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Upgrading an analog DC drive to digital control does not always require a complete drive replacement. By retrofitting the existing power components with digital controls, all of the functionality of a modem digital DC drive can be achieved. Retrofitting can offer a sigruficant cost savings over a complete drive replacement, since the existing power components, motors, power cables and cable support system may be reused. The benefits of an upgrade to digital control include improved drive response, simplified troubleshooting, elimination of tuning parameter "drift", greater flexibility m operating with m e r e n t paper grades and orders, and an improved ability to control roll hardness. These benefits translate into reduced downtime, increased production efficiency and improved roll quality. The retrofit described in this case study has achieved the desired results in a cost-effective manner. A. Machine DowntimeThe existing analog master section was wired using pressure-crimping methods. Drive trips were being caused by insulation breakdown in this wiring, resulting in random grounding of circuits. Once a fault occurred, it was an extremely difficult ancl time-consuming task to locate the faulty wiring. The direct result was excessive machine downtime and lost production. The hardwired relay logic used for winder sequencing was another potential source of machine downtime due to troubleshooting d~fficulty.

Today's sophisticated digital drives provide an abundance of control and diagnostic data for which a man-machine interface is required in order for the operator to interact with the machine. This paper describes the application of off-the-shelf graphical user interface development software and personal computers to provide the man-machine interface for a Paper Machine Winder and Paper Machine drive system. INIROUCCTIONIn the not so distant past, the primary means with which to interface with a drive system was via an operator's benchboard(s) crammed with a multitude of industrial-sized pushbuttons, switches, potentiometers and gauges. These devices were then hardwired to drive system panels, relay panels or PLC's (programmable logic controllers) containing an assortment of analog and digital inputloutput modules.With the introduction of the digital drive came the high speed data highways of today's control systems. These data highways provided a means with which to transmit digital data, using a single communications module. at a speed which a1 lowcd for distributed control.It seemed the next logical step would be to incorporate the operator control or MMI (man-machine interface) as part of the distributed control architecture by having it communicate over the same data highways. In order to accomplish this the MMK must be transformed into the digital world using personal computers (PC's) running graphical user interface (GUI) software.Once transformed, a far greater amount of information is available to the operator in a more functional and digestible mannei This empowers the operator to make decisions at a much higher lekel than in the past and consequently. ha5 more control over the process and oftcn develops a new sense orpride and res~onsibility concerning his roll in the production of a qualit\ product ' ' MMI DESIGN CON\,ENTIONS lJsirc A GUIWhen designing if GlJI it is first necessary to define a set of conventions regarding presentation of data and use of color. The intmtion is to aid the operator in interpreting, quickly and easily, the information displayed on the screen. Often, conventions of this kind alrcady exist for traditional benchboard controls and need only be adapted slightly to suit the GIJI. The following are examples of conventions developed for the Paper Machine Winder and Paper Machine MMI's:A . Referenca'Setpoint data vs. ActuaUFeedbuck dafu numeric data used to indicate a reference or setpoint value is displayed as black numerals on a grey background, i.e. Winder speed setpoint. numeric data used to indicate an actual or feedback value is displayed as yellow numerals on a black background, i.e. Winder speed feedback numeric data used to indicate the magnitude of a parameter being trended IS displayed as black numerals on a background color that matches the color of the line the parameter is being trended in. R Sturt/Stop vs OtdOf pushhutton controlWhen graphical representations of pushbuttons are used for stadstop type control of a functionwhen the function is offor stopped (Fig.2): the...