Angular Position Research Articles

Compactness of supermassive dark objects at galactic centers

We define compactness of a gravitational lens as the scaled closest distance of approach (i.e., r0/ M) of the null geodesic giving rise to an image. We model 40 supermassive dark objects as Schwarzschild lenses and compute compactness of lenses (determined by the formation of the first-order relativistic image). We then obtain a novel formula for the compactness of a lens as a function of mass to the distance ratio ( M/ Dd) and the ratio of lens–source to the observer–source distances ( Dds/ Ds). This formula yields a very important result: Just an observation of a relativistic image would give an incredibly accurate upper bound to the physical compactness (the ratio of the radius to mass) of the lens without having any knowledge of mass of the lens, angular source position, and observer–source and lens–source distances. Similarly, we show that the observation of the second-order relativistic image would give a lower value of upper bound to the physical compactness. These results, though obtained for supermassive dark objects at galactic centers, are valid for any object compact enough to give rise to relativistic images.

A Non-destructive Evaluation of Microstructural Analysis in Sn-Ag-Cu Solder Joint by Synchrotron X-Ray Radiation Tomography

This paper demonstrates a non-destructive technique to evaluate the internal microstructure in the Sn-Ag-Cu (SAC) solder joint through synchrotron X-ray radiation tomography. Synchrotron X-ray tomography is increasingly utilized for characterizing the internal microstructure of materials in 3D images. A 3D model is reconstructed from a set of 2D projection images taken from different angles and angular position during the sample rotation, thus it could provide a more comprehensive description of the microstructure of an alloy compared to 2D images. In this paper, it is successfully observed and evaluated the internal microstructure of a 900 μm solder joint sample. The key principles and methods of synchrotron X-ray tomography are briefly described. Examples of quantitative and qualitative assessments on the grain refinement effect of Mg addition to SAC35 solder joint are also presented in this paper.

Design of an SMA-Based Actuator for Replicating Normal Gait Patterns in Pediatric Patients with Cerebral Palsy.

Cerebral Palsy refers to a group of incurable motor disorders affecting 0.22% of the global population. Symptoms are managed by physiotherapists, often using rehabilitation robotics. Exoskeletons, offering advantages over conventional therapies, are evolving to be more wearable and biomimetic, requiring new flexible actuators that mimic human tissue. The main objective behind this article is the design of a flexible exosuit based on shape-memory-alloy-based artificial muscles for pediatric patients that replicate the walking cycle pattern in the ankle joint. Thus, four shape-memory-alloy-based actuators were sewn to an exosuit at the desired actuation points and controlled by a two-level controller. The loop is closed through six inertial sensors that estimate the real angular position of both ankles. Different frequencies of actuation have been tested, along with the response of the actuators to different walking cycle patterns. These tests have been performed over long periods of time, comparing the reference created by a reference generator based on pediatric walking patterns and the response measured by the inertial sensors. The results provide important measurements concerning errors, working frequencies and cooling times, proving that this technology could be used in this and similar applications and highlighting its limitations.

Maternal immune activation affects female offspring whisker movements during object exploration in a rat model of neurodevelopmental disorders

Poly I:C rat offspring are used to investigate the effects of in utero exposure to maternal immune activation (MIA) and have been suggested as a model of neurodevelopmental disorders (NDD). The behavioural symptoms of this model are diverse and can vary with external factors, including the choice of background strain and husbandry practices. Measuring whisker movements provides quantitative, robust measurements of sensory, motor and cognitive behaviours in rodents. In this study, whisker movements were investigated in 50-day-old male and female offspring of MIA-exposed rat dams and compared to age-matched offspring of control (vehicle) dams. Rat offspring were filmed using high-speed videography in a sequential object exploration task with smooth and textured objects. Poly I:C treatment effects were found in female offspring that did not increase whisker mean angular position during object exploration, especially for the smooth object, indicating an attentional deficit. Whisker tracking during object exploration is demonstrated here, for the first time, as a useful, quick and non-invasive tool to identify both treatment effects and sex differences in a model of MIA-induced NDDs.

