Inertially Stabilized Platform Research Articles

Image stabilization of airborne inertial stabilization platform using fast steering mirror

Image stabilization of airborne inertial stabilization platform using fast steering mirror

Multi-Channel Phase-Compensated Active Disturbance Rejection Control with an Improved Backstepping Strategy for Electro-Optical Tracking Systems

A multi-channel phase-compensated active disturbance rejection control (MPADRC) incorporating an improved backstepping strategy is proposed in this paper to handle the phase lag in the extended state observer (ESO) and the residual uncertainty in the system. Firstly, a multi-channel phase-compensated ESO (MPESO) is constructed by adding phase-advanced networks to all output channels of the ESO, which allows disturbances and system states to be compensated and feedback in a more timely manner, respectively. Then, to estimate and offset the residual uncertainty in the system, an improved backstepping control method is employed and a Lyapunov function is designed to verify the convergence of the error between the estimated and actual values of the residual uncertainty. After that, the improved backstepping control is combined with MPADRC, and comparisons with the conventional linear active disturbance rejection control (LADRC) are conducted for a range of cases. Finally, on an inertial stabilization platform in the electro-optical tracking system (ETS), simulation and experimental results verified the effectiveness of the proposed method.

Accelerometer-Assisted Disturbance Feedforward Control of an Inertially Stabilized Platform

Inertially stabilized platforms (ISPs) are extensively utilized to stabilize the line of sight (LOS) and achieve precise tracking regardless of various disturbances, whereas their disturbance suppression ability (DSA) is always limited by the system bandwidth. Therefore a disturbance feedforward method based on accelerometer measuring is proposed in this article, which breaks the feedback loop bandwidth limitation and thus improves the closed-loop performance of an ISP. To avoid signal coupling effects between traditional inertial loops, the feedback loop is designed which encompasses the inner loop based on a high-bandwidth encoder as a non-inertial loop and the gyro-based outer loop as an inertial loop. The conventional model-based inverse control reduces the control bandwidth and high-frequency DSA due to the unrealizable differentiation in the system. Hence, the novel accelerometer-based feedforward controller is developed. We adopt the accelerometer integral to obtain high-bandwidth and high-precision disturbance signals and construct the low-pass filter instead of the conventional integrator. Finally, an accelerometer feedforward control scheme that combines acceleration integration with acceleration is conducted to further enhance the system DSA. Simulations and experiments demonstrate the validity of the presented approach.

Adaptive Multi-Parameter Estimation of Inertial Stabilization Platform with Unknown Load

In order to improve the state monitoring and adaptive control capability of inertial stabilization platforms (ISPs) with unknown loads, it is necessary to estimate the dynamic parameters comprehensively online. However, most current online estimation methods regard the system as a linear dual-inertia model which neglects the backlash and nonlinear friction torque. It reduces the accuracy of the model and leads to incomplete and low accuracy of the estimated parameters. The purpose of this research is to achieve a comprehensive and accurate online estimation of multiple parameters of ISPs and lay a foundation for state monitoring and adaptive control of ISPs. First, a dual-inertia model containing backlash and nonlinear friction torque of the motor and load is established. Then, the auto-regressive moving average (ARMA) model of the motor and load is established by the forward Euler method, which clearly expresses the online identification formula of the parameters. On this basis, the adaptive identification method based on the recursive extended least squares (RELS) algorithm is used to realize the online estimation of multiple parameters. The simulation and experimental results show that the proposed adaptive multi-parameter estimation method can realize the simultaneous online identification of the moment of inertia of the load, the damping coefficient of motor and load, the transmission stiffness, the Coulomb friction torque of motor and load, and the backlash, and the steady-state error is less than 10%. Compared with the traditional linear dual-inertia model, the similarity between the model based on the proposed adaptive parameter estimation algorithm and the actual system is increased by 65.3%.

Robust cascade control strategy for trajectory tracking to decouple disturbances using 3-degree-of-freedom inertial stabilized platform and its experimental validation

Inertial stabilized platform (ISP) is a vital component in modern tracking system which can segregate unsettling influence, keep altitude reference and rapidly realize identification and tracking of the target. For accurate tracking, the platform should be able to continuously point towards the target in presence of disturbances as well as parametric uncertainties associated with system modelling which normally degrade system performance. To tackle these challenges, different kinds of control strategies have been reported to achieve desired performance. However, there is an inevitable design trade-off between tracking and disturbance rejection capability as control performance decreases with the increase in system robustness. To alleviate this problem, the present work proposes a robust two-loop cascade control strategy where genetic algorithm (GA) optimized proportional–integral–derivative (PID) in the outer-loop facilitates precision tracking of the target. In the inner loop, lower-order robust controller designed by approximate generalized time moment (AGTM)/approximate generalized Markov parameter (AGMP) model matching approach is used to retain the robustness characteristics of [Formula: see text] controller to mitigate disturbances and model parametric uncertainties. System performance is verified through simulation as well as hardware implementation on a laboratory-fabricated three-axis gimbal platform prototype. The results show 48% improvement in tracking performance and 39.69% improvement in the rejection time of step disturbance in comparison with conventional PID control strategy.

