Optoelectronic Tracking System Research Articles

Dynamics modeling and simulation for satellites with optoelectronic tracking system

Abstract The optoelectronic tracking system has a strong coupling between the tracking platform and the satellite platform when rapidly capturing and precisely tracking targets. The high-precision coordinated pointing control between the two platforms is a key technology in the fields of space laser communication, debris monitoring, and astronomical observation. Firstly, a multi-level coupled dynamics model of spacecraft with two-dimensional (2D) motion platforms is derived based on the principles of momentum and angular momentum. Secondly, the coupling effects between the motion platform and the satellite platform are theoretically analyzed, highlighting the impact of platform orientation, configuration, mass properties, and motion characteristics on the coupling. Finally, a multi-level platform cooperative control strategy is proposed, and the model and control strategy are validated through mathematical simulations. The results show that the model is consistent with simulation results from ADAMS software, and the satellite attitude accuracy under the cooperative control strategy can be improved by 80%.

A Smith Predictor Modified with a Pseudo Feedforward Control for the Charge-Coupled Device-Based Optoelectronic Tracking System.

In the high-precision optoelectronic tracking system (OTS) based on a charge-coupled device (CCD), the boresight error extracted from the tracking image contains an undeniable delay, which directly limits the control bandwidth of visual tracking. High bandwidth means high response speed and tracking accuracy. Generally, a model-based delay compensation control method called the Smith predictor is utilized to separate time delay from the closed loop to promote the control bandwidth. However, due to the existence of errors between the established model and the real object, the improvement in the bandwidth is still limited to ensure system stability, resulting in insufficient tracking performance. In this paper, to solve the problem, a Smith predictor modified with pseudo feedforward control for the OTS is proposed. The experimental results demonstrate that the proposed method achieves significant improvements in tracking performance, reducing the maximum residual error at 1 Hz from 365 arcseconds (using the classic Smith predictor) to 283 arcseconds, a 22.5% improvement. Across the main frequency band (0.2 Hz to 2 Hz), the residual errors were consistently lower using the proposed method.

Muscle and joint mechanics during maximum force biting following total temporomandibular joint replacement surgery

Total temporomandibular joint replacement (TMJR) surgery is the established treatment for severe temporomandibular joint disorders. While TMJR surgery is known to increase mouth-opening capacity, reduce pain and improve quality of life, little is known about post-surgical jaw function during activities of daily living such as biting and chewing. The aim of this study was to use subject-specific 3D bite force measurements to evaluate the magnitude and direction of joint loading in unilateral total TMJR patients and compare these data to those in healthy control subjects. An optoelectronic tracking system was used to measure jaw kinematics while biting a rubber sample for 5 unilateral total TMJR patients and 8 controls. Finite element simulations driven by the measured kinematics were employed to calculate the resultant bite force generated when compressing the rubber between teeth during biting tasks. Subject-specific musculoskeletal models were subsequently used to calculate muscle and TMJ loading. Unilateral total TMJR patients generated a bite force of 249.6 ± 24.4 N and 164.2 ± 62.3 N when biting on the contralateral and ipsilateral molars, respectively. In contrast, controls generated a bite force of 317.1 ± 206.6 N. Unilateral total TMJR patients biting on the contralateral molars had a significantly higher lateral TMJ force direction (median difference: 63.6°, p = 0.028) and a significantly lower ratio of working TMJ force to bite force (median difference: 0.17, p = 0.049) than controls. Results of this study may guide TMJ prosthesis design and evaluation of dental implants.

