This document provides an overview of the Segway personal transporter. It describes the Segway's basic design as a self-balancing two-wheeled electric vehicle. It then models the Segway as an inverted pendulum, an inherently unstable system. It explains how sensors, PID control, and a motor are used in a closed-loop control system to stabilize the Segway and keep the rider upright through feedback of angle measurements. Applications of control theory allow the Segway to smoothly transition directions in response to the rider's movements.

2. CONTENTS
Introduction
Basic Design
Simplified Model
Closed Loop Control
Application of Sensors for Measurements
PID Control Action
Stabilization of System
Uses of the Commercial Model

3. INTRODUCTION
Segway is a two wheeled, battery powered
electric vehicle.
This self balancing Personal Transporter
can reach upto 20km/hr.
It was invented by Dean Kamen in the year
2001.
The name Segway is derived from segue,
meaning 'smooth transition'.

4. BASIC DESIGN
The vehicle consists of a platform on which
the user stands.
The platform has two wheels attached side
by side, parallel to each other on the same
axis.
A handlebar is provided for the user to hold
while riding.
But, why doesn't it fall?

5. BASIC DESIGN
That is because the vehicle is self
balancing.
It may look like that the user would fall off
such a vehicle.
But the use of 'Control Theory' stabilizes
this inherently unstable system.
So, are we curious to know about this
awesome application of our subject?

6. SIMPLIFIED MODEL
The Segway
represents an
'Inverted Pendulum'.
Unlike a regular
pendulum, it is an
inherently unstable
system.

7. SIMPLIFIED MODEL
Now we will use control theory to stabilize
the system.
The reference or desired value is 90° with
respect to horizontal.
At this point the pendulum is least likely to
fall off.
Now we need something to implement this
simple logic. What is that?

8. CLOSED LOOP CONTROL
So, we measure the angle, then at summing
point make adjustments to the error signal, then
controller adjusts the carts position to attain the
desired set point.

9. APPLICATION OF SENSORS
To measure the angle, many sensors can
be used. Here only 3 of them will be
discussed.
The cheapest and common is the
potentiometer.
The potentiometer provides a voltage
proportional to the angular displacement of
the pendulum.

10. APPLICATION OF SENSORS
Optical Encoder, this measures the angle
of the pendulum using light, and a circular
disk.
IMU Sensor, Inertial Measurement Unit. It
consists of 3-axis accelerometer and 3-axis
gyroscope.
The cost of these sensors are inversely
proportional to sensitivity.

11. PID CONTROLACTION
Now the error signal is modified to control
signal.
This control signal acts as the input to the
system.
Now the cart moves according to the
control signal, which tends to minimize the
error and stabilizes the system.

12. PID CONTROLACTION
P controller sends a control signal
proportional to the error.
I controller sends a control signal
proportional to the accumulated error over a
certain time interval.
D controller sends a control signal
proportional to the rate of change of error.

13. PID CONTROLACTION
Now since only P controller, or I controller
or D controller cannot stabilize the system,
we use them in parallel combination.
This sums up the control signal providing
optimum modification of the error signal.
Tuning the controller must be done to
make the cart functional.

14. STABILIZATION OF SYSTEM
The system can only be stabilized by
controlling the position.
To control the position a motor must be
used.
According to the control signal a DC motor
is controlled using PWM to bring the cart to
a position, at which, the pendulum is 90°.

15. STABILIZATION OF SYSTEM
The control of an inverted pendulum cart is
far more simple than controlling a Segway.
Segway is designed to handle disturbances
to the system.
Leaning forward accelerates, leaning
backward decelerates and leaning sideways
makes turns.

16. IMPORTANCE
Segway is an example of Control Theory
applied to a mechanical system.
This is used in many sectors.
Police departments use it to patrol the
streets smoothly.
This eco-friendly vehicle is an excellent
transporter.

17. My presentation couldn't cover the entire topic, but
I tried to uncover the subject to reveal it's true
beauty. The beauty we all should seek to attain
next level of perfection, to gift the subject a
devotion and sincerity it deserves.

18. Created and presented by
Debargha Chakraborty