Sensorless Electric Oil Pump Motor Speed Control
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Solution Overview
Problem
In hybrid vehicles, the rapid variation in hydraulic pressure and load conditions of electric oil pumps driven by brushless motors under sensorless control leads to uncontrollable motor operation and potential 'step-out' due to rapid changes in rotational speed, which existing technologies fail to stabilize effectively.
Innovation Solution
An apparatus and method for controlling the electric oil pump motor that includes a control command generating section, current control section, and electric motor control section to maintain rotational speed within defined limits, adjusting torque and power to suppress deviations and shift limits in response to load changes, ensuring stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If constant torque control is applied to the electric motor, then the motor can maintain steady power output, but the rotational speed varies rapidly under load changes causing step-out in sensorless control
Solution Approach 1:
The patent implements dynamic rotational speed limiting by comparing actual motor speed with predetermined limit values and adjusting the torque command signal in real-time. When speed exceeds the limit, the system dynamically reduces torque to bring speed back within acceptable ranges, preventing step-out while maintaining power output capability.
Solution Approach 2:
The control system continuously monitors the actual rotational speed of the motor and feeds this information back to the control unit. Based on the feedback signal, the system adjusts the torque command signal to maintain speed within predetermined limits, ensuring stable sensorless control operation.
2Speed
If the motor rotational speed is allowed to vary rapidly in response to load changes, then the motor can respond quickly to hydraulic pressure changes, but the sensorless control becomes uncontrollable and steps out
Solution Approach 1:
The system implements dynamic speed limiting that adapts to operating conditions by comparing actual speed with predetermined limit values and adjusting torque commands in real-time, allowing rapid yet controlled response to load changes without losing sensorless control stability.
3Stress or pressure
If the oil pump operates under heavy load condition to supply clutch pressure, then the hydraulic pressure is sufficient for clutch engagement, but the motor rotational speed drops rapidly causing control instability
Solution Approach 1:
The control system takes preliminary anti-action by detecting when the motor enters a heavy load condition and proactively adjusting the torque command signal to prevent excessive speed drops before they cause step-out, thereby maintaining control stability while ensuring sufficient hydraulic pressure for clutch engagement.
Data Source
AI summary
In an apparatus for controlling a sensorless electric motor that drives an electric oil pump, in a case where a rotational speed of the motor deviates from a first range defined between a first upper limit value and a first lower limit value, a rotational speed limiting section generates a current command signal acting for controlling the rotational speed of the motor to suppress deviation of the rotational speed of the motor from the first range, and in a case where deviation of the rotational speed of the motor from the first range is continued for a predetermined time or more, the rotational speed limiting section sets a second range defined between a second upper limit value and a second lower limit value which are respectively displaced from the first upper limit value and the first lower limit value in a direction in which the deviation is continued.