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Movement Intent Detection for Upper-Limb Rehabilitation Exoskeleton Based on Series Elastic Actuator as Force Sensor
Double Air Chambers Pneumatic Artificial Muscle and Non-Hysteresis Position Control
Increasing Payload Capacity of a Continuum Soft Robot Using Bio-Inspired Ossicle Reinforcement
Development of Anthropomorphic Arm for Service Robot CHARMIE
Design and Implementation of a Hardware-in-the-Loop Air Load Simulation System for Testing Aerospace Actuators

Journal Description

Actuators

Actuators is an international, peer-reviewed, open access journal on the science and technology of actuators and control systems published monthly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within SCIE (Web of Science), Scopus, Inspec, and other databases.
Journal Rank: JCR - Q2 (Engineering, Mechanical) / CiteScore - Q2 (Control and Optimization)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.5 days after submission; acceptance to publication is undertaken in 1.9 days (median values for papers published in this journal in the first half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 2.2 (2023); 5-Year Impact Factor: 2.4 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2076-0825

Latest Articles

27 pages, 1772 KiB

Open AccessArticle

Association Model-Based Intermittent Connection Fault Diagnosis for Controller Area Networks

by Longkai Wang, Shuqi Hu and Yong Lei

Actuators 2024, 13(9), 358; https://doi.org/10.3390/act13090358 (registering DOI) - 14 Sep 2024

Controller Area Networks (CANs) play an important role in many safety-critical industrial systems, which places high demands on their reliability performance. However, the intermittent connection (IC) of network cables, a random and transient connectivity problem, is a common but hard troubleshooting fault that [...] Read more.

Controller Area Networks (CANs) play an important role in many safety-critical industrial systems, which places high demands on their reliability performance. However, the intermittent connection (IC) of network cables, a random and transient connectivity problem, is a common but hard troubleshooting fault that can cause network performance degradation, system-level failures, and even safety issues. Therefore, to ensure the reliability of CANs, a fault symptom association model-based IC fault diagnosis method is proposed. Firstly, the symptoms are defined by examining the error records, and the domains of the symptoms are derived to represent the causal relationship between the fault locations and the symptoms. Secondly, the fault probability for each location is calculated by minimizing the difference between the symptom probabilities calculated from the count information and those fitted by the total probability formula. Then, the fault symptom association model is designed to synthesize the causal and the probabilistic diagnostic information. Finally, a model-based maximal contribution diagnosis algorithm is developed to locate the IC faults. Experimental results of three case studies show that the proposed method can accurately and efficiently identify various IC fault location scenarios in networks. Full article

(This article belongs to the Section Control Systems)

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36 pages, 9780 KiB

Open AccessArticle

Multivariate Prediction Soft Sensor Model for Truck Cranes Based on Graph Convolutional Network and Random Forest

by Shengfei Ji, Wei Li, Bo Zhang, Wen Ji, Yong Wang and See-Kiong Ng

Actuators 2024, 13(9), 357; https://doi.org/10.3390/act13090357 - 12 Sep 2024

Truck cranes, which are crucial construction equipment, need to maintain good operational performance to ensure safe use. However, the complex and ever-changing working conditions they face often make it challenging to test their performance effectively. To address this issue, a multi-input and multi-output [...] Read more.

Truck cranes, which are crucial construction equipment, need to maintain good operational performance to ensure safe use. However, the complex and ever-changing working conditions they face often make it challenging to test their performance effectively. To address this issue, a multi-input and multi-output soft sensor technology model is suggested, utilizing a graph convolutional network and random forest to predict key performance indicators of crane operations such as luffing, telescoping, winching, and slewing under varying conditions. This method aims to streamline the process of testing and debugging truck cranes, ultimately reducing time and costs. Initially, the graph convolutional network model is employed to extract relevant feature information linked to the target variable. Subsequently, using this feature information and the RF model, multiple decision trees are constructed for regression prediction of the target variables. An operational dataset reflecting the crane’s actual working conditions is then generated to assess the graph convolutional network and random forest model. The effectiveness of this approach is further confirmed through comparisons with other methods like gradient boosting trees, support vector regression, and multi-layer perceptron. Full article

(This article belongs to the Section High Torque/Power Density Actuators)

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18 pages, 9753 KiB

Open AccessArticle

Research on Vibration Reduction Characteristics of High-Speed Elevator with Rolling Guide Shoes Based on Hydraulic Damping Actuator

by Dongming Hu, Qibing Wang and Jianming Zhan

Actuators 2024, 13(9), 356; https://doi.org/10.3390/act13090356 - 12 Sep 2024

This paper endeavors to tackle the issue of horizontal vibrations encountered in high-speed and ultra-high-speed elevator cabins during operation. Given the limitations of traditional passive-control guide shoes in effectively mitigating these vibrations and the complexity and cost associated with active control systems, a [...] Read more.

