Control Of Mechanical Systems Research Articles

Correction to: Cooperative game-theoretic optimization of adaptive robust constraint-following control for fuzzy mechanical systems under inequality constraints

Correction to: Cooperative game-theoretic optimization of adaptive robust constraint-following control for fuzzy mechanical systems under inequality constraints

NMPC‐Based Control of Underactuated Spacecraft: A Neighboring Extremal Approach Extended to SE(3)

ABSTRACTThe present work revolves around employing the benefits of neighboring extremal approach in the nonlinear model predictive control of mechanical systems evolving on SE(3). In the NMPC process, necessary conditions of optimality are extracted based on some discrete‐time version of the equations of motion referred as LGVI and the obtained TPBVP equations are solved using simplified sensitivity derivatives by means of an indirect shooting method. Taking into consideration that the repetitive optimization process of the NMPC is time consuming, making its implementation challenging, a method of neighboring extremal is proposed here for recalculating the responses of the systems in scenarios that face some unexpected changes in their parameters or are encountering some last‐minute re‐planning schemes. Based on the existing responses of the system to the first set of initial conditions, the reaction of the system to the altered set of initial conditions can be reconstructed without the need to solve the whole optimization process from scratch by utilizing the features of the NE method. A spacecraft model evolving on SE(3) with actuation constraints confirms the efficiency of the whole process in term of accuracy versus computation burden. Forasmuch as actuator failure is a probable yet important event in aerial/spatial missions, the performance of the control system in dealing with such situations is examined. The algorithm robustness and its capability to compensate the effects of the actuator loss is checked.

Analysis of a Dry Friction Force Law for the Covariant Optimal Control of Mechanical Systems with Revolute Joints

This contribution shows a geometric optimal control procedure to solve the trajectory generation problem for the navigation (generic motion) of mechanical systems with revolute joints. The mechanical system is analyzed as a nonlinear Lagrangian system affected by dry friction at the joint level. Rayleigh’s dissipation function is used to model this dissipative effect of joint-level friction, and regarded as a potential. Rayleigh’s potential is an invariant scalar quantity from which friction forces derive and are represented by a smooth model that approaches the traditional Coulomb’s law in our proposal. For the optimal control procedure, an invariant cost function is formed with the motion equations and a Riemannian metric. The goal is to minimize the consumed energy per unit time of the system. Covariant control equations are obtained by applying Pontryagin’s principle, and time-integrated using a Finite Elements Method-based solver. The obtained solution is an optimal trajectory that is then applied to a mechanical system using a proportional–derivative plus feedforward controller to guarantee the trajectory tracking control problem. Simulations and experiments confirm that including joint-level friction forces at the modeling stage of the optimal control procedure increases performance, compared with scenarios where the friction is not taken into account, or when friction compensation is performed at the feedback level during motion control.

Diallyl disulfide alleviates hepatic steatosis by the conservative mechanism from fish to tetrapod: Augment Mfn2/Atgl-Mediated lipid droplet-mitochondria coupling

Despite increasing evidences has highlighted the importance of mitochondria-lipid droplet (LD) coupling in maintaining lipid homeostasis, little progress in unraveling the role of mitochondria-LD coupling in hepatic lipid metabolism has been made. Additionally, diallyl disulfide (DADS), a garlic organosulfur compound, has been proposed to prevent hepatic steatosis; however, no studies have focused on the molecular mechanism to date. To address these gaps, this study investigated the systemic control mechanisms of mitochondria-LD coupling regulating hepatic lipid metabolism, and also explored their function in the process of DADS alleviating hepatic steatosis. To this end, an animal model of lipid metabolism, yellow catfish Pelteobagrus fulvidraco were fed four different diets (control, high-fat, DADS and high-fat + DADS diet) in vivo for 8 weeks; in vitro experiments were conducted to inhibit Mfn2/Atgl-mediated mitochondria-LD coupling in isolated hepatocytes. The key findings are: (1) the activations of hepatic LDs lipolysis and mitochondrial β-oxidation are likely the major drivers for DADS alleviating hepatic steatosis; (2) the underlying mechanism is that DADS enhances mitochondria-LD coupling by promoting the interaction between mitochondrion-localized Mfn2 with LD-localized Atgl, which facilitates the hepatic LDs lipolysis and the transfer of fatty acids (FAs) from LDs to mitochondria for subsequent β-oxidation; (3) Mfn2-mediated mitochondrial fusion facilitates mitochondria to form more PDM, which possess higher β-oxidation capacity in hepatocytes. Significantly, the present research unveils a previously undisclosed mechanism by which Mfn2/Atgl-mitochondria-LD coupling relieves hepatic LDs accumulation, which is a conserved strategy from fish to tetrapod. This study provides another dimension for mitochondria-LD coupling and opens up new avenues for the therapeutic interventions in hepatic steatosis.

