Project RoboSnomo

Converting a 1976 Polaris Colt into a fully autonomous vehicle
70s mechanical soul meets 2020s artificial intelligence

67
AI TOPS
500
kbps CAN Bus
1976
Polaris Colt
3
System Layers

Project robosnomo: Technical Overview

Project RoboSnomo represents a unique convergence of vintage mechanical engineering and modern autonomous vehicle technology. We are converting a 1976 Polaris Colt snowmobile into a fully autonomous vehicle using a Tesla-inspired three-layer architecture, implemented at a hobbyist-plus engineering level.

Architecture Philosophy

The system is designed around three distinct layers, each with specific responsibilities and communication protocols:

Layer 1: The Brain (AI & Perception)

Hardware: NVIDIA Jetson Orin Nano Super (67 TOPS AI performance)

Functions: Stereo vision processing, object detection (YOLOv8), semantic segmentation, path planning, sensor fusion, high-level decision making

Acquired

Layer 2: The Heart (Engine Control)

Hardware: Speeduino v0.4 ECM (STM32F407 preferred for dual CAN bus)

Functions: 2-stroke engine management, RPM monitoring, temperature sensing, fuel injection control, telemetry reporting to AI layer

Sourcing

Layer 3: The Muscle (Actuation)

Hardware: Industrial linear actuators (400-1000 lbs force), high-torque servos

Functions: Steering control (±30° range), hydraulic brake actuation, throttle cable control, position feedback

Sourcing

Communication Backbone: CAN Bus

All layers communicate via a 500 kbps CAN 2.0B network, providing deterministic real-time performance with <2ms worst-case latency for critical commands. CAN bus offers proven automotive-grade reliability with built-in error detection, fault confinement, and priority-based arbitration.

Development Timeline

  • Winter 2025: Hardware procurement, Jetson development environment setup, CAN bus bench testing
  • Spring 2025: Core systems integration, Speeduino ECM installation, actuator mounting and testing
  • Summer 2025: Vision system calibration, AI model training on winter dataset, sensor fusion implementation
  • Fall 2025: Progressive field testing (tethered → low-speed → full autonomous), safety validation

Current Status

Architecture Design
Complete 3-layer system design
Jetson Orin Nano
Hardware acquired (1TB model)
Component Sourcing
ECM, actuators, vision sensors
Software Development
Vision pipeline, control systems

Layer 1: The Brain - NVIDIA Jetson Orin Nano Super

Compute Specifications

AI Performance
67 TOPS
INT8 sparse, Super Mode enabled
GPU Architecture
NVIDIA Ampere
1,024 CUDA cores, 32 Tensor cores
CPU
6-core ARM Cortex-A78AE
1.7 GHz (Super Mode), 64-bit ARMv8.2
Memory
8 GB LPDDR5
102 GB/s bandwidth (Super Mode)
Storage
1 TB NVMe SSD
M.2 2280 PCIe 3.0 x4
Power Consumption
25W MaxN Mode
Configurable 7W-25W power profiles

Camera & Vision Interfaces

MIPI CSI-2 Connectors: 2x 22-pin connectors supporting up to 6 simultaneous camera streams

  • CAM0: 1x 2-lane CSI interface
  • CAM1: 1x 4-lane CSI interface (configurable as 2x 2-lane)
  • Maximum Resolution: 4K @ 90 FPS with compatible sensors
  • Image Signal Processor: ISP 6.x with hardware-accelerated debayering, HDR, noise reduction

I/O Capabilities

  • USB: 1x USB-C 3.2 (10 Gbps) + 4x USB-A 3.2 ports
  • Ethernet: 1x Gigabit Ethernet (10/100/1000 Mbps)
  • GPIO: 40-pin expansion header (Raspberry Pi compatible layout) with I2C, SPI, UART, PWM
  • PCIe: Gen 3 support (1x x4 + 1x x2 or 2x x1 lanes)
  • DisplayPort: 1x DP 1.2 output (4K @ 30 Hz max)

