Table of Contents Subject Page Driving Dynamics Systems Objectives of the M odule .2 Purpose of the Systems.3 Dynamic Stability Control (DSC) History.6 Principle of Operation.7 System Components.10 Sensors.12 Electronic Damper Control - Continuous (EDC-K) History.13 System Components.14 Damper Valve Details.15 Principle of Operation.17 System Faults and Reactions.21 Workshop Hints.23 Dynamic Drive - Active Roll Stabilizer Bar (ARS) Stabilizer Bars.24 Purpose of the System.25 System Components.28 Sensor System.31 Actuator System.32 Valve Block.33 Active Stabilizer Bars.34 Hydraulic Components .36 Principle of Operation.38 Workshop Hints.41 Review Questions 46 DRIVING DYNAMICS SYSTEMS Model: E65 - 7451 Production Date: 11/2001 Objectives of The Module After Completing this module, you will be able to: List the Driving Dynamics Systems. Demonstrate how to deactivate Dynamic Traction Control. Explain how EDC-K influences hydraulic damper operation. Identify the correct EDC-K solenoid valve resistance value. Describe the Dynamic Drive influence on the stabilizer bars. Name the Dynamic Drive components and locations. Understand the Valve Block sub-components and functions. Explain the Oscillating Motors hydraulic/mechanical operation. Describe "Failsafe" hydraulic flow. Demonstrate Dynamic Drive Commissioning. 2 E65 Driving Dynamics Systems Driving Dynamics Systems Purpose of The Systems The E65 chassis offers the driver optimum ride comfort, driving safety, good agility and excellent handling. The chassis also adapts to changes in road conditions: traffic, ice, snow etc. Vehicle speed and changes in the direction of travel generate forces that have an effect on the chassis which requires the driver to react correctly to maintain safe driving. The following forces occur while driving: Vertical forces - uneven road surfaces, bumps and potholes Lateral forces centrifugal forces during cornering and crosswinds Longitudinal forces - acceleration, deceleration and braking The following vehicle structure movements occur as a result of these forces: Around the transverse axis: pitch Around the longitudinal axis: roll Around the vertical axis: yaw Yaw, Vertical axis 42 - 06-28 3 E65 Driving Dynamics Systems Active Driving Dynamics Systems are integrated in the E65 chassis which support the dri¬ ver both actively and passively by suppressing the effects of these forces as much as pos¬ sible. The Driving Dynamics Systems include: Dynamic Stability Control (DSC) with subsystems Electronic Damping Control (EDC-K) continually adjustable system Dynamic Drive active roll stabilizer bar (ARS) The Driving Dynamics Systems monitor the driving conditions using sensors. The sensor signals are transmitted to the control modules that interpret and evaluate the driving con¬ ditions. The control modules send output signals to actuators that will counter these forces providing adaptation for the road and driving situations. Systems Indications The indicator/warning lamps, Check Control, On-board Computer messages and Control Displays as well as the respective activation are described in the Drive display and controls. Dynamic Stability Control (DSC) The DSC controls the vehicle stability in all driving conditions, counteracting the driving dynamics forces by using brake intervention or engine load control depending on the situ¬ ation. DSC consists of the following subsystems: ABS Anti-Lock Braking System ASC Automatic Stability Control MSR Engine Drag Torque Reduction DBC Dynamic Brake Control CBC Cornering Brake Control The following are new in the E65: FBS Fading Brake Support FLR Driving Performance Control DTC Dynamic Traction Control Parking Brake (hydraulic service brakes) 4 E65 Driving Dynamics Systems Electronic Damping Control (EDC-K) The continuous Electronic Damping Control (EDC-K) absorbs vertical forces while driving and dampens these forces to the chassis. The forces are measured by two vertical accel¬ eration sensors on the front axle (left and right) and one at the rear axle (right). The front sensors are located in the wheel housings and the rear on the trunk tray underneath the trunk ventilation ports. The dampening characteristics are mapped in the control module to continuously regulate the EDC-K providing maximum comfort. The EDC-K works with infinitely variable valves in the dampers to regulate the hydraulic fluid flow using electromagnetic control valves. EDC- K provides the actual damping force required at any time. The steering angle sensor is used along with the front wheel speed sensors to determine the lat¬ eral acceleration. The controller provides the opportunity to select from two basic settings: Comfort or Sports. 42 - 06-09 Dynamic Drive Dynamic Drive controls two active stabilizer bars based on the lateral acceleration. The active stabilizers are split with a hydraulic actuator in between them so that the left and right sides can be turned in opposing directions. These active stabilizers set the stabilizing torque using hydraulic actuators so that: The rolling motion of the body is minimized or eliminated while cornering. The extent to which the body rolls on straight, uneven road surfaces is reduced. A high degree of agility and precision adjust¬ ment is achieved using the full speed range. An optimum self steering characteristic is produced. 