vertical axis the bottom of fig2 contains the antilock braking system abs anti slip regulation system asr and motor speed regulator system msr these systems receive the parameters concerning the behavior of the vehicle and of the wheels rotation speed and provide appropriate controls to the vehicle engine management system and to the hydraulic system management system the middle part of the figure contains the electronic stability program esp this esp system comprises a comparator that receives the various quantities recorded by the vehicle sensors and that calculates at each moment the various forces exerted on the vehicle a circuit for calculating the setpoint yaw speed yaw value and the drift angle value according to the instructions supplied by the driver acceleration steering wheel lock angle etc a regulator circuit that calculates the acceptable yaw moment based on the quantities supplied by the comparator and the calculated setpoint values finally a circuit that calculates the brake locking torque and tire skid setpoint values and that supplies appropriate instructions to the antilock braking system the anti slip regulation system and the motor speed regulator system in observing the behavior of the vehicle one key element is the quantity supplied at each moment by the yaw sensor when the yaw sensor supplies a yaw speed greater than a predetermined value esp threshold the electronic stability program must intervene to rectify the path of the vehicle one of the means available to the esp is to brake one or more wheels of the vehicle as is known in the art however the problem is how to give the system an operating threshold that does not.