Questions tagged [control]

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

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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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81 views

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
34 views

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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1answer
171 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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15 views

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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44 views

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
106 views

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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28 views

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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40 views

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
123 views

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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1answer
2k views

(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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26 views

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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1answer
57 views

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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2answers
62 views

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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84 views

Modeling of Robots

There are mainly two approaches for controlling robots (mobile robots and static robots): 1) working with kinematic equations, controlling joint or wheel speeds , 2) working with dynamic equations and ...
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3answers
505 views

Implementation of Velocity Control Algorithm Based on PID

I'm very familiar with the traditional position form of PID. The error is just the difference between some setpoint encoder value and the current encoder value. Although this suffices for basic ...
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853 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 ...
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68 views

Multithreading on robot control

Is it wise / possible to use multithreading to handle control system on robot? For example, a line follower robot with PID control flowchart would be: read_sensor() -> calculate_control() -> ...
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208 views

Why am I unable to tune the PID parameters on my quadcopter?

I am building a nano quadcopter in X-Configuration with coreless DC motors, 65mm 2 blade propellers and a 1S Lipo battery (860mAh, 25C). The weight of the assembly is around 70g in total. I am ...
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1answer
61 views

Control loop in or outside of main loop

I've been working on some small projects for fun to learn more control theory things and embedded programming. Thank the esp32 and Arduino! Either way I've been programming everything entirely in a ...
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56 views

Is it possible to make a self balancing robot using small or medium scale integrated circuits?

Almost all the information I've seen about self-balancing robots implies the use of an Arduino to implement the control. I'm wondering if it is possible to implement the control using just small or ...
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1answer
136 views

Inverted pendulum controller

I had an exam yesterday, and I was asked the following question: Why PID controller is necessary for stabilizing the inverted pendulum on a cart, why not we just use PI or PD? Now I've seen some ...
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1answer
35 views

What is the Control mixer block that is usually found in control schemes?

There is usually a control mixer block in control schemes in robotics. What is it and what is the functionality and where can I read more about it. Reference to the paper: https://giuseppesilano.net/...
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1answer
113 views

Compensator design

I got a plant $G(s)=\left(0.13s+1\right)/s^2$ to design a compensator which provides below demands: Settling time : max 2s Overshoot : max %35 Gain margin : min 10 dB Phase margin : min 30 deg ...
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How does TTS TacTile Code Reader work?

This is the TTS TacTile Code Reader: https://www.tts-international.com/tactile-code-reader/1010494.html?cgid=Primary-Computing_--_ICT-Bee-Bot_Blue-Bot_--_Pro-Bot There aren't any connection pins, I ...
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64 views

feedback linearization for a quadrotor

I am trying to develop a controller for a quadrotor using dynamic feedback linearization technique, but I am not sure I am doing thigs correctly. I know that for designing such controller I have to ...
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3answers
519 views

How to control the velocity of a mobile robot?

I have a differential drive robot whose linear velocity and angular velocity is to be controlled. The current strategy for doing that is: A high level path tracking module spits out the reference ...
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121 views

Partial CoM, the velocity Jacobian and Control

New to robotic arms here. I am currently working with a 6-DOF robotic arm shown below: I have derived the FWD Kinematics and mapped the joint angles and the resulting end-effector positions. When I ...
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51 views

Finding transfer function from bode plot

I try to estimate a system transfer function by hand calculation from a bode plot data but I could not succeed yet and I need someone help. it will be appreciated if anyone explains or refer me to a ...
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2answers
65 views

Block algebra and normal algebra inconsistent

I've been playing around with some block maths, mostly trying to remember how it actually works, and I've come to a simple example that should be reduced, however when doing the normal maths, compared ...
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2answers
345 views

Why would I use three state variables for a second order system? [state space modeling]

I'm currently being asked to write a state space model of a falling object (equation attached). I had taken a linear systems course five years ago in which I did a lot of conversion between high ...
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1answer
34 views

Constant Offset matrix

I've been reading about controlling systems via momentum wheels. Such as in Satellites, or fancy inverse pendulums. In a particular paper, the writer tries to explain away an offset and settling of ...
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1answer
34 views

Autonomous quadcopter: How to transform setpoint into motor inputs?

