Questions tagged [pid-control]

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7
votes
2answers
2k views

Writing a filtered derivative term of the PID controller into the C++ code

Everywhere I look, be it a PID, lead, lag control or anything else, there are Simulink schematics with transfer functions. This is all nice for system response simulation, however currently I have to ...
5
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1answer
141 views

When are overshooting controllers preferred over asymptotic ones?

Disclaimer Designing the behavior of controllers is an important task for many applications. Every application needs its own requirements fulfilled. For example a CNC machine needs a controller with ...
5
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4answers
3k views

Why can't proportional gain alone, reduce the error to zero?

I was told that the proportional gain alone cannot the drive the error signal to zero in a feedback loop. Why is that? If there is a tiny error, there will be a tiny or larger (depending on the number ...
5
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1answer
128 views

Square shaped position error

I got a position error measured by a linear encoder like in the picture below. Could anyone explain some possible reasons for this kind of shape to occur in control theory? My system looks like ...
5
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1answer
229 views

PI-Controler: Comparison of characteristic equations

I have to design a PI-controller with zero order hold for the plant $G_s(s) = \frac{0.24}{(s+4)(s+12)}$ to meet the specifications of $\omega_n=5\,s^{-1}$ and $\zeta = 0.6$. I choose a $T=0.12\,s$ ...
4
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1answer
66 views

What's a control system architecture that can track a ramping reference signal?

It's well-known that a control system with integral control can track a constant reference signal (command) with zero steady-state error. What is needed to generate a controller that can track a ...
4
votes
2answers
170 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^\...
4
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1answer
3k views

How to design a PID controller for MIMO systems in which there are more outputs than inputs?

How do you design a PID controller for MIMO systems in which the outputs outnumber the inputs? It's typical to design a PID controller for MIMO industrial process with the same number of inputs and ...
4
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1answer
4k views

what is a quarter wave decay response after Ziegler–Nichols tuning?

Ziegler–Nichols tuning creates a "quarter wave decay". What does that mean? I cannot find anything online!
4
votes
1answer
228 views

what's wrong with this robust control scheme?

I'm learning how to control a double integrator with $H_\infty$. my model is simply $$\begin{gather} \dot{r} = v \\ \dot{v} = F/m \\ r(t_0) = 0\text{ m}, $v(t_0) = 0\text{ m/s}, m = 1000\text{ kg} \...
3
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1answer
382 views

Advantage of anti-windup

What is the definition of anti-windup? How does it impose the constraints? What are the advantages of MPC and anti-windup over each other? Does anti-windup guarantee the constraints or does it just ...
3
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2answers
118 views

Controlling temperature using PIDs on two separate controllers

I have a pellet smoker, and I am customizing it for tighter temperature control. Currently, I am controlling how much material is burning to control temperature using a PID loop. I want to achieve ...
3
votes
1answer
77 views

Are all motors controlled with G-Code?

So I have laser cutter. And I am thinking about buying a control unit (this one, to be exact). But my concern here is the following: If the input DXF file contains splines, they will be converted to ...
3
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1answer
126 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 ...
3
votes
1answer
1k views

Controls Project: Help needed finding 3rd order system

I'm in need of help finding a third-order or higher system in which I can derive a transfer function. We have a class project in which we need to find a real-life example of the system that equates to ...
3
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1answer
85 views

Differential Equation for: Locking a laser's frequency with a PI controller

I think I have a good understanding of differential equations, so I would like to first try to understand my system in terms of differential equations before transforming my system into the more ...
3
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2answers
3k views

Replacing PID with Lead–lag compensator?

I have a vehicle (I bought it and it proprietary and I have no information about any internals) which I want to integrate into my simulation environment. So far I have a physical model of it which I ...
3
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0answers
48 views

PI or PID-regulator for control system with hysteresis relay in inner loop

I have such control system (sorry for rough drawing :) ) $G(s)$ - stable object with proper transfer function. $1/s$ - integrator. I need to clarify, how synthesized PI or PID controller for such ...
3
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1answer
191 views

Model-based Ziegler-Nichols tuning of a hover PID controller

Doing a fun project to reconnect with my engineering training: I would like to design a control scheme for hovering in-place at a set altitude with a vertically-oriented propeller, rocket, etc. Right ...
2
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3answers
256 views

How to convert a DC motor into a servo motor using a rotary encoder and a microcontroller?

Operating/ Rated Voltage: 24V No load Speed: 350 rpm No load Current: 150mA (max) Max efficiency: 1.4 Kg-cm/300 rpm/ 14.2W/ 0.87A Max power: 4.5 Kg-cm/180 rpm/28.2W/1.4A Stall Current: 2.9 A (max) ...
2
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1answer
184 views

Is the PID just an outdated control method and state-space is superior?

So I've been wondering this for a while; is PID just a simple but slightly outdated control method / isn't state-space (SS) a far superior method in pretty much every way? SS allows for MIMO, PID just ...
2
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2answers
323 views

How do I interpret the following Bode, Nyquist and Nichols diagrams?

I am working with an arbitrarily complicated and long-winded transfer function that looks something like this: $$ H(s) = \frac{as^4+\cdots+b}{cs^6+\cdots+ds^2} $$ where letters represent constants. ...
2
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1answer
47 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 ...
2
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1answer
75 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 ...
2
votes
1answer
1k views

PI controller for second order system

I have a second order system and I need to control it using a PI controller. I need to tune the gains of the controller in order for the system to satisfy the below specifications: $$ OS\% < 10\% \...
2
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1answer
759 views

Design op-amp circuit from transfer function? [closed]

What is the best way to design a circuit based on the following transfer function: (0.0364*s)/(0.0002*s + 1) ? I am trying to design the derivative stage of a PIDF controller using op-amps EDIT: This ...
2
votes
2answers
126 views

Why does accuracy of temperature PID controller drop over time and how to eliminate it?