CAN Bus Integration

Implementation: MCP2515 SPI-to-CAN controller + MCP2551 transceiver

Software Stack: SocketCAN Linux driver, python-can library for application layer

# SPI Connections (Jetson 40-pin header)
MCP2515 VCC → Pin 1 (3.3V)
MCP2515 GND → Pin 6 (Ground)
MCP2515 SCK → Pin 23 (SPI1_SCK)
MCP2515 MOSI → Pin 19 (SPI1_MOSI)
MCP2515 MISO → Pin 21 (SPI1_MISO)
MCP2515 CS → Pin 24 (SPI1_CS0)
MCP2515 INT → Pin 18 (GPIO for interrupts)

Environmental Specifications

  • Operating Temperature: -25°C to +90°C (junction temperature)
  • Recommended Range: 0°C to 50°C for standard applications
  • Winter Operation: Suitable for snowmobile use with proper enclosure and thermal management
  • Cooling: Active cooling (fan) required for sustained 25W MaxN mode

Software & AI Framework Support

  • JetPack SDK: Version 6.2 (Ubuntu 22.04 L4T base)
  • CUDA: Version 12.6 with cuDNN and cuBLAS libraries
  • Deep Learning: TensorFlow 2.15, PyTorch 2.x, TensorRT optimization
  • Computer Vision: OpenCV with CUDA acceleration, VisionWorks SDK, DeepStream
  • ROS Support: ROS 2 Humble for robotics middleware (sensor fusion, path planning)

Layer 2: The Heart - Speeduino ECM

Hardware Platform

Recommended: STM32F407-based Speeduino (not Arduino Mega) for native dual CAN bus support

Microcontroller
STM32F407VGT6
168 MHz ARM Cortex-M4F
Flash Memory
1 MB
4x larger than Arduino Mega
SRAM
192 KB
24x larger than Mega
CAN Controllers
Dual CAN (CAN0 + CAN1)
Native hardware support
Injector Outputs
4 channels @ 2A each
High-Z injectors only
Ignition Outputs
4 channels (5V/12V)
Logic-level for CDI trigger

2-Stroke Engine Configuration

Challenge: Speeduino is optimized for 4-stroke engines. 2-stroke single-cylinder requires configuration workarounds.

Recommended Configuration

  • Displacement: Enter half of actual engine displacement (e.g., 100cc for 200cc engine)
  • Cylinders: Set to 2 (even though it's single-cylinder)
  • Stroke: 2-stroke mode
  • Injectors: 1 (single injector)
  • Spark Mode: Single channel or wasted spark
  • Load Algorithm: Alpha-N (TPS-based) recommended over Speed Density due to expansion chamber pressure pulses

Rationale: Most 2-stroke single-cylinder engines provide 1 trigger pulse per crankshaft revolution (360°). Speeduino's "Basic Distributor" mode expects 1 pulse per 720°, causing RPM to read at 2x actual speed. Configuring as a 2-cylinder engine compensates for this.

Sensor Inputs

Sensor Type Voltage Range Purpose
CLT (Coolant Temp) NTC Thermistor 0-5V analog Engine protection, warmup enrichment
IAT (Intake Air Temp) NTC Thermistor 0-5V analog Density compensation, fuel corrections
TPS (Throttle Position) 3-wire Potentiometer 0-5V analog Alpha-N load source, acceleration detection
RPM/Crank Position Hall Effect or VR 0-5V or 0-12V digital Engine speed, ignition timing reference
O2 Sensor (Optional) Wideband Controller 0-5V analog Closed-loop fuel tuning, autotune

Fuel & Ignition Management

Fuel Mapping

  • VE Table Resolution: 16x16 grid (256 cells)
  • Axes: RPM (X-axis) vs Load (Y-axis, TPS % for Alpha-N)
  • Interpolation: 3D interpolation for smooth transitions between cells
  • Corrections: Coolant temp, air temp, acceleration enrichment, cranking enrichment

Ignition Timing

  • Advance Table: 16x16 grid matching fuel table axes
  • Range: Typically -10° to +40° BTDC (user-configurable)
  • Dwell Control: Variable dwell map with battery voltage compensation
  • CDI Integration: Use 5V logic output to trigger stock CDI (maintains proven high-energy spark)

CAN Bus Communication

Protocol: OBD2 standard PIDs + custom message definitions

Telemetry to Jetson (100 Hz):

