Balancing Electronics

The balancing electronics consist of a gyro and accelerometer. The outputs of these are combined with complementary filters as the gyro works best at high speed, and the accelerometer works best at low speed. (More precisely- the gyro drifts over time, so a high pass filter will eliminate this drift from the output, like eliminating DC offset. Also, summing the accelerometer over time will equal zero, whereas integrating the gyro over time will equal the drift offset, not zero.)

Gyro

Product Number	DC-SS010
Product Name	Angular Rate Sensor XV-3500CB Gyroscope Prototype PCB
Operating Temperature	0℃to+80℃
Storage Temperature	-10℃ to 85℃
Defection Range	-100deg/s to +100deg/s
Scale Factor	0.65mV/deg/s
Voltage output of sensor in static Typical Value	1320mV~1380mV 1350mV
Dimensions	32(mm) x 19(mm)
Net Weight	10g/0.3oz

I bought this gyro breakout board from eBay, and time will tell whether it will serve my purpose nicely. Key specs of the XV-3500cb is:

Frequency response: 200hz
Angular response: +/- 100 degrees/sec

Accelerometer

Quick features list:

• Supply voltage: 5V.
• X/Y/Z Axis analogue output voltage: 1.65V at zero g (ratiometric output).
• Audio amplifier output: 250mW into 8 ohm.
• Multiplexer control voltage 0/5V.
• 0-2kHz bandwidth (can be limited by adding external capacitance to analogue axis output).
• Module uses standard 0.1" pitch DIP pin spacing and is breadboard/stripboard friendly for fast prototyping without special tools.
• The module dimensions are approximately 10mm x 20mm.
• Acceleration range +/-2g.
• On-board stable 3V3 supply for sensor.
• No external components required for most applications.
• Power 'ON' LED

I bought this accelerometer breakout from eBay. It uses the LIS302SG accelerometer IC. This looks like an ideal accelerometer.

What? Why? How?

A few years ago, I had seen Trevor Blackwell's page on building a vehicle inspired by the segway™, which he subsequently followed up with an updated version. I was very impressed but not inspired to build my own just yet.

I went on holiday to Jersey and had a go on a segway there, and I just knew I had to have/build one.

The basic plan:

Frame

Build from steel box section, using a minimal amount to maximum effectiveness. Can not use aluminium as cannot weld this myself, but I can use a MIG welder to weld a steel frame together.

Wheels

Use 20" bicycle wheel with disc brake mount hubs. This allows me to bolt on a sprocket to the standard 6 bolt disc brake mount.

Motors

Use 750W motors for upto 1HP rated operation. Use 1:5.4 chain drive reduction ratio to bring 2800RPM down to 520RPM for an approximate top speed of 31MPH.

Electronics

Use OSMC H-Bridge to drive the motors at upto 160A continuous if needed. Use Arduino to control OSMC and keep the balance by reading a gyro and an accelerometer.