Abstract
In this study, we propose a force sensor using a shape-memory polymer (SMP) whose stiffness varies according to the temperature. An SMP can be deformed above its glass transition temperature (Tg) by applying a small load. A deformed SMP maintains its shape when cooled below Tg and returns to its predefined shape when subsequently heated above Tg. The reversible change in the elastic modulus between the glassy and rubbery states of an SMP can be on the order of several hundred-fold. The relationship between the applied force and the deformation of the SMP changes depending on the temperature. Our sensor consists of strain gauges bonded to an SMP bending beam and senses the applied force by measuring the strain. Therefore, the force measuring range and the sensitivity can be changed according to the temperature. In this study, we evaluate a prototype of the sensor using the SMP sheet with embedded electrical heating wire. Moreover, we improve the sensor by combining the SMP and a stainless steel plate. The enhanced versatility of SMP force sensors is demonstrated through a series of experiments conducted using the prototype.
Highlights
In today’s rapidly aging societies, robotic technology has been applied to various fields including industrial as well as nursing and welfare
One reason is that the embedded heating wire is stiffer than the shape-memory polymer (SMP) sheet in the rubbery state, and the change of the elastic modulus between two states became small to as observed in our previous study [7]
We could construct a force sensor using both SMP and steel plates whose measurement can change according to the temperature without the replacing the sensor
Summary
In today’s rapidly aging societies, robotic technology has been applied to various fields including industrial as well as nursing and welfare. Several power-assist suits and power assist apparatus have been proposed as wearable robots for caregivers and rehabilitation systems [1]. In these applications, it is necessary to measure a wide range of forces to grasp and lift various objects in the various operating environment accurately [1]. For example, a wide-range and sensitive force sensor using a quartz crystal resonator was proposed [2]. The characteristic of our proposed sensor is the utilization of the stiffness change of the material based on the temperature. The stiffness change of the material has not yet been utilized for wide-range and sensitive force sensors.
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