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# Questions tagged [control-system]

A system that may be electronic circuits or even software that uses control theory (principally differential equations) to control an output by monitoring various aspects of the system under control and varying inputs all towards meeting a defined goal. Some famous examples are controlling a rockets thrust angle to ensure directional control.

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988 views

### How to determine the phase margin and transfer function of this bode plot?

I have some struggles to find the transfer function of this plot. We got the hint, that the "breaks" of slope can be assumed to be on vertical and horizontal lines. Also we should pay attention on the ...
140 views

### Meaning of the “pole” of a transfer function with time delay

I learned in basic control theory that we can determine the stability of an LTI system by the signs of the real part of the poles of its transfer function $H(s)=\frac{N(s)}{D(s)}$. For a rational ...
204 views

### PID Tuning Issue

I'm having issues tuning a PID controller - specifically the I-term. First - here's a little info about my system: I'm heating a coil (R ~= 1.8 Ohms) to 750°F. My power delivery system is working ...
365 views

### Solving the differential equation in control system engineering

While I am continuing my studies of the Norman S. Nise book about Control System Engineering, and while trying to solve exercises of chapter 1, I noticed that I am out of the scope of solving ...
479 views

### Block diagrams can be different and still works for the same system?

I am an telecommunications engineer who is working now as a programmer. At university we took a class on digital filters, Laplace transformation and working in the frequency and time domain. At the ...
285 views

### PID tuning without plant model

My aim is to keep temperature constant at a certain place. I don't have a mathematical model of the plant. Currently, PID is used with some fixed Kp, Ki, and Kd, and I want to optimize these ...
2k views

### Should cable shields be connected to earth ground, or to power supply negative?

I'm working on a PLC cabinet, and I'm wondering whether I should hook cable shields to earth ground, or to the power supply negative. I checked and the power supply DC output is isolated. There's no ...
965 views

### Three-phase thyristor rectifier - Minimum firing angle

Why is a minimum firing angle (>0, usually 5-15°) defined for three-phase thyristor rectifier? I would like a technical explanation. Thanks
66 views

### Why is this derivation of the unit step function in the Z-domain valid?

This source states that the unit step function in the Z-domain is $\frac{z}{z-1}$. However, in its derivation it states $\sum_{k=0}^{\infty} z^{-k} = \frac{z}{z-1}$. But doesn't that last ...
368 views

### Finding the transfer function of an non-inverting audio op-amp

I am just doing some independent re-search for myself in audio amplifier (CHIP AMPS) such as the LM1875. I want to learn more about how to compensate for audio chip amps and how their bode plot ...
42 views

### What's oscillatory instability in the delay differential equations?

Does DDE’s stability depend on forcing term and ODE’s stability does not depend?If yes, then is frequency analysis of stability applicable only to DDE and not ODE? In control systems, we study ...
50 views

### Control system error based on differential process value

In a basic PID controller, you measure the process value y (such as temperature) directly; then the error e is equal to the difference between the process value and the set point r. The error feeds a ...
176 views

### design of compensator type 2 for current mode control of boost converter?

I have designed boost converter with Peak current mode control in PLECS. I have used the method of k factor approach to design the compensator. the bode plot transfer function of the power stage is ...
1k views

### Approximation of second order system, by step response

I am trying to aproximate a transfer function of a system. The system is a linear actuator, connected to a feedback potentiometer. The following figure is a step respons, with 24 V as input, and the ...
125 views

### Why linearise around an equilibrium point?

In the control theory dealt in class I was taught to always linearise a nonlinear system around an equilibrium point, i.e., where $$\dot x = 0$$ However, linearization is a Taylor series expansion, ...
58 views

### How to go about determing the System Type of my setup?

I have a small project where I am PID tuning two servo motors. Something very similar to this: I am interested in finding the system type of the above setup, which includes the PID loop I have tuned. ...
88 views

### Help with identifying a transfer function - with neuroscience application

This is a question for you electrical network engineers. The problem has arisen in a neuroscience study I am working on, but I hope to be able to glean some insight from other domains that deal with ...
114 views

### Gain of proportional Controller with distubance $sin(10t)$

The diagram below represents the position of ocean oil platform system which use the proportional controller with gain $k$. The output $x(s)$ is the platform deflection regards the position ...
71 views

### Pole-placement problem

I was following this example of implementing a pole-placement with an Integral controller. Matrices A_star=[-5 -3 0;1 0 0;0 -1 0] B_star=[1;0;0] desired poles -100,-8+i*11,-8-i*11 I know the ...
499 views

### Why is phase margin considered more important than gain margin in dc-dc converters?

Control theory text books say both gain margin and phase margin give information about relative stability. These quantities also give an idea about the corresponding closed loop system's transient ...
61 views

### What does asymptotic stability mean ? and can a system have lower than 90deg of phase margin and still be stable?

why bode stability criteria dictates 90deg of phase margin ? my understanding is that it is so when a system is cascaded with another there's a margin so the phase doesn't get to 180 and over, am i ...
111 views

### How can infer instability from the frequency response of control system?

When can we judge a control system to be unstable from its frequency response?.For example, thermostat computes the error signal (desired room temperature - actual room temperature) and then actuates ...
122 views

### PR controller electrical circuit

I am attempting to design a PR control feedback loop for a grid tie inverter. The math checks out but I can't seem to convert the transfer function and/or block diagram into an actual electrical ...
481 views

340 views

### Effects of feedback

After doing some exercises in control theory I realized that one don't really need feedback to fulfill a lot of specifications. One could in principal introduce a controller giving us stability etc ...
127 views

### Difference between compensation and using a PID contoller?

I have a hard time understanding the differnce between the two techniques that are introduces in my textbook, a PID controller and Lead/Lag compensation. Ultimately we add a new box to our "loop" and ...
74 views

### tracking error state space, linear control example

I am trying to understand a detail from an example, from the control textbook Slotine and Li (1991) "Applied Nonlinear Control", Prentice-Hall, Example 6.4, pag. 220. A linear system is given: \...
Let $G(s) = \frac{Y(s)}{R(s)}$ be the loop gain of a negative feedback loop system. For example a system like this, where Y(s) and R(s) are the laplace transformed functions y(t) and r(t): ...