Search Results (145)

Continuous impact vibrations caused by uneven road surfaces (such as speed bumps) can significantly reduce the trajectory tracking accuracy of mobile manipulator. This study proposes for the first time an integrated framework combining a semi-active magnetorheological elastomer (MRE) intelligent isolation system with an active trajectory tracking controller to improve the operational accuracy of mobile manipulator under continuous impact excitation, and numerically evaluates the effect of the MRE isolation system. The working principle and design method of the MRE isolation system for mobile manipulators are described, and a multi-layer MRE isolator is fabricated and experimentally characterized. A semi-active control strategy is developed to adaptively adjust the stiffness and damping of the isolator based on continuous impact input. To further compensate for residual disturbances transmitted through the isolator, an enhanced computational torque control (CTC) and proportional-derivative (PD) controller with predefined-time disturbance observer (DOB) is designed for the mobile manipulator. This ensures that the disturbance estimate converges within a predefined time window, thereby improving the robustness of the closed-loop system. By constructing a comprehensive multibody dynamics model coupling the vehicle, the MRE isolator, and the manipulator, vibration transmission is analyzed and trajectory tracking performance is evaluated. Simulation results under continuous road impact excitation demonstrate that the proposed semi-active MRE intelligent isolation system can significantly suppress base vibration and greatly improve the trajectory tracking accuracy of the mobile manipulator end-effector and its joints. This study proves the feasibility of the semi-active MRE isolation system in the trajectory tracking application of mobile manipulator and provides a new approach for the collaborative design of intelligent vibration isolation and control strategies for mobile robot systems operating in harsh and frequently impacted environments. Full article

Reinforcement learning controllers for robot manipulators depend strongly on reward tuning, and fixed weights may yield poor trade-offs under uncertainty and disturbances. This paper proposes a disturbance observer-based actor–critic RL (DOB–ACRL) with adaptive multi-objective reward shaping for a torque-saturated 2-DOF manipulator, where the reward weights are updated online using normalized indicators of tracking error, control energy, and effort. A Lyapunov analysis guarantees the uniform ultimate boundedness of closed-loop signals. The simulations show improved learning and performance over a static reward actor–critic baseline, reducing the RMS tracking error by up to 22.8%, the control energy by ~4.6%, the control effort by 1.9%, and the settling time by up to 29.2%. Full article

Practical robotic systems require control methods that remain reliable under limited computational resources, uncertain environments, and frequent changes in operating conditions. Although model-based control forms the foundation of high-performance robotics, real-world deployment is often hindered by model uncertainty, time-varying dynamics, and costly identification. As a result, low-order and intuitive control schemes remain dominant, yet such approaches often fail to sustain consistent performance under disturbances and parameter variations. Robust and adaptive control provide representative paradigms to address this gap, where a Disturbance Observer (DOB) suppresses uncertainty through disturbance rejection and a Parameter Adaptation Algorithm (PAA) improves model fidelity through online identification. However, direct integration of a DOB and a PAA often introduces functional interference, including mutual masking between disturbance compensation and parameter estimation, which compromises closed-loop stability. This paper proposes an Adaptive Disturbance Observer (ADOB) that integrates a DOB with online parameter adaptation. The ADOB updates the nominal model of the DOB in real time using a Recursive Least Squares (RLS)-based PAA, while a dual-filtering structure separates disturbance rejection and parameter identification. Stability is analyzed using hyperstability theory, where a smoothing mechanism enforces the slowly varying parameter assumption. Experiments on a one-Degree-of-Freedom (DOF) electromagnetic actuator and a three-DOF robotic manipulator demonstrate reductions in model uncertainty and tracking error compared with a conventional DOB. Full article

While the Internal Model Principle (IMP) and Disturbance Observer (DOB) are fundamental to robust control, their systematic equivalence within a unified framework has received limited attention. IMP-based control achieves robustness through the structural inclusion of signal generators, whereas DOB-based methods rely on extended state representations for disturbance estimation. This paper bridges this gap by designing a state-space Reduced-Order Disturbance Observer (RODOB)-based controller that achieves systematic equivalence with an IMP-based transfer function controller. As a design example, an IMP-based controller is synthesized using a Linear Quadratic Regulator (LQR) for an augmented system in error space, with reference inputs directly integrated into the RODOB structure to eliminate the need for additional filters. Simulations and hardware experiments on a Brushless DC (BLDC) motor verify that both structures exhibit consistent control input and output characteristics, significantly outperforming conventional cascade and PID strategies. Numerical stability during digital implementation is ensured via partial fraction expansion. Furthermore, a method for estimating equivalent disturbances—encompassing both external loads and model uncertainties—is proposed by leveraging RODOB states. These findings suggest significant potential for future applications in fault diagnosis and real-time condition monitoring. Full article

