This paper investigates the cooperative output regulation problem for heterogeneous linear multiagent systems under fixed communication graphs via event-triggered control. A fully distributed event-triggered dynamic output feedback control law is proposed based on the feedforward design approach. At the same time, a fully distributed dynamic event-triggering mechanism is designed so that each agent can determine when to broadcast its information to its neighbors. Compared with existing related results, both the control law and the event-triggering mechanism in this paper are independent of any global information. It is shown that with the proposed dynamic event-triggered control strategy, the cooperative output regulation problem can be solved in a fully distributed manner by intermittent communication. Moreover, Zeno behavior can be strictly ruled out for each agent. Finally, the effectiveness of the proposed dynamic event-triggered control strategy is validated by a numerical example.
This paper deals with the robust control problem for linear systems with both gain and time constants variations under fractional order PI λ D μ controller. A robustness specification to the parameters variations is proposed. For those systems with more than one uncertain time constant, the robustness specifications are analyzed and simplified. To minimize the phase offset nearby the crossover frequency, the PI λ D μ parameters tuning is formulated as a nonlinear optimization problem with the specifications and controller structure constraints, meanwhile the initial values of optimization is preprocessed by solving nonlinear equations. Numerical examples have illustrated the effectiveness of the tuning method and advantages of the proposed PI λ D μ controller.
Hierarchical control architectures are a common approach when hydraulic systems are under study; provided their multi-domain nature, the control scheme is commonly split into different hierarchical levels each one associated with a particular physical domain. This paper presents the application of a model-based control structure called Embedded Model Control (EMC) when a hierarchical scheme is implemented on an electro-hydraulic proportional valve. The overall control consists of two hierarchical loops: the inner loop is the solenoid current regulator with a closed loop bandwidth close to 1 kHz. The outer loop is a position tracking control, in charge of the accurate positioning of the spool with respect to valve openings. The paper addresses the outer loop, i.e., the tracking of mechanical spool position by using the EMC. Analysis and synthesis are presented as well as experimental results obtained from a test rig provided by an industrial manufacturer.
In order to realize tracking control for underactuated surface vessels with parameter uncertainties and external disturbances, a nonsingular terminal sliding mode method was proposed. The controller was divided by backstepping method into the kinetic part and the dynamic part. In the kinetic process, the reference surge and sway velocities are employed as the virtual control law in stabilizing the position errors. In the dynamic process, the virtual control law was considered the new tracking target, and the real control law was designed by the nonsingular terminal sliding-mode method to realize the tracking control of the reference velocities. This method can not only guarantee the position tracking error converge finite time, but also ensure yawing motion is BIBO stable. Eventually, simulation experiment of real ship is performed. Results validate the proposed controller can achieve fast tracking control of USV in finite time under parameter uncertainties and external disturbances.
