Traction Control System (TCS)

TCS INTRODUCTION
The Traction Control System (TCS) incorporate with two independent control algorithms, drive moment control (AMR) and brake moment control (BMR), that can be applied simultaneously to improves traction and keeps the vehicle in line and it apply on all road surface with the whole speed range. TCS is developing on the basis of ABS in order to ensure the wheels neither lock-up during braking, nor should they spin when driving off.

CAN INTERFACE
During TCS operation, TCS system need communicate with different system control unit such as EMS (Engine Management System) and TCU (Transmission Control Unit) to share the important message as list below in order to ensure TCS performance and comfort.
1. CAN Interface:
^ Serial asynchronous bus system
^ Maximum bus transfer rate up to 1 Mbit/s
^ The CAN data bus uses a data transfer rate of 500 kbit/sec
2. Mainly signals from TCU:
^ Gear shift information
^ Torque converter information
^ TCU requested engine torque
3. Mainly signals from EMS:
^ EMS status
^ Engine torque information:
- Indicated engine torque
- Engine torque after correction
- Torque of friction
- Torque scaling factor
^ Engine speed
^ Acknowledge for TCS
4. Mainly signal from TCS:
^ TCS request
^ TCS defect
^ TCS passive
^ TCS requested engine torque
^ TCS gear shift characteristic
^ Wheel velocity of all wheels

CONTROL ALGORITHM
The TCS control algorithm has two independent control algorithms, drive moment control (AMR) and brake moment control (BMR). TCS evaluated the filtered wheel speed signal from ABS speed processing to recognizes when a wheel is going to start slipping. As soon as wheel(s) spin was detected, BMR will intervene automatically in the brake system to increase traction and AMR intervenes in the engine function to reduce engine torque and keep vehicle stable via connected to ECM by CAN data bus.
The BMR increases the pressure actively in the brakes either to generate a brake differential effect by means of pressure increase in one wheel on split friction situation or on homogeneous friction, to reduce quickly the wheel spin and stabilize the car by increase pressure in both rear wheels simultaneously. In order to compensate the clearance of the brake, BMR control starts with a filling pulse.
The following control algorithm is on the basis of comparison between slip threshold and control deviation (RA), the slip difference of driven wheel. The slip threshold is calculated depends on the vehicle speed, acceleration, driving condition such as driving straight or in the curve, split friction or homogeneous friction road surface. Pressure modulation will be applied by pressure increase or decrease pulse to satisfy the different control condition that dependence of control deviations, wheel acceleration and driving condition.
The AMR controls the engine torque by means of spark retard and ignition cut off. The control concept and the calculation of slip threshold of AMR is similar to that of BMR. However, the threshold values of AMR and BMR are different, but tuned to each other. Whenever the wheel slip is higher than the slip threshold value then AMR calculated the optimal engine torque reduce value and transmitted it via CAN bus to the EMS. Then EMS will response to reduce engine torque accordingly by spark retard and/or ignition cutoff. AMR will request EMS to increase torque as long as the wheel slip value is lower than slip threshold.





ABS WARNING LAMP CONTROL

1. ABS warning lamp module
The active ABS warning lamp module indicates the operating condition of the ABS.
The ABS warning lamp is turned on under the following conditions.
^ During the initialization phase after ignition switch ON (3 seconds).
^ In the event of inhibition of ABS functions by failure.
^ When the system ECU is shut down even though ignition power is applied.
^ During diagnostic mode.
2. EBD warning lamp module
The active EBD warning lamp module indicates the operating condition of the EBD.
However, in case the parking brake switch is turned on, the EBD warning lamp is always turned on regardless of EBD functions.
The EBD warning lamp is turned on under the following conditions.
^ During the initialization phase after ignition switch ON. (3 seconds).
^ When the system ECU is shut down even though ignition power is applied.
^ When the parking brake switch is ON or brake fluid is low level.
^ In the event of inhibition of EBD functions by failure.
3. TCS lamp module
TCS warning lamp module indicates the operating condition of the TCS.
The TCS warning lamp is turned on under the following conditions.
^ During the initialization phase after ignition switch ON (3 seconds).
^ In the event of inhibition of TCS functions by failure.
^ When the TCS OFF switch is turned on
^ During diagnostic mode.
^ TCS warning lamp blinks when the TCS functions are operating (Blinking-2Hz)