Fig. 07 · Delivery · ArduCopter V4.7.2

Autonomous delivery quad

Fly it

Parts: …
Battery: unplugged
Fault: none

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Pick the battery, motors and props. Every number below is recalculated from this craft's own model.

Battery

Motors

Props

Calculated for this build

All-up weight: 5,177 g
Thrust : weight: 1.9 : 1
Hover throttle: 72%
Max current: 126 A
Hover time: 19.6 min
Hard-flying time: 16.6 min

Checks

Parts match: 1.9:1 with the parcel aboard, enough to climb out of a gust and land on a tired pack. The calculator's hover throttle is pessimistic for big props: on this build ArduPilot learns a hover near 50 % (MOT_THST_HOVER), and the real full-throttle current is nearer 75 A than the calculator's figure.

WarningIt hovers at 72% throttle: too little headroom to climb out or correct a gust.

Cost

Category	Parts	Cost
Electrical	11	$1,375
Mechanical	5	$367
Total (approx.)	16	$1,742

Every connection on the craft. Choose one to select both ends on the figure, or open the hand-inked wiring sheet.

power
motor phases
data / signal

power:XT90-S · 6S 22.2 V
The 6S pack's XT90-S plug into the power board's lead. The anti-spark plug stops the big capacitor's inrush from pitting the contacts.
power:PDB pads · VBAT to 4 ESCs
Battery voltage from the power-board pads to each ESC, a red and a black lead along every arm.
motor phases:3-phase × 4
Three phase wires per motor. The order of the three sets the spin direction.
power:POWER1 · power module · V/I sense
The power module's 6-pin lead into POWER1: a clean 5 V supply for the Pixhawk, plus the voltage and current readings the battery failsafes need.
power:5 V 5 A BEC · header pins 2/4 + 6
5 V from a 5 A BEC into the Pi's header (pins 2 or 4, and ground on pin 6). The Pi 5 with a depth camera and a modem on its USB needs it; the Pixhawk's TELEM port can't supply it.
data / signal:TELEM2 · MAVLink2 · 921600 · TX, RX, GND
MAVLink2 at 921600 baud on TELEM2: three wires, TX to RX, RX to TX, ground. Both sides are 3.3 V, so no level shifter, and the 5 V pin stays unconnected.
data / signal:TELEM1 · MAVLink2 · 57600
The SiK radio on TELEM1: MAVLink2 at 57600 baud to the ground station.
data / signal:TELEM3 · CRSF
The ELRS receiver on TELEM3: CRSF needs a full UART, so it goes on a TELEM port, not the RCIN pin.
data / signal:GPS1 · UART + I²C compass · 10-pin
One 10-pin lead into GPS1: the GPS's serial data, the compass on I²C, the LED, buzzer and safety-switch lines, and 5 V.
data / signal:AUX 1-4 · DShot600
DShot600 on AUX 1 to 4 (SERVO9 to 12 set to Motor1 to Motor4). The Pixhawk's own FMU outputs do DShot without any extra setting.
data / signal:AUX 5 · winch PWM · 6 V BEC on the rail
The winch servo on AUX 5 (SERVO13, Winch), powered from the 6 V BEC on the servo rail: a big servo on the Pixhawk's own 5 V could brown it out.
data / signal:USB 3 · depth frames
The depth camera on a USB 3 port of the Pi: the depth pictures the avoidance pipeline turns into obstacle distances.
data / signal:USB · 4G modem
The 4G modem on a USB port of the Pi, carrying MAVLink to the ground station.

A working emulation of the ArduPilot Copter command line for this craft: real setting names, real limits and real error messages.

Connect tcp:127.0.0.1:5760 source_system=255

Up and down recall earlier commands.

Configuration snippets

Frame, motor outputs and power after the build

In ArduCopter 4.7.2 you set parameters, not commands: in MAVProxy each param set is stored at once. Quad X frame, the four motors on AUX 1 to 4 with DShot600 (AUX 5 and 6 are another timer group, so the winch on AUX 5 can stay PWM), thrust linearisation for 15-inch props, the 6S pack's full and empty voltage, a lower gyro filter for slow big props, and the power module as an analog battery monitor.

