Aspects of Modelling: Examples from Consideration of Unusual Movements. in Crash Simulation

Size: px

Start display at page:

Download "Aspects of Modelling: Examples from Consideration of Unusual Movements. in Crash Simulation"

Emma Payne
5 years ago
Views:

1 Examples fom Consideation of Unusual Movements Univ.-Pof. D.-Ing. Matin Meywek Depatment of Automotive and Powe Tain Engineeing Helmut-Schmidt-Univesity Univesity of the Fedeal Amed Foces, Hambug 1/17

2 Unusual movements: Example 1: Example 2: Displacements / vibations of the engine in pedestian potection Influence of otations Why ae these unusual movements? Because the engine is usually not unning in cash tests. 2/17

3 Expeimental setup: head flying against engine hood; HIC is calculated o measued Automotive and Powe Tain Engineeing Pedestian potection 3/17

4 Passenge potection eality: - head contacts the engine hood; the pobability of a load change is high (dive s shock) a consequence of load change: displacement of the engine distance between engine hood and engine deceases isk of sevee injuies inceases 4/17

5 x in mm 20 Automotive and Powe Tain Engineeing Engine movement Measuements: coodinates of a point of the engine y in mm 0-20 z in mm /17

6 engine movement engine movement 6/17 Acceleation in mm/s^2 Time in ms

7 Quintessence In standad tests no displacements of the engine is pescibed in eality displacements of the engine ae likely in simulation displacements of the engine ae easy to conside in tests the displacement is difficult to implement Simulation shows geat advantages in compaison to tests; this could be one eason fo eplacing moe tests by simulations in pedestian laws. Simulating o testing fo pedestian laws without movement of the engine could yield bad esult in compaison with eality. 7/17

8 Cash Simulation e.g. RCAR, ODB: both offset cashs What is the CAE enginee doing? cashmodel; definition of initial velocity (e.g. 15 km/h) definition of all initial angula velocities fo the coect inetias and a suitable gea atio? 8/17

9 Effect 1: Initial angula velocity gyoscopic effects ω flywheel Ωvehicle M gyoscopic = 2 J Ωω offset J flywheel = 0.1 kg m ω flywheel = 2π100 Ω = 1.75 vehicle ad s 2 ad s baie v M gyoscopic 110 Nm 9/17

10 Effect 1: Initial angula velocity gyoscopic effects otating flywheel 10/17

11 Effect 1: Initial angula velocity gyoscopic effects ω flywheel >0 ω flywheel <0 Diffeences in Displacements: < 2mm 11/17

12 ω flywheel =0 Effect 1: Initial angula velocity z-coodinate Scatteing esults fom paallelization 12/17

13 Effect 1: Initial angula velocity gyoscopic effects influences the esults; because angula velocity is not known exactly, this is an additional stochastic paamete; a geat advantage of simulation becomes obvious: analysing this influence is possible in an easy way 13/17

14 Effect 2: Coection of otational inetias ipv 1 ipigv kin = + P + E E mv J J v 1 v + Jwf + Jw 2 2 Neglecting slips = 0, S = 0 f E kin 1 2 = mv λ JP ip J i E pig λ= 1+ + m m 1 J J w m m wf lumped mass facto of otational inetia 14/17

15 Effect 2: Coection of otational inetias E kin 1 2 = mv λ JP ip J i E pig λ= 1+ + λ 1 = λ = m m 1 J J w m m wf J E 0.1kgm ip 4 ig = 4 m = 1000kg = 0.3m J ip ig m moment of inetia of flywheel gea atio diffeential gea gea atio tansmission gea total mass adius of wheel E 2 p G = J E i i m Typical values of the lumped mass facto fo fist and fouth gea /17

16 Effect 2: Coection of otational inetias you ty to back you ca out of the gaage you mistake the fist gea with the evese gea you step on the gas pedal and bump into a pat of the wall of the gaage 2 p G = J E i i m λ 1 = λ = Typical case of RCAR low speed 15 km/h offset insuance test: 5.1 The test vehicle may be popelled by its own engine o by any othe popelling device. It is not common to conside all otational inetias, in paticula the inetias of the engine and flywheel, in cash simulation. Consequence: eo in kinetic enegy (30% in the example) 16/17

17 Summay Vibations/displacements could have much influence on pedestian injuies. It could be essential to eithe conside o neglect otations of masses in cash simulation. In case of deviations between simulation and expeiment it could be woth to compae otational inetias. To impove simulation thee ae moe physical effects which should be consideed, e.g. liquid filled pats (flexible ubbe tubes) 17/17

Experiment I Voltage Variation and Control

Experiment I Voltage Variation and Control ELE303 Electicity Netwoks Expeiment I oltage aiation and ontol Objective To demonstate that the voltage diffeence between the sending end of a tansmission line and the load o eceiving end depends mainly