Distributed Simulation Latency Compensation via Master-Slave Synchronization
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Solution Overview
Problem
Distributed simulation systems experience latency issues when multiple users interact with each other in close proximity, leading to unrealistic and undesirable jittery interactions, particularly in scenarios like dogfighting or in-flight refueling, where precise spatial relationships are critical, resulting in ineffective training due to position and velocity oscillations.
Innovation Solution
A distributed simulation system where each simulator determines the position of its vehicle and transmits position data to the other, using a master/slave synchronizer approach to maintain accurate relative positioning and orientation between vehicles, minimizing latency effects by controlling the movement of slave vehicles based on received data without relying on prediction techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional prediction techniques are used to compensate for latency, then the system attempts to maintain position accuracy, but overshoot and oscillation occur causing unrealistic interactions
Solution Approach 1:
The system implements a feedback mechanism where each simulator continuously receives position data from other simulators and adjusts the slave vehicle positions accordingly. The feedback loop processes position data at a rate of 60 Hz or higher, allowing real-time correction of latency effects without prediction, thereby eliminating overshoot and oscillation while maintaining position accuracy.
Solution Approach 2:
The system performs preliminary synchronization by establishing master/slave relationships between simulators before interactions occur. The master simulator's position data is pre-synchronized across all slave simulators, ensuring that all participants start with consistent spatial understanding before any dynamic interaction begins, preventing subsequent oscillations.
2Measurement precision
If dead reckoning is used to maintain position during latency, then position estimation is attempted, but sudden jumping occurs requiring additional filtering that increases error
Solution Approach 1:
The system replaces dead reckoning (a mechanical estimation approach) with direct position data transmission and synchronization. Instead of estimating position based on velocity and time, the system directly transmits position data from master to slave simulators at high rates, eliminating the need for filtering and reducing cumulative errors associated with mechanical estimation methods.
Solution Approach 2:
The system creates copies of the master simulator's position data and distributes them to all slave simulators. This copying approach ensures that every simulator has an identical view of the master vehicle's position, eliminating the need for local estimation algorithms and their associated errors.
3Measurement precision
If tight dead reckoning tolerance settings are used, then position accuracy is improved, but a flood of high rate packets is required consuming unacceptable bandwidth
Solution Approach 1:
The system segments the position data transmission into efficient packets structured according to DIS protocol standards. By organizing data into standardized segments with appropriate timing, the system achieves high position accuracy without requiring excessive packet rates, thereby reducing bandwidth consumption while maintaining precision.
4Ease of operation
If physics-based movement is implemented, then realistic interaction is achieved, but latency causes compound error producing jittery interaction in close proximity scenarios
Solution Approach 1:
The system implements feedback at the physics level by continuously synchronizing position data between master and slave simulators. This feedback ensures that physics-based movements remain coordinated across all simulators, eliminating jittery interactions while preserving realistic physics-based movement and collision detection.
Data Source
AI summary
A distributed, networked simulation system has two or more vehicle simulators that resists latency errors when the vehicles are close to each other, and is especially useful for close maneuvering training such as tanker and receiver aircraft refueling exercises or combat exercises where one aircraft closely follows another. One simulator sends the other simulator data defining the relative linear displacements and rotations between their two vehicles. The receiving simulator uses the data to maintain the relative position of the other vehicle in its local scene data based on the defined relative displacement and rotation between the vehicles. An additional simulator may simulate the boom control on the tanker using similar relative position data. The system starts relative displacement data operation when one vehicle approaches another in the virtual world, and returns to normal operation when the vehicles separate.