This paper endeavors to tackle the issue of horizontal vibrations encountered in high-speed and ultra-high-speed elevator cabins during operation. Given the limitations of traditional passive-control guide shoes in effectively mitigating these vibrations and the complexity and cost associated with active control systems, a novel approach involving passive-control rolling guide shoes (PCRGS) integrated with hydraulic damping is explored. The PCRGS incorporates a hydraulic actuator and hydraulic damping, which can be modeled by a mechanical and hydraulic co-simulation model using AMESim2020 software. The simulation reveals a substantial reduction in cabin vibrations equipped with PCRGS. Specifically, under pulse excitation, the reduction ranges from 26.2% to 27.5%; under white noise excitation, it varies between 14.3% and 17.1%; and under sine wave excitation, the reduction spans 21.2% to 24.1%. Notably, the system meets the stringent ‘Excellent’ (<=0.07 m/s²) performance criteria under sine wave excitation at lower frequencies, signifying its high effectiveness. These findings not only underscore the potential of hydraulic passive-control guide shoes in mitigating elevator vibrations but also provide invaluable guidance for their further development and refinement. Full article

(This article belongs to the Special Issue Intelligent and Precision Control for Mechatronic/Electro-Hydraulic Systems)

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14 pages, 3525 KiB

Open AccessArticle

Restoring Model of a Pneumatic Artificial Muscle with Structure Parameters: Analysis and Identification

by Minh Ky Nguyen, Van Chon Trinh, Ngoc Yen Phuong Vo and Thanh Danh Le

Actuators 2024, 13(9), 355; https://doi.org/10.3390/act13090355 - 12 Sep 2024

This paper will develop the restoring model of a commercial pneumatic artificial muscle (PAM) based on a McKibben structure, which comprises an elastic element connected with a viscoelastic element in parallel. The elastic element is generated by compressed air inside the rubber bellow; [...] Read more.

This paper will develop the restoring model of a commercial pneumatic artificial muscle (PAM) based on a McKibben structure, which comprises an elastic element connected with a viscoelastic element in parallel. The elastic element is generated by compressed air inside the rubber bellow; meanwhile, the viscoelasticity is affected by the rubber material. In particular, the viscoelastic property of the rubber material is proposed based on the Maxwell model. Instead of derivative of integer orders, an equation of motion of the fractional model is introduced to better capture the amplitude- and frequency-dependent property of the viscoelasticity of the PAM. The equation expressing the hysteresis loop due to the viscoelasticity of the PAM material will then be analyzed and built. A water cycle algorithm is employed to determine the optimal set of the proposed model. To evaluate the effectiveness of the proposed model, a comparison between the simulation calculated from the proposed model and experimental data is considered under harmonic force excitation. This study’s results give potential insight into the field of system dynamic analysis with the elastic element being PAM. Full article

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23 pages, 40746 KiB

Open AccessArticle

An Admittance Parameter Optimization Method Based on Reinforcement Learning for Robot Force Control

by Xiaoyi Hu, Gongping Liu, Peipei Ren, Bing Jia, Yiwen Liang, Longxi Li and Shilin Duan

Actuators 2024, 13(9), 354; https://doi.org/10.3390/act13090354 - 12 Sep 2024

When a robot performs tasks such as assembly or human–robot interaction, it is inevitable for it to collide with the unknown environment, resulting in potential safety hazards. In order to improve the compliance of robots to cope with unknown environments and enhance their [...] Read more.

When a robot performs tasks such as assembly or human–robot interaction, it is inevitable for it to collide with the unknown environment, resulting in potential safety hazards. In order to improve the compliance of robots to cope with unknown environments and enhance their intelligence in contact force-sensitive tasks, this paper proposes an improved admittance force control method, which combines classical adaptive control and machine learning methods to make them use their respective advantages in different stages of training and, ultimately, achieve better performance. In addition, this paper proposes an improved Deep Deterministic Policy Gradient (DDPG)-based optimizer, which is combined with the Gaussian process (GP) model to optimize the admittance parameters. In order to verify the feasibility of the algorithm, simulations and experiments are carried out in MATLAB and on a UR10e robot, respectively. The experimental results show that the algorithm improves the convergence speed by 33% in comparison to the general model-free learning method, and has better control performance and robustness. Finally, the adjustment time required by the algorithm is 44% shorter than that of classical adaptive admittance control. Full article

(This article belongs to the Section Actuators for Robotics)

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13 pages, 25407 KiB

Open AccessArticle

Mechanical Design of a New Hybrid 3R-DoF Bioinspired Robotic Fin Based on Kinematics Modeling and Analysis

by Eliseo de J. Cortés Torres, Luis E. García Gonzales, Luis E. Villamizar Marin and Cecilia E. García Cena

Actuators 2024, 13(9), 353; https://doi.org/10.3390/act13090353 - 11 Sep 2024

The field of bioinspired underwater robots aims to replicate the capabilities of marine animals in artificial systems. Stingrays have emerged as highly promising species to be mimicked because of their flat body morphology and size. Furthermore, they are considered high-performance species due to [...] Read more.

