Questions tagged [control]

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

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213 views

Impedance Control vs Position Control

I have been reading up on impedance control, and several sources have stated that it is much safer than position control. However, frustratingly, none of these sources have explained why this is. So......
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1answer
30 views

How to estimate gradient of Jerk

A trajectory is described by a position vector, i.e., traj = $[q_0, q_1,...,q_n]$. The objective is to minimize the jerk of the trajectory. I am referring to this code to understand how the gradient ...
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1answer
28 views

Control signal of an LQR Controller

I'm working on building an LQR for a system which consists of a ball in a vertical tube, a fan is situated at the bottom of the tube and a distance sensor is at the top, a raspberry Pi is used to send ...
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18 views

Path curvature in kinematic bicycle model

I'm trying to develop an understanding of the control law for longitudinal and lateral control for self driving cars. While doing so, I came across the kinematic bicycle model which is used to derive ...
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1answer
24 views

How to simulate a system output with a sine wave input?

I wish to simulate the output of a certain gear system I have. How the gear system looks isn't particularly important to the problem, I managed to get the differential equation needed from the ...
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0answers
38 views

Kalman filter for visual tracking of a ball sliding on a gutter

I'm working on a project where a robot needs to keep a ball at a desired position on a gutter. The gutter is fixed at one end and held at the other end by the robot’s ...
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1answer
23 views

Does the Grbl have S-curve or harmonic velocity profiles?

I'm working on a machine and the position has a high impact by the jerk and acceleration of the machine. I'm using Grbl for my machine. Does Grbl has S-curve or Harmonic velocity profiles?
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1answer
56 views

What can cause yaw rotation on a multirotor when yaw control is disabled?

Let's assume that I assembled a multicopter (quadcopter, hexacopter or octocopter) and let's say that I disable yaw control on it while roll and pitch controllers are enabled. Now let's assume that I ...
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2answers
73 views

PID Control: Is adding a delay before the next loop a good idea?

I am implementing PID control in c++ to make a differential drive robot turn an accurate number of degrees, but I am having many issues. Exiting control loop early due to fast loop runtime If the ...
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24 views

Is Image Based Visual Servoing a non-linear controller?

Is Image Based Visual Servoing a non-linear controller? I think it is as the Image Jacobian has square terms of u & v (image-plane coords). Where $p_u, p_v$ are the width & height of each ...
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1answer
24 views

Dynamics with error term

How do the dynamics of a system change when an error term is introduced? For instance, if I have a system (computed torque control - robot manipulator): $$M\ddot{q} + C\dot{q} + G = u$$ and $e = q-q_{...
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65 views

How to obtain the state space representation of a computed torque control system?

Assuming I have a system: $$ a \, \ddot{x}_1 + b \, \ddot{x}_2 + c \,\dot{x_1} + d \,\dot{x_2} + e = u_1 \\ f \, \ddot{x}_1 + g \, \ddot{x}_2 + h \,\dot{x_1} + i \,\dot{x_2} + j = u_2 $$ How would I ...
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47 views

High derivative gain in PD control

Why does high derivative gain in PD control results in motor noise or chatter? The graph that I see on MATLAB simulation is smooth enough, so following that it should not make noise..
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1answer
39 views

How do I compute the feedforward terms in a control law using Matlab?

I have the following situation. I have computed the linear and angular velocity which are the controls for a mobile robot, which have the form: $v_d=v_{fb}+v_{ff}$ $\omega_d=\omega_{fb}+\omega_{ff}$ ...
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1answer
76 views

How can I define the saturation function in Matlab?

I would like to write a Matlab code for an angular velocity of this type: $\omega=\omega_{fb}+sat(\omega_{ff})$ where $\omega_{fb}$ is a feedback angular velocity and $\omega_{ff}$ is a feedforward ...
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2answers
84 views

How to consider gravity for the state space modeling

I'm trying to find the state-space model of the following ball-in-tube system. I designed the SISO system, with the h(ball height), w(angular velocity of propeller), and I(current) as the system ...
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1answer
32 views

Control method advice for Markov (?) process

I'm experimenting with a device for tuning piano strings. It attaches to the piano's tuning pins and turns them slightly by applying a torque impulse. It is a semi-automatic process, handled by a ...
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1answer
35 views

Matlab code to take time derivatives

I have a velocity command, which is: $v=k_1\rho cos(\alpha)$ where each quantity $\rho$ and $\alpha$ depend by the time. I would like now to take the time derivative of this, in order to use it as ...
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1answer
29 views

What is the difference between The state-space equation and The configuration-space equation

The craig(p.180) states that equations can be made to represent the dynamic equations. The first one being the state space equation. $\tau=M(\Theta)\cdot\ddot{\Theta} + V(\Theta,\dot{\Theta}) + G(\...
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2answers
71 views

Is it better to use Jacobians to compute IK when a closed form for IK is available?

I hope that my question is not too stupid ... but I have a hard time to understand why Jacobians computed from forward kinematics would allow a better and smoother control than using pure inverse ...
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1answer
56 views

How do I apply a disturbance observer to a mobile robot?

I have to design a observer to estimate disturbances which are applied to a unicycle model. So, the unicycle model with disturbances is: $\dot{x}=v cos\theta + d_x$ $\dot{y}=v sin\theta + d_y$ $\dot{\...
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37 views

Reliably enabling/disabling a PID loop via FSM in a microcontroller

I have a PID loop for a small vehicle implemented in a microcontroller. Currently the PID loop is implemented in a timer interrupt. I want to implement an FSM that will have states that enable or ...
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1answer
172 views

How can I solve this block diagram problem?

