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Soft robot with new pneumatic rubber actuators for medical assisting device

Ribuan , Mohamed Najib (2016) Soft robot with new pneumatic rubber actuators for medical assisting device. PhD thesis, Okayama University, Japan.


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Soft robots came into focus after for a long time the coexistence between human and conventional robot has never been an achievement. Unlike hard robot, soft robot has the potential to be more adaptable, capable, and safer devices especially in conditions where the robot has a close contact with human in unstructured environment such as in homes, offices, and public places. However, actuating soft robot is a challenging task as any rigid mechanism and electrical motor will impair the soft and safe characteristics of the robot. Therefore, pneumatic and/ or fluidic type of actuation became common for robot operation. Basically, the motion generated from soft material such as rubber and silicone, is by the deformation of the soft structure when pneumatic pressure is applied. Only 1 and/ or 2 degree of freedom (DOF) can be achieved through this soft actuator mechanism. Nevertheless, to produce a significant motion of actuation, large deformation is necessary resulting a slow and rough movement if such actuators are to be employed in soft robot as a means of locomotion. In this research, a novel mechanism of fast response and an omnidirectional soft actuator is proposed. The actuators serve as soft robot legs with 6 DOFs for omnidirectional, smooth and precise locomotion ability. One interesting application of such soft robot; and taking the advantage of transparence characteristic of silicone material, is in fluoroscopy examination. In this examination, an X-ray is used to scan a small lesion and polyps inside stomach as an early detection of stomach cancer. Due to shrinking nature of stomach, it has to be compressed from an external force in order to expose any concealed lesion. Normally, radiologist used a commercialized compression paddle and folded towel as an assisting medical device, positioned manually under the patient stomach to give a pressure to the stomach. The adjustment of the device is bothersome to the patient and here the soft robot has the opportunity to be employed and operated remotely without being detected by the X-ray image. The development of soft actuator as pneumatic rubber leg for our robot begins with the idea, operating principle and the design of the leg. The design parameters were identified and simulation was conducted to achieve the optimum design from the construction of the leg. For elastomeric material simulation, Finite Element Analysis (FEA) was employed with several prototype designs were simulated until the optimum results is achieved for the specific design parameters. In addition, simulation works provides better understanding of the leg motion and any modification can possibly be made before fabrication of the prototype. Then, the fabrication of the prototype took place based on the optimum results obtained in the simulation works. Computer Aided Design (CAD) was used to design the leg and silicone molds of the leg. The information in CAD was then used in Computer Aided Manufacturing (CAM) for rapid prototyping and the silicone mold was produced using polyester resin plate. Two-component Room Temperature Vulcanizing (RTV) silicone rubber were used to produce the rubber leg where the process involves mixing of the silicone material, bubble elimination, and heating. Since the fabrication of the leg was layer by layer, the assembly of the layer was done before tubes were connected to the chambers inside the leg. The leg prototype was then tested in experimental works in order to achieve the characteristics of the leg prototype. Leg displacement and deflection in vertical, sideway and diagonal direction were measured with different pressure ranging from 0 to 150 kPa. The results were compared with simulation works and show an agreement between the experiment and simulation data thus validating the static analysis characteristics of the leg. In addition, force generated from the deflection in sideway and diagonal direction was also measured using force gauge to identify leg ability in climbing a slope, a condition that may require the robot to perform during the fluoroscopy examination. An achievement in establishing the leg prototype and its characteristic led to the design of soft robot. Eight legs were arranged in square to form a square-shaped walking soft robot without a leg at the center as the center leg will provide unnecessary analysis during locomotion. The locomotion gait was identified to generate a thrusting force for robot movement. Four stages of locomotion gait was achieved and corresponding pressurized chambers were identified in order to control the pneumatic valve for locomotion direction. The information is crucial in developing the programming of valve activation that dictates the direction of robot locomotion. Furthermore, locomotion pattern were decided where the legs were categorized into two groups in order to achieve static stability locomotion. Afterwards, the development of soft robot that involve fabrication and control system setup were accomplished. The fabrication process was principally the same as in the fabrication of leg prototype. However, the new molds were produced as the soft robot was fabricated in one complete unit instead of combining each single leg together as it was time consuming and energy wasting. Forty pneumatic valves were used to control the pressure to the chambers

Item Type: Thesis (PhD)
Subjects: T Technology > TJ Mechanical engineering and machinery > TJ210.2-211 Mechanical devices and figures. Automata. Ingenious mechanisms.
Depositing User: Mr. Mohammad Shaifulrip Ithnin
Date Deposited: 13 Aug 2018 03:27
Last Modified: 13 Aug 2018 03:27
URI: http://eprints.uthm.edu.my/id/eprint/10257
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