(Microsoft Word - 55- 63 \310\324\307\321 \335\307\312\315 \346\307\343\314\317) Al-Khwarizmi Engineering Journal Al-Khwarizmi Engineering Journal,Vol. 13, No. 3, P.P. 55- 63 (2017) Performance Comparison of Different Advanced Control Schemes for Glucose Level Control under Disturbing Meal Bashar Fateh Midhat* Amjad Jaleel Humaidi** *,**Department of Control and Systems Engineering / University of Technology *Email: basharfm88@yahoo.com **Email: aaaacontrol2010@yahoo.com (Received 30 October 2016; accepted 7 March 2017) https://doi.org/10.22153/kej.2017.03.003 Abstract In this work, diabetic glucose concentration level control under disturbing meal has been controlled using two set of advanced controllers. The first set is sliding mode controllers (classical and integral) and the second set is represented by optimal LQR controllers (classical and Min-, ax). Due to their characteristic features of disturbance rejection, both integral sliding mode controller and LQR Minmax controller are dedicated here for comparison. The Bergman minimal mathematical model was used to represent the dynamic behavior of a diabetic patient’s blood glucose concentration to the insulin injection. Simulations based on Matlab/Simulink, were performed to verify the performance of each controller. In spite that Min-max optimal controller gave better disturbance rejection capability than classical optimal controller, classical sliding mode controller could outperform Min-max controller. However, it has been shown that integral sliding mode controller is the best of all in terms of disturbance rejection capability. Key words: Optimal LQR control, Optimalminimax control, Sliding mode control, Integral sliding mode control. 1. Introduction Diabetes mellitus is the human disease which results from the presence of high level of blood sugar for prolonged period due to inadequate generation of insulin in blood [1]. In human body, the beta cells in pancreas are responsible for producing the insulin, which regulates the glucose consumption. In diabetes, beta cells fails to produce enough insulin concentration in blood and the human body will be unable to control the blood glucose level. Type I diabetes mellitus patients cannot produce any insulin and insulin shots are given several times a day to help regulate their blood glucose level. A typical patient is then serving himself as a control system [2]. On the other hand, any patient that suffers from diabetes and not receives the insulin cure properly can lead to complications such as nerve damage, brain damage, amputation and eventually death. In the human body, the normal blood glucose level varies in a narrow range (70-110) mg/dL. The diabetes is diagnosed if the human body is not able to control the normal glucose-insulin interaction [3]. For this reason, the blood glucose must be regulated by injecting the insulin [4]. In general, the closed loop glucose regulation system requires three components, which are: glucose sensor, insulin pump and control method for determining the necessary insulin dosage based on the glucose measurements [5]. Figure (1) shows the block diagram of closed loop glucose control system. Bashar Fateh Midhat Al-Khwarizmi Engineering Journal, Vol. 13, No. 3, P.P. 55- 63 (2017) 56 Fig. 1. Block diagram of closed loop insulin regulation system [10]. Several approaches have been previously addressed to design the feedback controller for insulin delivery, such as classical methods like Proportional Integral Derivative (PID) controllers [6, 7] and pole placement [8], which require a linearized mathematical model for the design of the controller, as well as model predictive control (MPC) [9, 10]. In [6] a PID controller based on BP neural networks is proposed in order to reduce the time of lowering blood glucose. In [11], the parameters of Hammerstein controller were optimized in order to minimize the time that takes for blood glucose to come back to its basal level. Also there are some efforts to use model independent based controller such as fuzzy controllers. In [12], a closed-loop control system applying fuzzy logic control introduced and the performance of this controller is tested on three different diabetic patients. Maryam [13] tried to tune the PD fuzzy controller with PSO algorithm. These fuzzy controllers were just able to control the glucose concentration, and suffer from lack of insulin and pump control. The works referred in [14, 15] suggested robust controllers such as disturbance rejection LQ controller, �� and �� controller to regulate glucose-insulin system for Type I diabetic patients under meal disturbance. In this paper, four different controllers (optimal LQR, minimax optimal, sliding mode, integral sliding mode) are addressed and designed for the glucose concentration level control problem in diabetic patients under meal disturbance. 