• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.6
• /
• pp.518-523
• /
• 2015

This paper proposes a gait phase classifier using a Recurrent Neural Network (RNN). Walking is a type of dynamic system, and as such it seems that the classifier made by using a general feed forward neural network structure is not appropriate. It is known that an RNN is suitable to model a dynamic system. Because the proposed RNN is simple, we use a back propagation algorithm to train the weights of the network. The input data of the RNN is the lower body's joint angles and angular velocities which are acquired by using the lower limb exoskeleton robot, ROBIN-H1. The classifier categorizes a gait cycle as two phases, swing and stance. In the experiment for performance verification, we compared the proposed method and general feed forward neural network based method and showed that the proposed method is superior.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.48 no.9
• /
• pp.1140-1146
• /
• 1999

In this paper, a force estimation method is proposed for force control without force sensor. For this , a disturbance observer is applied to each joint of an {{{{ { n}_{ } }}}} degrees of freedom manipulator to obtain a simple equivalent robot dynamics(SERD) being represented as an n independent double integrator system. To estimate the output of disturbance observer due to internal torque, the disturbance observer output estimator(DOOE) is designed, where uncertain parameters of the robot manipulator are adjusted by the gradient method to minimize the performance index which is defined as the quadratic form of the error signal between the output of disturbance observer and that of DOOE. when the external force is exerted, the external force is estimated by the difference between the output of disturbance observer and DOOE, since output of disturbance observer includes the external torque signal as well as the internal torque estimated by the output of DOOE. And then, a force controller is designed for force feedback control employing the estimated force signal. To verify the effectiveness of the proposed force estimation method, several numerical examples and experimental results are illustrated for the 2-axis direct drive robot manipulator.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.5
• /
• pp.2346-2362
• /
• 2016

As one of the most important issues in computer vision and image processing, online object tracking plays a key role in numerous areas of research and in many real applications. In this study, we present a novel tracking method based on the proposed structured sparse representation model, in which the tracked object is assumed to be sparsely represented by a set of object and background templates. The contributions of this work are threefold. First, the structure information of all the candidate samples is utilized by a joint sparse representation model, where the representation coefficients of these candidates are promoted to share the same sparse patterns. This representation model can be effectively solved by the simultaneous orthogonal matching pursuit method. In addition, we develop a tracking algorithm based on the proposed representation model, a discriminative candidate selection scheme, and a simple model updating method. Finally, we conduct numerous experiments on several challenging video clips to evaluate the proposed tracker in comparison with various state-of-the-art tracking algorithms. Both qualitative and quantitative evaluations on a number of challenging video clips show that our tracker achieves better performance than the other state-of-the-art methods.

• Journal of the Korea Computer Graphics Society
• /
• v.19 no.4
• /
• pp.13-22
• /
• 2013

A motion capture system is widely used in movies, computer game, and computer animation industries because it allows for creating realistic human motions efficiently. The inertial motion capture system has several advantages over more popular vision-based systems in terms of the required space and cost. However, it suffers from low accuracy due to the relatively high noise levels of the inertial sensors. In particular, the accelerometer used for measuring gravity direction loses the accuracy when the sensor is moving with non-zero linear acceleration. In this paper, we propose a method to remove the linear acceleration component from the accelerometer data in order to improve the accuracy of measuring gravity direction. In addition, we develop a simple method to calibrate the joint axis of a link to which an inertial sensor belongs as well as the position of a sensor with respect to the link. The calibration enables attaching inertial sensors in an arbitrary position and orientation with respect to a link.

