The output feedback active disturbance rejection control of a valve-controlled cylinder electro-hydraulic servo system is investigated in this ***,a comprehensive nonlinear mathematical model that encompasses both mat...
详细信息
The output feedback active disturbance rejection control of a valve-controlled cylinder electro-hydraulic servo system is investigated in this ***,a comprehensive nonlinear mathematical model that encompasses both matched and mismatched disturbances is *** to the fact that only position information can be measured,a linear Extended State Observer(ESO)is introduced to estimate unknown states and matched disturbances,while a dedicated disturbance observer is constructed to estimate mismatched *** from the traditional observer results,the design of the disturbance observer used in this study is carried out under the constraint of output ***,an output feedback nonlinear controller is proposed leveraging the aforementioned observers to achieve accurate trajectory *** mitigate the inherent differential explosion problem of the traditional backstepping framework,a finite-time stable command filter is ***,considering transient filtering errors,a set of error compensation signals are designed to counter their negative impact *** analysis affirms that the proposed control strategy ensures the boundedness of all signals within the closed-loop ***,under the specific condition of only time-invariant disturbances in the system,the conclusion of asymptotic stability is ***,the algorithm’s efficacy is validated through comparative experiments.
The ammunition loading system manipulator is susceptible to gear failure due to high-frequency,heavyload reciprocating motions and the absence of protective gear *** a fault occurs,the distribution of fault characteri...
详细信息
The ammunition loading system manipulator is susceptible to gear failure due to high-frequency,heavyload reciprocating motions and the absence of protective gear *** a fault occurs,the distribution of fault characteristics under different loads is markedly inconsistent,and data is hard to label,which makes it difficult for the traditional diagnosis method based on single-condition training to generalize to different *** address these issues,the paper proposes a novel transfer discriminant neural network(TDNN)for gear fault ***,an optimized joint distribution adaptive mechanism(OJDA)is designed to solve the distribution alignment problem between two *** improve the classification effect within the domain and the feature recognition capability for a few labeled data,metric learning is introduced to distinguish features from different fault *** addition,TDNN adopts a new pseudo-label training strategy to achieve label replacement by comparing the maximum probability of the pseudo-label with the test *** proposed TDNN is verified in the experimental data set of the artillery manipulator device,and the diagnosis can achieve 99.5%,significantly outperforming other traditional adaptation methods.
Self-supervised learning is attracting significant attention from researchers in the point cloud processing field. However, due to the natural sparsity and irregularity of point clouds, effectively extracting discrimi...
详细信息
Self-supervised learning is attracting significant attention from researchers in the point cloud processing field. However, due to the natural sparsity and irregularity of point clouds, effectively extracting discriminative and transferable features for efficient training on downstream tasks remains an unsolved challenge. Consequently, we propose PointSmile, a reconstruction-free self-supervised learning paradigm by maximizing curriculum mutual information(CMI) across the replicas of point cloud objects. From the perspective of how-and-what-to-learn, PointSmile is designed to imitate human curriculum learning, i.e.,starting with easier topics in a curriculum and gradually progressing to learning more complex topics in the curriculum. To solve “how-to-learn”, we introduce curriculum data augmentation(CDA) of point *** encourages PointSmile to follow a learning path that starts from learning easy data samples and progresses to learning hard data samples, such that the latent space can be dynamically affected to create better embeddings. To solve “what-to-learn”, we propose maximizing both feature-and class-wise CMI to better extract discriminative features of point clouds. Unlike most existing methods, PointSmile does not require a pretext task or cross-modal data to yield rich latent representations; additionally, it can be easily transferred to various backbones. We demonstrate the effectiveness and robustness of PointSmile in downstream tasks such as object classification and segmentation. The study results show that PointSmile outperforms existing self-supervised methods and compares favorably with popular fully supervised methods on various standard architectures. The code is available at https://***/theaalee/PointSmile.
A simplified calculation of the specimen’s stress-strain curve is generally conducted using the two-wave method by the split Hopkinson pressure bar(SHPB),which aligns the onset of the transmitted and reflected ***,th...
详细信息
A simplified calculation of the specimen’s stress-strain curve is generally conducted using the two-wave method by the split Hopkinson pressure bar(SHPB),which aligns the onset of the transmitted and reflected ***,this approach neglects the travel time of elastic waves within the *** the travel time of elastic waves,this study quantitatively investigates the error characteristics and patterns of stress,strain,and strain rate in the specimen under different conditions using the theoretical two-wave method,and compares the results with those obtained using the onset-aligned twowave *** study reveals that the stress-time curves derived from the theoretical two-wave method are lower than the actual stress curves,whereas those obtained from the onset-aligned two-wave method are consistently higher than the actual stress curves,with the stress deviation approximating a constant value when the dimensionless time exceeds *** starting point of the stress-strain curves obtained by the theoretical two-wave method is not zero but a point on the strain axis,whereas the onset-aligned two-wave method always starts at ***,the slopes of the stress-strain curves obtained by both methods differ from the actual Young’s modulus of the material,and functional relationships between the slopes and the actual Young’s modulus are *** research offers theoretical guidance for the refined design of SHPB experiments and the accurate processing of data.
This paper proposes a Markov decision process based service migration algorithm to satisfy quality of service(QoS) requirements when the terminals leave the original server. Services were divided into real-time servic...
详细信息
This paper proposes a Markov decision process based service migration algorithm to satisfy quality of service(QoS) requirements when the terminals leave the original server. Services were divided into real-time services and non-real-time services, each type of them has different requirements on transmission bandwidth and latency,which were considered in the revenue function. Different values were assigned to the weight coefficients of QoS parameters for different service types in the revenue and cost functions so as to distinguish the differences between the two service types. The overall revenue was used for migration decisions, rather than fixed threshold or instant *** Markov decision process was used to maximize the overall revenue of the system. Simulation results show that the proposed algorithm obtained more revenue compared with the existing works.
