Torque Requirements Research Articles

Theory analyses and experimental study on starting torque and seal capacity of field-control magnetic fluid seal

Magnetic fluid seal(MFS) is one of the most mature applications of magnetic fluid(MF) and is widely used in numerous fields. The permanent magnet is an integral component of the classic MFS and provides a stable and robust magnetic field. However, this leads to a high initial torque requirement and a noticeable separation between ferromagnetic particles and the base liquid in the presence of such a strong magnetic field. This situation results in starting difficulties and impedes the normal device startup, particularly in low-temperature environments. Moreover, a constant magnetic field fails to address fluctuating pressure. To address these issues, we have introduced a novel design for the field-controlled MFS. Through theoretical and finite element analyses(FEA), we derived the magnetic field distribution within the seal gap. Additionally, we established the theoretical range for the sealing capacity of the field-control MFS. Experimental results demonstrate that the magnetic field, sealing capacity, and starting torque all increase with higher coil currents. The reduction in starting torque is particularly pronounced at lower temperatures. By manipulating the magnetic field, the starting torque can be reduced by over 50%. The field-controlled MFS exhibits a 0.24 MPa sealing capacity without requiring cooling equipment, representing a 33% improvement in sealing capacity compared to the classic MFS without a coil.

Actuator optimization and deep learning-based control of pediatric knee exoskeleton for community-based mobility assistance

Lightweight and smart exoskeletons offer the potential to improve mobility in children. State-of-the-art pediatric exoskeletons are typically clinic-based since they are either tethered or portable but cumbersome and their design is often not optimized across a range of environments and users. To facilitate pediatric exoskeleton in community settings, we first proposed an actuator optimization framework that identified the optimal design parameters for both motor and transmission while minimizing the actuator mass and satisfying the output torque, speed, bandwidth, and resistance torque requirements. Guided by the optimization results, we customized a simple, lightweight actuator that met all mechatronic constraints for our portable exoskeleton (1.78 kg unilateral). Secondly, we adopted deep learning (Long Short Term Memory) based on gait phase estimation to facilitate stable control for community use. The models accurately estimated the gait phase on irregular walking patterns (accuracy 94.60%) without explicit training in children (typically developing and with cerebral palsy). The controller results demonstrated an elevated ability to adapt to the irregular gait patterns of the child with cerebral palsy. The experimental results in the child with typical development and four healthy adults demonstrated accurate assistive torque tracking performance (accuracy 97.00%) at different walking speeds (i.e., under uncertain torque to wearers). This work presented a holistic solution that includes both hardware innovation (actuator optimization framework) and software innovation (deep learning-based control) towards the paradigm shift of pediatric exoskeletons from clinic to community setting.

Design control and actuator selection of a lower body assistive exoskeleton with 3-D passive compliant supports

Physical human–robotic interaction is a crucial area of concern for robotic exoskeletons. Lower weight requirement for the worn exoskeletons limits the number and size of joint actuators, resulting in a low active degree of freedom for the exoskeletons with joint actuators having limited power and bandwidth. This limitation invariably results in reduced physical human–robotic interaction performance for the exoskeleton. Recently several techniques have been proposed for the low active degree of freedom exoskeletons with improved physical human–robotic interaction performance using better load torque compensators and improved active compliance. However, effective practical implementation of these techniques requires special hardware and software design considerations. A detailed design of a new lower body exoskeleton is proposed in this paper that can apply these recently developed techniques to practically improve the physical human–robotic interaction performance of the worn exoskeletons. The design presented includes the exoskeleton's structural design, new joint assemblies and the design of novel 3-D passive, compliant supports. A methodology of selecting and verifying the joint actuators and estimating the desired assistive forces at the contact supports based on human user joint torque requirements and the degree of assistance is also thoroughly presented. A new CAN-based master–slave control architecture that supports the implementation of recent techniques for improved physical human–robotic interaction is also fully presented. A new control strategy capable of imparting simultaneous impedance-based force tracking control of the exoskeleton in task space using DOB-based-DLTC at joint space is also thoroughly presented. Simulation verification of the proposed strategy based on the actual gait data of elderly is presented lastly.

