Questions tagged [control]

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

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48 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
81 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
256 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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172 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
303 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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8 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
28 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
40 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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1answer
66 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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2answers
697 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
45 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 ...
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2answers
484 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 ...
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3answers
59 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
38 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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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
140 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 =...
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3answers
2k 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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170 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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3answers
752 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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1answer
88 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
408 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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2answers
211 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 ...
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1answer
183 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
274 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)...
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1answer
40 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
53 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 ...
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1answer
189 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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63 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
354 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
77 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 ...
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1answer
196 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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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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2answers
2k 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
349 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
384 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
120 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 ...
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1answer
198 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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1answer
50 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
52 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
249 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
52 views

Quadcopter bldc PID control

Working on stabilizing a Quad using Arduino Due. I have slightly modified one of the examples of Jeff Rowberg's library to give yaw, pitch and roll angles (zero initialized angles). Moreover, I am ...
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1answer
231 views

State space model

I want to design a LQR controller for my two wheeled mobile robot. While designing the controller, I need to find gain, K for the LQR which this required the state space model of wheeled mobile robot. ...
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1answer
64 views

Torque commands for velocity reference motor

I have a controller board for a motor, where I can read the motor current (to transform to torque), the position, the velocity and I can give a velocity command. There is not really a torque mode on ...
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2answers
111 views

Controlling a servocity planetary motor?

I know this might sound like a stupid question, but I actually need help with this. So, I'm looking at this motor: https://www.servocity.com/2737-rpm-premium-planetary-gear-motor. I have a raspberry ...
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2answers
73 views

How to start as a control system engineer and to make advanced projects using PID [closed]

I am new to the field of control systems, PID and robotics and I want to enhance my knowledge in the field. Can you recommend me books where I can start learning about control system engineering (with ...
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3answers
117 views

Making a tunnel follower robot with 2 IR side sensors and 1 ultrasonic sensor

We have a tunnel and the distance from the walls to the robot is about 30cm when the robot is centered, the tunnel curves to the right. The robot has an infrared sensor on its left and one on its ...
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1answer
52 views

Strange phase case in Bode diagram of a transfer function [closed]

Please help me to solve my problem: This is the transfer function: $G(s)=10\frac{(s^2+1)(s-10)}{s(s+0.1)(s^2+2s+100)}$ I calculated properly the whole Bode diagram apart from the phase of the complex ...
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2answers
47 views

Powering Off Main Processor Without Software shutdown

I am building a robot that uses an Intel NUC (running ArchLinux) as its main processing unit to run some machine learning and ROS programs scripts. One of the requirements for the robot is that it ...
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1answer
60 views

Control geared DC motor based on timing?

According to this video from Khan Academy about electronics of a DVD drive the position of the sled (which moves the reading head) is controlled by a geared DC motor by using only timing and one end-...
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1answer
326 views

Quadrotor 2D Dynamics

I am trying to understand the control of the quadrotor in 2 dimensions from the Penn course on aerial robotics. The attached image describes the linearization of the control efforts assuming that the ...

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