It is often easier to manufacture and experimentally characterize a soft robotic actuator than it is to construct a theoretical or finite element model to understand its mechanics. In many cases, soft actuators with reinforcement materials need to be homogenized to ascertain models for modeling and control, or a high fidelity model is needed, which is often computationally intractable to solve in real time. The modeling of soft robotic actuators should consider the micro-and mesoscale mechanics that impact the macroscale actuator response. Building on recent developments in both data-driven control and full-field measurement techniques of local strain deformations, we propose using Digital Image Correlation (DIC) to ascertain observables to relate the length scales in soft robotic actuators for rapid dynamic modeling. Using flexible structures with rotating squares as a demonstrating example, we fabricate tubular actuators and characterize their motions using DIC. Nonlinear models relating the length scales are constructed from observables ascertained via DIC using Sparse Identification of Nonlinear Dynamical Systems (SINDy). We demonstrate the goodness-of-fit of several models and discuss limitations in extending these models for control. This work provides a general recipe for the data-driven identification of dynamic models for soft robotic actuators from observables at multiple length scales.
Recent catheter designs have considered the use of magnetically active soft continuum robots controlled via external magnetic actuation systems. These have proven effective for minimally invasive applications due to their soft structure, high dexterity, and wireless actuation, all at small scales. Single and multiple magnetic segment configurations have been proposed to allow tip-only control or full shapeforming, respectively. However, these approaches utilize fixed-length magnetic segments, which require advancement from the proximal end to enhance the reachability and workspace coverage of the steerable tip. To address this limitation, we propose a dual-actuated catheter tip design comprising a 3D-printed soft tendon-driven helical body for length adaptability coupled with a tip-mounted permanent magnet for steering. We achieve a compact design of 2.4 mm outer diameter and 18 mm nominal length, suitable for carotid artery aneurysm intervention. An existing analytical model based on the Euler-Bernoulli beam theory is adapted to predict tip deflection and tip angle under magnetic actuation at three different actuation lengths: contracted, normal, and extended. We demonstrate tip length actuation spanning from a 37.2% reduction to a 35.6% extension, corresponding to 11.3 mm and 24.4 mm when fully contracted and extended, respectively. The experimental magnetic actuation shows a maximum deflection angle of 89.5 degrees with >68 degrees achievable across all length configurations. We subsequently demonstrate how the proposed hybrid tendon and magnetic actuation approach enables enhanced workspace access when compared to a fixed-length design, improving access within simple and more complex aneurysm phantoms.
This paper presents the design, development, and control of a low-cost two-flexible-finger robotic gripper for grasping fragile objects. The gripper is fabricated using 3D-printed materials, with flexible fingers made from TPU (95A shore hardness), equipped with conductive gel-based contact sensors and strain gauges for force feedback. The system is driven by a DC motor, and the control scheme includes position-force control to ensure delicate grasping. The gripper operates in two stages: object approach and controlled force application, with adaptive control parameters based on sensor feedback to prevent damage to fragile items. Experimental tests demonstrate the gripper’s capability to grasp fragile objects such as Christmas ornaments and eggs, validating the design and control strategy.
Soft-growing robots excel in navigating complex environments due to their flexibility and significant length extension, making them ideal for data collection where human access is restricted by hazards. However, integrating the reliable power and signal connections needed for these sensors without compromising the robot’s growth and steering abilities has proven challenging in previous designs. In this paper, the impact of wire attachment and routing paths on the performance of soft-growing robots is characterized by comparing straight and helical configurations in both a quasi-static bending test for steering and an eversion test for growth. Results show that helical routing improves steering by maintaining flexibility and maneuverability, whereas straight wires reduce steering and cause unpredictable rolling. While all configurations could grow, the effects of wire stiffness and configuration on growth were more nuanced; in some situations, the wire’s structure aided growth, while in others the wire hindered it. Overall, a medium helical pitch effectively balanced growth speed and steering capability, retaining functionality while adding the possibility of electrical integration. These findings support the integration of wires in soft-growing robots to ensure robust electrical connection with minimal performance impact.
Fluidic elastomer actuators have emerged as one of the most promising candidates for modular and reconfigurable soft robotics devices, especially for wearable and healthcare applications, due to their inherent compliance, robustness, cost-effectiveness, and ease of fabrication. However, a significant challenge in the widespread adoption of fluid-driven soft robots is their reliance on bulky and heavy external pumps and compressors, which fundamentally limit their portability and versatility. To address this challenge, our research introduces an approach utilizing the liquid-vapor phase transition of a low-boiling point liquid to develop a portable pump, without using any rigid mechanical moving component. This low voltage-driven electrothermal pump employs the Peltier effect for rapid and reversible active heating and cooling, allowing for more efficient heat transfer compared to joule heating and natural passive cooling. A maximum output pressure of 43.2 kPa and a maximum flow of 72 ml/min is achieved using a battery. This pump stands out for its portability, versatility, and potential to function as a modular self-contained fluidic source for soft robots. It is poised to revolutionize various applications, including home-based wearable devices, thermally active clothing, and autonomous untethered soft robots.
