Angle Tracking Error Research Articles

Novel high-safety aeroengine performance predictive control method based on adaptive tracking weight

Increasing attention has been attracted to the dynamic performance and safety of advanced performance predictive control systems of the next-generation aeroengine. The latest research demonstrates that Subspace-based Improved Model Predictive Control (SIMPC) can overcome the difficulty in solving the predictive model in MPC/NMPC applications. However, applying constant design parameters cannot maintain consistent control effects in all states. Meanwhile, the designed system relies too much on sensor-measured data, and thus it is difficult to thoroughly validate the safety of the system because of its high complexity. This means that any potential hardware/software faults will endanger the engine. Therefore, this paper first presents a novel nonlinear mapping relationship to adaptively tune the tracking weight online with the change of Power Lever Angle (PLA) and real-time relative tracking error. Thus, without introducing additional design parameters, an Adaptive Tracking Weight-based SIMPC (ATW-SIMPC) controller is designed to improve the control performance in all operating states effectively. Then, a Primary/Backup Hybrid Control (PBHC) strategy with the ATW-SIMPC controller as the primary system and the traditional speed (Nf) controller as the backup system is proposed to ensure safety. The designed affiliated switching controller and the real-time monitor therein can be used to realize reasonable and smooth switching between primary/backup systems, so as to avoid bump transition. The PBHC system switches to the Nf controller when the ATW-SIMPC controller is wrong because of potential hardware/software faults; otherwise, the ATW-SIMPC controller keeps acting on the engine. The main results prove that the ATW-SIMPC controller with the optimal nonlinear mapping relationship, compared with the existing SIMPC controller, uplifts the dynamic control performance by 32% and reduces overshoots to an allowable limit, resulting in a better control effect in full state. The comparison results consistently indicate that the PBHC can guarantee engine safety in occurrence of hardware/software faults, such as sensor/onboard adaptive model faults. The approach proposed is applicable to the design of a model-based engine intelligent control system.

Trajectory Re-Planning and Tracking Control for a Tractor–Trailer Mobile Robot Subject to Multiple Constraints

Autonomous tractor–trailer robots possess a broad spectrum of applications but pose significant challenges in control due to their nonlinear and underactuated dynamics. Unlike the tractor, the motion of the trailer cannot be directly actuated, which often results in a deviation from the intended path. In this study, we introduce a novel method for generating and following trajectories that circumvent obstacles, tailored for a tractor–trailer robotic system constrained by multiple factors. Firstly, leveraging the state information of both the obstacles and the desired trajectory, we formulate an improved trajectory for obstacle avoidance using the nonlinear least squares method. Subsequently, we propose an innovative tracking controller that integrates a universal barrier function with a state transformation strategy. This amalgamation facilitates the accurate tracking of the prescribed trajectory. Our theoretical analysis substantiates that the proposed control methodology ensures exponential convergence of the line-of-sight (LOS) distance and angle tracking errors, while enhancing the transient performance. To validate the efficacy of our approach, we present a series of simulation results, which demonstrate the applicability of the developed control strategy in managing the complex dynamics of tractor–trailer robots.

Research on anti-swing control strategies for three-dimensional overhead cranes with non-stationary enhanced swing angle suppression

In this paper, a non-stationary enhanced swing angle suppression control strategy is proposed to address the issue of excessive swinging angles during the transportation process of a three-dimensional overhead crane. Firstly, in response to the substantial non-stationary initial swing angle resulting from the abrupt increase in driving force during the startup of the overhead crane, we have devised a time-varying damping resistance model. This model is specifically designed to curtail the rapid force surge, subsequently diminishing the swing angle of the payload. Secondly, during the transport phase of the overhead crane, we have established an augmented coupling signal between the displacement tracking error and the payload swing angle tracking error. Drawing upon the principles of energy dissipation, we have devised a nonlinear sway controller. Next, the closed-loop stability of the control system is validated through the use of Lyapunov’s method and the LaSalle invariance principle. Finally, the proposed control strategy’s effectiveness has been substantiated through simulation analysis and physical experiments. This approach not only proves capable of effectively suppressing excessive payload swing angles during the transportation process of the overhead crane but also facilitates the rapid and precise positioning of the payload. This significantly enhances the efficiency of the overhead crane’s transport operations.

