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Questions tagged [control]

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

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18 views

Can you buy a torque-controlled motor? [on hold]

I'm reading a book on robot manipulator control, and it assumes that you have control either of the joint velocity, or the torque acting on them. It motivates this by stating that there is an inner ...
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1answer
21 views

PID Tuning. Does Setpoint Affect Gain for Tuning

So I understand that a heuristic way of determining values for PID would be to use the Ziegler method, having zero I and D and then adjusting P until you have oscillations. Wouldn't the setpoint ...
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2answers
46 views

Why do we need to design controllers (feedback) for controlling a quadrotor?

For example if I want to make my quadrotor hover at a particular height, can't this be achieved by using an altitude sensor, and to correct it's position due to disturbances, can't we just write some ...
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1answer
81 views

Control system in Matlab with RSA encryption

I want to implement an encrypted controller in Matlab using RSA. I am trying to replicate what is written in this scheme from 'Cyber-Security Enhancement of Networked Control Systems Using Homomorphic ...
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51 views

Incremental (on-the-fly) smooth trajectory interpolation algorithm from waypoints?

short version (TL;DR): I'm receiving x(t) waypoints "online", which I must travel through at the specified times. I need an algorithm that would plan a smooth trajectory in-between them without ...
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1answer
26 views

How to calculate effort/torque values of a joint

I have a robotic arm with 6 DOF. For each joint, I get get the Joint Wrench, which is composed by the force and torque of the parent and child links of the joints. In other works, for joint 1 I can ...
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0answers
7 views

How to interpret the passivity criteria equation?

In Passivity-Based Control and Estimation in Networked Robotics (among others), a passive system is defined as one that: $$\int_0^t y^T(t)u(t) dt \geq -\beta $$ for output $y$ and input $u$. I have ...
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1answer
21 views

Will a change of motor driver improve motor performance?

I have this motor, from datasheet it works on the 6-12V range and has a no load current of 0.52A, and a stall current of 20A. I want to test the motor before buying an expensive motor driver. I have ...
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1answer
39 views

project to create a lighter wall [duplicate]

We are working in a project to help blind people cross the street alone .so ,Can I create a Virtual reality wall or a holographic 3d one that is visible in the Street and in all day times ?? ( morning ...
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0answers
9 views

Program EV3 in C to compensate for the robot movement offset

I am using c4ev3 library in C to program my EV3 brick to move the robot across a discretized grid using a path-finding algorithm. But the problem is, the robot getting offsets on turns and even when ...
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0answers
17 views

Why are strain-wave/harmonic gears used in robots?

Also, what is the difference between the above gear drive vs other gear drives?
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32 views

Why equilibrium is also called a fixed point?

In algebra, a fixed point of a function is $x$ where $x = f(x)$. But in control theory, a fixed point (or equilibrium) is $x$ where $\frac{dx}{dt} = 0$. The two definitions don't seem to have anything ...
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2answers
56 views

Inconsistent results between Simulink derivative model and tf for PD controller

I'm designing a PD controller so that the response due to unit step should exhibit an overshoot of 20% and steady-state error less 0.01. I've computed the parameters Kp and Kd and double-checked the ...
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1answer
35 views

Robotic Arm Senior Capstone. Electronics/Controls/Sensors Questions

I am a mechanical engineering student currently working on my senior capstone. My team of all MechEs has to build a robotic "arm" where the arm is really just a link/bar of aluminum. The thing we ...
2
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0answers
32 views

Multivariable PID controller

I'm making a robot that uses two DC motors to move, and has two distance sensors on its right side. I want to make a PID controller to control the angle of the robot (using a wall as reference) and ...
2
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3answers
46 views

Benfit of behaviors & benefit of hybrid systems

I have two questions that I think are closely related: Why is it useful to introduce behaviors, e.g., goal-to-goal + obstacle avoidance? (The alternative would have been to just use a single behavior ...
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1answer
24 views

What limits the observer eigenvalues size?

