Questions tagged [kinematics]

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

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2answers
64 views

Vertically moving robot

I want to build a 4WD robot that can travel vertically by pushing against opposite rails. The wheels push against the rails and generate friction, the robot moves upwards as the wheels rotate. This is ...
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1answer
141 views

Wrong forward-kinematic after calculating from DH-parameters

I'm working on an exercise about DH-parameters for my robotics course in university and I ran into a problem, because my solution is different from the one given by my professor. I calculated the DH-...
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2answers
525 views

Struggling to understand Jacobian Inverse Kinematics

I'm trying to find a method to control a moveo 5dof arm. My goal is to calculate the right angle to turn for each stepper motor to reach a desired point in real environment. I've spent time looking at ...
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0answers
34 views

how to normalize PWM if the value exceeds the maximum speed limit

I have implemented inverse kinematics for nonholonomic mobile wheeled robots, and the RPM range of the motor that I used is -50 to 50, while for PWM is from 1300 to 1700. But in certain cases, the RPM ...
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1answer
88 views

How do I compute the translation and rotation velocities of a robot

I am stuck at computing the translation and rotation of a robot moving onto an ellipse given by: $$ p(t) =(m) + \cos(t)∗a + \sin(t)*b $$ where m = center of ellipse and the two axes a (horizontal) ...
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1answer
83 views

Can somebody explain how these forward kinematics matrix equations were formulaed?

Here's the link to the entire answer: Designing a 5 bar linkage robot: Plot Clock
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1answer
3k views

Using pre multiply or post multipy for rotational matrix to get a new homogenous transformation matrix?

I am confused about how do I multiply the rotational matrix in this case. I know that both T1 and T2 needs to be multiplied by a rotational matrix but I don't know how to multiply the rotational ...
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1answer
204 views

Why using screws instead of homogeneous transforms in kinematics and dynamics?

Can anyone give a justification for using screws (twists, wrenches) instead of the traditional approach (rotation matrices, homogeneous transforms)? Even if screws are more compact, the situation gets ...
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1answer
332 views

Finding Joint speeds for each joint of a 6DOF arm (UR10) using the Inverse Jacobian

Background: I have access to a UR-10, 6DOF robotic arm through my school (I'm very new to robotics). I know the desired set of linear speeds that I want in the x,y, z-direction in terms of the end ...
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1answer
261 views

Creating linear end effector motion using joint speeds: Converting tool speed to joint speeds

Background Information: I'm new to robotics and my school currently has access to a 6DOF Universal Robot (UR-10). I'm programming it using its scripting language URscript and the arm has these two ...
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1answer
26 views

Motorised Stage for laser

The problem I want to be able to move the direction a laser is pointing. This means I need to have motorised rotation of the laser head in the x direction and in the y direction. I am unsure of the ...
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5answers
1k 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, ...
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0answers
90 views

Algorithm for orientation (pan/tilt) towards a moving point

Main Question: note: The code in this question is pseudo-code, I'm using Python, but my pseudo-code is a mix of Python and C++. I have a camera on the top of my robot's "head" which has pan and tilt ...
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2answers
86 views

Help to get robot jacobian from system of implicit equations

I have system of two equations that describes position of robot end-effector ($X_C, Y_C, Z_C$), in accordance to prismatic joints position ($S_A, S_B$): $S^2_A - \sqrt3(S_A + S_B)X_C = S^2_B + (S_A - ...
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2answers
602 views

Denavit-Hartenberg Exam Question

I am having a bit of trouble with the pictured question: I am able to do part a and b, however c is proving very difficult. My lecturer never really explained much beyond what is asked in a and b. ...
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0answers
263 views

Treatment of euler angles in quadcopter control

In most implementations of quadcopter control systems I've seen, each axis of the quadcopter is controlled independently. For example, to control the rate in the roll axis, the desired output is ...
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2answers
280 views

