Variable Displacement Pump Control via Virtual Pressure
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Solution Overview
Problem
Existing methods for controlling variable displacement pumps in construction machines, such as those using closed-center-type directional control valves, face inefficiencies and risk of engine stall due to inadequate flow rate management and lack of consideration for engine horse power, leading to suboptimal utilization and potential engine overload.
Innovation Solution
The method involves detecting real discharge flow rates and operation amounts to determine virtual discharge pressures, distributing engine horse power among pumps, and adjusting the distribution ratio based on operational conditions to prioritize actuators and prevent engine stall, thereby optimizing pump utilization and avoiding engine overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump discharge flow rate is increased to improve utilization of the variable displacement pump, then productivity is improved, but the engine may stall due to excessive load
Solution Approach 1:
The control method dynamically adjusts the commanded pump discharge pressure based on real-time operating conditions including engine horsepower and pump flow rate characteristics. The controller continuously monitors and modifies pressure commands to optimize pump utilization while preventing engine overload and stall conditions
Solution Approach 2:
The system changes the commanded pump discharge pressure parameter based on the relationship between pump discharge flow rate and pressure, taking into account engine horsepower limitations. This allows the pump to operate at optimal points on its characteristic curve without exceeding engine capacity
2Productivity
If the commanded pump discharge pressure is calculated without considering engine horsepower, then the pump can operate at optimal pressure points, but the engine load becomes too high leading to engine stall
Solution Approach 1:
The control method incorporates feedback from engine horsepower measurements to adjust the commanded pump discharge pressure. The controller uses real-time engine performance data to modify pressure commands, ensuring the pump operates optimally while keeping engine load within safe limits
Solution Approach 2:
The system dynamically adapts the pressure command based on actual engine horsepower output rather than using fixed or predetermined pressure values. This dynamic adjustment allows the pump to operate at optimal pressure points while responding to changing engine capacity conditions
3Reliability
If the pump discharge flow rate is limited by engine horsepower division, then engine stall is prevented, but the pump utilization becomes suboptimal when pressure exceeds predetermined pressure P1
Solution Approach 1:
The system changes the pressure command parameter based on the pump's characteristic curve and actual operating conditions. When pressure exceeds P1, the controller adjusts the commanded pressure to allow higher flow rates that are consistent with engine horsepower capacity, rather than applying a fixed flow rate limit
Solution Approach 2:
The control method dynamically determines the appropriate pump discharge flow rate based on the relationship between pressure and flow rate on the pump's characteristic curve, rather than applying a static flow rate limit. This allows the system to maximize pump utilization while preventing engine stall
Data Source
AI summary
A method for controlling a variable displacement pump by calculation by a controller using a closed-center-type directional control valve, the method allowing effective utilization of the variable displacement pump while avoiding the risk of engine stall is provided. The method includes determining a first virtual discharge pressure and a second virtual discharge pressure. The method includes controlling the variable displacement pump based on a smaller value of the first virtual discharge pressure and the second virtual discharge pressure.