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Overview of the 3 DOF Parallel- Architecture Wrist Mechanism Stephen Canfield, Professor Department of Mechanical Engineering Tennessee Technological University.

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Presentation on theme: "Overview of the 3 DOF Parallel- Architecture Wrist Mechanism Stephen Canfield, Professor Department of Mechanical Engineering Tennessee Technological University."— Presentation transcript:

1 Overview of the 3 DOF Parallel- Architecture Wrist Mechanism Stephen Canfield, Professor Department of Mechanical Engineering Tennessee Technological University November 10, 2008

2 Overview

3 About Parallel Mechanisms  Multiple load-bearing chains b/n output and base  Kinematics  Advantages Stronger, lighter  Disadvantages Reduced range of motion, kinematics

4 About the PAW  3-5R Spatial Parallel-architecture mechanism  3dof Pitch, yaw, plunge

5 Characteristics of the PAW  High payload-to-weight, good dynamic performance  Ground-relative actuation  All-revolute design  Closed-form forward/inverse kinematics exist  Large range of motion in orientation  Singularity free workspace (interior),greater than hemisphere  Removes constraint on control algorithms  Improved dexterity

6 Advantages of proposed design  Parallel-architecture: High payload, accuracy, good dynamic performance in light-weight system  Large, singularity-free range of motion  Eliminate need for slip-rings  Provide accuracy needed for solar concentrators  Inherently redundant system  - Application for pointing solar arrays – Video

7 Gimbal Kinematics, Options

8 Past applications Robotic end-effector, compliant design for pointing mirrors, sub 10nm precision manipulator

9 Point Design Applications: Thruster

10 Part Layout

11 Thruster as built

12 Application for pointing thruster

13 Design Point: Solar-Array Mount

14 Solary Array Mount

15 Solar Array Mount Table I: Summary of 3D solar-array tracking mechanism Component DescriptionMass/ Workspace Motor Drive:Maxon EC90 Flat Motor1.5 lb Drive reductionHarmonic Drive HDC 1M2.6 lb BearingsBronze bushings, ¾, 3/8 ID Shaft440c SS Link components7075 Al Mechanism weight *(without actuation)14.75 lb 3D Mechanism weight(with actuation, includes a 20% factor) 32.5 lb Working Volume*5.5 inch radius cylinder Height is selectable 5.5 inch cylinder Stowed Volume*3 high x 7 radius cylinder (inches) 7x3 inch cylinder

16 Miniature Gimbal:

17

18

19 Compliant mechanism applications Conventional 3 dof manipulator (pointing task) Compliant 3 dof manipulator High precision compact design From known topology Compact, 6 dof compliant manipulator

20 Kinematics

21 Force Analysis  Closed-form kinetostatic analysis Beta=60 degreesBeta=30 degrees

22 Path planning and trajectory control

23 Embedded electronics  Currently Motorola S-12 family MCU  IK ~ 12k in HCS-12 CPU assembly (unoptimized)  8 channel PWM, Quadrature encoders, drivers

24 Summary


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