Screw based Jacobian

I am working on kinematics of 5-DOF robot. I already derived geometric Jacobian for position and orientation control. But for singularity analysis, I require a simplified jacobian. And that can be ...
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1answer
370 views

State space model

I want to design a LQR controller for my two wheeled mobile robot. While designing the controller, I need to find gain, K for the LQR which this required the state space model of wheeled mobile robot. ...
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1answer
50 views

Metrics for rigid body motions in SE(3)

As SE(3) does not have any bi-invariant metric, what are the available pseudo metrics for comparing two homogeneous matrices for rigid body motions ? In other words, how to compare two dual ...
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1answer
65 views

What is an "actuation state"

The paper A Feedforward Control Approach to the Local Navigation Problem for Autonomous Vehicles by Alonzo Kelly uses the term actuation space. Feedforward solves the historically significant ...
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1answer
135 views

Jacobian of kinematic IMU Model

I have the following problem: given two Input Vectors $x = \begin{pmatrix}x\\y\\z\\v_x\\v_y\\v_z\\q_1\\q_2\\q_3\\q_4\end{pmatrix}$, $u = \begin{pmatrix}a_x\\a_y\\a_z\\w_x\\w_y\\w_z\end{pmatrix}$ time $...
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1answer
539 views

What is difference between 2 wheels and 4 wheels and tracked differential mobile base kinematics?

In generally I know that no difference between 2WD and 4WD mobile base control kinematics equations. but is there really difference between two wheels differential mobile base and tracked/...
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1answer
2k views

calculating differential drive robot ICC position

I don't understand how to calculate the ICC position with the given coordinates. I somehow just have to use basic trigonometry but I just can't find a way to calculate the ICC position based on the ...
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1answer
623 views

State prediction of vehicle with Ackermann steering geometry using Kalman-Filter

I am trying to have a Kalman-Filter (or Extended-KF) give me positions for a small remotely controlled vehicle with an Ackermann steering geometry (moving on a plane surface). The control commands I ...
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1answer
598 views

Inverse Kinematics 5DOF - general approach - Wrong solution MATLAB

Can anyone name a good source for a general approach (cookbook-like) for the inverse kinematics regarding a 5-DOF? The paper by De Xu et al. is aiming for a general approach, but it doesn't work for ...
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0answers
118 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 ...
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2answers
4k views

Understanding the Robot Jacobian

Although I have an understanding of what Jacobians are in general and how to calculate Jacobians, I fail to understand how the idea of Jacobian came for use in kinematics and why they are used for ...
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2answers
752 views

Quadrotor Dynamics: Calculating angular velocity of quadrotor

I am trying to simulate and implement the controller of the paper Geometric Tracking Control of a Quadrotor UAV on SE(3). To do this I need to first implement the dynamics of the quadrotor. According ...
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1answer
115 views

Urdf as a way to model dynamics?

Since urdf format serves the purpose of kinematic model but also extends for dynamical properties such as mass,moment of inertia and centre of masses, can it be considered a viable dynamical model of ...
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2answers
289 views

Inverse Kinematics problem formulation (optimization)

Note:Q is a diagonal posituve semi-definite matrix Why is the IK formulation like that? It looks like it's trying to find the optimum dq/dt that will minimize the magnitude dq/dt. How is that giving ...
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1answer
399 views

Significance of link length ratio in serial manipulator

I am formulating a problem to optimize link lengths of 3R serial manipulator shown below : I do not assume any explicit relationship between the link lengths, but in one of the papers (http://www....
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1answer
84 views

Expressing a global point in different frames

I am trying to express a vector defined in global coordinates in different frames using homogeneous transformation matrices. There are in total 3 frames. Frame 1 lies in the origin and is fixed to ...
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2answers
590 views

Using jacobian of arm robot to calculate transformation matrices?

I have been given a Jacobian for a 3 revolute joint robot. I need to obtain the origins of each of the joint. Origins of the joints can be obtained once I get $T^0_1$, $T^0_2$, $T^0_3$ and $T^0_4$. ...
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2answers
1k views

How to check reachability of manipulator to a point?

