Brushless Starter Motor Control for Voltage Overshoot
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Solution Overview
Problem
Existing starter systems for internal combustion engines lack efficient control methods to manage electrical current and rotational position during engine starting, leading to potential voltage overshoot and instability.
Innovation Solution
A multi-phase brushless electric motor starter system with a controller and inverter that determines initial current commands, interim voltage commands, and final voltage commands, incorporating rotational position compensation, and employs a decoupled current controller with dynamic integrator clamping to limit voltage overshoot, thereby controlling the electric motor without an intervening current prediction step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional starter control methods are used, then the system is simpler to implement, but voltage overshoot occurs and system stability deteriorates
Solution Approach 1:
The control method performs preliminary determination of initial current commands and interim voltage commands before final voltage application. The interim voltage commands are calculated based on initial current commands and monitored currents, then subjected to voltage limits to determine final voltage commands. This preliminary action sequence prevents voltage overshoot before it occurs, improving reliability without requiring complex hardware modifications.
Solution Approach 2:
The system continuously monitors electrical current supplied to the electric motor and rotational position of the output member, using this feedback to adjust control commands in real-time. The monitored currents are directly used to determine interim voltage commands, creating a closed-loop feedback system that maintains stability and prevents voltage overshoot during dynamic operation.
2Productivity
If current prediction step is used in control, then control accuracy may be improved, but response time increases and productivity decreases
Solution Approach 1:
The control method explicitly removes the current prediction step from the control algorithm. Instead of predicting future current values, the system directly uses monitored current measurements to determine interim voltage commands. This extraction of the prediction step eliminates the associated time delay and computational overhead, enabling faster response and achieving 25,000 rpm in less than 200 ms.
Solution Approach 2:
The control method skips the intermediate current prediction calculation phase and directly transitions from monitoring currents to determining voltage commands. This rushing through the control sequence by eliminating unnecessary computational steps reduces overall response time and increases productivity during engine starting.
3Reliability
If dynamic integrator clamping element with d-scale and q-scale voltage limits is used, then voltage overshoot is minimized, but control algorithm complexity increases
Solution Approach 1:
The voltage control is segmented into separate d-axis and q-axis components, each with its own dynamic integrator clamping element and voltage limits. The d-scale voltage limit is determined based on the interim d-axis voltage command and system voltage, while the q-scale voltage limit is determined based on the interim q-axis voltage command and system voltage. This segmentation allows independent optimization of each axis, minimizing voltage overshoot through targeted control rather than requiring complex overall control algorithms.
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
The solution provides a fast and robust engine starting performance with minimized voltage overshoot, achieving a significant speed increase of 25,000 rpm in less than 200 ms and consistent torque/output over a wide range of conditions, ensuring reliable engine starting without current prediction routines.
Implementation Method 1
A multi-phase brushless electric motor, a controller and an inverter
Data Source
AI summary
A starter for an internal combustion engine includes a multi-phase brushless electric motor, a controller and an inverter. A method for controlling the starter includes determining initial current commands for operating the electric motor in response to an activation command. Electrical current supplied to the electric motor and a rotational position of an output member of the electric motor are monitored. The electrical current is monitored directly without an intervening current prediction step. Interim voltage commands are determined based upon the initial current commands and the monitored currents, and final voltage commands are determined by subjecting the interim voltage commands to voltage limits. A rotational position compensation term is determined based upon the rotational position and rotational speed of the electric motor, and operation of the inverter is controlled to control the electric motor based upon the final voltage commands and the rotational position compensation term.