Search Results (1,723)

This research aims to investigate the practicality and feasibility of pneumatic muscle actuators (PMAs) applied in the pneumatic servo system. The mechanism consists of closed symmetrical planar robotic arms driven by two pairs of opposing PMAs, whose structure is similar to human arms. Importantly, the two distal links (or wrist parts) are combined into a collective end-effector, whose desired position is controlled only by the two shoulder angle joints. When two pairs of PMAs are attached to the upper arms, they actuate each shoulder and assist in the movement of the arms. However, the nonlinear behavior, high hysteresis, low damping, and time-varying characteristics of PMAs significantly limit their controllability. Therefore, to effectively address these challenges, a Fourier series-based adaptive sliding mode controller with H_∞ (FSB-ASMC + H_∞) is employed to achieve accurate path tracking of the PMAs. This control approach not only compensates for approximation errors, disturbances, and unmodeled dynamics but also ensures the desired H_∞ positioning performance of the overall system. The controller method can not only effectively prevent approximation errors, disturbances, and un-modeled dynamics but can also ensure the required H_∞ positioning performance of the whole system. Thus, the results of the experiment showed that the control strategy for the system collocating the FSB-ASMC + H_∞ can attain excellent control performance. Full article

This work introduces two cooperative dielectric elastomer actuator (DEA) array designs, enabling comparison between a fully soft, wearable-oriented system and a rigid, high-performance platform. The soft silicone-based array achieves strokes up to 1.9 mm and maintains 44% displacement under strong bending, demonstrating suitability for haptic feedback in wearable applications. The rigid prototype, based on thermoformed buckling beams, provides strokes up to 2.8 mm, reduced hysteresis, improved stability, and reproducible fabrication, while allowing fine-tuning of preload conditions. Experiments revealed frequency-dependent coupling, enabling stimulation of defective actuators via neighboring elements and amplification of single-element strokes through cooperative excitation. Furthermore, self-sensing effects were exploited for error detection. These results underline the potential of DEA arrays for decentralized control, fault-tolerant actuation, and future applications in soft robotics and wearable systems. Full article

The global agricultural sector faces escalating labor shortages and post-harvest losses, particularly in delicate crop handling. This study introduces an integrated soft robotic harvesting system addressing these challenges through four key innovations. First, a low-cost, high-yield fabrication method for silicone-based soft grippers is proposed, reducing production costs by 60% via compressive-sealing molds. Second, a decentralized IoT architecture with edge computing achieves real-time performance (42 fps to 73 fps) on affordable hardware (around $180 per node). Third, a lightweight vision pipeline combines handcrafted geometric features and contrast analysis for crop maturity assessment and gripper tracking under occlusion. Fourth, a Neo-Hookean-based statics model incorporating circumferential stress and variable cross-sections reduces tip position errors to 5.138 mm. Experimental validation demonstrates 100% gripper fabrication yield and hybrid feedforward–feedback control efficacy. These advancements bridge the gap between laboratory prototypes and field-deployable solutions, offering scalable automation for perishable crop harvesting. Full article

This paper deals with the mechanical design and kinematic analysis of an autonomous wrist for space assembly (AWSA) whose actuators are activated by DC motors and ball screw drives. This robotic wrist was developed and built as a prototype to investigate in-space robotic operations, including maintaining and repairing spacecraft of the US National Aeronautics and Space Administration (NASA), such as the International Space Station (ISS) or satellites. Despite its disadvantages, such as a small workspace and low maneuverability, a parallel structure instead of a serial structure was selected for the design of the AWSA due to several advantages it has over a serial robot manipulator (SRM), including higher payload, greater stiffness, and better stability. The present paper also introduces a hybrid concept for robotic space operations, which combines an SRM performing gross motion and a parallel robot manipulator (PRM) performing fine motion. It then discusses the design and construction of the DC motor actuators and ball screw drives and presents the kinematic equations developed for the AWSA. This paper provides a closed-form solution to the inverse kinematics of the AWSA and a numerical solution using the Newton–Raphson method for its forward kinematics. Full article

