> FIGURE 4. Kinematic
diagram of DARwIn.
joint. They are the simplest joints in the
entire robot since they are only one
degree of freedom (DOF). Figure 7
shows a simple way of designing a
bracket for the elbow joint.
Kinematically Spherical Joint
Design — The Easy One
In our opinion, the next “easy”
joint to design is the kinematically
spherical joint at the shoulder. You
have a lot of freedom when placing the
motors and mounting them for the
shoulders since the shoulders are naturally broad. In order to create a kinematically spherical joint, all three axes
of rotation must intersect at the same
point (Figure 8). This is fairly simple in
concept, but getting configuration and
dimensions correct for the design can
be tricky. Figure 7 shows how we used
> FIGURE 8. Photo with lines showing
spherical joints on DARwIn.
a series of brackets to create kinematically spherical joints for the shoulders.
A Step Up — The Ankle
If you are comfortable with designing the arms and knees, try designing
∧ FIGURE 5. Exploded view of chest.
∧ FIGURE 6. New hip design that will
use a CNC mill.
∧ FIGURE 7. Exploded view of arm.
SERVO 01.2007 41