I practiced various examples of block algebra and I came across this example where I have to reduce the block diagram. The problem now is that I have there successively set branching points and sum ...
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1answer
33 views

Cartesian control for $z$ vector of end effector frame to point towards a specific direction

Consider a robotic manipulator with 7-DOF (all joints are revolute) that accepts joint velocities as execution commands. What I am trying to achieve is the following: I want to calculate the ...
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1answer
56 views

Problem designing acceleration inputs controller

I am reading this paper: https://www.researchgate.net/publication/224635390_The_motion_control_problem_for_the_CyberCarpet in which is implemented a cartesian regulator to bring the position $(x,y)$ ...
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1answer
41 views

Motion profile and Motion control scheme, how do they interact?

I'm studying motion control and I start with the simplest case, I have to go from A to B in a straight line using a trapezoidal motion profile. I understand that in a real case, due to the fact that ...
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1answer
28 views

I'm looking for a simplified control scheme for a game-rendered robotic arm

I'm a programmer, but not savvy with robotics (to lay a baseline for my lack of knowledge). I have a game-simulated arm that allows me to set joint angles which it will automatically move the joints ...
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2answers
95 views

No electric motors can handle being stalled for even short periods of time, even at low power. Is this statement true in all cases?

We were using a regular POLOLU d.c motor whose stall current is 0.36A. We want to use this motor in a robotic hand where the motor will be stalled while holding the object. We are limiting the current ...
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1answer
56 views

Error in Pose(): All values are zero for turtlesim/Pose

Here is the program I have written. The function is to make the turtlesim complete one revolution, with a fixed angular velocity and speed. ...
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3answers
93 views

Quadcopter PID Controller for distance

I am trying to use a PID controller to stop a quadcopter at a specific location while travelling horizontally, however currently it overshoots/undershoots depending on the max velocity. I have tried ...
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1answer
55 views

Res-Scaling method beats PID controller. How?

Scenario: I have a robotic arm that has a (1D) lidar on its end, to orient itself with respect to the slant table in front of it. The lidar returns pretty accurate distance values in mm. The motor ...
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1answer
28 views

Understanding across gravity compensation, demonstration (Kinesthetic Teaching vs. Teleoperation) and inverse dynamics

I first state my humble probably wrong opinion on the connection of these concepts: In gravity compensation mode, each joint has equilibrium as its set point, a human demonstrator can effortlessly ...
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1answer
53 views

How do I call Matlab code into Simulink for doing a simulation for doing plots?

I have built a simulink model for performing cartesian regulation on a unicycle: and plot the results with a Matlab code but, I am not very confident with Simulink and so I don't know how to call ...
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1answer
48 views

Imaginary part in result of inverse laplace transform

I am working with a system(closed-loop feedback control) that has a transfer function like this F = 20*(s+5)/(s^4+13.5s^3+41s^2+80*s+100) this one is in the s-domain but for the response analysis, I ...
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1answer
29 views

Rotary Stage (high resolution controller for BLDC motor)

I am building a 3phase BLDC motor controller based on an STM32 MCU, a high resolution 26 bit optical encoder and a DRV8301 motor driver from TI. This is a for a high precision rotary stage for an ...
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1answer
41 views

Synthesis gradient observer

I ask the advice of specialists on control systems. We have the following system. Where $u(t)$ and $y(t)$ time-varying input and output. The characteristic $y(t)=f(u(t))$ is assumed to be non-...
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23 views

Is every state space model transformable to transfer function and vice versa?

I'm looking for a mathematical proof or example of non tranformable model, and I couldn't find any.
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50 views

What is the correct architecture of quadcopter control?

I want to make a quadcopter flight controller for my University project. Lately I was searching for systematic architecture of control system used by quadrotors. I have implemented one of the ...
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3answers
67 views

irobot create 2: random changes in driving speed

I am trying to make the Create2 dance a specific choreography. I´m not using the sensors, I just let it drive and turn for a specific amount of time. In general it works fine. But after working with ...
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1answer
30 views

difference between non-holonomic and linear control systems

I already asked this question in the mathoverflow forum, but no one could answer. Probably it is not a question of mathematics but robotics. I'm struggling with the definitions and differences between ...
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23 views

Relation between control and reinforcement learning

Has the relation between Control and reinforcement learning been studied by the scientific community? I would like to read credible studies about each ones pros and cons when it comes to control ...
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1answer
126 views

What can a Point-to-Point Robot do?

What are point-to-point controlled robots actually good for? Only pick and place tasks? Since continuous path controlled manipulators can do anything a p2p robot can do, plus tasks that require a &...
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1answer
39 views

PID on DC motor turning on both directions

I have a skid steer robot where I have four individual DC motors with an H bridge so I can control speed and direction. There are also four quadrature encoders with 6000 ticks per revolution. The ...
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1answer
24 views

Is it possible to control a 5 DOF manipulator in the 6 DOF Task Space?

I am referring to pre-computed torque control techniques that are based on the Task Space dynamic model. Maybe by using pseudo-inverse for the Jacobian and the task space inertia matrix ? Cheers, ...
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1answer
36 views

Real Time Motion Control [closed]

How is real time control normally handled? Do you run a separate motor control unit which has its own RTOS or is there some other way?
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2answers
114 views

Cartesian Velocity Control between Two 3D Poses

I am really struggling to understand how to do Cartesian velocity control when 3D rotations are involved. So, below is a very simple example which I am hoping somebody can help me with. Let's say the ...
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48 views

output velocity equation of compliance control

I am trying to implement a compliance controller for a robot arm and stumbled upon an existing code snippet where the compliance velocity of the endeffector is calculated by: $v_{out} = v_{in} + \frac{...
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2answers
50 views

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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1answer
24 views

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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1answer
322 views

Why can't 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 ...

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