Without a desired delivery date, target budget, and expected capabilities, a control system is of little interest to those providing the money at business level. There is no way to assure those needs – date, budget, capabilities – can be met with the current capacity for work, efficacy of that work process, or budget absorption of that work.
With a need date, target budget, and expected capability outcome, a control system is the basis of increasing the probability of success. These targets are the baseline to steer toward. Without a steering target the management of the project is Open Loop. There are two types of control systems
- Closed Loop Control – where the output signal has direct impact on the control action.
- Open Loop Control – where the output signal has no direct impact on the control action.
An Open Loop Control control system is a non-feedback system, where the output – the desired state – has no influence or effect on the control action of the input signal. In an Open-Loop control system the output – the desired state– 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 – the difference between desired state and actual state – 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.
An Closed-loop Control System, is a feedback control system which uses the concept of an open loop system as its forward path but has one or more feedback loops between its output and its input. In Closed Loop control, there is a “feedback,” signal that means some portion of the output is returned “back” to the input to form part of the systems excitation.
Closed-loop systems are designed to automatically achieve and maintain the desired output condition by comparing it with the actual condition. Closed Loop control systems do this 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.
Key Differences Between Open Loop and Closed Loop control
Open Loop Control
- Controller has some knowledge of the output condition.
- The desired condition is not present in the control loop – hence the Open Loop.
- Any corrective action requires an operator input to change the behavior of the system to achieve a desired output condition
- No comparison between actual output condition and the desired output conditions.
- Close Loop control has no regulation or control action over the output condition ! Each input condition determine a fixed operating condition for the controller.
- Changes or disturbances in external conditions does not result in a direct output change unless the controller and manually altered.
Closed Loop Control
- Controller has some knowledge of the output condition.
- The desired condition is compared to the actual condition to create an error signal. This signal is the difference between the input signal (the desired dryness) and the output signal (the current dryness).
- Closed loop means feedback not just for recording the output, but for comparing with the desired state to take corrective action.
- Output condition errors are adjust by changes in the controller function by measure difference between output and desired condition.
- Output conditions are stable in the presence of an unstable system.
- Reliable and repeatable output performance results from corrective actions taken from the error signal.
Using Closed Loop Control for a Project
- The Setting – we work in an enterprise IT environment, a product development company, or on a mission critical software project.
- The Protagonist – Those providing the money need information to make decisions
- The Imbalance – it’s not clear how to make decisions in the absence of information about, the cost, schedule, and technical outcomes from those decisions.
- Restoring the Balance – when a decision is made, it needs to based on the principles of microeconomics, at least in a governance based organization. The decision
- Recommended Solution – start with a baseline estimate of the cost, schedule, and technical performance. Execute work and measure the productivity of that work.
Using these measures to calculate the variance between planned and actual. Take management action to adjust the productivity, the end date, the budget – using all variables produce a new Estimate To Complete to manage toward.
This is a closed loop control system
The Microeconomics of Decision in Closed Loop Control
Microeconomics is the study of how people make decisions in resource-limited situation on a person scale. It deals with decision that individual and organizations make on such issues as how much insurance to buy, which word processor to buy, what prices to change for pro ducts and services, which path to take in a project. Throughput the project lifecycle, these decision making opportunities. Each decision impacts the future behavior of the project and is informed by past performance and the probabilistic and statistical processes of the underlying project activities. To make an informed decision about the project, estimates are made using this information.
Microeconomics applied to projects is a well understood and broadly applied discipline in cost account and business strategy and execution. Decision making based on alternatives, their assessed value and forecast cost. Both these values are probabilistic. Microeconomics is the basis of Real Options and other statistical decision making. Without this paradigm decision are made not knowing the future impact of those decisions, their cost, schedule, or technical impacts. This is counter to good business practices in any domain.
Let's Look At An Open Loop Control System
This is all fine and dandy. But where are we going? What's the probability we will arrive at our desired destination if we knew what that destination was? Do we have what we need to reach that desired destination if we knew what it was? In Open Loop Control these questions have no answers.
Let's Look at a Closed Loop Control System
We want to manage our projects with Closed Loop Control Systems
