Drivetrain

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This class simulates the engine and the driveline.
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This class simulates the '''engine''' and the '''driveline'''. The engine generates the torque (and consequently the power) which is used to move the vehicle. The driveline represents everything needed to transfer the engine torque to the wheels: clutch, transmission and differential.
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__TOC__
== Engine ==
== Engine ==
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The engine torque can be simulated in two different ways: using the function CalcEngineTorqueInt or writing an external torque file.
 
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The engine generates the torque (and consequently the power) which is used to move the vehicle. Parameters:
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==== Calculate the torque curve using the function CalcEngineTorqueInt ====
 
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Uncheck '''Load External Torque Data''' checkbox in order to use this function.
 
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Using CalcEngineTorqueInt means that the engine torque is calculated by a polynomial expression which needs the following parameters:
 
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#'''max Power''', which represents the max power (in HP) produced by the engine. Typical value for a medium car is 150 HP, for a powerful car is 450 HP;
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*  '''max Power''', which represents the max power (in HP) produced by the engine. Typical value for a medium car is 150 HP, for a powerful car is 450 HP.
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#'''max Power RPM''', which represents the RPM (Revs Per Minute) at which the '''max Power''' is produced. Typical values are in the range 5000 – 9000 RPM. Should be lower or equal than '''max RPM''';
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#'''min RPM''', which represents the minimum RPM (Revs Per Minute) for the engine to work. This is the idle RPM. Typical values are in the range 500 – 1500 RPM;
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#'''max RPM''', which represents the maximum RPM (Revs Per Minute) for the engine to work. Typical values are in the range 6000 – 10000 RPM. Should be higher or equal than '''max Power RPM''';
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As you can see, in this case you don't need to set the '''engine torque''' but only the '''engine power'''. Engine torque is calculated automatically from the engine power. More info on this function can be found in Motor Vehicle Dynamics, Giancarlo Genta 1997.
 
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* '''max Power RPM''', which represents the RPM (Revs Per Minute) at which the max Power is produced. Typical values are in the range 5000 – 9000 RPM. Should be lower or equal than max RPM.
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==== Calculate the torque curve using an external torque file ====
 
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Check '''Load External Torque Data''' checkbox in order to use this function.
 
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Using an external torque file means that you specify the torque (and consequently the power) of the engine in a discrete way, specifying a certain numbers of steps (interpolated internally by the script). Each step consists of a couple of value, the torque (in Nm) and the RPM (Revs Per Minute) at which the torque is expressed.
 
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This is an example of a torque file:
 
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<pre>
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* '''max Torque''', which represents the max torque(in N*m) produced by the engine. Typical value for a medium car is 200 Nm, for a powerful car is 500 Nm.
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[engine]
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torque-curve = 500, 240
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torque-curve = 700, 408
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torque-curve = 1000, 530
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torque-curve = 1500, 598
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torque-curve = 2000, 650
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torque-curve = 3000, 680
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torque-curve = 4000, 693
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torque-curve = 5000, 466
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torque-curve = 6000, 112
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torque-curve = 6500, 10
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</pre>
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The first value is the RPM (Revs Per Minute), the second is the torque (in Nm). You can specify as many steps as you want. Engine power is calculated from its torque. In order to UnityCar to load the torque file properly, the file must be in the same directory of the unity3d package and must be called with the same name as the car in the inspector (with space character " " substituted with the underscore "_") and must have the extension  ".ini".
 
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So for example:
 
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unity3d_package_directory\Monster_Truck.ini
 
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unity3d_package_directory\Catamount_UM001.ini
 
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unity3d_package_directory\Peugeot_205_T16.ini
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* '''max Torque RPM''', which represents the RPM (Revs Per Minute) at which the max Torque is produced. Typical values are in the range 2000 – 5000 RPM. Should be lower or equal than max RPM.
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* '''min RPM''', which represents the idle RPM (Revs Per Minute). Typical values are in the range 500 – 1500 RPM.
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* '''max RPM''', which represents the maximum RPM (Revs Per Minute) for the engine to work (when revLimiter is enabled). Typical values are in the range 6000 – 10000 RPM. Should be higher or equal than max Power RPM;
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* '''Can Stall''' if checked, the engine can stall if the clutch is engaged too quickly. Otherwise RPM is always kept equal or higher than min RPM.
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* '''Rev Limiter''' if checked, when RPM becomes equal or greater than max RPM rev limiter kicks in and cuts off the throttle for rev Limiter Time seconds.
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* '''Rev Limiter Time''' amount of time for the engine to be cutted if Rev Limiter is checked.
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* '''Engine Inertia''' this value slows down engine revving up. The higher the engine inertia, the slower the engine revs up.
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* '''Engine Friction Factor''' this value causes the engine to slow down and cause engine braking. The higher this value, the quicker the engine is slowed down. Typical value is 0.25. Important: as in real life, Engine Friction Factor causes power loss. With a value of 0.25 the power loss is about 23% (typical real life value).
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* '''Engine orientation''' determines how the car body moves as the engine revs up in neutral.Typically either Vector3.forward or Vector3.right.
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Its important to define some steps for the lowest RPMs of the engine in order to obtain smooth starts.
 