42 - 06-03 5 E65 Driving Dynamics Systems Dynamic Stability Control (DSC) History The history of wheel slip control systems used in B M Ws is covered in the Chassis Dynamics course (ST056). DSC III was technically modified (deletion of the pre-charging unit), the functions were extended and renamed DSC 5.3. The DSC 5.3 was further developed into DSC 5.7 by adding these functions: Dynamic Brake Control (DBC) Maximum Brake Support (MBS) Dynamic Brake Support (DBS) These functions have been used in Bosch systems since 1999. For the E65, DSC 5.7 is further developed and expanded to include the software functions to achieve improved sys¬ tem operation: FBS Fading Brake Support Parking Brake (hydraulic service brakes) FLR Driving Performance Control DTC Dynamic Traction Control In addition, the evaluation of the 2-stage brake lining wear sensors is integrated in the DSC control module. The DSC system is connected to the PT-CAN Bus. aj-tJ cm 1 vu 1 31 5kuF RLE TrfAT 1__J H TuflFT i^B ■c™ -y 3-D FATH r-H TJJ- H=m LM 3H 1 5WQIH DM RTj^F | HK1 |J rntu V—-I WM D-iUS EEL AftS > 4 Ei»* ytUL Sim stvk * I SEW EC-5 G"E ESEl EBEK EDCH S8H K-CAN P MOST P7-GA.N 42 - 06-04 6 E65 Driving Dynamics Systems Principle of Operation DSC DSC calculates the current driving conditions and cor¬ rects detected driving instability through active brake interventions. Forexample, in the event of vehicle over¬ steer, DSC initiates brake intervention at the front wheel furthest from the curve to create a stabilizing, opposing torgue. In the event of vehicle understeer, active interventions at the wheels nearest to the curve provide a stabilizing counter torgue. DSC stabilization is performed in all driving situations: normal running, acceleration and braking. The DSC control module is combined with the hydraulic unit and is located on the right front strut tower in the engine compartment. The DSC function can be deactivated by the Controller in the Control Display menu and the DSC light in the instrument cluster will illuminate to alert the driver. DSC can be reactivated by the Controller or automatically when the ignition is cycled. Bi cck AUtri P — "zn u .pin Cmnfnrt EDC fti' 10 Q Fixed current, fault in memory, gong at end of trip Acceleration sensors (front, left, right, rear) Fixed current output for front axle, rear axle Fault in memory, gong at end of trip Wheel speed front left/right 1) Control operation with replacement sensor 2) Fixed current output for front and rear axles External voltage supply fault fluctuation (nominal should be 5 V +/- 10%) Fixed current output for front axle, rear axle Fault in memory, gong at end of trip Voltage supply to EDC control module between 2 V and 8 V Valves de-energized, fault in memory, gong During trip Valve failure Valves de-energized, fault in memory, gong during trip Voltage wake up, <2V standing & wake up>7V Valves de-energized, fault in memory, gong during trip No vehicle speed via CAN Bus Fixed current, fault in memory, gong at end of trip Control module EEPROM faulty Fixed current, fault in memory Control module - no alive message from EDC-K Valves de-energized, fault in memory, gong during trip CAN Interface The steering angle value is prepared and is transmitted by the 5ZL overthe CAN Bus. Both of the front wheel speed signals (including the direct DSC wheel speed signal), the vehicle speed reference value and the mileage reading are provided by the DSC control module overthe CAN Bus to the EDC-K control module. Power Supply Low current supply to the damper valves results in hard damping and a high current results in soft damping. The EDC-K control module determines the setpoints and outputs pulse- width modulated (PWM) signals to the damper valves to regulate the current flow. Current flow limitation is ensured by an overcurrent detection and deactivation. All of the analog inputs are protected by diodes against positive and negative overvoltage. The following analog signals are processed by the EDC-K control module: Vehicle supply voltage EDC-K switched output voltage Damper valve voltage and current 21 E65 Driving Dynamics Systems Valve Activation/Output Stage Circuit The solenoid valves have low resistance, approximately 2.2 ohms per valve at room tem¬ perature because high current is needed at a low voltage. The current is set in the 0 to 2 Amps range depending on the desired damping force. The setpoint value will not exceed 2 Amps to avoid valve damage. The solenoid valves are connected in series for each axle and are supplied with a ground (PWM for continuous adjustment) from the EDC-K control module. Rear Axle EDC-K Valves Series Connection uC = M icrocontroller (EDC-K control module) PWM = Pulse width modulation (output signal) DVHR = Right rear damper valve DVHL = Left rear damper valve Controller and Control Display Operation 42-06-18 Sports program: The driver can activate/deacti¬ vate the sports program by the Controller in the Control Display menu. A firmer damping is set when the EDC-K request is set to "SPORT". EDC-K always reverts back to the comfort program each time the engine is restarted. 42-06-02 Notes: 22 E65 Driving Dynamics Systems Workshop Hints Diagnosis System monitoring and plausibility: For safety reasons, faults with one damper valve will result in deactivation of all damper valves. Fault detection takes place on each axle. To pin¬ point which valve is faulty, use the DISplus to measure the resistance of the individual valves (per axle). The resistance of a good valve is 2.2 ohms ±10% at room temperature (20 2 C). Acceleration sensors: The EDC-K control module does not distinguish individual malfunc¬ tions between the sensors. The power supply to the three sensors is connected in parallel in the control module (without isolation). A short circuit in the supply voltage to one of the sensors will also affect the supply to the other sensors. A maximum of seven different faults can be stored for the acceleration sensors. The cod¬ ing data will indicate the functions of the control module (vehicle and country specific). Notes on Service When the steering angle sensor is removed, the steering wheel must be manually posi¬ tioned to the straight ahead position and this position