Engine Speed Offset Control for Transport Refrigeration Stability
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Solution Overview
Problem
Existing transport refrigeration systems experience instability and potential engine overload or shutdown due to rapid changes in system load, especially during high ambient temperatures and high altitude operations, leading to inefficient temperature control and risk of engine stall.
Innovation Solution
A method and system for controlling engine speed in transport refrigeration units by generating a speed request offset based on predicted changes in system parameters, such as temperature, to anticipate and adjust engine speed proactively, thereby stabilizing engine operation and preventing overdrives or stalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the engine speed is adjusted rapidly to meet changing system load demands, then the temperature control responsiveness is improved, but the engine speed stability deteriorates causing droop or overdrive
Solution Approach 1:
The system performs preliminary action by predicting future refrigeration load requirements based on current temperature deviations and rate of change. The controller calculates anticipated engine power needs before the actual load change occurs, allowing the engine speed to be adjusted proactively rather than reactively. This prevents the engine speed from drooping or overdriving when the load changes, as the speed adjustment has already been made in anticipation of the required power level.
2Power
If the engine speed is increased to meet high cooling capacity demand, then the power availability is improved, but the risk of engine overload or stall increases
Solution Approach 1:
The system implements feedback by continuously monitoring actual engine speed, refrigeration load conditions, and temperature parameters. The controller compares actual engine performance against predicted requirements and adjusts the speed request accordingly. This closed-loop feedback ensures the engine operates within safe limits while providing sufficient power, preventing both overload and stall conditions by making real-time adjustments based on actual system state.
3Stability of the object's composition
If the engine speed control algorithm adjusts slowly to maintain stability, then the engine speed stability is improved, but the temperature control precision deteriorates
Solution Approach 1:
By predicting future temperature trends and power requirements, the system makes engine speed adjustments before temperature deviations become significant. This preliminary action allows the system to maintain precise temperature control without requiring rapid, destabilizing engine speed changes. The controller anticipates when power adjustments will be needed and implements them smoothly, maintaining both stability and precision.
Data Source
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AI summary
A method for controlling speed 122 of an engine, the engine providing power to a compressor of a transport refrigeration unit, the method including generating a speed request 124, the engine speed responsive to the speed request; and generating a speed request offset, the speed request offset being added to the speed request to adjust the speed of the engine.