Little Bot, Big Project: building a mechatronic drumming robot

Masters student Trent Little took on more than he bargained for when he began work on a mechatronic percussion system—with no training as a musician.

Man sits adjusting dials on a mechatronic robot system and drum

Trent’s system, currently nicknamed ‘Little Drummer Bot’, is relatively novel even within the innovative musical robotics field. “There haven’t been that many professional attempts at robotic percussion systems in the past,” Trent explains. “I had no musical background, so I saw it as a real challenge to get my bearings and take the project on.” The work has given Trent tremendous respect for interdisciplinary researchers such as his co-supervisor Jim Murphy from the University’s New Zealand School of Music. “I listen to music in a different way now, having had to learn all the timings and tempo, the quarter notes and eighth notes, and just how hard it is to be a drummer!”

The Drummer Bot, like many of the School’s hardware projects, has passed between a number of students in consecutive years, each of whom refine and improve on the mechanism. In Trent’s hands, the direction and design of the Bot has changed dramatically. “Instead of telling it ‘motor one moves here, motor two moves here’, all you have to do is enter in the name of the drum that you want to strike, the velocity and the distance from the drum before you strike.”

Trent has also worked to significantly expand the percussive range of the robot. “The design of the robot centered on surpassing the limitations of human drummers without losing their expressive sound. I designed and tested one robotic arm to begin with—now there are three identical robots, connected by one board that controls each arm. Each one is able to play an entire drum kit horizontally or vertically.”

It’s also the first mechatronic percussion system to take into account the variability and compliance of human grip when playing. Trent’s sticks range in size from 12mm to 19mm in diameter and are made of brass or wood; you can change the Bot’s silicone grips to use different sticks and vary the tension on the stick to gain a range of percussive expressivity. “The ability to change the strength of grip or compliance hasn’t been seen in robotic percussion before, so it’s really exciting to be the first to play with it.”

“A lot of the common uses of musical mechatronics are for kitschy installation pieces,” Trent notes. “But I would like to see this project used as a way to surpass the limitations of analog and digital synthesisers in drumming packages for composers—because they’re limited by how many audio recordings they have of a certain instrument being hit a certain way as to how much they can reproduce musically, whereas this robot means you can create any sound with any drum or stick you want.”

The Drummer Bot, he believes, can potentially even surpass the abilities of a human. “The system can already play continuously for at least five hours. So the idea is that you can work at a computer and compose music far longer than you can have someone sit and play those pieces for you to have real time feedback as a composer. The Bot responds to the messages you give it, instantly. The maximum stroke rate is 3100 per minute—that’s about two and a half times what the fastest person could do. It doesn’t care if the piece has never been played before—there are no human limitations.”

Trent admits that his own limits were tested during the year-long Masters project, but says that completion was a hugely satisfying aspect of his postgraduate study. “There was definitely an ‘aha’ moment of ‘I’ve actually done it, it’s not theoretical anymore. I can send a signal and tell it to go to a place, and it does’. At the end of it I looked back and went—wow, if I can do that, where’s my limit? How far can I push myself?”

The confidence gained during his Masters is a key component in Trent’s new role as an Electronics and Quality Design Engineer for Compac Industries Ltd. “The freedom of postgraduate study in engineering and the direction provided by both of my supervisors allowed me to develop my skills further than I ever could have imagined. I really feel that the knowledge grown from the ECEN degree culminated in this project—and I couldn’t be happier with the result.”