  • Engine RPM (PID 0x0C)
  • Coolant temperature (PID 0x05)
  • Intake air temperature (PID 0x0F)
  • Throttle position (PID 0x11)
  • Battery voltage, error codes, injector duty cycle

Commands from Jetson:

  • Throttle position setpoint (autonomous mode)
  • Engine enable/disable (safety override)

TunerStudio Configuration

All ECM parameters are configured via TunerStudio MS software (Windows/Mac/Linux):

  • Connection: Serial over USB (115200 baud)
  • Real-Time Tuning: Modify fuel/ignition tables while engine running
  • Autotune: Laptop-based algorithm automatically adjusts VE table using wideband O2 feedback
  • Data Logging: 10-20 samples/second for post-analysis

Layer 3: The Muscle - Actuation Systems

Steering Actuation

Recommended: Progressive Automations PA-04-12-400

Force Rating
400 lbs
1780 N push/pull force
Stroke Length
12 inches
305 mm total travel
Speed
20-30 mm/s
Responsive navigation control
Voltage
12V DC
Matches snowmobile electrical
Current Draw
10-12A peak
6-8A typical operation
IP Rating
IP66
Dust-tight, water jet resistant
Temperature Range
-26°C to +65°C
Adequate for most winter use
Position Feedback
Potentiometer
0-5V analog output

Professional Upgrade Option: LINAK LA77 or TiMOTION MA2 (6000-10000N force, IP69K rated, CAN bus interface, -40°C to +85°C, $600-1500)

Brake Actuation

Recommended: Progressive Automations PA-04-6-400

Force Calculation: Target brake pressure of 1200 PSI requires ~530 lbf (2360N). A 400 lb actuator is adequate for most scenarios; 800-1000 lb provides safety margin for emergency stops.

Force Rating
400 lbs
Adequate for hydraulic actuation
Stroke Length
6 inches
152 mm travel for full brake range
Speed
40-50 mm/s
Fast response for emergency stops
Response Time
<100ms
From CAN command to actuation

Safety Feature: Consider spring-applied hydraulic release (SAHR) brake system for true fail-safe operation—automatic braking on power loss.

Throttle Control

High-Performance: Dynamixel MX-106T

Torque
84 kg·cm
8.4 N·m holding torque
Position Resolution
4096 positions
12-bit absolute encoder
Communication
RS-485
Daisy-chain multiple servos
Feedback
Full telemetry
Position, velocity, current, temp

Budget Alternative: Hitec HS-7950TH RC servo (32 kg·cm torque, standard RC PWM, $100-120, weatherproof with enclosure)

Note: Dynamixel rated -5°C to +80°C; requires heated enclosure for extreme cold snowmobile operation.

Control Interfaces

Interface Best For Advantages Disadvantages
CAN Bus / CANopen Professional multi-actuator system Position control, diagnostics, standardized protocol Requires CAN-enabled actuators (higher cost)
RS-485 Dynamixel servo motors Long-distance, robust, multiple devices on one bus Requires Dynamixel protocol library
PWM Budget RC servos, proof-of-concept Simple, widely supported No built-in feedback (requires separate sensors)
Analog (0-5V or 0-10V) Industrial actuators without digital interface Simple wiring, reliable No protocol-based diagnostics

Power Requirements

Peak Current Draw (All Systems):

  • Steering actuator: 10-12A peak
  • Brake actuator: 10-12A peak
  • Throttle servo: 2-5A peak
  • Jetson Orin Nano: 5A typical (25W MaxN mode @ 12V with DC-DC converter)
  • Total System: ~37A peak draw

Battery Recommendation:

  • Budget: 60Ah AGM battery (Optima YellowTop D31A, $250-300)
  • Performance: 50Ah LiFePO4 with heating blanket ($600-800) for better cold-weather performance
  • Cold Weather Adjustment: Battery capacity drops 20-40% at -20°C; size accordingly

Mounting & Mechanical Integration

  • Linkage Type: Clevis (dual-pivot) mounting most common for linear actuators
  • Rod Ends: Use quality spherical bearings (robosnomo COM-series, QA1 Precision) to minimize backlash
  • Backlash Target: <5mm at ski for steering precision
  • Mechanical Advantage: Optimize linkage geometry to reduce actuator force requirements
  • Vibration Damping: Rubber bushings at pivot points, isolate electronics with Lord Micromounts
  • Materials: Aluminum 6061-T6 (lightweight, corrosion-resistant), stainless steel for high-stress applications

