In the last few weeks, Greg has been providing his readers with checklists for control issues. In his "Checklist for Cascade Control," Greg calls cascade control "an effective way of providing better feedback and feed-forward control. The peak error in the primary loop can be reduced by more than an order of magnitude for disturbances originating in the secondary loop. The nonlinearity of a control valve can be removed from the primary control loop. Flow feed-forward and ratio control can become more effective.
The other hit is "Checklist for Batch Reactor Temperature Control." Greg says, "Tight reactor temperature control enables the optimization of capacity and yield. What happens upfront in the reaction sets the stage for downstream processing and what ultimately ends up in the final product. Generally, increasing reactor temperature will increase reaction rate (capacity), but if the temperature is too high, side reactions may develop reducing reaction selectivity (yield). Oscillations and errors will prevent operating closer to the optimum temperature. This checklist offers questions to improve reactions by addressing the heating and cooling system design, thermal lags, split ranged discontinuities, tuning, reactant feed and the need for a measurement of fouling and conversion."
Our resident expert on cybersecurity is Joe Weiss. He is a principal at Applied Control Solutions and an authority on cybersecurity and control systems. In his "Unfettered" blog, he crusades for better, more effective security of critical infrastructure and process control systems.
Joe's most popular post of recent weeks has been "Lessons Learned from Aurora." He begins, "On the SCADASEC list, Ed Beroset stated the following: 'I've attended a number of security conferences at which speakers would gravely intone that ‘we have not yet learned the lessons of Aurora.
'I've found that there's a very wide range of interpretations as to what those might be. My questions for this group are: 1) what is the lesson of Aurora? and 2) what has been done about it? and 3) what's left to do?' In response to Ed, there are a number of lessons learned specifically from Aurora."
In his post, "Legacy Control System Cybersecurity/Reliability Test Bed," Joe reports, "There has long been a strong desire to find solutions for securing industrial control systems that go beyond simply exposing problems and risks. What is so difficult about finding solutions? The answer is technology, use and compliance. Solutions exist for some parts of the control system that have been adopted/adapted from the IT community."