Li Qiu

Network-Based Robust

This paper focuses on the robust output feedback ℋ₂/ℋ_∞ control issue for a class of discrete-time networked control systems with uncertain parameters and external disturbance. Sensor-to-controller and controller-to-actuator packet dropouts and time delays are considered simultaneously. According to the stochastic characteristic of the packet dropouts and time delays, a model based on a Markov jump system framework is proposed to randomly compensate for the adverse effect of the two-channel packet dropouts and time delays. To analyze the robust stability of the resulting closed-loop system, a Lyapunov function is proposed, based on which sufficient conditions for the existence of the ℋ₂/ℋ_∞ controller are derived in terms of linear matrix inequalities, ensuring robust stochastic stability as well as the prescribed ℋ₂ and ℋ_∞ performance. Finally, an angular positioning system is exploited to demonstrate the effectiveness and applicability of the proposed design strategy.

\mathscr {H}_{2}/\mathscr {H}_\infty

This study focuses on the output feedback guaranteed cost control issue for networked control systems with random packet dropouts and time delays. The plant considered in this study is characterized by an uncertain linear discrete-time system, wherein random packet dropouts and time delays exist in forward controller-to-actuator and feedback sensor-to-controller communication links that are modeled as unified multiple Markov chains. The resulting closed-loop system is modeled as a Markovian jump linear system. The guaranteed cost control issue is solved via Lyapunov stability theory and the linear matrix inequality approach. The design of the mode-independent robust output feedback controller is derived under the Markov jump unified framework. The closed-loop system is not only stochastically stable but it also guarantees an adequate level of performance. A simulation example illustrates the effectiveness of the proposed method.

Control for Linear Systems With Two-Channel Random Packet Dropouts and Time Delays

The coordinated tracking control for the group motion control system based on three direct-drive double-sided linear switched reluctance motors (LSRMs) is investigated in this paper. The system construction for the proposed coordinated tracking system is elaborated, including the unit system and group system design, communication configuration among unit systems, and stability and performance analysis of the group system. The coordinated control performance is concentrated on three identical LSRMs with different communication topologies. Experimental results demonstrate that necessary bidirectional interactions between the unit systems contribute to the coordination performance. The maximum dynamic tracking error within ±0.4 mm can be achieved under the sinusoidal reference of 30-mm amplitude and 0.2-Hz frequency.

Output Feedback Guaranteed Cost Control for Networked Control Systems With Random Packet Dropouts and Time Delays in Forward and Feedback Communication Links

This paper investigates the collaborative tracking control for dual linear switched reluctance machines (LSRMs) over a communication network with random time delays. Considering the spatio-temporal constraint relationship of the dual LSRMs in complex industrial processes, the collaborative tracking control scheme is proposed based on the networked motion control method. The stability conditions and the controller design method for the networked dual LSRMs are obtained from the two motors relative position error by using Lyapunov theory and delay systems approach. Four different allocation schemes combined with two kinds of external control signals are applied onto the collaborative tracking control experiment platform of the dual LSRMs to validate the effectiveness of the proposed method. The maximum steady-state relative position error within 0.104 mm can be achieved under the constant absolute position reference input signal of 3 mm, and the maximum absolute relative position error within ±0.46 mm can be achieved under the sinusoidal reference of 8 mm amplitude and 0.2 Hz.

Distributed Coordinated Motion Tracking of the Linear Switched Reluctance Machine-Based Group Control System

This paper investigates the robust control method for networked dynamic systems and its application for a direct-drive linear motion control system in a network environment. The unavoidable network-induced random delays are modeled as Markov chains. The control object of the linear motion control system in this study is a double-sided linear switched reluctance machine (DLSRM). To tackle the inherent uncertainties in the DLSRM, a robust control strategy is designed by proposing a new Lyapunov function and applying the free-weighting matrix technique. A state feedback robust controller is designed such that the closed-loop direct-drive linear motion control system over a network is stochastically robust stable. The robust controller can be conveniently obtained by solving a set of linear matrix inequalities. The numerical simulation of an angular positioning system is presented to illustrate the effectiveness of the proposed robust control method. Furthermore, the experimental tests on the networked direct-drive linear motion control system verify the practicability of the proposed method.

Collaborative Tracking Control of Dual Linear Switched Reluctance Machines Over Communication Network With Time Delays

This study addresses the robust stability problem of Markovian jump time-delay systems with mixed H2 and H∞ control and uncertain transition probabilities in the discrete-time domain. The transition probabilities are considered to be uncertain but bounded. By proposing a new Lyapunov functional and applying the free-weighting matrix technique, we design the mode-dependent mixed H2/H∞ controller such that the resultant closed-loop systems possess stochastic stability and are prescribed with H∞ performance indices. These results generalize several results reported in previous literature, which consider the Markovian transition probabilities to be known a priori or partially unknown transition probabilities. Numerical examples and a practical motion control system are presented to illustrate the effectiveness of this technique.

Robust control for a networked direct-drive linear motion control system

This paper focuses on the H∞ state feedback control method for networked control systems and its application to the discrete-time direct-drive linear motion control system over a communication network with external disturbances and network-induced random time delay. The unavoidable network-induced random delay is modeled by a Markov chain with the uncertain transition probability. In this paper, the experimental linear motion control system is a double-sided linear switched reluctance machine (DLSRM). To tackle the external disturbances in the DLSRM, an H∞ control strategy is designed by using Lyapunov stability theory and linear matrix inequalities technique. A mode-dependent state feedback H∞ controller is designed for the closed-loop discrete-time direct-drive linear motion control system over a network to achieve a high-precision position control performance with antidisturbance capability. The experimental tests on the networked DLSRM system are presented to verify the effectiveness and practicability of the proposed H∞ control method for industrial applications of networked control systems.

Mixed H2/H∞ control of markovian jump time-delay systems with uncertain transition probabilities

This paper investigates a distributed, coordinated motion control network based on multiple direct-drive, linear switched reluctance machines (LSRMs). A hierarchical, two-level synchronization control strategy is proposed for the four LSRMs based motion control network. The high-level, reference signals agreement algorithm is first employed to correct the asynchronous behaviors of the position commands. Then, the low-level tracking synchronization method is applied for the collaborative position control of the four LSRMs. The proposed two-level, fault-tolerant control strategy eliminates the asynchrony of the reference signals and it also guarantees the coordinated tracking control performance of the four LSRMs. Experimental results demonstrate that effective coordinated tracking control can be ensured, based on the successful agreement of reference signals and an absolute tracking error falling within 2 mm can be achieved.

Networked

This paper proposes a long-stroke linear switched reluctance machine (LSRM) with a primary and a secondary translator for industrial conveyance applications. The secondary one can translate according to the primary one so that linear compound motions can be achieved. Considering the fact that either one translator imposes a time-variant, nonlinear disturbance onto the other, the self-tuning position controllers are implemented for the compound machine and experimental results demonstrate that the absolute steady-state error values can fall into 0.03 mm and 0.05 mm for the secondary and primary translator, respectively. A composite absolute precision of less than 0.6 mm can be achieved under the proposed control strategy.