9 research outputs found
A GAIN-SCHEDULED CONTROL SCHEME FOR IMPROVED MANEUVERABILITY AND POWER EFFICIENCY OF UNDERWATER GLIDERS
Underwater gliders are a relatively new type of low-power, long duration underwater
vehicle that use changes in buoyancy to propel themselves forward. They are widely
used today for oceanographic research, and a number of theoretical control schemes
have been derived over the years. However, despite their nonlinear dynamics that
evolve as a function of their environment and operating conditions, most fielded
gliders use linear control methods, such as static-gain proportional-integral (PI) or
proportional-integral-derivative (PID) compensators for motion control, which can
significantly limit vehicle performance.
This thesis develops an alternative approach to underwater glider control that employs
control system gain-scheduling to improve vehicle performance and efficiency over a
wider range of operating conditions as compared to static or fixed-gain approaches. The
primary contribution of this thesis is the development of a practical gain-scheduling
procedure using linearized models of the decoupled pitch and yaw dynamics of the
vehicle. This methodology improves on the current fixed-gain topologies used on
fielded gliders today, while being straightforward and cost-effective to implement.
In this thesis, the development of a nonlinear dynamical model of a Slocum glider using
computer-aided design (CAD) and computational fluid dynamics (CFD) simulations
was also carried out to support the high-fidelity characterization of the controller
topologies. A nonlinear numerical simulation of the Slocum glider was developed in Matlab and was used to assess the performance improvements and the increased
robustness of the gain-scheduled PID method to a standard fixed-gain PID approach
Variable Gain Super Twisting Sliding Mode Control (VGSTW) application in longitudinal plane of Autonomous Underwater Glider (AUG)
904-913This paper presents a robust control design using variable gain super twisting sliding mode control application in
Autonomous Underwater Glider (AUG). AUGs are known as underactuated systems and very nonlinear in nature make
difficult to control. The controller is designed for longitudinal plane of an AUG that tracks the pitching angle and net
buoyancy of a ballast pump for nominal system, system in existence of external disturbance and parameter variations in
hydrodynamic coefficients. The Lyapunov stability theorem has proved that the proposed control law is satisfied the
stability sufficient condition. The simulation results have shown that the proposed controller has improved the transient
response, reduced steady error and chattering effects in control input and sliding surface in all cases
Variable Gain Super Twisting Sliding Mode Control (VGSTW) application in longitudinal plane of Autonomous Underwater Glider (AUG)
This paper presents a robust control design using variable gain super twisting sliding mode control application in Autonomous Underwater Glider (AUG). AUGs are known as underactuated systems and very nonlinear in nature make difficult to control. The controller is designed for longitudinal plane of an AUG that tracks the pitching angle and net buoyancy of a ballast pump for nominal system, system in existence of external disturbance and parameter variations in hydrodynamic coefficients. The Lyapunov stability theorem has proved that the proposed control law is satisfied the stability sufficient condition. The simulation results have shown that the proposed controller has improved the transient response, reduced steady error and chattering effects in control input and sliding surface in all cases
Time-optimal trajectory and robust adaptive control for hybrid underwater glider
The undersea environment is generally still a mystery for the human race, although it has been with us for a long time. To explore under the sea, the underwater glider is the efficient equipment capable of sustainable operation for several months. For faster and longer duration performance, a new design of underwater glider (UG) shaping ray type is proposed. To have the shortest settling time, a new design of time-optimal trajectory (TOT) for controlling the states of the ray-type hybrid underwater glider (RHUG) is proposed. And for the stable flight control, a robust adaptive controller is designed for the RHUG with unknown parameters and environmental disturbances.
The heading dynamics of the RHUG is presented with linear and quadratic damping. A closed form solution of the heading dynamics is realized for designing the time-optimal trajectory. The conventional and super-twisting sliding mode control will be constructed for tracking this trajectory. The tracking performance considering the disturbance effect will be discussed in simulations. For identification of unknown parameters of the system, the adaptive control is designed and implemented by the heading experiment.