CAN Bus Integration & Communication

Protocol Specifications

Protocol
CAN 2.0B
ISO 11898 standard
Bit Rate
500 kbps
Optimal speed/reliability balance
Identifier Format
11-bit Standard
2048 unique message IDs
Max Cable Length
100 meters
At 500 kbps with proper termination
Worst-Case Latency
<2 ms
For highest priority messages
Bus Utilization Target
<80%
Maintains deterministic timing

Physical Layer

Differential Signaling

  • Recessive State (Logic 1): CAN-H = 2.5V, CAN-L = 2.5V, Differential = 0V
  • Dominant State (Logic 0): CAN-H = 3.5V, CAN-L = 1.5V, Differential = 2.0V
  • Principle: Dominant (0) overrides recessive (1), enabling priority-based arbitration

Wiring Requirements

  • Cable Type: Shielded twisted pair, 120Ω characteristic impedance
  • Twist Rate: Minimum 40 twists/meter (ideally 1 twist per 25mm)
  • Wire Gauge: 20-24 AWG for automotive applications
  • Recommended Cable: Belden 3084A, DeviceNet cable, or automotive-grade CAN cable
  • Termination: 120Ω resistors at both ends of bus only (measure 60Ω total)
  • Stub Length: Keep actuator/sensor connections under 30cm maximum
  • Shielding: Ground shield at ONE point only to prevent ground loops

Network Topology

[Jetson Orin Nano]────────[CAN BUS 500 kbps]────────[Speeduino ECM]
(120Ω) (120Ω)
│ │
├─── MCP2515 SPI-to-CAN │
│ │
[Vision/Radar] [Actuator Nodes]
│ ├─ Steering (0x200)
│ ├─ Brake (0x210)
│ └─ Throttle (0x220)

[GPS/IMU Module]

Message ID Architecture (Priority-Based)

ID Range Subsystem Priority Examples
0x001-0x0FF Safety & Emergency Highest Emergency stop (0x001), Kill switch (0x002)
0x100-0x1FF ECM Critical Data High Engine RPM (0x100), Coolant temp (0x110)
0x200-0x2FF Actuator Commands High Steering (0x200), Brake (0x210), Throttle (0x220)
0x300-0x3FF Vision/Sensor Data Medium Obstacle detection (0x300), GPS (0x310)
0x400-0x4FF Telemetry/Diagnostics Low Status messages (0x400), Logs (0x410)
0x500-0x7FF Future Expansion Variable System heartbeat (0x500), Reserved

Note: Lower ID numbers have higher priority. During arbitration, ID 0x001 will always win over ID 0x100.

Message Timing & Frequency

Message Type ID Frequency Sender Receivers
Emergency Stop 0x001 Event-driven Any node All
Engine RPM 0x100 100 Hz (10ms) Speeduino Jetson, Android App
Steering Command 0x200 50 Hz (20ms) Jetson Steering Actuator
Brake Command 0x210 50 Hz (20ms) Jetson Brake Actuator
Obstacle Detected 0x300 Event-driven Jetson All
System Heartbeat 0x500 10 Hz (100ms) Jetson All actuators

Error Handling & Fault Confinement

CAN bus includes five built-in error detection mechanisms:

  1. Bit Error: Node detects mismatch between transmitted and received bit
  2. Stuff Error: More than 5 consecutive identical bits (violates bit stuffing rule)
  3. CRC Error: Cyclic redundancy check fails
  4. Form Error: Fixed-format fields contain illegal values
  5. Acknowledgment Error: No node acknowledges message reception

Three Error States

  • Error Active: Normal operation (TEC < 128 && REC < 128), sends active error frames
  • Error Passive: Degraded mode (128 ≤ TEC or REC < 256), sends passive error frames
  • Bus-Off: Node disconnected (TEC ≥ 256), requires recovery sequence

Safety Feature: Faulty nodes automatically remove themselves from the bus before disrupting communication.

Safety Heartbeat Implementation

Concept: Jetson sends periodic "alive" message every 100ms. Actuators expect heartbeat; if missing >300ms, enter safe mode (stop movement, engage brake).