re-initialized in the SZL. The steering wheel straight ahead position is permanently monitored while driving. EDC-K diagnosis detects electronic damper faults on the complete axle only. Mechanical testing of individual dampers can be carried out in the dampertest. Mechanical wearcaus- es the dampers to weaken over the service life, therefore a running time memory adapts the damper curves towards a harder setting (over time). Faulty dampers must be replaced together (in pairs) on a single axle. After a replacement, the running time memory for the front or rear axle must be reset with the DISplus. A 10 Pin Adapter Cable is available to adapt the M FK cables to the EDC-K control module when using the DISplus (Test Plan). Special Tool #90 88 6 372 050 42-06-20 23 E65 Driving Dynamics Systems Dynamic Drive - Active Roll Stabilizer Bar (ARS) Stabilizer Bars on the Front and Rear Axles Body roll is built up over the vehicle's longitudinal axis as a result of the centrifugal force at the center of gravity. This force causes the vehicle body to lean towards the outside wheels while cornering and quickly draws the vehicle closer to the limits of driving dynamics. The tilt angle of the body and the increased wheel load is counteracted by the use of stabilizer bars. Yaw, I tolling Longitudinal axis Transverse axis —■ Vertical axis 42-06-08 When cornering, the wheel on the outside of the corner compresses the spring, and the inner wheel extends the spring which causes the the stabilizer bar to turn (twist). The forces on the mounting points of the stabi¬ lizer bar generate a torque that counteracts the body angle providing better load distribution on both wheels on the same axle. 42-06-20 The suspension is firmer with a solid stabilizer bar. The disadvantage is that when you are driving straightahead during a one-sided compression (bounce), this transmits a "copying” effect through the suspension, which reduces comfort. 24 E65 Driving Dynamics Systems Purpose of the System The Dynamic Drive - Active Roll Stabilizer Bar (ARS) is a revolutionary step forchassis tech¬ nology. ARS goes a long way towards removing the conflict between handling/agility and comfort. ARS has two stabilizer bars that have a positive effect on the body roll and han¬ dling, allowing softer springs and dampers to increase comfort. Active Stabilizer Baron the Rear Axle Dynamic Drive controls two active stabilizer bars on the axles depending on the lateral acceleration. Oscillating Motor The two separate stabilizer bars on each axle are mounted in roller bearings and are connect¬ ed by a hydraulic oscillating motor. One half of the stabilizer bar is connected to the oscillating motor shaft and the other is con¬ nected to the oscillating motor housing. Active stabilizer bars introduce fewer forces into the body as compared to solid stabilizer bars- because the separate "halves" will not copy one sided suspension compressions (bounces). 42-06-22 25 E65 Driving Dynamics Systems The active stabilizer bars set the stabilizing torque, resulting in M inimizing or completely eliminating body roll while cornering Reduction in the "copying effect" of the vehicle A high degree of agility and precision throughout the entire speed range Produces optimum self steering characteristics Improved suspension comfort (when driving straight ahead) because the stabilizer bar halves are independent and do not stiffen the basic suspension during a one-sided compression. The distribution of the active body torque between the front and rear axle depends on the road speed. The following describes the different body torque distribution. Self Steering Affect The self steering affect is influenced by the distribution of the stabilizing torque on the axles. The greater the stabilizing torque on an axle, the lower the lateral forces will be that are transmitted on this axle. Two situations are described below with a different distribution of stabilizing torque on the axles: Identical stabilizing torque on both axles: Handling is "NEUTRAL". The front wheels will apply about the same amount of lateral force to the road as the rear wheels (without drive torque). A vehicle that is tuned to neutral handling provides very agile handling and the steering reacts very quickly. The driver experiences precise handling. Larger stabilizing torque on the front axle: Handling is "UNDERSTEERING". The front wheels cannot apply the same amount of lateral force to the road as the rear axle wheels. The vehicle tends to go straight requiring an increase in steering to make the vehicle turn. Dynamic Drive sets the stabilizing torque on the front and rear axle to create a different handling characteristic for low and high speeds. Road Speed Handling Low Neutral High Understeer 26 E65 Driving Dynamics Systems Passenger vehicles are designed for slight understeer depending on the speed range. Dynamic Drive is tuned to neutral in the lower speed range, requiring less steering to go around the same corner. This produces optimum handling and agility. In a higher speed range, Dynamic Drive is designed so that a larger active stabilizing torque will occur on the front axle as compared to the rear axle This means that the vehicle with Dynamic Drive reduces over sensitive steering a higher speeds to enhance handling characteristics. System Dynamics When the vehicle changes lanes, corners or changes direction quickly (winding roads), Dynamic Drive reacts very quickly. The system dynamics reaction time is shown in the fol¬ lowing steps: Process Signal detection by sensors, processing of sensor signals and valve control. Change of direction, switching over the torque direction, direction valve. Pressure build up (force per wheel). 0 to 30 bar ( 0 to 350 N) 0 to 180 bar (0 to 2100 N) Time approx. 