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Planar rotation

Let frame B (with unit vectors b1, b2 and b3) rotates with respect to A frame (with unit vectors a1, a2 and a3). Figure 0.3 shows a special case when B rotates about b3 = a3 with angle θ with respect to A.


PIC

Figure 0.3: Planar angular velocity– a1 -a2 plane


       ⌊                  ⌋
         cosΦ   - sin Φ  0
CBA  = ⌈ sinΦ    cosΦ   0 ⌉
           0       0    1
(0.2)

Similarly in the case shown in Fig. 0.4, direction cosine matrix is
       ⌊                  ⌋
         1    0       0
CBA  = ⌈ 0  cosΦ   - sin Φ ⌉
         0  sinΦ    cosΦ
(0.3)


PIC

Figure 0.4: Planar angular velocity– a2 -a3 plane


and in the case shown in Fig. 0.5, direction cosine matrix is
       ⌊                  ⌋
          cosΦ    0  sin Φ
CBA  = ⌈    0     1   0   ⌉
         - sinΦ   0  cosΦ
(0.4)


PIC

Figure 0.5: Planar angular velocity– a3 -a1 plane


Any of these cases are called simple rotation.

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