A Modified Van Der Pol Oscillator Model for the Unsteady Lift Produced by a Flapping Flat Plate for Different Positions of the Rotation Axis

To understand the nonlinear interaction between unsteady aerodynamic forces and the kinematics of structures, we theoretically and numerically investigated the characteristics of lift coefficients produced by a flapping thin flat plate controlled by the rotation axis position. The flat plate was placed in a 2-D incompressible flow at a very low Reynolds number (Re = 300). We showed that the behavior of the unsteady aerodynamic forces suggests the existence of a limit cycle. In this context, we developed a Reduced Order Model (ROM) by resolving the modified van der Pol oscillator using the Taylor development method and computational fluid dynamics (CFD) solutions. A numerical solution was obtained by integrating the differential equation of the modified van der Pol oscillator using the fourth-order Runge–Kutta method (RK4). The model was validated by comparing this solution with the reformulated equation of the added mass lift coefficient. Using CFD and ROM solutions, we analyzed the dependency of the unsteady lift coefficient generation on the kinematics of the flapping flat plate. We showed that the evolution of the lift coefficient is influenced by the importance of the rotation motion of the Leading Edge (LE) or Trailing Edge (TE), according to the position of the rotation axis. Indeed, when the rotation axis is moved towards the LE, the maximum and the minimum values of the lift coefficient are proportional to the downward and upward motions respectively of the TE and the rotation axis. However, when the rotation axis is moved towards the TE, the maximum and the minimum values of the lift coefficient are proportional to the downward and upward motions respectively of the LE and the rotation axis.

Dynamic Modelling of Piston the Motion in Combustion Engines

The presented work discusses a methodology for analysis of noise emissions from a diesel engine. A numerical model of the piston motion, analyzing its lateral, reciprocating and rotation motion, has been presented in order to investigate the lateral motion of the piston skirt assembly and resulting vibrations induced as a result of these motions in the engine block. Various parameters of modal analysis were obtained using the mobility analysis. The presented methodology was validated by data obtained from a diesel engine test set up. The predicted results matched well with those of measured data, hence validating the presented scheme.

Automated 3D reconstruction of the fetal thorax in the standard atlas space from motion-corrupted MRI stacks for 21-36 weeks GA range

Slice-to-volume registration (SVR) methods allow reconstruction of high-resolution 3D images from multiple motion-corrupted stacks. SVR-based pipelines have been increas- ingly used for motion correction for fetal MRI since they allow more informed and de- tailed diagnosis of brain and body anomalies including congenital heart defects (Lloyd et al., 2019). Recently, fully automated rigid SVR reconstruction of the fetal brain in the atlas space was achieved in (Salehi et al., 2019) that used segmentation and pose es- timation convolutional neural networks (CNNs). However, these CNN-based methods have not yet been applied to the fetal body region. Meanwhile, the existing rigid and deformable SVR (DSVR) solutions (Uus et al., 2020) for the fetal trunk region are limited by the requirement of manual input as well the narrow capture range of the classical gradient descent based registration methods that cannot resolve severe fetal motion fre- quently occurring at the early gestational age (GA). Furthermore, in our experience, the conventional 2D slice-wise CNN-based brain masking solutions are reportedly prone to errors that require manual corrections when applied on a wide range of acquisition protocols or abnormal cases in clinical setting. In this work, we propose a fully automated pipeline for reconstruction of the fetal thorax region for 21-36 weeks GA range MRI datasets. It includes 3D CNN-based intra-uterine localisation of the fetal trunk and landmark-guided pose estimation steps that allow automated DSVR reconstruction in the standard radiological space irrespec- tive of the fetal body position or the regional stack coverage. The additional step for generation of the common template space and rejection of outliers provides the means for automated exclusion of stacks affected by low image quality or extreme motion. The pipeline was evaluated on a series of experiments including fetal MRI datasets and simulated rotation motion. Furthermore, we performed a qualitative assessment of the image reconstruction quality in terms of the definition of vascular structures on 100 early (median 23.14 weeks) and late (median 31.79 weeks) GA group MRI datasets covering 21 to 36 weeks GA range.

