ROS2 Parameter Demo - Workflow Components

This project contains a ROS2-based ultrasonic data acquisition and processing system with real-time visualization and parameter control capabilities.

Overview

The system consists of five main ROS2 nodes that work together:

1. Publisher Node (publisher.py) - Interfaces with Vitesse hardware to acquire ultrasonic A-scan data
2. Processor Node (processor.py) - Processes raw A-scan data and displays real-time visualizations
3. Controller Node (controller.py) - Provides a GUI for monitoring and controlling system parameters
4. Forward Node (forward_node.py) - Exposes a Trigger service that moves the actuator forward when requested
5. Backward Node (backward_node.py) - Exposes a Trigger service that moves the actuator backward when requested

Architecture

┌─────────────────┐      Ascan Message      ┌─────────────────┐
│                 │ ──────────────────────> │                 │
│    Publisher    │                         │    Processor    │
│  (Hardware I/O) │                         │ (Visualization) │
└─────────────────┘                         └─────────────────┘
         ↑                                           ↑
         │                                           │
         │          ROS2 Parameters                  │
         └───────────────────┬───────────────────────┘
                             │
                    ┌────────────────┐
                    │   Controller   │
                    │     (GUI)      │
                    └────────────────┘

Components

Publisher Node (ascan_publisher)

Purpose: Interfaces with Vitesse ultrasonic hardware to acquire A-scan waveform data from up to 8 channels.

The publisher does not include code on temperature gathering. You should implement your own temperature aquisition code, and there is a segment in the code where you can do this.

Key Features:

• Configures and initializes Vitesse hardware via SPI interface
• Publishes A-scan data at a configurable rate (PRF)
• Supports multi-channel operation with individual channel enable/disable

Parameters:

• numAverages (int, 1-1000): Number of waveform averages for noise reduction
• channelsOnReceive (int[8]): Receive channel enable flags [1,0,0,0,0,0,0,0] (read-only)
• channelsOnDrive (int[8]): Channels on driver array (which channels to drive)
• numCycles (int, 1-3): Number of excitation cycles (read-only)
• recordLength (float): Recording duration in seconds (read-only)
• PRF (int, 1-5000 Hz): Pulse repetition frequency (read-only)
• phaseArrayMicro (int[8]): Per-channel phase delays in microseconds (read-only)
• delayArrayMicro (int[8]): Per-channel recording delays in microseconds (read-only)
• samplingMode (int, 16 or 24): Sampling mode (16 or 24 bit)
• pulseFrequency (int): Pulse frequency in Hz
• opFrequency (int): Operation frequency in Hz

Published Topics:

• /ascan (interfaces/msg/Ascan): Contains active channels, encoded waveform data, and temperature

Processor Node (ascan_processor)

Purpose: Processes raw A-scan data and provides real-time visualization with automatic peak detection.

Key Features:

• Real-time matplotlib-based visualization for active channels
• Automatic subplot arrangement based on number of active channels
• Peak detection and thickness calculation
• Multiple processing modes (first peak, multi-echo, zero crossing)
• Temperature-corrected measurements

Parameters (per channel, ch1-ch8):

• ch{N}_sampling_freq (int): Sampling frequency in Hz
• ch{N}_lowbound_time (int): Lower bound time in microseconds
• ch{N}_minimum_thickness (float): Minimum detectable thickness in mm
• ch{N}_wave_velocity (float): Wave velocity in m/s
• ch{N}_num_cycles (int): Number of cycles for processing
• ch{N}_signal_frequency (int): Signal frequency in Hz
• ch{N}_threshold_snr (float): SNR threshold in dB
• ch{N}_noise_width (int): Noise calculation window width
• ch{N}_calibration_index (int): Calibration reference index
• ch{N}_firstPeak (bool): Enable first peak detection mode
• ch{N}_multiEcho (bool): Enable multi-echo mode
• ch{N}_zeroCrossing (bool): Enable zero crossing detection
• ch{N}_temperatureCorrected (bool): Enable temperature correction

Subscribed Topics:

• /ascan (interfaces/msg/Ascan): Receives waveform data from publisher

Controller Node (parameter_manager_gui)

Purpose: Provides a PyQt5-based GUI for real-time parameter monitoring and control.

