Pitch Roll Research Articles

A Numerical Method on Large Roll Motion in Beam Seas Under Intact and Damaged Conditions

The second-generation intact stability criteria, including five stability failure modes, were approved by the International Maritime Organization (IMO) in 2020, and it is an urgent task to develop the numerical method for the significant roll motion under dead conditions. Both intact and damaged stability focus on the large roll motion in beam seas. A unified numerical method is studied to predict the large roll motion in regular and irregular beam seas under intact and damaged conditions. Firstly, a sway–heave–pitch–roll–yaw coupled equation named 5-DOF and a sway-roll-yaw coupled motion with the roll-righting arm in still water named 3-DOF are used to predict the large roll motion in regular beam seas under the intact and damaged conditions. Secondly, the method is extended for the large roll motion in irregular beam seas, where the diffraction force in the roll direction and the sway and yaw motion under intact and damaged conditions are calculated by the subharmonic superposition method. Thirdly, the roll-righting arm in the calm water, roll-damping coefficients, and the roll natural roll period, under the intact and damaged conditions, are obtained by software and a free roll decay experiment, respectively. Finally, the numerical results of a patrol boat under intact and damaged conditions are compared to the experimental results. The results show that the sway-roll-yaw coupled motion with the roll-righting arm in still water named 3-DOF can predict the large roll motion in regular and irregular beam seas under intact and damaged conditions.

Uncertainty of Wave Spectral Shape and Parameters Associated with the Spectral Estimation

The uncertainty in estimating the wave spectrum from the records of wave elevation by heave–pitch–roll buoys is studied, considering the effects of the estimation method and the spectral resolution adopted in the process. This investigation utilizes measurements from a wave buoy moored in deep water in the South Atlantic Ocean. First, the spectra are computed using the autocorrelation function and the direct Fourier method. Second, the spectral resolution is tested in terms of degrees of freedom. The degrees of freedom are varied, and the resulting spectra and integrated parameters are computed, showing significant variability. A simple and robust methodology for determining the wave spectrum is suggested, which involves calculating the average energy density in each frequency band. The results of this methodology reduce the variability of the estimated parameters, improving overall accuracy while preserving frequency resolution, which is crucial in complex sea states. Additionally, to demonstrate the feasibility of the implemented approach, the final spectrum is fitted using an empirical model ideal for that type of spectrum. Finally, the performance and the goodness of the fit process for the final averaged curve are checked by widely used statistical metrics, such as R2 = 0.97 and root mean square error = 0.49.

Prediction of Human Reaching Pose Sequences in Human–Robot Collaboration

Abstract In human–robot collaboration, robots and humans must work together in shared, overlapping, workspaces to accomplish tasks. If human and robot motion can be coordinated, then collisions between robot and human can seamlessly be avoided without requiring either of them to stop work. A key part of this coordination is anticipating humans’ future motion so robot motion can be adapted proactively. In this work, a generative neural network predicts a multi-step sequence of human poses for tabletop reaching motions. The multi-step sequence is mapped to a time-series based on a human speed versus motion distance model. The input to the network is the human’s reaching target relative to current pelvis location combined with current human pose. A dataset was generated of human motions to reach various positions on or above the table in front of the human starting from a wide variety of initial human poses. After training the network, experiments showed that the predicted sequences generated by this method matched the actual recordings of human motion within an L2 joint error of 7.6 cm and L2 link roll–pitch–yaw error of 0.301 rad on average. This method predicts motion for an entire reach motion without suffering from the exponential propagation of prediction error that limits the horizon of prior works.

