Compliant Parallel Kinematic Machines Applying Distributed Compliance to PKMs for sub-micron

accuracy and durability.

Compliant Parallel Kinematic Machine A 3-D manipulator with sub-micron accuracy

Ultra-Precision Mobile Control Surface (platform) •  Solid-state mechanism with no pivots

• No conventional pivots; hence no joint play

• No conventional flexures; hence no stress concentrations

•  Employs large displacement compliant joints •  Very high off-axis stiffness •  Embedded sensors to directly read 3d positions and orientations

Existing Parallel Kinematic Machines

3 DoF CPKM

x

z

Compliant Parallel Kinematic Machine Design

Compliant Joints

Compliant Revolute Joint and Universal Joints Compliant Translational Joint

•  Notch type Flexible Joint –  Limited range of motion –  Stress concentration –  Axis drift

Compliant Parallel Kinematic Machine Design

CPKM Synthesis with Dual Vector

1.  Mo&on  Modeling  –  The  required  mo&on  is  represented  in  dual  vector  form:  (Magnitude)

(Pitch){Direc&on  +ε  Posi&on}  

–  The  mo&on  is  decomposed  into  single  DoF  to  match  with  joints  

2.  Constraining  Leg  Design  –  The  compliant  joints  are  represented  in  dual  vector:    

(mo&on  range)(1+  ε  0)  {Direc&on  +ε  Posi&on}  ⇒  CR  Joint  (mo&on  range)(0+  ε  1)  {Direc&on  +ε  Posi&on}  ⇒  CT  Joint  

3.  Ac&ve  Leg  Design  –  The  generic  ac&ve  legs  are  added  according  to  the  required  DoF  –  The  legs  should  be  linearly  independent  –  Detail  design  of    joints  through  kinema&c  analysis  

Compliant Parallel Kinematic Machine Design

Case #1: Design for DoF

The motion requirement is specified only by DoF

1. Select joints with corresponding dof by comparing pitches

2. Align the selected joints using dual-vectors

3. Add active legs

Compliant Parallel Kinematic Machine Design

Case #2: Design for Analytic Motion

X!

Y!

Z!

Ellipse Generating 3-DoF problem

Decomposed Motions

Compliant Parallel Kinematic Machine Design

Constraining Leg Design

1. Match Pitches

2. Locate with Line Vectors

Compliant Parallel Kinematic Machine Design

Active Leg Design

•  Active Legs are generic: CU+2DoF Actuator+CU=6-DoF (1 active)

•  The final dimensions of the joints are determined through kinematic analysis.

•  The active legs are located so that all the legs are linearly independent.

Compliant Parallel Kinematic Machine Design

Summary of CPKM Design Example

•  Generalized  design  method  for  parallel  kinema&c  machines  –  Constraining  leg  for  arbitrary  DoF  –  Building  block  approach  using  dual  vector  for  kinema&c  

analysis  and  synthesis  –  Forward  kinema&cs  of  the  Parallel  Kinema&c  Machines  is  

straight  forward    by  embedding  a  sensor  in  the  constraining  leg  

•  High  precision  mechanism  design  with  compliant  joints  –  Large  displacement  compliant  joints  that  eliminate  the  

problems  of  generic  mechanical  joints  

Novel Devices and Ideas (with Northwest University)

Embedded Sensor with Compliant Joint

Artificial Muscle

Polymer

Composite

Conventionally assembled design versus a compliant system with an embedded actuator

A three-degree-of-freedom parallel kinematic platform comprising of highly accurate and precision zero-play compliant “joints” assembled with error-prone pneumatic actuators

Conceptual rendering of a single-piece multi-material, compliant gripper with embedded artificial muscle – an example of no-assembly, bio-inspired, compliant system

Compliant Parallel Kinematic Machine A 3-D manipulator with sub-micron accuracy

Ultra-Precision Mobile Control Surface (platform) •  Solid-state mechanism with no pivots

• No conventional pivots; hence no joint play

• No conventional flexures; hence no stress concentrations

•  Employs large displacement compliant joints •  Very high off-axis stiffness •  Embedded sensors to directly read 3d positions and orientations

Manipulating, pointing and tracking applications for Missile seekers

Adaptive Optics

x

z

Compliant Parallel Kinematic Machine Design

Compliant Joints

Compliant Revolute Joint and Universal Joints Compliant Translational Joint

•  Notch type Flexible Joint –  Limited range of motion –  Stress concentration –  Axis drift

2 Dof CPKM (Y.M. Moon & S, Kota 2001)"

Ultra-Precision Mobile Control Surface (platform) •  Employs large displacement compliant joints •  Very high off-axis stiffness •  Embedded sensors to directly read

3d positions and orientations

Compliant Parallel Kinematic Machine A 3-D manipulator with sub-micron accuracy

Ultra-Precision Mobile Control Surface (platform) •  Solid-state mechanism with no pivots

• No conventional pivots; hence no joint play

• No conventional flexures; hence no stress concentrations

•  Employs large displacement compliant joints •  Very high off-axis stiffness •  Embedded sensors to directly read 3d positions and orientations

Manipulating, pointing and tracking applications for Missile seekers

Adaptive Optics

Compliant Parallel Kinematic Machine Design

3 DoF CPKM

Steel Construction