Head Rotation Angles Research Articles

Control method of tool axis vector based on kinematics characteristics for five-axis NC machining

The complexity of tool path in the machining of complex curved surface is often accompanied by the large change of tool axis vector and the large change of tool axis vector can cause larger machining error and is easily beyond the restrictions of angular velocity and angular acceleration for the rotation angle of swing head or turntable of machine tool under a constant feed speed. The optimisation of the planning for the tool axis vector is very important based on the kinematics characteristics. The control method of tool axis vector based on the kinematics characteristics for five-axis NC machining of complex curved surface is studied. Experimental results show that the planning of tool axis vector based on the kinematics characteristics for five-axis NC machining can guarantee the smooth movement of the rotation axis and the machining process for complex curved surface can be more stable and reliable.

Simultaneous Three-Dimensional Analysis of Cervical Spine Kinematics in the Axial and Sagittal Views during a Simulated Frontal Impact: Differences between Tensed and Relaxed States.

Study DesignProspective experimental study on humans.PurposeTo determine whether postural differences during a low-speed impact are observed in the sagittal and axial views, particularly in a relaxed state.Overview of Literature: Three-dimensional motion capture systems have been used to analyze posture and head-neck-torso kinematics in humans during a simulated low-speed impact, yet little research has focused on the axial view. Since a seatbelt asymmetrically stabilizes a drivers right shoulder and left lower waist into the seat, it potentially creates movement in the axial view.MethodsThree healthy adult men participated in the experimental series, which used a low-speed sled system. The acceleration pulse created a full sine shape with a maximum acceleration of 8.0 m/s2 at 500 ms, during which the kinematics were evaluated in relaxed and tensed states. The three-dimensional motion capture system used eight markers to record and analyze body movement and head-neck-torso kinematics in the sagittal and axial views during the low-speed impact. Head and trunk rotation angles were also calculated.ResultsLarger movements were observed in the relaxed than in the tensed state in the sagittal view. The cervical and thoracic spine flexed and extended, respectively, in the relaxed state. In the axial view, larger movements were also observed in the relaxed state than in the tensed state, and the left shoulder rotated.ConclusionsDuring simulated frontal impact, the rotation angle between the head and trunk was significantly larger in the relaxed state. Therefore, we recommend also observing movement in the axial view during impact tests.

A Human Body Model With Active Muscles for Simulation of Pretensioned Restraints in Autonomous Braking Interventions

Objective: The aim of this work is to study driver and passenger kinematics in autonomous braking scenarios, with and without pretensioned seat belts, using a whole-body finite element (FE) human body model (HBM) with active muscles.Methods: Upper extremity musculature for elbow and shoulder flexion–extension feedback control was added to an HBM that was previously complemented with feedback controlled muscles for the trunk and neck. Controller gains were found using a radial basis function metamodel sampled by making 144 simulations of an 8 ms−2 volunteer sled test. The HBM kinematics, interaction forces, and muscle activations were validated using a second volunteer data set for the passenger and driver positions, with and without 170 N seat belt pretension, in 11 ms−2 autonomous braking deceleration. The HBM was then used for a parameter study in which seat belt pretension force and timing were varied from 170 to 570 N and from 0.25 s before to 0.15 s after deceleration onset, in an 11 ms−2 autonomous braking scenario.Results: The model validation showed that the forward displacements and interaction forces of the HBM correlated with those of corresponding volunteer tests. Muscle activations and head rotation angles were overestimated in the HBM when compared with volunteer data. With a standard seat belt in 11 ms−2 autonomous braking interventions, the HBM exhibited peak forward head displacements of 153 and 232 mm for the driver and passenger positions. When 570 N seat belt pretension was applied 0.15 s before deceleration onset, a reduction of peak head displacements to 60 and 75 mm was predicted.Conclusions: Driver and passenger responses to autonomous braking with standard and pretensioned restraints were successfully modeled in a whole-body FE HBM with feedback controlled active muscles. Variations of belt pretension force level and timing revealed that belt pretension 0.15 s before deceleration onset had the largest effect in reducing forward head and torso movement caused by the autonomous brake intervention. The displacement of the head relative to the torso for the HBM is quite constant for all variations in timing and belt force; it is the reduced torso displacements that lead to reduced forward head displacements.

