Angular Rate Control Research Articles

Robust-augmentation nonlinear dynamic inversion control of over-actuated coaxial high-speed helicopter in transition mode

As the elevator and rudder can be used actively for control, in addition to the rotors, Coaxial High-speed Helicopters (CHHs) have the problems of control redundancy and changing control authority in the transition mode. This paper presents a robust-augmentation transitioning flight control design for a CHH under the adverse conditions of parametric uncertainties and external disturbances. First, based on control characteristic analysis, an Adaptive Filtered Nonlinear Dynamic Inversion (AFNDI) controller is proposed for the angular rate to handle the effect of unknown unstructured uncertainties and external turbulence. Theoretical analysis proves that the presented angular rate controller can guarantee steady-state and transient performance. Furthermore, the attitude angle and velocity controllers are also added. Then, an Incremental-based Nonlinear Prioritizing Control Allocation (INPCA) method is designed to take into account control surface transition and changing control authority, which efficiently distributes the required moments between coaxial rotors and aero-surfaces, and avoids the control reversal problem of the yaw channel. In the proposed control architecture, the low-pass filter is introduced to alleviate the adverse influence of time delay and measurement noise. Finally, the effectiveness of the proposed controller is demonstrated through nonlinear numerical simulations, and is compared with existing methods. Simulation results show that the proposed control law can improve both capabilities of disturbance rejection and fast response, and works satisfactorily for the CHH transitioning control characteristic.

Adaptive Controller Based on Estimated Parameters for Quadcopter Trajectory Tracking

This paper presents a trajectory control system design for a quadcopter, an unmanned aerial vehicle (UAV), which is based on estimated parameters that are assumed to exhibit random walk behavior. Initially, the rotational dynamic model of the UAV is formulated using the Newton Euler method in terms of angular velocity about the x, y, and z axes. This model is then simplified into three separated-first-order linear differential equations, with coefficients derived from the combined effects of inertia, aerodynamic drag, and gyroscopic effects, referred to as lumped parameters. A Proportional-Integral (PI) controller with feed-forward design is then developed to control this simplified model. To adapt the controller to the lumped parameters that exhibit random walk behavior, each simplified equation is restructured into a processing and measurement model. The states of these models are estimated by using the Unscented Kalman Filter (UKF). These estimated values are then utilized to adjust the PI gains and compensate the signal of the designed angular velocity controller, transforming it into an adaptive controller. The entire UAV controller comprises two main parts, an inner loop for adaptive angular rate control and an outer loop serving as an attitude-thrust controller. The proposed controller is simulated using Simulink, with circular and square trajectories. The simulation results demonstrate that the quadcopter successfully follows the desired circular and square paths. The steady-state error for the x and y axes in the square trajectory is less than 0.05 meters within 5 seconds, and for the z axis, it is less than 0.02 meters within 2.5 seconds. The controller gains do not require adjustment when changing trajectories. Moreover, the estimated parameters remain nearly constant at steady state.

A backlash identification and compensation method for high-speed aircraft angular rate control

This paper focus on the hysteresis phenomenon of the roll angular rate control resulting from the backlash of the actuators for a high-speed aircraft in real flight. First, the backlash is analyzed in the time and frequency domain, and then the backlash parameters are identified using the statistic method. Second, based on the inverse backlash model, the L 1 adaptive controller with the backlash compensation is designed. Third, two simulation tests with and without the backlash compensation are conducted and the simulation results are compared which show the effectiveness of the backlash-compensation-based controller.

Short Landing for Flying-Wing Unmanned Aircraft with Thrust Vector

The task of achieving a safe and short landing for a flying-wing unmanned aircraft with a three-bearing-swivel thrust vector is highly challenging. The process is further complicated due to the need to switch between multiple control modes, while also ensuring the protection of the flight boundaries from environmental disturbances and model uncertainties to ensure flight safety. To address this challenge, this paper proposes a short-landing strategy that employs mixed control using lift fans, thrust vectors, and aerodynamic control surfaces. The extended state observer (ESO) is integrated into the inner angular rate control and outer sink rate control to account for environmental disturbances and model uncertainties. To ensure flight safety, the attainable linear and angular acceleration is calculated through a trim analysis to determine the command value of velocity and angle of attack during a short landing. Additionally, a flight boundary protection method is employed which includes an additional command value of the angle of attack, resulting in a higher probability of a successful landing. This paper provides a detailed description of the short-landing strategy, including the control objectives for each phase. Finally, a Monte Carlo simulation is conducted to evaluate the effectiveness and robustness of the short-landing strategy, and the landing accuracy is assessed using the circular error probability metric.

