AR_AttitudeControl: disable limits when _ACCEL_MAX is zero

libraries/APM_Control/AR_AttitudeControl.cpp

@@ -161,7 +161,7 @@ const AP_Param::GroupInfo AR_AttitudeControl::var_info[] = {
 
     // @Param: _DECEL_MAX
     // @DisplayName: Speed control deceleration maximum in m/s/s
-    // @Description: Speed control and deceleration maximum in m/s/s.  0 to disable deceleration limiting
+    // @Description: Speed control and deceleration maximum in m/s/s.  0 to use ATC_ACCEL_MAX for deceleration
     // @Range: 0.0 10.0
     // @Increment: 0.1
     // @Units: m/s/s
@@ -495,6 +495,13 @@ float AR_AttitudeControl::get_desired_speed() const
 // get acceleration limited desired speed
 float AR_AttitudeControl::get_desired_speed_accel_limited(float desired_speed, float dt) const
 {
+    // return input value if no recent calls to speed controller
+	// apply no limiting when ATC_ACCEL_MAX is set to zero
+    const uint32_t now = AP_HAL::millis();
+    if ((_speed_last_ms == 0) || ((now - _speed_last_ms) > AR_ATTCONTROL_TIMEOUT_MS) || !is_positive(_throttle_accel_max)) {
+        return desired_speed;
+    }
+
     // sanity check dt
     dt = constrain_float(dt, 0.0f, 1.0f);
 

libraries/APM_Control/AR_AttitudeControl.h

@@ -120,7 +120,7 @@ private:
     AC_PID   _steer_rate_pid;       // steering rate controller
     AC_PID   _throttle_speed_pid;   // throttle speed controller
     AP_Float _throttle_accel_max;   // speed/throttle control acceleration (and deceleration) maximum in m/s/s.  0 to disable limits
-    AP_Float _throttle_decel_max;    // speed/throttle control deceleration maximum in m/s/s. 0 to disable limits
+    AP_Float _throttle_decel_max;    // speed/throttle control deceleration maximum in m/s/s. 0 to use ATC_ACCEL_MAX for deceleration
     AP_Int8  _brake_enable;         // speed control brake enable/disable. if set to 1 a reversed output to the motors to slow the vehicle.
     AP_Float _stop_speed;           // speed control stop speed.  Motor outputs to zero once vehicle speed falls below this value
     AP_Float _steer_accel_max;      // steering angle acceleration max in deg/s/s