Questions tagged [robotic-arm]

The arm tag is intended to be used for questions relating to robotic arms from, small hobby arms with only 1 or 2 degrees of freedom to large industrial robots with complex joint assemblies. For the ARM CPU, use the tag arm-cpu.

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30 votes
6 answers
61k views

Which type of actuator will be suitable for a very strong robot arm?

I wish to build a robotic arm that can lift a useful amount of weight (such as 3-6 kg on an arm that can extend to approx 1.25 meters). What actuators are available to accomplish this? The main ...
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21 votes
3 answers
14k views

How can the inverse kinematics problem be solved?

The forward kinematics of a robot arm can be solved easily. We can represent each joint using Denavit–Hartenberg transformation matrices. For example, if the $i^{th}$ joint is a linear actuator, it ...
  • 3,034
13 votes
3 answers
3k views

Inter-processor communication for robotic arm

I'm building a hobby 6-DOF robotic arm and am wondering what the best way is to communicate between the processors (3-4 AVRs, 18 inches max separation). I'd like to have the control loop run on the ...
  • 233
11 votes
3 answers
602 views

Which is model is best for feedback control of robotic manipulators: MIMO or parallel SISO?

I'm currently designing a robotic arm with 6-DOF, and my goal is to be able to give setpoints for 3d position, velocity and orientation ($x,y,z,\dot{x},\dot{y},\dot{z},\theta,\alpha,\gamma$). I only ...
  • 111
10 votes
2 answers
4k views

Why do we generally prefer DH parameters over other kinematic representations of robot arms?

I am specifically interested in DH parameters versus other representations in terms of kinematic calibration. The best (clearest) source of information I could find on kinematic calibration is in the ...
  • 5,455
10 votes
4 answers
2k views

Implementing a torque-controlled method on a position-controlled robot

I am working with a position-controlled manipulator. However, I want to implement a torque-controlled method on this robot. Is there any way to convert a torque command to a position command? I try ...
9 votes
1 answer
4k views

Building Robotic arm joint

I am very new to robotic design and I need to determine what parts I will need to assemble an arm joint. The joint will contain one timing belt pulley which a remote motor will be turning, a forearm ...
8 votes
2 answers
210 views

What to do when position control with trajectories is interrupted?

What are strategies used when trajectories, which are applied to a robotic joint, are interrupted? Say a robotic arm hits an obstacle, the controller just keeps applying the trajectory. Then at the ...
  • 481
8 votes
2 answers
940 views

Getting started with robotic arm design

I would like to design a robotic arm to hold a weight X at length Y (in my case I want to hold X=2.5 lbs at Y = 4 inches). Starting out simply, I would like try building an arm with a gripper plus one ...
  • 141
8 votes
2 answers
3k views

Solving Inverse Kinematics with Gradient Descent

I am trying to implement my own inverse kinematics solver for a robot arm. My solution is a standard iterative one, where at each step, I compute the Jacobian and the pseudo-inverse Jacobian, then ...
7 votes
3 answers
790 views

Is there a way to determine which degrees of freedom are lost in a robot at a singularity position by looking at the jacobian?

For a 6DoF robot with all revolute joints the Jacobian is given by: $$ \mathbf{J} = \begin{bmatrix} \hat{z_0} \times (\vec{o_6}-\vec{o_0}) & \ldots & \hat{z_5} \times (\vec{o_6}-\vec{o_5})\\ \...
7 votes
3 answers
3k views

What are these mechanical parts attached to robot arm structures, seen on larger robots?

Between the shoulder and elbow pitch joints, I see two types of connecting structures on larger robots. I've attached a picture. My questions: 1) What are each of the respective mechanical parts ...
  • 409
6 votes
3 answers
14k views

Hand Eye Calibration

I'm trying to use a dual quaternion Hand Eye Calibration Algorithm Header and Implementation, and I'm getting values that are way off. I'm using a robot arm and an optical tracker, aka camera, plus a ...
6 votes
1 answer
498 views

Stabilizing a Robot Arm at a Specified Height

I have a 4-bar linkage arm (or similar design) for a telerobot used in the VEX Robotics Competition. I want to be able to press buttons on my PS3-style controller to have the arm raise to certain ...
  • 411
6 votes
3 answers
13k views

Stereo camera Vs Kinect

Any one can advice me on the ideal perception sensors for pick and place application using a robotic manipulator with ROS support. I have generally looked at things like Kinect and stereo cameras (...
  • 63
6 votes
3 answers
2k views

Generate transformation matrices for rotating around a object?

