Evaluation the Dissipated Energy by the Automobile Dampers

Table of contents

1.

I. Introduction haracterization of automotive suspensions, in terms of energy dissipated by the suspension dampers while running, is a complex process that takes into account a number of factors, such as road profile, vehicle characteristics, running speed. All these factors contribute to determining the conditions under which the dampers dissipate a large amount of possible energy. In order to simulate the systems suspension operation and to evaluate the dissipated energy by the system, there were considered the following parameters:

? road profile; ? mass parameters and general organization of the car; ? operating parameters of the suspension; ? simulation conditions.

2. II. Road Profile

The road profile is comprised of two components: ? the road microstructure; ? the road macrostructure.

The road microstructure road represents the uneven humps of tread, felt by the vehicle driver as vibrations or small oscillations. This is divided into four classes, depending on the variation of high road irregularities (Î?"h) in relation with theoretical nominal profile, measured in mm, [1]: Depending on the mentioned macrostructures parameters, there were defined eight road profiles, whose design speeds are in the range 25 km/h -120 km/h, with the following characteristics: Following the conditions from the table 1, it results a sequence of road characteristics used in simulation:

? ISO A-B, Î?"h = ±

3. B

The road profile sequences with a concave and convex radius, will be repeated until the length of road, in horizontally profile, will have the value of 1 km (distance used in simulation).

4. V. Conditions of Simulation

The conditions required for vehicle during the simulation are: ? simulation performed in two conditions, the car's unladed weight and with total weight; ? straight displacement at a constant speed; ? all the profiles road used in simulation have a length of 1 km;

? the cross profile of the road is symmetrical.

5. VI. Suspension Mathematical Model

Each suspension vehicle consists of: ? the suspension itself; ? the tyres. The suspension itself includes the springs, the dampers and the arms of the car body. Here it was defined the suspension mass (m s ), vehicle sprung mass (m 1 ), the suspension spring rate (k s ) and the suspension damping (c s ).The tire was defined as an independent suspension with the same elements, spring and damper. It was considered the tire stiffness (k t ) and tire damping (c t ).The suspension excitation is characteristic for every road profile (X r ) and is identical between the front and rear axle, but out of phase with the length of the wheelbase. For a qualitative representation of dissipated energy by the dampers, in relation to the energy consumed by the car in order to cover the distance of 1 km, it is considered the car has tires rolling resistance coefficient f = 0.008, the drag coefficient cx = 0.28 and the frontal area A x = 2 m 2 . The resistances who acts on the car are: rolling resistance and aerodynamic drag. The results are presented in the figure 7

