Questions tagged [kinematics]
The kinematics tag has no usage guidance.
79
questions
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0answers
6 views
Question about a Force in FBD of a garage door
I am not sure how to draw a certain force in a FBD (Free Body Diagram) of a garage door.
The Garage door is indicated by B-C (2m height) in the picture below. If this door is closing, how should the ...
-1
votes
0answers
22 views
Gear Terminology [closed]
Can someone please explain to me what are each of the radii that are involved in creating an involute spur gear. There are so many, if you can please explain to me what the difference between each one ...
0
votes
1answer
47 views
Is there a formula that relates the two angles in a crank rocker?
I'm working on a mechanism that requires a crank rocker - is there a formula that relates the angle (to some fixed reference; horizontal, vertical, whatever) of the driving "crank" to the ...
2
votes
0answers
28 views
inverse kinematic of modified Rodriquez parameters
as you know, the attitude of a robot is represented using many ways, euler angles, quaternion, rodriquez parameters, and so on. I should use rodriquez representation in a problem formulated same as a ...
1
vote
1answer
74 views
Where/How to Build a Ball Joint
I am trying to mimic the behavior of the following video:
https://www.youtube.com/watch?v=6pfnKuKy6Lg
I'm interested in the ball joints connected to the platform. I've searched for them online, but I ...
3
votes
1answer
124 views
Modeling rigid body dynamics: Trouble with equations, encountering nonsense answers
Hi, I am working on modeling a simple rigid body dynamic system through a certain range of motion. Here is the picture of the system.
I am trying to solve the system for the variables $x_1'', y_1'', ...
2
votes
0answers
44 views
Solve quaternion kinematic
In a robot or spacecraft attitude representation, using quaternion is relevant.
The kinematic equation is as below
$$
\begin{bmatrix}
\dot{q}_0 \\ \dot{q}
\end{bmatrix} =
\frac{1}{2}
\begin{bmatrix}
-...
2
votes
1answer
49 views
Degree of freedom of a mechanism
A mechanism popped up in my mind when I was studying kinematics, see picture below
$J1,\ J2,\ J3$ are rotational joints and there are two translational joints $J4$ and $J5$ between two sliders and the ...
2
votes
3answers
83 views
Would a car slip down on a frictionless banked road and situation for friction road
Here , we have a car on a banking road. Considering two cases :
Frictionless and friction surface of the road.
I give an initial velocity to the car by a push for a second. Then , the cases discuss ...
1
vote
3answers
74 views
Why do I get pushed back when I’m in a car at high speed?
When I’m in a car at high speed , I get kind of like pushed back if I’m sitting on the cars seat. How does it happen and why ?
If I’m in a car , then I have the same speed as car and for the car , I ...
0
votes
1answer
35 views
Resolving the forces into components [closed]
okay so I am really struggling to see how to resolve the Normal reaction force and Weight into the r and theta direction please? Why is it that the angle is taken to the left of N and right of mg ...
1
vote
1answer
55 views
Inverse of quaternion kinematic matrix
In a robot or spacecraft attitude representation, using quaternion is relevant.
The kinematic equation is as below
$$
\begin{bmatrix}
\dot{q}_0 \\ \dot{q}
\end{bmatrix} =
\frac{1}{2}
\begin{bmatrix}
-...
1
vote
2answers
49 views
Find the acceleration of a block relative to incline plane in non and inertial frames?
A block can slide on a smooth inclined plane of inclination $\theta$ kept on the floor of a lift. When the lift is descending with retardation i.e. $ a \; m/s^2 $. Find the acceleration of the block ...
0
votes
2answers
75 views
Why does the 1kg mass move towards inclined plane here?
Assumption :All frictionless surfaces.
EDIT: In the book , it doesn’t say friction has to be present but as PeteW has mentioned , i think it should be necessary too. So , in that case let me take two ...
0
votes
0answers
36 views
Number of Kinematic Pairs
Kinematic pairs are the connection between 2 links that can have relative motion between them.
But In six bar chain as shown below:
There are five pairs for them to be a kinematic chain. But if I ...
1
vote
0answers
47 views
Are equilibrium values of a differential equation uniquely dependent on its constants?
I have a dynamic model which undergoes two distinct stages. The system starts out with certain initial conditions and once a specific point is reached in stage 1, these ending conditions are used as ...
