There are two interviews:

• An online video interview
• A phone interview

I stopped at the phone interview.

Math:

• What is an invertible matrix?
• What is the rank of a matrix? Calculate the rank: [1 1 0; 1 2 1; 0 1 1]
• How to calculate eigenvalues? Calculate the eigenvalues: [3 -1; 1 5]
• What's the difference between a finite integral and an infinite integral?
• Calculate the limit of sin(x)/x as x approaches 0. How to calculate it.

Control Theory:

• Difference between open-loop and closed-loop control.
• Solve the transfer function of the equation: y'' + 4y' + 20y = u
• What is the criterion for an LTI system to be stable in the continuous-time domain? Why?
• What is the criterion for an LTI system to be stable in the discrete-time domain?
• For a second-order system, what are rise time and settling time?
• Given tf = 4/(s^2 + 4s + 4), calculate the natural frequency and damping ratio.
• PID controller: If P changes, what will change? If I want to improve the steady-state output error, what needs to be changed?
• Bode Plot.
• Gain Margin.
• State Space Formulation.
• Describe controllability.

C language:

• How to find if a number is even or odd?
• Null pointer.
• Rename a data type, like int a, then rename int.
• Given int *p; *p = 5;, is the code above correct? What will happen when compiling?
• Difference between struct and union.
• Dynamic memory allocation, malloc.
• What data types can be returned?
• Inline function.
• Recursive exit condition.
• Difference between pass by value and pass by reference.
• Find repeat elements of an array.
• Difference between continue and break.

MATLAB:

• What is %?
• What is @?
• How to concatenate two strings?
• How to change the title of a plot?
• What is startup.m?
• How to clear variables in the workspace?