Geometry-optimized pleated soft pneumatic actuators with integral sliding-mode control for versatile robotic grasping

We present the design, optimization, and closed-loop pressure control of a three-finger soft gripper composed of dual-cavity pleated soft pneumatic actuators (DCPS-SPAs). Each finger integrates a pleated actuation chamber and a stabilizing cavity to enable large bending with low supply pressure while preserving structural stiffness for load transfer. We derive an Integral-augmented Sliding Mode Control (ISMC) law for valve-based pressure regulation using a previously established DCPS-SPA pressure model and implement a real-time control on a dSPACE MicroLabBox/Simulink platform. Finite element analysis (using Abaqus/CAE) and experimental tests are used to compare two DCPS-SPA lengths, quantify deformation, and measure tip force. The shorter actuator exhibits higher tip force for the same pressure, whereas the longer achieves larger workspace; we therefore select and further optimize the short geometry by varying chamber width, spacing, and pitch. Pressure-controlled gripping tests with diverse objects demonstrate stable tracking, low overshoot, and consistent grasping performance. Key findings include: (i) deformation up to 159 mm for the longer SPA vs. 120 mm for the shorter at 0.5 bar; (ii) higher tip force for the shorter SPA across 0 bar to 0.8 bar; and (iii) controlled gripping with rise times 0.63 s to 1.88 s, steady-state errors ≤ 0.0256 bar, and RMS errors ≤ 0.1113 bar. The proposed architecture offers a rigorously validated pathway towards low-pressure, high-stability, multi-object dexterous grasping. Remaining gaps include precise modeling of material viscoelasticity, contact/friction variability, and multi-finger force distribution under object-dependent constraints. • Dual-cavity pleated SPA fingers deliver high tip force at low pressure. • Abaqus FEM + experiments mapped pressure–motion–force for design tuning. • ISMC enables robust pressure control with reduced chattering and error. • Three-finger DCPS-SPA gripper showed stable grasps and pressure dynamics.