Combined Fuzzy-PID Controller of an Inertial Stabilized Platform

An Inertially Stabilized Platform (ISP) is used when certain sensors are meant to be stable around a required orientation regardless of any movements of the carrier platform. ISPs are essential for vision-guided flying vehicles to stabilize the equipped seeker attached to the guided vehicle body for efficient target tracking and guidance. This work aims to design a suitable and robust controller for an ISP that can mitigate the disturbances and noise expected when attached to a guided vehicle seeker system. The ISP system is modeled, designed, and implemented. To overcome system uncertainties, external disturbances, and coupling, an efficient controller is to be designed to meet stability and performance requirements. In this research, a decoupled dynamic modelling of a two-axis ISP while accounting for system uncertainties is introduced. In addition to that, a combined fuzzy-PID controller is designed. To evaluate the proposed system's performance, a series of experiments based on two axes and transformations between two frames are carried out. The proposed controllers are compared to traditional PID controllers. The simulation and laboratory tests show the high performance achieved by the proposed combined fuzzy-PID controller for the designed ISP, where better robustness, transient response, and steady-state error are obtained when compared to the conventional controllers.

Non-model friction disturbance compensation for an inertially stabilized platform based on type-2 fuzzy control with self-adjusting correction factor

To decrease the effect of nonlinear friction disturbance on the control accuracy of the inertially stabilized platform (ISP) for aerial remote sensing applications, a non-model friction compensation method based on type-2 fuzzy control (T-2 FC) is proposed. To improve the controller’s adaptability, an online complex self-adjusting correction factor method is designed, in which both the fuzzy regulator and the improved integral time absolute error method are combined to adjust the weighting factor and the quantitative factor of the T-2 FC online, respectively. In this way, the nonlinear friction disturbance error is compensated in real-time to obtain high system control accuracy. The experimental results show that compared with traditional PID control and the single T-2 FC, the proposed T-2 FC with self-adjusting correction factor has better disturbance rejection capability to the nonlinear friction disturbance. The ISP has seen a tremendous improvement in both stability and control precision.

Efficient disturbance rejection of gimbaled inertial stabilization platform via relay controller

In this article a relay controller is introduced in the simple motor driven gimbaled inertial stabilization platform (ISP) to improve disturbance rejection capacity. This improvement is possible through the manipulation of the adaptive feature of a limit cycle inherent in relay control systems. We present the sufficient condition for the existence of a limit cycle and its stability analysis in the relay control system, along with how this limit cycle can suppress the exogenous torque disturbance efficiently even in the presence of randomly distributed exogenous inputs. As a disturbance rejection measure, line-of-sight stabilization accuracy was obtained with an ISP driven by a typical linear controller and one by a relay controller, respectively. The results of numerical examples show the effectiveness and efficiency of the relay controller over a typical linear controller.

A High-Performance Compound Control Method for a Three-Axis Inertially Stabilized Platform under Multiple Disturbances

Symmetry is presented in the frame structure, modeling, and disturbance analysis of the three-axis inertially stabilized platform (ISP), which affects the control performance of the ISP. To realize high-performance control for the ISP, a nonlinear dynamic model based on the geographic coordinates and a compound control method based on the adaptive extended state observer (ESO) and adaptive back-stepping integral sliding mode control (SMC) are proposed. The nonlinear dynamic model based on geographic coordinates could avoid the degradation of measurement and control performance due to complex coordinate transformations. An adaptive ESO (AESO) has been developed to estimate the unknown disturbances of ISP. With the information from the ISP system, the adaptive bandwidth of AESO can deal with the peaking phenomenon without introducing excessive noise. Furthermore, based on the integral sliding mode, the adaptation laws of parameter uncertainty and disturbance estimation compensation have been developed for the back-stepping integral SMC method, which can reduce the estimation burden and improve the disturbance estimation accuracy of AESO. The asymptotic stability of the compound control method has been proven by the Lyapunov stability theory. Through a series of simulations and experiments, the effectiveness of the compound method is validated.