# Python example: Jetson heartbeat sender
import can

bus = can.interface.Bus(channel='can0', bustype='socketcan')
msg = can.Message(arbitration_id=0x500, data=[0x01])
task = bus.send_periodic(msg, 0.1) # 100ms period, kernel-managed

Actuator Response: If heartbeat timeout exceeds 300ms, actuator controller immediately stops all motors, engages brake, and enters fail-safe mode until heartbeat resumes.

Vision System & AI Models

Stereo Camera System

Recommended: Arducam IMX477 Stereo Camera Kit

Sensor
Sony IMX477
12.3 MP backside illuminated
Resolution
1080p @ 240 FPS
4K @ 60 FPS max capability
HDR Mode
60 FPS HDR
Critical for high-contrast snow
Baseline
20-30 cm
Effective range: 2-25 meters
Synchronization
Hardware Sync
Arducam kit includes sync board
Cost
~$250
Includes 2 cameras + sync board

Vision Processing Pipeline

  1. Image Acquisition: Synchronized stereo frame capture at 60 FPS (720p for real-time performance)
  2. Rectification: Transform images to align epipolar lines (one-time calibration matrix applied)
  3. Stereo Matching: SGBM (Semi-Global Block Matching) algorithm generates disparity map
  4. Depth Estimation: Convert disparity to 3D point cloud (depth = baseline × focal_length / disparity)
  5. Object Detection: YOLOv8 identifies obstacles (trees, rocks, other vehicles)
  6. Semantic Segmentation: Classify terrain (snow, ice, trail, vegetation)

Performance: End-to-end latency of 44-78ms for full 1080p pipeline. Using 720p resolution achieves 60+ FPS for real-time autonomous control.

Object Detection Models

Recommended: YOLOv8n (Nano) with INT8 Quantization

Model
YOLOv8n-INT8
Smallest, fastest YOLO variant
FPS on Jetson Orin Nano
65 FPS
With TensorRT optimization
Power Consumption
7.4 W
Most energy-efficient option
Accuracy Loss
-3% mAP
Minimal degradation from FP32

Custom Training: Retrain on winter-specific dataset (15,000+ images of snow, trees, rocks, trails, other snowmobiles). Use RSOD (Remote Sensing Object Detection) dataset as starting point.

Semantic Segmentation

Recommended: MFA-DeepLabv3+ (Multi-Feature Aggregation)

  • FPS on Jetson Orin Nano: 36.4 FPS (real-time capable)
  • Purpose: Classify each pixel as snow, ice, rock, vegetation, trail, sky
  • Integration: Combines with stereo depth for 3D terrain understanding
  • Training: Use Cityscapes dataset augmented with winter off-road images

Path Planning Algorithms

Hybrid Approach (Recommended)

  • Global Planner: A* algorithm on GPS waypoint map (runs at 1 Hz, generates optimal route)
  • Local Planner: DWA (Dynamic Window Approach) for real-time obstacle avoidance (10-20 Hz)
  • Rationale: A* provides optimal long-range path; DWA handles dynamic obstacles detected by vision

Alternative: RRT (Rapidly-exploring Random Tree)

  • Speed: 0.23s planning time (very fast)
  • Trade-off: Sub-optimal paths (longer routes)
  • Use Case: Fallback when A* takes too long in complex environments

Sensor Fusion Architecture

Fusion Rate: 100 Hz using Extended Kalman Filter (EKF)

Sensors Integrated:

  • Stereo Vision: 3D obstacle positions, terrain classification (20 Hz)
  • 77GHz Radar: Long-range obstacle detection (200m range), penetrates snow/fog (10 Hz)
  • IMU (BNO085): Acceleration, gyroscope, magnetometer (100 Hz)
  • GPS (ZED-F9P RTK): High-precision positioning (10 Hz, <2cm accuracy with RTK correction)

Software: ROS 2 robot_localization package implements EKF fusion, outputs fused pose estimate at 100 Hz.

