In this paper, we propose an earthworm-inspired miniature pipeline robot capable of self-sensing odometry. The robot features a dielectric elastomer actuator as its elongation body and two specially designed passive anchors to achieve unidirectional motion without slipping. The odometry was achieved through the self-sensing scheme of DEAs and the summation of all step sizes over a period. The careful implementation of the self-sensing method resulted in a small sensing resolution of 0.05 mm at a high actuation frequency of 20 Hz for a cylindrical DEA. Finally, the robot obtained a self-sensing odometry in a pipe, showing good consistency with the ground truth. This work paves a new way for a miniature in-pipe robot to sense its own state without additional sensors to save space and power.

In this work, we propose a high-voltage, high-frequency control circuit for the untethered applications of dielectric elastomer actuators (DEAs). The circuit board leverages low-voltage resistive components connected in series to control voltages of up to 1.8 kV within a compact size, suitable for frequencies ranging from 0 to 1kHz. A single-channel control board weighs only 2.5 g. We tested the performance of the control circuit under different load conditions and power supplies. Based on this control circuit, along with a commercial miniature high-voltage power converter, we construct an untethered crawling robot driven by a cylindrical DEA. The 42-g untethered robots successfully obtained crawling locomotion on a bench and within a pipeline at a driving frequency of 15 Hz, while simultaneously transmitting real-time video data via an onboard camera and antenna. Our work provides a practical way to use low-voltage control electronics to achieve the untethered driving of DEAs, and therefore portable and wearable devices.

Exploring high hydrostatic pressure environments such as deep sea presents significant challenges to robotic devices, for they often rely on strong yet heavy and costly protective structures to shield components from being crushed by the extreme pressure. To dismiss the need for bulky protection shells for actuation devices, we reported an extreme-hydrostatic-pressure resilient rotary dielectric elastomer actuator (DEA) for propulsion application in deep-sea pressure condition. DEAs are inherently resistant to damage caused by external pressure, due to their uniform and cavity-free structure. In this study, we analyzed the material properties of the DEA’s elastomer, evaluated the rotary actuator’s lifespan at up to 110 MPa high-pressure liquid conditions, and output performance under both ambient and 30 MPa (equivalent to 3,000 m underwater). Our results show that the rotary actuator maintained functionality at such hydrostatic pressure, with a lifespan exceeding 300,000 cycles and a high rotational output speed of 820 rpm. The rotary actuator was subsequently used to drive the robot with a propeller in a simulated deep-sea pressure fluidic environment, demonstrating our DEA’s performance as well as design simplicity for deep-sea applications without protection structures. While high hydrostatic pressure negatively impacted the actuator’s lifespan and slightly reduced its dynamic performance, our results confirmed that the DEA was a viable solution for deep-sea exploration, laying a solid foundation for the further development of DEA-powered devices for underwater missions.

Negative pressure (NP) therapy with sliding suction is an effective method for limb lymphedema. Due to the caregiver shortage and the patients increase, the robotic NP therapeutic system with a variable-sized suction head can be used to help the lymphedema therapy. However, the varying complexity of different limb regions can affect the accuracy of the suction path. Moreover, the moving suction path should maintain smoothness to ensure therapeutic efficacy. Therefore, finding a smooth sliding path with highly accurate suction poses on the unstructured limb surface poses a significant challenge for robotic therapy. In this paper, a smooth sliding path planning method is proposed for robotic continuous suction in limb lymphedema therapy. The easily-sealed region is identified by comparing point normals to the lip’s suction angle, simplifying path planning to a 2D plane due to lip and limb flexibility. The conjugate gradient method optimizes the path with centroid distance and smoothness constraints. Finally, after the generation of suction poses under the constraints of the lip shape, a smooth sliding path along with lip pressure commands, is obtained to regulate the robot in performing continuous suction therapy. In the experiment, the manipulator with a variable-sized head has been used to finish 10 sliding suctions from different planning path. From the result, the robot could complete 6 times sliding suctions on the phantom arm.

The development of high-performance bionic legged robots can benefit from the continued advancements in various actuation methods, such as artificial muscles. This work presents a musculoskeletal bionic leg driven by fluidic elastomer actuators (FEAs), showcasing their potential as artificial muscles for legged robots. Our approach integrates three key innovations: First, we established a mechanics model using thin plate theory to optimize the bellows shell structure of the FEAs, achieving high force output while maintaining inherent compliance. Second, we developed a lightweight embedded optoelectronic sensing system that enables closed-loop control without significantly increasing mass. Third, we designed a two-joint leg in the sagittal plane that utilizes a bionic configuration incorporating both monoarticular and biarticular FEAs. The leg demonstrated robust performance across various tasks including extreme positional movements, load-bearing squats supporting up to 2.45 times its body weight, vertical jumping with 147 mm ground clearance, and stable walking. Notably, our embedded sensing system successfully detected ground contact states without additional foot sensors, enabling reliable gait control while minimizing complexity and weight. The experimental results validate both the mechanical capabilities of the optimized FEAs and their controllability through embedded sensing, laying a foundation for developing full legged robots with muscle-like actuation.

