Control Theorem: Gains for PD Controller of Acceleration

In summary, the concept of proportional, derivative, and integral (PID) control was derived from studies on ship helmsmen and their methods of steering large ships. This method involves taking into account both the error in position and the rate of change to correct for errors and steady-state issues. The gains in this equation, which is a control feedback signal rather than direct acceleration, can be tuned based on observations of the system. However, this is just a starting point and the final controller is typically more complex.
  • #1
G Man
1
0
I'm trying to understand the derivation of what appears to be a basic concept in control. This is for a PD controller of acceleration. I believe there would be similar derivation for other controllers, but I do not understand its origin let alone other examples?

x.. = Ks.x + Kv.x.
also written as:
acceleration = (gain x displacement) + (gain x velocity)
 
  • #3
AFAIK, I believe the technique for PD (and PID controllers for that matter) was based on people doing studies on ship helmsmen and how they steered large ships. They noticed that the helmsmen wouldn't simply just correct for an error in position (proportional control), but also take the rate of change into account (derivative control). Sometimes, to correct for "droop" or steady-state error, they would correct it by adding up the error in the position and use that to correct for the difference (integral control). This I believe is the origin of PID control.

The idea is that you can tune the gains based on what you observe about the system. Often, mathematical techniques are used to determine the gains (to get in the ballpark) based on properties of the system you are trying to control, but often the models are insufficient so these numbers are "tuned" to get the desired results.
 
  • #4
G Man said:
acceleration = (gain1 x displacement) + (gain2 x velocity)
In addition to what @timethereaper has said, I think that your equation here is misleading. This is not necessarily the acceleration, it is the control feedback signal. So if you want to control something, you need to know where it is (displacement) and how it is moving (velocity). Then your control feedback signal will be some weighted (gain1, gain2) combination of those two. Other than that simple thinking, I don't think there is any derivation. It is just an idea of how to control something and applies to anything you want to control. It often will end up in some way affecting acceleration. It is usually just a starting point and the final working controller is much more complicated.
 
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1. What is a Control Theorem?

A Control Theorem is a mathematical principle used in control engineering to analyze and design control systems. It involves using mathematical models to describe the behavior of a system and then using control theory to determine the best way to manipulate the inputs of the system to achieve a desired output.

2. What is a PD controller?

A PD controller is a type of feedback controller that uses proportional and derivative control to regulate the output of a system. It calculates the error between the desired output and the actual output, and then uses that error to adjust the input to the system. The proportional term is based on the current error, while the derivative term is based on the rate of change of the error.

3. How does a PD controller control acceleration?

A PD controller controls acceleration by adjusting the input to the system based on the error between the desired acceleration and the actual acceleration. The controller calculates the error and uses the proportional and derivative terms to determine the appropriate input to achieve the desired acceleration.

4. What are the gains in a PD controller?

The gains in a PD controller refer to the values assigned to the proportional and derivative terms. These gains determine how much the controller will respond to changes in the error and its rate of change. Choosing the right gains is crucial in designing an effective PD controller.

5. How is the effectiveness of a PD controller measured?

The effectiveness of a PD controller can be measured by its ability to reduce the error between the desired output and the actual output. This is typically done by analyzing the controller's response to different input signals and evaluating its performance based on criteria such as settling time, overshoot, and steady-state error.

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