when i take of the altitude hold mode engaged my coptor is able to maintain altitude when my transmitter throttle stick is at centre position. Now if i switch to stabilize mode from alt hold my quad shoots up very fast untill I lower my throttle is it expected behaviour?
And if i take off at stabilize mode and at around 12-15% throttle my quad hover and reach my desired altitude and if i switch to alt hold without touching throttle my quad just lands.
In AltHold, the stick position commands a change in altitude, with center stick meaning no change. With a MOT_THST_HOVER = 0.125 the quad needs about 12.5% of max thrust to keep the altitude. When you switch to stabilize, the stick position controls the amount of thrust directly, with center stick meaning (without set expo/etc) about 50% of max thrust, which is about 4x what you need to hoover, therefore the quad shoots upwards.
Similarly when starting in stabilize where your stick is at ~12-15% and you switch to AltHold, you now command a rapid decrease of altitude, because your stick is far below 50%.
I would advise you to read up on what the flight modes are doing, especially stabilize and AltHold
Is there any way to charge the behaviour? when i switch to AltHold from stabilize mode hover position the current stick position should considered as a mid throttle and position above it command the craft to ascend and below should decent.
No, that would just be confusing. What if you switched when you are climbing and the throttle is really high? You would have 7/8 of the stick to go down and 1/8 of the stick to go up. How much sense would that make?
Yes thats make sense, it would be great if ardupilot has config to set althold throttle like INav which can be changed depending on the craft . nav_mc_althold_throttle in inav when the value is set to STICK ,then when enabling ALTHOLD it treats current stick position as the neutral midpoint for holding altitude and when set to MID_STICK it use transmitter physical midpoint is set to the mid stick position for holding altitude.
Most users often discard the Stablize mode from flight mode selection very early once a good attitude hold is achieved. Users will quickly replace it with alt-hold and Loiter for further tuning and never return to Stabilize (maybe for Race drone).