Maritime Moving Target Reconstruction via MBLCFD in Staggered SAR System

Imaging maritime targets requires a high resolution and wide swath (HWRS) in a synthetic aperture radar (SAR). When operated with a variable pulse repetition interval (PRI), a staggered SAR can realize HRWS imaging, which needs to be reconstructed due to echo pulse loss and a nonuniformly sampled signal along the azimuth. The existing reconstruction algorithms are designed for stationary scenes in a staggered SAR mode, and thus, produce evident image defocusing caused by complex target motion for moving targets. Typically, the nonuniform sampling and complex motion of maritime targets aggravate the spectrum aliasing in a staggered SAR mode, causing inevitable ambiguity and degradation in its reconstruction performance. To this end, this study analyzed the spectrum of maritime targets in a staggered SAR system through theoretical derivation. After this, a reconstruction method named MBLCFD (Modified Best Linear Unbaised and Complex-Lag Time-Frequency Distribution) is proposed to refocus the blurred maritime target. First, the signal model of the maritime target with 3D rotation accompanying roll–pitch–yaw movement was established under the curved orbit of the satellite. The best linear unbiased (BLU) method was modified to alleviate the coupling of nonuniform sampling and target motion. A precise SAR algorithm was performed based on the method of inverse reversion to counteract the effect of a curved orbit and wide swath. Based on the hybrid SAR/ISAR technique, the complex-lag time-frequency distribution was exploited to refocus the maritime target images. Simulations and experiments were carried out to verify the effectiveness of the proposed method, providing precise refocusing performance in staggered mode.

Research on the Influence of the Disturbance Rejection Rate of a Roll–Pitch Seeker on Stable Tracking Characteristics

The disturbance rejection rate (DRR) is an inherent problem of the seeker. The additional line-of-sight (LOS) angular velocity information of the seeker caused by the DRR will affect the attitude of the aircraft through the guidance system, thus forming a parasitic loop in the guidance and control system of the aircraft, which has a great influence on the guidance accuracy. In this study, the influence of the DRR of the roll–pitch seeker on the stable tracking of a maneuvering target is explored. First, the tracking principle of the roll–pitch seeker is analyzed and the conditions for completely isolating the disturbance of the aircraft attitude are deduced. Then, the expression of the frame error angle is derived, a semi-strap-down stable control closed-loop scheme is established, and the DRR transfer function is derived by adding different disturbance torque models. Finally, the simulation of stability tracking characteristics is carried out. The results show that when the aircraft attitude is disturbed at a low frequency or the target is maneuvering at a low frequency, the DRR caused by the spring torque has a great influence on the tracking angle of the two frames, the line of-sight rate accuracy of the optical axis output and the detector error angle. On the contrary, the damping torque DRR plays a leading role in tracking accuracy.

Development of a Novel Implementation of a Remotely Piloted Aircraft System over 25 kg for Hyperspectral Payloads

A main aspect limiting the operation of low-altitude remotely piloted aircraft systems (RPAS) over 25 kg, integrating pushbroom hyperspectral sensors, comes from the challenges related to aircraft performance (e.g., flight time) and regulatory aspects deterring the users from pushing beyond this weight limit. In this study, we showcase a novel implementation using the DJI Agras T30 as an aerial system for integrating an advanced hyperspectral imager (HSI, Hyspex VS-620). We present the design and fabrication approach applied to integrate the HSI payload, the key considerations for powering the HSI and its gimbal, and the results from vibration and wind tunnel tests. We also evaluate the system’s flight capacity and the HSI’s geometric and radiometric data qualities. The final weight of the T30 after the integration of the HSI payload and ancillary hardware was 43 kg. Our vibration test showed that the vibration isolator and the gimbal reduced the vibration transmission to above 15 Hz but also introduced a resonant peak at 9.6 Hz that led to vibration amplification in the low-frequency range near 9.6 Hz (on the order of an RMS of ~0.08 g). The wind tunnel test revealed that the system is stable up to nearly twice the wind speed rating of the manufacturer’s specifications (i.e., 8 m/s). Based on the requirements of the Canadian Special Flight Operations Certificate (RPAS > 25 kg) to land at a minimal battery level of ≥30%, the system was able to cover an area of ~2.25 ha at a speed of 3.7 m/s and an altitude of 100 m above ground level (AGL) in 7 min. The results with the HSI payload at different speeds and altitudes from 50 m to 100 m AGL show hyperspectral imagery with minimal roll–pitch–yaw artefacts prior to geocorrection and consistent spectra when compared to nominal reflectance targets. Finally, we discuss the steps followed to deal with the continuously evolving regulatory framework developed by Transport Canada for systems > 25 kg. Our work advances low-altitude HSI applications and encourages remote sensing scientists to take advantage of national regulatory frameworks, which ultimately improve the overall quality of HSI data and safety of operations with RPAS > 25 kg.