Adaptive synergetic control for electronic throttle valve system

AbstractThis study has developed adaptive synergetic control (ASC) algorithm to control the angular position of moving plate in the electronic throttle valve (ETV) system. This control approach is inspired by synergetic control theory. The adaptive controller has addressed the problem of variation in systems parameters. The control design includes two elements: the control law and adaptive law. The adaptive law is developed based on Lyupunov stability analysis of the controlled system, and it is responsible for estimating the potential uncertainties in the system. The effectiveness of the proposed adaptive synergetic control has been verified by numerical simulation using MATLAB/Simulink. The results showed that the ASC algorithm could give good tracking performance in the presence of uncertainty perturbations. In addition, a comparison study has been made to compare the tracking performance of ASC and that based on conventional synergetic control (CSC) for the ETV system. The simulated results showed that the performance of ASC outperforms that based on CSC. Moreover, the results showed that the estimation errors between the actual and estimated uncertainties are bounded and there is no drift in the developed adaptive law of ASC.

Wake-induced vibration suppression for a circular cylinder using a pair of jets

The wake-induced vibration (WIV) presents significant challenges to the structural integrity of multi-cylinder configurations. To effectively alleviate this problem, a numerical simulation is conducted to assess the effect of an active control technique that uses two jets located at the shoulder region of a cylinder to suppress WIV in two-degree-of-freedom. The equations of motion for the WIV response are solved using the Newmark-β method. The Newmark-β method is employed to solve the equations of motion governing the WIV response. Three kinds of angular position (β) on WIV suppression are investigated in detail, including 30°, 60°, and 90°. The angular position β is defined as the angle between the injection angle and the horizontal line. When the angular position (β) is 30°, the maximum cross-flow amplitude ratio (CFAR) is reduced from 0.9 (uncontrolled) to 0.5 (β = 30°), a reduction of approximately 44%. On the contrary, the maximum CFARs remain approximately 1.0 for the case 3 (β = 60°) and case 4 (β = 90°). Especially for the case 4, the cylinder showed the galloping response after the upper branch region. Since the jets are positioned on the vibration cylinder shoulders, the vortexes caused by the jets are opposite to the main vortexes induced by the cylinder. As a consequence, the jets shred the main vortexes in the wake of the cylinder, which leads to the driving force of the vibration reduction. Therefore, the cylinder's WIV amplitude is significantly suppressed.

Kinematic modelling of three link robot manipulator and joint torque optimization using genetic algorithm in MATLAB

This research article presents the non-linear dynamic of a three-link robotic manipulator formulated by the Newton-Euler method. The planar manipulator is composed of three links and three revolute joints rotating about the z-axis. The three nonlinear non-homogeneous dynamic equations have been solved graphically with the help of MATLAB by phase variable method. The work represents the graphical solution of the transient response of angular position, and angular velocity of each link member for a predetermined interval of time. With the help of simulated value from MATLAB, torque characteristics have been determined for different torque ratios and optimum torque has been derived using a genetic algorithm to move the manipulator in a proper direction.

Control system of the electric drive of a robot with a dc motor

Problem. Robotics and flexible production systems are the most important technical basis for the intensification of production. The use of robotic systems is expanding every year. This paper considers a two-circuit servo control system using the example of a DC motor current and speed control system and examines the functional diagram of the third circuit, a digital angle control system. Using the Matlab + SIMULINK software package, the servo drive and the digital system for controlling the angular position of the robot manipulator were modelled. Goal. As a result of the analysis, the purpose of the study was highlighted: the development of a digital system for adjusting the angular position of the manipulator, improve the quality of its positioning. Tasks: to study work management systems; to study the drives of robots; to get a mathematical model of an electric motor; to develop a machine diagram of a digital electric drive; to synthesize a three-loop robot positioning control system. Methodology. The research problems should be solved by methods of analysis and synthesis of automatic control systems. Results. In the work, a three-circuit control system of the electric drive of a robot with a direct current motor was developed. Thus, as a result of modeling the operation of a digital electric drive with three control circuits for current, speed and positioning, an aperiodic transient process was provided with quality indicators. Originality. Thus, the results of simulation of the two-loop servo control system showed that the dynamic characteristics of the electric motor in terms of current and speed of rotation, which meet the requirements of the task, are provided by the PI controller in the current control circuit and the PID controller in the speed control circuit. Thus, as a result of modeling the operation of a digital electric drive with three control circuits for current, speed and positioning, an aperiodic transient process was provided with quality indicators. Practical value. The following results were obtained during the research: the best control law for the current circuit is the proportional-integral (PI) law; the best control law for the speed contour is the proportional-integral-differential (PID) law; the best control law for a digital positioning control loop is the proportional (P) law.

