An Experimental Investigation of Human/Bicycle Dynamics and Rider Skill in Children and Adults.

Abstract

While humans have been riding bicycles for nearly 200 years, the dynamics of how exactly they achieve this are not well understood. The overall goals of this dissertation were to identify the major control strategies that humans use to balance and steer bicycles, as well as to identify performance metrics that reliably distinguish rider skill level. To achieve these goals, we introduced: a) a novel instrumented bicycle to measure rider control inputs and bicycle response outputs, b) an experimental design and analytical approach for tracking and quantifying rider learning, and c) an experimental design and analytical approaches to measure the dynamics of human/bicycle balance and quantify rider balance performance. We employed variations of the instrumented bicycle in three studies that focused on: 1) how adult riders control bicycle kinematics during steady-state turning, 2) the initial learning of steering and balance control as children learn to ride bicycles, and 3) the balance skill of adult expert and novice riders.

The findings from these studies advance our understanding of the types of control used by human riders, and simultaneously, quantify rider learning and skill. During steady-state turning, rider lean strongly influences steering torque, suggesting that rider lean plays an important role in bicycle control. Children learned to ride after successfully learning how to steer in the direction of bicycle roll, thereby increasing the correlation between steer and bicycle roll angular velocities (coefficient of determination increased from 0.22 to 0.75 during the learning process). In adults, the superior balance performance of skilled versus novice riders is revealed by highly correlated lateral positions of the center of pressure and center of mass (coefficients of determination of 0.97 versus 0.89, respectively). In achieving their superior balance performance, skilled riders employed more rider lean control, less steer control, and used less control effort than novice riders. We conclude that rider lean (i.e., any lateral movements of the rider) plays a dominant role in both steering and balancing a bicycle, and that achieving balance requires coordinating both steer and rider lean (the two rider control inputs) with bicycle roll (the bicycle response).