Variable Buoyancy or Propeller-Based Systems for Hovering Capable Vehicles: An Energetic Comparison

This paper develops a systematic method to assess the suitability of buoyancy control systems to different mission profiles, risk acceptance thresholds and environmental sensitivities. We analyse various existing variable buoyancy engines (VBE) for different platforms and mission profiles. Our results identify a capability gap for low-energy seafloor survey platforms such as the Lagrangian imaging float that conduct most of their buoyancy control manoeuvres at depth and rely on end of missions recovery for data extraction. Based on these requirements, we introduce a novel VBE concept that uses the energy mechanically stored in a pre-tensioned spring to passively surface in the event of power loss and reduce power consumption when changing buoyancy at depth. The equations to size the pre-tensioning spring are developed and simulations are performed to demonstrate the reduced power consumption at depth. Unlike safety systems that use drop weights, the pre-tensioned VBE minimises environmental impact by achieving net positive buoyancy without leaving anything behind in the environment.

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“…VBEs can be classified based on the energy transformation they use to displace water from a floodable volume [5] as follows:…”

Section: Problem Formulationmentioning

confidence: 99%

“…• The remaining available compression length of the spring is sufficient for the required volume change to be achieved. The force needed to move the piston at depth is defined by equation (5).…”

Section: A Spring Sizingmentioning

confidence: 99%

Development of a passively pre-tensioned buoyancy engine for fail-safe underwater vehicle operation

Rolfe

Thomton

Massot-Campos

2020

2020 IEEE/OES Autonomous Underwater Vehicles Symposium (AUV)(50043)

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“…Electromechanical systems rely on linear actuators to move the piston to change the buoyancy of the system, and the construction is straightforward to integrate (Ranganathan et al , 2015). In Ranganathan and Thondiyath (2016), Carneiro et al (2020) and Masmitjà et al (2014), VBS modules with linear actuator units as the power source are designed, but the module space utilization is poor and a single linear actuator is prone to leakage due to uneven force during operation. Furthermore, these studies neither included extensible designs nor investigated the regulation performance of the VBS at different depths.…”

Section: Introductionmentioning

confidence: 99%

Design and extensibility analysis of a variable buoyancy system for small autonomous underwater vehicles

Xia,

Li,

Zang

et al. 2024

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Purpose A switching depth controller based on a variable buoyancy system (VBS) is proposed to improve the performance of small autonomous underwater vehicles (AUVs). First, the requirements of VBS for small AUVs are analyzed. Second, a modular VBS with high extensibility and easy integration is proposed based on the concepts of generality and interchangeability. Subsequently, a depth-switching controller is proposed based on the modular VBS, which combines the best features of the linear active disturbance rejection controller and the nonlinear active disturbance rejection controller. Design/methodology/approach The controller design and endurance of tiny AUVs are challenging because of their low environmental adaptation, limited energy resources and nonlinear dynamics. Traditional and single linear controllers cannot solve these problems efficiently. Although the VBS can improve the endurance of AUVs, the current VBS is not extensible for small AUVs in terms of the differences in individuals and operating environments. Findings The switching controller’s performance was examined using simulation with water flow and external disturbances, and the controller’s performance was compared in pool experiments. The results show that switching controllers have greater effectiveness, disturbance rejection capability and robustness even in the face of various disturbances. Practical implications A high degree of standardization and integration of VBS significantly enhances the performance of small AUVs. This will help expand the market for small AUV applications. Originality/value This solution improves the extensibility of the VBS, making it easier to integrate into different models of small AUVs. The device enhances the endurance and maneuverability of the small AUVs by adjusting buoyancy and center of gravity for low-power hovering and pitch angle control.

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“…It also allows the angle of attack of the vehicle in horizontal motion to be reduced, thus reducing drag and increasing horizontal propeller efficiency [5]. Moreover, it has been recently shown [6] that the use of BCMs is significantly beneficial in hovering tasks compared to the use of vertical propellers, even for relatively small depths and mission lengths. The use of BCMs has, however, some drawbacks, namely regarding the maneuverability of the vehicle.…”

Section: Introductionmentioning

confidence: 99%

“…The most common ones are linear electric drives using seawater as working fluid [8][9][10][11][12] and hydraulic pumping systems [13][14][15][16]. A description of more particular solutions involving the use of pneumatic, thermal and hybrid solutions can be found in [6,17]. Hydraulic solutions typically lead to more compact devices than exclusively electric ones but are, however, less efficient at shallower depths (up to 100 m) due to the high relative weight of mechanical friction losses at low pressures [6].…”

Section: Introductionmentioning

confidence: 99%

Design and Experimental Tests of a Buoyancy Change Module for Autonomous Underwater Vehicles

2022

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Ocean exploration is of major importance for several reasons, including energy and mineral resource retrieval, sovereignty, and environmental concerns. The use of autonomous underwater vehicles (AUV) has thus been receiving increased attention from the scientific community. In this context, it has been shown that the use of buoyancy change modules (BCMs) can significantly improve the energy efficiency of an AUV. However, the literature regarding the detailed design of these modules is scarce. This paper contributes to this field by describing the development of an electromechanical buoyancy change module prototype to be incorporated into an existing AUV. A detailed description of the constraints and compromises existing in the design of the device components is presented. In addition, the mechanical design of the hull based on FEM simulations is described in detail. The prototype is experimentally tested in a shallow pool where its full functionality is shown. The paper also presents preliminary experimental values of the power consumption of the device and compares them with the ones provided by existing models in the literature.

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Variable Buoyancy or Propeller-Based Systems for Hovering Capable Vehicles: An Energetic Comparison

Cited by 8 publications

References 31 publications

Development of a passively pre-tensioned buoyancy engine for fail-safe underwater vehicle operation

Development of a passively pre-tensioned buoyancy engine for fail-safe underwater vehicle operation

Design and extensibility analysis of a variable buoyancy system for small autonomous underwater vehicles

Design and Experimental Tests of a Buoyancy Change Module for Autonomous Underwater Vehicles

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