Control of a diesel engine equipped with Variable Geometry Turbine (VGT) and Exhaust Gas Recirculation (EGR) requires a multivariable control method. One problem is that the engine system is non-linear. Furthermore there are strong cross-connections between inputs and outputs and the inputs have alsoboundaries. To be able to manage these control problems, MPC has been used that is a multivariable method. The MPC-controller consists of an optimization problem and therefore MPC can find the optimum control signals in an easy way. Furthermore the boundaries of the control signals can be handled with by-conditions in the optimization. The disadvantage with MPC is that it requires a lot of amount of calculations and memory, which are important factors when a control system should be implemented. Therefore it has been chosen to compare MPC with PID, that is a common and simpler method. The results from this thesis are that MPC is a method that gives more optimal and faster control. Furthermore MPC can handle different control cases much better, without changing the settings. On the other hand PID requires considerable fewer amounts of calculations and memory. In one case that has been examined, MPC requires 40 times more amounts of calculations than PID. To be able to control a non-linear system, both MPC and PID must be implemented in several different working points. Furthermore decoupling must be used in the PID-controller to be able to manage cross-connections that seems to be a very important problem.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:liu-1400 |
| Date | January 2003 |
| Creators | Wahlström, Johan |
| Publisher | Linköpings universitet, Institutionen för systemteknik, Institutionen för systemteknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | LiTH-ISY-Ex, ; 3385 |
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