Showing papers by "Yonghua Chen published in 2010"

Flexion-relaxation ratio in sitting: application in low back pain rehabilitation.

Abstract: STUDY DESIGN: A multiple-comparative study between normal and low back pain (LBP) patients before and after rehabilitation. OBJECTIVE: To examine whether there is a change in flexion-relaxation phenomenon in sitting in LBP patient following a rehabilitation treatment. SUMMARY OF BACKGROUND DATA: There is an association between LBP and seated spine posture. Previous study has reported an absence of flexion-relaxation phenomenon in LBP patients during sitting. However, it is unknown whether there is a difference in flexion-relaxation phenomenon in sitting in LBP patients before and after rehabilitation treatment. METHODS: A total of 20 normal subjects and 25 chronic LBP patients who underwent a 12 weeks rehabilitation program were recruited. Surface electromyography recordings during upright sitting and flexed sitting were taken from the paraspinal muscles (L3) bilaterally from the normal subjects, and in the LBP patients before and after the rehabilitation treatment. The main outcome measures for patients include the visual analogue scale, Oswestry disability index, subjective tolerance for sitting, standing and walking, trunk muscle endurance, lifting capacity, and range of trunk motion in the sagittal plane. Flexion-relaxation phenomenon in sitting, expressed as a ratio between the average surface electromyography activity during upright and flexed sitting, was compared between normal and patients; and in LBP patients before and after rehabilitation. RESULTS: Flexion-relaxation ratio in sitting in normal subjects (Left: 6.83 +/- 3.79; Right: 3.45 +/- 2.2) presented a significantly higher (Left: P < 0.001; Right: P < 0.05) value than LBP patients (Left: 3.04 +/- 2.36; Right: 2.02 +/- 1.49). An increase in flexion-relaxation ratio in sitting was observed in LBP patients after rehabilitation (Left: 4.69 +/- 3.94, P < 0.05; Right: 3.58 +/- 2.97, P < 0.001), together with a significant improvement (P < 0.05) in subjective tolerance in sitting and standing, abdominal and back muscle endurance, lifting capacity, and range of motion. There were no significant changes in disability and pain scores, and subjective tolerance in walking. CONCLUSION: Flexion-relaxation ratio in sitting has demonstrated its ability to discriminate LBP patients from normal subjects, and to identify changes in pattern of muscular activity during postural control after rehabilitation.

Major Factors in Rapid Prototyping of Mechanisms

Abstract: Nowadays, layer based rapid prototyping (RP) technologies have been used not only to make product prototypes but also to manufacture small batch functional parts. For RP parts fabrication, build directions play an important role. There were many reports about optimal build directions for RP part fabrication, yet factors influencing build directions of mechanism joint have not been studied. This paper will look into the factors affecting build directions of mechanisms. A slider-crank mechanism is used as an example as it is the fundamental mechanism for many machine designs. Apart from factors affecting mechanism build directions, guidelines for mechanism joint design are also discussed.

Design and Rapid Fabrication of Non-assembly Mechanisms

Abstract: Layer based rapid fabrication technologies have seen rapid progress in recent years in terms of both material choices and part accuracy. Given the great progress, such technologies still have difficulties in meeting the accuracy requirements of functional parts such as mechanisms with joints. In mechanism fabrication, one of the critical factors is the joint clearance. With the limited accuracy of current layer based fabrication technologies, only mechanism joints with large clearance could be made. Thus how to reduce the joint clearance is a major research issue for layer based rapid fabrication of non-assembly mechanisms. In this paper, both joint design (revolute pin joint only) and process control will be analyzed in order to fabricate non-assembly mechanisms with a minimum joint clearance. In order to demonstrate the usefulness of non-assembly mechanisms, metal parts are fabricated by selective laser melting. Such parts have the strength that can stand the load in actual operations.

Selection of Build Orientation with Minimum Tensile Strain

Abstract: Parts built from rapid prototyping processes have heterogeneous properties in both geometric form and mechanical strength. Build orientation is one of the key factors that determine how such properties are distributed in the parts. In previous studies, the selection of build orientations for the shortest build time, the best part accuracy has been reported. This study aims to investigate how to determine the build orientation so that a part built in the orientation can be subjected to the same load with the minimum deformation or strain. In the research, the selective laser sintering (SLS) technique has been used to make the test specimens. The relationships between stress/strain against build orientations are obtained through tensile test experiments. Such relationships are modeled as mathematic equations which are used for the selection of the best build orientation so that parts built in such orientation will have minimum tensile strain when subjected to the same load pattern.