How do i compute all transformation matrices which places a robot endeffector at the shell of this sphere, with the end effector pointing toward the object in the center. I know at all time how far ...
  • 111
6 votes
2 answers
2k views

How to speed up robotic arm?

I need my robotic arm to ring a desk bell. I one on the maplins site usb robotic arm. It does seem very slow. What can I hack on it to boost the downwards and upwards speed. I need it hit the bell ...
6 votes
1 answer
213 views

Path planning for visual servoing

I am at moment trying to implement a visual servoing application. the robot I am using is a UR5, and TCP has a stereo camera mounted on to it. The idea is to move the end effector according to the ...
6 votes
1 answer
3k views

What are some good cheap, silent, motors for mannequin robots and what kind of controller should I use? [closed]

What are some good cheap, silent, motors for mannequin robots and what kind of controller should I use? I'm creating mannequin robots that require 24 motors: 2 neck, 4 shoulder, 2 elbow, 4 wrist, 2 ...
  • 69
6 votes
2 answers
825 views

SCARA Arm Lead Screw Choices

I'm thinking about building a SCARA Arm to lift moderate loads(5lbs) with a high degree of accuracy. I want a relatively quick and inexpensive Z axis gantry, and I was thinking about using a lead ...
  • 61
6 votes
1 answer
291 views

Using Armatures in Morse Robotic Simulator

I'm trying to add my own robot in Morse 1.1 (using Ubuntu 12.04). I am struggling to add an armature actuator and armature pose sensor to an existing robot. Can someone please explain how this can be ...
  • 61
6 votes
3 answers
2k views

How to apply Inverse Kinematics with angle constrained servos?

I want to implement Inverse Kinematics and i understand the inverse jacobian method but the servos i have only have a range from -90 to +90 degrees, how can i implement this detail in the algorithm? I ...
6 votes
1 answer
1k views

Poor accuracy of hand eye calibration when using vanilla Tsai's method

I’m working on the hand eye calibration for the robotic arm. I attached the camera near the tip of the robot (or end effector) and took around 40 pictures of an asymmetric circles pattern. I ...
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5 votes
5 answers
2k views

Why don't cheap toy robotic arms move smoothly?

Why don't cheap toy robotic arms like this move smoothly? Why can't it even move itself smoothly, (even without any load)? In other words - what do real industrial robotic arms have, that cheap toys ...
5 votes
2 answers
1k 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......
5 votes
2 answers
2k views

How would I go about making an art drawing robot like this?

I saw this art drawing robot on youtube: http://www.youtube.com/watch?v=Wo15zXhFdzo What do I need to learn in order to build something like that? What are some beginner oriented projects that could ...
  • 151
5 votes
1 answer
5k views

How to create a Industrial Robotic arm controller?

Can anyone explain me in detail, what a industrial robotic arm controller does? What are its components? Does the industry use the opensource controllers like Arduino? I saw most of industrial ...
5 votes
3 answers
1k views

Computing the Jacobian Matrix -- chain rule?

I am learning about robot kinematics and the Jacobian matrix, and I'm trying to understand how to compute the Jacobian matrix given a kinematic chain, such as a robot arm. I understand the theory ...
5 votes
2 answers
4k views

Designing a 5 bar linkage robot: Plot Clock

I am a beginner at robotics. I recently stumbled across this robotic clock on youtube. I am an electrical engineering student and am interested in submitting it as my minor project. I have studied ...
5 votes
3 answers
292 views

What is the technology used for no-resistance robot arms?

I saw a high end robot arm once that I could move and bend it to any form I wanted with no resistance, as if the robot arm didn't have any weight. I'd like to know more about them. What is this class ...
5 votes
3 answers
755 views

Confusion in fixing DH frames

I am analyzing a concept of a surgical robot with 4 revolute joints and one sliding joint. I am not able to fix the coordinate frame for last prismatic joint. Following are the schematics of robot and ...
  • 193
5 votes
4 answers
3k views

Dynamic torque simulation for a 6 DOF robotic arm

I am working on a 6 DOF robotic arm(industrial manipulator). I have the basic structural specs (dimensions, weights etc) for the links and joints with me. Basically, I want to simulate both static ...
5 votes
1 answer
1k views

velocity of the end-effector

The joint velocities are constant and equal to $\dot{\theta}_{2}$ = 1 and $\dot{\theta}_{1}$ = 1. How to Compute the velocity of the end-effector when $\theta_{2} =\pi/2$ and $\theta_{1} = \pi/6$
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5 votes
2 answers
3k views

What type of servos are used in industrial robot arms like Universal Robot UR5?

