Driving Mode, Basic Function - GF08.00-P-1003A
Electric vehicles
Overview
This document contains information on:
- General
- Function requirements
- Function
- Transmission modes
- Range maximization
- Controlling the drive torque of the electric machine
- Distributing the total drive torque to the front and rear axle
- Activating the sound generator
General
In the drive mode the electrical power from the high-voltage battery system is converted to mechanical drive energy. The electric machine works in engine mode.
Function requirements
- Circuit 15 ON
- Drive train operational
Function
Transmission modes
The user can switch between the drive programs using the DYNAMIC SELECT switch. The powertrain control unit implements the selected drive program.
The letter of the selected drive program is displayed in the multimedia display. After the ignition is switched on, drive program C (Comfort) is active.
Depending on the model and equipment, different drive programs are available. Depending on the selected drive program, the following vehicle characteristics - among others - are changed:
- Drive
- Chassis
- Steering
- ESP®
- Sound of drive system in vehicle interior
- Pressure point in haptic accelerator pedal
| Transmission mode | Driving style | Properties |
|---|---|---|
| MR (Max Range) | Sparing | Maximum range and consumption optimization: Pressure point in the haptic accelerator pedal limits the speed in order to increase the range, and signals, in conjunction with the Range Assistant, a changed speed to suit the situation in order to reach the destination. |
| E (Eco) | defensive | Efficient and consumption-optimized driving characteristics: Pressure point in the haptic accelerator pedal signals an efficient, consumption-optimized driving style. |
| C (Comfort) | comfortable | Comfort program for a compromise between range and operating energy input: if necessary (e. g. when overtaking) automatically higher operating energy input. |
| Sport (S) | sporty | Maximum operating energy input always available. |
| I (Individual) | Individually | Drive program that can be set by driver. |
Range maximization
The range maximization function (model- and equipment-dependent) allows a maximum increase in range. To do this, the function partially or completely switches off comfort systems that are not relevant for driving and activates driving functions that increase efficiency. The range maximization is activated not with the DYNAMIC SELECT switch, but via the multimedia system. When range maximization is switched on, drive program E (Eco) and recuperation level D are also automatically AUTO activated.
If the user then switches to a different drive program or recuperation level, the maximum increase in range is reduced. The range is also reduced if the user switches comfort functions back on despite range maximization being active.
Controlling the drive torque of the electric machine
In the case of vehicles with two electric machines, the following explanations apply for each machine.
The power electronics control unit constantly reads in the engine speed of the electric machine via the rpm sensors. Furthermore the power electronics control unit monitors the status of the integral power inverter in the power electronics control unit. It evaluates the performance of the electric drive system and transmits the currently available torque to the powertrain control unit.
The powertrain control unit reads in the accelerator pedal's position. On the basis of the accelerator pedal position and the operating state of the electric drive system, the powertrain control unit calculates a torque value.
After taking different power output limitation criteria into consideration, the powertrain control unit requests a suitable torque from the power electronics control unit.
The power inverter integrated in the power electronics control unit converts the high voltage direct voltage into a 3-phase alternating voltage and supplies this to the electric machine. The power electronics control unit regulates the frequency and amplitude of the alternating stress and therefore directly the generated drive torque dependent on the performance specifications.
Distributing the total drive torque to the front and rear axle
Vehicles with all-wheel drive
The powertrain control unit reads in the accelerator pedal's position.
The accelerator pedal position corresponds to an entire specified torque. In the case of vehicles with two electric machines, the drive control distributes this to a specified torque for the front axle and a specified torque for the rear axle. The distribution of the entire specified torque takes place among other things in accordance with the criteria of axle load distribution and acceleration skid control.
Depending on the situation, only the front or only the rear axle can be activated or the drive is distributed steplessly among both axles. In the case of low torque requests, the machine that is not required is switched off completely in order to reduce the base load.
The powertrain control unit requests the partial torques from the respective power electronics control unit.
Activating the sound generator
Vehicles with acoustic presence indicator
The electric drive system is very quiet at low speed. Since pedestrians and bike riders are used to the noise of conventional drives, they can easily not hear electrically driven vehicles. To reduce the risks associated with this, the sound generator generate an artificial warning noise.
Depending on the accelerator pedal position, speed-dependent noise is emitted via the sound generator and rear sound generator at speeds of between 0 and 30 km/h. At speeds greater than 30 km/h, the sound generators are deactivated because the rolling and wind noise are loud enough.
| Function schematics | |||
| Function schematic for driving mode | Model 293 | PE08.00-P-2501-97A | |
| Model 243 | PE08.00-P-2501-97D | ||
| Model 295, 296, 297 | PE08.00-P-2501-97F | ||
| Additional basic functions | |||
| Electric drive sound generator, basic function | GF08.20-P-9890A | ||
| Power electronics control unit, basic function | GF08.20-P-9891A | ||
| Electric drive powertrain control unit, basic function | GF08.20-P-9892A | ||
| Electric machine, basic function | GF08.10-P-2000A | ||
| Accelerator pedal sensor, basic function | GF30.20-P-2000A |