FPGA model based within-a-cycle estimation of rate shaping for a piezoelectric fuel injector
Abstract
Piezoelectric injectors are capable of delivering a wide range of injection profiles including tightly spaced multiple pulses as well as continuously variable injection called rate shaping. Rate shaping has been recognized as an effective way to reduce the nitrogen oxide (NOx) emissions without a huge detriment in particulate matter (PM) and fuel consumption. Piezoelectric injectors are highly dynamic systems, requiring careful input modulation to achieve sophisticated flow profiles. Within-a-cycle closed-loop feedback control techniques could prove to be a key enabler for this technology, but will require on-line estimation of the injected fuel flow rate to be realized because of the inability to measure the injector flow rate when used on an actual engine. This thesis describes the development and implementation of a physics-based fuel flow estimator which can be used as feedback to a closed-loop controller. Available measurements on the piezoelectric injector rig are used for dynamic state estimation. The estimator is realized in hardware using a Field Programmable Gate Array (FPGA) to reduce the loop computation time and provide a platform for within-a-cycle controller design. Real-time estimator results are compared against measurement data from the rig for a variety of flow profiles at different toe heights and different operating rail pressures. Estimator results, in general also show notable improvement against pure open-loop simulation results. Also, the thesis summarizes the development of an on-the-fly modifiable input voltage generation technique for the rate shaping injector and a high speed data acquisition system for the sensor signals, implemented using the NI hardware. Overall, this thesis describes a generalizable method to produce estimates of the rate shape injection flow profiles for the purpose of subsequent within-a-cycle controller design. The controller can provide a platform for making substantial improvements in combustion-related efficiency and emissions by increasing the flexibility of the fuel injection system.
Degree
M.S.E.
Advisors
Shaver, Purdue University.
Subject Area
Electrical engineering|Mechanical engineering
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