Merge pull request #1028 from PX4/inav_gps_delay

position_estimator_inav: GPS delay compensation

5 files changed, 122 insertions, 28 deletions

diff --git a/src/drivers/gps/ubx.cpp b/src/drivers/gps/ubx.cpp
index 7502809bd..c143eeb0c 100644
--- a/src/drivers/gps/ubx.cpp
+++ b/src/drivers/gps/ubx.cpp
@@ -69,6 +69,9 @@ UBX::UBX(const int &fd, struct vehicle_gps_position_s *gps_position) :
 	_gps_position(gps_position),
 	_configured(false),
 	_waiting_for_ack(false),
+	_got_posllh(false),
+	_got_velned(false),
+	_got_timeutc(false),
 	_disable_cmd_last(0)
 {
 	decode_init();
@@ -275,9 +278,10 @@ UBX::receive(unsigned timeout)
 	bool handled = false;
 
 	while (true) {
+		bool ready_to_return = _configured ? (_got_posllh && _got_velned && _got_timeutc) : handled;
 
 		/* poll for new data, wait for only UBX_PACKET_TIMEOUT (2ms) if something already received */
-		int ret = poll(fds, sizeof(fds) / sizeof(fds[0]), handled ? UBX_PACKET_TIMEOUT : timeout);
+		int ret = poll(fds, sizeof(fds) / sizeof(fds[0]), ready_to_return ? UBX_PACKET_TIMEOUT : timeout);
 
 		if (ret < 0) {
 			/* something went wrong when polling */
@@ -286,7 +290,10 @@ UBX::receive(unsigned timeout)
 
 		} else if (ret == 0) {
 			/* return success after short delay after receiving a packet or timeout after long delay */
-			if (handled) {
+			if (ready_to_return) {
+				_got_posllh = false;
+				_got_velned = false;
+				_got_timeutc = false;
 				return 1;
 
 			} else {
@@ -438,6 +445,7 @@ UBX::handle_message()
 
 					_rate_count_lat_lon++;
 
+					_got_posllh = true;
 					ret = 1;
 					break;
 				}
@@ -482,6 +490,7 @@ UBX::handle_message()
 					_gps_position->time_gps_usec += (uint64_t)(packet->time_nanoseconds * 1e-3f);
 					_gps_position->timestamp_time = hrt_absolute_time();
 
+					_got_timeutc = true;
 					ret = 1;
 					break;
 				}
@@ -557,6 +566,7 @@ UBX::handle_message()
 
 					_rate_count_vel++;
 
+					_got_velned = true;
 					ret = 1;
 					break;
 				}
diff --git a/src/drivers/gps/ubx.h b/src/drivers/gps/ubx.h
index 5cf47b60b..43d688893 100644
--- a/src/drivers/gps/ubx.h
+++ b/src/drivers/gps/ubx.h
@@ -397,6 +397,9 @@ private:
 	struct vehicle_gps_position_s *_gps_position;
 	bool			_configured;
 	bool			_waiting_for_ack;
+	bool			_got_posllh;
+	bool			_got_velned;
+	bool			_got_timeutc;
 	uint8_t			_message_class_needed;
 	uint8_t			_message_id_needed;
 	ubx_decode_state_t	_decode_state;
diff --git a/src/modules/position_estimator_inav/position_estimator_inav_main.c b/src/modules/position_estimator_inav/position_estimator_inav_main.c
index d7503e42d..f908d7a3b 100644
--- a/src/modules/position_estimator_inav/position_estimator_inav_main.c
+++ b/src/modules/position_estimator_inav/position_estimator_inav_main.c
@@ -71,19 +71,20 @@
 #include "inertial_filter.h"
 
 #define MIN_VALID_W 0.00001f
+#define PUB_INTERVAL 10000	// limit publish rate to 100 Hz
+#define EST_BUF_SIZE 250000 / PUB_INTERVAL		// buffer size is 0.5s
 
 static bool thread_should_exit = false; /**< Deamon exit flag */
 static bool thread_running = false; /**< Deamon status flag */
 static int position_estimator_inav_task; /**< Handle of deamon task / thread */
 static bool verbose_mode = false;
 
-static const hrt_abstime gps_topic_timeout = 1000000;		// GPS topic timeout = 1s
+static const hrt_abstime gps_topic_timeout = 500000;		// GPS topic timeout = 0.5s
 static const hrt_abstime flow_topic_timeout = 1000000;	// optical flow topic timeout = 1s
 static const hrt_abstime sonar_timeout = 150000;	// sonar timeout = 150ms
 static const hrt_abstime sonar_valid_timeout = 1000000;	// estimate sonar distance during this time after sonar loss
 static const hrt_abstime xy_src_timeout = 2000000;	// estimate position during this time after position sources loss
 static const uint32_t updates_counter_len = 1000000;
-static const uint32_t pub_interval = 10000;	// limit publish rate to 100 Hz
 static const float max_flow = 1.0f;	// max flow value that can be used, rad/s
 