THREE-DIMENSIONAL KINEMATICS OF THE JAW FOLLOWING UNILATERAL AND BILATERAL PROSTHETIC TMJ SURGERY

Total temporomandibular joint (TMJ) replacements reduce pain and improve quality of life in patients suffering from end-stage TMJ disorders, such as osteoarthritis and trauma. Jaw kinematics measurements following TMJ arthroplasty provide a basis for evaluating implant performance and jaw function. The aim of this study is to provide the first measurements of three-dimensional kinematics of the jaw in patients following unilateral and bilateral prosthetic TMJ surgeries.Jaw motion tracking experiments were performed on 7 healthy control participants, 3 unilateral and 1 bilateral TMJ replacement patients. Custom-made mouthpieces were manufactured for each participant's mandibular and maxillary teeth, with each supporting three retroreflective markers anterior to the participant's lip line. Participants performed 15 trials each of maximum jaw opening, lateral and protrusive movements. Marker trajectories were simultaneously measured using an optoelectronic tracking system. Laser scans taken of each dental plate, together with CT scans of each patient, were used to register the plate position to each participant's jaw geometry, allowing 3D condylar motion to be quantified from the marker trajectories.The maximum mouth opening capacity of joint replacement patients was comparable to healthy controls with average incisal inferior translations of 37.5mm, 38.4mm and 33.6mm for the controls, unilateral and bilateral joint replacement patients respectively. During mouth opening the maximum anterior translation of prosthetic condyles was 2.4mm, compared to 10.6mm for controls. Prosthetic condyles had limited anterior motion compared to natural condyles, in unilateral patients this resulted in asymmetric opening and protrusive movements and the capacity to laterally move their jaw towards their pathological side only. For the bilateral patient, protrusive and lateral jaw movement capacity was minimal.Total TMJ replacement surgery facilitates normal mouth opening capacity and lateral and inferior condylar movements but limits anterior condylar motion. This study provides future direction for TMJ implant design.

Line of Sight Tracking Method Based on Feedback Linearization and Command Planning

When the target just enters the field of view of the optoelectronic tracking system, there is a big pointing deviation. If the closed-loop control is directly performed at this time, overshoot or even oscillation will occur, which will easily cause the target to leave the field of view again. At present, most control algorithms are concerned about enhancing the steady-state tracking precision of the system, but seldom consider the transient performance of the system. In this paper, a new definition of pointing deviation is given, in addition, the model of the line-of-sight (LOS) tracking system is realized. On this basis, a method based on feedback linearization is raised, which can compensate measurable disturbance. For both transient response and steady-state performance, a new LOS planning method is presented, which accomplishes the planning and design of the target motion trajectory on the imaging plane. It can be able to avoid the target departing from the field of view and speed up the system response based on fixed control parameters. Through the analysis of experimental results, it can be indicated that the LOS tracking method proposed in this paper can availably promote the transient performance of the system and is existent of real value.

Wavelet denoising approach in long-distance optical communications.

For free-space optical communication links, the light spot collected by the photodetector at the receiving terminal is not an ideal light spot that is affected by atmospheric turbulence. The light spot collected by the photodetector will also be accompanied by various noises. More importantly, the presence of all noise will bring errors to acquire the light spot's center. As a result, the tracking error can affect the stability of the optoelectronic tracking system. Therefore, it is necessary to remove noise from the collected images. The method of removing noise needs to be effective, but it cannot bring a large amount of calculation to affect the real-time performance. The calculation amount of wavelet transform is small, and the effect of noise removal is better, which can focus on local details with arbitrary expansion coefficients. An improved wavelet denoising method is proposed. The long-distance verification experiment (11.16 km) verified the effectiveness of this approach, compared with the traditional method. Furthermore, to the best of our knowledge, this new approach would be beneficial for the design of optical communication systems.

On the feasibility of the monostatic scheme for constructing the land-based telescope at supervision of space objects

In modern large aperture optical systems for tracking astronomical objects, the technology of bistatic schemes is widely introduced, in which the laser, the main and auxiliary telescopes are spatially separated. This requires additional measures to be taken when aligning the optical axes of telescopes, especially when tracking LEO space objects. The choice of bistatic schemes in astronomical telescopes is due to the problem of “tilt uncertainty” inherent in monostatic schemes for the formation of a laser reference star. This problem is caused by the difficulty or even the impossibility of determining the tilt of the wavefront when the laser guide star jitters in the image plane. The article discusses a monostatic scheme for constructing ground-based adaptive optoelectronic systems. The monostatic scheme combines the optical axis of the laser, which forms the laser guiding star, and the optical axis of the telescope, which serves to obtain images of space objects by eliminating phase disturbances of the atmosphere due to the radiation of the laser guiding star. The proposed method for determining the tilt of the wavefront in a monostatic scheme is based on the analysis of expressions for the dispersion of the tilt jitter of the images of a laser reference star and a space object for the case when the diameter of the receiving aperture of the telescope is much larger than the diameter of the aperture of the laser forming the laser reference star. This approach is based on the long-elicited strong correlation between the instantaneous values of the tilt of the laser beam and the received beam from a natural star, transmitted towards each other. When observing low-orbit small-sized space objects and laser reference stars, it is assumed that they are in the Fresnel zone of the receiving aperture of the optoelectronic system and within the isoplanatism angle of the atmosphere, determined within the framework of an isotropic and locally homogeneous model of atmospheric turbulence. The proposed solution made it possible to determine the value of the instantaneous tilt angle for the image of an inconspicuous space object in the focal plane of the receiving aperture of the telescope on the basis of measuring the instantaneous tilt angle for the actually observed image of the laser reference star. The results can be used in the development of ground-based adaptive optoelectronic tracking systems for low-orbit small-sized space objects.

