Cablegation is a simple system for automating surface irrigation in small- and medium-sized fields using a gated pipe. In this work, a programmable Logic Control, PLC, was used to develop an adaptive cablegation syste...
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Cablegation is a simple system for automating surface irrigation in small- and medium-sized fields using a gated pipe. In this work, a programmable Logic Control, PLC, was used to develop an adaptive cablegation system capable of establishing the infiltration equation in real time and then adjusting the irrigation times to the infiltration rate and field geometry. A controlling program was developed for the on-field determination of the infiltration equation, simulation of advance in each furrow, and the optimization and management of the irrigation event. The equipment was tested in three experimental stations, including a Luvissol field organized in contour terraces with furrows of various lengths. The results demonstrate the capability of the system to adapt the application times to the different furrow lengths and the gradual decrease in the soil infiltration and to recommend an application depth that optimizes the Application Efficiency. Various improvements were made to this solar-powered cablegation, resulting in a reliable surface irrigation system capable of unsupervised operation.
This paper presents a new interpolation method that utilizes a Newton backward interpolation formula for the discretization of a continuous-time system with state and input delays. Also, a new output feedback state-ma...
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This paper presents a new interpolation method that utilizes a Newton backward interpolation formula for the discretization of a continuous-time system with state and input delays. Also, a new output feedback state-matching digital redesign method, which utilizes the Newton extrapolation formula and the Chebyshev quadrature formula, enables the discretization of a cascaded continuous-time controller or filter for the continuous-time systems with delayed input and states, without employing a discrete-time observer. The proposed method provides an alternative methodology for indirect digital design of a continuous-time unity-output feedback delayed system and enables us to implement accurately and effectively an existing or pre-designed cascaded analogue controller or filter via a digital controller.
A minimax approach for multi-objective controller design is proposed, ill which structured uncertainty is characterized by multiple discrete-time SISO models. Typical engineering objectives are optimized for all model...
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A minimax approach for multi-objective controller design is proposed, ill which structured uncertainty is characterized by multiple discrete-time SISO models. Typical engineering objectives are optimized for all models, such as bounds on different sensitivity functions and time-domain responses. The approach is illustrated by improving the best performing controller of a flexible arm benchmark example.
This paper is concerned with the finite-time stability, boundedness and H-infinity control problems for a class of switched stochastic systems. Using the average dwell time method and the multiple Lyapunov-like functi...
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This paper is concerned with the finite-time stability, boundedness and H-infinity control problems for a class of switched stochastic systems. Using the average dwell time method and the multiple Lyapunov-like function technique, some sufficient conditions are proposed to guarantee the finite-time properties for the switched stochastic systems in the form of matrix inequalities. Also, a state feedback controller for the finite-time H-infinity control problem is obtained. An example is employed to verify the effectiveness of the proposed method. (C) 2011 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
Thickness of tundish cover flux (TCF) plays an important role in continuous casting (CC) steelmaking process. Traditional measurement method of TCF thickness is single/double wire methods, which have several problems ...
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Thickness of tundish cover flux (TCF) plays an important role in continuous casting (CC) steelmaking process. Traditional measurement method of TCF thickness is single/double wire methods, which have several problems such as personal security, easily affected by operators, and poor repeatability. To solve all these problems, in this paper, we specifically designed and built an instrumentation and presented a novel method to measure the TCF thickness. The instrumentation was composed of a measurement bar, a mechanical device, a high-definition industrial camera, a Siemens S7-200 programmable logic controller (PLC), and a computer. Our measurement method was based on the computer vision algorithms, including image denoising method, monocular range measurement method, scale invariant feature transform(SIFT), and image gray gradient detection method. Using the present instrumentation and method, images in the CC tundish can be collected by camera and transferred to computer to do imaging processing. Experiments showed that our instrumentation and method worked well at scene of steel plants, can accurately measure the thickness of TCF, and overcome the disadvantages of traditional measurement methods, or even replace the traditional ones.
Petri nets have been extensively applied for specification, design, veri cation, performance evaluation, and simulation of discrete event control systems (DECS). The usual way to verify the dynamic behaviour of DECS d...
