Starter-Generator Speed Control Using FPGA Lookup Tables
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Solution Overview
Problem
Current starter-generator speed control methods, such as field oriented control and space vector modulation, require software code and digital signal processors, posing certification challenges for airborne systems, and there is a need for a simplified algorithm that can be implemented in field-programmable gate array based start controllers without extensive re-certification.
Innovation Solution
A hardware-based starter-generator speed control system that operates in two modes: torque mode and speed mode, using lookup tables and a speed control algorithm to adjust current values, allowing for simplified implementation and certification, and incorporates a coast state and randomization to mitigate mechanical and electrical resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field oriented control or space vector modulation algorithms are used for starter-generator speed control, then accurate and stable speed control is achieved, but certification challenges arise due to the use of software code and digital signal processors in airborne systems
Solution Approach 1:
The patent replaces complex software-based control algorithms (field oriented control and space vector modulation) with a hardware-based lookup table approach implemented in FPGA. This substitution eliminates the need for complex digital signal processing software, thereby reducing certification complexity while maintaining control functionality through pre-computed torque and current values stored in lookup tables.
2Device complexity
If a simplified speed control algorithm is used for FPGA-based start controllers, then certification burden is reduced, but control accuracy and stability may be compromised
Solution Approach 1:
The patent pre-computes and stores optimal torque and current values in lookup tables before runtime operation. During actual control, the system simply retrieves pre-calculated values based on current speed and operational mode, eliminating the need for complex real-time calculations. This preliminary action ensures both simplicity for FPGA implementation and accuracy through pre-optimized control parameters.
Solution Approach 2:
The patent changes the control approach from continuous mathematical computation to discrete lookup table retrieval. By transforming the control problem into parameter selection based on speed bands and operational modes, the system achieves both simplicity and accuracy. The lookup tables contain pre-determined parameter sets that maintain control precision without requiring complex algorithms.
3Ease of operation
If traditional control methods are used, then speed control functionality is achieved, but mechanical and electrical resonance causes torque ripple that reduces system reliability
Solution Approach 1:
The patent implements a coast state that periodically interrupts continuous motor operation. By allowing the motor to coast between controlled acceleration phases, the system breaks up continuous torque application that causes resonance. This periodic on-off control pattern reduces mechanical and electrical resonance while maintaining the ability to control engine start functionality.
Data Source
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AI summary
Systems and techniques for engine starter control may include determining a current speed band associated with an engine start for a current time increment, determining a previous speed band associated with the engine start for a previous time increment within the engine start, receiving a measured current value, determining a target current value based on the current speed band, the previous speed band, whether an acceleration or deceleration occurred between the current speed band and the previous speed band, and a mode of a system for engine starter control, and adjusting a current for the engine start based on the target current value.