RflyUdpRaw Module Documentation

Toolbox: RflySim Swarm

Introduction

One-sentence Description: Implements MAVLink data transmission and reception for multiple UAVs based on the UDP protocol, supporting both multi-vehicle simulation networking and real-vehicle swarm control.

This module serves as the core communication interface within the RflySim Swarm cluster toolchain, enabling simultaneous control command delivery and state data acquisition for multiple UAVs specified by an ID list. It is suitable for multi-vehicle simulation scenarios within the RflySim platform as well as for algorithm validation on real UAV clusters.

When real-flight mode is disabled, the module communicates via UDP with multiple CopterSim simulation processes running on the local or remote host, following RflySim’s default IP and port rules, and collaborates with RflySim3D to achieve visualization of multi-UAV swarm simulations. When real-flight mode is enabled, users can customize the base IP and base port rules; the module establishes UDP connections with multiple real PX4 UAVs on the local network according to predefined increment rules, directly deploying Simulink-designed swarm algorithms onto actual hardware platforms.

Port Descriptions

Input Ports (Inputs)

Port Name	Data Type	Dimension	1×(10×N)	Input contains control command data for N UAVs; N is determined by the UAV count specified in parameters, with each UAV corresponding to a 10-dimensional control signal

Output Ports (Outputs)

Port Name	Data Type	Dimension	1×(36×N)	Output contains state feedback data for N UAVs; N is determined by the UAV count specified in parameters, with each UAV corresponding to a 36-dimensional state vector

Parameter Configuration (Parameters)

The following parameters can be configured in the Mask dialog box opened by double-clicking the module:

Parameter Name	Type	Default Value	Optional Values / Range	Description
Vehicle number or CopterID list	vector	[1 2]	Any vector of positive integers	Specifies the list of UAV IDs managed by this module; the vector length equals the number of UAVs managed
Sample Time	double	0.01	>0	Module sampling time in seconds
Enable real flight (RealflyMode)	bool	false	true/false	Whether to enable real-flight communication mode
Target IP Address	string	127.0.0.1	Valid IPv4 address string	In non-real-flight mode, the IP address of the host where the target CopterSim resides
Base IP Address	string	192.168.151.101	Valid IPv4 address string	In real-flight mode, the base IP address of the first UAV
Base Udp Port	int	15501	1024~65535	In real-flight mode, the base UDP port number of the first UAV

Parameter Setting Notes

Vehicle number or CopterID list

This parameter specifies the list of UAV IDs managed by the module; the vector length equals the total number of UAVs managed by the current module, and each element corresponds to the CopterID of a UAV. For example, inputting [1:5] is equivalent to [1 2 3 4 5], indicating management of five UAVs with IDs 1 through 5; inputting [1 3 5 6] indicates management of four UAVs with IDs 1, 3, 5, and 6.

RealflyMode

• Unselected (Non-real-flight mode: default for simulation environment control): Uses a unified Target IP Address; UDP ports for all UAVs follow a base-port increment rule: UAV #1 uses port 15501, and each increment in ID increases the port by 2.
• Selected (Real-flight mode: controls real UAVs): Follows base IP and base port increment rules: the IP address of UAV #N is base IP last octet + (N-1), and the port is base port + (N-1). For example, with base IP 192.168.151.101 and base port 15501, UAV #5 has IP 192.168.151.105 and port 15505. All UAVs must be pre-configured with static IPs and fixed port rules.

Sample Time

This parameter corresponds to the Simulink model’s sampling step size; the default value of 10 ms suits most UAV control scenarios.

Module Characteristics (Block Characteristics)

Characteristic	Value
Supported Data Types	double, single
Direct Feedthrough	Yes
Sample Time	Discrete
Code Generation Support	No

Data Communication Protocol

This module transmits MAVLink data over UDP, with IP and port rules differing between two modes:

Non-Real-Flight Mode (RealflyMode unchecked)

• Default target IP address is 127.0.0.1, customizable to the IP of the host where the target CopterSim resides
• Port rules follow a base-port increment scheme: each UAV’s port number increases by 2 relative to the previous UAV

Real-Flight Mode (RealflyMode checked)

• IP Rule: All UAVs are configured with static IPs following a base IP increment scheme: the IP address of UAV #N is base IP last octet + (N-1). For example, with base IP 192.168.151.101, UAV #1 uses 192.168.151.101, and UAV #5 uses 192.168.151.105.
• Port Rule: All UAVs are configured with fixed ports following a base port increment scheme: the MAVLink communication port of UAV #N is base port + (N-1). For example, with base port 15501, UAV #1 uses port 15501, and UAV #5 uses port 15505.
• Transmission Content: Inputs consist of control signals for multiple UAVs; outputs consist of state feedback data for multiple UAVs, all encapsulated in MAVLink format for transmission.

Related Modules

Module Name	Description
RflySwarmJoystick	Generates joystick control signals for swarm models across multiple UAVs
RflySwarmWaypoint	Implements waypoint-based path planning for multiple UAVs
RflyUdpOffboardRaw	Multi-UAV raw offline control communication module, compatible with the interface specification of RflyUdpRaw

Usage Examples

For usage examples, refer to the following path:

``` [RflySim Installation Path]/RflySimAPIs/10.RflySimSwarm/1.BasicExps/e2_RflyUdpSwarmExp/Readme.pdf

Please refer to Readme.pdf in the path above for complete example descriptions and operational steps.

Notes and Common Issues

• Initialization Order: During the simulation startup phase, the module initializes UDP communication sockets based on the configured CopterID list, IP addresses, and port rules. Ensure that the corresponding real drones or CopterSim processes have already been started and network configurations completed before launching the Simulink simulation; otherwise, communication connection failures and data packet loss may occur.
• Sample Time Matching: The Sample Time configured for the module must match the base sample time of your Simulink model. For real-drone communication, it is recommended to set this value to no less than 2 ms to prevent UDP buffer overflow and abnormal data reception.
• IP Rules in Real-Drone Mode: When RealflyMode is enabled, all drones must be preconfigured with static IPs that follow the rule: the last octet increments by 1 from a base IP. If the IP format does not conform to this rule, the module will fail to correctly parse the target IP, resulting in complete communication failure.
• Port Rules in Real-Drone Mode: When RealflyMode is enabled, all drones’ MAVLink transmission ports must follow the rule: incrementing by 1 from a base port. Additionally, local network access permissions for the corresponding ports must be granted, and firewalls should be disabled or port-allowing rules added; otherwise, drone data cannot be received.
• Cross-Machine Communication Configuration: When controlling CopterSim running on another computer in non-real-drone mode, the actual local IP address of the target computer must be specified, and both computers must reside in the same subnet. The target computer’s firewall should be disabled or UDP port-allowing rules added; otherwise, communication cannot be established.
• CopterID Conflicts: Within the same simulation project, multiple RflyUdpRaw modules must not be assigned duplicate CopterIDs; otherwise, port conflicts will occur, leading to communication anomalies.
• Input/Output Dimension Matching: The dimensions of input control signals, output state ports, and the length of the configured CopterID list must be consistent. Each CopterID corresponds to one set of input control signals and one set of output state data; dimension mismatches will cause simulation errors.

Changelog

• v4.0 (2024-05-03): Initial release. Supports UDP-based multi-drone MAVLink data transmission and reception, with configuration options for both simulation mode and real-drone flight mode.