GF42.45-P-5118TX Description of Components In ESP Control Unit
GF42.45-P-5118TX Description of components in ESP control unit
MODEL 219.3 up to 31.5.06
except CODE (494) USA version
MODEL 219.3 up to 30.6.06
with CODE (494) USA version
Component Identification:
The ESP control unit is located in the fuse and relay box (1) in the left front of the engine compartment next to the driver-side SAM control unit with fuse and relay module (N10/1).
Task
The ESP control unit takes priority over the SBC control unit (A7/3n1) as master.
The ESP control unit has all brake control functions of the ABS, BAS, ASR, DTR and ESP to be carried out by the SBC control unit via CAN-SBC (system's own CAN). The SBC control unit subsequently actuates the actuators in the traction system hydraulic unit (A7/3).
The following systems influencing vehicle dynamics are integrated in the ESP control unit:
^ Electronic stability program (ESP)
^ Acceleration Slip Regulation (ASR)
^ Engine braking regulation control (MSR)
^ Antilock brake system (ABS)
^ Electronic brake force distribution (EBV)
^ Brake Assist (BAS)
^ Speed-sensitive power steering (SPS [PML])
^ Pressure control of the Sensotronic Brake Control (SBC) (electrohydraulic brake)
^ Multiple value functions (SBC-Hold, Softstop, precharging, dry braking)
^ Deceleration coordination of Distronic (DTR)
Communication and influence of ESP control unit on other systems in the vehicle:
^ Influencing the engine and transmission management in the case of an ESP control.
^ The ESP control unit also contains the necessary electronics and control logic of the speed-sensitive power steering (SPS [PML]).
^ For driver information the ESP control unit actuates the instrument cluster (A1) via the CAN engine compartment; the instrument cluster actuates the ABS indicator lamp (A1e17) and the ESP and ABS warning lamp (A1e41)
^ Supplies the instrument cluster with the signals for the multifunction display (A1p13).
^ The SBC control unit passes on the stop light signal via a discrete line to the rear SAM control unit with fuse and relay module (N10/2) for actuating the stop lamps or suppresses this during an active ESP control.
For the control of ASR, MSR and ESP data is exchanged between the ESP control unit and the control units of the engine control and transmission control via the CAN engine compartment.
Component Identification:
Function overview
The ESP control unit receives the data from the SBC pedal value sensor (driver's braking requirement) via the CAN SBC (separate CAN-connection) from the SBC control unit. The ESP control unit takes the values as the computation basis for the individual wheel pressures. The required individual wheel pressure is calculated by the ESP control unit taking into account the algorithms of the ESP, ABS, ASR, EBV or the "multiple value functions" of the ESP control unit and conveys it to the SBC control unit via CAN-SBC. The pressure regulators of the SBC control unit adjust the required brake pressure in each brake caliper. In the event of failure of the ESP control unit, the CAN-SBC or missing data between the control units, only one basic braking function without the usability of the ESP control unit and a set brake force distribution is available. Regarding the multiple value function SBC-Hold all the specified pressures requested by the ESP control unit are monitored by the SBC control unit so that a possible pressure takeover by the SBC control unit can take place at any time.
This monitoring is confirmed by a signal which the SBC control unit sends back to the multiple value module via the CAN SBC (software module in the ESP control unit) and confirms a takeover or monitoring of the specified pressures.
Should no specified pressure be able to be sent from the ESP control unit to the SBC control unit (CAN-SBC inactive due to ignition "OFF" or the case of a CAN-SBC), the last specified pressures are taken over by the SBC control unit and also held by it. This is signaled to the SBC control unit via a fault signal. Temporary faults in the ESP control unit are processed by the multiple value module.
Variants
^ with speed-sensitive power steering (SPS [PML])
^ without speed-sensitive power steering (SPS [PML])
^ National version :
In USA/CDN the "multiple value function "SBC-Hold" is deactivated by coding.
The detection takes place by the CAN engine compartment via the corresponding national code.
The ESP control unit is divided up functionally as follows:
^ Signal conditioning
^ Function logic component
^ Safety circuit
^ Additional functions
Signal conditioning
The following input signals are processed by the function logic component for computations or as information:
^ Computation of vehicle speed/slip
Left front rpm sensor signal
Right front rpm sensor signal
Left rear rpm sensor signal
- Right rear rpm sensor signal (via CAN SBC and direct)
^ Computation of lateral forces
Steering angle sensor signal from steering column module
via CAN engine compartment
Sensor for rotational speed and lateral acceleration
^ Computation of longitudinal forces
- CAN message - engine torque from CDI control unit (diesel engine) or ME-SFI [ME] control unit (gasoline injection engine)
- CAN message - current gear (from fully integrated transmission control (VGS) control unit (series production) or ETC [EGS] control unit (AMG vehicles only)
- CAN message - actual brake pressures (via CAN SBC from SBC control unit)
^ Information signals (operation)
- Stop lamp switch signal (via CAN SBC)
- Parking brake indicator switch signal (S12) (CAN message from driver-side SAM control unit with fuse and relay module (N10/1))
- ESP Off switch signal (CAN message from upper control panel control unit)
- SBC pedal value sensor (via CAN SBC)
Function logic component
The conditioned input signals are processed in the logic section and converted into output signals.
^ Rpm sensor signals via CAN SBC and direct from SBC control unit:
The processed 4 wheel speed signals are constantly compared with each other and with specified slip thresholds at the front and rear wheels, depending on the vehicle speed.
The following values and controlled variables are determined by this comparison process:
- Vehicle speed
- Acceleration/deceleration
- Wheel slip (during normal braking and ABS control)
- Drive slip (for ASR control)
- Decal slip (for MSR control)
^ Steering angle sensor signal via CAN engine compartment from the
steering column module:
The change in the direction of travel or cornering is detected via the steering angle sensor signal and the different wheel speeds of the front wheels.
