Assembly Definition

This section describes the MDL description of the powertrain in MotionView.

Entities

Engine and Clutch Body: This body represents the lumped mass and inertia of the engine and clutch. By default, the body has two attachment candidates with two tags – ‘b_engine’ and ‘b_clutch’.; You must ensure the mass and inertia of this body are correctly set up as per your model.
Note: The reaction torques that the Body produced as a result of the generated engine torque and clutch torque is currently not computed or applied in the model.
Engine Mounts: The powertrain model by default contains three engine mounts. These mounts are attached to the ‘Powertrain attach body’ which is an attachment body to which the powertrain is connected to (as described in the section below). The Engine and Clutch Body is connected to the attached body via bushings at each mounting positions.; You must provide the mount locations on the attachment body by specifying the coordinates of the mounts. The orientation of the bushings must be specified using the vectors corresponding to each mount.

Inputs and Attachment Tags

The CSE Powertrain model requires the following inputs for interface with the rest of the vehicle:


Input Attachments	Type	Description	Attachment Tag
Throttle Demand	Solver Variable	Continuous signal between 0 and 1 (scaled by throttle signal scaling factor) that represents the throttle demand by the driver of the vehicle.	sv_throttle_demand
Clutch Demand	Solver Variable	Continuous signal between 0 and 1 (scaled by clutch signal scaling factor) that represents the clutch demand by the driver of the vehicle. 0 represents a fully engaged clutch, 1 represents a fully disengaged clutch, intermediate values representative of the level of partial engagement.	sv_clutch_demand
Transmission Speed	Solver Variable	Continuous signal that is speed of the transmission [rad/sec] at the gear box side of the clutch.	sv_transmission_speed
Gear Demand	Solver Variable	A discreet integer signal that represents the gear the vehicle is currently running at.	sv_gear_demand
Powertrain Attach Body	Body	The body to which the powertrain needs to be attached.	b_pwr_attach

Outputs and Attachment Candidates

The output of the Control State Equation is in the form of a seven element Solver Array that is an attachment candidate with the tag ‘pwr_out’. The elements of the Solver Array are described below:


Element	Description	Units
1	Throttle Position	[0-1]
2	Engine Speed	[rad/sec]
3	Clutch Slip	[rad/sec]
4	Clutch Slip Velocity	[rad/sec2]
5	Engine Torque	[Model Units]
6	Clutch Torque	[Model Units]
7	Throttle Position At Static	[0-1]

Model Parameters

In order to model different sizes and types of engine and the clutch, the engine and clutch models are parameterized. The parameters are entered into the CSE using Solver Arrays. These parameters can be set using the Data Set present in the assembly.

The parameters are as follows:

Table 1. Clutch Parameters
Parameter	Description	Units
Clutch Capacity	The maximum torque the clutch can transmit when fully engaged.	[Nmm]
Clutch Stiffness	The stiffness of the clutch.	[Nmm/rad]
Clutch Damping	The damping of the clutch.	[Nmm/rad²]
Clutch Open	The value of the clutch signal above which the clutch is considered as fully disengaged. *	[No-Units]
Clutch Closed	The value of the clutch signal below which the clutch is considered as fully engaged.*	[No-Units]
Clutch Tau	Clutch time constant – the time constant for the clutch-slip decay when the clutch is open (for Anti-Windup).	[sec]
Clutch Scaling	[Optional] The value by which the Input Clutch signal is scaled with respect to the [0 to 1] scale (Default 1.0).	[No-Units]

* 0 <= Clutch Closed < Clutch Open <= Clutch Scaling

Table 2. Engine Parameters
Parameter	Description	Units
Engine Inertia	The combined effective inertia of the rotating parts inside the engine.	[kgmm²]
Rev Limit	The maximum engine speed that can be attained.	[rad/sec]
Engine Torque Map	The ID of the `reference_string` that holds the path of the Engine Torque Map.
Idle Speed	The engine speed of a free revving engine.	[rad/sec]
Stall Speed	[Optional] The engine speed at which the engine stalls (Default 0.0).	[rad/sec]
Throttle Scaling	[Optional] The value by which the Input Throttle signal is scaled with respect to the [0 to 1] scale (Default 100.0).	[No-Units]
Anti-Stall Flag	[Optional] If set to 1 the anti-stall throttle modulation kicks in at engine speed close to stall (Default switched off).
Rev-Limiter Flag	[Optional] If set to 1 the rev-limiter cuts throttle when the engine reaches rev limit (Default switched off).
Limit Engine Speed derivative	[Optional] If value > 0 then is saturated at the given value, if value < 0 then it is disabled (Default disabled).	[rad/sec²]