Cascade PID Control for Altitude and Angular Position Stabilization of 6-DOF UAV Quadcopter

UAVs are commonly used in transportation, especially in the express delivery of light cargo parcels. However, controlling UAVs is difficult because of their complex structure and wide range of operations in space. The research contribution is proposed a cascade control structure using six PID controllers for the 6-DOF UAV quadcopter, that ensures the altitude angulars positions control at the desired values and maintains flight balance stability for the 6-DOF UAV quadcopter. First, the mathematical dynamic models for the 6-DOF UAV quadcopter have been researched and developed, including the translational dynamic mathematical model and the rotational dynamic mathematical model of the 6-DOF UAV quadcopter. This is a complex object with strong nonlinearity and difficult control. And then, the article introduces the method of designing six PID controllers for 6-DOF UAV quadcopter to meet the requirements, based on applying the Ziegler-Nichols experimental method. Applying the Ziegler-Nichols experimental method makes the process of designing a UAV quadcopter control system simple, straightforward and heuristics with fast controller parameters tuning. Next, the article presents the results of modeling and simulation of the 6-DOF UAV quadcopter control system on Matlab/Simulink. The simulation results show that the six proposed PID controllers have ensured the flight balance stability at the desired altitude and angular positions with overshoot less than 20%, steady-state error less than 1%. This shows the prospect of applying the proposed PID control method to physical UAVs, easily adjusting PID parameters to suit the flight environment.

Operational Radiation Safety Considerations During Equine Superficial Radiation Treatment Using Portable X-Ray Devices

Abstract Veterinary personnel exposure due to scattered x rays, when present during superficial radiation treatment (SRT), was evaluated. Veterinary personnel presence is needed during SRT to minimize the degree of required aesthesia to horses. Animal treatment was simulated, and exposure rates determined for 50, 70, and 100 kV x rays using eight different SRT applicators. Exposure rates at the surface of a solid water phantom (SWP) phantom ranged from 3.9 mR h−1 to 396 mR h−1 for 50 kV, from 41 mR h−1 to 2,880 mR h−1 for 70 kV, and from 235 mR h−1 to 7,500 mR h−1, for 100 kV, respectively. A horse phantom was used to mimic SRT equine ocular treatment creating a spatial exposure field where the directional scatter was measured at 1 m. The minimum distance away from the source to reach < 2 mR h−1 varied with angular position and energy and was lowest for all energies directly behind the x-ray tube. The closest distance before exceeding 2 mR h−1 at 50 kVp was determined to 1.96 m. A worker could stand 1 m behind the x-ray tube at 50 kVp with 0.25 mm lead for 15,106 hours. Typical SRT treatment times for horse eyelid squamous cell carcinoma are less than 5 minutes, and radiation doses to practitioners are expected to be well below local administrative ALARA limits.

Development of controller for position sensor on the base of sine-cosine rotary transformer

Background: Sine-cosine rotary transformers, being electromechanical position sensors, have a relatively high accuracy and resistance to harsh operating conditions, which makes them attractive for use in automotive technique and equipment installed on its base. To generate excitation voltages, process measuring signals and calculate, depending on them, the angular position of the axis on which such a sensor is installed, special controllers with software and hardware implementation are designed. Aims: The development of software and hardware for a controller of position sensor which is based on a sine-cosine rotary transformer in the amplitude mode. Methods and materials: Taking into account electromagnetic processes on which the operation of a sine-cosine rotary transformer in the amplitude mode is based, methods of system analysis, methods of developing and debugging software, methods of experimental researches and processing their results were applied. Results: A detailed description of the controller of a sine-cosine rotary transformer in amplitude mode is given, as well as its implementation using microprocessor technology and specialized tools for generating, capturing and processing signals. The structure of the controller software is given, as well as technical solutions are described aimed at improving the accuracy of measuring the angular position and the rational implementation of computational processes. The results of the experimental researches illustrate the achievement of the given purpose. Conclusion: The development of a controller for a sine-cosine rotary transformer in the amplitude mode required the detailed consideration and coordination of electromagnetic, electrical and computational processes, as well as the use of various technical solutions aimed at improving the accuracy of measuring the angular position. The results obtained can be applied in the development of controllers for various electromechanical position sensors.