== Driveline ==
== Driveline ==
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The Driveline represents everything needed to transfer the engine torque to the wheels. Parameters:
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The driveline represents everything needed to transfer the engine torque to the wheels: clutch,transmission and differential. Parameters:
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* '''Drivetrain Inertia''' this value represents the inertia of the drivetrain. It works in a similar way of the engine inertia, and it adds a further inertia to the system.
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* '''Transmission''' specify the number and which wheels are used to transfer power to the ground. Values are FWD (front axle wheels), RWD (rear axle wheels), AWD (all axles wheels) and XWD (any combination of any axles can be used).
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*'''Load External Torque Data''' when checked, UnityCar calculates the torque (and consequently the power) of the engine using an external file called the same as the car's name in the inspector with space character " " substituted with the underscore "_" and with extension  ".ini". This file must be in the same directory of the unity3d package. So for example unity3d_package_directory\Catamount_UM001.ini.
 
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* '''Gear Ratios''' represents the number and the ratio of the gears. The size value represents the numbers of the gears (included neutral and reverse). The value of each element represents the ratio, that is the length of that gear. The smaller the value, the longer the gear. The first element should be reverse (so its value should be negative), the second element should neutral (so its value should be zero), the third element should first gear and so on. Anyway you can use as many reverse and as many forward gear, provided that in the middle there is a neutral gear (that is with value zero).
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*'''Transmission''' specify the number and which wheels are used to transfer power to the ground. Values are '''FWD''' (two front wheels), '''RWD''' (two rear wheels) and '''AWD''' (both the two front wheels and the two rear wheels).
 
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*'''Gear Ratios''' represents the number and the ratio of the gears. The size value represents the numbers of the gears (included neutral and reverse). The value of each element represents the ratio, that is the length of that gear. The smaller the value, the longer the gear. The first element is the reverse (so its value should be negative), the second element is the neutral (so its value should be zero), the third element is the first gear and soon. Anyway you can use as many reverse and as many forward gear, provided that in the middle there is a neutral gear (that is with value zero).  
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* '''Final Drive Ratio''' represents the ratio of all gears. So if you want to make all gears longer, just decrease this value, if you want to make all gears shorter, increase this value. Typical values are 3.5 for a medium car and 6.0 for a powerful car.
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*'''Final Drive Ratio''' represents the ratio of all gears. So if you want to make all gearslonger, just decrease this value, if you want to make all gears shorter, increase this value.Typical values are 3.5 for a medium car and 6.0 for a powerful car.
 
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* '''Differential Lock Coefficient''' Coefficient determining how much torque is Transferred between the wheels when they move at different speeds, to simulate differential locking.
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*'''max Power''' represents the max power (in HP) produced by the engine. Typical value for a medium car is 150 HP, for a powerful car is 450 HP;
 
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*'''max Power RPM''' represents the RPM (Revs Per Minute) at which the '''max Power''' is produced. Typical values are in the range 5000 – 9000 RPM. Should be lower than '''max RPM''';
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* '''Shifter''' if checked, gears are shifted using a button for every gear (by default set to work with G25/G27 shifter).
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*'''min RPM''' represents the minimum RPM (Revs Per Minute)  for the engine to work. This is the idle RPM. Typical values are in the range 500 – 1500 RPM;
 
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* '''Automatic''' if checked, gears are shifted automatically.
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*'''max RPM''' represents the maximum RPM (Revs Per Minute)  for the engine to work. Typical values are in the range 6000 – 10000 RPM. Should be higher than '''max Power RPM''';
 
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*'''Rev limiter''' when engine RPM gets highier than '''max RPM''', the rev limiter kicks in and cuts off the throttle for a small period of time.
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* '''Auto Reverse''' if checked, shift from first gear to reverse is done automatically.
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*'''Engage RPM''' this value represents the RPM (Revs Per Minute) at which the clutch starts engaging (that is the clutch starts connecting the engine to the wheel). Should be higher than the '''minRPM'''.
 
