Furuta Pendulum

Overview

We were tasked with constructing and programming a Furuta pendulum, the goal of which is to hold the vertical arm up through horizontal rotation of the horizontal arm connected to the motor shaft. Essentially, there were two separate projects: constructing the physical pendulum assembly, and programming the PIC to control the motor so the pendulum would function. The basic mechanism consists of an encoder measuring the angle of rotation of the vertical arm, and the PIC receiving that information and controlling the motor to keep the arm in the vertical position.

Team Members

• Matthel Luther (Electrical Engineering, Class of 2010)
• Krystian Zimowski (Mechanical Engineering, Class of 2010)
• Gabriel Haack (Mechanical Engineering, Class of 2011)

Mechanical Design

There are three sections of the pendulum that can each be addressed separately: the base assembly with motor housing (including the motor itself); the arm assembly, which includes the horizontal arm, the vertical arm, and the encoder apparatus; and the box into which the whole pendulum was placed, including mechanical stops, the PIC and electrical circuitry, and a button to start the program. Each section begins with a parts list; generic terms like "block" or "slab" indicate that these parts were made from aluminum scraps and can be just as effective with a different size or shape, or that they can be easily machined to fit any design.

Base Assembly

• Base - large aluminum block
• Support columns - 3/4" solid aluminum tubing
• Top platform - 1/4" acrylic
• Lazy susan - McMaster-Carr 4" Aluminum Turntable
• Motor - Pittman something or other

The aluminum block used was cylindrical: a hole was end-milled into the center to fit the encoder on the motor. As you can see, the motor fits right in, preventing any rotation of the motor itself. Two holes were drilled into the block on either side of the motor hole for the support columns, which were cut to be even with the top of the motor casing (not the motor shaft) once they were press-fit into the holes. The tops of the columns were drilled and tapped. Acrylic was cut to the size of the turntable and clearance holes were drilled to screw it to the motor, the support columns, and the turntable and a hole was cut in the center for the motor shaft. Once the support columns were in place, the motor was placed in the base, the platform was screwed onto the motor and columns, and the turntable was screwed onto the platform.

Arm Assembly

• Horizontal arm - 3/4" hollow aluminum tubing
• Vertical arm - 1/2" hollow aluminum tubing
• Press-fits for set screws - solid aluminum tubing with diameters equal to the inner diameter of the arms
• Weight - small aluminum block
• Encoder supports - flat aluminum slab
• Encoder shaft - machined solid aluminum tube
• Bearings
• Encoder - whatever model # it is

The horizontal arm was cut to be long enough to stick out well past the edge of the turntable. A short piece of tubing was press-fit into one end, and a hole was drilled through it for the motor shaft and another for a set screw. The same was done for the vertical arm, in this case for the encoder shaft.

Electrical Design

There were wires and stuff.

Code

It told the motor what to do.

Results

It worked!

Reflections

We're awesome.