Yaw Torque Research Articles

Döner Kanatlı İHA’larda İçe Eğimli Yerleştirilmiş Pervanelerin Askıda Kalma Direngenliğine Etkisi

Rotary Wing UAVs (RWUAV) with control inputs (thrust, pitch torque, roll torque, yaw torque; 4 at total) less than the degree of freedom (3 angular motion, 3 linear motion; 6 at total) can move in the X-Y plane by rotating the thrust vectors, i.e their bodies. Deflections caused by external disturbances like winds are also eliminated by angular positioning which creates tractions against disruptive drag forces. However, the fact that the thrust vectors (propeller axis) placed perpendicular to the flight plane do not intersect in space carries the outer center of rotation of the platform to infinity, causing linear acting forces to deflect the system in the same direction in both translation and rotation. This coupling leads to an increase in the net deflection of the geometric center. It is observed that the deflection of the geometric center decreased and converged to the pure translation curve as the propeller placement angles decreased. With the study reported here, it has been analytically modeled and demonstrated how inward tilted propellers increase the hover stiffness of the platform against external disturbances. For future studies, the phenomenon suggesting inward tilted propellers may enhance the platform maneuverability by forming the outer rotation center (thrust vectors’ intersection point) is developed.

Design of Distributed Drive Control Strategy for Wheel Side Rear Drive Electric Bus Based on Neural Network Algorithm.

The electric bus driven by the wheel-side motor has a natural advantage for the driving stability control of the vehicle because the torque of each driving wheel is independently controllable. Based on the advantages of the artificial neural network control algorithm, this paper designs a direct yaw torque control strategy based on neural network PID control, and combines the steering characteristics of the vehicle to distribute the driving torque. The co-simulation results of Matlab/Simulink and TruckSim show that the designed control strategy can effectively reduce the vehicle’s center of mass slip angle and lateral acceleration under medium and high speed conditions, and ensure the stable driving of the bus.

Modeling and Control of Flapping-Wing Micro-Aerial Vehicles With Harmonic Sinusoids

Flapping-wing micro-aerial vehicles (FWMAVs) provide unique control challenges both in control authority and in the complexity of modeling flapping-wing aeromechanics. We provide a control-critical, closed-form model for FWMAV flight, particularly tailored to augmenting yaw torque authority of the vehicle (a common challenge for FWMAVs). The model provides invertible nonlinear closed-form expressions for thrust and moments in terms of trigonometric polynomial input voltages and the wingstroke shape, and respects asymmetries inherent to the vehicle. We apply the model to characterize the Harvard RoboBee, providing an optimization-based system identification process. Using the inverted mapping between wingstroke shape and control axes, we achieve lateral and heading control of the vehicle. Our model and asymmetric system identification, in collaboration with the chosen control scheme, allow full control authority of the position and the heading of the vehicle.

Vehicle yaw stability control with a two-layered learning MPC

This paper proposes a novel framework to address the model-vehicle mismatch (MVM) challenge of yaw stability control, which introduces the Gaussian Process-based Model Predictive Control into the classical two-layer structure. In the upper layer, the supervisor controller calculates the compensation torque required for vehicle turning. Gaussian Process regression is employed to compensate model mismatch and unmodelled dynamics. The chance constraints on sideslip angle are converted into double half-space constraints by the normal distribution quantile function. In the lower layer, the subordinate controller utilises the nonlinear slip rate model to distribute torque to the wheels in the form of braking torque. A new assignment rule of braking torque weight is proposed according to the yaw torque analysis. The stability of the two-layered learning MPC is ensured through proof and simulation. In the Simulink and Carsim co-simulation environment, the superiority of the proposed method is verified in the task of rapid double-lane change. Compared with the traditional MPC-based yaw stability controller, the proposed method has increased the stability tracking index and energy consumption index by around 13% and 8%.

Flying Into the Wind: Insects and Bio-Inspired Micro-Air-Vehicles With a Wing-Stroke Dihedral Steer Passively Into Wind-Gusts.

