RobUST Robot Control Framework

A Unity-based real-time control system for RobUST cable-driven robotic platform. This framework provides Soft real-time deterministic motor control, multi-sensor integration, and tension planning for cable actuation.

Project Architecture

Core Design Philosophy

Unlike typical Unity projects where each MonoBehaviour operates independently with its own Update() loop, this framework implements a centralized control architecture for more (soft) deterministic real-time robotic control. The system uses a single main control loop with dedicated driver threads for hardware interfaces.

Key Components

Unity Scripts are always located in Assets/Scripts. These scripts can be attached to specific game objects in the Unity Scene. A basic Unity Scene for this project is implemented with a default MainCamera, an empty RobotSystem GameObject, and 3 tracker visuals for the robot frame, end-effector, and user center of mass.

Script	Function
RobotController.cs	Main control loop coordinating all subsystems
LabviewTcpCommunicator.cs	TCP interface to LabVIEW motor controllers
TrackerManager.cs	HTC Vive tracker interface via OpenVR
ForcePlateManager.cs	Vicon force plate integration via .NET SDK
CableTensionPlanner.cs	Quadratic programming solver for cable tensions
RobotVisualizer.cs	Unity scene visualization updates
DataStructures.cs	Shared data types and utilities

Driver Architecture

The framework employs three main driver scripts (LabviewTcpCommunicator, TrackerManager, ForcePlateManager) designed as standalone, reusable components. Each driver:

• Runs in its own thread with high-precision timing using Unity's System.Diagnostics.Stopwatch
• Maintains pseudo-deterministic sampling frequencies
• Uses data locks for thread-safe communication with the main control loop
• Can be integrated into other robotic projects without modification

LabviewTcpCommunicator.cs

Manages communication with the low-level motor controller running on a PXIe system:

• Frequency: 500 Hz TCP transmission
• Configuration: Motor indices set during initialization
• Interface: UpdateTensionSetpoint(double[] setpoints) for real-time updates
• Protocol: Sends motor index and tension setpoint pairs via TCP
• Port: 8052 (configurable)

TrackerManager.cs

Interfaces with HTC Vive tracking system for pose estimation:

• Frequency: 90 Hz (limited by HTC hardware)
• API: OpenVR for direct access to tracker transformation matrices
• Configuration: Supports 3 trackers (frame reference, end-effector, center of mass)
• Setup: Automatically discovers connected trackers and displays serial numbers for configuration
• Coordinate System: Uses HTC Vive tracker orientation guidelines

ForcePlateManager.cs

Integrates with Vicon force measurement systems:

• Status: Have to test in live mode on RobUST
• Interface: Vicon DataStream SDK via Unity Vicon Plugin
• Architecture: Utilizies ServerPush mode meaning Vicon Box triggers timing

Physics and Control

CableTensionPlanner

Solves the cable tension optimization problem using quadratic programming:

• Solver: Alglib Convex QP implementation (dense IPM)
• Objective: achieve desired wrench while minimizing parasitic wrench and maintaining minimum cable tensions
• Configuration Parameters:
  • Number of cables
  • Chest anteroposterior distance
  • Chest mediolateral distance
  • Belt size (small/medium/large)
• Primary Function: CalculateTensions(Matrix4x4 endEffectorPose, Vector3 desiredForce, Vector3 desiredTorque, Matrix4x4 robotFramePose)

RobotVisualizer

Handles Unity scene updates and coordinate frame transformations for visualization only:

• Coordinate Conversion: Right-handed tracker data to left-handed Unity coordinate system
• Initialization: Captures single frame tracker snapshot for reference positioning
• Camera Setup: Positions Unity camera relative to frame tracker for optimal viewing

Setup and Installation

Prerequisites

• Unity Hub with Unity Editor installed
• Steam account with SteamVR
• HTC Vive base stations and headset
• 3 HTC Vive trackers

Quick Start

1. Clone Repository
2. Open Project in Unity

• Launch Unity Hub
• Select "Open Project"
• Navigate to and select the "Darren RobUST Controller" folder

3. Load Scene

• Open the "Robot Controller Scene" in Unity

4. Configure SteamVR

• Install SteamVR through Steam
• Connect and power on base stations and headset
• Pair the 3 Vive trackers using "Pair Controller" in SteamVR
• Verify tracker status icons are lit in SteamVR interface

5. Configure Tracker Serial Numbers

• Run the project once to see discovered tracker serial numbers in console
• Copy serial numbers to appropriate variables in TrackerManager:
  • Frame tracker serial
  • End-effector tracker serial
  • Center of mass tracker serial

6. Open Preferred Vicon Software

Testing Without Hardware For development and testing without the full LabVIEW motor control system: Simulate Local TCP Listener

ncat -l 8052

This will display incoming motor commands for verification of communication protocols.

Dependencies

• Unity: 2021.3 LTS or newer recommended
• SteamVR: Latest version through Steam
• OpenVR: Included with SteamVR installation
• Vicon Unity Plugin 1.3 .unitypackage
• Vicon System compatible with ViconDataStreamSDK
• Alglib: Included for quadratic programming solver ---> Plugins Folder

Usage Notes

• Ensure all trackers are awake before starting
• Frame tracker position is captured once during initialization and used as reference
• System requires SteamVR to be running and trackers connected before Unity execution
• Motor indices must be configured before runtime - no dynamic motor discovery supported