Questions tagged [joint]

The point of contact between elements of a robot with the parts that surround and support it

Filter by
Sorted by
Tagged with
0 votes
1 answer
39 views

Adding joint plugins cause ODE internal error

I designed a model in Fusion and exported it to to SDF using SDFusion script. Till now everything seems to work fine, the 2 of the 4 joints did not cause any problems and worked ok, but when I add ...
Vacoff's user avatar
  • 11
0 votes
0 answers
13 views

Gazebo-11, Get forces in joint in current step

I have a model plugin that read the joint wrench (GetForceTorque) and update it beforePhysicsUpdate. But I realize that the GetForceTorque, called in beforePhysicsUpdate, provides the resultant wrench ...
cbn.joao's user avatar
0 votes
1 answer
122 views

Joint Position Controller Plugin doesn't subscribe to any topics

I am trying to get the Joint Position Controller working with either Gazebo Fortress of Gazebo Garden. For the former I start the demo simulation with: ...
fortytwo's user avatar
0 votes
0 answers
14 views

In ignition fortress, how to get components of an universal joint in system plugins?

I'm having problems in developing a system plugin for Ignition. In the case the robot has a universal joint, creating/updating component data related to the entity, returns something like: ...
Vincenzo Ruotolo's user avatar
0 votes
1 answer
101 views

joints not showing up in rviz

First of all, I'm not a native speaker sorry for my English, I'll try to fully demonstrate my problems. I wrote a urdf file that contains a base, four wheels, and a lidar. Everything is showing up ...
cwliu2040's user avatar
0 votes
0 answers
83 views

Sdf Joint not connecting parent model to included model

for the past month I've been working in an ignition gazebo simulation using SDF file to describe my robot model. Since the robot has some repeated parts I created a different file and included it in ...
amsantos's user avatar
2 votes
1 answer
153 views

How to implement self-locking motor in Gazebo/SDF?

I have a model with a few joints controlled by self-locking motors. The joints can be prismatic or revolute, but the real robot has a very high gear ratio in the motors, so the joints are basically ...
Martin Pecka's user avatar
1 vote
1 answer
142 views

How to design shafts and select bearings

I am trying to design robotic joints for a SCARA arm, I am mainly missing information about the shaft and bearings components. Design would be similar to MakerArm / Dobot M1 kickstarter projects. So ...
LiohAu's user avatar
  • 161
0 votes
2 answers
64 views

Why aren't more bipedal (or even quadruped) robots made with joints/articulations similar with those found on atmospheric deep dive suits?

The sole reason I'm making this question is due to the fact that such joints/articulations would allow the electric motors to continuously move while the walking motion is performed, instead of the ...
Fulano's user avatar
  • 43
0 votes
1 answer
1k views

What is the meaning of joint space and configuration space and task space?

I'm reading an article about teleoperation systems and it talks about three spaces that include joint space, configuration space and task space frames. I do not know what these are, can you explain?
Elham sadeghinezhad's user avatar
0 votes
0 answers
40 views

How to translate a joint configuration

I'm currently working on a basic implementation of the RRT algorithm to control my 6DOF robotic arm. But how can I reduce the node to be in the radius of the nearest node of my graph without using the ...
Justin M's user avatar
0 votes
1 answer
561 views

DH Parameters of a 2 DOF RP Robot

How can I determine the DH parameters of the robot shown in the figure ? As i know, the z axis should show the rotation axis for rotary joints and direction of extension for prismatic joints, so the ...
Berkay Taskin's user avatar
2 votes
1 answer
200 views

Estimating distance between joint positions

I was wondering if there is any good way to estimate the difference between two joint states of a robotic arm. Currently I am using something like this: $\sqrt{\sum_i^N{(JStateA[i]-JStateB[i])^2}}$. ...
Iñigo Moreno's user avatar
0 votes
0 answers
194 views

I would like to add a prismatic joint to the Z axis of the 6th joint of Urdf

I have a urdf file,urdf of UR5 robot and added a prismatic joint to the end of 6th joint of the robot with the "prismatic_joint" tag (By copying other joints and links) ...
Meric Ozcan's user avatar
0 votes
0 answers
149 views

Joint space trajectory script unclear

I have a script provided by The MathWorks Inc. that makes a robot end-effector follow both a task space and a joint space trajectory through several waypoints. These trajectories are then plotted in ...
user463102's user avatar
4 votes
1 answer
189 views

Why are serial manipulators almost always made of single dof joints?

I am currently taking my first robotics class and I found it curious that all serial manipulators have single dof joints. Why not use joints with more dof and reduce the number of components? Will ...
Eyas Ayesh's user avatar
0 votes
1 answer
2 views

Is it possible to find the parent frame of a joint knowing the joint name?