CNN-based track reconstruction study for gamma-ray pair telescope

MeV Gamma-ray Telescope (MGT) is a conceptual mission aimed at improving the detection sensitivity of gamma-ray astronomy in the MeV energy range. It consists of three sub-detectors: Gamma-ray Conversion silicon tracker, CALOrimeter and Anti-Coincident Detector. In this paper, a track reconstruction algorithm based on Convolutional Neural Networks (CNN) is developed for MGT. In order to train and test the model, Geant4 simulation is used and generates a large number of gamma-ray events at nine energy points in the energy band from 0.5 GeV to 10 GeV. Finally, the reconstruction results of angular resolution, position resolution and acceptance are shown. The testing results indicate that the angular resolution of MGT significantly improves in the 0.5∼10 GeV range compared with Fermi-LAT.

Sorting infrared optical vortices with a nonlinear angular lens.

Analogous to the regular lens, which spatially maps plane waves in the space domain to distinct points in the Fourier domain, the angular lens establishes the mapping relations between an angular mode and angular position, thus providing an effective toolkit for detecting an optical vortex. However, using the angular lens to sort infrared optical vortex modes via nonlinear optical processes remains relatively unexplored. Here, we design a nonlinear optical version of the angular lens to map the various infrared optical vortex modes to different angular positions in the visible region. We successfully sort nine infrared optical vortex modes of different topological charges with a visible camera, showing the cost-effective ability to sort infrared vortices compared to a relatively expensive infrared camera. Our scheme holds promise for infrared remote sensing, infrared vortex-encoded optical communications, and so on.

Geometric Error Identification of Gantry-Type CNC Machine Tool Based on Multi-Station Synchronization Laser Tracers

Laser tracers are a three-dimensional coordinate measurement system that are widely used in industrial measurement. We propose a geometric error identification method based on multi-station synchronization laser tracers to enable the rapid and high-precision measurement of geometric errors for gantry-type computer numerical control (CNC) machine tools. This method also improves on the existing measurement efficiency issues in the single-base station measurement method and multi-base station time-sharing measurement method. We consider a three-axis gantry-type CNC machine tool, and the geometric error mathematical model is derived and established based on the combination of screw theory and a topological analysis of the machine kinematic chain. The four-station laser tracers position and measurement points are realized based on the multi-point positioning principle. A self-calibration algorithm is proposed for the coordinate calibration process of a laser tracer using the Levenberg–Marquardt nonlinear least squares method, and the geometric error is solved using Taylor’s first-order linearization iteration. The experimental results show that the geometric error calculated based on this modeling method is comparable to the results from the Etalon laser tracer. For a volume of 800 mm × 1000 mm × 350 mm, the maximum differences of the linear, angular, and spatial position errors were 2.0 μm, 2.7 μrad, and 12.0 μm, respectively, which verifies the accuracy of the proposed algorithm. This research proposes a modeling method for the precise measurement of errors in machine tools, and the applied nature of this study also makes it relevant both to researchers and those in the industrial sector.

Wide Linearity Range 3D Magnetic Sensor and Angular Position Detector Based on a Single FePt Spin-Orbit Torque Device.

Three-dimensional (3D) vector magnetic sensors play a significant role in a variety of industries, especially in the automotive industry, which enables the control of precise position, angle, and rotation of motion elements. Traditional 3D magnetic sensors integrate multiple sensors with their sensing orientations along the three coordinate axes, leading to a large size and inevitable nonorthogonal misalignment. Here, we demonstrate a wide linearity range 3D magnetic sensor utilizing a single L10-FePt Hall-bar device, whose sensitivity is 291 VA-1 T-1 in the z-axis and 27 VA-1 T-1 in the in-plane axis. Based on the spin-orbit torque-dominated magnetization reversal, the linear response of anomalous Hall resistance within a large linear range (±200 Oe) for the x, y, and z components of magnetic fields has been obtained, respectively. Typically, it exhibits a relatively lower magnetic noise level of 7.9 nV at 1 Hz than previous results, improving measurement resolution at the low frequency. Furthermore, we provide a straightforward approach for noncontact angular position detection based on a single Hall-bar device, which shows great potential for application in rotational motion control.

