MoveIt
Is there a way for MoveIt2 to only output the final goal position rather than the entire path? #3256
Replies: 2 comments 4 replies
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Perhaps not the kind of solution you were looking for, but it sounds like your "CNC shield" is interpreting all motions as relative/incremental motions -- perhaps/probably due to using steppers. If you have encoders on those steppers, try switching the shield to absolute mode. Provided your board / gcode interpreter / motion controller supports blending as well, that should make a 1-to-1 conversion of If you have no encoders, or absolute mode is not supported, you could consider extending your |
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Thanks. The code I'm using is modified from a Udemy course and just reads whatever is sent to the topic before sending it on to the CNC controller. I can set the controller to use absolute rather than relative mode, however it would still be passed a series of strings rather than the final result. I was hoping there would be a flag somewhere in Moveit2 that said "don't send the entire sequence of events, because the controller you're talking to is intelligent and can work out how to get to the end goal from where it currently is, it just can't do the IK side of things", but I'm guessing that's not the case. I'll see if switching to absolute mode works and feed back, but I don't have sensors as I'm trying to only use hardware that I already have to save money! |
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Ideally what's proposed above would be a better solution by adapting your HW to MoveIt. Otherwise, calling the IK directly and using the joint state values would be a start to work out something of your style: // Define the robot_state ptr with the robot model used.
auto robot_state = std::make_shared<moveit::core::RobotState>(move_group->getRobotModel());
// optional
robot_state->setVariablePositions(move_group->getCurrentJointValues().data());
// Compute IK
auto success = robot_state->setFromIK(joint_model_group, pose, end_effector_link, 0.1);
if (success)
{
RCLCPP_INFO(logger_, "Solved IK.");
std::vector<double> joint_values;
robot_state->copyJointGroupPositions(joint_model_group, joint_values);
for (size_t i = 0; i < joint_values.size(); ++i)
{
RCLCPP_INFO(logger_, "Joint value %i is: %f", i, joint_values[i]);
}
return planning_result;
} |
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Nice suggestion. Seems I missed
If that's indeed the main goal, your suggestion is all that would be needed. But I would question the need for a full-blown MoveIt instance in that case (unless it's for collision detection of individual states). The rest of the post confused/es me though: performing FK/IK on single states should not result in trajectories, which is what the output of the GCode converter seems to suggest are being processed by it. |
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Agreed, depending on what is being done, a full MoveIt instance may not be the best case. There are out there a few toolboxes that can do the trick probably. |
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Thanks - I'm relatively new to ROS2 and didn't realise you could access MoveIT without the UI. This (or one of the toolboxes) is probably what I'm looking for. With GCode set to the default configuration, you ask it to move X/Y/Z to a specific location in milimeters. CNC Software sends it one line at a time ("move here, now go there"), but it tends to be target-focused rather than increment focused. As an example, if I wanted the X axis to travel from Whereas the output from MoveIt2 by default is: Calculating this for one axis is fairly straight forward, but for three it's quite hard. What I want to do is have the controller work out where the end needs to be, then pass it to MoveIt2 (or similar) to calculate the measurements for all three axis, then send that "final position" to the GCode interpreter (for example, Not sure if this is making more or less sense the more I explain it! 🤣 |
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I'm working with a robot arm of my own design and I want to use Moveit2 for the IK calculations, however I'm driving the motors via a CNC shield so all that needs is the last set of coordinates from the path, not each step along the way as the GCode I am sending dictates
For example, if I want to rotate a joint connected to the "X" by 45 degrees, I need to send the GCode
G21 F250 X10which moves the stepper 10mm clockwise and, because of the size of the gears, the joint rotates 45 degrees.What I need to avoid is sending a GCode step for each movement between
<current>and the goal, because the GCode controller will then try and move X by 1, then by 2, then by 3 etc. which means by the time Moveit thinks that the goal has been reached, it's actually several orders of magnitude away from where it needs to be!Is there a way to tell Moveit2 to calculate the end state, and then only send that end state to the controller?
The CNC Shield isn't capable of calculating the IK, but it knows where it is and how far it needs to move in order to get to the specified location, so I'm hoping I can pair the both and get the result I need!
Here's the example output from the current code:
All I need the controller to receive is the last value
G21 F250 X156 Y0Beta Was this translation helpful? Give feedback.
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