I've noticed that the industrial robot arms have very smooth, fast, and strong movement. Does anyone know what type of servos they use. I'm trying to build my own and don't want to have the jerky ...
  • 153
5 votes
2 answers
1k views

Natural frequency computation (for PID gains computations)

I am currently trying to parametrize the low-level gains of a robotic arm. This arm uses a classical PID for each joint. I am trying to use a method based on computation rather than a trial-and-error/...
  • 599
5 votes
2 answers
655 views

The Jacobian resulted from Screw method is different from analytical one (Example Inside)

I am currently solving a kinematics example that asks for the Jacobian. However, when I solve it using the Screw method I get different results from the analytical method, The example is kinda hard to ...
5 votes
1 answer
245 views

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 ...
  • 324
5 votes
1 answer
644 views

How can a coaxial stepper motor be used to drive the Z axis effector of a SCARA robot?

I am new to robotics and mechanical engineering. I am trying to understand how the Z-axis (and effector) of a SCARA robot can be driven by a stepper motor with it's shaft coaxially aligned along the ...
5 votes
2 answers
641 views

Humanoid robot arm - inverse kinematics - choose joint solutions

I have developed a 7DOF arm for a humanoid robot (see pic below for more details) I have implemented the IK using a closed form solution and of course I come up with eight solutions - each one is ...
  • 121
5 votes
2 answers
3k views

How to determine x-axis if the two z-axis are intersecting in Denavit Hartenberg representation

Suppose I have a 3 link(1 dimensional) chain in which all the joints are revolutes, the axis of first revolute joint is along Z-axis(global) and axis of second joint is along X-axis(global). The first ...
  • 171
5 votes
1 answer
7k views

Create a simple C++ client Application to control KUKA's Robot-arm LBR iiwa via FRI

Until now I have been programming the robot using Java on KUKA's IDE "KUKA Sunrise.Workbench", what I want to do is control the robot arm via my C++.Net application (I would use a camera or Kinect to ...
  • 168
5 votes
3 answers
3k views

2DOF arm with quick movement: Stepper, servo, or DC motor?

To make a two degree of freedom arm capable of speeds needed to play air hockey, how should the arm be controlled? I'm wondering about speed vs accuracy. The following image is from a project ...
  • 152
5 votes
2 answers
3k views

Robotic arm ["FAiL"] error display. - Festo / Mitsubishi Melfa RV-2AJ (Controller CR1-571)

To avoid wasting your time on this question, you might only want to react on this if you have knowledge of industrial robotic arms specific. Common troubleshooting is unlikely to fix this problem or ...
  • 221
5 votes
1 answer
587 views

How to get pure end-effector translation through Jacobian?

I have a 7 DOF arm that I am controlling with joint velocities computed from the Jacobian in the standard way. For example: $$ {\Large J} = \begin{bmatrix} J_P \\J_O \end{bmatrix} $$ $$ J^{\dagger} = ...
  • 5,455
5 votes
1 answer
331 views

Is this a singularity or incorrect implementation of inverse kinematics?

I at moment trying to compute the Q configuration that moves my robot from it current state described by this transformation matrix. with rotation ...
5 votes
2 answers
981 views

Udoo board + Kinect sensor?

I am wondering if it would be possible to get Kinect to work with Udoo board (Quad). I have found that there is now support for ROS + Udoo. Also saw a question asked about Xtion + Udoo which shows ...
  • 51
4 votes
4 answers
3k views

What is the advantage having seven degrees of freedom in a robotic arm?

I understand what six degrees of freedom is, but I encountered the term of seven degrees of freedom at multiple occasions in robotics. What does is the purpose of that extra degree of freedom?
4 votes
3 answers
5k views

Harmonic drives in hobby projects

After a fair bit of research into industrial robot arms I've learned that a lot of them use components like harmonic drives and sometimes cycloidal gearboxes. Two main questions: How feasible are ...
  • 409
4 votes
3 answers
705 views

Degree of Freedom

A robotic arm should pick a cuboid up of a table, rotate it around its vertical axis and put it down on all possible positions. How many degrees of freedom are at least necessary? (All coordinates, ...
  • 41
4 votes
2 answers
6k views

Using brushless motors for very high torque

I'm currently building an robotic arm and I want the elbow joint to be comparable to a human one But here's the problem, electric linear actuators are too slow and have low torque, same goes with ...

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