tendon-driven actuation

This work addresses the longstanding trade-off between compliance and high-performance dynamic control in continuum soft robots by proposing a co-designed approach that preserves full intrinsic compliance while achieving unprecedented speed and precision. Through an integrated framework combining direct-drive actuation, a tendon routing scheme enabling coupled bending–torsion deformation, and a structured nonlinear control architecture grounded in a reduced-order strain model of the underactuated system, the study demonstrates—for the first time—the concurrent realization of distributed compliance and high-bandwidth, accurate task-space control without relying on hardware discretization or stiffness constraints. Experimental results show that the system executes Cartesian tasks such as rapid positioning and dynamic interaction at speeds nearly four times faster than existing methods while maintaining sub-millimeter accuracy, establishing a new benchmark for speed in soft robotics.

Conventional rigid wearable assistive devices for aging populations and individuals with neuromusculoskeletal disorders suffer from low force transmission efficiency and poor anatomical conformity. Method: This study proposes an integrated compliant pneumatic soft sleeve actuator fabricated from thermoplastic elastomer via an enhanced fused deposition modeling process, enabling hermetic, elastic actuators capable of linear, bending, torsional, and omnidirectional compound motions—without requiring complex anchoring mechanisms and operating stably at low pneumatic pressure. Contribution/Results: Experimental evaluation demonstrates substantial improvements in force transmission efficiency and wearer comfort, alongside advantages in lightweight design, high integration density, and multi-degree-of-freedom actuation capability. The architecture establishes an engineering-feasible paradigm for next-generation soft wearable assistive systems.

Soft robotic manipulators exhibit limited load-bearing capacity under gravity, hindering applications such as pipeline inspection, heavy-object pushing, and active grasping. To address this, we propose a high-load soft robotic arm leveraging a synergistic design of a novel chiral shear-mode negative Poisson’s ratio metamaterial (HSA) and a nestable bend–torsion coupled transmission shaft (BETR), enabling, for the first time, integrated high-fidelity large-torque transmission and self-support within a soft architecture. The system employs electrically driven soft actuators and a modular nested integration process. It achieves a vertical thrust of 2.3 kg, horizontal load capacity >600 g, base torsional resistance of 0.33 N·m, path-tracking error <5 mm, and grasp pull-off force of 20 N. Furthermore, it successfully performs autonomous in-pipe inspection with full defect identification. This work overcomes critical performance bottlenecks of soft robots under high axial loads and large torques.

To address the challenge of achieving both high load capacity and adaptive compliance in tendon-driven underactuated fingers, this paper proposes a compact, single-actuator design featuring full-joint mechanical coupling. A novel fixed-ratio synchronous tendon routing mechanism enables predictable stiffness and underactuated kinematic constraints while ensuring whole-finger unified actuation. We develop a static and kinematic model incorporating tendon elasticity and validate it experimentally using a 3D-printed prototype: under a 3 kg fingertip load, the finger achieves a stiffness of 1.2×10³ N/m, with deformation prediction error of only 1.0 mm (0.322% of finger length). This design significantly reduces complexity and weight in multi-fingered robotic hands; integrated into a five-fingered hand, it successfully accomplishes stable, adaptive grasping of diverse objects.

Addressing the challenge of simultaneously achieving high-precision manipulation and collision safety in unstructured human–robot collaborative environments, this paper proposes a passive dual-mode stiffness flexible wrist mechanism. The core innovation is a novel sensor-free, passive stiffness-switching mechanism based on soft buckling honeycomb structures, enabling autonomous, adaptive transitions between high- and low-stiffness states without sensors or active control. The mechanism features a modular mechanical interface compatible with mainstream grippers—including Panda, Robotiq, and BaRiFlex. Experimental results demonstrate that the wrist sustains a 500 g load stably under ≤1 cm fingertip deflection. In surface wiping, precise pick-and-place, and confined-space grasping tasks, it significantly simplifies control logic while enhancing operational robustness and contact safety.

