linear axis values are in millimeters instead of meters

[schornakj]

I have a GP180 arm mounted on a linear rail which serves as a base axis, both connected to a DX200 controller. When I run MotoROS2 the joint state for the linear rail is reported in units of millimeters rather than in units of meters like I'd expect.

It looks like the GP_getPulseToMeter() function retrieves the conversion factor from axis pulses to meters for a specific control group from the controller's memory, and then that value is used when creating JointState messages to convert to meters. Based on how the code is written I'd expect that all joint states published will either be in radians or meters.

I think that this conversion is something I can configure somewhere on the controller, but I haven't found what menu contains this setting yet. I also want to make sure I correctly understand how this data gets retrieved by MotoROS2. Am I on the right track with all this so far?

[gavanderhoorn]

I've converted this to a discussion in the Troubleshooting category as MotoROS2 should already be reporting JointState values in metres (for linear axes). Always.

If it doesn't, something is wrong.

@schornakj: could you provide a couple of sample JointState messages from your DX200 published by MotoROS2?

---

Edit: and I also expect @ted-miller will ask for a PANELBOX.LOG copy and possibly a CMOS.BIN copy.

[schornakj]

Thank you, I'll get this info for you.

[schornakj]

@ted-miller Here are PANELBOX.LOG and CMOS.BIN from my robot:

joe_robot_diagnostics.zip

@gavanderhoorn here is a sample joint state:

header:
  stamp:
    sec: 1736882630
    nanosec: 168289013
  frame_id: ''
name:
- joint_1_s
- joint_2_l
- joint_3_u
- joint_4_r
- joint_5_b
- joint_6_t
- joint_0_rail
position:
- 0.0
- 6.9410895379440775e-06
- -7.631745213361399e-06
- 0.0
- 0.0
- 0.0
- -610.4629943469697
velocity:
- 0.0
- 0.0
- 0.0
- 0.0
- 0.0
- 0.0
- 0.0
effort:
- 0.0
- 0.0
- 0.0
- 0.0
- 0.0
- 0.0
- 0.0

As currently configured, the zero position of the rail is at the far right side of the workcell, and as the rail moves to the left the position increases in magnitude. At the far left side of the workcell the reported position is about -9000.0 mm.

[gavanderhoorn]

I'm not @ted-miller, but this confuses me a bit:

CONNECT :                             DETAIL        
...
S1      : TURN-1                      DETAIL        
...

you mention a linear track, but the controller appears to be configured for a positioner (TURN-1):

AXES CONFIG
S1  : TURN-1          
AXIS  AXIS TYPE     
------------------------------------------------------------
1   : ROTATION                     
============================================================
MECHANICAL SPEC
S1       : TURN-1                 AXIS: 1
AXIS TYPE: ROTATION      
------------------------------------------------------------
MOTION RANGE(+)                   360.000 deg   
MOTION RANGE(-)                  -360.000 deg   
REDUCTION RATIO(NUMER)              8.000       
REDUCTION RATIO(DENOM)              1.000       

?

Is this the correct controller?

[ted-miller]

The way that this controller is configured will not work correctly for the calculations in MotoROS2.

Since this is configured as a rotational axis, it will use the pulseToRad rather than pulseToMeter.

motoros2/src/CtrlGroup.c

Line 531 in 8feb9c6

conversion = ctrlGroup->pulseToRad.PtoR[i];

So, the units are actually in radians.

This would need to be reconfigured as a base axis (B1) as RECT-X.

When configuring this, it will ask for the gearing ratios between your motor and the track.

I suggest contacting techsupport@motoman.com (in the US) for the proper procedure to avoid any loss of data.

[schornakj]

Well that's odd. None of our robots have a rotary positioner, so assuming this isn't somehow stale log data from a historical configuration of this robot then that's how the controller is configured currently.

One simple thing I should double-check too is that the physical position of the robot on the rail is actually changing by the reported amount.

[schornakj]

Thank you @gavanderhoorn and @ted-miller for your help here. I'll switch this over to a support ticket with Yaskawa. Since this is an issue with our specific controller configuration rather than an issue with MotoROS2 I'll mark this discussion as answered.

[gavanderhoorn]

Any update here @schornakj ?

[schornakj]

@gavanderhoorn Part of the backstory here is we'd gotten this robot and controller refurbished rather than new, and there were config settings leftover from the previous owner's setup that we didn't expect we would need to change. After setting the linear axis to be the correct type of system (RECT-X instead of TURN) and filling in correct motor and pinion data for the axis drive we do get correct position reported in meters for this axis through MotoROS2.