Backhoe Pump Torque Control for Engine Speed Stability
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Solution Overview
Problem
Construction machines operating in highlands with low atmospheric pressure experience engine stalls due to decreased air intake and increased absorption torque from hydraulic pumps, leading to unstable engine speed control.
Innovation Solution
A control system that adjusts the swash plate angle of a variable capacity hydraulic pump based on the difference between actual and target engine speeds, switching between isochronous control and droop control to maintain optimal engine torque and prevent speed hunting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If droop control is used to prevent engine speed hunting, then engine speed stability is improved, but travelling speed control precision deteriorates
Solution Approach 1:
The patent dynamically switches between droop control and isochronous control modes based on operating conditions. During engine startup or high-load operations, droop control is applied to stabilize engine speed. During travel operations, isochronous control is applied to maintain constant travelling speed. This dynamic mode switching resolves the contradiction by applying the appropriate control strategy for each operational phase.
Solution Approach 2:
The control mode parameter is changed based on detected operating conditions. The system monitors parameters such as engine speed, load conditions, and operational state to determine when to switch between control modes. This parameter-based mode selection allows the system to optimize for either speed stability or travelling precision depending on current requirements.
2Stability of the object's composition
If isochronous control is used to maintain constant engine speed, then speed stability is improved, but adaptability to load changes deteriorates
Solution Approach 1:
The system dynamically transitions between isochronous control and droop control based on operational needs. During travel phases, isochronous control maintains constant speed. During startup or high-load phases, the system switches to droop control which allows speed variation to accommodate load changes. This dynamic adaptation resolves the contradiction between speed stability and load adaptability.
Solution Approach 2:
The control parameter (control mode) is changed in response to detected operational conditions. When the system detects startup conditions or high-load operations, it switches from isochronous to droop control, allowing the engine speed parameter to vary appropriately with load changes while maintaining overall system performance.
3Reliability
If pump discharge amount is reduced to prevent engine stalling, then engine reliability is improved, but productivity deteriorates
Solution Approach 1:
The hydraulic pump operates in different discharge modes dynamically. During high-load operations or startup, the pump reduces discharge amount to prevent engine stalling. During normal travel or work operations, the pump increases discharge to maintain productivity. This dynamic discharge adjustment resolves the contradiction between engine reliability and productivity.
Solution Approach 2:
The pump discharge parameter is changed based on engine load conditions and operational phase. The control system monitors engine performance and adjusts pump discharge accordingly, reducing it only when necessary to prevent stalling while maintaining high discharge during phases where productivity is prioritized. This parameter-based control optimizes both reliability and productivity.
Data Source
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AI summary
An object is to provide a backhoe that is a construction machine that selects a mode for controlling an engine in accordance with a task, and can prevent an engine speed hunting of the engine by controlling a discharge amount of a hydraulic pump. In a backhoe (1) that is a construction machine in which a swash plate angle of a variable capacity hydraulic pump (29) driven by an engine (19) is controlled based on a difference (ΔN) between an actual engine speed (N) of the engine (19) and a target engine speed (Nt) calculated from an accelerator position (Sn), the engine (19) is controlled through isochronous control when the actual engine speed (N) of the engine (19) is equal to or higher than a maximum torque engine speed (Np) with which a maximum torque of the engine (19) is able to be output, and the engine (19) is controlled through droop control when the actual engine speed (N) of the engine (19) is lower than the maximum torque engine speed (Np) with which the maximum torque of the engine (19) is able to be output.