Configuration detection and external force tuning for soft-bending actuators under position constraint

Abstract

Nowadays, soft actuator development has become a big trend due to higher safety and more complex movements. One of the most interesting types of these actuators is called the “soft fiber-reinforced bending actuator,” which has been chosen for investigation in this study. The aim is to provide a codified model to investigate the static behavior and deformation of the actuator in both free and positional constrained conditions. Indeed, modeling of these actuators in the presence of external factors and constraints is significantly challenging due to distortion of conventional constant curvature assumptions applied in free motion. In this paper, hyper-elastic theories have been utilized to model the free motion behavior of a soft-bending actuator made from elastomeric materials. Then, the Euler–Bernoulli beam theory for bending deformation is used to investigate the effect of positional constraints on the actuator’s deformation. In addition, an optimization method is utilized to estimate the required internal pressure, which in turn tunes the contact force between the actuator tip and desired objects/obstacles. The experimental results are presented to validate the proposed theories in both free and constrained conditions. In this regard, first, the actuator’s behavior in free motion is properly investigated and proven valid. Then, the effects of positional constraints on the actuator and their contact force tuning are analyzed.

Design and motion analysis of a bidirectional parallel-chamber soft pneumatic actuator

“…The method for measuring the bending angle of soft actuators can be found in reference. 22 As depicted in Figure 9, pressures of 5, 10, 15, and 20 kPa were applied to the longitudinal chamber, resulting in bending angles of 98°, 160°, 206.8°, and 266.6°, respectively. Figure 10 shows that when pressures of 10, 15, 25, and 35 kPa were applied to the transverse chamber, the bending angles were 6.2°, 27.5°, 48°, and 60.8°, respectively.…”

“…19 The structural design and modeling methods, as well as the manufacturing techniques of SPAs have been widely investigated. SPAs can be generally divided into two types: fiber-reinforced SPAs [20][21][22][23] and PneuNet-type SPAs. 24,25 By setting multiple cavities in the elastomer and applying pneumatic pressure to drive the soft material to produce large-area deformation, these actuators can be inflated and deflated to grip and release objects, exhibiting remarkable flexibility.…”