Owing to certain inherent deficiencies in their properties, fine reclaimed asphalt pavement (RAP) particles have not yet been widely reused worldwide, resulting in significant environmental pollution and economic waste. Currently, a diverse array of design methods for asphalt mixes has been proposed. These methods can exert a varying influence on the degree of blending (DoB) and the performance of recycled hot-mix asphalt containing fine RAP particles, and some methods may be better suited for recycling fine RAP particles. However, the specific effects and differences among these various methods have yet to be fully revealed. Therefore, this research comprehensively explored these behaviors. Four distinct mix design formulations were investigated: the dense-graded Asphalt Concrete Group (Group AC), the Stone Mastic Asphalt Group (Group SMA), the High-modulus Asphalt Concrete Group (Group HMAC), and the rejuvenator-modified Asphalt Concrete Group (Group AC+Re). It can be found that the DoB and performance varied across different groups. The DoB spanned from 69% to 82%, with Group SMA showing the highest and Group HMAC exhibiting the lowest. The tensile strength ratio (TSR) of Group AC performed only 73.7%, failing to meet the specification threshold; nevertheless, this shortfall can be compensated by employing alternative methods or adding rejuvenator. Group HMAC exhibited the highest splitting-tensile strength and fracture energy. In addition, the incorporation of rejuvenator can enhance most performance of mixes. Some findings may provide a new perspective for the application of fine RAP particles. Full article

The article discusses the control of nonlinear processes with first-order dominant dynamics, focusing on implementation using modern hardware available in various programmable devices and embedded systems. The first two approaches rely on linearization with an ultra-local process model, considering small changes of the process input and output around a fixed operating point, which can be adjusted through gain scheduling with the setpoint variable. This model is used to configure either the historically established automatic reset controller (ARC) or a stabilizing proportional (P) controller enhanced by an inversion-based disturbance observer (DOB). This solution can be interpreted as an application of modern control theory (MCT), as DOB-based control (DOBC) or as advanced disturbance rejection control (ADRC). Alternatively, they can be viewed as a special case of automatic offset control (AOC) based on two types of linear process models. In the third design method, setpoint tracking by exact linearization (EL) is extended with a nonlinear DOB designed using the inverse of the nonlinear process dynamics (EEL). The fourth approach augments EL-based tracking with a DOB derived from the transfer functions of nonlinear processes (NTF). An illustrative example involving the control of a liquid reservoir with a variable cross-section clarifies motivation for the definition of (linear) local and ultra-local process models as well as their advantages in designing robust control that accounts for process uncertainties. Thus, the speed, homogeneity, and shape of transient responses, the ability to reconstruct disturbances, control signal saturation, and measurement noise attenuation are evaluated according to the assumptions specified in the controller design. The novelty of the paper lies in presenting a unifying perspective on several seemingly different control options under the impact of measurement noise. By explaining their essence, advantages, and disadvantages, it provides a foundation for controlling more complex time-delayed systems. The paper emphasizes that certain aspects of controller design, often overlooked in traditional linearization procedures, can significantly improve closed-loop properties. Full article

Background: Skin cancer is known to be associated with aging, oxidative stress, and inflammation. The present study aimed to explore the association between PhenoAge, dietary inflammatory index (DII), and dietary oxidative balance index (DOBS) with skin cancer risk. Methods: A total of 474 individuals aged over 20 years who had information on DII, DOBS, PhenoAge, socioeconomic and demographic factors, and self-reported skin cancer, and 16,154 without skin cancer were included in the National Health and Nutrition Examination Survey database (2005–2018). The combination of DII/DOBS was categorized into 3 categories: inflammation- and oxidation-promoting diet, inflammation- and oxidation-reducing diet, and composite diet. We applied logistic regression to estimate odds ratios (ORs) for the association of DII/DOBS and PhenoAge with skin cancer risk, after adjusting for covariates and survey year. Results: PhenoAge was associated with an increased likelihood of skin cancer (OR 1.07, 95% CI 1.06 to 1.08, p < 0.001). DII and DOBS were associated with PhenoAge advancement of OR 1.28 (95% CI 1.20 to 1.36), OR 0.95 (95% CI 0.94 to 0.96), respectively (p < 0.001). After adjusting for all covariates, the comparison between the inflammation–oxidation-promoting diet and the inflammation–oxidation-reducing diet had a positive relationship with skin cancer (OR 2.19, 95% CI 1.29 to 3.72, p = 0.004). PhenoAge mediated 28.06% of the associations between DII/DOBS and skin cancer risk (p < 0.05). The association remained in the subgroup analysis. Conclusion: Our results suggest that an inflammation- and oxidation-promoting diet is related to increased skin cancer risk and may be partly mediated by PhenoAge. Full article