The field of bioinspired underwater robots aims to replicate the capabilities of marine animals in artificial systems. Stingrays have emerged as highly promising species to be mimicked because of their flat body morphology and size. Furthermore, they are considered high-performance species due to their maneuverability, propulsion mode, and sliding efficiency. Designing and developing mechanisms to imitate their pectoral fins is a challenge for underwater robotic researchers mainly because the locomotion characteristics depend on the coordinated movement of the fins. In the state of the art, several mechanisms were proposed with 2 active rotation degrees of freedom (DoFs) to replicate fin movement. In this paper, we propose adding an additional active DoF in order to improve the realism in the robotic manta ray movement. Therefore, in this article, we present the mechanical design, modeling, and kinematics analysis of a 3-active-and-rotational-DoF pectoral fin inspired by the Mobula Alfredi or reef manta ray. Additionally, by using the kinematics model, we were able to simulate and compare the behaviour of both mechanisms, that is, those with 2 and 3 DoFs. Our simulation results reveal an improvement in the locomotion, and we hypothesized that with the third DoF, some specific missions, such as hovering or fast emergence to the surface, will have a better performance. Full article

(This article belongs to the Special Issue Bio-Inspired Soft Robotics)

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18 pages, 8956 KiB

Open AccessArticle

Development and Experimental Study of a Mixed-Mode Vibration Isolator Using Magnetorheological Elastomer

by Qianjie Liu, Zhirong Guo, Wei Liu, Gang Li, Shengzhi Jin, Lei Yu and Guoliang Hu

Actuators 2024, 13(9), 352; https://doi.org/10.3390/act13090352 - 11 Sep 2024

This paper proposes a mixed-mode (combining shear and squeeze working modes) vibration isolator using magnetorheological elastomer (MRE), which enables the isolator to have a larger working area and better isolation performance by combining the working modes of the MRE. Firstly, based on the [...] Read more.

This paper proposes a mixed-mode (combining shear and squeeze working modes) vibration isolator using magnetorheological elastomer (MRE), which enables the isolator to have a larger working area and better isolation performance by combining the working modes of the MRE. Firstly, based on the magnetorheological effect working principle of the MRE, the material selection and dimensional parameters of each component are determined through structural design and magnetic circuit calculation. On this basis, magnetic field simulation is conducted using Maxwell 16.0 software to analyze the distribution of magnetic field lines and magnetic induction in the working area. Simultaneously, equivalent stiffness and equivalent damping models are established to explore the variation of vibration response with external current and excitation frequency conditions. Finally, a vibration isolation experimental platform is built to test the mixed-mode MRE isolator. The experimental results are basically consistent with the simulation modeling results. The experimental results showed that when the external excitation is in the frequency range of 16 Hz, effective semi-active vibration isolation control could be achieved by applying different current inputs. The isolation effect of the system is difficult to effectively control using current input when the external excitation is at high frequency. These results validate the rationality and feasibility of the mixed-mode MRE isolator structure, which provides a good reference for the design of MRE isolators. Full article

(This article belongs to the Special Issue Magnetorheological Actuators and Dampers)

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14 pages, 6557 KiB

Open AccessArticle

A Novel Design of Soft Corrugated Actuator for Creating Precise Head and Neck Positioning System

by Veysel Erel, Sanjana Suresh, Inderjeet Singh, Allison Palomino, Faiza Tafannum, Seyedehhelya Hosseini Nami, Steve Jiang, Hao Peng, Nicholas Gans and Muthu B. J. Wijesundara

Actuators 2024, 13(9), 351; https://doi.org/10.3390/act13090351 - 11 Sep 2024

Soft robots are increasingly gaining popularity as a preferred choice for designing medical devices due to their inherently compliant and adaptable nature. As research continues to advance in this field, soft robots are poised to revolutionize healthcare by providing safer, more patient-centric solutions. [...] Read more.