# ArduCopter 4.7.2 on a Pixhawk 6C: quad X, DShot600 on AUX 1-4, power module on POWER1
param set FRAME_CLASS 1         # Quad
param set FRAME_TYPE 1          # X: M1 front right, M2 rear left, M3 front left, M4 rear right
param set SERVO9_FUNCTION 33    # AUX 1: Motor1
param set SERVO10_FUNCTION 34   # AUX 2: Motor2
param set SERVO11_FUNCTION 35   # AUX 3: Motor3
param set SERVO12_FUNCTION 36   # AUX 4: Motor4
param set MOT_PWM_TYPE 6        # DShot600: the FMU (AUX) outputs do DShot as they are
param set MOT_THST_EXPO 0.7     # 15-inch props: 0.65 suits 10 in, 0.75 suits 20 in
param set MOT_BAT_VOLT_MAX 25.2 # 4.2 V x 6 cells
param set MOT_BAT_VOLT_MIN 19.8 # 3.3 V x 6 cells
param set INS_GYRO_FILTER 30    # Hz: big props turn slowly, so filter lower than a 10-inch quad
param set BATT_MONITOR 4        # analog voltage and current on POWER1
param set BATT_CAPACITY 10000   # mAh
param set AHRS_ORIENTATION 0    # Pixhawk arrow to the nose; 4 = Yaw180 if it points back
# FRAME_CLASS, the SERVOn_FUNCTIONs and AHRS_ORIENTATION take effect after a reboot

Radio, companion and GPS ports after the build

Every serial port gets a protocol. TELEM1 is MAVLink2 to the SiK radio at 57600, TELEM2 is MAVLink2 to the Pi at 921600 (the fast link the depth data needs), TELEM3 (SERIAL5) is RCIN for the ELRS receiver at 420 kbaud, and GPS1 is the GPS.

# SiK on TELEM1, the Raspberry Pi on TELEM2, ELRS on TELEM3, GPS on GPS1
param set SERIAL1_PROTOCOL 2    # MAVLink2 to the ground radio
param set SERIAL1_BAUD 57       # 57600, the SiK default
param set SERIAL2_PROTOCOL 2    # MAVLink2 to the Pi 5
param set SERIAL2_BAUD 921      # 921600
param set SERIAL5_PROTOCOL 23   # TELEM3: RCIN, the ELRS receiver speaks CRSF
param set RSSI_TYPE 3           # link quality from the receiver protocol
param set RC_OPTIONS 8192       # bit 13: 420 kbaud for ELRS
param set SERIAL3_PROTOCOL 5    # GPS1
param set GPS1_TYPE 1           # auto-detect the u-blox M10
param set COMPASS_ORIENT 0      # puck arrow forward

The winch on AUX 5 after the build

A PWM winch is a continuous-rotation servo: the pulse width sets the line speed. ArduPilot drives it up to WINCH_RATE_MAX and works out the line length by adding up the speed it asked for, so the length drifts. The mission's DO_WINCH asks for a length; RC8_OPTION 45 puts the winch on a knob for the safety pilot.

# A PWM winch on AUX 5: the pulse width sets the line speed, not its length
param set WINCH_TYPE 1          # PWM (2 = Daiwa smart winch)
param set SERVO13_FUNCTION 88   # AUX 5: Winch
param set WINCH_RATE_MAX 1      # m/s of line
param set WINCH_POS_P 1         # how hard it chases the length it was asked for
param set RC8_OPTION 45         # a knob on channel 8 winches by hand (Winch Control)

Obstacle avoidance with the depth camera after the build

The Pi sends the depth camera's obstacle distances as a MAVLink proximity sensor (PRX1_TYPE 2). In Loiter, simple avoidance stops 1.5 m short of anything ahead (AVOID_*); in AUTO, BendyRuler (OA_TYPE 1) steers the route round obstacles it has seen. The camera looks forward only, so it can't see a wire beside or a tree behind.

