Electrohydraulic Motor-Pump Unit Torque Modulation
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Solution Overview
Problem
Existing hydraulic systems with positive displacement pumps experience pressure pulsation due to non-steady fluid delivery, leading to noise and vibration issues, which are typically addressed with secondary measures like pulsation dampers or flexible hoses, incurring additional effort and costs.
Innovation Solution
An electrohydraulic motor-pump unit modulates the drive torque or rotational speed of the electric drive based on recorded pulsation parameters, such as pressure pulsation or torque pulsation, to compensate for torque discontinuity and smooth out fluid delivery, using a fast-reacting electric control device with FPGAs and a suitable electric motor with sufficient dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If positive displacement pumps are used to deliver hydraulic fluid, then hydraulic energy can be generated and delivered to the system, but pressure pulsation and noise occur due to non-steady delivery
Solution Approach 1:
The patent applies dynamics by modulating the rotational speed of the electric motor driving the displacement pump according to a predetermined modulation curve. This dynamic speed adjustment compensates for the inherent pulsation in positive displacement pumps, transforming the static delivery pattern into a dynamically adjusted one that minimizes pressure fluctuations and noise while maintaining effective hydraulic energy delivery.
2Object-generated harmful factors
If secondary measures like pulsation dampers or flexible hoses are integrated into the hydraulic system, then pressure pulsation can be reduced, but device complexity and costs increase
Solution Approach 1:
The patent extracts the pulsation reduction function from separate secondary components (pulsation dampers, flexible hoses) and integrates it directly into the motor control system. By implementing speed modulation through the electric motor controller, the system achieves pulsation reduction without adding separate mechanical components, thereby reducing device complexity and costs while effectively minimizing pressure pulsation.
3Power
If the rotational speed of the electric motor is kept constant, then efficient power delivery is maintained, but torque discontinuity and pulsation occur in the displacement pump
Solution Approach 1:
The patent applies periodic action by modulating the motor rotational speed according to a predetermined periodic modulation curve that corresponds to the delivery frequency of the displacement pump. This periodic speed variation compensates for the torque discontinuity inherent in positive displacement pumps, maintaining smooth operation and stable hydraulic delivery while preserving overall power efficiency.
Data Source
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AI summary
An electro-hydraulic motor-pump unit comprises an intermittently operating positive displacement pump (1) for pumping hydraulic fluid in a hydraulic system, an electric motor (2) coupled to the positive displacement pump (1) for driving the positive displacement pump (1), and an electrical control unit (3) coupled to the electric motor (2) for controlling the electric motor (2). A detector (5) detects a pulsation parameter, for example, a hydraulic pressure (p0) in the hydraulic system or a drive torque (M0) of the electric motor, which results from a pulsation caused by the intermittent pumping of hydraulic fluid in the hydraulic system. A modulator, as part of the electrical control unit (3), modulates the drive torque (M) or the rotational speed of the electric motor (2) for driving the positive displacement pump (1) based on the detected pulsation parameter. As a result, the drive torque (M) or the rotational speed of the electric motor (2) is adjusted.the rotational speed of the electric motor (2) is modulated according to the delivery frequency of the positive displacement pump (1).