Dynamic Analysis of Transfemoral Prosthesis Function using Finite Element Method

芝浦工業大学2019年

Kinematic and Dynamic Model Analysis for An Improved Design of Home-Based Wearable Lower Limb Rehabilitation Robot

This paper presents the analysis of the kinematic and dynamic modeling of a wearable lower-limb robot (WLLR) for home-based applications. SOLIDWORKS software was utilized, and the concept of modular configuration was adopted into the design. The Denavit Hartenberg (DH) and geometric methods were employed to obtain the theoretical of forward and inverse kinematics models respectively. The Lagrangian formulation of the kinetic and potential energy method was selected to derive the joint torque equation. For validation, MATLAB Robotic ToolBox was utilized to simulate forward and inverse kinematic behaviour of the WLLR while MATLAB SimMechanics was used to investigate the maximum torque for the hip and knee joint in various ranges of motion (ROM) and walking conditions. The results showed a strong agreement of the simulation and the theoretical model for the forward and inverse kinematic of WLLR. The torque required for the hip and knee joints in walking conditions was less than the torque required in various ranges of motion. The maximum torque recorded at the hip and knee in ROM condition is 74.73 Nm and 15.05 Nm respectively while the maximum torque recorded for the hip and knee in the walking condition is 55.00 Nm and 11.01 Nm respectively. This analysis is essential as a basis for further actuator selection and control system development

Considering the effects of a cross-arm on a contaminated polymer insulator at different angles

This paper considers the effects of a cross-arm on a contaminated polymer insulator at different angles (90°, 60° and 45°) with negative and positive impulses. An experiment was conducted using a 10 kV polymer insulator that was contaminated with 4 % salt (a mixture of distilled water and sodium chloride). From the experiment, the behaviour of the voltage breakdown and leakage current of the contaminated insulator positioned at different angles from the cross-arm was evaluated under different impulse polarities. The results show that the values of the breakdown voltage and leakage current decrease with angle when using the 90° angle as a reference. The reason for this study into the effects of the cross-arm on a contaminated polymer insulator is because in the real case, when the insulators are installed on an angle tower, the forces or tensions due to the weather conditions (especially under strong winds) and from the distribution lines themselves will force the installed insulators to be tilted from its original 90° angle position

Considering the effects of a RTV coating to improve electrical insulation against lightning

One of the factors that cause power outages on distribution lines is being struck by lightning. Cloud to ground lightning often affects overhead distribution lines and can occur with negative or positive polarities. It can affect the performance of insulators and cause power line failure. Furthermore, outdoor polymer insulators are exposed to extreme weathering and pollution, which can cause chemical changes in the material properties and further leads to material degradation. These can cause a reduction in the insulator withstand capabilities and may lead to flashover. This paper investigates the effects of a RTV (room temperature vulcanisation) coating on a 10 kV polymer insulator in order to improve the electrical insulation performance against a lightning impulse under clean and polluted conditions. The up and down test method was used to evaluate the withstand voltage capabilities of an RTV coated polymer insulator. For reference, the withstand voltage for a basic setting polymer insulator was measured for comparison

Development of an Evaluation System for Magnetic Resonance Imaging Based Three-Dimensional Modeling of a Transfemoral Prosthetic Socket Using Finite Elements

Recent technologies have suggested the utilization of three-dimensional (3D) printingtechnology to enhance the fabrication accuracy of prosthetics. Accordingly, simulations are used toobtain precise parameters for subject-specified prosthetic socket. This study proposes an evaluationsystem to measure the accuracy of a subject-specific 3D transfemoral residuum model duringthe interaction with the socket in conjunction with the application of finite element methods.The proposed system can be used in future validations of socket fabrication. The evaluation isbased on the measurement of the residuum’s soft tissue deformation inside two types of prostheticsockets. In comparison with other studies, the 3D models were constructed with magnetic resonanceimages (MRI) with the aid of computer-aided design (CAD) software. The measurement of soft tissuedeformation was conducted based on the measurement of the volumetric value of fat, muscle andskin in the pre- and post-donning phases. The result yielded a promising correlation coefficient valuebetween the simulation and the experiment in the soft tissue deformation evaluation. The relationof the muscle–fat ratio in the residuum is extremely important in the determination of the abilityof the prosthetic to deform. The environment during the socket fitting session was similar to thatdefined by the set boundary conditions in simulations. In view of the promising results of thisstudy, the evaluation system proposed herein is considered reliable and is envisaged to be used infuture research

Considering the effect of angle on polymer insulator performance under wet condition