Composite adaptive control of submarine and parameter identification by integral regressor excitation

In this article, we develop a novel composite adaptive control system for the dive-plane maneuvers and parameter identification of a multi-input multi-output submarine model. The composite adaptive control system consists of (1) an input–output feedback linearizing control law and (2) an identifier formed by gradient algorithm-based two-parameter estimation laws. Unlike the existing adaptive systems for autonomous underwater vehicles and submarines, a novelty of this composite identifier lies in the use of regressor matrix integral feedback for enhancement in parameter excitation. By the Lyapunov analysis, asymptotic convergence of the depth and pitch angle tracking errors is established. Simulation results show precise depth and pitch angle control, estimation of all model parameters, and robustness to random and sinusoidal disturbance inputs.

Optimized Trajectory Tracking for Robot Manipulators with Uncertain Dynamics: A Composite Position Predictive Control Approach

This study addresses the trajectory tracking control challenges of robot manipulators with uncertain dynamics. The aim is to achieve precise and smooth trajectory regulation through a novel composite position predictive control (PPC) scheme that integrates motion profile and disturbance preview techniques. First, we perform offline dynamics identification and feedforward compensation alongside a pre-defined motion profile. To handle the disturbances arising from uncertain dynamics, a super-twisting disturbance observer is designed, resulting in a dynamically compensated prediction model. Furthermore, the receding optimization operations for PPC are executed by solving an optimal solution associated with a joint angle tracking error. The combination of feedforward and feedback control improves the robot manipulator’s absolute positioning accuracy as opposed to the conventional model predictive control method, especially when dealing with uncertain dynamics. The effectiveness of the proposed control method is confirmed through trajectory tracking experiments conducted on a six-degree-of-freedom robot platform with varying end-effector loads. The experimental results demonstrate that the proposed PPC method enhances tracking accuracy by approximately 45% and 25% when compared to the traditional inverse dynamic control (IDC) and the robust IDC approaches, respectively.

Finite-time terminal sliding mode attitude control for tailless full-wing configuration UAVs based on extended state observers and auxiliary compensators

Considering the sensitivity of the tailless full-wing configuration unmanned aerial vehicle to disturbance and the strong nonlinearity and coupling caused by the manipulation combining the propeller and rudder, a finite-time terminal sliding mode controller with compound compensation is proposed in this paper to ensure stable attitude control. Based on singular perturbation theory, the inner loop sliding mode controller is designed so that the supremum of the convergence time of the rotational angular velocity tracking error in the sliding phase can be directly determined by the control parameters without requiring the initial state, and the outer loop sliding mode controller is designed so that the sliding surface function of the attitude angle tracking error has a fast convergence speed when it is far from and close to the origin. The compound compensation design further addresses the manipulation nonlinearity and disturbance sensitivity of the research object. Based on the minimum Euclidean norm optimization, the designed control allocator achieves command decoupling and reduces the desired control command. Through comprehensive verification, the proposed controller shows superior control performance and low energy consumption and exhibits strong robustness in the cruising flight envelope.

The influence of three-aircraft formation blinking jamming on the performance of ground monopulse radar

The purpose of this study is to evaluate the jamming effectiveness evaluation against monopulse radar when using a non-coherent blinking jamming model at regular intervals based on three aircraft flight trajectories. To begin, the formation trajectory is solved under various aircraft attitudes to provide the radar cross section model for three-aircraft formation flying. Following that, the jamming angle tracking error model for three-aircraft formation flying is built and coupled with the features of monopulse radar angle tracking. The effective decoy angle and other criteria are used to measure the variance in jamming performance and the efficacy of formation flying radar jamming under varying jamming power and jamming gain. Finally, using the jamming effectiveness assessment criterion, the jamming effectiveness of formation flight is calculated. The findings demonstrate that the three-aircraft formation based on time transformation jamming model can successfully induce the monopulse radar angular tracking error, enhance it to 1.54 times, and stabilize the jamming effectiveness at 0.84, and it also has a relatively good jamming effect under straight flight trajectory and circular flight trajectory. Our jamming strategy will contribute to the design of electronic countermeasures, of which the findings of this research have practical significance for the application of new jamming styles.

A vision-based robotic system following the human upper-limb sewing action

Abstract. In human–robot collaborative sewing, the robot follows the sewing action of a worker to complete the corresponding sewing action, which can enhance production efficiency. When the robot follows the sewing action of the worker through interactive information, it still faces the problem of low accuracy. In order to improve the accuracy of the robot following the sewing action, a human upper-limb sewing-action-following system based on visual information is designed in this paper. The system is composed of an improved OpenPose model, Gaussian mixture model (GMM), and Gaussian mixture regression (GMR). In the system, an improved OpenPose model is used to identify the sewing action of the human upper limb, and the label fusion method is used to correct the joint point labels when the upper limb is covered by fabric. Then the GMM is used to encode each motion element and time to obtain the regression work of the Gaussian component. GMR is adopted to predict connections between moving elements and generate sewing motion trajectories. Finally, the experimental verification and simulation are carried out in the experimental platform and simulation environment of the collaborative robot. The experimental results show that the tracking error angle can be controlled within 0.04 rad in the first 2 s of robot movement. Therefore, it can be considered that the sewing-action-following system can realize higher precision and promote the development of human–robot collaboration technology to a certain extent.