Model-Based Optimization Approach for PID Control of Pitch–Roll UAV Orientation

This study focuses on the modeling and control optimization of the pitch–roll angles orientation in a quad-rotor UAV (unmanned aerial vehicle) drone system. To address the control challenge, PID (proportional–integral–derivative) controllers are used, which have been tuned through a model-based optimization approach. A non-linear model of the system is obtained and further validated experimentally. The model is implemented in Simulink to conduct model-based optimization. The controller design uses an IMC (internal model control) model-based approach to establish the initial parameters for a PID controller. In the subsequent design phase, a multiobjective approach is taken, incorporating weighted cost functions that account for IAE (integral absolute error) and ITAE (integral of time-weighted absolute error) forms, along with battery usage. The outcomes of this design are showcased through simulations and real-world platform testing.

Initial end-to-end testing of the ExacTrac dynamic deep inspiration breath hold workflow using a breath hold breast phantom

ExacTrac Dynamic (ETD) provides a Deep Inspiration Breath Hold (DIBH) workflow for breast patients. Stereoscopic x-ray imaging combined with optical and thermal mapping allows localisation against simulation imaging, alongside surface guided breath hold monitoring. This work aimed to determine appropriate imaging parameters, the optimal Hounsfield Unit (HU) threshold for patient contour generation and workflow evaluation via end-to-end (E2E) positioning using a custom breast DIBH phantom. After localisation via existing Image Guidance (IG), stereoscopic imaging was performed with a range of parameters to determine best agreement. Similarly, residual errors in prepositioning were minimised using a range of HU threshold contours. E2E positioning was completed for clinical workflows allowing residual isocentre position error measurement and existing IG comparison. Parameters of 60 kV and 25mAs were determined appropriate for patient imaging and HU thresholds between −600 HU and −200 HU enabled adequate prepositioning. The average and standard deviation in residual isocentre position error was 1.0 ± 0.9 mm, 0.4 ± 1.0 mm and 0.1 ± 0.5 mm in the lateral, longitudinal and vertical directions, respectively. Errors measured using existing IG were −0.6 ± 1.1 mm, 0.5 ± 0.7 mm and 0.2 ± 0.4 mm in the lateral, longitudinal and vertical directions, and 0.0 ± 1.0o, 0.5 ± 1.7o and −0.8 ± 1.8o for pitch roll and yaw. The use of bone weighted matching increased residual error, while simulated reduction of DIBH volume maintained isocentre positioning accuracy despite anatomical changes. This initial testing indicated suitability for clinical implementation during DIBH breast treatments.

New Analytical Model for Determining the Roll Pitch Diameter in Three-Roll Continuous Retained Mandrel Rolling