The RHUG uses the net buoyancy force for gliding under the water, so the depth control is essential. In this dissertation, a robust control algorithm with TOT will be carried out for the heaving motion using a hybrid actuation of the buoyancy engine and the propeller. The net buoyancy force with a constant rate is generated by the buoyancy engine for both descending and ascending motion. And the second actuator for the depth control is the propeller with quick response in producing thrusting force. To apply the robust control with TOT, the control input is designed for the buoyancy engine and thruster individually. And finally, the robust control with TOT using the buoyancy engine and thruster is simulated with consideration of external disturbances.
When the RHUG is the underactuated system, a robust adaptive control is designed for the RHUG dynamics based on Lyapunov’s direct method using the backstepping and sliding mode control techniques. The performance of this controller is simulated for gliding motion and depth control with unknown parameters and bounded disturbances.Contents
Contents i
List of Tables iv
List of Figures v
Chapter 1. Introduction 1
1.1. Hybrid underwater glider 1
1.2. Time-optimal trajectory 4
1.3. Nonlinear control design 5
Chapter 2. Dynamics of RHUG 8
2.1 Dynamics of underwater vehicles 8
2.2 Design of RHUG platform 11
2.2.1 Hull design 11
2.2.2 Buoyancy engine and mass-shifter 12
2.2.3 Battery 13
2.2.4 Sensors 14
2.2.5 Assembly 16
2.3 Dynamics of RHUG 17
2.4 Hydrodynamic coefficients 19
2.5 Thruster modeling 21
2.6 Buoyancy engine modeling 22
2.7 Mass-shifter modeling 23
Chapter 3. Time-optimal trajectory with actuator saturation for heading control 25
3.1 Time-optimal trajectory 25
3.2 Heading motion 25
3.3 Analytic solution of heading dynamic equation 26
3.3.1 Right-hand direction 29
3.3.2 Left-hand direction 36
3.4 Time-optimal trajectory 42
3.5 Super-twisting sliding mode control 44
3.6 Computer simulation 46
3.6.1 Simulation 1 46
3.6.2 Simulation 2 47
3.6.3 Simulation 3 49
Chapter 4. Time-optimal trajectory for heaving motion control using buoyancy engine and propeller individually 51
4.1. Heave dynamics and TOT 51
4.2. Analytical solution of heave dynamics with buoyancy and thruster force individually 54
4.2.1 First segment with positive rate 54
4.2.2 Second segment with maximum input 55
4.2.3 Third segment with constant velocity 56
4.2.4 Fourth segment with negative rate 57
4.2.5 Fifth segment with minimum input 58
4.3. Time-optimal trajectory for depth motion 59
4.3.1 Find z1, w1 and w1 59
4.3.2 Find t2, z2, w2 and w2 61
4.3.3 Find w3, z4 and w4 62
4.3.4 Find z3, t3 and t4 63
4.3.5 Find α and t5 64
4.4. Sliding mode control for heave dynamics 64
4.5. Computer simulation 66
4.5.1. Simulation 1 66
4.5.2. Simulation 2 69
Chapter 5. Experimental study of direct adaptive control along TOT for heading motion 72
5.1. Motivation 72
5.2. Composition of RHUG 73
5.3. Robust adaptive control for heading dynamics 77
5.4. Computer simulation 79
5.5 Experiment 82
5.5.1 First experiment with k1=2.5,k2=30 82
5.5.2 Second experiment with k1=2,k2=30 83
5.5.3 Third experiment with k1=2,k2=50 85
Chapter 6. Robust adaptive control design for vertical motion 89
6.1. Dynamics of vertical plane 89
6.2. Adaptive sliding-mode control for pitch motion 91
6.3. Adaptive sliding-mode control for surge motion 93
6.4. LOS and PI depth-keeping guidance 95
6.5. Computer simulation 97
6.5.1 Simulation 1 97
6.5.2 Simulation 2 104
Chapter 7. Conclusion 111
Reference 113Docto
Underwater Vehicles
For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties
Autonomous Vehicles
This edited volume, Autonomous Vehicles, is a collection of reviewed and relevant research chapters, offering a comprehensive overview of recent developments in the field of vehicle autonomy. The book comprises nine chapters authored by various researchers and edited by an expert active in the field of study. All chapters are complete in itself but united under a common research study topic. This publication aims to provide a thorough overview of the latest research efforts by international authors, open new possible research paths for further novel developments, and to inspire the younger generations into pursuing relevant academic studies and professional careers within the autonomous vehicle field
