Angle Constraints Research Articles

Three-dimensional terminal angle constraint guidance law with class [formula omitted] function-based adaptive sliding mode control

This paper investigates the three-dimensional (3-D) interception guidance problem, where the missile is required to intercept the maneuvering target with the desired terminal angles. For the nonlinear relative kinematic model, a class K∞ function-based adaptive sliding mode guidance law is proposed, which ensures that the errors of terminal Line-of-Sight (LOS) angles converge to the small neighborhoods of origin at the time of interception, without relying on information about the target's acceleration. To overcome the challenges of large initial control input and chattering in existing sliding mode guidance laws, two improved control schemes are introduced. The first scheme is to directly impose saturation constraints into the adaptive gain. However, it is important to ensure that the unknown disturbance remains within the prescribed saturation bound. To avoid the limitation, another approach involves introducing auxiliary dynamics to eliminate the reaching phase and slow down the convergence of LOS angles by presetting the convergence time of the sliding mode variables, which helps mitigate excessive initial control inputs. Numerical simulations are conducted using a realistic missile model and considering a 3-DOF point-mass aircraft as the target to evaluate three different guidance laws. The results indicate that the proposed guidance law ensures interception accuracy while substantially reducing the control gain.

Motion planning framework based on dual-agent DDPG method for dual-arm robots guided by human joint angle constraints.

Reinforcement learning has been widely used in robot motion planning. However, for multi-step complex tasks of dual-arm robots, the trajectory planning method based on reinforcement learning still has some problems, such as ample exploration space, long training time, and uncontrollable training process. Based on the dual-agent depth deterministic strategy gradient (DADDPG) algorithm, this study proposes a motion planning framework constrained by the human joint angle, simultaneously realizing the humanization of learning content and learning style. It quickly plans the coordinated trajectory of dual-arm for complex multi-step tasks. The proposed framework mainly includes two parts: one is the modeling of human joint angle constraints. The joint angle is calculated from the human arm motion data measured by the inertial measurement unit (IMU) by establishing a human-robot dual-arm kinematic mapping model. Then, the joint angle range constraints are extracted from multiple groups of demonstration data and expressed as inequalities. Second, the segmented reward function is designed. The human joint angle constraint guides the exploratory learning process of the reinforcement learning method in the form of step reward. Therefore, the exploration space is reduced, the training speed is accelerated, and the learning process is controllable to a certain extent. The effectiveness of the framework was verified in the gym simulation environment of the Baxter robot's reach-grasp-align task. The results show that in this framework, human experience knowledge has a significant impact on the guidance of learning, and this method can more quickly plan the coordinated trajectory of dual-arm for multi-step tasks.

Optimal sliding mode guidance law against maneuvering target with impact angle constraint

In this paper, an optimal sliding mode guidance law with impact angle constraint is proposed against maneuvering targets. Firstly, the impact angle frame for a static target is extended to a maneuvering target. Then, in this impact angle frame, the optimal reaching law of sliding mode is proposed to design an optimal sliding mode guidance law which is robust to target maneuvers and satisfies an impact angle constraint. The optimal sliding mode guidance law with impact angle constraint is also extended to the three-dimensional case. Numerical simulations in different scenarios with a realistic missile model show that the guidance law can intercept a maneuvering target with a desired impact angle, and the control effort is close to the optimal value, which verifies that the proposed optimal sliding mode guidance law has both robustness and optimality.

Fixed Time Cooperative Scheme Design for Missiles Salvo Attack

This paper proposes a fixed-time cooperative control strategy for multiple missiles with impact angle constraints to accomplish the salvo attack guidance scenario on maneuvering targets. A fixed-time extended state observer (ESO) is proposed to estimate the target accelerations. In order to execute the salvo attack, along the line of sight (LOS) direction guidance law and the LOS normal direction guidance law are the two components of the proposed fixed time guidance scheme. The efficiency of the designed method is demonstrated through simulation results.

