This paper deals with the use of SAE J1922 as a control data link. This application involves a direct data link connection between the ECU of an electronic engine and the ECU for an Antilock Braking System (ABS) with integrated Drive Slip Control-also referred to as Anti-wheel Spin Regulation (ASR), or as Automatic Traction Control (ATC).
The application calls for an automatic reduction of engine output torque when the ABS/ATC controller determines excessive wheel spin has occurred. This most often occurs on slippery surfaces such as ice or snow when the vehicle is first started into motion, or on similarly slippery surfaces when accelerating or cornering. The engine torque reduction continues until wheel spin is brought within an acceptable limit. Control of engine output is then returned to the driver.
Extensive testing was conducted at WABCO's winter test site in northern Finland. It was necessary to determine tradeoffs on performance as data update rates were altered. For some applications where the J1922 data link was multiplexed on the same line as the J1587 diagnostic data link, bus utilization was a prime consideration. To minimize the bus usage, the J1922 commands were reduced to the minimum required.
Testing of the data link scheme was required to optimize the control algorithms. From a driver comfort perspective, harshness had to be eliminated in the control implementation to satisfy expectations and thus assure success of the system.