Ashoke Sutradhar

Nonparametric modeling of glucose-insulin process in IDDM patient using Hammerstein-Wiener model

This paper deals with an identification problem of modeling a nonlinear dynamic system of multivariable glucose-insulin process in an IDDM patient. Out of many model structures that can represent a nonlinear process effectively; the Hammerstein-Wiener model has attracted a lot of attention. The present work proposes a generalized identification method of Hammer stein-Wiener model from the input-output data of multivariable nonlinear glucose-insulin process. The present algorithm consists of a three-block (LNL) realization. For the multivariable system, the first and third blocks are standard impulse response filter (TRF) realization applied to an equivalent linear system using adaptive recursive least square (ARLS) algorithms. In the second block, i.e. the nonlinear part, ARLS algorithms have been used to solve up to second order kernels of Volterra equations with extended input vector consisting of cross components as well. The input-output data taken from the simulated nonlinear process have been used to identify the system with a filter memory length of M=3 and the validation results have shown good fit and in concordance with predicted output.

Frequency domain hammerstein model of glucose-insulin process in IDDM patient

This paper deals with a frequency domain kernel estimation problem for modeling a nonlinear dynamic system of multivariable glucose-insulin process in an insulin dependent diabetes mellitus (IDDM) patient. For such a process with uncertainties and parameter variations, the nonparametric models are most useful for closed loop model predictive control. The present work proposes a frequency domain kernel estimation of a Hammerstein model using the harmonic excitation input by taking FFT on the input data sequence from the glucose-insulin process of IDDM patient model. For the multivariable system, the first block is a two-input single output nonlinear block followed by a SISO linear filter. The adaptive recursive least square (ARLS) algorithm is used to solve up to second order kernels of Volterra equations with extended input vector consisting of self and cross components. Twice the length of the extended input vector for the MISO system was considered for finding the kernels and the output in frequency domain. The input-output data taken from the first principle model of nonlinear process, have been used to identify the system with a short filter memory length of M=2 and the validation results have shown good fit both in frequency and time domain responses.

Blood glucose regulation in IDDM patient by H ∞ control: An LMI approach

This paper addresses the design of output feedback h-infinity controller to deliver insulin via an implantable micro-insulin dispenser for insulin-dependent diabetes mellitus (IDDM) patients. The concept of Linear Matrix Inequality (LMI) has been used for the design of the h-infinity controller. For synthesis of the controller, a 9th order linear state-space model of the multivariable nonlinear dynamic glucose-insulin process of the IDDM patient has been used. The performance of the resulting controller was tested on the nonlinear model of the process in simulation platform with necessary implants of the insulin pump and glucose sensor. The controller performance was assessed in terms of its ability to track a normoglycemic set point of 81mg/dl in presence of thrice daily meal disturbance and once daily exercise disturbance with other stochastic noises. The designed controller gives robust performance with good noise rejection.

Estimation of tire-road friction coefficient and frictional force for Active Vehicle safety system

An increasing number of accidents of Vehicles has led to the study and design of Active safety systems in modern automobiles. For the purpose, a number of sensors for the measurement of Vehicle yaw, wheel velocities and acceleration are deployed. However, some key parameters like slip angle and frictional forces are hard to be determined using sensors and also cost prohibitive. Estimation of friction coefficient and frictional forces has been of wide importance for the design of Active safety systems as the information is required for the design of efficient control system. Besides, the system being highly nonlinear in nature, linearized estimation technique may lead to high approximation errors. This paper presents an unscented Kalman Filter based estimation algorithm for a specific nonlinear tire model for the estimation of friction coefficient and lateral and longitudinal frictional forces.

Evolutionary Smith Predictor for Control of Time-Delay Systems

The paper presents smith predictor scheme for the control of systems having dead time or time delay. The control algorithm has improved the smith predictor scheme of Liu et al. for reference inputs in proximity with load disturbances. Grey Wolf Optimization technique has been used for tuning the parameters of the controller and disturbance estimator for the discussed plant. Comparisons had been made on the tuning capability of different optimization algorithms for estimating the controller and estimator coefficients (disturbance estimator plus setpoint tracking controller). Simulation of two plants are included to show the effectiveness of the proposed technique

Two-stage adaptive sliding-mode controller for vehicle yaw stability using differential ABS

With increasing number of on-road transportation vehicles, the demand for passenger safety and comfort is inevitable. This inspired to develop technologically sophisticated automobiles with active safety systems that provide improved vehicle handling during critical driving situations. Yaw stability controller prevents the vehicle from spinning and drifting-out under loss of traction during a turning maneuver. This paper presents a controller design based on sliding mode principle with two-stage sliding surfaces considering yaw rate and body sideslip angle errors as primary and secondary surfaces respectively. A simplified model of the vehicle during a turning (Slalom + DLC) maneuver is been considered and the dynamic equations of the desired states were summed up and used to design the sliding surface. Computer simulations have been conducted to verify the proposed approach, with results indicating its effectiveness and robustness for yaw stability control.

Design and realization of a multi-objective controller for a MIMO coupled tank system

This paper presents a design of multi-objective controller for a two input two output interacting Coupled Tank System (CTS) and its real time implementation. The multi-objective control has been achieved by satisfying time domain objective like pole placement and frequency domain objective like H-infinity condition. This multi-objective control has been formulated using Linear Matrix Inequality (LMI) criteria and solved as a convex optimization problem. The multi-objective controller gain thus computed has been implemented in real time dSPACE hardware platform with a laboratory scale process. The resulting controller yields improved performance of the closed loop system for reference tracking with robustness in presence of parameter variation and various uncertainties.

Estimation of tire slip-angles for vehicle stability control using Kalman filtering approach

The increasing number of accidents worldwide has motivated the need to develop technologically sophisticated automobiles that provide improved vehicle handling, stability, comfort, fuel efficiency and safety. In automotive industry, current focus is on the development of active safety systems, which assist the driver in order to avoid critical situations. But, some key states which are valuable for the vehicle dynamics control system are not measurable or cost prohibitive. Hence, the states are to be estimated. This paper presents the estimation of tire slip-angles, which are among the essential states. A simplified model of the vehicle has been considered during a turning maneuver. Then, the interdependency of lateral and longitudinal velocities w.r.t yaw rate is depicted. Later, the longitudinal velocity is subsequently used for slip angle estimation for the front and the rear wheels using linear Kalman filter approach. Computer simulation have been conducted to verify the proposed approach with results indicating that the proposed approach is very effective and robust in estimating tire slip-angles of a vehicle.

Mystery of potentised substances: Some significant attempts to unveil it

Going by naive dilution concept, Avogadro Number puts 12th as the potency-limit (in the centesimal scale) beyond which a homoeopathic medicine cannot even theoretically contain any atom/molecule of the original substance with which potentisation starts. Continuing further, a single molecule of the original substance can be ensured in a 30th potency medicine by taking a medicinal mass of several thousand Suns!!! And that is impossible. Still, they are effective (and often better) curative agents. What is the secret of their medicinal value? — This is the standing challenge for more than two centuries. Several noteworthy attempts have been made to meet this challenge. Right now we may be on the verge of a solution. This paper is an attempt to address this issue.