Biomedical Engineering Reference
In-Depth Information
Figure 10.9 (See color insert following page 302) An android head and a robotic hand that serve as
biomimetic platforms for the development of artificial muscles. (Acknowledgement: This photograph was taken at
JPL where the head was sculptured and instrumented by D. Hanson, University of Texas, Dallas. The hand was
made by G. Whiteley, Sheffield Hallam University, U.K.)
android head that can make facial expressions and a robotic hand with activatable joints. Currently,
conventional electric motors produce the deformations required for the android to make relevant
facial expressions of the Android. Once effective EAP materials are available they will be modeled
into the head. There they can receive control instructions for the creation of desired facial ex-
pressions. The robotic hand is equipped with sensors for the operation of the various joints and is
capable of mimicking the human hand. The index finger of this hand is currently being driven by
conventional motors to establish a baseline. The motors would be replaced by EAP when they are
developed as effective actuators.
10.5.2.1
Gripper and Robotic Arm Lifter
To mimic a biological hand using simple elements, the author and his coinvestigators constructed a
miniature robotic arm that was lifted by a rolled dielectric elastomer EAP (Section 10.3.1.1) as a
linear actuator and four IPMC-based fingers as a bending actuator (Chapter 21 in Bar-Cohen, 2004).
The linear actuator was used to raise and drop a graphite or epoxy rod which served as a simplistic
representation of a robotic arm. Unfortunately, after activating this actuator, the arm sustains a
series of oscillations that need to be dampened to allow accurate positioning. This requires sensors
and a feedback loop to support the kinematics of the system control. Several alternatives were
explored, including establishment of a self-sensing capability, but more work is needed before such
an arm can become practical. To produce an end-effector for the arm, a four finger gripper was
developed (see Figure 10.10). These bending actuator fingers were made of IPMC (Section
10.3.2.2) strips with hooks at the bottom emulating fingernails. As shown in Figure 10.10, this
gripper grabs rocks just like the human hand.
10.5.2.2
Biologically Inspired Robots for Planetary Robotics
The evolution in the capabilities that are inspired by biology has increased to a level where more
sophisticated and demanding fields, such as space science, are considering the use of such robots.
At JPL, four- and six-legged robots are currently being developed for consideration in future
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