AP_MotorsMulticopter: add HOVER_LEARN param

libraries/AP_Motors/AP_MotorsMulticopter.cpp

@@ -115,6 +115,13 @@ const AP_Param::GroupInfo AP_MotorsMulticopter::var_info[] = {
     // @User: Advanced
     AP_GROUPINFO("THST_HOVER", 21, AP_MotorsMulticopter, _throttle_hover, AP_MOTORS_THST_HOVER_DEFAULT),
 
+    // @Param: HOVER_LEARN
+    // @DisplayName: Hover Value Learning
+    // @Description: Enable/Disable automatic learning of hover throttle
+    // @Values: 0:Disabled, 1:Enabled
+    // @User: Advanced
+    AP_GROUPINFO("HOVER_LEARN", 22, AP_MotorsMulticopter, _throttle_hover_learn, 1),
+
     AP_GROUPEND
 };
 
@@ -341,8 +348,10 @@ void AP_MotorsMulticopter::set_throttle_range(uint16_t min_throttle, int16_t rad
 // update the throttle input filter.  should be called at 100hz
 void AP_MotorsMulticopter::update_throttle_hover(float dt)
 {
+    if (_throttle_hover_learn > 0) {
         _throttle_hover = _throttle_hover + (dt/(dt+AP_MOTORS_THST_HOVER_TC))*(_throttle_in-_throttle_hover);
     }
+}
 
 void AP_MotorsMulticopter::output_logic()
 {
@@ -529,3 +538,12 @@ void AP_MotorsMulticopter::output_motor_mask(float thrust, uint8_t mask)
     }
     hal.rcout->push();
 }
+
+// save parameters as part of disarming
+void AP_MotorsMulticopter::save_params_on_disarm()
+{
+    // save hover throttle
+    if (_throttle_hover_learn > 0) {
+        _throttle_hover.save();
+    }
+}

libraries/AP_Motors/AP_MotorsMulticopter.h

@@ -131,6 +131,9 @@ protected:
     // apply any thrust compensation for the frame
     virtual void        thrust_compensation(void) {}
 
+    // save parameters as part of disarming
+    void save_params_on_disarm();
+
     // flag bitmask
     struct {
         spool_up_down_mode     spool_mode       : 3;    // motor's current spool mode
@@ -148,6 +151,7 @@ protected:
     AP_Int16            _pwm_min;               // minimum PWM value that will ever be output to the motors (if 0, vehicle's throttle input channel's min pwm used)
     AP_Int16            _pwm_max;               // maximum PWM value that will ever be output to the motors (if 0, vehicle's throttle input channel's max pwm used)
     AP_Float            _throttle_hover;        // estimated throttle required to hover throttle in the range 0 ~ 1
+    AP_Int8             _throttle_hover_learn;  // enable/disabled hover thrust learning
 
     // internal variables
     bool                motor_enabled[AP_MOTORS_MAX_NUM_MOTORS];    // true if motor is enabled

libraries/AP_Motors/AP_Motors_Class.cpp

@@ -59,8 +59,11 @@ AP_Motors::AP_Motors(uint16_t loop_rate, uint16_t speed_hz) :
 
 void AP_Motors::armed(bool arm)
 {
+    if (_flags.armed != arm) {
         _flags.armed = arm;
         AP_Notify::flags.armed = arm;
+        save_params_on_disarm();
+    }
 };
 
 // pilot input in the -1 ~ +1 range for roll, pitch and yaw. 0~1 range for throttle

libraries/AP_Motors/AP_Motors_Class.h

@@ -147,6 +147,9 @@ protected:
     // update the throttle input filter
     virtual void        update_throttle_filter() = 0;
 
+    // save parameters as part of disarming
+    virtual void save_params_on_disarm() {}
+
     // convert input in -1 to +1 range to pwm output
     int16_t calc_pwm_output_1to1(float input, const RC_Channel& servo);