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### Author Topic: Three Bar linkage with stiction at joints  (Read 2171 times)

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#### mjtripp

• Beginner
• Posts: 1
##### Three Bar linkage with stiction at joints
« on: March 13, 2015, 09:25:32 AM »
Hello!

I am looking for any references on formulation of the dynamic equations of motion for a three bar linkage.  Each link would have prescribed mass and inertia and the friction torque at the joints would be modeled as a constant value when the joints are moving.  This model would be used to solve an initial condition problem where initial joint angles and rotational velocities are prescribed and the model would solve for the joint angles as the linkage coasts down to rest.  Any pointers to references would help!

Thanks!
Mark

#### mklrobo

• Supreme Robot
• Posts: 559
• From Dream to Design at the speed of Imagination!
##### Re: Three Bar linkage with stiction at joints
« Reply #1 on: March 13, 2015, 09:37:36 AM »
Hello!
I would offer an opinion;
The academic part of your journey may begin with a free body diagram, which assigns
forces to all members of the device. Mass and Inertia follows the weight of the part,
along with speed, acceleration, etc. This direction can be found from REA's,
problem solvers series.
Titles such as, Statics, Physics, Strength of material, and
Machine Design
will help define the parameters that you may be looking for, and
give insight and examples of similar devices. To use a software to help, I would recommend
using autodesk Inventor to model the members, which may bring answers to light.
Good Luck!

#### bdeuell

• Robot Overlord
• Posts: 189
##### Re: Three Bar linkage with stiction at joints
« Reply #2 on: March 13, 2015, 10:00:36 PM »
i have not heard of a three bar linkage....from my learnings that would be i triangle which would be geometrically fully constrained. I have studied/designed four bar mechanisms/linkages, is this what you are describing? one side of a four bar mechanism is often fixed so there may only be three moving linkages but if you connected each of the vertices you would form a quadrilateral. I dont mean to dwell on terminology but if this is what you are looking for it might help to try some different search terms. a four bar mechanism is very common and should have plenty of documentation/resources describing the dynamics.

in the case this is not what you're looking for just ignore my comments.

« Last Edit: March 13, 2015, 10:02:07 PM by bdeuell »