Blood Glucose Regulation Via Double Loop Higher Order Sliding Mode Control and Multiple Sampling Rate
The normal blood glucose concentration level in human is in the narrow range of 70-110 mg/dl. This concentration is normally controlled within these limits by different factors in the body. The most important regulators of the glucose level are insulin an
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Keywords: Diabetes Control, Higher Order Sliding Mode Control and Differentiation, Multiple-loop control.
1 Introduction The normal blood glucose concentration level in human is in the narrow range of 70-110 mg/dl. This concentration is normally controlled within these limits by different factors in the body. The most important regulators of the glucose level are insulin and glucagon. These two hormones are secreted from the endocrine part of pancreas and stabilize the glucose level in the blood through two feedback loops that work inversely. Insulin stimulates the glucose uptake in the insulinsensitive tissues and therefore lowers the glucose level in the blood. Glucagon, on the other hand, stimulates the glucose production when needed and results in increasing the sugar level in the blood. Different factors including food intake, rate of digestion and exercise affect the glucose concentration. Failure in maintaining this value results in high blood sugar level, hyperglycemia, or low blood sugar level, hypoglycemia. Diabetes Mellitus is a disease in which blood glucose concentration is elevated because of deficient insulin secretion or abnormal insulin action due to autoimmune destruction of the insulin producing cells in pancreas. This disease is known to be a lifetime condition that cannot be cured and if not appropriately controlled, may lead to a variety of vascular, neurological or metabolic problems. Patients diagnosed with this disease require lifetime exogenous insulin injections, which is the hormone necessary for absorption of glucose by the cells. Diabetes is responsible for significant mortality and cost in society. Implementing tight glucose control in the patient is the most important issue in the management of this disease, since it can prevent or delay the progression of complications associated with it. The current treatments include three to four daily glucose measurements and an equivalent number of insulin injections [1]. Newly developed methods such as continuous glucose monitoring system suggest a less invasive approach, but still rely on finger prick glucose measurements for calibration. G. Bartolini et al. (Eds.): Modern Sliding Mode Control Theory, LNCIS 375, pp. 427–445, 2008. c Springer-Verlag Berlin Heidelberg 2008 springerlink.com
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P. Kaveh and Y.B. Shtessel
An alternative approach is to close the broken insulin feedback loop outside the body and deliver it using an external device such as a pump [2], [3]. This pump that acts like an artificial pancreas would include a sensor and an insulin container. The sensor provides the measurements of the blood glucose concentration and passes the information to a feedback control system that would calculate the necessary insulin delivery rate using robust higher order sliding mode control algorithms [11-13], to keep the patient under metabolic control. A signal is to be sent to an insulin Pump by the controller that delivers the desired amount of insulin. The pump injects insulin through a catheter placed under the patient’s skin. Since the la
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