Motor-Driven Hydraulic Pump Control for Stable Sensorless Operation
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Solution Overview
Problem
Existing control schemes for motor-driven oil pumps in hydraulic systems face challenges in maintaining stable sensorless control when hydraulic pressure increases at the discharge port, leading to potential loss of synchronism and difficulty in maintaining rotational speed.
Innovation Solution
A control device that performs torque increase control before hydraulic pressure increases, ensuring the electric motor's torque starts to rise before the hydraulic pressure at the discharge port, thereby minimizing rotational speed reduction and maintaining stable sensorless control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control is used for the electric motor, then the device complexity is reduced, but the reliability deteriorates when hydraulic pressure increases causing rotational speed to drop into the unstable range
Solution Approach 1:
The control device predicts the timing of hydraulic pressure increase based on control signals to the hydraulic control device, and performs torque increase control before the actual pressure increase occurs. This preliminary action prevents the rotational speed from dropping into the unstable range, maintaining sensorless control reliability without adding physical sensors.
Solution Approach 2:
The control device uses feedback from the control signals sent to the hydraulic control device to predict when hydraulic pressure will increase. This feedback mechanism allows the system to anticipate load changes and adjust motor torque proactively, preventing rotational speed instability while maintaining sensorless control simplicity.
2Measurement precision
If current feedback control is used for the electric motor, then the torque control precision is improved, but the reliability deteriorates when load increases causing rotational speed to decrease and loss of synchronism to occur
Solution Approach 1:
The control device performs torque increase control before hydraulic pressure increases by predicting the pressure increase timing from control signals to the hydraulic control device. This preliminary torque adjustment prevents rotational speed from dropping, thereby preventing loss of synchronism while maintaining current feedback control precision.
Solution Approach 2:
The control device dynamically switches between current feedback control and rotational speed control based on predicted operational conditions. When hydraulic pressure increase is predicted, the system transitions to rotational speed control to maintain synchronism, then returns to current feedback control for precise torque management, optimizing both precision and reliability.
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 allows for continuous stable drive of the electric motor even when hydraulic pressure increases, preventing rotational speed from dropping to levels where sensorless control becomes difficult, thus ensuring reliable operation.
Implementation Method 1
driving an electric motor 2 by sensorless control executed based on an estimated rotational position or an estimated rotational speed
Data Source
AI summary
A control device that includes an electronic control unit that is configured to perform, when specific control that causes a change in a state of a hydraulic circuit in the hydraulic control device that involves an increase in hydraulic pressure at the discharge port is performed in a state in which a rotational speed of the electric motor is a first rotational speed, torque increase control that controls drive of the electric motor such that torque of the electric motor starts to increase before hydraulic pressure at the discharge port increases by the specific control.