Finite-time disturbance observers based reliable control for a constrained autonomous flexible manipulator system with mismatched and matched disturbances

This study focuses on a control approach for a constrained autonomous flexible manipulator system (AFMS) with multiple disturbances comprising both matched and mismatched disturbances. First, we propose two disturbance observers to compensate for multiple unknown disturbances in finite time using the finite-time stability theory. Meanwhile, we design the auxiliary systems and barrier Lyapunov functions to tackle input saturations and output constraints. Then based on the proposed disturbance observers, the auxiliary systems, and barrier Lyapunov functions, we propose two reliable control laws to achieve deflection suppression and hub angular displacement tracking. Additionally, the deflection and hub angle tracking error of the AFMS are constrained to a small compact set through controller design. Finally, the deflection suppress control performance of the constrained AFMS with mismatched and matched disturbances is evaluated.

Design of Preset Performance Reverse Step Attitude Controller for Four-rotor UAV

Aiming at the attitude control problem in flight control of four-rotor UAV, a control scheme based on the preset performance backstepping controller (ESO-NPPCBSC) for attitude Angle of four-rotor UAV with extended state observer is proposed. A preset performance function with specified time convergence is designed to constrain the transient performance and steady-state performance of the tracking error. Compared with the traditional scheme, the preset performance function can make the tracking error of the controlled system converge to the preset precision range within the specified time, and the convergence rate can be adjusted flexibly and the error conversion function can be used to transform the tracking error without constraints. The attitude Angle tracking error satisfies the preset performance condition by controlling the conversion error. The control law of attitude Angle of four-rotor UAV is designed based on reverse step method, which solves the problem of low control accuracy of four-rotor UAV under the condition of uncertain interference.

Design of Photovoltaic Power Generation Servo System Based on Discrete Adaptive Network Dynamic Surface Control Technology

In recent years, under the development of the dual carbon goal, the energy crisis has become increasingly serious, and China has also experienced serious power rationing. However, the research on dynamic surface control technology in solar tracking systems in nonlinear control systems is mostly based on continuous-time systems, while adaptive dynamic surface control based on discrete-time nonlinear control systems can describe an actual control system more accurately in the production process. It can effectively suppress interference with extremely high stability and safety. To solve the problem of low efficiency in photovoltaic power generation, this research first built a photovoltaic power generation servo system model based on the parameter of uncertainty. Then, a discrete adaptive neural network dynamic surface (DANNDS) controller was designed to solve the problems in the design of the traditional backstepping method. Finally, based on the designed method of a dynamic surface controller, a discrete adaptive neural network quantization controller (DANNQC) for the photovoltaic power generation servo system was designed by introducing external disturbance. The control parameters and their studied ranges were as follows: The reference signals were or1=sin(0.1t) and or2=cos(0.1t). The parameters of the virtual control law and the final control law were m11=0.01, m22=0.01, m12=0.02, m13=0.02, and m23=0.02. The time constant of the low-pass filter was ζ12=ζ13=ζ22=ζ23=0.005. The parameters of the parameter regulation law were ρ12=ρ13=ρ22=ρ23=0.0005 and a12=a13=20, a22=a23=22. The research results show that the MTE, RMSTE, and 2NTE scores of the height angle servo motor of the DANNDS control method were 0.0026, 7.0279 × 10−4, and 0.3552, respectively. The scores for each index of the azimuth servo motor were 0.0028, 8.9237 × 10−4, and 0.4511, respectively. The height angle tracking error for the DANNQC control method was [−0.02,0.022]. The azimuth tracking error was [−0.03,0.03]. In summary, the photovoltaic power generation servo system based on the DANNQC has a better control performance. By controlling the height angle and azimuth angles, it can better track the position of the sun and adjust the position of the photovoltaic panel in real time. The sun’s rays illuminate the photovoltaic panel at an appropriate angle to achieve maximum power generation efficiency, which is of great practical significance for the development of solar technology.

