Abstract
A mathematical model of a forest crane that is suitable for dynamics analysis of its operation cycle is presented in this paper. The flexibility of the operator’s seat, drives and supports is taken into account. Joint coordinates are applied to describe the motion of the links together with the homogeneous transformations technique. Lagrange equations of the second order are used when deriving the equations of motions. Joint forces and torques are determined based on recursive Newton-Euler algorithms. These joint forces are then used in the LuGre friction model, which allows to calculate the friction coefficients and friction forces. Numerical analyses performed here show the influence of various friction forces on the vibration level as perceived by the operator of the crane. The level of discomfort is discussed based on standards commonly used in the vehicle and transportation industry for evaluations of vibration comfort
Highlights
Crane control problems are becoming increasingly important for designers and operators
The results show the strong influence of the load centre of gravity on crane dynamics
For the friction coefficients assumed in Set-1, the general level of discomfort can be estimated as “a little uncomfortable” when working with or without dampened seat
Summary
Crane control problems are becoming increasingly important for designers and operators. The efficiency of load handling and increased safety and level of comfort for all personnel involved and crane operators are the main driving factors for developments in this field. For this purpose, modern machines are equipped with quite advanced and expensive sensors and other control devices. One can simulate complex machine behaviour without the risk of damage or injuries In this context, many crane models have been developed with varying complexity and level of details. Prediction of the discomfort level, determined by vibrations transmitted from the column to the seat and the body, was examined by taking into account the standard approach [6, 10] applied in vehicle N.V.H. It is a common practice to simulate and test comfort parameters in special or construction machinery, as, for example, in [3] but especially in many branches of the ground vehicle industry
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