A new stability criterion on Nichols chart is presented. It provides an alternative graphical method for stability analysis on Nichols chart. Furthermore this result can be used to test the stability of the new nominal closed-loop system arising in QFT controller design method for non-minimum phase and unstable plants, which is diicult to test with the existing stability criterion.

Many PID controller tuning methods have been presented since Ziegler and Nichols published their method in 1942, but none of those methods were used widely. The Ziegler and Nichols method has several advantages over newer methods: it is easy to conduct, the relations for controller parameter computation are simple, the method relies on experiment, and it does not require any model. Newer tuning...

A novel experimental method – here denoted the Good Gain method – for tuning PI controllers is proposed. The method can be regarded as an alternative to the famous Ziegler-Nichols’ Ultimate Gain method. The approach taken resembles the Ziegler-Nichols’ method as it is based on experiments with the closed loop system with proportional control. However, the method does not require severe process ...

BACKGROUND The concentration of 25-hydroxyvitamin D [25(OH)D] in serum has been designated the functional indicator of vitamin D (VitD) nutritional status. Unfortunately, variability among 25(OH)D assays limits clinician ability to monitor VitD status, supplementation, and toxicity. METHODS We developed an HPLC method that selectively measures 25-hydroxyvitamin D2 [25(OH)D2] and D3 [25(OH)D3]...

The paper presents PID controller design using modification of the Aström and Hägglund’s generalized Ziegler-Nichols rules. The design procedure consists in shifting the plant critical point into a specific point. Its position is defined by desired performance specification in term of achieving maximum overshoot and specified settling time of the closed-loop response or phase margin. The method...

This paper introduces a method for formal and symbolic analysis of single–input single–output continuous–time control systems. The method is based on traditional control engineering analysis using Nichols plots and thus focuses on the properties of gain (amplitude) and phase–shift. We reduce Nichols plot requirements to a decision problem and present a procedure to decide problems of this type....

Among the five samples distributed in January 2004 were two (samples 4 and 5) containing endogenous 25OHD 2. A summary of the results is presented in Table 1. The wide range of results submitted by users of the same method illustrates the degree to which 25OHD assays are operator-dependent. The one automated procedure (Nichols) produced more consistent values, but for the samples (1, 2, and 3) ...

BACKGROUND Rapid intraoperative parathyroid hormone (PTH) measurements are an important prerequisite for minimally invasive parathyroidectomy, serving as a feasible marker for "cure" because of the short half-life of PTH. Because automated analysis may facilitate monitoring, two automated PTH assays were compared with an established manual method. METHODS We collected 109 plasma samples durin...

There are several methods for tuning a PID controller. This paper takes a qualitative look at three common methods, with comparisons of accuracy and effectiveness. These three methods include a guided Trial and Error method, the Ziegler-Nichols method, and the Cohen-Coon method. For an exceptionally responsive system the Trial and Error method is often used after the Ziegler-Nichols or Cohen-Co...