Control Method for a 3D Form Display with Coil-type Shape Memory Alloy

Abstract

We previously proposed a new 3D form display actuated by shape memory alloy (SMA), which is capable of displaying large scale objects sequentially. Based on our devised method, our display uses a 16 16 array of pin-rods with 30mm stroke at 5mm intervals. In this paper, we discuss the control method of the shape memory alloy with a simple matrix drive circuit. This type of drive circuit can dramatically reduce the number of switch. In addition, we propose a novel approach using linear programming, where the simulated time to display a whole shape is reduced by about 50% or more with a large number of actuators.

A control loop structure based on semi-nonnegative matrix factorization for input-coupled systems

“…Flemming and Mascaro used a scheduler to select among commands of a row, a column, or a box pattern depending on which combination of configurations was best suited to the required surface [12]. Nakatani et al used linear programming to select which actuators to command thus improving on the refresh rate over line scanning [13]. The result nevertheless involved a scheduling procedure where a subset of pins was switched on or off.…”

“…In addition to Digital Clay, other pin arrays have been created [6][7][8][9][10][11][12][13][14][15]. The major challenges facing these devices result from the desire for high pin resolution, sufficient force output, fast surface generation, and feasible cost.…”

“…The major challenges facing these devices result from the desire for high pin resolution, sufficient force output, fast surface generation, and feasible cost. Due to these criteria, many pin arrays use a row-column input method where the input to each pin is a combination of a row input and a column input [12][13][14][15]. The method reduces the number of components, the total device size, and the number of control signals.…”

“…For more on the hydraulic system and the line scanning technique see Zhu and Book [4]. The line scanning procedure has been employed on pin array devices other than Digital Clay [3,[12][13]. The line scanning procedure actuates one column of cylinders at a time, iterating through the columns to generate a surface.…”

Passivity and practical considerations for the SNMF System

“…The control of each pin in the row-column structure is no longer independent because the pins are coupled by their inputs. The most common way to control the pins in the row-column structure has been to use scheduling procedures, where only a subset of pins are controlled at any point in time [9]- [11]. The most common of this is a line-scanning procedure, as used in LCD screens.…”