Analysis and Design of Embedded High-Temperature Doubly Salient Electro-Magnetic Starter/Generator for Aviation

In view of the high temperature operation characteristics of the embedded starter/generator for the more electric engine (MEE), the influence of material property change on motor performance at high temperature is studied. Furthermore, considering the influence of high temperature, the electromagnetic calculation of doubly salient electro-magnetic machine (DSEM) is carried out, and the excitation design principle of DSEM under high temperature is pointed out. The performance of DSEMs using DW310 silicon steel and 1J22 iron-cobalt alloy material was compared. Based on the silicon steel material, the structural parameters of DSEM are analyzed. According to the key parameters obtained from structural parameter analysis, Box-Behnken method and genetic algorithm were used to carry out the multi-parameter and multi-objective optimization design. The optimization objectives include excitation current, voltage ripple and cogging torque, to meet the torque and power quality requirements of MEE. Then the performance of DSEM at room temperature and high temperature is analyzed by the finite element method, which verifies the effectiveness of the design. Finally, a high-temperature and high-speed DSEM prototype was processed. At the same time, in order to cooperate with the test, a DSEM ground simulation test system platform for MEE was built to test the prototype. Its design experience lays a foundation for the embedded DSEM design of more electric aircraft.

Modeling of novel circular gait motion through daisy sequence fitting algorithm in a vertical climbing snake robot

AbstractSnake robots can be used in multiple tasks, like, climbing, surveillance, pipe inspection, welding, and so forth. Current gaits of snake robots do not support rotation on a single horizontal plane in a circular fashion of a pole or tree at a fixed height. This makes snake robot extremely difficult to take the end effector to the desired target position and orientation. In addition, torque requirement of individual actuators or links of snake robot proportionally increases based on the number of links to be lifted while performing any task. In this paper, we propose a new gait called circular gait using the Daisy Sequence Fitting algorithm to solve the problems of circular rotation on a horizontal plane at a certain height with low torque. A sliding mode (SM) controller is implemented to achieve the circular gait's required position dynamically. Simulation results show that using the proposed circular gait, the end effector can be moved to any point on the circumference of the fixed horizontal plane of the pole or tree with a lesser torque. For the 0.5 kg module, circular gait moved the end effector to the target point using only 4.5 N m torque. The SM controller outperforms the proportional, integral, and derivative controllers in terms of response characteristics.

Complex dynamics of the passive biped robot with flat feet: Gait bifurcation, intermittency and crisis

During the past decades, the walking dynamics of different types of passive biped robots have garnered significant attention. This paper investigates the complex dynamics of a passive flat-footed robot, encompassing both the local bifurcation of limit cycles and global bifurcation, resulting in significant changes in the system’s walking pattern. To identify the robot’s dynamic behavior, the Lyapunov Exponents (LEs) are calculated using the small orthogonal perturbation vectors method. The obtained LEs diagram also unveils several subtle periodic windows scattered within the chaotic region, where interior crisis and intermittency occur. Moreover, two new kinds of gaits that coexist with the traditional period-1 ones are found. Of particular significance is the discovery of the double boundary crisis that caused by the critical period-3 unstable periodic orbit, and this crisis serves as the fundamental reason to the falling down on slopes of the flat-footed robots. By gaining a better understanding of the nature of passive dynamic walking, it becomes possible to design more efficient controllers that impose less stringent torque requirements on biped walking robots.

Influence of post-processing and build orientation on the micro-machinability and chip formation during micro-drilling of L-PBF AlSi10Mg

The requirement of micro holes or features on the additively manufactured (AM) components attract machinability investigations on Laser Powder Bed Fused (L-PBF) components, and directional anisotropy is one of the critical problems with parts made using L-PBF. As a result, the current study compares the machinability properties during the micro-drilling of several samples, including cast and L-PBF-produced AlSi10Mg. Moreover, the impact of T6 solution heat treatment and build orientation on microstructure, thrust force, cutting torque, surface roughness, and cutting temperature is analyzed. It was found that at a feed of 8 µm/rev and 5000 rpm, the force requirement perpendicular to the build direction (PPBD) was 23.11 % higher than parallel to the build plane direction (PBD). The force required is reduced after heat treatment because of the reduction in hardness. Similarly, a difference of 31.36 % in cutting torque requirement was observed, which increased to 46.82 % after heat treatment. At the same time, the difference in chip temperature in the as-built AlSi10Mg was less between PPBD and PBD. It was also observed that there is a reduction in the chip temperature with feed rate. The chip formation was further studied using a high-speed camera, and four stages of chip formation were identified. From the SEM analysis of the chips, microchips of different lengths and morphology can be identified, which are dissimilar to one another.