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* '''Shift Down RPM''' this value represents the RPM (Revs Per Minute) at which the automatic transmission shifts to the previous gear. Works only if Automatic is checked. Should be higher than minRPM and lower than Shift Up RPM.
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*'''Disengage RPM''' this value represents the RPM (Revs Per Minute) at which the clutch starts disengaging (that is the clutch starts disconnecting the engine from the wheel) when the RPM is too low for the current gear. Should be higher than the '''minRPM''' and lower than '''EngageRPM'''.
 
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*'''Engine Inertia Min and Max''' these values represent the engine inertia at '''low RPM''' (Engine Inertia Max) and engine inertia at '''high RPM''' (Engine Inertia Min). Engine inertia slow down engine revving up. The higher the engine inertia, the slower the engine revs up.
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* '''Shift Up RPM''' this value represents the RPM (Revs Per Minute) at which the automatic transmission shifts to the next gear. Works only if Automatic is checked. Should be lower than maxRPM and higher than Shift Down RPM.
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*'''Drivetrain Inertia''' this value represents the inertia of the drivetrain. It works in a similarway of the engine inertia, and it adds a further inertia to the system.
 
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* '''Shift Time''' this values represents how much time the automatic transmission takes to change gears (in seconds).Typical values are in the range of 0.2 – 0.8 seconds. Sports cars have lower values than offroad cars.
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*'''Engine Friction Factor''' this value causes the engine to slow down and cause enginebraking. The higher this value, the quicker the engine is slowed down. Typical value is 0.25. Important: Engine Friction Factor causes power loss. With a value of 0.25 the power loss is about 13%.
 
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*'''Engine orientation''' determines how the car body moves as the engine revs up in neutral. Typically either Vector3.forward or Vector3.right.  
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* '''Auto Clutch''' if checked, clutch is engaged and disengaged automatically.
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*'''Differential Lock Coefficient''' Coefficient determining how much torque is Transferred between the wheels when they move at different speeds, to simulate differential locking.
 
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* '''Engage RPM''' this value represents the RPM (Revs Per Minute) at which the clutch starts engaging (that is the clutch starts connecting the engine to the wheel). Should be higher than the minRPM and higher than DisengageRPM.
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*'''Automatic''' if checked, gears are shifted automatically.
 
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*'''Shift Down RPM''' this value represents the RPM (Revs Per Minute) at which the automatic transmissionshifts to the previous gear. Works only if Automatic is checked. Should be higher than '''minRPM'''. Please note that '''Shift Up RPM''' coincides with '''max Power RPM'''.
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* '''Disengage RPM''' this value represents the RPM (Revs Per Minute) at which the clutch starts disengaging (that is the clutch starts disconnecting the engine from the wheel) when the RPM is too low for the current gear. Should be higher than the minRPM and lower than EngageRPM.
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*'''Shift Speed''' this values represents how much time it takes to change gears (in seconds).Typical values are in the range of 0.2 – 0.8 seconds. Sports cars have lower values than offroad cars.
 
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* '''Fuel Consumption''' At Constant Speed this value represents engine fuel consumption (in litres/100km) at fuel Consumption Speed speed.
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*'''Clutch Max Torque''' represent the maximum torque that the clutch can generate. Typical values are 1.5 1.6 times engine max torque. If left to 0 its automatically calculated from engine torque.
 
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*'''Auto Clutch''' if checked, clutch is engaged and disengaged automatically.
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* '''Fuel Consumption Speed''' this value represents the speed (in km/h) at which vehicle consumes fuel Consumption At Constant Speed value.

Latest revision as of 10:51, 7 April 2015

This class simulates the engine and the driveline. The engine generates the torque (and consequently the power) which is used to move the vehicle. The driveline represents everything needed to transfer the engine torque to the wheels: clutch, transmission and differential.

Contents


Engine

The engine generates the torque (and consequently the power) which is used to move the vehicle. Parameters:


  • max Power, which represents the max power (in HP) produced by the engine. Typical value for a medium car is 150 HP, for a powerful car is 450 HP.


  • max Power RPM, which represents the RPM (Revs Per Minute) at which the max Power is produced. Typical values are in the range 5000 – 9000 RPM. Should be lower or equal than max RPM.