What am I trying to control? I have a container with approximately 3*2*6 meters (width, height, length). I am controlling through PID the ...
2
votes
2answers
275 views

How does a closed loop control system actually work?

I'm currently taking classical control theory and have some questions regarding basic concepts related to closed loop systems. Let's say I have a simple servo motor controlled by an electric current....
2
votes
1answer
719 views

Is lead filter same as PD combined with a low pass filter?

I am curious to know the difference between a lead compensator (lead filter) and a PD controller with a low pass filter. From the theory I can see that the transfer function of both these controllers ...
2
votes
1answer
46 views

Improving a PID controller from logged historical PID data

Part of our system involves a feedback loop with a PID controller. We log every call to the PID controller, and include in the log information about the Kp, Ki, Kd, the set point, the input, output, ...
2
votes
2answers
18 views

Does it make sense to have a pressure and flow controller on a single closed line?

I have seen P&IDs in which a single line has both a pressure and flow control valve. Based on my understanding of Bernoulli's equation however this doesn't make sense to me - because ultimately ...
2
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2answers
151 views

Analog PID Controller/Filter delay and stability

recently I had an exercise where I had to build and measure an analog PID controller/filter. The starting point was this circuit. This is a tamed PID controller implemented with a single opamp. ...
2
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2answers
161 views

Limiting the integral to a time window in PID controller

Would it make sense to integrate e(t) from t - c to t instead of 0 to t for the integral part of the PID controller? What are the most common deviation from classic PID controller definition?
2
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2answers
4k views

Can a PID controller have a simple on/off output?

The crux of a PID controller is:- output = Kp * error + Ki * integral + Kd * derivative So typically there is proportionality and a continuously varying (analogue) output. In the case of a simple ...
2
votes
2answers
650 views

How can we control the output temperature of a multi-input single-output pipe air-flow system?

I am trying to optimize the heat control of a test bench at our facility. The test bench is basically a pipe with an air flow that can be heated up to desired temperature. To heat the air flow up, ...
2
votes
1answer
215 views

Tuning PID Controller

I have to determinate the power (Watts) for an oven to reach the Temperature Reference. And I have been given only the function to apply power to the oven and read the temperature. I've reading the ...
2
votes
1answer
162 views

What means the velocity constant of the integration in PI controller formulas?

I have an equation of a PI controller. What means here the velocity constant "R" exactly? $$m(t)=K(e(t)+R{\int}e(t)dt)$$ $$R=1sec^{-1}$$
2
votes
1answer
146 views

What is the mathematical basis for the Ziegler-Nichols method for tuning a PID loop?

The Ziegler-Nichols method of tuning PID control loops has been around since the 1940's, and has been widely applied in many areas of engineering. I understand that it is really only a heuristic ...
2
votes
1answer
66 views

Interpreting Nyquist plot

When implementing the control for my application I got this Nyquist plot which made me flabbergasted. If I zoom on the point $-1 + 0j$ I get the following image How do I interpret this contour going ...
2
votes
3answers
777 views

PID control of a DC motor with PWM from Raspberry Pi - how to cross dead area?

I'm driving a DC motor (actually a linear actuator) with a Polulu motor controller from a Raspberry Pi. The motor drives if you ask for anything between 20 and 100% duty cycle, so there is a dead zone ...
2
votes
1answer
965 views

Suggestion to control a gimbal bldc motor for positioning

I try to understand what the PID controller of a gimbal stabilizer boards (e.g Storm32BGC) does influence? From the IMU we get position and velocity after sensor funsion. The input variable of the ...
2
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0answers
37 views

Is this function common in PID controllers?

I'm reading some old microcontroller code for a PID algorithm. There's a strange function (to me) that seems to work like this: $output = \frac{1}{n}input + \frac{n-1}{n}previous\_output$ The value $...
2
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0answers
37 views

How to control an underactuated platform with a single servo

What's the best way to control the following type of platform so that it remains balanced and upright? It's a box supported by a single leg that can pivot at the foot (F) and at the hip (H). The foot ...
2
votes
1answer
147 views

Tricks for controlling process with logaritmich characteristics over 20 orders of magnitude

I'm building a machine that operates over 20 orders of magnitude with logarithmic process characteristics. I have tried regular PID and also all sorts of variations of PID and did not get good results....
1
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1answer
52 views

Can I design/tune the outer loop controller without knowing the details of the inner loop controller?

In cascade PID control loops as below, can I make an assumption that the inner loop will respond much faster than the outer loop, hence I could simplify U1_CMD as U1 and I could design/tune the gains ...
1
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4answers
120 views

PID controller - Counterproductive derivative

I'm having trouble understanding the derivative part of a PID controller, because it sometimes seems to react the opposite way that I would like. Let's use a simple example where : the controlled ...
1
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1answer
96 views

Is it necessary to use PID control in my use case?

I have a workflow of two functions. Both of them aggregate the items that are receiving and only the first is adjustable. I mean that I can decide how many items to aggregate on the first function <...
1
vote
2answers
3k views

How do elevators stop at the exact landing spot when reaching a particular floor?

The floor the elevator moves to, is controlled by the lift PLC with all the algorithms developed over the years, and that I understand well. What I am not able to understand is how does the lift stop ...
1
vote
3answers
556 views

PID position control when setpoint does not require continuous force

I'm struggling with the practical application of a PID control algorithm when the set point does not require any external force to stay in position. For example, I have a geared electric motor that ...
1
vote
1answer
947 views

Best PID autotuning algorithm/library for simple heater problem

It's the 21st century, anything is possible. Except for PID autotuning for a simple problem, heating/cooling system - make robust and ready to use solution. I've found only one library for PID ...