10 ms approx. 30 ms approx. 120 ms approx. 400 ms Dynamic Drive Bus Structure AnA - FDC WWYA TUFAT 1M I i MTH H Uyi aj ! HKL fjJBF TMEFT Tm fc^H I M ;=Md Fm J ■=*.H 4 ihK* ClHy □= fc’Ll HLS sy-n ■Ji 'frwA L-3 l~L>Z I ■SE+: i.VT l L_ T*L LOGIC? l I~ SvS ^ Wh p S8h Mitt P k-Can £ PT-Cili 27 E65 Driving Dynamics Systems System Components Dynamic Drive (ARS) consists of the following components: Dynamic Drive (ARS) 5. Control module 6. Transverse acceleration sensor 7. Rear oscillating motor 1. Fluid reservoir 2. Tamdem pump 3. Front oscillating motor 4. Valve block ARS Control Module: The control module is located on the right side "A" pillar in front of the glovebox and is powered by B+through a 10 Amp fuse. The control module is activated by a CAN alarm lead from the CAS module when the ignition is switched "ON". A vehicle authentication process takes place when the system is started. This compares the vehicle identification number from CAS with the vehicle identification number which is encoded in the ARS control module. 28 E65 Driving Dynamics Systems After the ignition is switched "ON", the ARS hardware and software is self-checked. All of the outputs (magnetic valves) are checked for short circuits and breaks. When there is a fault, ARS switches the actuators to a safe driving condition. The control module will switch off in the event of undervoltage or overvoltage. Dynamic Drive (ARS) Component Overview: CAS K-GAH 5 * KlJ 5 W Dynamic Drive Component Overview 42 - 06-25 ARS - Control module VB - Valve block P - Pressure sensors G - Rotational rate (yaw) sensor CAS - Car Access System KOMBI- Instrument cluster LM - Light switch center LWS - Steering angle sensor SIM - Safety integration module ZGM - Central gateway module EDC - Electronic damping module DME - Digital engine electronics DSC - Dynamic stability control S3 - Lateral acceleration sensor 29 E65 Driving Dynamics Systems Inputs: The ARS control module requires dynamic driving input signals to calculate the required activation. The following input signals are monitored and checked for plausibility: Lateral acceleration PT-CAN Bus Front axle ARS circuit pressure Rear axle ARS circuit pressure Selector position recognition sensor (SSE) Fluid level sensor signal The PT-CAN provides additional information about lateral dynamics: Vehicle speed signal (DSC) Steering wheel turning angle (Steering Angle Sensor) Yaw velocity - Transversal acceleration (Roational Rate Sensor) These inputs allow the ARS control module to determine the stabilization requirement at the appropriate inertia moments. The reaction time is decreased by using the vehicle speed and steering angle inputs. Outputs: All of the outputs are check by diagnostics and are short circuit protected. The outputs (and control) include the following: Pressure control valves for the front and rear axle ARS Directional valve Failsafe valve 5 V sensor voltage supply The valves are controlled by pulse width modulation current. The individual coil current requirements are constantly checked for plausibility. The current measurements allows the pressures to be precisely set and electrical monitoring of the hydraulic the shift valves. The PT-CAN sends a message to the ECM indicating how much engine power is required to drive the tandem hydraulic pump to activate the ARS stabilizer bars. An "alive” data signal is provided and monitored by othercontrol modules to detect the sys¬ tem status. All signal faults are permanently stored. Output faults include short circuits (B + and ground) and open circuits. 30 E65 Driving Dynamics Systems Sensor System Lateral Acceleration Sensor: The lateral acceleration sensor is located under the carpet in front of the passenger's seat (1). While cor¬ nering, the vehicle's lateral acceleration is mea¬ sured (range is ±1.1 g). Transversal acceleration (yaw velocity) is provid¬ ed by the Rotation Rate Sensor (2) via the DSC control module. 42 - 06-15 Front and Rear Axle Stabilizer Bar Pressure Sensors: The pressure sensors provide the ARS control module with the front (1 below left) and rear (2 below left) axle stabilizer bar hydraulic operating pressures. The sensors are mounted on the valve block assembly and the pressure values are initialized in the control module (during assembly line commission¬ ing). The voltage value is proportional to the operating pressure (in bar shown below right). 0 SO 100 p [bar] 200 42 - 06-28 Selector Position Recognition Sensor (SSE): The SSE is mounted on the valve block assembly (3 above left). This sensor allows the ARS control module to detect the specific position of the directional valve (4 above left). The 2 positions detected are: Left hand control (direction of torsional twist) Right hand control (direction of torsional twist) 31 E65 Driving Dynamics Systems Fluid Level Sensor: The fluid level sensor allows the ARS control module to detect the fluid supply level in the reservoir (power steering reservoir) for the tandem pump. The fluid level sensor indicates when the fluid drops below the minimum level and triggers a warning message. Normal fluid movement (slosh) will not trigger the sensor. Short/open circuits are not detected by the fluid level sensor circuit and a circuit break is interpreted as a loss of fluid. 