William Enns-Bray, Mitchell Sharpe, Michael 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

Rack & Pinion Mechanism

3 major components: Rack, Pinion, Motor

Mobile Motor vs. Fixed Motor

Modular vs. Integrated design

Rack & Pinion Mechanism

Torque Requirements:( vf -

vi ) ( ∆ t )

Normal Force: Clip vs. Spring

Angular velocity controlF = (mass)*

Torque = Force Moment arm *

Rack & Pinion Mechanism

Advantages Disadvantages

Custom Dimensions Motor Specifications

Fully adjustable motion & mass Stability; linear path

Easily available parts & materials Difficult to verify performance

Low cost

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

Cam Profile(Simple Harmonic)

Motion Amplitude:

8 cmBase Circle Diameter

Maximum Pressure Angle

1 cm 59.94 cm 40.76 cm 34.28 cm 29.5

Cam Profile

Advantages Disadvantages

Simple to controlAmplitude and motion type only

controllable by use of different cams

With constant rotation perfect

vertical oscillations can be

guaranteed

Expensive to manufacture

Higher frequencies are easier to

achieveSize of device

Double Slider Mechanism

Rotating arms to raise and lower mass

Dual motor or single motor configurations

Motors reverse direction to create oscillation

Vertical guide to keep mass centered / level

Controlled by monitoring arm angle.

Double Slider Mechanism

Torque requirement : 400 mNm 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

Simple to manufactureWidth may cause a poor fit on narrow

body types

Fully controllable frequency and

amplitude

Dual motor configuration requires

synchronization

Dual motor configuration -- can use

small motors

Single motor configuration requires

additional system to prevent binding

QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.

Crank-Slider Mechanism

Modification of classic 4-bar mechanism

Converts angular motion to linear motion

Crank-Slider Mechanism

Torque requirement: 800 mNm

Crank length: 4 cm

Minimum rod length: 8 cm

Approx. dimensions: 8 cm W x 20 cm H

(excluding mass dimensions)

QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.

Crank-Slider Mechanism

Advantages Disadvantages

Minimalistic Fixed amplitude/motion

Rotational control only Large height requirement

Direction independent Relatively large torque requirements

Modular Design

Next Steps

Motor Research

Attachment System & Ergonomics

Control Systems

Thank you!

From Team BALTE