Research Abstracts Online
January - December 2011
University of Minnesota Twin Cities
College of Science and Engineering
of Mechanical Engineering
PI: Zongxuan Sun
Modeling and Control of Mechatronic Automotive Propulsion Systems
This research focuses on both understanding and controlling the conditions inside the cylinder of an internal combustion engine to ensure clean and efficient combustion. An additional benefit is the potential to enable advanced concepts such as HCCI (homogenous charge compression ignition), multi-fuel operation, etc. The major thrust is in two directions: the use of novel mechatronic devices to provide flexible operation; and modeling the effect of these new flexibilities on the thermodynamic and fluid dynamic phenomena to optimize the engine operation.
A “Camless Engine” uses individual electronic actuators in place of the camshaft to open and close the intake/exhaust valves provides significant benefits by optimizing the air-delivery to the combustion chamber based on the operating conditions of the engine. The independent control of the intake and exhaust valves is enabled using a novel camless hydraulic engine valve actuation system. Experimental and simulation studies using a prototype system have motivated the redesign of the system. CFD analysis using FLUENT is currently being used to optimize the designs for the various hydraulic components.
A “Free Piston Engine” is a device where, unlike the conventional IC engine, the linear motion of the piston is not constrained by a crankshaft. The advantage of this setup is the ability to run with varying compression ratios, which has a direct effect on the combustion efficiency. However, alternative methods are required to extract the power from linear motion. The use of a linear alternator for this purpose is investigated. A two-dimensional axisymmetric analysis of the linear alternator was performed using Maxwell-2D to calculate the induced voltages, currents and opposing forces for various alternator designs, which were later used for modeling, analysis and optimization of the design of the entire system.
These mechatronic actuation systems require the implementation of advanced control algorithms to achieve precise motion. One of the critical steps in the design of these controllers is the use of the LMI toolbox in MATLAB for the off-line synthesis of the controller coefficients. The dimensionality of the optimization algorithms increases with the accuracy of the control required and thus makes the problem computationally intensive.
One of the key processes that need to be modeled is the in-cylinder mixing between fresh air/fuel mixture and the residual exhaust gas. CFD analysis using KIVA/Fluent is used to characterize the behavior of in-cylinder fluid motion as a result of the intake/exhaust valve operation and the piston motion. The results of this characterization are used to quantify the degree of mixing in the cylinder, which leads to the development of a simplified control-oriented model, which can be implemented in real time to optimize the engine valve actuation and piston motion to enable clean and efficient combustion and advanced concepts such as HCCI.
Pradeep Kumar Gillella, Graduate Student
Ali Sadigni, Research Associate
Ke Li, Graduate Student
Matthew McCuen, Graduate Student
Xingyong Song, Graduate Student