ros2-assignments/doc/architecture/nodes/WheelDataSimulator.md

WheelDataSimulator (assignments::three::wheel_data_simulator_node)

The WheelDataSimulator node generates simulated wheel encoder/velocity data (std_msgs/msg/Float64MultiArray) based on configurable time-varying intervals. It publishes wheel values for a 4-wheel robot configuration that can follow constant, linear, or quadratic trajectories over time.

Implementation Details

Parameters

Parameter	Type	Default	Description
publish_rate	double	10.0	Publishing frequency in Hz
max_intervals	int	4	Maximum number of intervals per wheel
<wheel>.num_intervals	int	0	Number of intervals for each wheel
<wheel>.interval_<n>.*	various	-	Interval configuration (see Simulator)

Wheels Configured:

• wheel_fl - Front Left wheel
• wheel_fr - Front Right wheel
• wheel_rl - Rear Left wheel
• wheel_rr - Rear Right wheel

Constructor

DataSimulator()

• Initializes ROS2 node with name wheel_data_simulator
• Creates Simulator instance for value generation
• Creates publisher for simulated_wheel_data topic
• Sets up timer for periodic publishing

Core Functionality

void publish_wheel_data()

• Timer callback invoked at the configured publish rate
• Calculates elapsed time since node start
• Queries Simulator for current values of all 4 wheels
• Populates Float64MultiArray message with wheel values in order: [FL, FR, RL, RR]
• Publishes message to topic

ROS2 Interface

Publications

• simulated_wheel_data (std_msgs/msg/Float64MultiArray)
  • Publishes simulated wheel data at configured rate
  • Array contains 4 values: [front_left, front_right, rear_left, rear_right]

Usage Example

ros2 run g2_2025_odometry_pkg wheel_data_simulator_node --ros-args \
  -p publish_rate:=50.0 \
  -p wheel_fl.num_intervals:=1 \
  -p wheel_fl.interval_0.type:=linear \
  -p wheel_fl.interval_0.t_start:=0.0 \
  -p wheel_fl.interval_0.t_end:=10.0 \
  -p wheel_fl.interval_0.y_start:=0.0 \
  -p wheel_fl.interval_0.y_end:=5.0

Dependencies

• rclcpp - ROS2 C++ client library
• std_msgs - Standard message types
• Simulator - Internal simulation engine