CACR-SR02-AD1-FR Yaskawa Industrial Servo Driver Converter Servopack

Test Apparatus
The tests were performed using the rig shown in Figure 2 which consisted of a rigid steering wheel
connected to a shaft supported by 3 radial bearings. The shaft incorporates a lever arm which is
connected to an electrodynamic shaker unit by means of a stinger rod. All mechanical components (i.esteering wheel, shaft, bench) were modeled using the finite element method and were found rigid to
frequencies in excess of 300 Hz. The seat, guide-rail and the bench geometric dimensions (see Table 1)
were chosen based on average data from European B-segment automobiles. Seat horizontal travel and
back-rest inclination were fully adjustable.

 

 

 

 

Geometric Parameter Value
Steering column angle with respect to floor 23°
Steering wheel hub centre height above floor 710 mm
Seat H point height from floor 275 mm
Horizontal distance from H point to steering wheel hub centre 390 – 450 mm
Steering wheel handle diameter 12.5 mm
Steering wheel diameter 325 mm
Natural Frequency of the test bench 310 Hz.

 

 

The steering wheel was vibrated by means of a G&W V20 electrodynamic shaker driven by PA 100
amplifier [8], using the internal sine wave generator. The acceleration obtained at the steering wheel was
measured using an Entran EGAS-FS-25 accelerometer located on the top left side of the steering wheel.
The accelerometer signal was amplified by means of an Entran MSC6 signal-conditioning unit [6] and
monitored by Tektronix TDS210 digital oscilloscope

 

 

Three equal sensation tests; namely test 1, test 2 and test 3 were performed at different frequency and
amplitude values. The selection of test frequencies and amplitudes was based on the analysis of steering
wheel vibration levels obtained from tests of a Renault automobile on 7 road surfaces using 175/65 R14
and 225/45 R16 tyres driven at 45 m.p.h. [21]. An annoyance threshold test was also performed to
measure the maximum level of steering wheel vibration that the subjects were willing to withstand for 10
seconds of exposure time. The frequency range of interest was chosen to be from 5Hz to 315 Hz, using
the center frequencies of the 1/3 octave band scale. The reference frequencies for equal sensation test 2
and 3 were chosen at 0.2 and 0.4 ms-2
r.m.s respectively, both at 10 Hz. However, due to the limitation ofthe shaker, equal sensation test 1 was performed with reference amplitude of 0.5 ms-2
r.m.s at 40 Hz.
Table 3 summarizes the reference frequencies and amplitude levels.

 

 

 

A variation of the method of constant stimuli [4, 9] was used for the equal sensation tests. A reference
vibration stimuli was used for generating each of the three equal sensation curves. The three reference
stimuli were 0.5 ms-2
r.m.s at 40 Hz, 0.2 ms-2
r.m.s at 10 Hz and 0.4 ms-2
r.m.s at 10 Hz. Each reference
stimuli was presented to the test subjects for 20 seconds, then the frequency of the stimulus was
changed and the subjects were asked to give verbal instructions so as to adjust the amplitude of the new
stimuli until it produced a similar sensation to the reference. During each test, the subject was required to
compare the test signal to the reference within a 30 second time interval so as to remain within human
short term memory [1]. All 1/3 octave band frequencies in the range from 5 Hz to 315 Hz (i.e 5, 10, 12.5,
16, 20, 25, 31.5, 40, 50, 63, 80, 100, 125, 160, 200, 250 and 315 Hz) were tested. Since human
judgement has been shown to be relative rather than absolute [4 ], stimuli comparisons were limited to
occur between frequencies which were no more than one full octave (i.e doubling of frequency) apart.