Conceptual Framework for Modelling of an Electric Tractor and Its Performance Analysis Using a Permanent Magnet Synchronous Motor

The purpose of this article is to model and validate the propulsion system of an electric tractor. Initially, the mathematical model of the ET and its load characteristics are developed based on the velocity profiles used in the agriculture ploughing operations. A PMSM is selected from the torque and power requirement of the ET. In order to replicate the ET load on the PMSM, the load is simulated in accordance with the specifications of the PMSM drive system. This article proposes a novel load-tracking control of the propulsion unit with the arrangement of a PMSM and dynamometer. The speed and torque of the propulsion motor are controlled separately using a decoupled control algorithm. The performance of the propulsion unit is verified under different load profiles of the ET. The load-tracking algorithm is used to improve the dynamic response of the propulsion motor. The propulsion system containing the mathematical model of the ET, PMSM and dynamometer is developed in MATLAB/SIMULINK and validated in a real-time environment using a hardware-in-the-loop (HIL) simulator (OPAL-RT OP5700). The result proves that the proposed load-tracking algorithm provided a better dynamic performance of the propulsion unit.

Enhancing the Reliability Assessment System for Crucial Powertrain Components through Design, Simulation, and Experiment

Article Enhancing the Reliability Assessment System for Crucial Powertrain Components through Design, Simulation, and Experiment Xiaochun Zeng 1,2,3, Gongcheng Wang 1,* , Ying Liu 2,3, Jing Liu 1,2,3, Yinglian Feng 2,3,4, Xiuyong Shi 5,6, Diming Lou 5,6, Lei Zhang 4, Tao Wei 1, and Zhong Li 1 1 Jiangling Motors Co. Ltd., Nanchang 330001, China 2 Jiangxi Province Women Science and Technology Workers Association, Nanchang 330036, China 3 Jiangxi Mechanical Engineering Society, Nanchang 330002, China 4 Magna PT Powertrain (Jiangxi), Nanchang 330200, China 5 Nanchang Automotive Institute of Intelligence & New Energy, Nanchang 330052, China 6 Tongji University, Shanghai 200092, China * Correspondence: gwang7@jmc.com.cn Received: 5 September 2023 Accepted: 19 September 2023 Published: 20 September 2023 Abstract: This article conducted innovative research on heat balance, cooling and structural strength by using Computer Aided Engineering (CAE), design, and experiment. These multifaceted approaches rely on the meticulous application of dynamic analysis, combustion analysis, fluid dynamics, and finite element analysis. This research has devised a fatigue-oxidation-creep multi-fatigue life prediction technique for thermal engines, coupled with an innovative water jacket optimization method. By addressing the design challenges arising from the demanding requirements of high explosion pressure, formidable power, and significant torque in power systems, this study has made significant strides in advancing the field. And this method was used to establish the development capability of powertrain electric drive components. To enhance reliability and prediction accuracy, a simulation and test calibration method was devised for Crucial Powertrain Components. This article establishes a robust foundation by providing comprehensive data support for reliability target decomposition, facilitating the efficient derivation of component reliability metrics. Additionally, it explores potential customer scenario failures and investigates the underlying mechanisms of powertrain malfunctions. By establishing a correlation matrix between failure modes, mechanisms, and reliability experiments, the coverage of powertrain failure mode verification experiments was significantly increased by over 95%. Ultimately, this article contributes to the formation of a comprehensive technical system for evaluating the reliability of crucial powertrain components, integrating design, simulation, and experiment.

