Yaw Motion Research Articles

Integrated Adaptive Steering Stability Control for Ground Vehicle with Actuator Saturations

During a steering manoeuvre in a ground vehicle, both yaw motion and roll motion can occur simultaneously, and their dynamics can be coupled, as the roll motion is generalized directly from the tires’ lateral force under steering. Hence, it is of significance to analyze them as an integrated plant in the vehicle steering stability control problem. Furthermore, the actuator saturation of yaw control cannot be neglected, as vehicles often steer at a high velocity or on low-friction roads. In this paper, an integrated steering dynamics model is established considering the coupling between the roll motion and lateral motion, then a novel nonlinear adaptive controller is proposed to stabilize the steering motion considering the actuator saturation of yaw motion control. Simulation results indicate that the designed integrated controller is effective in improving the performance of both the yaw rate tracking error and ride comfort taking into account vehicle parameter uncertainties and actuator saturation; the steering stability of ground vehicles can consequently be guaranteed.

A novel framework for modeling floating offshore wind turbines based on the vector form intrinsic finite element (VFIFE) method

Currently, there is a rapid demand for the development of floating offshore wind turbines (FOWTs) for deployment in sites with deep water depths. FOWTs are highly complex structures that are subjected to combined loading from wind, hydrodynamic, hydrostatic, and mooring loads, and these loads have a significant influence on their dynamic behavior. The complexity of such a multi-body system makes the dynamic analysis considerably challenging and demands an efficient model to capture the physical characteristics of the system accurately. This paper proposes a novel framework for modeling floating offshore wind turbines (FOWTs) based on the vector form intrinsic finite element (VFIFE) method. In this framework, the multi-body dynamics (MBD) is used to handle the rigid body motion, and the analysis of structural deformation and the solution of governing equation of motions (EOMs) is implemented based on the VFIFE method. The methodology considers the FOWT as two rigid bodies: (a) the tower, which is a structural assembly of platform and nacelle; and (b) the rotor that can mechanically rotate relative to the nacelle. Further, a dynamic and flexible model of the mooring system is included, and their axial extension, inertia, and hydrodynamic loads are considered. The EOMs of the FOWT and mooring system are derived by the Newton-Euler (NE) and Newton's second law, respectively and the central difference scheme is implemented to solve the EOMs. Finally, the developed model is subjected to different load cases under the combined action of wind and waves, and the responses of platform motion and the axial tension of the mooring system are calculated and verified against the FAST. After thorough verification of the VFIFE model which showed excellent agreement with FAST results, the proposed model is used (a) to highlight the variations caused by neglecting the dynamic of the mooring system where the results are compared with the quasi-static mooring model developed using the MAP++ module in FAST, and (b) reveal the coupled mechanism of the platform pitch and yaw motion when the rotor is spinning.

Investigation of dynamical stability of vehicle lateral motion control system with feedback delay

<p indent="0mm">Time delay is one of the key factors damaging the driving safety in a vehicle lateral motion control system. This paper establishes a nonlinear vehicle model considering yaw and lateral motion, and two types of nonlinear steering characteristics and motion stability conditions are analyzed using handling diagrams. Next, a PD-based active yaw moment controller with time delay is applied to construct a complete hybrid vehicle system with delayed control. Firstly, the effect of time delay on the general stability and stability boundary of the vehicle system is studied using the location of the characteristic roots and the frequency domain method, wherein the results indicate that the lateral stability of the vehicle is significantly weakened under time delay, and the instability boundary can be reached under a substantial time delay. Furthermore, the optimization factor characterizing the system decay rate is introduced, and the optimization method for the control parameter of the vehicle lateral system is designed. The stability region is optimally divided to select the optimal control gain set under some delay. The optimization is compared and verified based on the steady-state simulation and dynamic test, and the results validate its effectiveness in improving the lateral stability and suppressing the effect of time delay, wherein the optimized dynamic responses of the system follow the target trajectory. Based on the relations between the optimization factor and vehicle characteristics, the critical maximum of the optimization factor is proposed as the quantitative index to evaluate the vehicle lateral stability under time delay, where its general parametric expressions are derived by exploring two types of critical instability conditions. Finally, the effectiveness and efficiency of the index in quantifying the delayed system stability and predicting the time-delay boundary of instability are sufficiently verified in steady-state and dynamic simulation.