Soft robots are increasingly gaining popularity as a preferred choice for designing medical devices due to their inherently compliant and adaptable nature. As research continues to advance in this field, soft robots are poised to revolutionize healthcare by providing safer, more patient-centric solutions. This paper presents the design of a novel soft corrugated actuator to create a system for positioning the head during head and neck cancer radiation therapy. Simulation and experimental data show that the presented actuator design can achieve linear expansion with respect to pressure in both free and under loading conditions. A machine learning model of the single actuator is created using experimental data (pressure, expansion, and weight) to predict the required pressure. The single actuator model’s validity is confirmed by using four actuators to achieve head flexion at a specific angle, illustrating its potential for implementation in a multi-actuator system. The preliminary design of the multi-actuator head and neck positioning system demonstrates its capability to achieve four degrees of freedom. Full article

(This article belongs to the Special Issue Actuators and Robots for Biomedical Applications)

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23 pages, 21925 KiB

Open AccessArticle

Optimising Sodium Borohydride Reduction of Platinum onto Nafion-117 in the Electroless Plating of Ionic Polymer–Metal Composites

by Eyman Manaf, Daniel P. Fitzpatrick, Clement L. Higginbotham and John G. Lyons

Actuators 2024, 13(9), 350; https://doi.org/10.3390/act13090350 - 10 Sep 2024

The effects of process parameters on the electroless plating of ionic polymer–metal composites (IPMCs) were studied in this work. Specifically, the NaBH₄ reduction of platinum onto Nafion-117 was characterised. The effects of the concurrent variation of NaBH₄ concentration, stir time and [...] Read more.

The effects of process parameters on the electroless plating of ionic polymer–metal composites (IPMCs) were studied in this work. Specifically, the NaBH₄ reduction of platinum onto Nafion-117 was characterised. The effects of the concurrent variation of NaBH₄ concentration, stir time and temperature on surface resistance were studied through a full factorial design. The three-factor three-level factorial design resulted in 27 runs. Surface resistance was measured using a four-point probe. A regression model with an R² value of 97.45% was obtained. Surface resistance was found to decrease with increasing stir time (20 to 60 min) and temperature (20 to 60 °C). These responses were attributed to increased platinisation rates, resulting in more uniform electrode deposition, confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDAX) analysis. Surface resistance decreased, going from 1% to 5% NaBH₄ concentration, but increased from 5% to 10% concentration. This behaviour was attributed to surface morphology: increased grain size inducing porous electrodes, in line with findings in the literature. The maximum tip displacement, measured through a computer vision system, as well as the maximum blocking force, measured through an analytical balance setup, were obtained for all 27 samples. The varying results were discussed with regards to surface and cross-sectional SEMs, alongside EDAX analysis. Full article

(This article belongs to the Special Issue Electroactive Polymer (EAP) for Actuators and Sensors Applications)

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18 pages, 13914 KiB

Open AccessArticle

Development of a Small-Sized Urban Cable Conduit Inspection Robot

by Yiqiang You, Yichen Zheng, Kangle Huang, Yuling He, Zhiqing Huang and Lulin Zhan

Actuators 2024, 13(9), 349; https://doi.org/10.3390/act13090349 - 10 Sep 2024

Cable conduits are crucial for urban power transmission and distribution systems. However, current conduit robots are often large and susceptible to tilting issues, which hampers the effective and intelligent inspection of these conduits. Therefore, there is an urgent need to develop a smaller-sized [...] Read more.

Cable conduits are crucial for urban power transmission and distribution systems. However, current conduit robots are often large and susceptible to tilting issues, which hampers the effective and intelligent inspection of these conduits. Therefore, there is an urgent need to develop a smaller-sized conduit inspection robot to address these challenges. Based on an in-depth analysis of the characteristics of the cable conduit working environment and the associated functional requirements, this study successfully developed a small-scale urban cable conduit inspection robot prototype. This development was grounded in relevant design theories, simulation analyses, and experimental tests. The test results demonstrate that the robot’s bracing module effectively prevents tilting within the conduit. Additionally, the detection module enables comprehensive 360-degree conduit inspections, and the vacuuming module meets the negative pressure requirements for efficient absorption of dust and foreign matter. The robot has met the expected design goals, effectively enhanced the automation of the cable conduit construction process, and improved the quality control of cable laying. Full article

(This article belongs to the Special Issue Advanced Robots: Design, Control and Application—2nd Edition)

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17 pages, 4899 KiB

Open AccessArticle

Design and Validation of an Ambulatory User Support Gait Rehabilitation Robot: NIMBLE

by Jaime Ramos-Rojas, Juan A. Castano, Pedro R. Fernández, Juan Carballeira, Emma Pérez-Martín, Julio S. Lora-Millan, Susana Borromeo and Antonio J. del-Ama

Actuators 2024, 13(9), 348; https://doi.org/10.3390/act13090348 - 9 Sep 2024

Relearning to walk requires progressive training in real scenarios—overground—along with assistance in basic tasks, such as balancing. In addition, user ability must be maximized through compliant robotic assistance as needed. Despite decades of research, gait rehabilitation robotic devices yield controversial results. This article [...] Read more.