The continuous tube-rolling method has been widely used to manufacture high-quality seamless pipes and tubes. However, the analytical model for determining the roll pitch diameter in three-roll continuous retained mandrel rolling from first principles has not yet been presented, which has, thus, hindered the development of rolling control technology in tube manufacturing. In this work, a new analytical model has been established from the force–equilibrium principles. The modelling has taken the tube-roll contact geometry, roll pressure, mandrel pull forces, inter-stand tensions, and friction coefficients into account for its formulations. Seen from the experimental results of the rolling at the plant, the maximum deviation of the predicted projected contact area is less than 6% and the maximum deviation of the calculated roll speed from the satisfactory data in field operation is less than 3.9%. The proposed model has enabled the influence of the friction coefficients on the roll pitch diameter to be quantified in theoretical analysis, and it was found that the changing amplitude of the theoretical roll pitch diameter corresponding to the commonly used data range of the friction coefficients can be above 9%. Having overcome the shortcomings of the empirical model, this model has the required prediction accuracy and flexibility for being applied to flexible tube rolling. By building the key algorithms around physical models, this modelling has advanced not only the rolling control at the plant, but also our scientific understanding of the mechanics of the continuous tube-rolling process.

A Study on the Control Method of 6-DOF Magnetic Levitation System Using Non-Contact Position Sensors

Recently, due to the development of semiconductor technology, high-performance memory and digital convergence technology that integrates and implements various functions into one semiconductor chip has been regarded as the next-generation core technology. In the semiconductor manufacturing process, various motors are being applied for automated processes and high product reliability. However, dust and shaft loss due to mechanical friction of a general motor system composed of motor-bearing are problematic for semiconductor wafer processing. In addition, in the edge bread remove (EBR) process after the photoresist application process, a nozzle position control system for removing unnecessary portions of the wafer edge is absolutely necessary. Therefore, in this paper, in order to solve the problems occurring in the semiconductor process, a six-degrees-of-freedom (6-DOF) magnetic levitation system without shaft and bearing was designed for application to the semiconductor process system; and an integrated driving control algorithm for 6-DOF control (levitation, rotation, tilt (Roll-Pitch), X-Y axis movement) using the force of each current component derived through current vector control was proposed. Finally, the 6-DOF magnetic levitation system with the non-contact position sensors was fabricated and the validity of the 6-DOF magnetic levitation control method proposed in this paper was verified through a performance test using a prototype.

Formal Verification of Robot Rotary Kinematics

With the widespread application of robots in aerospace, medicine, automation, and other fields, their motion safety is essential for the well-being of humans and the accomplishment of vital socially beneficial programs. Conventional robot hardware and software designs mainly rely on experiential knowledge and manual testing to ensure safety, but this fails to cover all possible testing paths and adds risks. Alternatively, formal, mathematically rigorous verifications can provide predictable and reliable guarantees of robot motion safety. To demonstrate the feasibility of this approach, we formalize the mathematical coordinate transformation of a robot’s rigid-body kinematics using the Coq Proof Assistant to verify the correctness of its theoretical design. First, based on record-type matrix formalization, we define and verify a robot’s spatial geometry by constructing formal expressions of the matrix’ Frobenius norm, trace, and inner product. Second, we divide rotary motion into revolution and rotation construct and provide their formal definitions. Next, we formally verify the rotational matrices of angle conventions (e.g., roll–pitch–yaw and Euler), and we complete the formal verification of the Rodriguez formula to formally verify the correctness of the motion theory in specific rotating kinematics problems. The formal work of this paper has a variety of essential applications and provides a generalizable kinematics analysis framework for robot control system verification. Moreover, it paves the way for automatic programming capabilities.

Frame Selection Method for ISAR Imaging of 3-D Rotating Target Based on Time–Frequency Analysis and Radon Transform

When a target has 3-D rotation accompanying roll–pitch–yaw movement, it yields an additional phase component, which cannot be compensated for by any of the existing inverse synthetic aperture radar (ISAR) imaging methods. Under this condition, the resulting ISAR image will be severely distorted. Accordingly, selecting a proper imaging frame, where the target has only 2-D rotation, becomes the only solution, especially for range-Doppler (RD) algorithm. To do this, the conventional approach is to directly use the phase of the received signal, and however, this approach is vulnerable to noise and the cross-term interference of multiple scattering centers (SCs) in the range bin. To address these issues, we propose a new frame selection method using the range-instantaneous Doppler (RID) technique and Radon transform to detect the presence of 3-D rotation of the target within imaging frame. The proposed method comprises three steps: 1) obtain joint time–frequency distribution (JTFD) via the smoothed pseudo Wigner–Ville distribution (SPWVD); 2) estimate the orientation angle of the Radon image of the JTFD spectrum; and 3) select the suitable imaging frame using the estimated angle. Furthermore, to demonstrate the effectiveness of the proposed method, experimental results based on simulated and real measured data are provided.

