Applications of feedback control to musical instrument design [electronic resource]

In feedback control systems, the system variables being controlled—such as the velocity of vibrating strings or the position of motors—are estimated from sensor measurements, and the estimated information is fed back in order to influence the controlled variables. By controlling the system variables in this manner, the dynamics of the system can be fundamentally changed. We study how feedback control enables the design of radically new forms of musical instruments, with emphasis on two paradigms. The first paradigm is Feedback Controlled Acoustic Musical Instruments (FCAMI). Traditionally, musicians have owned many different kinds of acoustic instruments. Rather than requiring multiple instruments that have characteristic sound qualities, a musician might prefer to have a single instrument whose acoustics are essentially programmable. To achieve different or new sound characteristics, the musician could simply load a different instrument program, while the interface to the instrument would remain similar thus promoting skill transfer. We explain how to design feedback controllers with the goal of altering the dynamics of an acoustic instrument in musically salient ways. Positive real controllers are passive, so they are guaranteed not to add any energy to the acoustic musical instrument. As a consequence, they can be applied to any passive acoustic musical instrument in any configuration without driving it unstable. Finally, we relate positive real controllers to self-sustaining controllers for applications such as electromechanical bowing. The second paradigm is Haptic Musical Instruments (HMI). A haptic device can mechanically connect a musician to a virtual environment that synthesizes sound and provides force feedback. In this work, we study how to design the virtual haptic environment to assist a musician in making gestures to a musical instrument in a practical context. For example, the haptic drum provides a musician's drumstick with an extra push every time that the musician strikes the drum. This device allows the musician to make gestures that would otherwise be very difficult or impossible, such as arbitrarily long one-handed drum rolls and arbitrarily complex rudiments. To elucidate its behavior, we perform a nonlinear systems analysis of its dynamics. Next, we explain how to assist a musician in accurately selecting pitches from a continuous range on a Theremin-like haptic interface. We augment it with detents allowing the musician to feel the locations of equal-tempered pitches, yet the musician can still perform arbitrary pitch inflections such as glissandi, falls, and scoops. With the help of a subject test, we demonstrate that traditional detents as well as novel force-sensitive detents can provide accuracy improvements over simpler types of haptic feedback, such as spring feedback. In closing, we emphasize that the most appropriate type of haptic assistance depends on the task.

Keywords: Electrical Engineering
Advisor: Smith Julius O. (Julius Orion) primary advisor. Thesis advisor
Niemeyer Gunter advisor. Thesis advisor
Salisbury J. Kenneth advisor. Thesis advisor