Optic flow neurons in area PEc integrate eye and head position signals

Neurons in area PEc, a visual area located in the superior parietal lobule, are activated by optic flow stimuli. An important issue is whether PEc neurons are able to integrate multimodal signals, such as those related to optic flow selectivity with those about eye and head position. The aim of this study was to assess if angle of gaze and/or head rotation modify the spatial representation of the focus of expansion (FOE), varying FOE, fixation point and head position in space. We found that the rotation of head modulated the firing activity of PEc optic flow neurons. The head position also changed the angle of gaze effect on the PEc neuronal activity. All recorded neurons showed a main interaction effect between head and eye position upon the selectivity for optic flow stimuli. These results seem to suggest that PEc optic flow neurons use different reference frames depending on the position of the eye and/or the head in space emphasizing a possible contribution of this area in guiding locomotion by integrating multiple extraretinal inputs.

Pose robust face recognition based on kernel regression in Bayesian framework

To reduce the effect brought by variation of pose, a face recognition system is proposed, in which the correlation between two faces by probabilistic models is computed and the gallery is extended with profile faces generated by a regression-based method. Each face is divided into 3 × 3 regions, and by measuring the distance between the two corresponding regions the distributions of similarities are learned and Bayesian models are formed for each region. These probabilistic models are used to determine whether two faces belong to the same subject. Besides, the gallery is expanded with profile facial images. With this approach, the landmarks on non-frontal faces can be estimated from their frontal landmarks by the mappings learned offline via kernel rank reduced regression (KRRR). Then the profile images are achieved by piecewise affine warping from the corresponding frontal face. Experiments indicate the proposed method performed well, especially when the head rotation angle is large.

Human recognition based on retinal images and using new similarity function

This paper presents a new human recognition method based on features extracted from retinal images. The proposed method is composed of some steps including feature extraction, phase correlation technique, and feature matching for recognition. In the proposed method, Harris corner detector is used for feature extraction. Then, phase correlation technique is applied to estimate the rotation angle of head or eye movement in front of a retina fundus camera. Finally, a new similarity function is used to compute the similarity between features of different retina images. Experimental results on a database, including 480 retinal images obtained from 40 subjects of DRIVE dataset and 40 subjects from STARE dataset, demonstrated an average true recognition accuracy rate equal to 100% for the proposed method. The success rate and number of images used in the proposed method show the effectiveness of the proposed method in comparison to the counterpart methods.

Development of a vision non-contact sensing system for telerobotic applications

The study presented here describes a novel vision-based motion detection system for telerobotic operations such as distant surgical procedures. The system uses a CCD camera and image processing to detect the motion of a master robot or operator. Colour tags are placed on the arm and head of a human operator to detect the up/down, right/left motion of the head as well as the right/left motion of the arm. The motion of the colour tags are used to actuate a slave robot or a remote system. The determination of the colour tags’ motion is achieved through image processing using eigenvectors and colour system morphology and the relative head, shoulder and wrist rotation angles through inverse dynamics and coordinate transformation. A program is used to transform this motion data into motor control commands and transmit them to a slave robot or remote system through wireless internet. The system performed well even in complex environments with errors that did not exceed 2 pixels with a response time of about 0.1 s. The results of the experiments are available at: http://www.youtube.com/watch?v=yFxLaVWE3f8 and http://www.youtube.com/watch?v=_nvRcOzlWHw

An assessment of lead eyewear in interventional radiology

The International Commission on Radiological Protection (ICRP) has recently issued a proposal to reduce the occupational eye dose limit from 150 to 20 mSv. A series of experiments has been performed to determine the level of protection from scattered radiation afforded to the interventional radiology operator by protective lead glasses, taking into account variation in operator position and angle of head rotation. The lenses of the glasses have a lead equivalence of 0.75 mm lead with 0.5 mm lead present in the side shields. Our results have led us to propose the use of a general dose reduction factor of 5 when using eyewear with this lead equivalence and construction. We have also concluded that the forehead of the wearer provides the most robust position to site a dosemeter that will be used to estimate the dose to both eyes as part of a personal monitoring regime. We have confirmed that backscatter from the head itself is the limiting factor for the dose reduction potential of lead eyewear.

