A Study on Automated Ribbon Bridge Installation Strategy and Control System Design

Abstract

Recently, Ribbon Floating Bridges are widely utilized in transportation, especially for emergency restoration in both military and civil fields thanks to their great advantages of ability to transport heavy combat vehicles, trucks, quick installation, and low environmental impacts. Since the installation and operation of the ribbon floating bridge are mainly carried by manual work, these jobs may contain high risks, particularly in dangerous situation and combat time. Therefore, it is critical to propose an installation strategy and self-operation automatically.

This dissertation aims to present a new approach for automated installation and operation of the ribbon floating bridge by proposing a mathematical modeling and designing a control system with different approaches.

The floating bridge system consists a series of interior and ram bays connected that can be considered as the multi-link manipulator. It is confirmed that there is no previous study related to this object although a lot of researchers paid attention to dynamic analysis. Besides, the floating bridge systems normally work in continuous changing environment and are affected by various of uncertainties such as current flow, moving load, and other external disturbances that can lead to position displacement.

To successfully achieve the automatic installation and self-correction positional displacement of the ribbon floating bridge, the integrated propulsion systems are included and the yaw motion of every single bay is measured by the incremental encoder. The ribbon floating bridge is loaded in one riverside and then is rotated to the desired position across the river. In order to maintain the structure and operation of the bridge system, it is required to ensure the linearity of the whole bridge and keep its desired position. To completely perform these task, the followings are carried out:

Firstly, the ribbon floating bridge system structure description and dynamic analysis are discussed and system modeling of the ribbon floating bridge consisting of five individual coupled floating units is given. In this system, there will be existences of two passive bays that do not have propulsion systems. The remaining three active bays are designed to integrate with three propulsion systems containing azimuth propellers, direct current motors and motor drivers. Besides, the yaw displacement between two continuous floating units is measured by the incremental encoder. The system modeling of the ribbon floating bridge describes the kinematics and kinetic of mechanical and electrical operation to obtain a dynamic system expressed by state equations.

Secondly, a number of experimental studies is conducted in order to identify the dynamic characteristics of the floating unit. Besides, the propulsion system is also identified through variety of experiments with different step inputs. In order to estimate the affection of current flow disturbance, an experiment was carried out with several assumed water velocities. Among the obtained data, a representative model is selected. In addition, there are variety of states cannot be measured directly for feedback, therefore, it is necessary to include a state estimator in control system. The linear state observer is designed and implemented. The effectiveness and robustness of the proposed state estimator are verified by numerical simulations and experimental results.

Thirdly, an optimal controller using Linear Quadratic Regulator (LQR) technique is designed and implemented. For the class of MIMO linear system, the optimal control method is common used for robust achievement. Based on previous proposed state observer, the controller gains are defined with the assistance of Matlab software. To verify the sufficiency of the given observer-based controller, a number of numerical simulations with various desired outputs and distinctive environmental conditions are investigated. For further confirmation of practical feasibility of the proposed installation strategy and control system, the experiment is executed in both calm water basin and under wave disturbance attack. The obtained results indicate that the proposed control system satisfies the initial objectives.

Finally, although the optimal LQR based state estimator controller is eligible to achieve the desired control performance, there will be a raised problem caused by the uncertainties of external disturbance leading to slow response of controller to cope with continuous wave/current flow force. Hence, it is critical to improve the reaction time of controller that quickly adapts with uncertainties as well as external disturbance. To eliminate with the unexpected attacks of external disturbance and improve the reaction time, a sliding mode controller (SMC) is proposed for under-actuated system. Simulation and experimental results illustrate the effectiveness of the proposed controller including the ability to overcome continuous wave during installation phase and the robust stable of position keeping phase.