Acceleration Estimation Method Research Articles

Angular acceleration estimation and aerodynamic parameter identification based on angular velocity equivalent model

Conventional angular acceleration estimation methods generate non-negligible errors when the control surface rapidly deflects; hence, the estimated angular acceleration cannot be used for aerodynamic parameter identification directly. This paper proposes an angular acceleration estimation method based on angular velocity equivalent model. The angular acceleration of the angular velocity equivalent model, whose angular velocity response is consistent with the flight test data, is used as the estimated angular acceleration. Firstly, the equivalent angular velocity model is established by combining the generic aerodynamic model with the rotational dynamic equations of aircraft. Secondly, the angular velocity data and the control surface deflection data are synchronized. Finally, the angular velocity response of the equivalent model is used as the predictor, and the estimated angular acceleration is obtained by extended Kalman filter. The aerodynamic parameter identification and validation are carried out using the estimated angular acceleration of a large civil aircraft flight test data. The results show that the angular acceleration obtained through the proposed angular acceleration estimation method meets the accuracy requirement of aerodynamic parameter identification.

Dynamic characteristics analysis and robust transition control of tail-sitter VTOL UAVs

The strong nonlinear dynamics of tail-sitter vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) have consistently constrained their applications. Particularly, the widely-varying flight speed and attitude during the transition flights pose substantial challenges for the controller design. In order to gain a clear understanding of the nonlinear transition flights, the long- and short- period dynamic characteristics of tail-sitter UAVs are investigated for the first time. The results reveal that the short-period mode exhibits either sluggish response or excessive overshoot in different transition stages, primarily due to the widely-varying damping ratio and natural angular frequency. Even worse, the long-period mode can diverge due to positive poles. To address these issues, a systematic controller is proposed. First, the transition trajectory is optimized and the optimal control inputs are employed in a feedforward manner to trim the nominal forces and moments. On this basis, a discrete-time linear quadratic regulation (LQR) controller with a predefined decay rate is developed to position the desired poles, and a novel angular acceleration estimation method is introduced to compensate for unmodeled dynamics. Simulations under different uncertainties indicate that the proposed control method performs better in both transition trajectory tracking and uncertainty suppression, compared to the PID and incremental nonlinear dynamic inversion (INDI) controllers.

Using High-speed Train Induced Signal to Estimate High-Speed Train Acceleration

A moving high-speed train (HST) stimulates various seismic waves near a high-speed railroad (HSR). Thus, the HST has been treated as a combined and moving seismic source. Moreover, the speed and acceleration of HST are typical moving parameters for this HST seismic source. Certain devices, such as GPS, Doppler radar, and cameras, can be used to estimate the HST’s speed. However, they are inconvenient or can be affected by the obstacles. The geophone near an HSR continuously receives the seismic signal induced by the moving HST. This work focuses on the HST acceleration estimation using only one geophone near the HSR and proposes an acceleration estimation method based on the time-frequency spectrum. The experimental field result for a viaduct situation shows the proposed method’s ability to estimate a passing HST’s acceleration, which is verified by acceleration estimation results based on a 14-geophones array along the HSR.

Seismic Acceleration Estimation Method at Arbitrary Position Using Observations and Machine Learning

This study proposes a method of estimating the measurement data of nearby seismic stations by training an artificial neural network (ANN) through machine learning to understand the seismic acceleration time history at an arbitrary location where seismic acceleration time history is unknown. The ANN is trained using the observation data of 6 earthquakes at 10 ground seismic stations in Korea and 12 earthquakes at 212 underground seismic stations from the Korea Meteorological Administration. The location of the seismic station is assumed to be arbitrary in the untrained observation data to verify the validity of the trained ANN, and the measured and estimated data are compared. It is confirmed that the estimation accuracy of the ANN trained with the observation data of the underground seismic station is higher than that of the ANN trained with the observation data of the ground seismic station. The accuracy of the seismic acceleration estimation method proposed in this study is improved according to the level of learning data. It can also be applied as seismic acceleration to evaluate seismic damage or behavior of structures or facilities, even in places without seismic acceleration.

A Joint Acceleration Estimation Method Based on a High-Order Disturbance Observer

Joint acceleration feedback is widely used in the design of controllers and observers since joint accelerations reflect the joint dynamics of robots, especially in physical human-robot interaction. However, joint acceleration acquisition is a technical difficulty for robots. The dynamics-based methods can achieve joint acceleration estimation using only a nominal model. Still, the performance of these methods is limited by the fast time-varying disturbances in the system. This letter proposes a joint acceleration estimation method based on a high-order disturbance observer. This method can observe and compensate for fast time-varying lumped disturbances in the observer while maintaining joint acceleration estimation performance at low frequencies. The finite-time stability of the proposed estimation method is proved using the Lyapunov theory. Simulations and experiments with a lower limb rehabilitation robot are implemented to verify the performance of the proposed method.

