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SubjectRe: patent on O_ATOMICLOOKUP [Re: [PATCH] loopable tmpfs (2.4.17)]
On Sat, May 25, 2002 at 06:48:53PM -0600, Erik Andersen wrote:
> Indeed. For example -- suppose I have an application that is driving a
> robot. My application needs to calculate the target values for
> each joint position in such that I can plot out the jerk,
> acceleration, velocity, and position in cartesian space of a tool
> moving in joint space (i.e. lots of 4x4 matrix multiplications,
> often involving a full 3D model of the workcell) And I need to
> send each new set of target values to the controller at the servo
> rate or the robot will stutter.
> But if only it were that easy... Since the target values we are
> talking about is actually just the amount of current being sent
> to the servo motors. So also at the servo rate, I must read the
> encoders for each joint to get its actual position (as opposed to
> nominal postition) and feed that into a control routine
> (typically using a PID routine using PID gains that vary
> non-linearly per arm position, intertial loading, phase of the
> moon, etc) which then varies the actual per-axis servo motor
> current to make the cartesian-space path of the tool match the
> nominal path.
> So now we have a full 3D model of the robot, the non-liner model
> of the robot PID-gain space, the entire (application specific)
> workcell model, the robot specific forward and inverse kinematics
> routines, and the entire trajectory planning subsystem. And of
> course we now need the real-time IO subsystem to handle are the
> thousands of this-and-that sensors (think PLC-type behavior).
> etc, etc, etc. All this in the kernel? Nah...

People are doing this (or at least something similar) in reality these
days... :-)

Hopefully, your post shows clearly why there are users out there who don't
want to make such complex algorithms open source, and I must say I can
understand them.

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