) ( ) ( 1 1 1 1 1 1 1 1 = ? ? ? ? S S S S x x k x x c x m ? ? ? ? (1.a) 0 ) ( ) ( ) ( ) ( 1 1 1 1 1 1 1 1 1 1 1 1 1 1 = ? ? ? ? ? + ? + r S t r S t S S S S S S x x k x x c x x k x x c x m ? ? ? ? ? ? (1.b) 0 ) ( ) ( 2 2 2 2 2 2 2 2 = ? ? ? ? S S S S x x k x x c x m ? ? ? ? (2.a) 0 ) ( ) ( ) ( ) ( 2 2 2 2 2 2 2 2 2 2 2 2 2 2 = ? ? ? ? ? + ? + r S t r S t S S S S S S x x k x x c x x k x x c x m ? ? ? ? ? ?
Figure 1.
15 mm; ? ISO B-C, Î?"h = ± 25 mm; ? ISO C-D, Î?"h = ± 50 mm; ? ISO D-E, Î?"h = ± 100 mm;
Figure 2. Figure 1 :Figure 2 :
12Figure 1: Microstructure of road profileThe road macrostructure is the longitudinal profile of the road, being characterized by the following parameters,[2]: ? the maximum longitudinal gradients, ? ;
Figure 3. Figure 3 :
3Figure 3: Characteristics of macrostructure road profile sequence
Figure 4. Figure 4 :Table 3 :
43Figure 4: Road profiling of macrostructures sequences The road profiles used in the simulation consists of overlapping macrostructures and microstructures. Thus, a combination of 27 profiles road results. Due to passenger's discomfort caused by strong vibrations, the ISO profile B-C, C-D and D-E will not be subject of the simulation in high speeds area.Table 3: The road profiles used in simulation
Figure 5. Figure 5 :
5Figure 5: The suspension model
Figure 6.
0
Figure 7. ( 2 B
2.b) The (1.a) and (1.b) formulas are applied to the front axle and the (2.a) and (2.b) formulas are applied to the rear axle. The figure 4 presents the MatLab Simulink model achieved for a single axle. The input data are: the sprung mass, corresponding to the front/rear axle, the suspension weight and the road profile. Using these data, as well as operating parameters and the suspension of the car, it was determined the total energy dissipated by the respective axle shock absorbers. Global Journal of Researches in Engineering ( ) Volume XVI Issue I Version I 8 Year 2016 The mathematical model includes the entire vehicle, the suspension of front and rear axle, [9].
Figure 8. Figure 6 :
6Figure 6: The suspension model used in MatLab SimulinkVII. ResultsFor each road profile, the energies dissipated by the car suspensions were calculated. The values
Figure 9.
and figure 8.
Figure 10. Figure 7 :Figure 8 :
78Figure 7: Percentage of energy dissipated by the dampers, in relation to the energy consumed by the engine car with unladed weight, to cover the distance of 1 km
Figure 11. Table 1 :
1
Road profile speed [km/h] ? [ ° ] R convex [m] R concav [m]
25 8 500 300
30 7,5 800 500
40 7 1000 1000
50 7 1300 1000
60 6,5 1600 1500
80 6 4500 2200
100 5 10000 3000
120 5 18000 6500
Figure 12. Table 2 :
2
Road profile speed [km/h] H [m] h [m] D [m] d [m]
25 1.6 0.9 80 48
30 2.2 1.4 120 75
40 2.4 2.4 140 140
50 3.1 2.4 181 140
60 3.3 3.2 207 196
80 8.1 3.9 538 224
100 7.1 2.1 748 263
120 12.2 4.5 1330 480
Note: Global Journal of Researches in Engineering ( ) Volume XVI Issue I Version I 6 Year 2016
Figure 13. Table 4 :
4
ISO A-B ISO B-C ISO C-D ISO D-E
25 km/h 8877 8011 8444 8852
30 km/h 8610 8491 9920 9905
40 km/h 6567 6151 8198 8519
50 km/h 6525 6322 7956 7905
60 km/h 5914 5954 6755 8125
80 km/h 5351 5341 6290 6771
100 km/h 4222 3792 - -
120 km/h 3062 - - -
Figure 14. Table 5 :
5
ISO A-B ISO B-C ISO C-D ISO D-E
25 km/h 13930 12380 14760 13650
30 km/h 13000 12730 15000 15490
40 km/h 9328 9577 12240 12880
50 km/h 9363 9482 11960 11670
60 km/h 8502 8339 9830 11300
80 km/h 7592 7323 8855 9553
100 km/h 5735 5449 - -
120 km/h 4297 - - -
1
2

Appendix A

Appendix A.1 VIII. Conclusions

The simulation of system suspension shows a relation between the energy dissipated by the damping car and vehicle and road profile properties. Among the properties of the car, it results that the mass of the car (m), the suspension spring (k s ) and the suspension damping (c s ) are the elements that influence the dissipated energy. An increase of mass vehicle and damping coefficient, corroborated with a decrease of spring rate, will produce a higher energy dissipation for the dampers. The road profile subcomponent who have the biggest influence on the suspension excitation is the microstructure. The macrostructure has an important role only if the road profile speeds is below 60 km/h. Thus, a car loaded, with elastic suspension and stiff dampers, will require to dissipate more energy through the dampers. However, macrostructure profiles of road categories with maximum speeds between 25 km/h -60 km/h and microstructures profiles of road categories ISO C-D and ISO D-E contributes to increased suspension load.

Appendix B

  1. D R Unaune , M J Pawar , Dr S S Mohite . Ride Analysis of Quarter Vehicle Model, International Conference on Modern Trends in Industrial Engineering, November 17-19, 2011. (pg. 1: 1 -6. 2. Books)
  2. Theory of Pneumatic Tires, part 5, pg, Lotus Talk . 78 p. .
  3. Theory of Pneumatic Tires, part 5, pg, Lotus Talk . 80 p. .
  4. The vibrations induced by surface irregularities in road pavements -a Matlab® approach. M Agostinacchio & D. Ciampa , & S Olita . Eur. Transp. Res. Rev 2014. 271 p. .
  5. , Marin ; Untaru , Fratila , ; Gheorghe , Potincu , ; Gheorghe , Seitz , ; Nicolae , Gheorghe Peres .
  6. Calculul si constructia automobilelor. Editura Didactica si Pedagogiga. Bucuresti. 1982. pg, Tabacu , Ion , Tiberiu Macarie . 579 p. .
  7. Technical Specification 27/01/1998 for the design, construction and modernization of roads, 3 p. . (Published in 06/04/1998, no. 138bis. Entered into force on 06.04.1998. pg)
Notes
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© 2016 Global Journals Inc. (US)
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© 2016 Global Journals Inc. (US) Evaluation the Dissipated Energy by the Automobile Dampers
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Date: 2016-01-15