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!