Gimbal System Research Articles

Drone-based mobile full-duplex optical communication

Wireless optical communication plays a vital role in mobile communication networks, and both drones and vehicles are essential mobile communication nodes. Here, image identification technology, gimbal, and full-duplex optical communication systems are integrated to manage the challenging issues of light alignment and target tracking for mobile full-duplex optical communication under the transmission control protocol/internet protocol (TCP/IP) scheme. Both drones and vehicles are equipped with the proposed setup to realize full-duplex wireless optical data transmission at a communication rate of 2 Mbps in both air-to-ground and air-to-air scenarios. By further integrating wireless-fidelity (Wi-Fi) modules, drone-based mobile optical communication systems (MOCSs) can be interconnected with the network via the TCP/IP scheme, and real-time video transmission can be demonstrated. This work provides a feasible route toward a mobile optical communication network (MOCN) for diverse applications.

Research on coupling analysis and decoupling control of two-degree-of-freedom PTZ system

Abstract With the development of technology, especially in areas such as robotics, aerospace, photography, and videography, gimbal systems, as an important stabilization device, have been widely used. However, the two-degree-of-freedom gimbal system also faces a series of challenges in practical applications. Among them, one of the most critical issues is the internal coupling phenomenon in the system. The coupling phenomenon refers to the mutual influence and a constraint relationship between different degrees of freedom in the system, which may increase the complexity of the system’s dynamic characteristics and make the design and implementation of control strategies difficult. This study aims at explore more advanced and practical decoupling control strategies through in-depth analysis of the coupling characteristics of the two-degree-of-freedom gimbal system, providing new ideas and methods for the further optimization and application of the gimbal system.

Design and Implementation of a Micro Controller for Robot Sensing and Driving

According to the control requirements of robot, the micro controller was designed, including the interface for the wireless transmission module NRF24L01, the sampling circuit for collecting the pressure sensing value, the DC motor drive function module, and the auxiliary circuit for ensuring the normal operation of the controller. After passing the hardware testing, the design of the PTZ control system is completed. The virtual reality environment is constructed using unity and VS software, Oculus is used as the head-mounted display, and then the pose sensor of Oculus is used to analyze and extract the pose sensing data for the control of the PTZ. The industrial camera is used to send back video, based on HSV algorithm for target recognition, and displaying video images in the virtual environment. And the above data was sent to the gimbal control system to finalize the virtual reality environment. Finally, the debugging and verification of the hardware architecture based on sensing and driving and the virtual reality environment were completed. And the scenario tests were conducted for the gimbal following and force feedback virtual interaction ball respectively, which verified the use of virtual reality technology to assist in controlling the robot and obtain the sense of immersive control experience.

Adaptive zone based active noise control for a moving target

This study focuses on enhancing active noise control (ANC) in room enclosures, specifically targeting zones of quiet (ZoQ) around aircraft passenger seats. By integrating virtual sensing and motion tracking techniques, we aim to dynamically adapt the ZoQ to moving targets. Key to our approach is the strategic placement of actuators and sensors, forming the core of the ANC system. Our methodology includes virtual sensing for ANC analysis, ZoQ optimization for varied applications, and in-depth case studies. We introduce an innovative combination of a speaker gimbal system, a vision system, and custom software for precise motion tracking, significantly improving ZoQ localization. The findings offer insights into maintaining effective ZoQs for multiple input multiple output (MIMO) local ANC configurations, laying the groundwork for adaptive ZoQ control about sound sources and desired cancellation locations. This research marks a significant step towards more effective and adaptable noise cancellation in enclosed spaces.

Active Object Detection and Tracking Using Gimbal Mechanisms for Autonomous Drone Applications

Object recognition, localization, and tracking play a role of primordial importance in computer vision applications. However, it is still an extremely difficult task, particularly in scenarios where objects are attended to using fast-moving UAVs that need to robustly operate in real time. Typically the performance of these vision-based systems is affected by motion blur and geometric distortions, to name but two issues. Gimbal systems are thus essential to compensate for motion blur and ensure visual streams are stable. In this work, we investigate the advantages of active tracking approaches using a three-degrees-of-freedom (DoF) gimbal system mounted on UAVs. A method that utilizes joint movement and visual information for actively tracking spherical and planar objects in real time is proposed. Tracking methodologies are tested and evaluated in two different realistic Gazebo simulation environments: the first on 3D positional tracking (sphere) and the second on tracking of 6D poses (planar fiducial markers). We show that active object tracking is advantageous for UAV applications, first, by reducing motion blur, caused by fast camera motion and vibrations, and, second, by fixating the object of interest within the center of the field of view and thus reducing re-projection errors due to peripheral distortion. The results demonstrate significant object pose estimation accuracy improvements of active approaches when compared with traditional passive ones. More specifically, a set of experiments suggests that active gimbal tracking can increase the spatial estimation accuracy of known-size moving objects, under conditions of challenging motion patterns and in the presence of image distortion.

