Torque Expression Research Articles

Comparative Analysis of Displacements and Stress Produced by Square and Rectangular Bracket Slot With Incremental Torque: A Finite Element Analysis Study.

This study aimed to perform a comparative analysis of stresses and displacements with incremental torque on the maxillary incisors and surrounding cortical bone using conventional metal brackets with rectangular slots and passive self-ligating brackets with square slots using finite element analysis (FEA). An in vitro FEA study was conducted, in which a three-dimensional (3D) model of the maxilla was built using ANSYS softwareversion 18 (ANSYS Inc., Canonsburg, PA). The conventional McLaughlin, Bennet, and Trevisi (MBT) bracket (3M Unitek, Monrovia, CA) of 0.022 × 0.028-inch slot with a 0.019 × 0.025-inch rectangular stainless steel (SS) archwire (model 1) was compared with the Pitts 21™ self-ligating bracket system (OC Orthodontics, McMinnville, OR) of 0.021 x 0.21-inch slot with a 0.020 × 0.020-inch square SS archwire (model 2) at incremental torques of 5°, 10°, 15°, and 20°. The von Mises stress was evaluated at the maxillary incisors and surrounding cortical bone. The torque moment, tipping angle, and displacement of the maxillary incisors were also measured and compared between the bracket systems. The highest torque expression of 13.8 N-mm was observed in model 2, compared to a torque expression of 10.68 N-mm in model 1. The torque expression increased in both models from 0°to 20°. There was a play of 6.2°at 20°torquein model 2, whereas it was 9.32°​​​​​​​play in model 1. The torque expressions were better for the lateral incisors than for the central incisors. Increased incremental torque was associated with increased proclination of the incisors, and this movement was more pronounced for the central incisor and model 1. Furthermore, it was revealed that the stresses on the cortical bone and teeth were higher in model 2 than in model 1. It was concluded that the Pitts 21™ passive self-ligating system produced better torque expression and less play with square SS archwire compared to conventional brackets with rectangular SS archwire.

Position Servo Control of Electromotive Valve Driven by Centralized Winding LATM Using a Kalman Filter Based Load Observer

The exhaust gas recirculation (EGR) valve plays an important role in improving engine fuel economy and reducing emissions. In order to improve the positioning accuracy and robustness of the EGR valve under uncertain dynamics and external disturbances, this paper proposes a positioning servo system design for an electromotive (EM) EGR valve based on the Kalman filter. Taking a novel valve driven by a central winding limited angle torque motor (LATM) as the object, we have fully considered the influence of the motor rotor position and load current, as well as the magnetic field saturation and cogging effect, improved the existing LTAM model, and derived accurate torque expression. The parameter uncertainty of the above internal model and the external stochastic disturbance were unified as “total disturbance”, and a Kalman filter-based observer was designed for disturbance estimations and real-time feed-forward compensation. Furthermore, using non-contact magnetic angle measurements to obtain accurate valve position information, a position control model with real-time response and high accuracy was established. Numerous simulated and experimental data show that in the presence of ± 25% plant model parameter fluctuations and random shock-type disturbances, the servo system scheme proposed in this paper achieves a maximum position deviation of 0.3 mm, a repeatability of positioning accuracy after disturbances of 0.01 mm, and a disturbance recovery time of not more than 250 ms. In addition, the above performance is insensitive to the duration of the disturbance, which demonstrates the strong robustness, high accuracy, and excellent dynamic response capability of the proposed design.

Torque expression of superelastic NiTi V-Slot and conventional stainless steel orthodontic bracket-archwire combinations - A finite element analysis

