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
# 無人機通過mavlink實現apriltag定點降落例程
#
# 這個腳本使用MAVLink協議發送監測到的AprilTag信息到 ArduPilot / PixHawk控制器,使用OpenMV Cam精確着陸。
#
# P4 = TXD
import image, math, pyb, sensor, struct, time
# 參數#################################################################
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.
# 下面字典中只有標籤ID的標籤纔會被此代碼接受。您可以添加儘可能多的標籤ID到下面的字典
# 對於每個標籤ID,您需要提供黑色標籤邊界的長度(毫米)。標籤黑色邊框正方形的任何一邊將工作。
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)