I have written a MATLAB code for inverse kinematics of 3R robotic arm, which returns value of joint angles for given link lengths and end effector position and orientation. But if location of point is ...
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1answer
537 views

Optimization of link lengths for 3R serial manipulator

I am trying to formulate an optimization problem for determining link lengths of 3R manipulator shown in picture below, Following are the constraints, Robot arm should be reachable at point x = 100, ...
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1answer
87 views

How can serial manipulator have unique condition number for given end effector position?

I am reading about Condition Number which is considered as measure of manipulability of robotic arm, it is defined as $$ k = \parallel J \parallel \parallel J^{-1} \parallel $$ Where, $$ \parallel J \...
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3answers
509 views

DH Parameters with offset base

I'm looking at a pan tilt (RR) system. I want to define the kinematics between a world frame and the end effector. Every example I've seen looks at the world frame as being at the first joint (the ...
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0answers
173 views

Beginners guide to Inverse Kinematics for biped robots? [closed]

I'm building a LynxMotion Scout biped and believe that IK are the best way to develop an effective gait. I'm a mechanical design engineer - I currently have minimal skills / experience with ...
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3answers
673 views

Confusion in fixing DH frames

I am analyzing a concept of a surgical robot with 4 revolute joints and one sliding joint. I am not able to fix the coordinate frame for last prismatic joint. Following are the schematics of robot and ...
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2answers
772 views

Holonomics Movement vs Holonomics Constraint

I'm reading Mechanics of Robotic Manipulation by Matthew T Mason and I stumbled upon the concept of kinematic constraints. The book mentioned about two types of constraints: holonomic and nonholonomic ...
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1answer
430 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 ...
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1answer
530 views

IMU measurement model

I read in this set of slides on p.11 that the IMU measurements, such as acceleration are affected by bias and noise, as expressed in this equation: $_B \mathbf {\tilde a} _{WB}(t) =\ \mathbf R_{BW}(...
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1answer
530 views

DH- Parameters of BCN3D Arm

Consider the following Arm: https://www.bcn3dtechnologies.com/en/bcn3d-moveo-the-future-of-learning/ I looked for the DH-Parameters of this arm and I found this: ...
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1answer
121 views

How do CAD programs solve for Inverse/Forward Kinematics problem in Assembly?

I am trying to solve for the Forward kinematics of a spatial parallel manipulator. Its loop closure (LC) equations are pretty long, and are being solved using numerical methods. As I am adding more ...
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1answer
97 views

clarity in understanding the moment of inertia matrix D and Coriolisis and centripetal matrix C as per attached equations

Would appreciate if anyone could help me understand the how if equation 6 and 7 are derived. Helping with any one D22 and C32 would suffice.
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1answer
2k views

How rotate a point around an arbitrary line in 3D?

I have a body with origin at point A which is represented in homogeneous coordinate of matrix 4x4 and I would like to rotate it around an arbitrary vector in 3D space. I understand how to rotate the ...
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2answers
382 views

Localization within a map with gyro, accelerometer and magnetometer

My goal is to locate precision within a known map. If the size of the map is known, a rectangle 4 x 3 m, and I know the initial position and orientation of the robot, after a certain period of time ...
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2answers
443 views

Compensation for IMU mounting misalignment

I have an MPU6050 IMU and I would like to mount it on an FSAE car and use it to measure the yaw, pitch, roll, and angular velocities as it drives. As it's impossible to mount it perfectly flat and ...
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1answer
799 views

Understanding inverse kinematics with the Jacobian

I'm learning about inverse kinematics with Jacobians, and getting a little confused. So, let's say I have a robot arm with two joints with angles Y = (a, b) whose ...
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1answer
64 views

I need help figuring out what motor is used in this design

I am learning how to make rigs for high speed motion control. Basically, whatever action needs to be executed must be done by a rig that is triggered at an exact moment. In this particular case, I ...

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