As a classical type of smart materials, shape memory alloys (SMAs) are of high energy density, light weight, and low actuating voltage, and therefore are of great potential to be used as actuators for robots. Major challenges in controlling an SMA-driven soft robot are the limited bandwidth and in cases with external loads. Active cooling has been demonstrated to dramatically increase its bandwidth, but external load may cause severe inaccuracy in the system modeling. Controllers that do not rely on accurate modeling of the SMA-driven soft robot is essential. In this article, we designed an elastomeric soft robotic tentacle actuated by three pieces of SMA springs with both active heating (Joule heating) and active cooling (compressed air). We proposed a multi-input-multi-output controller that directly uses the heating and cooling states of the three SMAs to control the tentacle's bending posture in three-dimensional (3-D) space. The successful implementation of the controller is attributed to a novel dual-channel control algorithm that integrates the bending motion control and swing motion control, and a state-machine controller for coordinating the three SMAs' actuations to achieve robust swing motion control. The system with such hardware and control algorithm was capable of performing bending motions with maximum actuating speed$ > $90$^\circ /$s, deactuating speed$ > $25$^\circ /$s, closed-loop motions with rapidity (6–41$^\circ /$s for heating, 4–19$^\circ /$s for cooling), accuracy (steady-state error$ < $0.1$^\circ$for no load, 0.13$\%$of the full range; steady-state error$ < $1.2$^\circ$with load of 1 bodyweight, 1.6$\%$of the full range), and load-bearing capability (dynamic load: 1 bodyweight, static load: 8.8 bodyweights). Besides, the tentacle achieved efficient motion tracking by coordinating the bending and swing motion through the controller, for both predefined trajectories and random trajectories. We demonstrated a remotely controlled 360$^\circ$image scanning of a room using our proposed robotic tentacle equipped with a camera at its top end to intuitively show its performances. We believe this work will advance the design and control of SMA-driven soft continuum robots for potential uses in surgery and explorations of unknown areas.

As the focus on highly intelligent robots continues, a problem that cannot be ignored has emerged: resource con-straints. Considering the game problem of resource limitation and the level of intelligence, we focus on lightweight intelligence. This work is a further refinement of our previous work, a heterogeneous lightweight intelligent multi-robot system. In-spired by the nature creatures “octopus” and “ants”. First, we propose a heterogeneous centralized-distributed architecture, which can make robots collaboration more flexible and non-redundant. Second, to reflect lightweight intelligence, we use the Raspberry Pi, a low computing and power consumption internet of things (IoT) device, as a processing platform and first propose a quantitative definition of the lightweight intelligent system. Then, combining the centralized-distributed architecture and the lightweight computing platform, we propose an adapted algorithm called OCTOANTS and apply it to the simultaneous localization and mapping (SLAM) field. The OCTOANTS architecture consists of one brain and eight tentacles, which can achieve complex things with proper collaboration between them. Finally, we use heterogeneous cameras and heterogeneous algorithms to form a lightweight intelligent collaborative system that can run in the real world. On the low-grade platform Raspberry Pi our heterogeneous tentacles frame rate can reach 41fps and 99.8fps respectively, power consumption is only 2W and 1.2W. At the same time, our heterogeneous system is on average 7.2% more accurate than the state-of-the-art homogeneous system and can be applied to a wider range of application scenarios, demonstrating the superiority and feasibility of our OCTOANTS.

Recently, various soft universal grippers have been developed due to their reduced control complexity and satisfying grasping capability. The gripping range of a gripper plays a key role in its universality. This article presents a pneumatically actuated soft-rigid hybrid multifinger gripper that has a wide gripping range by adjusting its initial grasp postures. The gripper is compact (dimensions:$\text{100} \times \text{60} \times \text{170}$mm), lightweight (weight: 380 g), and modular. It consists of four modules, with each module containing three pneumatic actuators (a distance-adjusting actuator, an angle-adjusting actuator, and a finger actuator) and rigid connectors. Through initial grasp posture adjustment, and fingers with tapered angles to generate nonconstant bending while grasping, the gripper can grasp objects of a wide variety of sizes and weights, thus increasing its universality. The gripper is tested to characterize its distance adjustment range, angle adjustment range, and stiffnesses in load-bearing directions, at continuously changing pneumatic pressures. The distance adjustment range and angle adjustment range of the gripper are 0–64.4 mm (64.4% of the initial gripper length) and 0$^{\circ}$–140$^{\circ}$, respectively. The maximum stiffnesses of distance-adjusting actuator and angle-adjusting actuator are 3331 and 1.15 N$\cdot$m/rad, respectively. Finally, grasping experiments show that our gripper can successfully grasp objects with diameters ranging from 0.5 to 180 mm, lengths ranging from 10 to 325 mm, and the heaviest object it can grasp is 2.1 kg (more than five folds of its own weight). The results demonstrated that our pneumatic gripper has an increased gripping range without adding other types of energy sources and its enhanced universality will expedite various applications in daily life and industry.

A soft orthotic with position control enabled via embedded optical fiber is presented. The design, manufacture, and integration of both the pneumatically powered actuators and optical sensors are described. This orthotic actuator-sensor pair is self-contained and worn on a human finger. When un-powered, the elastomeric actuator allows facile movement and, when pneumatically actuated, the orthotic causes bending of the wearer's finger. Position control is achieved by measurement of signal intensity from a light-emitting diode (LED) input traveling through an embedded optical fiber—greater curvature results in increased light intensity. Both the static and dynamic states are monitored via the optical sensor and the prescribed curvatures are achieved accurately and with stability by a gain-scheduled proportional-integral-derivative (PID) controller implemented by applying pulse-width-modulation (PWM) signals to a solenoid valve to adjust the internal pressure of the actuator.