Variability reduction in stencil printing of solder paste for surface mount technology

Competition in stencil printing to produce excellence in the finished product is intense. Faults in the printing process are a major source of board failure. Studies have shown that over 63% of defects identified after reDow originated from the solder paste printing ( A. Lotfi ,1998 ) . However. understanding these failures are a challenging problem as the printing process has a large number of non linearly dependent variables such as factors relating to paste (formulation. viscosity), the environment (temperature, humidity) and machine parameter (alignment, pressure and speed of squeegee, blade hardness etc). The process engineer is challenged to widen the process window so that future modifications to the process, such as the addition of a new component, can be achieved with little. if any, change in materials or process parameters. This thesis reports the effect of temperature and humidity variation from the manufacturing environment on the solder paste consistency and optimization of the essential parameters of squeegee pressure, squeegee speed. separation speed and print gap. The outcome of variation in temperature and humidity to the solder paste viscosity were analyzed and tests were done to determine the characteristic of the solder paste. The tests results indicate that the temperature and humidity has an impact on the solder paste printability. thus some attempts must be taken to control these variables. For parameter optimization. the analysis was carried out using statistical optimization. The main aim was to combine these parameters with three main pitch categories to produce the acceptable print formation. The results showed that. the ideal print result requires optimum statistical combinations of four parameters essentially related to a particular pitch. It is also shown that there is a diversity and contrasts of the combination of the parameters for each category of pitch. Detailed explanations as to the phenomenon are outlined in the thesis

A KINEMATICAL AND KINETICAL ANALYSIS ON THE SWING PHASE OF AMPUTEE GAIT

The authors investigated the swing phase of the transfemoral and transtibial amputees by using optical motion capture system. The thigh, shank foot were modeled as a three-linked rigid segment model. Kinematical parameters, such as joint angle, angular velocity/acceleration and linear acceleration of the center of mass were also calculated by the obtained coordinates of the anatomical landmark markers. Using the inverse dynamics, the kinetical parameters, such as the joint force and torque acting at each joint were calculated. The authors focused on the initiation of the swing phase caused by the force at both the hip and knee joints. In addition, the relationships between the internal/external rotation and the abduction/adduction of the lower extremity during the swing phase was also discussed in this study

Gait pattern detection for amputated prosthetic using fuzzy algorithm

Conventional gait rehabilitation treatment does not provide quantitative and graphical information on abnormal gait kinematics, and the match of the intervention strategy to the underlying clinical presentation may be limited by clinical expertise and experience. Amputated patient with prosthetic leg suffered with gait deviation due to variety causes commonly alignment and fitting problem. Gait analysis using wearable sensors is an inexpensive, convenient, and efficient manner of providing useful information for multiple health-related applications. The work included in this project focuses on developing a system to measure the angular displacement of human joint of lower part with patients having this problem and then applying gait phase detection using intelligent algorithm. The developed prototype has three inertial measurement units (IMU) sensor to measure and quantify body gait on thigh, shank and foot. The data from specific placement sensor on body part was evaluated and process in Arduino and MATLAB via serial communication. IMU provides the orientation of two axes and from this, it determined elevated position of each joint by using well established trigonometry technique in board to generate displacement angle during walking. The data acquired from the motion tests was displayed graphically through GUI MATLAB. A fuzzy inference system (FIS) was implementing to improve precision of the detection of gait phase from obtained gait trajectories. The prototype and FIS system showed satisfactory performance and has potential to emerge as a tool in diagnosing and predicting the pace of the disease and a possible feedback system for rehabilitation of prosthetic patients

