Soft robots are compliant, impact resistant, and relatively safe in comparison to hard robots. However, the development of untethered soft robots is still a major challenge because soft legs cannot effectively support the power and control systems. Most untethered soft robots apply a crawling or walking gait, which limits their locomotion speed and mobility. This paper presents an untethered soft robot that can move with a bioinspired dynamic trotting gait. The robot is driven by inflatable soft legs designed on the basis of the pre-charged pneumatic (PCP) actuation principle. Experimental results demonstrate that the developed robot can trot stably with the fastest speed of 23 cm/s (0.97 body length per second) and can trot over different terrains (slope, step, rough terrain, and natural terrains). The robotic dog can hold up to a 5.5 kg load in the static state and can carry up to 1.5 kg in the trotting state. Without any rigid components inside the legs, the developed robotic dog exhibits resistance to large impacts, i.e., after withstanding a 73 kg adult (46 times its body mass), the robotic dog can stand up and continue its trotting gait. This innovative robotic system has great potential in equipment inspection, field exploration, and disaster rescue.

Untethered soft robots (USRs) based on single‐actuation methods face inherent limitations due to restricted energy resources, which adversely affect their performance. Pneumatic‐tendon‐coupled actuators (PTCAs) offer an effective approach for USRs by combining the compliance and variable stiffness of pneumatic actuation with the precision and rapid motion control of tendon‐driven actuation. However, current PTCA‐based USRs are limited in versatility and efficiency when executing complex tasks. This research introduces discrete pneumatic‐tendon‐coupled actuators with interconnected air circuit (DPTCAs‐IAC) to address these limitations through two major design approaches: 1) multiple discrete DPTCAs with integrated micro pump, providing additional degrees of freedom and independent motion control while regulating internal pressure without significantly adding weight; and 2) interconnecting multiple DPTCAs through air circuits to facilitate gas flow and enhance efficiency. Theoretical modeling and experimental tests conducted on single DPTCA and DPTCAs‐IAC show that the IAC effectively reduces actuation torque and that opposite‐direction movements consume less energy compared to same‐direction movements. An untethered soft robotic gripper and an untethered quadruped robot with soft legs based on DPTCAs‐IAC are developed. Both demonstrate excellent controllability, compact system integration, and multifunctionality, highlighting the potential of DPTCAs‐IAC in advancing the development of complex untethered soft robots.

The Soft Rolling Robot (SRR) excels in adaptability across diverse natural terrains, demonstrating significant flexibility, environmental interaction capabilities, and impact resistance. However, the development of Untethered Soft Rolling Robots (USRR) faces challenges in locomotion speed and controllability due to the limited load-carrying capacity of untethered systems. This study introduces a novel actuation system that combines pneumatic actuation with tendon actuation to enhance USRR performance. We propose a pneumatic-tendon coupled actuated telescopic soft leg structure that uses tendons for precise position and velocity control, while concurrently adjusting stiffness through air pressure modulation. This system interconnects the gas circuits of multiple soft legs, enabling internal gas circulation during rolling motion. An octagonal planar rolling robot with a radial skeleton structure was designed and fabricated to validate this actuation method. Theoretical analysis and experimental research have shown that the interconnected gas circuit design can significantly reduce tendon tension in actuation of soft legs and enhance their output force and range of motion. Performance tests on the USRR reveal excellent speed regulation capabilities, achieving a maximum speed of 0.19 m/s, and demonstrate adaptability to various terrains including slopes, steps, grasslands, gravel roads, and shallow water.

The compliance of soft wearable robots driven by fluids is high, but their portability and controllability are limited due to complex fluidic systems. On the other hand, tendon-driven soft wearable robots are compact and easy to control, but they have lower compliance when actively interacting with unknown environments. To address this trade-off between compliance and controllability, we propose a novel actuator design for soft wearable robots, named the passive bellow actuator (PBA). The PBA is 3D-printed using elastic materials, which enables it to be easily customized into various shapes and sizes. When tendons running through the PBA are pulled, it contracts and preserves elastic potential energy. When the tendons are released, the PBA extends like a spring and exerts the stored elastic energy to drive the human body. Additionally, programmable deformation can be easily achieved by adjusting the thickness of the PBA chamber. By utilizing these effects, the PBA can be used to assist human flexion and extension movements. We developed a portable soft robotic glove to demonstrate the feasibility of the PBA. The glove is light weight, power safe, and is inherently compliant when grasping irregular objects. Theoretical modeling and experimental tests were conducted to characterize the PBA, and experimental tests were conducted to demonstrate the performance of the soft robotic gloves.

Haptic perception is essential for robotic grippers performing delicate handling tasks, yet designing a tactile sensor that is both low-cost and high-performance remains a challenge. This article addresses this issue by developing an optical blocking structure (OBS) sensor for tactile perception in robotic grippers. The OBS sensor is characterized by its ease of fabrication, cost-effectiveness (with a unit cost of $1.45), and high-performance metrics, including a maximum sensitivity of approximately 2.18 V/N, a wide pressure response range (>4 N), high resolution (0.009 N), a fast response time (15 ms), and a minimal dead zone (around 0.026 N). Experimental results demonstrate that a robotic gripper equipped with the OBS sensor can effectively detect object hardness, surface texture, and perform delicate force control tasks. Additionally, the OBS sensor exhibits high scalability. It can be configured into various array forms to enhance the gripper's sensing capabilities based on its structural characteristics. Validation experiments confirm that robotic grippers integrated with 2 × 2 and 1 × 6 array configurations of the OBS sensor can accurately detect multiple contact positions and forces. Consequently, the OBS sensor offers a straightforward and effective solution for enhancing tactile sensing in robotic grippers.

Mammal-inspired quadruped robots excel in traversing diverse terrestrial terrains but often lack aquatic mobility, limiting their effectiveness in amphibious environments. To address this challenge, an amphibious robotic dog (ARD) was developed, integrating efficient paddling gait in water with trotting capabilities on land. A canine-inspired paddling trajectory was first developed for a two-segment leg, and validated through theoretical modeling and experimental measurements of hydrodynamic forces. A waterproof ARD was then fabricated, with careful consideration of center-of-gravity and center-of-buoyancy relationships to ensure stable aquatic movement. Three distinct paddling gaits were developed and tested to evaluate the ARD’s swimming speed and stability: two lateral sequence paddling gaits (LSPG) featuring 25% and 33% power phases (PP), and one trot-like paddling gait (TLPG) featuring a 50% PP. Theoretical modeling and numerical calculations were conducted to analyze the stability of different paddling gaits. Static water experiments measured gait-specific hydrodynamic forces, followed by dynamic swimming tests demonstrating that LSPG delivers superior propulsion and speed, while TLPG offers enhanced stability. The ARD achieved a maximum water speed of 0.16 m s⁻¹ (0.54 BL s⁻¹) and a land speed of 0.35 m s⁻¹ (1.2 BL s⁻¹). These findings provide theoretical and practical guidance for the development of mammal-inspired amphibious quadruped robots, particularly in structural design and paddling gait planning.