Analytical study on the aerodynamic and hydrodynamic damping of the platform in an operating spar-type floating offshore wind turbine

Accurate evaluation of aerodynamic damping and hydrodynamic damping is critical to response prediction and vibration control of spar-type floating offshore wind turbines. This paper presents a comprehensive analytical study of these two damping sources with respect to platform motions. Aerodynamic damping is evaluated by a newly derived aerodynamic damping matrix based on linearisation of aerodynamic resultant forces at tower top. Both radiation and viscous drag effects are considered for hydrodynamic damping. The former is analytically expressed in the form of a radiation damping matrix, while the latter is derived based on Morison's equation and strip theory. A simplified model is established based on the analytical damping expressions and successfully verified against FAST and Aqwa. Under various operational conditions, the damping ratios for different degrees of freedom of the platform are estimated using complex modal analysis. It is found that the modal damping ratios arising from different sources can be very different for different vibration modes of the platform, and the tower flexibility is proved to have negligible impact on the platform damping. For a typical operational state, surge, sway, pitch and yaw motions are highly damped, with the roll motion intermediately damped and the heave motion nearly undamped.

PASSIVE CONTROL OF VORTEX-INDUCED MOTIONS ON DEEP-DRAFT SEMISUBMERSIBLE PLATFORMS

The deep-draft semisubmersible (DDSS) platform is well known due to its favourable vertical motion routine. However, DDSS platforms face a serious challenge in vortex-induced motion (VIM) due to the changing forces of the column. A computational fluid dynamic (CFD) simulation using AcuSolve is conducted to investigate the effect of a twisted-square column with different twisted angles, 0°, 22.5°, 45.0°, 67.5° and 90.0°, on the VIM responses and performance at current incidence angles of 0° and 45°.Platform models at a scale of 1:70 are studied to determine that the alteration of vortex shedding due the separation line at the twisted column expressively influences the mean and fluctuation of hydrodynamic forces and motion. In particular interest is the drag and lift coefficients, surge, sway amplitudes, as well as the yaw motion of the DDSS platform. The simulation was conducted at a velocity of 0.16 m/s.

A novel enhanced convolution neural network with extreme learning machine: facial emotional recognition in psychology practices

Facial emotional recognition is one of the essential tools used by recognition psychology to diagnose patients. Face and facial emotional recognition are areas where machine learning is excelling. Facial Emotion Recognition in an unconstrained environment is an open challenge for digital image processing due to different environments, such as lighting conditions, pose variation, yaw motion, and occlusions. Deep learning approaches have shown significant improvements in image recognition. However, accuracy and time still need improvements. This research aims to improve facial emotion recognition accuracy during the training session and reduce processing time using a modified Convolution Neural Network Enhanced with Extreme Learning Machine (CNNEELM). The system entails (CNNEELM) improving the accuracy in image registration during the training session. Furthermore, the system recognizes six facial emotions happy, sad, disgust, fear, surprise, and neutral with the proposed CNNEELM model. The study shows that the overall facial emotion recognition accuracy is improved by 2% than the state of art solutions with a modified Stochastic Gradient Descent (SGD) technique. With the Extreme Learning Machine (ELM) classifier, the processing time is brought down to 65ms from 113ms, which can smoothly classify each frame from a video clip at 20fps. With the pre-trained InceptionV3 model, the proposed CNNEELM model is trained with JAFFE, CK+, and FER2013 expression datasets. The simulation results show significant improvements in accuracy and processing time, making the model suitable for the video analysis process. Besides, the study solves the issue of the large processing time required to process the facial images.