Recognition of a Driver's Gaze for Vehicle Headlamp Control

In this paper, we propose a novel method for gaze recognition of a driver coping with rotation of a driver's face. Frontal face images and left half profile images were separately trained using the Viola-Jones (V-J) algorithm to produce classifiers that can detect faces. The right half profile can be detected by mirroring the entire image when neither a frontal face nor a left half profile was detected. As an initial step, this method was used to simultaneously detect the driver's face. Then, we applied a regressional version of linear discriminant analysis (LDAr) to the detected facial region to extract important features for classification. Finally, these features were used to classify the driver's gaze in seven directions. In the feature extraction step, LDAr tries to find features that maximize the ratio of interdistances among samples with large differences in the target value to those with small differences in the target value. Therefore, the resultant features are more fitted to regression problems than conventional feature extraction methods. In addition to LDAr, in this paper, a 2-D extension of LDAr is also developed and used as a feature extraction method for gaze recognition. The experimental results show that the proposed method achieves a good gaze recognition rate under various rotation angles of a driver's head, resulting in a reliable headlamp control performance.

Mapping magnetic susceptibility anisotropies of white matter in vivo in the human brain at 7T

High-resolution magnetic resonance phase- or frequency-shift images acquired at high field show contrast related to magnetic susceptibility differences between tissues. Such contrast varies with the orientation of the organ in the field, but the development of quantitative susceptibility mapping (QSM) has made it possible to reproducibly image the intrinsic tissue susceptibility contrast. However, recent studies indicate that magnetic susceptibility is anisotropic in brain white matter and, as such, needs to be described by a symmetric second-rank tensor( ̅χ). To fully determine the elements of this tensor, it would be necessary to acquire frequency data at six or more orientations. Assuming cylindrical symmetry of the susceptibility tensor in myelinated white matter fibers, we propose a simplified method to reconstruct the susceptibility tensor in terms of a mean magnetic susceptibility, MMS=(χ(//)+2 χ(⊥))/3 and a magnetic susceptibility anisotropy, MSA=χ(//)-χ(⊥), where χ(//) and χ(⊥) are susceptibility parallel and perpendicular to the white matter fiber direction, respectively. Computer simulations show that with a practical head rotation angle of around 20°-30°, four head orientations suffice to reproducibly reconstruct the tensor with good accuracy. We tested this approach on whole brain 1 × 1 × 1 mm(3) frequency data acquired from five healthy subjects at 7 T. The frequency information from phase images collected at four head orientations was combined with the fiber direction information extracted from diffusion tensor imaging (DTI) to map the white matter susceptibility tensor. The MMS and MSA were quantified for regions in several large white matter fiber structures, including the corona radiata, posterior thalamic radiation and corpus callosum. MMS ranged from -0.037 to -0.053 ppm (referenced to CSF being about zero). MSA values could be quantified without the need for a reference and ranged between 0.004 and 0.029 ppm, in line with the expectation that the susceptibility perpendicular to the fiber is more diamagnetic than the one parallel to it.

A Wireless Head-Controlled Mouse Design Using Adaptive Unscented Kalman Filter Algorithm

For some disabled people can’t use hand to control the mouse, this paper designs a novel head-controlled mouse. Using accelerometers and gyroscopes as the sensitive element of the system measure the head rotation angle. The mouse is controlled as for the relationship between the head rotation angle and the mouse move distance. For mouse click operation, this article designed a software to achieve. Considering the MEMS sensor noise affect the mouse control accuracy, using the unscented Kalman filter (UKF) to fusion the data of accelerometers and gyroscopes to obtain the optimal angle estimation. Compared with only using an accelerometer or gyroscope sensor, the method proposed in this paper for angle measurement can have high accuracy and stability, thereby improving the mouse control precision and maneuverability.

