Position form, digital controllers

The foregoing two digital approximations for PI and PID controllers are known as the position form of the algorithms, because at each sampling instant they compute the actual value (position) of the con-... 

A simple digital form of this equation may be written for the nth time interval using the rectangular rule of integration approximation to the integral and a first-order backward finite difference approximation of the derivative to yield the positional form, Eq. (92), where are the error and controller output respectively... 

There are two alternative forms of the digital PID control equation, the position form and the velocity form, A straightforward way of deriving a digital version of the parallel form of the PID controller (Eq. 8-13) is to replace the integral and derivative terms by finite difference approximations. 

The PFT NMR spectrum can then be recorded in analog or digital form by a plotter controlled by the computer. If the computer core memory allows, additional subroutines may be stored which automatically compute signal intensities and positions (in ppm values relative to some standard or in Hz) and outputs them to the printer. 

The collected data were analyzed with the microprocessor and either a Digital Equipment PDF 11/34 minicomputer or a Control Data Cyber 175 mainframe computer (2,5). The digitized data from the 0MA2 could then be presented In several forms (1) an Iso-lntenslty contour plot, (2) a three dimensional Intensity versus x-y position plot, or (3) an Intensity versus scattering angle plot from a specified azimuthal data slice. 

To monitor and control a tablet press, certain sensors must be installed at specific locations on the machine. These sensors are called transducers. In general, a transducer is a device that converts energy from one form to another (e.g., force to voltage). Tablet press transducers typically measure applied force, turret speed, or punch position. Because the signals coming from such transducers are normally in millivolts, they need to be amplified and then converted to digital form in order to be processed by a data acquisition system. 

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