Common Pitfalls in Feedback Based Control Systems

Our goal is to build a process that is completely in control. That is what Six Sigma methodology is all about, control and consistency. Therefore after understanding, how a feedback based control loop really works, it is essential to also understand what the common errors are that take place when this methodology is implemented. This will help us over overcome these errors and build a more robust process control system. Here are the common errors:

Measurement Error: These were the earliest errors that took place when statistical process control was just introduced. However, it is likely that they may take place in any process. These types of errors take place because of wrong measurements. Consider in the air-conditioner example, if the air conditioner did not accurately measure the outside temperature, the whole control process would fail. Studies have shown that wrong measurements are the result of faulty measurement systems or human bias. Faulty measurement systems can be taken care of measurement systems analysis, however to eradicate human bias, one needs to ensure that the measurement process is automated. This will eliminate any chance of favouritism or bias by the supervisors that can be detrimental to the interests of the organization.

Reporting Delays: The management needs to get the reports on time, in case corrective action needs to be initiated. It is for this reason that the measurements must be compared with the desired state of affairs on a real time basis. As soon as a discrepancy is sighted, it must be brought to the notice of the senior management. However, in many processes, reporting is built at end of day, end of week or end of month basis. However, when it comes to process control, the discrepancies must be notified real time or else the process will continue to function in a faulty manner.

Delay in Taking Corrective Action: Management has a tendency to get into a state of analysis paralysis once reports arrive. However, in case of process control, this cannot be the case. There must be scenarios identified and the correct people must be set into action promptly to bring the process back under control immediately. The entire control process must be treated like an emergency, mission critical process if Six Sigma is to be achieved. Over the period of time, processes become so streamlined and efficient that control processes, seldom have to be activated.

Scenario Not Anticipated: The foundation of an effective control process is that there must be no surprises. The management must have anticipated the ways in which a process can fail by ways of a Failure Modes and Effects Analysis (FMEA). They must then design plans which simply need to be put into action when the scenario arrives. However, if scenarios are not anticipated, then the management has to do the thinking and time is lost leading to the process remaining in a malfunctioning state till the resolution is reached.

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