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Plain Language Summary: Poa annua is a troublesome weed in turfgrass areas such as golf courses, athletic fields, lawns, and sod farms. Controlling P. annua is made more difficult by the growing problem of herbicide resistance, the inherited ability of plants to survive herbicide applications that would normally be lethal. Researchers from 13 academic institutions collected 866 P. annua populations from different states and turfgrass systems to better understand the extent of this problem. Collections were divided and treated with four herbicides and one plant growth regulator. Plants were categorized as “susceptible” or “suspected resistant” based on their response to treatments. Suspected resistance (to at least one or more treatments) was observed in 16.8% of P. annua collections. Herbicide resistance in P. annua is a problem spanning different geographies and management practices. Therefore, coordinated research is needed to explore the scope and nature of the problem in a systematic way. [ABSTRACT FROM AUTHOR]

Presented in this paper is a multivariable linear feedback controller design methodology for idle speed control of spark-ignition engines. The engine is modeled as a multi-input, single-output system. The proposed feedback control system employs both throttle and ignition timing to control engine speed and engine roughness. Throttle is used to attenuate low frequency components of the speed error and reject mean speed errors. Spark advance is used to reduce cylinder-to-cylinder differences in torque production by limiting high frequency speed deviations. The algorithm is executed in the crank-angle domain, and the internal model principle serves as the basis for cylinder torque balancing. The nonlinear relationship between ignition timing and torque production is explicitly incorporated into the design process using a sector bound. A loop shaping approach is proposed to design the feedback controller, and absolute stability of the nonlinear closedloop system is guaranteed through the Tsypkin Criterion. Experimental results from implementation on a Ford 4.6L V-8 engine are provided. [DOI: 10.1115/1.2361324] Keywords: engine governors, cylinder balancing, automotive, transportation

A method for designing repetitive feedback controllers using nonparametric frequency response plant models is developed. In comparison to the zero-phase-error (ZPE) controller (ASME J. Dyn. Syst. Meas. Control 111, pp. 353-358), this method has the added benefit of providing improved transient performance when the plant inverse is unstable. In this controller design process, a connection is made between model uncertainty and the desired frequency response of the so-called q filter. Also, it will be shown that an optimal equiripple filter is useful when designing high-order q filters. The entire process was experimentally verified on an engine control application. A repetitive controller was used to determine the dynamic fueling requirements of a fuel injected, spark-ignition engine subjected to periodic changes in the throttle position. This fueling information is necessary when designing feedforward fueling algorithms. [DOI: 10.1115/1.1849248]

Presented in this paper is a feedforward controller identification process for the transient fueling control of spark ignition (SI) engines. The objective of an SI fueling control system is to guarantee a prespecified air-fuel (A/F) ratio, despite changing driver demands commanded through the throttle. The controller identification process is based on standard system identification tools and is comprised of three steps. The first step involves the design and implementation of a repetitive feedback controller. Next, the engine is subjected to a prespecified periodic throttle motion for which the repetitive controller achieves precise A/F control as t [right arrow] [infinity]. Finally, using the engine speed, the mass airflow, and the fuel pulsewidth information during precise fueling conditions, the feedforward fueling controller is identified using standard parametric system identification tools. This identification process can be performed during engine warm-up, thereby enabling a rapid determination of the fueling requirements as a function of temperature. Experimental validation is provided on a 1999 Ford 4.6L V-8 fuel injected engine with sequential port injection. [DOI: 10.1115/1.1849249]