Robot-Enabled Uterus Manipulator for Laparoscopic Hysterectomy With Soft RCM Constraints: Design, Control, and Evaluation

Laparoscopic hysterectomy is a common minimally invasive gynecologic surgery in which an assistant is required to manipulate the uterus during the procedure according to the verbal commands of the primary surgeon. However, uterus manipulation is a lengthy and laborious task, where human fatigue may lower operating safety. This paper presents a novel robot-enabled uterus manipulation system that provides accurate, tireless, and direct uterus manipulation. The system consists primarily of a 7-DoF robotic arm tailored for uterus manipulation in laparoscopic hysterectomy. The primary surgeon can directly control the robot using a footswitch pedal to move within the constraint of the Remote Center of Motion (RCM) via software and achieve the desired range of pitch and yaw motion. An additional rotational motion around the instrument axis is provided for twisting the uterus to enhance the exposure of the ligaments and peritoneum for resection. In addition, the robot arm consists of 7 compact modular actuators that provide the target payload for holding the uterus while maintaining a small footprint in a constrained operating environment. To facilitate operation, a passive mobile base is provided for supporting and positioning the robot. A 6-D force sensor is equipped that allows the assistant to quickly guide the robot into the work area and move the robot under RCM constraint using an admittance control approach. The uterus manipulation rod can be easily detached from the robot body by a quick pluggable mechanism for preoperative sterilization. A quick pluggable mechanism was proposed for easy separation and mounting of the uterus manipulation rod from the robot body for preoperative sterilization. Experiments were performed to measure the performance of the modular joints, RCM repeatability, and evaluate the feasibility of the robot in the simulated laparoscopic hysterectomy.

Machine learning prediction of 6-DOF motions of KVLCC2 ship based on RC model

This study uses a machine learning technique based on the Reservoir Computing (RC) model to predict the surge, sway, heave, roll, pitch, and yaw (6-DOF) motions of the KVLCC2 ship in an irregular wave environment. The trained RC model can predict the 6-DOF motions and give the predicted length of 2–5 wave cycles ahead with good accuracy. This work shows the strong ability of machine learning to predict vessel wave-excited motions. It implies that machine learning has important guiding significance in real-time forecasting for motions of both manned and unmanned ships.

A Numerical Study on the Performance Evaluation of a Semi-Type Floating Offshore Wind Turbine System According to the Direction of the Incoming Waves

In this study, the performance evaluation of a semi-type floating offshore wind turbine system according to the direction of the incoming waves is investigated. The target model in this this study is a DTU 10 MW reference wind turbine and a LIFES50+ OO-Star Wind Floater Semi 10 MW, which is the semisubmersible platform. Numerical simulation is performed using FAST developed by National Renewable Energy Laboratory (NREL), which is an aero-hydro-servo-elastic fully coupled simulation tool. The analysis condition used in this study is the misalignment condition, which is the wind direction fixed at 0 degree and the wave direction changed at 15 degrees intervals. In this study, two main contents could be confirmed. First, it is confirmed that sway, roll, and yaw motions occur even though the direction of the incoming waves is 0 degree. The cause of the platform’s motion such as sway, roll and yaw is the turbulent wind and gyroscope phenomenon. In addition, the optimal value for the nacelle–yaw angle that maximizes the rotor power and minimizes the tower load is confirmed by solving the multiobjective optimization problem. These results show the conclusion that setting the initial nacelle–yaw angle can reduce the tower load and get a higher generator power. Second, it is confirmed that the platform’s motion and loads may be underestimated depending on the interval angle of incidence of the wind and waves. In particular, through the load diagram results, it is confirmed that most of the results are asymmetric, and the blade and tower loads are especially spiky. Through these results, the importance of examining the interval angle of incidence of the wind and waves is confirmed. Unlike previous studies, this will be a more considerable issue as turbines become larger and platforms become more complex.

Encapsulated trajectory tracking control for autonomous vehicles

The motion control of autonomous vehicles with a modular, service-oriented system architecture poses new challenges, as trajectory-planning and -execution are independent software functions. In this paper, requirements for an encapsulated trajectory tracking control are derived and it’s shown that key differences to conventional vehicles with an integrated system architecture exist, requiring additional attention during controller design. A novel, encapsulated control architecture is presented that incorporates multiple extensions and support functions, fulfilling the derived requirements. It allows the application within the modular architecture without loss of functionality or performance. The controller considers vehicle stability and enables the yaw motion as an independent degree of freedom. The concept is applied and validated within the vehicles of the UNICARagil research project, that feature the previously described system architecture to increase flexibility of application by dynamically interconnecting services based on the current use-case.

