Method for controlling an electric drive of a vehicle

A method of controlling a drive of a rail vehicle of the type having wheels supported on rails and a car supported on the wheels, an electric drive motor powering the wheels, and wherein a setpoint output torque is prescribed by an operator of the rail vehicle for the electric drive motor, the method which comprises:

• reducing a setpoint torque prescribed for the electric drive motor of the rail vehicle to an input torque which allows an operation of the rail vehicle substantially at a maximum frictional engagement between the wheel and the underlying rail;
• wherein the step of reducing includes:
• a) continuously determining a curve representing a current frictional engagement between the vehicle wheel and the underlying rail;
• b) measuring a substitute variable having a defined physical relationship with a gradient of the curve, and determining the gradient of the curve from the substitute variable;
• c) forming a reduction factor from a difference between a current gradient of the curve and a predetermined set-point gradient;
• and
• d) forming the input torque by multiplying the setpoint torque with the reduction factor.