42 - 00-29 Actuator System Pressure Control Valves: There is a pressure control valve for both the front (1 below) and rear (2 below) axle hydraulic circuits. The valves adjust the front and rear axle stabilizer bar actuation pressures. When driving straight ahead, the pressure control valves are de-ener- gized opening the valve diameters allowing the fluid to return to the reservoir (circulating). i „ When cornering, the valves are energized to readily increases the pressure in the oscillating motors to the setpoint value. Depending on the lateral acceleration and the vehicle speed, the pressures for the front axle are regulated between 5 to 180 bar and 5 to 170 bar for the rear axle. Directional Valve: The directional valve (3 above right) is electrically actuated by the ARS control module to control the direction of the hydraulic pressure for right and left hand twists. Failsafe Valve: The failsafe valve (4 above right) is electrically actuated by the ARS control module to open the front axle hydraulic circuit to the oscillating motor. The circuit is closed when the failsafe valve is de-energized, decreasing the system pressure (circulating). Check Valves: The check valves (internal in the valve block) allow the hydraulic fluid to be drawn from the reservoir preventing cavitation in the oscillating motor. 32 E65 Driving Dynamics Systems Valve Block: The valve block is an electrically controlled hydraulic distribution assembly and is located behind the right front wheel housing panel (at the base of the A-pillar). 42 - 06-31 Valve Block Functions Distribution of hydraulic fluid flow to the oscillating motors: The pressure at the front axle oscillating motor is greater than or equal to the pressure at the rear axle oscillating motor. Measuring the actual pressure of the high pressure hydraulic fluid: There is a pressure sensor for both the front and rear axle oscillating motor hydraulic circuits on the valve block. Fast and precise regulation via the pressure control valves: Introduced pressure changes as a result of uneven roads are passively regulated to reduce noise as much as possi¬ ble. Adjustment of the volume flow direction (left hand/right hand twist) via a directional valve: The directional valve position is detected by a selector position recognition sensor (S5E). Switch to Failsafe mode in the event of power supply failure ora fault is detected in the system: The front axle oscillating motor hydraulic circuit is closed off and hydraulic flow is diverted to the reservoir. The check valves will open to allow the hydraulic fluid to be drawn from the reservoir. The rear axle oscillating motor hydraulic circuit is also deacti¬ vated and hydraulic flow is diverted to the reservoir. Limiting the system pressure in the event of a fault: The Failsafe valve causes the circuit to close when de-energized, decreasing the system pressure (circulating). 33 E65 Driving Dynamics Systems Valve Block Sub-Components: Components Description Pressure control valves The pressure control valves are electrically actuated. They set the active pressure for the front and rear axle stabilizer bars. When driving straight ahead, the pressure control valves are de-energized and the valve diameters are open. The fluid can flow freely to the reservoir. The valves are energized when the vehicle is cornering. The pressure in the oscillating motors increases rapidly and is regulated to the setpoint value. Directional valve The directional valve is electrically actuated. It specifies the direction of the high pressure fluid (active pressure) and the return fluid pressure for the right hand and left hand twists. SSE There is a selector position recognition sensor (SSE) for monitoring the directional valve position in the directional valve. Failsafe valve The Failsafe valve is electrically actuated. It closes the front axle oscillating motor circuit, when de-energized. The system pressure is limited by the circulation position and causes a circulating flow. Check valves The check valves are located in the valve block. They allow the fluid to be drawn from the reservoir to prevent cavitations in the oscillating motor. Pressure sensors The stabilizer bar pressure sensor signals are used to monitor the hydromechanics. In addition, the pressure control pressure signals are used. Active Stabilizer Bar (one assembly per axle): The active stabilizer bar consists an oscillating motor and two stabilizer bar halves with press fit roller bearings to mount the assembly to the axle carrier. The oscillating motor and the oscillating motor housing joins the two halves of the stabilizer bar The rear axle Active Stabilizer Bar is shown on the right. 34 E65 Driving Dynamics Systems 42 - 06-32 The Active Stabilizer Bar assembly has three tasks: The oscillating motor decouples the two halves of the stabilizer bar. The oscillating motor guides the torque into the two halves of the stabilizer bar. In the event of system failure (Failsafe mode), the front axle stabilizer bar creates suffi¬ cient damping from the oscillating motor hydraulic fluid (hydraulic locking) to work like a conventional stabilizer bar. Exception: If the oscillating motor chambers do not contain any fluid as a result of a leak, the front axle stabilizer bar will not dampen and rely on the spring strut assemblies. Oscillating Motors: The oscillating motors are split chamber hydraulically controlled rotary actuators. This motor contains a total of four chambers, opposing chambers are connect¬ ed with one another and receive the same hydraulic pressure. Two chambers are supplied with high pressure through an internal connection and the other two chambers are connected to the reservoir return line. The pressure and drain (return) is switched between the two pairs for right or left hand tor¬ sional twists. The different pressures result in the high and low forces that apply torque. One half of the stabiliz¬ er bar is connected to the shaft and the other half is connected to the housing. The two halves will turn in opposite directions. As a result, the shaft will turn in an opposite direction of the housing. The stabilizer bar is mounted to the axle carrier. The torque generated while cornering will force the body upwards on the outside of the curve and pull it down on the inside of the curve. 