Stability analysis of yaw motion for sandglass-type floating body with dynamic positioning system under regular excitation

For the new sandglass-type floating body with special shape, this paper mainly analyzes its yaw stability under dynamic positioning system. Firstly, by considering the construction tolerance within the range of engineering accuracy, surge and yaw coupled motion equations of the sandglass-type FPSO based on dynamic positioning system are established. Secondly, the yaw instability phenomena of sandglass-type model can be found by Runge-Kutta numerical method. On this basis, a nonlinear yaw motion equation of parametric excitation can be reasonably deduced. Then the multi-scale method and LP (Lindstedt-Poincaré) method are used to study the stability characteristic of yaw motion for sandglass-type floating body. Finally, the effects of initial heading angle and control parameters on the yawing stability of the sandglass-type floating body are discussed.

A comparative numerical study of bank effects on a cruise ship in crabbing motion based on URANS method

The crabbing motion of a cruise ship perpendicularly towards a quay wall is investigated by an unsteady Reynolds-averaged Navier-Stokes (URANS) method. In the numerical simulations, the cruise ship is approaching the quay wall at a constant lateral speed and stops at a rather small ship-quay distance. The crabbing motion with multiple degrees of freedom is simulated by the dynamic overset mesh technique, while the free surface elevation is simulated by the Volume of Fluid method. To obtain reliable temporal discretization for the crabbing process, the time-step dependence study is conducted first, from which a suitable time step is determined. From the computations, the hydrodynamic performances of the cruise ship including: longitudinal force, lateral force, roll moment and yaw moment, as well as surge, heave, roll, pitch and yaw motions are predicted. To evaluate the importance of numerical models used in the URANS method, a comparative investigation is carried out to evaluate the impacts of boundary condition, turbulence model and temporal discretization scheme on the numerical results. From the comparisons, notable influences by the turbulence model and the temporal discretization scheme on both hydrodynamic quantities and flow field features can be observed, especially when the bank effects tend to be pronounced; while the boundary conditions are shown to be less significant. The numerical results indicate remarkable variations of the hydrodynamic quantities in the crabbing process under the influences of ship speed and bank effects. Given that the surge motion is one of the most principal crabbing performances, the initial drift angle with a set of deviations is also computed, coupled with two typical ship speeds in terms of practical navigation. It suggests that more attentions should be paid to the low-speed crabbing to minimize the surge variations. The present study demonstrates promising abilities of CFD methods to deal with the hydrodynamic predictions of harbour manoeuvres in restricted waters.

Performance Examinations of Quadrotor with Sliding Mode Control-Neural Network on Various Trajectory and Conditions

In this article, the performance of the sliding mode control (SMC) that is combined with the backpropagation neural network (NN) as the main control of quadrotor’s dynamic systems was examined on various trajectories and conditions, through numerical simulation. The simulation is conducted with three different trajectories in the absence and presence of the time-varying external disturbances that were adopted from previous studies. The time-varying external disturbances are implemented for the roll, pitch, yaw, and altitude movement simultaneously with the gain set up at the value of 0.8. The simulation results show that the SMC-NN scheme was able to control the quadrotor either in the absence or in the presence of time-varying external disturbances, for each trajectory without any chattering or vibration issues in the quadrotor’s dynamic system. It can be concluded that the SMC-NN is one of the control strategies that are appropriate for the mission with various conditions and circumstances.

Wrench Capability Analysis and Control Allocation of a Collaborative Multi-Drone Grasping Robot

Abstract This paper presents the wrench capability analysis, the controller design, and experimental results of an aerial robot flying gripper. This robot uses four quadrotors to actuate four fingers such as to grasp and manipulate large size objects. The yaw motion of each quadrotor is used to open/close one of the four fingers. A method is proposed to analyze its manipulability considering inequality constraints such as the propellers’ capabilities and equality constraints such as the yaw torque applied by each quadrotor to open or close a finger and the equilibrium conditions of passive joints. This allows concluding on the full manipulability of the robot and evaluating its force and torque capabilities. A dynamic control allocation algorithm is implemented to distribute the control effort among all quadrotors while guaranteeing an achievable solution satisfying the aforementioned constraints. A proof of concept is realized and allows presenting preliminary experimental results of the flying gripper.