This paper reviews a study of the inclination angle of an insulator due to mechanical forces imposed by overhead conductors. The angle theoretically shortens the effective leakage path and flashover distance of the insulator, thus change the electrical performance of the insulator. To take it into consideration, this study had focused on experimental works to investigate effect of insulator inclination to the breakdown voltage and leakage current. Regards to the important of wetness to improve surface conductivity of insulator surface, authors have considered to conduct the test in wet conditions. In addition, standard lightning voltage was applied according to IEC 60060 in both positive and negative impulses. Based on the test, the performance of an insulator under positive and negative impulses was compared accordingly. A significant reduction of breakdown voltage was recorded when the angle decreased. The reduction was recorded as high as 17 %. Meanwhile, the breakdown voltage was much higher under negative impulses compared to positive impulses which showed a difference of 12 % to 14 % and the leakage current increased by 17 % due to the inclination angle. The calculation of U50 with consideration of the reduction factor was suggested and briefly discussed

Evaluation of electromagnetic fields on polluted polymer insulator under lightning impulse current

This paper presents a simulation study of a polluted insulator under a direct lightning impulse current. The pollution condition was considered and divided into two cases which are partial and full pollution. Under those conditions, the electromagnetic profiles of the insulator were evaluated. In the study, six points of measurement recognised as the weak points of the insulator were introduced to be evaluated. Meanwhile the electric field and magnetic field values at the points were related to the common discharge and damage of polymer insulators. It was found that the pollution condition effectively influenced the electric field and magnetic field profile. A significant difference in the electric field value indicated at least 65.15 % in both cases. For the magnetic field, at least a 10.9 % percentage difference was recorded

Development of Cleaning Device for In-pipe Robot Application

AbstractPipelines are essential tools for transporting water, oils, gases and sewer from one place to another. Pipelines are used to interconnect networks from one station to another that involved various diameter sizes and fittings to compensate intended directions. There are many issues that influenced performance of the pipelines namely aging, corrosion, cracks and use to clog up with debris, or sediments after long use. There are number of methods available to clean the inside of the closed pipeline namely traditional method like boiling, picking, alcohol and salt and cleaning kits, or tools kits such as wire and plunger or large-gauge snake. However, all the methods can over-stress older pipeline and cause leaks that make even more extensive repair procedures needed to fix the problem. Chemical fluid for pipe cleaning is also not suitable to all types of pipeline because the chemical can erode the pipe wall. Currently, service robot is the best solution that purposely developed to facilitate humans being activities including cleaning, inspection for cracks or repairing damage in pipeline. This paper intends to report about the development of cleaning device for in-pipe robot application. The development covers both software and hardware of the device. Significant experiment has been designed to validate the function of the device. It is proof that the device has successfully clean the soft and moderate clog. The success of the cleaning device can be attached to the in-pipe robot and the outcome is expected to assist pipeline cleaning operations. Thus, enable the pipelines to transport efficiently with minimum cost of operation

Effect of RTV coating material on electric field distribution and voltage profiles on polymer insulator under lightning impulse

Lightning has been known as one of major factors that cause power line failure in Malaysia. Presence of contaminants on polymer insulator surface will reduce voltage withstand capabilities in the event of lightning and could lead to insulator failure or worst power line disruptions. This paper presents a study on effects of Room Temperature Vulcanisation (RTV) coating material in order to improve electrical performances of polymer insulator and its effect towards electric field distribution and voltage profile. This study involves both experimental and simulation works. For experimental works, polymer insulator is tested inside fog chamber and voltage breakdown under lightning impulse were evaluated for clean and salt conditions. 3-Dimensional model of polymer insulator were simulated using ANSYS Maxwell and electric field distribution and voltage profile were evaluated. From the study, it shows that RTV coating material helps to improve voltage breakdown level of insulator and reduce concentration of electric field at triple region

Collision Free Control of Variable Length Hyper Redundant Robot Manipulator

Hyper-redundant robot (HRR) manipulators are useful at navigating convoluted paths, but conventionally complicated to control. The control of a hyper-redundant manipulator is complex due to its redundancy. In this paper, a simple but effective control algorithm for obstacle avoidance is proposed. The algorithm derives a collision free path around known obstacles so that the end-effector of a variable length hyper redundant robot (VHRR) is able to reach the target location following the path without hitting the obstacles. The algorithm can be grouped into two tasks to drive the endeffector along the collision free trajectories: first, solve the inverse kinematics without disregarding the existence of obstacles in the system; and second, fit the manipulator to the respective prescribe trajectories. This method has the capability to allow VHRR maneuver within its workspace without penetrating to the neighboring obstruction. Further, this method is very effective in the sense that it forms a nice coil profile avoiding zig-zag configuration, and thus eliminates sharp turn on the robot. The performance of a VHRR was tested through simulation to demonstrate the effectiveness of the proposed method. The approach succeeded in delivering the path that avoids obstacle