A simple and consistent technique for ventricular catheter insertion using a tripod

ObjectiveFor long-term preservation of ventriculo-peritoneal (VP) shunt function, it is essential to place the ventricular catheter tip above the foramen of Monro. But the free-hand technique for ventricular catheter passage is not consistent. MethodsSupposing that a convex of skull matches to a sphere, in which the foramen of Monro is the center, a perpendicular direction from the surface of the sphere to inside always directs toward the center. The authors identified the range of skull where corresponded to the sphere by magnetic resonance imaging assessment and utilized tripod to achieve exactly perpendicular insertion of ventricular catheter. And an optimal length of catheter insertion was investigated by navigation system. ResultsThe anterior–posterior range of the spherical portion was from coronal suture to 20mm anterior, and the lateral range of it was between 15 and 35mm lateral from sagittal suture. The optimal catheter length for insertion was between 55 and 58mm from the brain surface. Ideal placement of a ventricular catheter tip was achieved in more than 90% of cases (31/34) with this technique. ConclusionTripod-guided ventricular catheter insertion is a simple and reliable method for VP shunt at any angle of head-rotation.

Temporal integration in sound localization via head rotation

Information about a sound source’s location in the front/back dimension is present in the relation between head rotation and the resulting changes in interaural time- or level-difference cues. The use of such dynamic cues for localization requires the auditory system to have access to an accurate representation of the orientation and motion of the head in space. We measured, in active and passive rotation conditions, and as a function of head-rotation angle and velocity, normally hearing human listeners’ ability to localize front and rear sources of a low-frequency (0.5–1 kHz) noise band that was not accurately localizable in the absence of head motion. Targets were presented while the head was in motion at velocities of 50–400°/s (active neck rotation) or 25–100°/s (whole-body passive rotation), and were gated on and off as the head passed through a variable-width spatial window. Accuracy increased as window width was increased, which provided access to larger interaural cue changes, but decreased as head-turn velocity increased, which reduced the duration of the stimuli. For both active and passive rotation, these effects were almost exactly reciprocal, such that performance was related primarily to the duration of the stimulus, with ∼100 ms duration required for 75% correct front/back discrimination regardless of the cue-change magnitude or mode of rotation. The efficacy of the dynamic auditory cues in the passive rotation condition suggests that vestibular input is sufficient to inform the auditory system about head motion.

Analysis on the Thermal Error Compensation Model of Direct-Drive A/C Bi-Rotary Milling Head

The thermal deformation error that is the biggest error of effecting the machining precision of Direct-drive A/C Bi-rotary Milling Head was narrated in brief. Based on the introduce of the study status on the thermal error compensation techniques of CNC Machine tool, the momentum of thermal deformation of Bi-rotary Milling Head was analyzed. According to the Trigonometric Relations in A/C axis rotation angle of Bi-rotary Milling Head and the momentum of thermal deformation in Bi-rotary Milling Head and -axis respectively, a thermal error compensation model was established to make the Machine tool to compensate for thermal errors in -axis.

Changes in the relationship between the right internal jugular vein and an anatomical landmark after head rotation

BackgroundThis study was performed to ultrasonographically demonstrate the changes in relationship between the right internal jugular vein (IJV) and an anatomical landmark in two different head positions: neutral and rotated.MethodsThis was a randomized clinical trial. One hundred patients scheduled for elective surgery under general anesthesia with endotracheal intubation were enrolled in this study. The patients were placed in the supine position with a neutral head position and without a pillow. The apex of the triangle formed by the sternal and clavicular heads of the sternocleidomastoid muscle and clavicle was marked (AL point : anatomical landmark point). Ultrasonography of the neck anatomy was performed and the skin was marked at the central point of the IJV (US point: ultrasonography point). The other investigator measured the distance from the AL point to the US point (AL-US distance). The patient's head was then turned 30° to the left; the same procedure was repeated and the AL-US distance was again measured. The changes in AL-US distance were calculated.ResultsThe AL-US distance increased significantly after 30° head rotation compared with that in a head neutral position. The mean ± SD of the AL-US distance was 0.28 ± 0.78 cm in the neutral head position and 0.83 ± 1.03 cm in the head rotated position.ConclusionsThe anatomical landmark point becomes more distant from the actual right IJV point and moves more medially after head rotation. We suggest minimizing the angle of head rotation and taking this distance into consideration when using the landmark-guided method.

