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Lab 11 - Motors and Controls

In this lab we simulated the avionics, controls, and motors used in the Believer aircraft, focusing on powering, arming, and ensuring proper connection and calibration of the system components. This lab involved setting up and calibrating the DATX, verifying its inputs and outputs, and ensuring proper parameter settings in the hardware and LUA script. We also created a mock-up of the Believer's avionics by connecting sensors to the Cube and testing system health, mapping control inputs to servo outputs, and preparing tables for RCMAP_X and SERVO#_FUNCTION parameters. Additionally, we set up the motors and controls by connecting servos and ESCs, calibrating the ESC according to the provided guide, and testing motor function with a throttle ramp-up. Finally we updated the team wiring diagram.

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Resources

Ardupilot Parameters

Open Link

Servo

Open Link

ESC

Open Link

Motor

Open Link

RX/TX

Open Link

Cube Wiring Quick Start Guide

Open Link

Servo Functions

Open Link

ArduPilot Overview

Open Link

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General Lab info

Modifications to DATX: The two main things we did was calibrate the sticks for more accuracy and enabled multibind so we are able to pair with multiple receivers,

How ESC and Motors are connected: Battery → BEC → ESC → Motor

The ESC doesn’t rely off of the power from the flight controller. This is because if the cable from the BEC to the flight controller fails you will still have access to servo control. Just no telemetry.

DATX Setup

Questions:

1. What is CRSF and SBUS? What are the differences?

An SBUS is a serial Bus and CRSF is crossfire. CRSF allows for better performance but is more complex whereas SBUS is more simplistic and compatible.

2. What is Multi-Bind on the TBS Tracer?

Multi-bind allows one transmitter to bind to multiple receivers at one time

Task

The following where done to ensure that the DATX had the proper parameters

Power on your DATX.

Move your sticks around and observe and note where your DATX believes your sticks are.

Navigate to the “HAREWARE” screen and perform a sticks calibration

Navigate back to your home screen and ensure that your controller is now calibrated by moving the sticks and observing the onscreen position indicator.

Navigate to your LUA Script and Click on the “Tracer Micro TX”

In Radio Setting, ensure that your Multi-Bind is enabled.

Connect your RX to the cube and power it on.

Navigate back to your LUA Script and Select “Tracer Nano RX”

(if you do not have this option please bind your RX under “Tracer Micro TX”)

Select Output Map and make sure that Channel 1 is SBUS. Do not modify any other channel.

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Avionics Setup

Task

In this section, we built a mock-up of the avionics as they will be installed in the Believer. These are the instructions we followed

Using the previous labs as a guide, connect all sensors to the Cube.

Test that all systems are a go.

Attach a screenshot of the Platform Health Status from GCS below.

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With your FCU connected to GCS, make a table for the following parameter sets

RCMAP_X

RCMAP_X

Name

Setting

RCMAP_BRAKE

RCMAP_FLAP

RCMAP_PITCH

RCMAP_ROLL

RCMAP_THROTTLE

RCMAP_YAW

There are no rows in this table

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SERVO#_FUNCTION

SERVO#_FUNCTION

Name

Setting

SERVO1_FUNCTION

FlaperonRight

SERVO2_FUNCTION

FlaperonLeft

SERVO3_FUNCTION

Throttle

SERVO4_FUNCTION

Throttle

SERVO5_FUNCTION

VTailLeft

SERVO6_FUNCTION

VTailRight

SERVO7_FUNCTION

Rudder

There are no rows in this table

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Connect your DATX and verify connectivity in the ribbon.

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View your servo outputs in the Live Data tab (more on this in the next section)

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DATX Control Inputs and corresponding Servo Output

DATX Control Inputs and corresponding Servo Output

DATX Control Input Stick

Servo Output

Column 3

Column 5

Right Stick

FlaperonRight

FlaperonLeft

VTailLeft and VTailRight

Left Stick

Throttle (3 and 4)

VTailLeft and VTailRight

Rudder

There are no rows in this table

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Motor and Control Setup

Questions:

What does the RCMAP_X parameter control?

Which port on the bottom of the FCU that each RC control correlates to.

What does the SERVO#_FUNCTION control

Which flight parameter output correlates to each movement of the VTail, flaperons and throttle.

List all possible power sources for the following systems:

Servo: BECs to Battery

Motor: Directly from ESCs then into BECs then to Battery

Cube/FCU: Battery + BEC

Task

Obtain the remaining electronics to complete your set (two ESCs, two motors, and four servos)

Based on your tables above, connect one servo and one ESC to FlaperonRight and Throttle as appropriate.

Obtain instructor sign off: 👍

Before moving to the next step, try to move the connected servo. Does it work? No

Connect your ESC to the thrust stand and apply power.

Include a photo of your setup:

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Now try moving the servo again. Does it work now? Yes

Find the ESC Calibration Guide for your ESC in the

Resources Section⁠

Perform a ESC Calibration augmenting the manufacturer’s instructions with the following caveats:

The aircraft must in manual mode and be armed in GCS.

Note: with the aircraft armed, the motor can spin up.

Confirm with instructor that Calibration was performed correctly.

Gently ramp up the throttle to 100% to verify that the motor works.

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Notes about the wiring for the FC:

Servo rail is powered from ESC

Everything else is powered from external BEC into the Power port

Receiver port is powered by both BEC and ESC

Individual Reflection

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Overview of Lab

In this lab, our group brought the Believer’s motors and controls one step closer to a flyable configuration. We focused on verifying that:

The DATX transmitter and TBS Tracer receiver were correctly set up and calibrated

The RC inputs were mapped properly into the Cube (RCMAP)

The servo outputs on the FCU matched the correct control surfaces and throttle channels (SERVO#_FUNCTION)

The ESCs, servos, and motors were powered and controlled safely through the FCU

I was in Group 5 and worked mainly on the DATX setup, RC mapping checks, and initial motor/ESC testing, including stick calibration, Multi-Bind configuration, and verifying that servo outputs behaved as expected in Ground Control.