Null-Space-Excitation-Based Adaptive Control for an Overactuated Hexacopter Model

This paper proposes a novel adaptive control structure featured by large closed-loop bandwidth and satisfactory parameter estimation results. The proposed baseline control structure is consisted of a velocity controller, an angular rate controller, and a pseudo-inverse-method-based control allocation module. For multirotor systems with immobile propellers, this structure is able to provide commands of pseudo inputs without redundancy. These commands will then be allocated through control allocation matrix possessing necessary elements. By using noncascaded velocity controller and considering actuator dynamics, the bandwidth of whole controller is broadened and a chance of estimating control effectiveness together with bandwidths of actuators appears. The null space excitation method is developed in this paper for assisting in parameter estimation, which will inject excitation signals in null space of control allocation matrix and therefore will not influence allocation results. This method is able to enlarge data information evaluated by Fisher information matrix. Hence, estimating parameters with these excitation signals is faster and more accurate than estimations in common methods. Designed null-space-excitation-based adaptive controller is validated on a complex high-fidelity hexacopter model and shows satisfactory performance in terms of control and parameter estimation.

CFD-based UAV automatic take-off ground roll control method

Aiming at the problems of low control accuracy and long control time in traditional UAV automatic takeoff ground roll control method, a CFD based UAV automatic takeoff ground roll control method was proposed. Firstly, the flow field calculation formula is defined in the inertial coordinate system, and the rotor flow field generated between UAV and automatic take-off ground roll is solved by CFD method. Then according to the value, the unmanned aerial vehicle (UAV) rotor flow field flow rate from the air spring force, tire spring force, buffer damping force and under the action of ground support, analysis the stress of the roll on the ground, finally on this basis, through the pitching Angle and angular rate control design protection design, airspeed protection design complete automation design, realizes the unmanned aerial vehicle (UAV) automatic take-off and roll control. The simulation results show that the control accuracy of the proposed UAV automatic take-off ground taxiing is 99.5% and the control time is less than 5 s. This method has good control performance and is worth popularizing.

Neural-Adaptive Constrained Flight Control for Air–Ground Recovery Under Terrain Obstacles

This article contrives a neural-adaptive constrained controller of the cable towed air–ground recovery system subject to terrain obstacles, unmeasurable cable tensions, trailing vortex, wind gust, and actuator saturation. In air–ground recovery system modeling, the towed vehicle's nominal 6 DOF affine nonlinear dynamics and the cable system's finite links-joints dynamics are formulated. To achieve accurate air–ground recovery under terrain obstacles, an asymmetric barrier Lyapunov function-based flight controller of the towed vehicle is proposed, by transforming the terrain obstacles into time-varying constraints on the vehicle's trajectory. Then, to approximate the towed vehicle's lumped unknown dynamics caused by the unmeasurable cable tensions and airflows, several echo state network (ESN) approximators are established for velocity and attitude subsystems. By using the state approximation errors-based neural weights learning strategy and minimal learning parameter technique, these ESNs possess better transient behaviors and lower online computational burden. Furthermore, the actuator saturation is automatically monitored and released, by incorporating a specially designed auxiliary compensating system into the angular rate control law for compensation. The stability of the closed-loop system is analyzed. Finally, numerical simulations under two air–ground recovery scenarios are performed to demonstrate the performance of the proposed controller.

Control design for maximal capability of disturbance rejection under general control input saturation

This paper focuses on the control problem for a basic class of nonaffine uncertain systems with general control input saturation (CIS) and piecewise constant disturbance. Instead of traditional CIS, the considered general CIS model includes the case that larger control input generates smaller control capability to capture more general engineering systems. Also, the saturation point, at which the maximum or minimum value of the saturation function of general CIS can be obtained, is assumed to be unknown. To achieve the maximal capability of disturbance rejection, this paper proposes a novel active disturbance rejection control design with online estimating both disturbance and the saturation points. Firstly, the control capability under the nominal saturation points is discussed. We demonstrate that the corresponding capability of disturbance rejection can be discussed via the domain of attraction or invariant set of the systems with general CIS despite of disturbance. Furthermore, we design an algorithm to online identify the saturation points based on the estimation of “total disturbance” obtained by extended state observer (ESO). It is proven that the maximal capability of disturbance rejection can be approached by tuning the parameters of the proposed controller. In addition, simulation results for the angular rate control of aircraft show the superiority of our control law to the traditional disturbance rejection control law.