BackgroundTo investigate the torque expression of conventional stainless steel (SS) brackets in combination with rectangular SS archwires and nickel-titanium (NiTi) V-slot brackets in combination with V-shaped NiTi archwires using finite element analysis (FEA). MethodsCAD models were created for a conventional bracket and rectangular archwires with dimensions of 0.018″x0.025″ and 0.019″x0.025″, and for a V-slot bracket and V-shaped archwires with heights of 0.55 mm, 0.60 mm and 0.70 mm. FEA was performed using Ansys 2022R2 software to assess the forces and moments during simulated torsion of the archwires in the brackets between 0° and 25° with varying interbracket distances and free path lengths. ResultsThe V-slot bracket-archwire combination exhibited force transmission and moment generation within 1° of torsion. The transmissible force increased with the torsion angle, but showed an upper limit of about 13–14 Nmm. The SS bracket-archwire combination showed negligible forces and moments for simulated torsion between 0° and 15°. At torsions of 25°, moments of 12 Nmm and 14 Nmm occurred for the 0.018″x0.025″ and 0.019″x0.025″ archwire dimensions, respectively. ConclusionsThe V-slot bracket-archwire combination is effective in expressing torque and preventing both over- and under-activation. Conventional bracket-archwire combinations showed torsional losses due to play between 10 and 15°, depending on the dimensions of the respective archwire, and no upper torsional moment limit.

Impact of Invisalign® first system on molar width and incisor torque in malocclusion during the mixed dentition period.

In orthodontic treatment of patients during the mixed dentition period, arch expansion and opening deep overbite are one of the objectives to achieve proper alignment of the teeth and correction of sagittal and vertical discrepancies. However, the expected outcomes of most therapeutic regimens are not clear, making it impossible to standardize early treatment effects. Therefore, this study was designed to evaluate the impact of the Invisalign® First System on the dental arch circumference and incisor inclination in patients during the mixed dentition period. A total of 21 children during the mixed dentition period (10 females and 11 males, with an average age of 8.76 years) were included in this study. The patients received non-extraction treatment through Invisalign® First System clear aligners, and no other auxiliary devices were used except Invisalign® accessories. Subsequently, the cooperation degree of patients during treatment and the oral measurement parameters at the beginning (T1) and the end (T2) of treatment were collected. All patients showed moderate/good cooperation degree during treatment. Besides, horizontal width of the maxillary first molar increased significantly; the designed arch expansion was 4.1 mm (±1.4 mm), while the actual arch expansion was 3.0 mm (±1.7 mm). Furthermore, the torque expression rate of upper anterior teeth reached 56.53%. Invisalign® First System clear aligners can effectively correct the teeth of patients during the mixed dentition period, widen the circumference of dental arch, and control the torque of incisors.

Torque moments and stress analysis in two passive self-ligating brackets across different incisor inclinations: A 3-dimensional finite element study

ObjectiveTo compare torque expression characteristics between rectangular slot (0.022″ x 0.028″) Damon Q passive self-ligating brackets (Ormco, Glendora, Calif) and square slot (0.021″ x 0.021″) Pitts 21 brackets (OC Orthodontics) using 0.019″ x 0.025″ Stainless Steel and 0.020″ x 0.020” Titanium Molybdenum alloy wires at various incisal inclinations using finite element analysis. The null hypothesis was that there were no differences in torque expression in both tested groups. MethodsReporting guidelines for in-silico studies using finite element analysis in medicine (RIFEM) were used. Damon Q and Pitts 21 brackets were scanned and 3D models generated. Brackets were placed on a 3-D model of a maxillary central incisor with its long axis inclined at 0⁰,5⁰,10⁰,15⁰ and 20⁰ to the occlusal plane. Final 0.019″ x 0.025″ SS and 0.020″ x 0.020” TMA archwires were inserted into slots of both tested brackets. Geometric models were converted into finite element models. Material properties were assigned for involved structures with automatic meshing performed by software. Torque movements were simulated with the FE program Ansys Space claim R 22. ResultsTorque moment values, torque expression and Von - Mises stress was higher in Pitts 21 than Damon Q at all inclination angles. There was a gradual increase in the magnitude of values with decrease in incisal inclination. ConclusionSquare slot passive self-ligating brackets show superior torque expression characteristics as compared to rectangular wire-rectangular slot combinations. The FEM results should be validated with in-vivo studies in order to confirm the findings.

