# Questions tagged [dynamics]

Questions about the dynamics of a system. Currently there is a very large scope ranging from from dynamics in mechanics, vehicle and flight dynamics, to system dynamics and fluid dynamics.

93 questions with no upvoted or accepted answers
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489 views

### Questions regarding Cornering Stiffness for RC Car

I am a bachelor's level student tasked with modeling the vehicle dynamics of an RC Car that will be made to drive autonomously. I lack prior experience or particularly specific education with vehicle ...
314 views

### Explicit Dynamic ANSYS - Origami structure

I am working on a flat-foldable conical structure and I would like to carry out some dynamic tests on it (deployment to get the displacements and accelerations...). I have designed the folded ...
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### What is the deflection of planet-ring Gear Mesh along the pressure line and the position of the Plant gear?

For a Sun-Planet mesh in a planetary gear train, there will be a deflection $\delta_{sn}=\delta_{s}-\delta_{n}$ along the pressure line and the position of the planet will be determined by $\psi_{n}$, ...
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### What is the theory that makes this method work when dynamically balancing this system

Sorry for my bad english in advance I am not a native speaker. I have a system similar to the one above and we are supposed to statically and then dynamically balance it. To statically balance it we ...
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### "Bicycle model" in vehicle dynamics

I have been repeatedly told when dealing with some data for Navigation purposes that I can assume it follows a "bicycle model". I am not very familiar with vehicle dynamics so I consulted online. I ...
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### Inverted pendulum PID: controller causes cart to move at constant velocity?

I am trying to understand the PID controller of an inverted pendulum on cart system through this MATLAB article: https://ctms.engin.umich.edu/CTMS/index.php?example=InvertedPendulum&section=...
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### Relationship between the infinity norm of estimation error and the trace of estimation error covariance matrix in Kalman filter

I am working on designing an interconnected distributed control system. In this system, I need to use Kalman filter because the measurements are noisy. I have two questions: 1 - What is the ...
537 views

### Torque Required From Motor For a Project

The device I am building is responsible for supporting 200 lbs and is required to accelerate 10 feet per second. The device will have two 8 inch diameter wheels. I have worked out what I believe to be ...
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### Plane Wave Expansion method

I have very recently ventured into the domain of periodic structures. In the literature, I came across the Plane Wave Expansion method to compute the dispersion curves. I managed to code it in 1D . ...
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### 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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### How are circular dependencies dealt with inside MBSE?

How are circular dependencies (best) managed inside of MBSE environments? Let's say I have two properties that are linked to each other / they are linked to properties that affect each other. How is ...
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### Force on suspension when hitting a step

I'm trying to calculate the magnitude and direction of the force exerted on a wheel when encountering a step. The wheel and the steps are non-deformable. I found two different approaches: energy ...
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### 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 ...
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### Linearly Damped Harmonic Motion with Sliding Friction

In Problem 2/54, I have come up with a solution only one decimal place off from the books results. I am posting to see if someone can look over my solution to see if it is correct. To begin the ...
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### How to control an underactuated platform with a single servo

What's the best way to control the following type of platform so that it remains balanced and upright? It's a box supported by a single leg that can pivot at the foot (F) and at the hip (H). The foot ...
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### Plot zero-pole from frequency response matrix

I've represented with Matlab a system with three degrees of freedom. I'm trying to plot a pole-zero map from my Frequency Response Matrix H(w) in the case of Damped-...
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### Combining critical speeds for a shaft of variable cross-section

I am looking to determine the critical speed for a shaft with universal joints at each end, where the halves are joined by telescoping profile members. I can calculate the critical speed of each ...
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### Impact force with unknown deformations or time duration?

I expected to find more documentation on analytical solutions to determine the contact force between bodies, where deformations ($\delta = \delta_{1} + \delta_{2}$) and impact time ($t = t_{f} - t_{i}$...
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### Modeling of Wheel Rolling Resistance

I have been working on longitudinal tire model for a while and constantly encounter problems with the formulation of rolling resistance. Consider one wheel model coming down from a damp. It is a 2DOF ...
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### Confusion with Measuring Velocities in a Translating/Rotating Reference Frame: Combining Transport Theorem and Homogeneous Transformations

The inertial reference frame is denoted by $I$, the position, velocity, acceleration, angular velocity, and angular acceleration of reference frame $S$ is measured in the inertial frame, reference ...
1 vote
281 views

### How to calculate the degrees of freedom, constraints and the generalized coordinates in this dynamic system

The rope lengths are taken to be constant. Solution: $N$ particles with $k$ constraints. . Then the Degree of Freedom (DOF) is $3N-k$. In Figure 1, we have two particles $m_1$ and $m_2$, so $N=2$. But ...
1 vote
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### Increasing convergence rate using Optimal Control and Pontryagin Maximum Principle

My question is in addition to Tuning the optimal control synthesized according to the Pontryagin maximum/minimum principle and choosing the cost function, but requires help from the mathematical side ...
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### Trajectory of the center of mass of a vehicle

The problem is to find the trajectory of the center of mass of a car when it is rotating and translating (after an off center collision, for instance) What i know as input is the trajectory of the ...
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### 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 ...
1 vote
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### Shell Breathing Modes and Base Excitation

I have been reviewing "Vibration of Continuous System" by S. Rao as part of self-studying to help with work. I started reviewing the chapter regarding shells and noticed that shells have ...
1 vote
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### Why is longitidunal force of tyre calculated negative in SIMULINK?

