Active Modeling and Control for Shape Memory Alloy Actuators

Abstract

In this paper, an active modeling and control scheme is developed for Shape Memory Alloy (SMA) actuators to eliminate the negative influences caused by the uncertainties in its dynamics. First, a nonlinear SMA dynamic model based on Liang model and the empirical models is built and linearized, and all the uncertainties due to time-varying parameters, external disturbances, as well as the linearization, are considered as model error of the linearized model. Secondly, an active modeling based on Kalman filter is constructed to estimate the model error in real time, which intends to improve the model accuracy actively. Finally, an active modeling based control method is proposed to compensate the model error in order to improve control performance of SMA actuators. Experiments are conducted on a one degree-of-freedom (DOF) testbed actuated by a SMA wire. The experimental results of the active model error estimation, and the control performance with and without the active model based compensation are presented and compared to demonstrate the improvements of the proposed scheme. INDEX TERMS Shape memory alloy (SMA), model error, active modeling, active compensation control.

Modelling of a shape memory alloy actuator for feedforward hysteresis compensator considering load fluctuation

“…Thermal model is defined by the heat transfer equation, where it is assumed that heat loss occurs only via natural convection. The temperature dynamics are given by the following differential equation [27, 28] as $$$\begin{array}{l}m{c}_{p}\frac{dT}{dt}={I}^{2}R-{h}_{c}{A}_{s}\left(T-{T}_{\text{room}}\right)\hfill \end{array}$$$ where I (A) stands for the electric current, A s (m 2 ) denotes the surface area, c p (J/kg°C) signifies the specific heat, m (kg) expresses the mass, h c (W/m 2 °C) represents the heat convection coefficient, and T room (°C) is the ambient temperature. Although the wire surface area will change during the SMA actuator operation, it is assumed that these effects are negligible.…”

“…Thermal model is defined by the heat transfer equation, where it is assumed that heat loss occurs only via natural convection. The temperature dynamics are given by the following differential equation [27,28] as…”

Actuation response of typical biased shape memory alloy wire under variable electric heating rates: Experimental investigation and modeling

“…Using higher current or voltage appeared to actuate SMA in a shorter time, but it contributed to overheating (Velázquez et al, 2006) and high inertia loads (Dynalloy, Inc., 2013). To avoid such situations, actuation times of cycle-worked SMA wire actuators were typically in the range of 1.0–20 s (Copaci et al, 2020; Jayender et al, 2008; Zhang et al, 2019). As a result, the actuation of SMA actuators was considered as a quasi-static process approximately.…”

An Investigation of the Effects of Thermal Interference between Adjacent Nitinol Spring Actuators in a Tactile Display

“…Shape Memory Alloys (SMAs) are exceptional smart materials with properties of pseudoelasticity (PE) and shape memory effect (SME) due to their thermomechanical characteristics and phase transformations [10]. SMAs fulfil several important characteristics; in particular, they are lightweight, have a high energy density, reduced power to weight ratio [11], and extremely high fatigue resistance to cyclic motion, compactness [12] and noiseless operation [1]. SMAs have found applications as sensors and actuators in several industries including aerospace, biomedicine [13], and robotics.…”