This chapter presents a narrative, beginning with pieces (likeSpatial String) that used mechatronic instruments still in their prototype stages and progressing through to en- semble compositions featuring an array of networked mechatronic instruments. By fol- lowing the works from earliest to most recent, a cycle is evident wherein new robots motivate new works, which in turn motivate changes and improvements to the robots. Of things learnt in the creation and execution of the works described in this chapter, three stand out as key lessons that centrally informed subsequent works. Firstly, afterSpatial
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String, it became clear that the bulky Swivel 1.0 (equipped with complicated power requirements, actuators, and pickup systems) needed to be replaced with a simpler, more portable system. This decision resulted not only in the development of Swivel 2 but also in the decision to create a lightweight, easy-to-build mechatronic drumming system in favour of a heavy system with potentially more degrees of freedom. The final appearance of Swivel 2 and Nudge, then, can be directly traced to the findings ofSpatial String.
Secondly, after the complicated deployment of Swivel 2, Nudge, Kritaanjli, and Mech- Bass inBhairavi Procedure 2, it became clear that a more streamlined means by which the robots could be used in an installation or performance setup was needed. This find- ing resulted in the decision to design and implement the Tangle suite of musical robotic networking tools.
Finally, after composing and performing Robotic Consistency, it was found that the abundance of actuator-specific commands required to instigate even a single note playing event on Swivel 2 resulted in prohibitively long composition times. As a result of this, to allow musical ideas to more rapidly be explored on Swivel 2, it was decided that the Tangle network should be equipped with the ability to output sequences of actuator instructions in response to a single client input event.
These three main lessons, learnt in the course of the compositions presented in this chapter, so directly informed the work presented throughout this thesis document that it is evident that musical robotic systems need to be tested in performance and instal- lation settings in order for their functionality to be properly understood. As crucial as laboratory-based characterisation is, such performance and installation use allows the lab-derived characterisations to be pitted against the non-ideal conditions encountered in real-world performance and installation contexts. For roboticists seeking to create in- struments for performance and installation use, it is imperative that every opportunity be taken to test their in-development systems outside of the laboratory.
The works presented in this chapter serve as the first existent collected body of new compositions and installations for musical robots designed with high degrees-of-freedom as a goal. It is hoped that these new works and the aforementioned lessons gained from them during their execution will allow future artists and composers to work with
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such instruments endowed with knowledge of the challenges and artistic affordances that accompany them.
Chapter 10
Summary & Conclusions
During the course of the work presented in this document, four new musical robots were built. These robots are each endowed with actuators placed in such a manner as to afford musical expressivity: MechBass and Swivel allow for portamento or discrete pitch-shifts; MechBass can vary the intensity of its note-picking events; Kritaanjli is capable of playing large numbers of notes at a time with adjustable loudness; Nudge can be set to hit many positions on one or more drums with a drumstick able to adjust its height above the drum head. The robots and their behaviours are described in Part 1 of this thesis.
These parametrically-rich musical robots allow composers to explore more musical ideas than is typical with many existent systems. However, when faced with an ensemble of such actuator-studded mechatrons, a challenge appears: to individually address the 92 actuators present in Nudge, MechBass, Kritaanjli, and Swivel is somewhat akin to writing software in assembly language: every event must be precisely and accurately specified by the user. What is needed is a paradigm for encoding these low-level actions in a musically-sensible manner. Part 2 of this thesis describes a number of methods for doing so: self-tuning for mechatronic chordophones (tested on Swivel 2) and a software suite that enables customised, potentially complicated output in response to simplified user input.
While both Part 1 and Part 2 of this thesis can be seen as freestanding, taken together they go toward realising what was a major goal in this project: to build expressive musical robots usable in live performance and installation contexts. While many previous
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works achieved one or the other, the work presented herein endeavours to achieve both: expressive musical robots belong in galleries, in museums, on stages, and in other live contexts, and it is a goal of this work to help to catalyse such a move out of the laboratory. During the course of this research, a number of conclusions were reached about the technical act of building musical robots, as well as the artisanal act of building musical robotic instruments. The next three sections detail summarise this document’s contri- butions and detail these conclusions, and are followed by a final section containing a number of immediate and long-term ideas for subsequent work.
10.1
Summary of Contributions
The goal of this work has been to create performance-oriented and installation-oriented musical robotic systems which employ new techniques to better function as expressive musical instruments. Toward this goal, the contributions that this work makes to the field of musical robotics fall into two main categories: work focusing on designing and building expressive musical robotic systems, and work focusing on enabling users to interface with these complicated parametrically-rich musical robots. The following list includes design and construction-related contributions. Collectively, they represent a body of new research into the engineering of mechatronic instruments.
• Two new mechatronic chordophones have been presented. These instruments fea- ture a number of subsystems novel to musical robotics, including new fretting systems, one based on a rotary motion-based fretting and the other based upon linear motion with string clamping. Also presented are novel approaches for vari- able pick intensity on robotic guitar systems.
• A polyphonic robotic harmonium with a novel variable pumping intensity system has been presented. The mechatronic design of this instrument is detailed, and its performance evaluated.
• The design and construction of a novel closed-loop robotic drum system has been detailed. This system can rotate to reposition its drum beater to various striking positions above one or more drums. Additionally, the beater’s proximity to the
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drum head may be changed in an online manner. Both the drumstick height- adjustment mechanism and the rotary-motion drumstick positioner are novel.
In addition to design and construction contributions, this work contains new research in networking and interfacing with expressive musical robots, as well as calibration and fail-safety systems. The following list highlights these contributions.
• A novel automated tuning system for robotic guitars has been presented. This system is based upon a pre-performance calibration routine wherein a string’s response to varying fretter positions is recorded. The string is then tuned at runtime by interpolating its current detuned value between previously-populated characterisation curves. This novel approach allows for user-defined intonation schemes to be played.
• A network for complicated musical robotics has been introduced. This network features numerous novel elements, including:
– The ability to customise the server’s output to a robot in response to input events from a client. These parametric encodings are detailed in Chapter 7. This novel parametric encoding system allows users to create custom map- pings from input interfaces.
– The integration of a number of fail-safe features, novel to musical robotics, intended to prevent the musical robots from entering into or remaining in unsafe states.
– A latency calibration routine, novel to mechatronic percussion systems, al- lowing multiple timers with different latencies to synchronise their actuation times.
• Also presented is the first user study in the discipline of musical mechatronics wherein a number of musicians were asked to use musical robots and to express their experiences with the use of parametrically-complicated networked mecha- tronic instruments.
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