Development of Robust Control Strategies for Autonomous Underwater Vehicles
The resources of the energy and chemical balance in the ocean sustain mankind in many ways. Therefore, ocean exploration is an essential task that is accomplished by deploying Underwater Vehicles. An Underwater Vehicle with autonomy feature for its navigation and control is called
Autonomous Underwater Vehicle (AUV). Among the task handled by an AUV, accurately positioning itself at a desired position with respect to the reference objects is called set-point control. Similarly, tracking of the reference trajectory is also another important task. Battery recharging of AUV, positioning with respect to underwater structure, cable, seabed, tracking of reference trajectory with desired accuracy and speed to avoid collision with the guiding vehicle in the last phase of docking are some significant applications where an AUV needs to perform
the above tasks. Parametric uncertainties in AUV dynamics and actuator torque limitation necessitate to design robust control algorithms to achieve motion control objectives in the face of uncertainties. Sliding Mode Controller (SMC), H / μ synthesis, model based PID group controllers are some of the robust controllers which have been applied to AUV. But SMC suffers from less efficient tuning of its switching gains due to model parameters and noisy estimated acceleration states appearing in its control law. In addition, demand of high control effort due to high frequency chattering is another drawback of SMC. Furthermore, real-time implementation of H / μ synthesis controller based on its stability study is restricted due to use of linearly approximated dynamic model of an AUV, which hinders achieving robustness. Moreover, model based PID group controllers suffer from implementation complexities and exhibit poor transient and steady-state performances under parametric uncertainties. On the other hand model free
Linear PID (LPID) has inherent problem of narrow convergence region, i.e.it can not ensure convergence of large initial error to zero. Additionally, it suffers from integrator-wind-up and subsequent saturation of actuator during the occurrence of large initial error. But LPID controller
has inherent capability to cope up with the uncertainties. In view of addressing the above said problem, this work proposes wind-up free Nonlinear PID with Bounded Integral (BI) and Bounded Derivative (BD) for set-point control and combination of continuous SMC with Nonlinear PID with BI and BD namely SM-N-PID with BI and BD for trajectory tracking.
Nonlinear functions are used for all P,I and D controllers (for both of set-point and tracking control) in addition to use of nonlinear tan hyperbolic function in SMC(for tracking only) such that torque demand from the controller can be kept within a limit. A direct Lyapunov analysis is pursued to prove stable motion of AUV. The efficacies of the proposed controllers are compared with other two controllers namely PD and N-PID without BI and BD for set-point control and PD plus Feedforward Compensation (FC) and SM-NPID without BI and BD for tracking control.
Multiple AUVs cooperatively performing a mission offers several advantages over a single AUV in a non-cooperative manner; such as reliability and increased work efficiency, etc. Bandwidth limitation in acoustic medium possess challenges in designing cooperative motion control
algorithm for multiple AUVs owing to the necessity of communication of sensors and actuator signals among AUVs. In literature, undirected graph based approach is used for control design under communication constraints and thus it is not suitable for large number of AUVs participating in a cooperative motion plan. Formation control is a popular cooperative motion control paradigm. This thesis models the formation as a minimally persistent directed graph and
proposes control schemes for maintaining the distance constraints during the course of motion of entire formation. For formation control each AUV uses Sliding Mode Nonlinear PID controller with Bounded Integrator and Bounded Derivative. Direct Lyapunov stability analysis in the
framework of input-to-state stability ensures the stable motion of formation while maintaining the desired distance constraints among the AUVs
Actas de las XXXIV Jornadas de Automática
Postprint (published version