IIUC, the recommendation here of increasing the absolute size of the real part of observer eigenvalues is based on two factors: We want the observer to be updated as fast as possible (I suppose up to ...
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0answers
15 views

Hover control for quadcopter doubt?

For my project I need to make a hover control using state space approach for a quadcopter. So far I have taken a non linear state space model from a research paper that used 12 states, 4 inputs and ...
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0answers
26 views

Why differential flatness is called “flat”?

A system is differentially flat if the state and control input can be written as functions of the flat outputs and their time derivatives. In other words, if a system is differentially flat, we can ...
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5answers
110 views

Why we want to write all linear system into form of first order differential equations?

It seems to be taken granted that when we deal with some control system, the first thing we want to do is to linearize the system and put it in form of first order differential equations like $\dot x =...
2
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3answers
56 views

PID and Kalman filters

Both PID and Kalman filters are used extensively in Robotics. I gather, Kalman filters for sensing and PID for control. What is the mathematical, statistical or other relationship between them?
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1answer
59 views

How to implement a novel control algorithm for a drone

I and my research team are working on a novel drone design based on trirotor. The difference between this design and a trirotor is that it has an extra propeller to generate additional thrust, ...
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1answer
32 views

How many independent control inputs does a hexarotor have?

6, because a rigid body has six degrees of freedom 4, since it is similar to a quadrotor, except with more motors 6, because there are six motors I was taking an online quiz, and I thought option 3 ...
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6 views

where to apply state space model, controllability, observability and pole placement in robotics?

In a course named modern control systems I have just finished learning: State models for LTI systems Diagnolization Solution of state equations Controllabilty & Observability Pole ...
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1answer
41 views

PID control related to lagrange equation

I'm a beginner in robotics and so far followed the lecture series by Prof. Oussama Khatib and some blogs and papers. currently I'm following this studywolf blog. in the end I plan on building a simple ...
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2answers
82 views

Problem with tuning PID for motor

I am trying to tune my PID to make my motor have a consistent output: input(pidOutput) => 100rpm I used the following step to tune my PID: Set all gains to zero. Increase the P gain until ...
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0answers
16 views

Help required using hammerstein weiner model implementation in simulink

I have identified a 2 inputs 1 output (MISO) model using Hammerstein weiner model with the System Identification toolbox. Now, I wish to implement the identified idnarlx model into a generic ...
3
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2answers
55 views

Meaning of a negative step response with quaternion

It's not technically robotics but: I've been trying to reproduce in Simulink a spacecraft attitude simulation using quaternions, and the kinematics and dynamics seem to work fine, however I'm having ...
0
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1answer
58 views

stable altitude quadcopter

I'm currently working on a project to generate a stable altitude and automatic control for a quadcopter I'm using arduino as the flight controller Ultrasonic sensor HC-SR04 MPU-6050 However my ...
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1answer
71 views

Quad-rotor 1-D Linear Control Simulation with MATLAB

I was Performing Programming Assignment with MATLAB for Quad Thrust and Height for an Introductory Course. The control input for a PD controller was According to the Equation u = mass*(diff(s_des, 2)...
2
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1answer
27 views

How can I limit the current sent to my 6V servos to ensure they don't burn out?

I'm using an adjustable desktop power supply (0-30 volt DC, 0-10 amp) to power my robot which has 7 standard 6-volt servos. There are some situations where the robot gets jammed, and power draw ...
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1answer
42 views

Could a quadrocopter still be controllable if its payload was wider than the quadrocopter?

