Questions tagged [control]

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

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How does the autopilot (control) logic block work in a drone (quad-copter)?

I want to design a firmware/code/flight-controller that can give robust control for a quad-copter. I was trying some of the resources one of which is here. Also from Mr. Brooking. in books: i referred ...
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How do I get competent in using c++ for my projects? [closed]

I am a PhD student, working on Sensor Fusion and estimation problems. I would like as I finish my PhD to have acquired sound knowledge in what seems to be the industry norm for working with real ...
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Given this old pin diagram and numbers on this old encoder, what would be a suitable modern encoder to use?

My place of work has recently acquired a Hydraulic Press Break from the 80's. It has a CNC controlled back stop which is driven by a DC motor and Screw drive. The encoder which couples to the motor ...
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Why cant the Controller Spawner find the expected controller_manager ROS interface?

I have a quadruped robot with base link (BL), 4 child links called LFT,LFT, RFT,RFT, T for thigh and each having 4 children with name LFC,LBC,RFC,RBC, C for Calf. 8 joints - Base link to 4 thighs and ...
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problem in understanding this part of the RRTx path finding algorithm

this is a paragraph from the paper of the RRTx algorithm and below it a figure referenced in the paragraph however the No and Nr nodes types are unclear to me what are they exactly ?
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Can ROS be an alternative for a KFLOP or RUMBA Board?

I have a few questions about controlling robot arm motion. I see that some have used Dynomotion KFLOP and other CNC motion controllers to control arms. Some have used Rumba board as well as several ...
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Quaternionic feedback for for cartesian impedance control

I've seen that there are plenty of ways of generating orientation errors with quaternions. But the one I've seen most often is the following: For example, say that for a quaternion $Q = \{\eta, \...
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Feed both position and speed errors to one single PID

I have seen in the documentation of an old subcontractor's product that the controller of a robotic arm joint was basically feeding error position + error rate directly into one single PID. It feels ...
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Cartesian Impedance control Damping Design (Double Diagonalization)

In the literature, it is often seen that for a system: \begin{align} \Lambda \ddot{e} + D_d \dot{e} + K_d e = F_{ext} \end{align} A dynamic damping matrix is required for a robot to take ...
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HTTP requestes for Robot Teleoperation

I'm new to this forum so I apologise if I disrespect some rules. I am considering using HTTP requests to control a robot remotely. The design problem I am trying to solve is that I would like to ...
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Robust Controls of Quadcopter

Can anybody please guide me about the robust modeling and control of a quadcopter. Where can i find the robust modeling that can be understandable for me as i am a undergraduate student. I am doing ...
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What are the uncertainites in the Quadcopter model for which we make a Robust Controller?

A quadcopter model may have some uncertainties for which we usually use a robust control. Can please someone specifies some uncertainties? like for what kind of uncertainties do we make a robust ...
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Controller Design Using Webots! (Heading, Velocity, tilt,balance)

I am trying to design and implement certain controllers for a robot. I am currently designing controllers for the robot, where it aims to control the Heading, Velocity, Tilt, Balance of the robot. ...
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Measurements of IMU (accelerometer and gyroscope) are drifted or with too much error

I placed my drone on a table (i.e, at rest) and save (using a ROS topic) the IMU readings: As you can see, there's a lot of drift or error. I would expect the $x$ and $y$ acceleration to be 0 (I know ...
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On a multirotor, how effective is braiding of power wires from the ESC to the BLDC Motor(s) in reducing or eliminate emf?

Assuming BLDC motors with the ESC positioned at the 'worst cased' (furthest distance) with longest power wires between the ESC and the motor, will braiding these three wires reduce the EMF that would ...
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Robot dynamic control

This can be a basic question but according to my knowledge I don’t know answer. We can use control system theories to control the position of motor. Considering two motor joint leg it can model and ...
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How can I modeling a simple haptic interface system to obtain results similar to the paper “Time-Domain Passivity Control of Haptic Interfaces”?

