Robogames 2024 Build

[mikeferguson]

Preliminaries

• [x] Validate sensored motor control (especially odometry, 11.1v operation)
• [x] Validate servo control with 3v3 signals (can be done with signal generator rather than MCU)
• [x] Determine camera for cone detection

Mechanical Design

• [x] Minimal CAD for Redcat 4x4 for connection points.
• [x] Design center carriage:
  • [x] Design and attach battery side pods
  • [x] Attachment points for head box
• [x] Attach MID-360 to front shock tower. Should be on a 3mm thick piece of metal, at least 10000 mm^2. Needs 10mm for airflow on all sides. Needs to tilt downward about 20 degrees
• [x] Attach camera to front shock tower
• [x] Attach GPS antenna to rear shock tower
• [x] Layout head box - WQ-48-03
  • [x] Mount NUC on top plate
  • [x] Mount IMU on bottom plate
  • [x] Mount GPS-RTK-SMA on bottom plate
  • [x] Mount TP Link Switch on bottom plate
  • [x] Mount access point on bottom plate
  • [x] Mount power distribution board?

Control and Power Board Design

• [x] Ethernet RPi Pico board
• [x] Head box battery power inlet: 11.1V: MiniFit Jr 2P
• [x] Head box shore power inlet: 12V: MiniFit Jr 2P
• [x] Hot Swap Shore Power support: 2x LM5050 (battery, shore power)
• [x] Head box power outlet: MiniFit Jr 2P
• [x] Motor battery power inlet: 11.1V: MiniFit Jr 2P
• [x] Isolated part comms to motor controller: Microfit 3P
• [x] Servo: MicroFit 3P
• [x] MiniIMU-9 v6
• [x] Safety stop circuitry TBD

Software

• [x] ROS2 Drivers for custom motor/power board
• [ ] Ackermann model for robot_controllers
• [ ] Cone finding routine
• [ ] Stuck detector and recovery behaviors
• [x] Merge IMU, GPS, Odom into localization
• [x] Improved IMU bias estimation turned out to be wrong topics
• [x] GPS breadcrumbs (blind)
• [x] Obstacle avoidance with ground filter
  • [x] Segment into polar bins (similar to Patchwork++, but bin structure/layout is different)
  • [x] Find planes (currently uses RANSAC, maybe the PCA approach of Patchwork++ would be better?)
  • [x] Use adjacent bins to re-ground bins when normals are close enough (for hills)
  • [x] Use adjacent bins to classify ground/obstacle for bins with insufficient points
  • [x] Filter obstacle cloud using clustering
  • [ ] Consider using covariance of ground plane to determine "roughness"
  • [x] Insert filtered data into costmaps
• [ ] Add negative space / drop / cliff detection

Obstacle Testing

• [ ] Ditches
• [ ] Curb
• [ ] Hills
• [ ] Chain link fence (can we see it with the livox?)
• [ ] Tall, wet grass

Onsite/Tools

• [ ] Make sure it fits in Pelican case for shipping
• [ ] Phone app/webpage to track progress?

References

• Livox Mid-360 Protocol
• Livox camera calibration
• Tutorial on using eagleye
• Sparkfun GPS-RTK2 Hookup Guide
• Sparkfun Building a GNSS Base Station Guide
• GTSAM Factor Graph Tutorial - possible approach to fusing IMU/Odom/GPS
• Proj - recommended alternative to GeographicLib
• Patchwork++: Fast and Robust Ground Segmentation Solving Partial Under-Segmentation Using 3D Point Cloud
• Bayesian Generalized Kernal Inference for Terrain Traversability Mapping - uses step height, slope and roughness (from covariance of points) to estimate traversability of uniform grid cells

[mikeferguson]

Odometry/IMU/GPS fusion is working pretty well - need a better method for IMU bias removal - robot rotates significantly when sitting in place.

[mikeferguson]

After a bit of testing/tuning with Patchwork++, going in a different direction for ground filtering/segmentation. New node is in robomagellan package - uses a similar polar format:

But then does RANSAC and some bin-to-bin checking

Could still use some tuning, additional post filtering, and especially needs better drop/cliff detection logic (although maybe we can do that in cost maps?)

[mikeferguson]

Considering using RPi Pico (w/ ethernet, from SparkFun):

• GP0 - Servo PWM
• GP1 - Livox Breaker EN
• GP2 - Ethernet Switch EN
• GP3 - Access Point EN
• GP4 - UART1_TX - to VESC (isolated)
• GP5 - UART1_RX - to VESC (isolated)
• GP6 - Spare Breaker 1 EN
• GP7 - Spare Breaker 2 EN
• GP8 - I2C0 SDA - IMU
• GP9 - I2C0 SCL - IMU
• GP10
• GP11
• GP12 - UART0_TX
• GP13 - UART0_RX - Safety Stop Input
• GP14
• GP15
• GP16 - GP21 - ETH
• GP22
• GP26/ADC0 - Battery Voltage
• GP27/ADC1 - Input current
• GP28/ADC2

[mikeferguson]

Changing design direction quite a bit - putting most of the electronics in an enclosure:

[mikeferguson]

Majority of mechanical design is done:

• [x] Front bracket for Livox mounting almost certainly will require some tweaking
• [x] Need to create enclosure for base control board (mount points already exist on the structure). This will also serve as support spacer for the left side of the robot
• [x] Need to create support spacer on right side of robot

[mikeferguson]

CAD Updates:

• [x] Merge tray into a single piece
• [x] Move control box forward 5mm for better clearance to rear mounting screws
• [x] Add 10mm of clearance below tray (update both tray and livox mount
• [x] Update battery tray to actually fit batteries, countersink screws that attach to tray
• [x] Update waterproofing covers for adjusted mounting pattern and height

Parts to reprint:

• [x] Tray
• [x] Livox mount
• [x] Battery trays
• [x] Waterproofing covers