Just to clear up, DH allows you to specify any set of translation and rotation devices, one mounted on the other. The normal XYZ mill is very simple case, but as soon as you bolt on a rotary table, especially if the axis of ration is not parallel to the XYZ axis is gets complex.
The best feature of DH is that is already list software that can compute forward and inverse kinematics from a file of DH parameters, you don't need to write that very dificult part. In fact you can have high acceleration rates of the tool path even while the motors are running at constant speed. Computing a motor speed so as to keep acceleration and velocity under a specified limit is non-trivial. But the problem is solved. Google will return thousands of hits On Sun, Nov 6, 2016 at 12:54 PM, Chris Albertson <albertson.ch...@gmail.com> wrote: > > > On Sun, Nov 6, 2016 at 9:48 AM, Robert Ellenberg <rwe...@gmail.com> wrote: > >> >> The hard part is making the effective radius change with tool tip >> position. >> That's my long-term goal with this fix, but it may still be a big >> improvement to assume a constant effective radius. >> > > I assume what you need is to know the location of the axis in XYZ space. > This would have to be input for each set up and would depend on how you > bolted the rotary table to the mill table. In the general case the rotary > table might be bolted to some other rotary table and so on. This actually > happens in the case of an industrial robots > > There is already an industry standard for describing the general case of > rotary and translational links bolted together serially and even better > already software for working out the kinematics and joint and movement > rates and accelerations > > A good introduction is here: https://en.wikipedia.org/wiki/ > Denavit–Hartenberg_parameters > > If you google Denavit-Hartenburg you will find software to read this > description and to visualize it to a computer screen > > The job then of supporting the full general case because one of software > integration, not inventing new methods > > Think of apian spray machine where the paint nozzle must always be kept at > a fixed distance and angle from the car fender being sprayed and must > always move at a fixed rate measured tangent to the surface. These spray > machine are made mostly of rotary joints were the servo motors are > controlled to a given angular rate. A walking robot has the same > problem. Its foot must stay on the ground while the robot translates in > the direction of motion. The problem is common and open source solution > exist > > > > >> > -- > > Chris Albertson > Redondo Beach, California > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today. http://sdm.link/xeonphi _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
