自行車重心與煞車性能分析

本研究主要分析騎乘自行車時，騎乘姿勢與自行車參數對重心與煞車性能的影響。為求得騎乘時重心的變化，將騎乘者與自行車分成五個部份，並由重心原理與幾何關係，推得以人體與自行車尺寸比例為變數的重心方程式，再使用Matlab程式設計軟體進行實例運算，以探討重心位置變化的情形及分析自行車各參數對重心變化與煞車性能的影響。由結果可知，車把高度主要影響重心的水平距離；座墊高度主要影響重心的垂直高度；車架影響重心的起始位置與重心的變動間距，但對重心變化的型態影響甚小；在安全的考量下，同時制動前、後煞車器時，重心往後移，可獲得較佳的減速度；最大減速度受限於地面摩擦係數，且重心的水平距離與垂直高度的比值小於地面摩擦係數時，則會發生後輪鎖死的現象。

關鍵字

自行車；重心；煞車性能； Matlab

並列摘要

This paper focuses on the center of gravity and breaking performance analysis of the different riding forms. In order to obtain the changes of the center of gravity, the rider and the bicycle are divided into five parts in this research. Both the gravity theory and geometry relations are applied to derive the equation of the center of gravity. Matlab, a programming software for instance mathematical operation, is applied to analyze the effects of the different riding forms and bicycle parameters for the center of gravity and braking performance. From the research results, the major parameters that affect the center of gravity in horizontal distance and vertical height are the handlebar’s height and the seat’s height, respectively. The frame is to affect the initial position and spacing changes of the center of gravity, but it changes the type of the center of gravity to be small. When both the front and rear brake are acted simultaneously, the center of gravity is to shift to the rear and it results in that the better deceleration can be obtained. The maximum deceleration is limited by the ground friction coefficient, and the rear wheel will be locked if the center of gravity of the horizontal distance and vertical height ratio is less than the ground friction coefficient.