Background We explored whether a non-invasive, handheld device using Active Cancellation of Tremor (ACT) technology could stabilize tremor-induced motion of a spoon in individuals with essential tremor (ET). Methods Fifteen ET subjects (9M/6F) performed 3 tasks with the ACT device turned on and off. Tremor severity was rated with the Fahn-Tolosa-Marin Tremor Rating Scale (TRS). Subjective improvement was rated by subjects with the Clinical Global Impression Scale (CGI-S). Tremor amplitude was measured using device-embedded accelerometers in 11 subjects. Results TRS scores improved with ACT on (versus off) in all 3 tasks: holding (1.00±0.76 vs. 0.27±0.70, p=0.016), eating (1.47±1.06 vs. 0.13±0.64, p=0.001) and transferring (1.33±0.82 vs. 0.27±0.59, p=0.001). CGI-S improved with eating and transferring, but not the holding task. Accelerometer measurements demonstrated 71-76% reduction in tremor with ACT device on. Conclusions This non-invasive, handheld ACT device can reduce tremor amplitude and severity for eating and transferring tasks in individuals with ET.

Latches are essential machine elements utilized by all sectors (military, automotive, consumer, manufacturing, etc.) with a growing need for active capabilities such as automatic release and reset, which require actuation. Shape memory alloy (SMA) actuation is an attractive alternative technology to conventional actuation (electrical, hydraulic, etc.) because SMA, particularly in the wire form, is simple, inexpensive, lightweight, and compact. This paper introduces a fundamental latch technology, referred to as the T-latch, which is driven by an ultrafast SMA wire actuator that employs a novel spool-packaged architecture to produce the necessary rotary release motion within a compact footprint. The T-latch technology can engage passively, maintain a strong structural connection in multiple degrees of freedom with zero power consumption, actively release within a very short timeframe (<20 ms, utilizing the SMA spooled actuator), and then repeat operation with automatic reset. The generic architecture of the T-latch and governing operational behavioral models discussed within this paper provide the background for synthesizing basic active latches across a broad range of applications. To illustrate the utility and general operation of the T-latch, a proof-of-concept prototype was designed, built, and experimentally characterized regarding the basic functions of engagement, retention, release, and reset for a common case study of automotive panel lockdown. Based on the successful demonstration and model validation presented in this study, the T-latch demonstrates its promise as an attractive alternative technology to conventional technologies with the potential to enable simple, low-cost, lightweight, and compact active latches across a broad range of industrial applications.

Shape memory alloy (SMA) actuators in the wire form are attractive because of their simplistic architecture and electrical operation, and their manufacturability at high yields and low cost. While SMA actuators are known for their superior work density among smart materials, packaging long lengths of SMA wire needed for moderate to large motions is an ongoing technical challenge. This article investigates spooling as a packaging approach to provide more compact actuator footprints. An analytical, quasi-static model is derived to provide a foundational tool for the analysis and synthesis of spool-packaged SMA wire actuators. The model predicts motion with respect to a generalized architecture, and specifiable geometric, material, and loading parameters. The model prediction accounts for the effects of local friction loss and bending strains, and for a “binding” limitation due to accumulated friction. An experimental validation study demonstrates the model’s ability to predict actuator motion well in terms of form and magnitude with respect to load and packaging geometry. This model provides a basis for a systematic application of spooled-packaging techniques to overcome packaging limitations of SMA, positioning SMA wire actuators as a viable alternative in many applications.

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