Development of an Antagonistic SMA Actuator for Instar Rifle Stabilization System

Abstract

Shape memory alloys are notoriously slow and suffer from creep and controllability issues [1,2]. This paper presents three methods to address these issues: a high-stress cyclic conditioning regime to reduce creep to operationally insignificant levels, an unconventional pulse-width-modulated duty cycle with heatsink to increase frequency to the ten hertz range, and simple position feedback control strategy for motion control. These methods are discussed within the context of a simple antagonistic leveraged SMA actuation system developed for an INertially STAbilized Rifle (INSTAR). An overview of design and basic parameter models for the L-Lever is provided along with benchtop experimental characterization of the quasistatic and dynamic behavior. The actuator was integrated into a one degree of freedom INSTAR platform to demonstrate the insitu methods via barrel control. The methods discussed in this paper led to a fast, low-creep, controllable actuator with outstanding authority resulting in precise barrel control with capabilities to greatly increase shooter accuracy.

Control of an automotive shape memory alloy mirror actuator

“…Joule heating is an effective and simple way for actuating SMA components. Existing applications of SMA actuators include devices such as active endoscopes, rifle stabilizer systems and commercial linear actuators [22][23][24].…”

An Automotive SMA Mirror Actuator: Modeling, Design, and Experimental Evaluation

“…It has been shown that creep can be a significant design factor for SMA actuators as referenced in Barnes et al (2005). To account for creep in the design of the mirror, the initial strain in the wire should exceed the strain required for actuation by 20% [double the reported creep strain maximum (Barnes et al, 2005)].…”

“…To account for creep in the design of the mirror, the initial strain in the wire should exceed the strain required for actuation by 20% [double the reported creep strain maximum (Barnes et al, 2005)]. …”

Transient Thermodynamic Modelling and Experimental Validation of an Antagonistic SMA Actuator

“…However, many of these issues are being addressed and resolved through active research [11,[16][17][18][19]. With the cost of the material becoming more competitive and quality control improving [2,20], particularly for SMA material in wire form, several industries such as automotive and appliances are now considering sma actuation for high yield, low cost components [20] that replace existing technologies (e.g.…”

“…Many applications have been addressed with antagonistic wire actuations including that for human tremor cancellation [11,17], automotive mirror positioners [25], and microgrippers [26]. Such applications commonly use ad-hoc (typically PID) and heuristic control approaches and have produced accurate, precise, and relatively high-speed control of SMA motion in antagonistic SMA wire actuators [23,24].…”