Questions tagged [kinematics]

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3answers
84 views

Is there a simple trigonometric relationship between these two angles?

The setup shows 3 rigid links (with fixed lengths) constrained by 4 joints. The blue joints are fixed in place and only allow rotation, while the black joints can move and also allow rotation. ...
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0answers
34 views

Is there an equation that can automatically tune a PID controller?

Is there an equation that can automatically tune PID controllers? or do I have to do manually/make an AI to do it for me?
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1answer
49 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 ...
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1answer
101 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 ...
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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 ...
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1answer
76 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 ...
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1answer
162 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'', ...
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0answers
50 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
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1answer
52 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 ...
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3answers
88 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 ...
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3answers
109 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 ...
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1answer
37 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 ...
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1answer
61 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
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2answers
60 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 ...
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2answers
76 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 ...
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0answers
55 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 ...
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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 ...
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1answer
44 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$ ...
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2answers
61 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 . ...
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0answers
32 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 ...
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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 ...
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1answer
146 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 ...
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3answers
73 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 ...
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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 ...
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0answers
23 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
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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 ...
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2answers
387 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 ...
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3answers
75 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 ...
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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
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1answer
104 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 ...
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0answers
16 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
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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 ...
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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 ...
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2answers
58 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 ...
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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,...
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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. ...
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1answer
46 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 velocities are: $\omega_2$ (precession), $\omega_1$ (nutation) and ...
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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 ...
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1answer
39 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
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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
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1answer
41 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
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1answer
123 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
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1answer
92 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
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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
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1answer
987 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 ...
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1answer
267 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 (...
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1answer
135 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 ...
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1answer
48 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
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1answer
116 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
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1answer
672 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 ...