74
Biologically Inspired Robotics
Trajectory
generation
Robot
manipulator
.
.
PD
controller
τ ff
τ fb
τ
+
+
+
−
θ, θ
θ r , θ r
FIGURE 4.7
Control system.
4.4 S imulation and Experimental Results
for the Golf Swing Robot
4.4.1 Simulation
Using the above-discussed motion generation method, simulations of the
golf swing motion with joint stops for an impact speed of 25 m/s are implemented and the results are shown in Figure 4.8.
From Figure 4.8, the following features can be concluded.
1. In the backswing phase from the address position to the top position, the arm and the club are taken back by their motors just like
in conventional motion control, because the angular velocity in this
period is not so high.
2. During the downswing phase, the shoulder joint is accelerated first,
and the wrist joint is accelerated later. At the beginning of the downswing, the wrist joint is kept in contact with the joint stop and a large
constraint (passive) torque by the joint stop is generated (Figures 4.8b
and 4.8d). This passive torque plays an important role in the initial
acceleration of the wrist joint, because the active torque by the wrist
joint is too small to accelerate the wrist joint itself at the beginning
of the downswing. Just before the impact time, the shoulder joint
is decelerated first, but the wrist joint is still accelerated rapidly to
realize a very high head speed at the impact time (Figure 4.8b). This
multistep acceleration is due to the utilization of dynamically coupled driving in joint 2, as discussed in Section 4.2. From Figure 4.8e,
it can be observed that the dynamically coupled driving torque of
joint 2 is mainly utilized to accelerate the golf club (Figure 4.6) in the
downswing phase.
3. In the follow-through phase from impact position to finish position, an inverse behavior to that in the downswing period can
be observed. That is, the wrist joint is decelerated and stopped
mainly by dynamically coupled driving torque and passive torque