Questions tagged [control]

A method or device to manage, command or regulate some part of a system.

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70
votes
9answers
262k views

What are good strategies for tuning PID loops?

Tuning controller gains can be difficult, what general strategies work well to get a stable system that converges to the right solution?
25
votes
3answers
3k views

What algorithm should I use for balancing a two wheeled robot using a gyroscope?

Is there a good, popular and reliable algorithm I can use by taking input from a gyroscope and using this to control two independant wheels to keep such a balanced robot reliably upright? I'm looking ...
19
votes
6answers
6k views

Robot never goes straight

I am using 2 identical DC motors and a castor wheel. The motors are connected to L293D motor driver and are controlled by RPi. The robot is not going straight. It veers off to the right. I am ...
16
votes
1answer
3k views

ROS: Best practices?

I'm going to build a small robot system, and it seems like that ROS serves a nice framework to control and program the system. However, I am wondering which is the best practice to manage the ...
15
votes
4answers
6k views

How can I modify a low cost hobby servo to run 'freely'?

I've got some hobby servos (Power HD 1501MGs) and I'd like to be able to control them (via an Arduino) so they will either go to the angle I set, or put them in a 'free running' mode, where the load ...
15
votes
3answers
5k views

How can I automatically adjust PID parameters on the fly?

I have a simple servo system that uses a PID controller implemented in an MCU to perform the feedback. However, the properties of the system change dynamically, and so the PID parameters can never be ...
15
votes
2answers
2k views

Optimal Control for a simple pendulum

I'm studying various optimal control methods (and implements them in Matlab), and as test case I choose (for now) a simple pendulum (fixed to the ground), which I want to control to the upper position....
14
votes
2answers
278 views

What is the right approach to write the spin controller for a soccer robot?

Imagine programming a 3 wheel soccer robot. What type of controller would you use for spinning it? P? PID? The goal for this controller is that it should make the robot stand in a defined angle ( 0 ...
14
votes
3answers
5k views

How is PIV control performed?

I'm considering experimenting with PIV control instead of PID control. Contrary to PID, PIV control has very little explanation on the internet and literature. There is almost a single source of ...
12
votes
3answers
8k views

I don't understand Integral part of PID controller

I dont understand integral part of PID controller. Let's assume this pseudocode from Wikipedia: ...
12
votes
3answers
833 views

How can I control a fast (200Hz) realtime system with a slow (30Hz) system?

We are currently designing a mobile robot + mounted arm with multiple controlled degrees of freedom and sensors. I am considering an architecture in two parts: A set of realtime controllers (either ...
12
votes
4answers
539 views

Why is it so hard to walk?

At least, on two legs. Asimo, one of the best known humanoid robots, is already capable to walk, although it doesn't seem to do this very stable. And it is a recent result. As far I know, the legs ...
11
votes
3answers
7k views

In PID control, what do the poles and zeros represent?

Whenever I read a text about control (e.g. PID control) it often mentions 'poles' and 'zeros'. What do they mean by that? What physical state does a pole or a zero describe?
11
votes
2answers
11k views

How do I calculate the required loop frequency for a servo controller?

I have a motor which drives a string connected to a load cell. I would like to implement a closed loop controller to control the load applied by the motor to the string. How do I go about determining ...
11
votes
3answers
499 views

Which is model is best for feedback control of robotic manipulators: MIMO or parallel SISO?

I'm currently designing a robotic arm with 6-DOF, and my goal is to be able to give setpoints for 3d position, velocity and orientation ($x,y,z,\dot{x},\dot{y},\dot{z},\theta,\alpha,\gamma$). I only ...
10
votes
3answers
17k views

Position Control vs Velocity Control vs Torque Control

Please can somebody explain to me the difference between Position Control, Velocity Control, and Torque Control? Specifically, I am thinking in terms of a robot arm. I understand that position control ...
10
votes
4answers
3k views

What are human-friendly terms for mobile-robot orientation and relative direction of non-robot objects?

