The combination of flexible structures, external forces, and various soft material blends commonly causes complex deformations in continuum robots, making their modeling challenging. In this paper, we propose a bending model for pneumatic soft actuators. The chamber layer is being modeled as two states: (1) Free space expansion: using a modified virtual work principle, that is, algebraic calculation of the deformed volume of the chamber; (2) Contact expansion: Finite-strain membrane theory for modeling chamber layers. Modeling of constrained layers using Euler-Bernoulli finite-strain hyperelastic beam theory. Influence of gravity and axial tension is taken into account in the model; the model only requires input material parameters, structural parameters, and pressure for both the constraint and chamber layers. The data are then used to predict the bending behavior of soft actuators in free space. Soft actuators with different combinations of constraint and chamber layers were produced to carry out the experiment, enabling the validation of theoretical predictions. Additionally, the results were compared with those obtained via finite element analysis models. The proposed approach applies to Soft PneuNet Actuators (SPNA) with similar structures.

Soft-body grippers are highly pliable due to the use of flexible materials, which enable safe grasping of objects, but their load-bearing capacity is limited by the mechanical properties of the materials themselves. To address the problem of insufficient stiffness of traditional soft-body grippers, this paper proposes a reconfigurable exoskeleton bionic stiff-flexible gripper inspired by the hydraulic legs of spiders. The gripper is designed with three switchable working modes, and the quick-connect removal mechanism works in concert with the lower fixed jaws to adapt to the grasping needs of objects of different sizes and masses. The joints adopt balloon actuators that mimic the hydraulic leg mechanism of a spider, which can realize adaptive adjustment of the center position and drive the exoskeleton structure to complete the deformation action. Based on the contact-induced extrusion interaction between the balloon and the exoskeleton, a theoretical model of nonlinear actuation is developed. The balloon is simulated using finite element analysis to determine its effective operating range. Furthermore, a rectangular silicone membrane is designed to envelop the exoskeleton surface, enhancing the system’s flexibility and ensuring consistent structural support. The experimental evaluation of the comprehensive grasping performance of the gripper shows that the reconfigurable exoskeleton gripper can effectively grasp objects in the size range of 3–230 mm with a maximum weight of 1 kg, which significantly extends the application range and load-bearing capacity of the traditional soft gripper.

Conventional pneumatic bending actuators cannot perform the in-grasp twisting required to detach mature Agaricus bisporus from the cultivation substrate. Manual harvesting was characterized by measuring fingertip contact forces, fruiting-body rotation, and motion timing using flexible-film force sensors and an inertial measurement unit. The resulting grasp–twist–lift characteristics informed the design of a three-finger segmented variable-angle symmetric oblique-chamber (SVA-SOC) pneu-net soft gripper. Each SVA-SOC actuator integrates upper parallel chambers and lower symmetric oblique chambers that are synchronously pressurized to generate inward bending for grasping; after grasp establishment, differential pressure between the lower oblique chamber groups induces torsional deformation while the grasping pressure is maintained. A reduced-order model based on the Yeoh constitutive model and segmented constant-curvature assumption was validated against finite-element simulations and experiments, yielding root mean square error (RMSE) values of 12.82° and 3.36° for bending and twisting angles, respectively. At 85 kPa, a single actuator generated bending and tangential contact forces of 1.41 and 1.31 N, respectively. The three-finger gripper achieved a maximum target rotation of 44.59°, an initial grasping force of 5.38 N, and a pull-off force of 18.59 N. In 50 harvesting trials, grasping, harvesting, and undamaged harvesting rates were 100%, 94% and 86%, respectively, indicating feasibility for low-damage harvesting of mature Agaricus bisporus.

It is an essential design requirement to understand the method to represent the pressure deformation of elastomers as a crucial aspect of pneumatic actuator behavior. Most research focus on the motion of positive pressure kinematics and ignore the contribution of negative pressure to soft actuators in free space. This study presents an analytical model for soft pneumatic networks (Pneu-net) at both positive and negative pressures. The analytical model, based on finite strain membrane and hyperelastic material models, describes the relationship between pressures and volume change in the actuator’s chamber, and predicts the Pneu-net’s deformation and tip force under both positive and negative pressures. Experimental validation shows that the model can accurately predict the Pneu-net’s deformation behavior under low pressure (−20 to 20 kPa) with an error band of less than 15%. The model’s accuracy decreases beyond ±20 kPa due to material nonlinearity. This model addresses a gap in the research of Pneu-net kinematics at negative pressure, which will put forward the optimal design of Pneu-net and its potential applications in soft robotics such as soft grippers and biomimetics at both positive and negative pressure.

Advanced sensing is rapidly reshaping intelligent robotic systems by enabling robots to perceive, reason, and interact with the physical world under real-world uncertainty