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Procedures Completed – My Work

1. DATX Setup and TBS Tracer Configuration

Our team started by checking the DATX transmitter configuration with the TBS Tracer system:

We powered on the DATX and went through the sticks calibration in the hardware menu so that the full range of stick motion was correctly registered.

Using the LUA scripts on the transmitter, we opened the Tracer Micro TX menu and confirmed that Multi-Bind was enabled. This allows the same transmitter to bind with multiple receivers.

After powering the receiver through the Cube, we used the Tracer Nano RX LUA menu to confirm the receiver configuration.

In the Output Map, we ensured that Channel 1 was set to SBUS while leaving the other channels unchanged, so that SBUS would carry all RC channels from the receiver into the Cube.

I helped step through the DATX menus, verify the calibration results, and double-check that Multi-Bind and the SBUS output were set correctly according to the lab instructions.

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2. Avionics Setup and RC/Servo Mapping

Next, we moved on to checking how the RC inputs and servo outputs were mapped inside the flight controller:

We connected the Cube to the GCS and opened the Platform Health view to make sure all connected subsystems (RC link, GPS, airspeed sensor, telemetry) were visible and healthy.

In the parameters, we examined the RCMAP values and confirmed the standard mapping:

RCMAP_ROLL = 1

RCMAP_PITCH = 2

RCMAP_THROTTLE = 3

RCMAP_YAW = 4

RCMAP_FLAP = 5

RCMAP_BRAKE = 0

We then looked at the SERVO#_FUNCTION settings to see which outputs controlled which functions:

SERVO1_FUNCTION = FlaperonRight

SERVO2_FUNCTION = FlaperonLeft

SERVO3_FUNCTION = Throttle

SERVO4_FUNCTION = Throttle

SERVO5_FUNCTION = VTailLeft

SERVO6_FUNCTION = VTailRight

SERVO7_FUNCTION = Rudder

With the DATX bound and powered, we watched the RC input indicators and the servo output bars in the GCS. I helped move the sticks and recorded which stick motions (roll, pitch, yaw, throttle) caused changes in each servo output channel. This gave us a clear mapping from stick input → RCMAP channel → SERVO output function.

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3. Motor, Servo, and ESC Power and Calibration

Finally, we worked on connecting a servo and ESC/motor pair and understanding the power path:

We connected one servo to the output assigned to a control surface (e.g., FlaperonRight) and one ESC + motor to a throttle output (e.g., SERVO3_FUNCTION = Throttle).

At first, with only the FCU powered via its main power input and no battery connected to the ESC, we tried moving the sticks and saw that the servo did not move. This showed that the servo rail did not have power yet.

After connecting a battery to the ESC, the BEC in the ESC supplied power to the servo rail. When we repeated the stick test, the servo responded correctly. I helped with this wiring and with observing the difference before and after powering the ESC.

For ESC calibration, we followed the safety instructions:

We ensured the aircraft was in Manual mode and Armed in the GCS.

With the prop area treated carefully as “live,” we followed the ESC’s calibration sequence using the throttle stick.

After calibration, we slowly advanced the throttle from idle toward 100% and confirmed that the motor spooled up smoothly.

I assisted with monitoring the GCS status, checking that the system was armed, and carefully controlling the throttle during the ramp-up test.

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Connection to Lab Objectives

This lab directly connected to the objectives about motors and controls integration:

The questions about CRSF vs SBUS and Multi-Bind became clearer after working with the DATX and TBS Tracer menus. I could see that CRSF/Tracer provides a fast link, but using SBUS on Channel 1 is how we feed all RC channels into the Cube in a standardized way.

The RCMAP_X questions were tied to how the FCU interprets the incoming SBUS channels. By verifying RCMAP_ROLL, RCMAP_PITCH, RCMAP_YAW, and RCMAP_THROTTLE, I understood why a wrong mapping could cause the aircraft to react incorrectly even if the transmitter looks fine.

The SERVO#_FUNCTION questions connected directly to how the FCU sends signals out to the aircraft. Confirming which servo port controls which surface or throttle channel helped me see how the logical functions in software map to physical wiring.

The power-source questions (what powers the servos, ESCs, and Cube) were answered by the experiment where the servo only started moving after we powered the ESC and its BEC supplied voltage to the servo rail.

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Reflection on the Lab

Before this lab, I mostly thought of the RC system, Cube, and motors as separate pieces: transmitter and receiver over here, sensors in the middle, and motors/servos at the end. Lab 11 made it very clear that they are all part of a single control chain, and a failure in any mapping or power step can break the whole system.

Seeing the servo not move until the ESC/BEC powered the servo rail was especially memorable. It showed that even when the software configuration looks correct, the physical power path is just as important. Likewise, working with RCMAP and SERVO#_FUNCTION made me realize that a mis-assigned channel can make the aircraft respond in unexpected—and potentially dangerous—ways.

I also appreciated the emphasis on calibration and safety: stick calibration on the DATX, checking Multi-Bind, confirming RC link in the GCS, and treating the motor as live once the system is armed. These are habits that matter a lot more once the aircraft is in the air.

Overall, this lab helped me understand the Believer’s control system from stick to surface: DATX → TBS Tracer → SBUS → RCMAP → SERVO outputs → ESCs and servos. Going forward, I want to keep applying this systems-level view, carefully checking both configuration and power paths whenever I work on UAS motors and controls.

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