1,721,037 research outputs found
Fractional robust PID control of a solar furnace
No full textThis paper deals with the fractional control of the temperature in solar furnace plants. As for all the concentrated solar plants, the solar furnace can be modeled as a nonlinear system, where the dynamics strongly depends on the operating temperature. However, to improve the effectiveness of this technology, the control system should guarantee an acceptable performance independently from the operating point. In order to overcome this problem, we propose to use the generalized isodamping technique, where we aim at achieving the invariance of the control loop phase margin with respect to the plant operating point through a properly designed fractional-order proportional-integral-derivative controller. A gain-scheduling algorithm is also introduced to cope with wide plant variations. Simulation and experimental results show the effectiveness of the proposed methodology
The generalised isodamping approach for robust fractional PID controllers design
No full textIn this paper, we present a novel methodology to design fractional-order proportional-integral-derivative controllers. Based on the description of the controlled system by means of a family of linear models parameterised with respect to a free variable that describes the real process operating point, we design the controller by solving a constrained min-max optimisation problem where the maximum sensitivity has to be minimised. Among the imposed constraints, the most important one is the new generalised isodamping condition, that defines the invariancy of the phase margin with respect to the free parameter variations. It is also shown that the well-known classical isodamping condition is a special case of the new technique proposed in this paper. Simulation results show the effectiveness of the proposed technique and the superiority of the fractional-order controller compared to its integer counterpart
An interactive software tool for the study of event-based PI controller
No full textThe paper describes an interactive tool focused on the study of a new family of event-based PI controller. Most research in control engineering considers periodic or time-driven control systems. Event-based control is particularly a very promising alternative when systems with reduced computation and
communication capacities are considered. For event-driven controllers it is the occurrence of an event, instead of the autonomous progression of the time what decides when the signal sampling should be made. The tool has been developed using Sysquake, a Matlab-like language with fast execution and excellent facilities for interactive graphics. The highly visual and strongly coupled nature of event based control
system is very amenable to interactive tools. The tool presented in this paper enables to discover a myriad
of important properties of these systems
A new friction model for mechanical transmissions considering joint temperature
No full textThis article illustrates a model that describes the behaviour of power loss (friction) in mechanical transmissions. The model is applied to joints of an industrial manipulator, it is justified on the bases of preliminary observations of some robot behaviour and it is validated with an extensive experimentation on a commercial 6 degrees of freedom anthropomorphic manipulator. The paper shows that friction decreases with increasing temperature which in turn depends on the working cycle of the manipulator. The proposed model permits a prediction of the variation of the friction contribution during extensive working operations and it is suitable for industrial applications to improve the control performance or to predict the energy consumption
An experimental framework to analyze limit cycles generated by event-based sampling
No full textIn this work a remote lab developed to explore the properties of event-based controllers is presented. The architecture is based on the decomposition of the system in three tiers. The server layer is directly connected to the plant, the client side implements the controller and the graphical interface, and the middle-tier acts as interface between client and server. The implementation of the remote lab allows the control of a Coupled Tank plant through a generic network. The platform is used to evaluate the effectiveness of an algorithm that allows the user to find numerically the limit cycles in control schemes where the feedback is done through a level crossing sampling, and which can be applied to LTI systems with delay
Two degree-of-freedom design for a send-on-delta sampling PI control strategy
No full textA complete event-based two-degree-of-freedom PI controller is presented. The architecture of the control system is based on two decoupled PI controllers, one for the set-point following and one for the load disturbance rejection task. The distinctive feature of the proposed approach is that the two controllers have the same parameters and the reference tracking performance is improved by suitably modifying the reference signal applied to the set-point following controller. Examples of the technique are given. In particular, the control strategy has been applied to a distributed solar collector field
On the stability of an event-based PI controller for FOPDT processes
No full textThis paper deals with the stability of an event-based proportional-integral controller. In particular, necessary and sufficient conditions on the controller parameters for the existence of equilibrium points without limit cycles are given for a first-order-plus-dead-time process. Practical issues related to the controller implementation are also addressed. The presented conditions enable a simpler tuning of the controller. Simulation and experimental results are
provided as illustrative examples
Event-based PI controller with exponential thresholds
No full textThis paper deals with an event-based PI control strategy for event occurrences reduction. The methodology is based on the send-on-delta technique where the measured value of the error signal is sent to the controller when it crosses predefined quantization levels. We propose to increase exponentially the distance between the thresholds in such a way that the number of events decreases by keeping a satisfactory transient performance and by fixing the maximum steady-state error independently. Simulation results show the effectiveness of the methodology and clarify the physical meaning of the design parameters of the controller
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