# Questions tagged [control-theory]

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### Do transfer function changed in vertically placed spring damper system when an additional mass is added

Title: Calculating the Transfer Function and Displacement for a Spring-Damper System with Additional Mass I am working on a problem involving a spring-damper system, and I need help with calculating ...
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### Continuous Discrete State Space Properties

When we have a continuous model that we try to discretize it by using ZOH, if the first state is reachable, then what can we say about the reachability, observability and stability of the discrete ...
32 views

### Closed loop motor speed algorithms

TLDR; looking for algorithms to control a motor. I have a near-random torque, a battery current that can destroy my motor driver, and I aim for a stable output speed regardless of torque. My inputs ...
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### Block Diagram Reduction in Control Systems

My professor provided a code that shows the different ways to reduce a multiple block diagram. ...
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### A question about the necessity of the observer in control theory

I am major in mathematics and also a beginner in control theory. I have a question about the necessity of observer in control theory. Take a linear system as an example, for state variable $x(t)$ ...
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### Understanding Block Diagrams in Control Setups

Working on some automation for a Boeing 747 autopilot, I am trying to wrap my head around what sections of block diagrams like this one mean: I understand that something is being done to the yaw rate ...
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### Can we reshape the root locus by adding a pole instead of a zero (as is done in PD controller) to get required Ts while O.S. being the same?

I was studying about PD controllers, which made use of adding a zero at such location which gave the required settling time(Ts) while keeping the overshoot same as it was in the uncompensated system. ...
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### What is the relationship between classical control: transfer functions/frequency domain and the swing-up problem of an inverted pendulum

I am still pretty new to control theory, but I have been studying both classical and modern state space/optimal control ideas. I am having trouble understanding what the frequency domain/transfer ...
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1 vote
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### How to design the control loop to synchronize two rotational objects?

There is a rotating object (object A) that rotates at about 50 rpm. Its rotational speed may change slowly. I need to control another object B via a variable frequency motor, so that the objects' ...
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### Does H infinity control have to be limited to a simple 1Dof feedback architecture?

So I understand how H infinity control can be used to synthesize a controller that is in the standard error-feedback framework shown here: https://www.researchgate.net/figure/1-DOF-feedback-control-...
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### I need to design a controller for a system, need to choose between P, PI, PD, and PID, given only the desired ss, settling, and overshoot %

(Apologies for terrible formatting, first post and don't know how to make equations look nice) The system is $$G(s)=\frac{10}{4s^2+7s+23}$$ and the requirements are steady state error of zero, $10ms$ ...
87 views

### How does frequency-response and lead-lag compensators fit in with PID or State Space control

I am new to control theory, as my background is in statistics. In watching a wonderful set of lectures by John Rossiter, and am feeling pretty comfortable with my understanding of the basic concepts ...
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### Routh's algorithm and root analysis give contradictory results

I am designing a control system : with open loop gain equal to : $\frac{K}{s(s^{2}+4s+3)}$ The closed loop gain is obviously :$\frac{K}{s(s^{2}+4s+3)+K}$ I tried finding the critical frequency but ...
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### Different kinds of control loops

I am wondering about different categorizations of control loops. One categorization differentiates control loops with respect to what inputs they take: Open control loops. Closed control loops. 1a. ...
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### Error Equation of a Control Loop

I want to calculate the error of a control loop. Therefore, the system and the general processes and models are defined as follows: The equation for error is described as follows: I do not ...
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### What is the intuitive explanation for why a system can be stable with a negative gain margin?

Beyond the math which shows that a gain of -1 and a phase of -180 (G(s)=-1)causes instability when the open-loop TF is taken to closed loop, the way I've always justified the instability of G(s)=-1 ...
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### How to re-write systems of two linear second order ODEs in a state space form

I have recently been working on how to convert ODES into state space form, and I came across this problem that has me confused. Should B in the state space be [1; -2] or [1 0; 0 -2]? I think the ...
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1 vote
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### How often is discrete-time control used in industry?

Although in reality I know that computers handle all systems in discrete time, in my limited industry work experience I've only used continuous-time control system analysis/standard frequency domain ...
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### MATLAB allmargin() function return multiple GainMargin, but how to identify them on the Bode plot?

I have a high order discrete transfer function model which has the following form. When I use the allmargin function to get the gain margin, I get the following result: ...
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1 vote
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### why Type III systems has at least two gain margins?

I heard the following statement https://engineering.stackexchange.com/a/54322/40848 if we have a type III system, or one that has three or more low-frequency poles that we're closing around, then we ...
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### Why are the phase indicators different between the open loop bode plot and the closed loop bode plot?

I have an open-loop transfer function G num=105*conv([1 1],[1 2 43.25]); den=conv([2 0 0],conv([1 2 82],[1 2 101])); G=tf(num,den); and a closed-loop function of G/(1+G). Here are the open-loop bode ...
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