G-code *is* how you specify your Cartesian motion. Kinematics converts that to motions of each joint or axis.
-- Ralph rayj <raymo...@frontiernet.net> wrote: On 05/14/2014 09:43 PM, Stuart Stevenson wrote: > On Wed, May 14, 2014 at 8:31 PM, rayj <raymo...@frontiernet.net> wrote: > >> I understand Cartesian and Polar coordinate systems. I'm looking for >> the actual method of deriving the commands that need to be sent to the >> motor (assuming the motor shaft is the axis of rotation for the arm >> segment under discussion). >> > The Cartesian and Polar coordinate system are on the same side of the > kinematics. > The Joint system is on the other side of the kinematics. > > >> Example: you want to move the tip of the mill in a vertical line >> parallel to the Z axis. How do you take the description of that line >> (motion from the Cartesian point <a,b,c1> to point <a,b,c2) and >> calculate (ow!) or use software to generate the commands to be sent to >> the (3, I'm guessing)motors? >> > You program the machine to move in the Cartesian coordinate system using > Cartesian and/or Polar coordinates. > LinuxCNC reads what you want, calculates where you want to move, sends the > move coordinates to the kinematics module, the kinematics module calculates > where the motor/slides should be to give you what you want then sends its > calculation to the control to move the motor/slide to position. > > >> And back to the original question, are those joints designated by one of >> the xyzabcuvw designations, or is there a completely different >> designation system. >> > Axes in LinuxCNC are labeled XYZABCUVW > Joints in LinuxCNC are labeled joint0, joint1 ... > > There are some confusing areas where the labels are mixed but the context > should make it clear for you. "crossed fingers" > > >> >> Is there a robotics textbook out there that anyone can recommend? I've >> found that out of date textbooks can be gotten for very little and are a >> wealth of information. >> > Robotics kinematics is a different animal than the trivial kinematics of > the 3 axis mill. > But the hard work has been done for most robot configurations. > The robot kinematics is one aspect that I'm interested in. That's one of the reasons I chose to work with LCNC for my machining setup. It has far wider applications. So when I designate a motion in Cartesian space, the kinematics module generates the G code to make the motors move. So the setup for a given system is the programing the kinematics module with the information about what G code, or perhaps a lower level language, that will result in the commanded Cartesian space motion. Is most of this information in the integrators manual, or some other LCNC manual? Thanks very much for taking the time to reply. I can't imagine how long it would have taken me to get the overall view you've explained to me. Assuming I have understood correctly. :>) Raymond Julian Kettle River, MN > >> >> Raymond Julian >> Kettle River, MN >> >> The things we admire in men, kindness and generosity, openness, honesty, >> understanding and feeling are the concomitants of failure in our system. >> And those traits we detest, sharpness, greed, acquisitiveness, meanness, >> egotism and self-interest are the traits of success. And while men >> admire the quality of the first they love the produce of the second. >> -John Steinbeck, novelist, Nobel laureate (1902-1968) >> >> On 05/14/2014 07:40 PM, Stuart Stevenson wrote: >>> Joint space is the physical movement of the machine components. >>> Cartesian space perfect theoretical XYZ space sitting on the machine >> table >>> It is the desired path of the tool (end effector). >>> With a robot you can move the joints but a single joint movement likely >>> would not give you the tool motion you were trying to achieve. >>> On a 3 axis mill you can have the same effect if the X and Y axes are not >>> square with one another. >>> Let's say you move the X axis only: >>> in joint space only the X axis moves and if the X and Y are not square >> you >>> would cut a corner that would not be 90 degrees. >>> On the same machine cartesian space X motion would also see the Y move to >>> compensate for the squareness problem. >>> In other words your Cartesian space would be square (as assumed) but your >>> joint space is not square. >>> This compensation would have required you to input correction amounts in >>> the kinematics to describe to the control the out of square condition. >>> Kinematics is the mathematical description of the joint space converted >> to >>> cartesian space. >>> as Sam said - clear as mud >>> >>> >>> >>> On Wed, May 14, 2014 at 6:57 PM, rayj <raymo...@frontiernet.net> wrote: >>> >>>> >>>> >>>> Raymond Julian >>>> Kettle River, MN >>>> >>>> The things we admire in men, kindness and generosity, openness, honesty, >>>> understanding and feeling are the concomitants of failure in our system. >>>> And those traits we detest, sharpness, greed, acquisitiveness, meanness, >>>> egotism and self-interest are the traits of success. And while men >>>> admire the quality of the first they love the produce of the second. >>>> -John Steinbeck, novelist, Nobel laureate (1902-1968) >>>> >>>> On 05/14/2014 06:43 PM, andy pugh wrote: >>>>> On 15 May 2014 00:17, rayj <raymo...@frontiernet.net> wrote: >>>>> >>>>>> Is there a similar standard in the control of robotic arms? >>>>> >>>>> It is the same there. (Or it can be). >>>>> >>>>> XYZ is end-effector point in space (room coordinates). >>>>> ABC are end-effector angles >>>>> UVW (could) be ways to define moves in end-effector space. >>>>> >>>>> But that rather depends on if you are moving the robot in cartesian >>>>> space or joint space. >>>>> >>>> >>>> There's what I'm trying to learn. I'd never heard of joint space! Does >>>> this stuff fall under the category of "robotics" or "kinematics", or >> what? >>>> >>>> >>>> >> ------------------------------------------------------------------------------ >>>> "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE >>>> Instantly run your Selenium tests across 300+ browser/OS combos. >>>> Get unparalleled scalability from the best Selenium testing platform >>>> available >>>> Simple to use. Nothing to install. 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