Electric Hydraulic Pump Control for Power-Limited Operation
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Solution Overview
Problem
Electrically driven hydraulic work machines, such as hydraulic excavators, face issues with sudden stops due to abnormal battery voltage drops and commercial power supply breaker interruptions, leading to instability and operational inconvenience when power consumption exceeds predetermined limits.
Innovation Solution
A controller system that calculates and limits the electric motor's power consumption by adjusting the target revolution speed based on the hydraulic pump's capacity and delivery pressure, ensuring power remains within the maximum allowable range, preventing voltage drops and breaker interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric motor drives the hydraulic pump at high power to increase work capacity, then the productivity is improved, but the battery voltage suddenly drops below the allowable range causing the inverter to stop operation
Solution Approach 1:
The control device performs preliminary calculation of the maximum allowable power based on battery state (voltage, temperature, charge level) before the voltage drops occur. By pre-determining the power limits and proactively controlling the motor output to stay within these limits, the system prevents voltage drops that would cause inverter shutdown, thus maintaining operation continuity while maximizing productivity.
2Productivity
If the electric motor consumes more power to increase hydraulic pump capacity, then the productivity is improved, but the commercial power supply breaker carries out interrupt operation
Solution Approach 1:
The control device dynamically adjusts the maximum allowable power parameter based on the power supply source (battery or commercial power supply) and its current state. When connected to commercial power supply, the controller calculates and enforces power limits that prevent breaker interruption, allowing the system to operate at optimal productivity levels without exceeding power supply capacity.
Solution Approach 2:
The control device continuously monitors the actual power consumption and compares it against the calculated maximum allowable power. When the actual power approaches or exceeds the limit, the controller adjusts the motor output to maintain power within safe boundaries, preventing breaker interruption and ensuring stable operation.
3Reliability
If the controller limits the electric motor power consumption to prevent voltage drops and breaker interruptions, then the reliability is improved, but the productivity decreases
Solution Approach 1:
The maximum allowable power is not a fixed value but dynamically adjusted based on real-time battery state (voltage, temperature, charge level) and power supply conditions. This dynamic adjustment allows the system to operate at the highest possible productivity level within safe boundaries, maximizing work output while maintaining operation stability and preventing sudden stops.
Data Source
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AI summary
In a hydraulic drive system used for an electrically driven hydraulic work machine that drives a hydraulic pump by an electric motor and supplies a hydraulic fluid to plural actuators to carry out work, the power consumption of the hydraulic pump is kept from exceeding a value decided in advance. For this purpose, a controller calculates target power to be consumed by the hydraulic pump on the basis of the capacity of the hydraulic pump, the delivery pressure of the hydraulic pump sensed by a pressure sensor, and a target revolution speed of the electric motor, and limits the target revolution speed of the electric motor in such a manner that the target power falls within a range of the maximum allowable power.