Flexible-joint robots (FJRs) offer safety and energy efficiency in collaborative tasks, yet achieving high-precision tracking remains challenging under strict state and safety constraints due to elastic coupling, model mismatch, and external disturbances. To address this issue, this paper proposes a safe and disturbance-compensated model predictive control (SDC-MPC) method that integrates model predictive control (MPC) with a disturbance observer (DOB) to estimate and compensate lumped uncertainties and disturbances in real time. To enforce safety, a control barrier function (CBF) is incorporated as an online inequality to maintain forward-invariance safety constraints. The method adapts safety margins to disturbances and allows soft relaxations of constraints when necessary, thereby ensuring feasibility under strong disturbances. A discrete-time implementation makes the approach suitable for real-time applications. Experiments on a single-joint platform demonstrate improved tracking performance and robustness. Full article

This paper introduces an adaptive impedance control strategy for robotic manipulators, developed through the extremum seeking technique. A model-based disturbance observer (DOB) is employed to estimate contact forces, removing the dependency on torque sensors. An impedance vector is constructed to correct the errors arising from motor uncertainties and unknown couplings, without considering the threshold value of the control parameters. Joint tracking errors and fluctuations in contact force are incorporated into the cost function. For various tasks, suitable control parameters are adaptively optimized in real time using an extremum seeking approach, which continuously evaluates the cost function. A rigorous analysis is conducted on the stability of the proposed controller. Compared to conventional approaches, the proposed adaptive impedance control offers a more streamlined design for adjusting the manipulator’s contact impedance. Experimental results confirm that the extremum seeking strategy successfully tuned the controller parameters online according to variations in the cost function. Full article

To evaluate the shear performance of circumferential joints in super-large cross-section shield tunnels featuring inclined bolts and distributed mortises and tenons, refined numerical models were developed for three distinct configurations: single-bolt aligned mortise and tenon (SAB), single-bolt offset (SOB), and double-bolt offset (DOB). This study focuses on assessing how variations in bolt arrangement influence the shear behavior of these joints. The results are as follows: Under the effect of the ordinal shearing loading scenario (OSLS), bolts can significantly bear the load, resulting in the superior shear performance of DOB over SAB and SOB. Under the reverse shearing loading scenario (RSLS), bolts exhibit noticeable pullout phenomena, leading to minimal differences in the shear-dislocation curves of the three bolt arrangement pattern joints. The shear mechanical performance of SOB is notably better than that of SAB and SOB under OSLS, but this difference is less evident under RSLS. The mechanical behavior of bolts remains consistent across different bolt arrangement pattern joints during shear deformation. The bolt holes in SAB passing through the mortise and tenon weaken them, and contact failure between bolts and bolt holes further damages the mortise and tenon. Full article

Background/Objectives: Obesity and dysglycemia are increasingly associated with intestinal barrier dysfunction and alterations in gut microbiota. Intestinal hyperpermeability is emerging as a therapeutic target in metabolic disorders, but human data integrating barrier biomarkers, epithelial morphology, and microbial composition remain scarce. Methods: Forty-six adults (82.6% female; 38.3 ± 7.8 years) were stratified into lean normoglycemic controls (CON), individuals with obesity and normoglycemia (NOB), and those with obesity and dysglycemia (DOB). Biochemical/inflammatory biomarkers, such as lipopolysaccharide (LPS) and LPS-binding protein (LBP), were measured. Duodenal biopsies were obtained by upper digestive videoendoscopy. Histomorphometry, expression of junctional and cytoskeletal proteins, and enzymatic activity of the duodenal epithelium were used as markers of intestinal permeability. Fecal microbiota composition (FMC) was analyzed by amplifying the V4 region of the 16S rRNA gene, which was sequenced using next-generation sequencing technology. Results: Duodenal histomorphometry did not differ across groups. Intestinal alkaline phosphatase (IAP) was significantly lower in DOB compared to CON. LPS correlated positively with fat mass, and LBP with the waist-to-hip ratio. The villus-to-crypt ratio correlated negatively with BMI, while IAP correlated inversely with fasting glucose and HbA1c. β-actin expression was inversely associated with BMI, glucose, insulin, and HOMA-IR. Microbiota diversity indices were similar between groups, although specific taxa, particularly within the Clostridiales order, were reduced in dysglycemia. Conclusions: Reduced IAP activity and consistent correlations between barrier biomarkers and metabolic parameters highlight intestinal barrier dysfunction as a relevant feature of obesity and dysglycemia. Subtle microbiota alterations further support a link between gut ecology and metabolic control. These findings underscore the intestinal barrier as a promising therapeutic target in metabolic disorders. Full article