• Steel and Composite Structures
• /
• v.7 no.2
• /
• pp.87-103
• /
• 2007

This paper presents some of the results from an experimental research project on the behavior of extended end-plate connections subjected to moment conducted at the Structural Laboratory of Jordan University of Science and Technology. Since the connection behavior affects the structural frame response, it must be included in the global analysis and design. In this study, the behavior of six full-scale stiffened and unstiffened cantilever connections of HEA- and IPE-sections has been investigated. Eight high strength bolts were used to connect the extended end-plate to the column flange in each case. Strain gauges were installed inside each of the top six bolts in order to obtain experimentally the actual tension force induced within each bolt. Then the connection behavior is characterized by the tension force in the bolt, extended end-plate behavior, moment-rotation relation, and beam and column strains. Some or all of these characteristics are used by many Standards; therefore, it is essential to predict the global behavior of column-beam connections by their geometrical and mechanical properties. The experimental test results are compared with two theoretical (equal distribution and linear distribution) approaches in order to assess the capabilities and accuracy of the theoretical models. A simple model of the joint is established and the essential parameters to predict its strength and deformational behavior are determined. The equal distribution method reasonably determined the tension forces in the upper two bolts while the linear distribution method underestimated them. The deformation behavior of the tested connections was characterized by separation of the column-flange from the extended end-plate almost down to the level of the upper two bolts of the lower group and below this level the two parts remained in full contact. The neutral axis of the deformed joint is reasonably assumed to pass very close to the line joining the upper two bolts of the lower group. Smooth monotonic moment-rotation relations for the all tested frames were observed.

• Transactions of Materials Processing
• /
• v.16 no.8
• /
• pp.603-613
• /
• 2007

This paper is concerned with joining of thin metal sheets by single stroke clinching process. This method has been used in sheet metal work as it is a simple process and offers the possibility of joining similar-dissimilar thin sheet metals. Clinching generates a joint by overlapping metal sheets deforming plastically by punching and squeezing sequence. AA 5754 aluminum alloy of 0.5 mm thick sheets have been selected as a modal material and the process has been simulated under different process conditions and the results have been analyzed in terms of the quality of clinch joints which are influenced mainly by tool geometries. The rigid-plastic finite element method is applied to analyses in this paper. Analysis is focused mainly on investigation of deformation and material flow patterns influenced by major geometrical parameters such as die diameter, die depth, groove width, and groove corner radius, respectively. To evaluate the quality of clinch joints, four controlling or evaluation parameters have been chosen and they are bottom, neck thickness of bottom and top sheets, and undercut thickness, respectively. It has been concluded from the simulation results that the die geometries such as die depth and diameters are the most decisive process parameters influencing on the quality of clinch joints, and the bottom thickness is the most important evaluation parameter to determine if the quality of clinch joints satisfies the demand for industrial application.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.8
• /
• pp.79-88
• /
• 2009

This paper presents the analytical stiffness analysis method for a low-DOF planar parallel manipulator. An n-DOF (n<3) planar parallel manipulator to which 1- or 2-DOF serial mechanism is connected in series may be used as a positioning device in planar tasks requring high payload and high speed. Differently from a 3-DOF planar parallel manipulator, an n-DOF planar parallel counterpart may be subject to constraint forces as well as actuation forces. Using the theory of reciprocal screws, the planar stiffness is modeled such that the moving platform is supported by three springs related to the reciprocal screws of actuations (n) and constraints (3-n). Then, the spring constants can be precisely determined by modeling the compliances of joints and links in serial chains. Finally, the stiffness of two kinds of 2-DOF planar parallel manipulators with simple and complex springs is analyzed. In order to show the effectiveness of the suggested method, the results of analytical stiffness analysis are compared to those of numerical stiffness analysis by using ADAMS.

• Journal of Biomedical Engineering Research
• /
• v.28 no.3
• /
• pp.332-337
• /
• 2007

In the early twenty-first century, minimally invasive surgery is the mainstay of various kinds of surgical fields. Surgeons gave percutaneously surgical treatment of the screw directly using a fluoroscopic view in the past. The latest date, they began to operate the fractured carpal bone surgery using Computerized Tomography (CT). Carpal bones composed of wrist joint consist of eight small bones which have hexahedron and sponge shape. Because of these shape, it is difficult to grasp the shape of carpal bones using only CT image data. Although several image segmentation studies have been conducted with carpal bone CT image data, more studies about carpal bone using CT data are still required. Especially, to apply the software implemented from the studies to clinical fIeld, the outcomes should be user friendly and very accurate. To satisfy those conditions, we propose modified multi-seed region growing segmentation method which uses simple threshold and the canny edge detector for finding edge information more accurately. This method is able to use very easily and gives us high accuracy and high speed for extracting the edge information of carpal bones. Especially, using multi-seed points, multi-bone objects of the carpal bone are extracted simultaneously.

