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© 2011 ANSYS, Inc. August 30, 20111

Simulation Driven Optimized Mechanism Drive

Elias Taye, PhDWm Wrigley Jr. CompanySubsidiary of Mars Inc.

August 30, 2011


AGENDA Introduction of Wm Wrigley Jr. Company

Original Design of the Mechanical Linkage Objective of Simulation Rigid Dynamic Analysis Transient Structural Analysis Issues

First Design Optimization Objective of Simulation Rigid Dynamic Analysis Transient Structural Analysis 1st Optimization Summary

Second Design Optimization Objective of Simulation Rigid Dynamic Analysis Transient Structural Analysis 2nd Optimization Summary

Experimental Validation of Actuator Driven Mechanical Linkage Conclusion


Wrigley is a recognized leader in confections. – Headquarter is in Chicago, IL, & operates as subsidiary of Mars Inc.– Family owned company founded in 1911

Products Gum, Mints, Hard & Chewy Candies, Lollipops and Chocolate

Operates in more than 40 countries and distributes in 180 countries

Benefits of Chewing:– Increased alertness, focus and concentration– Improve Oral Health: helps fight cavities, neutralize plaque acids, remineralize enamel

to strengthen teeth and wash away food particles.– Weight management help control cravings– Stress relief

Wm Wrigley Jr. Company


ORIGINAL DESIGN

Mechanism Has one rotational input that further splits into two different translation motions All components are made of structural steel

Boundary Condition Input: Angular Rotation of cam shaft (0) Constraints: Applied joints between rigid & flexible bodies

Objective of modeling: Calculate the Shaking Force, Bearing load and structural

stiffness for current speed (0) To model the mechanism for high speed (2x0)


Original design

Simulation Results and Issues Has high max. Shaking Force 464 Lbf (2063N) Has high max. Driving Torque 590 Lbf‐ft (800Nm) Cam generating the vertical motion has the max load The cams have harmonic motion profile

– The jerk function is infinite at dwell ends– Has sudden change in acceleration

This is a source for vibration and noise The Fork performs a triangular motion

– abrupt of smooth motion Stresses are within the material strength limit

Transfer Fork Total Reaction Force, 600 RPM

-1500

-1000

-500

0

500

1000

1500

2000

2500

0 60 120 180 240 300 360

Rotation (°)

Forc

e (N

)

FxFyFzSum

Shaking ForceInput Torque

Fork Motion Profile

590Lbf‐ft590Lbf‐ft

2063N2063N


1st design optimization - cam

Objective: Reduce Dynamic Load1. Redesign both Cams2. Improve Fork motion profile

1. Cam Synthesis Current Design Harmonic Cams

– Sudden change of acceleration at dwell– The jerk function is infinite at dwell two jerks per revolution this generates vibration & noise

New Design Cycloidal Cams– NO Sudden change in acceleration– Used for high speed application– Very low vibration– Jerk function is finite across the entire 360° interval – The first and second derivatives of displacement are continuous – reduces the dynamic inertia of machine


1st design optimizationRedesign linkage & Motion profile

2. Optimizing Fork Motion Profile Understand existing motion profile Eliminate the abrupt motion and redesignnew cams timing

Modified Motion Profile

Original Motion Profile

3. Redesign Linkage To reduce bearing load To fit within packaging constrain on horizontal direction


1st design Optimization dynamic analysis - Bearing Load

F = 305Lbf (1356N) F = 286Lbf (1272N) F = 239Lbf (1063N)

F = 89Lbf (395N) F = 89Lbf (395N) F = 74Lbf (329N) F = 74Lbf (329N) F = 100Lbf (445N) F = 100Lbf (445N)

Max. Bearing Load has Reduced


1st design Optimization dynamic analysis – Input torque

T = 1082Lbf‐in (122Nm) T = 1207Lbf‐in (136Nm)

Input Torque has significantly REDUCED

© 2011 ANSYS, Inc. August 30, 201110

1st design Optimization kinematic analysis

Calculated also Speed & Acceleration at each Kinematic Pairs

These are important information for the next Design Optimization

1 = 8.0679° 2 = 13.057° 3 = 22.3174°

© 2011 ANSYS, Inc. August 30, 201111

1st design Optimization Transient structural Analysis

Fork Displacement Max. VM Stress = 8.56E6Pa (1241psi)

