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Human-Inspired Hyper Dynamic Manipulation
are the action ranges of joint stops in clockwise and counterclockwise
directions, respectively.
According to Equations (4.10) and (4.11), it is possible to utilize the passive torque resulting from the joint stop as part of the driving torque in the
joint, similar to the utilization of dynamically coupled driving to improve
the capability of hyper dynamic manipulation for the whole manipulator.
Actually, this is also due to the transference of power from the base to the
end-effector through the contact of joint stops. Additionally, the load capability of the end-effector can be improved to exceed the limitation of the active
torque of actuators when the link is in contact with the joint stop.
Another useful method is forming the joint stop by the mechanism
configuration of a manipulator itself. That is, by contacting one arm with
another arm, this contact can be regarded as an available joint stop. In this
case, some flexible skin on the arm is necessary to supply elastic and damping characteristics. This is especially useful for the redundant manipulator.
Because the utilization of this kind of joint stop is similar to the aforementioned joint stop, the following discussions are limited to the case of the
structural joint stop.
4.2.3 Case Study: Mechanism Design of a Golf Swing Robot
As a case study to utilize dynamically coupled driving and joint stops in a
manipulator, a golf swing robot with a smart structure is considered that can
imitate the golf swing motion by a human.
Figure 4.4 shows an overview of the developed prototype of the golf swing
robot and its configuration. The robot consists of a base frame, the first joint
(shoulder joint), an arm, the second joint (wrist joint), and a club. The first
joint is to realize the equivalent function of shoulder in human and is driven
by a direct drive (DD) motor, which is suitable for dynamically coupled driving. In the second joint a small DD motor with two joint stops to realize the
function of wrist in human is used. The small DD motor in the wrist joint is
selected so that its load capability is only a little greater than the static torque
due to the weight of the club. Because a small DD motor is used in the wrist
joint, the structure of the wrist joint, as well as that of the whole manipulator,
becomes very compact and light; that is, smart. Distribution of the actuators
is an important point to realize hyper dynamic manipulations in a smart
structure. On the other hand, the small DD motor in the wrist joint does not
directly contribute to the acceleration of the wrist joint in a high-speed swing
motion. Therefore, in this mechanism, the dynamic manipulation is mainly
realized by the power of the DD motor in the shoulder joint; that is, dynamically coupled driving is to be utilized for hyper dynamic manipulations.
The detailed structure of the joint stops is shown in Figure 4.5. Each joint
stop consists of a pair of magnets and a shock absorber. The elastic force is
derived from the repelling force between two magnets, and the viscous force