Prosthetics, orthotics, rehabilitation/assistive living devices, and robotics in general have progressed greatly as a result of recent advances in linear actuation technology. Nevertheless, the best linear actuator technology in existence remains biological muscle tissue. Despite being inferior to modern artifical actuators in many respects, muscle exhibits many deisrable features which have been difficult to artificially replicate.Current "bio-mimetic" devices make use of a variety of materials ranging from shape memory alloys (such as Nitinol (NiTi)), to conductive or chemo-resistive polymers. While these systems tend to mimicthe function of muscle to some degree, they are not satisfactory. Some require chemical changes, which cannot mimic the quick response time of muscle, while others lack fuel (power) efficiency comparable to that of the muscle. Some researchers have discovered ways to compensate for, or to correct these limitations, but almost always the solutions come at the expense of verall device mass; the end results feeling unnatural or being unwieldy to end-users.NiTi has been at the forefront of the medical, aeronautical, and industrial fields; finding uses in artierial and vascular stents, motors, micro-circuitry, and space satellite actuators. The use of this material as an actuator has been limited due to significant tradeoffs between power consumption, force, percent compression, and lenght for this lightweight memory wire. Conventional solutions to these limitations have come at the expense of, once again, increasing device weight. As a result, NiTi actuators have had a difficulty finding uses replacing biological muscle.However, some of these tradeoffs have now been reconciled with a new staggered (combinational parallel and series) configuation of NiTi wires. A light weight, low power cartridge-like, muscle-staggered array (MSA) is under development for prosthetics or exoskeleton assist devices. the intellectual merit of the project is to develop a low-cost MSA device that is easily and quickly manufactured, and which is easily adaptable to a variety of functional uses well beyond the prosethic or rehabilitative fields. Robotics, micro-electronics, and aeronautics for example, could all benefit from affordable, small integrated actuators. Preliminary results suggest that an MSA of 9 wire bundles, with ideal overlap of 5-6% of their length, can simulate a muscle-like compression of over 30%. This requires under 18V and 20mA for the compression to occur under 1s; this is achieved with less than 5.7% error.
|Original language||English (US)|
|State||Published - Jul 25 2006|