Optimization Of The Seating Position In A Human-Powered Vehicle

  • Y. Lei
  • M. B. Trabia
  • D. Too
Keywords: cycling, seat position, pedals, bicycle

Abstract

An aerobic and an anaerobic designs for a human-powered vehicle (HPV) are considered. In both cases the rider's seating position is an important design factor for either maximizing the vehicle's speed or minimizing the rider's energy requirement. The rider's seating position affects not only the aerodynamic performance of the vehicle, but more importantly the rider's physical performance. The goal of this study is to use optimization methods to improve the HPV design. The paper starts by deriving equation for torque produced by the hip and knee joints during pedaling. These equations include inertial and gravity effects. In the aerobic design the objective function is to reduce both the average and maximum variation of the torques on the hip and knee joints. In the anaerobic design, the objective function is to maximize the average of the torques on the hip and knee joints. Hip and joint torques are function of the vehicle's speed and the aerodynamic coefficient as well as the road conditions. The design variables are: 1. the seat inclination angle 2. the seat to pedal angle 3. the seat to pedal distance 4. the crank length. The search for optimal solution in both cases is constrained by: 1. the motion limits of hip and knee joints 2. conditions to ensure that the seat to crank position results in full rotation of the crank. 3. visibility of the road that limits how far the seat can be inclined for safe driving. The results have been verified by comparing it to the experimental data of Too [ 1991] for maximum anaerobic performance of a stationary bike. Both experimental and analytical techniques produced close values of the seat to pedal angles.