• The Journal of Korean Orthopaedic Ultrasound Society
• /
• v.4 no.1
• /
• pp.7-14
• /
• 2011

Purpose: The purpose of this study was to analyze the correlation between the medial joint space on weight bearing simple X-ray and the ultrasonographic articular cartilage thickness. Materials and Methods: The articular cartilage thickness of 91 osteoarthritic knees of 73 patients were measured with weight bearing simple X-ray and ultrasonography between June 2010 and September 2010. Male were 13 and female were 60. Right knees were 35, left knees were 20 and bilateral involvements were 18. Medial joint spaces on X-ray were measured in full extension view and $45^{\circ}$ PA(Rosenberg) view. Femoral cartilage thicknesses at and those at the point between the middle 1/3 and posterior 1/3 area were measured by ultrasonography, that were scanned coronally at $30^{\circ}$ flexion and $130^{\circ}$ flexion respectively. The results were analyzed statistically by Pearson correlation test and Bland-Altman plot test. Results: Medial joint spaces measured in full extension view and femoral articular cartilage thicknesses at the point between the anterior 1/3 and middle 1/3 area measured with sonography were statistically correlated and medial joint spaces measured in $45^{\circ}$ PA view and those at the point between the middle 1/3 and posterior 1/3 area measured with sonography were also correlated (P<0.05, $SD{\pm}2$). Conclusion: The measurement of articular cartilage thicknesses by the ultrasonography was easy even in the patient who are unable to take weight bearing view and was thought to be a useful diagnostic and follow up method to examine the degenerative change in addition to simple radiographic examination in the knee osteoarthritis.

• The Journal of the Korean bone and joint tumor society
• /
• v.3 no.1
• /
• pp.32-38
• /
• 1997

PURPOSE : For the reconstruction of large bone defect after tumor resection, it is possible to reuse the bone involved by tumor with some treatment to it. Several bone-reusing methods have been reported such as autoclaving, low-heat treatment(pasteurization) and intraoperative radiotherapy. We have used extracorporeally radiated autogenous bone graft for reconstruction after tumor resection, and analyzed the periods for junctional union, functional results and complications to know the indications of this method. METHODS : From Dec. 1993 to Sept. 1995, nine patients had taken autogenous bone graft with extracorporeal irradiation. Eight cases were osteosarcoma and 1 giant cell tumor. The graft sites were 5 in femur, 3 proximal tibia and 1 femur and tibia. Stage 3 was 1 case(GCT), Stage IIB 3 and Stage IIIB 5. After wide resection, surrounding soft tissue and intramedullary and extramedullary portion of the tumor were removed. Radiation was done in 5000cGy to the resected bone. Ender nails and bone cement were inserted and filled into the medulla to prevent fracture. RESULTS : Average follow-up period was 12.3(4 to 21) months. Average junctional union period in simple X-ray was 6.5 months in 4 cases. Average functional score following Enneking's criteria was 19(12-27). Complications were as follows ; condylar fractures and femur neck fracture in 4 cases, subluxation of the knee joint 3 and infection 1. Although local recurrence was detected in 1 case, the site of recurrence was not in the radiated bone but surrounding soft tissue. At final follow-up, no recurrence was found in one case(GCT), CDF 2, AWD 2, DOD 3, and died of chemotherapy related sepsis 1. CONCLUSIONS : Extracorporeally radiated bone autograft is considered to be a method for reconstruction of the large bone defect made by tumor resection, especially in the reconstruction around the joint.