2
votes
1answer
38 views
Firing a bullet on wooden block and then finding the average resistive force by block?
For a Q in which we are firing a bullet of 0.04kg onto a wooden block which is stopped after a distance of 60cm after penetrating inside it. It’s u=90m/s.
For this Q , we can find a=-6750m/s^2. Using$ ...
0
votes
2answers
59 views
Why is final momentum found by two formulae in case of increasing force not equal?
So, let us say a body moves with 10 m/s, mass = 10 kg.
At time t=0 a force of 30 N is acting on it. Gradually (linearly) the force increases and finally it becomes 130 N after a period of 2 second .
...
2
votes
0answers
25 views
Velocity and Acceleration Polygons for Mechanism
I need to determine the velocity and acceleration of point H using vector equations and drawing a polygon. Given data is shown. $\omega$2 is 5.8 rad/s and $\phi$2 is 120 degrees
I know how I can draw ...
0
votes
0answers
14 views
How to show that the total angular velocity vector of a rigid body is the sum of all angular velocity vectors acting on it
I am trying to prove the additivity propety for the angular velocity vectors acting on a body in three dimensions. Particularly also in the case when the axes of rotation do not cross each other (the ...
2
votes
1answer
87 views
Relation between links and pairs in Kinematic chain
I came across a equation for kinematic chain (for lower pairs only) :
L = 2P-4
where L: Number of Links;
P is the number of pairs
how could this equation be derived ?
EDIT: I tried putting values in ...
1
vote
3answers
69 views
Mechanical Engineering: How To Amplify Kinetic Energy In Axial Rotational Gear Machinery? [closed]
When I originally posted this question 2021-04-08, I was inspired by pulley physics, especially after viewing these videos at this link and this link and this link. It is not necessary to go to these ...
2
votes
0answers
37 views
Linearisation of the Equations of Motion of an Inverted Double Pendulum
I am working to develop a deep reinforcement learning model for balancing an inverted double pendulum.
To do so, I needed to derive the equations of motion, via the Euler-Lagrange (EL) method and now ...
1
vote
0answers
21 views
Sprocket Angular Velocity [duplicate]
I have a question please that I need help on.
Consider the chain that is draped over the sprocket with mass moment of inertia of 0.005kgm^2 about central axis. If 4kg block is released from rest from ...
2
votes
1answer
65 views
To stop or to go around?
Let us we are moving in a car. There is a wall in front of us, we need to decide can we go around it or not. It is known that width of the wall is $w$ and our speed is $v = const$.
What is a simple ...
3
votes
2answers
197 views
Degrees of Freedom for Complex Pulley Systems
I'm trying to understand DOF clearly, but this pulley system has me doubting myself. When I try to determine the degrees of freedom, I sum the DOF of each object, and subtract the constraints. for ...
1
vote
3answers
69 views
In circular motion , why do we say this is centripetal acceleration
Let us say a particle is moving in a circle with Uniform circular motion .
Then , if I take an equation like this .
$\theta$ = S(Arc length or Total distance covered ) / Radius of circle *( time ...
1
vote
2answers
38 views
Did not understand this regarding angular velocity
It says $V\sin \alpha$ (component of velocity perpendicular to OP) is the cause of angular displacement. How is it?
if only $V\cos \alpha$ existed, we need not turn over head to always to look at a ...
3
votes
1answer
78 views
Gear Ratio of a Stepped Planetary Gearset
I was looking into planetary gearsets, and came upon the concept of a stepped planetary gearset. In the image shown above, if my input was the blue sun gear, the output was the planet gear, and the ...
0
votes
0answers
14 views
3DOF end effector control
I have created a simple serial robot with some servos and CAD.
Each joint has 180 degrees of freedom, where they all have 180 degrees of freedom.
I haven't specified where the 180 degrees of freedom ...
2
votes
1answer
25 views
differential drive vehicle in screen coords
differential drive vehicle in world frame
what would change in the kinematic model of the differential drive vehicle if i wanted to simulate it
using pygame module in python ( pygame or opencv or any ...
3
votes
0answers
26 views
Problem in the inverse kinematic model of a car like vehicle?
I'm a electrical engineering student and i am building a simulation of a car like vehicle .
As I understand it:
The input for the forward kinematic model are the control
variables and the output is ...
1
vote
2answers
57 views
What does it mean for a machine design to be “kinematic”?
