Traction force balance and vehicle drive assist. prof. Simon Oman Vehicle – interactions and effectiveness Effectiveness as a cross- Vehicle section of probability domains 2 Vehicle – interactions and effectiveness Driver FunctionalityVEHICLE Effectiveness Operating conditions A vehicle effectiveness is a probability that the vehicle fulfils its requirements on operation readiness, availability and characteristics for the given operating conditions, maintenance conditions and environmental influence . 3 Driving resistances • Resistance of bearings • Rolling resistance • Aerodynamic resistance (Drag resistance) • Resistance of a hill • Trailer resistance 4 Resistance of bearings M izg,L RL RL = Mizg,L rst rst 5 Rolling resistance ω Pz = Z U x = R f Z Rf ∑ M = 0 Z ⋅e − R ⋅r = 0 e rst f st e R = Z ⋅ = Z ⋅ f Ux f rst Pz σ Loading Hysteresis Unloading ε 6 Rolling resistance • Typical values of the rolling resistance for a road vehicle with rubber tires: – f = 0,01 – 0,015 (a tire on asphalt or concrete) – f = 0,035 (a tire on a macadam road) – f = 0,3 (a tire on a dry and non-compacted sand) • A typical value of the rolling resistance for a railway vehicle: – f = 0,001 7 Aerodynamic (Drag) resistance v2 R = c* ⋅ A ⋅ ρ ⋅ v z v z 2 8 Aerodynamic (Drag) resistance • An augmented aerodynamic-resistance coefficient c* includes the following influences: – An aerodynamic resistance of the air flow around the vehicle; – A friction between the air and the vehicle (can be neglected); – A resistance of the air flow through the vehicle (e.g. ventilation losses). 9 Aerodynamic (Drag) resistance • Typical values of the augmented aerodynamic-resistance coefficient c* are the following: – c* = 0,3 … a car – c* = 0,6 … a bus – c* = 0,9 … a truck – c* = 0,98 … a truck with a trailer / train 10 Resistance of a hill Rs = G ⋅sinα = m⋅ g ⋅sinα 11 Trailer resistance Rp = ∑(RB + R f + Rz + Rs ) prikolica _ trailer 12 A sum of driving resistances Rs( ) 13 A sum of driving resistances Rz Rs DO TU Rf,L;1 Rf,L;2 Rp F1 F2 • A sum of driving resistances is equal to the sum of the resistance of bearings, the rolling resistance, the aerodynamic resistance, the resistance of a hill and the trailer resistance. • During vehicle movement the tangential forces between the wheels and driving surface (F 1,2 ) must overcome the sum of the driving resistances (and the inertial forces at accelera- ting/braking if applicable). • The tangential forces acting on the wheels F 1,2 result from the transformed torque of the driving engine or brakes. 14 Ideal characteristics of a driving engine P F R( =max) R( =0) v vmax v 15 Characteristics of an electric motor 16 ICE characteristics 17 Multiple gear mechanical transmission Typical gear ratios : M m ⋅ig,i ⋅i0 ⋅ηT • i0 = 3,7 Fk = • i = 1,2 rst • ig,1 = 3,9 g,4 • i = 1,0 • ig,2 = 2,2 g,5 • i = 3,8 • ig,3 = 1,5 g,R • = 0,96 ηT rst ig,i i0 i= 5 1 2 3 4 R Angle gear with differential gear ICE Cardan shaft Gear box Clutch Wheel 18 ICE elasticity and gear influence Fk R( =max) P, M ( ) M, P [kW] 1. posp max q Mmax 2. R( >0) Mposp ( i=2) 3. q [g(l)/km] 4. Mposp ( i=3) R( =0) M [Nm] 5. qmin -1 800 6000 n [min ] vmax v 19 ICE elasticity and gear influence Fk Start : Lack of torque is compensated by a clutch slip ΣR(α=max) 1. 2. 3. 4. ΣR(α=0) 5. Lack of torque vmax v 20 Dynamic coefficient of a vehicle Fk ≥ RL + R f + Rz + Rs ⋅ /1 G F R + R + R + R k = L f z s G G F − R R + R + R k z = D = L f s G G Dynamic coefficient D is a specific traction force relative to a vehicle‘s weight that is available for accelerating the vehicle and surpassing the rolling resistance, resistance of bearings and resistance of the hill. 21 Vehicle power balance Fk ⋅v = RL ⋅v + R f ⋅v + Rz ⋅v + Rs ⋅v ⇒ ⇒ Pk = PL + Pf + Pz + Ps P Pind,i=5 Pk,i=1 Pk,i=2 Pk,i=3 Pk,i=4 Pk,i=5= = T Pind,i=5 Pposp Pz P R Ps Pf PL v vmax 22 Hybrid vehicles (HV) DEFINITION of a HV: in the hybrid road vehicle a propulsion energy is available from two or more sources and/or energy storage devices and/or energy converter devices [1]. A scheme of a conventional vehicle with the ICE: 23 Hybrid vehicles (HV) Assembly of a hybrid drive: – Internal combustion engine (ICE); – Energy storage and/or converter device; – Power splitter (planetary or CVT/RVT gear), dependent on the HV type (serial, parallel or combined hybrid). Pogonsko kolo / Pogonsko kolo / Pretvornik Traction wheel Pretvornik Traction wheel energije 1 / Shranjevalnik energije 2 / Shranjevalnik Energy energije / Energy energije / converter 1 Energy storage converter 2 Energy storage Pretvornik Delilnik moči / Transmisija / energije 1 / Power splitter Transmission Energy Motor z notranjim Motor z notranjim converter 1 zgorevanjem / zgorevanjem / ICE ICE Kotno gonilo z Kotno gonilo z diferencialom / diferencialom / Angle