# Obstacle distances from the depth camera arrive from the Pi as MAVLink OBSTACLE_DISTANCE
param set PRX1_TYPE 2           # proximity sensor 1: MAVLink
param set AVOID_ENABLE 7        # use the fence, the proximity sensor and beacons
param set AVOID_MARGIN 1.5      # m kept from obstacles in Loiter
param set AVOID_BEHAVE 1        # stop, rather than slide along
param set OA_TYPE 1             # BendyRuler: AUTO steers round what it sees
param set OA_BR_LOOKAHEAD 5     # m
param set OA_MARGIN_MAX 2       # m
param set OA_DB_SIZE 100        # obstacle points remembered
param set OA_DB_EXPIRE 10       # s

Failsafes and fence after the build

Radio lost: RTL. Ground station lost for 5 s (both the SiK and the 4G link): RTL. Battery low (3.5 V a cell or 3000 mAh left, a 30 % reserve): RTL. Critical (3.3 V a cell): land where it is. A pack below 23.4 V won't arm. The fence caps it at 30 m up and 300 m from home. ARMING_SKIPCHK 0 runs every pre-arm check: 4.7 replaced ARMING_CHECK, which listed the checks to run, with a list of checks to skip.

# Radio lost, ground station lost, battery low and critical, and a fence round the depot
param set FS_THR_ENABLE 1       # radio lost: RTL
param set FS_GCS_ENABLE 1       # no ground-station heartbeat (SiK and LTE both gone): RTL
param set FS_GCS_TIMEOUT 5      # s
param set BATT_LOW_VOLT 21      # 3.5 V per cell under load
param set BATT_LOW_MAH 3000     # or 30 % of the pack left
param set BATT_FS_LOW_ACT 2     # low: RTL
param set BATT_CRT_VOLT 19.8    # 3.3 V per cell
param set BATT_CRT_MAH 1500
param set BATT_FS_CRT_ACT 1     # critical: land where it is
param set BATT_ARM_VOLT 23.4    # no take-off on a part-charged pack
param set FENCE_ENABLE 1
param set FENCE_TYPE 7          # max altitude + circle + polygon
param set FENCE_ALT_MAX 30      # m
param set FENCE_RADIUS 300      # m round home
param set ARMING_SKIPCHK 0      # run every pre-arm check (4.7; was ARMING_CHECK 1)

Stabilize for Stabilize

The drone levels itself and the throttle stick drives the motors directly, so the pilot holds the height. It needs no GPS and no barometer, which makes it the safety pilot's last resort. ATC_ANGLE_MAX caps the lean in every mode, in degrees since 4.7.

# Stabilize: self-levelling, the throttle stick is the motors. The backup pilot's last resort
param set ATC_ANGLE_MAX 30      # max lean in every mode, degrees
mode STABILIZE

AltHold for AltHold

The barometer holds the height; the throttle stick asks for a climb or descent, up to PILOT_SPD_UP. With 5 kg aboard, 1.5 m/s is plenty. Nothing holds the position, so the wind pushes it along.

# AltHold: the barometer holds the height, the throttle stick asks for a climb rate
param set PILOT_SPD_UP 1.5      # m/s at full stick: gentle with 5 kg aboard (was PILOT_SPEED_UP 150)
mode ALT_HOLD

Loiter for Loiter

GPS and compass hold the position as well: let go and it brakes and stops. LOIT_SPEED_MS caps the speed and LOIT_ACC_MAX_M the acceleration, kept low so a parcel on the line doesn't start swinging. 4.7 renamed these to SI units: LOIT_SPEED 500 (cm/s) is now LOIT_SPEED_MS 5.

