Universal direct tuner for loop control in industry

This paper introduces a direct universal (automatic) tuner for basic loop control in industrial applications. The direct feature refers to the fact that a first-hand model, such as a step response first-order plus dead time approximation, is not required. Instead, a point in the frequency domain and the corresponding slope of the loop frequency response is identified by single test suitable for industrial applications. The proposed method has been shown to overcome pitfalls found in other (automatic) tuning methods and has been validated in a wide range of common and exotic processes in simulation and experimental conditions. The method is very robust to noise, an important feature for real life industrial applications. Comparison is performed with other well-known methods, such as approximate M-constrained integral gain optimization (AMIGO) and Skogestad internal model controller (SIMC), which are indirect methods, i.e., they are based on a first-hand approximation of step response data. The results indicate great similarity between the results, whereas the direct method has the advantage of skipping this intermediate step of identification. The control structure is the most commonly used in industry, i.e., proportional-integral-derivative (PID) type. As the derivative action is often not used in industry due to its difficult choice, in the proposed method, we use a direct relation between the integral and derivative gains. This enables the user to have in the tuning structure the advantages of the derivative action, therefore much improving the potential of good performance in real life control applications

Does the motor system need intermittent control?

Explanation of motor control is dominated by continuous neurophysiological pathways (e.g. trans-cortical, spinal) and the continuous control paradigm. Using new theoretical development, methodology and evidence, we propose intermittent control, which incorporates a serial ballistic process within the main feedback loop, provides a more general and more accurate paradigm necessary to explain attributes highly advantageous for competitive survival and performance

Control of open-loop unstable processes with time delay using PI/PID controllers specified using tuning rules: An outline survey

The ability of PI and PID controllers to compensate many practical processes has led to their wide acceptance in industrial applications. The requirement to choose two or three controller parameters is conveniently done using tuning rules. Starting with a general discussion of industrial practice, the paper provides a survey of tuning rules for continuous time PI and PID control of open-loop unstable time-delayed single-input, single-output (SISO) processes

Automatic Tuning of PID Controllers Based on Asymmetric Relay Feedback

This thesis presents an improved version of the classic relay autotuner. The proposed autotuner uses an asymmetric relay function to better excite the process in the experiment phase. The improved excitation provides the possibility to obtain better models and hence better tuning, without making the autotuner more complicated or time consuming.Some processes demand more accurate modeling and tuning to obtain con-trollers of sufficient performance. The proposed autotuner can classify these processes from the experiment. In an advanced version of the autotuner an additional experiment could be dhttps://localhost/admin/login.phpesigned for these processes, in order to further increase the possibilities in modeling and tuning. The experiment design would then rely on information from the relay experiment. A simple version of the autotuner could instead make a somewhat better model estimation immediately, or suggest that some extra effort may be put in modeling if the control performance of the loop is crucial. The main focus in this thesis is on the simple version of the autotuner.The proposed autotuner uses the process classification for model and controller selection also in the simple version. The processes are classified according to their normalized time delays. In this thesis a simple method of finding the normalized time delay from the asymmetric relay experiment is presented and evaluated.Research presented on different versions of the relay autotuner is often based solely on simulations. In large simulation environments, the ability to automatically tune the large amount of PID controllers is practical and time-saving. However, the ability to use the autotuner in an industrial setting, requires considerations not always present in a simulation environment. This thesis investigates many of these issues, regarding parameter settings and possible error sources. The proposed autotuner is implemented, tested and evaluated both in a simulation environment and by industrial experiments. The simple version of the autotuner gives satisfactory results, both in simulations and on the industrial processes. Still, there is a possibility to further increase the performance by an advanced version of the autotuner

Improved Relay Autotuning using Normalized Time Delay

The relay autotuner provides a simple way offinding PID controllers of sufficient performance. By usingan asymmetric relay function the excitation of the process isimproved. This gives better models, and hence a better tuning,without increasing the time consumption or complexity of theexperiment. Some processes demand more accurate modelingand tuning to obtain controllers of sufficient performance.These processes can be singled out by their normalized timedelays and be subject to further modeling efforts. The autotunerproposed in this paper provides a simple way of findingthe normalized time delay from the experiment, and uses itfor model and controller selection. The autotuner has beenimplemented and evaluated both in a simulation environmentand by industrial experiments

PID control system analysis, design, and technology

Designing and tuning a proportional-integral-derivative (PID) controller appears to be conceptually intuitive, but can be hard in practice, if multiple (and often conflicting) objectives such as short transient and high stability are to be achieved. Usually, initial designs obtained by all means need to be adjusted repeatedly through computer simulations until the closed-loop system performs or compromises as desired. This stimulates the development of "intelligent" tools that can assist engineers to achieve the best overall PID control for the entire operating envelope. This development has further led to the incorporation of some advanced tuning algorithms into PID hardware modules. Corresponding to these developments, this paper presents a modern overview of functionalities and tuning methods in patents, software packages and commercial hardware modules. It is seen that many PID variants have been developed in order to improve transient performance, but standardising and modularising PID control are desired, although challenging. The inclusion of system identification and "intelligent" techniques in software based PID systems helps automate the entire design and tuning process to a useful degree. This should also assist future development of "plug-and-play" PID controllers that are widely applicable and can be set up easily and operate optimally for enhanced productivity, improved quality and reduced maintenance requirements