Vehicle Simulator with J1939 CAN Support

Overview

The Vehicle Simulator (gva-vehicle-sim) is a comprehensive testing and development tool for the GVA (Generic Vehicle Architecture) platform. It provides realistic vehicle dynamics simulation with integrated J1939 CAN bus message generation, enabling hardware-in-the-loop testing without requiring physical vehicle hardware.

Benefits of J1939 Simulation for Message Generation

🎯 Development & Testing Advantages

1. Hardware-Independent Development

   • Develop and test GVA applications without physical CAN hardware
   • No need for expensive vehicle ECUs or test benches
   • Parallel development across multiple teams

2. Realistic Vehicle Behavior

   • Generates authentic J1939 Parameter Group Numbers (PGNs) and Suspect Parameter Numbers (SPNs)
   • Simulates realistic vehicle dynamics (speed, RPM, gear changes, braking)
   • Provides time-synchronized sensor data

3. Cost Reduction

   • Eliminates need for physical test vehicles in early development
   • Virtual CAN interface (vcan0) enables testing on any Linux workstation
   • Reduces wear and tear on physical hardware

4. Rapid Prototyping

   • Instant feedback loop for algorithm development
   • Easy scenario creation and replay
   • Configurable message rates and data patterns

5. Integration Testing

   • Validate J1939 gateway functionality
   • Test data flow from CAN to DDS topics
   • Verify HMI responsiveness to vehicle parameters

6. Reproducible Testing

   • Deterministic vehicle behavior
   • Repeatable test scenarios
   • Consistent baseline for regression testing

📊 J1939 Message Support

✅ Fully Supported PGNs (Implemented in Vehicle Simulator)

The vehicle simulator actively generates the following J1939 messages over CAN and publishes them to DDS via the gateway:

Detailed SPN List (All Supported Parameters)

Total: 15 PGNs, 33 SPNs actively simulated

🔲 Unsupported PGNs (Not Yet Implemented)

The following J1939 messages are not currently generated by the vehicle simulator. These represent potential future enhancements:

Why These Are Not Implemented

Total: 22 unsupported PGNs

🛠️ Technical Features

• OpenDRIVE Road Network Support: Follow realistic road geometry
• Automatic Transmission Simulation: Gear changes based on speed and throttle
• Physics-Based Dynamics: Acceleration, braking, steering with realistic constraints
• DDS Integration: Direct publishing to J1939 Automotive PSM topics
• Qt6 GUI: Real-time visualization and manual control

J1939 to DDS Gateway Architecture

The following sequence diagram illustrates the complete data flow from J1939 CAN bus messages through the gateway to DDS subscribers:

Sequence Diagram Explanation

1. Message Generation Phase

• Vehicle Simulator calculates realistic vehicle parameters based on driver inputs and physics
• Encodes parameters into J1939 CAN frames with proper PGN/SPN structure
• Transmits to virtual CAN interface (vcan0)

2. CAN Reception Phase

• SocketCanReader Qt thread continuously reads from CAN interface
• Validates CAN frame format (29-bit extended ID)
• Emits Qt signal with raw frame data

3. J1939 Decode Phase

• J1939Decoder extracts protocol information from CAN ID:
  • PGN: Parameter Group Number (identifies message type)
  • Source Address: ECU identifier (0-253)
  • Priority: Message urgency (0=highest, 7=lowest)
• Decodes data payload into individual SPNs using configuration:
  • Bit position and length
  • Scale factor and offset
  • Engineering units

4. DDS Publishing Phase

• Gateway publishes C_Parameter_Group_Definition (PGN metadata) on first occurrence
• For each SPN in the message:
  • Creates C_Parameter message with value and status
  • Adds timestamp and source identification
  • Publishes to DDS topic
• Periodic status updates (1 Hz) publish gateway health