# Loiter: GPS holds the position too; slow speeds and soft accelerations for the parcel
param set LOIT_SPEED_MS 5       # m/s at full stick (was LOIT_SPEED 500)
param set LOIT_ACC_MAX_M 2.5    # m/s/s (was LOIT_ACC_MAX 250)
mode LOITER

Return to launch for RTL

It climbs to RTL_ALT_M (or stays higher), flies home at RTL_SPEED_MS, hovers over home for RTL_LOIT_TIME and lands at LAND_SPD_MS. Here 12 m clears the 7 m roofs and the 9 m power line. RTL works from any mode once it has a position and a home, but it is not a mode you can arm in: arm in Loiter, take off, then switch.

# Return to launch: climb to 12 m, fly home, wait 5 s, land
param set RTL_ALT_M 12          # m: above the roofs (7 m) and the power line (9 m)
param set RTL_SPEED_MS 3        # m/s home (was RTL_SPEED 300)
param set RTL_ALT_FINAL_M 0     # 0 = land at home
param set RTL_LOIT_TIME 5000    # ms over home before it descends
param set LAND_SPD_MS 0.5       # m/s for the last metres
mode RTL

AUTO: the delivery for AUTO delivery

The Pi uploads the mission: take off to 12 m, fly to the garden, down to 3.5 m, DO_WINCH pays out 3.4 m of line while a 4 s loiter holds the drone still, the hook opens on the ground, DO_WINCH reels it in during a second loiter, then RTL. DO commands don't hold the drone, so the loiters are what keep it in place while the line moves. Arm in Loiter, then switch to AUTO.

# The delivery mission, uploaded from the Pi (MAVSDK) or the ground station:
#   1 NAV_TAKEOFF 12 m             2 NAV_WAYPOINT drop zone, 12 m
#   3 NAV_WAYPOINT drop zone, 3.5 m  4 DO_WINCH length +3.4 m
#   5 NAV_LOITER_TIME 4 s           6 DO_WINCH length -3.4 m
#   7 NAV_LOITER_TIME 4 s           8 NAV_RETURN_TO_LAUNCH
param set WP_SPD 5              # m/s cruise (was WPNAV_SPEED 500)
param set WP_SPD_DN 1.5         # m/s down to the drop height
param set WP_RADIUS_M 2         # m: how close counts as reached
mode LOITER
arm throttle                    # AUTO cannot arm by itself
mode AUTO

Meet the delivery drone

Two computers share this airframe. The Pixhawk 6C runs ArduCopter: the attitude loop, the EKF3 estimator, GPS navigation, the mission and every failsafe. The Raspberry Pi 5 does the slow thinking: the delivery logic (a MAVSDK script), turning the depth camera's picture into obstacle distances for the Pixhawk, and a 4G link to the ground station. They talk MAVLink2 over one 921600-baud serial cable. On a delivery it takes off from the depot, climbs above the roofs and the power line, flies to the address, comes down to a hover 3.5 m up, winches the parcel to the ground and lets it go, reels the line back in and flies home. Lowering on a line keeps the 15-inch props, which cut to the bone, far from people, pets and fences; Wing, Flytrex and Manna deliver the same way. Pick the parts and watch the numbers, build it, run the bench checks, then fly the delivery by hand or let AUTO fly it.

Practice task

Fly the delivery in Loiter first: climb to 12 m over the pad, fly to the garden, come down slowly to 3.5 m over the red drop disc, climb back out and bring it home to land. It is heavy: it climbs at 1.5 m/s and leans no more than 30°, so plan ahead. Try AltHold to feel the wind push a 5 kg drone about, then let AUTO fly the whole mission and watch it hold over the garden while the parcel goes down. On a real build: smoke stopper on the first plug, motor test with the props off (A front right, then clockwise), accelerometer and compass calibration, a GPS lock outdoors, the winch test, both failsafe tests with the props off, and read every PreArm message before the first flight.

Build a delivery drone, test its winch and failsafes, then fly a parcel to a back garden

Category

Parts

Cost

Electrical

$1,375

Mechanical

$367

Total (approx.)

