Hydraulic Pump Torque Allocation for Low-Flow Excavator 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 the ratio of estimated demanded powers of actuators, ensuring efficient torque allocation and utilization without exceeding the prime mover's output torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If total horsepower control is performed by giving feedback only about delivery pressure of each hydraulic pump to the other pump, then the control system is simple, but the consumed torque cannot be monitored accurately when delivery flow rate is low, leading to unnecessary torque reduction
Solution Approach 1:
The system introduces feedback about the delivery flow rate of each hydraulic pump to the regulator of the other pump, in addition to the existing delivery pressure feedback. This dual-parameter feedback enables accurate calculation of consumed torque (consumed horsepower) for each pump, allowing the control system to make informed adjustments to allowable torque allocation based on actual pump performance rather than just pressure signals.
Solution Approach 2:
The control system acts as an intermediary that receives both pressure and flow rate information from each pump, calculates the consumed torque, and then determines appropriate allowable torque values for each pump's regulator. This intermediary processing ensures that torque allocation decisions are based on comprehensive pump performance data, resolving the inaccuracy that occurs when only pressure feedback is used.
2Use of energy by moving object
If the delivery flow rate of a hydraulic pump is low, then the pump consumes less horsepower, but the existing control system cannot detect this and unnecessarily reduces the allowable torque of the other pump
Solution Approach 1:
By introducing flow rate feedback in addition to pressure feedback, the system can accurately calculate the actual consumed horsepower of each pump (since horsepower = pressure × flow rate). This enables the control system to distinguish between low horsepower consumption due to actual low demand versus low consumption due to limited flow rate capability, preventing unnecessary torque reduction of the other pump.
Solution Approach 2:
The system changes from monitoring only pressure parameters to monitoring both pressure and flow rate parameters. This parameter expansion allows accurate determination of actual horsepower consumption, enabling dynamic adjustment of allowable torque allocation that reflects real pump performance rather than assuming torque demand based solely on pressure signals.
3Speed
If total horsepower control is performed using only delivery pressure feedback, then the system responds quickly to pressure changes, but torque allocation is inefficient when delivery flow rates vary
Solution Approach 1:
The system maintains fast pressure-based response while adding flow rate feedback to enable accurate torque calculation. The regulator uses both pressure and flow rate information to determine allowable torque, ensuring that quick pressure responses are combined with accurate horsepower-based torque allocation, preventing inefficient torque distribution when flow rates vary.
Solution Approach 2:
The system dynamically adjusts allowable torque allocation based on real-time measurements of both pressure and flow rate for each pump. This dynamic adjustment ensures that torque distribution optimally reflects actual pump performance and demand conditions, maintaining responsiveness while improving overall torque utilization efficiency.
Data Source
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.