Design, modeling, manufacturing, and control of dual axis stabilized system

Recently, Inertial Stabilized Systems (ISS) are widely spread either in military or civilian applications. It’s used to stabilize and point the onboard sensors. Therefore, the accurate modeling and control is a crucial factor to design a suitable control system. In this work, two axes gimbal system is designed, modeled, manufactured, and controlled. Firstly, the stabilized system is built using solid work software. Secondly, the system mathematical model is derived for the physical system with its actuators and encoders. Thirdly, the designed model is manufactured and integrated with the suitable motors; the overall open loop system model is implemented in MATLAB (Simulink). Finally, a modified PI-D structure is designed to stabilize the ISS in an efficient manner, the simulation results show the superiority of the designed controller’s performance and robustness compared to the classical PID in transient and steady state responses.

Collision Tolerant Gimbal Drone for Sewage Treatment and Industrial Pipelines

This report presents the design and development of a lightweight mechanical gimbal ring system enclosed within a protective cage for unmanned aerial vehicles (UAVs), commonly known as drones. The objective of this project was to create a drone that can be safely operated by unskilled individuals without causing damage to the drone itself. The mechanical gimbal ring system ensures stability during flight while maintaining independent movement between the drone and the protective cage. By implementing this innovative design, the drone can be effectively used for industrial inspection in environments such as large pipelines and Indian sewage tunnels, reducing the risk to human safety by minimizing the need for human presence in hazardous locations. The components were carefully selected and calibrated, and the gimbal rings and cage were fabricated using Fused Deposition Modeling (FDM) technology.

Stability and dynamical analysis of whirl flutter in a gimballed rotor-nacelle system with a smooth nonlinearity – CORRIGENDUM

Stability and dynamical analysis of whirl flutter in a gimballed rotor-nacelle system with a smooth nonlinearity – CORRIGENDUM

Composite Control for Gimbal Systems With Multiple Disturbances: Analysis, Design, and Experiment

The proportional-integral (PI) controller has proven to be a remarkably effective control strategy in the servo field. However, it is difficult for PI to handle the problem of multiple disturbances degrading the velocity-tracking capability of the gimbal system in the control moment gyro (CMG). In this article, we propose a solution to this problem while preserving the advantages of PI from an engineering standpoint. Starting from the refined disturbance analysis based on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5$</tex-math> </inline-formula> Nms CMG gimbal system experimental tests, multiple disturbances of the gimbal system can be classified according to frequency distribution in terms of 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 5 and 128 Hz. Subsequently, under the composite hierarchical anti-disturbance control frame, a peak filter and a disturbance observer addition improve the anti-disturbance capability of the PI-based gimbal system at the frequencies of 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 5 and 128 Hz. Notably, the proposed method has a relatively low order, which is appropriate for the processing power limit. Finally, the experimental results reveal that compared to three effective control schemes (PI, extended state observer-based composite controller, and PI-resonant controller), the proposed method can strikingly enhance the anti-disturbance ability and velocity-tracking performance of the gimbal system.

Autonomous multicopter landing on a moving vehicle based on RSSI

AbstractCurrently, most of the studies on unmanned aerial vehicle (UAV) automatic landing systems mainly depend on image information to determine the landing location. However, the system requires a camera, a gimbal system and a separate image-processing device, which increases the weight and power consumption of the UAV, resulting in a shorter flight time. In addition, a large amount of computation and slow reaction speed can cause the camera to miss a proper landing moment. To solve these problems, in this study, the moving direction and relative distance between an object and the automatic landing system were measured using a receive signal strength indicator of the radio-frequency (RF) signal. To improve the movement direction and relative distance estimation accuracy, the noise in the RF signal was minimised using a low pass filter and moving average filter. Based on the filtered RF signal, the acceleration of the multicopter to reach the object was estimated by adopting the proportional navigation algorithm. The performance of the proposed algorithm for precise landing on a moving vehicle was demonstrated through experiments.

Antenna Directional Pattern Testing System Based on Multirotor Unmanned Aerial Vehicles

Obtaining azimuth data of antennas after installation on actual platforms (such as large aircraft, ships, etc.) is crucial for effectively analyzing the platform's impact on the antennas and facilitating optimization and improvement. Traditional testing methods are unable to accurately and efficiently acquire azimuth data due to significant differences between measurements in a dark room and the actual conditions. With the rapid development of drone technology, unmanned aerial platforms have been widely utilized in various engineering fields. Utilizing the flexibility of drones in three-dimensional space and their ability to be precisely controlled through RTK technology, it is possible to use drones equipped with test antennas to measure the azimuth pattern by receiving spectrum signals transmitted by antennas on real platforms. In order to achieve precise angle control, a gimbal system is designed to control the angle of the test antenna. The effectiveness of the entire testing system is verified through experimental results.

