Tolgay Kara

Experimental nonlinear identification of a two mass system

The paper presents nonlinear modeling and on-line identification of a two mass mechanical system driven by a DC motor together with real-time experiments made. The paper also describes how to obtain a simpler identification routine for the nonlinear systems. Linear and nonlinear models for the system are obtained for identification purposes and the major nonlinearities in the system such as the Coulomb friction and the dead-zone are investigated and integrated in the nonlinear model. Hammerstein nonlinear system approach is used for the identification of the nonlinear system model. On-line identification of the linear and nonlinear system models is performed using the Recursive Least Squares (RLS) method. Results of the real-time experiments are graphically and numerically presented, and advantages of the nonlinear identification approach are definitely revealed.

Operation and control of a water supply system.

The control of water supply systems is becoming more important, since there are increasing requirements to improve operation. A need exists to model and simulate water supply systems so that their behavior can be fully understood and the total process optimized. This paper describes the simulation and control of a water supply system consisting of a sequence of pumping stations that deliver water through pipelines to intermediate storage reservoirs. The system is represented by dominant system variables that represent active and passive dynamical elements. The hydraulic models include the nonlinear coupling between flow rates and reservoir heads. The bisection numerical solution approach is used to obtain a roughness dependent friction coefficient. The whole system is simulated and the results are presented and compared with the real-time measured data. A water level controller using the robust polynomial H(infinity) optimization method by manipulating pump speed is obtained. The stochastic nature of the disturbance and loads is considered for controller design. The parametrized dynamic weighting functions of the design theory are selected to achieve the required control functions and robustness.

Operation and simulation of city of Gaziantep water supply system in Turkey

Water supply systems are becoming more important, since there are increasing requirements to improve operation whilst improving the environment so that their behaviour can be fully understood and the total process is optimised. This paper presents simulation and control of water supply system of Gaziantep city in Turkey for management purposes. The main objectives are to ensure the behaviour of a water supply system and to regulate the water flow and heads by manipulating the water pumps. The system consists of a sequence of pumping stations that deliver water through pipelines to intermediate storage reservoirs. The model used is obtained using dominant system variables that represent active and passive dynamical elements. The hydraulic models also include the nonlinear coupling between flows and reservoir heads. The polynomial H∞ optimisation method is used to design a level controller that regulates water flow and heads through the system. The whole system is simulated, and the results are presented and compared with the real-time measured data.

Experimental and model-assisted investigation of activities in a water supply system

This paper presents experimental and model-assisted investigation of activities in a water supply system to manage water transfer using some experiments that are performed on the real system, and simulations obtained from a nonlinear model of the system. The physical system consists of a sequence of pumping stations that deliver water through pipelines to intermediate storage reservoirs. The nonlinear model is obtained using dominant system variables that represent active and passive dynamical elements. The hydraulic models include nonlinear coupling between flow rates and reservoir heads. Validation of the nonlinear model is accomplished through comparing with system observations and using data validation and face validity approaches. The results demonstrate the dynamical behaviour of the system regarding flow stability, water heads in the reservoirs, head losses and measure of the friction at different sections of the water supply system.

Adaptive approximate input–output linearizing control with applications to ball and beam mechanism

This paper presents the design and implementation of adaptive control with approximate input–output linearization for underactuated open-loop unstable non-linear mechanical systems. Control of a ball and beam (BB) mechanism is selected as a benchmark problem for testing the designed control. The method of input–output linearization is reviewed and an adaptive input–output linearizing control design procedure is given. An approximate BB model is developed using Euler–Lagrange equations, and input–output linearization-based adaptive tracking control is designed for the system. The model is parameterized with respect to ball mass for adaptive tracking, and the proposed control structure is tested via computer simulations and experiments. The results present the tracking performance of designed control for various ball masses, and reveal the proposed method’s capability to cover ball mass variations over non-adaptive control. The proposed control exhibits improved error performance in the presence of parametric variations in the plant. Results of the BB control case reveal successful control of underactuated non-linear mechanisms when a system parameter is unknown or time varying.

State Feedback Switching Control of an Underactuated Planar Manipulator with Partial Feedback Linearization

In this paper, position control problem of a two-degree-of-freedom underactuated manipulator is considered and a state feedback control structure with energy-based switching is proposed. The mechanism has two revolute joints that move the two links on horizontal plane. Difficulties in system control arise with the fact that the manipulator has less control input signals than system degrees of freedom, and has complex nonholonomic structure. Furthermore, in horizontal operational conditions, position control of the system is a challenging work since free joint is not affected by the gravity. The system has only one actuator at the shoulder joint and the elbow joint is completely free. Therefore, the system cannot be stabilized around any equilibrium point by a linear state feedback control method. In this study, a control system that utilizes two stabilizing state feedback controllers and an energy-based supervisory switching mechanism is proposed. Stabilizing controllers are obtained utilizing the partial feedback linearization method. Proposed control is tested by computer simulations. First the open-loop plant dynamic model is obtained by Euler-Lagrange formulation and state-space modeling approach. Then, a simulation model of the system in closed loop with proposed control scheme is developed using the dynamic model and control law. Simulation tests are performed with respect to three different initial conditions. Performance of the control system is observed and revealed via simulations.

Inverse kinematics solution for robotic manipulators based on fuzzy logic and PD control

This paper presents a new general and fast scheme for solving the inverse kinematics problem (IKP) of the multilink robot arm. The proposed strategy is general as in it is independent of the geometry of the robot arm or its number of degrees of freedom (DOF) and only the forward kinematics is required. The proposed method is a closed-loop strategy in which the IKP is restated as a control problem for a dynamic system and the objective is providing a good trajectory tracking performance. Therefore, PD-like fuzzy controller is used as the controller for this system. Different Cartesian trajectories with different configurations of robotic arm are simulated to demonstrate the effectiveness and generality of the proposed method.

Experimental nonlinear identification of a three-mass system rotating in two directions

Diagram of the experimental set-up is shown in Figure 1. Two signal generators are used to provide test signal to the motor. The generators produce sinusoids of different amplitudes and frequencies, which are summed up to constitute a persistently exciting signal for the identification process. The signals are carefully adjusted to provide very low speed operation, which is essential for the examination of the system nonlinearities. The measured input-output data are transferred to the computer (Pentiwn III 700 MHz in speed with a memory of256 MB RAM) by a data acquisition card (ADVANTECH PCL-1800, 330 kHz in speecL 12 bit high-speed AID converter with a conversion time of 2.5IlSec). The data acquisition card permits use of user defined programs interfaced with Mat/ab. The output speed is obtained from the tacho-generator. The output shaft speed is also measured from an optical sensor as rev/s that is connected to the motor shaft. The slotted opto-sensor consists of a gallium-arsenide infrared L.E.D. and silicon phototransistor mounted in a special plastic case, which is transparent to light of the wavelength. A series of pulses is generated when the slotted disk, that is mounted on the motor shaft, is rotated. The permanent-magnet DC Total load ~:~:a~~r~