Relearning to walk requires progressive training in real scenarios—overground—along with assistance in basic tasks, such as balancing. In addition, user ability must be maximized through compliant robotic assistance as needed. Despite decades of research, gait rehabilitation robotic devices yield controversial results. This article presents the conceptual design of a novel walking assistance and rehabilitation robot, the NIMBLE robot, aimed at providing ambulatory, bodyweight-supported gait training, assisting the user’s center of mass trajectory to aid weight transfer and dynamic balance during walking. NIMBLE consists of a robotic mobile frame, a partial bodyweight support (PBWS) system, an ambulatory lower-limb exoskeleton (Exo-H3) and a cable-driven pelvis-assisting robot. Designed as a modular structure, it differentiates hierarchical communication levels through a Robot Operating System (ROS) 2 network. We present the mechatronic design and experimental results assessing the impact of the mechatronic coupling between the robotic modules on the walking kinematics and the frame movement control performance. The robotic frame hardly affects the walking kinematics up to 2 degrees in both the sagittal and frontal planes, making it feasible for lateral balance and weight translation training. Moreover, it successfully tracks and follows user trajectories. The NIMBLE robotic frame assessment shows promising results for ambulatory gait rehabilitation. Full article

(This article belongs to the Special Issue Actuators and Robots for Biomedical Applications)

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18 pages, 5388 KiB

Open AccessArticle

Research on the Control Method of a 2DOF Parallel Platform Based on Electromagnetic Drive

by Wei Wang, Jinlong Cao, Xu Liu, Yangguang Ye, Hao Yang, Weilun Zhang and Xudong Huang

Actuators 2024, 13(9), 347; https://doi.org/10.3390/act13090347 - 9 Sep 2024

In this paper, a spatial two-degree-of-freedom (2DOF) parallel platform based on electromagnetic redundant drive and its control method are investigated. The platform is redundantly driven by three electromagnetic-spring conforming branched chains, and the design provides better flexibility and responsiveness than conventional parallel structures. [...] Read more.

In this paper, a spatial two-degree-of-freedom (2DOF) parallel platform based on electromagnetic redundant drive and its control method are investigated. The platform is redundantly driven by three electromagnetic-spring conforming branched chains, and the design provides better flexibility and responsiveness than conventional parallel structures. The introduction of the electromagnetic drive alleviates the stresses within the conventional rigid redundant drive structure and reduces the detrimental effects associated with rigid redundancy. In this paper, the structure and equivalent SPU model of the platform are first introduced, with S referring to the kinematic sub, P to the spherical sub, and U to the universal joint. The degrees of freedom of the platform are analyzed, and the inverse kinematic model and velocity Jacobi matrix are derived, so as to derive the relationship between the pitch, roll angles, and length of the gimbal chain, and the relational equation between the angle and the current is further established to realize the electromagnetic control of the parallel redundant platform. The control part is realized as follows. Firstly, the angle information of the platform is obtained from the gyroscope to the microcontroller, the filtered angle is derived through the Untraceable Kalman Filter (UKF), and the angle value can be fused with data by both the mathematical model and PID algorithm to introduce the current value required to achieve the balance and realize the balance. In the simulation part, this paper uses Simulink and Simscape in MATLAB for joint simulation, and by giving the simulated trajectory and the desired trajectory of the joints, the driving force diagrams of the three branched chains based on the Least-Second Paradigm method are derived, and the trajectory error and driving force error are given to validate the reliability of the method of this paper. Full article

(This article belongs to the Special Issue Advanced Technologies on the Control Method of Electromagnetic Actuator—Second Edition)

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23 pages, 12357 KiB

Open AccessArticle

Electro-Mechanical Brake System Architectural Design and Analysis Based on Functional Safety of Vehicles

by Jing Peng, Tong Wu, Liang Chu, Jin Rong, Xiaojun Yang and Yang Meng

Actuators 2024, 13(9), 346; https://doi.org/10.3390/act13090346 - 9 Sep 2024

Electro-mechanical brake (EMB) systems have garnered significant attention due to their distributed architecture. However, their signals from the brake pedal to the wheel-end actuators (WEAs) are transmitted electrically, meaning that any fault in EMB systems can severely impair the braking performance of vehicles. [...] Read more.