Integration sliding mode control for vehicle yaw and rollover stability based on nonlinear observation

An active rear steering and direct yaw moment (ARS-DYC) coordination control is conducted on the basis of nonlinear fuzzy observation to improve yaw and roll stability control of vehicles under extreme conditions. First, a Takagi–Sugeno (T-S) model of yaw and roll motion is established, and tire nonlinearity at emergency steering is approximated with sector domain. A nonlinear fuzzy observation model is established on the basis of the extended Kalman filter (EKF) to observe the sideslip angle, yaw rate, and roll state accurately under extreme conditions in real time. Second, an improved ideal yaw reference model under the T-S framework is constructed in accordance with the effect of yaw rate on roll stability, and the feedforward control of roll stability is achieved through yaw motion tracking. A fuzzy sliding mode controller is designed on the basis of nonlinear fuzzy observation considering tire sideslip stiffness and actuator constraints, and the coordinated control strategy of layered sliding mode surface for yaw and roll is constructed. Finally, the parameters of sub-sliding mode surface are adjusted with the 4-wire phase plane stability domain, the main sliding mode surface parameters are adjusted following the roll stability index, and the stability of the fuzzy sliding mode controller is proven in the Lyapunov framework. A hardware-in-loop simulation test is established with Carsim-Labview software, and results show that the proposed controller significantly enhances the yaw and roll stability of vehicles under the extreme steering process, due to the accuracy of nonlinear dynamic observation and the flexibility of layered sliding surface coordinated control.

The cascade optimal control of steer by wire system using hardware in the loop simulations

This paper aims to further improve the performance of the control system on the steer by wire (SbW) of vehicle steering system, by presenting the development of optimal control system strategy for lateral motion and yaw motion which is arranged in a cascade so that the vehicle can always be maintained on the desired trajectory. The control system strategy to be developed is fuzzy logic control (FLC) as a lateral motion control and proportional integral derivative (PID) control as a yaw motion control, and to obtain an optimal control system, the modified-quantum particle swarm optimization (MQPSO) optimization method is used. The simulations are carried out using hardware in the loop simulations (HILS) which involve hardware, namely; motor stepper actuator and rotary encoder to determine and monitor the direction of the front wheels which are applied to the vehicle dynamics model in a real time. HILS test results show that vehicle movement can be maintained according to the desired trajectory (double lane change) with an average continues-root mean square (C-RMS) error of 0.015366 for lateral motion and 0.014967 for yaw motion, the average C-RMS error is greater 23.75% for lateral motion and 28.18% for yaw motion against the results of the software in the loop simulations (SILS) test.

Flight Control System Simulation for Quadcopter Unmanned Aerial Vehicle (UAV) based on Matlab Simulink

Unmanned aerial vehicle (UAV) are widely used in military and civilian applications due to its advantages of strong maneuverability. Flight control system simulation of a UAV is always a research focus. At present, there are three major algorithms for a UAV flight control: strapdown inertial navigation system, Kalman filter algorithm, flight control Proportional-Integral-Derivative (PID) algorithm. In this study, UAV flight control system and quadcopter drone flight control principle are discussed. In addition, this research developed a dynamic model based on a thorough examination of the quadcopter drone’s frame construction and features. This dynamic model describes the transformation matrix of UAV coordinate system to ground coordinate system. Matlab Simulink was used to simulate a flight control system. A quadcopter drone’s vertical movement, yaw motion, pitching motion, and roll motion, as well as its flight attitude, were simulated and described. Dynamic modeling is developed based on the drone’s flight principle and force relationship in different motion states, as well as the Newton-Eulerian model. Matlab Simulink was used to simulate the trajectory of a quadcopter drone. The red line denotes the trajectory, while the black x markings denote a change in trajectory or a specific position. Blue lines that reflect the waypoint’s heading accompany specific poses. The results of this study could provide a good reference for the simulation of a UAV flight control system.

