Multispectral Imaging Drone

Multispectral Imaging Drone

P17231

Handoff Document

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Table of Contents

1. Bill of Materials
2. Manufacturing and Assembly Documents
3. Gimbal
4. Electronics
5. Operator Manual
6. Service Manual
7. Software
8. Recommendations for future work

1. Bill of Materials

2. Manufacturing and Assembly

a. Gimbal

Required materials:

-⅛” Carbon Fiber Plate (12x24”) x 1

-Spray Max 2k Glamour Aerosol clear coat x 1

-Loctite E120-HP epoxy x 1

-¼ - 20 bolt (¾” length) x 1

-4-40 socket cap bolt (length) x 12

-M3 socket cap bolt (8 mm length) x 24

-iPower gimbal motors x 3

Carbon fiber will need to be machined into (qty) individual parts, the details of each is documented in the .pdf files attached.

CF_Sensor_Bracket_Rev5 x 1

CF_PitchBaseRev5 x 1

CF_PitchConnection1 x 1

CF_PitchConnection2 x 1

Carbon_Tab x 26

New_BracketConnection x 1

New_BracketConnection_Bearing x 1

Rib x 4

Carbon_VertPlate_eng x 1

Carbon_Yaw_Side_eng x 2

Carbon_HorzPlate_eng x 1

Carbon_AngPlat_eng x 1

The quality of these parts is paramount to proper alignment and fit-up of the finished product. In order to achieve the tolerances required for this, the Brinkman Lab water jet was used for all carbon fiber part production. The .dxf files can be used to submit for water jet machining.

Following the water jet, some additional sanding may be needed to remove burrs and ensure proper fit up of the mating parts. Assemble the gimbal per the assembly images below.

Figure 2.1: 3D modeled gimbal components

In order to permanently fix the gimbal design together, Loctite E120-HP epoxy was applied to all mating parts. Allow the epoxy to set for at least 24 hours. Afterwards, some additional sanding may be needed to smooth the surfaces. To finish the assembly, Spray Max 2k Glamour Aerosol clear coat was applied to all surfaces. The iPower motors are to be installed in the locations shown in the Gimbal Assembly with M3 socket cap bolts - four bolts to each side of the motors. The bolt pattern on the Mounting Plate may need to be modified to suit the correct model drone rails.

b. Electronics

Once the gimbal assembly has been completed please reference document Gimbal Plate Layout.pdf to begin to layout the electronic devices. The initial electronic devices required for this process will be:

●Raspberry Pi

●Video Capture Card

●Tetracam GPS

●Pixhawk Flight Controller

●Power Module

Note: The battery is shown in the Gimbal Plate Layout.pdf document, but is not necessary for placement on plate until the time of a flight.

Plate Layout

1. Align the Raspberry Pi over the predrilled holes in the plate and fasten down using M2.5 screws and locknuts through the case.
2. For the Video Card, Tetracam GPS and Battery use velcro strips in relation to where the components will lay per the drawing.
3. Lastly, place the power module using velcro on the underside of the gimbal plate.

Note: Be mindful of the mounting screw for the yaw axis of the gimbal in the middle of the plate.

Gimbal Layout

1. Align 1” M2.5 standoffs over predrilled holes on the back side of the gimbal and fasten them down.
2. Place Storm32 Gimbal Control in its appropriate case and fasten down to standoffs using M2.5 screws.

Note: Do not overtighten screws due to the possibility of cracking the Storm32 Gimbal Controller case

1. Use rubber cement to mount camera IMU on the concave side of the pitch plate with plug side facing up

Note: See gimbal configuration instructions to program IMU orientation into controller

1. Using range finder bracket fasten into the base of the gimbal arm where pre-drilled holes are using provided hardware from Lightware manufacturer
2. After the rubber cement has dried for camera IMU align the tetracam on the concave side of the pitch plate with the cameras facing down line the mounting holes up with the slots on plate
3. Use two M2.5 screws to fasten down the tetracam to the pitch plate.
4. On the convex side of the pitch plate line up the mounting hole of the thermal camera with the larger center slot of the plate and fasten down with a ¼-20screw and straighten as much as possible using a level with camera facing down.