Fresnel Lens Solar Pumping for Uniform and Stable Emission of Six Sustainable Laser Beams under Non-Continuous Solar Tracking

A multirod solar laser approach is here proposed to attain uniform and stable multibeam emission under non-continuous solar tracking. A Fresnel lens was used as the primary concentrator. The laser head was composed of a second-stage aspherical lens with a light-guide homogenizer and a third-stage conical pump cavity with six Nd:YAG rods. The solar laser system was optimized through numerical analysis in both Zemax® and LASCAD™ software to obtain six 1064 nm laser beams of similar multimode power. To investigate the effect of the homogenizer on the laser performance, the laser head was compared with a similar one that only used the aspherical lens in the second stage. The approach with the light guide attained a slightly lower efficiency than the one without the light guide; however, the tracking error width at 10% laser power loss was higher and, most importantly, only a 2.17% coefficient of variation of the laser power emitted by the six rods at the tracking error angle of ±0.5° was obtained. This is 4.2 times better than the 52.31% obtained with the laser head without the homogenizer and 76 times better than that of the previous numerical work. The light guide is thus essential to ensure uniform and stable solar laser power extraction from all rods even under non-continuous solar tracking, making this prototype the ideal for multibeam laser applications where uniformity and stability of the laser power are indispensable. This renewable multibeam solar laser may replace the classical lamp- and diode-pumped lasers, therefore ensuring a sustainable laser power production pattern for both space and terrestrial applications.

Dynamic modeling and neural network compensation for rotating Euler-Bernoulli beam using a novel deformation description method

Dynamic models that consider multiple nonlinear factors including the two-dimensional deformation and higher-order modes are too computationally complex to be suitable for real-time control of the rotating Euler-Bernoulli beam. This article proposes a new dynamic modeling method according to the assumed mode method. The new modeling method not only has high modeling accuracy but also has a brief mathematical expression. In addition, based on the new modeling method, a neural network sliding mode control strategy using the saturation function is designed to improve the rotational accuracy of the Euler-Bernoulli beam. In the control law design, the saturation function is proposed instead of the unit step function to reduce the chattering phenomenon. Simulation and control experiments describe that the new dynamic modeling method has higher modeling accuracy than the modeling method based on the one-dimensional deformation; the proposed strategy can effectively decrease the rotation angle tracking error of the rotating Euler-Bernoulli beam and improve the control accuracy.

Nussbaum function‐based adaptive boundary control for flexible manipulator with unknown control directions and nonlinear time‐varying actuator faults

AbstractThis study proposes a novel boundary control strategy for a vibrating single‐link flexible manipulator system modeled by partial differential equations. The system has uncertain control directions and actuator faults. Existing research studies model fault‐tolerant control systems with fixed fault coefficients; in this study, the actuator faults are nonlinear and time‐varying, and the control directions are unknown. To circumvent the obstacles introduced by the unknown control directions and nonlinear varying actuator failures, an adaptive boundary controller is designed by using Nussbaum functions with fast growth rates and the bound estimation method. In the developed control scheme, all closed‐loop signals are shown to be uniformly bounded. Additionally, the angle tracking error and vibration asymptotically converge to zero. Finally, numerical simulations for five cases demonstrate the effectiveness of the modeled boundary controller.

Reference Modulation for High-Quality Scan Images of 2-D Laser Scanner Systems

For laser scanner systems, the most critical issue for high-quality images is the linearity of the slow axis. The laser scanner systems have various disturbances and uncertainties, such as manufacturing tolerances, structure vibrations, and parameter uncertainties. Further, there are vertical and horizontal resonance modes that hinder controller design. In this letter, we propose a reference modulation technique to enhance the vertical angle linearity of the slow axis for two-dimensional laser scanner systems. First, the laser scanner system is mathematically modeled in the state-space form. Then, the reference modulation is designed to boost the loop gain over the desired frequency range. The reference modulation can guarantee high-quality scan images by redesigning the desired reference based on the output feedback. The current tracking controller was then implemented with virtual references for the states. We investigated its tracking performance via sensitivity function analysis against the disturbances. Experiments were performed to evaluate the effectiveness of the proposed method using four different laser scanners. We confirmed that the proposed method achieved up to 48% improvement in the angle tracking error from the experimental results.