Flow Estimation by Flow Induced Vibration of Bluff Bodies

The study confirms the feasibility of using information from flow-induced vibration generated by bluff bodies for measurement of flow. The proposed methodology is based on experiments conducted for recording acceleration signals from vibration sensors embedded along with bluff bodies in cross flow. The studies were undertaken in a wide Reynolds number range of 4700 to 5.655x105, with five different geometries of bluff bodies for shape optimization. Resonance and vortex shedding frequencies of samples are determined experimentally. The recorded acceleration signals are analysed using three different techniques such as frequency shift method, resonance amplitude method and overall acceleration estimation method. In this, the frequency shift method shows correlation at low flow velocities. In the resonance amplitude method and overall acceleration method, acceleration levels show a cubic relation with the flow rate. In the resonance amplitude method, obtained R2 values are from 0.93 to 0.99. Overall acceleration estimation method has shown better correlation with flow rate and its R2 values were above 0.99. The study confirms that application of all three methods together yields reasonably good estimation for a wide range of flow.

Acceleration Estimation for Linear Oscillatory Actuator with 2 pole and 3 pole movers.

Recently, a linear oscillatory actuator with two movers are developed and are applied as active vibration control devices that can reduce vibration in a wide frequency range. In the system, inertial force is controlled by using acceleration information on movers that obtained from acceleration sensors. In this paper, an acceleration estimation method using extended Kalman filter is suggested for sensorless control. The future of the suggested method is that nonlinear detent characteristics depending positions on two movers are considered in the state model of extended Kalman filter. As a result of online estimation using a controller and prototype, estimation values agreed with measured.

Robust proportional incremental nonlinear dynamic inversion control of a flying-wing tailsitter

Tailsitter unmanned aerial vehicles are utilized extensively nowadays since they merge advantages of both fixed-wing unmanned aerial vehicles and rotary-wing unmanned aerial vehicles. However, their attitude control suffers from unknown nonlinearities and disturbances due to the wide flight envelope. To solve the problems, a robust attitude controller based on a newly designed flying-wing tailsitter is proposed in this paper. By employing the angular acceleration feedback to compensate unmodeled dynamics, the proportional incremental nonlinear dynamic inversion control law is first developed. The proportional incremental nonlinear dynamic inversion strengthens the conventional nominal gain incremental nonlinear dynamic inversion with a proportional term to reflect the change of the angular acceleration more directly. Therefore, the tailsitter has a quicker response and performs better in suppressing model uncertainties and external disturbances. Since the angular acceleration is difficult to measure in practice, an angular acceleration estimation method is then established to provide accurate signals for the proportional incremental nonlinear dynamic inversion. The signals are derived as complementary results of model prediction method and direct differential method. Theoretical analysis and systematic simulations are conducted to corroborate the effectiveness of the developed estimation method as well as the robustness of the proposed controller.

Research on Integrated Control Method for Helicopter/Turboshaft Engine with Variable Rotor Speed Based on the Error Between Engine Required and Real Output Torque

In order to achieve more rapid response control for integrated helicopter/turboshaft engine system with variable rotor speed, an integrated control method based on the error feedforward between engine required and real output torque is proposed. Firstly, based on the principle of incremental nonlinear dynamic inversion, an online acceleration estimation method of gas turbine speed (Ngdot) is proposed to realize the cascade control for turboshaft engine based on Ngdot. Then, a rotor demanded torque predicted model is developed through min-batch gradient descent-neural network. Meanwhile, a feedforward compensation method based on the error between engine required and real output torque is proposed according to the rotor dynamics characteristics of engine output shaft with variable rotor speed to suppress the interference of the rotor demanded power during variable rotor speed. The simulation results show that under different flight conditions, compared with the collective pitch feedforward and the rotor predicted torque feedforward control, the feedforward control method based on the error between engine required and real output torque can effectively reduce the overshoot of the relative speed of power turbine by about 14%. In addition, the settling time of power turbine speed is shorter, and the dynamic performance is superior, which can realize the rapid response control of turboshaft engine better.