Optoelectronic tracking system for shooting simulator - tests in a virtual reality application

We present test results of an authorial tracking device developed in the SteamVR system, optimized for use in a missile launcher shooting simulator. Data for analysis was collected using the virtual reality training application, with the launcher set on a stable tripod and held by a trainee who executed two scenarios with static and movable targets. The analysis of experimental data confirms that the SteamVR system together with the developed tracker can be successfully implemented in the virtual shooting simulator. Full Text: PDF ReferencesD. Bogatinov, P. Lameski, V. Trajkovik, K.M. Trendova, "Firearms training simulator based on low cost motion tracking sensor", Multimed. Tools Appl. 76(1) (2017) CrossRef D.C. Niehorster, L. Li, M. Lappe, "The Accuracy and Precision of Position and Orientation Tracking in the HTC Vive Virtual Reality System for Scientific Research", Iperception. 8(3) (2017) CrossRef A. Yates, J. Selan, POSITIONAL TRACKING SYSTEMS AND METHODS. US20160131761A1, (2016) DirectLink P. Caserman, A. Garcia-Agundez, R. Konrad, S. Göbel, R. Steinmetz, Virtual Real. 23(2) (2019) 155-68. CrossRef

Parameter Tuning of PID-I Controller for Optoelectronic Tracking System Based on NSGA-II Multi-Objective Optimization

In order to solve the delay in the optoelectronic tracking system, some scholars have proposed the PID-I controllerbased on the traditional PID controller. PID-I controller is formed by connecting an integrator in series to improve the system performance of the CCD position closed loop. But how to choose controller parameters is a key factor in determining system performance. The open-loop gain and bandwidth of the system are two important indicators for selecting the controller parameters, but these two indicators are coupled and cannot achieve the optimal performance at the same time. Meanwhilethe multidimensionality of the controller parameters also makes it difficult to set the parameters. In view of the above problems, traditional numerical methods and artificial experience methods cannot obtain good controller parameters. Therefore, this paper uses the NSGA-II multi-objective optimization algorithm to optimize the open-loop gain and bandwidth of the system at the same time by a non-inferior ranking method to achieve the purpose of optimizing the controller parameters. The theory and simulation show that the performance of the optoelectronic tracking system using this multi-objective optimized PID-I controller is better than that of the PID-I controller optimized by numerical methods in closed-loop bandwidth and step response indicators.

Adaptive sliding mode control based on friction compensation for opto-electronic tracking system using neural network approximations

In this paper, an adaptive sliding mode control algorithm based on friction compensation utilizing neural network (NN) is designed for an opto-electronic tracking system under the circumstance of friction and external disturbance. Since neural networks can approximate any nonlinear function, the developed NN controller can approximate the nonlinear friction which is integrated into the adaptive sliding mode control system in the Lyapunov framework. The adaptive sliding mode controller with friction compensation can effectively reduce the effects of nonlinear friction and external disturbance of the opto-electronic tracking system utilizing neural network approximations. The stability of the proposed method is guaranteed according to Lyapunov criterion. Simulation and experimental validation results for a nonlinear LuGre dynamic model of the opto-electronic tracking system are provided to validate the effectiveness of the proposed control method.

Feedforward Control Based on Error and Disturbance Observation for the CCD and Fiber-Optic Gyroscope-Based Mobile Optoelectronic Tracking System

In the mobile optoelectronic tracking system (MOTS) based on charge-coupled device (CCD) and fiber-optic gyroscope (FOG), the tracking performance (TP) and anti-disturbance ability (ADA) characterized by boresight error are of equal importance. Generally, the position tracking loop, limited by the image integration time of CCD, would be subject to a non-negligible delay and low-sampling rate, which could not minimize the boresight error. Although the FOG-based velocity loop could enhance the ADA of the system, it is still insufficient in the case of some uncertain disturbances. In this paper, a feedforward control method based on the results of error and disturbance observation was proposed. The error observer (EOB) based on the CCD data and model output essentially combined the low-frequency tracking feedforward and closed-loop disturbance observer (DOB), which could simultaneously enhance the low-frequency TP and ADA. In addition, in view of the poor low-frequency performance of the FOG due to drift and noise that may result in the inaccuracy of the observed low-frequency disturbance, the FOG-based DOB was used to improve the relatively high-frequency ADA. The proposed method could make EOB and DOB complementary and help to obtain a high-precision MOTS, for in practical engineering, we give more attention to the low-frequency TP and full-band ADA. Simulations and experiments demonstrated that the proposed method was valid and had a much better performance than the traditional velocity and position double-loop control (VPDC).

