45
Analysis and Design of a Bionic Fitness Cycle
0°
270°
90°
180°
Area I
Area II
Area III
Area IV
FIGURE 3.11
Distribution area of the crank position.
traditional fitness cycles, the pedal can only fit the treading motion, and the
feet do not produce a driving effect while lifting because the two pedals are
fixed at a 180-degree angle. Thus, when the foot on one side is treading, the
pedal will drive the foot on the other side to lift at the same time. Finally, a
circular motion is completed.
For the Bio-Cycle, the driving force in a cycle of motion has its own characteristics. Because they are driving separately, the two feet need to produce
a driving force in both treading and lifting motions. The driving force in the
whole circular motion is always positive and has two peak values as shown
in Figure 3.12. One peak value is in area II for treading motion, and another
peak value is in area IV for lifting motion. The lifting motion is rarely used
in normal human sport, so the lifting peak value is much smaller than the
treading peak value and will cause discomfort while riding. Therefore, the
range of such cyclical fluctuation must be reduced.
In addition, the Bio-Cycle can achieve many motion modes, and different motions have different driving characteristics. So when the user changes
500.0
400.0
300.0
200.0
100.0
0.0
Crank Angle (°)
Fe (N)
0
45
90 135 180 225 270 315 360
FIGURE 3.12
Driving force in one cycle.