landdetector groundcontact: adjust climbrate if landing speed is low #7831
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@PX4TestFlights Please cross test by flying very low and very slow with low land speed in position control mode. |
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| // Check if we are moving vertically - this might see a spike after arming due to | ||
| // throttle-up vibration. If accelerating fast the throttle thresholds will still give | ||
| // an accurate in-air indication. | ||
| bool verticalMovement = fabsf(_vehicleLocalPosition.vz) > _params.maxClimbRate * landThresholdFactor; | ||
| bool verticalMovement; |
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I would initialize this to true, just for any future errors in the code.
| if (hrt_elapsed_time(&_landed_time) < LAND_DETECTOR_LAND_PHASE_TIME_US) { | ||
| landThresholdFactor = 2.5f; | ||
| } | ||
| // land speed threshold |
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this comment says nothing, a descripion even if only with keywords would help more then duplicating the title.
| // Adjust maxClimbRate if land_speed is lower than 2x maxClimbrate | ||
| float maxClimbRate = ((land_speed_threshold * 0.5f) < _params.maxClimbRate) ? (0.5f * land_speed_threshold) : | ||
| _params.maxClimbRate; | ||
| verticalMovement = fabsf(_vehicleLocalPosition.vz) > maxClimbRate; |
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If I calculate this through with a very low land speed I get vz will be compared to 0.045 m/s.
Was that the intention? Seems like a too low value to me...
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what is a very low land speed?
yes, it is intended. the land speed should be limited to the ekf resolution (ekf can have an error of +-0.3m/s). If you go below such a land speed, then you cannot expect that landdection works. therefore it is better to have no landed at all (as opposed to false positive).
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@bkueng, can you please retest with the Intel Aero? |
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I tested this branch on the aero. It does not have any thrust dropouts anymore while flying downwards at higher or lower altitudes and higher or lower stick inputs. Landing detection still worked consistently the two times I flew. Therefore it fixes #7811
… speed threshold It's very important that the in descend detection is always at a strictly higher velocity than the vertical movement check. This combination is basically used to check for vertical downwards velocity tracking. Desired descend, no movement -> ground If in descend threshold is lower than vertical movement it is by definition even with perfect tracking the case that with any velocity between the two thresholds there is no movement even though a descend is commanded. See first fix of this problem #7831 e39b38b
… speed threshold It's very important that the in descend detection is always at a strictly higher velocity than the vertical movement check. This combination is basically used to check for vertical downwards velocity tracking. Desired descend, no movement -> ground If in descend threshold is lower than vertical movement it is by definition even with perfect tracking the case that with any velocity between the two thresholds there is no movement even though a descend is commanded. See first fix of this problem #7831 e39b38b
… speed threshold It's very important that the in descend detection is always at a strictly higher velocity than the vertical movement check. This combination is basically used to check for vertical downwards velocity tracking. Desired descend, no movement -> ground If in descend threshold is lower than vertical movement it is by definition even with perfect tracking the case that with any velocity between the two thresholds there is no movement even though a descend is commanded. See first fix of this problem #7831 e39b38b
… speed threshold It's very important that the in descend detection is always at a strictly higher velocity than the vertical movement check. This combination is basically used to check for vertical downwards velocity tracking. Desired descend, no movement -> ground If in descend threshold is lower than vertical movement it is by definition even with perfect tracking the case that with any velocity between the two thresholds there is no movement even though a descend is commanded. See first fix of this problem #7831 e39b38b
The threshold for no vertical movement is a constant value of 0.5. If the parameter landspeed is set low (for instance below 0.5), then the landdetector will always detect no vertical movement. This PR is a protection for having low landspeed.
Fixes #7811