Obstacle negotiation analysis of track-legged robot based on terramechanics

Purpose This paper aims to present a new method to analyze the robot’s obstacle negotiation based on the terramechanics, where the terrain physical parameters, the sinkage and the slippage of the robot are taken into account, to enhance the robot’s trafficability. Design/methodology/approach In this paper, terramechanics is used in motion planning for all-terrain obstacle negotiation. First, wheel/track-terrain interaction models are established and used to analyze traction performances in different locomotion modes of the reconfigurable robot. Next, several key steps of obstacle-climbing are reanalyzed and the sinkage, the slippage and the drawbar pull are obtained by the models in these steps. In addition, an obstacle negotiation analysis method on loose soil is proposed. Finally, experiments in different locomotion modes are conducted and the results demonstrate that the model is more suitable for practical applications than the center of gravity (CoG) kinematic model. Findings Using the traction performance experimental platform, the relationships between the drawbar pull and the slippage in different locomotion modes are obtained, and then the traction performances are obtained. The experimental results show that the relationships obtained by the models are in good agreement with the measured. The obstacle-climbing experiments are carried out to confirm the availability of the method, and the experimental results demonstrate that the model is more suitable for practical applications than the CoG kinematic model. Originality/value Comparing with the results without considering Terramechanics, obstacle-negotiation analysis based on the proposed track-terrain interaction model considering Terramechanics is much more accurate than without considering Terramechanics.

DEMANDA ENERGÉTICA NA SEMEADURA DA SOJA COM DIFERENTES CONFIGURAÇÕES DE SULCADORES

DEMANDA ENERGÉTICA NA SEMEADURA DA SOJA COM DIFERENTES CONFIGURAÇÕES DE SULCADORES MARCELO SILVEIRA DE FARIAS1, JOSÉ FERNANDO SCHLOSSER2, LEONARDO CASALI2, MATEUS CASSOL CELLA3, ALFRAN TELLECHEA MARTINI4 1 Departamento de Ciências Agronômicas e Ambientais, Universidade Federal de Santa Maria, Campus de Frederico Westphalen, Linha 7 de Setembro, s/n, BR 386, km 40, CEP 98400-000, Frederico Westphalen, Rio Grande do Sul, Brasil, [email protected]. 2 Departamento de Engenharia Rural, Universidade Federal de Santa Maria, Avenida Roraima n°1000, Bairro Camobi, CEP 97105-900, Santa Maria, Rio Grande do Sul, Brasil, [email protected]; [email protected]. 3 Departamento de Engenharia Mecânica, Universidade Federal de Santa Maria, Avenida Roraima n°1000, Bairro Camobi, CEP 97105-900, Santa Maria, Rio Grande do Sul, Brasil, [email protected]. 4 Coordenadoria Acadêmica, Universidade Federal de Santa Maria, Campus de Cachoeira do Sul, Rua Ernesto Barros, n° 1345, Bairro Santo Antônio, CEP 96506-310, Cachoeira do Sul, Rio Grande do Sul, Brasil, [email protected]. RESUMO: O objetivo deste trabalho foi avaliar a demanda energética requerida por uma semeadora-adubadora para plantio direto, com diferentes configurações de sulcadores na implantação da cultura da soja, em áreas de várzea. O experimento foi conduzido em duas áreas agrícolas, tipicamente cultivadas com arroz irrigado, localizadas na região Central do estado do Rio Grande do Sul. Utilizou-se o delineamento de blocos aleatorizados, em arranjo bifatorial, sendo avaliadas quatro configurações de sulcadores (haste sulcadora, haste sulcadora com sistema tapa-sulco, disco ondulado e disco duplo), em duas áreas de características distintas (área agrícola 1 e área agrícola 2). As variáveis estudadas foram: força na barra de tração, velocidade real de trabalho, patinamento das rodas motrizes do trator e consumo específico de combustível. Com base nas análises dos resultados obtidos neste estudo pode-se afirmar que, os mecanismos sulcadores influenciam na demanda energética do conjunto mecanizado, independentemente da área agrícola. O consumo específico de combustível com o uso de hastes sulcadoras quando comparado aos discos foi 0,7 vezes menor, para ambas as áreas. Palavras-chave: mecanização agrícola, força de tração, consumo de combustível, eficiência. ENERGY DEMAND OF IN SOYBEAN SOWING WITH DIFFERENT FURROWER CONFIGURATIONS ABSTRACT: This research aimed to evaluate the energy demand required by a seeder-fertilizer for direct planting, with different configurations of furrowers in the implantation of soybean culture, in lowland areas. The experiment was conducted in two agricultural areas, typically cultivated with irrigated rice, located in the central region of the state of Rio Grande do Sul. A randomized block design was used, in a bifactorial arrangement, and four furrow configurations (shank, shank with furrow-groove system, corrugated disc and double disc) were evaluated in two areas with different characteristics (agricultural area 1 and agricultural area 2). The variables studied were drawbar pull, real travel speed, the slippage of the driving wheels of the tractor and specific fuel consumption. Based on the analysis of the results obtained in this study, it can be said that the furrow mechanisms influence the energy demand of the mechanized set, regardless of the agricultural area. Specific fuel consumption with the use of shanks instead of disks was 0.7 times lower, for both areas. Keywords: Agricultural mechanization, drawbar pull, fuel consumption, efficiency

