Motor Control Device for Electric Oil Pump Low-Speed Stability
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Solution Overview
Problem
Existing control devices for electric oil pumps struggle to maintain low-speed rotation of motors due to sudden changes in rotation speed, which can lead to motor stoppage under the influence of cogging torque or external loads.
Innovation Solution
A control device that includes a detector for rotational position, calculators for actual and estimated rotation speeds, a comparator, and a controller to adjust voltage applied to the motor coil based on comparisons between actual, estimated, and predetermined speeds, ensuring continuous low-speed rotation by increasing or decreasing voltage as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the motor is rotated at a lower speed to maintain high responsiveness of the electric oil pump, then the responsiveness is improved, but the motor may stop due to sudden changes in rotation speed under the influence of cogging torque or external loads
Solution Approach 1:
The control device calculates an estimated rotation speed in advance based on the time interval between the current positional signal and a previous positional signal. This preliminary estimation allows the control to anticipate potential speed drops before they occur, enabling proactive voltage adjustment to prevent motor stoppage while maintaining low-speed rotation for high responsiveness.
Solution Approach 2:
The control device continuously compares the actual rotation speed (calculated from current and previous positional signals) with the estimated rotation speed (calculated from current and assumed future positional signals). This feedback mechanism allows real-time detection of speed trends and automatic voltage adjustment to maintain continuous rotation, resolving the contradiction between low-speed operation and rotation stability.
2Productivity
If the rotation speed is suddenly changed to maintain low-speed rotation, then the responsiveness is improved, but the motor stoppage occurs due to the sudden change
Solution Approach 1:
The control device performs preliminary calculation of the estimated rotation speed using the time interval to an assumed future positional signal reception time. This allows the system to prepare control signals in advance that prevent sudden speed changes, maintaining both responsiveness and continuous operation by avoiding abrupt corrections.
Solution Approach 2:
The control device dynamically adjusts the voltage applied to the coil based on the comparison between actual and estimated rotation speeds. By changing the voltage parameter smoothly rather than suddenly, the system maintains low-speed rotation for responsiveness while preventing motor stoppage through gradual parameter adjustment.
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 control device effectively maintains low-speed rotation of the motor, preventing stoppage due to cogging torque and external loads, while ensuring high responsiveness of the electric oil pump by driving the pump unit at a low rotation speed.
Implementation Method 1
a detector that detects a rotational position of the rotor for each predetermined rotary angle and outputs a positional signal indicating the detected rotational position
Implementation Method 2
a motor that includes a stator including a coil and a rotor including a permanent magnet
Data Source
AI summary
A controller of a motor control device increases a voltage to be applied to a coil based on a control signal calculated from an estimated rotation speed, when the estimated rotation speed becomes equal to or lower than a predetermined rotation speed, increases the voltage to be applied to the coil based on a control signal calculated from an actual rotation speed, in a case where the actual rotation speed is lower than the predetermined rotation speed when the estimated rotation speed becomes higher than the predetermined rotation speed, and decreases the voltage to be applied to the coil based on a control signal calculated from the actual rotation speed, in a case where the actual rotation speed is higher than the predetermined rotation speed when the estimated rotation speed becomes higher than the predetermined rotation speed.