Electro-mechanical brake (EMB) systems have garnered significant attention due to their distributed architecture. However, their signals from the brake pedal to the wheel-end actuators (WEAs) are transmitted electrically, meaning that any fault in EMB systems can severely impair the braking performance of vehicles. Consequently, the functional safety issues of EMB systems are the primary limitation of their widespread adoption. In response, this study first introduced the typical architectures of EMB and evaluated the automotive safety integrity level (ASIL) that must be achieved. Based on this, an EMB system architecture that satisfies functional safety standards was proposed. To accurately analyze the main factors affecting the probabilistic metric for hardware failures (PMHF) of the architecture, the failure rate of WEAs is further discussed. Specifically, a Markov chain was employed to define the operating states of the WEA matrix. The availability of each operating state was assessed based on the fault-tolerant control strategy. Finally, the failure rates of critical EMB parts, particularly the WEA matrix, were calculated. The results indicate that the unavailability of the WEA matrix is 9.244 × 10⁻³ FIT. Furthermore, the PMHFs of the EMB system for each safety goal are 6.14 FIT, 5.89 FIT, and 6.03 FIT, respectively, satisfying the ASIL-D requirements. Full article

(This article belongs to the Special Issue Fault Detection and Isolation, Fault Tolerant Control for Autonomous and Transport Vehicles)

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20 pages, 29955 KiB

Open AccessArticle

Clamping Force Control of Electromechanical Brake Actuator Considering Contact Point between Friction Lining and Brake Disc

by Yang Meng, Tong Wu, Jin Rong, Xiaojun Yang, Jing Peng and Liang Chu

Actuators 2024, 13(9), 345; https://doi.org/10.3390/act13090345 - 9 Sep 2024

Currently, most electromechanical brake (EMB) schemes are only suitable for passenger cars, and their maximum clamping force is insufficient to satisfy the braking demands of commercial vehicles. Additionally, previous studies on clamping force control are largely based on an EMB equipped with sensors. [...] Read more.

Currently, most electromechanical brake (EMB) schemes are only suitable for passenger cars, and their maximum clamping force is insufficient to satisfy the braking demands of commercial vehicles. Additionally, previous studies on clamping force control are largely based on an EMB equipped with sensors. Due to constraints in installation space and cost, sensorless EMBs are gradually gaining attention. Furthermore, accurately identifying the contact point between the friction lining and the brake disc is the promise of clamping force control for sensorless EMBs. Hence, a sensorless EMB scheme suitable for commercial vehicles is proposed in this study. Secondly, a dynamics model of the EMB actuator is established. After a comprehensive analysis of the proposed EMB actuator, a clamping force control strategy considering the contact points between the friction lining and the brake disc is proposed. Finally, simulation analyses of the strategy are carried out. The results show that the axial length of the proposed EMB actuator is shortened by 17.6% compared with a mainstream pneumatic disc brake. Furthermore, the proposed method can accurately identify the contact points between the friction lining and the brake disc, and the proposed control strategy enables the EMB actuator to achieve the fast response, accurate tracking, and stable maintenance of the target clamping force. Full article

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14 pages, 4053 KiB

Open AccessArticle

Research on Lower Limb Exoskeleton Trajectory Tracking Control Based on the Dung Beetle Optimizer and Feedforward Proportional–Integral–Derivative Controller

by Changming Li, Haiting Di, Yongwang Liu and Ke Liu

Actuators 2024, 13(9), 344; https://doi.org/10.3390/act13090344 - 6 Sep 2024

The lower limb exoskeleton (LLE) plays an important role in production activities requiring assistance and load bearing. One of the challenges is to propose a control strategy that can meet the requirements of LLE trajectory tracking in different scenes. Therefore, this study proposes [...] Read more.

The lower limb exoskeleton (LLE) plays an important role in production activities requiring assistance and load bearing. One of the challenges is to propose a control strategy that can meet the requirements of LLE trajectory tracking in different scenes. Therefore, this study proposes a control strategy (DBO–FPID) that combines the dung beetle optimizer (DBO) with feedforward proportional–integral–derivative controller (FPID) to improve the performance of LLE trajectory tracking in different scenes. The Lagrange method is used to establish the dynamic model of the LLE rod, and it is combined with the dynamic equations of the motor to obtain the LLE transfer function model. Based on the LLE model and target trajectory compensation, the feedforward controller is designed to achieve trajectory tracking in different scenes. To obtain the best performance of the controller, the DBO is utilized to perform offline parameter tuning of the feedforward controller and PID controller. The proposed control strategy is compared with the DBO tuning PID (DBO–PID), particle swarm optimizer (PSO) tuning FPID (PSO–FPID), and PSO tuning PID (PSO–PID) in simulation and joint module experiments. The results show that DBO–FPID has the best accuracy and robustness in trajectory tracking in different scenes, which has the smallest sum of absolute error (IAE), mean absolute error (MEAE), maximum absolute error (MAE), and root mean square error (RMSE). In addition, the MEAE of DBO–FPID is lower than 1.5 degrees in unloaded tests and lower than 3.6 degrees in the hip load tests, with only a few iterations, showing great practical potential. Full article

