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Developing a specific model for a tractor-trailer system subject to slips in real working environment is essential for understanding its system behavior and designing controllers. This paper presents a comprehensive analysis of the kinematics of the tractor-trailer under the influence of disturbances caused by the ground onto the implements and wheels. An error model is then derived, based on the...
This paper describes a novel approach to surface fitting for the creation of a 3D surface map for use by a small articulated wall-climbing robot. Both a laser range finder and a low-resolution camera are used to acquire data in a sparse manner. By scanning at large intervals, such as every 5-10°, and then fusing the data, it is shown that it is possible to fit planar surfaces at an accuracy comparable...
Precise path tracking control of autonomous vehicles is an area which is beginning to benefit from an increased awareness of its importance and its challenge. One of the challenges comes about due to the need for increased accuracy and robustness. Kinematic models are primarily used for path tracking control due to their generic and more simplistic nature when compared to dynamic models. However,...
Ground plane detection plays an important role in stereo vision based obstacle detection methods. Recently, V-disparity image has been widely used for ground plane detection. The existing approach based on V-disparity image can detect flat ground successfully but have difficulty in detecting non-flat ground. In this paper, we discuss the representation of non-flat ground in V-disparity image, based...
This paper presents the derivation of the mathematical model for a three-body articulated agricultural vehicle such as a tractor that drags behind two agricultural implements connected in series. It is then used in a simulation to study the effects of slippage. The model is developed with the aim of designing robust controllers that ensure high-precision path-tracking control of such articulated systems...
Precise guidance of agricultural vehicles is an area which is beginning to benefit from an increased awareness of its importance and its challenge. It is important as farming is becoming increasingly and justifiably automated, and because precision and autonomous farming is more necessary now, in order for the industry and individual farms to be competitive. It is a challenge because agricultural...
GreenWeeder is a non-herbicidal autonomous weeding robot that is being developed to autonomously track crop rows to target inter-row spacing for weeding through electrocution. This work presents the experimental system identification to identify the steering system dynamics and the development of a controller to track an especially laid strip mimicking a crop row. The results of the designed controller...
This paper describes an approach to recognizing and localizing centers of mature lettuce heads in the field when the lettuce leaves obscure the distinctions between plants. This is of great value when using an automatic harvester in cluttered or closely planted vegetation. The aim of this work is to investigate and verify the potential use of spatial rather than visual clues for recognition and localization,...
Bidens pilosa L (commonly known as cobbler's peg) is an annual broad leaf weed widely distributed in tropical and subtropical regions of the world and is reported to be a weed of 31 crops including wheat. Automatic detection of Bidens in wheat farms is a nontrivial problem due to their similarity in color and presence of occlusions. This paper proposes a methodology which could be used to discriminate...
Currently, there are significant challenges faced by the farming industry, not least of which are a reduction in the available labour workforce, and a more 'corporate' style of farming. Such factors demand an increase in farming efficiency and productivity. This paper looks forward to the not too distant future, where the realisation of autonomous farming will aid in the farming communities surviving...
The agricultural industry is undergoing significant cultural shifts at present and will continue to do so into the future. These shifts have come about due to the emergence of more 'corporate' style farming, where declines in the labour workforce and increased emphasis on global competition, means a demand for increased efficiency and productivity in farming operations. Such a demand in turn lends...
This work presents the derivation of a comprehensive mathematical model for an off-road vehicle such as an agricultural tractor that drags behind it a heavy implement. The models are being developed with the aim of designing robust controllers that will enable the high precision control of the implement's trajectory. The developed model is subjected to real conditions, such as ground undulation and...
The position estimation techniques based on particle filters use a motion model, to predict the possible robot poses, called particles, when a motion command is executed, and a measurement model to update the weights of these particles. Assigning weights to these particles on arrival of a new measurement is a fundamental problem. Different models mostly ad-hoc exist for this measurement update. Laser...
This paper presents a streamlined approach to future Precision Autonomous Farming (PAF). It focuses on the preferred specification of the farming systems including the farming system layout, sensing systems and actuation units such as tractor-implement combinations. The authors propose the development of the Precision Farming Data Set (PFDS) which is formed off-line before the commencement of the...
This paper presents the Systems Engineering approach to future Precision Autonomous Farming (PAF). It focuses on the preferred specification of the farming systems including the farming system layout, sensing systems and actuation units such as tractors-implement combinations. The authors propose the development of the Precision Farming Data Set (PFDS) which is formed off-line before the commencement...
Conventional correlation based stereo vision algorithms have poor performance at object borders due to occlusion. In this paper, a new matching sequence has been introduced. To detect left object border, a left shifted window is used with right image as the reference image and process from left to right. This method gives excellent left object border detection while detection of right object border...
A new method for calculating the collision free areas of a manipulator's configuration space (C-space) is demonstrated in this paper. Rather than mapping a point obstacle to an n-dimensional surface in the C-space, the dual problem is considered. That is, regions of the C-space that are guaranteed to be collision free are determined. Whilst some configurations that are collision free are not captured...
This paper presents the estimation of the position of the ground plane for navigation of on-road or off-road vehicles, in particular for obstacle detection using stereo vision. Ground plane estimation plays an important role in stereo vision based obstacle detection tasks. V-disparity image is widely used for ground plane estimation. However, it heavily relies on distinct road features which may not...
This paper describes a new approach to align the laser scans in order to build a consistent map of the environment of a mobile robot. There are no physical landmarks and the environment is completely unknown. Our method finds the nearest matching lines in the scans and resolves the data correspondence problem. The global consistency and final map is achieved by the formulation of geometrical constraints...
We present a new and completely probabilistic approach to extract the unknown motion model of an autonomous wheelchair. This method is, however, general and can be applied to any mobile robot. Particle filter based methods are very popular for localization and navigation of mobile robots. These methods use motion model for the prediction of robot states when a control action is taken. Well theoretical...
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