Degree Of Freedom Information Research Articles

A novel cost-effective postural tracking algorithm by using marker-based video processing

Recently, many postural analysis techniques are developed in order to reduce the risk of musculoskeletal problems. Methods such as Rapid Entire Body Assessment are capable of analyzing the most constant or awkward positions, but the selection of these postures are subjective. To make an objective postural analysis, devices such as Electro Magnetic Trackers can be used continuously during the job task, but utilizing such devices are costly. Therefore, in this study a cost-effective marker-based video processing algorithm is developed for measuring 3-dimensional information regarding both the location and the orientation of human posture. To investigate the precision of the measurements, an experiment was designed. With the average of 2.88 mm and 1.34° for location and orientation, respectively, the algorithm was able to measure 6 degrees of freedom information regarding 3D space. Furthermore, the precision of the algorithm is found to be significantly affected by the marker pattern.

Close-Range Electromagnetic Tracking of Pulse Induction Search Coils for Subsurface Sensing

In this article, we investigate a specific search coil tracking problem arising from the use of electromagnetic induction (EMI) sensors to classify buried low metal objects. In the proposed approach, a moving search coil is used as a magnetic field beacon, two triaxial tunnel magnetoresistance (TMR) sensors are used as anchors, and the extended Kalman filter (EKF) is used to estimate five degrees of freedom information on coil’s relative pose. A specific feature of the analyzed application is the pulsed beacon field and the coil’s size comparable to the tracking distance. To address the resulting near-field effects and improve the tracking accuracy, we include a rigorous analytical multiloop model of the search coil into the EKF estimation algorithm and introduce a novel sensor calibration scheme. The system is experimentally validated in realistic dynamic conditions using a handheld pulse induction metal detector as a beacon, and a laboratory-grade optical tracking system with declared sub-millimeter accuracy as a source of ground truth data. For a near-horizontal zigzag scan pattern within a volume of $\sim \,\,40\times 50\times 5$ cm, our system yields mean absolute errors x- and $y$ -coordinates, $z$ -coordinates, and <0.5° for the pitch and roll angles, making it a viable solution for pose-referenced EMI sensing.

Object Recognition Method for Home Robot Using 3D Model Data Including Grasp Area and Degree of Freedom Information of Household Items

Object Recognition Method for Home Robot Using 3D Model Data Including Grasp Area and Degree of Freedom Information of Household Items

Decomposition-based calibration/validation metrics for use with full-field measurement situations

Calibration and validation metrics that involve decomposition of simulation and test data have been developed for potential use in the quantification of margin and uncertainty. The uniqueness of these validation metrics allows for nearly full-field, simulation and test data over a wide range of spatial realizations (three-dimensional responses over multiple input conditions) and temporal (time or frequency) information, as needed. Currently, no other calibration/validation metrics have been developed that span multiple spatial realizations and temporal information simultaneously. A demonstration example utilizing two datasets explains how the calibration/validation metrics are formed and how they can be used to quantify the margin between the simulation and the test data as well as how it can quantify the uncertainty. The primary advantage of a proposed principal component analysis validation metric is that it preserves the engineering units of the original data so that the quantifications of margin and uncertainty can be made in engineering unit. A second advantage of the principal component analysis validation metric is that it can be used over a wide range of temporal information. The potential case of using sets of data with mismatched degree of freedom information is also explored. The general approach of using decomposition methods as the basis for calibration/validation metrics is extended to image decomposition methods. All decomposition methods successfully quantify margin and uncertainty in this general calibration/validation metric approach.

A Three-Dimensional Mechanical Model Preprocessing Method Based on Modeling Software

Three-dimensional model is high degree of freedom information. In order to realize content-based 3D model retrieval, normalization preprocessing of 3D models is needed. This paper have proposed a normalization method with 3D modeling software based on center of mass, principal axis of inertia and volume parameters to carry out coordinate system normalization of three-dimensional mechanical entity models. In this paper, Specific method is listed. Application examples are given to show the feasibility of this method.

3D Tracking and Positioning of Surgical Instruments in Virtual Surgery Simulation

3D tracking and positioning of surgical instruments is an indispensable part of virtual Surgery training system, because it is the unique interface for trainee to communicate with virtual environment. A suit of 3D tracking and positioning of surgical instruments based on stereoscopic vision is proposed. It can capture spatial movements of simulated surgical instrument in real time, and provide 6 degree of freedom information with the absolute error of less than 1 mm. The experimental results show that the 3D tracking and positioning of surgical instruments is highly accurate, easily operated, and inexpensive. Combining with force sensor and embedded acquisition device, this 3D tracking and positioning method can be used as a measurement platform of physical parameters to realize the measurement of soft tissue parameters.

In vivo and noninvasive six degrees of freedom patellar tracking during voluntary knee movement

Objective. The purpose of this study was to investigate in vivo and noninvasively patellar tracking in six degrees of freedom during voluntary knee extension and flexion. Design. Patellar tracking was evaluated in vivo and noninvasively with corroboration using in vivo fluoroscopy and in vitro cadaver measurements. Background. Patellofemoral pain is closely related to abnormal patellar tracking and malalignment. However, there is a lack of quantitative and convenient methods to evaluate six degrees of freedom in vivo patellar tracking, partly due to difficulty in evaluating 3-D patellar tracking noninvasively. Methods. Six degrees of freedom patellar tracking was measured in vivo and noninvasively using a small clamp mounted onto the patella and an optoelectronic motion capture system in 18 knees of 12 healthy subjects during voluntary knee extension and flexion. Results. The patella tracked systematically following a certain pattern during knee extension and flexion. Patellar tracking patterns during knee extension and flexion were not significantly different in the 18 knees tested. When the knee was voluntarily extended from 15° flexion to full extension, the patella was extended 8°, laterally tilted 2°, and shifted 3 mm laterally and 10 mm proximally. The results were consistent with previous in vitro and in vivo studies. Conclusions. Six degrees of freedom patellar tracking can be evaluated in vivo and noninvasively within the range of 20° flexion to full knee extension. Relevance The study provided us quantitative six degrees of freedom information about patellar tracking during knee flexion/extension, which can be used to investigate patellar tracking in vivo and noninvasively in both healthy subjects and patients with patellofemoral disorder and patellar malalignment.

Feature-based assembly modeling and sequence generation

A feature-based model is proposed for assembly sequence planning automation. The fundamental assembly modeling strategy for a product is based on the mating features of its components. The objectives of this study are to integrate assembly planning of a product with its CAD model, generate a correct and practical assembly sequence and establish a software system to carry out the planning process. A disassembly approach in assembly planning is used in this study. The degree of freedom information between two mating features is used to characterize their kinematic conditions. Boolean operations of the degrees of freedom on all features of a component provides its local degree of freedom, which is used to set up the functional precedence relation. In some cases, where the functional precedence relation cannot be detected by geometric reasoning, clipping of the known `common sense' relation is applied by a user. A bounding box checking approach is used to ensure no global collision during assembly. Furthermore, a set of criteria based on assembly feasibility, manipulability, assembly direction, cost and stability is used to choose a good assembly sequence.

Flight model for unmanned simulated helicopters

This paper presents a flight model for use in simulating computer generated helicopters. Momentum and energy balance is used to define a rotor thrust envelope. The four basic control inputs take the form of thrust components and the sideslip angle. Time integrations are performed for the three center of mass degrees of freedom only. Six degrees of freedom information is derived for the visual displays. The model can inexpensively function in real time and faster than real time. Validity is demonstrated by comparing model performance predictions with published data.