I've seen the term "kinematic" used qualitatively to describe machines several times in books and on YouTube. I think I understand what kinematics is as a study, but I'm not sure what people ...
-1
votes
1answer
33 views
Stewart platform 6DOF parrallel manipulator static force diagram
I am trying to develop a statics free body diagram of a stewart platform 6dof parallel manipulator motion table. I have the base points (B1,B2,B3,B4,B5,B6) and the top platform points (P1,P2,P3,P4,P5,...
4
votes
2answers
91 views
What do I need to operate this motor?
I am currently designing a tennis ball launcher. I am looking to use the friction wheel approach, where you have the ball passing through 2 spinning wheels and being launched by the frictional force. ...
0
votes
1answer
34 views
Euler rotations and acceleration
I have a system determined by 3 Euler angles that describe the orientation with respect to a fixed coordinate system XYZ.
The angular velocioties are: $\omega_2$ (precession), $\omega_1$ (nutation) ...
3
votes
0answers
28 views
How to measure / calculate Tait-Bryan angles of a moving platform in SimMechanics
I exported a model of the mechanism created in SolidWorks to SimMechanics in order to explore the possibilities of control. To solve the problem, i need to know the angular position of the mobile ...
-2
votes
1answer
38 views
Maximum velocity of an athlete [closed]
I was solving a mechanics sum
An athlete running a 100m run starts from rest and reaches the maximum speed in a distance of 15 m. He runs the remaining distance with that velocity and reaches the ...
2
votes
1answer
21 views
Purpose of normalization of Jacobian in a parallel manipulator
I am currently studying a robotics paper, where a normalized frobenius norm of a matrix is calculated as part of determining the condition number of the corresponding linear system of equation:
$\...
2
votes
1answer
37 views
I have the yaw rate, rear wheel speeds, and the radius of tires, how to find x and y speeds?
I only have these 3 data sets:
rear right and left wheel speeds (they change with time)
yaw rate (also changes with time)
constant dynamic rolling radius
How am I supposed to find the directional ...
3
votes
1answer
108 views
Center of rotation (rigid body)
I know the meaning of (instantaneous) “center of rotation” and “center of zero acceleration” for a rigid body. I know that they do not coincide (in general) and that their positions change with the ...
2
votes
1answer
85 views
How to compute the size of a polygon moving along non-circular guide rails
I am trying to compute the optimal (a non-optimal solution would also work) size of carts that can move along guiding rails. Each cart is connected to the rails at two points. Each cart is also ...
3
votes
1answer
54 views
How do I call a kinematic assembly that converts rotary motion to sawtooth linear?
I have in mind a device somewhere in between a firearms trigger and a clock escapement. One way it could be constructed is as follows:
A crank would displace a linearly moving slider backwards, so ...
2
votes
1answer
894 views
What are displacement field and Deformation field?
I am studying mechanics of materials while I came across these terms called the displacement fields and the deformation fields. I am not able to understand the difference between them. Can someone ...
1
vote
1answer
243 views
Designing cylindrical cam
So I need to design a cylindrical cam (aka barrel cam I think). I'm an aerospace engineer so I've never had a course on cams/gear design (wish I had though). Is there a general equation for the curve (...
1
vote
1answer
120 views
Moment of Inertia of a Rotor System
I need to settle a discussion on the following question:
Part A:
Find the equivalent spring constant for springs in series
Use equations of motion, sum of torques to find natural frequency of the ...
2
votes
1answer
47 views
Torque computation for different attachment point
I have a pretty basic question but I would like to be sure of what I think.
I have a setup like the one in the figure. I have two motors which can generate two forces $F_1$ and $F_2$ perpendicular ...
3
votes
1answer
106 views
Dynamics of a rigid body in a system of two linear drives
I've been trying to solve the dynamics of this system for quite a while, but cannot seem to get the right answer. I've tried solving it with Lagrangian method but I am not so confident with the ...
0
votes
1answer
623 views
Deriving the equations of motion for free-floating spacecraft with a single link robot arm
Note: I had previously posted this question on the Space and Robotics SE sites, but received little/no response. So I've deleted the previous posts and repasted my question here in the hope of ...
-1
votes
1answer
311 views
Inertia relief in ANSYS - rotating model
I'm trying to use ANSYS to solve statically a dynamic problem.
As shown in the image below, there is an orange bar that is constraint to slide horizontally only and attached to another bar (pink) ...