Partial maximum satisfiability(PMS) is a significant generalization of Boolean satisfiability(SAT) and maximum satisfiability(MaxSAT), by introducing hard clauses and soft clauses. Compared with SAT and MaxSAT, the PM...
详细信息
Partial maximum satisfiability(PMS) is a significant generalization of Boolean satisfiability(SAT) and maximum satisfiability(MaxSAT), by introducing hard clauses and soft clauses. Compared with SAT and MaxSAT, the PMS problem has more real-world applications where both hard and soft constraints are involved. Local search is an effective incomplete method for solving PMS and is useful for important domains where good-quality solutions are desired within reasonable *** local search PMS solvers, the approach for initial assignment generation is crucial because its effectiveness significantly affects practical performance. In this study, we propose a novel initial assignment prediction approach, called InitPMS. When predicting an assignment for PMS, InitPMS considers the specific structure of PMS instances, i.e., distinguishing hard and soft clauses. Our experiments on extensive PMS instances from MaxSAT evaluations(MSEs) 2020 and 2021 show that InitPMS significantly boosts the performance of five state-of-the-art local search PMS solvers, demonstrating its generality. In addition,our results indicate that incorporating InitPMS could improve the performance of one of the best incomplete PMS solvers in MaxSAT Evaluation 2021, indicating that InitPMS might help advance the state of the art in PMS solving.
Continuum robots with high flexibility and compliance have the capability to operate in confined and cluttered environments. To enhance the load capacity while maintaining robot dexterity, we propose a novel non-const...
详细信息
Continuum robots with high flexibility and compliance have the capability to operate in confined and cluttered environments. To enhance the load capacity while maintaining robot dexterity, we propose a novel non-constant subsegment stiffness structure for tendon-driven quasi continuum robots(TDQCRs) comprising rigid-flexible coupling *** at real-time control applications, we present a novel static-to-kinematic modeling approach to gain a comprehensive understanding of the TDQCR model. The analytical subsegment-based kinematics for the multisection manipulator is derived based on screw theory and product of exponentials formula, and the static model considering gravity loading,actuation loading, and robot constitutive laws is established. Additionally, the effect of tension attenuation caused by routing channel friction is considered in the robot statics, resulting in improved model accuracy. The root-mean-square error between the outputs of the static model and the experimental system is less than 1.63% of the arm length(0.5 m). By employing the proposed static model, a mapping of bending angles between the configuration space and the subsegment space is established. Furthermore, motion control experiments are conducted on our TDQCR system, and the results demonstrate the effectiveness of the static-to-kinematic model.
This paper investigates the stability problem for sampled-data systems by adopting a refined semi-looped-functional,which is with the following two ***,the new functional term is with a new integral vectorη0,which co...
详细信息
This paper investigates the stability problem for sampled-data systems by adopting a refined semi-looped-functional,which is with the following two ***,the new functional term is with a new integral vectorη0,which contains sampling information of the systems and associates two commonly used ***,the vectorη0 is combined into various zero equations for processing the functional,especially where a new equation is derived fromη*** on the refined functional,further stability results for sampled-data systems are *** the effectiveness of the results is numerically verified through two examples at the end.
Permanent magnet synchronous motor(PMSM)speed control systems with conventional linear active disturbance rejection control(CLADRC)strategy encounter issues regarding the coupling between dynamic response and disturba...
详细信息
Permanent magnet synchronous motor(PMSM)speed control systems with conventional linear active disturbance rejection control(CLADRC)strategy encounter issues regarding the coupling between dynamic response and disturbance suppression and have poor performance in suppressing complex nonlinear *** order to address these issues,this paper proposes an improved two-degree-of-freedom LADRC(TDOF-LADRC)strategy,which can enhance the disturbance rejection performance of the system while decoupling entirely the system's dynamic and anti-disturbance performance to boost the system robustness and simplify controller parameter *** models that consider total disturbances are developed to design the TDOF-LADRC speed controller ***,to evaluate the control performance of the TDOF-LADRC strategy,its stability is proven,and the influence of each controller parameter on the system control performance is *** on it,a comparison is made between the disturbance observation ability and anti-disturbance performance of TDOF-LADRC and CLADRC to prove the superiority of TDOF-LADRC in rejecting ***,experiments are performed on a 750 W PMSM experimental platform,and the results demonstrate that the proposed TDOF-LADRC exhibits the properties of two degrees of freedom and improves the disturbance rejection performance of the PMSM system.
UAV networks often encounter jamming attacks, under which multi-radio protocols have to switch radios to accelerate communication recovery. However, the existing protocols rely on exchange of hello messages to detect ...
详细信息
UAV networks often encounter jamming attacks, under which multi-radio protocols have to switch radios to accelerate communication recovery. However, the existing protocols rely on exchange of hello messages to detect jamming, leading to long sensing time and thus slow routing recovery. To address the issues raised by jamming attacks, we propose a new routing protocol, Electromagnetic Spectrum situation awareness Optimized Link State Routing (ESOLSR) protocol, to improve the existing OLSRv2 protocol. ESOLSR utilizes the spectrum situation awareness capability from the physical layer, and adopts joint-updating of link status, updating of interface functions, and adaptive adjustment of parameters. Our simulation results show that the improved protocol, ESOLSR, can recover routing and resume normal communication 26.6% faster compared to the existing protocols.
暂无评论