Questions tagged [control-engineering]

Questions about the models and theories of control engineering and the application of control theory to design systems with desired behaviors.

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Passivity in State Space Systems

Suppose I have the state space system $a\dot{x} = -x + \frac{1}{k}h(x) + u$, and output $y = h(x)$, where $a,k > 0$. The only information I'm given about $h(x)$ is that $h\in[0,k]$. I want to show ...
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24 views

Bounds to prove exponential stablity for given Lyapunov function

Problem 3.6 in Khalil's Nonlinear Control: Use given Lypunov candidate function to prove that the origin is exponentially stable. The system is $$\dot{x}=\begin{bmatrix}x_2\\-h(x_1)-2x_2\end{bmatrix},...
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Backstepping control of second order nonlinear system

$\dot{x_{1}}=x_{2}^2-3sin(x_{1})x_{2}$ $\dot{x_{2}}=x_{1}^3-3x_{2}cos(x_{1})+u^\frac{1}{2}$ Question: Using the backstepping method and Lyapunov function, design the controller(u) that will make the ...
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26 views

avoidance with LQR

I'm interested in using linear quadratic regulators (LQR) to model prey avoidance behaviors. I want to adapt the LQR algorithm to incorporate dynamics and state costs that maximize the distance from a ...
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1answer
38 views

Modeling the torque of a real motor

I am trying to control a real inverted pendulum by means of a DC motor, for this I must model the torque of the motor, the work I've done in this direction is the following (which I believe is right): ...
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2answers
71 views

How to obtain transfer function of control diagram with Internal Model Control?

I want to design a robust control system using the internal model design specifications. The block diagram is the one shown below: I am trying to obtain the transfer function $\ \frac{Y(s)}{R(s)} $ ...
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Evaluate “damping” of higher-order transfer function - something similar to settling time without the discontinuities

I have an 11th order transfer function in the continuous domain (simplified linearized model of a grid-forming converter) and I'm looking for a way to characterize it with a single number for ...
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1answer
35 views

Find the transfer function of a basic block diagram

I'm new to Control Systems. I've been given this block diagram and I would like to find the overall transfer function. How can I do it? I was thinking about simplifying the diagram by placing in ...
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69 views

How many kWh this turbine would generate?

My grandfather and I are running some experiments down the river, however we don't have expertise in engineering so I bring up this question to the community and hope someone could help. How many kWh ...
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1answer
19 views

Noise sensitivity transfer function

Consider we have a second order system (plant) described by the following transfer function: $$ P(s) = \frac{b_0}{s^2+a_1*s+a_2} $$ which is controller by a PD-controller: $$ C(s) = K_p+K_ds $$ ...
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32 views

Simple dynamic simulation of a pump in a fluid network

I need to calculate the behaviour of head/pressure and volume flow for an arbitrary pump. The only papers I find go way too deep into detail, using CFD for a given pump geometry, but for me it's just ...
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24 views

Compare Genetic Algorithms and Markov Chain Monte Carlo in their statistical properties in parameter estimation task

I am using GA and MCMC for estimating the parameters of a transfer function. GA returns results that each parameter has one value when minimizing the error function, and MCMC returns the whole chain ...
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1answer
41 views

How to reduce oscillations (rapid changes of control signal) when controlling a real system, which occur due to noise in measurement from sensors?

I have a real mechanical system (ball & beam) which I want to control. The system is approximated by the second order transfer function: $$ T(s) = \frac{b_0}{s^2+a_1s+a_2} $$ and in state-space ...
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1answer
48 views

How to find closed loop transfer function and use it to identify τ and k?

I have to answer a few questions on transfer functions using Matlab. The first question, which I solved without Matlab, gives a time response graph for an LR circuit, and asks me to find the first ...
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1answer
70 views

Proportional-Derivative compensator design

I have been struggling with the following problem for a few days now and would greatly appreciate some assistance. I'm new to control systems and have very little experience with PD controllers and ...
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2answers
71 views

Increasing Kd in PID control loop

Why does increasing derivative gain $K_d$ in a PID controller loop lead to a reduction in overshoot and an increase in rise time? This is not a homework question, it is a question to improve my ...
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1answer
99 views

Does this PID-like algorithm make any sense for a solar inverter?

