Method and arrangement for determining the internal resistance of a lambda probe and for the closed-loop heating control with the aid of the internal resistance

A computer-implemented method for controlling heating of a lambda probe equipped with heater control and having a temperature dependent actual internal resistance R.sub.S, said method including the steps of:

• (a) comparing the probe voltage U.sub.S to a predetermined threshold U.sub.min below which the actual internal resistance value can no longer be reliably determined and determining said actual internal resistance value when said probe voltage U.sub.S is higher than said threshold U.sub.min ;
• (b) forming a variable imaginary internal resistance value by incrementally increasing an initial internal resistance value in steps by a pregiven difference value .DELTA.R.sub.S while assuming that said initial resistance value matches said actual internal resistance value when said probe voltage U.sub.S falls below said threshold U.sub.min ;
• (c) obtaining a control deviation value .DELTA.R.sub.i by forming the difference of said variable imaginary internal resistance value and a predetermined desired internal resistance value corresponding to a desired probe temperature when said probe voltage U.sub.S is less than said threshold U.sub.min or by forming the difference of the determined actual internal resistance value and said predetermined desired internal resistance value when said probe voltage U.sub.S is higher than said threshold U.sub.min ;
• (d) forming an actuating variable from control deviation value .DELTA.R.sub.i for said heater control;
• and,
• (e) applying said actuating variable to the probe to control the heating.