Torque Characterization of a Novel Pneumatic Soft-and-Rigid Hybrid Actuator

Abstract

This paper presents development of a theoretical model for predicting the torque generated by a pneumatic soft-and-rigid hybrid actuator at a given actuation pressure and bending angle. The soft actuator with a novel architecture is comprised of half bellow-shaped flexible hollow structure (soft section) in-between block-shaped semi-rigid sections made of silicone rubber materials. This actuator provides forward and backward bending motion when air pressure and vacuum are applied into the soft section, respectively. A simplified steady-state model was developed based on the quasi-static assumption when the system dynamics is slow enough that all of the interacting forces comes to an equilibrium at any given bending angle during the motion. The elastomeric material was modeled using the Yeoh 3rd order model to capture its nonlinear behavior. The model was studied for the soft actuators with different geometrical features in two cases of the free end motion (without external force) and the constrained end motion (with external force). Experimental testing and finite element simulations were carried out corresponding to the case-studies to validate the model. Comparison of the results obtained by these two approaches show a good agreement with the theoretical model’s prediction.

Modeling multi-contact point physical interaction between the anthropomorphic finger and soft robotic exo-digit for wearable rehabilitation robotics applications

“…In Eq. 13 , σ i is the normal Cauchy stress at the cross-section of the soft actuator determined based on a hyperelastic constitute model ( Haghshenas-Jaryani et al, 2017a ; Haghshenas-Jaryani and Wijesundara, 2018 ; Haghshenas-Jaryani, 2020 ), which is discussed in Section 2.1.3 ; r si is the moment arm distance; and A si is the cross-sectional area for the soft continuous joint section; therefore, r s , i d A s , i is the first moment of area corresponding to the shaded part of the cross-section of the soft segment, as shown in Figure 2 . It should be noted that Eq.…”

“…It should be noted that Eq. 13 does not have an analytical solution due to the complex nonlinear form of the integrand, so it will be determined numerically ( Haghshenas-Jaryani et al, 2017a ; Haghshenas-Jaryani and Wijesundara, 2018 ; Haghshenas-Jaryani, 2020 ). Applying τ i = 0 to (10) yields a quasi-static equation for a single soft segment.…”

“…A simple force analysis and interaction model was developed for a cybernetic finger for hand paralysis ( Yoshikawa et al, 2019) , a bionic soft robotic glove ( Zhao et al, 2021 ) with a hybrid soft-and-rigid architecture, and a torque characterization for enfolded textile-based soft actuators ( Nassour and Hamker, 2019) . Extensive work has been carried out on a hybrid soft-and-rigid actuator-based hand rehabilitation robot (UTARI REHAB Glove), where the soft robotic finger was made of an elastomer ( Haghshenas-Jaryani et al, 2016a ; Haghshenas-Jaryani et al, 2017b ; Haghshenas-Jaryani et al, 2020 ), including pHRI kinematic and modeling and characterization ( Haghshenas-Jaryani et al, 2017a ; Haghshenas-Jaryani and Wijesundara, 2018 ). The results of these models were utilized for a kinematic-based adaptive control of a bilateral rehabilitation robot ( Haghshenas-Jaryani et al, 2019 ), a simulation-based quasi-static force and position control ( Haghshenas-Jaryani, 2020 ).…”

3D-Printed Soft Pneumatic Robotic Digit Based on Parametric Kinematic Model for Finger Action Mimicking

“…The pneumatic bellows actuators are made from TPU 801, and the nonlinear mechanical properties of such material could be examined using nonlinear elasticity theory [ 55 , 56 ]. The Yeoh third-order model is an available model that is suitable for the nonlinear behavior characterization of materials, despite its elongation percentage being above 300% [ 55 , 57 ].…”

Trajectory Control in Discrete-Time Nonlinear Coupling Dynamics of a Soft Exo-Digit and a Human Finger Using Input–Output Feedback Linearization

“…None of these works has considered multi-contact-point interaction between the soft robotic digit and the human finger. Our previous work includes extensive studies of design, modeling, and kinematic-based control algorithms on a hybrid soft-and-rigid actuator-based hand rehabilitation robot (REHAB Glove) [10,11,34]; modeling and characterization of physical human-robot interaction (pHRI) in wearable soft hand robots [68,69]; a kinematic-based adaptive control of a bilateral rehabilitation robot [14]; and simulation-based quasi-static force and position control [70]. In our recent work, single-input single-output (SISO) quasi-static model-based adaptive position control of soft exo-digit and the human finger physical interaction was developed and experimentally verified for a step input and trajectory tracking cases [63].…”