THE SAMPLING PERIOD AS A CONTROL PARAMETER

Recently, the Plant Input Mapping (PIM) method was proposed as a digital-redesign (or an emulation) approach in digital control system design. This method guarantees stability of a redesigned digital control system for a wide range of sampling periods. In this paper the PIM method is applied to the design of a digital model-matching flight control system. In the model-matching control system design a plant must have no unstable zeros. However, unstable zeros appear for small sampling periods in a step invariance model of a continuous-time (CT) plant with the relative degree greater than two, even if the CT plant has no unstable zeros. Hence, in such a case, the direct-digital approach cannot be applied to the design of a digital model-matching control system. By contrast, the digital-redesign approach such as the Tustin's method or the PIM method is free from the problem. Simulation results for an unstable VTOL aircraft show that the proposed method gives better performance than the conventional design methods.

The DC-DC converters at the Advanced Photo Source at Argonne National Laboratory are over 15 years old. An upgrade to digital control system is being evaluated to resolve the aging and obsolescence issues. These converters supply power to electromagnets that are used to guide high energy beams. Thus a highly accurate control system is required for the DC-DC converters. This paper describes the design and evaluation of a digital control system to regulate the output current. The digital control system is proposed to replace the current analog control system thereby resolving the aging and obsolescence issues. A digital controller is first designed based on the small signal model of the converter. Experimental data of the output current is analyzed. The complete control system is then simulated and results are evaluated.

Control Systems Analysis and Design Labs with Educational Plants

This paper considers the application of error analysis algorithms for the linear quadratic gaussian problem to the design of digital control systems for a simple model of a helicopter in hover. Particularly, we investigate the influence on the performance of modelling errors in the stability derivatives and correlation time of the wind gust model. The algorithms presented enable the determination of performance loss in the case of reduced order models. As an example of this possibility we will consider the case when colored system noise is misindentified as a gaussian white noise. The simulated results, for a helicopter in hover, given in the paper indicate that the extra effort expended in parameter identification may not be justified as the optimal trajectory and final performance is practically insensitive to errors in most of the model parameters.

In the design of digital control systems, the time delay due to computation time of a processor cannot be often neglected. In this paper, we consider the problem of synthesizing a type-1 optimal digital servosystem taking account of controller delay of one sampling period.It is first shown that the optimal digital servo problem in which a quadratic criterion function is defined for a given continuous-time plant can be reasonably reformulated to a discrete optimal regulator problem. To assure the solvability of this problem, some conditions for the preservation of stabilizability and detectability of the plant under sampling are given. In the discrete optimal regulator problem considered here, not only control input but also the initial state of the servocompensator are referred as free design parameters. The obtained optimal digital control law contains a feedforward term of reference signal in addition to a feedback term. It is also shown that the optimal control law has a function of estimating the state variables at the following sampling period in order to recover the controller delay.

Quantization error in the design of digital control systems.

This paper presents t he design and implementation (using a TI 9900 microcomputer system) of digital control systems for an environmental chamber utilized in the study of plant growth. Two control systems were implemented - one to control dry-bulb temperature and the o ther to control the carbon dioxide content in the chamber atmosphere. In addition, real-time data acquisition, automatic restart following power outages, and an interactive operating system have been achieved. The CO system is a closed-loop modified proportional control system. The closed-loop temperature control system uti1 ized a proportional-plusintegral-plus-de rivative digital controller. The environmental chamber is presently used in research by the USDA at Auburn University. 2

Microcontroller(MCF5213CAF80) and FPGA based control system for pulsed MIG welding power source is presented, aiming at some of deficiencies in the control system based on analogous control technology and single-chip control technology, such as poor flexibility, control precision and reliability. The overall hardware circuit scheme, sampling and A/D converter circuits and PWM drive circuits are designed. Then, the software design of FPGA and the software design of real-time embedded operating system μC/OS-II on MCF5213CAF80 are proposed. The experimental results show that the microcontroller and FPGA based control system for pulsed MIG welding power source has the advantages of quicker response, better reliability and more stable arc length.

A special problem in digital control systems design is solved. The solution is found by the parametric transfer function method, which is applicable to various problems in analysis and design of linear systems involving continuous and time-discrete signals. >

It is demonstrated that reconfigurable digital multiple model-following flight control systems incorporating fast-sampling error-actuated digital PID (proportional plus integral plus derivative) controllers can be easily designed using directly measurable input/output data. Thus, for example, it is shown in the case of the F-16 aircraft that desired flying qualities with respect to both pitch-rate and angle-of-attack response characteristics can be simultaneously achieved in the absence of sensor failures. In addition, in the case of failure of the angle-of-attack sensor, it is shown that desired flying qualities with respect to pitch-rate response characteristics and satisfactory flying qualities with respect to angle-of-attack response characteristics can still be achieved by reconfiguring the digital controller. >

The availability of digital MSI and LSI has made digital flight control systems more cost effective than analog systems for all but the simplest systems. The organization of a digital flight control system is concerned not only with implementation of the control laws and associated logic but also with the management of the data used in these computations and the organization of the computation. The configuration taken by a digital flight control system is dominated by the integrity and data handling requirements. This paper considers the impact of these factors on the design and operation of digital flight control systems with particular emphasis on the use of fiber optics for transmission of data between lanes.

Pulse-width modulation (PWM) is a widely used strategy for operating switch controlled systems. A model for PWM systems is reported which provides the discrete-time response of the one-cycle-average value of any signal in the system. The model typically has unstable zero dynamics, as well as a nonlinear dependence on the duty ratio input. Using scheduled output redefinition, an approximate design model is derived which has stable zero dynamics. A controller based on discrete-time input-output linearization is then developed using this approximate design model. Although this approach leads to approximate rather than perfect output tracking, it guarantees internal stability.

Aiming at the problem of MIG welding and considering the existing analog control wire feed system has the disadvantages of low response speed, low control accuracy and poor stability. This thesis designs a set of digital control wire feed system based on LPC2132 microprocessor and introduces the control principle of wire feed motor, CAN bus interface circuit and PID control algorithm. Under the condition of power grid voltage fluctuation and load change, we do a lot of experiments. The results show that: the wire feed change rate of designed system is very small, which not only meets the requirements of JB/T-1998.MIG/MAG arc welding standard, but also greatly improves the accuracy and stability of control system.

Modern High performance control applications demanded from mixed-signal and digital signal processors (DSPs) are ever increasing. As digital circuits and DSP operate at a higher rate, a considerable amount of noise and radiation degrades the system?s performance and creates EMI problems that make it difficult to pass tests required to obtain certification by the EMC regulations. In this paper, we introduce some effective methods for reduced EMI of the measurement and control systems, which are power supply design, clock and phase-locked loop (PLL) isolation, decoupling techniques, digital and analog partitioning, printed circuit board (PCB) layout, and so on for meeting many challenges of mixed-signal and DSP systems design. Design guidelines for improved EMC and signal integrity are derived from the results obtained, thus, the evaluation board of the measurement and control systems is especially suitable for performing function in high definition array induction log (HDAIL).

According to the study of series of related standards, the defense-in-depth and diversity have become the basic requirements for digital I&C and should be strictly followed when carrying out the overall scheme design of Digital Control System, in which the risk of Common Cause Failure has to be prevented or coped with. This paper analyzes the requirements according to the diversity principle and illustrates the typical solution of the diversified protection base on the CPR1000 NPP. Some concepts will be helpful to the design of DCS.