This question was asked inGPSC Deputy Executive Engineer (Electrical) Class-2 Master Paper 2026Question 129 of 195 published · Gujarat Public Service CommissionOpen paper
Q129ModerateState-Space Analysis

A system is represented in state-space form with two state variables and stable eigenvalues, then
1. The system order is two.
2. The system is stable since eigenvalues lie in left half-plane.
3. State variables completely describe system dynamics.
4. Output depends only on input and not on state variables.
Which of the above statements is/are correct?

Answer & step-by-step solution
Correct answer: C. 1, 2 and 3 only
Quick explanation

A state-space model represents internal dynamics using a minimal set of state variables. Output generally depends on both state and direct input through y=Cx+Du. Key relation: ẋ=Ax+Bu; y=Cx+Du.

Exam focus: Eigenvalues of A are the state-model characteristic roots. Common trap: Output is not generally independent of state variables.

ẋ=Ax+Bu; y=Cx+Du.

Statement-wise Verification

  • Statement 1 - Correct.
    The system order is two.
    Ẋ=Ax+Bu; y=Cx+Du.
  • Statement 2 - Correct.
    The system is stable since eigenvalues lie in left half-plane.
    Eigenvalues of A are the state-model characteristic roots.
  • Statement 3 - Correct.
    State variables completely describe system dynamics.
    A state-space model represents internal dynamics using a minimal set of state variables.
  • Statement 4 - Incorrect.
    Output depends only on input and not on state variables.
    State-space output is generally y=Cx+Du and therefore depends on states

Core Concept

A state-space model represents internal dynamics using a minimal set of state variables. It naturally handles MIMO systems and incorporates initial conditions. Stability of a continuous-time LTI model is tied to eigenvalues of A: strictly negative real parts imply asymptotic stability. Output generally depends on both state and direct input through y=Cx+Du.

Formula / Key Relationship

ẋ=Ax+Bu; y=Cx+Du.

Why the Other Options Are Wrong

Option A is incorrect because it omits correct statement(s) 1. Option B is incorrect because it omits correct statement(s) 2. Option D is incorrect because it includes incorrect statement(s) 4.

Exam Shortcut / Approach

Eigenvalues of A are the state-model characteristic roots.

Common Mistake

Output is not generally independent of state variables.

Quick Revision

System Order Eigenvalues and Output Equation is linked with State Variables, State-Space Analysis and Control Systems. Eigenvalues of A are the state-model characteristic roots.

Exam tipEigenvalues of A are the state-model characteristic roots.
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