Safety Control for Quadrotor UAV Against Ground Effect and Blade Damage

This article proposes a safety control scheme for quadrotor unmanned aerial vehicle (UAV) to counteract ground effect and blade damage. The impacts of ground effect and blade damage are quantitatively analyzed in the established model. The proposed safety control scheme consists of position and attitude loops. Specifically, a proportional and derivative controller is designed as a baseline control with acceleration feedforward in the position loop. A disturbance observer (DO) using the measured Euler angles is exploited to estimate the lumped disturbance forces. The developed DO can effectively mitigate the estimation deviation caused by the angle tracking error. Subsequently, differential flatness theory is used to obtain the Euler angle references and the derivatives. In the attitude loop, sliding mode control and fixed-time sliding mode observer (SMO) are integrated to deal with ground effect and blade damage promptly. To demonstrate the effectiveness of the proposed safety control scheme, flight experiments are carried out, where the quadrotor UAV flies close to the rugged ground in the presence of blade damage.

Adaptive Event-Triggered Boundary Control for a Flexible Manipulator With Input Quantization

In this article, an adaptive event-triggered boundary control scheme is proposed for a flexible single-link manipulator (FSLM) system with communication constraints. The hysteresis quantizer with unknown parameters is applied to the control input, which brings a negative effect on the control performance. To reduce the communication burden, we take into account a relative threshold event-triggered mechanism. An adaptive strategy is adopted to compensate for the quantization error and evaluate the unknown parameters. In terms of the Lyapunov direct method, the angle tracking error and the vibration displacement of the FSLM are proved to exponentially converge to the neighborhood of zero. Furthermore, the performance of the developed control algorithm is presented by numerical simulations and experiments.

A Novel Nonlinear Quadrotor Attitude Regulation with Disturbances and Preassigned Convergences

This article develops a novel unknown system dynamic estimator-based funnel control scheme for nonlinear quadrotor attitude regulation with preassigned convergence subject to parametric uncertainties and external perturbations. An invariant manifold equipped with first-order filtering is established. To online identify the lump disturbances, an unknown system dynamic estimator is employed with a simple formula, which need a lower computation burden. Based on aforementioned estimator, a novel funnel control via utilizing funnel variable is investigated, where an exponentially decaying funnel function is preset with a prior preassigned convergence for regulation angle error. The angle tracking errors are proved to be ultimately uniformly bounded, and angle regulation error can evolve within the preset funnel boundary. Simulation results demonstrate the effectiveness of the developed control scheme.

Development of an EMG-based Elbow- Exoskeleton with Twisted String Actuation

Abstract This paper presents an exoskeleton for upper extremity rehabilitation of stroke patients. In order to make rehabilitation widely available, the goal is an inexpensive, portable, and easy-to-use therapy for paralysis of the arm. The exoskeleton is actuated by twisted string actuators (TSA). To reduce the length of the TSA a motor with hollow shaft was chosen, as this allows the string to run through the motor. The control of the exoskeleton is designed for predefined elbow flexion exercises. The start of the movement is triggered by a threshold value in the sEMG of the m. biceps brachii. To evaluate the controller, the exoskeleton performed a flexion movement (5° to 115°) in 2 s and then an extension back to 5° in the same time after a 1 s wait. To simulate different force requirements, additional weights up to 1500 g were attached. During both, the flexion and extension movement, that angle tracking error was sufficiently small and the steady state error was zero. The angular velocity of the elbow joint showed pronounced oscillations with increasing weights. The results show that TSAs can be used to actuate elbow exoskeletons. Thus lightweight, ergonomic, simple and small rehabilitation devices can now be built on this basis. The elasticity of the system must be considered in future work. sEMG must be further implemented to control more sophisticated functions of the rehabilitation device.

3D Human Motion Posture Tracking Method Using Multilabel Transfer Learning

To overcome the high position and posture angle tracking error, long tracking loss time and posture tracking update response time, and low fitness problem of traditional human motion posture tracking methods, in this paper, a three-dimensional (3D) human motion posture tracking method using multilabel transfer learning is proposed. According to the human structure composition and degree of freedom constraints, the 3D human joint skeleton model is constructed to generate the 3D human pose image and perform the noise reduction operation. The background difference is used to detect the 3D human moving target. Using multilabel transfer learning, human motion posture features are extracted from joint position and joint angle, and the estimation results of 3D human motion posture are obtained. The tracking error of human motion posture is corrected by three-step search, and the visual 3D human motion posture tracking results are output. The results show that, compared with the traditional human motion posture tracking method, the position and posture angle tracking errors of the proposed method are 2.18 mm and 0.178 deg, respectively. The tracking loss time and posture tracking update response time are shorter, which proves that the proposed method has more advantages in tracking accuracy and higher adaptability.