2. Mathematical Model Bergman minimal mathematical model, which is the most common referenced model in the literature, approximates the dynamic behavior of a diabetic patient’s blood glucose concentration to the insulin injection. The main advantage of using Bergman minimal model is that the number of parameters is minimum and it describes the relation between main two factors, insulin and glucose concentrations, without getting into biological complicated details. In the present work, nonlinear three-state minimal model of Bergman is considered [7]; �� ��� = −������ − �������� + �� � + ℎ��� � ��� = −�� ��� + ������ �� ��� = −������� + �� � + ���� ��⁄ …(1) Where G(t) is plasma glucose deviation, [mg/dL], X(t) is remote compartment insulin utilization, [1/min] and Y (t) is plasma insulin deviation, [mU/dL]. The control variable ���� is the exogenous insulin infusion rate (mU/min), while the disturbance ℎ ��� represents the exogenous glucose infusion rate (mg/dL min). The physical parameters ��and�� are the basal glucose level (��/��), and basal insulin level (��/��), respectively, and �� is the insulin distribution volume (��). The model parameters are: �� �1 �� ⁄ �, �� �1 �� ⁄ �, �� ��� ��� �� �⁄ �� and �� �1 �� ⁄ �. If the unmeasurable variable ��� is assumed a slow variable, then � ��� = 0. From Eq.(1), the expression ��� = ���/��� � ��� can be found. Substitution this expression into the first equation, the model of Eq.(1) is reduced to the following [13]: �� ��� = −������ − ���� ��������� + �� � + ℎ��� �� ��� = −������� + �� � + ���� ��⁄ …(2) The linearization of Eq.(2) is performed by taking the variation of ���� = �" + ∆���� and ���� =�" + ∆����around equilibrium points (�", Y0, ℎ", �"). The perturbed version of Eq.(2) is given by; ∆�� = $−�� − ���� �"% ∆���� − ��& + �� � ���� ∆���� ∆�� ��� = −�� ∆���� + ∆ ���� ��⁄ …(3) If∆���� is defined as the first state variable'����, ∆���� is set as second state variable '���� and(��� is assigned to control input variation∆����, then the previous equation can be written in the following state space form, )� ��� = *−�� − �� �"�� − ��& + �� � ����0 −�� + )��� + , 01 ��⁄ - (��� + .10/ ℎ��� …(4) 0��� = .1 00 1/ )��� Bashar Fateh Midhat Al-Khwarizmi Engineering Journal, Vol. 13, No. 3, P.P. 55- 63 (2017) 57 For control objectives, the linearization in state space of the above model is taken at the equilibrium points of the following specified values; ℎ" = 0, �" = ���� �� , �" = 0 Therefore, the obtained linearized model can be written as; '� ��� = *−�� − �� ����0 −�� + '��� + ,10 01 ��⁄ - (1 ��� 2��� = .1 00 1/ '��� + …(5) where (1 ��� = 3ℎ��� (���45. Equation(5) can be written in compact form as; '� ��� = 6 '��� + 7 (��� …(6) 2��� = 8 '��� It is easily to show that the linearized model is completely controllable. 3. Controller Design Four structures of advanced controllers will be presented and designed here for controlling the glucose level in human blood under meal disturbance. Later, the performance of such controllers will be verified and compared to each other using Matlab/Sumlink. 3.1. Sliding Mode Controller Sliding mode control is a discontinuous feedback control forces the system states to reach and remain on a specific surface within the state space (called sliding surface). The first stage of design is the selection of the discontinuity surface such that sliding motion would exhibit desired properties. Let us define a surface 9 in the state space as follows [16, 17]; 9 = '� + : '� …(7) If a controller ( was designed to make the system trajectories head to the surface 9 = 0, then Eq.(7) can be written as, '� + :'� = 0 …(8) From Eq. (5), one can find that '� � = −��'� − ��� �� ��⁄ �'� …(9) Rearranging the above equation results in '� = − �����'� + '� �� ��� ���⁄ …(10) Substituting '� from the above equation into Eq.(8) results in − �����'� + '� �� ��� ���⁄ + :'� = 0 …(11) or, '� � + ��� − : �� �� ��⁄ �'� = 0 …(12) The time solution for the equation above is written as '� = '��0�;<�=>