Il giorno lun, 12/12/2011 alle 13.30 +0200, Alex Joni ha scritto: > > > Il giorno lun, 12/12/2011 alle 12.02 +0100, Spiderdab ha scritto: > >> Hi, there's one thing isn't clear for me with speed. > >> I have an inverted tetrapod. > >> I've set [AXIS_n]MAX_VELOCITY to 1000.0 (in my case mm/s) > >> when i jog in teleop mode in X or Y or Z axis, i have this speed. > >> but when i jog in XY direction jog velocity is the sum-vector between X > >> and Y speed, so 1.4* resulting in something like 1400 mm/s. > >> if then i jog to XYZ direction (all 3 dir together..) again the > >> resulting speed is the sum-vector, so something near 1,8*, and the > >> resulting speed is 1800 mm/s. > >> Said that, what i see in [TRAJ]MAX_VELOCITY or MAX_LINEAR_VELOCITY > >> should set the max speed independently of jog direction, but it doesn't > >> change anything. > >> As a result, when i jog at max speed to a diagonal direction, i have a > >> following error, because jogging speed exceeds what the machine can do. > >> What do you think about it? > > To be precise, i just discovered that [TRAJ]MAX_LINEAR_VELOCITY works as > > a general vel_limit if i write manual MDI command. But doesn't work as a > > limiter for manual jogging speed. > > I have to solve this, because i think that if you jog in teleop mode you > > should have the same speed apart from the direction you're jogging. the > > machine shouldn't go faster in diagonal movements!! > > Yes, it should (kinda)! > Remember we are talking about tooltip velocity here, not the velocity of the > individual motors. > > The problem with the original emc2 code was that there was no difference > between motor velocity and axis velocity. > [AXIS_n]MAX_VELOCITY - limited both motor and carthesian velocity > That is certainly wrong (it is correct only for trivial kinematics where > motor 0 = X, motor 1 = Y, etc). > In order to fix that we started ja3 a while ago, but it isn't finished. > > The idea is to have separate [AXIS_n]MAX_VELOCITY - to limit carthesian > velocity, e.g. tooltip velocity > and [JOINT_n]MAX_VELOCITY - to limit motor velocity. > > When doing a move (doesn't matter if coordinated, e.g. G1 ..Fxx, or MDI or > by jogging) the planner should take all velocities into considerations. > > The problem with this is the functions are not linear. That means that > during the move, one of the joints might need to go faster than it's limit. > That need can be for a very small portion of the move, that's why it's hard > to implement this. > > There are basicly 2 approaches: > > 1. simulate the move (before actually doing it), and look for max vels for > each joint. Then scale the move accordingly, so that none of the joint vels > is exceeded. > 2. start the move with a certain speed, and when approaching a joint vel > limit, reduce the speed accordingly. > > #1 will move the entire path slower > #2 will move as fast as possible, and only slow down on trouble locations. > > That said, afaik, currently none of them are implemented in ja3, and the > planner gladly violates joint vel limits if asked to. > > JA3 is still the place to be for nontrivkins, because those fixes (#1 or #2) > are quite possible, opposed to the regular code where it's impossible to > implement any of them. > > Regards, > Alex Hi Alex, and thanks for answering. I understood the logic under ja3, and i really think that's the right logic for every machine, also carthesians. said that, i think your 2nd solution is what i expect machine should behave, maybe adding an advice if planned vels couldn't be achieved.
But, what seems strange to me is that if i set i.e.: X max-vel to 1000 Y max-vel to 1000 Z max-vel to 1000 when i jog a traverse to +X+Y+Z direction speed goes to 1740! and it has nothing to do with joints speed. It should be limited by [TRAJ]MAX_LINEAR_VELOCITY. but this value only works with MDI commands. So, apart from controlling that joint speed isn't violated into traj planner, i think there's an error into the code that should be fixed to make traj_max_vel work also on manual jog. ------------------------------------------------------------------------------ Learn Windows Azure Live! Tuesday, Dec 13, 2011 Microsoft is holding a special Learn Windows Azure training event for developers. It will provide a great way to learn Windows Azure and what it provides. You can attend the event by watching it streamed LIVE online. Learn more at http://p.sf.net/sfu/ms-windowsazure _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
