Abstract
This paper presents the development of an automated torque matching methodology for torque-based Diesel engine management systems. Most engine management strategies use indicated torque and engine speed as inputs to engine maps which control performance and emissions. Indicated torque is the torque generated by the gases in the combustion chamber during the engine cycle. Typically, estimated torque losses are subtracted from indicated torque in the management system to yield estimated net torque. It is important that the estimated net torque is equal to the actual net torque which can be measured using an engine dynamometer. This avoids the problem of emissions calibration drift, which increases the difficulty in developing calibrations to meet legislative requirements. It is also important as this estimated net torque will be utilised in many different parts of the management strategy.
A dynamometer-based on-line optimisation process to match the two net torque levels throughout the development of an engine calibration is presented. The torque matching process is laborious and time consuming when carried out manually and therefore an automated tool has been developed, which saves valuable dynamometer testing time and offline data analysis. The tool utilises communication with the engine management system in order to control the engine and perform all relevant functions. It also employs root finding algorithms and engine application specific coding to provide a robust and efficient functionality. Control, monitoring and data evaluation is conducted in an automated fashion via the use of a Matlab-based Graphical User Interface.
The tool has been developed and tested on a 1.6L turbocharged Diesel engine and results show the tool provides accurately torque matched calibrations which ensure a given indicated torque always yields a given actual engine torque, thereby eliminating emissions calibration drift. The automated nature of the tool ensures that the process can be carried out quickly on a regular basis throughout the development of the calibration. The proposed process has sufficient flexibility that the tool can be easily adapted for various applications.
Keywords: diesel, torque, calibration, automation, algorithm