Questions tagged [kinematics]

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

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How to convert between classic and modified DH parameters?

I currently have a description of my 22 joint robot in "classic" DH parameters. However, I would like the "modified" parameters. Is this conversion as simple as shifting the $a$ and $alpha$ columns ...
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1answer
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How to use the Homogeneous transformation matrix?

I am trying to understand how to use, what it requires compute the homogenous transformation matrix. I know 2 points from 2 different frames, and 2 origins from their corresponding frames. I how ...
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1answer
297 views

Measuring angular displacement using the TI-SensorTag

I've looked around but can't find the answer, to what I hope is a simple question. I'm working with a TI-SensorTag, and I want to be able measure the rotation around the unit's Z-axis. Basically I ...
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jacobian of Abb irb140 robot

Can someone please help me with the jacobian matrix equations for Abb irb140 robot. Or an easy way by which I can derive it given the DH parameters. I need it to implement some form of control that am ...
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3answers
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Mathematical Moddeling of Elastic Robots [closed]

We can easily compute the rigid robot kinematics and dynamics. There is many resources, simulators and modelling tools about it. But i couldnt find any of these for elastic robots. Can you suggest ...
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1answer
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How can a memory alloy be used as an alternative to a compressor found in a refrigerator? [closed]

I'm curious about this alloy and how they say it can be used as an alternative to a traditional compressor. Can anyone explain how this would work? My goal is to understand that use case so I can ...
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4answers
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Assuming I have the angle with respect to two beacons, and know the distance between them, can I localize myself?

Let's assume I have the following situation, and need to find (x,y). Is it possible? There does not appear to be more than one solution to the system, but my trigonometry is a bit rusty. I feel ...
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6answers
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How do I work out the kinematic solution of a robot arm?

I draw a robotic arm in Solidworks, but I'm not so sure about how to find out the DOF, forward and backward kinematic. Could anyone help me understand how to work out the kinematic solution of this ...
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How to get the 4*4 matrix from the twist using product of exponentials, in robot kinematics?

In robot kinematics, we have $e^{(\theta*twist)}$, where $twist$ is 6*1 vector. How do I get the 4 by 4 transformation matrix by using product of exponentials?
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3answers
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DH Matrix to homogeneous transformation matrix for each joint

Given a DH matrix for a set of joints, how would you convert the data into homogeneous transformation matrices for each joint? I've looked online, but can't find a good tutorial.
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1answer
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Can a Jacobian be used to determine required joint angles for end effector velocity/position?

I'm in the early stages of working with a simple robot arm, and learning about the Jacobian and inverse kinematics. From my understanding, the Jacobian can be used to determine the linear and angular ...
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1answer
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How do you calculate the moment of inertia of a Quadcopter?

I'm building a quadcopter for my final year project. I have a set of equations describing attitude and altitude but they involve $I_{xx}$, $I_{yy}$ and $I_{zz}$. None of the papers I have read ...
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2answers
539 views

How to invert D-H parameters

I currently have a working kinematic chain made by a set of ten links in D-H convention (with usual parameters [ $A_i, D_i, \alpha_i, \theta_i$]). But my task currently requires the inversion of some ...
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2answers
371 views

following a trajectory with LQR controller

We want our wheeled robot to follow a (rather short) trajectory. We wrote an LQR controller, which works well in simulation. However, our robot offers two problems: 1.) The reported state information ...
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1answer
654 views

How to correctly compute direct kinematics for a delta robot?

I'm trying to put together a simple simulation for a delta robot and I'd like to use forward kinematics (direct kinematics) to compute the end effector's position in space by passing 3 angles. I've ...
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3answers
709 views

is it possible to track movement on a tennis court?

I'd like to track my run in an indoor tennis court. GPS won't be available so I was thinking researching for other solutions: Accelerometer: I concluded it's a no go because while playing tennis the ...
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2answers
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Short distance ball transport

I'm looking for a way to transport balls (diameter 50mm) 220 mm up with over a slope with a length of 120 mm. Currently I'm considering the usage of a belt system but I cannot seem to find a good belt ...
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1answer
463 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} = ...
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1answer
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Velocity Model Motion in Matlab (Probabilistic Robotics)

I want to implement the velocity motion model in Matlab. According to Probabilistic Robotics page 124, the model is as following \begin{align*} \hat{v} &= v + sample(\alpha_{1} v^{2} + \...
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2answers
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What are the advantages of using the Denavit-Hartenberg representation?

When one wants to model a kinematic chain and in particular define the frames attached to each body, it is common to use the Denavit-Hartenberg parameters. What are the advantages of this ...
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2answers
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Position Control of an Omni Wheel Drive Robot

I want to create a robot that will navigate on a desired path! That path can be a straight line or a circular path with a given radius. I will use 3 or 4 omni wheel drive platform and for positioning,...
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1answer
190 views

One of the best ways to numerically integrate the velocity?

