Generator Torque Control via Dual-Loop Voltage Regulation
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Solution Overview
Problem
Existing engine-driven generator systems lack precise control over generator output torque, which is essential for optimal engine torque management, particularly during vehicle coasting and braking maneuvers, and are often influenced by temperature and ambient conditions.
Innovation Solution
A hybrid control system with inner and outer control loops within the engine control module allows direct control of generator output torque, maintaining voltage within specific limits, and using temperature-independent parameters for torque estimation, enabling independent torque-based voltage control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing generator control systems vary voltage set point based on ambient temperature and battery state-of-charge, then the system adapts to changing environmental conditions, but the control precision over generator output torque deteriorates and temperature dependencies are introduced
Solution Approach 1:
The control system is segmented into two independent control loops: an outer control loop that commands torque-based voltage signals independent of temperature, and an inner control loop that handles voltage regulation. This segmentation allows the outer loop to focus on precise torque control while the inner loop manages voltage adaptation, thereby resolving the contradiction between control precision and environmental adaptability.
Solution Approach 2:
The inner control loop acts as an intermediary between the outer torque-commanding loop and the generator voltage output. It receives the torque-based voltage command from the outer loop and adjusts the actual generator voltage based on real-time voltage measurements, thereby decoupling the torque control precision from temperature dependencies while still maintaining voltage within acceptable limits.
2Loss of energy
If direct control of generator output torque is implemented, then energy recuperation is maximized during coasting and braking, but the system complexity increases with inner and outer control loops
Solution Approach 1:
The dual-loop control system serves multiple functions: the outer loop provides torque-based voltage commanding for precise torque control and energy recuperation, while the inner loop provides voltage regulation and maintains voltage within acceptable limits. This multi-functionality justifies the increased system complexity by delivering superior energy recuperation performance and precise torque control that single-loop systems cannot achieve.
Solution Approach 2:
The inner control loop implements voltage feedback by continuously monitoring the generator voltage and adjusting the field duty cycle signal to maintain voltage within acceptable limits. This feedback mechanism enables the system to handle the increased complexity through automated closed-loop control, maximizing energy recuperation while maintaining stable voltage operation during coasting and braking maneuvers.
3Reliability
If temperature-independent parameters are used for torque estimation, then control signals become independent of ambient temperature, but the system requires precise measurement of multiple parameters at a single temperature
Solution Approach 1:
The system performs preliminary characterization and calibration at a single reference temperature, storing the measured parameters for use in temperature-independent torque estimation. By completing the complex measurement and calibration process in advance during manufacturing or initial setup, the system achieves reliable temperature-independent operation during actual use without requiring continuous multi-parameter measurements under varying temperature conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise control of generator output torque to within ±5 percent or ±1-2 Nm at the crankshaft, maximizing energy recuperation during specific operating modes by maintaining generator voltage within predetermined limits, independent of temperature, and allowing mode-specific torque control operations.
Implementation Method 1
Mechanical energy generated via the engine's fuel combustion process is converted to electrical energy by operation of the electric generator
Implementation Method 2
A voltage rectifier outputs a direct current generator output voltage in response to controller-originated electrical control signals
Data Source
AI summary
A system includes an engine, a generator assembly, a direct current voltage bus, and a controller. The assembly is coupled to and driven via the engine, and has an electric generator, field windings, and a voltage rectifier collectively producing a generator output voltage. An inner control loop of the controller provides a field duty cycle signal to the field windings in response to an adjusted voltage control signal. An outer control loop of the controller provides a torque-based voltage control signal as an input to the inner control loop in response to a commanded engine torque and an estimated generator torque. An output torque of the generator is directly controlled via the outer control loop. The inner control loop calculates the adjusted voltage control signal as a difference between the torque-based voltage control signal and the output voltage.