Wiring

For all wiring follow document Harnessing Layout Rev D.pdf for guidance. For wiring specifications use these guidelines:

●+16.5VDC Power - Red, 12AWG

●-16.5VDC Power - Black, 12AWG

●USB Communication/Power Black Cable

●+5VDC Power - Red, 26AWG

●+5VDC Power - Black, 26AWG

●5VDC Signal - White, 26AWG

●Tx - Yellow, 26AWG

●Rx - Orange, 26 AWG

Note: These specifications can and may be disregarded when using pre-harnessed materials (i.e. PixHawk GPS) or multiconductor cables.

To ensure the durability and longevity of all harnessing and wiring please be sure to use shrink tube around any exposed wiring when possible. In order to maintain a product that is easily maintenanced be sure to use crimp connections where possible and avoid using soldering connections. There will be some cases where soldering cannot be avoided however (i.e. tetracam multi I/O connector). Using the properly sized tools for crimping will also ensure the longevity of all connections.

3. Operator Manual

Operation of the gimbal and drone is fairly straightforward. Data collection missions will be planned both Universal Ground-Control Software (UGCS) and Mission Planner, both of which are free applications available for download on the internet. All flight of the flight planning, including choosing where to fly and how fast is done in UGCS. Flight planning for the data collection system is done in Mission Planner. In order for automated data capture to occur, both flight plans in both software must align within approximately 5m accuracy. For data capture to trigger properly, waypoints issuing data collection commands must issue the following commands with proper delays,

The trigger output for the thermal camera is set to Relay 0 in the Mission Planner software and Relay 1 is set to trigger the Tetracam captures. Care must be taken to plan flights in order to ensure quick and accurate data collection. Flight planning can be done remotely anywhere in the world and the missions sent via email and uploaded to the drone through the mission planning software.

Upon arrival at the desired data collection site the system must be thoroughly checked to ensure proper functionality. Auxiliary gimbal battery must be plugged in, powering up the data collection system and gimbal. A series of beeps will be heard coming from the Pixhawk speaker. This is normal and indicates standard operation. If an alarm buzzing sound is heard, this means the auxiliary battery being used is low and must be replaced. Ensure the drone is rested in a flat space and not disturbed during the startup process as IMUs for both the gimbal and flight controller are being calibrated. Upon proper initialization the gimbal controller will be indicating the startup process has run successfully. The Pixhawk RGB LED in the center of the flight controller will flash a green color indicating that the Pixhawk has a 3D GPS lock and is ready for operation. The status LED on the Tetracam will also turn green indicating it is ready for image capture.

The sensors should be tested on the ground prior to the first flight to ensure functionality. This can be done using the Pixhawk transmitter. Toggle the CH8 switch on the controller to initiate a thermal video capture. The data storage space on the Pi should be checked to ensure a video file was properly written. Toggling the CH7 switch on the controller will initiate a tetracam capture. The green status LED will turn red for approximately half a second as the camera captures and stores its data to the onboard SD cards. Upon verification of functionality of the data collection system the standard setup procedure for the DJI S1000/S600 can be performed.

The gimbal can be tested by lifting up the drone using two of the motor arms on opposite sides and tilting it in various directions. The gimbal should operate properly and keep the imaging sensors facing the ground.

Once all the preflight checks have been completed, all that remains is the operator clicking go in UGCS to begin the flight. The drone will take off, fly, capture data, and land all autonomously. Care should be taken to monitor the flight status using the telemetry downlink in both mission planning softwares to ensure the flight is going as planned and there is enough battery life remaining. A registered FAA drone pilot should also be present with controller in hand to take over the automated flight should an issue arise.

Data can then be taken off the Pi and tetracam for later processing.

4. Service Manual

This portion of the document highlights potential problems that the user may have in the field and the solutions for those specific problems.