Natural fliers utilize passive and active flight control strategies to cope with windy conditions. This capability makes them incredibly agile and resistant to wind gusts. Here, we study how insects achieve this, by combining Computational Fluid Dynamics (CFD) analyses of flying fruit flies with freely-flying robotic experiments. The CFD analysis shows that flying flies are partly passively stable in side-wind conditions due to their dorsal-ventral wing-beat asymmetry defined as wing-stroke dihedral. Our robotic experiments confirm that this mechanism also stabilizes free-moving flapping robots with similar asymmetric dihedral wing-beats. This shows that both animals and robots with asymmetric wing-beats are dynamically stable in sideways wind gusts. Based on these results, we developed an improved model for the aerodynamic yaw and roll torques caused by the coupling between lateral motion and the stroke dihedral. The yaw coupling passively steers an asymmetric flapping flyer into the direction of a sideways wind gust; in contrast, roll torques are only stabilizing at high air gust velocities, due to non-linear coupling effects. The combined CFD simulations, robot experiments, and stability modeling help explain why the majority of flying insects exhibit wing-beats with positive stroke dihedral and can be used to develop more stable and robust flapping-wing Micro-Air-Vehicles.

Downstroke and upstroke conflict during banked turns in butterflies.

For all flyers, aeroplanes or animals, making banked turns involve a rolling motion which, due to higher induced drag on the outer than the inner wing, results in a yawing torque opposite to the turn. This adverse yaw torque can be counteracted using a tail, but how animals that lack tail, e.g. all insects, handle this problem is not fully understood. Here, we quantify the performance of turning take-off flights in butterflies and find that they use force vectoring during banked turns without fully compensating for adverse yaw. This lowers their turning performance, increasing turn radius, since thrust becomes misaligned with the flight path. The separation of function between downstroke (lift production) and upstroke (thrust production) in our butterflies, in combination with a more pronounced adverse yaw during the upstroke increases the misalignment of the thrust. This may be a cost the butterflies pay for the efficient thrust-generating upstroke clap, but also other insects fail to rectify adverse yaw during escape manoeuvres, suggesting a general feature in functionally two-winged insect flight. When lacking tail and left with costly approaches to counteract adverse yaw, costs of flying with adverse yaw may be outweighed by the benefits of maintaining thrust and flight speed.

Effects of X Rudder Area on the Horizontal Mechanical Properties and Wake Flow Field of Submarines

X rudder is particularly important for submarine maneuverability, but its influence on wake flow field remains largely unknown. In this study, the X rudder was scaled down three-dimensionally to 80%, 85%, 90%, 95% and 100% of the original rudder area with unchanged aspect ratio and installation position of rudder shaft. Next, the effects of X rudder area on the horizontal mechanical properties and wake flow field of the submarine with a tail control plane were analyzed using the CFD method. The results showed that when the X rudder area was reduced by 20%, the resistance was not significantly affected, and the yaw torque was still larger than that of cross-shaped rudder submarine. At the rudder angles of 0°, 2° and 5°, the velocity non-uniformity coefficients of S1 were reduced by about 9%, 25% and 71%, respectively, when compared to those of S5.

Research on Stability of the Four-wheeled Robot for Emergency Obstacle Avoidance on the Slope

