Low profile stretch sensor for soft wearable robotics

Abstract

this paper presents a low profile stretch sensor for integration into soft structures, robots and wearables. The sensor mechanism uses a single piece of highly flexible and light weight optical fibre and is based on the notion that bending an optical fibre modulates the intensity of the light transmitted through the fibre, a technique often referred as macrobending light loss. In this arrangement, the optical fibre originates from sensor's electronic unit, passes through a stretchable encasing structure in a macrobend pattern, and then loop back to the same unit resulting in a simplified electrical and optical design; the closed optical loop allows for no electronics at one end of the sensor making it safe for human robotics applications, and no optical interference with the external environment eliminating the need for complex conditioning circuitries. Of particular interest of the soft robotics community, the ability of this custom macrobend stretch sensor to flexibly adapt its configuration allows preserving the inherent softness and compliance of the robot which it is installed on. Our experimental results indicate that the optical fibre's bending radius is the dominant design parameter for sufficiently complex patterns, a finding that can facilitate generalisation of the sensing methods across different scales. The measurement performance of the mechanism and its impact on the stiffness of the encasing structure is benchmarked against a custom calibration and testing system. I.

A Contact Force Sensor Based on S-Shaped Beams and Optoelectronic Sensors for Flexible Manipulators for Minimally Invasive Surgery (MIS)

“…Recently, state-of-the-art flexible manipulators [23][24][25][26][27][28] have integrated various sensing modalities such as shape and stretch sensing units, tactile sensing units and multi-axis force/torque sensors. For example, the continuum manipulators are integrated with light intensity modulation based fibre optic sensors to measure force/torque [19,23] as well as the manipulators' shape [29] based on stretch sensing elements [49]. The fibre-optic sensors can be designed to provide a high sensing resolution and sensitivity, at a relatively low-cost.…”

Wearable Optical Fiber Sensors in Medical Monitoring Applications: A Review

“…Optical fiber sensor has the character electromagnetic interference characteristicsility, small size, flexibility, multiplexing ability, and high accuracy [ 1 ]. In addition, because no current is required at the point of measurement, the technology provides the security needed to operate in wet or humid environments, such as sweating or water-based physical therapy procedures [ 2 , 4 , 5 , 6 , 7 ]. These features provide reliable technical support for continuous monitoring devices in physical applications.…”

“…This is primarily due to their exceptional flexibility, ease of wear, and high precision. These unique features make them highly suitable for continuously monitoring physiological parameters in medical settings [ 2 , 4 , 6 , 8 , 9 , 10 , 11 ]. With the continuous improvement of living standards and medical conditions, the life expectancy of human beings continues to rise.…”

A highly stretchable optical strain sensor monitoring dynamically large strain for deformation-controllable soft actuator

“…Among these sensing methodologies, light intensity modulation that uses the correlation of transmitted light intensity with external disturbances imposed onto the optical fiber has been intensively studied as forming a flat optical fiber to macro-bended structure such as single loop, U-shape, and figure-of-eight configuration [32,33]. The macro-bending optical fiber sensors, which is embedded into an elastic textile fabric or soft curvilinear structure, have shown a capability to monitor physiological parameters [31,34,35] or posture of human [34,36] and motion of soft robots [37][38][39][40]. However, there is only few efforts to realize macro-bending based optical strain sensor that can secure a consistent sensitivity and dynamic strain detection in a wide range of strains.…”