Effect of ethanol addition on enhancing the cooling performance improvement of spray system

The widespread application of spray technology has significantly improved outdoor environmental thermal comfort. However, the spray system is unable to fulfill special comfort requirements. Utilizing mechanical ventilation and control systems effectively enhances the cooling performance of spray systems; however, those approaches are associated with elevated costs and maintenance complexities. The combination of ethanol and water has been demonstrated to produce a lower surface tension and a higher latent heat of evaporation, a property that contributes to the heat transfer efficiency and evaporation rate of the droplets. Considering the convenience and cost-effectiveness of adding ethanol as an additive, it emerges as the optimal choice. To evaluate the effectiveness of ethanol on the evaporative cooling performance of the spray system, a comparative study was conducted, comparing the cooling performances of different concentrations of ethanol with a spray system without ethanol addition. Five operating conditions were designed, including a no-spray case, a non-additive case, a 0.5% ethanol concentration case, a 1.0% ethanol concentration case, and a 1.5% ethanol concentration case. The results demonstrated that adding ethanol effectively enhanced the cooling performance of the spray system. At 1.7m above ground level (0.4m away from the nozzle), compared to the non-additive case without ethanol, the 0.5% ethanol concentration case, 1.0% ethanol concentration case, and 1.5% ethanol concentration case further reduced the temperature by 0.95°C, 1.64°C, and 2.27°C. Moreover, the relative humidity grew by 3.57%, 9.25%, and 13.5%, respectively. Adding ethanol significantly enhanced the evaporative cooling effect of the spray system, with the optimal concentration observed at 1.5%. The results demonstrate that enhancing the evaporative cooling efficacy of a spray system by introducing ethanol into the spray medium represents a viable strategy and improve urban thermal environment in summer. Furthermore, this study aims to examine the impact of droplet evaporation on relative humidity, establishing a foundation for future enhancements aimed at addressing the issue of over-humidification in spray systems.

Prescribed performance nonholonomic trajectory-tracking control of uncertain mechanical systems: a transformation-free approach

Prescribed performance nonholonomic trajectory-tracking control of uncertain mechanical systems: a transformation-free approach

Development of a robotic wheel door opener system assistive device

Physical disabilities significantly impact individuals' ability to perform activities of daily living (ADL), leading to reduced autonomy and difficulty to accomplish daily living tasks. One such barrier is the difficulty or inability to open doors, preventing access to different rooms in their residence (bathroom, bedroom, etc.), rooms at work, or shopping areas. Existing solutions, such as robotic arms on wheelchairs and door openers mounted at the top of doors, remain expensive, complex to install, and relatively difficult for the target population to use. Addressing this challenge, this study introduces a Robotic Wheel Door Opener System (RWDOS) designed to facilitate the opening and closing of the door. The RWDOS is installed at the bottom of a door and is controlled remotely through a smartphone application. The paper presents the mechanical design and control system along with a cost analysis. It concludes with initial results and outlines the future directions for the project.

Research on the Safety Design and Trajectory Planning for a New Dual Upper Limb Rehabilitation Robot

The increasing utilization of upper limb rehabilitation robots in rehabilitation therapy has brought to light significant safety concerns regarding their mechanical structures and control systems. This study focuses on a six degrees of freedom (DOF) upper limb rehabilitation robot, which has been designed with an emphasis on safety through careful consideration of its mechanical structure and trajectory planning. Various parameter schemes for the shoulder joint angles were proposed, and the robotic arm’s structure was developed by analyzing the spatial motion trajectories of the shoulder joint motor. This design successfully achieves the objective of minimizing the installation space while maximizing the range of motion. Additionally, an enhanced artificial field method is introduced to facilitate the planning of self-collision avoidance trajectories for dual-arm movements. This approach effectively mitigates the risk of collisions between the robotic arm and the human body, as well as between the two robotic arms, during movement. The efficacy of this method has been validated through experimental testing.

Cooperative game-theoretic optimization of adaptive robust constraint-following control for fuzzy mechanical systems under inequality constraints

Cooperative game-theoretic optimization of adaptive robust constraint-following control for fuzzy mechanical systems under inequality constraints

Study On the Mechanical Device, Control System, and Sensor of Biaxial Actuated Artificial Anal Sphincter Actuator for Treating Fecal Incontinence

Abstract Artificial anal sphincter, Actuator, Mechanical device, Control system, Pressure sensor

Development of Lightweight 6 m Deployable Mesh Reflector Antenna Mechanisms Based on a Superelastic Shape Memory Alloy