Effect of initial roll or pitch angles on the vortex-induced motions (VIM) of floating circular cylinders with a low aspect ratio

The vortex-induced motions (VIM) is a phenomenon that can promote large oscillatory amplitudes on circular platforms in the horizontal plane, such as spar or monocolumn production, storage, and offloading system (MPSO). Floating offshore wind turbines (FOWT) can use a spar-type platform to support the turbine, and due to the wind incidence, roll or pitch angles can occur. The main goal of this work was to experimentally investigate the effect of the initial roll or pitch angles on the VIM amplitudes of a floating circular cylinder with a low aspect ratio. Four different initial angle conditions were carried out, namely vertical, roll angle, positive pitch angle, and negative pitch angle. The Reynolds number range performed was 12,000<R<100,000. The results of VIM amplitudes showed that the yaw motion was affected by the initial pitch angle. The initial pitch angles proved to be responsible for creating a geometric asymmetry of the body and promoted more significant yaw motions than the case without initial angle conditions. The yaw motions started to be substantial after the mean pitch angle of the cylinder reached 3°. The yaw motion increased as the reduced velocity was increased and showed to be essential to be correctly modeled and analyzed in the case of VIM on FOWT.

Influence of Fluid Viscosity and Compressibility on Nonlinearities in Generalized Aerodynamic Forces for T-Tail Flutter

The numerical assessment of T-tail flutter requires a nonlinear description of the structural deformations when the unsteady aerodynamic forces comprise terms from lifting surface roll motion. For linear flutter, a linear deformation description of the vertical tail plane (VTP) out-of-plane bending results in a spurious stiffening proportional to the steady lift forces, which is corrected by incorporating second-order deformation terms in the equations of motion. While the effect of these nonlinear deformation components on the stiffness of the VTP out-of-plane bending mode shape is known from the literature, their impact on the aerodynamic coupling terms involved in T-tail flutter has not been studied so far, especially regarding amplitude-dependent characteristics. This term affects numerical results targeting common flutter analysis, as well as the study of amplitude-dependent dynamic aeroelastic stability phenomena, e.g., Limit Cycle Oscillations (LCOs). As LCOs might occur below the linear flutter boundary, fundamental knowledge about the structural and aerodynamic nonlinearities occurring in the dynamical system is essential. This paper gives an insight into the aerodynamic nonlinearities for representative structural deformations usually encountered in T-tail flutter mechanisms using a CFD approach in the time domain. It further outlines the impact of geometrically nonlinear deformations on the aerodynamic nonlinearities. For this, the horizontal tail plane (HTP) is considered in isolated form to exclude aerodynamic interference effects from the studies and subjected to rigid body roll and yaw motion as an approximation to the structural mode shapes. The complexity of the aerodynamics is increased successively from subsonic inviscid flow to transonic viscous flow. At a subsonic Mach number, a distinct aerodynamic nonlinearity in stiffness and damping in the aerodynamic coupling term HTP roll on yaw is shown. Geometric nonlinearities result in an almost entire cancellation of the stiffness nonlinearity and an increase in damping nonlinearity. The viscous forces result in a stiffness offset with respect to the inviscid results, but do not alter the observed nonlinearities, as well as the impact of geometric nonlinearities. At a transonic Mach number, the aerodynamic stiffness nonlinearity is amplified further and the damping nonlinearity is reduced considerably. Here, the geometrically nonlinear motion description reduces the aerodynamic stiffness nonlinearity as well, but does not cancel it.

An Innovative Pose Control Mechanism for a Small Rudderless Underwater Vehicle

Current and conventional pose (position and orientation) control of a small underwater vehicle is achieved by using rudders (yaw motion control) and elevators (pitch motion control), but these suffer from non-linear, indirect and complex control issues. This paper proposes an innovative pose control mechanism for small underwater vehicles. The mass shifter mechanism is designed and fabricated to control pitch and yaw motion with a single propeller only. The center of mass of the underwater vehicle is altered by moving a pair of counterweights on fixed tracks. The pitch and yaw are achieved by controlling the position of the counterweight pairs. The proposed system is designed, fabricated and tested in a real underwater environment for proof-of-concept. The result shows a simpler, more efficient and more effective pose control mechanism than conventional technology.