Comparing head rotation angle, visual localization, and recall‐proficiency of school‐aged children 8–12 while listening to a story by multiple discreet talkers in a virtual classroom.

In general, children perform more poorly in speech intelligibility tasks than adults while in a noisy environment such as a classroom. This is especially true in discussion situations where the active talkers often are located to the side or behind the student. The purpose of this study was to obtain baseline data for normal hearing (NH) students who experienced multiple‐talker stimuli in a controlled virtual classroom environment. Data were gathered using a gyroscopic head‐tracker and a post‐story comprehension task. Twenty elementary‐aged students (ages 8–12, four students per year) were positioned in the center of the classroom and presented a story read by five talkers positioned around the student (reproduced by means of loudspeakers and LCD monitors). Students used different strategies in terms of head rotation over time while performing the experiment and individual differences were seen both across subjects within an age group and between age groups. The post‐test comprehension task was used as a metric of performance in the environment. Results from the NH students are compared to a control group of adult NH listeners using head rotation angle over time, comprehension scores, and localization accuracy as salient metrics.

머리전달함수 측정시스템의 개발과 분석

When we render 3D sound images using headphones or speakers, the main key of this technology is the Head-related transfer function (HRTF) database. Even though there are various HRTF databases, they have some drawbacks such as detrimental effects caused by imperfect measuring environment and insufficient measurement points. Moreover there is no database with Korean subjects. We are planning to develop the HRTF database for Korean. As a first step to establish the HRTF database aimed at Korean, the new HRTF measurement system with minimized aforementioned drawbacks is designed. In this paper, the newly designed HRTF measurement system is introduced and the overall effects caused by the diffraction of the apparatus, especially the headrest and backrest of the chair, are analyzed. The backrest of the chair does not distort the HRTFs significantly while the headrest makes significant distortion on the HRTFs and it could have significant effects on directional perception. We determined acceptable head rotation angle and head position of the subject for accurate HRTF measurement based on the experiments with B&K HATS. We conclude that the 3 degrees of the head rotation and the 1.5cm front/back/left/right shift of the head do not distort the HRTFs significantly.

Effect of Head Rotation Angles on Pharyngeal Bolus Passage during Swallowing

Effect of Head Rotation Angles on Pharyngeal Bolus Passage during Swallowing

MRI‐based surgical simulation of transtrochanteric rotational osteotomy for femoral head osteonecrosis

Transtrochanteric rotational osteotomy (TRO) is one of the joint-preserving surgical treatments for osteonecrosis of the femoral head (ONFH). It can prevent collapse of the femoral head as necrotic lesions in the weight-bearing portion can be moved sufficiently to a less weight-bearing portion by anterior rotation, posterior rotation, or varus angulation. Patient selection and preoperative planning are important to determine indications for TRO. It has been reported that successful TRO requires at least 34% of the weight-bearing area supported by the intact part of the femoral head. However, this ratio is difficult to preoperatively quantify according to the rotation angle using conventional two-dimensional MR images or X-rays. Therefore, we developed a method of simulating TRO using three-dimensional (3D) models reconstructed from 3D MR images and applied it to serial patients with types C1 and C2 osteonecrosis at stage 1 or 2. The simulation visualized positional changes of the necrotic lesion in the weight-bearing area and enabled quantitation of the postoperative intact ratio. Our surgical simulation is useful for evaluating the postoperative intact ratio and for determining indications for TRO as well as the optimal angle of femoral head rotation and varus angulation.

Facial expression recognition system based on rigid and non-rigid motion separation and 3D pose estimation

This study presents a facial expression recognition system which separates the non-rigid facial expression from the rigid head rotation and estimates the 3D rigid head rotation angle in real time. The extracted trajectories of the feature points contain both rigid head motion components and non-rigid facial expression motion components. A 3D virtual face model is used to obtain accurate estimation of the head rotation angle such that the non-rigid motion components can be precisely separated to enhance the facial expression recognition performance. The separation performance of the proposed system is further improved through the use of a restoration mechanism designed to recover feature points lost during large pan rotations. Having separated the rigid and non-rigid motions, hidden Markov models (HMMs) are employed to recognize a prescribed set of facial expressions defined in terms of facial action coding system (FACS) action units (AUs).