Line-of-sight stabilization of roll-pitch seeker using differentiator-based disturbance compensation control

A new control problem of roll-pitch seeker about the disturbance coupling is investigated in this work. Previous control strategies of roll-pitch seeker rarely considered the effects of the dynamic coupling disturbances from the missile angular motion, and because of the polar coordinate structure, the disturbance rejection strategies of yaw-pitch seeker cannot be utilized directly on roll-pitch seeker. Thus this article presents a new control strategy to improve the disturbance rejection ability of roll-pitch seeker. To analyze the disturbance coupling problem, the roll-pitch seeker model is derived with consideration of the missile body angular motion and torque disturbances. The motion equation of roll-pitch seeker shows that part of the dynamic coupling disturbance can be eliminated by certain choices of inertial parameters. The rest of disturbance is reduced by the stabilization loops using a differentiator-based disturbance compensation controller. Particularly, a missile body angular acceleration estimation method is designed for the compensator based on an adaptive differentiator. In addition, comparisons with other control strategies are carried out via numerical simulations, and the results confirm the effectiveness of the proposed method.

Linear motor acceleration estimation method based on grating signals

Linear motor acceleration estimation method based on grating signals

Curve Model of Adaptive Interaction Model Algorithm Tracking Method

Firstly, through the principle analysis and simulation experiment, the maneuvering target tracking algorithm of curve model interacting multiple model tracking algorithm was given. Because the algorithm is simple structure and high cost efficiency, it becomes generally applicable algorithm for curve tracking model. But, the target mobility is very high in practice, Single target tracking model is no longer applicable curve tracking model. To improve the accuracy of tracking, the adaptive grid interacting multiple model (AGIMM) algorithm was given. The algorithm has two fatal weaknesses in the practical application. First, the process of maneuvering target tracking, when the model changes and gradient, the tracking precision is not high ;Second, because the changing model structure is very large model sets, the algorithm is complexity and system processing speed is very slow, which cannot be widely used. In order to improve the algorithm and its scope of application, The paper proposed the adaptive Kalman filter adaptive interacting multiple model algorithm (AKFAIMM).The algorithm introduced the parameter in the adaptive Kalman filter, and adjusted parameter in maneuvering target tracking, the parameter was adjusted Continuously in the curve motion model, it could greatly improve the tracking precision and the application of the model. Second, to improve the algorithm complexity. The paper improved on turning curve. The angular velocity estimation method replaced centripetal acceleration estimation method. The estimation method reduced the number of model set and reduced greatly of computation.

Estimation of target's acceleration based on empirical wavelet transform

Target's accelerations lead to spectrum shift and broadening of target's echo signal,resulting in the inaccuracy estimation of target's Doppler frequency with traditional pulse radar velocity measurement method. To overcome the effect of acceleration on pulse radar velocity measurement,an empirical wavelet transform( EWT) based radial acceleration estimation method was proposed. The instantaneous frequency of the echo signal can be extracted through EWT and energy-oriented principal frequency components extraction method. The high order coefficients of the phase were obtained through robust least square fitting on the instantaneous frequency,which correspond to the radial velocity and radial acceleration respectively. After compensating the echo signal with estimated accelerations,the Doppler frequency of echo signal can be accurately estimated. Simulations show that the EWT method is a fast algorithm with high estimation accuracy,and the estimation error is close to Cramer-Rao lower bound. Applying EWT method on measured pulse radar data of high speed vehicle,the estimated acceleration error is smaller than 0. 4 m / s2. EWT method is applicable in real time pulse radar acceleration estimation.

Acceleration estimation method and sliding mode control design for car-following distance control

Vehicle following for traffic safety has been an active area of research. Car-following distance control is key for vehicle following mode in autonomous cruise system. Sliding mode control has been applied in vehicle longitudinal distance control. But most of them ignore or simplify acceleration information and reduce control performance. The purpose of this paper is to design sliding mode control method considering relative acceleration parameter to control car-following distance for autonomous cruise control (ACC). Meanwhile, tracking-differentiator is designed to estimate acceleration information as the control parameter and enhances the control system performance. Theoretical analysis and computer simulation prove that the designed linear tracking-differentiator can effectively estimate the relative acceleration and sliding mode control method considering relative acceleration parameter can also effectively control headway distance.

Maneuver target tracking with an acceleration estimator using target past positions

AbstractTarget tracking filters with a low computational load are desired in air traffic control systems in order to simultaneously search and track multiple aircraft. The applications of the α−β filter and the Kalman filter have been widely studied. Although excellent tracking accuracy can be obtained for linear motion by the α−β filter, the tracking accuracy degrades for a maneuvering target, the difference between the predicted position and the actual target position becomes large, and mistracking where the target is lost may occur. While there has been research on filters that estimate the acceleration, these filters could only be used when there is little maneuvering and the computational load is huge. In this research, we propose a method that adds an acceleration term during turning motion as the tracking filter for maneuvering motion and not just linear motion and estimates the turning acceleration from past estimated positions of the target. We also reduce the tracking errors for a maneuvering target. We use simple trajectories of the target in computer simulations and compare the proposed method to conventional filters to demonstrate its effectiveness. And we evaluate the performance of the proposed acceleration estimation method. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(12): 29–37, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10026