42 - 06-33 35 E65 Driving Dynamics Systems 42 - 06-35 The maximum torque influence on the front and rear axle occurs when there is a high degree of lateral acceleration (producing body roll). During this situation, the system pres¬ sure is 180 bar at the front axle and 170 bar at the rear axle. The front oscillating motor is smaller than the rear one and builds up a force of 600 N m at 180 bar. The rear oscillating motor builds up a force of 800 N m at 170 bar. The oscillating motors also act as torsional vibration dampers (hydraulic cushion). During torsional twists, the fluid is displaced from two chambers returning through the lines and the valve block to the reservoir. The return path has a slight hydraulic resistance which creates damping. With failsafe (hydraulic blocking), the oscillating motor will turn as a unit because of the closed circuit hydraulic locking occurring internally (like a conventional sta¬ bilizer bar). Tandem Pump: The tandem pump mounted on the engine and is driven by the ribbed V- belt. The pump assembly consists of a radial piston pump for Dynamic Drive and a vane pump for the power steering. When the engine is idling, the pump speed is approx. 750 rpm providing a minimum flow rate of 4.5 l/min at 0 - 5 bar and 3.3 l/min at 180 bar. This volume and pressure provides sufficient system dynamics when the engine is idling. At a pump speed of approx. 1165 rpm, the flow rate is limited to 7 l/min. Dynamic Drive and power steering share the fluid reservoir and fluid cooler. 36 E65 Driving Dynamics Systems 42 - 06-36 Fluid Reservoir: The fluid reservoir is identical on all E65 vehicles, whether equipped with Dynamic Drive or not. The fluid reservoir also supplies the power steering hydraulic circuit. The reservoir contains a fluid filter (as on mod¬ els in current use) and a fluid level sensor to detect when the fluid level drops below the min¬ imum amount. 42 - 06-29 Fluid Cooler: The cooler ensures a long term fluid temperature of < 120 2 C and a short term fluid temperature of < 135 2 C in all hydromechanical components under all operating conditions. 42 - 06-38 Hydraulic Lines and Hoses: The hydraulic lines and hoses are designed for extremely high pressures. The hydraulic component connections and fittings are designed with dif¬ ferent dimensions and lengths to avoid improper installation. Hydraulic noises transmitted to the vehicle interior predominantly occurs through the assemblies and connections. The lines and hoses must be properly positioned through the mounting supports (noise insulation) and not touch the body surface. The supply hose in the engine compartment has excess loops (and length) to also reduce hydraulic noise. 37 E65 Driving Dynamics Systems Principle of Operation Dynamic Drive System Pre-drive Procedure When the ignition is switched "ON", the ARS control module self test is first performed. The electrical valve functions are conducted to detect short/open circuits in the valve solenoid coils, connectors and harness. The sensors are checked for short/open circuits in the har¬ ness, connectors or the internal electronics. Finally, the hydraulic safety functions are checked before the vehicle moves as part of the "Pre-drive Check". fiMY SMH A test pressure (<60 bar) is set between the pump and the failsafe valve. This allows the ARS control module to check if the failsafe valve is actually in the de-energized failsafe position. When in this position, the system pressure is decreased (circu¬ lating). When the failsafe valve is energized (FS as shown to the right) by the ARS control module, the front axle hydr¬ aulic circuit is open providing pres¬ sure to the oscillating motor (S M V). The front axle pressure control valve function is tested simultaneously. If pressure does not build up at the front axle stabilizer bar, the Predrive Check criteria will not be met. The Dynamic Drive function is deactivated when the vehicle is stationary (inertia is not pre¬ sent) and all the valves are de-energized. This also applies when the vehicle is at a stand¬ still on an incline (one sided load). Even though the lateral acceleration sensor provides a signal, the vehicle speed signal is not present. When the vehicle speed is >15 km/h, the ARS function is started. 38 E65 Driving Dynamics Systems Straight Ahead Driving When the engine is running, the tandem pump supplies hydraulic fluid to the system at a pressure of 3 to 5 bar. The front and rear axle stabilizer bar pressure valves are de-ener¬ gized (open) and pressure is not applied to the oscillating motors. The hydraulic fluid circu¬ lates directly back to the reservoir for as long as the vehicle is driven straightahead. Cornering When cornering, the signals from the lateral acceleration sensor are conveyed to the AR5 control module. The control module outputs a pulse width modulated signal (PWM) to the front and rear axle stabilizer bar pressure valves. The stronger the lateral acceleration, the greater the signal (current flow). The increasing valve current will progressively close the valves forming a higher pressure in the stabilizer bar oscillating motors. The pressure sensors provide the ARS control module with the stabilizer bar oscillating motor pressures. To direct the buildup pressure according to the corner (left hand or right hand twist), the directional valve is actuated by the control module. The S5E sensordetects the directional valve selector position. E MU Restricted Function The system reverts to failsafe mode when a fault is detected. The control module stores the fault and indicates failsafe mode in the instrument cluster. The fail¬ safe situation is shown to the right in the hydraulic overview diagram. In the event of system failure, the failsafe valve (F5) is