Brushless Motor Starter Control Algorithms for Hybrid Vehicles
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Solution Overview
Problem
Conventional brushed motor starters in vehicle propulsion systems face issues with motor degradation due to physical contact wear and limited torque delivery near the upper speed range, leading to inefficiencies and increased restart times.
Innovation Solution
A brushless permanent magnet DC motor is used as the starter, controlled by a multi-tiered algorithm that switches between trapezoidal current control with pulse width modulation, six-step voltage control with a variable phase advance angle, and six-step voltage control with a fixed phase advance angle, based on output speed thresholds, to optimize torque and speed performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a brushed motor is used for engine starting, then the system structure is simple and cost is reduced, but the motor degrades over time due to contact brush wear and delivers zero torque near upper speed range
Solution Approach 1:
The patent replaces the mechanical contact brush system with a brushless permanent magnet DC motor that uses electronic commutation via solid-state switches. This substitution eliminates physical wear contacts while providing reliable torque delivery across the full speed range, including near zero torque at upper speeds where brushed motors fail.
Solution Approach 2:
The patent implements multi-tiered control algorithms that dynamically adjust electrical parameters (current control vs. voltage control with variable/fixed phase advance angles) based on output speed thresholds. This allows the motor to optimize torque delivery across different operating conditions, particularly maintaining performance near the upper speed boundary where brushed motors deliver substantially zero torque.
2Reliability
If a brushless permanent magnet DC motor with multi-tiered control is used, then torque delivery and reliability are improved, but device complexity and control algorithm complexity increase
Solution Approach 1:
The patent divides the speed control range into multiple tiers with distinct control algorithms: first control algorithm for low speeds, second control algorithm for medium speeds, and third control algorithm for high speeds. This segmentation allows each algorithm to be optimized for its specific operating range while keeping individual algorithm complexity manageable.
Solution Approach 2:
The patent implements dynamic switching between different control algorithms based on real-time output speed measurements. The controller automatically transitions between control strategies as speed thresholds are crossed, enabling adaptive optimization without requiring overly complex single-algorithm solutions.
3Device complexity
If sequential solenoid actuation is used in conventional starters, then the system is simple, but restart time increases and perceived lag in propulsion occurs
Solution Approach 1:
The patent replaces the sequential mechanical solenoid actuation system with an electrically-controlled brushless motor system. This allows simultaneous or near-simultaneous engagement of all starter components through electronic control, eliminating the sequential mechanical timing delays inherent in solenoid-based systems.
Solution Approach 2:
The control system prepares the motor and control algorithms in advance, with pre-programmed control strategies ready to execute immediately when starting is required. The multi-tiered control algorithms are pre-configured to engage at appropriate speed thresholds, eliminating delays associated with real-time decision-making during the starting process.
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 solution enables rapid and efficient engine restarts, improved torque delivery, and reduced complexity and cost by eliminating the need for sequential solenoid actuation and additional voltage compensation, while maintaining smooth power delivery and reducing perceived lag in propulsion.
Implementation Method 1
The electric machine is configured to start the engine from an inactive state
Implementation Method 2
The electric machine may include a plurality of Hall effect sensors spaced about a stator to output signals indicative of a rotor position
Data Source
AI summary
A system includes an electric machine coupled to an engine and configured to start the engine from an inactive state. A controller executes a first control algorithm while output speed of the electric machine is less than a first speed threshold, and also executes a second control algorithm while the output speed is greater than the first speed threshold and less than a second speed threshold. Additionally, the controller is programmed to execute a third control algorithm while the output speed is greater than the second speed threshold. The first control algorithm includes operating the electric machine using trapezoidal current control with pulse width modulation. The second control algorithm includes operating the electric machine using six-step voltage control with a variable phase advance angle. The third control algorithm includes operating the electric machine using six-step voltage control with a predetermined fixed phase advance angle.