Traction Control System
Use of this system requires some knowledge of how a PID system works. The current system is using only the P and I components at this time. Proportional control is a direct acting parameter based on the immediate offset of the value from the target value. Integral is a reaction to the difference between the target value and the current value which adds or subtracts against itself over time.
Enable Switch (Traction Control) will need to be set to 1 for the system to apply power reductions based on slip. If the system is disabled, calculations will still be available to monitor, but no ignition reductions will be applied. Traction Control can be enabled or disabled in realtime with Accesstuner software.
The values used in Slip Reduction (Spark) will have an effect on the values that you use for P and I, since P and I values calculate the (TRAC) Slip Reduction value which is referenced in the Slip Reduction (Spark) table. If you lower the values for ignition timing you will find that you need a higher P and I to produce same ignition reduction result. The opposite would be true if you raised the values.
The base table values for the Traction Control system are a generic and may need further adjustment for each vehicle. You may or may not be able to take the calibration settings from one application and transfer them to others, even for the exact same mechanical setup! Take the time to adjust each component for the specific use case scenarios applicable to your customers.
In order to tune the system quickly using real time tables you have the option of setting (TRAC) Slip Target Multiplier (Mode) to 9. This will allow you to change the values of any table whose label starts with Mode 9 in real time. Using modes 1-8 will result in various 1D and 2D table lookups to be used from ROM values (normal per-gear and base table mode), and using mode 9 will allow you to tune and run the real time tables. Keep in mind that tables with the BR icon can also be adjusted in realtime regardless of the mode!
I-Term Limit (High) can be used like a hysteresis for the system becoming active due to wheel slip.
I-Term Limit (Low) is the maximum correction the integral and proportional component will be able to apply and will also limit the maximum (TRAC) Slip Reduction which can be calculated. You can use the parameter to limit the maximum amount of timing you would like to see removed.
The COBB traction control system has a special designation for a shift event for more accurate torque control during shift events. While traction is still being controlled heavily, especially in lower gears, the system is very useful. In order to tell the system that a shift is occurring we use Slip Reduction Delay Limit (Shifting) to offset Gear Commanded before the shift is accounted for by the traction system. The reason for this offset is the length of time from when the gear shift is started electronically and then actually physically achieved. This parameter is configurable in real time. You will want to monitor the parameter (TRAC) Shift Delay Count, and the start of the actual shift event where you will see the rpm monitor start to decrease. Taking that value where rpm is about to or has just started to decrease for the delay count will let the system know when to freeze torque reduction calculation. (TRAC) Slip Reduction calculation will hold a constant value until Gear Current matches Gear Commanded, signaling that the shift has been completed, and (TRAC) Slip Reduction calculations can resume.
Stagger (Tire Circumference) Compensation
The COBB traction control system includes compensation to account for mismatched front/rear tires. This feature was designed originally for drag-racers who run "slicks and skinnies". The system works ONLY for the Traction Control feature, and will not correct any other wheel speed measurements. The reason for this compensation is to ensure appropriate slip can be calculated when there are rotational speed differences between axles. This system is not for individual wheels, but paired axles. This means both FL/FR, or RL/RR wheels will need to match for the compensation to be useful. This compensation is configurable in real time, and default values may not be sufficient for most users. Once the system is activated, simply adjust the Tire Circumference (Front) and Tire Circumference (Rear) tables as needed.
Steering Wheel Angle Compensation (except Fiesta ST)
The COBB traction control system includes compensation to account for changes in steering angle. The input is measured using (TRAC) Steering Wheel Angle and feeds directly into the Slip Compensation (SWA) table. The reason for this compensation is to ensure appropriate slip is accounted for as the wheels begin to turn at different speeds when turning. This table is not configurable in real time, but default values may be sufficient for most users. If this system is going to be used outside of straight line acceleration, it will be important to adjust this compensation along with the Slip Target: table for the application.
YAW Compensation (except Fiesta ST)
The COBB traction control system includes compensation to account for changes in YAW. The input is measured using (TRAC) YAW Rate and feeds directly into the Slip Compensation (YAW) table. The reason for this compensation is to ensure appropriate slip is accounted for as the wheels begin to turn at different speeds when the vehicle begins to rotate. This table is not configurable in real time, but default values may be sufficient for most users. If this system is going to be used outside of straight line acceleration, it will be important to adjust this compensation along with the Slip Target: table for the application.