Dynamic modeling and study of the response of three automated guided vehicles proposals

Abstract

The automatically guided vehicles (AGVs) are a technology widely used in industry for the trans portation of the most diverse products. Its advantages in speed, safety and logistics in warehouses or production lines are remarkable. Despite their frequent use, the academy approaches in AGVs are, generally, towards their automation, sensoring and locomotion trails, being little explored, for example, the manufacturing of prototypes and the study and developing of their suspension. Considering the application of AGVs in outdoor environments, such as sandy terrains or snow, the present work intends to investigate three models among those available in market, being: two of them of the unit load type (one with four driving wheels and the other with six wheels, being only the central pair driving) and the third one a forklift with four wheels. More specifically, the linear vertical displacement of the set load + chassis and the angular displacement (pitch) around their gravitational center are evaluated. To reach this, the state space method was applied together with the Matlab - Simulink software in order to obtain the responses in time domain for the inputs pulse, step and ramp. Frequency stability analyses also took place and were performed with the aid of Bode diagrams and maps of poles and zeros for the three systems. All concepts were proved stable, even though the damping (defined with support on literature) was found insufficient for the four-wheel models. Finally, it was verified for all cases that the pitch has more influence on the load then vertical displacement, which brings the need of optimizing damping and stiffness coefficients to attenuate such an effect or even implement an alternative control for the vehicles’ suspension. keywords: AGV, dynamic modeling, suspension, time response, Bode diagrams, stability