Background: In recent years, patents suggest that four-wheeled robots have been widely used in outdoor reconnaissance fields. However, the emergency obstacle avoidance of the four-wheeled robot on the slope is affected by the slope angle and the friction coefficient of the slope, and its motor torque and yaw torque are prone to abrupt changes, causing the four-wheeled robot to slip greatly. According to relevant literature, PID control methods (dual-loop PID control and linear PID control) make the robot control motor current fluctuate greatly during the emergency obstacle avoidance process. Hence, the PID controller of the four-wheeled robot needs to be optimized. Objective: This study aims to establish a novel dual-loop fuzzy PID controller to improve the stability of the four-wheeled robot during emergency obstacle avoidance on the slope. Methods: Establishing the kinematics and dynamics equations of the four-wheeled robot, and determining the speed of the center of mass and the yaw rate are important control parameters for controlling the steering motion of the robot. Aiming at the PID controller of the past four-wheeled robot, its response speed is slow, and the overshoot of the speed of the center of mass and the yaw rate is large. For this reason, the dual-loop fuzzy PID controller is designed. Comparison simulation is carried out by the MATLAB programming. Results: It is concluded that the control effect of the four-wheel robot with the dual-loop fuzzy PID controller is the best. The steering angle and displacement response speed of the four-wheel robot are faster, and there is basically no overshoot. The response of the yaw rate is increased by 30%, the average deviation of the linear motion trajectory is reduced by 41.27%, and the average deviation of the circular steering motion trajectory is reduced by 29.51%. Conclusion: The dual-loop fuzzy PID controller can provide reference for the PID control research of other four-wheeled robots.

Yaw Control of a Hovering Flapping-Wing Aerial Vehicle With a Passive Wing Hinge

Flapping-wing insect-scale robots (<;$500 mg) rely on small changes in drive signals supplied to actuators to generate angular torques. Previous results on vehicles with passive wing hinges have demonstrated roll, pitch, and position control, but they have not yet been able to control their yaw (heading) angle while hovering. To actuate yaw, the speed of the downstroke can be changed relative to the upstroke by adding a second harmonic signal at double the fundamental flapping frequency. Previous work has shown that pitching dynamics of a passive spring-like wing hinge reduces the aerodynamic drag available to produce yaw torque. We introduce three innovations that increase yaw actuation torque: 1) a new two-actuator robot fly design that increases the moment arm, 2) wider actuators that increase the operating frequency, and 3) a phase shift to the second harmonic signal. We validated these results through simulation and experiment. Further, we present the first demonstration of yaw angle control on a passive-hinge vehicle in a controlled flight. Our new robot fly design, UW Robofly-Expanded, weighs 160 mg (two toothpicks) and requires only two piezo actuators to steer itself.

Method of Improving Lateral Stability by Using Additional Yaw Moment of Semi-Trailer

The lateral stability control of tractor semi-trailer plays a vital role for enhancing its driving safety, and the distributed electric drive structure of a hub motor creates opportunities and challenges for realising the lateral stability accurately. Based on the dynamics simulation software TruckSim, a nonlinear dynamic tractor semi-trailer model is established, and a MATLAB/Simulink linear three-degree-of-freedom monorail reference model is established. The upper controller adopts fuzzy proportional–integral–derivative control to export active yaw torque values of the tractor and semi-trailer. The lower controller outputs the driving/braking torque of each wheel according to the target wheel driving/braking rules and torque distribution rules. The tractor produce an active yaw torque through conventional differential braking the hub motor is installed on both sides of the semi-trailer, and the active yaw torque is produced by the coordinated control of the driving/braking torque of the hub motor and the differential braking of the mechanical braking system. To prevent wheel locking, the slip rate of each wheel is controlled. Finally, based on the TruckSim–MATLAB/Simulink cosimulation platform, cosimulation is performed under typical working conditions. The simulation results show that the control strategy proposed in this report is superior to the conventional differential braking control (ESP). It can not only improve the lateral stability of the vehicle more effectively, but also improve the roll stability.