The application I want to implement the control of a photovoltaic inverter. The goal would be to keep the consumption of a microgrid (the power absorbed from the grid) to a constant value. Notes: I ...
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1answer
43 views

Control System; Finding resonant frequency of 3rd order

We've been requested to find the resonant frequencies of a 3rd order plant in class and were presented to the following method to do so: My question is, when using the $\ \omega_r $ formula, to find ...
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21 views

Kalman Filter by Orthogonal Projection

I'm working through the derivation for the Kalman filter using orthogonal projections. It's pretty intuitive that if we want to generate the best linear estimate for an $n$-vector $x$ using some $m$-...
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1answer
57 views

How to obtain linear parametric model of given system?

Consider the system: $$ y(s)=b\frac{e^{−sτ}}{s+a}u(s) $$ where a,b are unknown, constant parameters and $\ τ>0 $ is an unknown delay constant. How can I obtain a linear parametric model for this ...
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32 views

LQR Implementation in MATLAB

I am trying to implement a simple LQR controller in MATLAB for a purely deterministic system. The code is shown below: ...
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1answer
39 views

What are the drawbacks of inceasing the bandwidth of the system?

I have a doubt concerning the closed loop frequency responce of a control system. Suppose I have the following situation: in which is plotted the frequency response of a system with different ...
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1answer
40 views

Develop linear parametric model of a third order plant

Consider we have the third order plant described by the equation: $$ y = G(s)u $$ where $\ G(s) = \frac{b_{2}s^{2}+b_{1}s+b_{0}}{s^{3}+a_2s^2+a_1s+a_0} $ If we assume that all parameters $\ a_0,a_1,...
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1answer
34 views

Understanding oversampling in control system

Oversampling means to sample at significantly more than the Nyquist Rate. I can well understand it in signal re-construction: more samples can improve the ADC's resolution, signal-to-error ratio, etc. ...
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1answer
39 views

Problem finding value of the gain such that the closed loop is stable

I have the following transfer function: $G(s)=\frac{-s^3 +s}{s^4+3s^3+2s^2}$ and this is a transfer function of a plant with two poles in the origin. So I want to desing a controller with two poles ...
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114 views

P&ID Symbol identification, unknown meaning

I'm aware that answers may vary and it really does depend on the company/country where the PID was drawn but I have checked back for the last 30 years and found no drawing legend that describes what ...
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1answer
28 views

Stepper motor speed control problem

For brushless DC motors we have hall sensors to keep track of rotor; however, for stepper motor we don't know the actual position of the rotor and therefore while changing pulses with some speed it ...
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1answer
21 views

Problem with RHP zero in transfer function

I have a transfer function with a RHP zero in $s=+1$, and I am trying to show in Matlab thath this limitation is present. In particular, initially I had a MIMO system, which I decoupled and then I ...
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1answer
31 views

Doubt on bandwidth of a control system

Consider this image of a loop shaping design: here which is the bandwidth of the system? I have a doubt because until now I have considered as bandwidth to the system the one of the complementary ...
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1answer
30 views

Any idea about what does this image represent in control systems?

I just need a hint , I know it's out of context but that's how I found it in a Facebook group, I thought someone might have seen this before, I study automation and I know that Kp is the proportional ...
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1answer
22 views

Nyquist stability criterion for positive feedback

it is known that the stability of a system with negative feedback may be analized through the Nyquist stability criterion, which is based on observing the number of turns around the point (-1;0) in ...
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50 views

How do I add unmodeled dynamics to the system?

