Pitch Axis Research Articles

A trim problem formulation for maximum control authority using the Attainable Moment Set geometry

This paper presents a generic trim problem formulation, in the form of a constrained optimization problem, which employs forces and moments due to the aircraft control surfaces as decision variables. The geometry of the Attainable Moment Set (AMS), i.e. the set of all control forces and moments attainable by the control surfaces, is used to define linear equality and inequality constraints for the control forces decision variables. Trim control forces and moments are mapped to control surface deflections at every solver iteration through a linear programming formulation of the direct Control Allocation algorithm. The methodology is applied to an innovative box-wing aircraft configuration with redundant control surfaces, which can partially decouple lift and pitch control, and allow direct lift control. Novel trim applications are presented to maximize control authority about the lift and pitch axes, and a “balanced” control authority. The latter can be intended as equivalent to the classic concept of minimum control effort. Control authority is defined on the basis of control forces and moments, and interpreted geometrically as a distance within the AMS. Results show that the method is able to capitalize on the angle of attack or the throttle setting to obtain the control surfaces deflections which maximize control authority in the assigned direction. More conventional trim applications for minimum total drag and for assigned angle of elevation are also explored.

Solar sail attitude control using shape variation of booms

Active attitude control of solar sails is required to control the direction of the force generated by Solar Radiation Pressure (SRP). It is desirable to control the attitude through propellant-free means. This paper proposes a new method for attitude control of solar sails: A boom consisting of “smart” structural material can be deformed by the piezoelectric actuator, and Solar Radiation Pressure torque will be generated due to shape variation of sail membrane caused by boom deformation. The method has the advantages of simple structure, small disturbance and small additional load, and is not limited by the size of the solar sail. The case of rendezvous with the Asteroid 2000 SG344 is used to verify the attitude control around the pitch and yaw axes.

Research on Image Motion Compensation of an Airborne Camera with a Focal Plane Charge-Coupled Device Camera and an Analysis of Image Motion

The imaging quality of a target is dramatically influenced by image motion (IM), which results from the relative movement between a charge-coupled device (CCD) camera and an aircraft during the exposure time. Therefore, it is quite necessary to produce appropriate systems to compensate for this kind of movement and achieve high-quality, real-time imaging. The image motion velocity should be precisely calculated to compensate for the image motion as much as possible. In the paper, several methods were introduced to calculate the image motion velocity by using coordinate transformation, which deduced the image motion value of a given point by considering the difference before and after the gesture angles and position changes. Furthermore, both a theoretical and a mechanical image motion compensation (IMC) method were analyzed. A three-axis stable platform was assembled between the camera system and the unmanned aircraft. The IM caused by variation in the airplane gesture angles, including the pitch angle, yaw angle and roll angle, could be compensated by the reverse rotation of the stable platform in the corresponding axis. Similarly, the IM caused by the aircraft’s continuing flight could be compensated by the reverse rotation in the pitch axis. The residual errors of the IMC of the camera from the aircraft navigation were analyzed and calculated in detail. The residual errors of the image points were less than one third of the diameter of a CCD pixel, which demonstrates that the IMC system satisfied the imaging system.

Research on control technology of tip-tilt mirror system in adaptive optics

In order to solve the control problem of the tip-tilt mirror under the unknown disturbance, a nonlinear disturbance observer with adaptive ability based on the sliding mode control is designed.Firstly, the sliding mode control method of the tip-tilt mirror system is established with Lyapunov functions. Secondly, an adaptive nonlinear disturbance observer is developed on a basis of observer model. Finally, the proposed sliding mode control method is combined with a nonlinear observer with adaptive capability to achieve the goal of improving the control accuracy of the system, while also reducing the chattering caused by the system. The experiment proves that this method is achievable. The experimental results show that the tracking error of the azimuth axis is reduced from 1.637μrad to 1.083μrad, and the accuracy is improved by about 51.2%. The tracking error of the pitch axis is reduced from 1.966μrad to 1.614μrad, and the accuracy is improved by about 21.8%. This method can greatly weaken the inherent chattering and external disturbance of the system, and improve the stability of the tip-tilt mirror system.

