Table of Contents Dynamic Stability Control 8+ Subject Page Introduction .3 Successor of DSC8.3 System Overview .4 System Components.6 Bosch DSC8+Module .6 Sensor System.7 DSC Sensor.7 Yaw Rate .7 Acceleration/Gradient .7 Wheel Speed Sensors .8 Functions.9 Operating Modes.9 Dry Braking .10 Brake Standby .11 Soft Stop.12 Fading Compensation .13 Start Assistant .14 Electric Steering Column Lock (ELV) .15 Service Information.16 Initial Print Date: 09/05 Revision Date: Dynamic Stability Control 8+(DSC8+) Model: E60, E61, E63, E64 Production: from 9/2005 ■biictihis After completion of this module you will be able to: • Understand the improvements made to the DSC8+system 2 Dynamic Stability Control 8 + Introduction Successorof DSC8 The Bosch traction control and stability system DSC8+will be phased-in on the E6x model series as from 09/2005. E6x all-wheel drive model series are equipped with DXC8+. The main differences between the DSC8 and the DSC8+are in the software of the DSC control unit and the further-optimized components within the DSC module. Further comfort and safety functions have been achieved with the introduction of the DSC8 + Overview of expanded functions: • Dry Braking • Brake Standby • Automatic Soft-Stop Function • Fading Assistance • Start Assistant Forthe first time, activation of the fading-brake support function is indicated by a yellow indicator in the instrument cluster. 3 Dynamic Stability Control 8 + fc ■ System Overview Index Explanation 1 DSC8+ Control M odule 2 DSC SensorCluster(3.22 or3.8) 3 Steering Column Switch Cluster 4 Wheel Speed Sensors 5 DTC Button 4 Dynamic Stability Control 8 + DSC8+Hydraulic System Circuit Diagram Index Explanation Index Explanation 1 Tandem Brake M aster Cylinder 10 Wheel Brake, front left 2 Pressure Sensor 11 Wheel Brake, front right 3 Changeover Valves 12 Wheel Brake, rear right 4 High Pressure Shift Valve 13 Wheel Brake, rear left 5 Return Pump 14 Outlet Valve, rear right 6 Inlet Valve, front right 15 Outlet Valve, rear left 7 Inlet Valve, front left 16 Inlet Valve, rear right 8 Outlet Valve, front right 17 Inlet Valve, rear left 9 Outlet Valve, front left 5 Dynamic Stability Control 8 + System Components Bosch DSC8+Module The DSC8+module essentially consists of two components: • Add-on control unit • Valve block with integrated pressure sensor. On exceeding a speed of approximately 4 mph (6 km/h), an electronic self-test is started, involving brief activation of the pump motor and all solenoid valves. If the brake is operated at a driving speed of 4 mph (6 km/h) the self-test will be per¬ formed at approximately 9 mph (15 km/h). The check of the wheel speed signals is already started at approximately 1.5 mph (2.75 km/h). The analog-controlled valves provide even more exact control particularly in the low pressure range. Advantages: • Reduced control noise • Improved control quality and control convenience • Improved brake intervention through active/dynamic cruise control AC C/DC C. 6 Dynamic Stability Control 8 + Sensor System DSC Sensor The DSC sensor MM 3.8 registers following parameters: • lxTransverse acceleration • lx Yaw rate • lx Longitudinal acceleration (uphill gradient, downhill incline) The DSC sensor MM 3.22 is used on vehicles with active steering. This sensor redundantly measures the most important variables for the active steering. • 2xTransverse acceleration • 2xYaw rate • lx Longitudinal acceleration (uphill gradient, downhill incline) Initially, the plausibility of each measured value is checked in the sensor before this value is sent on the CAN. Yaw Rate The sensor element forthe yaw rate consists of a surface mounted micro-mechanical measuring element and a digital sensor evaluation circuit. The sensor is based on the CVG principle (Coriolis Vibratory Gyroscope). An electrostatic diaphragm drive generates the opposite phase oscillation of the seismic masses. One rotation about the x-axis of the vehicle, i.e. one rotation rate, generates a Coriolis force on the acceleration sensors that is measured capacitively. Synchronous demodulation of the Coriolis acceleration, utilizing the velocity of the seismic masses, generates a signal that is proportional to the rotation rate. Acceleration/Gradient The sensor element for acceleration also consists of a surface-mounted micromechanical element and a digital sensor evaluation circuit and is used for measuring the transverse and longitudinal acceleration of the vehicle. Likewise, its operating principle is based on capacitive measurement. 