I am trying to simulate the experiments in the paper "Time-Domain Passivity Control of Haptic Interfaces", Hanaford and Ryu, 2002, IEEE transactions on robotics and automation vol .18, No1 about the ...
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Control a servo (two position 180-degree swing) with an On/Off switch without microcontrollers [closed]

For my application, I need to be able to control a servo with a simple on/off switch. When it's off (pulled LOW), I need to servo to go at -90 degrees and stay there - possibly for a prolonged time. ...
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Matlab Simulation using Webots!

I am trying to run this youbot ( sample world) from webots, where the controller is implemented in MATLAB, on running the code it pops out the following error seen in the picture attached. I have also ...
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Controller Design using Webots!

I am trying to work on a Digital Twin of a Physical Robot which is used at my uni. I made a rough model of the robot using Webots (Open source). I need to design certain controllers aiming at the Tilt,...
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How to create a Complementary Filter for a linearly accelerating body to obtain estimate of orientation in quaternion?

A complementary filter (CF) uses orientation obtained calculated from gyroscope, accelerometer and magnetometer to find a more accurate measurement of orientation. However, when my sensor is ...
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Is it possible to track position using gyroscope and accelerometer without a magnetometer?

I'm looking for help on a project where I will be placing sensor data in 3D space using augmented reality. Most solutions I have found for finding position with an IMU involve the magnetometer, but ...
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Can badly tuned Feedforward still decrease following error?

Let's say we're trying to control the speed of a motor to 20 revs/sec, and we know that our controller output for that speed is approximately 5. We currently have a Proportional controller to drive ...
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What is a low level controller for a quadrotor?

I am studying control systems, and I was reading a paper about quadrotors. In the paper it is said that in the platform of the robot it has to be present a low level controller. But what is a low ...
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DC motors are stalling at low voltage (L298N controller)

I'm building a small tracked robot. Currently it's just a Raspberry Pi, two motors and an L298N controller. The problem I'm facing is that the motors are stalling at low voltages (which is what I ...
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Self motion with multiple constraints

I am trying to control a 7 DOF robot (a Franka Panda). I use jacobian based control (resolved rate motion control) to generate a joint trajectory from a cartesian trajectory. My contraints for the ...
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Using Integral gain for motor positioning

I'm struggling to see how Integral gain is used for motor positioning (with an encoder on the shaft). Suppose we have an AC motor connected to a winch which drives an object forwards and backwards. ...
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Use polynomials to detach number of MPC controls from size of time-horizon?

Model Predictive Control (MPC) works by finding a set of controls $u_0, \dots, u_n$ that minimize a cost function $J$ over a time-horizon $[t, t + T]$. Typically when MPC is used on mobile robots, ...
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Numeric integration problem in a quadrotor vertical descend code

I'm trying to implement a drone in vertical descend. As for maximum simplification, I maintain all its angles to 0, and just try to get to the my desired descend. However, when I debug, I see that my ...
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Link collision avoidance for redundant manipulator

I am trying to have my robot arm follow a trajectory while avoiding collisions between obstacles and the robot links. The way I go about it is to find the closest point on the robot arm, and treat the ...
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1answer
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Good Software Projects for Aspiring Engineers [closed]

With the pandemic going on, our school has decided to officially shutdown all sponsored club meetings. Now that we are all digital, our robotics club was looking for projects that students can do at ...
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How do I convert centre-returning joystick values to dual hobby-motor direction?

Currently my setup is: 2x hobby TT motors connected to a Pi Zero with a motor HAT Python script running on the Pi which runs a Blynk python client and controls motors via the gpiozero library Blynk ...
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How do “process gain” and “proportional gain” affect the Steady State Error in a PID Controlled machine?