Optimizing cotton‐picking robotic manipulator and inverse kinematics modeling using evolutionary algorithm‐assisted artificial neural network

AbstractThis study presents a particle swarm optimization (PSO) algorithm‐assisted neural‐network‐based inverse kinematics solution for a 4‐DoF (degree‐of‐freedom) cotton harvesting robot. A novel setup was developed to measure the three‐dimensional locations of in‐field cotton bolls. Dimensional optimization of the manipulator was conducted using the PSO algorithm to minimize torque requirements at joints. With the optimized links’ lengths, the targeted end‐effector positions were achieved effectively (coefficient of determination (R2) > 99.88). The genetic algorithm optimized the neural network architecture to include three hidden layers with [64 64 32] neurons, identifying the Tanh activation function as the optimal configuration. A custom loss function was used during the training of artificial neural network (ANN). Using angles predicted by the trained ANN, the end‐effector reached targeted positions with positioning errors below 13.0 mm. A hybrid model consisting of an ANN and PSO algorithm was developed to further reduce the error. This trained hybrid model resulted in a positioning error below 1.0 mm with inference time of 6.07 s during simulation phase. As compared to the ANN and PSO algorithm, hybrid model reduced the positioning error and inference time (>40.0%), respectively. For hybrid model, the mean percentage errors of 0.25%, 0.39%, and 0.84% were observed along the x‐, y‐, and z‐axis. A positioning error below 9.0 mm occurred during evaluation of the hybrid model with the fabricated manipulator. Hence, the developed hybrid model precisely determines the joint angles, allowing the end‐effector of the cotton harvesting robot to reach at targeted pose with minimum error.

Effect of Stem Diameter, Cutting Speed and Moisture Content on Cutting Torque for Green Gram Harvesting

The study was conducted during November, 2021 at Department of FMPE, CAET, OUAT, Bhubaneswar, Odisha, India to investigate the torque requirement and ascertain optimum peripheral cutting velocity of rotary cutting disc based on varying stem diameter and moisture content of green gram . The cutting operation was simulated to find the cutting torque in the instrumented soil bin, which comprises of test trolley, processing trolley and vertical rotor assembly with vertical shaft having serrated cutting disc. Sample plant stems of green gram were firmly fixed in the plant stem holder, and buried beneath the soil to simulate the natural standing of the crop as in the actual field condition. The cutting torque required to cut the stem of green gram at different crop moisture content (39.2, 41.4 and 42.9% (wb)), peripheral cutting velocity (20, 25, 30, and 35 ms-1) and plant stem diameter (2.95, 3.97 and 4.96 mm) was measured. It has been observed that peripheral cutting velocity of disc, stem diameter and moisture content of plant affected cutting torque at 1% level of significance. The cutting torque increased with decrease in moisture content and increase in diameter of plant stem of green gram. The cutting torque increased with an increase in peripheral cutting velocity up to the critical velocity of 30 ms-1, but the value decreased after critical peripheral velocity.

Development, analysis, and verification of an intelligent auxiliary beekeeping device mounted on a crawler transporter

The transportation of beehives poses a significant challenge in the beekeeping industry. To address the manual handling practices prevalent in the beekeeping industry and enhance the automation level, this study attempts the design and development of a mobile auxiliary beekeeping device mounted on a caterpillar vehicle for beehive transportation. Specifically, the design of the auxiliary device was completed in SolidWorks with the notion of the cylindrical mechanical arm. Subsequently, a dynamic model of the simulated environment is constructed using RecurDyn, facilitating the determination of the torque requirements for each joint based on the dynamic model. Furthermore, the multi-flexible body dynamics analysis is utilized to conduct a flexible analysis of the auxiliary beekeeping device’s three principal components and the maximum beehive weight, which can be safely transported, is estimated through simulation analysis. Particularly, field experiments involve the use of strain gauges to measure the stress exerted on the components of the auxiliary beekeeping device during actual beehive transportation. Additionally, it incorporates the errors and precision associated with each joint, and the planar positioning accuracy result. Meanwhile, the maximum torque required for the joints, which is about 5 N·m was determined by simulation results, affirming that the selected drive motors can meet the operational requirements. Through simulation, it is determined that the auxiliary device can handle a maximum beehive weight of 126 kg, approximately three times the weight of the standard beehives (40 kg) utilized in beekeeping farms. This ensured that the auxiliary device poses no risk of overturning during the beehive transportation. In addition, the stress levels at crucial locations are ascertained through on-site strain experiments. Interestingly, the auxiliary support part (57.68 MPa) and the spindle connection (58.8 MPa) experienced the highest stress levels; and the stress levels in the telescopic rod and lower support part remained below 5 MPa. In particular, these stress levels fall within the permissible range of the materials employed (200 MPa), which ensures the auxiliary device’s safe utilization. An evaluation of each joint’s operational accuracy showed that the planar positioning accuracy result of joint 1 and joint 2 is 9.65 mm for 50% CEP and 23.55 mm for 95% CEP, respectively. Furthermore, the highest final error was exhibited by the vertical extension joint (11.48 mm), indicating that the auxiliary device can successfully accomplish the beehive transportation tasks within beekeeping farms. Overall, this research provides a solid foundation for the subsequent development of automated beehive handling devices.

