# Questions tagged [joint]

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

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### 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 ...
267 views

### Inferring joint orientation on multi-joint arm

Not a robotics question in the strictest sense, I guess, but related closely enough, I hope: I have an arm-like articulated two(-plus-one)-joint appliance that I want to use as a 3D input device. It ...
20 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: $\sqrt{\sum_i^N{(JStateA[i]-JStateB[i])^2}}$. ...
111 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 ...
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### 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) ...
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### 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 ...
51 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 ...
102 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 ...
39 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 ...
489 views

### Adding an Actuator or Force to a (Featherstone) Articulated Rigid Body Model

I'm working on a project where I need to model a system that is essentially comprised of a series of ball-and-socket joints attached to a base, which is attached in turn to a prismatic joint (rail). ...
58 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 ...
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### 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 ...
138 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 ...
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### 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?
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### 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 ...
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### 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: ...
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### 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 ...
3k views

### Gazebo: moving joint with model plugin

This is my first week with Gazebo. The tutorials are clear (except for my dearth of C++ knowledge) but now that I'm working to move out on my own things are getting cloudy. I made a model comprising ...
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### 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 ...
123 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 ...
111 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 ...
1k 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 ...
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### 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 ...
767 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 ...
13k 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 ...
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### Joint Space Singularities [closed]

I would like to clarify my self on singularity configurations. If I am moving the robot in joint space only one joint at a time, can I come to a singular configuration? If so how? Thanks
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### 3 DOF Inverse Kinematics Implementation: What's wrong with my code?

I am currently trying to implement an Inverse Kinematics solver for Baxter's arm using only 3 pitch DOF (that is why the yGoal value is redundant, that is the axis of revolution). I for the most part ...
1k views

### What is torque bandwidth in actuated joints and how does it affect the control systems?

The rest of my student team and I are in the process of redesigning an exoskeleton and building it based on an existing one. From the papers that we have been reading there are some references to low, ...
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 ...