I need to get position $x$ from integrating velocity $v$. One could use 1st order Euler integration as $x_{t+1} = x_t + \delta * v_t.$ However, doing so leads to errors proportional to sampling time ...
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Calculate position of differential drive robot

How do you calculate or update the position of a differential drive robot with incremental sensors? There is one incremental sensor attatched to each of the two differential wheels. Both sensors ...
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0answers
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Can active sensor data be fed into an Autodesk Inventor Simulation?

I'd like to drive the position of various components within a virtual assembly based on sensor data being collected in real time from an external device. Does Inventor support such a setup? The goal ...
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1answer
156 views

How to make one robot follow the other in parallel formation

This is quite a basic question. I'm practising robot programming with VRep. I have 2 K3 robots in the scene. One robot follows a predefined path. I want the second robot to move "in parallel" with the ...
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1answer
164 views

Forward Kinematics Two fixed standard wheels

What would the equations be for the robot's angular and linear velocity at P and also P2? I think I'm doing it wrong... WL = left wheels angular velocity WR = right wheels angular velocity For P I ...
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1answer
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Denavit–Hartenberg parameters of a robot with spherical wrist

What are valid values for the Denavit-Hartenberg parameters $d$ and $a$ (sometimes called $r$) of the last 3 links of a robot with spherical wrist? From this reference, "A spherical joint can be ...
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2answers
196 views

How does one calculate the angular motion of each node in a robotic arm

A robotic usually consists of joints with sections of possibly varying width connected together. Considering we know how much each is bent and the length of each section, and their location in 3D ...
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2answers
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What is a suitable model for four-wheeled differential drive rigid-body robots?

I found a model for 2-wheeled robots here: What is a suitable model for two-wheeled robots? How should I adapt it to a 4-wheeled setting?
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2answers
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Assigning Frames and Deriving Link Parameters

The textbook I'm using doesn't have the answers to the practice questions, so I'm not sure how I'm doing. Are the following DH parameters correct given the frames I assigned? The original question is ...
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2answers
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How much accuracy could I get position tracking with a 3-axis accelerometer and gyro sensor, and compass, and how would I do it?

Given a 12' x 12' field (4m x 4m), a reasonably cheap 3-axis gyro sensor and accelerometer, and compass, I plan to design a device capable of tracking its position to sub-centimeter accuracy for a ...
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2answers
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How to calculate the right and left speed for a tank-like rover?

I am trying to control the Rover 5 robot using an Android app with a touch-based joystick control in the app UI. I want to calculate the speed of the left and right motors in the rover when joystick ...
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3answers
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With a 6-axis robot, given end-effector position and range of orientations, how to find optimal joint values

Given a six-axis articulated robot arm holding a tool at its end-effector, if I have a desired tool position and tool orientation, there will be exactly 1 solution to the inverse kinematics equation ...
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0answers
106 views

Turning a differential drive robot to a specific angle [duplicate]

Given a robot with 2 wheels with radius r on one axle with length D, I want to set the wheel speed so that it turns to an angle phi as fast as possible. The timestep t is 64 milliseconds. I thought ...
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1answer
140 views

Defining frames for 5DOF robotics arm

For examples if i have this robotic arm: Example, for the base rotation (5th DOF in the clip at 0:58), we know that the Z axis for that joint will be the same as the Z axis for the base frame{0}, but ...
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1answer
269 views

Performing the proper coordinate system transformation

I could use some guidance regarding a coordinate system transform problem. My situation is this: my system begins at some unknown location, which I initialize the location (x y) and orientation (roll, ...
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2answers
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Computing the Jacobian matrix for Inverse Kinematics

When computing the Jacobian matrix for solving an Inverse Kinematic analytically,I read from many places that I could use this formula to create each of the columns of a joint in the Jacobian matrix: ...
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1answer
420 views

How to control velocity ratio when turning angle is θ?

Im designing a differential steering mechanism for my robot. Supposing my robot is going in a straight line and I want it to change it direction by a certain angle( $θ$ in the diagram). What should ...
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1answer
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How to design a differential steering mechanism?

I want to give my robot a differential mechanism for the system of turning and steering. Considering the case of turning a right-angled corner, the robot will achieve this by following a gradual ...
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2answers
315 views

Drone targeting

Imagine a "drone" and a target point on a 2d plane. Assuming the target is stationary, there are eight parameters: ...
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2answers
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Is there a tool for building and analysing robots (kinematics, control) visually?

I am reading research papers about robotics and many of them follow the same pattern: some construction is established kinematical formulas are read from the mechanical structure the state space is ...
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1answer
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Numpy alternatives for linear algebra and kinematics in python?

Are there any decent python numerical package libraries besides numpy for python? Numpy relies on gfortan which itself must be compiled correctly for your platform to avoid hidden/insidious numerical ...
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1answer
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How do I convert link parameters and angles (in kinematics) into transformation matrices in programming logic?

I'm doing robotics research as an undergraduate, and I understand the conceptual math for the most part; however, when it comes to actually implementing code to calculate the forward kinematics for my ...
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2answers
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Differences between Ackermann steering and standard bi/tricycles concerning kinematics?

I got the following homework question: What are the general differences between robots with Ackermann steering and standard bicycles or tricycles concerning the kinematics? But, I don't see what ...