Biomechanical Load of Neck and Lumbar Joints in Open-Surgery Training.

The prevalence of musculoskeletal symptoms (MSS) like neck and back pain is high among open-surgery surgeons. Prolonged working in the same posture and unfavourable postures are biomechanical risk factors for developing MSS. Ergonomic devices such as exoskeletons are possible solutions that can reduce muscle and joint load. To design effective exoskeletons for surgeons, one needs to quantify which neck and trunk postures are seen and how much support during actual surgery is required. Hence, this study aimed to establish the biomechanical profile of neck and trunk postures and neck and lumbar joint loads during open surgery (training). Eight surgical trainees volunteered to participate in this research. Neck and trunk segment orientations were recorded using an inertial measurement unit (IMU) system during open surgery (training). Neck and lumbar joint kinematics, joint moments and compression forces were computed using OpenSim modelling software and a musculoskeletal model. Histograms were used to illustrate the joint angle and load distribution of the neck and lumbar joints over time. During open surgery, the neck flexion angle was 71.6% of the total duration in the range of 10~40 degrees, and lumbar flexion was 68.9% of the duration in the range of 10~30 degrees. The normalized neck and lumbar flexion moments were 53.8% and 35.5% of the time in the range of 0.04~0.06 Nm/kg and 0.4~0.6 Nm/kg, respectively. Furthermore, the neck and lumbar compression forces were 32.9% and 38.2% of the time in the range of 2.0~2.5 N/kg and 15~20 N/kg, respectively. In contrast to exoskeletons used for heavy lifting tasks, exoskeletons designed for surgeons exhibit lower support torque requirements while additional degrees of freedom (DOF) are needed to accommodate combinations of neck and trunk postures.

Processing and Friction Properties Evaluation of Multilayer CU Matrix Hybrid Composite Brake Pads for a Trainer Aircraft

We have developed three types of multi layer Cu matrix composite brake pads, namely, Copper-silica-BN, Copper-Si3N4-graphite, and Copper-mullite-MoS2 to solve the problem of static torque, friction coefficient in the upgraded version of Trainer aircraft. These composite brake pads were tested in a full scale brake dynamometer and static torque testing unit at ARDC, HAL. Our results shows that the braking requirements of static torque (~ 204 Kgfm), friction coefficient (~0.3-0.45) were very well met in the multilayer Copper-mullite-MoS2 composite brake pads. The role of MoS2 and Mullite in improving static torque, friction coefficient and stabilizing frictional properties in this composite brake pads were explained in detail.

Torque coordinated control of the through-the-road (TTR) 4-wheel-drive (4WD) hybrid vehicle under extreme road conditions

Vehicular safety is of considerable significance to the intelligent development of hybrid vehicles. However, the real-time stability control or reasonable torque distribution under the extreme road conditions remain a huge challenge due to the multiple uncertain parameters and difficulties to reconcile the handling and stability performance. To address the above problems for a through-the-road (TTR) 4-wheel-drive (4WD) hybrid vehicle, this study provides a handling and stability management (HSM) approach by incorporating the offline optimization rules and on-line model predictive control (MPC). Firstly, the vehicle dynamic model with seven degrees of freedom (7-DOF) is used to offline extract torque distribution rules (Offline-ETDR), and the online MPC feedback (Online-MPCF) is utilized to compensate the extra torque requirements for the poor effect under the extreme conditions. Accordingly, the offline optimization results and online correction are fused to provide the total torque demand given the real-time road condition detection. Finally, the real vehicle test are implemented to validate the effectiveness of the proposed torque coordination strategy. In comparison to the vehicle with no torque control strategy, the proposed method significantly improves the vehicle's cornering ability while also ensuring the high stability performance.