Kinematic differences between children with obstetric brachial plexus palsy and healthy controls while performing activities of daily living

BackgroundResidual shoulder dysfunction and deformity impacts on functional performance in children with obstetric brachial plexus palsy. Clinical understanding of upper limb dynamic movement patterns is difficult with observation alone. This case-control study describes the significant kinematic differences between children with obstetric brachial plexus palsy compared to typically developing children while performing tasks of the modified Mallet Scale. MethodsEleven children with obstetric brachial plexus palsy (mean 10 years, range 7–15 years, Narakas group I-III) and 10 typically developing children (mean 9 years 9 months, range 6–15 years) completed three-dimensional upper limb motion analysis using the acromion method to track dynamic scapular movement. Kinematic data were captured by a 4-CODA cx1 optoelectronic tracking system. Participants performed three trials of the modified Mallet scale tasks. Local coordinate systems, segment and joint rotations were defined as recommended by the International Society of Biomechanics. FindingsJoint rotation angles against time of the glenohumeral, thoracohumeral and scapulohumeral joints were calculated. Kinematic findings demonstrated increased internal rotation in all postures, reduced glenohumeral excursion, habitual “trumpet” posture of glenohumeral abduction/elevation and variability in movement strategies. Scapulohumeral rhythm during abduction task was 1.88:1 in typically developing children and 1.04:1 in children with obstetric brachial plexus palsy. InterpretationChildren with obstetric brachial plexus palsy demonstrate deficient external rotation in all tasks. Despite increased postural internal rotation, ability to move through internal rotation range is compromised. The glenohumeral joint showed the greatest range deficit, contributing to abnormal scapulohumeral rhythm. Future sub-group analysis of Narakas Classification is recommended.

Robust adaptive integral backstepping control for opto-electronic tracking system based on modified LuGre friction model

This paper presents a robust adaptive integral backstepping control strategy with friction compensation for realizing accurate and stable control of opto-electronic tracking system in the presence of nonlinear friction and external disturbance. With the help of integral control term to decrease the steady-state error of the system and combining robust adaptive control approach with the backstepping design method, a novel control method is constructed. Nonlinear modified LuGre observer is designed to estimate friction behavior. Robust adaptive integral backstepping control strategy is developed to compensate the changes in friction behavior and external disturbance of the servo system. The stability of the opto-electronic tracking system is proved by Lyapunov criterion. The performance of robust adaptive integral backstepping controller is verified by the opto-electronic tracking system with modified LuGre model in simulation and practical experiments. Compared to the adaptive integral backstepping sliding mode control method, the root mean square of angle error is reduced by 26.6% when the proposed control method is used. The experiment results demonstrate the effectiveness and robustness of the proposed strategy.

Improved kernelized correlation filter algorithm and application in the optoelectronic tracking system

In order to improve the tracking accuracy and real-time performance of the optoelectronic tracking system, an improved kernelized correlation filter approach is developed to obtain precise tracking of a maneuvering object. The proposed strategy contains merits of adaptive threshold approach, kernelized correlation filter method, and Kalman filter algorithm. The adaptive threshold approach can choose the suitable threshold in accordance with the size of the target in the image to improve the tracking performance of the kernelized correlation filter method. When the change between previous position and current position is larger than the distance threshold, Kalman filter algorithm is used to predict the target position for tracking. The tracking accuracy of the proposed algorithm is improved by updating the prediction of the target position with a trusted algorithm. The experimental results on comparison with some state-of-the-art trackers, such as kernelized correlation filter; Tracking-Learning-Detection; scale adaptive with multiple features; minimum output sum of squared error; and dual correlation filter, demonstrate that the proposed approach has the effectiveness of tracking accuracy and real-time performance in tracking the maneuvering object.