Radar Sensor (Recommended)

Budget Option: Texas Instruments AWR1843 (77 GHz)

  • Frequency: 77 GHz (20x better range resolution than 24 GHz)
  • Range: 200-300 meters
  • Range Resolution: 4 cm (vs 75 cm for 24 GHz)
  • Snow/Fog Performance: Radar >> LiDAR > Camera in adverse weather
  • Interface: UART/SPI to Jetson
  • Cost: ~$300 (development kit)

Edge AI Optimization

TensorRT Optimization Pipeline

  1. Train model in PyTorch/TensorFlow
  2. Export to ONNX format
  3. Convert to TensorRT engine with INT8 calibration
  4. Benchmark: Measure FPS and accuracy on Jetson
  5. Deploy: Load TensorRT engine in Python/C++ inference code

Performance Gains: 3-15x speedup depending on model and precision (FP32 → FP16 → INT8)

INT8 Quantization Benefits

  • Speed: 2-4x faster inference vs FP32
  • Power: 16% reduction in energy consumption
  • Accuracy: Typically <3% mAP loss for well-calibrated models
  • Memory: 4x smaller model size (fits in cache, reduces bandwidth)

Winter-Specific Challenges & Solutions

Challenge Impact Solution
Low Contrast (White Snow) Stereo matching struggles with textureless surfaces Use HDR imaging (IMX477 supports 60 FPS HDR), radar fusion
Sun Reflections on Snow Overexposure, false obstacle detection HDR capture, polarizing filters, adaptive exposure control
Hidden Obstacles (Under Snow) Vision cannot detect buried rocks/logs Radar penetrates snow surface, combines with GPS trail map
Variable Lighting (Sunrise/Sunset) Inconsistent detection performance Train models on diverse lighting conditions, use normalized image preprocessing
Falling Snow/Fog Obscures vision, false positives Radar primary sensor in poor visibility, reduce speed in degraded mode

Complete Bill of Materials

Layer 1: AI & Perception

Component Model / Specification Quantity Est. Cost Status
Main Computer NVIDIA Jetson Orin Nano Super (1TB) 1 $599 Acquired
Stereo Cameras Arducam IMX477 Stereo Kit (12.3MP, HDR) 1 kit $250 Sourcing
Radar Sensor Texas Instruments AWR1843 (77 GHz) 1 $300 Planned
IMU BNO085 9-DOF (100 Hz fusion) 1 $20 Planned
GPS (RTK) u-blox ZED-F9P (<2cm accuracy) 1 $200 Planned
CAN Controller MCP2515 SPI-to-CAN + MCP2551 Transceiver 1-2 $15 ea Planned
Enclosure Weatherproof IP65+ (Pelican or similar) 1 $60 Planned

Layer 2: Engine Control

Component Model / Specification Quantity Est. Cost Status
ECM Board Speeduino v0.4 (STM32F407-based preferred) 1 $150 Sourcing
CAN Transceiver MCP2551 or TJA1050 (if not on board) 1 $5 Planned
Coolant Temp Sensor NTC Thermistor (automotive-grade) 1 $15 Planned
Intake Air Temp Sensor NTC Thermistor 1 $15 Planned
Throttle Position Sensor 3-wire potentiometer (0-5V) 1 $20 Planned
Wideband O2 Sensor AEM 30-0300 X-Series + Controller 1 $200 Planned
Fuel Injector High-Z (12-14Ω), sized for engine displacement 1 $50 Planned

Layer 3: Actuation

Component Model / Specification Quantity Est. Cost Status
Steering Actuator Progressive Automations PA-04-12-400 (400 lbs, 12", IP66) 1 $450 Sourcing
Brake Actuator Progressive Automations PA-04-6-400 (400 lbs, 6") 1 $380 Sourcing
Throttle Servo Dynamixel MX-106T (84 kg·cm, RS-485) 1 $480 Planned
Position Sensors Redundant Hall effect + Potentiometer per actuator 3 sets $60 Planned
Rod Ends / Clevis robosnomo COM-series spherical bearings 6 $120 Planned

Communication & Wiring

Component Specification Quantity Est. Cost
CAN Bus Cable Belden 3084A or DeviceNet, 120Ω shielded twisted pair 10 meters $50
120Ω Termination Resistors 1/4W, 1% tolerance 4 (2 spares) $2
Weatherproof Connectors Deutsch DT or TE Superseal series 10 $50
Wiring Harness Materials 18-20 AWG wire, heat shrink, split loom 1 set $100