Neural-Network-Based Nonlinear Optimal Terminal Guidance With Impact Angle Constraints

Neural-Network-Based Nonlinear Optimal Terminal Guidance With Impact Angle Constraints

Mesoscopic irreversible thermodynamics of aging kinetics of alpha polypeptides [DNA] under various constraints: Special reference to the simple spring mechanics

The mesoscopic irreversible thermodynamic treatment of α-polypeptides and the helical polynucleotides (DNA) furnishes two sets of analytical expressions, which allow us not only to analyze the reversible force–extension experiments performed by atomic force microscopy (AFM) but also to predict the irreversible “aging” kinetics of the single-stranded and double-stranded polynucleotides (ssDNA and dsDNA) helical conformations exposed to aqueous solutions and applied static stress systems under the various constraints. The present physicochemical cage model emphasizes the fact that the global Helmholtz free energy of the helical conformation acts not only under the stored “intrinsic” unusual torsional and bending elastic energies inherited by the unfolded helical structure of the amino-acid (peptides) or the nucleic-acid (nucleotide) backbone but also reveals the importance of the interfacial Helmholtz free energy density associated with the interaction of the side-wall branches within the surrounding aqueous solutions. The analytical expression obtained for the unfolding force vs extension (FE) shows a strong non-linear elasticity behavior under the twist angle constraint when the interfacial Helmholtz energy term is incorporating into the scenario. This behavior is in excellent quantitative agreement with the AFM test results obtained by Idiris et al. (2000) on the poly-L-glutamic acid [Glu(n)-Cys] exposed to aqueous solutions, which show that acidity increases the degrees of helicity.

Balanced prescribed-distance guidance with impact angle constraint and input saturation

This paper presents a cooperative approach combining a prescribed-distance inverse-optimal guidance law with balanced control for intercepting a maneuvering target, while considering input saturation. By employing a distance-dependent scale transformation, the guidance interception problem is converted into a prescribed-distance regulation form. A prescribed-distance guidance law is then implemented building upon the inverse problem of optimal control theory to minimize a specific quadratic performance index. To address the challenges posed by input saturation, a performance safety evaluation (PSE) function is introduced. This function assesses the system’s safety and determines whether compensation for saturation is necessary. As a result, a balance between performance and saturation is achieved. The effectiveness of our proposed guidance law is evaluated through numerical simulations.

Ultraviolet and Blue Optical Imaging of UVCANDELS

The UltraViolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey Fields (UVCANDELS) survey provided ultraviolet F275W imaging with coordinated parallel optical F435W imaging in four of the five CANDELS fields: GOODS-N, GOODS-S, EGS, and COSMOS, covering a total area of ∼426 arcmin2. UVCANDELS takes primary WFC3/UVIS F275W exposures at a uniform 3-orbit depth and ACS F435W exposures (in parallel) at slightly varying depth due to the roll angle constraints and the overlap from the increased field of view of the ACS camera, reaching a limiting magnitude of ∼27 and ∼28 ABmag (5σ in 0.″2 apertures) for F275W and F435W, respectively. We present the results of the UVCANDELS observations, custom calibrations, and the creation of F275W and F435W imaging mosaics, which have been made publicly available on the Barbara A. Mikulski Archive for Space Telescopes.

Finite-time error convergent trajectory generation with field-of-view and angle constraints

Finite-time error convergent trajectory generation with field-of-view and angle constraints

Tackling Modern Sailing Challenges with a CFD-based Dynamic VPP

A dynamic Velocity Prediction Program (VPP) integrated in a Computational Fluid Dynamics (CFD) code is described. Aerodynamic forces are obtained either through empirical coefficients or interpolated from aerodynamics matrices. These aerodynamic forces are then input to the hydrodynamics CFD solver, which solves both the flow and the motions of the boat, resulting in a closely coupled VPP. For a given True Wind Angle and True Wind Speed a sail power parameter is optimised to obtain the best possible boat speed within heel angle constraints. This approach allows naval architects to swiftly and precisely compare several yacht designs in real sailing configurations using only a few CFD computations. Several advanced features recently added to this program are covered in this paper including convergence criteria, automatic grid refinement, foil fluid-structure interaction, multiple aerodynamics models and rudder control. Results obtained from our CFD VPP on a 40-feet fast-cruising yacht demonstrates promising agreement with other existing VPP polars, affirming the accuracy and reliability of our approach. The CFD VPP presented was also successfully applied to an IMOCA, a 60-feet racing yacht.