(This article belongs to the Special Issue Actuators and Robotic Devices for Rehabilitation and Assistance)

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17 pages, 8500 KiB

Open AccessArticle

Stiffness Analysis of Cable-Driven Parallel Robot for UAV Aerial Recovery System

by Jun Wu, Honghao Yue, Xueting Pan, Yanbing Wang, Yong Zhao and Fei Yang

Actuators 2024, 13(9), 343; https://doi.org/10.3390/act13090343 - 6 Sep 2024

Unmanned Aerial Vehicle (UAV) aerial recovery is a challenging task due to the limited maneuverability of both the transport aircraft and the UAV, making it difficult to establish an effective capture connection in the airflow field. In previous studies, we proposed using a [...] Read more.

Unmanned Aerial Vehicle (UAV) aerial recovery is a challenging task due to the limited maneuverability of both the transport aircraft and the UAV, making it difficult to establish an effective capture connection in the airflow field. In previous studies, we proposed using a Cable-Driven Parallel Robot (CDPR) for active interception and recovery of UAVs. However, during the aerial recovery process, the CDPR is continuously subjected to aerodynamic loads, which significantly affect the stiffness characteristics of the CDPR. This paper conducts a stiffness analysis of a single cable and a CDPR in a flow field environment. Firstly, we derive the stiffness matrix of a single cable based on a model that considers aerodynamic loads. The CDPR is then divided into elements using the finite element method (FEM), and the stiffness matrix for each element is obtained. These element stiffness matrices are assembled to form the stiffness matrix of the CDPR system. Secondly, we analyze the stiffness distribution of a single cable at various equilibrium positions within a flow field environment. Aerodynamic loads were observed to alter the equilibrium position of the cable, thereby impacting its stiffness. The more the cable bends, the greater the reduction in its stiffness. We examine the stiffness distribution characteristics of the CDPR’s end-effector within its workspace and analyze the impact of varying flow velocities and different cable materials on the system’s stiffness. This research offers a methodology for analyzing the stiffness of CDPR systems operating in a flow field environment. Full article

(This article belongs to the Special Issue Soft Robotics: Actuation, Control, and Application)

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30 pages, 7382 KiB

Open AccessArticle

Research on the Methods for Correcting Helicopter Position on Deck Using a Carrier Robot

by Yuhang Zhong, Dingxuan Zhao and Xiaolong Zhao

Actuators 2024, 13(9), 342; https://doi.org/10.3390/act13090342 - 5 Sep 2024

When the landing position of a shipborne helicopter on the deck does not meet the requirements for towing it into the hangar, its position must first be corrected before towing can proceed. This paper studied the methods for using Shipborne Rapid Carrier Robots [...] Read more.

When the landing position of a shipborne helicopter on the deck does not meet the requirements for towing it into the hangar, its position must first be corrected before towing can proceed. This paper studied the methods for using Shipborne Rapid Carrier Robots (SRCRs) to correct helicopter positions on the deck and proposed two correction methods, the stepwise correction method and the continuous correction method, aiming to improve the efficiency of the position adjustment process. Firstly, the actual helicopter landing position deviation was divided into two components—lateral offset and fuselage yaw angle—to quantitatively assess the deviations. Then, a mathematical model of the SRCR traction system was established, and its traction motion characteristics were analyzed. The kinematic characteristics and control processes of the two proposed position correction methods were subsequently studied, revealing the coordinated control relationships between key control elements. Finally, simulations were conducted to validate the feasibility of the proposed correction methods and compare their efficiencies. The results indicated that both the stepwise and continuous correction methods effectively achieved the position correction objectives. The stepwise method was more efficient when the initial yaw angle was small, while the continuous method proved more efficient when the initial yaw angle was large and the lateral offset was minimal. The results of this study may provide a valuable reference for correcting the positions of helicopters on deck. Full article

(This article belongs to the Special Issue Advanced Robots: Design, Control and Application—2nd Edition)

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15 pages, 7996 KiB

Open AccessArticle

Wireless Hybrid-Actuated Soft Miniature Robot for Biomedical Applications

by Heera Kim, Kyongsu Lee and Gwangjun Go

Actuators 2024, 13(9), 341; https://doi.org/10.3390/act13090341 - 5 Sep 2024

Wireless soft miniature robots have been studied for biomedical applications. However, the wireless soft miniature robots developed so far are mainly composed of synthetic polymers that do not guarantee biocompatibility and biodegradability. Additionally, current soft robots have limitations in demonstrating mobility in narrow [...] Read more.

