A 3D cycling model has been developed that combines bicycle mechanics, rider biomechanics and environmental factors into a single dynamic system. The aim of the model is to identify mechanical mechanisms that influence performance in a road cycling time trial with simulations representing real cyclists competing over an actual course. The model is constructed using the Matlab toolbox SimMechanics to model physical entities and Simulink to model control structures. The system is actuated by force or motion actuators applied to joints or bodies with sensors measuring the resulting forces and motion. SimMechanics automatically derives the equations of motion leaving the developer free to concentrate on defining the mechanics of the system. Initial conditions are specified and a variable step ODE solver numerically integrates solutions that meet defined tolerances. Initial validation compared model simulations with data reported in the literature. Rider-less self-stability after a perturbation was found to compare well with previous work. Weave eigenvalues became negative at 4.2 m/s and capsize eigenvalues became almost positive at 6.1 m/s. Crank torque over a cycle at 255 W was recorded from the model and found to correlate well (R2 =0.97) with previously published experimental data. Finally, the tyre model generated tyre cornering stiffness of 62N/degree which closely matched the 60 N/degree reported by a previous investigation. Experimental field validation compared actual and model predicted time taken by 14 experienced cyclists to complete a time trial over an undulating 2.5 mile road course. The course was digitised and loaded into the model and the model parameterised with individual mass and aero-dynamic characteristics. Wind strength and direction were also measured. An error level of 1.4% (±1.5%) was found between actual and predicted time. This compares well with the average 1.32% error reported by existing road cycling models over less complex courses. (Author/publisher) For this paper, other papers and posters presented at this Symposium see http://bicycle.tudelft.nl/bmd2010/
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