# Questions tagged [kinematics]

Kinematics is the branch of mechanics dealing with the motion of points and objects.

330 questions
Filter by
Sorted by
Tagged with
0 votes
1 answer
16 views

### Classical DH and Euler angles parametrization

Let DH convention is carried out as $$A_i = \text{Rot}_{z,\theta_i}\text{Trans}_{z,d_i}\text{Trans}_{x,a_i}\text{Rot}_{x,\alpha_i}$$ This is the classical DH method stated in Spong's book. The ...
2 votes
1 answer
71 views

### Redundancy and Null space projection

I'm reading "Theory of Robot Control" by Carlos Canudas Wit, Bruno Siciliano, Georges Bastin. In Task space control chapter, exploiting the redundancy by means of null space as shown below ...
1 vote
1 answer
52 views

### How can I find a robot's distance from an object given FOV, bounding box measure, and image width and height in pixels?

The robot is standing in the middle of the arena. I am confused on how to convert the pixels into a real life distance and how to use the bounding box. Starting help is appreciated.
3 votes
1 answer
85 views

### Difference between Denavit-Hartenberg and Rodrigues formulas/conventions

I am trying to compute the forward kinematics for a 6 DOF robot arm. I've found two methods : the Denavit-Hartenberg (original and modified) and the product of exponentials with the Rodrigues formula. ...
0 votes
1 answer
81 views

0 votes
1 answer
175 views

### What is my last rotation matrix for the last three angles when i have found the first three when doing inverse kinematics to a 6dof robot?

I am doing inverse kinematics for a 6dof robot. I have used the geometrical method to describe the angles from one to three. I have trouble doing the next part. I know I that I have found the ...
3 votes
3 answers
2k views

### Finding correct RPY for approaching a known point on a plane

I have a robot with 6 DOF that I want to use to grab a hanging sheet at a specific point near its edge. The grip needs to be perpendicular to the edge and co-planar with the point of course. I have ...
8 votes
1 answer
2k views

### Hand Eye Calibration Solver [closed]

I have a rig for which I have a pretty good estimate of the static transformation between the camera and a joint based off of the CAD. It has some errors though and I was hoping to fix it by doing a ...
0 votes
1 answer
46 views

### How can I find the kinematics 2 differential drives attached together along their axes?

I have a system like shown in the diagram where 2 robots having differential drive are physically constrained together. Traditionally for a single robot, we find the Instantaneous center of curvature (...
3 votes
1 answer
290 views

### How to find angular velocity using pure pursuit algorithm?

I have implemented the pure pursuit algorithm for my differential wheeled robot as described in the following paper: http://www.enseignement.polytechnique.fr/profs/informatique/Eric.Goubault/MRIS/...
0 votes
2 answers
173 views

### Orientation Problem of a 4-DOF manipulator

As shown in figure, I have a 4-DOF manipulator. I want to control the robot such that the end-effector should always be pointing down no matter where the robot is in the end space. For the ...
0 votes
1 answer
72 views

### Design optimization method using indices

There are several methods like manipulability and conditioning index for design optimization kinematics performance, but these methods rely on the singular values of the jacobian matrix. I described ...
2 votes
1 answer
63 views

### What is the consquence of Gimbal lock?

I'm learning about Gimbal lock and I understand the reason why that happened. But I don't understand why that is a big deal because it only affect this rotation. After this rotation finished, we have ...
0 votes
1 answer
268 views

### Robotic Manipulator 3-RRP v2

I recently asked a question about a 3-RRP manipulator but the only answer didn't work for my robot. I would describe the manipulator as an arm that rotates around the shoulder over the x-y axis, the ...
0 votes
0 answers
22 views

### Robot increases in length, trying to keep robotic along previous position trajectory

Sorry for the confusing title, this seems to be a difficult problem to concisely describe. I am working on a 50-DOF (yes, 50) robot that is comprised of "elbow macaroni" links that rotate ...
1 vote
1 answer
121 views

### How to solve this basic dynamics/inverse kinematics problem

Suppose I have a 6-DOF robot arm with revolute joints whose tooltip is at some position $\bf{r_0}$ and I want to move it through some trajectory ${\bf r}(t)$. For simplicity, assume there are just 2 ...
0 votes
2 answers
189 views

### How can I input joint angles to transformation matrix to get position in matlab?

I am trying to get the forward kinematics for a robot model in matlab (rigid body tree). I created a 4 x4 transformation matrix from the base to the end-effector using the gettransform() function. I ...
0 votes
1 answer
20 views

### VR: is it possible to calculate hand position relative to head based off these known orientations and lengths?

If we have 3, 9DoF IMUs for absolute orientation data on the: wrist upper arm forehead and we know the length of the: wrist upper arm shoulder to base of neck neck and we also know the global ...
3 votes
1 answer
93 views

### Forward kinematics confusing point

I am studying robot arm kinematics. In order to construct a transformation from a global coordinate frame to the end effector frame, I have seen references to the Denavit–Hartenberg (DH) convention. ...
1 vote
1 answer
73 views

### Finding torque equation for my robotic arm

I am designing a 5 dof robotic arm, and for that I would like to find a torque equation. However, I am a little confused here: According to me the torque equation for M1 should be l2m2+l3m3+l4m4+l5m5 (...
1 vote
1 answer
83 views

