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 09CV-0117 / 2009-01-2831
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 This system is for a broad range of steering wheels. On/Off Maximum speed Forward/Reverse Motor braking Motor speed s/w no s/w no s/w no s/w no The experimental system uses a motor controller with 12 VDC in 2 KΩ potentiometer a range of speeds, emergency stop with braking, rotational direction, on/off, and full speed bypass 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 Steering Wheel Control wire
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
Speed of Vehicle in mph Results 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 0.4 V 0.5 V 0.6 V 0.7 V 0.8 V 0.9 V 1 V 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 2.1 V 2.2 V 2.3 V 2.4 V 2.5 V 2.6 V 2.7 V 0 10 20 30 40 50 60 70 80-10 -20 Amplitude (db) -30-40 -50-60 -70 Frequency (Hz)
Natural Frequency (Hz) of the three test systems as a function of motor voltage 60 50 Natural Frequency (Hz) 40 30 20 Fn (On-Vehicle) Fn (Lab test) Fn (Driving) 10 0 0 1 2 3 4 5 Motor voltage
20 Amplitude of Vibration at the Natural Frequency for each Motor Voltage 15 Amplitude of vibration 10 5 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5-5 -10 Motor Voltage
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.
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