I came across this doubt while reading the Wikipedia page on PID Control. The section on Steady-state error states: Steady-state error (SSE) is proportional to the process gain and inversely ...
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discrete control in continuous spaces

I asked this question on AI stack exchange but didn't get a response. Basically I'm interested in how you deal with inherent error between your ideal discrete state and your actual state in control ...
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1answer
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How to design a controller for a robotic arm given two velocity profiles

See image for reference: Essentially I have a robotic arm with two linear actuators. Lets say, for example, I wanted the endpoint on the arm (where you see the stepper motors) to move purely in the x ...
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PD controller tuning for flexible joint robotic arm

I am trying to tune the gains of my PD controller for a single axis flexible joint robot. The controller output is the motor torque. My question is: how can i tune the PD gains if the output (torque) ...
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What should be the ideal ratio for link lengths ( L1/ L2) of a 2 link manipuator robot with revolute joints?

I am working on making a CAD model of a two link robotic manipulator, with link lengths around 15-20 cm. I am unable to figure how to set their mutual ratio and I want to know whether there is some ...
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1answer
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Why applied joint torque will affect another joint?

I want to ask a very simple question. For the robot dynamics Newton-Euler algorithm, suppose there is a two-link planar robot, we can write the simple dynamic equation form as $M(\theta)\ddot{\theta} ...
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134 views

Understanding Impedance Control

I have a question regarding impedance control for a robotic manipulator. Given that we have a task space trajectory: $\ddot{x}$, $\dot{x}$ and $x$ And the dynamics model of the robot: $$\tau = M(q)\...
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Increase frequency of status messages from UR5

I know the UR5 is sending me messages with its status (I can't yet understand them though, but I'm already working on that). However, they are too far apart to be useful: It sends them every 0.1 s. ...
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Interpret 560 byte msg from UR5 firmware 1.8 through TCP socket

I am trying to use the UR5 from my computer without having to write any script on the robot. For that, I opened a TCP socket as a client from my computer (in a C program), and the robot indeed does ...
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1answer
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Controlling a robot arm to follow an SE(3) trajectory

I have a 7-DOF robot arm, and I want it to follow a trajectory. This trajectory is defined as a dense sequence of SE(3) waypoints, which were collected by moving the robot arm manually (i.e. by ...
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Algorithms for controlling low-speed movement of gearless robots

Collegues, i am a little discouraged by the lack of a clearly formed section in the literature on which algorithms are used to control the low-speed movement of gearless robots. In my opinion, it is ...
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Constructing control system

The problem i have is more or less is biology related, but I can simplify the problem as such. I have a tank of water. I try to increase the concentration level of this tank of a certain substance (X) ...
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1answer
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Going from Spline to Differential Drive Command

I have a differential drive robot that needs to move along a path stored in its memory as a spline. I am currently trying to understand the mathematics of determining how much power to apply to each ...
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(not trivial) ROS how to subscribe to multiple topics and publish to another topic within one loop

My question is related to this one (here) but not exactly. Assume now I have 4 topics: topic_A,topic_B,topic_C,topic_D. Inside my control loop, I need to read the sensor values from the first three ...
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implement torque control on a robot with some joints supporting torque control while others only supporting velocity control [closed]

I have a robot, some joints of which supports torque control,while the rest only supports velocity control. What should I do to implement torque control on the whole system?
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Why are the angular velocities of concentrated masses in Lagrangian independent?

There is an ordinary linear three-mass system. If we write its Lagrangian, we get the following equation. where $W_k$ and $W_n$ - kinetic and potential energy. To find the moment of rotation of the ...
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Robot-telescope prototype controlled by a PC

Has anyone developed mechatronic systems for DIY-telescopes running a PC? Please share your experience, knowledge and nuances (how you acquired current sensors, speeds, electric motors, about ...
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2answers
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Dynamic models of parallel robots in the form of multi-mass systems with stiffness coefficients

I want to develop a dynamic model of a parallel robot for control tasks. It is known that equations of motion based on Lagrange equations can be transformed into a state space and use such a model. ...

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