Topology Optimization of a Prosthetic Knee Joint Component

Abstract: In order to simulate the damping effect of cartilage at human’s knee joint, the component of a prosthetic knee joint is topology optimized as a compliant mechanism. After optimization, the component not only has the desired damping effect, but also has a lightweight structure, which is still capable of withstanding the prescribed loads. The SIMP (Solid Isotropic Material with Penalization) interpolation scheme for topology optimization is used here with OC (Optimality Criteria) method as optimizer. The optimization is implemented by a MATLAB code. A proof test by ANSYS has shown that the optimized component with Polyethylene Terephthalate (PET) as material has a displacement about 1.65 mm within constraints of material volume and strength.

Study on one-direction bendable articulated needle

Abstract: In minimally invasive surgery, steerable needle is needed to perform medical tasks in the deep of a human body In some cases, a one-direction bendable needle can satisfy actual needs Therefore, a one-direction bendable articulated needle is proposed in this paper The proposed needle consists of a beveltip head, articulations, and sections Articulations can only be bent along the tip direction Needle's structures are analyzed with different head lengths, section lengths, and bending angles of articulations Basic force analysis is performed to indentify the steering force and the force acting on an articulation Finally, basic steering analysis is performed to understand a needle's trajectory The proposed needle is more easily to be controlled to avoid obstacles in human body while insertion

Factors in Practical Manufacturability Analysis of Layer-Based Machining (LBM)

Abstract: In layer based machining (LBM), a part is sliced into thick layers, and each layer is shaped by 5-axis robot machining. Therefore, this technique is expected to have the merits of both layered manufacturing and CNC machining. As a new process, manufacturability analysis of LBM is carried out to determine whether a given part is suitable for LBM or not. This analysis is further studied based on supportability analysis and machinability analysis. Results of the manufacturability analysis are used for LBM process parameter selection and build orientation determination.

Kinematic analysis in femur fracture reduction

Abstract: Femur fracture is a frequently occurred injury and usually treated by surgeries. In order to overcome problems involved in the surgeries and improve the surgical operation efficiency, some researches on automated or semi-automated robot-assisted surgery have been carried out. Yet few literature reports on velocity and acceleration planning can be found. In this paper, two algorithms dealing with computation of acceleration are proposed and velocity is computed according to acceleration. The algorithms use information obtained from the surroundings to calculate acceleration. One algorithm evaluates risk of trauma induced by bone fragment motion, and the other one computes acceleration based on the information of reduction path and risk of inducing trauma. From the simulation results, velocity of bone fragment is slowed down reasonably and smoothly when the risk of inducing trauma is high. When the risk falls, meaning that the probability of trauma caused by bone fragment motion is low, moving velocity of bone fragment rises. These results have validated the performance of the proposed algorithms.

A Haptic Method for Conceptual Design of Multi-material Product

Abstract: Multi-material products are getting increasingly popular in recent years. Yet no systems have been developed to support the design of such products. In this paper, a haptic-based method for designing multi-material products is proposed. The proposed method consists of three main parts: haptic painting/marking, boundary smoothing/fitting, and volume decomposition. A prototype system based on the three parts has been implemented using a haptic input device. The haptic device provides an intuitive user interface for quick volume mark up in a multi-material product by direct mesh painting. Each painted region represents a material volume whose boundary can be automatically traced and smoothed. Based on the boundaries of painted regions, volume decomposition can be done automatically when needed. Each decomposed volume can be assigned a different material or color. The numerous iterations of volume mark up and decomposition in the early stage of multi-material product design can now be made easy and effective with the proposed method.

Selection of Build Orientation in FDM with Allowed Maximum Tensile Strain

Abstract: FDM is one of popular rapid prototyping methods. Build orientation of an object using FDM is usually determined by the object’s structure after considering build feasibility, build efficiency, and build accuracy. In this paper, a novel object build orientation selection method in FDM is proposed based on the tensile strain of an object to be built. Test specimens with different build orientations are built with FDM to investigate the relationship between build orientation and allowed maximum tensile strain through tensile test experiments. Based on the relationship, golden section search is employed to determine the build orientation of an object consisting of multi-parts in order to get allowed maximum tensile strain. The build orientation of a truss is determined with the proposed method to verify its feasibility and reliability with satisfied results.