 __EXPORT int position_estimator_inav_main(int argc, char *argv[]);
@@ -92,6 +93,16 @@ int position_estimator_inav_thread_main(int argc, char *argv[]);
 
 static void usage(const char *reason);
 
+static inline int min(int val1, int val2)
+{
+	return (val1 < val2) ? val1 : val2;
+}
+
+static inline int max(int val1, int val2)
+{
+	return (val1 > val2) ? val1 : val2;
+}
+
 /**
  * Print the correct usage.
  */
@@ -135,7 +146,7 @@ int position_estimator_inav_main(int argc, char *argv[])
 
 		thread_should_exit = false;
 		position_estimator_inav_task = task_spawn_cmd("position_estimator_inav",
-					       SCHED_DEFAULT, SCHED_PRIORITY_MAX - 5, 4000,
+					       SCHED_DEFAULT, SCHED_PRIORITY_MAX - 5, 5000,
 					       position_estimator_inav_thread_main,
 					       (argv) ? (const char **) &argv[2] : (const char **) NULL);
 		exit(0);
@@ -199,8 +210,21 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 	float y_est[2] = { 0.0f, 0.0f };	// pos, vel
 	float z_est[2] = { 0.0f, 0.0f };	// pos, vel
 
-	float eph = 1.0;
-	float epv = 1.0;
+	float est_buf[EST_BUF_SIZE][3][2];	// estimated position buffer
+	float R_buf[EST_BUF_SIZE][3][3];	// rotation matrix buffer
+	float R_gps[3][3];					// rotation matrix for GPS correction moment
+	memset(est_buf, 0, sizeof(est_buf));
+	memset(R_buf, 0, sizeof(R_buf));
+	memset(R_gps, 0, sizeof(R_gps));
+	int buf_ptr = 0;
+
+	static const float min_eph_epv = 2.0f;	// min EPH/EPV, used for weight calculation
+	static const float max_eph_epv = 20.0f;	// max EPH/EPV acceptable for estimation
+
+	float eph = max_eph_epv;
+	float epv = 1.0f;
+
+	float eph_flow = 1.0f;
 
 	float x_est_prev[2], y_est_prev[2], z_est_prev[2];
 	memset(x_est_prev, 0, sizeof(x_est_prev));
@@ -257,9 +281,6 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 	float corr_flow[] = { 0.0f, 0.0f };	// N E
 	float w_flow = 0.0f;
 
-	static float min_eph_epv = 2.0f;	// min EPH/EPV, used for weight calculation
-	static float max_eph_epv = 10.0f;	// max EPH/EPV acceptable for estimation
-
 	float sonar_prev = 0.0f;
 	hrt_abstime flow_prev = 0;			// time of last flow measurement
 	hrt_abstime sonar_time = 0;			// time of last sonar measurement (not filtered)
@@ -536,9 +557,10 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 						w_flow *= 0.05f;
 					}
 
-					flow_valid = true;
+					/* under ideal conditions, on 1m distance assume EPH = 10cm */
+					eph_flow = 0.1 / w_flow;
 
-					eph = fminf(eph, 0.1 / att.R[2][2] / flow_q * fmaxf(1.0f, flow_dist));	// under ideal conditions, on 1m distance assume EPH = 10cm
+					flow_valid = true;
 
 				} else {
 					w_flow = 0.0f;
@@ -597,13 +619,13 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 
 				/* hysteresis for GPS quality */
 				if (gps_valid) {
-					if (gps.eph_m > max_eph_epv * 1.5f || gps.epv_m > max_eph_epv * 1.5f || gps.fix_type < 3) {
+					if (gps.eph_m > max_eph_epv || gps.epv_m > max_eph_epv || gps.fix_type < 3) {
 						gps_valid = false;
 						mavlink_log_info(mavlink_fd, "[inav] GPS signal lost");
 					}
 
 				} else {
-					if (gps.eph_m < max_eph_epv && gps.epv_m < max_eph_epv && gps.fix_type >= 3) {
+					if (gps.eph_m < max_eph_epv * 0.7f && gps.epv_m < max_eph_epv * 0.7f && gps.fix_type >= 3) {
 						gps_valid = true;
 						reset_est = true;
 						mavlink_log_info(mavlink_fd, "[inav] GPS signal found");
@@ -657,16 +679,22 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 							y_est[1] = gps.vel_e_m_s;
 						}
 
