Skin Deformation Display for Enhanced Driver Situational Awareness

Chris Ploch

Haptic Feedback

• Driver should have situational awareness if car is not fully autonomous.

• Visual and Auditory channels are possible means of conveying information, but are already used heavily in driving.

• Haptics is another possibility.• What kinds of information are haptics

especially suited for?

• As an information channel, what is haptics good for?– Not object geometry– Object properties (fuzzy, smooth, soft, slippery – related to road

conditions)– Also informational cues (navigation, lane-keeping, collision avoidance)– Can be especially effective if it taps into a reflex.

Provancher 2010

Johansson and Flanagan 2009

Meissner

Merkel

Pacini

Ruffini

Lateral skin deformation uses 3 out of 4, meaning a variety of cues are possible Provides direction + magnitude

Vehicle-specific Motivation

• Under less than ideal road conditions, want driver to know if tires are losing grip.

• Modern cars have reduced road feel.• How should the car inform you?• Haptics could provide

continuous sense of road friction.

• Also suitable for informational cues (lane-keeping, collision avoidance): event & location

6

Skin Stretch Feedback• Skin stretch is a promising means of conveying information, and its

use in cars is relatively unexplored.• Richer than an event cue.• Can give information on hardness,

stiffness, apparent friction (Okamura, Provancher)

• Can give direction & magnitude

http://heml.eng.utah.edu/index.php/Haptics/ShearFeedback

Okamura 2013

Skin Stretch Navigational Cues• Communication of direction through skin stretch

has been examined by Provancher and others.• 0.05 mm is enough to distinguish direction.• Skin stretch on a steering wheel was an effective

replacement for an audio GPS navigation system, especially when the driver was distracted or on the phone.

Proposed Solution: wheel version• Low power, high frequency perceptual overlay– Does not interfere with driver/steering dynamics

Provide direction, magnitude cues for navigation, road conditions, etc.

At specific locationsor as thin ring in wheel

Proposed Solution: console version

Provide direction, magnitude cues for navigation, road conditions, etc.

Skin stretch tactors

• Haptic actuators are compact, low-power, don’t interfere with steering system dynamics.

• Can supplement torque feedback at high frequencies.– Humans use information up to 60 Hz when

perceiving road surfaces, conditions.• Can render event cues with added analog

magnitude and direction.

Advantages of Proposed Solution

11

First Prototype Design• Rough prototype to test if skin stretch feedback

makes sense on a steering wheel.• Rotating ring attached to rim.• Actuated by DC motor, cable, and pulley.• Large display surface.

Stationary side

Rotating side

First Prototype Actuation

Drum

Capstan

Cable

13

First Prototype Design Schematic

13

Encoder Counter IC

Microcontroller

Motor Driver

DC Motor

Spring Cable

Pulley

Bearing

To 12 V AC Adapter

To USB

Steering Wheel

Skin Deformation Mapping Experiment

• Can users perceive magnitude and direction when turning wheel?

• Mapping made by users was found to be repeatable, monotonic, bipolar, and centered around zero (analog).

• Wheel was simple to use, but form factor not ideal.

Positioning Task Result

Conclusion: people canmap steering wheel-inducedskin stretch to a linearlyvarying quantity (analog)

Second Prototype• 4 skin deformation displays (one under the palm and

fingers of each hand)• For console or wheel display• Force: 1.5 kg-cm -> 10.4 N• Bandwidth tests:

– ~5 Hz at 2 mm– ~2 Hz at 10 mm

Collision Avoidance Experiment

• Have access to autonomous test vehicle through Dynamic Design Lab (DDL).

• Current DDL experiment: – An obstacle appears in front of driver.– Controller optimizes steering angle to avoid

collision.– Wheel torque feedback proportional to steering

wheel error given to driver before they see obstacle.– Feedback was found useful.

• This experiment models how a car with V2V communication could convey information to the driver of an impending collision.

Collision Avoidance Experiment Plan

• We plan to run a modified version of the DDL experiment to test skin stretch collision avoidance cues.

• Does directional information help? Buzz (event) vs. directional feedback

• Two loops vs. one loop: wheel torque vs. skin deformation• 3 cases:

– Wheel torque– Skin deformation– Buzz

Road Conditions Display: motivation

• Under less than ideal road conditions, want to know if tires are losing grip.

• Modern cars have reduced road feel.• How should car inform you?• Also suitable for informational

cues (lane-keeping, collision avoidance)

To be explored in future tests…

Next Steps

• Return to question of road condition display (higher bandwidth prototype)

• Evaluate other information particularly suited for proportional cutaneous display (navigation with anticipation, lane-keeping, collision avoidance)

In Summary

• Skin stretch feedback provides direction and magnitude information in addition to the “event cue” one gets from a vibrator or buzzer.

• It has potential for:– Navigational cues– Collision Avoidance cues – Lane-keeping cues– Conveying road surface/friction properties