Boosting Encrypted Traffic Classification Using Feature-Enhanced Recurrent Neural Network with Angle Constraint

Boosting Encrypted Traffic Classification Using Feature-Enhanced Recurrent Neural Network with Angle Constraint

MNTZNN for Solving Hybrid Double-Deck Dynamic Nonlinear Equation System Applied to Robot Manipulator Control.

Compared with conventional dynamic nonlinear equation systems, a hybrid double-deck dynamic nonlinear equation system (H3DNES) not only has multiple layers describing more different tasks in practice, but also has a hybrid nonlinear structure of solution and its derivative describing their nonlinear constraints. Its characteristics lead to the ability to describe more complicated problems involving multiple constraints, and strong nonlinear and dynamic features, such as robot manipulator tracking control. Besides, noises are inevitable in practice and thus strong robustness of models solving H3DNES is also necessary. In this work, a multilayered noise-tolerant zeroing neural network (MNTZNN) model is proposed for solving H3DNES. MNTZNN model has strong robustness and it solves H3DNES successfully even when noises exist in both the two layers of H3DNES. In order to develop the MNTZNN model, a new zeroing neural network (ZNN) design formula is proposed. It not only enables equations with respect to solutions to become equations with respect to the second-order derivatives of solutions but also makes the corresponding model have strong robustness. The robustness of the MNTZNN model is proved when parameters in the model satisfy a loose constraint and the error bounds are programmable via setting appropriate parameter values. Finally, the MNTZNN model is applied to the tracking control of the six-link planar robot manipulator and PUMA560 robot manipulator with hybrid nonlinear constraints of joint angle and velocity.

Prescribed-Time Chattering-Free Sliding Mode Guidance Law with Terminal Angle Constraint Based on Periodic Delayed Feedback

Prescribed-Time Chattering-Free Sliding Mode Guidance Law with Terminal Angle Constraint Based on Periodic Delayed Feedback

Prescribed-Time Guidance Law with Approach Angle Constraint and Actuator Faults

Prescribed-Time Guidance Law with Approach Angle Constraint and Actuator Faults

Impact Angle Constraint Guidance Against Active Defense Target Based on Partial Differential Games

For intercepting active defense target, an impact angle constraint guidance law is proposed based on partial differential games. First, the relative motion models of three‐player games between interceptor, target, and defense missile are established. The problem of intercepting active defense target is separated into two partial games. Then, two partial coupled game guidance laws are obtained, respectively. Impact angle constraint is taken into account in the game between attacker and defender (D). Finally, a combined guidance law is calculated by the two partial differential games. The performance of the strategy can be adjusted by the weight coefficient related to the miss distance between the attacker and the D. Simulations show that the guidance law can intercept the target with impact angle constraint and evade D’s interception at the same time.

Three-dimensional modeling of ancient yiyuan architecture using static laser scanning technology

Abstract The awareness of protecting traditional culture and humanistic landscapes is increasing year by year, and the protection of ancient gardens is becoming more and more a consensus among people. This paper takes the architectural profile of Guyi Garden as the research basis, introduces the specific application of 3D laser scanning technology, plans the scope of architectural data acquisition in Guyi Garden, and designs the corresponding architectural data acquisition program. With respect to the acquired point cloud data of GuYiYuan, the bilateral filtering algorithm is used to reduce the noise of the data, the curvature thinning algorithm is combined to reduce the point cloud data of the buildings in GuYiYuan, the point cloud data are spliced based on the connection point, and the ICP algorithm with the introduction of the optimization of the rotational angle constraints is introduced to realize the alignment of the point cloud data. In addition, the shadows generated from the point cloud data are removed by combining the relighting method, and the linear transformation method is also used to globally correct the texture image generated from the point cloud data. The point cloud density was reduced from 0.95m² to 0.01m² when the thinning rate was increased from 8% to 96%, and the alignment error of the improved ICP algorithm under 25dB Gaussian white noise was only 0.083*10-4mm. The maximum error accuracy of the two-dimensional model of Yiyi Nodang generated based on the point cloud data was only 0.007m, and the error of the three-dimensional model was controlled to be within the range of ±9mm. Accurate architectural data can be obtained through the use of 3D laser scanning technology, leading to a new method for digitally preserving historical buildings.

