Hydraulic Pump Torque Allocation for Excavator Horsepower Control
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Solution Overview
Problem
Existing hydraulic drive systems for construction machines, such as hydraulic excavators, face inefficiencies in total horsepower control, where the consumed torque of hydraulic pumps cannot be accurately monitored due to low delivery flow rates, leading to unnecessary reduction in torque utilization from the prime mover.
Innovation Solution
A hydraulic drive system that includes multiple pumps, flow control valves, regulators, and sensors to calculate and adjust the allowable torques of each pump based on estimated demanded powers, ensuring that the total consumed torque does not exceed a predetermined limit, thereby optimizing torque allocation and utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If total horsepower control is performed by giving feedback about the delivery pressure of each hydraulic pump to the regulator of the other pump, then horsepower allocation between pumps can be controlled, but the consumed torque cannot be accurately monitored when delivery flow rate is low, leading to unnecessary torque reduction
Solution Approach 1:
The system introduces a feedback mechanism where the controller receives delivery pressure signals from pressure sensors connected to each hydraulic pump, estimates demanded power based on operation lever positions and delivery pressures, and uses this feedback to dynamically adjust the allowable torque of each pump. This ensures accurate monitoring of consumed torque even when delivery flow rate is low, preventing unnecessary torque reduction while maintaining total horsepower control.
2Reliability
If the delivery flow rate of a hydraulic pump is low, then consumed horsepower may be smaller even with high delivery pressure, but existing systems cannot accurately monitor this condition, causing unnecessary torque reduction
Solution Approach 1:
The controller performs preliminary estimation of demanded power for each hydraulic pump based on the position of operation levers and delivery pressure before actual torque control is executed. This preliminary action allows the system to predict the required torque and adjust allowable torque settings in advance, ensuring reliable torque control while preventing unnecessary reductions in operational efficiency.
Solution Approach 2:
The system replaces traditional mechanical torque monitoring mechanisms with an electronic control system that uses pressure sensors and operation lever position sensors to estimate demanded power. This substitution enables more accurate and responsive torque monitoring, particularly in conditions where mechanical monitoring would fail to detect low flow rate scenarios accurately.
3Ease of operation
If multiple hydraulic pumps are controlled with individual regulators, then each pump can be controlled independently, but the total consumed torque may exceed the prime mover's output torque without proper coordination
Solution Approach 1:
The controller performs multiple functions: it estimates demanded power for each pump based on operation lever positions, calculates total demanded power, determines appropriate allowable torque for each pump, and adjusts regulator settings accordingly. This multi-functionality allows independent control of each pump while ensuring coordinated operation within the prime mover's total power capacity, maintaining both operational flexibility and total horsepower capacity.
Solution Approach 2:
The system dynamically adjusts the allowable torque of each hydraulic pump based on real-time conditions including operation lever positions and delivery pressures. This dynamic control allows the system to optimize power distribution between pumps during operation, ensuring that the total consumed torque never exceeds the prime mover's output torque while maintaining maximum operational flexibility.
Data Source
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AI summary
A controller calculates the ratio between the sum of estimated demanded powers of a plurality of first actuators and the sum of estimated demanded powers of a plurality of second actuators, and calculates, on the basis of the ratio, first and second command values for adjusting allocation between a first allowable torque of a first pump and a second allowable torque of a second pump, and first and second regulators adjust the first and second allowable torques, on the basis of first and second output pressures of first and second torque control valves, such that the first and second allowable torques become values to which a predetermined allowable torque is allocated according to the ratio described above, and control the delivery flow rates of the first and second pumps such that the respective consumed torques of the first and second pumps do not become larger than the first and second allowable torques. Thus, the present invention efficiently performs torque allocation between the first and second pumps (a plurality of hydraulic pumps) to thereby enable effective utilization of the torque generated by the prime mover without wasting the torque.