From: 

To: 

Subject: 

Date: 

Attachments: 

Hi Angie, 

Mjlls Alberta E 

Heggs Angela 

FW: Materials from March 10 Meeting 

Wednesday, March 25, 2015 1:59:49 PM 

cpsc J Tum Djscussjon updated pdf 

cesc Tilt Table pdf 

CfSC Smooth Tire Comparjsoo pdf 

Handling Metrjc - 03-10-15 pdf 

Please include the attached documents with the ROV rulemaking comments. 

- - ·- ----------- From: Borlase, George 

Sent: Wednesday, March 25, 2015 1:44 PM 

To: Mills, Alberta E. 

Subject: FW: Materials from March 10 Meeting 

Alberta, 

Would you please make sure these are entered in the public record as part of the open 

rulemaking docket on ROV s? They are the presentations from the March 1oth open public 

meeting with Polaris, Inc. 

Sincerely, 

George 

George A. Borlase, Ph.D., P.E. 

Assistant Executive Director for Hazard Identification and Reduction 

U.S. Consumer Product Safety Commission 

4330 East-West Highway 

Bethesda, MD 20814 

Phone: (301) 504-7622 

Cell: (240)429-5868 

"These comments are those of the CPSC staff, and have not been reviewed or approved by, 

and may not necessarily reflect the views of, the Commission. " 

From: Paul Vitrano [maj!to:Pau! Vitraoo@polarjs com] 

Sent: Friday, March 20, 2015 3:32 PM 

To: Borlase, George 

Subject: Materials from March 10 Meeting 

George, 

Thanks again to you and the staff for meeting with my colleagues and me on March 10 to review 

Polaris' dynamic stability and handling testing and development. Attached are .pdfs of the two slide 

deck presentations. 

In addition, attached are .pdfs of two other slides decks covering subjects discussed during the 
meeting: 

1. Comparative Metrics: J-Turn and Tilt Table Correlation 

2. Constant Radius Test Results Comparing On-Road vs. Off-Road Tires 

We will provide additional information concerning our proposed handling metric as it is available. 

Please do not hesitate to contact me if you have questions. 

Paul 

Paul C. Vitrano 

VP, Global Government Relations 

Polaris Industries Inc. 

1999 K Street, N.W., Box 9 

Washington, D.C. 20006 

202-714-3386 

paul.yjtrano@polarjs com 

CONFIDENTIAL: The information contained in this email communication is confidential 

information intended only for the use of the addressee. Unauthorized use, disclosure or 

copying of this communication is strictly prohibited and may be unlawful. If you have 

received this communication in error, please notify us immediately by return email and 

destroy all copies of this comtnunication, including all attachments. 
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

J-Turn Discussion
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

From safecar.gov Website

2

NHTSA Rollover Definitions

TRIPPED ROLLOVERS

NHTSA data show that 95% of single-vehicle rollovers are tripped. This happens when a vehicle leaves the roadway and slides 

sideways, digging its tires into soft soil or striking an object such as a curb or guardrail. The high tripping force applied to the tires 

in these situations can cause the vehicle to roll over.

UN-TRIPPED

Un-tripped rollovers are less common than tripped 

rollovers, occurring less than 5% of the time, and 

mostly to top-heavy vehicles. Instead of an object 

serving as a tripping mechanism, un-tripped rollovers 

usually occur during high-speed collision avoidance 

maneuvers.
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

NPR Ay Requirement Can Not Prevent Tripping Rollovers

3

Off Road Vehicle Tripping Condition 

Environment

Sand

Soil Berm

Rock

Tree Stump

Incline

Resistance 

Center of Gravity 

Sliding Force

Moment 

Of Inertia Force = Mass times Acceleration (Spike Load Condition) 

Can easily exceed 2G

Tipping Force

Off Road driving conditions can result in a tripping condition

http://www.safercar.gov/Vehicle+Shoppers/Rollover/Types+of+Rollovers
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Video shown at half speed – actually traveling 25mph

4

Sand J-Turn Video
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Off-road behaviors can vary greatly from on-road – unintended consequences

5

Off-Road Testing

Notes:

1) On pavement, the locked differential is oversteer and the 

open differential is understeer

2) In sand and gravel, the understeered vehicle rolled much 

easier than the oversteered vehicle
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Off-road behaviors can vary greatly from on-road – unintended consequences

6

Off-Road Testing

Notes:

1) On pavement, the locked differential is oversteer and the open 

differential is understeer

2) As the surface roughness increased, less steering angle was 

required and the differential position had less effect
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Sliding Begins Well Below 0.7 G, Tripping Occurs Well Above 0.7G

7

Lateral Acceleration Comparison

Sand

(Peak Ay @ 1.1)

Gravel

(Peak Ay @ 0.9)

Pavement

(Peak Ay @ .72)

All runs shown ended in roll:

• Off-road runs begin sliding at less than 0.3G and can reach lateral accelerations well above 

1.0

• Spikes are noticeable of the tire tripping/skipping over the ground

• Once the vehicle begins sliding, well below 0.3G, it really doesn’t matter what its Ay on 

pavement is because it will trip and spike well above that value

0.7G

0.7G

0.7G

Tire Slip

Tire Slip

Tire Slip
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Sliding Begins Well Below 0.7 G, Tripping Occurs Well Above 0.7G

8

Lateral Acceleration Comparison

Plowed Dirt

(Peak Ay @ 0.96)

Rough Grass

(Peak Ay @ 0.87)

0.7G

0.7G

Pavement

(Peak Ay @ .72)

0.7G

Tire Slip

All runs shown ended in roll:

• Off-road runs begin sliding at less than 0.3G and can reach lateral accelerations well above 

1.0

• Spikes are noticeable of the tire tripping/skipping over the ground

• Once the vehicle begins sliding, well below 0.3G, it really doesn’t matter what its Ay on 

pavement is because it will trip and spike well above that value

Tire Slip

Tire Slip
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Steer input on Pavement Is A Better Pass/Fail Metric

9

Vast majority of Off-Road rollovers are tripped

On-Road J-Turn does not predict tripped rollover 

resistance

Off-road terrain causes tires to slip well below 0.7g, 

proposed threshold is not connected to the terrain failure 

limit

Once tires begin to slip, a tripped rollover is highly likely

Lateral acceleration at trip is well above .7g

Steer input at roll consistently higher off road vs on 

pavement

Focus vehicle designs to increase slip resistance & 

improve handling predictability

Summary
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Comparative Metrics: J-Turn 

and Tilt Table Correlation
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

TTA Hang Tag Would Provide Comparable Comparison of Vehicles

2

Correlation: J-Turn Ay and TTA

Return
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Constant Radius Test 

Results Comparing OnRoad vs. Off-Road Tires

3/12/15
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

2

Compare data from the same vehicle model using different tires

• Steering Wheel Input Plots

• Lateral Acceleration Plots

• Combined Understeer Plots

Vehicle: 2015 Polaris RZR 900 (locked differential) used for all tests

Objective

OEM Tire

Carlise PXT

26” OD; 10-12 psi

Automotive Tire

Kingstar Centum SK72

26” OD; 10-12 psi

Racing Slick Tire

Hoosier

22” OD; 10-12 psi
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Steering input improves slightly with smoother tires

3

Unfiltered Steering Wheel Input

OEM Tire

Carlise PXT

26” OD; 10-12 psi

Automotive Tire

Kingstar Centum SK72

26” OD; 10-12 psi

Racing Slick Tire

Hoosier

22” OD; 10-12 psi

Max 

Fluctuation 

~140

Max 

Fluctuation 

~70

Max 

Fluctuation 

~100
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

After filtering, lateral acceleration is still noisy 

4

2Hz Filtered Lateral Acceleration Plots

OEM Tire

Carlise PXT

26” OD; 10-12 psi

Automotive Tire

Kingstar Centum SK72

26” OD; 10-12 psi

Racing Slick Tire

Hoosier

22” OD; 10-12 psi

2Hz

6Hz

As the tires get smoother, lateral acceleration increases and noise decreases
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

Even with smooth tires and filtering, understeer plots are not desirable

5

Filtered Understeer Plots

2Hz

6Hz

OEM Tire

Carlise PXT

26” OD; 10-12 psi

Automotive Tire

Kingstar Centum SK72

26” OD; 10-12 psi

Racing Slick Tire

Hoosier

22” OD; 10-12 psi

As the tires get smoother, the understeer plot is less chaotic
Attorney-Client Privileged and Confidential

Off Road Vehicle

Division

6

Driver input is a source of error and noise. It improves 

with smoother tires.