Stabilization of Two Axis Gimbal System with Self Tuning PID Control

Gimbal is a system that provides locking and tracking of the seeker on the target in missiles and increases the angle of view with its mobility in two axes. In this study, stabilization of a two-axis gimbal system used in the missile was carried out. In gimbal stabilization, adaptive controllers are preferred instead of classical controllers due to unbalance, cross-coupling, and unmeasurable disturbances. A Self Tuning PID controller based on Fuzzy Logic was developed for axis controls in the stabilization algorithm. Thanks to this controller, which works with the principle of choosing the most appropriate coefficient at every step, it was possible to control with less than 3% errors in the tests performed with the flight simulator. In addition, a PID controller whose coefficients are optimized with Particle Swarm Optimization is designed for comparison purposes. In experimental studies, it was seen that PID with adjustable coefficients gave better results than the fixed PID.

Finite-Time Refined Antidisturbance Velocity Tracking Control for Gimbal System of Control Moment Gyros With Harmonic Drive

This paper is concerned with high-precision and fast velocity-tracking control for the harmonic drive-based gimbal system of control moment gyro (CMG). As a major challenge in the controller design, the simultaneous presence of multiple matched and mismatched disturbances should be carefully addressed. Specifically, the rotor imbalance inherent in the CMG will cause vibration of the output torque that significantly degrades the tracking performance. On the other hand, the integration of harmonic drives will lead to nonlinear torsional stiffness and introduce additional frictions into the control system. Furthermore, practical tasks such as fast attitude maneuver have posed higher requirement on the rapidity of the anti-disturbance control schemes. To overcome the aforementioned difficulties, we propose a finite-time refined anti-disturbance velocity tracking controller, which consists of a finite-time harmonic disturbance observer (FTHDO) to compensate for the imbalance vibration, an adaptive finite-time extended state observer (AFTESO) to handle the remaining disturbances with unknown rate of change, and a finite-time controller to ensure fast convergence of the tracking error. Both numerical simulation and hardware-in-the-loop (HIL) experimental results show that the proposed scheme outperforms the existing methods in terms of accuracy and rapidity.

Composite Control Based on Feed-Forward and FISMC Method for Accurate Speed of Gimbal System With Harmonic Drive

In the gimbal system of single gimbal magnetically suspended control moment gyroscope (SGMSCMG), harmonic drive is usually installed to ensure the large output torque and reduce the volume and weight of the servo motor. Nevertheless, its nonlinear characteristics make the transmission torque fluctuate and decrease the performance of the gimbal system. The disturbance torque fluctuations can be divided into ‘gear wave torque’ and ‘non-gear wave torque,’ and to suppress the different types of fluctuations, a composite control method based on model-based feed-forward and fuzzy integral sliding mode control (FISMC) method is proposed. The former method is adopted to restrain the gear wave torque. Then, for the rest of the disturbance torques, the FISMC with new dynamic sliding mode surface is put forward to enhance the robustness and improve the performance of the speed. Finally, the simulation and experiments are carried out on SGMSCMG to validate the effectiveness of the composite method. The results show that the torque fluctuation can be effectively suppressed and the performance of the gimbal system can be significantly improved.

A refined anti‐disturbance control method for gimbal servo systems subject to multiple disturbances under constraints

AbstractThe performance of the gimbal servo system in control moment gyro (CMG), which includes precision, lifespan etc., is one of the crucial factors of spacecraft attitude control. The various practical disturbances, however, will not only deteriorate the velocity‐tracking accuracy but will also cause the abnormal gimbal velocity problem (especially peak phenomenon). To this end, this paper proposes a refined anti‐disturbance control method to deal with velocity output constraints and multiple disturbances. Starting with fully understanding the prior information of multiple disturbances, a refined disturbance observer with a low conservativeness is designed to accurately estimate disturbances. The disturbance‐estimation error is analyzed in detail to ensure convergence to a bounded region. Subsequently, a novel barrier Lyapunov function‐based backstepping controller is proposed that considers the residuals of disturbance estimation to simultaneously achieve multiple disturbances attenuation and compensation, and handle velocity output constraints. Notably, the gimbal's maximum velocity is precisely limited to a pre‐specified low range, which benefits the CMG's lifespan and performance. Finally, both simulation and experimental results show that the proposed method performs better in disturbance estimation, velocity tracking, and robustness.