Low Back Pain-Behavior Correction by Providing Haptic Feedbacks: A Preliminary Investigation.

The activities performed by nurses in their daily activities involve frequent forward bending and awkward back postures. These movements contribute to the prevalence and development of low back pain (LBP). In previous studies, it has been shown that modifying their posture by education and training in proper lifting techniques decreases the prevalence of LBP. However, this education and training needs to be implemented daily. Hence, implementing the use of a wearable device to monitor the back posture with haptic feedback would be of importance to prevent LBP. This paper proposes a wearable device to monitor the back posture of the user and provide feedback when the participant is performing a possible hurtful movement. In this study, a group of participants was asked to wear the device while performing three of the most common activities performed by nurses. The study was divided into three sessions: In the first session, the participants performed the activities without feedback (baseline). During the second session, the participants received feedback from the wearable device (training) while performing the three tasks. Finally, for the third session, the participants performed the three tasks again, but the haptic feedback was turned off (validation). We found an improvement in the posture of more than 40% for the pitch (lateral bending) and roll (forward/backward bending) axes and 7% for the yaw (twisting) axis when comparing to the results from session 1 and session 2. The comparison between session 1 and session 3 showed an overall improvement of more than 50% for the pitch (lateral bending) and roll (forward/backward bending) axes and more than 20% for the yaw axis. These results hinted at the impact of the haptic feedback on the participants to correct their posture.

Modelling and Analysis of Laser Beam rider Guided Tank Ammunition with a Diameter of 155 mm


 
 
 On the battlefield of today, it has become an important requirement to hit moving or fixed targets by using tank or artillery ammunition with high precision. However, while there are many articles on guiding tactical missiles, it cannot found sufficient scientific study for guiding tank ammunition in the related literature. In this study, the laser BR-guidance method is offered to the classic tank ammunition with a diameter of 155 mm in order to give the tank a precision strike capacity, as different from the literature. First of all, an ammunition model is created with coefficients of the mass, inertia, and surface area and friction. In addition, an autopilot dynamic is modeled for the pitch and roll axes of the ammunition. Also, the atmosphere model and environmental factors are added to the model. In order to control this nonlinear model, a lead-compensator and a PD-controller are designed. In order for the results to be transferred to a real application, the accelerations obtained must basically be produced by the electric motors that will drive the control surfaces to be designed. At the end of the study, it is seen that both controllers can produce lateral accelerations within limits without reaching high saturation.
 
 

Direct Phase Measurement and Compensation to Enhance MEMS Gyroscopes ZRO Stability

This research introduces a closed-loop method to improve the zero-rate output (ZRO) stability of amplitude-modulated (AM) capacitive MEMS gyroscopes, even in absence of quadrature compensation electrodes. The method relies on the direct measurement and closed-loop compensation of the variation of the relative phase between the quadrature output, modulated by the drive carrier frequency, and the demodulation reference. The closed loop includes a phase meter, whose output regulates the phase of the lock-in amplifier inside the sense-mode, open-loop, demodulation chain. The proposed technique, tested on the pitch axis of a consumer-grade commercial monolithic 3-axis gyroscope, brings up to 300-fold stability improvements over temperature transients, without affecting noise and scale-factor performance. Stability limits depend on the phase meter resolution and on the lock-in granularity in regulating the phase. Overall, a mdps/K stability is obtained with a one-time calibration at ambient temperature and no post-acquisition processing. [2021-0049]

Facial Asymmetry in Unilateral Congenital Superior Oblique Muscle Palsy.