5. Consumption Phase

• GVA applications (HMI, LDMX) subscribe to J1939 DDS topics
• Receive parameter updates via DDS middleware
• Update UI elements (speedometer, tachometer, gear display)

Protocol Details

J1939 CAN ID Structure (29-bit)

Bits 28-26: Priority (0-7)
Bit  25:    Reserved
Bit  24:    Data Page (DP)
Bits 23-16: PDU Format (PF)
Bits 15-8:  PDU Specific (PS) - group extension or destination
Bits 7-0:   Source Address (SA)

PGN = (DP << 16) | (PF << 8) | (PS if PF >= 240 else 0)

Example CAN Frame Decoding

CAN ID: 0x18F00400
Binary: 00011000111100000000010000000000

Priority:  0x6 (bits 28-26) = 6 (normal priority)
Reserved:  0   (bit 25)
DP:        0   (bit 24)
PF:        0xF0 (bits 23-16) = 240 (broadcast)
PS:        0x04 (bits 15-8)  = 4 (group extension)
SA:        0x00 (bits 7-0)   = 0 (engine controller)

PGN = (0 << 16) | (240 << 8) | 4 = 61444 (EEC1 - Engine Controller 1)

Quick Start

1. Build Vehicle Simulator

cd build
cmake ..
make gva-vehicle-sim

2. Setup Virtual CAN

sudo scripts/test/j1939/setup-vcan.sh

3. Start Vehicle Simulator

# GUI mode with OpenDRIVE track
./build/bin/gva-vehicle-sim \
  --domain=0 \
  --opendrive=data/opendrive/ZalaZONE_full.xodr \
  --can-interface=vcan0

# Headless mode with J1939 only
./build/bin/gva-vehicle-sim \
  --domain=0 \
  --can-interface=vcan0 \
  --headless

4. Start J1939 Gateway

./build/bin/gva-j1939-gateway \
  --domain=0 \
  --interface=vcan0 \
  --config=/etc/gva/j1939-config.json

5. Monitor with LDMX

./build/bin/ldmx
# Navigate to J1939 tab to see live parameters

Configuration

Vehicle Simulator Configuration

Create vehicle-sim-config.json:

{
  "j1939": {
    "enabled": true,
    "sourceAddress": 0,
    "gatewayResourceId": 1000,
    "updateRateHz": 10
  },
  "vehicle": {
    "maxSpeed": 120.0,
    "maxRpm": 6000,
    "gearRatios": [3.5, 2.5, 1.8, 1.3, 1.0, 0.8],
    "engineIdleRpm": 800
  }
}

J1939 Gateway Configuration

See /etc/gva/j1939-config.json for PGN/SPN definitions and scaling parameters.

Use Cases

1. HMI Development

• Develop vehicle dashboard without physical vehicle
• Test instrument cluster rendering and animations
• Validate warning/alarm thresholds

2. Algorithm Testing

• Test eco-driving algorithms with simulated fuel consumption
• Validate predictive maintenance logic
• Test autonomous driving decision-making

3. Integration Testing

• Verify end-to-end data flow: CAN → DDS → Application
• Test gateway performance under load
• Validate data synchronization across subsystems

4. Training & Demonstration

• Safe environment for operator training
• Customer demonstrations without vehicle
• Educational tool for GVA architecture

Performance Characteristics

Comparison: Physical vs. Simulated

Troubleshooting

Common Issues

CAN Interface Not Found

# Verify vcan0 exists
ip link show vcan0

# Recreate if needed
sudo scripts/test/j1939/setup-vcan.sh

No DDS Messages

# Check gateway is running
pgrep -a gva-j1939-gateway

# Verify domain ID matches
./build/bin/gva-j1939-gateway --domain=0
./build/bin/gva-vehicle-sim --domain=0

Gateway Not Decoding Messages

# Check CAN frames are being sent
candump vcan0

# Verify configuration file
cat /etc/gva/j1939-config.json

Reqest a demonstartion today.