**MINIATURE MANIPULATOR ACTUATED BY ELECTROSTRICTIVE POLYMERS (ESP)**

Principal Investigator; Yoseph Bar‑Cohen, Sect. 355, 125-112, x4-2610
January 12, 1995

**OBJECTIVES**: The objective is to use an interdisciplinary approach to
form an alternative actuation drive for a miniature manipulator using
efficient electrostrictive polymers (ESP). To develop an efficient
muscle actuation mechanism, an electromechanical analysis will be
performed and ESP materials will be synthesized with a strong
electrostriction effect. A muscle actuator and a manipulator will be
designed and fabricated using ESP to demonstrate the capability of this
technology as a viable alternative actuation material to reduce the
actuator mass, size and power requirements while providing precise
positioning and effective actuation characteristics for potential
spacecraft applications.

**JUSTIFICATION**: Electroceramic (piezoelectric and electrostrictive)
actuators are used increasingly to articulate spacecraft components
(e.g. WF/PC II) and to perform various robotic tasks. A wide variety of
such solid state devices are becoming available and they include motors,
translators and manipulators. In contrast to electroceramics, ESP is an
emerging new actuation material technology with capabilities that cannot
be matched by the rigid ceramics. We are proposing herein to develop an
effective actuator that is driven by an ESP material and to take
advantage of these materials resilience and the ability to engineer
their properties to the design requirements. ESP can be easily mass‑
produced at low cost and in any desired shape. They can be designed to
emulate the operation of muscles while maintaining low mass, resilience,
high toughness, no strain hysteresis, no need for poling (as compared to
piezoelectric elements), provide higher electrostrictive strain constant
than piezoceramics (potentially, 2 orders of magnitude higher) and have
high inherent vibration dampening characteristics.

**APPROACH**: We are proposing to develop a low mass, compact and low
power actuator that is driven by an efficient ESP material in the form.
The ESP will be synthesized with a high conversion efficiency and the
actuator will be developed as an emulation of muscles action for the
articulation of a miniature manipulator. The basic mechanism of
electrostriction in organic polymers involves the alignment of highly
dipolar pendant groups by the action of an applied electric field.
Jointly with Case Western University and Stanford Research Institute, we
will develop the required ESP material by synthesizing a backbone
polymer with a high free-volume to allow easy alignment of the pendant
group in response to electric field activation. Results from prior
studies that were sponsored by the Navy and others will be incorporated
herein. The program will be proposed as a three years effort and will
consist of the following tasks:

TASK 1: SYNTHESIS OF AN EFFECTIVE ESP MATERIAL - A dipolar pendant group
that can create a strong dipolar interaction and a backbone polymer will
be selected through chemical and electromechanical analysis to develop
an ESP with effective electrostriction effect. The mechanical properties
of the ESP will be enhanced by selecting a high modulus backbone
thermoelastic polymer. Computer algorithm will be developed to assist in
the effective selection and synthesis of the material.

TASK 2: DESIGN AN ESP ACTUATION DEVICE ‑ An compact muscle actuator that
employs ESP will be developed to provide a high stroke at low power,
mass and size. To allow effective design of this electro‑mechanical
device we will mechanically analyze the operation/performance of ESP
driven actuator. Design software will be developed to assure the
effective use of the characteristics of ESP materials. The actuator will
be tested and evaluated at the Actuators Characterization Lab of Section
355.

TASK 3: DEVELOP A MANIPULATOR ‑ A manipulator will be designed and
fabricated using the ESP muscle actuator. The manipulator will be
subjected to a series of electrical, mechanical and thermal tests to
determine the performance envelop and to form a baseline comparison with
conventional drive mechanisms.

**DELIVERABLES**:

-   An effecient electrostrictive polymer (ESP) for a muscle actuator.

-   A muscle actuation mechanism that uses effectively the capability of
    ESP materials.

-   A manipulator actuated by an ESP actuator consuming lower power,
    significantly lower mass and size to form an effective alternative
    to current actuators.

**RESOURCES REQUIREMENTS** FY\'96 FY\'97 FY\'98

\$245K \$390K \$235K

**SCHEDULE** Year FY\'96 FY97 FY\'98

Quarter 1 2 3 4 1 2 3 4 1 2 3 4

[TASK 1]{.underline}

Definition of actuation specifications \-\-\--\"

Electromechanical analysis \-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\"\-\-\-\-- \"

Materials synthesis \-\-\-\-\-\-\-\-\-\-\--\"\-\-\-\-\-\-\-\-\-\-\--\"

Demonstration and documentation \--\"

[TASK 2]{.underline}

Design muscle actuator
\-\-\-\-\-\-\-\--\"\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\"\-\-\--

Develop muscle actuator \-\-\-\-\-\-\-\--\"\-\-\-\-\-\-\-\--\"

Tests and performance-evaluation \-\-\-\--\"\-\-\-\-\-\-\-\-\-\--\"

Demonstration and documentation \--\"

[TASK 3]{.underline}

Design miniature manipulator \-\-\-\-\-\-\-\-\-\-\--\"

Fabricate manipulator \-\--\"\-\-\-\-\-\-\-\-\-\--\"

Performance envelop analysis -\"\-\-\-\-\-\-\-\-\-\-\-\--\"

Demonstration and documentation \--\"

**DUAL USE POTENTIAL** ‑ The low cost and mass production potential of
ESPs can open a wide range of commercial applications including
actuation of mechanisms in automobiles (e.g. mirror adjustment) and
toys. Further, these materials can potentialy be used for active noise
damping in aircraft cabinets for passengers comfort.

**PARTNERSHIP AND PARTICIPANTS** - The synthesis of effective ESP
materials will be made jointly with Prof. Morton Litt of Case‑Western
University and with Prof. Janathan How from Stanford Research Institute,
the design and fabrication of the ESP muscle actuator and the
manipulator will be done jointly with Section 345 and with John Vranish
from GSFC. Section 355 will perform the electromechanical analysis and
the material/actuators/arm performance tests and evaluation.