• By using the Polaris proposed fixed steer test, the driver steering 

input is completely eliminated, removing that source of error

Lateral acceleration is also a source of error even after it 

has been highly filtered. It improves with smoother tires.

• Lateral acceleration is not an acceptable pass/fail metric for testing 

vehicles with off-road tires

Summary
A Handling Quality Metric 
A Given: Instability is A Bad Thing Instability implies response is unbounded with time; in vehicle control terms, an uncommanded spin Spins not preferred because they may lead to tripped rollover by presenting the vehicle sideways to obstacles/terrain Four states possible for systems generally[1,2]: 

Asymptotic Stability Neutral Stability Divergent Instability Oscillatory Instability 

[1] Fundamentals of Vehicle Dynamics, Gillespie, p402 [2] The Multibody Systems Approach to Vehicle Dynamics, Blundell & Harty, p172 [3] Race Car Vehicle Dynamics, Milliken & Milliken, p245 

Understeer/Oversteer aSAE Understeer guarantees stability in absence of driver SAE Oversteer does not predFrom Fundamentals of Vehicle Dynamics, Gille

r Vehicle Dynamics, Milliken & Milliken, p245

Divergent Instability Better Surrogate for Tripped Roll

A Given: Instability is A Bad Thing

Handling Metric Context 
Lateral Acceleration Very Noisy Measurement noise very high on lugged tires with non-deformable terrain 

Polynomial Fit ArVehicle motion is the forces divided by reluto move (mass, inertiTires are often represcalled “Magic Formul

There is no good reapolynomial to the dat

[4] Newton’s 2nd Law 

[5] Tyre Modelling for Use in Vehicle Dynamics Pacejka

Discerning Turning Point Unsatisfactory Experime

L t l A l ti V

N

Measurement Noise 

Y X D C Bx E 

  sin arctan 

^ 

 

a ¬ 
The Fixed Steer Test Extremely repeatable and requires no special facilities other than a consistent surface Unlike constant radius test, it is not a test of the steering robot quality, driver skill, etc While not directly comparable to other tests (none are directly comparable with each other), will nevertheless expose a vehicle that seeks to spin (“divergent”)

Yaw Rate Gives CYaw rate is rotation vData not so susceptib(magenta) when comacceleration (green) Mount location insenreadings anywhere o

Fixed Steer is Repeatable, Driver-Independent and gives 

The Fixed Steer Test Ya

Another Possible Test Protocol 

D t t tib
Yaw Rate is Directly Connected to Lateral Acceler

A Geometric Connection 

“Non Spin” (aka No-Slip, Steady State) Yaw rate connects to Lateral Acceleration simplyA “geometric” vehicle will have a yaw rate which is identical to a neutral steer v[3] Race Car Vehicle Dynamics, Milliken & Milliken, p159 

U

δ

r

L

 
Visually a Strong Difference – No Filtering/Processing 

Divergent Spin Condition Instability is shown by a large cha(slope) of the plot for a small spe

vertical”

Detecting Divergence – Fixed Steer Results 

0.5g Hyperbola Measured 

Yaw Rate vs Vehicle Speed

Extrapolated line from on-center fit – 5 seconds after 2m/s (5 repeats) 

No Spin Condition Plotting yaw rate against vehicle speed will show its character compared to a “geometric” vehiclePlotting 0.5g*9.81ms-2/Vehicle Speed(ms-1) gives a “0.5g 