This work proposes SoFiE, a modular soft finger exoskeleton designed to overcome the limitations of conventional rigid hand exoskeletons, which are often bulky and incompatible with natural finger kinematics. The system employs a 3D-printed compliant structure actuated by tendon-driven DC motors to provide lightweight, low-profile flexion assistance, while passive elastic elements enable extension. Innovatively integrating StretchSense resistive proprioceptive springs and MagSense magnetic tactile sensors—fused with motor encoder feedback—SoFiE achieves accurate finger pose estimation, object stiffness recognition, and grasp-type classification. Its fully wireless, co-located actuation-sensing architecture demonstrates high-fidelity finger state perception and adaptability across multiple tasks in experimental validation, offering an effective solution for soft wearable hand-assistive robotics.

This work addresses the challenge that existing soft metamaterials struggle to achieve controllable, long-range transmission of localized deformations within modular assemblies, limiting their application in complex functionalities required by soft robotics and wearable electronics. The study introduces, for the first time, the concept of mechanical impedance into soft metamaterial design, proposing a mechanical impedance–guided framework based on unit-cell topological optimization. By tailoring nonlinear interactions between modules, this approach enables programmable deformation transmission in both homogeneous and heterogeneous assemblies solely through unit topology, while supporting reconfiguration and reassembly. Integrating a position-dependent nonlinear mechanical model with compliant switching control, the method successfully demonstrates obstacle-avoiding deformation transmission, fault-tolerant grasping, intrinsic signal processing, low-latency mechanical LED displays, and gesture sensing, thereby validating its high composability, scalability, and multifunctionality.

This work proposes a humanoid tendon-driven robotic hand powered by remotely located Peano-HASEL electrohydraulic soft actuators to achieve safe and dexterous manipulation in unstructured environments. By relocating the actuators to the forearm, electrical components are isolated from the hand, enhancing safety, while a 1:2 pulley mechanism amplifies tendon displacement for improved range of motion. Leveraging the intrinsic force-limiting behavior of HASEL actuators and real-time actuator current signals, the system enables self-sensing grasp control without external force or position sensors, facilitating contact detection and closed-loop manipulation. The platform successfully executes diverse grasping tasks, including damage-free handling of extremely fragile objects such as paper balloons, demonstrating high dexterity and inherent safety.

This work proposes a tendon-driven continuum robot featuring a tapered flexible backbone fabricated from thermoplastic polyurethane (TPU), addressing limitations of conventional designs—such as high cost, poor customizability, and the difficulty of simultaneously achieving high curvature and distal compliance—in flexible manipulation tasks. An integrated electronic base enables precise tendon tension control and sensing. For the first time, the spatially varying tapered cross-section is explicitly incorporated into a forward dynamic-static model based on Cosserat rod theory to capture the influence of geometric tapering on stiffness distribution. Leveraging fused deposition modeling 3D printing and parametric CAD design, the system achieves low-cost, rapid assembly, and high customizability. Experimental calibration demonstrates centimeter-level shape prediction accuracy, and successful teleoperated endoscopic grasper tasks validate the robot’s efficacy in complex flexible manipulation scenarios.

This work addresses the limitations of high-degree-of-freedom dexterous hands—namely, bulky actuators, excessive distal mass, and severe heat generation—which hinder sensing capabilities and maintainability. The authors propose a remote tendon-driven design that relocates motors away from the hand, integrating modular 3D-printed structures with a multimodal sensing system encompassing joint angles, tactile feedback, motor current, and intra-palm stereo vision. This approach yields a lightweight, highly maintainable 21-degree-of-freedom hand with rich perceptual capabilities. Key innovations include spring-return tendon-driven fingers, rapid tendon connectors, and a systematic analysis of sheath length and friction losses to optimize transmission efficiency and control performance. The system achieves 25 N fingertip force under 1-meter remote actuation, demonstrating robust load capacity, sensing accuracy, and closed-loop control efficacy. All hardware and software are openly released.