Browsing by Subject "Time Delay Systems"

Now showing 1 - 6 of 6

Open Access
An anti-windup compensator for systems with time delay and integral action
(2017-08) Öztürk, Dilan
Being one of the most popular saturation compensator methods, anti-windup mechanism is commonly used in various control applications. The problems arising from the system nonlinearities are prone to change the behaviors of the system adversely in time such as performance degradation or instability. Anti-windup schemes including internal model structure with the robust compensator are crucial in terms of preserving the system stability and minimizing the tracking error when controller operates at the limits of the actuator. Saturation problem is further aggravated by the dead-time that appears frequently in the systems depending on processing of sensed signals or transferring control signals to plants. Smith predictor based controllers are e cient in the compensation of time delay, indeed the controller is designed by eliminating the delay element from the characteristic equation of the closed-loop system. We apply Smith predictor based controller design for the system incorporating time delay and integral action to achieve high performance sinusoidal tracking. This study extends an anti-windup scheme via Smith predictor based controller approach by redesigning the transfer functions within the anti-windup structure. We present simulation studies on the plant transfer function including time delay and integrator to illustrate that our extended structure successfully accomplish accurate tracking under the saturation nonlinearity.
Open Access
Design of first order controllers for a flexible robot arm with time delay
(2016-06) Kuralay, Gökçe
In an earlier work, Gündeş et al. (2007), stabilizing PID controllers for a class of unstable plants with time delays (I/O delays) are obtained. By utilizing this approach and methods given in Özbay and Gündeş (2007, 2014) we aim to investigate appropriate PI, PD and PID controllers by finding the maximum allowable boundaries for each controller parameter. A model of a flexible robot arm which includes a time delay and an integrator is considered as an application example. It is aimed to find the optimal coefficients for the derivative and integral gains such that the designs achieve a set of performance and robustness objectives. Stability and robustness properties of the closed-loop system are also investigated. Specifically, for PD controller design, optimal derivative action gain is determined under various performance objectives. For PI controller design, optimal P (proportional) and D (derivative) gains are determined to achieve the least fragile integral action gain. Moreover, system performance is compared with other PID designs considering different types of control objectives.
Open Access
H (formula) based filtering for systems with time delays and application to vehicle tracking
(2007) Ezercan, Mehmet Sami
In this thesis, the filtering problem for linear systems with time delay is studied. The standard mixed sensitivity problem is investigated and the duality between H∞ control problem and H∞ filtering problem is established. By using this duality an alternative H∞ filtering method is proposed. An optimum H∞ filter is designed for single output system. However the proposed technique does not only work for single delay in the measurement but also works for multiple delays in both state and measurement if the linear system has more than one outputs with delay. For this case, different suboptimal filters are designed. This work also deals with an important aspect of tracking problems appearing in many different applications, namely state estimation under delayed and noisy measurements. A typical vehicle model is chosen to estimate the delayed state and the performances of the designed filters are examined under several scenarios based on different parameters such as amount of delays and disturbances.
Open Access
H∞ Filter based target tracking under time delayed measurements
(2015-09) Ateş, Ezgi
In this thesis target traking problem for time delayed linear systems is studied. The standard mixed sensitivity problem is considered with time delayed continuous time processes. Using the duality between control and ltering methods, the H∞ control problem is converted to H∞ filtering problem and a new H∞ optimal filtering approach is proposed. To investigate state estimation for target tracking, a typi cal vehicle model moving in 1-D is used but the proposed method can be expanded for movements in 3-D. Delay in both process and measurement is considered. The estimation of the states and their performances are analyzed under different scenarios including change in delay, input pattern, noise parameters etc.The results obtained by proposed H∞ optimal filtering are compared with the results obtained by H2 filter and simulation results are shown.
Open Access
Observer based friction cancellation in mechanical systems
(2014) Odabaş, Caner
In real life feedback control applications of mechanical systems, friction and time delays are two important issues that might have direct effects on the performance of systems. Hence, an adaptive nonlinear observer based friction compensation for a special time delayed system is presented in this thesis. Considering existing delay, an available Coulomb observer is modified and closed loop system is formed by using a Smith predictor based controller as if the process is delay free. Implemented hierarchical feedback system structure provides two-degree of freedom and controls both velocity and position separately. For this purpose, controller parametrization method is used to extend Smith predictor structure to the position control loop for different types of inputs and disturbance attenuation. Simulation results demonstrate that without requiring much information about friction force, the method can significantly improve the performance of a control system in which it is applied.
Open Access
Smith predictor based controller design for a flexible robot arm
(2013) Taşdelen, Uğur
In this thesis, a new Smith predictor based controller is proposed for a flexible robot arm. A typical robot arm model includes high order modes with integral action from torque input to velocity output. Here we can also consider the effect of possible delays between the plant and the controller. The controller structure considered has an extended Smith predictor form. The designs use controller parametrization for stability and they also achieve certain performance objectives via interpolation conditions based on the disturbance rejection and setpoint tracking properties. This parametrization method allows widest freedom in controller parameters and this results in improved performance, both in set-point response and disturbance rejection. Free parameters in the controller determines the location of closed-loop poles. A hierarchical structure is used to extend Smith predictor structure to the position control loop. By protecting proposed structure, different approaches are shown to control the position. Compared to existing Smith predictor based designs, disturbance attenuation property with respect to periodic disturbances at a known frequency is improved. A two-degree of freedom controller structure is shown to be helpful in shaping the transient response under constant reference inputs. Stability robustness properties of this system are also investigated. Simulation results demonstrate the effectiveness of the proposed controller.