This study was conducted to evaluate facial asymmetry in unilateral congenital superior oblique muscle palsy (SOP). The results showed that all facial asymmetry parameters had a higher frequency in SOP patients compared with orthotropic individuals. This study aimed to evaluate the characteristics of facial asymmetry in unilateral congenital SOP and compare with orthotropic individuals. This cross-sectional comparative case series was conducted in 58 patients with ocular torticollis caused by SOP (mean ± standard deviation age, 18 ± 12 years) and 58 orthotropic individuals (mean ± standard deviation age, 19 ± 13 years). The exact form of torticollis was determined by direct observation from yaw, roll, and pitch axes. Four photographs were taken from patients: (1) with torticollis to calculate the amount of head tilt; (2) with the head in the straight position to calculate the facial angle and relative facial size (RFS); and (3 and 4) with the head positioned downward (to compare the cheek size) and upward (to assess columella deviation and nostril asymmetry). Twenty-nine patients (50%) had a head tilt, 23 (39.66%) had combined head tilt and a face turn, and 6 (10.44%) had a pure face turn. The mean ± standard deviation of head tilt, facial angle, and RFS was 10.11 ± 6.31°, 1.11 ± 1.67°, and 1.003 ± 0.126 in SOP patients, respectively, and the mean RFS and facial angle were significantly higher in SOP patients compared with orthotropic individuals (both P < .001). Facial hemihypoplasia, unilateral cheek compression, nostril asymmetry, and columella deviation were observed in 43 (74.1%), 31 (53.4%), 39 (67.2%), and 38 patients (65.5%), respectively, which were all significantly more common compared orthotropic individuals (P < .001). Facial asymmetry was seen in 52 patients (91.2%) and 17 orthotropic subjects (29.3%), respectively (P < .001). All quantitative and qualitative facial asymmetry parameters had a higher frequency in SOP patients compared with orthotropic subjects.

Feedback-linearization based robust relatively optimal trajectory tracking controller for 3-DOF helicopter

This paper proposes a feedback linearization-based robust trajectory tracking controller for the elevation and pitch axes of three degrees of freedom (3-DOF) helicopter. The 3-DOF helicopter is a benchmark system that operates on the same principle of operation as that of a tandem-rotor helicopter. Accurate control of this laboratory set up in the presence of external disturbances is a sophisticated problem as it is easily affected by external disturbances due to its low weight. Hence, to ensure efficient trajectory tracking performance in the presence of uncertainties and disturbances a nonlinear disturbance observer is integrated with a feedback linearization (FL) based relatively optimal trajectory tracking controller (ROTTC). Feedback linearization of the nonlinear model results in a decoupled linear error dynamics for each axis, which is used for the design of the ROTTC. The stability of the 3-DOF helicopter in the presence of estimation error and parameter uncertainties is analyzed using the Lyapunov method. A comparison study with an FL-based robust linear quadratic regulator (RLQR) method illustrates the superiority of the proposed method in terms of tracking error and disturbance estimation. The efficacy of the proposed controller to accommodate external disturbances is demonstrated with real-time implementation on the 3-DOF helicopter with a strong wind disturbance as well as an impulse disturbance.

Improve the performance of a semi-active flapping airfoil power generator by adjusting both offsetting mass center displacement and changing pitching axis position

A comprehensive investigation was carried out in this study, to evaluate the effect of changing pitching axis position and offsetting mass center displacement on the power extraction performance of a semi-active flapping airfoil power generator (FAPG). Unlike previously published literature, the pitching axis position and the mass center position of the airfoil are not to be located at the same position in the current work. A numerical method for accurately simulating the interaction between the fluid and semi-active FAPG was developed and validated to fulfill this objective. The analysis results showed that the optimized pitching axis position and offsetting mass center displacement are found at the value of d= c/2 and xθ=−0.15c respectively, and compared with the offsetting mass center displacement, the effect of the pitching axis position on the performance of the FAPG is weak. Vortex structure analysis found that the leading-edge vortex is promoted to separate at initial or middle flapping, and it is delayed to separate at down or up flapping, which is the characteristics of the enhanced power extraction performance airfoil.