This paper describes the design and experimental verification of a 6 m parabolic deployable mesh reflector antenna mechanism based on a superelastic shape memory alloy. This antenna mainly consists of a deployable primary reflector with a superelastic shape memory alloy-based hinge mechanism and a fixed-type secondary reflector mast, where a rotary-type holding and release mechanism and deployment speed control system are installed. The main feature of this antenna is the application of a superelastic shape memory alloy to the mechanism, which has the advantages of plastic deformation resistance, high damping, and fatigue resistance. A shape memory alloy is applied to the hinge mechanism of each primary reflector rib and to the rotary-type holding and release mechanism as a deployment mechanism. In addition, a superelastic shape memory alloy wire is applied to the antenna in the circumferential direction to maintain the curvature of the primary reflector. The effectiveness of the proposed mechanism design was verified through repeated deployment tests on models of the superelastic shape memory alloy-based hinge mechanism and the antenna system.

Managerial ability, digital transformation and innovation efficiency: empirical evidence from Chinese manufacturing listed companies

Purpose This study aims to examine the relationship between managerial ability and innovation efficiency, the mediating effect of digital transformation and the moderating effect of internal control. Design/methodology/approach This study collected A-share manufacturing listed companies in China from 2008 to 2019 and analyzed the data by means of multiple regression analysis, mediating effect test, moderating effect test and heterogeneity test. Finally, the authors conducted robustness test by remeasuring key variables and adding control variables. Findings The empirical results show that the higher managerial ability can improve innovation efficiency, internal control has a positive moderating effect and digital transformation plays a partial mediating effect on the relationship between managerial ability and innovation efficiency. Specially, it is found that the mediating effect of digital transformation is not significant in non-state-owned firms. Practical implications This study suggests that it is necessary to focus on the managerial ability in terms of both cultivation and supervision, to further deepen the digital transformation from the aspects of firms, government and society, especially to support the digital transformation of non-state-owned firms, and to make efforts to improve the corporate governance mechanism and internal control system, so as to better comprehensively realize the improvement of enterprise innovation efficiency. Originality/value Based on the mediating effect analysis of digital transformation and the moderating effect analysis of internal control, this study explores the role of managerial ability on innovation efficiency from a new perspective, expanding the related theoretical framework and research boundaries.

Analysis of oscillations of the center of pressure in postural control

Posture results from intricate interactions between the central nervous system's control mechanisms, sensory integration, and musculoskeletal responses, encompassing two levels: sustaining tonic muscle activity for posture and making adjustments to maintain balance in response to disturbances. Due to its complexity, assessing posture with simple methods is challenging, necessitating the use of advanced techniques like stabilometric platforms to measure postural stability through the center of pressure oscillations, akin to an inverted pendulum concept, offering a comprehensive understanding of postural control mechanisms. Materials and Methods: The study aims to analyze the trajectory of the center of pressure (COP) in relation to the gender of the subjects, through directional indices (DI) and oscillation ratio (OR), in the process of posture maintenance. The study included a sample of 50 young subjects (21-24 years), sports practitioners, divided into two equal groups. Results: The study findings indicate that gender does not influence COP DI. However, there's a significant disparity between anteroposterior (AP) DI values (0.70) and mediolateral (ML) DI values (0.54). The results suggest a predominant reliance on AP control mechanisms for maintaining balance, regardless of gender. When visual input is absent, there's a slight increase in AP DI (0.72) and a decrease in ML DI (0.52), indicating a shift in balance strategies. In terms of OR, significant differences are observed based on gender, oscillation direction, and visual input. Female subjects exhibit higher AP OR (6.5) compared to males (5.1). Under closed eyes conditions, both genders show decreased AP OR (6.0 for females, 4.7 for males), indicating a reliance on alternative balance strategies in the absence of visual cues. Conclusion: The study highlights the complexity of postural control and empha-sizes the influence of factors like gender and visual input on postural stability metrics, providing valuable insights for further research and clinical practice. The analysis reveals that around 60% of COP oscillations occur in the AP direction, regardless of visual input changes. This underscores the critical role of AP control in maintaining balance, suggesting targeted interventions to enhance stability should prioritize this aspect. Keywords: postural control, oscillations of the center of pressure, stabilometric platform.

Safety-critical formation control of switching uncertain Euler-Lagrange systems with control barrier functions

This paper investigates the safety-critical formation control problem with disturbance rejection for switching uncertain EL MASs in the presence of multiple stationary/moving obstacles. A safety-critical control method is proposed for achieving a collision-free formation for a group of EL systems subject to safety constraints, model uncertainties, and external disturbances. Specifically, a distributed adaptive nominal control law is designed to accomplish the formation control task. Then, based on ISSf-CBF derived safety constraints, a distributed quadratic programming problem is established for computing the optimal control input subject to safety constraints. The safety and stability of the closed-loop control system have been demonstrated. Finally, one exemplary application to safety-critical formation control of some practical multiple mechanical systems is provided to illustrate the effectiveness of the main result.

