How does Typhoon H calculate its altitude on landing?
- Thread starter Icarus-50
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When it is approaching the ground it knows where it is mainly via its internal barometer, which is roughly about equal to GPS in accuracy ie good to within a meter or 3.
There are no ground-sensing sensors, so nothing is looking downwards and obstructing the underbelly would have no noticeable effect in that area.
There are no ground-sensing sensors, so nothing is looking downwards and obstructing the underbelly would have no noticeable effect in that area.
PatR
Premium Pilot
It does not calculate ground altitude at all. It does not know where the ground is, ever. Without RealSense it has no ground sensors, and stops when it meets the ground. If landed at too high of a descent rate it will bounce back up some amount, which is why manually controlling the descent speed when landing is a critical aspect of a good landing.
Thank you, PatR, but something (barometer or ?) tells the processor to slowdown the rotors as the drone approaches the ground, because the rotors do slowdown, what is that then? Where is the processor getting the data that the drone is close and closer to the ground? My H has RealSense. In any case, my larger question still is whether if the underbelly is obstructed, would the the H land as normal with RTH or my hand controls.
I know what you are talking about as the H plus behaves the same way when landing. Pretty sure this is a function of the GPS/Barometric sensor recording take off location along with current barometric pressure to determine what is considered a ground reference point for the drone upon take off. Sure this is only used for RTH and when you manually land in the same take off area so you are unable to slam the drone into the ground upon landing.
h-elsner
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My understanding is that landing on the ground is detected by the MPU-6050 chip on the flight controller. This chip contains a 3-axis gyroscope, 3-axis accelerometer and a Digital Motion Processor that tells the flight controller if the copter is moving or not.
br HE
br HE
PatR
Premium Pilot
With your eyes and brain as backup, just in case those gizmos don't do what they ought' too.
His post is more about how does it know it is close to ground when landing since the H slows its decent when approaching the ground.
FlushVision
Premium Pilot
The H 'knows' it's height above the place it took off from using its internal barometer. When that height is approaching zero the aircraft will slow it's descent. But that doesn't mean that the H knows where the ground is...only that it knows that it is approaching a 'zero' height...the height of the ground it took off from. For example, If you take off from the top of a hill the height will be zeroed at take off so that zero height will be the top of the hill. But if you fly out over the valley the actual ground will be lower than that zero value. When descending down into the valley, then, the aircraft will slow its descent at it approaches that zero value, but the actual ground could be a further 100' below it. The aircraft would then continue its descent past that zero value and increase its descent speed when the height is in negative values. It has absolutely no idea where the ground is...it only knows that zero value which isn't necessarily where the ground is.
^^^^ That right there. I never had a chance to write it out but that description right there is what happens. I've had this happen several times where I have taken off from a low point and landed at a high point and the H+ didn't adjust its decent speed to slow down since it still thought it was not close to it's last recorded ground level take off point.
If only they had equipped it with an under belly ultrasonic sensor, would solve that issue.
If only they had equipped it with an under belly ultrasonic sensor, would solve that issue.
Yes. And that descent gradient is dependent on the barometer being vaguely right. If, for example it had done that thing it sometimes does where it jumps 50 ft wrong on motor start, and you ignore that and carry on, then your descent slow-down will happen in the wrong place or not at all. In a few, special circumstances it may even result in the craft's refusal to come down at all (it literally gets stuck at a certain level) until you take some specific action to countermand that. There are whole threads where we go over what those options are in case anyone new is wondering (search 'H won't descend')...
Some people remain unconvinced the 2 things are related, but my own tests certainly confirm my contention (after maybe 30 flights) that if I never let it launch with the barometer being spectacularly wrong I will likely never see the 'refusal-to-land' problem again, and that has been the case in 100% of flights so far.
Some people remain unconvinced the 2 things are related, but my own tests certainly confirm my contention (after maybe 30 flights) that if I never let it launch with the barometer being spectacularly wrong I will likely never see the 'refusal-to-land' problem again, and that has been the case in 100% of flights so far.
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Thank you AeroJ. And I imagine from reading other posts that there is no way to "reset" the barometer reading to zero, prior to take off, to ensure an accurate start. Would you agree? But if there is, how do you do it? In other words, how do you "launch with the barometer being" 'right'?
I did read in another thread where you wrote that if the altitude reading is wrong when you start the motors, you should shut the motors & restart.
My final conclusion is that no reading takes place from the under belly.
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Shouldn't rely on the Typhoon, but take control and land yourself, best to be in control, just in case.
You are not fully landed until the motors shut off. If not descending and you can get within arms length, this is an excellent opportunity to avail yourself of a landing specifically for the H, the Red Button landing option.
As a last resort, you can also attempt a hand catch... however I caution people, that if you are comfortable with attempting this type of landing, please practice this multiple times under non-emergency circumstances. When you have an airframe hanging in the air, is NOT the time to see if you can figure out how to do it with a maximum amount of safety margin.
On the flip side of the coin (pun intended
), if you do land and the airframe starts to tip, follow the procedures full scale pilots do... by always being prepared to do a Touch and Go... re-lifting off before she goes over.
One of the best reasons to land at 14.5V... you'll still have a least another minute or two of flight time, to let things sort themselves out if a landing goes south. Knowing you still have that cushion will reduce the initial reaction to panic... which in and of itself will increase the likelihood of a successful outcome.
I'm done editing... I promise...
As a last resort, you can also attempt a hand catch... however I caution people, that if you are comfortable with attempting this type of landing, please practice this multiple times under non-emergency circumstances. When you have an airframe hanging in the air, is NOT the time to see if you can figure out how to do it with a maximum amount of safety margin.
On the flip side of the coin (pun intended
), if you do land and the airframe starts to tip, follow the procedures full scale pilots do... by always being prepared to do a Touch and Go... re-lifting off before she goes over.One of the best reasons to land at 14.5V... you'll still have a least another minute or two of flight time, to let things sort themselves out if a landing goes south. Knowing you still have that cushion will reduce the initial reaction to panic... which in and of itself will increase the likelihood of a successful outcome.
I'm done editing... I promise...
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PatR
Premium Pilot
You simply stop and restart the motors. it resets to 0 whenever you start them, and usually it remains stable the second time.
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