Hybrid system torque coordination, basic function

Overview

This document contains information on:

 General

 Function requirements

 Coordination of torque generation

General

The operation strategy in the powertrain control unit collects and prioritizes the torque requests and coordinates the torque generation, i.e. the portions to which the requested torque is generated by the combustion engine or by the electric machine. To do this, it monitors the state of the combustion engine and electric machine along with the charge level of the high-voltage battery and the status of the automatic transmission.

 The coordination of the torque requests is described in the torque coordination basic function document.

Function requirements

 Hybrid system operational

 Engine separator clutch closed

Coordination of torque generation

The operation strategy coordinates the torque generation based on the following parameters, among others:

 Status of power electronics

 Available torque from electrical machine

 Generative torque from electrical machine

 Motor-generated torque from electrical machine

 Engine speed of electric machine

 Status of electrical machine

 Tolerable discharge voltage/current, signal

 Tolerable charging voltage/current, signal

 Charging voltage/current, signal

 High-voltage battery voltage

 Temperature of high-voltage battery

 Selected transmission mode

 Engine clutch, status

Dynamic torque interventions in hybrid mode are implemented via the combination of the combustion engine and electric machine. Initially, the operation strategy implements torque interventions via the electric machine in the current drive torque. For this purpose, the powertrain control unit requests motor-generated torque from the power electronics control unit of the electric machine to increase the drive torque. Reducing torque interventions are realized through requests for a generated torque.

The power electronics control unit implements these requests and reports the generated torque back to the powertrain control unit.

If the torque interventions of the electric machine are not sufficient, the torque of the combustion engine is additionally reduced or raised.

Moreover, the operation strategy can also request a load point shifting of the combustion engine. The objective is to improve the current efficiency of the combustion engine. During this process, the operation strategy changes the division of the drive torque between the combustion engine and the electric machine. As a result, the combustion engine is relieved or loaded by the electric machine and brought into a more efficient efficiency range.