Combined Control for a Piezoelectric Actuator Using a Feed-Forward Neural Network and Feedback Integral Fast Terminal Sliding Mode Control.

In recent years, there has been significant interest in incorporating micro-actuators into industrial environments; this interest is driven by advancements in fabrication methods. Piezoelectric actuators (PEAs) have emerged as vital components in various applications that require precise control and manipulation of mechanical systems. These actuators play a crucial role in the micro-positioning systems utilized in nanotechnology, microscopy, and semiconductor manufacturing; they enable extremely fine movements and adjustments and contribute to vibration control systems. More specifically, they are frequently used in precision positioning systems for optical components, mirrors, and lenses, and they enhance the accuracy of laser systems, telescopes, and image stabilization devices. Despite their numerous advantages, PEAs exhibit complex dynamics characterized by phenomena such as hysteresis, which can significantly impact accuracy and performance. The characterization of these non-linearities remains a challenge for PEA modeling. Recurrent artificial neural networks (ANNs) may simplify the modeling of the hysteresis dynamics for feed-forward compensation. To address these challenges, robust control strategies such as integral fast terminal sliding mode control (IFTSMC) have been proposed. Unlike traditional fast terminal sliding mode control methods, IFTSMC includes integral action to minimize steady-state errors, improving the tracking accuracy and disturbance rejection capabilities. However, accurate modeling of the non-linear dynamics of PEAs remains a challenge. In this study, we propose an ANN-based IFTSMC controller to address this issue and to enhance the precision and reliability of PEA positioning systems. We implement and validate the proposed controller in a real-time setup and compare its performance with that of a PID controller. The results obtained from real PEA experiments demonstrate the stability of the novel control structure, as corroborated by the theoretical analysis. Furthermore, experimental validation reveals a notable reduction in error compared to the PID controller.

Input‐output linearization and decoupling of mechanical control systems

AbstractIn this article, we present the problem of simultaneous input‐output feedback linearization and decoupling (noninteracting) for mechanical control systems with outputs. We show that the natural requirement of preserving mechanical structure of the system and of transformations imposes supplementary conditions when compared to the classical solution of the same problem for general control systems. These conditions can be expressed using objects on the configuration space only. We illustrate our results with several examples of mechanical control systems.

Output Feedback Based Adaptive Continuous Sliding Mode Control for Mechanical Systems With Actuator Faults

Output Feedback Based Adaptive Continuous Sliding Mode Control for Mechanical Systems With Actuator Faults

Integrated Vehicle-Following Control for Four-Wheel Independent Drive Based on Regenerative Braking System Control Mechanism for Battery Electric Vehicle Conversion Driven by PMSM 30 kW

Integrated Vehicle-Following Control for Four-Wheel Independent Drive Based on Regenerative Braking System Control Mechanism for Battery Electric Vehicle Conversion Driven by PMSM 30 kW

Adaptable robotics for disaster response and search & rescue: Integration of deformable smart car design and pi control

In the context of disaster response and search and rescue operations, the need for adaptable and efficient robotic systems has become increasingly evident. This research paper addresses the evolving challenges in this domain by introducing a novel DIY deformable robot equipped with advanced PI (Proportional-Integral) control. The background of this study emerges from the growing urgency to enhance the capabilities of robotics in post-disaster scenarios, where navigation through complex terrains and the swift delivery of supplies are paramount.The primary objective of this paper is to develop and assess a versatile robotic platform using a multidisciplinary approach encompassing mechanical engineering, electronics, and control systems. The core of the investigation is a DIY deformable car consisting of two sensor-equipped containers and a linking module, making it well-suited for search and rescue missions. This paper contains the implementation of a PI control system to govern the robot's mobility and adaptability. This includes a detailed examination and demonstration of the PI control mechanism, encompassing its proportional and integral components. The actual results also indicate that the smart car controlled by the PI controller has better performance in both stability and speed.

A novel finite-time leader-follower consensus control for a disturbed mechanical nonlinear system in presence of actuator saturation

This paper presents a novel leader-follower consensus control for a particular class of nonlinear multi-agent mechanical systems in the presence of control input constraints and external disturbances which includes robot system dynamics with a wide range of potential applications in industry. In this case, one of the agents is selected as the leader to direct the other agents in such a way that the whole system can reach consensus within certain prescribed performance transient bounds. Due to the presence of disturbances in most practical systems, the effect of limited disturbance in the consensus control method has been investigated, and actuator saturation is included in the design process. A terminal sliding mode control method has been adapted to ensure the stability of the overall system and fast finite-time leader-follower consensus control. The simulation results of the multi-agent nonlinear robot system in MATLAB environment, in different scenarios with simultaneous consideration of actuator saturation and external disturbance, will show the efficiency of the proposed control method.