Phase difference detecting apparatus and wheelchair using the same

A wheelchair, comprising:

• a pair of wheels;
• a first rotating axis and a second rotating axis provided at a same axis and each connected with said pair of wheels;
• and
• a phase difference detecting apparatus including:
• a frame;
• a first planetary gear train, said first planetary gear train including first elements of a first sun gear, a first ring gear, and a first planetary gear carrier, one first element of said first sun gear, said first ring gear, and said first planetary gear is fixed to the frame, another first element is connected to a first rotating axis, and a final first element is unconnected to the frame and the first rotating axis;
• a second planetary gear train, said second planetary gear train including second elements of a second sun gear, a second ring gear, and a second planetary gear carrier, one second element of said second sun gear, second ring gear, and second planetary gear carrier corresponding to said first element of said first planetary gear train fixed to the frame is rotatably mounted, one second element corresponding to said first element of said first planetary gear train connected to the first rotating axis is connected to a second rotating axis, said second rotating axis rotating independently of said first rotating axis, and one second element is connected to the corresponding first element of said first planetary gear train unconnected to the frame and first rotating axis;
• and
• means for detecting a phase difference with respect to rotations of said first rotating axis and said second rotating axis by measuring a rotation degree of said second element corresponding to said first element of said planetary gear train fixed to the frame.