Robotic weeding of a maize field based on navigation data of the tractor that performed the seeding (Preprint)

This research presents robotic weeding of a maize field based on navigation data of the tractor that performed the seeding. The availability of tractors equipped with RTK-DGPS based automatic guidance potentially enables robots to perform subsequent tasks in the same field. In an experiment a tractor guidance system generated a route for sowing based on an initial path consisting of two logged positions (A-B line) and then planned the subsequent paths parallel to the initial path one working width apart. After sowing the maize, the A-B line was transferred to the Intelligent Autonomous Weeder (IAW) of Wageningen University. The IAW generated a route plan based on this A-B line and eight coordinates defining the borders of the field and the two headlands. It then successfully performed autonomous weeding of the entire field except of the headlands. The row width was 75 cm and the width of the hoes mounted on the robot was 50 cm. The results show that it is possible to perform robot weeding at field level with high accuracy based on navigation data of the tractor that performed the sowin

A path following algorithm for mobile robots

This paper considers path following control for a robotic platform. The vehicle used for the experiments is a specially designed robotic platform for performing autonomous weed control. The platform is four-wheel steered and four-wheel driven. A diesel engine powers the wheels via a hydraulic transmission. The robot uses a Real Time Kinematic Differential Global Positioning System to determine both position and orientation relative to the path. The deviation of the robot to the desired path is supplied to two high level controllers minimizing the orthogonal distance and orientation to the path. Wheel angle setpoints are determined from inversion of the kinematic model. At low level each wheel angle is controlled by a proportional controller combined with a Smith predictor. Results show the controller performance following different paths shapes including a step, a ramp, and a typical headland path. A refined tuning method calculates controller settings that let the robot drive as much as possible along the same path to its setpoint, but also limit the gains at higher speeds to prevent the closed loop system to become unstable due to the time delay in the system. Mean, minimum and maximum orthogonal distance errors while following a straight path on a paving at a speed of 0.5 m/s are 0.0, -2.4 and 3.0 cm respectively and the standard deviation is 1.2 cm. The control method for four wheel steered vehicles presented in this paper has the unique feature that it enables control of a user definable position relative to the robot frame and can deal with limitations on the wheel angles. The method is very well practical applicable for a manufacturer: all parameters needed are known by the manufacturer or can be determined easily, user settings have an easy interpretation and the only complex part can be supplied as a generic software modul

Low Temperature Drying With Air Dehumidified by Zeolite for Food Products: Energy Efficiency Aspect Analysis

Developments in low temperature drying of food products are still an interesting issue; especially with respect to the energy efficiency. This research studies the energy efficiency that can be achieved by a dryer using air which is dehumidified by zeolite. Experimental results are fitted to a dynamic model to find important variables for the drying operation. The results show that ambient air temperature as well as the ratio between air flow for drying and air flow for regeneration, affect the energy efficiency significantly. Relative humidity of used air, and shift time have a minor effect on the dryer performance. From the total work, it can be noted that the dryer efficiency operated at 50-60°C achieves 75 percent, which is attractive for drying of food products

Robotisering in de landbouw: autonome agrarische voertuigen

Robotisering in de landbouw is een thema waaraan op verschillende plaatsen wordt gewerkt. De uitdaging van automatisering in de landbouw is gelegen in de specifieke kenmerken van het systeem, waardoor het probleem zich onderscheidt van automatisering in meer technische systemen. Deze kenmerken zijn: matig gestructureerde omgeving, variabiliteit in ruimte en tijd van het product waar het om gaat, en een variabele omgeving (zie bijdrage Van Henten in dit nummer). Een deel van de huidige ontwikkeling heeft betrekking op gesloten teelten en de veeteelt, terwijl een ander deel zich richt op de open teelt. In deze trend past de Wageningse autonome wiedrobot, waarvan de ontwikkeling in dit artikel wordt beschreven

Path following with a robotic platform

This paper considers path following control for a four-wheel steered robotic platform. The vehicle used for the experiments is a specially designed robotic platform for performing autonomous weed control. The robot uses RTK- DGPS to determine both position and orientation relative to the path. The deviation of the robot to the desired path is supplied to a high level controller that determines the setpoints of the wheel angles and wheel speeds. At low level each wheel angle is controlled by a P controller combined with a Smith predictor. Results are presented of a preliminary navigation test on a paving

Calsequestrin as a risk factor in Graves’ hyperthyroidism and Graves’ ophthalmopathy patients

Background: The pathogenesis of Graves’ ophthalmopathy (GO), Graves’ hyperthyroidism (GH) and the mechanisms for its link to thyroid autoimmunity are poorly understood. Our research focuses on the role of the skeletal muscle calcium binding protein calsequestrin (CASQ1) in thyroid. We measured the concentration of the CASQ1 protein correlating levels with parameters of the eye signs, CASQ1 antibody levels and CASQ1 gene polymorphism rs3838284. Methods: CASQ1 protein was measured by quantitative Western Blotting. The protein concentrations were expressed as pmol/mg total protein by reference to CASQ1 standards. Results: Western blot analysis showed the presence of two forms of CASQ1 in the thyroid. The mean concentration of CASQ1 protein was significantly reduced in patients with Graves’ disease, compared to thyroid from control subjects with multi-nodular goitre or thyroid cancer. Although in patients with GO it was lower than that, compared with patients with GH this difference was not significant. Reduced CASQ1 in Graves’ thyroid correlated with the homozygous genotype of the rs3838284 CASQ1 polymorphism. Conclusions: Decreased CASQ1 in the thyroid of patients with Graves’ disease compared to thyroid from control subjects is not explained but may reflect consumption of the protein during an autoimmune reaction against CASQ1 in the thyroid