I would like to know how to transform a setpoint to inputs for the motors of a quadcopter. I would like a function like that: ...
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1answer
995 views

teleop_twist_joy with Logitech F710 Joystick force feedback error

I am using a Logitech F710 joystick game controller in ROS Kinetic Kame. I was able to perform jstest testing, and can see my joystick works well. But when I try ...
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43 views

Relation between PWM frequency and torque

I am using Pololu G2 18v15 to drive a maxon motor. The motor is supposed to drive a load in a sinusoidal trajectory against gravity with maximum torque of 0.0634 NM with max speed of 5 rpm. I am using ...
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2answers
119 views

Why is behavior-based robotics not as popular as deep learning or reinforcement learning?

I am a master student in Germany and one of our professors is doing robotics research but with a different paradigm - the behavior-based robotics based on Subsumption Architecture developed by prof. ...
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1answer
71 views

For what step disturbance value the system will become unstable?

I am new to control theory and have difficulties about this question R is the input, Td is the disturbance, C is the output Given that G1=K/(s^2+A*s), where K is the gain and A is a parameter greater ...
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29 views

How to make x variable change each time and read its value from txt file

I am working on my undergraduate project and this is my first time in using use python to control parrot bebop 2 drone and use BCI or BMI technology. I have x variable (int) and I want to read its ...
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1answer
32 views

Do I have to use the CAN protocol that the motor controller uses in order to communicate with it?

I have a question about using the CAN bus to control motor controllers. Do I have to use the CAN protocol that the motor controller uses, e.g. CANopen CiA DS 301 CiA profile 402, in order to ...
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1answer
47 views

Fuzzy logic controller for controlling a four-bar linkage

I am trying to design a control system to move a joint of four bar linkage according to desired trajectory. A dc-motor is used to move the joint. Can fuzzy logic controller be used to solve this ...
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3answers
70 views

Simple explanation of PID control [duplicate]

I tried reading and searching different books and links for understanding PID control but not much progress Can some one please give me simple explanation of PID control?or atleast links where easy ...
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3answers
1k views

Control VS artificial intelligence?

I have heard of both the terms AI (artificial intelligence) based robots and control based robots. Although they are both different fields, what is the difference between AI and control in regards to ...
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1answer
29 views

Max motor voltage for RoboClaw controller

The RoboClaw data sheet from ServoCity mentions various current limits, but what about voltage? Can I run a 110 Vdc treadmill motor?
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1answer
65 views

Sampling time selection

I'm trying to design a compensator for a pendulum type plant with arduino mega. As you can see from the picture, the system bandwidth is 9 rad/sec. I calculated the sampling time as ws=10*wb=90, so, ...
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1answer
249 views

PID control: zero out integral on error sign change?

I am learning about PID as a novice to robotics (background in software engineering). One common problem with PID is that if the PV is below the SP for a long time, integral term will accumulate a ...
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734 views

moveit! trajectory execution aborted

I'm trying to send a custom arm to a pose through moveit_commander_cmdline.py, it fails after sending to the said pose using " go default_pose" and returns an error. ...
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1answer
152 views

Joint torque sensor vs end-effector force sensor

I am trying to understand the difference between joint torque sensors, and force sensors, in a robot arm. From what I understand, joint torque sensors estimate the torque at each joint, whereas a ...
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1answer
26 views

Transform this matrix of distances into a more general one

I need to make the navigation and guidance of a vehicle (a quadcopter) in a platform. This platform can be seen like this: where the blue dots are the center of each square, and the $x$ distances are ...
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2answers
94 views

Which controller (PI or PD) is generally more robust to noisy sensor measurements and why?

Assuming no filter is used to measure error (or rate of change in error) with respect to a desired state, would a PI controller more/less/about equally robust to signal input noise compared to a PD ...
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97 views

PID control loop and feedback acquisition synchronization

In many real-time PID control loop application I have seen that the control loop is triggered exactly as the ADC interrupts arrives in order to achieve maximum synchronization between feedback ...

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