Efficacy of planned moderate to severe torque changes in maxillary central incisors with the Invisalign appliance: A retrospective investigation

This study aimed to investigate whether there was a difference between the planned and achieved lingual root torque of the maxillary central incisors in patients treated with an initial series of Invisalign (Align Technology, Santa Clara, Calif) aligners in which>10° change in the inclination of these teeth was prescribed via the ClinCheck facility. The pretreatment, planned, and the digital models after wear of the initial series of aligners regarding adult patients who satisfied selection criteria and were treated using the Invisalign appliance were measured using the Geomagic Control X software (version 2017.0.3; 3D systems, Rock Hill, SC). A sample of 63 patients with 126 maxillary central incisors satisfied the inclusion criteria. The mean accuracy of the planned torque change of the maxillary central incisors that was achieved was 41.9%. A clinically significant shortfall (≥5°) was detected in 78.6% of the incisors, with the majority showing an underexpression between 10°-15°. Linear regression analyses indicated that weekly or biweekly wear protocols or the presence or absence of power ridges did not influence the accuracy of planned torque expression (P>0.05). The changes in torque expression with an initial series of Invisalign aligners were less than half of what was planned in patients in which at least a 10° change in lingual root torque of these teeth was prescribed. The presence of power ridges and the aligner change protocol did not appear to significantly affect the accuracy of maxillary central incisor torque expression.

Comparison of Collum Angle in Different Skeletal Growth Pattern using Cephalometric Radiographs among Orthodontic Patients in Tertiary Dental Care Center of Kathmandu

Collum angle has been previously studied in different types of sagittal malocclusion but very few studies have focused on vertical malocclusion in our population. Since collum angle is responsible for variation in torque expression, root resorption, fenestration and dehiscence, with prior knowledge of collum angle in high angle and low angle cases, operator can prevent above deleterious effects and accompanied better bracket positioning in future orthodontic treatment. Lateral cephalograms of all the patients of age group 13-30 years attending Department of Orthodontics in Nepal Medical College from October 2023 to March 2024, having clinically harmonious and symmetrical face, full complement of dentition except third molar, minimum crowding were taken. Based on the value of SNMP (Sella-Nasion and Mandipular plane), and Jarabak ratio, the samples were divided into high angle and low angle. Collum angle was drawn and measured in terms of degrees. The data were transferred to SPSS-17 for further analysis. A total of 60 study participants were included in the study with an equal number of male and females. (30 each with age ranging from 13 to 30 years with mean age 19.18±3.89 years) There was an equal distribution of study participants in horizontal and vertical growth patterns (30 each). There was no statistically significant difference in mean collum angle between study participants in horizontal and vertical growth patterns (p = 0.09). No statistically significant difference in mean collum angle between study participants in horizontal and vertical growth patterns in relation to gender was found (Male p = 0.08 and female - p-value 0.55).

Aggressive flight control of quadrotors using incremental nonlinear dynamic inversion with a high-fidelity thrust unit model

The application of quadrotors has been expanded into aggressive tasks such as military confrontation and aerobatics shows, making it crucial to enhance flight maneuverability to adapt to rapid and large-scale command changes. Unlike hovering or low-speed modes, aggressive flight exacerbates quadrotor model uncertainty, making it challenging for controllers to balance response speed and robustness. This paper proposes an INDI control method that integrates a high-fidelity thrust model unit to address this practical need. First, based on the pole distribution theory and the application of INDI on quadrotors, it is concluded that the dynamic response of quadrotor flight is impacted by the accuracy of the thrust model. Second, consider the airflow velocity and angles, the high-fidelity modeling approach, and the aerodynamic forces and torque expression validated through wind tunnel experiments are provided. Then the flight controller for the quadrotor is designed with the established high-fidelity thrust unit model. Finally, aggressive trajectory-tracking flight tests are set to evaluate the improvement of our work. The results demonstrate that our proposed method indeed enhances the response speed and tracking accuracy, as well as the flight stability of the quadrotor.