Water Surface Flight Control of a Cross Domain Robot Based on an Adaptive and Robust Sliding Mode Barrier Control Algorithm

When a cross-domain robot (CDR) flies on the water surface, the large pitch angle and roll angle may lead to water flooding into the robot cabin or even overturning. In addition, the CDR is influenced by some uncertain parameters and external disturbances, such as the water resistance and current. To constrain the robot attitude angle and improve the robustness of the controller, a non-singular terminal sliding mode asymmetric barrier control (NTSMABC) algorithm is proposed. All the uncertain disturbances are regarded as a lump disturbance, and a radial basis function neural network (RBFNN) is designed to compensate for the output of the controllers. Unlike the traditional quadrotors, the robot controls the yaw angle by paddles when the robot flies on the water surface. To prevent the actuator saturation and the robot from rolling over due to excessive yaw angular velocity, an adaptive integral sliding mode barrier control (AISMBC) algorithm is proposed to constrain the yaw angular velocity directly. This algorithm adaptively adjusts the gain of the sliding surface to suppress the influence of the lump disturbance on the robot. Another RBFNN is designed to compensate for the output of the controller. Simulation results demonstrate the effectiveness of the proposed control methods.

AN INITIAL ALIGNMENT METHOD OF INERTIAL NAVIGATION SYSTEM FOR THE STATIC STATE

Abstract. The navigation means the process of determining the position, velocity, and orientation of the moving object such as the land vehicle, aerial vehicle, and even autonomous vehicle. Nowadays, Global Navigation Satellite System (GNSS) is most used for positioning. Nevertheless, the navigation system based on GNSS would be interrupted in the challenging environments. Therefore, the inertial navigation system (INS) has been widely combined with GNSS to overcome this issue. For INS, the core concept is the measurements of Inertial Measurement Unit (IMU). In order to integrate the measurements of IMU with several sensors such as GNSS receivers, odometers, and so on, we should transform the measurements of IMU from body frame to navigation frame. The initial alignment just represents the process of finding the accurate initial rotation matrix between body frame and navigation frame in the beginning of navigation. However, initial misalignment angles would cause large error of INS. Hence, obtaining an accurate initial rotation matrix from body frame to navigation frame is an important issue to get the better navigation performance. In the research, an integrated navigation system is developed to validate the initial alignment algorithm. With the data pre-processing and accurate calibration. the proposed method of initial alignment can get precise initial ration matrix. The errors of roll pitch, and yaw angle are all smaller than 1 degree after initial alignment. Moreover, the time threshold of initial alignment is set by manual traditionally. A method of finding threshold of coarse alignment is proposed in this research.

Singular Zone in Quadrotor Yaw–Position Feedback Linearization

Feedback linearization-based controllers are widely exploited in stabilizing a tilt rotor (eight or twelve inputs); each degree of freedom (six degrees of freedom in total) is manipulated individually to track the desired trajectory, since no singular decoupling matrix is introduced while applying this method. The conventional quadrotor (four inputs), on the other hand, is an under-actuated MIMO system that can directly track four independent degrees of freedom at most. Common selections of these outputs can be yaw–position and attitude–altitude. It is reported that no singularity is found in the decoupling matrix while applying feedback linearization in the yaw–position-tracking problem. However, in this research, we argue the existence of the ignored singular zone within the range of interest, which can cause the failure in the controller design. This paper visualizes this noninvertible area and details the process of deduction for the first time. An attempt (switch controller) to avert the singular problem is later discussed with the verification by simulation in Simulink and MATLAB. All the results are sketched in the roll–pitch diagram.

