Hybrid System Monitoring, Basic Function - GF08.30-P-1014A

Hybrid vehicles 

Overview 

This document contains information on:

• General 
• Function 
  • Monitoring the control units functions 
  • Hardware monitoring of control unit functions 
  • Interlock circuit 
  • Decentralized interlock 

General 

Monitoring within the powertrain control unit and power electronics is divided into the following levels:

• function level (Level 1)
• first monitoring level (Level 2)
• second monitoring level (Level 3)

Depending on the model, interlock monitoring occurs using the interlock circuit via the battery management system control unit or is decentralized.

Function 

All functions of the hybrid system implemented in the powertrain control unit are contained in the monitoring on the function level. These are, for example, torque coordination, energy management, and sensor and actuator control.

Monitoring the control units functions 

The first monitoring level (level 2) contains the specified/actual comparison of the driver's requested torque (accelerator pedal position) and total drive torque (sum of the torques from the combustion engine and electric machine).

In the powertrain control unit, level 2 checks whether the total drive torque generated is greater than that requested by the driver via the accelerator pedal sensor. If this is the case, it is assumed that there is a fault in the powertrain control unit and the system changes to the limp-home function of the combustion engine (rpm limitation 1500 rpm).

In the power electronics control unit, an additional check is performed in level 2 to determine whether the drive torque requested by the powertrain control unit is consistently greater than the engine torque of the electric machine as calculated from the currents and position angle of the rotor. The electric machine is switched to passive by the power electronics control unit if this is the case.

Hardware monitoring of control unit functions 

The second monitoring level (level 3) is based on self-contained hardware monitoring. This hardware-implemented monitoring function involves a control monitor, which checks the basic functions of the first monitoring level in the powertrain control unit (checking the checker).

Interlock circuit 

The interlock provides protection against accidental touching of live parts of high-voltage components. An interlock voltage signal is looped through all high-voltage on-board electrical system component parts that can be removed or opened (interlock circuit). To do this there is a jumper in each removable high-voltage connection which interrupts the interlock circuit if the high-voltage connection is removed.

The interlock circuit is also led switched in a series over the 12 V control units plug connection of the high-voltage components. When detaching a control units plug connection the interlock circuit is interrupted via the contacts interlock input and output.

A discontinuity of the interlock circuit while driving does not lead to switching off of the high voltage on-board electrical system. The high-voltage on-board electrical system is not switched off until selector lever position "N" or "P" > 3 s is engaged and the vehicle speed is < 5 km/h. Furthermore, the high-voltage on-board electrical system in selector lever position "D" is also switched off when the hood is opened. If the ignition is switched off and interlock circuit has an open circuit, the vehicle can no longer be driven.

Decentralized interlock 

The interlock provides protection against accidental touching of live parts of high-voltage components. Each high-voltage component that has a removable high-voltage connection monitors this connection on its own (decentralized interlock). This occurs using an interlock voltage signal that is looped through all of its own high-voltage connections.

There is a jumper in these that interrupts the voltage signal if the high-voltage connection is removed. Evaluation in the high-voltage component thus detects the opening of a high-voltage connection and transmits an interlock message via the network to the powertrain control unit.

An interlock message does not cause the high-voltage on-board electrical system to be shut off when driving. The high-voltage on-board electrical system is not switched off until selector lever position "N" or "P">3s is engaged and the vehicle speed is<5km/h.

Furthermore, the high-voltage on-board electrical system in selector lever position "D" is also switched off when the hood is opened. If the ignition is switched off and there is an active interlock message, the vehicle cannot be driven.

In the pyrofuse, circuit 30t becomes circuit 30c. This is used by the battery management system control unit and the power electronics control unit as a signal line for recognizing a crash event and as a power supply for the contactor.

If the Supplemental Restraint System (SRS) control unit trips the fuse in the pyrofuse or the high-voltage disconnect device is opened, the signal line for circuit 30c is interrupted and the contactor in the high-voltage battery interrupts the connection between the high-voltage battery and high-voltage on-board electrical system.

	Additional basic functions
	Power electronics control unit, basic function		GF08.20-P-9891A
	Powertrain control unit, basic function		GF54.21-P-9894A
	Detailed information
	Detailed information on interlock circuit	Model 177, 247 with code ME08 (Hybrid drive 75-84 kW VARIANT (INCLUDING PLUGIN))	GF47.70-P-1100A
		Model 213 as of model year 2021 with code ME05 (hybrid drive 85 kW-94 kW - variant (including plug-in)) or with code ME08 (hybrid drive 75-84 KW-VARIANT (INCLUDING PLUG-IN))	GF47.70-P-1100B
		Model 206 with code ME10 (Hybrid vehicle (plug-in, PHEV)) Model 223 with engine 256 with code ME10 (Hybrid vehicle (plug-in, PHEV))	GF47.70-P-1100D
		Model 223, 232, 290 with engine 177 with code ME10 (Hybrid vehicle (plug-in, PHEV))	GF47.70-P-1100E
		Model 167 with code ME05 (Hybrid drive 85 kW-94 kW variant (incl. plug-in))	GF47.70-P-1100F