A system, method, and computer storage configured for determining period-ending positions of multiple parts movable by select actuation of corresponding active materials. The operations include receiving, from a work-source sensor, work-source input indicating a distance moved by the work source and a direction of the movement, and determining, based on the work-source input and a first and second status histories, corresponding to a first and a second part, respectively, first and second distances travelled by the parts, respectively. Operations also include calculating, based on the first and second distances determined and first and second period-starting positions, corresponding to the first and second parts, respectively, first and second period-ending positions for the first and second parts, respectively.