### Parallel spatial mechanism - DOF

The parallel mechanism is composed of a moving platform and a base (or frame) connected by four legs. Each leg is composed of five revolute joints numbered 1, 2, … 5 from the base to the moving ...
1 vote
1 answer
123 views

### Multiple Rotations via Matrix Multiplication

so I am having an issue understanding why you right multiply for current frame rotation vs left multiply for fixed frame. Let us say you want to: Rotate about x, then Rotate about current y, then ...
0 votes
1 answer
51 views

### Inverse kinematics for 2DOF robotic arm in 3D

i am trying to find the inverse kinematics for quadrotor with 2Dof robotic arm, which has first joint rotation axis perpendicular with second joint. So, for the inverse kinematics i use two equations ...
0 votes
1 answer
88 views

### How do you end up with 1 degree of freedom with one big link connecting 3 other links?

I was reading Modern Robotics by Kevin Lynch et al. and this robot was presented. They had introduced Grubler's formula which assumes independent joint which gives $dof = 0$ but this is not the case ...
0 votes
0 answers
39 views

### Problem with Inverse Kinematics Solver (Jacobian Inverse Method)

I am trying to create an inverse kinematics solver for my 4-dof (all revolute joints) robot using the inverse Jacobian Method. However, it does not seem to be working as the distance between target ...
0 votes
1 answer
25 views

### Defining the specifications required by a 6DOF robot to impose a harmonic sinusoidal motion

Perhaps a bit of a simple question, but since I don't have a background in robotics/engineering, then I imagine this would be the perfect place to ask such a question. I am buying a 6-DOF Stewart ...
3 votes
1 answer
149 views

### From a linear force actuator that spans multiple links and joints to the equivalent motor torque

I am programming/using a rigid body joint-space dynamics solver for robots in which I want to implement linear force actuators between links with their equivalent torque sources that are 'spanned' by ...
9 votes
6 answers
2k views

### What is the best SE3 library for python?

I am currently googling on this topic but I would like to hear your opinion. What is the best self-contained SE3 library that offers interconversion between quaternion, rotation vector, ...
2 votes
1 answer
53 views

### Equations of motion with mass attached to end effector and external force

I have to find the equations of motion for the given manipulator: The links of the manipulator are considered weightless and the equations of motion have to be derived by using the Lagrange equations....
0 votes
2 answers
57 views

### control of a rod attached to a motor

I have a 76 cm, aluminum rod, attached to the shaft of a 12v DC banebot motor. The rod is hanging vertically initially, and rotates in the vertical plane. The task is to control the rod to make it ...
0 votes
1 answer
68 views

0 votes
1 answer
133 views

### How to calculate potential enegy of manipulator?

I'm trying to obtain dynamics of a 4 DOF robot. Firstly, I calculated all Transformation matrices and Jacobians. While solving Lagrangian there is two main things one is kinetic energy and the other ...
2 votes
1 answer
70 views

### Holonomic constraints on an upright wheel

A wheel moving in free space has the six degrees of freedom of a rigid body. If we constrain it to be upright on a plane and to roll without slipping, how many holonomic and nonholonomic constraints ...
4 votes
1 answer
514 views

### Extended Kalman Filter in robotics - Worth it?

I wonder if Extended Kalman Filter(EKF) is used in robotics, or is only Kalman Filter(KF) used in robotics. Kalman Filter is included in Linear Quadratic Gaussian(LQG) controllers. But how would EKF ...
0 votes
0 answers
235 views

### In MuJoCo why do some XML files have objects fall to the ground while others are just fixed above the ground?

Why do some models, or objects in a MuJoCo XML script fall to the floor while others don't? In the models files that come with the MuJoCo zip, the robot arm (arm26) does not fall to the ground while ...
0 votes
1 answer
43 views

### How to calculate DH parameters for Higher Pair?

I am trying to build a robot which is having Bevel Gears connecting two links. I want to calculate DH parameters, but i am stuck with this bevel gear as when the joint rotates both angle and ...
0 votes
1 answer
49 views

### Forward Kinematics for articulated manipulator not giving right answer

I calculated the forward kinematics for an articulated manipulator robot in ROS, but I am not getting the right answer. Here is the diagram for the robot configuration I used- When Q1,Q2,and Q3 are ...
4 votes
2 answers
597 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 ...
1 vote
1 answer
60 views

### C space for R5 manipulator

Trying to create a collision avoidance model (RRT) for an RRRRR manipulator. I am unable to wrap my head around how to represent the same in configuration space. Anything upto 3 joint variables is ...
1 vote
1 answer
39 views

### Elegant way to mathematically relate joint positions (without a root/base joint) for easy re-rooting?

I'm pretty new to robotics, but have learned about the tranformation matrices and how to relate relationships between joints using transformation matrices. I just wonder if there is a system that ...
0 votes
0 answers
27 views

### Maximizing the Coefficient of Friction Between Two Surfaces

I am new to this site so please let me know if I can improve my question. A component of a robot I am designing includes a four-wheeled carriage that travels linearly on an aluminum surface. The ...