Discrete-time Sliding Mode Control Scheme Research Articles

Chattering-free discrete-time sliding mode control for integrated missile guidance and control system

With the development and validation of flight control devices, electronic equipment is widely used in current flight vehicles, which results in a series of control signals in the discrete-time domain. However, many mature integrated guidance and control schemes are designed in the continuous-time domain, and some results of them may not be preserved in the discrete-time domain especially for the sliding mode control. To address this issue, a chattering-free discrete-time sliding mode control scheme is proposed for the integrated guidance and control systems of missiles. By applying the Euler’s discretization method, an approximated discrete-time model with matched and mismatched disturbances is first derived for integrated guidance and control system. Then, the estimates of the disturbances are obtained by using discrete-time generalized proportion integral observers. Integrating the estimated disturbances into the sliding mode variable, a discrete-time sliding mode controller is established by utilizing a modified chattering-free reaching law. The reachability of quasi-sliding mode band, states boundedness, and output convergence performance are analyzed rigorously. Finally, comparative numerical simulations are conducted to verify the effectiveness of the proposed control scheme in the presence of unknown target maneuvers and parameter uncertainties.

Discrete-Time Sliding Mode Spatial Control of Advanced Heavy Water Reactor

This brief presents the design of a discrete-time sliding mode control (DSMC) for spatial power stabilization of advanced heavy water reactor (AHWR). Mathematical model of AHWR is represented by 90 first-order nonlinear differential equations with 18 outputs and five inputs. The linear model is obtained by linearizing nonlinear equations over the rated power. This linear model is found to be highly ill conditioned and is possessing three-time-scale property. Initially, the linear model is transformed into block diagonal form to separate slow, fast 1, and fast 2 subsystems and then DSMC is designed using slow subsystem alone since fast 1 and fast 2 subsystems are stable. The proposed DSMC strategy is designed using the constant plus proportional rate reaching law with matched disturbance. Finally, the nonlinear multivariable model of AHWR is simulated with the designed controller and the results are generated under different transients. The efficacy of the proposed DSMC is demonstrated with the comparison of prevalent controllers in the literature and the performance is evaluated under the same transient levels.

Discrete-Time Sliding Mode Control for Uncertain Networked System Subject to Time Delay

We deal with uncertain systems with networked sliding mode control, subject to time delay. To minimize the degenerative effects of the time delay, a simpler format of state predictor is proposed in the control law. Some ultimate bounded stability analyses and stabilization conditions are provided for the uncertain time delay system with proposed discrete-time sliding mode control strategy. A numerical example is presented to corroborate the analyses.

Global synchronization of uncertain chaotic systems via discrete-time sliding mode control

This paper presents a discrete-time sliding mode control scheme for a class of master–slave (or drive-response) chaotic synchronization systems. The proposed scheme guarantees the stability of closed-loop system and achieves the global synchronization between the master and slave systems. The structure of slave system is simple and needs not be identical to the master system. Moreover, the selection of switching surface and the existence of sliding mode have been addressed. Numerical simulations are given to validate the proposed synchronization approach.

Enhanced discrete‐time sliding mode strategy with application to piezoelectric actuator control

This study presents a new discrete-time sliding mode control (DSMC) scheme with applications to precise motion control of piezoelectric actuators. Different from existing DSMC algorithms whose implementations rely on the construction of state observers for providing the state feedback, a simple yet effective DSMC strategy is developed based on a discrete-time model without using the state observer. Hence, one distinctive feature of the proposed DSMC lies in that it is very easy to implement. Only a second-order plant model is needed whereas the modelling of piezoelectric non-linearities is not required, which further simplifies the practical implementation process. The local stability of the closed-loop system is proved in theory and the effectiveness of the DSMC is demonstrated by several experimental studies. Results show that the DSMC strategy is superior to proportional-integral-derivative control in terms of transient response speed, positioning accuracy and robustness against external disturbances. The reported method can be extended for precise motion control of other second-order systems as well.

Output-based discrete-time sliding mode control for a piezoelectrically actuated system

This paper presents a new scheme of discrete-time sliding mode control (DSMC) dedicated to precision positioning control of a piezoelectrically actuated system. Traditionally, a hysteresis model is required to compensate for the piezoelectric nonlinearity and a state observer is needed to implement the DSMC, which renders a time-consuming procedure. The proposed output-based DSMC scheme allows the relief of these computational burdens. Specifically, the piezoelectric nonlinearity is considered as a lumped perturbation term which is predicted by a perturbation estimation technique. The elimination of state observer is realized by establishing a control scheme based on the system output only. In addition, the stability of the control system is proved in theory. The effectiveness of the reported scheme is validated on a prototype piezoelectric actuation system by carrying out several experimental investigations.