Hi. I am using the ros control JointStateController to publish the JointStates from gazebo. I get the messages and it is working well. Now that I have the joint state I would also like to find the ...
user avatar
0 votes
2 answers
5 views

Why only is a PID controller used in ROS Control?

In the ros_control set of packages, why PID controller specifically is used in joint_state_controller, ...
user avatar
1 vote
0 answers
80 views

Why do some humanoid robots use a slanted yaw joint on the hip?

In this image, we see LHipYawPitch, as well as a dedicated LHipPitch. Why would they combine the yaw and pitch in the upper joint instead of making a dedicated yaw joint? I understand that this makes ...
pinkie pAI's user avatar
0 votes
1 answer
286 views

How to calculate displacement of the end effector by the yaw, pitch, and roll in the spherical joint?

For planar robots, we can calculate how small changes in the angle of each joint corresponds to the displacement of the end effector, by constructing a jacobian consisting of cross products between ...
Lenny White's user avatar
0 votes
1 answer
147 views

What are joint angles of Kinova Jaco in home position?

I want to work with Kinova Jaco with spherical wrist in CoppeliaSim, because currently I do not have access to a physical manipulator. The model there is in reset configuration (arm fully extended and ...
Anton Kim's user avatar
2 votes
1 answer
88 views

How do I decide the minimum number of link lengths and joints my manipulator must have from the configuration space?

I have a configuration space in 3D where my manipulator must reach certain points. Taking into account all the factors how do I decide the mininum number of links and joints my arm must have?
GlassAnimals's user avatar
0 votes
1 answer
60 views

what are shoulder ball and socket joints called? (i am trying to design and build a hydraulic assistance mech suit)

I'm having problems finding the right sort of joint for my shoulder connection. It is a flat surface on the side of the mech body and I need to create a joint with maximum movement rotating: up, down ...
tom b's user avatar
  • 1
0 votes
1 answer
52 views

My robot keeps getting saved as one cylinder leaving out the bottom cube

I created a robot in the model editor that is made up of a cube and a cylinder with a revolute joint between them but after saving it and inserting another instance into the world, I only get the ...
heretoinfinity's user avatar
1 vote
1 answer
196 views

What is the purpose of an empty link without any child elements?

I was looking at a model xacro [urdf] file in a ROS tutorial when I saw: ...
heretoinfinity's user avatar
4 votes
1 answer
76 views

Velocity description in Screw Motion Theory

As described in the book Modern Robotics by Frank C. Park the velocity of a reference frame can be described as : $$V_s = J_s(\theta)\dot{\theta}$$ $$V_b = J_b(\theta)\dot{\theta}$$ However in the ...
Ricardo Mostalac's user avatar
0 votes
1 answer
16 views

Model on RViz / Gazebo with wrong orientation and incorrect links' position! How to fix?

Hi, everyone! I’m newbie at ROS, URDF, Rviz, Gazebo... I’m learning about these topics for research. Running Ubuntu 18.04, ROS Melodic Morenia, RViz version 1.13.7 and Gazebo 9.12. I’ve build a model ...
user avatar
1 vote
1 answer
257 views

How does this end effector work?

I've seen this linear actuator end effector on a few industrial SCARA 'bots but I am having trouble visualizing how it works internally: It looks like a type of lead screw, but the nut must spin ...
kp122's user avatar
  • 13
3 votes
2 answers
489 views

How to compute associated (partial) Jacobian matrix for each joint of a serial manipulator?

Given DH parameters of a serial manipulator, the forward kinematics gives me T0n = T01*T12*T23*...*Tn-1n , n is the DOF of manipulator. I can calculate the Jacobian matrix J for the end-effector by ...
Michael's user avatar
  • 33
0 votes
1 answer
3 views

Compute joint angles of movement without execution

I am planning, executing and recording linear robot movement with computeCartesianPath(). I would like to "simulate" this program. Essentially just ...
user avatar
0 votes
1 answer
2 views

joint state publisher dies, cannot attach wheels with continuous joint

Hi, I am currently trying to create a simple differential drive robot model with 2 wheels and 2 caster wheels, but I cannot attach the wheels to the chassis with continuous/revolute joints and I do ...
user avatar
2 votes
1 answer
164 views

IMU based joint angle measurement

Let us assume we have a two 2-DoF robot. Both axes rotate around x. And the goal is to measure the joint angle values with the roll value from IMUs attached on each link. However, the problem is that ...
Joe's user avatar
  • 324
0 votes
1 answer
171 views