+						/* calculate index of estimated values in buffer */
+						int est_i = buf_ptr - 1 - min(EST_BUF_SIZE - 1, max(0, (int)(params.delay_gps * 1000000.0f / PUB_INTERVAL)));
+						if (est_i < 0) {
+							est_i += EST_BUF_SIZE;
+						}
+
 						/* calculate correction for position */
-						corr_gps[0][0] = gps_proj[0] - x_est[0];
-						corr_gps[1][0] = gps_proj[1] - y_est[0];
-						corr_gps[2][0] = local_pos.ref_alt - alt - z_est[0];
+						corr_gps[0][0] = gps_proj[0] - est_buf[est_i][0][0];
+						corr_gps[1][0] = gps_proj[1] - est_buf[est_i][1][0];
+						corr_gps[2][0] = local_pos.ref_alt - alt - est_buf[est_i][2][0];
 
 						/* calculate correction for velocity */
 						if (gps.vel_ned_valid) {
-							corr_gps[0][1] = gps.vel_n_m_s - x_est[1];
-							corr_gps[1][1] = gps.vel_e_m_s - y_est[1];
-							corr_gps[2][1] = gps.vel_d_m_s - z_est[1];
+							corr_gps[0][1] = gps.vel_n_m_s - est_buf[est_i][0][1];
+							corr_gps[1][1] = gps.vel_e_m_s - est_buf[est_i][1][1];
+							corr_gps[2][1] = gps.vel_d_m_s - est_buf[est_i][2][1];
 
 						} else {
 							corr_gps[0][1] = 0.0f;
@@ -674,8 +702,8 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 							corr_gps[2][1] = 0.0f;
 						}
 
-						eph = fminf(eph, gps.eph_m);
-						epv = fminf(epv, gps.epv_m);
+						/* save rotation matrix at this moment */
+						memcpy(R_gps, R_buf[est_i], sizeof(R_gps));
 
 						w_gps_xy = min_eph_epv / fmaxf(min_eph_epv, gps.eph_m);
 						w_gps_z = min_eph_epv / fmaxf(min_eph_epv, gps.epv_m);
@@ -717,8 +745,12 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 		t_prev = t;
 
 		/* increase EPH/EPV on each step */
-		eph *= 1.0 + dt;
-		epv += 0.005 * dt;	// add 1m to EPV each 200s (baro drift)
+		if (eph < max_eph_epv) {
+			eph *= 1.0 + dt;
+		}
+		if (epv < max_eph_epv) {
+			epv += 0.005 * dt;	// add 1m to EPV each 200s (baro drift)
+		}
 
 		/* use GPS if it's valid and reference position initialized */
 		bool use_gps_xy = ref_inited && gps_valid && params.w_xy_gps_p > MIN_VALID_W;
@@ -731,7 +763,7 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 			xy_src_time = t;
 		}
 
-		bool can_estimate_xy = eph < max_eph_epv * 1.5;
+		bool can_estimate_xy = (eph < max_eph_epv) || use_gps_xy || use_flow;
 
 		bool dist_bottom_valid = (t < sonar_valid_time + sonar_valid_timeout);
 
@@ -763,7 +795,7 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 			corr_baro += offs_corr;
 		}
 
-		/* accelerometer bias correction */
+		/* accelerometer bias correction for GPS (use buffered rotation matrix) */
 		float accel_bias_corr[3] = { 0.0f, 0.0f, 0.0f };
 
 		if (use_gps_xy) {
@@ -777,6 +809,24 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 			accel_bias_corr[2] -= corr_gps[2][0] * w_z_gps_p * w_z_gps_p;
 		}
 
+		/* transform error vector from NED frame to body frame */
+		for (int i = 0; i < 3; i++) {
+			float c = 0.0f;
+
+			for (int j = 0; j < 3; j++) {
+				c += R_gps[j][i] * accel_bias_corr[j];
+			}
+
+			if (isfinite(c)) {
+				acc_bias[i] += c * params.w_acc_bias * dt;
+			}
+		}
+
+		/* accelerometer bias correction for flow and baro (assume that there is no delay) */
+		accel_bias_corr[0] = 0.0f;
+		accel_bias_corr[1] = 0.0f;
+		accel_bias_corr[2] = 0.0f;
+
 		if (use_flow) {
 			accel_bias_corr[0] -= corr_flow[0] * params.w_xy_flow;
 			accel_bias_corr[1] -= corr_flow[1] * params.w_xy_flow;
@@ -807,7 +857,12 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 
 		/* inertial filter correction for altitude */
 		inertial_filter_correct(corr_baro, dt, z_est, 0, params.w_z_baro);
-		inertial_filter_correct(corr_gps[2][0], dt, z_est, 0, w_z_gps_p);
+
+		if (use_gps_z) {
+			epv = fminf(epv, gps.epv_m);
+
+			inertial_filter_correct(corr_gps[2][0], dt, z_est, 0, w_z_gps_p);
+		}
 