Flight Stability Control Mechanism Of Ski Jumping In Lateral Wind Environment

Wind is not only closely associated with the discussion of fairness in ski jumping, but also very important to flight safety. Flight stability is essential for performance and safety in ski jumping, and mainly involved several factors, such as environmental wind and flight posture. However, the flight stability control mechanism of ski jumping in lateral wind environment remains unclear. PURPOSE: To determine the flight stability control mechanism of ski jumping in lateral wind environment. METHODS: The aerodynamic characteristics of ski jumping during flight under different lateral wind and yaw angles are predicted by numerical simulation of computational fluid dynamics , and the effects of the above two elements on flight stability are compared and analyzed. The jumper and skis were regarded as a multi-body system, and partially averaged Navier-Stokes turbulence model was used to simulate aerodynamic characteristics of the system based on a general flight attitude and then the forces and torques were obtained. The lateral wind speed involved in the numerical prediction includes 1.5 m/s,3 m/s, 4.5m/s and 7.5m/s, and the flight yaw angle involved includes 2.5°, 5° and 7.5°. RESULTS: When lateral wind speed is small (less than 3m/s), yaw force, yaw torque and rolling torque are small and almost negligible, and when lateral wind speed is larger than 4.5m/s, yaw force, yaw torque and rolling torque are more obvious. When wind speed is 4.5m/s and 7.5m/s, yaw force, yaw torque and rolling torque are 9.5 N and 26.3 N, 2.3 Nm and 6.3 Nm, 2.8 Nm and 7.8 Nm, respectively. When yaw angles are 2.5 °, 5 ° and 7.5 °, yaw force, yaw torque and rolling torque are 6.8 N, 12.9 N and 21.9 N, 2.5 Nm, 5.0 Nm and 6.8 Nm, 2.7 Nm, 5.7 Nm and 8.3 Nm, respectively. When wind speed is 4.5 m/s and yaw angle is 2.5 °, yaw force, yaw torque and rolling torque results of these two conditions are close to each other. Similarly, When wind speed is 7.5 m/s and yaw angle is 7.5 °, yaw force, yaw torque and rolling torque results of these two conditions are close to each other. CONCLUSION: The larger lateral wind can have a significant adverse effect on flight stability control of ski jumping, but it is possible to compensate or even eliminate this adverse effect by taking the appropriate flight yaw angle. Supported by the National Natural Science Foundation of China (Grant No. 11802068).

A Super-twisting Controller for Active Control of Ground Vehicles with Lateral Tire-road Friction Estimation and CarSim Validation

In this paper, a ground vehicle equipped with Active Front Steering (AFS) and Rear Torque Vectoring (RTV) is considered. The AFS, actuated through the front tires, adds an incremental steer angle on top of the driver’s input, whereas the RTV, actuated through the rear tires, imposes a yaw torque to the vehicle. These actuators allow the active control of the vehicle chassis, so that a feasible and safe reference trajectory can be tracked. To obtain such a feasible reference generation and an efficient control action, the lateral tire-road friction coefficient has to be estimated. To this aim, in this paper the lateral tire-road friction coefficient is estimated in finite-time by means of a high-order sliding mode differentiator. Then, based on this estimation, a high-order sliding mode controller is designed to track the desired references. The performance of the dynamic controller is evaluated using a CarSim virtual vehicle, and the simulation results highlight the characteristics of the proposed observer-based control.

Modulating yaw with an unstable rigid body and a course-stabilizing or steering caudal fin in the yellow boxfish (Ostracion cubicus).

Despite that boxfishes have a rigid carapace that restricts body undulation, they are highly manoeuvrable and manage to swim with remarkably dynamic stability. Recent research has indicated that the rigid body shape of boxfishes shows an inherently unstable response in its rotations caused by course-disturbing flows. Hence, any net stabilizing effect should come from the fishes' fins. The aim of the current study was to determine the effect of the surface area and orientation of the caudal fin on the yaw torque exerted on the yellow boxfish, Ostracion cubicus, a square cross-sectional shaped species of boxfish. Yaw torques quantified in a flow tank using a physical model with an attachable closed or open caudal fin at different body and tail angles and at different water flow speeds showed that the caudal fin is crucial for controlling yaw. These flow tank results were confirmed by computational fluid dynamics simulations. The caudal fin acts as both a course-stabilizer and rudder for the naturally unstable rigid body with regard to yaw. Boxfishes seem to use the interaction of the unstable body and active changes in the shape and orientation of the caudal fin to modulate manoeuvrability and stability.