A Second-Order Cone Programming (SOCP) Based Optimal Power Flow (OPF) Model With Cyclic Constraints for Power Transmission Systems

For meshed power networks, even though the conic relaxation is shown to be exact, the relaxation of angles may not be exact using the existing Second-Order Cone Programming (SOCP) based optimal power flow (OPF) models. Power transmission networks generally have meshed orientation, and the cyclic angle constraints are not satisfied with the existing SOCP-OPF models. This work proposes a SOCP-OPF model for power transmission networks that satisfies the cyclic angle constraints for any mesh in the network. The novelty of the proposed OPF model is that it defines a convex envelope to represent the relative bus voltage angles that satisfy the cyclic constraint criteria for a meshed network. The proposed SOCP-OPF model is tested on the IEEE 14-bus, 57-bus, 118-bus, 500-bus, and 2736-bus networks. The case studies demonstrate that the proposed model is computationally efficient and scalable for large transmission networks compared to the Nonlinear Programming (NLP) and semi-definite programming (SDP) counterparts.

Optimal Fully Actuated System Approach-Based Trajectory Tracking Control for Robot Manipulators.

In this article, a trajectory tracking control strategy is proposed for robot manipulators via a fully actuated system (FAS) approach, which has shown its simplicity and flexibility for most of the nonlinear controller design. However, the motion control for robot manipulators is more complicated since unknown dynamical model, external disturbances, friction forces, and various physical constraints are required to be considered. Therefore, the FAS approach cannot be straightforwardly applied. To address these challenges, the dynamic model of robot manipulators is established via model identification methods. Furthermore, based on the identified model, an FAS composite control strategy with simple structure is designed, which is achieved by integrating a high-order disturbance observer (HODO) in the inner loop, with an FAS trajectory tracking controller in the outer loop. Specifically, the HODO is utilized for handling the uncertain dynamics and external disturbances. Moreover, the controller gains are optimized using a gradient-based optimal parameter tuning method (OPTM). By imposing joint angle constraints, joint angular velocity constraints, and input torque limits into the formulation, the OPTM also ensures the satisfaction of these physical constraints. Numerical simulations and experiments are provided to validate the performance of the proposed controller.

Automated Flight Technology for Integral Path Planning and Trajectory Tracking of the UAV

In view of the problem that path planning and trajectory tracking are rarely solved simultaneously in the current research, which hinders their practical implementation, this paper focuses on enhancing the autonomous flight planning capability of unmanned aerial vehicles (UAVs) by investigating integrated path planning and trajectory tracking technologies. The autonomous flight process is divided into two sub-problems: waypoint designing/optimizing and waypoint tracking. Firstly, an improved DB-RRT* algorithm is proposed for waypoint planning to make the algorithm have higher planning efficiency, better optimization results, and overcome the defects of accidental and low reliability of single RRT* planning results. Secondly, the scheme of “offline design + online flight” is adopted to lead the UAV to fly online according to the waypoints’ instructions by using the sliding mode guidance based on angle constraint with finite-time convergence so that it can fly to the destination autonomously. In order to check the performance of the proposed algorithm, a variety of simulations are conducted to verify the feasibility of the proposed algorithm.

Vibration-polynomial-based optimal trajectory planning for mobile concrete pumping equipment with state constraints

To improve the operating stabilities of the flexible hydraulic manipulator in concrete pumping equipment, a trajectory planning method based on optimal vibration energy is presented. First, predefined trajectories are generated by the quintic polynomial method, and kinematic inversions are established by unifying the velocity and angle constraints into the velocity level. Then, relationships between the boom vibration and the vibration energy are solved in modal space. Specifically, hydraulic actuators are regarded as spring-damping systems to calculate generalized forces into the vibration equation. The vibration equation can solve the modal coordinate and vibration model function, such that the elastic potential energy to cause vibration is completely described. Next, floating values are captured by a genetic algorithm to minimize vibration energy, and then introduced to the predefined trajectory to weaken the boom vibration. Last, the proposed trajectory planning method is verified by a concrete pumping spreader with a 13 m hydraulic manipulator.