A novel reaching law approach of quasi-sliding-mode control for uncertain discrete-time systems

A novel discrete-time reaching law was proposed for uncertain discrete-time system, which contained process noise and measurement noise. The proposed method reserves all the advantages of discrete-time reaching law, which not only decreases the band width of sliding mode and strengthens the system robustness, but also improves the dynamic performance and stability capability of the system. Moreover, a discrete-time sliding mode control strategy based on Kalman filter method was designed, and Kalman filter was employed to eliminate the influence of system noise. Simulation results show that there is no chattering phenomenon in the output of controller and the state variables of controlled system, and the proposed algorithm is also feasible and has strong robustness to external disturbances.

Robust discrete-time sliding mode control for multi-input uncertain time-delay systems

A robust discrete-time sliding mode control scheme is proposed for a class of linear multi-input uncertain systems with state delays. Systems are assumed to have structured mismatched time-varying parameter uncertainties and unknown bounded nonlinear function. A novel integral sliding surface is introduced to eliminate the reaching phase and a sliding mode controller is derived to ensure existence of the quasi-sliding mode. Based on an improved Lyapunov function and the linear matrix inequality technique, a sufficient condition for existence of a stable sliding surface is given and stability of the overall closed-loop system is guaranteed. The chattering phenomenon is eliminated and knowledge of the upper bound of external disturbances is not required. Both theoretical analysis and illustrative examples demonstrate the validity of the proposed scheme.

불확실성을 포함한 차량 조향장치의 강인 이산시간 슬라이딩 모드 제어

This paper deals with the design of robust DSMC (Discrete-Time Sliding Mode Control) scheme in order to overcome system uncertainty in steering system with mechanically joined structure. The proposed control scheme is one of robust control schemes based on system dynamics. Therefore, system dynamics required is not obtained from physical law but SCM (Signal Compression Method) through experiment in order to avoid complicate mathematical development and save time. However, SCM has a shortcoming that is the limitation of with <TEX>$2^{nd}$</TEX> order linear model which does not include the dynamic of high-frequency band. Thus, considering system uncertainty, DSMC is designed. In addition, to reduce the chattering problem of DSMC, DSMC is derived from the reaching law and the Lyapunov stability condition. It is found that the proposed control scheme has robustness in spite of the perturbation of system uncertainty through computer simulation.

Discrete-time Sliding Mode Direct Power Control For Threephase Rectifiers

&#x0D; In this paper a new discrete-time sliding mode control scheme for three-phase PWM rectifiers is proposed. Active and reactive powers are directly controlled using a virtual-flux oriented reference frame. Robustness of the proposed methodology under inductance variation is shown. Simulation results of a rectifier connected to a large power system are presented to compare the proposed strategy and the voltage oriented control scheme. Experimental results also show the better performance of the proposed scheme.&#x0D;

Robust motion control of a clamp-cylinder for energy-saving injection moulding machines

This paper deals with the issue of robust motion control of a clamp-cylinder for injection moulding machines driven by a pair of speed-controlled fixed displacement pumps. As a fundamental step prior to tracking controller design, a feedback control system is suggested by implementing a position control loop in parallel with a system pressure control loop. A discrete-time sliding mode control scheme is developed for enhancing the tracking performance under inherent nonlinearities. Consequently, a significant reduction in tracking error is achieved for both position and pressure control applications.

Multirate output feedback discrete-time sliding mode control for a prescribed sliding sector

This paper presents an output feedback based discrete-time sliding mode control strategy using the concept of a PdRd sliding sector. The resulting control is based on the system output and immediate past control input and is independent of the system states. It ensures that the norm of the system states decreases monotonically and continue to do so even with a zero input inside the designed sliding sector.

Discrete-Time Sliding Mode Controller Design with Weak Pseudo Sliding Condition

In this paper, a discrete-time sliding mode control law is developed to guarantee the existence of the weak pseudo sliding mode along the prescribed hyperplane. Meanwhile, the upper bound of the sampling period is also determined in order to ensure the stability of the controlled system. Finally, some simulation results are given to illustrate the performance of the proposed discrete-time sliding mode control scheme.

A DSP-based variable AC power source

This paper presents the development of a single-phase AC power source. The power source described is capable of providing a stable AC voltage with variable amplitude and variable frequency over a wide range. Moreover, it can generate various high-quality low-frequency arbitrary waveforms. This is achieved by applying advanced digital control techniques to perform closed-loop control of the single-phase inverter used in the circuit. In this system, a high-performance digital signal processor has been used to realize the discrete-time sliding-mode control strategy. This leads to a system that is robust with respect to system parameter variations and external disturbances. Consequently, high-quality output waveforms can be maintained despite dynamic loading conditions. Some experimental results are demonstrated.