 		if (!(isfinite(z_est[0]) && isfinite(z_est[1]))) {
 			write_debug_log("BAD ESTIMATE AFTER Z CORRECTION", dt, x_est, y_est, z_est, x_est_prev, y_est_prev, z_est_prev, acc, corr_gps, w_xy_gps_p, w_xy_gps_v);
@@ -832,11 +887,15 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 
 			/* inertial filter correction for position */
 			if (use_flow) {
+				eph = fminf(eph, eph_flow);
+
 				inertial_filter_correct(corr_flow[0], dt, x_est, 1, params.w_xy_flow * w_flow);
 				inertial_filter_correct(corr_flow[1], dt, y_est, 1, params.w_xy_flow * w_flow);
 			}
 
 			if (use_gps_xy) {
+				eph = fminf(eph, gps.eph_m);
+
 				inertial_filter_correct(corr_gps[0][0], dt, x_est, 0, w_xy_gps_p);
 				inertial_filter_correct(corr_gps[1][0], dt, y_est, 0, w_xy_gps_p);
 
@@ -910,8 +969,25 @@ int position_estimator_inav_thread_main(int argc, char *argv[])
 			}
 		}
 
-		if (t > pub_last + pub_interval) {
+		if (t > pub_last + PUB_INTERVAL) {
 			pub_last = t;
+
+			/* push current estimate to buffer */
+			est_buf[buf_ptr][0][0] = x_est[0];
+			est_buf[buf_ptr][0][1] = x_est[1];
+			est_buf[buf_ptr][1][0] = y_est[0];
+			est_buf[buf_ptr][1][1] = y_est[1];
+			est_buf[buf_ptr][2][0] = z_est[0];
+			est_buf[buf_ptr][2][1] = z_est[1];
+
+			/* push current rotation matrix to buffer */
+			memcpy(R_buf[buf_ptr], att.R, sizeof(att.R));
+
+			buf_ptr++;
+			if (buf_ptr >= EST_BUF_SIZE) {
+				buf_ptr = 0;
+			}
+
 			/* publish local position */
 			local_pos.xy_valid = can_estimate_xy;
 			local_pos.v_xy_valid = can_estimate_xy;
diff --git a/src/modules/position_estimator_inav/position_estimator_inav_params.c b/src/modules/position_estimator_inav/position_estimator_inav_params.c
index 8aa08b6f2..d88419c25 100644
--- a/src/modules/position_estimator_inav/position_estimator_inav_params.c
+++ b/src/modules/position_estimator_inav/position_estimator_inav_params.c
@@ -55,6 +55,7 @@ PARAM_DEFINE_FLOAT(INAV_SONAR_ERR, 0.5f);
 PARAM_DEFINE_FLOAT(INAV_LAND_T, 3.0f);
 PARAM_DEFINE_FLOAT(INAV_LAND_DISP, 0.7f);
 PARAM_DEFINE_FLOAT(INAV_LAND_THR, 0.2f);
+PARAM_DEFINE_FLOAT(INAV_DELAY_GPS, 0.2f);
 
 int parameters_init(struct position_estimator_inav_param_handles *h)
 {
@@ -73,6 +74,7 @@ int parameters_init(struct position_estimator_inav_param_handles *h)
 	h->land_t = param_find("INAV_LAND_T");
 	h->land_disp = param_find("INAV_LAND_DISP");
 	h->land_thr = param_find("INAV_LAND_THR");
+	h->delay_gps = param_find("INAV_DELAY_GPS");
 
 	return OK;
 }
@@ -94,6 +96,7 @@ int parameters_update(const struct position_estimator_inav_param_handles *h, str
 	param_get(h->land_t, &(p->land_t));
 	param_get(h->land_disp, &(p->land_disp));
 	param_get(h->land_thr, &(p->land_thr));
+	param_get(h->delay_gps, &(p->delay_gps));
 
 	return OK;
 }
diff --git a/src/modules/position_estimator_inav/position_estimator_inav_params.h b/src/modules/position_estimator_inav/position_estimator_inav_params.h
index 08ec996a1..df1cfaa71 100644
--- a/src/modules/position_estimator_inav/position_estimator_inav_params.h
+++ b/src/modules/position_estimator_inav/position_estimator_inav_params.h
@@ -56,6 +56,7 @@ struct position_estimator_inav_params {
 	float land_t;
 	float land_disp;
 	float land_thr;
+	float delay_gps;
 };
 
 struct position_estimator_inav_param_handles {
@@ -74,6 +75,7 @@ struct position_estimator_inav_param_handles {
 	param_t land_t;
 	param_t land_disp;
 	param_t land_thr;
+	param_t delay_gps;
 };
 
 /**