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Petri nets have been extensively applied for specification, design, veri cation, performance evaluation, and simulation of discrete event control systems (DECS). The usual way to verify the dynamic behaviour of DECS design is to employ a process-based model, which proves to be impractical in application because the process-based model does not usually fully correspond to the control programming behaviour. This paper proposes a sensor-based stage Petri net (SBSPN) to represent a programmable logic controller (PLC) stage logic diagram (LD) for discrete-event control design. The new technique is able to simplify the modelling process of the complex PLC program without considering the interlocking problem within the ladder diagram. An illustrated example is used to explore the new methodology. The proposed method contains the power and flexibility of the Petri net analysis prior to the PLC implementation. It is believed that this technique is significant for industry practice.
A digital spectrometer for low-field magnetic resonance imaging is described. A digital signal processor (DSP) is utilized as the pulse programmer on which a pulse sequence is executed as a subroutine. Field programma...
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A digital spectrometer for low-field magnetic resonance imaging is described. A digital signal processor (DSP) is utilized as the pulse programmer on which a pulse sequence is executed as a subroutine. Field programmable gate array (FPGA) devices that are logically mapped into the external addressing space of the DSP work as auxiliary controllers of gradient control, radio frequency (rf) generation, and rf receiving separately. The pulse programmer triggers an event by setting the 32-bit control register of the corresponding FPGA, and then the FPGA automatically carries out the event function according to preset configurations in cooperation with other devices;accordingly, event control of the spectrometer is flexible and efficient. Digital techniques are in widespread use: gradient control is implemented in real-time by a FPGA;rf source is constructed using direct digital synthesis technique, and rf receiver is constructed using digital quadrature detection technique. Well-designed performance is achieved, including 1 mu s time resolution of the gradient waveform, 1 mu s time resolution of the soft pulse, and 2 MHz signal receiving bandwidth. Both rf synthesis and rf digitalization operate at the same 60 MHz clock, therefore, the frequency range of transmitting and receiving is from DC to similar to 27 MHz. A majority of pulse sequences have been developed, and the imaging performance of the spectrometer has been validated through a large number of experiments. Furthermore, the spectrometer is also suitable for relaxation measurement in nuclear magnetic resonance field. (C) 2013 AIP Publishing LLC.
The problem of modal sampled-data control for continuous-time linear time-invariant plant with delay is considered. The characteristic matrix of the system is constructed. An algorithm is given for generating the set ...
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The problem of modal sampled-data control for continuous-time linear time-invariant plant with delay is considered. The characteristic matrix of the system is constructed. An algorithm is given for generating the set of causal discrete-time controllers that place eigenvalues of the characteristic matrix at specified points of the complex plane.
CNC grinding machines are widely used to obtain a good surface finish and tight tolerances. However, these machines are expensive, therefore manufacturers are considering adding a grinding spindle, interchangeable wit...
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CNC grinding machines are widely used to obtain a good surface finish and tight tolerances. However, these machines are expensive, therefore manufacturers are considering adding a grinding spindle, interchangeable with a boring bar, to a turning lathe. To facilitate this, complex software is required because the programmer must control the whole surface of the grinding wheel not just the tool or cutter tip, as in turning or milling. This paper presents a general algorithm to simplify the grinding programme. The programmer will use this algorithm to create a subroutine suitable for the machine. The subroutine may then be used for all grinding operations. The programmer will need only to describe the contour of each workpiece, as for a CNC lathe program, in a separate small program. The algorithm has been applied to a hollow spindle lathe equipped with Sinumeric 840 C numerical control, and several gun barrels were turned and ground using the proposed approach. Satisfactory results were obtained.
In this paper, a new gain self-tuning method for PI controllers based on a fuzzy inference mechanism has been proposed and implemented. The essential idea is: (1) define a dynamically changed reference trajectory in t...
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In this paper, a new gain self-tuning method for PI controllers based on a fuzzy inference mechanism has been proposed and implemented. The essential idea is: (1) define a dynamically changed reference trajectory in the error and error derivative plane, called a 'sliding trajectory';(2) compute the error area between the sliding trajectory and the effective one with a special algorithm, and use this quantity as a performance index to evaluate the system response;(3) draw a fuzzy relationship between a PI gain correction parameter and the performance index;(4) based on the fuzzy inference mechanism, PI gains are calculated and tuned. The proposed method has been verified through simulations, using the speed control of a PM synchronous motor drive system as a testbed. The results obtained demonstrate the effectiveness of this novel method.
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