Adaptive sliding‐mode‐assisted disturbance observer‐based decoupling control for inertially stabilized platforms with a spherical mechanism

An inertially stabilized platform (ISP) is a gimbal used to hold a camera. It is essential for isolating the attitude sway during an imaging process. To make the platform more compact, the implementation of an ISP with a spherical mechanism has been proposed. However, this design introduces complex non-linear coupling characteristics, significantly increasing the complexity of control. This study aims to solve this problem and present an algorithm to achieve high-performance inertial stabilization control. To achieve this, kinematic and dynamic models were established, and the proposed control algorithm was then designed in three parts. Gravity compensation control was set up in the internal loop to counter the influence of unbalanced gravity moment. An adaptive sliding-mode-assisted disturbance observer (ASMADO) was also included in the joint space to decouple the influence of complex non-linear characteristics on the platform. Further, a feedback controller was added to the workspace based on the kinematic model. This design simplifies the control algorithm for novel ISPs with a spherical mechanism. It effectively compensates for the complex non-linear characteristics and enables superior inertial stabilization control. Experimental results show that the proposed method effectively decreases the motion isolation error for the line-of-sight of the camera compared to traditional control methods.

An LADRC Controller to Improve the Robustness of the Visual Tracking and Inertial Stabilized System in Luminance Variation Conditions

Disturbance from luminance variation in the identification of visual sensors causes instability in the control system of target tracking, which leads to field of vision (FOV) motion and even the target missing. To solve this problem, a linear active disturbance reject controller (LADRC) is adopted to the visual tracking and inertial stable platform (VTISP) for the first time to improve the system’s robustness. As a result, the random disturbance from identification can be smoothed by the tracking differentiator (TD).An improved linear extended state observer (LESO) modified by the TD is provided to obtain the high-order state variables for feedback. That makes the system avoid noise in a differential process from the MEMS gyroscope and enhances the response time and stability in tracking control. Finally, simulation and experimental studies are conducted, and the feasibility of the LADRC is verified. Moreover, compared with the other controller in the VTISP for remote sensing, the superiority of the LADRC in system response time and stability is proved by the experiments.

Constrained Adaptive Backstepping Sliding Mode Control for Inertial Stable Platform

Constrained Adaptive Backstepping Sliding Mode Control for Inertial Stable Platform

Resonance Suppression of a Maglev Inertially Stabilized Platform Based on an Improved Recursive Least Square Algorithm

Mechanical resonance occurs during the operation of a maglev inertially stabilized platform (MISP). The MISP is driven by the motor gear and the gear clearance changes during commutation, which makes the resonance frequency variable. Conventional notch filters with constant parameters are not ideal for variable frequency resonance suppression. In this study, the forgetting factor in the recursive least squares (RLS) algorithm was improved to estimate the resonance frequency online. By adjusting the frequency parameters of the notch filter, the proposed measures can effectively suppress the variable frequency resonance in a dual-stage MISP system. Finally, a simulation example is presented to validate the arguments in this study.

Ship-borne dynamic absolute gravity measurement based on cold atom gravimeter

Cold atom gravimeter is gradually developing towards miniaturization, dynamics and practicality. It is of great significance to apply it to deep and far sea absolute gravity measurement and underwater long navigation time and high-precision navigation. At present, most cold atom gravimeters are still in the state of laboratory static base or quasi-static base measurement, which is difficult to meet the gravity measurement needs in dynamic application scenarios. Therefore, the research on "static to dynamic" of cold atom interferometric gravity measurement is very urgent and key. In this paper, the basic principle of dynamic measurement is analyzed, the basic method of combined measurement of cold atom gravimeter and accelerometer is given, a set of absolute dynamic gravity measurement system based on cold atom gravimeter and inertial stabilization platform is built, and the ship-borne dynamic measurement experiment is carried out by using the combined measurement method of cold atom gravimeter and traditional accelerometer. Firstly, the continuous absolute gravity measurement for about 40 h is carried out in the laboratory static environment to preliminarily evaluate the performance of the cold atom gravimeter. The sensitivity is 447 µGal/<inline-formula><tex-math id="M2">\begin{document}$\sqrt {{\text{Hz}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20220113_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20220113_M2.png"/></alternatives></inline-formula>, and the long-term stability can reach 2.7 µgal. On this basis, the ship-borne experiment is conducted, the survey ship sails on the lake at a speed of about 4.6 kn, and the ship-borne absolute dynamic gravity measurement is carried out by means of repeated survey lines. After evaluation, the internal coincidence accuracy of the four repeated survey lines is 2.272 mGal, and the external coincidence accuracy values of the four voyages are 2.331, 1.837, 3.988 and 2.589 mGal respectively. Finally, according to the experimental results, the possible problems are further analyzed and summarized. This experimental study provides preliminary verification and technical scheme reference for marine absolute dynamic gravity measurement.

