Electric Drive Monitoring, Basic Function - GF08.00-P-1006A

Electric vehicles 

Overview 

This document contains information on:

• General 
• Function 
  • Function level 
  • Monitoring of the control unit functions (torque) 
  • Hardware-implemented monitoring function of the control units monitoring 
  • Interlock circuit 
  • Decentralized interlock 

General 

Monitoring in the powertrain control unit is divided into the following levels:

• function level (Level 1)
• First monitoring level (level 2, monitoring of the function level)
• Second monitoring level (level 3, hardware monitoring)

The battery management system control unit takes on the monitoring of the interlock circuit.

Function 

Function level 

All functions of the electric drive implemented in the powertrain control unit are contained in the monitoring on the function level.

Monitoring of the control unit functions (torque) The first monitoring level (level 2) contains the specified-actual comparison of the specified drive torque (calculated from the accelerator pedal position, recuperation level, and information of the ESP®) and actual drive torque.

In the powertrain control unit, level 2 checks whether the specified torque of the function level is located within the scope of the information presented by the accelerator pedal position, recuperation level and ESP®. If this is not the case, the specified torque of the function level is limited accordingly before it is requested by the power electronics control unit.

In level 2, in the power electronics control unit, the plausibility of the torque requested by the powertrain control unit is checked using the information of the ESP® and the torque is limited if necessary. Apart from that, the set actual drive torque of the electric machine is calculated. The power electronics control unit checks whether the plausibility value of the specified drive torque is always larger than the calculated actual drive torque.

In addition, the direction of the torque and compliance with a permanently set maximum torque are checked. In the event of deviations, the electric machine is passively switched by the power electronics control unit, i.e. it does not generate any torque.

In addition to the torque, further variables are monitored at level 2, e.g. the recuperation request, the drive range, or the park pawl.

Hardware-implemented monitoring function of the control units monitoring 

The second monitoring level (level 3) is based on hardware monitoring. For this purpose, level 3 carries out checks that ensure the correct version of the function software and level 2. In the event of an error, the electric machine is passively switched by the power electronics control unit.

Apart from that, a self-sufficient control monitor also exists, which checks the basic functions of the first monitoring level in the powertrain control unit.

Interlock circuit 

The interlock circuit provides protection against accidental touching of live parts of the 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. 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.

Furthermore, the high-voltage on-board electrical system in selector lever position "D" will also be 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 the 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. An evaluation in the high-voltage component thus detects the opening of a high-voltage connection and transmits an interlock message via the network for central evaluation in 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 will be switched off only once the selector lever position "N" or "P" is engaged for longer than 3s and the vehicle speed is <5km/h.

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

	Detailed information
	Detailed information on interlock circuit	Model 243	GF47.70-P-1100C
		Model 293	GF47.70-P-1100G
		Model 295, 296, 297	GF47.70-P-1100H