Frequency Spectra Analysis of Drawbar Pulls Generated by Special Driving Wheels Improving Tractive Performance

Driving wheel operation is characterized by force interactions with the ground, manifested in the form of vibrations. Signals generated by driving wheels can be analyzed in the frequency spectrum of tractor drawbar pull. The paper presents the analysis of a drawbar pull signal generated by a tractor equipped with two types of special driving wheels and standard tires. Beside the evaluation of special driving wheels’ properties according to drawbar power, the frequency spectra of measured signals were analyzed using a fast Fourier transformation. The model spectrum intervals for the standard tires, spike tires, and blade wheels were calculated according to the number of rubber lugs, blades, or spikes and compared with the experimental results. The results showed that the specific frequencies typical for blades and spikes were identified in model spectrum intervals. In the case of standard tires, the spectrum components typical for rubber lugs of the tire tread pattern were not identified. The highest amplitude of the typical frequency component was detected in the case of blades wheels, which showed the highest difference in drawbar power in comparison with the standard tires. Smaller dimensions of spikes resulted in lower amplitude and lower difference in drawbar power in comparison with the standard tires.

REALIZATION OF TRACTION CAPABILITIES OF A TRACTOR WITH AN ELECTROMECHANICAL POWER TRAIN

A method has been developed to assess the traction capabilities of a tractor with an electromechanical power train and determine the actual speed taking into account three restrictions: on the permissible slip of the tractor, the maximum power of the used internal combustion engine (ICE) and the permissible mode of operation of the traction induction motor (TIM). The developed mathematical model makes it possible to determine the drawbar pull and the actual speed of the tractor when regulating the TIM in the entire operating frequency range of the voltage supplied to the TIM for a comparative assessment of the traction capabilities of the tractor when using different gear ratios of the mechanical part of the power train (MPPT), as well as determine the slip and other parameters of the TIM when it works as a part of the electromechanical power train of the tractor. Calculations show that: 1) if the MPPT ratio is too high, the whole range of tractor operating speeds on the plowing will not be provided, and if the MPPT ratio is too low, the tractor will not be able to develop the maximum possible drawbar pull based on the permissible slip at any voltage frequency from the TIM control range without exceeding the nominal mode of operation of the TIM; 2) the higher the TIM gear ratio, the larger the section of the TIM frequency control range will be, in which the TIM will not be able to develop even the nominal slip due to the restriction on the permissible slip of the tractor, and for the same frequencies in this section, the TIM slip will be more limited at a higher MPPT gear ratio; the lower the transmission ratio of the MPPT, the more the nominal slip of the TIM will be exceeded during acceleration of the tractor with maintaining the maximum possible based on the permissible slip of the thrust force from the minimum speed to the speeds corresponding to plowing.

Experimental Investigation of Traction Power Transfer Indices of Farm-Tractors for Efficient Energy Utilization in Soil Tillage and Cultivation Operations

Farm tractors in cultivation consume a big amount of fossil fuels and emit greenhouse gases to the atmosphere. Improving traction performance and power transfer indices of wheeled tractors and field terrain soil with higher traction (pull ability) at optimal travel reduction (TR) can optimize energy utilization. This study compares the traction performance, fuel consumption, and field productivity, of a farm tractor equipped with a new drive wheel “rigid lugged wheel (RLW)” and conventional tire wheel (CTW) in field tillage operations. Tractor with RLW resulted 24.6 kN drawbar pull and 6.6 km.h−1 travel speed at 80% tractive efficiency and 15.6% TR. While with CTW, the drawbar pull and the travel speed were 23.2 kN and 6.0 km h−1 respectively at 68% tractive efficiency and 36.3% TR. The RLW resulted in improved traction performance with similar equipment weight. Tractor with RLW also resulted 220.5% lower TR, 14.8% higher field productivity, and 15.4% lower fuel consumption. RLW can control equipment weight and field traffic intensity with the improved traction performance of wheeled tractors and will make the field operations more energy-efficient and economical. For enhanced field drivability of RLW, further work is required to test for diverse field conditions and differently sized tractors.