Adaptive integral backstepping sliding mode control for opto-electronic tracking system based on modified LuGre friction model

ABSTRACTIn order to improve the control accuracy and stability of opto-electronic tracking system fixed on reef or airport under friction and external disturbance conditions, adaptive integral backstepping sliding mode control approach with friction compensation is developed to achieve accurate and stable tracking for fast moving target. The nonlinear observer and slide mode controller based on modified LuGre model with friction compensation can effectively reduce the influence of nonlinear friction and disturbance of this servo system. The stability of the closed-loop system is guaranteed by Lyapunov theory. The steady-state error of the system is eliminated by integral action. The adaptive integral backstepping sliding mode controller and its performance are validated by a nonlinear modified LuGre dynamic model of the opto-electronic tracking system in simulation and practical experiments. The experiment results demonstrate that the proposed controller can effectively realise the accuracy and stability control of opto-electronic tracking system.

Reliability of 3D upper limb motion analysis in children with obstetric brachial plexus palsy

Kinematics, measured by 3D upper limb motion analysis (3D-ULMA), can potentially increase understanding of movement patterns by quantifying individual joint contributions. Reliability in children with obstetric brachial plexus palsy (OBPP) has not been established.Objective: This study aimed to determine between session reliability and measurement errors of 3D-ULMA using the acromion method (AM) in children with OBPP.Approach: Ten participants (mean 10 years, range 7–15 years, Narakas classification I–III) completed 3D-ULMA on two occasions, mean interval of 8.6 d (±2.8 d). Kinematic data were captured by a 4-CODA cx1 optoelectronic tracking system. Participants performed three trials of the modified Mallet scale tasks. Local coordinate systems, segment and joint rotations were defined as recommended by the International Society of Biomechanics. The intraclass correlation coefficient (ICC 2,K) and standard error of measurement (SEM) were calculated for task duration, range and joint angle at point of task achievement (PTA).Main Results: Results indicated poor reliability for spatiotemporal parameters and range. Moderate to excellent reliability at PTA was observed in 19/60 variables (ICC: 0.77–0.98; SEM: 3.5°–10.4°). The Abduction Task had the highest (ICC: 0.79–0.98; SEM: 3.5°–10.3°) with External Rotation the lowest reliability. Glenohumeral and thoracohumeral elevation had the most consistent reliability. Scapular protraction/retraction had consistently poor reliability (ICC: 0–0.72; SEM: 3.5°–10.2°) with axial rotation also poor (ICC: 0.00–0.91; SEM: 6.3°–32.8°).This study determined inconsistent test–retest reliability of 3D-ULMA, using AM, to track dynamic performance of functional tasks in children with OBPP. It is the first study to outline measurement error in this population. This information permits more reliable interpretation of future studies of kinematic patterns in children with OBPP.

Integrated design method of control loop in optoelectronic tracking system

Integrated design method of control loop in optoelectronic tracking system

Mean-shift跟踪算法及其在光电跟踪系统中的应用

Mean-shift跟踪算法及其在光电跟踪系统中的应用

Study on Robust Control Technology of Opto-Electronic Tracking System

Classic control algorithm can improve dynamic performance of opto-electronic tracking system, but the tracking system often has little robust performance. From the standpoint of inproving robust performance, modern robust control technology was adopted to design the controller of opto-electronic tracking system in this paper. On the basis of considering the system tracking precision requirement and main disturbance, the mathematical model of the system augmented objict was established. By repeatly testing, the suitable weighted functions were selected. Finally, the robust controller of opto-electronic tracking system was designed by synthesis method of modern robust control theory. The simulation result shows that the adjusting time of the system is 0.3S, and it can satisfy the requirements of the tracking speed. Robust controller has improved the system dynamic response characteristics and makes the system fast and no overshoot, and the opto-electronic tracking system has stronger robust stability and robust performance.

A Chattering Free Discrete-Time Global Sliding Mode Controller for Optoelectronic Tracking System

Aiming at the uncertainties including parameter variations and external disturbances in optoelectronic tracking system, a discrete-time global sliding mode controller (DGSMC) is proposed. By the design of nonlinear switching function, the initial state of control system is set on the switching surface. An adaptive discrete-time reaching law is introduced to suppress the high-frequency chattering at control input, and a linear extrapolation method is employed to estimate the unknown uncertainties and commands. The global reachability for sliding mode and the chattering-free property are proven by means of mathematical derivation. Numerical simulation presents that the proposed DGSMC scheme not only ensures strong robustness against system uncertainties and small tracking error, but also suppresses the high-frequency chattering at control input effectively, compared with the SMC scheme using conventional discrete-time reaching law.