Novel signal modulation methods for electrostatic actuators and multimodal sensors of wearable systems

Abstract

This study aims to enhance the functionality of wearable systems by implementing innovative activation methods for soft actuators and sensors. The effectiveness of these systems is increased through signal modulation techniques. Specifically, phase modulation is used for soft actuators and frequency modula- tion is applied to soft sensors. These methods are crucial to improving actuator control and performance, as well as enhancing the sensitivity and signal clarity of sensors. Consequently, the integration and over- all performance of these components within wearable systems are substantially improved. The objective is to imitate the functionalities of muscles and the sensory characteristics of the skin in wearable sys- tems. These soft actuation and sensing suits are designed to be versatile and suitable for a wide range of activities. At first, this research focuses on mimicking human muscle functions through soft electrostatic force driven actuators. An electrostatic zipping actuator is introduced that operates using a dielectric flu- idic transducer (DFT) mechanism and utilizes a combination of electrostatic force and silicone oil to achieve deformation and provide tactile feedback. The research also involves the design of a multi-layer electrostatic (ES) clutch that is specifically designed to offer adequate support for isometric muscle con- tractions. To assist in holding tasks and reduce the risks of musculoskeletal disorders (MSDs), a semi- active suit has been created. The ES clutches in this suit are notable for their compact and lightweight construction, as well as their ability to consistently generate supportive force through electrostatic prin- ciples. This is demonstrated by their fast response times in real-world applications. Furthermore, the research introduces a novel 3-phase ES clutch system that aims to address the issues of residual charge and force degradation commonly observed in conventional ES clutches. Incorporation of a 3-phase volt- age application in this system significantly improves control, reduces the effects of residual charges, and consequently enhances both the performance and stability, surpassing that of standard ES clutches. Secondly, to mimic the sensation of human skin, there is a need to develop a high-resolution sens- ing array and multi-modal sensing capabilities. The research introduces a single-line multi-channel sensing system, which significantly simplifies wiring complexity while maintaining multi-touch func- tionality and performance. This innovative system combines swept frequency capacitive sensing (SFCS) with frequency division multiplexing (FDM), enabling the efficient transmission of multi-touch signals through a minimal two-wire setup, thus expanding its potential applications. Additionally, the study develops a multifunctional sensor system capable of simultaneously measuring strain and force signals through a two-wire connection. This system utilizes a frequency domain approach for multimodal signal measurement and models the frequency characteristics of various sensing signals. This configuration al- lows independent and simultaneous signal measurements from multiple sensors, effectively overcoming the complexities associated with wiring in wearable sensor systems. In summary, this study makes significant advances in two important areas: the advancement of soft actuators and sensors system for wearable technologies. It effectively applies phase modulation to electrostatic actuators to imitate the function of human muscle contractions and incorporates them into wearable systems. In order to replicate the sensing capabilities of human skin, research addresses challenges related to complex wiring and the interpretation of multiple signals. In addition, there is a growing need for adaptable wearable systems that can be used in various activities and settings. These advances have the potential to greatly improve user experience and safety in a wide range of fields, including industrial applications, interactive technologies, and various wearable systems.