3D electromagnetic analytical model for radial-flux eddy-current couplers

PurposeThis paper aims to develop a new 3D analytical model in cylindrical coordinates to study radial flux eddy current couplers (RFECC) while considering the magnetic edge and 3D curvature effects, and the field reaction due to the induced currents.Design/methodology/approachThe analytical model is developed by combining two formulations. A magnetic scalar potential formulation in the air and the magnets regions and a current density formulation in the conductive region. The magnetic field and eddy currents expressions are obtained by solving the 3D Maxwell equations in 3D cylindrical coordinates with the variable separation method. The torque expression is derived from the field solution using the Maxwell stress tensor. In addition to 3D magnetic edge effects, the proposed model takes into account the reaction field effect due to the induced currents in the conducting part. To show the accuracy of the developed 3D analytical model, its results are compared to those from the 3D finite element simulation.FindingsThe obtained results prove the accuracy of the new developed 3D analytical model. The comparison of the 3D analytical model with the 2D simulation proves the strong magnetic edge effects impact (in the axial direction) in these devices which must be considered in the modelling. The new analytical model allows the magnetic edge effects consideration without any correction factor and also presents a good compromise between precision and computation time.Practical implicationsThe proposed 3D analytical model presents a considerably reduced computation time compared to 3D finite element simulation which makes it efficient as an accurate design and optimization tool for radial flux eddy current devices.Originality/valueA new analytical model in 3D cylindrical coordinates has been developed to find the electromagnetic torque in radial flux eddy current couplers. This model considers the magnetic edge effects, the 3D curvature effects and the field reaction (without correction factors) while improving the computation time.

A Hypothesis Testing of Archwire Rounding for the Efficacy of Torque Springs in Orthodontics: A Finite Element Study.

Achieving the proper buccolingual inclination of teeth is a cornerstone in orthodontic treatment, directly impacting the attainment of ideal occlusal relationships and long-term stability. A practical torque expression that moves the tooth in its proper position across all three planes is imperative to finish orthodontic cases optimally. The primary focus of this research is to investigate Burstone's hypothesis about Warren torque springs when applied to the rectangular wire. Additionally, it examines the hypothesis of rounding these wires in between the bracket wings of the target tooth to be moved. This study aims to determine whether the rounding of wires, in conjunction with the use of torque springs, influences orthodontic outcomes, addressing a notable gap in current literature and resolving controversies in orthodontic practice. A three-dimensional set of maxillary teeth was modeled. A 0.022" MiniSprint™ brackets and Stainless steel archwires of 0.019" × 0.025" and 0.017" × 0.025" (Forestadent, Pforzheim, Germany) were generated. Warren torque spring was modeled and used in the simulation on the upper right central incisor. Four case scenarios were simulated. In two scenarios, the archwires were untouched for both archwire sizes. In comparison, in the other two scenarios, each archwire size was rounded for the upper right maxillary incisor bracket area. Stresses in the Warren torque springs were calculated, the root tip displacement in the four scenarios was measured in millimeters, and both were analyzed. The root tip displacement was highly affected by rounding the archwire. The increase in root tip displacement was 1538% for the Warren torque spring on 0.019" × 0.025" and 783% for 0.017" × 0.025". The amount of root tip displacement was about 18.8 mm for 0.017" × 0.025" with rounding and 12.2 mm for 0.019" × 0.025". The concentration of the stresses in the Warren torque spring was in the neck of the spring next to the coils. Rounding the archwires while using the Warren torque spring on a rectangular archwire will increase the efficiency of the spring and, in turn, will exhibit more torque on the tooth. Smaller dimensions of rectangular archwires will give more torque in conjunction with Warren torque springs compared to larger sizes of archwires.

Maximum Torque per Ampere Operation of Brushless Doubly Fed Induction Machines

In this paper, an analytical method for increasing the steady state torque per ampere capability for BDFMs, using equivalent circuit is presented. In this approach, uni-current proposition proposed to define a unique current value for optimization, and find the current angel corresponding to maximum torque. The accuracy of the proposition is verified by simulation. The effect of pole pair number selection of power and control windings on maximum torque is explained by dividing torque expression into synchronous and asynchronous terms. Finally, the optimal current values and optimal torque are achieved. Based on the optimal value of torque, or MTPA index, analytical optimization of machine design is suggested, which can be performed by manipulation of components of the MTPA index

Incisor torque expression characteristics in two passive self-ligating brackets placed at different heights. A finite element investigation

