# What The Bicycle Can Tell Us About Human Control ¶

Jason K. Moore

EME 1 Lecture

November 28, 2016

# In 2004, I wanted to be¶

Sam Whittingham, world record (~80 mph)

# Questions raised¶

• Why is one bicycle harder to control than another?
• How can we design a bicycle such that it is easy to control?

# A little about bicycle dynamics¶

Bicycles are curious machines

• Bicycles are the most efficient from of human transportation (lowest energy per person per distance)
• In general, you have to balance a bicycle before directing it from point A to B
• It is possible to balance a bicycle without touching the handlebars
• People can do all kinds of stunts on bicycles

# Question¶

If you want you bicycle to turn to the left, what direction do you turn the handlebars?

# Why do you have to countersteer?¶

If you are in a steady right hand turn, you must be leaning to the right. So, the only way to initiate a right hand lean is to move the wheel contact points out to the left.

# Bicycles can be stable¶

Also predicted by Newton's Laws!

$F = m a$

Most bicycles are stable once they reach a certain speed, i.e. if you try to knock it over it rights itself.

# Gyroscopic Action¶

"The wheel is a gyroscope so it always steers in the correct direction"

# Caster Trail¶

"The front wheel of a bicycle trails behind the steering axis just like a caster on an office chair, so the wheel always corrects the steering."

# What if gryoscopic action and caster are removed!¶

TU Delft Two Mass Skate Bicycle

# Human Sensory Feedback¶

## Sensors¶

• We sense our body position, orientation, and configuration with our eyes
• We sense our body's configuration with muscle spindles
• We sense our orientation wrt to gravity, orientation rate, and angular acceleration with the utricle in our ear
• We sense forces being applied to our body with our proceptive system

## Limitations¶

• Time delays from sensing to acutation
• Limits in acutation forces
• Limits in frequency of motion

# Mathematical models of human control¶

Feedforward and feedback mathematical models can predict the human sensing and actuation relationship.

# Why does any of this matter?¶

1. The dynamics of the bicycle describe how it moves when forces are applied to it.
2. Humans apply forces to a bicycle to make it transport them where they want to go.
3. The dynamics can be changed by changing the vehicles physical properties, i.e. mass, geometry, tires, etc.

This leads to my research interests:

How do we design human controlled machines (e.g. vehicles) such that they perfectly compliment the human's intentions?

# The approach¶

• Create mathematical models that predict how machines move if forces are applied to them.
• Create mathematical models that predict how a person will actuate their muscles to complete if they sense certain cues.
• Design optimal machines with optimal control systems such that the human can easily, efficiently, and accurately control the machine.

# Optimal Bicycle Designs¶

Design can be treated as an optimization.

Once you have mathematical definitions of a system you can then use mathematical and computational techniques to answer questions like:

"What would the geometry of the vehicle be if it was the easiest to control?"

F-22 Raptor

BMW's Concept

# Powered Exoskeletons¶

Parker Hannafin Indego Exoskeleton