Soft limits with non trivial kins

I am having an issue where I can jog or mpg into the soft limits on my machine when not in trivial kins. The machine has a tilting spindle head so when the B axis is at any position other than 0 I can jog or mpg into the soft limits. When at B is at 0 the soft limits work just as expected.

Once on the soft limits I have to unhome and rehome the machine to get it to work again.

Any thoughts on this issue.

If this belongs in the Kinematics section I can post there also?

Thanks,

Jim

We have the same problem but I have not investigated a fix yet. Ther are Hal pins for the soft limits that can be changed

I don't think you need to unhome to recover though, you can switch to joint mode and jog back into the tilted b working space and switch back

I did not implement switchkins in my kinematics module. Is there a way to switch to joint mode without switchkins?

The only way I have found is to uhome and rehome.

I thought the soft limits were to keep you from exceeding a limit and getting stuck (can't move the machine) like I am right now. I guess the soft limits for the axis is only checked against a jog or mpg move and the joint is not checked. That is what it appears anyway.

It is checked and throws the error and locks up the machine. Is there an override for soft limits like there is for hard limits?

I don't see these pins for the soft limits that you are talking about. What hal module are they in?

It is a custom kins file.

When I say not trivial kins I mean there is an adjustment in the joint position vs the axis position. It has a tilting head B axis. if the B axis is at 0 degrees it is essentially trivial kins and the joints and axis movements are the same.

When the head tilts the x axis, joint 0 and the z axis, joint 2 are adjusted to keep the tool tip at the same point in the xyz coordinate system. With a long tool this can cause large discrepancies in the x axis and joint zero limits. As such I can easily jog into the joint soft limits on joint 0 and joint 2.

I can attach the kins file but it will be a couple days as I am away from the machine for now.

I was thinking that I could make X axis And Z axis limit adjustment pins in the kins module. Then in HAL I could add the adjustment to the ini limits. I don't see any way to do this in HAL. Motion does not have pins to set limits that I see.

IF I remember correctly an adjustment of the INI limit values requires a "queue buster" which means that the motion planner cannot continuously be fed with updated limit values. One way I have thought of dealing with this is to continuously calculate the limits according to joint positions and then use feed override to avoid hitting any hard limits during jogging. So calculation in the kinematic file and a connection from there to HAL.
But as andy says the calculation of the limits might well become more complex then the calculation of the forward/inverse kinematics.
Getting the existing motion planner to find limit violations for non trivial kinematics in the look ahead is not going to an easy task because the custom kinematic is just transforming the finished output of the planner.
To find limit violations before actually running a gcode requires a simulation of the code before running it on the actual machine.

The way I deal with this is to change the affected ini values for the axis limits to large values when using non trivial kinematics and changing them back when switching back to trivial kinematics. This can be done in a custom MCode.

An example for limit value switching can be found here: github.com/LinuxCNC/linuxcnc/tree/master...xis/vismach/millturn