scholarly journals New Volume Change Mechanism Using Metal Bellows for Buoyancy Control Device of Underwater Robots

ISRN Robotics ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Koji Shibuya ◽  
Sho Yoshii
Keyword(s):  
Phase Change ◽  
Volume Change ◽  
Control Method ◽  
Control Device ◽  
Paraffin Wax ◽  
Underwater Robots ◽  
Nichrome Wire ◽  
Change Mechanism ◽  
Metal Bellows ◽  
Buoyancy Control

We propose a new volume change mechanism using a metal bellows for a buoyancy control device of underwater robots and vehicles. Our proposed buoyancy control method utilizes the volume change caused by the phase-change of materials. We chose paraffin wax as a phase-change material because its volume change exceeds other candidates. Our proposed device consists of a metal bellows and an aluminum housing that contains paraffin wax and water. The paraffin wax is heated and cooled by a nichrome wire and a peltier device. We conducted two experiments and confirmed that the heat sink in the aluminum housing increases the speed of the buoyancy change and that the thickness of the air layer is crucial for efficient insulating. Then, we built a prototype robot with the four devices and confirmed that the robot can change its buoyancy up to its maximum value.

Depth Control of Underwater Robot with Metal Bellows Mechanism for Buoyancy Control Device Utilizing Phase Transition

2013 ◽  
Vol 25 (5) ◽  
pp. 795-803
Author(s):  
Koji Shibuya ◽  
◽  
Yukihiro Kishimoto ◽  
Sho Yoshii
Keyword(s):  
Phase Transition ◽  
Control Method ◽  
Control Device ◽  
Underwater Robot ◽  
Maximum Output ◽  
Depth Control ◽  
Metal Bellows ◽  
Control Devices ◽  
Target Depth ◽  
Buoyancy Control

The ultimate goal of this study is to develop a buoyancy control device that utilizes volume change due to phase transition of material between solid and liquid states. This paper describes the depth control method for an underwater robot fitted with the metal bellows buoyancy control devices that we have developed in this study. Four metal bellows buoyancy control devices are installed on an underwater robot. We first measured underwater robot buoyancy change and found that it agreed roughly with theoretical values. We then checked whether the robot could change buoyancy successively so that the robot rises or sinks as commanded. We then conducted a series of experiments on robot depth control in which if the robot depth is more than a certain distance different from the target depth, control devices are either heated or cooled at maximum output. If such a difference is within the threshold, proportional control is applied to develop output in proportion to the distance to the target depth. Experimental results showed that the underwater robot followed varied target depth with a steady-state deviation of a few cmor so, except in some cases of failure.

Buoyancy Control Device Enabled by Reversible Proton Exchange Membrane Fuel Cells for Fine Depth Control

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Jalal Yazji ◽  
Alicia Li Jen Keow ◽  
Hamza Zaidi ◽  
Luke T. Torres ◽  
Christopher Leroy ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Dynamic Model ◽  
Proton Exchange Membrane ◽  
Water Electrolysis ◽  
Control Device ◽  
Proton Exchange ◽  
Underwater Robots ◽  
Neutral Buoyancy ◽  
Depth Control ◽  
Buoyancy Control

Abstract Fine buoyancy control is essential for underwater robots to maintain neutral buoyancy despite dynamic changes in environmental conditions. This paper introduces a novel buoyancy control system that uses reversible fuel cells (RFC) as a mass-to-volume engine to change the underwater robots' buoyancy. The RFC uses both the water electrolysis process and fuel cell reaction to produce and consume gases in a flexible bladder for volume change. Unlike conventional actuators such as motors and pistons used in buoyancy control, this mechanism is silent, compact, and energy-efficient. A dynamic model that described the dynamics of the RFC-enabled buoyancy change is presented. Then, a proportional-derivative (PD) controller is designed to position the device at any depth underwater. A prototype device is built to validate the dynamic model and the performance of the feedback controller. Experimental results demonstrate a fine depth control performance with 4 cm accuracy and 90 s settling time. The compact buoyancy design is readily integrable with small underwater robots for fine depth change allowing the robots to save actuation energy.

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