With the help of the Vehicle Dynamics Blockset of SIMULINK, it is easy to obtain longitidunal force (tractive force) of tyre by some of inputs. You can see one of examples below. In this simulation, ...
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### What is the best way to find solved problems similar to the one at hand?

This is a general question, so sorry if it breaks the rules. However, I think it is very important as more often than not someone else has already solved a similar problem that can be applied to solve ...
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### The optical encoder resolution

The optical encoder has a code wheel with a single track of slots and two photodetectors. The photodetectors are positioned so that they produce signals with a 90 degree phase difference. I want to ...
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### Angular acceleration and the moment of inertia

The wheel is made from a 10-kg thin ring and four 0,5-kg slender rods. If the torsinal spring attached to the wheel's center has a stiffnes $k = 2 N*m/rad$, so that the torque on the center of the ...
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### How to run a steady state dynamics, Modal step based optimisation using TOSCA?

What design responses must be given in the TOSCA gui. I chose volume reduction as an objective function with the constraints of displacement. Is this approach correct?
1 vote
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### What constructive solid geometry CAD programs can accurately model and simulate structural rope, cable, pulleys, and dynamic motion elements?

It seems that flexible objects just don't model well in many popular constructive solid geometry (CSG) CAD programs. Most CSG modelers seem to assume exclusively rigid bodies with sharply defined and ...
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### Maximum slope of the road for a car pulling a trailer

I have a five meter long, 2.40 meter wide, 200 kg portable catamaran I've built at home. To transport, I bought a semi-finished trailer, just the running chassis; and built the upper structure, namely ...
1 vote
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### How to get mass normalized mode shapes?

I have an MDOF system with 4 degrees of freedom with forced input at one of the dof (4th dof)(it is a sinusoidal wave with a particular frequency expected to be generated using a shaker); displacement ...
1 vote
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### What are the various lumped element dynamic system models called?

What are the various lumped element dynamic system models called? By lumped element dynamic system models, I mean the various nodal models comprised of things that look like capacitors, inductors, ...
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### Is this metal-ball launching device realistic?

For a school project (college level in "engineering" studies), a classmate and I are trying to design a device that would propel a metal ball of about 0.8 kg to distances up to 12-14m. Its ...
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### How to write Generalized-$\alpha$ methods in a Runge-Kutta-Nystrom tableau?

How can I write Generalized-$\alpha$ methods in a Runge-Kutta-Nystrom tableau? Thanks
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### translational kinetic energy and rotational kinetic energy

In a lever system, are there translational kinetic energy and rotational kinetic energy if the center of mass is at the centroid? and If the center of mass changes?
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### A transfer function relating jet engine thrust to pitch angle during a phugoid motion

I am doing a school project that requires me to find a transfer function that relates the thrust of a jet engine (which could change with time in one way or another) and the aircraft's pitch angle ...
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### How and why is kinematic control implemented?

First off, I apologize for what is likely a rather broad and formless question (and an even more broad and formless title). I'm a mathematician whose work sometimes carries him to control systems due ...
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### Topology optimization issue (or not an issue, which is the issue)

I am currently doing some work in topology optimization regarding optimizing for the dynamic compliance of a beam structure but I am running into some issues. Well actually I am not running into some ...
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### Is it possible to design the gain Kp for the system in the image, given it is underdamped and has a settling time of 2 seconds. Thank you

$$G(s) = \frac{K_P}{(s+2)^2}$$ $$H(s) = s+4$$ I keep getting Kp = 0 which leads to a damping ratio of 1 which isn't underdamped. To find Kp = 0, I found the closed loop transfer function and compared ...
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### System identification of Blue Robotics Thruster with Simscape multibody

I have CAD design of a Blue Robotics Thruster 200. The thruster is imported to Simulink. From data given Blue Robotics Thruster 200 have MATLAB system identification toolbox been used to generate ...
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### How do you go about picking a belt in design?

So when you want to pick a beam to use or determining the thickness of a load bearing beam, or picking bearings, there is some calculations you do to see if its life expectancy or f.s or to see if the ...
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### Question about dynamics n-t coordinate system

et = tangential unit vector en = unit vector in normal direction I'm currently studying dynamics and I'm having difficulty understanding the process of obtaining det and det/dt in the n-t coordinate ...
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### Would the angular acceleration be the same but in the opposite direction?

The acceleration of point B of a on a rigid body would be: Problem what im confused about is if you were to find the acceleration of A, would alpha be the same magnitude but in the opposite direction?...
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