Measuring the difference in natural head position between the standing and sitting positions using an inertial measurement unit

AimsThe purpose of this study was to compare the natural head position (NHP) in the sitting position to the NHP in a standing position using inertial measurement unit (IMU) and lateral photographs.Matierials & MethodsTwenty healthy young adult volunteers were asked to look at a mirror located at 1 metre in front of their eyes while being recorded with the IMU system. Lateral photographs were also taken. This procedure was undertaken for the standing and sitting positions, on two separate occasions within a one‐week interval.ResultsA strong correlation was found between the IMU system and the lateral photographs (r > .99) with regard to the pitch axis, the absolute mean difference was 0.4 ± 0.5 (p = .99) for both standing and sitting positions. We found that in the sitting position the head was elevated by 2.5 ± 2.4 (p < .05) more than in the standing position, but no significant differences were observed for the other two axes (roll and yaw).ConclusionThe IMU system is comparable to lateral photographs for pitch assessment. Except for a slight elevation of the head in the sitting position, no clinical differences were observed for the NHP when comparing the standing and sitting positions.

Partitioned iterated function systems by regression models for head pose estimation

Head pose estimation represents an important computer vision technique in different contexts where image acquisition cannot be controlled by an operator, making face recognition of unknown subjects more accurate and efficient. In this work, starting from partitioned iterated function systems to identify the pose, different regression models are adopted to predict the angular value errors (yaw, pitch and roll axes, respectively). This method combines the fractal image compression characteristics, such as self-similar structures in order to identify similar head rotation, with regression analysis prediction. The experimental evaluation is performed on widely used benchmark datasets, i.e., Biwi and AFLW2000, and the results are compared with many existing state-of-the-art methods, demonstrating the robustness of the proposed fusion approach and excellent performance.

Approximate ship wake solution for fast computation

An approximate ship wake solution that accurately predicts both the wake patterns and the wake amplitudes in any water depth is proposed and validated. Derivation based on the small-amplitude wave theory is first revisited, treating a ship as a moving pressure field acting on the water surface. For ship shapes symmetric about the transverse (pitch) axis and away from the immediate vicinity of the ship, an approximate solution is sought. In contrast to the exact analytical solution consisting of a double integral, the approximate solution is simplified through analytical means to consist of a single integral. Singularities inside the integrand of the exact solution have also been removed. Hence, the computational effort is greatly reduced. Two extreme ship shape functions are considered to plot the solutions: a sharp rectangular shape and a smooth Gaussian shape. The newly derived approximate solution is validated using 37 satellite images of ship wakes, one towing tank experiment, and two field experiments. Then, water depth effects on wake patterns are discussed. Providing means to quickly relate the ship shape, weight, speed, and water depth to the wake characteristics, the new ship wake solution is a potentially powerful tool in the study of ship wake inversion.

2-DOF Spherical Parallel Mechanism Capable of Biaxial Swing Motion with Active Arc Sliders

Most articulated robots comprise multiple joints and links that control the position and posture of the end effector. The kinematic pair arrangement determines characteristics such as output force. The link configurations can be classified as serial link and parallel link mechanisms. A typical parallel link mechanism is the spherical parallel mechanism (SPM), designed to ensure that the end effector has only rotational degrees of freedom. However, the kinematic pair arrangement has not been sufficiently examined in two degrees of freedom (2-DOF) SPMs. Herein, we present a basic design method for the proposed 2-DOF SPM curved biaxial swing mechanism, with inputs comprising arc sliders. The swinging area of the passive link was small, and infinite rotation around a certain axis was achieved without collision or transfer to a singular posture. Using the kinematics of this mechanism, we clarified the linear roll output and non-linear pitch output. Moreover, we fabricated a prototype and measured its basic drive characteristics. The results revealed that the output performance was greatly dependent on the rotation angle, high movable range in the roll axis, and low movable range in the pitch axis.

Development of a distributed microprocessor control system for the 6 degree of freedom motion simulator

The article deals with the design issues of a microprocessor control system for the 6 degrees of freedom motion simulator. This motion simulator is a high performance, electro-pneumatic simulator, used for test evaluation of small high dynamic flying objects. With pneumatic actuated yaw and pitch axes and an electric motor on the roll axis, the Motion simulator reproduce, in real-time, the flight motions of the actual object. The presence of a large number of servo drives with different types of executive elements in the Motion simulator required the development of a distributed multiprocessor control system. The equipment of the Motion simulator includes a number of microprocessor control units. Each contains a microprocessor control system with high-performance microcontroller having specialized peripherals, as well as equipped with all the necessary communication interfaces. Control units are maximally unified, which significantly reduces the time of their development and debugging. Due to this, units firmware is mostly identical and uses the same set of libraries.

