Posted 28 October 2023

Field test starting in bedroom hallway, just before MBR door. I have elected to start here, as WallE3 has been consistently making it this far with no problems whatsoever. Everything wen OK except for a couple of strange occurrences where it appeared that WallE3 was simply going straight without tracking anything. One of these occurrences was right at the end of the run. Here’s the video of the run:

And here’s the telemetry:

The strange behavior occurs just after WallE3 changed from the left to right-hand wall when it hits the open doorway of the larger guest bedroom, and then makes the hard right-hand turn to follow the near wall when it exits the hallway into the dining room area.

From the video, this occurs at approximately 203 sec, so I have excerpted the telemetry starting at the point where the robot transitions from the left to right wall.

At 215.3 sec WallE3 experiences another EXCESS_STEER_VAL anomaly (as the robot exits the hallway into the dining room area). WallE3 makes a slight right turn, moves forward a bit, and stops; this is the normal ‘move ahead one skosh’ after an EXCESS_STEER_VAL anomaly detection.

Then at 216.6 sec with gl_Left/RightCenterCm = 219.7/77.2, Left/RightSteerVal = 1.00/-1.00 it makes another right turn to, presumably, follow the right-hand wall, but it doesn’t try to capture the 30 cm offset and track – it just goes straight, eventually running into the wall on the far side of the open doorway into the kitchen area bathroom. From the telemetry it looks like WallE3 called ‘MoveToDesiredFrontDistCm() with a target distance of 30 cm as part of ‘CaptureWallOffset()’ but started the process almost parallel to the wall rather than perpendicular.

Matching the code up with the telemetry and the video, it becomes apparent that ‘HandleExcessSteervalCase(RIGHT)’ is called by HandleAnomalousConditions(RIGHT) as soon as the EXCESS_STEER_VAL anomaly is detected.

The first thing that HandleExcessSteervalCase() does it move forward for 500 mSec – the ‘skosh’ intended to clear the point where the anomaly occurred to obtain valid distance measurements. In this case, however, the video shows that the ‘forward’ direction was slanted off to the right instead of straight ahead, which meant that instead of detecting an ‘open corner’ condition with no trackable wall in range, the robot saw a trackable wall to the right at 77.2 cm, as the following telemetry line shows:

So, instead of the ‘open corner’ block in HandleExcessSteervalCase() executing, the ‘else if (trkcase == TRACKING_RIGHT)’ block was run , as shown below:

Since HandleExcessSteervalCase was called with TRACKING_RIGHT, and because gl_RightCenterCm = 77.2 was less than MAX_TRACKING_DISTANCE_CM (100 cm), ‘TrackRightWallOffset(WALL_OFFSET_TRACK_Kp, WALL_OFFSET_TRACK_Ki, WALL_OFFSET_TRACK_Kd, WALL_OFFSET_TGTDIST_CM)’ was called without running ‘ChooseBetterTrackingSide()’.

In TrackRightWallOffset(), CaptureWallOffset(TRACKING_RIGHT, 77.2) was called because the starting offset was too high for immediate tracking. In CaptureWallOffset(), a 90º CW turn was performed to (supposedly) point WallE3 directly at the wall to be tracked, and then ‘MoveToDesiredFrontDistCm(tgt_offset_cm)’ was called to capture the wall offset of 30 cm.

Unfortunately, the 90º CW turn step assumes the robot is already oriented parallel to the wall to be tracked, but because the actual physical configuration at this point was an open corner instead of an open doorway, WallE3 wasn’t at all parallel to the wall. So, the turn just oriented the robot to about 40-45º to the wall rather than 90º. The next step in the offset capture routine is to call MoveToDesiredFrontDistCm() to move the robot to the desired offset distance (in this case, 30 cm). But the front distance measurement never got down to 30 cm, as the robot wound up running along the baseboard, parallel to the wall. This would have continued indefinitely except WallE3 ran into the far edge of the doorway into the kitchen area bathroom.

So, everything worked just like it was supposed to, except that when the robot exited the bedroom hallway it was turned just enough so that it saw what looked like a trackable wall to the right, instead of gl_LeftCenterCm & gl_RightCenterCm > MAX_TRACKING_DIST_CM, so the open corner case wasn’t executed.

To fix this problem (and hopefully not create other ones) I added the condition that to bypass the ‘open corner’ case, the absolute value of the ‘trackable side’ steering value must be less than 1/2 the max steerval of +/- 1.

Well, that didn’t work as well as I thought. I made another field run, this time starting just before the end of the bedroom hallway where it opens into the dining area. What should have happened is the robot should have detected the ‘open corner’ configuration, made a 90º CW turn and carried on tracking the right-hand wall. What actually happened wasn’t that. Here’s a short video showing the action, along with the telemetry from the run

So, it appears the same sort of thing happened again, only this time it was the left-side distance that was less than MAX_TRACKING_DIST_CM. Since both steervals were +/- 1 this should have caused the ‘open corner’ block to execute.

Fixed (again!). Running another test.

ALRIGHT!! This time things worked just like they are supposed to! Here’s a short video showing the action, and the telemetry from the run.

As can be seen from the video and telemetry, the ‘open corner’ configuration was properly detected even with gl_Left/RightCenterCm = 84.1/235.6, Left/RightSteerVal = 1.00/1.00 (left side within MAX_TRACKING_DIST_CM but abs(left steerval) > MAX_STEERVAL ). Yay!!

Stay Tuned,

Frank