Various machines have been developed to address the need for countermeasures of bone and muscle deterioration when humans operate over extended time in space. Even though these machines are in use, each of them has many limitations that need to be addressed in an effort to prepare for human missions to distant bodies in the solar system.
The inside of the piston consists of parallel electrodes with alternating polarity that increase the ERF viscosity when activated. This increase leads to the formation of a virtual valve inside the piston creating impeding force to the piston motion. The cross-sectional area of the piston is mostly hollow to allow low piston resistance to the motion when the electrodes are not activated, and produce high impedance when the electrodes are activated. A balanced volume is created on the two sides of the piston so that pushing it will only involve fluid flow against the effect of the increased viscosity in the gaps between the electrodes.
The elements are shaped as a cylinder or donut with a piston that is moved inside the internal cavity containing ERF. The elements have a piston inside the cavity with shafts on its two sides. The piston is pushed or pulled inside the chambers and consists of parallel electrodes with opposing polarity wired through one of the shafts. When the electrodes are subjected to electric field, they form a virtual valve causing increased viscosity and impeded flow. Using ERF offers the ability to proportionally (as a function of the voltage) increase the viscosity of the fluid with a very fast reaction time on the order of milliseconds. The feasibility of this approach is straightforward from the nature of ERF materials and preliminary tests made in the lab.
ERF properties of high yield stress, low current density, and fast response (less than one millisecond) offer essential characteristics for the construction of the exoskeleton. ERFs can apply very high electrically controlled resistive forces or torque while their size (weight and geometric parameters) can be very small. Their long life and ability to function in a wide temperature range (from –40 to 200 ºC) allows for their use in extreme environments. ERFs are also non-abrasive, non-toxic, and nonpolluting (meet health and safety regulations).
The technology is applicable as a compact exercise machine for astronauts’ countermeasure of microgravity, an exercise machine for sport, or as a device for rehabilitation of patients with limb issues.
This work was done by Yoseph Bar-Cohen, Mircea Badescu, and Stewart Sherrit of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48393
This Brief includes a Technical Support Package (TSP).
On-Command Force and Torque Impeding Devices (OC-FTID) Using ERF
(reference NPO-48393) is currently available for download from the TSP library.
Don't have an account?
Overview
The document discusses the development of On-Command Force and Torque Impeding Devices (OC-FTID) utilizing Electro-Rheological Fluids (ERF) at NASA's Jet Propulsion Laboratory. The primary innovation involves a mechanism that employs ERF to control resistance to both linear and rotary movements, effectively creating a "virtual valve" that adjusts its resistivity based on an applied electric field.
Electro-rheological fluids are suspensions of fine particles in an insulating base fluid, which exhibit significant changes in viscosity when subjected to an electric field. This phenomenon, first explained by Winslow in the 1940s, allows ERFs to transition from a liquid state to a viscoelastic state (similar to a gel) in milliseconds. The document highlights the advantages of ERFs, including high yield stress, low current density, fast response times, and the ability to operate in extreme temperatures, making them suitable for various applications, including aerospace.
The OC-FTID devices consist of a chamber filled with ERF, where a piston with electrodes is positioned. When an electric field is applied, the ERF's viscosity increases, impeding the movement of the piston. This mechanism allows for proportional control of resistance based on the voltage applied, enabling precise adjustments in force and torque. The design is compact and lightweight, addressing the limitations of existing exercise machines used by astronauts, which are often bulky and require significant maintenance.
The document also emphasizes the importance of these devices in counteracting the effects of microgravity on astronauts, such as muscle and bone deterioration. Current exercise machines used in space missions have drawbacks, including large mass and operational volume, which the OC-FTID aims to overcome. By providing a more efficient and effective means of resistance training, these devices could enhance the fitness and health of astronauts during long-duration space missions.
In summary, the document outlines a novel approach to using ERF in creating devices that can dynamically control movement resistance, offering significant benefits for space exploration and potentially other applications. The technology represents a step forward in developing compact, efficient systems for maintaining physical fitness in challenging environments.