System identification and adaptive control of micro helicopter

This paper copes with the controller design problem of a micro helicopter, which is a multivariable and strongly coupled nonlinear system. The state-space model near the hovering condition of pitch and roll channels is acquired by least-square system identification method, with flight test verification. Based on the identified model, model reference adaptive control is designed as angular rate controller, and PID controller is used to stabilize attitude loop. State-space model helps to decouple the roll and pitch channels, and model reference adaptive control can address external disturbances, model uncertainties and nonlinearities of the dynamics, which can be estimated and further eliminated online. Eventually, both simulations and actual flight tests are conducted to verify the effectiveness of the proposed control scheme.

Research on Roll Attitude Control of UAV Based on Active Disturbance Rejection Control

The roll attitude control of small high-speed unmanned aerial vehicle (UAV) is very difficult compared to the conventional low-speed UAV. The dynamic pressure is large and the moment of inertia is too small, which cause the aileron is sensitive to manipulation. The roll attitude may oscillate due to the actuator rate limiting. In response to this feature, the active disturbance rejection control (ADRC) is added to compensate the nonlinear part of the system, so that the system is close to an integral link. The problem of the actuator rate limiting can be solved by tuning the gain of the angular rate control to change the system bandwidth. On the other hand, the rolling motion is, in general, coupled from the yawing and sideslip motions. ADRC can decouple the roll channel and the yaw channel, solving the nonlinear problem of control. Combination with the requirements of frequency and time domain, design the roll attitude controller. The UAV nonlinear simulation results show that the roll attitude control based on ADRC meets the flight control requirements.

Attitude control of tiltwing aircraft using a wing-fixed coordinate system and incremental nonlinear dynamic inversion

In this paper, we present a novel concept for robustly controlling the attitude of tiltwing aircraft. Our main contribution is the introduction of a wing-fixed coordinate system for angular acceleration control, which forms the basis of a simple and robust attitude controller. Using the wing-fixed coordinate system allows us to describe the actuator effectivity using simple approximations based on the current operating conditions of the aircraft. Coupled with a robust angular rate control concept, which does not rely on an accurate aerodynamic model, we present a controller stabilizing the entire flight envelope of a tiltwing aircraft. The underlying angular acceleration controller uses the concept of Incremental Nonlinear Dynamic Inversion (INDI) to achieve robustness against aerodynamic uncertainties. The resulting controller is evaluated in both simulation studies and flight tests.

Dynamics and Control of In-Flight Wing Tip Docking

Project Link! is a NASA-led effort to study the feasibility of multi-aircraft aerial docking systems. In these systems, a group of vehicles physically link to each other during flight to form a larger ensemble vehicle with increased aerodynamic performance and mission utility. This paper presents a dynamic model and control architecture for a system of fixed-wing vehicles with this capability. The dynamic model consists of the six-degree-of-freedom fixed-wing aircraft equations of motion, a spring–damper–magnet system to represent the linkage force between constituent vehicles, and the NASA Burnham–Hallock wing-tip vortex model to represent the close-proximity aerodynamic interactions between constituents before the linking occurs. The control architecture consists of a guidance algorithm to autonomously drive the constituents toward their linking partners and an inner-loop angular rate controller. A simulation was constructed from the model, and the flight dynamic modes of the linked system were compared to the individual vehicles. The main contributions of this work are twofold. First is the introduction of close-proximity aerodynamic effects to create a realistic simulation framework for this problem. Second is the application of a sophisticated leader–follower guidance algorithm to achieve in-air wing-tip docking. Simulation results for both before and after linking are presented.

Model reference adaptive attitude control for near space hypersonic vehicle with mismatched uncertainties

In this paper, a new model reference adaptive attitude control based on backstepping approach is presented for near space hypersonic vehicle with mismatched uncertainties. Firstly, the attitude dynamic model of near space hypersonic vehicle is divided into two control loops, which is composed of an attitude angle control loop and an attitude angular rate control loop. Secondly, a novel model reference adaptive attitude control approach is proposed by introducing reference model to avoid the calculating expansion problem in backstepping technique. Meanwhile, the reference models for every loop are independently designed to improve the tracking performance. The stability of attitude control system is strictly proven by using Lyapunov stability theory. Finally, the simulation results demonstrate that the attitude control system by applying the proposed method has good stability, dynamic property and strong robustness in the presence of input constraints and parameters perturbation.