de-energized and sprung closed. The hydraulic fluid in the front sta¬ bilizer bar is sealed in, ensuring the stabil¬ ity and understeer effect of a convention¬ al stabilizer bar. The check valves (RVV1, RVV2) allow the hydraulic fluid to be drawn from the reser¬ voir preventing cavitation in the oscillating motor when the vehicle is driven straight. External Leakage External leakage is detected by the front or rear pressure sensors and the ARS control module will deactivate Dynamic Drive (system failure). ARS Block Diagram » MJL-J » JJ 2h » 10 lie '77 ■ _d ■2 J J ■+3 ARS n /1 !. I -a i " . i : I FS n i—i w tL Ki, 11 42 - 06-41 ARS aq Lateral acceleration ARS Active roll stabilizer bar control unit SSE Selector position recogniton sensor DSV Front axle pressure sensor DSH Rear axle pressure sensor PVV Front axle pressure control valve PVH Rear axle pressure control valve RV Directional valve FS Fail-safe valve 40 E65 Driving Dynamics Systems Workshop Hints Diagnosis The following component faults can be detected: Component Type of fault Fault detection via: ARS control module De-energized or faulty Instrument cluster via omission of the Alive-Counter, vehicle identification number with authentication not recognized, watchdog Pump No pressure Target-performance comparison pressures Directional valve Stuck in the "energized" position (wire break) Stuck in the "de-energized" position (wire break) Directional valve sensor Pressure control valve Open (de-energized) Front axle target-performance comparison pressure, current M easurement Closed (mechanicalfault) Front axle target-performance comparison pressure Pressure control valve Open (de-energized) Rear axle target-performance comparison pressure and current measurement. Closed (mechanicalfault) Rear axle target-performance comparison pressure Failsafe valve Stuck open Predrive-Check Stuck closed Current measurement Actuator Front/rear axle Leaking (no moment) Target-performance compliance pressure Blocked Target-performance comparison pressure CAN bus Completely omitted (line out) CAN-timeout Steering angle Implausible, or omitted Plausible monitoring and fault detection CAN bus signals Sensor Completely omitted (line out) Voltage monitoring Incorrect signal Check p ausibility via CAN signals Fluid leve sensor No signa (ine) Front axle Pressure sensor No signal (line) Front axle target-performance comparison pressure Incorrect signa Rear axle pressure sensor No signal (line) Voltage monitoring Incorrect signal Target-performance comparison pressure Directional valve sensor No signal Voltage monitoring Incorrect signal SSE directional valve target - performance comparison 41 E65 Driving Dynamics Systems Depending on the fault, the system exhibits one of the reactions listed below: System shutdown (Failsafe mode) The following faults lead to system shutdown and all output stages are de-energized Fault in the front axle stabilizer bar Fault on the front axle pressure sensor Fault with pressure build up (pump, pressure relief valve on the front axle) Fault in the control module Vehicle identification number is not conveyed by the CAS/is missing/is incorrect Directional valve positioning fault, faulty SSE Omitted PT-CAN signal The de-energized failsafe valve blocks the chambers of the active stabilizer bar on the front axle. The fluid is only equalized via the internal oscillating motor and valve block leakage. The check valves in the valve block make it possible Warning message Handling instructions Cornering stability. Take corners slowly Directional stability system with unlimited Directional stability. No high road speeds When cornering. Drive on, contact BMW Center immediately If there is a fluid loss in the ARS or the steering circuit, the fluid level sensor in the fluid level sensor in the fluid reservoir responds to this. The driver is informed in order to avoid damaging the tandem pump by driving on. _ Handling instructions Fluid loss in the chassis and steering system Do not drive on, contact BMW Center immediately A 12 Pin Adapter Cable, Special Tool #90 88 6 372 040 is used in conjunction with the DISplus to adapt the MFK cables when diagnosing the ARS system. Warning message Fluid loss. Stop carefully, switch off the engine 42 E65 Driving Dynamics Systems Restricted Control Comfort Lateral acceleration is calculated from the vehicle speed and steering wheel angle (CAN signals). This signal is fasterthan the actual lateral acceleration and compensates forthe hydromechanics time delay. If there is a fault with these two signals, the system reacts with delayed rolling compen¬ sation. This only happens with extremely fast steering, when cornering normally it is barely detectable. If the lateral acceleration senor is faulty, the lateral acceleration is calculated solely from the can signals. The driver will not feel any restriction in function. If there is a fault in the rear axle circuit and there is stabilizing on the front axle only, the d river feels that the vehicle is making larger rolling movements. Agility is reduced at road speeds <120 km/h. The system also reacts this way if the Pre-drive Check brings up the "failsafe valve stuck open" message. In the event of an electrical fault on the rear axle pressure sensor, there may be roll angle compensation defects. To be on the safe side, slightly more stabilization torgue is transferred to the front axle than in the normal operating mode (this can be felt by the driver). Warning message Handling instructions Cornering stability slightly restricted Chassis stability slightly restricted when cornering. Drive on, contact BMW Center as soon as possible Restricted System Monitoring Dynamic Drive receives the following sensor signals from the DSC and SZL via the PT CAN Bus: Lateral acceleration Yaw velocity Road speed Steering wheel angle These signals are used to check the lateral acceleration sensors. Control comfort is restricted if the engine speed signal (DmE) fails. In the event of a fault with the CAN signals and the yaw velocity, the system is missing two pieces of information. Since this information is used solely to check the other signals, the ARS function remains available with full control. Although there is no restriction of the Dynamic Drive function, the driver will be shown the "chassis control comfort" display. The driver is instructed to drive to the workshop if possible. Warning message Handling instructions Cornering stability slightly restricted Chassis stability slightly restricted when cornering. Drive on, contact BMW Center as soon as possible. 