Questions tagged [joint]

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

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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 Denavitâ€“Hartenberg transformation matrices. For example, if the $i^{th}$ joint is a linear actuator, it ...
420 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). ...
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 ...
187 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 ...
2k views

restricting range of motion with complex constraints

I am looking for a way to restrict a robot's range of motion, using complex constraints such as not tearing of a cable attached to the robot. Take an articulated 6-axis robot arm as shown below, with ...
251 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 ...
179 views

134 views

What type of mechanism is this?

Held and rotated by the knurled ends, one in each hand, the silver spokes rise and fall in order for the assembly to rotate. What is it, some companies' salesmen show tool? Found in an old building, ...
24 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: ...
509 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 ...
933 views

joint positions of a robot

I would likte to find the joints positions using joint angles, link lengths etc. How can I define the position of the each joint using DH parameters?
21 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 ...
53 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 ...
90 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?
56 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 ...
601 views

how to find maximum force of a robot joint

I want to know if there is any equation that calculates the maximum force of a robot joint. The force that we should not exceed. For example in human leg, if we apply a big external force to the knee,...
203 views

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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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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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 ...
44 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 ...
57 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 ...
429 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 ...
800 views

Parallel axis theorem to determine the moment of inertia

I need to use the parallel axis theorem to determine the moment of inertia of each robotic arm link referred to the joints of the 3 DOF manipulator. The moments of each link's centre of mass are: The ...
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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 ...
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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 ...