Soft robotics has emerged as a promising approach for safe human–machine interaction, adaptive manipulation, and bioinspired motion, yet its progress relies on accurate material characterization and structural analysis of actuators. This study presents the mechanical behavior and stress analysis of a stereolithography-printed pneumatic actuator with antagonistic architecture, fabricated using Elastic 50A resin V2. Uniaxial tensile tests were performed according to ASTM D412 to derive material parameters, which were fitted to hyperelastic constitutive models. The Yeoh model was identified as the most accurate and implemented in finite element simulations to predict actuator deformation under multiple pressurization modes. Results revealed critical stress zones and established operational pressure limits of 110–130 kPa, beyond which the material approaches its tensile strength. Experimental testing with a controlled pneumatic system validated the numerical predictions, confirming both bending and multidirectional actuation as well as structural failure thresholds. The integration of material characterization, numerical modeling, and experimental validation provides a robust workflow for the design of SLA-fabricated antagonistic actuators. These findings highlight the advantages of combining digital fabrication with antagonistic actuation and material modeling to expand the understanding of soft robots’ behavior. Full article

In modern robotics, actuator performance is fundamental to achieving efficient and durable motion, with compactness and torque density being especially critical. Compact actuators enable integration in space-constrained systems without compromising functionality, while high torque density ensures powerful output relative to size, enhancing efficiency and versatility. Harmonic gearboxes embody these qualities, offering lightweight design, zero backlash, and excellent torque density, which have made them a standard choice in robotics. However, their widespread adoption is limited by high manufacturing costs due to the precision machining required. To address this challenge, the authors previously introduced RM-Act, a Radial Modular Actuator employing two synchronous belts as harmonic speed reducers. Building on this concept, RM-Act 2.0 is introduced as an improved version that employs a single synchronous belt. This design reduces transmission slippage, improves torque density, and offers greater modularity with a wider range of reduction ratios. The work details the development and validation of RM-Act 2.0 through a functional prototype and performance model, highlighting its advancements over the original RM-Act in compactness and torque density. Full article

If elastic elements are introduced into the mechanical architecture of a robotic manipulator, a free vibration response (Natural Motion) arises that can be exploited to reduce energy consumption in cyclic motions, such as pick-and-place tasks. In this work, this approach is applied to the RR-4R-R manipulator, which is derived from the SCARA robot by replacing the prismatic joint that drives the vertical motion of the end-effector with a four-bar mechanism. This mechanical modification lowers friction and facilitates the introduction of a balancing elastic element. If the elastic element is designed to provide indifferent equilibrium at any position (exact elastic balancing), the actuators need only to overcome the inertial forces; this approach is convenient for slow motions. Conversely, if the elastic element balances gravity exactly only in the median vertical position of the end-effector, Natural Motion around this position arises, and it can be exploited to reduce energy consumption in fast cyclic motions, where inertial forces become prevalent. The threshold of convenience between exact balancing and natural balancing has been evaluated for the RR-4R-R robot by means of a multibody model, assessing different performance indices: the maximum torque of the four-bar actuator, the integral control effort, and the mechanical energy. The simulation campaign was carried out considering different trajectory shapes and the influence of finite stop phases, highlighting the potential benefits of exploiting Natural Motion in robotized manufacturing lines. Full article

Soft robots demonstrate great potential for underwater exploration, particularly in tasks such as locomotion and biological sampling in fragile marine habitats. However, developing new forms of interaction with underwater life remains a challenge due to inadequate soft mechanisms for studying the behavior of marine invertebrates. We present a 7-cm in diameter anemone robot (“Soromone”) capable of performing biological sea anemones’ wiggling behavior under the water. Inspired by the body forms of adult cnidaria, we developed a morphing mechanism that serves as both structure and actuator for the Soromone’s behavior using a soft tectonics approach—a multistep, multiscale, heterogeneous soft material fabrication technique. As an actuator, the morphing mechanism can precisely control the Soromone via a fluid system; as a structure, it can reinstate the Soromone’s original shape by incorporating various degrees of stiffness or softness into a single piece of material during fabrication. Our study demonstrates the advantages of applying a Soromone under water, including increasing water flow for enhanced nutrient uptake, waste removal, and gas exchange. This cnidaria-inspired soft robot could potentially be adapted for interaction with coral reef ecosystems by providing a safe environment for diverse species. Future soft robotics design paradigms based on a soft tectonics approach could expand the variability and applicability of soft robots for underwater exploration and habitation. Full article