© 2011 ANSYS, Inc. August 30, 201112

1st design Optimization Transient structural Analysis

Max. VM Strain = 0.0001 Max. Normal Stress9.16E6Pa (1347psi)

Max Principal Stress 1.138E7Pa (1673psi)

The stresses are way below the material strength limit Aluminum material 7075‐T6 (y ~ 36000psi)

© 2011 ANSYS, Inc. August 30, 201113

1st design Optimization - animation

Mechanism Animation

© 2011 ANSYS, Inc. August 30, 201114

1st Optimization summary

Analysis Result Dynamic load has reduced significantly Less bearing load Less input torque requirement observed less vibration/ noise Replaced the structural steel by Aluminum material Better Space usage behind the machine frame The improved fork motion profile (rectangular vs. triangular) reduces

the dynamic load

ANSYS Rigid Body Dynamic and Transient Structural Analysis have greatly helped us to improve our design within a short period of time. The final design of the First Design Optimization is built and installed in our machine.

© 2011 ANSYS, Inc. August 30, 201115

2nd Optimization Electronic Camming

Mechanical Cams are replaced by Electronic Camming

Servos Timing in angular position is calculated to

produce the same motion profile Results obtained from Rigid Body Dynamic Without ANSYS it would be difficult to extract this important

information

Developed Prototype

Pros of Servo Driven Mechanism Less mechanical components Less inertia Simplified design Less power, torque and current consumption Better position control

© 2011 ANSYS, Inc. August 30, 201116

2nd Optimization - Animation

Servo Driven Mechanism Animation

© 2011 ANSYS, Inc. August 30, 201117

2nd Optimization electronic Camming

Defining Cam Timing

Developed cam timing as a function of time Converted the timing to drive machine (master axis) angular position Modified the cam timing

© 2011 ANSYS, Inc. August 30, 201118

2nd Optimization Transient structural Analysis

VM Strain = 5.637e‐5 Von Mises Stress4.0E6Pa (588 psi)

Max Principal Stress 3.256E6Pa (479 psi)

The stresses are way below the material strength limitAluminum material 7075‐T6 (y ~ 36000psi)

© 2011 ANSYS, Inc. August 30, 201119

2nd Optimization Dynamic Analysis

F = 17Lbf (75N) F = 25Lbf (111N) F = 87Lbf (386N)

F = 29Lbf (129N) V = 42in/sec V = 90 in/sec

Bearing Load has Reduced significantly even without optimizing the linkage

© 2011 ANSYS, Inc. August 30, 201120

experimental validation

Front View of Test SetupFront View of Test Setup

Rear View of Test SetupRear View of Test Setup

Yaskawa Servo Control Test BenchYaskawa Servo Control Test Bench

© 2011 ANSYS, Inc. August 30, 201121

experimental validation video clip

SLOW SPEED run of Servo HIGH SPEED run of Servo

© 2011 ANSYS, Inc. August 30, 201122

experimental validation Modal analysis

At higher speed the motor starts chattering due to overload Lower Rated Motor Torque

Conducted Modal Analysis to make sure that the component or system is not operating close to its natural frequencies Excited frequencies are not close to its natural frequencies

309 Hz 309 Hz 622 Hz 622 Hz 1525 Hz 1525 Hz

6th Mode6th Mode 1st Mode1st Mode 4th Mode4th Mode

© 2011 ANSYS, Inc. August 30, 201123

2nd design optimization - conclusion

The Servo Driven Mechanism Design has been validated and showed significant improvement compared to Original & 1st Design Optimization

The prototype is designed to replace the existing mechanical cam linkagefor proof of concept has potential for further optimizing the linkage the mass can be reduced up to 60% or more which eventually reduces the dynamic

load of the system

The Servo Design has Less mechanical components Less inertial mass Less power, torque and current consumption

– this leads to cost reduction Very low vibration and noise

The Optimized Servo Design will be used in our new high speed machine.

simulation driven optimized mechanism drive - ansys · simulation driven optimized mechanism drive...

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