Project Management is a control system, subject to the theory and practice of control systems. The Project Management Control System provides for the management of systems and processes - cost estimating, work scope structuring and authorization, scheduling, performance measurement, reporting, for assessing the progress of spending other peoples money.
The level of formality for these processes varies according to domain and context. From sticky notes on the wall for a 3 person internal warehouse locator website of a plastic shoe manufacture - to a full DCMA ANSI-748C validated Earned Value Management System (EVMS) on a $1B software development project and everything in between.
The key here is if we're going to say we have a control system it needs to be a Closed Loop control system, not an Open Loop control system. On Open Loop system is called train watching, we sit by the side of the tracks and count the trains going by and report that number. How many trains should go by, could go by? We don't know. That's what's shown in the first picture. We sample the data, we apply that data to the process and it generates an output. There is no corrective action, it's just a signal based on the past performance of the system. Some examples of Open Loop control implemented in the first picture:
- A light switch. Turn it on the light goes on. Turn it off the light goes off. Turn it on and the light doesn't go on, don't know why. Could be the switch, could be the blub is burned out, could be the power is out in the neighborhood.
- Same for a faucet, the burned on the stove, a simple cloths dryer when you use the timer rather than the sense cloths are dry feature.
- The really cool shade we just installed for the upper deck. Push the button and it lowers to a present position, push it again and it goes back to the storage position.
The key attribute of Open Loop Control
- It is a non-feedback system, is a type of continuous control system in which the output has no influence or effect on the control action of the input signal.
- In an open-loop control system the output is neither measured nor fed back for comparison with the input.
- An open-loop system is expected to faithfully follow its input command or set point regardless of the final result.
- An open-loop system has no knowledge of the output condition so cannot self-correct any errors it could make when the preset value drifts, even if this results in large deviations from the preset value.
The key disadvantage of open-loop systems is it is poorly equipped to handle disturbances or changes in the conditions which that reduce its ability to complete the desired task.
A close loop system behaves differently. Here's some example of controllers used in the second picture
- Thermostat for the furnace or air conditioner - Set a target temperature and it holds that temperature pretty much constant
- Refrigerator cold/hot setting - keeps the food in the refrigerator at a preset temperature
- Same for the temperature setting for oven.
The key attributes of Close Loop Control, shown in the second picture
- Closed-loop systems are designed to automatically achieve and maintain the desired output condition by comparing it with the actual condition.
- This is done by generating an error signal which is the difference between the output and the reference input.
- A “closed-loop system” is a fully automatic control system in which its control action being dependent on the output in some way.
Because the closed-loop system has knowledge of the output condition - in the case of projects the desired cost, schedule, and technical performance, it is equipped to handle system disturbances or changes in the conditions which may reduce its ability to complete the desired task.
When we have a target cost - defined on day one by the target budget, a planned need date, and some technical performance target, closed loop control provides the needed feedback to make decisions along the when, when the actual performance is not meeting our planned or needed performance
In the end it comes back to the immutable principle of microeconomics. When we are spending money to produce a value, we need to make decisions about which is the best path to take, which are the best of multiple options to choose. In our to do this we need to know something about the cost, schedule, and performance forecasts from each of the choices. Then we need feedback from the actual performance to compare with our planned performance to create an error signal. With this error signal, we can then DECIDE what corrective actions to take.
Without this error signal, derived from the planned values compared with the actual values there is no information needed to decide. Sure we can measure what happened in the past and decide, just like we can count trains and make some decision. But that decision is not based on a planned outcome, a stated need, or an Estimated Arrival time for example.
Without that estimated arrival time, we can't tell if the train is late or early, just that it arrived. Same with the project measurements.
- We need on average 4.5 stories per iteration. How many stories did you need to do to finish the project on the planned day with the planned capabilities.
Open Loop provides no feedback, so you're essentially driving in the rear view mirror, when you should be looking out the windshield deciding where to go next to escape the problem.