7 Dynamic Stability Control 8 + Wheel Speed Sensors Active wheel speed sensors with an integrated evaluator circuit are used in connection with the DSC8+. The active wheel speed sensors require a supply voltage for their operation and output a square-wave signal that is dependent on the wheel speed. The output signal is transmitted as a data protocol using the pulse width modulation method (PWM). The PWM signal is used to determine the speed while the pulse width contains additional information on the direction of rotation, standstill detection, location detection and air gap (clearance) reserve to sensor ring. Detection of the direction of rotation is made possible by the internal signal offset of 3 correspondingly arranged Hall elements in the sensor 1C. When the wheel is stationary, the wheel speed sensor outputs a pulse every 0.75 sec¬ onds. It is therefore possible to check the operational readiness of the sensor even when the vehicle is stationary. Detection of the installation location indicates whether the change in the magnetic field strength is sufficient to ensure reliable operation. 1 j 2 , 3 / Index Explanation 1 Sensor Ring 2 Sensor 1C with Hall Sensors 3 Sensor Housing 8 Dynamic Stability Control 8 + Functions Operating Modes The DSC 8 +offers the customer3 different operating modes: • DSC ON • DSC OFF • DTC The various functions in the individual operating modes are illustrated in the following: Function DSC ON DTC DSC OFF DTC <£) ABS X X X ASC Engine intervention X X 1 ASC Brake intervention X X X MSR X EBV X X X DBC X X X CBC X X X Dry braking X X X Start assistant X X X Brake standby X X X Soft-stop X X X Fading assistance X X X Trailer stabilization logic X X Yaw moment control X X 2 X 3 1 = Thresholds increased 2 = Control thresholds increased 3 = Only active when brake light switch closed 9 Dynamic Stability Control 8 + Dry Braking In wet conditions, a film of water is formed on the brake discs, resulting in delayed response of the brakes. In connection with previous systems it was therefore recommended to operate the brake from time to time in wet conditions to wipe off the waterfilm. This dry braking function is dependent on the activity of the windscreen wiper. When the windscreen wiper is operating in continuous wipe mode, the wheel brakes are lightly applied againstthe brake disc cyclically every 90 seconds in orderto wipe off the waterfilm. Dry braking takes place underfollowing conditions: • Speed >70 km/h • In continuous wipe mode This applies only if the driver does not apply the brake himself during this period of time. A delay of operating noises are not perceivable forthe driver. Left Brake Disc with Water Film before Dry Braking Right Brake Disc After Dry Braking 10 Dynamic Stability Control 8 + Brake Standby The brake pads are applied againstthe brake disc when the accelerator pedal is released quickly thus reducing the emergency braking stopping distance (by approx. 30 cm/100 km/h).The DSC module builds up a low braking pressure (approx. 2.5 bar) within a short space of time (approx. 0.5 s) in orderto eliminate the clearance between the brake pad and brake disc by applying the brake pads. The brake standby function is activated under following conditions: • Speed >70 km/h • M inimum time between brake application 8 s • The brake standby function is not activated in response to performance-oriented driving. The signal indicating quick release of the accelerator pedal is made available by the DM E/DDE control unit via the PT-CAN. The sensitive driver may perceive a slightly harder brake pedal. A delay of operating nois¬ es are not perceivable for the driver. Index Explanation P Brake Pressure in bar t Time in milliseconds 1 Brake Pressure atTandem MasterBrake Cylinder 2 Brake Pressure Curve with Brake Standby at Wheel 3 Brake Pressure Curve without Brake Standby at Wheel 11 Dynamic Stability Control 8 + Soft Stop When braking to a standstill, a so-called stopping jerks occurs where the occupants per¬ ceive increased deceleration as a result of the transition from sliding friction to adhesion friction on the brake disc. When braking lightly (< 25 bar) at constant pressure to standstill, the soft-stop function automatically reduces the braking pressure on the rear axle just before reaching standstill. Consequently, the deceleration peak perceived by the occupants is reduced by approx. 