Flow past a random array of statistically homogeneously distributed stationary Platonic polyhedrons: Data analysis, Probability maps and Deep Learning models

We perform particle-resolved direct numerical simulations (PR-DNS) of the flow past a random array of stationary Platonic polyhedrons seeded in a tri-periodic box at Reynolds number Re=1, 10, and 100 and solid volume fraction 0.05, 0.1 and 0.2. Using Platonic polyhedrons enables us to examine the effects of particle angularity on the hydrodynamic force and torque exerted on the stationary particles in a controlled manner. We report the average drag, lift, and torque coefficients as well as their respective distribution. We explore the relationship between the particle angularity, particle angular position, flow disturbances created by the neighboring particles, and the hydrodynamic force and torque exerted on each individual particle. We attempt to extend our probability map based model (MPP), our Physics Informed neural network (PINN) model previously developed for spheres to Platonic polyhedrons, and propose an additional NN architecture. We show that ignoring the angular position and actual shape of the reference and neighboring particles constitutes a reasonable first order approximation that significantly simplifies the construction of deterministic models of hydrodynamic forces and torques at low Re=1 to moderate Re=10. At high Re=100, both the MPP model and the PINN model without any additional knowledge of the particle shape and angular position fail to properly predict the force and torque fluctuations. We then design a Convolutional Neural Network (CNN) architecture that is able to maintain a satisfactory performance at Re=100 but requires additional input data in the form of a coarse-grained velocity field around each particle. Overall, predicting the torque fluctuation remains a significant challenge.

A Bioinspired Control Strategy Ensures Maneuverability and Adaptability for Dynamic Environments in an Underactuated Robotic Fish

Bioinspired underwater robots can move efficiently, with agility, even in complex aquatic areas, reducing marine ecosystem disturbance during exploration and inspection. These robots can improve animal farming conditions and preserve wildlife. This study proposes a muscle-like control for an underactuated robot in carangiform swimming mode. The artifact exploits a single DC motor with a non-blocking transmission system to convert the motor’s oscillatory motion into the fishtail’s oscillation. The transmission system combines a magnetic coupling and a wire-driven mechanism. The control strategy was inspired by central pattern generators (CPGs) to control the torque exerted on the fishtail. It integrates proprioceptive sensory feedback to investigate the adaptability to different contexts. A parametrized control law relates the reference target to the fishtail’s angular position. Several tests were carried out to validate the control strategy. The proprioceptive feedback revealed that the controller can adapt to different environments and tail structure changes. The control law parameters variation accesses the robotic fish’s multi-modal swimming. Our solution can vary the swimming speed of 0.08 body lengths per second (BL/s), and change the steering direction and performance by an angular speed and turning curvature radius of 0.08 rad/s and 0.25 m, respectively. Performance can be improved with design changes, while still maintaining the developed control strategy. This approach ensures the robot’s maneuverability despite its underactuated structure. Energy consumption was evaluated under the robotic platform’s control and design. Our bioinspired control system offers an effective, reliable, and sustainable solution for exploring and monitoring aquatic environments, while minimizing human risks and preserving the ecosystem. Additionally, it creates new and innovative opportunities for interacting with marine species. Our findings demonstrate the potential of bioinspired technologies to advance the field of marine science and conservation.

Numerical Study of Wheat Particle Flow Characteristics in a Horizontal Curved Pipe

Energy consumption is one of the important indicators of green development. The pressure drop and the particle kinetic energy loss in the pipe bend result in high energy consumption of wheat pneumatic conveying. In this paper, the CFD-DEM method is used to study the characteristics of flow field in horizontal pipe bend. The results show that the particles converge together under the force of the curved pipe wall to form a particle rope. With increasing pipe bend ratio R/D, the aggregation of particle bundles becomes stronger and the particle spiral phenomenon decreases. The particles impact the pipe wall at an angular position of θ = 30–60° around the bend, and their velocity decreases slowly under the friction resistance of the pipe wall. The velocity loss caused by particles impacting on the pipe wall increases with increasing initial velocity. When the particle mass flow rate is 1.26 kg/s and the gas velocity is 10 m/s, the pressure drop in the bend decreases and then increases with increasing R/D. The pressure drop of the bend is smallest for R/D = 2 and increases gradually with increasing gas-phase velocity. With increasing of R/D, the wall shear force between the particles and the bending pipe decreases and then increases, and the position of the maximum force moves towards the bottom of the bending pipe. The area over which the wall shear force acts continues to decrease because of the aggregation of particle bundles. The research results provide a theory for optimal design and application of pneumatic conveying equipment for wheat particles.