Tunas as a high-performance fish platform for inspiring the next generation of autonomous underwater vehicles

Tunas of the genus Thunnus are a group of high-performance pelagic fishes with many locomotor traits that are convergently shared with other high-performance fish groups. Because of their swimming abilities, tunas continue to be an inspiration for both comparative biomechanics and the design of biomimetic autonomous underwater vehicles (AUVs). Despite the strong history of studies in tuna physiology and current interest in tuna biomechanics and bio-inspired design, we lack quantitative data on the function of many features of tunas. Here we present data on the morphology, behavior, and function of tunas, focusing especially on experimentally examining the function of tuna lateral keels, finlets, and pectoral fins by using simple physical models. We find that both triangular lateral keels and flexible finlets decrease power requirements during swimming, likely by reducing lateral forces and yaw torques (compared to models either without keels or with rectangular keels, and models with stiff finlets or strip fins of equal area, respectively). However, both triangular keels and flexible finlets generate less thrust than other models either without these features or with modified keels or finlets, leading to a tradeoff between power consumption and thrust. In addition, we use micro computed tomography (µCT) to show that the flexible lateral keels possess a lateral line canal, suggesting these keels have a sensory function. The curved and fully-attached base of tuna pectoral fins provides high lift-to-drag ratio at low angles of attack, and generates the highest torques across speeds and angles of attack. Therefore, curved, fully-attached pectoral fins grant both better gliding and maneuvering performance compared to flat or curved, partially-attached designs. We provide both 3D models of tuna morphology derived from µCT scans and conclusions about the performance effects of tuna-like features as a resource for future biological and engineering work for next-generation tuna-inspired AUV designs.

Hierarchical Control of a Quadcopter under Stuck Actuator Fault

Abstract We propose a hierarchical FTC (Fault Tolerant Control) scheme for trajectory tracking by a quadcopter system under stuck actuator fault and actuator saturation. Both the FDI (Fault Detection and Isolation) and control reconfiguration modules are implemented at the low-level associated with the rotation dynamics through a NMPC (Nonlinear Model Predictive Control) strategy. The uncontrolled (when under fault) yaw torque is predicted and compensated by the NMPC. It is shown that the overall control scheme succeeds in maintaining trajectory tracking for various fault events (both in the sense of having various stuck values and in the sense of changing the actuator under fault).

Steering Stability Control for Four-Motor Distributed Drive High-Speed Tracked Vehicles

A steering stability control method for four-motor distributed drive high-speed tracked vehicle is proposed to improve handling stability and safety. The dynamic analysis and calculation of center steering, small radius steering and large radius steering for the four-motor distributed drive tracked vehicle are carried out respectively. In order to meet the power requirements of the outer drive motor in high-speed steering, a steering coupling system is constructed, which uses a steering motor to couple with the traction motor at the rear left or rear right side of the tracks respectively. The steering stability control strategy with the steering coupling takes the yaw angular velocity and longitudinal speed of the vehicle as the control objectives, and a direct yaw torque control strategy is proposed to optimize and distribute the torque of four traction motors in real time according to different steering conditions, and considers the synchronization of two traction motors on one side of the track, so as to improve the steering stability, safety, comfort and steering trajectory performance of the four-motor drive tracked vehicle. The simulation results of 0B, 0.2B, 2B and 8B steering radius show that the proposed control strategy with coupling system can ensure the steering stability for the four-motor distributed drive high-speed tracked vehicle.

Integrated Active Control of Electric Vehicles

This work describes how it is possible to integrate active chassis control actions in an electric vehicle. A vehicle with Active Front Steering (AFS) is considered, which imposes an incremental steer angle to the front wheels. Using Permanent Magnet Synchronous Motors (PMSMs) as powertrain, fitting on the left/right wheel axle shafts, it is possible to impose not only a desired longitudinal traction, but also an appropriate active yaw torque, so mimicking a classic Rear Torque Vectoring (RTV). The AFS, along with the RTV, allow imposing a desired behavior for the active chassis control of the vehicle, so improving its safety.

