• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1120-1124
• /
• 2005

We reviewed controllers with a time delay estimation in this paper. Time delay control (TDC) and sliding mode control (SMC) are well known robust control schemes. Basically, the TDC has a main characteristic called a time delay estimation from which we can estimate the total uncertainty of a system. . The TDC causes the stick-slip in the case of systems with a friction. The so-called TDCSA which are short for TDC with switching action was developed to reduce the stick-slip. The TDC has the additional switching action term in the TDC structure. In the other hand, the SMC dose not have a time delay estimation but instead it can estimate the system uncertainty through the switching action. The SMC has a difficulty to estimate the total uncertainty of a system because it does not have a time delay estimation. In order to solve the difficulty, some control schemes were developed. Among them, we need to focus our attention on two control schemes: SMCPE and SMCTE, which are short for sliding mode control with a perturbation estimation and sliding mode control with a time delay estimation, respectively. In this paper, we analyzed and compared the characteristic of above three controllers. Even though the motives for the development of three control schemes are different, three control schemes have much in common in terms of their controller structures.

• Journal of the Korea Society of Computer and Information
• /
• v.20 no.11
• /
• pp.39-46
• /
• 2015

In this paper, we propose a performance-aware workload model for efficient implementation of control systems. When implementing a control algorithm as an embedded computer system, the control code executes periodically. For such systems, its control performance depends on not only the accuracy of the control algorithm itself but also temporal parameters such as control period and sensing to actuation delay. In this regard, this paper studies the relation between control period and delay by measuring and analyzing the control performance of LKAS (Lane Keeping Assist System) with varying period and delay combinations. Through this experimental study, this paper shows that the two timing parameters, i.e.,control period and delay, has a tradeoff relation in terms of control performance.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.68.1-68
• /
• 2001

This paper discusses tracking position control of linear actuator that has a time delay. The time delay happens when the process reads the sensor data and sends the control input to the plant located at a remote site in distributed control system. In this thesis, the time delay between the linear actuator and the discrete PID controller has constant value due to buffer device so the time delay can be modeled by Pade approximation but the large position error of the linear actuator is generated by the time delay. Therefore, the Smith predictor is used for tracking position control of the linear actuator with the time delay in order to minimize the effect of the time delay. The experimental and simulation results show that the ...

• Structural Engineering and Mechanics
• /
• v.20 no.2
• /
• pp.191-207
• /
• 2005

Time delay exists inevitably in active control, which may not only degrade the system performance but also render instability to the dynamic system. In this paper, a novel active controller is developed to solve the time delay problem in flexible structures. By using the independent modal space control method, the differential equation of the controlled mode with time delay is obtained from the time-delay system dynamics. Then it is discretized and changed into a first-order difference equation without any explicit time delay by augmenting the state variables. The modal controller is derived based on the augmented system using the discrete variable structure control method. The switching surface is determined by minimizing a discrete quadratic performance index. The modal coordinate is extracted from sensor measurements and the actuator control force is converted from the modal one. Since the time delay is explicitly included throughout the entire controller design without any approximation, the system performance and stability are guaranteed. Numerical simulations show that the proposed controller is feasible and effective in active vibration control of dynamic systems with time delay. If the time delay is not explicitly included in the controller design, instability may occur.

• Transactions on Control, Automation and Systems Engineering
• /
• v.4 no.2
• /
• pp.140-146
• /
• 2002

We consider a class of large-scale interconnected time delay systems and investigate a decentralized robust passive control problem. sufficient conditions for unforced interconnected uncertain systems with time delay to be robustly stable with extended strictly passivity is given in terms of algebraic Riccati inequality and linear matrix inequality. The decentralized robust passive control problem for norm-bounded and positive real uncertainty is shown to be converted to extended strictly positive real control problem for a modified system which contains neither time delay nor uncertainty.

• International journal of advanced smart convergence
• /
• v.5 no.1
• /
• pp.34-46
• /
• 2016

Networked Control System (NCS) has evolved in the past decade through the advances in communication technology. The problems involved in NCS are broadly classified into two categories namely network issues due to network and control performance due to system network. The network problems are related to bandwidth allocation, scheduling and network security, and the control problems deal with stability analysis and delay compensation. Various delays with variable length occur due to sharing a common network medium. Though most delays are very less and mostly neglected, the network induced delay is significant. It occurs when sensors, actuators, and controllers exchange data packet across the communication network. Networked induced delay arises from sensor to controller and controller to actuator. This paper presents an adaptive delay compensation process for efficient control. Though Smith predictor has been commonly used as dead time compensators, it is not adaptive to match with the stochastic behavior of network characteristics. Time delay adaptive compensation gives an effective control to solve dead time, and creates a virtual environment using the plant model and computed delay which is used to compensate the effect of delay. This approach is simulated using TrueTime simulator that is a Matlab Simulink based simulator facilitates co-simulation of controller task execution in real-time kernels, network transmissions and continuous plant dynamics for NCS. The simulation result is analyzed, and it is confirmed that this control provides good performance.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.270-270
• /
• 2000

Input delay is frequently encountered in the practical systems since measurement delay and computational delay can be represented by input delay. In this viewpoint, this paper deals with the robust control problem of input delayed systems with structured uncertainty. Robust stability conditions are provided in terms of linear matrix inequalities(LMIs) and it is shown that the proposed conditions can give less conservative maximum bound of input delay guaranteeing robust stability.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1136-1141
• /
• 2004

This paper presents a control method for time-delay systems and verifies the performance of the designed control system via real experiments. Specifically, the control method is applied to a flexible-link system with time delays. The method combines time- and frequency-domain controllers: linear quadratic optimal controller (or LQR) and lag compensator. The LQR is used to stabilize the system in optimal fashion, whereas the lag compensator is used to compensate time-delay effects by increasing the delay margin of the system. With this methodology, the maximum allowable time delay can be increased significantly. The proposed method is simple but quite practical for time-delay system control as it is based on the conventional loop-shaping method, which gives practical insights on delay-phase relationship. Simulation and experiment results show that the method presented in this paper is feasible and practical.

• Journal of Institute of Control, Robotics and Systems
• /
• v.9 no.12
• /
• pp.1001-1008
• /
• 2003

A time-delay compensation method for vector control system is proposed that can compensate for voltage and current distortions resulting from a time delay in the overall system due to the low pass filter, hysteresis control inverter, microprocessor program computation time, and so on. The proposed scheme estimates the time delay using the difference between the Q-axis stator current command and the time-delayed actual Q-axis stator current in a synchronous reference frame, then compensates the time delay in the voltage and current using the angular displacement of a DQ transformation. Accordingly, the proposed scheme can accurately compensate for the time delay related to the overall system, thereby significantly improving the performance of the vector control system, as verified by simulation and experiment.

• Proceedings of the KIEE Conference
• /
• 2004.11c
• /
• pp.82-85
• /
• 2004

This paper proposes the development of delay compensator to minimize performance degradation caused by time delays in network-based real-time control systems. The delay compensator uses the time-stamp method as a direct delay measuring method to measure time delays generated between network nodes. The delay compensator predicts the network time delays of next period in the views point of time delays and minimizes performance degradation from network through considering predicted time delays. Control output considering network time delays is generated by the defuzzification of probable time delays of next period. The time delays considered in the delay compensator are modeled by using a timed Petri net model. The proposed delay prediction mechanism for the delay compensator is evaluated through some simulation tests by measuring deviation of the predicted delays from simulated delays.