Here C1 refers to the cosine of angle 8, and S1
refers to the sine of angle 8,, and similar notations
apply to other terms.
From this, the rotational angles can be calculated
as shown below:
82 = arcsin(-K3 . J)
(2)
€4 = arcsin[(I3 * J)/cos(82)]
For the ankle joint, the direction cosine matrix relating
the foot frame and shank frame may be derived
based on two orthopedic angles 8, and 8, as
81 = arcsin[(K, . I)/cos(82)]
The rotational angles of the foot can now be calculated
as