Frequency Response Analysis of Actively Cooled Nylon Twisted Coiled Actuators for Use in Wrist Rehabilitation Devices

Edmonds, Brandon P.R.; Trejos, Ana Luisa

doi:10.1109/biorob49111.2020.9224459

Cited by 3 publications

(6 citation statements)

References 15 publications

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“…For example, in the case of a wrist SWRR, which requires a range of motion of 40 • extension and 38 • flexion during ADLs, a stroke of ≈23 mm is needed [22]. From the used actuators, the most similar to get this length with the maximum stroke will be 180 mm; at its maximum stroke ≈18 mm, the temperature is ≈82 • .…”

Section: Discussionmentioning

confidence: 99%

“…However, this strategy can only be used during the rising time but not during the falling time, as TCPs are unidirectionally actuated. A popular approach to reducing the response time during the falling time is to implement a cooling system, decreasing the overall response time, with the constraint of requiring external equipment like pumps or fans [21,22]. This section investigates a method to improve the actuation speed but using long actuators.…”

Section: Displacement Control Implementationmentioning

confidence: 99%

“…Yip and Niemeyer [21] used a closed-loop control strategy to improve the speed of the fibres during the heating phase. Edmonds and Trejos [22] showed how an active cooling system can increase the maximum frequency where the TCPs can work.…”

Section: Introductionmentioning

confidence: 99%

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Improved performance in temperature and speed of TCP artificial muscles for soft wearables robots by length modification

González

Garcia

Kilby

2023

Smart Mater. Struct.

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Artificial muscles provide a unique solution for wearable rehabilitation robots (WRRs) because they are compliant, compact, and lightweight. Twisted and coiled polymer actuators (TCPs) are artificial muscles from thermally activated polymer fibres. They present high power density, linearity, stress and strain compared to other artificial muscles. Nevertheless, as TCPs require heat to start, their main barrier for widespread use in WRRs are their slow reaction times and the high temperatures they reach. Previous studies have analysed different parameters, like fibre material, fibre diameter, and various cooling systems, to improve TCP frequency response and working temperature. Nevertheless, the length of the actuator has not been explored as a possible parameter to enhance the actuation performance in this regard. This work focuses on studying the behaviour of TCPs with different lengths and how the performance in frequency response and temperature can be improved using the length as a primary parameter, as they are critical for wearable robots. First, a characterisation of the TCPs was performed. Then, a method to improve frequency response, based on offsets on long actuators was implemented and validated using a chirp signal. The experimental results show that the mechanical characteristics are similar regardless of the actuator’s length. They reached a strain of 10 % with a power of 0.16 W/cm. However, the electrothermal properties changed as the power needed to increase temperature was higher when the actuator was enlarged. Therefore, an improvement in the required temperature was found, able to reduce the temperature with the same frequency response. Regarding the technique to enhance the speed of the actuator, it was possible to increase the frequency by 0.0006 Hz for each mm applied as an offset. Hence, the frequency response for the same displacement was increased linearly as the actuator was elongated.

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Section: Discussionmentioning

confidence: 99%

Section: Displacement Control Implementationmentioning

confidence: 99%

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Improved performance in temperature and speed of TCP artificial muscles for soft wearables robots by length modification

González

Garcia

Kilby

2023

Smart Mater. Struct.

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“…Researchers have been studying fabric muscles, i.e., fabric-type soft actuators that can be directly and evenly distributed in the area to be assisted similarly to skeletal muscles. Light and flexible materials such as twisted and coiled polymer actuators (TCPA) and shape memory alloy (SMA) actuators have been used in fabric muscles [17][18][19][20][21][22][23] . These actuators are contracted and actuated via Joule heating.…”

mentioning

confidence: 99%

“…These actuators are contracted and actuated via Joule heating. TCPA, which has a slow cooling rate, must be heated to temperatures exceeding 100 °C for sufficient contraction strain [18][19][20][21][22][23] . Previously, we proposed an SMA spring-based fabric muscle (SFM), and SMA springs comprising 0.5 mm diameter SMA wires were arranged inside the fabrics 21 .…”

mentioning

confidence: 99%

Fabric muscle with a cooling acceleration structure for upper limb assistance soft exosuits

Park

Choi

Rodrigue

et al. 2022

Sci Rep

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Soft exosuits used for supporting human muscle strength must be lightweight and wearable. Shape memory alloy (SMA) spring-based fabric muscles (SFM) are light and flexible, making them suitable for soft and shape-conformable exosuits. However, SFMs have a slow actuation speed owing to the slow cooling rate of the SMA spring. This paper proposes a forced air-cooling fan-integrated fabric muscle (FCFM) that improves the cooling rate by arranging a thin-diameter SMA spring bundle with a high surface-area-to-volume ratio inside a breathable fabric with integrated fans. The relaxation time of an FCFM weighing 30 g and containing a 2.6 g SMA spring bundle, which contains 200 thin springs, was reduced by over 70.2% via forced-air cooling using the integrated fans. A 4 kg weight, which is 1530 times the mass of the SMA spring bundle, was hung from the FCFM and was repeatedly actuated in ten-second cycles. An upper limb assistive soft exosuit with FCFMs was fabricated and worn on a mannequin holding a dumbbell, and the arm extension time after flexion was improved by 4.5 times. Additionally, the assistive performance of the exosuits for repetitive tasks in specific scenarios was evaluated, and the strong potential of the proposed FCFM for soft exosuits was verified.

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Improving the Cooling Time of Twisted Coiled Actuators in Soft Robotics

Lizotte,

Daemi,

DiFabio

et al. 2024

2024 10th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob)

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Frequency Response Analysis of Actively Cooled Nylon Twisted Coiled Actuators for Use in Wrist Rehabilitation Devices

Cited by 3 publications

References 15 publications

Improved performance in temperature and speed of TCP artificial muscles for soft wearables robots by length modification

Improved performance in temperature and speed of TCP artificial muscles for soft wearables robots by length modification

Fabric muscle with a cooling acceleration structure for upper limb assistance soft exosuits

Improving the Cooling Time of Twisted Coiled Actuators in Soft Robotics

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