William Enns Bray, Mitch Sharpe, Mike Kryski,Andrew Mattson, Nicole Marshall, Ashton Johnson
Sponsor: Dr. Bertram
Design Review 1
Human Locomotion
ResearchMillennium Bridge in
London
Design Goal
To design a wearable device that shifts the centre of mass of a subject.
The device will involve a mass of 2 kg oscillating at a frequency of up to 4 Hz with a full cycle amplitude of 8 cm.
Normal motion should not be affected when device is worn and not turned on.
Functional Objectives
Oscillate a 2 kg mass
Amplitude of 8 cm
Frequency of 4 Hz
Adjust mass so that it sits on test subjects centre of gravity
Adjustable device to fit most body types
Double Slider Mechanism
Rotating arms to raise and lower mass
Duel motor or single motor configurations
Motors reverse direction to create oscillation
Vertical guide to keep masscentered / level
Controlled by monitoring arm angle.
Double Slider Mechanism
Torque requirement :400 Nm on each side
89° rotation to achieve 8 cm vertical amplitude
3.1 rad/s (30RPM) to achieve 4Hz
Direction change 8 times per second
Approx. dimensions: 30 cm W x 18 cm H
Depth to be determined by motor requirements.
Double Slider Mechanism
Advantages Disadvantages
SimplisticWidth may cause a poor fit on narrow
body types
Fully controllable frequency and
amplitude
Duel motor configuration requires
synchronization
Duel motor configuration -- can use
small motors
Single motor configuration requires
additional system to prevent binding
Crank-Slider Mechanism
Modification of classic 4-bar mechanism
Converts angular motion to linear motion
Crank-Slider Mechanism
Torque requirement: 800 Nm
Crank length: 4 cm
Minimum rod length: 8 cm
Approx. dimensions: 8 cm W x 20 cm H
(excluding mass dimensions)
Crank-Slider Mechanism
Advantages Disadvantages
Simplistic Fixed amplitude
Rotational control only Large height requirement
Direction independent Relatively large torque requirements
Modular Design
Cam ProfileForce-closed or Form-closed Design
Different cam profiles can be cut to achieve different types of motion
i.e (Harmonic, Cycloidal etc.)
Mass attached to roller follower
Follower slides vertically with respect to mounting bracket
Cam Profile
Crossover Shock(For form-closed cam)
Possibility of “Follower Jump”(For force-closed cam)
Torque Requirement
Motion Amplitude:
8 cmBase Circle Diameter
Maximum Pressure Angle
1 cm 59.9°4 cm 40.7°6 cm 34.2°8 cm 29.5°
Cam Profile(Simple Harmonic)
Cam Profile
Advantages Disadvantages
SimplisticAmplitude and motion type only
controllable by use of different cams
Constant rotation then perfect
vertical oscillations can be
guaranteed
Expensive to manufacture(especially form-closed cam)
Single direction of rotation:
Higher frequencies are easier to
achieve
To lower torque requirements must make
device larger (lower pressure angle)
Rack & Pinion Mechanism
3 major components:Rack, Pinion, Motor
Mobile Motor vs. Fixed Motor
Modular vs. Integrated design
Rack & Pinion Mechanism
Torque Requirements
Normal Force:Clip vs. Spring
Angular velocity control
Rack & Pinion Mechanism
Advantages Disadvantages
Custom Dimensions Motor Specifications
Fully adjustable motion & mass Stability, gear normal force, linear path
Easily available parts & materials Difficult to verify performance
Easy to control
Simple Design and low cost
Thank you from team BALTE!