Charge Mixing Model and Robust Tracking Control for Mechatronic Engines

University of Minnesota Ph.D. dissertation. October 2015. Major: Mechanical Engineering. Advisor: Zongxuan Sun. 1 computer file (PDF); ix, 117 pages.The growing demand for sustainable technology in the automotive industry has led to vibrant research on mechatronic engines. The mechatronic engine replaces and integrates existing mechanical devices with advanced electronics to increase flexibility of engine control. The flexible engine control is to achieve optimal performance in regards to exhaust emissions and fuel efficiency. This thesis, in particular, concerns modeling, analysis, and tracking control of an electrohydraulic camless engine valve actuator for flexible gas flow control. The thesis consists of three main chapters. In the first chapter, a control-oriented charge mixing model is developed to analyze the effect of variable valve actuation on mixing of fresh charge and residual gas, referred to as charge mixing. The complex charge mixing is simplified by the enthalpy transfer between two control volumes: the mixed and unmixed zones. Then, thermodynamic interaction between two zones depending on variable valve actuation is modeled. The model is validated through engine simulations and optical engine tests. Further simulation studies are conducted to investigate the effect of different valve actuation strategies. In the second chapter, nonlinear frequency domain models of an electrohydraulic actuator are developed for spectral analysis and system identification. Both analytic and experimental approaches are presented. The analytic frequency domain model is derived from physical dynamics using Volterra series representation of a nonlinear system. Spectral analysis with the analytic model helps to uncover the critical nonlinear features of the electrohydraulic actuator in frequency domain. The experimental frequency domain model is identified from frequency response. With the assumption of the block-oriented model structures, the models are parametrized and the associated parameters are estimated based on spectral analysis. In the third chapter, internal model principle-based robust tracking control of an electrohydraulic actuator is presented to achieve nonstationary valve motion of a camless engine. As in many reciprocating machines, reference valve motion of an internal combustion engine is defined as a periodic signal in rotational angle domain of the engine. However, the reference valve motion is aperiodic in time domain, because rotational speed of the engine varies with time. Such motion is referred to as nonstationary motion whose frequency contents vary with time. Regarding a nonstationary reference signal modeled by a time varying exosystem, the high-order time varying internal model is proposed and its effectiveness is demonstrated by implementation on the prototype electrohydraulic camless engine valve actuator

Association between diet and gallstones of cholesterol and pigment among patients with cholecystectomy: a case-control study in Korea

Background: The prevalence of cholesterol gallstones is high in Western populations, while pigment gallstones are common in Asian populations. Dietary factors are suggested to be associated with gallstone risk, but their relationship with gallstone type has not been evaluated. This study investigated the association between diet and risk of cholesterol gallstone or pigment gallstone in a Korean population whose dietary pattern and type of gallstone were changed during the last 30 years. Methods: Patients with cholesterol (n = 40) and pigment (n = 59) gallstones were recruited after laparoscopic cholecystectomy and were compared with those of age- and sex-matched controls without gallstones (n = 99). Dietary intakes were assessed by trained dietitians using a semi-quantitative food frequency questionnaire. Multinomial logistic regression analysis was performed to calculate odds ratios and 95% confidence intervals to examine the associations between diet and risk for type of gallstones adjusted by potential confounders. Results: Patients with cholesterol gallstone consumed more lipid, animal lipid, beef, pork, and fried food than those with pigment gallstones and control, while patients with pigment gallstone consumed more carbohydrate and noodles than patients with cholesterol gallstone and control. In multinomial logistic regression analysis using control as reference group, dietary pattern with high consumption of beef, pork, and fried food was associated with risk of cholesterol gallstones, while there was no association between the risk of pigment gallstone and dietary pattern. In addition, control consumed more alcohol than patients with cholesterol and pigment gallstones. Conclusions: The present study suggested consumption of fat from meat and fried foods increased the risk of cholesterol gallstone, and intake of carbohydrate from noodles increased the risk of pigment gallstone

Additional file 2: of Association between diet and gallstones of cholesterol and pigment among patients with cholecystectomy: a case-control study in Korea

Scree plot. (DOC 69 kb

Protein Intake Recommendation for Korean Older Adults to Prevent Sarcopenia: Expert Consensus by the Korean Geriatric Society and the Korean Nutrition Society

Sarcopenia, a common clinical syndrome in older adults, is defined as decreased muscle mass, strength, and physical performance. Since sarcopenia is associated with the incidence of functional decline, falls, and even mortality in older adults, researchers and health care providers have been keen to accumulate clinical evidence to advocate the screening and prevention of sarcopenia progression in older adults. The factors that may accelerate the loss of muscle mass and function include chronic diseases, inactivity, and deficiency in appropriate nutritional support. Among these, nutritional support is considered an initial step to delay the progression of muscle wasting and improve physical performance in community-dwelling older adults. However, a nationwide study suggested that most Korean older adults do not consume sufficient dietary protein to maintain their muscle mass. Furthermore, considering age-associated anabolic resistance to dietary protein, higher protein intake should be emphasized in older adults than in younger people. To develop a dietary protein recommendation for older adults in Korea, we reviewed the relevant literature, including interventional studies from Korea. From these, we recommend that older adults consume at least 1.2 g of protein per kg of body weight per day (g/kg/day) to delay the progression of muscle wasting. The amount we recommend (1.2 g/kg/day) is 31.4% higher than the previously suggested recommended daily allowance (i.e., 0.91 g/kg/day) for the general population of Korea. Also, evidence to date suggests that the combination of exercise and nutritional support may enhance the beneficial effects of protein intake in older adults in Korea. We found that the current studies are insufficient to build population-based guidelines for older adults, and we call for further researches in Korea