Sensorless BLDC Oil Pump Control for Cold-Start Viscous Oil
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Solution Overview
Problem
Existing position-sensorless BLDC motors in oil pumps of electric drives face challenges in accurately determining rotor position and speed below a limiting speed, particularly at low temperatures, leading to inefficient operation and potential overheating of the controller.
Innovation Solution
The method involves operating the BLDC motor in a pre-controlled-excited mode to warm the oil, intermittently interrupting pre-control to detect rotor position and speed using induced voltages, and switching to controlled mode above the limiting speed, with temperature monitoring to prevent controller overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the BLDC motor is operated in pre-controlled-excited mode to warm the oil, then the oil temperature increases and viscosity decreases, but the controller experiences thermal loading and may overheat
Solution Approach 1:
The patent applies periodic action by intermittently interrupting the pre-control excitation during cold-start operation. The excitation is activated in cycles, allowing the oil to be warmed while providing cooling intervals for the controller. This periodic on/off pattern enables thermal management of both the oil and controller simultaneously.
Solution Approach 2:
The patent maintains continuity of useful action by resuming the pre-control excitation after interruption periods, once the controller temperature has decreased sufficiently. This ensures the oil warming process continues over time without permanent interruption, achieving both oil heating and controller cooling while maintaining progress toward the operational temperature.
2Measurement precision
If the pre-control is continuously interrupted to detect rotor position, then measurement accuracy improves, but the warming efficiency decreases
Solution Approach 1:
The patent uses periodic action by implementing scheduled interruption intervals for detecting rotor position through induced voltages. These periodic detection pauses occur at optimized intervals that balance the need for accurate position measurement with the requirement to maintain continuous warming of the oil, preventing excessive cooling during detection phases.
3Speed
If the BLDC motor operates below limiting speed, then the rotor position cannot be determined accurately, but operating above limiting speed requires accurate position detection
Solution Approach 1:
The patent applies preliminary action by using pre-control excitation to bring the rotor up to the limiting speed before attempting accurate position detection. This preliminary speed achievement creates the conditions necessary for subsequent accurate measurement of rotor position through induced voltage detection, establishing a prerequisite state for precise control.
Solution Approach 2:
The patent uses induced voltage as an intermediary to enable rotor position detection above limiting speed. The induced voltage generated by the rotating rotor in unexcited coils serves as a mediator that carries position information, allowing the controller to determine rotor position indirectly through voltage measurement rather than direct sensing.
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 approach effectively warms the oil to a usable viscosity while minimizing thermal loading on the controller, allowing efficient operation and accurate rotor position determination.
Implementation Method 1
Waste heat of the BLDC motor generated by the pre-control is in this case dissipated to the oil in the surrounding area of the oil pump and the oil is thereby successively warmed
Implementation Method 2
detect a voltage induced by the rotor in the unexcited coils of a stator of the BLDC motor
Data Source
AI summary
A method for operating a position-sensorless BLDC motor of an oil pump (19) is proposed. When the oil pump (19) is put into operation and run up to speed, to warm an oil that is transported by the oil pump (19), the BLDC motor is operated in a pre-controlled-excited mode until the oil has a kinematic viscosity that allows the BLDC motor to be operated in a controlled mode above a motor-specific limiting speed of a rotor of the BLDC motor. Waste heat of the BLDC motor generated by the pre-control is in this case dissipated to the oil in the surrounding area of the oil pump (19).This pre-control is intermittently interrupted in order to detect a voltage induced by the rotor in the unexcited coils of a stator of the BLDC motor, by means of which a rotor position and a rotor (rotational) speed are determined sufficiently accurately above the limiting speed of the rotor.Above this limiting speed, once it is detected that it has been exceeded, a changeover is made to a controlled-excited mode of the BLDC motor.Also proposed are a computer program, a computer program product, a heat-transfer medium system and a vehicle.