With the global ageing population and the increasing prevalence of mobility impairments, the demand for effective and comfortable rehabilitation and assistive solutions has grown rapidly. Soft exoskeletons have emerged as a key direction in the development of wearable rehabilitation devices. This review examines how these systems are designed and controlled, as well as how they differ from the rigid exoskeletons that preceded them. Made from flexible fabrics and lightweight components, soft exoskeletons use pneumatic or cable mechanisms to support movement while keeping close contact with the body. Their compliant structure helps to reduce joint stress and makes them more comfortable for long periods of use. The discussion in this paper covers recent work on lower-limb designs, focusing on actuation, power transmission, and human–robot coordination. It also considers the main technical barriers that remain, such as power supply limits, the wear and fatigue of soft materials, and the challenge of achieving accurate tracking performance, low latency, and resilience to external disturbances. Studies reviewed here show that these systems help users regain functionality and improve rehabilitation, while also easing caregivers’ workload. The paper ends by outlining several priorities for future development: lighter mechanical layouts, better energy systems, and adaptive control methods that make soft exoskeletons more practical for everyday use as well as clinical therapy. Full article

Industrial Robots (IRs) are typically employed as flexible machines to perform many types of repetitive and intensive tasks within fenced safe areas, ensuring high productivity and cost efficiency. However, their rigid programming approaches often pose challenges during cell commissioning and reset, hindering the implementation of self-reconfigurable systems. In addition, several production lines still need the presence of skilled operators to conduct assisted assembly operations and inspections. This motivates the growing interest in the development of innovative solutions for supporting safe and efficient human–robot collaborative applications. The manual guidance of the IR end-effector is a representative functionality of such collaboration, as it simplifies heavy-part manipulation and allows intuitive robot teaching and programming. The present study reports a sensor-based approach for enabling manual guidance operations with high-payload IRs and discusses its practical implementation on a production cell with an extended workspace. The setup features a KUKA robot mounted on a custom linear track actuated via Beckhoff technology to enable flexible assembly and machining operations. The developed logic and its software configuration, split into multiple control units to allow the manual guiding of both the 6-axis IR and the linear track unit, are described in detail. Finally, an experimental demonstration involving two users with different levels of expertise was conducted to evaluate the approach during target teaching on a physical cell. The results showed that the proposed manual guidance method significantly reduced task completion time by more than 55% compared with the conventional teach pendant, demonstrating the effectiveness and practical advantages of the developed framework. Full article

Structural heart interventions require precise navigation through tortuous and dynamic cardiac anatomies. However, current guide sheaths often lack sufficient maneuverability for positioning additional catheters. To address these limitations, this paper presents the design and evaluation of a robotic guide sheath with a dual-bendable, compressible tip. The sheath is capable of navigating complex cardiac anatomies for multiple valve interventions. The system consists of a soft continuum sheath tip driven by tendons, a laser-cut compact motorized actuation bed, and a joystick-controlled tendon actuation mechanism. A constant-curvature kinematic model maps actuation inputs to tip bending in 3D, while a custom software interface enables real-time control. Mechanical evaluation (tension, maximum bending, and contraction tests) demonstrated low actuation tension requirements (0.78 N), a wide bending range (from 80° to 90°), and promising tip compressibility (average 5 mm). Trajectory-following tests showed good accuracy, with an average error of 3.34 mm. Catheter guidance trials further validated the sheath’s ability to navigate to the right atrium and guide additional catheters effectively. This work presents a proof-of-concept robotic guide sheath with enhanced maneuverability and adaptability, establishing a foundation for future integration of sensing, automation, and clinical applications. Full article

This study presents a belt sanding robot for large convex surfaces together with a proportional–integral force control method. Sanding belt tension strongly affects area coverage and spatial normal-force uniformity on large curved surfaces; existing approaches typically use fixed tool positions or lack active tension regulation, which limits coverage and makes force distribution difficult to control. The mechanism consists of two series elastic actuator arms and an active re-tensioner that adjusts belt tension during contact. In contrast to a conventional belt sander, the series elastic configuration enables indirect estimation of the reaction force without load cells and provides compliant interaction with contact transients. The system is evaluated on curved steel plates using vertical scans with a belt width of 50 mm and a drive wheel speed of 300 rpm. Performance is reported for two target curvature values, namely 0.47 and 1.37, with five trials for each condition. The control objective is a constant normal force along the contact, achieved through proportional–integral control of the arms for normal-force tracking and the re-tensioner for belt tension regulation. To quantify spatial force uniformity, the distribution rate is defined as the ratio of the difference between the maximum and minimum normal forces to the maximum normal force measured across the belt–workpiece contact region. Compared with a simple belt sander baseline, the proposed system increased the sanded area coverage by 31.85%, from 62.20% to 94.05%, at the curvature value of 0.47, and by 8.49%, from 81.21% to 89.70%, at the curvature value of 1.37. The distribution rate improved by 113% at the curvature value of 0.47 and by 16.7% at the curvature value of 1.37. Under identical operating conditions of 50 mm belt width, 300 rpm, and five repeated trials, these results indicate higher area coverage and more uniform force distribution relative to the baseline. Full article

