPS base. The developed equipment contains a dedicated microcontroller connected to the GPS receiver, alphanumeric display and multifunction keyboard for configuration and operation of the system and communication interfaces. The electronic circuit has the function of receiving the information from GPS base; interpret them, converting the sentence in the RTCM SC-104 protocol. The microcontroller software makes the conversion of the signal received by the GPS base from the specific format to RTCM SC-104 protocol. The processing main board has two serials RS-232C standard interfaces. One of them is used for configuration and receiving the information generated by the GPS base. The other operates as output, sending the differential correction signal for the transmission system. The development of microprocessor-based equipment showed that it is possible the construction of a low cost private station for real time generation of differential GPS correction signal.

Dosador de fertilizante acionado eletricamente e controlado por lógica fuzzy

The present study shows the development, simulation and actual implementation of a closed-loop controller based on fuzzy logic that is able to regulate and standardize the mass flow of a helical fertilizer applicator. The control algorithm was developed using MATLABs Fuzzy Logic Toolbox. Both open and closed-loop simulations of the controller were performed in MATLABs Simulink environment. The instantaneous deviation of the mass flow from the set point (SP), its derivative, the equipment´s translation velocity and acceleration were all used as input signals for the controller, whereas the voltage of the applicators DC electric motor (DCEM) was driven by the controller as output signal. Calibration and validation of the rules and membership functions of the fuzzy logic were accomplished in the computer simulation phase, taking into account the systems response to SP changes. The mass flow variation coefficient, measured in experimental tests, ranged from 6.32 to 13.18%. The steady state error fell between -0.72 and 0.13g s-1 and the recorded average rise time of the system was 0.38 s. The implemented controller was able to both damp the oscillations in mass flow that are characteristic of helical fertilizer applicators, and to effectively respond to SP variations.

A Mathematical model for the cold storage of agricultural products

Studies of control strategies for refrigeration systems observe, among other variables, the dynamic behavior of temperature and the consumption of electrical energy. Aiming to contribute to these studies, this work presents the proposal and validation of a mathematical model for the cooling system of a cold-storage unit. The model approximates the dynamics and interdependence of the variables, to first-order systems with time delay and the summation of effects. The input variables available are the frequency of compressor activation and the thermal load imposed on the unit, and as output variables, the air temperature both at the evaporator inlet and at the centre of the chamber, as well as the electrical power consumed by the compressor. The results obtained were satisfactory, with an error of less than 0.11 °C for the air temperature at the evaporator inlet, of less than 0.09 °C for the temperature at the centre of the chamber, and of less than 1% for the electrical energy consumed.

Sistema para estudos de estratégias de controle aplicadas em câmaras frias

O processo de armazenamento refrigerado em câmaras contribui, em grande parte, para a qualidade e a longevidade dos produtos. Nos ultimos anos, tem-se intensificado os estudos de estrategias de controle com a finalidade de diminuir a variacao da temperatura dentro da câmara de armazenamento e de reduzir o consumo de energia eletrica. Neste trabalho, foi desenvolvido um sistema para aquisicao de dados e controle do processo, em linguagem LabVIEW, para ser aplicado no sistema de refrigeracao de uma câmara frigorifica de 30m3. A utilizacao da instrumentacao e do aplicativo desenvolvido possibilitou a realizacao de experimentos cientificos, com o objetivo de estudar o comportamento dinâmico do sistema de refrigeracao, comparar o desempenho das estrategias de controle da maquina termica, tanto em funcao da temperatura controlada, quanto ao consumo de energia eletrica. Neste sistema, foram testadas as estrategias de controle liga-desliga, PID e fuzzy. Em relacao ao consumo de energia eletrica, o controlador fuzzy obteve o melhor resultado, economizando 10% em relacao as outras estrategias testadas.