Writing Output in State Space Form: RLC Circuit Example

In summary, the general form of state space output is y=cx+du, meaning that the output is a linear combination of state variables and inputs. However, for cases where the output is not a combination of state variables, such as in an RLC circuit where the state variables are VC and IL, we can still write the output in the form y=cx+du. This can be achieved by using the phasor equivalents for the circuit and finding the transfer function (Vo/Vi). From there, the transfer function can be converted to state space form, allowing for the breaking down of the A, B, C, and D parts. It is important to note that all variables must be expressed as state space variables in order
  • #1
asad1111
51
0
the general form of state space output is y=cx+du which means that output is linear combination of state variables and inputs my question is can we write output in this form when our output is not combination of state variable for example in rlc circuit state variables are vc and IL now if we want to take output 'voltage across resistor' how can we represent it in form y=cx+du
 
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  • #2
Use the phasor equivalents for the circuit (capacitors = 1/sC and inductors = sL) and figure out the transfer function of your circuit (Vo/Vi). Then convert the transfer function to state space form and you will be able to break out the A, B, C, D parts.
 
  • #3
okay but how will you explain it to anybody by looking at output equation y=cx+d when output is merely combination of state space variables
 
  • #4
I'm a total newbie on this, but from what I've read, you need to express all variables as a state space variable if you want to use them in a state space form. For example, when you want to incorporate an excitation system into a SMIB model, you have to express the variables of the excitation system as a function of state variables. (Kundur Chapter 12) But like a said I'm a total newbie.
 

1. What is state space form in relation to RLC circuits?

State space form is a mathematical representation of a dynamic system, such as an RLC circuit, that describes the behavior of the system over time using a set of state variables. It is often used in control systems engineering and allows for a more flexible and efficient analysis of the system's behavior.

2. How is state space form different from other methods of analyzing RLC circuits?

State space form differs from other methods, such as differential equations or transfer functions, in that it considers the entire system rather than just a single input-output relationship. It also allows for the inclusion of multiple inputs and outputs, making it more suitable for complex systems.

3. What are the advantages of using state space form for RLC circuits?

State space form offers several advantages, including the ability to analyze nonlinear and time-varying systems, the ability to easily incorporate multiple inputs and outputs, and the ability to design controllers using modern control techniques. It also provides a more intuitive understanding of the system's behavior.

4. How do you convert an RLC circuit model into state space form?

To convert an RLC circuit model into state space form, you first need to derive the governing equations for the system using Kirchhoff's laws. These equations can then be rearranged into a set of first-order differential equations, which can be represented in state space form by defining the state variables and input/output variables.

5. Can state space form be used for any type of RLC circuit?

Yes, state space form can be used for any type of RLC circuit, including series, parallel, and mixed configurations. It can also be applied to more complex circuits with multiple energy storage elements, such as coupled inductors or capacitors. However, the process of deriving the state space model may vary slightly depending on the circuit's specific characteristics.

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