Proposals

To kick off our Final Project, we were asked by Prof. Brent Gillespie back on October 1st, 2009 to provide individual project proposals. After reviewing each we were placed into groups according to similar ideas. Our groups had the similar idea of a wireless drum stick and high bandwidth drum head response. Although each of our ideas varied we were able to compile important features of each into a final design idea.

In Scott's first proposal he mentions that "standard drum kits are very large and difficult to transport. The main advantage of the proposed instrument is that it is portable, which would allow musicians to practice and perform in any environment." As you will see in our design our intention to make a smaller drum set that is portable is possible. Although we all agreed on using MIDI as the musical interface to our synthesizer he also contributed the idea of using "either a Hall Effect sensor or potentiometer" to measure motor position. This idea came in handy when we encountered our first setbacks which we will mention later. A diagram of Scott's proposed idea can be seen in the figure below. There were also a few ideas implemented from Mike's first proposal. He suggested that we used force sensing resistors (FSRs) oriented specifically on a drum pad to sensor where a drum stick would hit. This information is important for sound because with conventional drums the closer to the rim you strike the higher the pitch or frequency. As you will find, this idea was implemented during part of the development process but was eventually removed due to poor sensing capabilities of the FSRs from a drum stick strike. However, with our final design there is still room for improvement to mimic this positional convention. Being a drummer himself, he was really interested in achieving "vibrotactile feedback for electronic drum pads because it could lead to improved use of fine control. Allowing the user to feel vibrations of the stick through this design will improve performance during rolls and flams (fine control beats). " A picture of his design from the first proposal can be seen below.

Eric's project idea to develop an "electronic MIDI drum set with variable stiffness and damping" was very similar to our combined final design. He makes the important point that "currently, most of these electronic drum sets are made of rubber pads for all of its components, which makes hitting all of these different drum components actually feel the same. The goal of this project is to design and create a haptic interface between the drum pads and the user so that each of these pads gives different “feel” to the user based on the mechanical response it produces." As you will see in our final design we used many of the important concepts Eric mentions here. He also suggest we use position and velocity sensors to control the "virtual" stiffness and damping of the haptic interface. A figure of Eric's proposed idea can be seen in the following diagram. We compiled all of our ideas and came up with the following design shown below. We decided to use a linear actuator (voice coil) provided by Prof. Gillespie and sense position using a hall-effect sensor. Then through a unanimous decision use MIDI and an Arduino to provide feedback through a synthesizer to the human user. The response of the drum head will be determined through initial characterization of a conventional drum. This system identification was to be conducted using LabView and a MEMS accelerometer. Then through modeling we proposed we could implement these effects virtually.

With this design there we provided important force analysis diagrams and equations which you can see below. In our second proposal we mentioned that "interactions with a stick and drumhead can generally be characterized into four different stages. These four stages are shown below along with their respective dynamic models. In the first mode the drumhead is initially in its stable configuration before the stick has struck its surface. The second stage occurs when a stick is in direct contact with the surface for a short period of time. Then once the stick is removed the head continues to vibrate, which is the third stage. The fourth and final stage can be classified as a complex interaction of an already vibrating head and a new stick strike. Each of these user interactions can be described in a quantitative manner as you will in the following diagrams."