Effects of strain rate and strain softening on the installation of helical pile in soft clay

Helical piles are alternative foundation for offshore wind turbine as a green foundation. When a helical pile is screwed into soft clay, the soils exhibit strain-rate dependency as well as strain softening effect when sheared and remolded. In this study, large deformation finite-element (LDFE) model is established to investigate the penetration behavior of helical pile, where the soil flow mechanism and penetration resistance are studied considering strain rate effect and strain softening effect in soil. The numerical model is validated by comparing with available centrifuge results. Parametric studies are then conducted covering a wide range of strain rate and strain softening parameters including the strain-rate parameter, the sensitivity and ductility of the soil, and the original shear strength. It is found that the penetration behavior of helical pile is significantly influenced by the strain rate and strain softening of soil. The difference of the torque profiles between the ideal Tresca soil and the rate-dependent, strain-softening soil is 0–30%. Based on the numerical modelling results, the theoretical model to predict torque requirements for the installation of helical piles is extended by accounting for the strain rate effect and strain softening effect.

Actuation system modelling and design optimization for an assistive exoskeleton for disabled and elderly with series and parallel elasticity.

The aim of a robotic exoskeleton is to match the torque and angular profile of a healthy human subject in performing activities of daily living. Power and mass are the main requirements considered in the robotic exoskeletons that need to be reduced so that portable designs to perform independent activities by the elderly users could be adopted. This paper evaluates a systematic approach for the design optimization strategies of elastic elements and implements an actuator design solution for an ideal combination of components of an elastic actuation system while providing the same level of support to the elderly. A multi-factor optimization technique was used to determine the optimum stiffness and engagement angle of the spring within its elastic limits at the hip, knee and ankle joints. An actuator design framework was developed for the elderly users to match the torque-angle characteristics of the healthy human with the best motor and transmission system combined with series or parallel elasticity in an elastic actuator. With the optimized spring stiffness, a parallel elastic element significantly reduced the torque and power requirements up to 90% for some manoeuvres for the users to perform ADL. When compared with the rigid actuation system, the optimized robotic exoskeleton actuation system reduced the power consumption of up to 52% using elastic elements. A lightweight, smaller design of an elastic actuation system consuming less power as compared to a rigid system was realized using this approach. This will help to reduce the battery size and hence the portability of the system could be better adopted to support elderly uses in performing daily living activities. It was established that parallel elastic actuators (PEA) can reduce the torque and power better than series elastic actuators (SEA) in performing everyday tasks for the elderly.

Optimization of cutting torque in a laboratory setup for harvesting cabbage following an AI-based approach

A harvesting mechanism for cabbage harvesters suitable in small-scale fields was developed in the laboratory. In the experiment, cutting speed, forward speed and cutting position were considered as independent parameters for the torque requirement to cut the cabbage stem in the harvesting process. The experiment was designed by full factorial design and ANN-PSO (Artificial Neural Network-Particle Swarm Optimization) technique was followed to optimize these cutting parameters to achieve minimum torque requirement for cutting. The cutting torque was found to be increased with an increase in the cutting position and a decrease in the cutting speed. An RBFNN (Radial Basis Function Neural Network) model was trained with 70% of the total cutting torque data, and the rest 30% of the data was used for testing the model. The mean square error (MSE) and coefficient of determination (R2) were obtained as 0.003 and 0.986, respectively which indicates the satisfactory performance of the model. The developed RBFNN-PSO model was validated against experimented data using four different combinations of input cutting parameters obtained from optimization. The optimized values of cutting speed (rpm), forward speed and cutting position were obtained as 590.75 rpm, 0.24 m s−1 and 0.825 cm, respectively with a deviation of 5.13%.

