Luc Clijmans

Structural modification effects on the dynamic behavior of an agricultural tractor

Even during normal operation, agricultural machines are exposed to a number of disturbances that can generate excessive vibration levels. The disturbances originate from soil roughness in combination with driving speed or from rotating elements within the machine. Machine vibrations may be uncomfortable to the driver. Vibrations may affect the manual or automatic controls and reduce the efficiency of the operations to be carried out such as field spraying and tillage. In this article, the dynamic behavior of a tractor is studied and the effects of possible structural modifications on its dynamic behavior are examined. Using the experimental modal analysis technique, a modal model is derived (with a correlation coefficient ranging from 0.90 to 0.95 of the measured values) that contains the eigenfrequencies and mode shapes of the machine. It is applied to predict the structural behavior of the machine under a set of excitation conditions. A frequency sensitivity analysis on the modal model gives information about the most critical locations on the structure with respect to local parameter changes. In a later stage, this is used to predict frequency shifts owing to structural modifications like localstiffness and inertia changes.

A non-linear model to approximate the dynamics of a pulse width-modulated spray nozzle

This paper deals with the mathematical model construction of a PWM-nozzle in order to analyse the impact of its dynamics on the flow discharge through multiple simulation tests. A structured analysis is proposed where the system is divided up into two linked subsystems: an electromagnetic subsystem and a mechanical subsystem. Due to the ferromagnetic property of the solenoid, hysteresis effects occur that have been approximately described by third order polynomial functions. The motion of the core inside the solenoid is defined by linear differential equations (mass spring-damper subsystem) with these differences that the displacement is physically restricted. Coulomb friction is appended and the initial preload of the spring is covered so that the final solution is non-linear. An experimental test in which the resulting displacements of the core due to a voltage pulse input are compared with the model simulations demonstrates the exactness of the model.

Comparison of Different Passive Horizontal Sprayer Boom Suspension Set-Ups

Abstract Existing boom suspensions are effective to reduce rolling boom motions, but reduction of horizontal boom vibrations is negligible. A prototype passive horizontal suspension is developed and different suspension set-ups are compared with regard to boom vibrations and spray pattern homogeneity. Boom vibrations are simulated with a non-linear finite element program. The corresponding spray pattern is obtained by combining the static spray pattern with the simulated boom movements. An appropriate passive suspension is able to almost halve the CV of spray deposition compared to a fixed boom.

Neural Network Based System Identification of Agricultural Machinery

Abstract A new method for on-line system identification based on the Self-Organizing Map is presented. The standard Self-Organizing Map (SOM) is extended with Local Linear Mappings. To every node in the SOM along with the input weight two output weights are assigned: one that stores the output part of an input-output pair and one that stores the local gradient matrix (Jacobian) that is calculated from the training pairs. A training algorithm for the Jacobian matrices is derived. The method is tested in system identification of two Agricultural Machines: a flexible Spray Boom and a shaker with a nonlinear spring.

Image Analysis for Planting Machine of White Cabbage

Abstract Image processing of the planting equipment is reported. The outline of the planting machine has been composed of belt conveyor and planting equipment which supply the nursery plants. CCD camera for image input was installed above the belt conveyor. The basic action in belt conveyor of the planting equipment is two described in the following. They are that it controls the speed of the belt conveyor by the interval of the seedling in order to efficiently do, and that it removes the nursery plants of the immaturity. Therefore, the data to be got by the image processing are the intervals of the nursery plants and positions of the nursery plants of the immaturity. This system has done practical application with the purpose, and maximum speed of the planting equipment is the 5 plants per second.