Geometric Calibration of Rotational Vision System for Dynamic Exterior Orientation

Rotational vision system (RVS) is a common type of active vision with only rotational freedom. Typically, the rotational freedom is provided by turntable and pan-tilt-zoom (PTZ). Or eye in hand (EIH) structure in an articulated arm robot. The ideal assumption that rotation axes are perfectly aligned with the coordinate axes of the local camera is mostly violated due to assembling deviations and limitations of manufacturing accuracy. To solve this problem, we propose a generalized deviation model for a specified rotation axis that relates the rotation motion of the platform to the exterior orientation (EO) of the camera. Based on it we put heuristic estimation algorithms through minimizing global reprojection error and fitting a circle in space respectively for rotating platform with or without accurate angle measurements with constrained global optimization. Implemented experiments on a servo pan-tilt turntable validate the accuracy and efficiency of the above models and calibration technique.

Cutting efficiency of two heat-treated files in rotation and reciprocation motions

Background This study aimed at assessing the effect of different kinematics as well as different instrument designs on efficiency of cutting of two heat-treated nickel–titanium systems. Forty resin canals with 30°-angle of curvature and a length of 16 mm were utilized in this research. They were divided into four groups depending on the instrument and the operating kinematic, group I; Azure rotary system in rotation motion, group II; Azure rotary system in Reciprocation motion, group III; Fanta AF One rotary system in rotation motion and group IV; Fanta AF One rotary system in reciprocation motion. Blocks were labeled and then weighed pre- and post-preparation with delta weight (Δ wt = wt pre − wt post) and data were documented for statistics evaluation. Results Resin canals prepared using Fanta AF One rotary system showed significantly higher weight loss than Azure rotary system in both rotation and reciprocation (P < 0.001). Insignificant difference was reported for rotation and reciprocation movements in both file systems. Conclusion The instrument’s cross section revealed a more significant impact on cutting efficiency than the motion used.

Rotational stability of thoracolumbar junction fixation systems

Objective To compare the rotational stability of fusion constructs using bisegmental fixation of Th12-L2 vertebrae with anterior stabilization or pedicle screw fixation.Material and Methods The strength, rigidity and limit of elasticity in the “injured vertebral motion segments (VMS) – bisegmental anterior stabilization” system under dislocating rotational loads were estimated. The data obtained were compared with the similar characteristics of the “injured VMS – bisegmental 4-screw transpedicular metal construction” system and intact spine segments.Results Under rotational loads the limits of elasticity of injured spine segments of Th12-L2 with anterior stabilization and transpedicular screw fixation (TSF) is 45.5 and 41.7%, respectively, and the general strength is 66.4% and 80%, respectively, as compared with those intact VMS. Rigidity parameters of anterior-stabilized and pedicle screw fixated VMS with unstable damage of L1 are 60.2 and 93.9%, accordingly, in comparison with those intact VMS.Conclusion No significant differences were observed between bisegmental anterior stabilization and bisegmental pedicle screw fixation of thoracolumbar junction in terms of the key mechanical properties. When treating patients with unstable thoracolumbar spine injuries using bisegmental anterior stabilization or transpedicular fixation with 4-screw spinal system possible rotation motion amplitude of operated segments must not exceed 50% of maximum physiological limits.

Modelling and implementation of soft bio-mimetic turtle using echo state network and soft pneumatic actuators

Advances of soft robotics enabled better mimicking of biological creatures and closer realization of animals’ motion in the robotics field. The biological creature’s movement has morphology and flexibility that is problematic deportation to a bio-inspired robot. This paper aims to study the ability to mimic turtle motion using a soft pneumatic actuator (SPA) as a turtle flipper limb. SPA’s behavior is simulated using finite element analysis to design turtle flipper at 22 different geometrical configurations, and the simulations are conducted on a large pressure range (0.11–0.4 Mpa). The simulation results are validated using vision feedback with respect to varying the air pillow orientation angle. Consequently, four SPAs with different inclination angles are selected to build a bio-mimetic turtle, which is tested at two different driving configurations. The nonlinear dynamics of soft actuators, which is challenging to model the motion using traditional modeling techniques affect the turtle’s motion. Conclusively, according to kinematics behavior, the turtle motion path is modeled using the Echo State Network (ESN) method, one of the reservoir computing techniques. The ESN models the turtle path with respect to the actuators’ rotation motion angle with maximum root-mean-square error of $$1.04 \times 10^{-11}$$ 1.04 × 10 - 11 . The turtle is designed to enhance the robot interaction with living creatures by mimicking their limbs’ flexibility and the way of their motion.