ObjectiveThis study investigated torque expression in maxillary incisors using two passive self-ligating bracket types (Damon Q and Pitts 21) placed at different heights using the Finite element method. Materials and methodsTwo passive self-ligating brackets, Damon Q (Ormco, USA) and Pitts 21 (OC Orthodontics, USA) were 3D modeled using micro-computed tomography. Damon Q (0.022ˮ x 0.028″ slot size) and Pitts 21 (0.021ˮ x 0.021″ slot size) brackets were placed on a maxillary central incisor at predetermined vertical heights. Arch wires of size 0.019ˮ x 0.025″ stainless steel (Damon Q) and 0.020ˮ x 0.020” Titanium Molybdenum (Pitts 21) were placed in the bracket slots. ResultsPitts 21 brackets showed higher torquing moments at all bonding heights as compared to Damon Q brackets. The minimum torquing moment was 9.03Nmm at 5 mm for Damon Q and the maximum torquing moment was 14.92Nmm for Pitts 21 at a bracket bonding height of 8 mm. Total deformation for Pitts 21 at a height of 5 mm from the incisal edge was 0.61 × 10−6mm as compared to that of Damon Q which was 0.41 × 10−6mm. Lowest Von Mises stress values were at 27.07 MPa in Damon Q brackets at a bracket height of 5 mm from the incisal edge. Highest Von Mises stress values were 36.80 MPa for Pitts 21 brackets at a bracket height of 8 mm from the incisal edge. ConclusionPitts 21 brackets exhibited superior torquing characteristics compared to Damon Q. Total deformation in Pitts 21 was higher than Damon Q at all tested bracket bonding heights.

Analytical calculation method of a liquid-cooling eddy current brake considering magnetic saturation and skin effect

In this article, a clear and concise analytical method for predicting the performance of a Liquid-cooling eddy current brake (LC-ECB) is proposed. The LC-ECB has a coolant channel in the rotor to allow direct cooling of the inner surface of the stator. The static air-gap magnetic field distribution is obtained by the dynamic magnetic equivalent circuit (MEC) method, and the magnetic flux leakage and global magnetic saturation effects are fully considered. The magnetic field intensity distribution function of the eddy current reaction magnetic field is derived for the first time based on Ampere circuital theorem. Considering the local magnetic saturation and skin effect, a novel double-iteration algorithm based on the conservation principle of magnetic pressure drop is applied to obtain the transient air-gap flux density distribution, and then the brake torque expression is obtained. The finite element method (FEM) and experimental results show that the proposed method is feasible and effective. The new model is easy to program and can be easily used in the initial design and optimization of LC-ECB.

Force-Controlled Biomechanical Simulation of Orthodontic Tooth Movement with Torque Archwires Using HOSEA (Hexapod for Orthodontic Simulation, Evaluation and Analysis).

This study aimed to investigate the dynamic behavior of different torque archwires for fixed orthodontic treatment using an automated, force-controlled biomechanical simulation system. A novel biomechanical simulation system (HOSEA) was used to simulate dynamic tooth movements and measure torque expression of four different archwire groups: 0.017″ x 0.025″ torque segmented archwires (TSA) with 30° torque bending, 0.018″ x 0.025″ TSA with 45° torque bending, 0.017″ x 0.025″ stainless steel (SS) archwires with 30° torque bending and 0.018″ x 0.025″ SS with 30° torque bending (n = 10/group) used with 0.022″ self-ligating brackets. The Kruskal-Wallis test was used for statistical analysis (p < 0.050). The 0.018″ x 0.025″ SS archwires produced the highest initial rotational torque moment (My) of -9.835 Nmm. The reduction in rotational moment per degree (My/Ry) was significantly lower for TSA compared to SS archwires (p < 0.001). TSA 0.018″ x 0.025″ was the only group in which all archwires induced a min. 10° rotation in the simulation. Collateral forces and moments, especially Fx, Fz and Mx, occurred during torque application. The measured forces and moments were within a suitable range for the application of palatal root torque to incisors for the 0.018″ x 0.025″ archwires. The 0.018″ x 0.025″ TSA reliably achieved at least 10° incisal rotation without reactivation.

The effects of regional quadriceps architecture on angle-specific rapid force expression.