Hyperbola” to determine test end 

Convergent vehicles typically keep a “substantially constant” slope of yaw rate with speed 
• Divergent response – trace “becomes steep” 

below 0.5g Hyperbola – divergence obvious 

• Extremely convergent veh

horizontal 

• Both vehicles very consis

Proposed Test Shows Large Difference 

• Divergent response trace “becomes steep” becom Extremely convergen

200ft Fixed Steer – Divergent/Convergent 

Left Turn 

Right Turn 
• Shows loss of path follow

–

“path error” (vehicle is le

Shows Both Divergence and Path Error Plainl

Shows loss of path f f path o

200ft Fixed Steer – Divergent/Convergent 

• Note very large increase in yaw rate for 1mph 

speed change (~0.5 m/s) 

Left Turn 

Right Turn 
• Difference still clear - divergent configuration is 

obvious (vehicle tips onto outriggers on right turn) 

• Excellent repeatability always 

Robust against Test Radius 

• Difference still clear divergent configuration c is

50ft Fixed Steer – Divergent/Convergent 

• Convergence remains cle

0.5g hyperbola for 50ft dia

• Path following less compr

Left Turn 

Right Turn 
Numerically Robust With Typical Data (20 Vehicle S

Plot 5 repeats in each direction For each repeat 

Fit on-center slope Fit limit slope 

Average on-center slopes between repeats Average limit slopes between repeats Evaluate relationship of averaged limit slope to averaged on-center slope Pass-fail criterion? 

Ratio preferred over arithmetical difference 

–

less sensitive to radius 

Plot 5 repeats in each direc

tion

Suggested Detail - Provisional 

0.5g Hyp

Measured Yaw Rate vs Vehicle Speed 

Fitted line on-center 5 seconds of data beyond 2 m/s 
Divergent Response Stands Out in Blind, Automated P

Sample Metric 

– Fleet Review (40/50ft) 

• 200

everatio 

• 100

somtwo 

• 100

goobetwand 

• All v

exce

• Not 

und

01234
• Test end detection – characteristic goes 

through 0.55g hyperbola or significant deceleration 

Process Automates Well 

• Test end detection characteristic g ristic

Process Automation 

• Limit identification – 0.5

crossing or maximum inAcceleration (some veh0.5g) 

• Fit window controllable 

examples so far Test end autodetected 

W ll

examples so far
100ft Data Comparison Expand Vehicle set 

eg Historic 

Test robustness of processing Refine Pass/Fail criteria Formalize Process Receive Inputs from others 

Early Promise Needs Verification & Formalizati

100ft D t C

Next Steps 
Method developed on first principles/best-practices Better Surrogate for Tripped Rollover Risk Repeatable methods with minimal test errors Drives predictable vehicle handling designs Discriminates and identifies unpredictable behaviors 

Superior Alternative to Understeer Bias 

M th d d l

Summary 
• What other signatures can the data show? 

• Fails to reach 0.5g • Convergent oversteer 

Other Numerical Measures of Interest to Manufacturers a

• What other signatures can the data show?

Broad Picture of Vehicle 

• Lack of symmetry left-to-right 

“Club-like” thickening of data 

associated with tire saturation 
• Vehicle 1 

Appendix – Real Vehicle Data – 50ft 

• Vehicle 1

Appendix – Real Vehicle Data – 50ft 

• Vehicle 2 
• Vehicle 3 

Appendix – Real Vehicle Data – 50ft 

• Vehicle 3

Appendix – Real Vehicle Data – 50ft 

• Vehicle 4 
• Vehicle 5 

Appendix – Real Vehicle Data – 50ft 

• Vehicle 5

Appendix – Real Vehicle Data – 50ft 

• Vehicle 6 
• Vehicle 7 

Appendix – Real Vehicle Data – 50ft 

• Vehicle 7

Appendix – Real Vehicle Data – 50ft 

• Vehicle 8 
• Vehicle 9 

Appendix – Real Vehicle Data – 50ft 

• Vehicle 9

Appendix – Real Vehicle Data – 50ft 

• Vehicle 10 
• Vehicle 11 

Appendix – Real Vehicle Data – 50ft 

• Vehicle 11

Appendix – Real Vehicle Data – 50ft 

• Vehicle 12 
Appendix – Real Vehicle Data – 50ft 

Appendix – Real Vehicle Data – 50ft 

• Summary • Ratio and Delta measures 

(ratio plot shown) 

• All vehicles converge exc