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William Enns Bray, Mitch Sharpe, Mike Kryski, Andrew Mattson, Nicole Marshall, Ashton Johnson Sponsor: Dr. Bertram Design Review 1. Human Locomotion Research. Millennium Bridge in London. Design Goal. To design a wearable device that shifts the centre of mass of a subject. - PowerPoint PPT Presentation
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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 massAmplitude of 8 cmFrequency of 4 HzAdjust mass so that it sits on test subjects centre of gravityAdjustable device to fit most body types
Double Slider MechanismRotating 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 MechanismTorque 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
Simplistic Width 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 MechanismModification of classic 4-bar mechanismConverts 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 DisadvantagesSimplistic 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 ProfileCrossover 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
Simplistic Amplitude 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 Mechanism3 major components:
Rack, Pinion, Motor
Mobile Motor vs. Fixed Motor
Modular vs. Integrated design
Rack & Pinion MechanismTorque Requirements
Normal Force:Clip vs. Spring
Angular velocity control
Rack & Pinion Mechanism
Advantages DisadvantagesCustom 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!