Within robotics programming, orientation is primarily given in terms of x, y, & z coordinates, from some central location. However x, y, z coordinates aren't convenient for rapid human ...
9
votes
3answers
666 views

Using genetic algorithm for tuning controllers

I've read some papers for controlling nonlinear systems (e.g. nonlinear pendulum). There are several approaches for targeting nonlinear systems. The most common ones are feedback linearizaing, ...
9
votes
1answer
3k views

How can we use the accelerometer for altitude estimation?

I am currently implementing an autonomous quadcopter which I recently got flying and which was stable, but is unable to correct itself in the presence of significant external disturbances. I assume ...
9
votes
1answer
3k views

Multiple control loops with overlapping effects

I'm familiar with using PID to perform closed loop control when there is a single output and a single error signal for how well the output is achieving the desired set-point. Suppose, however, there ...
9
votes
2answers
13k views

How to use Arduino for ESC control?

I am using an Arduino Uno to control an ESC for my (in progress) quadrocopter. I am currently using the servo library to control the ESC, which works great. Except.. A count of 100 is max speed, ...
9
votes
1answer
205 views

How do I decide the size of the time steps between sensing and control actuation?

My Background: My experience is in solid mechanics and FEA. So I have zero experience in robotics/controls. Problem Description I'm developing a control strategy to stabilize a complicated 6-...
9
votes
1answer
680 views

How can I optimise control parameters for a stepper motor?

As an industrial roboticist I spent most of my time working with robots and machines which used brushless DC motors or linear motors, so I have lots of experience tuning PID parameters for those ...
8
votes
2answers
4k views

How to calculate the right and left speed for a tank-like rover?

I am trying to control the Rover 5 robot using an Android app with a touch-based joystick control in the app UI. I want to calculate the speed of the left and right motors in the rover when joystick ...
8
votes
2answers
187 views

What to do when position control with trajectories is interrupted?

What are strategies used when trajectories, which are applied to a robotic joint, are interrupted? Say a robotic arm hits an obstacle, the controller just keeps applying the trajectory. Then at the ...
8
votes
1answer
594 views

Building a balancing robot with differential drive

I've already built a two wheeled balancing robot using some continuous rotation servos and an accelerometer/gyroscope. I upgraded the servos to some geared DC motors with 8-bit encoders with the goal ...
8
votes
2answers
291 views

Motion Planning vs. Control

Often I see positions for robotics companies split into planning and controls engineers. But motion planning and controls seem to have a lot of overlap. As I understand in motion planning the ...
8
votes
1answer
4k views

DC motor control - speed-torque curve

I am having some trouble understanding how to practically use the speed-torque curve of a DC motor. I understand that the gradient of the speed-torque curve is defined by the design of the motor, the ...
8
votes
1answer
232 views

Cable routing in theta, x, y motion control system. Better inside or outside?

I'm building a motion control platform with 3 DoF: 1 axis of rotation (theta) and 2 cartesian (x,y). In most applications, like wrist actuation, you have an X-Y stage with a rotating servo as the ...
8
votes
1answer
194 views

Which spline function would be best suited for the trajectory of a differential drive

What's the best kind of spline that can be used for generating trajectory that can be adapted during execution time? The use case is having a differential drive which has to move towards a point (x,y,...
7
votes
1answer
5k views

Quadcopter PID Algorithm

I'm trying to implement a PID control on my quadcopter using the Tiva C series microcontroller but I have trouble making the PID stabilize the system. While I was testing the PID, I noticed slow or ...
7
votes
2answers
208 views

How much can working with CNC machines teach you about robotics?

I have built a few simple X/Y/Z CNC machines. I've learned about G-Code, motor control, firmware and open loop systems. I see machines like rovers, big dog and factory arms that seem incredibly ...
7
votes
5answers
529 views

Arduino Motor control

I'm working on a rather low budget project, and need some way to control four or more motors using one Arduino. I've looked at motor shields a little, but I have a shield on top of it already, It does ...
7
votes
1answer
2k views

How to tune the PID parameters using Fuzzy Logic?