Kinematic consistency in the knee manipulation learning: A comparison between expert and beginner therapists

ObjectivesThe objective of this study is to analyse the kinematic parameters performed during knee manipulation in order to improve the manipulative learning in future students: the kinematic differences and the consistency of the manipulations. MethodsCross-sectional study. This study compared health professionals with no experience and with more than 15 years of manipulative techniques experience, using an inertial sensor located above the tuberosity of the tibia. Outcome variables were manipulation time, peaks of displacement, angulation range, translation range and areas under the curve of the movement. Angulation data were recorded on the pitch axis, whilst the translation data were recorded on the yaw axis. A Matlab algorithm was used to identify the start and end of the manipulation. ResultsThe expert therapist performed the technique with greater amounts of anterior and posterior tibial translation, greater area under the curve and quicker manipulation cycles were. No difference was found for variables associated with knee flexion and extension. The expert therapist showed a higher consistency during the technique execution. ConclusionsKnee manipulative technique was analyzed to quantify knee movement via single inertia sensor. The results of this study suggest translation displacement and manipulation consistency have to be taken into account to design learning strategies.

Concussions in Boxers: Head Rotations and Neck Stiffness

Background: The human head-and-neck has three degrees of rotational freedom – pitch, roll, and yaw. While the evolution of the head-and-neck mobility may have increased the overall fitness of homo sapiens, our head-and-neck mobility may have also introduced some differential vulnerability to injuries in impact-induced head rotations about the pitch, roll, and yaw axes. Methods and Findings: We examined impact-induced head rotations in boxing matches by analyzing videos. Our objective was to seek a quantitative relationship between impact-induced head kinematics and the knockout outcome. For each of the three rotational degrees of freedom, head angular velocities of impact-induced head rotations were significantly higher in knockout hits than in control hits without a knockout (p &lt; 0.02). Knockout thresholds in pitch-roll-yaw measured as impact-induced head angular velocities were anisotropic with the lowest threshold in roll and became progressively higher in yaw and pitch, in that order. Regardless of the pitch-roll-yaw bearing, the velocities of the striking fists in knockout hits were not significantly higher than those in control hits. Conclusions: Accurate prediction of knockout via head kinematics was possible with pitch-roll-yaw information. Impact-induced head kinematics was strongly influenced by neck stiffness, making a case for the utility of reflexively increasing neck stiffness as an effective way to reduce impact-induced head rotations and concussion risk.

Evolving Intelligent System for Trajectory Tracking of Unmanned Aerial Vehicles

This article develops an evolving type-2 quantum fuzzy neural network (eT2QFNN) control scheme for achieving trajectory tracking with unmanned aerial vehicles (UAVs). The proposed approach involves quantum membership functions, automatic rule growing process, and parameter adjustment learning scenario to deal with the problems of inadequacy, uncertainties, and noise in conventional control techniques. Furthermore, the proposed approach is operated in a parallel structure with the proportional derivative (PD) controller to compensate the transients in performance and learn the dynamic characteristics of the system. Besides, a sliding theory-based adaptive law is equipped with the control approach to compensate for the nonlinearity of the UAV. To assess the performance, numerical simulations and real-time experiments are carried for pitch and yaw axes control of two degrees of freedom (2DoF) helicopter test rig with the proposed approach. The simulations and experiments are aimed at achieving an offline path tracking with an objective to minimize the deviation error and improve the time response characteristics of the UAVs. The results depict the robustness of the proposed approach in terms of integral time absolute error for a helicopter following various trajectories. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This article addresses the problem of trajectory tracking and attitude control in a two-rotor UAV system. In practical application, there are multiple end users for an efficiently controlled UAV system. Generally, the trajectory tracking and attitude control are associated with the capability of UAVs to perform vertical take-off, landing, maneuver, and cyclic rotation as per the change in path. Furthermore, the control of UAVs for trajectory tracking and attitude provides a unified framework in efficiently following the desired path and maintaining the desired attitude. This has potential applications in the field of search and rescue operations, surveillance, military applications, environmental exploration, and aerial cinematography. Although trajectory tracking and attitude control problems have been studied a lot, the drawbacks due to uncertainties, immediate response to trajectory changes, and attitude settling are still open and challenging. This article proposed an eT2QFNN for a two rotor of UAV system with PD controller using automatic rule growing process. Sufficient trajectories are developed to make the UAV follow them under the proposed approach. Both simulation and real-time experiments were conducted and the results of the developed controller are compared with conventional approaches.

