altos: Correct incremental rotation computation

[fw/altos] / src / core / ao_sample.c

diff --git a/src/core/ao_sample.c b/src/core/ao_sample.c
index dec44f9fa0910aa422ce8e7771c75001aba3fb94..adf8399dd702535d960804791669cde9f204a812 100644 (file)
--- a/src/core/ao_sample.c
+++ b/src/core/ao_sample.c
@@ -20,6 +20,10 @@
 #include <ao_data.h>
 #endif
 
+#if HAS_GYRO
+#include <ao_quaternion.h>
+#endif
+
 /*
  * Current sensor values
  */
@@ -44,8 +48,7 @@ __pdata accel_t               ao_sample_accel_through;
 __pdata gyro_t         ao_sample_roll;
 __pdata gyro_t         ao_sample_pitch;
 __pdata gyro_t         ao_sample_yaw;
-__pdata angle_t                ao_sample_angle;
-__pdata angle_t                ao_sample_roll_angle;
+__pdata angle_t                ao_sample_orient;
 #endif
 
 __data uint8_t         ao_sample_data;
@@ -67,9 +70,9 @@ __pdata int32_t               ao_accel_scale;         /* sensor to m/s² conversion */
 __pdata accel_t                ao_ground_accel_along;
 __pdata accel_t                ao_ground_accel_across;
 __pdata accel_t                ao_ground_accel_through;
-__pdata gyro_t         ao_ground_pitch;
-__pdata gyro_t         ao_ground_yaw;
-__pdata gyro_t         ao_ground_roll;
+__pdata int32_t                ao_ground_pitch;
+__pdata int32_t                ao_ground_yaw;
+__pdata int32_t                ao_ground_roll;
 #endif
 
 static __pdata uint8_t ao_preflight;           /* in preflight mode */
@@ -86,6 +89,7 @@ __pdata int32_t       ao_sample_accel_through_sum;
 __pdata int32_t ao_sample_pitch_sum;
 __pdata int32_t ao_sample_yaw_sum;
 __pdata int32_t        ao_sample_roll_sum;
+static struct ao_quaternion ao_rotation;
 #endif
 
 static void
@@ -120,20 +124,95 @@ ao_sample_preflight_set(void)
        ao_ground_accel_along = ao_sample_accel_along_sum >> 9;
        ao_ground_accel_across = ao_sample_accel_across_sum >> 9;
        ao_ground_accel_through = ao_sample_accel_through_sum >> 9;
-       ao_ground_pitch = ao_sample_pitch_sum >> 9;
-       ao_ground_yaw = ao_sample_yaw_sum >> 9;
-       ao_ground_roll = ao_sample_roll_sum >> 9;
+       ao_ground_pitch = ao_sample_pitch_sum;
+       ao_ground_yaw = ao_sample_yaw_sum;
+       ao_ground_roll = ao_sample_roll_sum;
        ao_sample_accel_along_sum = 0;
        ao_sample_accel_across_sum = 0;
        ao_sample_accel_through_sum = 0;
        ao_sample_pitch_sum = 0;
        ao_sample_yaw_sum = 0;
        ao_sample_roll_sum = 0;
-       ao_sample_angle = 0;
+       ao_sample_orient = 0;
+
+       struct ao_quaternion    orient;
+
+       /* Take the pad IMU acceleration values and compute our current direction
+        */
+
+       ao_quaternion_init_vector(&orient,
+                                 (ao_ground_accel_across - ao_config.accel_zero_across),
+                                 (ao_ground_accel_through - ao_config.accel_zero_through),
+                                 (ao_ground_accel_along - ao_config.accel_zero_along));
+
+       ao_quaternion_normalize(&orient,
+                               &orient);
+
+       /* Here's up */
+
+       struct ao_quaternion    up = { .r = 0, .x = 0, .y = 0, .z = 1 };
+
+       if (ao_config.pad_orientation != AO_PAD_ORIENTATION_ANTENNA_UP)
+               up.z = -1;
+
+       /* Compute rotation to get from up to our current orientation, set
+        * that as the current rotation vector
+        */
+       ao_quaternion_vectors_to_rotation(&ao_rotation, &up, &orient);
 #endif 
        nsamples = 0;
 }
 
