Compliant Parallel Kinematic Machines

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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

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

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

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

Case #2: Design for Analytic Motion

Ellipse Generating 3-DoF problem

Decomposed Motions

Constraining Leg Design

1. Match Pitches

2. Locate with Line Vectors

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.

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

Manipulating, pointing and tracking applications for Missile seekers

Adaptive Optics

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

Manipulating, pointing and tracking applications for Missile seekers

Adaptive Optics

3 DoF CPKM

Steel Construction

Compliant Parallel Kinematic Machines

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