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Topic: Robot Differential Steering Angles with Different Ping Thresholds (Read 2174 times)previous topic - next topic

thomas3120

Jan 17, 2014, 10:56 pmLast Edit: Jan 17, 2014, 11:52 pm by thomas3120 Reason: 1
Hello,
Was wanting to see if I was on the right path before trying this out in a sketch.
Depending on the distance of forward obstructions (if any) I would like to make adjustments on how my robot turns.
If there are no forward obstructions detected, I would like my robot to make nice wide rounded turns around an origin point 'O'.  If there are some obstructions present but not near, make slightly tighter turns.  And if there are obstructions that are very close, have the robot rotate around it's axle center.
Here is a diagram I setup:

I was thinking of making the radius 'R' variable, setting a Rmax and Rmin.  Rmin would be zero or equal to 'C' the axle center, etc...
With the varying radius, I was thinking I could get possibly the left and right wheel linear velocities (VL & VR).

Also, VL & VR (left & right wheel velocities) would be velocities measured at the center of the wheel or axle?

Would appreciate any input or help.

jremington

Here is a good and rather complete analysis of differential steering (there are others) http://rossum.sourceforge.net/papers/DiffSteer/DiffSteer.html

thomas3120

Here is a good and rather complete analysis of differential steering (there are others) http://rossum.sourceforge.net/papers/DiffSteer/DiffSteer.html

Yeah, that was one of the first documents I looked at and very helpful.  Found a lot of other docs and my old Physics book...just trying to piece it all together.
One thing I never got to (unless it's some type of matrix, from Algebra...) is
Transformation Matrices?:

I do remember X' is a derivative (among a few other things).

Don't recall what the dot above X is here, but looks to be some sort of function of time:

I took a Differential Eq. class but it's been several years+.

These type of matrices were showing up quite a bit in the other robot turning examples.

Hopefully this won't turn out to be a nightmare

jremington

One thing I never got to (unless it's some type of matrix, from Algebra...) is
Transformation Matrices?:

I do remember X' is a derivative (among a few other things).

That is an expression for the new (x,y) coordinate of a point, after rotating the coordinate system by the angle theta.
Quote

Don't recall what the dot above X is here, but looks to be some sort of function of time:

The dot indicates the time derivative, also written as dx/dt (in this case), the time rate of change of x, or the x velocity. Unfortunately, you can't avoid the math, if you want to know where your robot is and how fast it is moving.

charliesixpack

If you are asking these questions, you may be interested in the Control of Mobile Robots course on Coursera.  I took this course last year and it was great!

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