gear with Angle gear with differential gear Pogonsko kolo / differential gear Pogonsko kolo / Traction wheel Traction wheel Schemes of three HV types (left - serial hybrid, middle – parallel hybrid, right – combined hybrid) 24 HV types • Hybrid electric vehicles (HEV) – Electric charge is stored in batteries. – Electric motor as a support or main drive. • Hybrid hydraulics vehicles (HHV) – Hydro-pneumatic accumulators store the energy from the transmission and return the energy back into transmission. • Mechanical hybrid vehicles (MHV) – A flywheel is used for energy storage. • Electro-mechanical hybrid vehicles (EMHV): – A combination of an electric motor/generator and electro- mechanical flywheel is used for energy storage and return. 25 Hybrid electric vehicle (HEV) • HEV combines propulsion power from an ICE and a battery driven electric motor. • The electric motor supports or replaces a power flow from ICE. • A transmission efficiency influences a fuel economy and reduces pollutant emissions. • The fuel economy and vehicle performances strongly depend on the vehicle mass. • A lack of charge storage in batteries significantly reduces the range applicability of the electric vehicles. • A vehicle-electrification levels are as follows: (vehicles Polni hibridi Polni Električna vozila Električna (Full hybrids) (Full range extender) range (Electric vehicles) (Electric Priključni hibridi Priključni Priključni hibridi s hibridi Priključni (Mild hybrids) (Mild hybrids) (Plug-in Srednji hibridi Srednji (Plug-in hybrids with a with hybrids (Plug-in Vozila ssistemom Vozila povečevalnikom dosega dosega povečevalnikom start/stop start/stop with a start/stop system) start/stop a with 26 Hybrid electric vehicle (HEV) An example of a (plug-in) parallel hybrid power train [1]: An example of a full electric vehicle [1]: 27 Hybrid hydraulic vehicle (HHV) • A kinetic energy during braking is stored into hydraulic- pneumatic accumulators. During the acceleration phase the energy (reduced for the energy losses) is returned into a transmission system. • Hybrid hydraulic vehicles (HHV) concepts can be designed in a serial (S-HHV) or a parallel configuration (P-HHV). Gas (N 2) and hydraulic fluid system of a manufacturer Bosch [2] 28 Serial hydraulic hybrid (S-HHV) • ICE is not mechanically linked to the wheels. • Hydraulic pump/motor in a drive mode uses high-pressure fluid from the hydraulic accumulator for the vehicle propulsion. • Three main operation modes of the S-HHV vehicle are: – mild acceleration / short cruising; – Extended cruising / strong acceleration; – regenerative braking. 29 Serial hydraulic hybrid (S-HHV) Visokotlačni Pogonsko kolo Visokotlačni vod akumulator (Traction wheel) (High-pressure pipe) (High-pressure accumulator) Nizkotlačni vod (Low-pressure pipe) Kotno gonilo z diferencialom (Angle gear with Hidravlična differential gear) črpalka 1 H-motor/črpalka (Hydraulic (H-motor/pump) Motor z pump 1) notranjim zgorevanjem Visokotlačni Pogonsko kolo (ICE) Visokotlačni vod akumulator (Traction wheel) Nizkotlačni (High-pressure pipe) (High-pressure akumulator accumulator) Pogonsko kolo Nizkotlačni vod (Low-pressure (Traction wheel) (Low-pressure pipe) Kotno gonilo z accumulator) diferencialom (Angle gear with Regenerative braking [2] Hidravlična differential gear) črpalka 1 H-motor/črpalka (Hydraulic (H-motor/pump) Motor z pump 1) notranjim zgorevanjem (ICE) Nizkotlačni akumulator Pogonsko kolo (Low-pressure (Traction wheel) accumulator) Extended cruising / strong acceleration [2] Mild acceleration / short cruising [2] 30 Parallel hydraulic hybrid (P-HHV) • ICE, standard powertrain transmission and hybrid hydraulic technology are linked to a main propulsion shaft. • ICE supplies the power to the traction wheels through the standard powertrain transmission. • Hydraulic components that support the powertrain during braking and accelerating are linked to the main propulsion shaft. 31 Parallel hydraulic hybrid (P-HHV) Visokotlačni akumulator (High-pressure accumulator) H-motor/črpalka (H-motor/pump) Pogonsko kolo (Traction wheel) Nizkotlačni akumulator Sklopka hidro-pogona / (Low-pressure Kotno gonilo z Clutch of a hydro-drive accumulator) diferencialom (Angle gear with differential gear) Menjalnik / Gearbox Motor z notranjim zgorevanjem Visokotlačni vod (ICE) (High-pressure pipe) Nizkotlačni vod Pogonsko kolo (Low-pressure pipe) (Traction wheel) 32 Vzporedni hidravlični hibrid / Parallel hydraulic hybrid (P-HHV) Visokotlačni Visokotlačni akumulator akumulator (High-pressure (High-pressure accumulator) accumulator) H-motor/črpalka H-motor/črpalka (H-motor/pump) Pogonsko kolo Pogonsko kolo (Traction wheel) (H-motor/pump) Nizkotlačni (Traction wheel) Nizkotlačni akumulator akumulator Sklopka hidro-pogona / (Low-pressure