Background: The distal oblique bundle (DOB) of the interosseous membrane (IOM) has been recognized as an important stabilizer of the distal radioulnar joint (DRUJ). However, its prevalence, morphology, and distal attachments—particularly its relationship to the articular disc and the extensor carpi ulnaris (ECU) tendon sheath—remain inconsistently described. Clarifying these anatomical details is essential for understanding DRUJ stability and guiding surgical reconstruction. Methods: The distal IOM was examined in 48 specimens from 24 embalmed Korean cadavers. In 46 dissected specimens, the presence, morphology, and attachment sites of distal interosseous structures were documented, and attachment levels were measured. In 38 specimens, attachment to the articular disc was assessed. In addition, serial transverse sections from one cadaver were analyzed to confirm three-dimensional relationships. Results: Two morphological patterns were identified: a distinct DOB (21/46, 45.7%) and, when absent, a membranous thickening of the distal IOM (25/46, 54.3%). The mean attachment level was 39.1 ± 9.7 mm for the DOB and 25.4 ± 4.8 mm for the membranous thickening. Both structures assumed an oblique orientation, fanning palmarly toward the capsule and articular disc and dorsally toward the ECU tendon sheath and dorsal septum. In 26 of 38 specimens (68.4%), these structures attached to the proximal palmar portion of the articular disc. Serial transverse sections confirmed this oblique configuration, linking palmar and dorsal stabilizers of the DRUJ. Conclusions: The distal IOM consistently forms specialized structures—either a DOB or a membranous thickening—that integrate with the triangular fibrocartilage complex. By bridging palmar and dorsal stabilizers, these structures contribute to joint congruency and load transfer during forearm rotation. A refined anatomical understanding of these patterns provides clinically relevant insights for surgical preservation or reconstruction, with the potential to improve outcomes in patients with chronic DRUJ instability. Full article

Corner modules decouple chassis functions and enable independent wheel steering, but their control is highly sensitive to external disturbances and feedback delays. Disturbance observers (DObs) are often introduced to mitigate such disturbances, yet their additional dynamics can also compromise closed-loop stability when delays are present. This paper establishes the closed-loop control system of a corner module steering system based on its dynamics, designs the corresponding control law, and incorporates a DOb. Classical stability analysis is carried out using D-curve mapping and eigenvalue validation. The results reveal that feedback delay progressively shrinks the stable domain. When a DOb is introduced, disturbance rejection is improved; however, the admissible control gain region becomes narrower, and larger observer gains further constrain the derivative action, generating additional unstable regions. This paper mechanistically elucidates the impact of disturbance observation on the stability of a time-delayed control system for a corner module with steering. Full article

With the rapid growth of autonomous vehicle technologies, effective path-tracking control has become a critical component in ensuring safety and efficiency in complex traffic scenarios. When a high-level decision-making agent generates a collision-free path, a robust low-level controller is required to precisely follow this trajectory. However, connected autonomous vehicles (CAV) are inherently affected by communication delays and computation delays, which significantly degrade the performance of conventional controllers such as PID or other more advanced controllers like disturbance observers (DOB). While DOB-based designs have shown effectiveness in rejecting disturbances under nominal conditions, their performance deteriorates considerably in the presence of unknown time delays. To address this challenge, this paper proposes a delay-tolerant communication disturbance observer (CDOB) framework for path-tracking control in delayed systems. The proposed CDOB compensates for the adverse effects of time delays, maintaining accurate trajectory tracking even under uncertain and varying delay conditions. It is shown through a simulation study that the proposed control architecture maintains close alignment with the reference trajectory across various scenarios, including single-lane change, double-lane change, and Elastic Band-generated collision avoidance paths under various time delays. Simulation results further demonstrate that the proposed method outperforms conventional approaches in both tracking accuracy and delay robustness, making it well-suited for connected autonomous driving applications. Full article

Five different 2,4-difluorobenzamide derivatives were synthesized and fully characterized by ¹H/¹³C/¹⁹F/2D NMR spectroscopy using DMSO-d₆ as solvent and MS. All compounds occur as rotation conformers resulting from the partial amide double bond with a solvent-dependent coalescence point. Temperature-dependent ¹H NMR techniques, as well as EXSY, were applied to determine the rate constants of exchange, and the resulting activation energy barriers were calculated. Regarding the N,N-diacylated piperazine, both conformers (syn and anti) were found in solution, whereas only the anti-conformer was found in the crystals. This result was verified by an XRD analysis. Single crystals of N,N-bis(2,4-difluorobenzoyl)piperazine 3b (monoclinic, space group P2₁/c, a = 7.2687(3), b = 17.2658(8), c = 6.9738(3) Å, β = 115.393(2)°, V = 790.65(6) ų, Z = 4, D_obs = 1.530 g/cm³) were obtained from a saturated chloroform solution. Full article