Wireless soft miniature robots have been studied for biomedical applications. However, the wireless soft miniature robots developed so far are mainly composed of synthetic polymers that do not guarantee biocompatibility and biodegradability. Additionally, current soft robots have limitations in demonstrating mobility in narrow spaces, such as blood vessels within the body, by using their flexible body. This study proposes a wireless hybrid-actuated soft miniature robot for biomedical applications. The proposed soft miniature robot consists of biodegradable chitosan and magnetic nanoparticles (MNPs) and is fabricated into an eight-arm shape by laser micromachining. The soft miniature robot can implement hydrogel swelling and magnetic-actuated shape morphing by using the difference in MNP density and magnetic field responsiveness within the robot body, respectively. Furthermore, the soft miniature robot can be guided by external magnetic fields. As feasibility tests, the soft miniature robot demonstrated on-demand pick-and-place motion, grasping a bead, moving it to a desired location, and releasing it. Furthermore, in an in-channel mobility test, the flexible body of the soft miniature robot passed through a tube smaller in size than the robot itself through magnetically actuated shape morphing. These results indicate that the soft miniature robot with controllable shape change and precise magnetic-driven mobility can be a minimally invasive surgical robot for disease diagnosis and treatment. Full article

(This article belongs to the Special Issue Bio-Inspired Soft Robotics)

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22 pages, 4230 KiB

Open AccessArticle

Active Disturbance Rejection Control for the Trajectory Tracking of a Quadrotor

by Mario Ramírez-Neria, Alberto Luviano-Juárez, Jaime González-Sierra, Rodrigo Ramírez-Juárez, Joaquín Aguerrebere and Eduardo G. Hernandez-Martinez

Actuators 2024, 13(9), 340; https://doi.org/10.3390/act13090340 - 5 Sep 2024

In the last decade, quadrotors have gained popularity among industry and academia due to their capabilities and the various applications in which they can be found. In addition to the above, because this is an underactuated system, researchers have found it a great [...] Read more.

In the last decade, quadrotors have gained popularity among industry and academia due to their capabilities and the various applications in which they can be found. In addition to the above, because this is an underactuated system, researchers have found it a great challenge to control. Despite this, there is a wide variety of methodologies in the literature to control this type of system. Based on the above, this work proposed an alternative to trajectory tracking control for quadrotor unmanned aerial vehicles (UAV). The problem was divided into two main control loops: an outer control loop for the position coordinates, tackled through linear active disturbance rejection controllers (ADRC), and an inner control loop related to the orientation variables, addressed via robust proportional-integral-differential (PID) controllers. Furthermore, a generalized proportional integral observer (GPIO) was implemented to estimate the velocity and internal and external disturbances; therefore, the control strategy only depended on the attitude (position and orientation) quadrotor measurements. Then, the control performance was tested through numerical simulations and experimental tests, including wind disturbance inputs. Full article

(This article belongs to the Special Issue Dynamics and Control of Underactuated Systems)

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21 pages, 5979 KiB

Open AccessArticle

Construction of Knowledge Graph for Air Compressor Fault Diagnosis Based on a Feature-Fusion RoBERTa-BiLSTM-CRF Model

by Xiaqiu Xiao, Buyun Sheng, Gaocai Fu and Yingkang Lu

Actuators 2024, 13(9), 339; https://doi.org/10.3390/act13090339 - 5 Sep 2024

Diagnosing complex air compressor systems with traditional data-driven deep learning models often results in isolated fault diagnosis, ignoring correlations between concurrent faults. This paper introduces a knowledge graph construction approach for the air compressor fault diagnosis field, using after-sales business data as the [...] Read more.

Diagnosing complex air compressor systems with traditional data-driven deep learning models often results in isolated fault diagnosis, ignoring correlations between concurrent faults. This paper introduces a knowledge graph construction approach for the air compressor fault diagnosis field, using after-sales business data as the source. We propose a model based on Robustly Optimized Bidirectional Encoder Representations from Transformers (RoBERTa), specifically tailored for constructing a knowledge graph for air compressor fault diagnosis. By integrating Whole Word Masking (WWM) technology, Bidirectional Long Short-Term Memory (BiLSTM), and Conditional Random Fields (CRFs), our approach effectively extracts specific entities from unstructured data. On our dataset, the model achieved an average accuracy of 0.7962 and an F1 score of 0.7956, demonstrating notable improvements in both accuracy and recall for entity recognition tasks. The extracted entities were subsequently stored in a Neo4j graph database, facilitating the construction of a domain-specific knowledge graph for air compressor fault diagnosis. Full article

(This article belongs to the Special Issue AI, Designing, Sensing, Instrumentation, Diagnosis, Controlling, and Integration of Actuators in Digital Manufacturing—Volume II)

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