Tab%209%20DSC%20Dynamic%20Stability%20Control, BMW educational info, Dokumentacja
[ Pobierz całość w formacie PDF ]//-->DYNAMIC STABILITY CONTROL SYSTEMSINTRODUCTIONDynamic Stability Control (DSC III version 5.3) was introduced on the 1998 Model Year E38and E39 - 540 vehicles. For Model Year 1999, the system is enhanced with additional con-trol functions and a new combined rotational rate/lateral acceleration sensor as version 5.7.It continues to be offered as standard equipment in the E38 and E39 - 540 models. Thenew functions are titled as the Dynamic Braking System and include the:• Dynamic Brake Control (DBC)• Maximum Brake Control (MBC)The DSC III 5.3 system for the E38 and E39 is supplied by Bosch and the complete sys-tem operation is covered in the 1997 Model year Update - Part Two training manual. Thenew functions of operation of the DSC III 5.7 system will be covered in this training manu-al.Dynamic Stability Control (DSC III) is also being introduced for the E46 vehicles as option-al equipment. This system is supplied by ITT Teves, however many of the system compo-nents and features are similar to the Bosch system. The full function description and oper-ation of the Teves system will be covered in this training manual.106DYNAMIC BRAKING SYSTEMThe dynamic braking system is designed to enhance the braking control of the DSC for thedriver of the vehicle. The dynamic braking control and maximum braking control are func-tions that are programmed into the control electronics of the DSC with no additional hard-ware changes.DYNAMIC BRAKING CONTROL (DBC)The DBC function is designed to provide the maximum braking force available during rapid(panic) braking situations. The DSC control module looks at the inputs from the brake pedalswitch and the signal from the brake pressure sensor on the master cylinder. The criteriafor activation of DBC is how rapidly is the brake pressure built up with the brake pedaldepressed. The total criteria required for DBC activation includes:•••••Brake switch ONBrake pressure build up > threshold valueVehicle road speed > 5MPHVehicle not in reverseNot all wheels in ABS regulationIf the threshold for DBC activation is achieved, the DSC control module will activate a pres-sure build up regulation phase through the hydraulic unit. The pressure at all wheels isincreased up to the ABS regulation point. This occurs even if the driver does not achievethe ABS regulation point with the pedal.The rear axle brakes are controlled with select-low regulation and the front axle brakes arecontrolled individually. ABS regulation will continue until the driver releases the pedal andthe pressure in the master cylinder drops below the threshold value stored in the DSC con-trol module.MAXIMUM BRAKE CONTROLThe MBC function is also designed to enhance a driver initiated braking procedure. TheMBC will build up the pressure in the rear brake circuit when the front brakes are already inan ABS regulation cycle. The additional braking pressure at the rear wheels will shorten thestopping distance. The following criteria must be met before the DSC control module willactivate MBC:•••••Both front wheel brakes in ABS regulationVehicle speed > 5 MPHVehicle not in reverseDBC and pressure sensor initialization test OKRear wheels not in ABS regulation107BOSCH DSC III - 5.7 COMPONENTSWith the exception of the following, all components of the DSC - 5.3 are carried over andtheir functional operation remains the same.• Control Module/Hydraulic Unit• Rotational Rate/Lateral Acceleration Sensor• Master Cylinder Pressure SensorCONTROL MODULE HYDRAULIC UNITThe control module is now integrated into the hydraulic unit as one compact unit. Thisreduces the size and wiring required for DSC operation. Additionally the motor relay andvalve relay have been replaced by solid state final stages in the control module. Thehydraulic unit continues to use:•••••Two pre-charge solenoid valvesTwo changeover solenoid valvesFour intake solenoid valvesFour outlet solenoid valvesOne return pump108ROTATION RATE/TRANSVERSE ACCELERATION SENSORLocated under the driver’s seat, the rotation rate and transverse acceleration sensor havebeen combined into one unit. The new sensor is smaller in size and weight and is isolatedfrom chassis vibrations through its rubber mounting.The sensor provides the same information as the two separate sensors used on the DSC5.3 version. It receives power and ground from the DSC control module.For rotational speed, the sensor produces a reference signal of 2.5 volts and a linear volt-age signal from 0.7 to 4.3 volts. This linear voltage input signal is used by the DSC controlmodule as the degree of rotational rate (yaw).The sensor also produces a linear voltage signal for the lateral acceleration (G-force) thatranges from 0.5 to 4.5 volts. The DCS control module uses this input to determine the sideforces acting on the vehicle for DSC regulation.109BRAKE PRESSURE SENSORA brake pressure sensor is installed in the master cylinder to determine the degree of pres-sure build-up for Dynamic Brake Control. It is installed in the front axle brake circuit.The sensor receives its power supply from the DSC control module and produces a linearvoltage input signal ranging from 0.5 to 4.5 volts depending on how hard the brakes areapplied.110 [ Pobierz całość w formacie PDF ]