Power System

Component Specification Quantity Est. Cost
Battery 60Ah AGM (Optima YellowTop D31A) or 50Ah LiFePO4 1 $280 / $700
DC-DC Converter (Jetson) 12V to 19V, 5A+ rated (for Jetson power) 1 $40
Fuses & Circuit Breakers Automotive blade fuses, 15A-30A 6 $30
Kill Switch (Hardware) Emergency stop relay, latching 1 $40

Cost Summary

Layer 1 (Brain)
~$1,444
Jetson + vision + sensors
Layer 2 (Heart)
~$455
Speeduino + sensors
Layer 3 (Muscle)
~$1,490
Actuators + linkages
Communication
~$202
CAN bus + wiring
Power System
~$390
Battery + distribution
Total Estimate
~$3,981
Hobbyist-plus system (AGM battery)

Note: Costs exclude vintage snowmobile chassis, mechanical fabrication materials, and tools. Budget assumes hobbyist-plus components; professional-grade system with LINAK actuators and LiFePO4 battery would be ~$5,500-6,000.

Safety Systems & Testing Protocols

Critical Safety Features

1. Hardware Emergency Stop (Kill Switch)

  • Implementation: Latching relay wired directly to ignition circuit, independent of all software
  • Activation: Physical button accessible to operator, wireless remote backup
  • Response Time: Immediate ignition cut (<10ms electrical propagation)
  • Failsafe: Power loss opens relay, killing engine (fail-safe state)
  • Manual Override: Retained manual brake lever and throttle cable for human takeover

2. CAN Bus Watchdog & Heartbeat

  • Jetson Heartbeat: Broadcast 0x500 message every 100ms (kernel-managed for reliability)
  • Actuator Timeout: If no heartbeat received for >300ms, enter fail-safe mode
  • Fail-Safe Actions: Stop all actuator movement, engage brake, center steering, throttle to idle
  • Recovery: Once heartbeat resumes for >1 second, allow autonomous control to resume

3. Redundant Position Sensors

  • Dual Sensors per Actuator: Hall effect encoder + analog potentiometer
  • Cross-Check: If sensors disagree by >5%, flag fault and enter limp mode
  • Rationale: Prevents runaway actuator due to single sensor failure

4. Vision System Failure Detection

  • Frame Loss Monitor: If camera FPS drops below 20 for >2 seconds, declare vision failure
  • Radar Fallback: Switch to radar-only navigation in degraded visual mode (reduced speed)
  • GPS Trail Mode: Follow pre-mapped GPS waypoints if both vision and radar compromised
  • Complete Failure: If all sensors fail, execute emergency stop sequence

5. Thermal & Power Monitoring

  • Jetson Temperature: Monitor GPU/CPU temps; throttle AI workload if >80°C, shut down if >95°C
  • Actuator Overcurrent: Monitor motor current; stop if >120% rated current for >5 seconds
  • Battery Voltage: Alert at <11.5V, enter low-power mode at <11.0V, emergency stop at <10.5V

6. Geofencing (Software Boundaries)

  • GPS Perimeter: Define allowed operating area as polygon on map
  • Boundary Action: If GPS position exits perimeter, stop forward movement and alert operator
  • Use Case: Prevent autonomous operation on roads, private property, or hazardous areas

Testing Protocols

Phase 1: Bench Testing (All Systems)

  1. Power-On Test: Verify all voltage rails, check for shorts, measure current draw
  2. CAN Bus Communication: Use candump/cansend to verify message transmission/reception
  3. Sensor Validation: Read all sensor values, verify ranges (CLT, IAT, TPS, position feedback)
  4. Actuator Stroke Test: Command full extension/retraction, verify position feedback accuracy
  5. Emergency Stop Test: Trigger kill switch, verify immediate ignition cut and actuator stop
  6. Jetson AI Performance: Run YOLOv8 inference, measure FPS and latency with test images

Success Criteria: All sensors reading within expected ranges, actuators respond to commands within 50ms, zero CAN bus errors over 1 hour operation, emergency stop <100ms response.

