Monday, October 16, 2006
1:30 p.m. to 5:30 p.m.
Flexures, Compliant Instruments and Multi-Axis
Compliant Positioning Stages
Martin L. Culpepper (Massachusetts Institute of Technology)
Compliant mechanisms and flexures rely on the deformation
of some or all of their components to create smooth and controlled precision
motions. They may be designed to posses sub-nanometer resolution, sub-nanometer
repeatability, and one to six axis motion capability. Their motion characteristics,
ease of fabrication and scalability to macro/meso/micro-scale devices
makes them attractive for many existing and emerging precision applications.
It is important for precision engineers to understand the fundamentals
of compliant design, traditional and new methods of creating/modeling
compliant device concepts, and the practical knowledge required to calibrate
and implement them within precision positioning systems. This course
was designed to provide an overview of the fundamentals of compliant
design and recent advances which enable precision engineers to create:
- Basic compliant machine elements/devices (e.g.
flexure hinges, flexure bearings, two-axis positioning stages)
- Complex mechanical devices/instruments (e.g. multi-axis nano-positioning
stages)
The tutorial consists of four sections:
(1) Fundamentals of compliant element/machine design [1.25 hours]:
This section covers the basic principles, concepts, and theory that
govern the design and optimization of flexible devices. We will examine:
(a) Important material properties and commonly used materials
(b) Some basic flexure building blocks (flexure hinges, bearings, etc...)
(c) Static and dynamic modeling of compliant devices
(d) Summary the positive and negative attributes of compliant devices
(2) Design, fabrication and implementation of multi-axis
compliant devices [1.25 hours]:
This section focuses on how one uses the fundamentals of compliant design
to create new compliant elements/devices. Although we will cover the
design of basic compliant elements/devices, emphasis will be placed
upon the design of multi-axis compliant devices. We will examine:
(a) Creation of new compliant device designs using the principles of
constraint-based design
(b) Tolerancing, fabrication and calibration
(c) Integration with actuators and sensors
(3) Design simulators [0.5 hours]:
Participants will learn how to use the CoMeT (Compliant Mechanisms Tool),
a freeware program, which may be used to design/optimize precision compliant
devices. Tablet PCs will be provided for the purpose of this exercise.
Participants will model and optimize a one DOF flexure bearing, a flexure
hinge, and a six-axis compliant nanopositioner.
(4) Hands-on experiments [1.0 hours]
Experiments will be run to characterize the compliant elements that
were modeled in section 3. These exercises are designed to demonstrate
the proper use of compliance-based technology and to enable attendees
to gain hands-on experience with these technologies. Exercises will
explore concepts such as stiffness, accuracy, repeatability, parasitic
errors, calibration, the effect of fabrication/assembly tolerances,
and bandwidth.
