Tuesday, April 13, 2010


Main Design Concept

Piano was originally invented to be played by human beings. Based on the fact that our hands are the most efficient tool to play the keyboards, the design of the robot imitates the form of a human hand, consisting five fingers mounted on the main carriage. The ability that each finger can move and strike independently of each other maximizes the functional efficiency and better simulates human hand motion.

Figure 1. Isometric View of the Hand

Figure 2. The Finger Range

System Overview

The design consists of three subsystems, the horizontal motion system, the finger rotational motion system, and the valve control system. The horizontal motion system consists of the hand and the track. The two-foot long track has two guiding bars to prevent the hand from tilting. The gear rack is installed on the back of the track. As shown in Figure 3, the DC motor mounted on the base plate of the hand can turn the pinion and move the carriage across the gear racks.
Theoretically, the track can provide enough space for the hand to play four octaves of notes.

Figure 3. The hand base and track

The finger rotational motion system consists of five servos controlling five acrylic fingers with the strikers. As shown in Figure 4, the striker has two main parts, the cylinder and the piston. The cylinder is made of stainless steel to have smooth surface without any scratch, and the piston is made of graphite because of its light weight and self-lubrication. These parts have to be machined to a precision of 0.0005” to maximize the performance. The striker will either stuck or leak air if the piston and cylinder do not match.

Figure 4. Striker piston and cylinder

The striker also has a spring return system as shown in Figure 5. When air is supplied, the piston will be pushed down instantly. The spring design ensures the mechanism to go back to its original position whenever the air intake is removed.

Figure 5. Section view of the key strikers

When air is supplied, the piston will be pushed down instantly. The key striker will return as the air intake is removed. Shown in Figure 6, the valve control system has a main manifold, five rotational passage cylinders, and five micro servos to turn the cylinders and line up the passage
holes to control the air flow. The manifold is made of delrin to minimize friction between the cylinders and the manifold. All the holes are tapped with 1/8” NPT (National Pipe Thread Tapered) tap to seal off any possible air leakage.

Figure 6. The complete valve control unit

Most of the structures, including the fingers, are laser-printed from 0.177” acrylic sheets and the striker cylinders are made of stainless steel. Rubber gaskets are also made to seal the space between the cylinders and cylinder caps. Shown in Figure 7, all other miscellaneous parts, including cylinder caps and striker tips, are made of delrin due to its light weight, high strength, and low price.

Figure 7. The components for strikers, including caps, cylinders, fingers, pistons and gaskets

Figure 8. The Final Overall System

How the System Works

Figure 9. General Flow Chart of the System

The flowchart above gives a basic overview of how the larger parts of the system fit together. When the system is idle, it can enter one of two modes based upon user input. The first mode parses and analyzes the Keyboard Input Protocol (KIP) while the other samples sound data and tries to do pitch detection. After the analysis is done, path planning is done to determing how best to play the notes. Finally, the mechanism is controlled to follow the designated path.

Team's Responsibility

Jung Hoon Sohn / Mechanism Control
Ana Isabel Flores / Electrical Circuit Implementation
Ryan Kenichiro Sakauye / Pitch Detection
Steven Yeh / Mechanism Design and Implementation