$1,742

# ArduCopter 4.7.2 on a Pixhawk 6C: quad X, DShot600 on AUX 1-4, power module on POWER1 param set FRAME_CLASS 1 # Quad param set FRAME_TYPE 1 # X: M1 front right, M2 rear left, M3 front left, M4 rear right param set SERVO9_FUNCTION 33 # AUX 1: Motor1 param set SERVO10_FUNCTION 34 # AUX 2: Motor2 param set SERVO11_FUNCTION 35 # AUX 3: Motor3 param set SERVO12_FUNCTION 36 # AUX 4: Motor4 param set MOT_PWM_TYPE 6 # DShot600: the FMU (AUX) outputs do DShot as they are param set MOT_THST_EXPO 0.7 # 15-inch props: 0.65 suits 10 in, 0.75 suits 20 in param set MOT_BAT_VOLT_MAX 25.2 # 4.2 V x 6 cells param set MOT_BAT_VOLT_MIN 19.8 # 3.3 V x 6 cells param set INS_GYRO_FILTER 30 # Hz: big props turn slowly, so filter lower than a 10-inch quad param set BATT_MONITOR 4 # analog voltage and current on POWER1 param set BATT_CAPACITY 10000 # mAh param set AHRS_ORIENTATION 0 # Pixhawk arrow to the nose; 4 = Yaw180 if it points back # FRAME_CLASS, the SERVOn_FUNCTIONs and AHRS_ORIENTATION take effect after a reboot

# SiK on TELEM1, the Raspberry Pi on TELEM2, ELRS on TELEM3, GPS on GPS1 param set SERIAL1_PROTOCOL 2 # MAVLink2 to the ground radio param set SERIAL1_BAUD 57 # 57600, the SiK default param set SERIAL2_PROTOCOL 2 # MAVLink2 to the Pi 5 param set SERIAL2_BAUD 921 # 921600 param set SERIAL5_PROTOCOL 23 # TELEM3: RCIN, the ELRS receiver speaks CRSF param set RSSI_TYPE 3 # link quality from the receiver protocol param set RC_OPTIONS 8192 # bit 13: 420 kbaud for ELRS param set SERIAL3_PROTOCOL 5 # GPS1 param set GPS1_TYPE 1 # auto-detect the u-blox M10 param set COMPASS_ORIENT 0 # puck arrow forward

# A PWM winch on AUX 5: the pulse width sets the line speed, not its length param set WINCH_TYPE 1 # PWM (2 = Daiwa smart winch) param set SERVO13_FUNCTION 88 # AUX 5: Winch param set WINCH_RATE_MAX 1 # m/s of line param set WINCH_POS_P 1 # how hard it chases the length it was asked for param set RC8_OPTION 45 # a knob on channel 8 winches by hand (Winch Control)

# Obstacle distances from the depth camera arrive from the Pi as MAVLink OBSTACLE_DISTANCE param set PRX1_TYPE 2 # proximity sensor 1: MAVLink param set AVOID_ENABLE 7 # use the fence, the proximity sensor and beacons param set AVOID_MARGIN 1.5 # m kept from obstacles in Loiter param set AVOID_BEHAVE 1 # stop, rather than slide along param set OA_TYPE 1 # BendyRuler: AUTO steers round what it sees param set OA_BR_LOOKAHEAD 5 # m param set OA_MARGIN_MAX 2 # m param set OA_DB_SIZE 100 # obstacle points remembered param set OA_DB_EXPIRE 10 # s

# Radio lost, ground station lost, battery low and critical, and a fence round the depot param set FS_THR_ENABLE 1 # radio lost: RTL param set FS_GCS_ENABLE 1 # no ground-station heartbeat (SiK and LTE both gone): RTL param set FS_GCS_TIMEOUT 5 # s param set BATT_LOW_VOLT 21 # 3.5 V per cell under load param set BATT_LOW_MAH 3000 # or 30 % of the pack left param set BATT_FS_LOW_ACT 2 # low: RTL param set BATT_CRT_VOLT 19.8 # 3.3 V per cell param set BATT_CRT_MAH 1500 param set BATT_FS_CRT_ACT 1 # critical: land where it is param set BATT_ARM_VOLT 23.4 # no take-off on a part-charged pack param set FENCE_ENABLE 1 param set FENCE_TYPE 7 # max altitude + circle + polygon param set FENCE_ALT_MAX 30 # m param set FENCE_RADIUS 300 # m round home param set ARMING_SKIPCHK 0 # run every pre-arm check (4.7; was ARMING_CHECK 1)

