Motor-Driven Oil Pump Torque Control for Stable Sensorless Operation
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Solution Overview
Problem
Existing control schemes for motor-driven oil pumps 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
Implementing torque increase control to boost the electric motor's torque before hydraulic pressure at the discharge port increases, ensuring the rotational speed remains within a stable range for sensorless control by initiating torque increase control when specific control changes the hydraulic circuit state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control is used to simplify the control system, then device complexity is reduced, but reliability deteriorates when hydraulic pressure increases causing loss of synchronism
Solution Approach 1:
The control device performs preliminary action by increasing motor torque before hydraulic pressure actually increases. When a change in hydraulic circuit state is detected, the control device increases the torque of the electric motor in advance, so that when hydraulic pressure increases and load increases, the motor rotational speed does not decrease to an unstable range. This prevents loss of synchronism in sensorless control while maintaining system simplicity.
2Reliability
If torque is increased to maintain rotational speed when hydraulic pressure increases, then reliability is improved, but use of energy worsens
Solution Approach 1:
The control device applies periodic action by temporarily increasing torque only when necessary - specifically when a change in hydraulic circuit state is detected. The torque increase control is activated only during the period when hydraulic pressure is increasing, and can be deactivated when the pressure stabilizes. This reduces overall energy consumption compared to continuous high-torque operation while maintaining reliability during critical transitions.
3Reliability
If rotational speed is maintained to prevent loss of synchronism, then reliability is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The control device applies self-service by using the existing sensorless control mechanism to detect changes in hydraulic circuit state through monitoring motor current and voltage. Instead of adding separate sensors or complex control systems, the existing control system serves multiple functions: it maintains sensorless operation, detects hydraulic circuit changes, and triggers torque increase control automatically. This maintains reliability while avoiding additional complexity.
Data Source
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AI summary
When a control device performs specific control that causes a change in a state of a hydraulic circuit in a hydraulic control device that involves an increase in hydraulic pressure at a discharge port of a motor-driven oil pump, in a state in which a rotational speed (N) of an electric motor that drives the motor-driven oil pump is a first rotational speed (N1), the control device performs torque increase control that controls drive of the electric motor such that torque (T) of the electric motor starts to increase before hydraulic pressure at the discharge port increases by the specific control.