Key Features:

• Automatic discovery of ROS2 nodes and their parameters
• Tabbed interface with separate tabs for each active channel
• Parameter filtering based on configuration file
• Support for various parameter types (sliders, spinboxes, checkboxes)
• Real-time parameter updates with visual feedback
• Configurable display names and parameter bounds
• Buttons to control actuation of motor driver

Configuration (config.json):

• multipleTabs: Enable/disable tabbed interface
• whitelist: Enable parameter whitelisting
• hideReadOnlyParameters: Hide read-only parameters
• whitelistNodes: List of nodes to display
• whitelistParameters: Parameters to show per node
• parameterDisplayNames: Custom display names for parameters
• parameter_bounds: Min/max bounds for numeric parameters

Calibration Functionality

Purpose: The controller includes a calibration mode that temporarily changes the publisher's numAverages parameter to a predetermined number, collects averaged A-scan measurements, and then computes a corrected wave velocity.

How it is used:

• Place the EMAT connected to the first enumerated channel on top of your calibration block
• Enter the calibration block's thickness in the controller GUI
• Start calibration, which sets numAverages to 100 on the active publisher
• Wait a fixed delay for the hardware to apply the averaging setting
• Collect a series of averaged thickness measurements from the A-scan stream
• Compute a calibrated speed of sound value based on the known thickness and measured average thickness
• Apply the calibrated wave_velocity value to the processor channels

Calculation:

• The controller records the average measured thickness from the acquired A-scan data

• It then computes the corrected speed of sound as:

  calibrated_speed = current_wave_velocity * (known_thickness / measured_average_thickness)

• This updated speed is applied to all processor channels so subsequent thickness calculations use the calibrated ultrasonic velocity.

Channel Numbering

The system uses 1-based channel numbering (1-8) for user-facing interfaces:

• Channel parameters are named ch1_* through ch8_*
• Display shows "Channel 1" through "Channel 8"
• The channelsOnReceive parameter uses array indices 0-7 internally but presents channels as 1-8 to users

Message Format

Ascan Message

int32[] active_channels    # List of active channel numbers (1-8)
string[] ascan_data       # Base64-encoded waveform data for each active channel
float32 temperature       # Current temperature reading

Actuation Nodes (forward_node, backward_node)

Usage:

• Start either node with ros2 run ros_parameter_demo forward or ros2 run ros_parameter_demo backward
• The controller GUI exposes "Actuate Forward" and "Actuate Backward" buttons which invoke the corresponding services and display the response in the status bar.

Dependencies

• ROS2 Humble or later (tested on Jazzy) (Desktop Variant is required for processor and controller)
• Vitesse ultrasonic system (for publisher)

Installation

1. Under the project root folder, run

colcon build

to build all the packages.

Usage

Starting the System

1. Launch the publisher node (requires Vitesse hardware):

ros2 run ros_parameter_demo publisher

2. Launch the processor node for visualization:

ros2 run ros_parameter_demo processor

3. Launch the controller GUI:

ros2 run ros_parameter_demo controller

4. If you have the actuator peripheral, launch the forward and backward nodes in separate terminals:

ros2 run ros_parameter_demo forward

ros2 run ros_parameter_demo backward

Configuring Channels

To enable specific receive channels, modify the channelsOnReceive parameter in the publisher file. For example:

• [1,0,0,0,0,0,0,0] - Only channel 1 active
• [1,0,1,1,0,0,0,0] - Channels 1, 3, and 4 active
• [1,1,1,1,1,1,1,1] - All 8 channels active

Processing Modes

Each channel can operate in different processing modes:

• First Peak: Detects the first significant peak in the waveform
• Multi-Echo: Processes multiple reflections
• Zero Crossing: Uses zero-crossing detection for improved accuracy
• Temperature Corrected: Applies temperature compensation to measurements

Note: First Peak and Multi-Echo modes are mutually exclusive.

If you set both in the controller, the processor falls back to which none of the four parameters are set.

Configuration Files

• config.json: Controller GUI configuration
• Channel parameters can be saved/loaded via ROS2 parameter services

Troubleshooting

1. No visualization appears: Ensure at least one channel is enabled in channelsOnReceive
2. Controller doesn't show parameters: Controller won't show anything until the publishing node is on. Check that nodes are running and config.json whitelist is correct.
3. Hardware errors: Verify Vitesse device is connected and permissions are set correctly.

Future Enhancements

• Add data logging capabilities
• Implement parameter presets
• Add export functionality for processed data
• Support for additional processing algorithms
• Integration with ROS2 bag recording