СТАБИЛИЗАЦИЯ ПРОЦЕССА – УСЛОВИЕ ЕГО ОБЪЕКТИВНОГО ИССЛЕДОВАНИЯ

Research of the interrelationships between the time periods of stabilization of the technological process of trier grain cleaning from: feeding the grain mixture into the trier; its initial contamination; speed mode of operation and angular position of the output tray relative to the horizon are satisfied. They were carried out using experimental equipment that provided separate, regulated and continuous supply of grain mixture components into the trier with a looped movement of purified grain. Standard methods and instruments, as well as special instruments developed at the Federal State Budgetary Institution VNIITiN, were used to assess the physical and mechanical properties of the components of the grain mixture. It was found that with a supply of 1.2 t/h, an initial contamination of 1.3% and a lifting angle of the output tray of 55°, the speed mode of operation of 36.0 rpm is excessive, while stabilization of the process is not completed even after 15 minutes (92% ), the length of the free section of the cellular surface is 0.70 - 0.75 m, which increases the level of residual grain contamination to 0.025 - 0.04%, which does not meet the requirements for seeds of the OS category. The possibility of reducing the comparable level of process stabilization by 6 times when the operating speed is reduced to 34.6 rpm (by 3.9%) has been confirmed. Reducing the operating speed to 34.0 rpm leads to an increase in process losses to 16.85%. It has been established that with an increase in the initial contamination of the grain mixture to 2.6%, the stabilization period of the process at a speed mode of 34.6 rpm increases from 4.5 to 5.5 minutes, and technological losses reach the maximum permissible value (5%). The method for calculating the actual degree of stabilization of the process with its assessment based on the removal of impurities has been refined.

ДВОКАНАЛЬНИЙ ГРАВІМЕТР АВІАЦІЙНОЇ ГРАВІМЕТРИЧНОЇ СИСТЕМИ

A two-gyro gravimeter of the aviation gravimetric system is proposed and investigated, which provides higher measurement accuracy than known gravimeters, due to the elimination of errors from the cross angular velocities of the base and the angular velocity of the Earth's rotation and the measurement of the full vector of the acceleration of gravity. To measure the acceleration of gravity, an AGS is proposed, which has greater accuracy and speed than known and consists of a three-stage gyroscope located in the inner and outer frames, equipped with interframe correction systems, which include an angle sensor (DC) located on the axis of the inner frame of the gyroscope and a torque sensor (DM) connected to its output is located on the axis of the outer frame. DM, located on the axis of the inner frame, is connected to the DC output. An additional, identical to the first, three-stage gyroscope, the rotor of which rotates in the opposite direction from the main gyroscope, is introduced in the AGS under consideration. The additional gyroscope of the AGS is also provided with similar correction systems, which consist of a DC located on the axis of the inner frame, and a DM located on the axis of the outer frame connected to its output, a DC located on the axis of the outer frame, to the output of which a DM located on the axis is connected inner frame The centers of gravity of two identical (main and additional) gyroscopes are shifted by the same distance in one direction along the axes of rotation of the rotors of the gyroscopes relative to the axes of the outer frames. The vectors of the kinetic moments of the two gyroscopes are oppositely directed. In the two-channel gravimeter, two output signals of linear acceleration are formed as the sum of signals from DC of two gyroscopes relative to one z-axis and as the sum of signals from DC of two gyroscopes relative to the second x-axis. The output signals are fed to the computer. Both gyroscopes of the system's gyrogravimeter are mounted on a platform whose angular position is controlled by a motor (DV) installed on the x-axis and a DV on the z-axis. Both motors control the angular position of the platform by signals. The computer also receives signals from the system for determining navigation parameters and from the height meter.