A study on life cycle of twisted string actuators: Preliminary results

Usman, Muhammad; Seong, Hyunseok; Suthar, Bhivraj; Gaponov, Igor; Ryu, Jee-Hwan

doi:10.1109/iros.2017.8206339

Cited by 15 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous studies report hysteresis in the twisting phase as well. 25 As Fig. 2(a) shows, under a symmetric motor turns input, the contraction output was not symmetric.…”

Section: Hysteresismentioning

confidence: 99%

Experimental investigation of the non-smooth actuation in twisted and coiled string artificial muscles

Konda

Zhang

2023

Bioinspiration, Biomimetics, and Bioreplication XIII

View full text Add to dashboard Cite

Twisted and coiled string (TCS) artificial muscles are recently discovered motor-driven compliant actuators that can consistently generate up to 70% strains. The TCS muscles’ actuation is realized in two sequential phases, namely, twisting and coiling. Actuation in the twisting phase results in smooth linear contraction along the TCS muscles’ length. This behavior is identical to that of the popular twisted string actuators. In the coiling phase, the TCS muscles are overtwisted to form coils that generate large and unique non-smooth contraction of strings. The coiling phase in actuation cycle is underexplored and exhibits unique characteristics: Firstly, at a constant motor speed, twisting of strings generates drastic contraction accompanying larger non-smooth actuation during coil formation as compared to the intermittence between adjacent coil formations. Secondly, evident hysteresis appears during the coiling-induced actuation, likely due to large friction between strings when coiled. Lastly, the muscles actuation transition between twisting to coiling is intricate and largely uninvestigated, especially when they operate under different loading conditions and different motor twisting inputs. In this study, a comprehensive experimental characterization of the coiling-based actuation of the TCS muscles is conducted. Firstly, the load dependence of the TCS muscles’ behavior is examined by applying input cycles under different loading conditions. Secondly, the non-smooth behavior is investigated by using sequences of input motor turns with different frequencies. Lastly, the hysteretic behavior and the properties of transitioning conditions are examined by applying different ranges of the input cycles under different loading conditions. The results serve as a basis for future studies on modeling and control of the TCS muscles’ coiling-based actuation.

show abstract

“…Previous studies report hysteresis in the twisting phase as well. 25 As Fig. 2(a) shows, under a symmetric motor turns input, the contraction output was not symmetric.…”

Section: Hysteresismentioning

confidence: 99%

Experimental investigation of the non-smooth actuation in twisted and coiled string artificial muscles

Konda

Zhang

2023

Bioinspiration, Biomimetics, and Bioreplication XIII

View full text Add to dashboard Cite

show abstract

“…4(b) and 4(d) show that the tensile strength of ϕ3 mm ropes decreased with an increase in the number of repetitions compared to ϕ2 mm ropes. This can be attributed to the damage of the rope caused by the linear contraction of the rope that occurs because of twisting as indicated in the relationship between linear contraction and lifecycle [16]. Based on the geometric model [17][20], the linear contraction ∆L of the rope due to torsion can be expressed as…”

Section: Relationship Between Diameter and Strengthmentioning

confidence: 99%

“…Further, the ropes used in their study were ϕ18 mm marine ropes, and thus, their results may not be directly applicable to ropes with smaller diameters. Usman et al [16] used two types of Dyneema ropes and showed that the number of repetitions that leads to the rope breaking decreases exponentially under applied tension; further, the number of repetitions that leads to breaking increases in proportion to the number of ropes. However, Usman et al did not discuss the change of tensile strength as a function of the angle of twist or rope type, which is critical for selecting ropes to use in robotic applications.…”

Section: Introductionmentioning

confidence: 99%

Repetitive Twisting Durability of Synthetic Fiber Ropes

Sadachika

Kanekiyo

Nabae

et al. 2023

2023 IEEE International Conference on Robotics and Automation (ICRA)

View full text Add to dashboard Cite

“…Despite the many attractive advantages of soft robots, soft robotic devices are more structurally vulnerable than rigid robots and have many uncertainties in their soft structural properties (Case et al, 2015; Cianchetti et al, 2018). Although soft robotic devices have suffered from reliability issues (Godler et al, 2012; Kramer et al, 2011; Krieger et al, 2017a; Liu et al, 2018; Sun et al, 2013; Usman et al, 2017; Wang et al, 2017; Yap et al, 2015), reliability has not yet been studied systemically in the soft robotics field. In one study, a self-healing concept for soft robots was proposed (Terryn et al, 2017), mimicking the healing capacities in nature to address the robot’s susceptibility to damage from unpredictable environments.…”

Section: Introductionmentioning

confidence: 99%

“…Repeatability and durability of the soft pneumatic actuators were investigated with different pressures using fatigue testing (Miron and Plante, 2016; Yap et al, 2016). The lifetime of twisted string actuators in various loads, strokes with different numbers of strings (Usman et al, 2017), and materials (Godler et al, 2012) have also been studied. Wang et al (2017) conducted a durability test of a soft gripper with different pressures and actuators.…”

Section: Introductionmentioning

confidence: 99%

Reliability analysis of a tendon-driven actuation for soft robots

Jeong

Kim

et al. 2020

The International Journal of Robotics Research

View full text Add to dashboard Cite

The reliability of soft robotic devices will be the bottleneck that slows their commercialization. In particular, fatigue failure issues are a major concern. Thus, reliability should be taken into account from the earliest stages of development. However, to date, there have been no attempts to analyze the reliability of soft robotic devices in a systematic manner. When soft robots are employed to force transmission applications, reliability is typically a dominant issue, since soft robotic structures are constructed with soft material components; these materials have highly nonlinear properties that arise due to the large distribution in the material properties. Furthermore, reliability should be analyzed from the robot’s system down to the components using domain knowledge about the system; this requires a systematic approach. This study presents a framework for reliability analysis of soft robotic devices taking into account a probability distribution that has not been considered before and examines a case study of a tendon-driven soft robot. This study focuses specifically on the (a) concept design process, (b) lifetime analysis process, and (c) design and optimization process. A life model that considers distribution is proposed using accelerated life testing based on analysis of the failure mechanism of the tendon-driven system. The tensile stress of the wire was varied during the experiment with different bend angles and output tension. The result was validated with different stress levels using a testbed to simulate an actual application. The proposed reliability analysis methodology could be applied to other soft robotic systems, such as pneumatic actuators, to improve the reliability-related properties during the robot design stage, and the life model can be used to estimate the device lifetime under various stress conditions.

show abstract

A study on life cycle of twisted string actuators: Preliminary results

Cited by 15 publications

References 12 publications

Experimental investigation of the non-smooth actuation in twisted and coiled string artificial muscles

Experimental investigation of the non-smooth actuation in twisted and coiled string artificial muscles

Repetitive Twisting Durability of Synthetic Fiber Ropes

Reliability analysis of a tendon-driven actuation for soft robots

Contact Info

Product

Resources

About