Pattern classification of terrain during amputee walking

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 113-116).In this thesis I study the role of extrinsic (sensors placed on the body) versus intrinsic sensing (instruments placed on an artificial limb) and determine a robust set of sensors from physical and reliability constraints for a terrain adaptation in a robotic ankle prosthesis. Further, during this thesis I collect a novel data-set that contains seven able-bodied participants walking over 19 terrain transitions and 7 non-amputees walking over 9 transitions, forming the largest collection of transitions to date using an exhaustive set of sensors: inertial measurement units, gyroscopes, kinematics from motion capture, and electromyography from 16 sites on the lower limbs for non-amputee subjects and 9 sites or amputee subjects. This work extends previous work [3] by using more conditions, a larger subject group, and more sensors on amputees, and includes non-amputees.I present a novel machine learning algorithm that uses sensor data during rapid transitions from pre-foothold to just prior to post-foothold to predict different terrain boundaries. This advances the field of biomechatronics, our understanding of terrain adaptation in people both with and without amputations, contributes to the development of a fully terrain adaptive robotic ankle prosthesis, and improves the quality of life for the physically challenged. Specifically we set out to prove between pre and post-foothold the ankle and knee positions calculated using an IMU attached to an amputees powered prosthetic ankle can discriminate with greater than 99% accuracy between 9 conditions. Our results suggest that myography as a non-volitional sensing modality for terrain adaptive prostheses was not needed.by Matthew Todd Farrell.Ph.D

Analyse biomécanique des pieds SACH et Seattle-Light durant la locomotion chez les personnes âgées amputées du membre inférieur

In North America and Europe, the elderly represent the largest percentage of individuals with a below the knee amputation. The purpose of this thesis was to compare two types of prosthetic feet, the Solid Ankle Cushion Heel (SACH) foot and the Seattle Light (SEAT-L) foot in a group of elderly unilateral below knee amputees (EBKA) during walking at a natural cadence. Ten EBKA aged 70.4 « 9.5 years and 18 healthy elderly (HE) subjects aged 70.8 « 7.0 years participated in this study; selection criteria required that the EBKA demonstrate sufficient locomotor potential in order to benefit from the SEAT-L foot's energy return capability. The EBKA underwent an initial gait evaluation with the SACH foot, this was followed by an eight session gait retraining program specific to the SEAT-L foot. Upon completion of the gait program, the EBKA underwent a final gait evaluation with the SEAT-L foot. In order to serve as a reference group, the 18 HE subject's gait was also evaluated once."--Résumé abrégé par UMI

Techniques to Assess Balance and Mobility in Lower-Limb Prosthesis Users

abstract: Lower-limb prosthesis users have commonly-recognized deficits in gait and posture control. However, existing methods in balance and mobility analysis fail to provide sufficient sensitivity to detect changes in prosthesis users' postural control and mobility in response to clinical intervention or experimental manipulations and often fail to detect differences between prosthesis users and non-amputee control subjects. This lack of sensitivity limits the ability of clinicians to make informed clinical decisions and presents challenges with insurance reimbursement for comprehensive clinical care and advanced prosthetic devices. These issues have directly impacted clinical care by restricting device options, increasing financial burden on clinics, and limiting support for research and development. This work aims to establish experimental methods and outcome measures that are more sensitive than traditional methods to balance and mobility changes in prosthesis users. Methods and analysis techniques were developed to probe aspects of balance and mobility control that may be specifically impacted by use of a prosthesis and present challenges similar to those experienced in daily life that could improve the detection of balance and mobility changes. Using the framework of cognitive resource allocation and dual-tasking, this work identified unique characteristics of prosthesis users’ postural control and developed sensitive measures of gait variability. The results also provide broader insight into dual-task analysis and the motor-cognitive response to demanding conditions. Specifically, this work identified altered motor behavior in prosthesis users and high cognitive demand of using a prosthesis. The residual standard deviation method was developed and demonstrated to be more effective than traditional gait variability measures at detecting the impact of dual-tasking. Additionally, spectral analysis of the center of pressure while standing identified altered somatosensory control in prosthesis users. These findings provide a new understanding of prosthetic use and new, highly sensitive techniques to assess balance and mobility in prosthesis users.Dissertation/ThesisDoctoral Dissertation Biomedical Engineering 201