I previously used the Ziegler method to tune the parameters of my PID controller to control my robot's position. I then implemented fuzzy logic for self-tuning the parameters. I have two inputs to ...
7
votes
5answers
5k views

Why does a ID controller not exist?

Why doesn't a PID only consisting of ID exist?
7
votes
1answer
468 views

Is the geometric inverse problem's solution “continuous” for a redundant robot?

Let's say my redundant robot is at an operationnal position $x$. Is the set of all possible joint configuration "continuous", which would mean that it is possible to explore all the possible ...
7
votes
2answers
3k views

Cascading PID DC Motor Position & Velocity Controllers

I'm trying to build a robot with a differential drive powered by two DC Motors. First I implemented a PID Controller to control the velocity of each motor independently. Estimated the TF using the ...
7
votes
1answer
1k views

Differential drive trajectory following control

I have a robot platform with differential drive which knows it's position and orientation. Lets say that the space through which the robot moves is known and it has only static obstacles. The task is ...
7
votes
2answers
278 views

“Time-varying” and “nonautonomous” dynamical systems and their Lyapunov analysis

It is possible to distinguish the properties "time-varying" and "nonautonomous" in dynamical systems regarding Lyapunov stability analysis? Does it make a difference if the system depends explicitly ...
7
votes
2answers
4k views

I want to control a sewing machine motor; need help with choices

I've got an industrial sewing machine (think "can sew with thread that looks like string, and has no trouble pounding through 20 layers of Sunbrella fabric"); it's got a 1 HP motor to power it. (I've ...
6
votes
2answers
535 views

Explanation of Quadcopter Dynamics, Components and Control

I am about to build my own quadcopter from scratch. However i am having problem with understanding how it is possible to control the quadcopter without knowing the current rpm of the BLDC motors. ...
6
votes
1answer
460 views

Stabilizing a Robot Arm at a Specified Height

I have a 4-bar linkage arm (or similar design) for a telerobot used in the VEX Robotics Competition. I want to be able to press buttons on my PS3-style controller to have the arm raise to certain ...
6
votes
1answer
214 views

Is subsumption architecture still an active area of research?

I am interested in learning more about subsumption architecture. I have read a number of books that talk about the idea but none of them go into great detail. I have also read a fair number of Dr. ...
6
votes
2answers
200 views

Controlling the Power of a Solenoid

I am trying to control the force of a solenoid. My current system has a bank of capacitors connected to a relay. In order to control the force (how hard I am trying to hit the object) I am increasing ...
6
votes
2answers
4k views

Programming an ESC to have reverse mode

How do you program an ESC to have a reverse mode? We're looking to control an ESC from a servo board (for a robotics project). Assuming that the input will be between 0 and 255, we're looking for 127 ...
6
votes
1answer
61 views

Keyboard control map for scalar based movement?

I'm working with a Wild Thumper 6 wheel chasis that is designed for use with an RC controller. However I'd like to have a mapping to a keyboard for control as well. Can you suggest a set of keys and ...
6
votes
2answers
4k views

Quadcopter PID Control: Is it possible to stabilize a quadcopter considering only angle measurements?

Good day, I am a student currently working on an autonomous quadcopter project, specifically the stabilization part as of now. I am using a tuned propeller system and I also already considered the ...
6
votes
4answers
1k views

Forward and Revers Kinematics For Modified Hanging Plotter

I'm building a modified version of the standard hanging plotter (v-plotter). The basic idea is that you have two cables hanging from stepper motors which form a triangle supporting the pen at the tip. ...
5
votes
3answers
538 views

Proportional controller error doesn't approach zero

I'm reading this pdf. The dynamic equation of one arm is provided which is $$ l \ddot{\theta} + d \dot{\theta} + mgL sin(\theta) = \tau $$ where $\theta$ : joint variable. $\tau$ : joint torque ...
5
votes
6answers
88k views

What's the difference between feedback and feedforward control?

I'm reading from Astrom & Murray (2008)'s Feedback Systems: An introduction for scientists and engineers about the difference between feedback and feedforward. The book states: Feedback is ...

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