Lets say a quadrocopter's rotors are 2 feet apart, and 2 feet beneath it is attached a symmetrical, balanced payload that was x feet wide (with space for air from the rotors to move through) - if the ...
2
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1answer
42 views

Creating linear end effector motion using joint speeds: Converting tool speed to joint speeds

Background Information: I'm new to robotics and my school currently has access to a 6DOF Universal Robot (UR-10). I'm programming it using its scripting language URscript and the arm has these two ...
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0answers
23 views

Trajectory following using LQR - Setting horizon time and intermediate points

I was going through UC Berkeley's CS287 - Advanced Robotics course. In particular - Optimal Control for Linear Dynamical Systems and Quadratic Cost (“LQR”) by Pieter Abbeel (Slide 10). Let us say we ...
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1answer
87 views

Control Pneumatic Cylinder Position with Potentiometer and Analog Comparator on Arduino Uno

I am building a robot arm that is actuated by a pneumatic cylinder. Extending and retracting the piston would increase and decrease the joint angle respectively. This is done using a 5/3 solenoid ...
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1answer
53 views

Math behind trajectory 2d planning

I have a case of a differential drive robot and a control system in a two-dimensional environment: Now the problem: we would like to make our particle move from point A to point B, and from there to ...
2
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1answer
72 views

Is orocos dead?

We are using orocos on the robot we have been developing for 3 years now and I have the feeling that Orocos is no longer maintained and the mailing lists are not only no longer active but also it is ...
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0answers
25 views

Sensored BLDC motor (sometimes) needs push to get started

I'm having a sensored BLDC motor (12V version though) connected to a suitable motor controller and powered through a 25A regulated power supply With an Arduino I'm able to control the motor just fine. ...
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1answer
23 views

Motorised Stage for laser

The problem I want to be able to move the direction a laser is pointing. This means I need to have motorised rotation of the laser head in the x direction and in the y direction. I am unsure of the ...
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1answer
209 views

Alternatives to Finite State Machines (FSM's)?

In Udacity's Self-Driving Car Engineer online course, one instructor claims that "[Finite State Machines are] not necessarily the most common [approach for behavior planning] anymore, for reasons we ...
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1answer
94 views

Pictures coordinates to robot coordinates

I have a picture on my C# software and the corresponding object in real world on 2d plane of motorized XY axis table. What I want is when I select a pixel on my picture, the motorized table should be ...
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2answers
49 views

Pole placement of the observer closed loop system (A-LC) in discrete system

*I'm rewriting the question after I deleted the previous one because I wasn't clear enough. Hope it's fair Given a system of the general form: \begin{align} x_{[k+1]} &= A\,x_{[k]} + B\,u_{[k]} \...
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2answers
108 views

Dynamic model using identification for control

I'm currently working of a 5 DOF robot, for which i'd like to compute the dynamic model through identification. I have experimental data representing torques (inputs) and positions (outputs). How can ...
0
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1answer
54 views

zero-g mode for UR10 gravity compensation

I would like to freely move my UR10 arm in response to an external force, just like the zero-g mode for Baxter robot, which can be activated by holding its wrist. The Baxter documentation on zero-g ...
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0answers
61 views

LQR Robotic Arm

I have a robotic arm model in Simulink and I'd like to control the position of the end-effector such that it follows a given trajectory. This is done by inputting joint angles and comparing the output ...
0
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1answer
30 views

Obstacle Avoidance: Detection of goal inside the obstacle

It is easy to understand how a robot can avoid obstacle if the goal point is not within the obstacle (Point A) as shown in the figure. But I'm curious how could a robot know that the the goal point is ...
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1answer
42 views

Inter-robot Collision Avoidance

I try to understand some MATLAB code (see below) i found from the web for inter-robot collision avoidance. But I'm not really understand, how the theory behind this code work. Can anyone help me ...
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2answers
108 views

Quadcopter mathematical model and controller design

if we just examine the translational dynamics (X and Y direction), the dynamics are coupled, So if I want to design a PID controller to control the position, the outcome will be unpredictable because ...
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0answers
15 views

Simulation of error in following trajectory for robot manipulator

I am working on a surgical manipulator project where I have optimized the link lengths of the manipulator for maximum isotropy. Does the maximum isotropy reduces the error in following predefined ...
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0answers
19 views

Designing systems for sharing resources on multiple SOC's

I have some Raspberry Pi's from previous projects/learning and I would like to pool their resources to make a differential drive robot. Two Pi's would have one camera each for a vision system, one ...