These two detection values in combination with the vehicle speed give the information to the ESP control unit on the driver's desired characteristics of the vehicle.
^ Yaw rate and lateral acceleration sensor signal:
From the signal from the yaw rate and lateral acceleration sensor the ESP control unit determines the lateral forces occurring when cornering. The drive status regulator in the ESP control unit detects an oversteering vehicle from the lateral acceleration signal and yaw rate signal.
The yaw rate and lateral acceleration sensor detects the movements (rotational speed) in the ESP control unit. The movements want to turn the vehicle about the vertical axis (yawing), as they occur when a vehicle skids. Thus the ESP control unit detects the effective handling characteristics of the vehicle from the signals from the yaw rate and lateral acceleration sensor.
^ CAN-message - engine torque:
The ESP control unit is informed about the torque delivered by the engine control unit via the CAN engine compartment.
In ASR and ESP closed-loop operation the function logic section of the ESP control unit requests the engine control unit to adjust a reduced engine torque. In MSR closed-loop operation a slight increase in engine torque.
^ CAN message - current gear:
Via the CAN engine compartment the function logic section (ESP) is constantly informed about the current gear by the ETC [EGS] control unit (AMG only) or the fully integrated transmission control (VGS) control unit. The current gear is used to calculate the drive forces acting on the drive wheels and for drive torque control.
^ CAN message - current gear:
Via the CAN engine compartment the function logic section (ESP) is constantly informed about the current gear by the ETC [EGS] control unit (AMG only) or the fully integrated transmission control (VGS) control unit via the CAN engine compartment. The current gear is used to calculate the drive forces acting on the drive wheels and for drive torque control.
^ CAN message - brake pressures
The ESP control unit is informed by the SBC control unit about the current brake pressures via the CAN SBC.
The brake pressure is recorded by the brake pressure sensors integrated in the traction system hydraulic unit and used by the function-logic section to calculate the wheel brake forces (longitudinal forces). If an ESP control is necessary during the brake application, then the existing wheel brake forces (longitudinal forces) are included at the same time to calculate the lateral stability (lateral forces)
^ Stop lamp switch signal (via CAN SBC):
Comes from the SBC control unit via CAN SBC. There it is formed from the values of pedal travel, pressure and stop lamp switch. It is detected and evaluated by the function logic section. Output of the signal from the ESP control unit to the CAN engine compartment for use for other systems.
^ Parking brake indicator switch signal (CAN message for driver-side SAM):
If a signal from the parking brake indicator switch exists, then no MSR closed-loop operation is permitted. Likewise the SBC multiple value functions "SBC-Hold" can only be activated when the parking brake is released.
^ ESP Off switch signal (CAN message from upper control panel control unit)
If a signal from the ESP Off switch is applied, the drive torque control circuit is switched off and the ESP and ABS warning lamp is actuated permanently.
Safety circuit
The task of the safety circuit is to detect faulty signals from the sensors, faults in the ESP control unit and in the electrical line system. The actuation of the High pressure/return flow pump in the SBC hydraulic unit is monitored during the control process. The solenoid valves and wheel speed sensors are monitored permanently via the CAN SBC. If a fault is detected, then the appropriate system is switched off and this is shown to the driver in the multifunction displays. In addition a fault code is stored in the ESP control unit. With faults which occur sporadically this is stored in the fault memory.
The safety circuit also constantly monitors battery voltage. If the voltage drops below 10.0 V or exceeds 17.0 V the complete system is shut down until the voltage is in the specified range again.
Indicator lamp actuation
The signals for the ABS indicator lamp, the ESP and ABS warning lamp and multifunction display are recorded by the ESP control unit and via the CAN engine compartment are passed on to the instrument cluster which actuates the appropriate displays.
Additional functions
Wheel speeds and speed status signal outputs
^ Output - wheel speeds: For systems which need a wheel speed signal, the ESP control unit supplies the current wheel speed of each wheel via the CAN-engine compartment. In addition the left front wheel speed is output discretely.
^ Output - rpm status signal: For systems which require information about the current vehicle status (vehicle stationary, vehicle being driven, rpm sensor defective), the ESP control unit supplies the rpm status signal via CAN engine compartment.
Partial function - speed-sensitive power steering
From the vehicle speed existing internally and the status signal, the ESP control unit calculates the speed-dependent specified current, set in a performance map, for actuating the SPS [PML] solenoid valve of the speed-sensitive power steering.
Distronic control function
The ESP control unit receives via the CAN engine compartment messages about the distance and relative speed of the objects recorded by the DTR control unit. On the basis of this information the ESP control unit decides whether the engine torque has to be reduced or increased and has this carried out by the ME-SFI [ME] control unit or the CDI control unit. If braking the vehicle or a shift down is necessary, the ESP control unit introduces braking or shift down via the fully integrated transmission control (VGS) control unit or the ETC [EGS] control unit (AMG only).
Partial function - Tire pressure loss warning (RDA)
On vehicles with code (477) Tire pressure loss warning the ESP control unit, warns against pressure losses in the tires by actuating the multifunction display in the instrument cluster. For this evaluation the ESP control unit compares the wheel speeds of the left wheel on an axle with the right wheel on an axle. As the tire internal pressure reduces the rolling circumference of the wheel reduces and the wheel speed of the damaged wheel increases compared to the speed of the other wheel.
As further vehicle dynamic values, such as slip or slip angle, the dynamic rolling circumference, as well as cornering influence the wheel speed, the signals from the yaw rate and lateral acceleration sensor (yaw rate and lateral acceleration), as well as wheel torque's are included in the computation at the same time.