https://book.openmv.cc/example/18-MAVLink/mavlink-apriltags-landing-target.html
https://mavlink.io/en/messages/common.html#mav_commands
https://mavlink.io/en/messages/common.html#LANDING_TARGET
https://ardupilot.org/copter/docs/parameters.html#frame-class
PLND_TYPE
# 无人机通过mavlink实现apriltag定点降落例程 # # 这个脚本使用MAVLink协议发送监测到的AprilTag信息到 ArduPilot / PixHawk控制器，使用OpenMV Cam精确着陆。 # # P4 = TXD import image, math, pyb, sensor, struct, time # 参数################################################################# uart_baudrate = 115200 MAV_system_id = 1 MAV_component_id = 0x54 MAX_DISTANCE_SENSOR_enable = True lens_mm = 2.8 # Standard Lens. lens_to_camera_mm = 22 # Standard Lens. sensor_w_mm = 3.984 # For OV7725 sensor - see datasheet. sensor_h_mm = 2.952 # For OV7725 sensor - see datasheet. # 下面字典中只有标签ID的标签才会被此代码接受。您可以添加尽可能多的标签ID到下面的字典 # 对于每个标签ID，您需要提供黑色标签边界的长度（毫米）。标签黑色边框正方形的任何一边将工作。 valid_tag_ids = { 0 : 165, # 8.5" x 11" tag black border size in mm 1 : 165, # 8.5" x 11" tag black border size in mm 2 : 165, # 8.5" x 11" tag black border size in mm } ############################################################################## # Camera Setup sensor.reset() sensor.set_pixformat(sensor.GRAYSCALE) sensor.set_framesize(sensor.QQVGA) sensor.skip_frames(time = 2000) x_res = 160 # QQVGA y_res = 120 # QQVGA f_x = (lens_mm / sensor_w_mm) * x_res f_y = (lens_mm / sensor_h_mm) * y_res c_x = x_res / 2 c_y = y_res / 2 h_fov = 2 * math.atan((sensor_w_mm / 2) / lens_mm) v_fov = 2 * math.atan((sensor_h_mm / 2) / lens_mm) def z_to_mm(z_translation, tag_size): # z_translation is in decimeters... return (((z_translation * 100) * tag_size) / 165) - lens_to_camera_mm # Link Setup uart = pyb.UART(3, uart_baudrate, timeout_char = 1000) # Helper Stuff packet_sequence = 0 def checksum(data, extra): # https://github.com/mavlink/c_library_v1/blob/master/checksum.h output = 0xFFFF for i in range(len(data)): tmp = data[i] ^ (output & 0xFF) tmp = (tmp ^ (tmp << 4)) & 0xFF output = ((output >> 8) ^ (tmp << 8) ^ (tmp << 3) ^ (tmp >> 4)) & 0xFFFF tmp = extra ^ (output & 0xFF) tmp = (tmp ^ (tmp << 4)) & 0xFF output = ((output >> 8) ^ (tmp << 8) ^ (tmp << 3) ^ (tmp >> 4)) & 0xFFFF return output MAV_DISTANCE_SENSOR_message_id = 132 MAV_DISTANCE_SENSOR_min_distance = 1 # in cm MAV_DISTANCE_SENSOR_max_distance = 10000 # in cm MAV_DISTANCE_SENSOR_type = 0 # MAV_DISTANCE_SENSOR_LASER MAV_DISTANCE_SENSOR_id = 0 # unused MAV_DISTANCE_SENSOR_orientation = 25 # MAV_SENSOR_ROTATION_PITCH_270 MAV_DISTANCE_SENSOR_covariance = 0 # unused MAV_DISTANCE_SENSOR_extra_crc = 85 # http://mavlink.org/messages/common#DISTANCE_SENSOR # https://github.com/mavlink/c_library_v1/blob/master/common/mavlink_msg_distance_sensor.h def send_distance_sensor_packet(tag, tag_size): global packet_sequence temp = struct.pack("<lhhhbbbb", 0, MAV_DISTANCE_SENSOR_min_distance, MAV_DISTANCE_SENSOR_max_distance, min(max(int(z_to_mm(tag.z_translation(), tag_size) / 10), MAV_DISTANCE_SENSOR_min_distance), MAV_DISTANCE_SENSOR_max_distance), MAV_DISTANCE_SENSOR_type, MAV_DISTANCE_SENSOR_id, MAV_DISTANCE_SENSOR_orientation, MAV_DISTANCE_SENSOR_covariance) temp = struct.pack("<bbbbb14s", 14, packet_sequence & 0xFF, MAV_system_id, MAV_component_id, MAV_DISTANCE_SENSOR_message_id, temp) temp = struct.pack("<b19sh", 0xFE, temp, checksum(temp, MAV_DISTANCE_SENSOR_extra_crc)) packet_sequence += 1 uart.write(temp) MAV_LANDING_TARGET_message_id = 149 MAV_LANDING_TARGET_min_distance = 1/100 # in meters MAV_LANDING_TARGET_max_distance = 10000/100 # in meters MAV_LANDING_TARGET_frame = 8 # MAV_FRAME_BODY_NED MAV_LANDING_TARGET_extra_crc = 200 # http://mavlink.org/messages/common#LANDING_TARGET # https://github.com/mavlink/c_library_v1/blob/master/common/mavlink_msg_landing_target.h def send_landing_target_packet(tag, w, h, tag_size): global packet_sequence temp = struct.pack("<qfffffbb", 0, ((tag.cx() / w) - 0.5) * h_fov, ((tag.cy() / h) - 0.5) * v_fov, min(max(z_to_mm(tag.z_translation(), tag_size) / 1000, MAV_LANDING_TARGET_min_distance), MAV_LANDING_TARGET_max_distance), 0.0, 0.0, 0, MAV_LANDING_TARGET_frame) temp = struct.pack("<bbbbb30s", 30, packet_sequence & 0xFF, MAV_system_id, MAV_component_id, MAV_LANDING_TARGET_message_id, temp) temp = struct.pack("<b35sh", 0xFE, temp, checksum(temp, MAV_LANDING_TARGET_extra_crc)) packet_sequence += 1 uart.write(temp) # Main Loop clock = time.clock() while(True): clock.tick() img = sensor.snapshot() tags = sorted(img.find_apriltags(fx=f_x, fy=f_y, cx=c_x, cy=c_y), key = lambda x: x.w() * x.h(), reverse = True) if tags and (tags[0].id() in valid_tag_ids): if MAX_DISTANCE_SENSOR_enable: send_distance_sensor_packet(tags[0], valid_tag_ids[tags[0].id()]) send_landing_target_packet(tags[0], img.width(), img.height(), valid_tag_ids[tags[0].id()]) img.draw_rectangle(tags[0].rect()) img.draw_cross(tags[0].cx(), tags[0].cy()) print("Distance %f mm - FPS %f" % (z_to_mm(tags[0].z_translation(), valid_tag_ids[tags[0].id()]), clock.fps())) else: print("FPS %f" % clock.fps())
landing_target_send(self, time_usec, target_num, frame, angle_x, angle_y, distance, size_x, size_y, force_mavlink1=False) method of pymavlink.dialects.v10.ardupilotmega.MAVLink instance The location of a landing target. See: https://mavlink.io/en/services/landing_target.html time_usec : Timestamp (UNIX Epoch time or time since system boot). The receiving end can infer timestamp format (since 1.1.1970 or since system boot) by checking for the magnitude the number. [us] (type:uint64_t) target_num : The ID of the target if multiple targets are present (type:uint8_t) frame : Coordinate frame used for following fields. (type:uint8_t, values:MAV_FRAME) angle_x : X-axis angular offset of the target from the center of the image [rad] (type:float) angle_y : Y-axis angular offset of the target from the center of the image [rad] (type:float) distance : Distance to the target from the vehicle [m] (type:float) size_x : Size of target along x-axis [rad] (type:float) size_y : Size of target along y-axis [rad] (type:float)
distance_sensor_send(self, time_boot_ms, min_distance, max_distance, current_distance, type, id, orientation, covariance, force_mavlink1=False) method of pymavlink.dialects.v10.ardupilotmega.MAVLink instance Distance sensor information for an onboard rangefinder. time_boot_ms : Timestamp (time since system boot). [ms] (type:uint32_t) min_distance : Minimum distance the sensor can measure [cm] (type:uint16_t) max_distance : Maximum distance the sensor can measure [cm] (type:uint16_t) current_distance : Current distance reading [cm] (type:uint16_t) type : Type of distance sensor. (type:uint8_t, values:MAV_DISTANCE_SENSOR) id : Onboard ID of the sensor (type:uint8_t) orientation : Direction the sensor faces. downward-facing: ROTATION_PITCH_270, upward-facing: ROTATION_PITCH_90, backward-facing: ROTATION_PITCH_180, forward-facing: ROTATION_NONE, left-facing: ROTATION_YAW_90, right-facing: ROTATION_YAW_270 (type:uint8_t, values:MAV_SENSOR_ORIENTATION) covariance : Measurement variance. Max standard deviation is 6cm. 255 if unknown. [cm^2] (type:uint8_t)
