# LPE Feedback **URL:** \ **Category:** Flight Testing & Log Analysis\ **Created:** [June 7, 2016, 11:53am UTC](https://discuss.px4.io/t/lpe-feedback/504 "2016-06-07T11:53:31Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![PKocmoud](https://discuss.px4.io/user_avatar/discuss.px4.io/pkocmoud/32/43_2.png) [@PKocmoud](https://discuss.px4.io/u/PKocmoud)\ **Post date:** [June 7, 2016, 11:53am UTC](https://discuss.px4.io/t/lpe-feedback/504/1 "2016-06-07T11:53:31Z")
Last night I flew master with LPE enabled and immediately followed up a 2nd flight with a change to INAV. PixRacer / GPS only I noted the following differences: -INAV altitude is much smoother. -LPE seems much more responsive to BARO changes but the response is almost like too much and then too little. The effect is audible from the aircraft. I wonder if there is a current draw penalty for that behavior. -LPE position hold was very solid, altitude excluded. -INAV using the same settings has a pronounced toilet bowl movement for me. LPE does not exhibit this. -Overall feeling during flights was INAV is smoother and more predictable. LPE LOG: [http://logs.uaventure.com/view/f7ckv9aTfuEss7VoXipQe7](http://logs.uaventure.com/view/f7ckv9aTfuEss7VoXipQe7) INAV LOG: [http://logs.uaventure.com/view/Wdi59ZGLdmsdhdRX63Bmx5](http://logs.uaventure.com/view/Wdi59ZGLdmsdhdRX63Bmx5) I hope this helps. ---
**Author:** ![LorenzMeier](https://discuss.px4.io/user_avatar/discuss.px4.io/lorenzmeier/32/17_2.png) [@LorenzMeier](https://discuss.px4.io/u/LorenzMeier)\ **Post date:** [June 7, 2016, 12:06pm UTC](https://discuss.px4.io/t/lpe-feedback/504/2 "2016-06-07T12:06:38Z")
Helps a ton, thanks! @jgoppert It would be great if you could chime in and have a look at the log. ---
**Author:** ![LorenzMeier](https://discuss.px4.io/user_avatar/discuss.px4.io/lorenzmeier/32/17_2.png) [@LorenzMeier](https://discuss.px4.io/u/LorenzMeier)\ **Post date:** [June 7, 2016, 12:35pm UTC](https://discuss.px4.io/t/lpe-feedback/504/3 "2016-06-07T12:35:29Z")
@PKocmoud Can you try to lower the MPC\_VEL\_P gain significantly and if that does not help, reduce the MPC\_POS\_P (try both independently)? It looks like your controller is unstable. I’m not sure yet why. But its certainly worth trying. ---
**Author:** ![jgoppert](https://discuss.px4.io/user_avatar/discuss.px4.io/jgoppert/32/938_2.png) [@jgoppert](https://discuss.px4.io/u/jgoppert)\ **Post date:** [June 7, 2016, 1:43pm UTC](https://discuss.px4.io/t/lpe-feedback/504/4 "2016-06-07T13:43:22Z")
![](https://discuss.px4.io/uploads/default/original/1X/ee1f0c893c88d87dbb2c5c67be6441d2a428c8ec.png) ![](https://discuss.px4.io/uploads/default/original/1X/a137c429acd4eae15b63620032764437de2a631e.png) ![](https://discuss.px4.io/uploads/default/original/1X/9bc36c1128757401ad1b850aae35043baeb0f3b2.png) After running the numbers, the baro standard deviation for hover is 3x what I have on the iris with a pixhawk. So this is probably why it isn’t tuned properly. I have it set to 1 m in the parameters, but this also accounts for long term drift. So I think you need to set LPE\_BAR\_Z to 2 or 3. This is sort of a chicken or the egg type of problem though, so see comment below. Baro variance iris, pixhawk, jgoppert: 0.35 m 250 quad, pixracer, pkocmoud: 1.2 m ---
**Author:** ![jgoppert](https://discuss.px4.io/user_avatar/discuss.px4.io/jgoppert/32/938_2.png) [@jgoppert](https://discuss.px4.io/u/jgoppert)\ **Post date:** [June 7, 2016, 1:46pm UTC](https://discuss.px4.io/t/lpe-feedback/504/5 "2016-06-07T13:46:44Z")
@PKocmoud Could you set your pixracer on the ground level for a bit, that will take all other variables out of the equation and we can compare raw data to make sure it really is the sensor difference causing this. ---
**Author:** ![jgoppert](https://discuss.px4.io/user_avatar/discuss.px4.io/jgoppert/32/938_2.png) [@jgoppert](https://discuss.px4.io/u/jgoppert)\ **Post date:** [June 7, 2016, 1:55pm UTC](https://discuss.px4.io/t/lpe-feedback/504/6 "2016-06-07T13:55:28Z")
Here is another comparison of the standard deviation of local z during hover for the 3 flights: In [80]: pl.sqrt(data\_pkocmoud.LPOS\_Z.var()) Out[80]: 0.34392730770541818 In [78]: pl.sqrt(data\_pkocmoud\_inav.LPOS\_Z.var()) Out[78]: 0.17970352544275056 In [76]: pl.sqrt(data\_jmg.LPOS\_Z.var()) Out[76]: 0.11418901826433966 ---
**Author:** ![jgoppert](https://discuss.px4.io/user_avatar/discuss.px4.io/jgoppert/32/938_2.png) [@jgoppert](https://discuss.px4.io/u/jgoppert)\ **Post date:** [June 7, 2016, 2:36pm UTC](https://discuss.px4.io/t/lpe-feedback/504/7 "2016-06-07T14:36:25Z")
If we get the same performance from a static test of the vehicle sitting on the ground, then I think we can say that it is the control gains that need to be adjusted as @LorenzMeier proposed.