Hybrid Electric Machine Torque Control via Battery Voltage Thresholds
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Solution Overview
Problem
In hybrid-electric vehicles, component failures can lead to complete shutdown, which is undesirable, as existing systems struggle to maintain propulsion while safely disabling faulty components without reducing vehicle performance.
Innovation Solution
A controller system that temporarily disables a faulty electric machine, routes high voltage to the battery via a Variable Voltage Converter (VVC) to dissipate excess voltage, and re-enables the machine in a torque-limited mode to maintain propulsion, ensuring continued vehicle operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fault condition is detected in one electric machine, the faulty machine is disabled to ensure safety, but this causes complete vehicle shutdown and loss of propulsion
Solution Approach 1:
The vehicle's electric propulsion system is segmented into multiple independent electric machines (first and second electric machines). When a fault is detected in one machine, only that specific machine is disabled while the other continues to provide propulsion, preventing complete system shutdown and maintaining partial vehicle operation.
Solution Approach 2:
The controller changes the operational parameters of the healthy electric machine by applying torque limits based on battery voltage thresholds. This parameter adjustment allows the single functioning machine to operate within safe limits while maintaining propulsion capability, resolving the contradiction between safety and productivity.
2Reliability
If torque limits are applied to the healthy electric machine to maintain safety, then vehicle propulsion is maintained, but vehicle performance is reduced
Solution Approach 1:
The torque limits applied to the healthy electric machine are not fixed but dynamically adjusted based on real-time battery voltage conditions. The controller monitors battery voltage and adjusts torque limits accordingly, allowing the system to maintain safe operation while optimizing performance within the constraints of the single-functioning machine.
3Reliability
If the healthy electric machine is temporarily disabled to dissipate high voltage, then power imbalances are prevented, but propulsion is interrupted
Solution Approach 1:
The healthy electric machine is temporarily disabled in periodic intervals specifically to dissipate accumulated high voltage and prevent power imbalances. This periodic action is carefully timed and controlled to maintain overall system reliability while minimizing the duration of propulsion interruption, thus resolving the contradiction between power balance and continuous operation.
Data Source
AI summary
A hybrid-electric vehicle method of controlling a hybrid electric vehicle is provided. The vehicle includes a traction battery, at least two electric-machines, and a controller. The controller is configured to, in response to a faulted condition one of the electric-machines during a drive cycle, command the other of the electric-machines to function in a mode in which torque output is restricted to a threshold value that depends on a voltage of the battery to maintain vehicle propulsion during the drive cycle.