MODELING TRACTOR PARAMETERS AND TILLAGE UNITCONFIGURATION TAKINGINTO ACCOUNT THE INFLUENCE OF NATURAL AND PRODUCTION FACTORS

The research goal was to substantiate the model and the algorithm of forming the parameters of a wheeled trac-tor and the configurationof a tillage unit taking into account the natural and production conditions. To evaluate the in-fluence of natural and production conditions on the param-eters of the tractor and the unit configuration, three groups of factors were considered: the class of run length which determined the optimal value of the net productivity of the unit at a particular operation withminimal operating costs; characteristics of the draught resistance of the working machine which formed the optimal speed mode of unit op-eration; the indices of the drawbar pull and coupling prop-erties of the tractor which determined the conditions for effective functioning in the working mode. We substantiat-ed a computational model representing the response of a multidimensional dynamic system to external disturbances, setting and controlling actions which performed the trans-formation according to the input-output type. The interrela-tion of the input actions of different groups and the output parameters of the system were determined using the rea-sonable indices and optimization criteria. The adaptation to operating tillage technologies is determined by the nominal values of the working speed set according to the criterion of minimum energy consumption per unit of net productivity taking into account the restrictions on the drawbar pull and coupling properties of the tractor ensuring operation in the zone of maximum pulling efficiency. The adapters to the production conditions are specific ones referred to the unit of net productivity at nominal speed, the working width of the unit, the operating weight and the required power of the tractor. The product of specific indices by the optimum for a given run length and type of operation, the value of net productivity determines the parameters of the tractor and the unit configuration taking into account the influence of natural and production factors. The algorithm for optimizing parameters was developed; four rational standard sizes of wheeled tractors with an operating power of 135 to 310 kW with adjustable weight and unit configuration for technical support of tillage technologies in the main natural and cli-matic zones of operation were substantiated with an adap-tation coefficient of 0.978-0.987.

Field Performance Evaluation of a Combined Cultivator Developed at Kenana Sugar Company- Sudan

Sugar cane production requires a number of operations to be carried out in the field through number of implements and machines. Therefore, time consuming and required large amount of energy. A combined field cultivator was designed in Kenana agricultural implements factory (KAIF) to carry out at one time multi operations, cultivation, furrow-reforming and Fertilizer placement. This is to increase field productivity, reduce farm power and lower operation time and cost. The combined implement was evaluated in Kenana cultivation fields and compared with the three individual implements, rigid tine cultivator, furrow reformer and fertilizer applicator. The measured parameters were drawbar pull, power requirements, field capacity, fuel consumption and total time in the field. The results showed highly significant differences at 1% level between the different implements for the field capacity, fuel consumption and significant differences at 5% for the drawbar pull. Power requirement in (kW) for the combined cultivator was 77% of those individual implements. Total time per feddan to accomplish the required operations by the combined cultivator was 57% of that required by the individual implements. Fuel consumption was reduced to 57% when combined implement was used compared to that consumed by individual implements. It was concluded that the combined cultivator was effective in increasing field productivity and reducing power and cost of operations.

Exploring Tractive Performance of Planetary Rover's Rigid Wheels on Mixed Terrain

Based on insufficient studies of the tractive performance of a planetary rover's rigid wheels in soft soil and hard mixed soil terrains, a method for studying the tractive performance is presented. The Wong-Reece' interaction model was used as the dynamic model for wheel-soil contact. The sinkage model and the drawbar pull force model were modified and then verified with experimental results. Based on the Hertz contact theory, a nonlinear friction spring damping model was adopted as the wheel-bedrock contact model. An additional terrain hardness array was introduced for setting and recognizing the mixed terrain with ground mechanics parameters. With the platform for co-simulating the navigation and dynamics of a planetary rover, the simulation program was developed to dynamically simulate the whole planetary rover with two wheel-ground contact models. Taking the Mars rover as an example, its whole model was established with the MSC.Adams software. The dynamic simulation of the Mars rover on the soft terrain and mixed terrain was carried out respectively. The simulation results show that the Mars rover's velocity fluctuates greatly on the mixed terrain, and that the Mars rover gains greater drawbar pull force when traveling on the mixed terrain than on the only soil terrain.