Work Machine Engine Speed Mapping to Avoid Resonance and Lug Down
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Solution Overview
Problem
Work machines face issues with engine speed resonance and lug down due to mechanical resonance-inducing speed ranges and drastic torque decreases, making fine adjustments difficult, especially in high-speed ranges where output power is high.
Innovation Solution
The implementation of a control system that adjusts engine speed using an EC dial, where the target engine speed is set to avoid resonance frequencies and torque decrease ranges by introducing intermediate speeds (N3 and N4) and modifying the slope of engine speed adjustments, allowing for finer control in high-speed ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the engine speed is set to any value between minimum and maximum speed using the EC dial, then the operator can freely adjust engine speed, but resonance may occur when setting engine speed in the vicinity of mechanical resonance frequencies
Solution Approach 1:
The continuous engine speed range is segmented into multiple control regions (first control region, second control region, third control region) with different control characteristics. Each region is optimized for specific operational requirements, allowing the system to avoid resonance frequencies while maintaining broad speed adjustability through region-based control strategies.
Solution Approach 2:
The control parameters (target engine speed determination method) are changed based on the current operating region. In the first control region, target speed is determined directly from EC dial input. In the second control region, target speed is set to the upper limit speed to avoid resonance. In the third control region, target speed is determined by adding a predetermined value to account for torque characteristics, preventing lug down while enabling fine adjustments in high-speed ranges.
2Reliability
If the excluded preset speed range is used to prevent resonance, then resonance is avoided, but fine adjustments of engine speed in high speed range become difficult
Solution Approach 1:
The control system dynamically adapts its behavior based on the current engine speed region. Rather than using a fixed excluded speed range, the system transitions between different control modes: direct EC dial control in the first region, upper limit speed control in the second region, and compensated target speed control in the third region. This dynamic adaptation enables fine adjustments in high-speed ranges while maintaining resonance prevention.
Solution Approach 2:
The target engine speed parameter is calculated differently depending on the control region. In the third control region (high-speed range), a predetermined value is added to the EC dial input to compensate for torque characteristics, creating a gentler slope that enables fine adjustments. This parameter transformation maintains reliability while improving ease of operation in frequently used high-speed ranges.
3Adaptability or versatility
If the engine speed is set in the vicinity of speed range where speed decrease results in drastic torque decrease, then the EC dial can control engine speed, but the engine is prone to lug down
Solution Approach 1:
The control system performs preliminary compensation by adding a predetermined value to the EC dial input in the third control region before the engine actually operates in the problematic speed range. This anticipatory adjustment prevents the engine from entering the lug down region by proactively modifying the target speed to account for the upcoming torque characteristics, thereby maintaining both control range and reliability.
Solution Approach 2:
The target engine speed parameter is modified in the third control region by adding a predetermined compensation value. This parameter change shifts the operating point away from the dangerous speed range where torque decreases drastically, preventing lug down while maintaining the ability to control engine speed across a broad range. The compensation amount is optimized to prevent lug down without sacrificing control versatility.
Data Source
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AI summary
The invention provides a work machine that is less prone to resonance and engine lug down even if there is a speed range where an engine speed decrease results in a drastic torque decrease between a minimum speed and a maximum speed and also allows fine adjustments of the engine speed in a high speed range. A target engine speed can be set excluding between a first engine speed and a second engine speed. The first engine speed is higher than the minimum engine speed, and the second engine speed is higher than the first engine speed and lower than the maximum engine speed. The ratio of the change in the target engine speed to the change in the operation amount of the engine speed instructing device when the operation amount of the engine speed instructing device is changed from the operation amount for instructing the minimum speed to the operation amount for instructing the first engine speed is larger than the ratio of the change in the target engine speed to the change in the operation amount of the engine speed instructing device when the operation amount of the engine speed instructing device is changed from the operation amount for instructing the second engine speed to the operation amount for instructing the maximum speed.