Experiment on dynamic absolute gravity measurement based on cold atom gravimeter

Dynamic gravity measurements can improve the survey efficiency of the gravity field, and can play an important role in implementing the basic geological surveys, resource exploration, and geophysical research. Based on cold atom gravimeter, inertial stabilization platform and the movable vehicle device, a system for dynamically measuring absolute gravity is built, and the dynamic measurement experiments are carried out. Firstly, the noise power spectra of the vertical vibration are measured at different moving velocities, and the influence of such a vibration on the measurement of absolute gravity is analyzed theoretically. Besides, the influence on the contrasts and offsets of the atomic interference fringes are evaluated from different moving velocities, then the effect of vibration compensation in the dynamic measurement environment is analyzed. When the maximum moving speed is 5.50 cm/s and the maximum vibration amplitude is 0.1 m/s<sup>2</sup>, the atomic interference fringes can still be rebuilt based on the technology of vibration compensation. On this basis, the atomic interference fringes are obtained at different values of <i>T</i> and different moving velocities, then the absolute gravity value in the dynamic measurement environment is evaluated. After the correction of the systematic system and subtraction by the initial value of absolute gravity, the final measured result is (–1.22 ± 2.42) mGal. Finally, the experiment on the static absolute gravity is conducted, and the two values are found to be not much different from each other through comparing the static measurement data with the dynamic measurement data. The experiment of dynamic absolute gravity measurement in this paper may provide the helpful reference data for the dynamic absolute gravity measurement with moving vehicles.

Robust Backstepping Control Based on Neural Network Stochastic Constrained for Three Axes Inertial Stable Platform

AbstractThe closed-loop performance of an inertial stable platform (ISP) affects the operation of navigation in moving objects. In this paper, the issue of high-performance control of ISP is discus...

Vision-Based Target Detection and Tracking for a Miniature Pan-Tilt Inertially Stabilized Platform

This paper presents a novel visual servoing sheme for a miniature pan-tilt intertially stabilized platform (ISP). A fully customized ISP can be mounted on a miniature quadcopter to achieve stationary or moving target detection and tracking. The airborne pan-tilt ISP can effectively isolate a disturbing rotational motion of the carrier, ensuring the stabilization of the optical axis of the camera in order to obtain a clear video image. Meanwhile, the ISP guarantees that the target is always on the optical axis of the camera, so as to achieve the target detection and tracking. The vision-based tracking control design adopts a cascaded control structure based on the mathematical model, which can accurately reflect the dynamic characteristics of the ISP. The inner loop of the proposed controller employs a proportional lag compensator to improve the stability of the optical axis, and the outer loop adopts the feedback linearization-based sliding mode control method to achieve the target tracking. Numerical simulations and laboratory experiments demonstrate that the proposed controller can achieve satisfactory tracking performance.

The Stability of a Two-Axis Gimbal System for the Camera.

Gimbal or an inertial stabilization platform (ISP) is used to stabilize the line of sight of an object or device that is tracking another object (LOS) with stationary or moving targets or targets moving forward. It can achieve precision when there is isolation between the tracker and the gimbal base. Studying the 2-axis tilt angle to create gimbal stability, especially in a camera, is a compelling subject for the automation field, as it is controlled by modern controllers. This paper presents a two-axis gimbal loop in which the LOS rate is stable, and I proceed to examine the stability of the system to get a better overview of the system properties. Through examining the stability of the system, I can choose from modern control methods to control them. The stability of the system used from the two analysis methods I present below gives me a visual view from the results achieved. The simulation is performed in MATLAB.

Gimbal control of inertially stabilized platform for airborne remote sensing system based on adaptive RBFNN feedback model

The attitude stabilization precision of inertially stabilized platform (ISP) directly affect the resolution of remote sensing image by stabilizing the airborne remote sensing system and holding the line of sight. Therefore, an adaptive control model based on radial basis function neural network (RBFNN) is designed to improve the attitude stabilization precision of ISP gimbal in this article. The adaptive control law and the RBFNN weight adaptive law are designed based on the Lyapunov stability theorem, and the inputs of state feedback control and disturbance observer are combined into the control input. Both simulation and experimental results indicate that the adaptive control based on RBFNN can improve the attitude stabilization precision of ISP gimbal compared to the state feedback control.

The airborne inertially stabilized platform suspend by an axial-radial integrated active magnetic actuator system

IntroductionThe inertial stabilization platform (ISP) is widely used in the earth observation system to stably track the line of sight of the payload because it could isolate vibrations and angular motions of the aviation platform. Objectivesan active magnetic actuator (AMA) system integrating the axial and the radial control is used to levitate the azimuth gimbal to improve attitude stabilization precision and dynamic performance of the ISP, and then the dynamic model of azimuth gimbal is developed. MethodsThe magnetic force and the gimbal torque of the axial-radial integrated AMA system are investigated, and the attitude information of the suspended azimuth gimbal is measured. ResultsThe attitude stabilization precision of azimuth gimbal is confined at 0.02°, and the control bandwidth of the axial-radial integrated AMA system could exceed 100 Hz. Conclusionthe ISP with an axial-radial integrated AMA system has better attitude stabilization precision and wider control frequency than the pure mechanical ISP, so it is potential to be applied in the airborne remote sensing system to improve the measurement precision.