Ray Eaton

Simulation of a tractor-implement model under the influence of lateral disturbances

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 implements trajectory. The developed model is subjected to real conditions, such as ground undulation and uncertainty, sloping terrain, tyre slippage, and constrained steering of the tractor. The implement is assumed to possess independently steered wheels for aiding in implement alignment. A complete model is presented and simulated under varying conditions. Primarily this work demonstrates and validates the trailed vehicle system behavior when the trailing implement is subjected to large drag forces due to ground engagement and the significantly large lateral disturbances that occur in real life broad acre farming conditions.

Fault accommodation for nonlinear systems using fuzzy adaptive sliding control

An active fault accommodation control law is developed for a class of nonlinear systems to guarantee the closed-loop stability in the presence of a fault, based on a fuzzy logic system representation of the dynamics due to faults. It uses fuzzy logic system to approximate the dynamic caused by the fault. Through the adaptive process of the parameters, the dynamics caused by the fault is counteracted. The fuzzy sliding mode control is introduced to attenuate the fuzzy approximation error. Simultaneity, the closed-loop system is stable in Lyapunov sense and the tracking error converges to a neighbourhood of zero. The example of the proposed design indicates that the fault accommodation control law is effective for a nonlinear system.

Agricultural robotics: A streamlined approach to realization of Autonomous Farming

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 crop cultivation and discusses its use in accomplishing reliable, cost effective and efficient farming systems. The work currently in progress towards the development of autonomous farming vehicles and the results obtained through detailed mathematical analysis of example actuation units will also be presented.

Robust sliding mode control of an agricultural tractor under the influence of slip

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 vehicles operate in quite uncertain and unpredictable environments. It is important that vehicles are guided with precision in a lateral as well as longitudinal direction, while being subjected to often significant disturbance forces, or slip, due to uncertain and sloping terrain. Little work has been carried out thus far in the guidance of such vehicles where vehicle slip is significant. In this paper, the authors provide an alternative approach to the robust trajectory tracking of an agricultural tractor under the influence of lateral and longitudinal velocity slip. This approach takes into account the dynamics of the steering system, and caters for slip velocities which are bounded but time varying. This is achieved via the use a robust combination of sliding mode control and integrator backstepping. Robust stability is achieved, ensuring the trajectory error is bounded to an adjustable region around the origin. Simulation results show that the alternative approach proposed yields suitable robust trajectory tracking.

Automation of an Agricultural Tractor for Fruit Picking

This paper presents the hardware and software architectures of a compact agricultural tractor, that is currently being developed as a generic mobile platform for agricultural tasks. The specific task that is being addressed is fruit picking. Such systems require precision outdoor maneuvering and coordination with the implement attached to the vehicle. The system described also includes a loader attached to the front of the tractor which carries the fruit picking robot. First the hardware associated with the safety subsystem, steering, traction and loader control systems are described. Then the real-time software that coordinates the control of all subsystems while maintaining a functional radio link to a remote station is described.

Derivation of an error model for tractor-trailer path tracking

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 open-loop kinematic model and the desired reference path. By applying basic theory of engineering mechanics for rigid body with slips, in the form of extra velocities and angles, exerting on rear axles and steered wheel as well as the trailers implements, the open-loop kinematic model is primarily established. Provided the current state of the vehicle and random disturbances of the environment are known with bounds, the next states of the system can be estimated, the vehicle running path is predicted, along with setting a basis for further controller design. The development is verified by simulation for both kinematic and error models with disturbances obeying the normal distribution.

ARCHITECTURE OF AN AUTOMATED AGRICULTURAL TRACTOR: HARDWARE, SOFTWARE AND CONTROL SYSTEMS

Abstract Using a compact agricultural tractor, an automated mobile platform is being developed to support precise agricultural tasks. The task being considered is fruit picking, however the platform developed should be generic. The need for precise control of the tractor, loader mechanism and the task implement attached to the tractor, is paramount. Development of the automated mobile platform can be broken down into various components, namely, the steering, loader, and traction control systems, and safety system. Development for each system includes modifications to hardware, and design of appropriate software to drive the systems automatically. Much work is needed to provide the expert control for the types of precision tasks envisaged. Preliminary work shows simple control of the steering and loader systems.

Simulation of an articulated tractor-implement-trailer model under the influence of lateral disturbances

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. In the simulations, the model was subjected to real conditions experienced in agricultural applications such as disturbances and uncertainties due to ground undulation, gravitational forces due to sloping ground, and lateral wheel slippage. The implement attached to the tractor is assumed to be steerable to enhance the pathtracking capability. This work aims to provide an insight in to the articulated tractor behaviour under the influence of real life farming condition.

Precision Autonomous Guidance of Agricultural Vehicles for Future Autonomous Farming

Due primarily to an increased emphasis on global competition, and a significant reduction in the available workforce, the agricultural industry is facing significant cultural shifts at present. These factors induce a demand for increased efficiency and productivity in farming operations, which in turn, lends itself to an increase in the need for so called Precision Autonomous Farming (PAF). This paper presents a systems engineering approach to precision autonomous farming in broad acre crops, and central to this approach, progress made in achieving precision guidance of agricultural vehicles. An overview of the farming system is presented, depicting a system-of-systems architecture, where a vital interplay between Precision Agricultural (PA) methods and precision machinery automation exists. Such autonomous machinery is assumed used for seeding, crop sensing, harvesting, weeding and other follow-up operations. The authors propose the development and ongoing management of two data sets, namely, a Precision Agricultural Data Set (PADS), used to ensure any agronomy requirements of the crop are met, and a Precision Farming Data Set (PFDS) formed off-line before crop cultivation, and used to achieve optimal performance of the farming system by specifying the spatial precision required for agricultural operations. Preliminary results are shown, highlighting the development and use of a fully instrumented tractor, as well as initial research into developing high level path tracking controller for such machinery.

Systems Engineering Approach to Agricultural Automation: New Developments

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 of the crop cultivation and discusses its use in accomplishing reliable, cost effective and efficient farming systems. The work currently in progress towards the development of autonomous farming vehicles and the results obtained through detailed mathematical analysis of example actuation units will also be presented.