Reorientation and propulsion in fast-starting zebrafish larvae: an inverse dynamics analysis.

Most fish species use fast starts to escape from predators. Zebrafish larvae perform effective fast starts immediately after hatching. They use a C-start, where the body curls into a C-shape, and then unfolds to accelerate. These escape responses need to fulfil a number of functional demands, under the constraints of the fluid environment and the larva's body shape. Primarily, the larvae need to generate sufficient escape speed in a wide range of possible directions, in a short-enough time. In this study, we examined how the larvae meet these demands. We filmed fast starts of zebrafish larvae with a unique five-camera setup with high spatiotemporal resolution. From these videos, we reconstructed the 3D swimming motion with an automated method and from these data calculated resultant hydrodynamic forces and, for the first time, 3D torques. We show that zebrafish larvae reorient mostly in the first stage of the start by producing a strong yaw torque, often without using the pectoral fins. This reorientation is expressed as the body angle, a measure that represents the rotation of the complete body, rather than the commonly used head angle. The fish accelerates its centre of mass mostly in stage 2 by generating a considerable force peak while the fish 'unfolds'. The escape direction of the fish correlates strongly with the amount of body curvature in stage 1, while the escape speed correlates strongly with the duration of the start. This may allow the fish to independently control the direction and speed of the escape.

Control allocation for all wheel drive sports cars with rear wheel steering

The increasing demands for driving comfort and driving dynamics lead to the introduction of a variety of control systems in modern vehicles. So far, these systems are working in peaceful coexistence and do not use potential synergies. This paper presents a modular control allocation, which combines lateral torque distribution at the rear axle, longitudinal torque distribution, and rear wheel steering. The previous investigations of torque vectoring mostly neglected the secondary yaw torque, which is a result of the dependency between lateral and longitudinal forces at the tyres. An increase in longitudinal forces leads to a decrease in lateral forces and, therefore, results in a yaw torque. A comprehensive vehicle and tyre model is used to analyze this secondary effect for different vehicle states and requested yaw torque. The investigation shows that the influence of the secondary yaw torque varies heavily depending on the vehicle state and the requested yaw torque. Especially, for stabilizing torque requests at high lateral acceleration, the secondary effect is significant and should not be neglected. The investigation shows that an optimal distribution for each yaw torque request exists and that results in maximum lateral forces and thereby maximum lateral acceleration. These results are used within the paper’s modular control allocation. A model-based reference generator delivers desirable yaw rates and side slip angles, which are transferred into necessary lateral forces at the wheels by the control allocation unit. This force-based approach enables modular expandability and usability across multiple vehicles. The proposed controller shows that using the available systems in conjunction helps to increase driving performance and the vehicles stability at the same time.

KUBeetle-S: An insect-like, tailless, hover-capable robot that can fly with a low-torque control mechanism

For an insect-like tailless flying robot, flapping wings should be able to produce control force as well as flight force to keep the robot staying airborne. This capability requires an active control mechanism, which should be integrated with lightweight microcontrol actuators that can produce sufficient control torques to stabilize the robot due to its inherent instability. In this work, we propose a control mechanism integrated in a hover-capable, two-winged, flapping-wing, 16.4 g flying robot (KUBeetle-S) that can simultaneously change the wing stroke-plane and wing twist. Tilting the stroke plane causes changes in the direction of average thrust and the wing twist distribution to produce control torques for pitch and roll. For yaw (heading change), root spars of left and right wings are adjusted asymmetrically to change the wing twist during flapping motion, resulting in yaw torque generation. Changes in wing kinematics were validated by measuring wing kinematics using three synchronized high-speed cameras. We then performed a series of experiments using a six-axis force/torque load cell to evaluate the effectiveness of the control mechanism via torque generation. We prototyped the robot by integrating the control mechanism with sub-micro servos as control actuators and flight control board. Free flight tests were finally conducted to verify the possibility of attitude control.