09CV-0117 / 2009-01-2831
Human Sensitivity in Forced Feedback Systems
as a Function of Frequency and Amplitude of
Steering Wheel Vibrations
Peter Thomas Tkacik
Assistant Professor Mechanical Engineering
The University of North Carolina at Charlotte
Introduction
•
A warning system is described as the one that improves the safety in an over the road truck
application by warning the driver with steering wheel vibration of impending roll over.
•
This work focuses on the driver response to a range of frequencies and amplitudes at the
steering wheel.
•
It does not depend on, but is in collaboration with a (heavy truck) trailer rollover sensor.
•
An experimental road going system is designed, presented, and tested.
•
An experimental lab based system is designed, presented, and tested.
•
The experimental data reveals information about the human sensitivity of the driver as a
function of steering wheel shake frequency and amplitude in a lab and while driving a
vehicle.
•
The experimental setup probing the amplitude and frequency information is analyzed.
Solution description
• The Haptic feedback system uses steering
wheel vibration
• A review of steering wheel vibration
frequency and amplitude
Visible and Audible Warnings
• These involve flashing lights on the driving panel of
the truck.
• But these warning systems make a sense of panic.
• Hence, better warnings are needed.
On-Road Sign Boards
• These sign boards have a lot more probability to
get lost in the plume of sign boards on the
Interstates.
• They have marginal effectiveness
On-board road warning systems
• DOT trucks beacons and
roadside beacons at selected
curves broadcast road warnings.
• The warning system includes
on-board instrumentation that
measures rollover.
Haptic (vibration) feedback to steering
wheel
• Reason for using Haptics:
– Any sort of disturbance directly to the human body is more
easily responded to than a warning system involving vision
or sound.
– The order of response to stimuli is :
• Touch > Visual > Sound
Experimental Steering Vibration
System
DB300-0 CD Brush Motor Driver
Common (ground)
•An experimental system was developed to test for
human sensitivity to vibration
On/Off
Maximum speed
Forward/Reverse
Motor braking
•This system is for a broad range of steering
wheels.
Motor speed
s/w no
s/w no
s/w no
s/w no
•The experimental system uses a motor controller
with
•a range of speeds,
•emergency stop with braking,
•rotational direction,
•on/off, and
•full speed bypass
12 VDC in
2 KΩ potentiometer
0 – 10 VDC power out to shaker
motor
Computer controlled experimental setup
Rotating disc with hole for safety reasons
Eccentric hole in
flywheel
Flywheel
Electric motor
Control wire
Steering
Wheel
Mobile Experimental Setup
Clamping device
Flywheel
DC Motor
Power supply
Control
Box
Spinning Eccentric Weight
Eccentric hole for safety reasons
Steering Wheel Shaker
adaptable to a range of Wheels
Adaptable Steering Wheel Clamp
Coiled cord for power to the
steering wheel
Coiled cord was fastened to the steering
wheel and allowed 5 rotations of motion
Results
Speed of Vehicle in
mph
Speed of the
flywheel in rpm
Sensation
12
700
Not Noticeable
10
900
Noticeable
11
1000
Strong
12
1100
Too Strong
14
1100
Not noticeable
Laboratory Based
Experimental Setup
Steering Wheel Shaker Laboratory Setup powered from 12 VDC wall adapter
Laboratory Based
Experimental Setup
Shaker Evaluator
preparing for test
Frequency vs amplitude at each voltage input to the motor
10
0
0
0.4 V
0.5 V
0.6 V
0.7 V
0.8 V
0.9 V
1V
1.1 V
1.2 V
1.3 V
1.4 V
1.5 V
1.6 V
1.7 V
1.8 V
1.9 V
2.0 V
10
2.1 V
20
2.2 V
30
2.3 V
2.6 V
2.7 V
70
40
-10
Amplitude (dB)
-20
-30
-40
-50
-60
Frequency (Hz)
-70
2.4 V
50
2.5 V
60
80
Natural Frequency (Hz) of the three test systems as a
function of motor voltage
60
Natural Frequency (Hz)
50
40
Fn (On-Vehicle)
30
Fn (Lab test)
Fn (Driving)
20
10
0
0
1
2
3
Motor voltage
4
5
Amplitude of Vibration at the Natural
Frequency for each Motor Voltage
20
Amplitude of vibration
15
10
5
0
0
0.5
1
1.5
2
2.5
-5
-10
Motor Voltage
3
3.5
4
4.5
Conclusion
• Faster response is expected to a warning
• The test system was easy to install and manufacture.
• The vibration feedback is not noticeable at low and very high rpm’s.
• It has been determined that the laboratory based steering wheel shaker test
can provide stationary on-vehicle test results by using a 0.66 correction factor
on the motor voltage. Therefore, on-vehicle tests may be simulated in the
laboratory using this correction.
Questions and Answers