The paper presents the design of a hardware in loop (HIL) simulator for the vertical motion of an autonomous underwater vehicle (AUV) operating under identical vertical thrusters. The thruster mathematical modelling along with the dynamic model of the AUV for its vertical motion is presented. The HIL simulates ocean currents of different speeds and direction at different depth ranges which displays how the AUV drifts from its initial dive position. A Graphical User Interface for the hardware in loop simulator is built on C# which provides various controls over the simulator like modifying the water currents, its initial dive location, maximum diving depth. The GUI is given a serial input (control voltage) which simulates the thruster and the two serial outputs- depth and altitude (or pressure at the depth) are used to study the behavior and motion of the AUV in the vertical direction, whereas the simulated ocean currents helps us to monitor the motion of the AUV in the horizontal direction.
Table of Contents
I. Introduction
II. Physics Model Estimation
A. Non Linear Model Estimation
B. Water Currents
C. Initial Dive Location
D. Conversion of Geodetic to ECEF coordinate system
E. Maximum Dive Depth
III. HILS Control Parameters
IV. AUV HILS Graphical User Interface
A. Start HIL and Stop HIL
B. Pause and Unpause HIL
C. Start Log and Stop Log
D. Config File
E. Clear Data
F. Show Receive
G. Simulation Info
H. Log Textbox
I. COM Port and Baud Rate
J. AUV Motion Charts
V. Conclusion and Future Work
Objectives and Topics
The paper focuses on the development of a Hardware-in-the-Loop (HIL) simulator designed to test the vertical motion of an Autonomous Underwater Vehicle (AUV) under various physical constraints, including simulated ocean currents and thruster dynamics.
- Mathematical modeling of AUV vertical dynamics and thruster performance.
- Simulation of ocean current impacts on AUV horizontal drift.
- Design and implementation of a Graphical User Interface (GUI) for system control and monitoring.
- Integration of real-time HIL parameters such as geodetic coordinates and depth settings.
- Logging and visualization of AUV performance data for system evaluation.
Excerpt from the book
II. Physics Model Estimation
The AUV Model with its one input(Actuator Voltage) ,truth or physics model and its two outputs (Depth and Altitude) is presented in Fig.1. A. Non Linear Model Estimation The model is estimated using dynamics of the AUV which is given by, Fext = Fdrag + Fthr + Fhs (1) Where Fdrag is the drag force , Fthr is the thrust force, Fhs is the hydrostatic force or the net force on the AUV due to gravity and buoyancy. Let ρ be the density of water , η be the drag coefficient, A be the area of cross section and v be the vertical velocity then Fdrag is given by Fdrag = 1/2 Av^2ηρ (2) Let W be the weight of the AUV and B be the buoyant force on the AUV then Fhs is given by, Fhs = W − B (3) For calculating the mathematical model of the thruster load cell experiment was performed. The applied voltage versus the thrust measured by the load cell was plotted and an approximate mathematical relation was estimated given by, Fthr = 0.082(Cv−1.5)^2 (4) Where Cv is the control voltage or actuator voltage. As there are 2 vertical thrusters the actual thrust force will be 2(Fthr). Substituting (2), (3), (4) in (1) we get the non linear dynamic system equation as, mv̇ = 1/2 Av^2ηρ + 0.164(Cv−1.5)^2 + W − B (5) Where v is the instantaneous vertical velocity A is the area of the projection. η is the drag coefficient. ρ is the density of water. Cv is the control voltage. W is the Weight of the AUV. B is the Buyoant force on the AUV. As the AUV hull is of cylindrical shape as shown in Fig.2 the approximate area of projection will be A = 2rh, where r is the equivalent radius of the AUV and h is the equivalent height of the AUV.
Summary of Chapters
I. Introduction: Presents the concept of Hardware-in-the-loop (HIL) simulators and their application in testing complex autonomous underwater vehicles.
II. Physics Model Estimation: Details the mathematical modeling of the AUV's vertical motion, including thruster force, drag, and the impact of ocean currents.
III. HILS Control Parameters: Explains the various operational parameters, such as water current settings, geodetic positioning, and coordinate conversion.
IV. AUV HILS Graphical User Interface: Describes the features and functional controls of the developed GUI for managing the simulation process.
V. Conclusion and Future Work: Summarizes the simulator's capabilities and outlines future plans for depth control and horizontal thruster integration.
Keywords
Hardware-in-the-loop, HILS, Autonomous Underwater Vehicle, AUV, Mathematical modeling, Thruster dynamics, Graphical User Interface, Simulation, Ocean currents, Geodetic coordinates, Vertical motion, Control system, Dynamic model, Real-time testing, Data logging
Frequently Asked Questions
What is the primary focus of this paper?
The paper focuses on designing a Hardware-in-the-loop (HIL) simulator to test the vertical motion and dynamic behavior of an Autonomous Underwater Vehicle (AUV).
What are the central themes of the study?
The study centers on physical modeling of AUV dynamics, thruster performance, environmental simulation (ocean currents), and the development of a supporting software interface.
What is the primary research objective?
The objective is to provide an economical solution for testing AUV dynamic models by simulating complex underwater environments using real control-loop components.
Which scientific method is utilized?
The researchers use mathematical dynamic modeling (incorporating drag, buoyancy, and thrust forces) and implement these via a serial-based HIL system.
What aspects are covered in the main section?
The main sections cover the physics-based mathematical derivation of motion, control parameter configuration, and the architecture of the custom-built GUI.
Which keywords characterize this work?
Key terms include Hardware-in-the-loop, AUV, dynamic modeling, thruster dynamics, and GUI-based simulation.
How is the thruster model determined?
The thruster model is derived empirically through a load cell experiment, resulting in an approximate quadratic relationship between control voltage and thrust.
What role does the GUI play in the simulator?
The GUI allows for real-time control of simulation parameters, data logging, and visual observation of the AUV's vertical and horizontal trajectory.
- Quote paper
- Prateek Murgai (Author), 2014, Design of a Hardware in Loop Simulator for Vertical Motion of an Autonomous Underwater Vehicle Under Simulated Ocean Currents, Munich, GRIN Verlag, https://www.grin.com/document/282862
