Investigation of mechanical and electrical characteristics of selfsensing pneumatic torsional actuators

Soft pneumatic actuators are one of the most promising actuation for soft robots,and great achievements have been obtained.But it remains challenging to endow sensing capabilities to pneumatic actuators,especially for the sensing ability originating directly from the actuator architecture.Herein,a self-sensing pneumatic torsional actuator(SPTA)is designed based on the electromagnetic induction effect and magnetically responsive materials.The SPTA can generate feedback voltage and current with the deformation,in which the sensing function comes from its inherent structure.To investigate the mechanical and electrical characteristics,an experimental platform and a finite element model are established,respectively.We find that the torsion angle and output torque increase in nonlinear with the actuating pressure.The maximum torsion angle is 66.35°,which is 84.34%of that for the actuator fabricated by pure rubber.The maximum output torque(24.9 N mm)improves by 23.19%compared with the actuator made by pure rubber.As regards the electrical characteristics,the maximum feedback voltage and current are 2.90μV and 29.50 nA when the SPTA is actuated by a pressure of−40 kPa.We also demonstrate that the relationship between the torsion angle and the magnetic flux change is approximately linear.Finally,the number of turns of wires,magnetic powders contents,and magnetic direction on the feedback voltage and current are studied.Results show that the feedback voltage and current can be enhanced by increasing the number of turns and magnetic powders contents.We envision that the SPTA would be promising for soft robots to realize their accuracy control and intelligentization.

Erratum to:Bio-inspired Filter Design Based on Vortex Control Mechanism of Parallel Groove Structure

Erratumto:Journal of Bionic Engineering(2023)20:338-348 https:/doi.0rg/10.1007/s42235-022-00247-4 In Table 1,the value of Mesh's Feature dimensions(mm)"0.42"should have read"0.04".The original article has been corrected.

Bio-inspired Filter Design Based on Vortex Control Mechanism of Parallel Groove Structure

Solid–liquid separation is widely used in daily life and practical engineering.Traditional industrial filters are prone to clogging,but this rarely occurs in filter-feeding organisms.Inspired by the filter feeding mechanism of balaenid whales and considering the local grooves in the fringes layer,a new bionic filter is produced by 3D printing technology through the bionic design of the parallel channels inside the mouth of balaenid whales.At the same time,a test platform composed of the bionic filter,peristaltic pump,fluid pulse rectifier and water tank is built to carry out the fluid flow pattern dyeing and particle filtration experiments.It is found that fluid separation occurs near the groove structure and local vortices are generated.The vortex control filtration mechanism makes the particles in the front grooves tend to accumulate on the left side,which has a certain anti-clogging effect.Moreover,the increase of flow velocity leads to the enhancement of vortices,which makes the accumulation effect on the left more obvious.This study initially practices the bionic application from biological model to engineering design,and the vortex control anti-clogging filtration mechanism proposed in the study has a wide range of application prospects and values.

Design,Characterization and Optimization of Multi-directional Bending Pneumatic Artificial Muscles

Bending Pneumatic Artificial Muscles(PAMs)are particularly attractive and extensively applied to the soft grasper,snake-like robot,etc.To extend the application of PAMs,we fabricate a Multi-directional Bending Pneumatic Artificial Muscle(MBPAM)that can bend in eight directions by changing the pressurized chambers.The maximum bending angle and output force are 151°and 0.643 N under the pressure of 100 kPa,respectively.Additionally,the Finite Element Model(FEM)is established to further investigate the performance.The experimental and numerical results demonstrate the nonlinear relationship between the pressure and the bending angle and output force.Moreover,the effects of parameters on the performance are studied with the validated FEM.The results reveal that the amplitude of waves and the thickness of the base layer can be optimized.Thus,multi-objective optimization is performed to improve the bending performance of the MBPAM.The optimization results indicate that the output force can be increased by 7.8%with the identical bending angle of the initial design,while the bending angle can be improved by 8.6%with the same output force.Finally,the grasp tests demonstrate the grip capability of the soft four-finger gripper and display the application prospect of the MBPAM in soft robots.

Structure Design and Energy Absorption Mechanism of a New Type of Armor Inspired from Armadillos

Dermal armor,such as fish scales or armadillo osteoderms,has been known to exhibit high performance and good flexibility defending against attack.The top layer of the dermal armor usually consists of a segmented hard bony layer.The soft inner layer composed of collagen fibers connects and holds the hard layer.Inspired by the dermal armor of armadillos,bioinspired protection armor is studied for impact resistance.The hexagonal scales tessellate the surface continuously and work as the hard bony layer protecting the soft inner layer from penetration.Ultra-high molecular weight polyethylene(UHMWPE)is used as the connectivity layer to support and hold the scales.To investigate the dynamic response of the bioinspired protection armor,drop weight impact tests are carried out.A finite element model is established to study the dynamic response of bioinspired protection armor.The impact process images captured by a high speed camera and the experimental data of drop hammer acceleration tests verify the validity of the numerical model.The dynamic resistance behavior and the synergy effect of each part of the bioinspired protection armor combined with the protected objects are studied in detail by numerical simulation.The results show that the bioinspired protection armor has marked energy absorption ability.A synergistic dissipation mechanism is activated in the impact process,which can dissipate impact energy and make the impact load distribution more uniform.The UHMWPE between the outer layer and the soft substrate plays a significant role not only related to support and connection,but also for the force balance and energy absorption.The mechanism of energy absorption of the bioinspired protection armor revealed in this paper can be taken as a new guideline for designing a novel protective armor.