Evaluating anatomical contributions to performance can increase understanding of muscle mechanics and guide physical preparation. While the impact of anatomy on muscular performance is well studied, the effects of regional quadriceps architecture on rapid torque or force expression are less clear. Regional (proximal, middle, and distal) quadriceps (vastus lateralis, rectus femoris, and vastus intermedius) thickness (MT), pennation angle (PA), and fascicle length (FL) of 24 males (48 limbs) were assessed via ultrasonography. Participants performed maximal isometric knee extensions at 40°, 70°, and 100° of knee flexion to evaluate rate of force development from 0 to 200ms (RFD0-200). Measurements were repeated on three occasions with the greatest RFD0-200 and mean muscle architecture measures used for analysis. Linear regression models predicting angle-specific RFD0-200 from regional anatomy provided adjusted correlations (√adjR2) with bootstrapped compatibility limits. Mid-rectus femoris MT (√adjR2=0.41-0.51) and proximal vastus lateralis FL (√adjR2=0.42-0.48) were the best single predictors of RFD0-200, and the only measures to reach precision with 99% compatibility limits. Small simple correlations were found across all regions and joint angles between RFD0-200 and vastus lateralis MT (√adjR2=0.28±0.13; mean±SD), vastus lateralis FL (√adjR2=0.33±0.10), rectus femoris MT (√adjR2=0.38±0.10), and lateral vastus intermedius MT (√adjR2=0.24±0.10). Between-correlation comparisons are reported within the article. Researchers should measure mid-region rectus femoris MT and vastus lateralis FL to efficiently and robustly evaluate potential anatomical contributions to rapid knee extension force changes, with distal and proximal measurements providing little additional value. However, correlations were generally small to moderate, suggesting that neurological factors may be critical in rapid force expression.

The movement mode optimization of the manipulator on the elastic base according to the criterion of the mean square value of the rate of change of the drive torque

It was established the presence of boom system oscillations in the process of changing the departure into previous studies of the optimization of the movement mode of the manipulator on an elastic base according to the criterion of the root mean square value of the driving moment of the drive. The purpose of the presented article is to solve the problem of reducing these fluctuations to a minimum. In this work, optimization was performed, where as a criterion for optimizing the motion mode of the boom system of the manipulator, it is proposed to use the root mean square value of the speed of change of the driving torque of the drive. Since this amount of power load is the main external factor of the occurrence of oscillations in the elements of the boom system of the manipulator. The driving torque of the drive was find from the dynamic equations of motion of the manipulator. The rate of change of the driving torque it was define as the time derivative of the driving torque expression by the drive. Such a criterion for optimizing the traffic mode is an integral functional. Its minimization it was carry out by methods of variational calculus.&#x0D; The results of the conducted research made it possible is significantly reduce the oscillations of the elements of the boom system of the manipulator on an elastic basis during the movement in comparison with the criterion of the root mean square moment. As result, to create a drive control system that allows to implement the obtained optimal mode of movement.

Evaluation of pain, alignment efficiency, and post alignment anterior torque between I –Archwires and superelastic NiTi wires: A comparative study

: to compare the aligning efficiency, pain experienced by the patient during alignment and the post alignment third order values of anterior teeth in I arch (study) group and conventional NiTi (control) wire group.: A prospective clinical study.: A total of 40 dental arches (maxilla/mandible) were divided into 2 study groups with 20 dental arches (maxilla/mandible) in each group based on the selection criteria. Group I. Twenty dental arches (maxillary/mandibular) having 0.018” preadjusted appliance (MBT) brackets (ORMCO), aligned with I –arch 0.016”x0.014” copper NiTi wires. Group II. Twenty dental arches (maxillary/mandibular) having 0.018” preadjusted appliance (MBT) brackets by ORMCO aligned with round super elastic NiTi archwires.: I -arch copper NiTi (study group) was more efficient in alignment compared to the superelastic NiTi (control group) in the lower arch and the values are statistically significant. There was torque expression in the I-arch group as compared to the superelastic NiTi group. The subjects in the I-arch (study group) experienced lesser pain compared to the superelastic NiTi (control group) and the pain values are statistically significant.