Robot arm with steppers - speed

I am using a 5 axis Robot arm (Robolink robot from Igus) to perform some 3D printing routines. By now I am trying to use them and have him have some good position (and speed) control. The robot is ...
João Sobral's user avatar
3 votes
2 answers
130 views

Making a motor controlled joint passive

Anyone know of a good (and economical) way to make a motor controlled arm become a passive link on trigger? That is, the joint can be active (motor controlled) or passive (rotate freely). The tip of ...
John M.'s user avatar
  • 563
1 vote
2 answers
3k views

How to determine the direction of X-Axis in Denavit Hartenberg process? [Sketch inside]

The rules of assigning axes for DH parameters are (as I know them): 1- Z: in the direction of the axis of rotation/translation of revolute/prismatic joints. 2- X: perpendicular to the previous Z axis ...
Forenkazan's user avatar
2 votes
1 answer
1k views

How can I attach an arm to a double-flat drive stepper motor?

This is my first robotics experience, outside of one class 10 years ago. I've been Googling this question for about an hour but I can't find an answer! I'm using a ROHS Step Motor 28BYJ-48 (with an ...
CreatedByBrett's user avatar
0 votes
1 answer
7 views

How to get joint, speed, acceleration values of cartesian path?

I'm currently working with OMPL and waypoints. This tutorial explains how to use them. Everything working fine and the plan from start to goal is executed. The terminal tells me the following: ...
user avatar
0 votes
1 answer
113 views

What are the differences between wheel and manipulator joint encoders?

As far as I understand the joint encoders output the angle and the wheel encoders output speed. Is that accurate? In either case, how do the differences affect the kinematic calculations, as in path ...
Leon Rai's user avatar
  • 155
0 votes
1 answer
7 views

STOMP planner: Can only handle joint space goals

I'm trying to use STOMP with this tutorial. I want to plan a path with STOMP using a relative command for the endeffector. I'm trying to execute the following command to achieve this: go x 0.5 I ...
user avatar
0 votes
1 answer
197 views

What is the rectangular-shaped joint in this diagram?

What is the rectangular-shaped joint under the M1? What does it do, and what is its DOF?
parvin's user avatar
  • 111
2 votes
1 answer
912 views

Spherical (Ball) Joint in Robot Model not Working in Gazebo

I'm having trouble including a spherical/ball joint in my robot model. I have tried using the 'ball' joint type defined by sdf (http://sdformat.org/spec?ver=1.6&elem=joint#joint_type) but the urdf ...
jstm's user avatar
  • 141
1 vote
1 answer
951 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 ...
Jonathan F's user avatar
0 votes
1 answer
11 views

Joint trajectory controller (client) not working

Hello list, Trying to get a trajectory controller working, but am unable to get a working action client. As a first test I tried to add it to the rrbot example from gazebo_ros_demos. As the ...
user avatar
0 votes
1 answer
1 view

Move It! polar robot configuration not moving second joint

Hi all! I'm fighting to create a polar robot configuration with Move It. The polar robot has 3 joints: rotational, rotational and prismatic. Polar robot http://www.robotpark.com/academy/PG/Spherical-...
user avatar
0 votes
1 answer
17 views

joint_state_publisher not showing joint sliders for URDF

Hi there. I'm working on a project to simulate a robot arm. I have a URDF file that I'm able to open and view in RVIZ using the following .launch file. Note: the URDF was created by the Solidworks to ...
user avatar
0 votes
1 answer
5 views

Gazebo model stuck in ground after enabling joint controllers

Hi there. I am struggling with getting my RC Car model to work properly with Gazebo. I have followed both the Gazebo and ROS tutorial on how to create the URDF (XACRO) files and the required Gazebo ...
user avatar
0 votes
2 answers
93 views

How to do mimic joints that work in Gazebo?

This question has been asked several times on this site (here and here) as well as on the Gazebo QA site (here and here) but its still not clear to me if mimic joints are supported in Gazebo. Or if ...
user avatar
0 votes
1 answer
11 views

MoveIt: how to actuate individual joints that do not form a chain?

Hi, I'm working on a project at my university in which we are designing and simulating an industrial robot system. We have created a URDF file that contains the robot system, as well as the platform ...
user avatar
0 votes
1 answer
68 views

State of the art trajectory for fine precision robots

Which kind of trajectory would one use for a fine precision robot? I know trapezoidal and cubic trajectories, but errors get very high when stopping at every configuration and when speeding up to ...
kassio's user avatar
  • 35
0 votes
2 answers
5 views

MoveIt Move only one Joint

Hello everybody, Can someone tell me, how to move only one joint with MoveIt - Move Group Interface and not the end-effector pose. Has someone experiences and can give me a some tips? Thanks! ...
user avatar