1. Ensure that all wires/cords and miscellaneous objects are not impeding the movement of the gimbal and the sensors and that the motors are connected to the board, along with external IMU.
2. Disconnect the power to the gimbal and verify that the resting position of the gimbal with the sensors connected is roughly in the position that is desired for data capture (level and pointing downwards).
3. If the sensors are resting unleveled in the Roll direction then the entire lower portion of the gimbal connected to the Roll motor needs to slide along along the slots into the proper position. To do this, loosen the screws that connect the Roll motor to the sensor plate slightly. Slide the entire lower portion of the gimbal to the balanced position and re-tighten the screws.
4. If the sensors are resting unleveled in the Pitch direction then their positions need to be adjusted on the sensor plate. This is done by first slightly loosening the screws that hold the sensor to the sensor plate, sliding the sensor to the balanced position, and re-tightening the screws. If no position appears to be leveled adequately, counterweights must be used to reach a desired position. Note, if counterweights are used, the increased weight may lead to other issues covered in this section.
5. If these are not the cause of the issue then the next step would be to reset the gimbal. This is done by pressing the RESET button on the STorM32 controller mounted on the back of the gimbal.
6. If the problem persists the next step would be to connect the STorM32 to a laptop with a USB mini cable and run the o323BGCTool_v090 application. Select Read to connect to the board.
7. Under the Dashboard tab, ensure that the motors are listed as ACTIVE and not OFF. If the motors are OFF, disconnect the board from power and reconnect it. Click Read again to reconnect. If the motors are still OFF it is possible that the Battery Voltage is too low.
8. If the voltage level is below ~9.5V, the battery needs to be switched. If the battery is not the issue, check to ensure that there are no I2C Errors.
9. If all of the above are not the issue, it is possible that the voltage set for the motors is too low and they are struggling to get the gimbal into position. Please note that if the gimbal appears to be turning in the wrong direction while trying to level itself, the voltage level on each motor is not the problem and the user should move on to item number 7. Under the PID tab, set the voltage for the appropriate motor 10-15 units higher. Note, this may lead to other issues covered in this section.
10. Regardless of the state of the motors or Battery Voltage, if there are I2C Errors, this is most likely the cause of the issues. There are a number of possible reasons why that must be fixed in order for the gimbal to level itself.
11. First, ensure that the external IMU wires are not near any motor or sensor wires; the EM fields produced by the motors and/or sensors can cause interference in the I2C communication.
12. Next try twisting the external IMU wires.
13. After performing the above I2C potential fixes, restart the gimbal using the Tools dropdown menu.
14. If there are still I2C Errors lower the voltage of the motors. Note, this may fix the I2C Errors but can lead to other issues covered in this section.
15. Check for a loose pin(s) on the connection from the external IMU to the STorM32 board. The pin needs to be reset into place within the connector housing in order for the I2C errors to potentially go away.
16. If all of the option above were exhausted and the I2C Errors persist, it is very possible that there is an unfixable hardware issue with either the external IMU or the STorM32, in which case one or both may need to be replaced.
17. If the Motors are ACTIVE, the Battery Voltage is OK, and there are no I2C Errors, go to the Gimbal Configuration tab and select the Configure Gimbal Tool on the left. This will deactivate the motors.
18. On the right hand side of the window that pops up, deselect all of the Step I check marks, the Yaw Motor Position check mark, and the Enable Motors and Restart Controller check mark.
19. Select Continue and run through the rest of the tool.
20. The Gimbal should produce and audible *beep* and should be ready to use.
21. If the problem persists, it may be a calibration issue with the IMU, in which case, please refer to the Calibrating IMUs section under the Appendix.

1. This error is caused by grossly incorrect PID values. In order to mitigate this please refer to the PID Tuning section of the Appendix.

1. Ensure that all wires/cords and miscellaneous objects are not impeding the movement of the gimbal and the sensors and that the motors are connected to the board, along with external IMU.
2. Ensure that the Battery Voltage is not below ~9.5V. This can be done by disconnecting the battery and probing its positive and negative terminals with an multimeter.
3. If there are no impedances and the Battery Voltage is OK then the cause of the issue is most likely the PID and voltage/motor settings. In order to fix this please refer to the PID Tuning section of the Appendix. Note, adjusting for this problem may lead to another one listed under this section. It is possible that the user will bounce back and forth between two problems to fix the initial issue.

1. The offsets need to be adjusted. To do this, connect the board to a computer and run the o323BGCTool_v090 application. Press Read to connect to the board and under the Setup tab adjust the Rc Pitch Offset or Rc Roll Offset accordingly. At the bottom of the window select Write and continue to repeat this process until the sensors are leveled.

5. Software

Obtaining Data from Raspberry Pi:

The Raspberry Pi is responsible for capturing videos from the thermal camera and copying the files from the Tetracam. The output is one folder named “yyyymmdd-HHMMSS” where yyyy is the year, mm is the month, dd is the day, HH is the hour, MM is the minute, and SS is the second of when the data capture was initiated (e.g., 20170407-151222 is April 7, 2017 at 3:12pm). This timestamp is obtained via a GPS receiver.