Comparison of palatal depth and intermolar width in class I and class II div 1 malocclusion and in class II div 1 with hyperdivergent and hypodivergent pattern

: To compare the aligning efficiency, pain experienced by the patient during alignment and the post alignment third order values of anterior teeth in I arch (study) group and conventional NiTi (control) wire group.: A prospective clinical study.: A total of 40 dental arches (maxilla/mandible) were divided into 2 study groups with 20 dental arches (maxilla/mandible) in each group based on the selection criteria. Group I. Twenty dental arches (maxillary/mandibular) having 0.018” preadjusted appliance (MBT) brackets (ORMCO), aligned with I –arch 0.016”x0.014” copper NiTi wires. Group II Twenty dental arches (maxillary/mandibular) having 0.018” preadjusted appliance (MBT) brackets by ORMCO aligned with round super elastic NiTi archwires.: I -arch copper NiTi (study group) was more efficient in alignment compared to the superelastic NiTi (control group) in the lower arch and the values are statistically significant. There was torque expression in the I-arch group as compared to the superelastic NiTi group. The subjects in the I-arch (study group) experienced lesser pain compared to the superelastic NiTi (control group) and the pain values are statistically significant.

Comparative evaluation of variations in torque expression in maxillary incisor and canine using different bracket prescriptions placed at different crown levels by finite element (FE) method: An in-vitro analysis.

While using preadjusted brackets, the position of the bracket on the crown is one of the deciding factors that determine the tooth's final tip, torque, height, and rotation. The final tooth position is not optimal if the bracket is placed incorrectly or if the varying crown morphology does not correspond with the bracket design. The present study was conducted to evaluate and compare the variations in torque expression in maxillary incisor and canine using different bracket prescriptions placed at different crown levels by finite element method. For the present study, three-dimensional models of maxillary right central incisor and canine were made using CREO version 4.0 software. CREO is a powerful three-dimensional (3-D) computer-based, computer-aided design (CAD) software developed by Parametric Technology Corporation (PTC) to aid in design processes. Simulation was done to replicate the clinical situation of an active palatal root torque acting on the incisor and canine. The induced palatal movement of root tips and labial movement of crowns tips, overall stress, and von Mises stress generated in the brackets and the total equivalent strains developed in the periodontal ligament (PDL) were calculated, while the values obtained were tabulated and subjected to statistical analysis. Based on the findings of the present study, the average maximum stress produced in the bracket was calculated as 265.069 Mpa in incisor and 166.742 Mpa in the canine. Likewise, the average of the maximum displacement of root apex observed in the present study was calculated as 0.01401 mm in the incisor and 0.00421 mm in the canine, while the average strain developed in the PDL was calculated as 0.0587 for incisor and 0.0498 for the canine. Furthermore, it was, also, observed that the magnitude of strain developed in the PDL increased with increase in the stress produced by the bracket prescription for both incisor and canine. Within the limitations of the present study, it was concluded that the magnitude of displacement of root apex was significantly influenced by bracket prescription and bracket position. Also, the stress developed in the bracket was influenced by bracket prescription and position, while the variation in crown morphology in the incisor and canine played a significant role in the eventual strain developed in the PDL after torque application.

Nonlinear hierarchical control for four-wheel-independent-drive electric vehicle

As under-constrained systems, four-wheel-independent-drive (4WID) electric vehicles have more driving degrees of freedom. In this context, reasonable control and distribution of driving or braking torque to each wheel is extremely important from the vehicle safety perspective. However, it is difficult to provide the optimal wheel torque because of the time-varying characteristics and typical over-actuated nature of the system. In light of these challenges, a novel hierarchical control scheme comprising a top- and bottom-level controller is proposed herein. First, for the top-level controller, a time-varying model-predictive-control (TV-MPC) controller is designed based on an extended 3-degree-of-freedom (3-DOF) reference vehicle model. The total driving force and additional yaw moment can be obtained using the TV-MPC. Second, for the bottom-level controller, the torque expression of each wheel is determined using the equal-adhesion-rate-rule -based algorithm. The co-simulation results obtained herein indicate that the proposed control scheme can effectively improve vehicle safety.