P18: Improving Hydraulic Performance of the Left Atrial Assist Device Using Computational Fluid Dynamics

Purpose of Study: The purpose of this study was to refine the initial design of a new left atrial assist device (LAAD) using the results from computational fluid dynamics analyses (CFD). The CFD results would help guide design changes that could improve the hydraulic performance and flow patterns within the LAAD. The LAAD is a novel continuous-flow pump, implanted in the mitral plane, designed to treat patients with heart failure with preserved ejection fraction. Methods: Four different LAAD designs were evaluated. The key differences among the designs included changes to the shape and dimensions of the primary impeller blades, and the number, size, and curvature of the diffuser vanes. Steady state, frozen-rotor CFD simulations were run at flow rates and rotor speeds spanning the LAAD’s intended range of use. Of the four designs studied, the first and final designs were prototyped and underwent in vitro hydraulic performance testing. The in vitro studies were conducted by connecting a prototype LAAD to a mock circulatory loop system designed to simulate various levels of diastolic heart failure. Static pressure measurements, taken upstream, downstream, and at two other locations within the pump, were compared with CFD-predicted pressures to validate the CFD modeling approach and results. Results: The CFD-predicted static pressures agreed within 12% for design #1 and 10% for design #4 over a wide range of flow rate/rotor speed conditions providing confidence in the CFD modeling results. Regions of flow separation downstream of the impeller blade tips and the diffuser vanes were reduced for each design iteration. Increasing the impeller blade diameter, provided increased pump pressure rise at the expense of significantly higher torque and power requirements. A comparison of the hydraulic performance for the four designs, as shown in Figure 1, reveals that design #4 was able to provide the same pump pressure rise as design #1 at 3,800 vs. 4,400 rpm. Conclusions: Guided by the insight gained from each design iteration, the fourth design incorporated impeller blades with an improved alignment with the incoming flow and wider, more curved diffuser vanes that aligned with the approaching flow from the volute. These changes reduced flow separation within the impeller and diffuser regions which significantly improved the LAAD’s hydraulic performance and internal flow patterns. In vitro testing of this fourth generation LAAD design confirmed the predicted improvement in hydraulic performance.Figure 1. Comparison of the hydraulic performance for the four LAAD designs at a flow rate of 4.5 L/min and varying rotor speeds.

Are aligners capable of inducing palatal bodily translation or palatal root torque of upper central incisors? A biomechanical in vitro study

ObjectivesPrevious studies have shown that aligners have limited ability to control root movements. The purpose of this study was to investigate which modification geometry and foil thickness are optimal for generating the force-moment (F/M) systems required for palatal root torque of maxillary central incisors.Materials and methodsTooth 11 was separated from a maxillary acrylic model and connected to a movement unit via a 3D F/M sensor. Different modification geometries (crescent, capsular, double-spherical) with different depths were digitally implemented in the labio-cervical region of tooth 11 to induce an increased contact force. We evaluated the F/M systems exerted by aligners with thicknesses of 0.4–1.0 mm. F/M measurements were taken with tooth 11 in the neutral position and during palatal displacement of tooth 11 (simulating its initial clinical movement).ResultsThe mechanical requirements of palatal root torque are a palatally directed force (− Fy) and a palatal root torquing moment (− Mx). These requirements were reliably achieved with modification depths > 0.5 mm. The modification depth and foil thickness had a significant influence on − Fy magnitudes (linear mixed-effect models, p < 0.01). With the 0.75-mm aligners combined with 1.5-mm deep modifications, the palatal root torque range (palTR) started after an initial palatal crown displacement of 0.09, 0.12, and 0.12 mm for the capsular, crescent, and double-spherical modification geometries, respectively.ConclusionsA relatively early start of the palatal torque range (after a 0.1-mm palatal crown displacement) and appropriate − Fy magnitudes were achieved with 0.75-mm-thick aligners containing 1.5-mm deep capsular or crescent pressure regions. Subsequent clinical trials are required to confirm the clinical effects of these modifications.Clinical relevanceIn vitro testing indicated that modified aligners are capable of generating the F/M components required for palatal root torque of upper central incisors.