43 E65 Driving Dynamics Systems A "dynamic" driver will notice the loss of the steering angle signal and the warning mes¬ sages will be acknowledged. The warning message will disappear once it has been ack¬ nowledged. When the cause of the fault is corrected, the ARS control module will have full capacity. Depending on how fast a fault is detected, there are two reset opportunities: When the ignition is off, all faults which have been corrected will be reset. You must wait until the sleep mode has been activated before switching the ignition back on. Faults that occur sporadically and can generally be traced back to CAN bus communi¬ cation malfunctions, are automatically reset when driving straight ahead or when sta¬ tionary. In this case, the driver may not be aware of the re-activation when driving or when the car is stationary. The faults are stored in memory with important additional information. The additional information includes the mileage when the fault occurred, details of whether the fault is present and the frequency of the fault occurance. Note: When there is a Dynamic Drive failure, the DSC can not be deactivated or if it is already deactivated it will not switch back on automatically. Dynamic Drive Commissioning The commissioning procedure must be earned out using the DISplus after the hydraulic system was opened or a component was replaced (in particular the lateral acceleration sensor). This procedure is found underServ/ce Functions - Chassis - Dynamic Drive - Start Startup - TestPlan and follow the on screen instructions. The following criteria must be met for matching the lateral acceleration sensor and the two pressure sensor offset values: The vehicle must stand level on all four wheels (on the ground). The vehicle must be unloaded. The engine must be idling at operating temperature. The doors must be closed and occupants are not allowed in the vehicle. Note: Stay clear of the moving chassis parts during the commissioning! The ground and side to side clearance must not be limited or obstructed and the doors must be closed. The arms of the lift hoist must not be situated underneath the vehicle. Vehicle will not be able to be driven (transmission will remain in "Park" during this procedure). 44 E65 Driving Dynamics Systems The commissioning is performed in five steps that are automatically carried out during the procedure: 1. Direction valve test (from 3 to 3.4 seconds) First the direction valve is tested by evaluating the SSE signals. 2. Low pressure test (from 3.4 to 4.3 seconds) The failsafe and direction valves are without power during this stage. Then tests are carried out with pressure control valves (with and without power) on the front and rear axle. The body is then tilted. The sides of the vehicle must be clear. 3. Front axle high pressure test (from 4.3 to 9.9 seconds) Pressure of 180 bar is applied to the front axle oscillating motor. Air in the system, internal leaks and a blocked oscillating motor is detected. 4. Rear axle high pressure test (from 9.9 to 15 seconds) Pressure of 170 bar is applied to the rear axle oscillating motor. Air in the system, internal leaks and a blocked oscillating motor is detected. 5. Pressure control valve test (from 15 to 25 seconds) The characteristic curves of the front and rear axle are checked. (Target/actual value comparison) Faulty pressure control valve is detected. Dynamic Drive Bleeding After all work on the Dynamic Drive and the steering system in which hydraulic lines have been opened, the steering system must be bled and initial operation of the Dynamic Drive (commissioning) must be performed with the DISplus. Procedure: 1. Check fluid level in the powersteering reservoir; if necessary, top up to the "MAX” level while the engine is stopped. 2. Start the engine. Turn the steering wheel left and right to the full lock twice. 3. Check the fluid level with the engine stopped; if necessary, top up to the "MAX" level. 4. Start the engine, connect vehicle to the DISplus. 5. Start the Commissioning procedure which is found under Serv/ce Functions - Chassis - Dynamic Drive - Start Startup - Test Plan and follow the on screen instructions. Note: Refer to the Repair Instructions for details on the Dynamic Drive bleeding procedure. 45 E65 Driving Dynamics Systems Review Questions 1. What identifies the correct installation of the twin tube gas pressurized shock absorbers 7 2. Explain the Crash Element function. 3. List the correct wheel bolt torque value. 4. Following a brake pad replacement, what must be performed to properly complete the repair 7 5. How is the "Auto Hold" parking brake function activated 7 6. Explain how the EMF applies the parking brake. 7. List the procedures to resume operation after an EM F emergency release. 8. Explain how EDC-K influences hydraulic damper operation. 9. Describe the Dynamic Drive influence on the stabilizer bars. 10. Describe "Failsafe" hydraulic flow (for the front axle). 46 E65 Driving Dynamics Systems