Vibration loads analysis of coaxial rigid rotor in rotor interaction

A vibration load computing method for a coaxial rigid rotor was developed and applied to analyzing its vibration load in rotor interference. The structural dynamics model based on the medium-size deformation beam theory and the double-rotor aerodynamics model that contains unsteady free wake were jointly used to develop the coaxial rigid rotor's vibration load computing method. The wind tunnel test data of the XH-59A helicopter was used to validate this computing method. The vibration load of a rotor hub was analyzed in detail. The results show that the 3Ω harmonic wave amplitude of the vertical force Fz of the rotor hub and that of its pitch moment My decrease in high pitch angle, but the 3Ω harmonic wave amplitude of the roll moment Mx of the rotor hub obviously increases. The vibration load of the rotor hub increases with the decrease of the range of the coaxial rigid rotor; the roll moment and pitch moment of the rotor hub are sensitive to phase angle. The results also show that the increase of the 3Ω harmonic wave amplitude of the roll moment Mx is greater than the decrease of that of the roll moment My at the phase angle of 30° and that the level of vibration load of the rotor hub is minimum at the phase angle of 0° in forward flight.

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 Command Generation Strategy of Roll and pitch seeker

The roll pitch seeker has a large field of view, which can achieve large off-axis angle attacks. At the same time, it has a simple structure and is easy to miniaturize, which is beneficial to the overall design of the missile. However, the over-tracking problem of the rolling seeker restricts her application in engineering. To solve this problem, this paper proposes a method to calculate the roll frame angle by using the angular rate of the projectile line of sight when the pitch frame angle is small. The simulation results show that this method is effective in the overhead tracking control.

A hybrid search based synthesis of static output feedback controllers for uncertain systems with application to multivariable PID control

AbstractThis article proposes a hybrid search (involving the performance level and a positive scalar variable in sequence) based method for synthesis of linear time‐invariant (LTI) static output feedback (SOF) controllers for a class of linear systems with norm‐bounded time‐varying parametric uncertainties. Using an available extended linear matrix inequality (LMI) formulation of bounded real lemma, a new sufficient condition in terms of LMIs is obtained for existence of SOF controllers, where a triangular structure in the variable part of the Lyapunov matrix is introduced, unlike the diagonal structure existing in direct synthesis methods in literature. To obtain as less as possible, the part of the Lyapunov matrix which is kept fixed while computing the variable part is first obtained using a ‐search based method. Then with this fixed part, the final variable triangular part of the Lyapunov matrix is obtained using a single positive scalar search based LMI method to further reduce . The efficacy of the proposed method is studied on a number of benchmark examples. The method is also extended for structured SOF design. Finally, the proposed method is applied to design two‐degree‐of‐freedom (2‐DOF) multivariable proportional‐integral‐derivative (PID) controllers for compensation of norm‐bounded uncertain plants. A case study on designing roll–pitch–yaw integrated missile autopilots is also considered to show the efficacy of the proposed multivariable PID compensation.

Laser reflection echo signal detection and calculation under multi-attitude intersection

To improve the detection capability of laser fuze, this paper researches the laser echo signal detection method and echo power calculation method on laser fuze. From the multi-attitude intersection relation of projectile and target, we analyze the laser echo characteristics of target, set up the modeling of laser echo power by using the finite element meshing method. Taking into account the parameters of yaw angle and pitch angle and roll angle, we derive the target reflection laser echo power calculation function by combining the non-Lambertian and bidirectional reflection function of target's surface, establish the target detection probability calculation model. According to the established laser echo signal and echo power calculation function, we calculate the laser echo power and detection probability under the multi-attitude intersection conditions and different detection distances. Through simulation tests, the test result accords with the theoretical model.