Geophysical Investigation Using 3-Dimensional Grid-Formation for Subsurface Lithology Characterization (A Case Study of Ovia North East, Edo State, South South Nigeria)

Geophysical investigations using three-dimensional (3D) grid formation was carried out in Ovia North East Local Government Area of Edo State, Nigeria for subsurface lithology characterisation so as to generate a comprehensive basemap of the study area. Twelve (12) traverses in form of a rectangular grid were occupied for the 2D Electrical Resistivity Imaging (ERI) using the Wenner array. The 2D were all collated to form the 3D grid. The 2D Electrical Resistivity data was processed by the inversion of the 2D apparent resistivity data using the DIPRO software to generate the 2D inverted resistivity section while the 3D inverted resistivity model was done by inverting all the twelve traverses using 3DEarthimager software to model the 3D cube. The results of the 2D ERI revealed three (03) to five (05) resistivity structures across the twelve traverses indicating clay/clayey sand, sand and sandstone on a 200 and 300 m lateral distance and corresponding depth of 39.6 and 57.3 m across each traverses. Resistivity values generally varies from 16.8 – 45302 Ωm across Traverse 1 – 12. The layer horizontal depth slices of the 3D inverted resistivity distribution are in six layers, which are; 0 - 5 m, 5 – 10.8 m, 10.8 – 17.4 m, 17.4 – 25 m, 25 – 33.7 m and 33.7 – 43.8 m. The 3D inverted resistivity model within the study area covered lateral plane (the roll axis), 300 m, in the x plane (the pitch axis), 200 m lateral distance was covered and in the depth plane (the yaw axis), a maximum depth of 66 m is imaged. The inverted 3D Resistivity values generally vary from 189 - 6149 Ωm across the study area. The resistivity structures delineated from the 3D model are clayey sand and sand.

On the Handling Qualities of Two Flying Wing Aircraft Configurations

The coupling of the longitudinal and lateral stability modes of an aeroplane is considered in two cases: (i) weak coupling, when the changes in the frequency and damping of the phugoid, short period, dutch roll, and helical modes are small, i.e., the square of the deviation is negligible compared to the square of the uncoupled value; (ii) strong coupling, when the coupled values may differ significantly from the uncoupled values. This allows a comparison of three values for the frequency and damping of each mode: (i) exact, i.e., fully coupled; (ii) with the approximation of weak coupling; (iii) with the assumption of decoupling. The comparison of these three values allows an assessment of the importance of coupling effects. The method is applied to two flying wing designs, concerning all modes in a total of eighteen flight conditions. It turns out that lateral-longitudinal coupling is small in all cases, and thus classical handling qualities criteria can be applied. The handling qualities are considered for all modes, namely the phugoid, short period, dutch roll, spiral, and roll modes. Additional focus is given to the pitch axis, considering the control anticipation parameter (CAP). The latter relates to the two kinds of manouever points, where damping vanishes, that are calculated for minimum speed, take-off, and initial and final cruise conditions. The conclusion compares two flying wings designs (the “long narrow” and “short wide” fuselage concepts) not only from the point of view of flight stability, but also from other viewpoints.