50% and extended overtime. The function is inactive at medium to high deceleration or during ABS control in order not to extend the braking distance. The speed and standstill status are detected via the wheel speed sensors. Deceleration with and without Soft Stop Index Explanation m/s 2 Deceleration s Time in seconds Red Deceleration without soft stop Blue Deceleration with soft stop -50% Reduction of occupant deceleration 12 Dynamic Stability Control 8 + Fading Compensation High temperatures (>550 °C) can occuratthe brake discs when driving downhill for longer periods of time or as the result of multiple braking operations (>80 bar). These high temperatures result in a change in the coefficient of friction of the brake pads, caus¬ ing the braking effect to diminish (fading). The brake disc temperature is calculated based on a temperature model contained in the DSC8+software. The braking pressure applied bythe driver is measured bythe pressure sensor and compared with the current vehicle deceleration (setpoint/target value). If the braking effect diminishes, the driver is assisted by the fading compensation with additional pressure build-up ofthe DSC module. A warning lamp in the instrument cluster informs the driver of the overheated brake. The DSC control unit enters information in the fault code memory in response to activa¬ tion ofthe facing compensation function. Function triggered at temperatures above 500 °C • HFC (Hydraulic Fading Control) is active for longerthan 500 ms and the brake disc temperature is above 500 °C. Function triggered at temperatures above 700 °C (multiple braking) • HFC is active and the brake disc temperature is above 700 °C.The warning light in the instrument cluster is activated if the fading compensation function is triggered at brake disc temperatures above 700 °C. A check control message is additionally out¬ put on vehicles equipped with a display. 13 Dynamic Stability Control 8 + Start Assistant This function provides assistance when driving off on uphill gradients by temporarily maintaining brake pressure in the wheel brakes. Based on the gradient, the DSC calculates the holding pressure required in the wheel brakes in orderto hold the vehicle. When the brake pedal is released, the pressure at the wheel brakes is immediately reduced to the holding pressure calculated by the DSC. After a further 0.7 seconds, the DSC reduces the pressure in the wheel brakes in stages to 0 bar and the vehicle starts off slowly providing the accelerator pedal is not pressed. Reducing the pressure at the wheel brakes decreases the breakaway noise of the brakes. This function is not active when the parking brake is applied. The angle of inclination is measured by the longitudinal acceleration sensor in the DSC sensor and made available in the form of a telegram on the CAN. This function is also effective on a downhill incline with reverse gear engaged. Brake Pressure at the Wheels 14 Dynamic Stability Control 8 + Electric Steering Column Lock (ELV) The ELV safety concept includes the monitoring of the vehicle status. The CAS will not permit the steering column to be locked if the speed signal from the DSC is not plausible orthere is no signal. The CAS deactivates terminal 15 when none of the wheel speed sensors send a valid signal while the vehicle is stationary. The DSC8+ informs the CAS of the vehicle status with regard to: • Standstill • Vehicle moving • Validity of speed signal The information is transmitted redundantly via the CAN and hard wiring between the control units. As from terminal position "R", the CAS supplies system voltage on the DFA CAS line to the DSC. When the DSC is operational, the voltage applied by the CAS is connected to ground in various frequencies. • 10 Hz vehicle stationary < 5 km/h • 50 Hz driving speed >5 km/h This function is a part of the safety concept of the electric steering column lock. The CAS does not permit locking of the ELV if it does not receive a valid speed signal. The DSC must detect at least 3 wheel speed sensors as valid forthe control unit to apply a frequency on the DFA CAS line. System Schematic ELV Index Explanation Index Explanation 1 DSC8+Dynamic stability control 3 ELV Electric steering lock 2 CAS2 Comfort access system 4 Wheel speed sensors 15 Dynamic Stability Control 8 + Service Information Some jobs on the DSC sensor system require adjustments in the DSC module as well as the LWS and DSC sensors to ensure correct operation. IMPORTANT!!! All DSC systems withouta pre-charge pump require the low-viscosity DOT4 brake fluid. Observe regula¬ tions governing fluids and lubricants. 16 Dynamic Stability Control 8 +