Multi-Motor Torque Allocation Using Physics-Based 3D Reduction
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Solution Overview
Problem
Conventional torque control systems for range-extended electrified vehicles with three or more electric motors face computational challenges due to the complexity of four-dimensional optimization problems, which exceed typical processing capabilities.
Innovation Solution
A physics-based approach reduces the four-dimensional optimization problem to a three-dimensional problem by determining a torque relationship between two electric motors using scalar coefficients and constants, allowing for online torque optimization through various dimension reduction strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a four-dimensional optimization problem is solved for torque control in electrified vehicles with three or more electric motors, then torque optimization performance is improved, but computational complexity and processing requirements increase substantially
Solution Approach 1:
The patent segments the four-dimensional optimization problem into multiple lower-dimensional sub-problems. Specifically, it divides the torque optimization across three electric motors and one torque generating system into separate controllable dimensions, allowing each to be optimized independently or in smaller groups, thereby reducing the overall computational burden while maintaining optimization effectiveness.
Solution Approach 2:
The patent transforms the four-dimensional optimization problem by introducing a torque relationship constraint that reduces the independent variables from four to three dimensions. This dimensionality reduction is achieved by establishing mathematical relationships between motor torques based on vehicle dynamics requirements, converting a complex 4D problem into a more manageable 3D problem that can be solved with available processing power.
2Reliability
If conventional torque control systems are used for electrified vehicles with three electric motors, then the system works for its intended purpose, but processing power requirements exceed what is typically available
Solution Approach 1:
The patent changes the parameters of the optimization problem by introducing torque relationship constraints that reduce the number of independent optimization variables. By establishing mathematical relationships between motor torques based on vehicle dynamics, the system transforms the problem from requiring four independent torque calculations to three, making it solvable with typical embedded processor capabilities while maintaining reliable torque control functionality.
3Adaptability or versatility
If the number of electric motors in the electrified powertrain is increased to three or more, then vehicle performance and drivability are improved, but the optimization problem becomes much more difficult to solve
Solution Approach 1:
The patent applies dynamic constraints to the torque optimization problem by establishing torque relationships between motors based on real-time vehicle dynamics requirements. These dynamic constraints adapt the optimization problem to current operating conditions, allowing the system to maintain high vehicle performance with three or more motors while reducing optimization complexity through physics-based relationships that naturally limit the solution space.
Data Source
AI summary
A torque optimization system for an electrified vehicle having an electrified powertrain including three electric motors a, b, and c and an additional torque generating system includes a set of sensors configured to measure a set of operating parameters of the electrified vehicle and a control system configured to determine a torque relationship between electric motors b and c, solving a three-dimensional (3D) optimization problem for the electrified powertrain, the 3D optimization problem defining torques generatable by one of electric motors b and c, electric motor a, and the additional torque generating system, determine torque commands for the three electric motors a, b, and c and the torque generating system based on the solving of the 3D optimization problem, the determined torque relationship, and the set of operating parameters, and control the electrified powertrain based on the determined torque commands.