Optimal Placement of Sensors and Actuators for Gyroelastic Body Using Genetic Algorithms

A flexible body with a distribution of stored angular momentum is viewed as a gyroelastic body. The flexible structure may require active vibration suppression, which can be controlled using a collection of control moment gyroscopes. This study investigates the optimal placement of collocated angular rate sensors and control moment gyroscope actuators for a constrained gyroelastic body based on genetic algorithms. First, the dynamics and modal analysis of the constrained gyroelastic body are presented. The state-space model is adopted that contains the distribution of actuators and sensors. Based on the concept of the controllability and the observability of the gyroelastic system, the objective functions are proposed aiming at the maximization of the controllability and observability of the constrained gyroelastic system. For situations with a fixed number of actuators and sensors, an exhaustive enumeration method and genetic algorithms are used to determine the locations of actuators and sensors. For a comprehensive optimization of the number and locations of actuator–sensor pairs, genetic algorithms are used to avoid calculating all possible combinations, increasing factorially in the enumeration method. The optimized results are verified by the responses of the constrained gyroelastic body. Numerical simulations are presented for a cantilevered plate.

An adaptive neural network approach to the tracking control of micro aerial vehicles in constrained space

ABSTRACTThis paper presents an adaptive neural network approach to the trajectory tracking control of micro aerial vehicles especially when they are flying in a limited indoor area. Differing from conventional controllers, the proposed controller employs the outer position loop to directly generate angular velocity commands in the presence of unknown aerodynamics and disturbances and then the fast inner loop to handle the angular rate control. Adaptive neural networks are deployed to estimate all the uncertain factors with the adaptation law derived from the Lyapunov function. To achieve a real-time performance, a norm estimation approach of ideal weights is designed to achieve a high bandwidth and lighten the burden of computation burden. Meanwhile, a barrier Lyapunov function is introduced to guarantee the constraint of vehicle positions as well as the validity of the neural network estimation. Simulations and practical flight tests are conducted to verify the feasibility and effectiveness of the proposed control strategy.

マルチロータヘリコプタの適応PID型角速度制御

In this paper, angular rate feedback control of multi-rotor helicpter is designed by using adaptive PID method. Adaptive PID controller with parallel feedforward conpensator : PFC is designed based on mathematical model of the helicopter. The effectiveness of the proposed control system is verified by numerical simulation and experiment. The results of the experiment with jig, and free flight experiment shows the efficiency of proposed adaptive angular rate controller.

A207 単純適応制御を用いたマルチロータヘリコプタの角速度制御(OS11 自律知能無人ビークルの運動と制御1)

A207 単純適応制御を用いたマルチロータヘリコプタの角速度制御(OS11 自律知能無人ビークルの運動と制御1)

Saturated control of flexible-joint manipulators using a Hammerstein strictly positive real compensator

SUMMARYIn this paper the control of flexible-joint manipulators while explicitly avoiding actuator saturation is considered. The controllers investigated are composed of a bounded proportional control term and a Hammerstein strictly positive real angular rate control term. This control structure ensures that the total torque demanded of each actuator is bounded by a value that is less than the maximum torque that each actuator is able to provide, thereby disallowing actuator saturation. The proposed controllers are shown to render the closed-loop system asymptotically stable, even in the presence of modeling uncertainties. The performance of the controllers is demonstrated experimentally and in simulation.

A Variable Structure Attitude Control System Design Based on Finite Time Stability

A variable structure attitude control system design method that guarantees the finite-time stability is proposed for hypersonic vehicle attitude control. According to the characteristics of the hypersonic vehicle longitudinal attitude model, it is considered to comprise attack angle control loop and angular rate control loop. The attack angle controller and pitch angular rate controller based on variable structure control are designed respectively which ensure the finite-time stability. The finite-time stability of the whole attitude control system has been proved .The simulation results illustrated that the proposed attitude controller has good rapidity and robustness.

Attitude control system for the nano‐astrometry satellite “Nano‐JASMINE”

PurposeThis paper aims to present an attitude determination and control system for a nano‐astrometry satellite which requires precise angular rate control. Focus of the research is methods to achieve the requirement.Design/methodology/approachIn order to obtain astrometry data, the satellite attitude should be controlled to an accuracy of 0.05°. Furthermore, attitude spin rate must be controlled to an accuracy of 4×10−7 rad/s during observation. In this paper the following unique ideas to achieve these requirements are introduced: magnetic disturbance compensation and rate estimation using star blurred images.FindingsThis paper presents the feasibility of a high accurate attitude control system in nano‐ and micro‐satellite missions.Practical implicationsThis paper presents a possibility of the application of nano‐satellites to remote‐sensing and astronomy mission, which requires accurate attitude control.Originality/valueOriginalities of the paper are the methods to achieve the high accurate attitude control: magnetic disturbance compensation and angular rate estimation using star images.