William Enns-Bray, Mitchell Sharpe, Michael 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. 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: ( v f - v i ) ( ∆ t ) Normal Force: Clip vs. Spring Angular velocity control F = (mass) * Torque = Force Moment arm *

Rack & Pinion Mechanism AdvantagesDisadvantages Custom DimensionsMotor Specifications Fully adjustable motion & massStability; linear path Easily available parts & materialsDifficult to verify performance Low cost

Cam Profile Force-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 cm Base Circle Diameter Maximum Pressure Angle 1 cm 59.9  4 cm 40.7  6 cm 34.2  8 cm 29.5 

Cam Profile AdvantagesDisadvantages Simple to control Amplitude 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 achieve Size 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 AdvantagesDisadvantages Simple to manufacture Width 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

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)

Crank-Slider Mechanism AdvantagesDisadvantages MinimalisticFixed amplitude/motion Rotational control only Large height requirement Direction independentRelatively large torque requirements Modular Design

Next Steps Motor Research Attachment System & Ergonomics Control Systems

Thank you! From Team BALTE