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Tempest Planning - Preliminary information and testing

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Hello All:

   This board, when open to public use, will be used to allow members to discuss , test , and provide feedback on the "Tempest" planning system.
Snapshots, explainations, and test evaluations will be topics of this group to allow the development of the planner to proceed into testing phases
as the theoretical models and algorithms are being completed.

  The Tempest planner is a proposal for the next generation of planning module. Its code is nearing completion and testing phases and builds
will be posted here for evaluation. Its specifications are as follows.

 Tempest is a 9 axis, 5th order planner with optimised segment blending and velocity control. It uses 6th order blending between lines of any length,
and 3rd order blending between arc/line junctions.  Orientation axis include a,b,c and u,v,w. In its end form it will allow task space or joint space control
and will include kinematic control extensions for a wide variety of configuration capabilities. It's planning order while set only by a jerk limitation factor, will
control both Jerk and snap through most of its trajectory with the exceptions of blends involving arc's. All blends ( or CV moves ) are set by the user
as a spherical tolerance where-in the blend will occur in an isoscelese triangle of the entrace and exit to the user defined sphere. This means a setting of
CV to 10mm will result in blending arcs of no more than 10mm at corners. Speeds are limited by the calculated acceleration constants involved with arc's
of various radii or in blends of various polynomial lengths. Arc involved blends are tangental matched for c2 continuity, joined with Hermite curves , while
line/line blends are joined with 6th order polynomial additions of 1st order linear equations.

  It is hoped the Tempest model will eliminate the problems involved in the Quantum experimental SCurve generator, and Tempest will reach speeds
orders of magnitudes higher than Quantum in small segement control and concatenation. Algorithmic modeling is near completion and this board will
be opened as soon as the first preliminary test builds are available to achive motion for user feedback testing. I will use this board for posting notes and
explainations of various features and options as well as to document its usage and any limitatiosn found in testing. This is a highly experimental module,
and while the math and graphing functions show high promise, only true machine testing and time evaluations of CPU usage in the calculation of the
real time motion waypoints will tell us if this may yet be used by cpu's of today or if more optimisation is required to the central calculation routines.

  So if your reading this, please feel free to download any test programs, and report any findings or opinions you may have. hopefully "Tempest" will
be the start of the next generation of CNC control. In theory, almost any machien will benifit from the incredibly smoothed motion and acceleration
control it offers.

Good luck, Thank you for testing.


Preliminary tests:

  Posted here are the first mixing tests of Tempest. The first photo shows a line from 0,0,0 to 50,0,0, this blends to an arc ending at 100,0,0 with radius 25, the motiosn then continues with a line to 50,0,0, and ends with a last line to 0,100,0.

  The first photo shows the resultand blend in positions. These are blended with the CV set to 5mm.
  The second photo shows the velocities involed. Red is the Y axis, Blue is the X axis, and the Green is the tool speed as the combined velocities of both X and Y.
  The Third photo shows acceleration. Looking carefully, one can see the 3rd order blends from line to arc, and in the final segment, a 6th order blend from line to line.

 Z axis was left out only for the sake of clarity but is fully functional as well.


Hi, Art

Was wondering where you were hiding out.

Chip  ;D

Hi All:

 Enclosed with this post is a versionof the analysis program , I post it to further any discussions on the properties of such a planner.
As of now, all 9 axis are responding, and Id liek to post some diiscussion posts on tradeoffs of such planners and how they operate.
This encosed program will facilitate the user understanding the issues discussed as you can try various situtations yourselves.

  Basically, you enter the x,y,z, and a coordinates of any motion group. You should note that the feedrate shown and selected is
in units/second, not units per minute. I defaulted it to 200 so thats ( 200 x 60 ) units per minute.. 12000 inches per minute. Very
high indeed, but using such high values allows one to better disect the operations of such a planner. Try the enclosed program and select
either velocity, acceleration, or position to see the various results of motions, feedrates, CV settings and how they affect accel and velocity.

  Next postings will be on tradeoffs and singularity handling and how they may affect users of such a planner.


Hi Guys:

  Now that a test program is released for visualising velocities ( see previous topic ), we can discuss
the limitations or tradeoff's involved in planning strategies.

  When you run the tempest velocity analyser, youll see its preset for a square. Playing with CV , you can see the effect
( on the position screen) of various CV's and motions. Youll note how the velocity in the corners slows or speeds up
dependend on how much cv there is, and the angle of the next line.

  First, lets talk about how Mach3, EMC and most other planners do their job. With the standard preset conditions, ( the square)
select accel and note how the acceleration looks with a jerk of 1000.  This is probablky the smoothest of all planners in this example.
TO see how MAch3 or EMC woudl look, select a jerk limit of 100,000. Note the square waves, thats typical bang-bang acelleration.
The curvy parts are the only difference from Mach3's typical planning. They represent a complex blend and are unaffected by jerk selection.

Tradeoff #1. - Speed.

This example then shows Mach3 with better . more controllable CV blends. Note the time of the 4 moves. ( the last move to 0,0,0,0 is automatic.).
Its about 3.7 seconds. That woudl be close to Mach3's time to do this square. Now set to 1000 jerk and note the time.  Youll see its now
7.4 seconds. SO we can see that SCurves take longer. This figures as it takes longer to drive somewhere if you dont hammer the gas pedal.
With a jerk of 1000, its about 40% longer. Set for 10,000, the time is now 3.94 seconds. Thats probably about where most woudl use such a planner.
Its about 7-10% longer. Thats Tradeoff #1, smoothness takes longer. On the other hand, the corners are better defined, and much more controllable.
Not bad for a 3% loss in iverall velocity. ( in this example anyway..).

Tradeoff #2 - Angular accuracy.

  Change the second waypoint  move ( set back jerk to 1000 for visual clarity ), so it has an A of 50. Notice how the A starts in the middle of the blend from
motion 1 to motion 2. This is because the rotary motion is commaned to match up with motion #2, but #2 is blended with #1. Orientation motion accuracy will depend
on a few things. In this case, the rotary motion WILL start as the motion #2 starts, ( in the middle of the blend) and end as motion #2 stops. However, for accuracy sake
the planner decided not to blend the next motion, but to stop and allow the rotary motion to catch up. The difference in speeds will produce a non-accuracy in the
lineup of the cartesion motion and the rotary motion. How much depends on speed, and time of motion. Changing to a 10,000 jerk will make it line up better.
In terms of accuracy, an Scurve planner will be slightly less acccurate, and speeds must be taken into account.  This is a tradeoff. Speed, smoothness, and complexity combine to
make rotary motion more difficult, but better at not being disjointed. Foir example, you needednt consider slowing the feedrate request for such a motion, they automatically are
fit into the main cartesian motion. Now try changin the waypoint #2 move from 100,100,0,50 to 100, 5, 0, 50. In this case the rotary just cannot fit in the short time it takes to move from
100,0,0 to 100,5,0. Notice what happens, the line is no longer blended to the first, ther eis no time, so the motion is now dead accurate, and the A move will match the Y move to 5, but blending
is prohibbited during this move. Again, this is automatic and done because the math processor decided the motion is so complex that the solution is intractable mathmatically except to
simply do the motion by itself. This is tradeoff #2, the fact that you must consider such impossibel motions, and how they are handled. I call this a CNC singularity, and one should
understand how a planner handles such things. Only real-time experience will tell how how this impacts CNC cutting in a general sense. ( SO far, this is all entirely math based theory. )

 Getting late, more later. This at least has given you something to play with and consider in terms of how a future planner may do its job. And hopefully, has increased your
understanding of motion math, velocity, jerk, acceleration, and rotary blending in moves.



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