I am considering the following paper: Stability‐and performance‐robustness tradeoffs: MIMO mixed‐µ vs complex‐µ design and I am having troubles understanding how to handle the unmodeled dynamics of ...
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19 views

Moisture sensor for Mixers

I'm looking for alternatives to measure the moisture content in a concrete mixer machine. The ones on the market are expensive, like Hidro-Mix for apparent reasons; mixers are a hostile environment ...
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1answer
49 views

analysis of PD controller vs static-gain

I have a plant $G(s)$ which gives position and velocity as output $$ G = [G_{ru}(s)\quad G_{vu}(s)]^T $$ where $G_{ru}$ is the integral of $G_{vu}$, and $u$ is the input to the system. Now if I want ...
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2answers
42 views

How to convert output of controller (control signal) into PWM signal?

I am trying to control a mechanical system with some transfer function T (output is position & input is voltage). I have implemented a state feedback controller in order for the output of the ...
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51 views

Finding coefficients for a PID controller that minimize the integral of the squared error (ISE)

The problem The problem is to find the coefficients for the P, I and D terms of a PID controller used to regulate the object that minimize the the integral of the squared error (ISE): $$Q = \int_0^\...
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1answer
53 views

what is the physical interpretation of poles and zeros of a mechanical system?

what is the physical interpretation of poles and zeros of a mechanical system? I'm asking things like the meaning if I have only 0 or only complex numbers. And about the number of the poles and zeros, ...
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1answer
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Limiting PID controller's output making the plant unstable and untunable

I am using the PID block in Simulink and limiting the output to (+/-)5. The plant becomes unstable and untunable after putting these limits. The plant is stable and tuneable otherwise if no limits are ...
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1answer
63 views

Optimal control vs. nonlinear control

I have tried to compare between two courses, and there seems to be some overlap, but not as much. Which method is better when controlling a nonlinear system? Also, what is the main difference between ...
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1answer
28 views

What is the minimum frictional force required for a vehicle to operate smoothly, retain traction, and prevent any skids?

I am not looking for a specific number of course. I know that it may perhaps vary with different vehicles. However, I'm trying to figure out how to theoretically calculate the minimum necessary ...
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1answer
33 views

Aircraft Longitudinal and Lateral Transfer Function Terms

The figure shows input and output variables for both longitudinal and lateral stability transfer functions. I completely understand what each term stands for but I was wondering what would be the ...
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1answer
29 views

Doubt on zero pole cancellation

I am looking at a control system which has an unstable pole in the process. The transfer functions of process and controller are the following: ...
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1answer
45 views

AC Motor On/OFF Control using SSR instead of contactor

I would like to control a 1-phase 3HP motor using a SSR ( the reason being, I need to switch it on/off using a signal (0-5VDC). Are normal SSRs (ex:Fotek 40A model) capable of handling the starting ...
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0answers
41 views

Why a zero too close to the imaginary axis gives bad berformances?

I am studying control systems, and I have found that if I consider I control scheme where I filter the reference , if the zero of the pre-filter is too close to the imaginary axis, we have a ...
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1answer
21 views

Control each axis separately - quadcopter

I would like to know why axis can be controlled independently in a quadcopter. I mean, I was told that you can control $x$ and $y$ independently but I couldn't find a demonstration Edit: the ...
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1answer
44 views

Limitations on the control effort

I am studying the mixed sensitivity design for control systems, and I have seen that the control effort has limitations given by the bandwidth of the process and by the bandwidth of the sensitivity ...
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29 views

Design compensator to improve yaw rate control performance for aircraft

I am trying to design a compensator to improve the yaw rate ($\dot{r}$) control performance of an aircraft. The lateral dynamics for this aircraft is given in steady space form as following: where A (...
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21 views

Control effort in mixed sensitivity design

I am dealing with mixed sensitivity controller design in SISO systems and I am comparing this approch with the classic approch. In particular, I have placed a weight for the sensitivity function in ...
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21 views

Relationship between conjugate poles and resonance peak in frequency response

I have two root locus of two closed loop transfer fuctions, which differ just by a different value of the gain. I have that the one with a larger gain has a reasonance peak bigger in the frequency ...
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33 views

How to choose a best sampling rate, according to time constant or bandwidth?

This is a follow up question of Rule of thumb for choosing a best sampling rate I have a discrete control system with a reference input. The goal is to keep the output close to the reference input (...

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