Control of Engine Systems
As discussed in the preceding chapters, engine systems incorporate a large number of control loops. For the design of these feedforward and feedback control systems, the main objectives are: The driver’s demands for immediate torque response, good drivabi
- PDF / 4,609,581 Bytes
- 49 Pages / 439.37 x 666.142 pts Page_size
- 16 Downloads / 204 Views
As discussed in the preceding chapters, engine systems incorporate a large number of control loops. For the design of these feed forward and feedback control systems, the main objectives are: • • •
The driver's demands for immediate torque response, good drivability, and low fuel consumption must be met. The engine must be kept in a safe operating region where material damage or fatigue is avoided. Knocking must be prevented, the catalytic converter must not overheat, etc. The emission limits must be met. In the case of SI engines, this requires a rapid light off of the catalytic converter, precise stationary air/fuel ratio control, and good compensations of the transient phenomena.
All these requirements are partially contradictory therefore, they must be fulfilled according to the priorities set by legislation and customer demands. Control systems play a major role as enabling technology in this optimization. Complete treatment of all control problems arising in engine systems is beyond the scope of this text. The following four important case studies are presented with the intention to show how model-based methods can be used to streamline the design process: • • • •
The air/fuel ratio control system as a typical example of a combined feedforward and feedback control problem. The combined engine speed and air/fuel ratio control system, as an example of a MIMO control problem. The SCR control system, as an example how sensor models can help to improve the system performance. The engine temperature control system or engine "thermomanagement," as an example of a control system that must cope with a changing system structure.
L. Guzzella et al., Introduction to Modeling and Control of Internal Combustion Engine Systems © Springer-Verlag Berlin Heidelberg 2004
174
4 Control of Engine Systems
4.1 Introduction 4.1.1 General Remarks
The general structure of automatic control systems is discussed in Appendix A. Readers not familiar with the main ideas of general control system theory may want to consult that section before starting this. Figure 4.1 shows the various actuators and sensors of a modern SI engine management system. The ECU must set all actuator commands according to driver demands and available sensor signals, taking into account constraints imposed by engine safety and pollutant emission limitations. Carboncal1ister
AcceleratOf pedal roodoJIe
...._ .....................JIbL.J low Delivery module with prllSSU/e pump ETC = EIectrlri: llvotlle Cootrol 080 = On-Boetd Oiagnoois System RlfS = Re!Umle$s Fuel Supply System
Camshaft phase/: Intake andIOf exhausl phasing
= BosdI
~IS
• optioo
Fig. 4.1. Layout of a modern engine management system, reprinted with the permission of Robert Bosch GmbH .
In the following, it is assumed that the engine system is equipped with an electronic throttle device, i.e., the driver does not directly control the throttle plate angle. Instead, an accelerator pedal module captures the driver's input and produces an electronic signal sent to the ECU. This signal is usual
Data Loading...