Torque Ripple Minimization of Low-Speed Gimbal Servo System Using Parameter-Optimized ESO

Torque ripple of permanent magnet synchronous motor (PMSM) and load disturbances are the main influencing factors which restrict the application of PMSM in low speed tracking system. In order to improve the speed tracking precision of gimbal servo system in control moment gyro (CMG) with multi-source disturbances, this paper proposes a composite control method based on parameter-optimized extended state observers (ESOs) with sliding mode control in the speed loop and PI control with a feed-forward compensation in the current loop. Three ESOs are employed to estimate the disturbances on d-axis current, q-axis current and the load torque, so that the controller can have the corresponding parts to compensate for the disturbances. In particular, aiming at the contradiction between the estimation quality of the observer and the sensitivity to the measurement noise, an appropriate cost function is designed to take a compromise between the lumped disturbances and measurement noise and optimize the parameters of the ESOs. Finally, simulation and experimental results on the gimbal servo system of magnetically suspended control moment gyroscope (MSCMG) show the effectiveness of the proposed methods.

Gimbal Axes Control with PID Controllers

Gimbal is a system in missiles that allows the seeker to lock onto the target and follow it and increases the angle of view with its mobility in two axes. In this study, the control of the axes of a two-axis gimbal system used in the missile was carried out. PID controller tuned with Particle Swarm Optimization (PSO) is used in the control algorithm. In the optimization, a smoother controller is aimed by using the multi-objective objective function, which also includes the controller output with the position error. At the same time, the bandwidth of the system is also included as a constraint. The Butterworth Polynomial Method (BPM), which can adjust the coefficient according to the bandwidth criterion, was used for comparison purposes. As a result of the experimental studies show that the PID tuned with PSO can control the system with a lower positional error by responding faster to external factors than the PID designed with BPM.

Stability and dynamical analysis of whirl flutter in a gimballed rotor-nacelle system with a smooth nonlinearity

AbstractWhirl flutter is an aeroelastic instability that affects aircraft with propellers/rotors. With their long and flexible rotor blades, tiltrotor aircraft are particularly susceptible. Whirl flutter is known to have destroyed aircraft and in the best case it constitutes a fatigue hazard. The complexity of whirl flutter analysis increases significantly with the addition of nonlinearities, due to the more complex dynamical behaviours that emerge as a result. Most whirl flutter stability analyses in current literature are grounded in linear theory, preventing the full discovery of the nonlinearities’ effects. Continuation and bifurcation methods (CBM) may instead be used to fully appreciate and analyse the effects of the presence of nonlinearities. Previous CBM-based work on nonlinear gimballed hub rotor-nacelle models, representing those found on tiltrotor aircraft, are capable of whirl flutter in parametric regions declared safe by linear analysis. Furthermore, it was found that they are capable of complex behaviours including limit cycle oscillations, quasi-periodic behaviour and even chaos, though the whirl flutter implications of such behaviours has not been explored. This paper investigates the impact of a smooth structural nonlinearity on the whirl flutter stability of a basic gimballed rotor-nacelle model, compared to its baseline linear stiffness version. A 9-DoF model with quasi-steady aerodynamics, a flexible wing and blades that can move both cyclically and collectively in both flapping and lead-lag motions, producing gimbal flap-like behaviour, was adopted from existing literature. A smooth stiffness nonlinearity was introduced in the blade flapping stiffness and CBM was used to find the new whirl flutter behaviours created by the presence of the nonlinearity. Time simulations, Poincaré sections and spectral analysis were then used to investigate the various behaviours found. This in turn allowed recommendations to be made concerning preferable and/or hazardous parameter combinations of use to the tiltrotor designer.

Toward the Light-weighted, Attachable, and Automated Control-enabled Gimbal Design for a Personal Weapon

A gimbal system is a mechanical apparatus that offers multiple degrees of freedom motions. Conventional gimbal motions are roll, pitch, and yaw (3 axes) or pan tilt motions (2 axes) in angles. In applications, these gimbal systems, in conjunction with cameras and other sensors, are used in footage recording for airplanes, helicopters, and UAVs (unmanned air vehicles) or as a handheld device for pictures. These applications are aligned with image tracking, surveillance, or even target tracking and engagement in more industry or military aspects.

Position Self-Correction of Resolver Based on a Composite Method in Gimbal System

This article explores a composite self-correction method for the angular position of the resolver in the gimbal system of the control moment gyroscope (CMG). The nonideal signals of the resolver in the gimbal resolver-to-digital conversion (RDC) system result in a systematic error, which can decrease the performance of the output torque of the CMG. However, it is impractical to adopt additional high-precision sensors to correct the angular position of the resolver in the installed gimbal system on account of the limitation of the structure and space. Therefore, a novel self-correction composite method based on a discrete extended state observer (DESO) and a harmonic observer method (HOM) is put forward to calibrate the angular position of the resolver. First, the sine and cosine signals with harmonics can be directly obtained. Then, the composite proposed method is performed to get the accurate angular position of the resolver, and the position error can also be acquired. Based on the position error, the compensation table can be established, and finally, the high-precision position can be acquired. The proposed self-correction method is verified by simulation and experiments, and the results show that the angular position accuracy is significantly improved.