+#if HAS_GYRO
+
+#define TIME_DIV       200.0f
+
+static void
+ao_sample_rotate(void)
+{
+#ifdef AO_FLIGHT_TEST
+       float   dt = (ao_sample_tick - ao_sample_prev_tick) / TIME_DIV;
+#else
+       static const float dt = 1/TIME_DIV;
+#endif
+       float   x = ao_mpu6000_gyro((float) ((ao_sample_pitch << 9) - ao_ground_pitch) / 512.0f) * dt;
+       float   y = ao_mpu6000_gyro((float) ((ao_sample_yaw << 9) - ao_ground_yaw) / 512.0f) * dt;
+       float   z = ao_mpu6000_gyro((float) ((ao_sample_roll << 9) - ao_ground_roll) / 512.0f) * dt;
+       struct ao_quaternion    rot;
+
+       ao_quaternion_init_half_euler(&rot, x, y, z);
+       ao_quaternion_multiply(&ao_rotation, &rot, &ao_rotation);
+
+       /* And normalize to make sure it remains a unit vector */
+       ao_quaternion_normalize(&ao_rotation, &ao_rotation);
+
+       /* Compute pitch angle from vertical by taking the pad
+        * orientation vector and rotating it by the current total
+        * rotation value. That will be a unit vector pointing along
+        * the airframe axis. The Z value will be the cosine of the
+        * change in the angle from vertical since boost.
+        *
+        * rot = ao_rotation * vertical * ao_rotation°
+        * rot = ao_rotation * (0,0,0,1) * ao_rotation°
+        *     = ((a.z, a.y, -a.x, a.r) * (a.r, -a.x, -a.y, -a.z)) .z
+        *
+        *     = (-a.z * -a.z) + (a.y * -a.y) - (-a.x * -a.x) + (a.r * a.r)
+        *     = a.z² - a.y² - a.x² + a.r²
+        *
+        * rot = ao_rotation * (0, 0, 0, -1) * ao_rotation°
+        *     = ((-a.z, -a.y, a.x, -a.r) * (a.r, -a.x, -a.y, -a.z)) .z
+        *
+        *     = (a.z * -a.z) + (-a.y * -a.y) - (a.x * -a.x) + (-a.r * a.r)
+        *     = -a.z² + a.y² + a.x² - a.r²
+        */
+
+       float rotz;
+       rotz = ao_rotation.z * ao_rotation.z - ao_rotation.y * ao_rotation.y - ao_rotation.x * ao_rotation.x + ao_rotation.r * ao_rotation.r;
+
+       ao_sample_orient = acosf(rotz) * (float) (180.0/M_PI);
+}
+#endif
+
 static void
 ao_sample_preflight(void)
 {
@@ -232,9 +311,12 @@ ao_sample(void)
                                ao_sample_preflight_update();
                        ao_kalman();
 #if HAS_GYRO
-                       /* do quaternion stuff here... */
+                       ao_sample_rotate();
 #endif
                }
+#ifdef AO_FLIGHT_TEST
+               ao_sample_prev_tick = ao_sample_tick;
+#endif
                ao_sample_data = ao_data_ring_next(ao_sample_data);
        }
        return !ao_preflight;
@@ -264,7 +346,7 @@ ao_sample_init(void)
        ao_sample_pitch = 0;
        ao_sample_yaw = 0;
        ao_sample_roll = 0;
-       ao_sample_angle = 0;
+       ao_sample_orient = 0;
 #endif
        ao_sample_data = ao_data_head;
        ao_preflight = TRUE;