This paper presents the design and testing of a lightweight, low-cost robotic arm with an extended vertical range. The 9-degree-of-freedom (DOF) system comprises a 6-DOF arm and a 3-DOF gripper. To minimize weight, the six wrist and gripper joints are cable-driven, with all actuators relocated to the shoulder assembly. As a result, the wrist and gripper only weigh 222 g and 113 g, respectively, significantly reducing the inertia on the end effector. The arm utilizes a SCARA-configuration that slides along a tower for extended vertical reach. A key innovation is a closed-section frame that attaches the arm to the tower, in which the bending and torsional loads from the payload can be directly transferred onto the static structure. In contrast to conventional design, this design does not require the shoulder motor to take the bending load directly. Instead, the motor only needs to overcome the rolling friction of the reaction load. Experimental results demonstrate that this approach reduces the required motor torque by a factor of 30. Consequently, the prototype can manipulate a 3 kg payload at a 0.5 m lateral reach while weighing only 4.5 kg, costing USD 1200, and consuming a maximum of 11.1 W of power. Full article

Soft robotic grippers have emerged as crucial tools for safe and adaptive manipulation of delicate and different objects, enabled by their compliant structures. These grippers need embedded sensing that offers proprioceptive and exteroceptive feedback in order to function consistently. Resistive sensing is unique among transduction processes since it is easy to use, scalable, and compatible with deformable materials. The three main classes of resistive sensors used in soft robotic grippers are systematically examined in this review: ionic sensors, which are emerging multimodal devices that can capture both mechanical and environmental cues; tactile sensors, which detect contact, pressure distribution, and slip; and strain sensors, which monitor deformation and actuation states. Their methods of operation, material systems, fabrication techniques, performance metrics, and integration plans are all compared in the survey. The results show that sensitivity, linearity, durability, and scalability are all trade-offs across sensor categories, with ionic sensors showing promise as a new development for multipurpose soft grippers. There is also a discussion of difficulties, including hysteresis, long-term stability, and signal processing complexity. In order to move resistive sensing from lab prototypes to reliable, practical applications in domains like healthcare, food handling, and human–robot collaboration, the review concludes that developments in hybrid material systems, additive manufacturing, and AI-enhanced signal interpretation will be crucial. Full article

Nowadays, grippers are extensively employed to interact with dynamic and variable objects. Therefore, enhancing the adaptability of grippers is crucial for improving production efficiency and product quality. To address the trade-off between load capacity and interaction safety in rigid and soft grippers, this paper proposes a rigid–flexible coupling gripper with high grasping adaptability based on an underactuated structure. We conduct static analysis on the underactuated mechanism, followed by dimensional optimization using a genetic algorithm. After optimization, the grasping force error at each knuckle is reduced to 2 N, and the total grasping force reaches 38 N. The soft actuators, integrated with a rigid framework, not only increase the contact area during grasping but also mitigate the excessive concentration of contact forces, significantly improving the compliance of the gripper. Additionally, to tackle the issue of weak interfacial bonding strength caused by rigidity mismatch between rigid components and soft materials, this paper proposes a novel method of applying embedded microstructures to enhance the interfacial toughness of rigid–flexible coupling. The elastic deformation of these microstructures ensures strong interfacial connection strength both under tensile and shear stresses. Lastly, a robotic grasping platform is developed to carry out diverse grasping experiments. Experimental results show that the underactuated linkage mechanism and the flexible structure can collaboratively adjust grasping strategies when handling objects of various types, enabling stable manipulation while preventing object damage. This design effectively expands the operational applicability of the gripper. Full article