# AltHold: the barometer holds the height, the throttle stick asks for a climb rate param set PILOT_SPD_UP 1.5 # m/s at full stick: gentle with 5 kg aboard (was PILOT_SPEED_UP 150) mode ALT_HOLD

# Loiter: GPS holds the position too; slow speeds and soft accelerations for the parcel param set LOIT_SPEED_MS 5 # m/s at full stick (was LOIT_SPEED 500) param set LOIT_ACC_MAX_M 2.5 # m/s/s (was LOIT_ACC_MAX 250) mode LOITER

# Return to launch: climb to 12 m, fly home, wait 5 s, land param set RTL_ALT_M 12 # m: above the roofs (7 m) and the power line (9 m) param set RTL_SPEED_MS 3 # m/s home (was RTL_SPEED 300) param set RTL_ALT_FINAL_M 0 # 0 = land at home param set RTL_LOIT_TIME 5000 # ms over home before it descends param set LAND_SPD_MS 0.5 # m/s for the last metres mode RTL

# The delivery mission, uploaded from the Pi (MAVSDK) or the ground station: # 1 NAV_TAKEOFF 12 m 2 NAV_WAYPOINT drop zone, 12 m # 3 NAV_WAYPOINT drop zone, 3.5 m 4 DO_WINCH length +3.4 m # 5 NAV_LOITER_TIME 4 s 6 DO_WINCH length -3.4 m # 7 NAV_LOITER_TIME 4 s 8 NAV_RETURN_TO_LAUNCH param set WP_SPD 5 # m/s cruise (was WPNAV_SPEED 500) param set WP_SPD_DN 1.5 # m/s down to the drop height param set WP_RADIUS_M 2 # m: how close counts as reached mode LOITER arm throttle # AUTO cannot arm by itself mode AUTO

Meet the delivery drone

Practice task

Build a delivery drone, test its winch and failsafes, then fly a parcel to a back garden

Autonomous delivery quad

Design it

Calculated for this build

Checks

Cost

Build it

Try a real mistake

Selected part

Parts in the box

Wiring

Safety tests

Smoke stopper test

Motor test (props off)

Accelerometer calibration

Compass calibration

GPS lock

Winch test

Radio failsafe (props off)

MAVProxy console

Configuration snippets

Frame, motor outputs and power after the build

Radio, companion and GPS ports after the build

The winch on AUX 5 after the build

Obstacle avoidance with the depth camera after the build

Failsafes and fence after the build

Stabilize for Stabilize

AltHold for AltHold

Loiter for Loiter

Return to launch for RTL

AUTO: the delivery for AUTO delivery

Check yourself · Fit the power board

Check yourself · Fit the Raspberry Pi 5

Check yourself · Hang the winch and cargo cage

Check yourself

Meet the delivery drone

Practice task

Autonomous delivery quad

Design it

Calculated for this build

Checks

Cost

Build it

Try a real mistake

Selected part

Parts in the box

Wiring

Safety tests

Smoke stopper test

Motor test (props off)

Accelerometer calibration

Compass calibration

GPS lock

Winch test

Radio failsafe (props off)

MAVProxy console

Configuration snippets

Frame, motor outputs and power after the build

Radio, companion and GPS ports after the build

The winch on AUX 5 after the build

Obstacle avoidance with the depth camera after the build

Failsafes and fence after the build

Stabilize for Stabilize

AltHold for AltHold

Loiter for Loiter

Return to launch for RTL

AUTO: the delivery for AUTO delivery

Check yourself · Fit the power board

Check yourself · Fit the Raspberry Pi 5

Check yourself · Hang the winch and cargo cage

Check yourself

Meet the delivery drone

Practice task