Written by: Romain Gillot – Project Engineer
The VeSyMA – Powertrain library (also known as “PTDynamics” library) is a library developed by Claytex for modelling rotating MultiBody systems, mainly automotive powertrains. It is built on the VeSyMA library and is fully compatible with the Modelica Standard and VehicleInterfaces libraries.
The purpose of this library is to provide ready-to-use subsystems to build a vehicle and test bed experiments to simulate it as a whole or subsystem by subsystem. It thus makes vehicle testing intuitive, fast, efficient and does not require an extensive knowledge of Modelica or extensive user coding. This library is oriented towards testing of vehicles over straight-line manoeuvres (NEDC or other drive cycles, Tip-In, Tip-Out, and many other drivability manoeuvres).
Figure 1: Vehicle animation (click on the image for animation).
The driver model is external to the vehicle. It can be a closed or open loop model. The atmosphere model allows the ambient air temperature and pressure as well as the wind velocity and air humidity to be set. There are different road models: flat road, road with a variable gradient and circular road.
An overview of the library
Figure 2: Library structure
In PTDynamics there are models for engines, transmissions, drivelines, suspensions, mounts, drivers, clutches, differentials, gears, joints as well as vehicle models that have been built using these subsystems. Each one of these models is ready to be used which means it is parameterised and has a dedicated experiment to test it.
All these models are based on templates that can be extended if one wishes to create their own variant.
All models have a 3D animation that allows to observe the system behaviour.
Figure 3: Vehicle model with all the subsystems.
All the subsystems are replaceable to make it easy to switch to an alternative variant. The level of detail in each subsystem can be adapted depending on what the area of interest is. Indeed, adding things such as lash can unfortunately have a huge simulation time impact.
The subsystems in the vehicle are:
- Fuel tank: see VeSyMA library
- Accessories: see VeSyMA library
- Engine: a model for a petrol engine using MEP maps is available within PTDynamics
- Transmission: this is the core of the library. Several models for manual, automatic and Dual Clutch transmissions exist as well as individual clutches, torque converters and synchronisers. The gear set models go from a simple variator type to a detailed physical gear set with gear mesh and mesh loss models and force and torque reactions. The clutches available are based on coulomb friction models with a reliable handling of the stuck to sliding phase transition. Elastoplastic models of clutches are also available within the library. To model the torque converter, the user can choose from either a static or dynamic (includes the fluid momentum) characteristics model.
Figure 4: Transmission animation with the forces represented
- Lubrication circuit: see VeSyMA library
- Cooling system: see VeSyMA library
- Mounts: models for rigid or compliant mounts using springs and dampers
- Driveline: front, rear and four-wheel drive, rigid or compliant driveline models. The drive shafts are compliant and include backlash. Different types of joints are available (plunging, Hookes, constant velocity, etc.).
- Brakes: see VeSyMA library
- Front and rear suspensions: models for compliant suspensions, 1 or 2D for the rear one (fore-aft motion). The springs and dampers used to model the suspensions are replaceable and many variants exist.
- Tyres: They are based on the Pacejka tyre model. A simpler model exists for increased simulation performance.
- Subframes: see VeSyMA library.
- Engine and automatic transmission controllers
In addition, the driverEnvironment component receives the signals from the driver and transforms them into information usable by the different subsystems.
Most of the templates and base classes of these subsystems are in the VeSyMA library.
The measured signals and the ones used for actuator control are passed from one subsystem to another via the control busses (shown in yellow within Figure 1).
Feel free to contact firstname.lastname@example.org to get more information on the VeSyMA – Powertrain library.
Please get in touch if you have any questions or have got a topic in mind that you would like us to write about. You can submit your questions / topics via: Tech Blog Questions / Topic Suggestion.