Phase 2: Static Engine Testing (Non-Moving)

  1. Speeduino Startup: Power on ECM, verify TunerStudio connection, check sensor readings
  2. Fuel System Priming: Test injector firing (engine not running), verify spray pattern
  3. Ignition Timing: Crank engine, use timing light to verify timing marks align with TunerStudio setting
  4. First Start: Use conservative fuel/timing maps, start engine, verify idle stability
  5. Sensor Validation: Rev engine, confirm RPM, CLT, TPS readings update correctly on CAN bus
  6. Autonomous Throttle Test: Command throttle position via CAN, verify servo response (engine running, stationary)

Success Criteria: Engine starts reliably, idles smoothly, all telemetry accurate, autonomous throttle control responsive without oscillation.

Phase 3: Tethered Testing (Limited Range)

  1. Steering Actuation: Test steering commands at standstill, verify ski movement matches command
  2. Brake Actuation: Test brake engagement, measure stopping force with scale
  3. Low-Speed Movement: Tether snowmobile to fixed point (10m rope), test forward/reverse/steering
  4. Vision Pipeline: Run stereo cameras + YOLO, verify object detection of obstacles in field of view
  5. Heartbeat Timeout Test: Disconnect Jetson CAN connection mid-operation, verify actuators enter fail-safe

Success Criteria: Actuators respond correctly to commands, vision system detects obstacles, fail-safe engages within 300ms of heartbeat loss.

Phase 4: Low-Speed Autonomous Testing

  1. Open Area Test: Flat snow field, no obstacles, clear weather
  2. Speed Limit: Maximum 5 mph (8 km/h) for initial tests
  3. Observer Present: Operator with kill switch remote walks alongside
  4. Waypoint Navigation: Follow simple GPS path (straight line, gentle turns)
  5. Obstacle Avoidance: Place cones in path, verify autonomous swerve or stop behavior
  6. Data Logging: Record all CAN messages, vision detections, GPS positions for post-analysis

Success Criteria: Completes waypoint path without human intervention, avoids all obstacles, stays within 2m of intended GPS path, zero safety system false triggers.

Phase 5: Progressive Speed Increases

  1. Incremental Speed: 5 mph → 10 mph → 15 mph → 20 mph over multiple test sessions
  2. Varied Terrain: Test on flat, gentle slopes, rough trails (progressively more challenging)
  3. Weather Conditions: Test in clear conditions first, then light snow, then poor visibility
  4. Emergency Stop Testing: Command emergency stop at each speed increment, measure stopping distance
  5. Sensor Fusion Validation: Verify radar and vision agree on obstacle positions

Success Criteria: Maintain stable control at each speed tier, obstacle detection reliable at increased speeds, stopping distance within safe limits for terrain.

Phase 6: Edge Case & Failure Mode Testing

  1. Single Sensor Failures: Disconnect camera, GPS, radar individually; verify graceful degradation
  2. Low Battery: Run until battery voltage triggers low-power mode, verify safe shutdown
  3. Extreme Cold: Test at -20°C to verify all components operational (actuators, battery, Jetson)
  4. Communication Loss: Simulate CAN bus wire disconnect, verify fail-safe engagement
  5. Mechanical Binding: Simulate actuator obstruction (steering blocked), verify overcurrent detection

Success Criteria: System enters safe mode for all single-point failures, no runaway behavior, operator alerted to fault via telemetry.

Safety Margins & Conservative Design

  • Actuator Force: Size actuators for 2x calculated force requirement (safety margin for icy conditions)
  • Speed Limits: Initial autonomous operation limited to 50% of maximum snowmobile speed
  • Obstacle Detection Range: Maintain 3x stopping distance margin (e.g., at 20 mph with 10m stop, detect obstacles at 30m)
  • Battery Capacity: Never discharge below 50% SoC to preserve battery life and maintain reserve
  • CAN Bus Utilization: Target <50% bus load (far below 80% limit) for timing headroom

Regulatory & Insurance Considerations

  • Off-Road Only: Not legal for on-road operation in most jurisdictions (no DOT approval)
  • Private Property: Conduct all testing on private land with owner permission
  • Liability Insurance: Consult with insurance provider; standard policies may not cover autonomous modifications
  • Safety Signage: Clearly mark vehicle as "AUTONOMOUS - TESTING IN PROGRESS"
  • Documentation: Maintain detailed logs of all tests, failures, and design changes for liability protection