Four-Bar Mechanism to Drive a Wheelchair
Gordon Farmer
Submitted to the
2007 ASME Student Mechanism Design Competition
Undergraduate Category
University of Notre Dame du Lac
Dr. M.M. Stanišić
September 5, 2007
Introduction
Design Problem
Shortcomings of
Traditional Driving
Method
Design Objectives
Four-Bar Overview
Kinematic Solution
Curvature Theory
Design Optimization
Final Design
Erdman, Arthur G., and Sandor N. George. Mechanism
Design: Analysis and Synthesis. Vol. 1. Englewood Cliffs,
New Jersey 07632: Prentice-Hall, Inc., 1991.
• Direct contact with wheels
• Poor braking
• Health issues
“More than 50% of […] respondents with spinal cord injury in a study […]
reported shoulder pain that was related to wheelchair use and transfers.”1
“Shoulder related injuries have been shown to be present in up to 51% of
manual wheelchair users.”2
“The prevalence of elbow, wrist, and hand pain has been reported to be 16%,
13%, and 11%, respectively.”2
“The incidence of carpal tunnel syndrome and rotator cuff tendonitis […] is
greater than 50% for people who
regularly use manual wheelchairs as
compared to 3% for the general
population.”2
1Koontz,
2Manual
Introduction
Design Problem
Shortcomings of
Traditional Driving
Method
Design Objectives
Four-Bar Overview
Kinematic Solution
Curvature Theory
Design Optimization
Final Design
PhD, ATP, Alicia M., and Michael L. Boninger, MD. "Proper Propulsion." Rehab Management July 2003. 29 June 2007 <www.rehabpub.com>.
Wheelchair Propulsion. Rehabilitation Engineering Research Center on Technology Transfer. Mid-Atlantic Region: Federal Laboratory Consortium.
1) Desired path of handlebar:
4 y = x2
2) High mechanical advantage
Introduction
Design Problem
Ma = TLoad/FDriver
Shortcomings of
Traditional Driving
Method
Design Objectives
3) Remain within wheelchair profile
Four-Bar Overview
Kinematic Solution
Curvature Theory
Design Optimization
Final Design
Introduction
Design Problem
Shortcomings of
Traditional Driving
Method
Design Objectives
Four-Bar Overview
Kinematic Solution
Curvature Theory
Design Optimization
Final Design
Introduction
Design Problem
Shortcomings of
Traditional Driving
Method
Design Objectives
Four-Bar Overview
Kinematic Solution
Curvature Theory
Design Optimization
Final Design
Introduction
Design Problem
Shortcomings of
Traditional Driving
Method
Design Objectives
Four-Bar Overview
Kinematic Solution
Curvature Theory
Design Optimization
Final Design
1) High, positive mechanical advantage
2) High mechanical advantage when
handle is pulled back
3) Mechanical advantage decreases in a
relatively linear fashion as the handle
moves forward
4) Span of four-bar mechanism is
reasonable, given an individual’s
normal reach. Between 0” and 20” on
y-axis.
Introduction
Design Problem
Shortcomings of
Traditional Driving
Method
Design Objectives
Four-Bar Overview
Kinematic Solution
Curvature Theory
Design Optimization
Final Design
Introduction
Design Problem
Shortcomings of
Traditional Driving
Method
Design Objectives
Four-Bar Overview
Kinematic Solution
Curvature Theory
Design Optimization
Final Design