A Soft, Controllable, High Force Density Linear Brake Utilizing Layer Jamming

While much work has focused on the design of actuators for inputting energy into robotic systems, less work has been dedicated to devices that remove energy in a controlled manner, especially in the field of soft robotics. Such devices have the potential to significantly modulate the dynamics of a system with very low required input power. In this letter, we leverage the concept of layer jamming, previously used for variable stiffness devices, to create a controllable, high force density, soft layer jamming brake (SLJB). We introduce the design, modeling, and performance analysis of the SLJB and demonstrate variable tensile resisting forces through the regulation of vacuum pressure. Further, we measure and model the tensile force with respect to different layer materials, vacuum pressures, and lengthening velocities, and show its ability to absorb energy during collisions. We hope to apply the SLJB in a number of applications in wearable technology.

I. Introduction

There are three main categories of devices that researchers investigate for controlling the dynamics of a robotic system: 1) actuators that create forces to add energy to a system, 2) variable stiffness mechanisms that modulate the form of the energy in the system (e.g., from kinetic to elastic potential energy), and 3) brakes and dampers to remove energy from the system. While many robotic systems rely on traditional actuators like servo motors, researchers have developed artificial muscles to create linear motions with high force density which offer alternatives to motors [1]–[3]. Others have focused on designing series elastic actuators or variable stiffness actuators to give compliance during collisions [4]–[6]. Finally, the work on energy-removing devices, such as brakes and dampers, includes devices based on varying physics. Researchers have modeled and characterized designs using magnetorheological fluid [7] –[9], electrorheological fluid [10] , [11], and piezoelectric actuated friction [12]. Other researchers have modeled eddy current brakes [13] and a hydraulic shock absorber [14] .