  • max Torque, which represents the max torque(in N*m) produced by the engine. Typical value for a medium car is 200 Nm, for a powerful car is 500 Nm.


  • max Torque RPM, which represents the RPM (Revs Per Minute) at which the max Torque is produced. Typical values are in the range 2000 – 5000 RPM. Should be lower or equal than max RPM.


  • min RPM, which represents the idle RPM (Revs Per Minute). Typical values are in the range 500 – 1500 RPM.


  • max RPM, which represents the maximum RPM (Revs Per Minute) for the engine to work (when revLimiter is enabled). Typical values are in the range 6000 – 10000 RPM. Should be higher or equal than max Power RPM;


  • Can Stall if checked, the engine can stall if the clutch is engaged too quickly. Otherwise RPM is always kept equal or higher than min RPM.


  • Rev Limiter if checked, when RPM becomes equal or greater than max RPM rev limiter kicks in and cuts off the throttle for rev Limiter Time seconds.


  • Rev Limiter Time amount of time for the engine to be cutted if Rev Limiter is checked.


  • Engine Inertia this value slows down engine revving up. The higher the engine inertia, the slower the engine revs up.


  • Engine Friction Factor this value causes the engine to slow down and cause engine braking. The higher this value, the quicker the engine is slowed down. Typical value is 0.25. Important: as in real life, Engine Friction Factor causes power loss. With a value of 0.25 the power loss is about 23% (typical real life value).


  • Engine orientation determines how the car body moves as the engine revs up in neutral.Typically either Vector3.forward or Vector3.right.


Driveline

The driveline represents everything needed to transfer the engine torque to the wheels: clutch,transmission and differential. Parameters:


  • Drivetrain Inertia this value represents the inertia of the drivetrain. It works in a similar way of the engine inertia, and it adds a further inertia to the system.


  • Transmission specify the number and which wheels are used to transfer power to the ground. Values are FWD (front axle wheels), RWD (rear axle wheels), AWD (all axles wheels) and XWD (any combination of any axles can be used).


  • Gear Ratios represents the number and the ratio of the gears. The size value represents the numbers of the gears (included neutral and reverse). The value of each element represents the ratio, that is the length of that gear. The smaller the value, the longer the gear. The first element should be reverse (so its value should be negative), the second element should neutral (so its value should be zero), the third element should first gear and so on. Anyway you can use as many reverse and as many forward gear, provided that in the middle there is a neutral gear (that is with value zero).


  • Final Drive Ratio represents the ratio of all gears. So if you want to make all gears longer, just decrease this value, if you want to make all gears shorter, increase this value. Typical values are 3.5 for a medium car and 6.0 for a powerful car.


  • Differential Lock Coefficient Coefficient determining how much torque is Transferred between the wheels when they move at different speeds, to simulate differential locking.


  • Shifter if checked, gears are shifted using a button for every gear (by default set to work with G25/G27 shifter).


  • Automatic if checked, gears are shifted automatically.


  • Auto Reverse if checked, shift from first gear to reverse is done automatically.


  • Shift Down RPM this value represents the RPM (Revs Per Minute) at which the automatic transmission shifts to the previous gear. Works only if Automatic is checked. Should be higher than minRPM and lower than Shift Up RPM.


  • Shift Up RPM this value represents the RPM (Revs Per Minute) at which the automatic transmission shifts to the next gear. Works only if Automatic is checked. Should be lower than maxRPM and higher than Shift Down RPM.


  • Shift Time this values represents how much time the automatic transmission takes to change gears (in seconds).Typical values are in the range of 0.2 – 0.8 seconds. Sports cars have lower values than offroad cars.


  • Auto Clutch if checked, clutch is engaged and disengaged automatically.


  • Engage RPM this value represents the RPM (Revs Per Minute) at which the clutch starts engaging (that is the clutch starts connecting the engine to the wheel). Should be higher than the minRPM and higher than DisengageRPM.


  • Disengage RPM this value represents the RPM (Revs Per Minute) at which the clutch starts disengaging (that is the clutch starts disconnecting the engine from the wheel) when the RPM is too low for the current gear. Should be higher than the minRPM and lower than EngageRPM.


  • Fuel Consumption At Constant Speed this value represents engine fuel consumption (in litres/100km) at fuel Consumption Speed speed.


  • Fuel Consumption Speed this value represents the speed (in km/h) at which vehicle consumes fuel Consumption At Constant Speed value.
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