Wheel Loader Torque Control for Slip Prevention
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Solution Overview
Problem
Construction vehicles face challenges in suppressing wheel slip during object lifting due to the difficulty in balancing excavating counteraction and driving force, particularly in hybrid wheel loaders where engine speed does not directly correlate with driving force, leading to issues like excessive plunging and wheel slipping.
Innovation Solution
A construction vehicle equipped with a hydraulic pump, hydraulic actuator, and a controller that adjusts the torque requirement increase rate for the traveling drive device based on the lift arm's operation and bucket cylinder stroke, limiting the driving force to prevent wheel slip by reducing the torque increase rate when the lift arm fails to operate or when the bucket cylinder stroke exceeds a setting value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driving force is increased to prevent wheel slip, then wheel slip is suppressed, but the bucket plunges too deeply into the object making it difficult to raise the bucket
Solution Approach 1:
The patent applies dynamics by making the driving force adjustable and time-dependent rather than fixed. The controller dynamically modifies the driving force based on real-time detection of bucket position and excavating counteraction, allowing the system to adapt between preventing wheel slip and enabling bucket raising according to actual working conditions
Solution Approach 2:
The patent implements feedback control by detecting the bucket position and excavating counteraction, then using this information to adjust the driving force. The controller continuously monitors the working conditions and modifies the driving force accordingly, creating a closed-loop control system that balances wheel slip prevention with bucket raising capability
2Ease of operation
If the driving force is limited to prevent excessive plunging, then the bucket can be raised easily, but wheel slip occurs due to insufficient frictional force
Solution Approach 1:
The system dynamically adjusts the driving force based on real-time working conditions rather than using a fixed limit. When the bucket is deeply plunged, the controller increases driving force to enable raising; when ground contact pressure is sufficient, it limits driving force to prevent wheel slip
Solution Approach 2:
The controller uses feedback from bucket position detection and excavating counteraction sensing to continuously adjust the driving force. This feedback mechanism allows the system to respond to changing conditions and optimize the balance between preventing wheel slip and enabling bucket raising
3Reliability
If the operator manually balances excavating counteraction and driving force, then wheel slip can be suppressed, but skill is required and operation becomes complex
Solution Approach 1:
The system performs self-service by automatically detecting working conditions and adjusting the driving force without operator intervention. The controller monitors bucket position and excavating counteraction, then autonomously modifies the driving force to prevent wheel slip, eliminating the need for operator skill in balancing forces
Solution Approach 2:
The patent replaces the mechanical skill-based balancing act with an automated control system. Instead of relying on operator skill to balance excavating counteraction and driving force, the system uses sensors and a controller to automatically perform this function, substituting human skill with automated detection and control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces wheel slip during object lifting by adjusting the driving force in real-time, ensuring stable operation and preventing wheel slipping, even in hybrid wheel loaders with varying energy levels.
Implementation Method 1
a hydraulic pump (9), a working implement (107) having a hydraulic actuator (13, 14) driven by a hydraulic fluid supplied from the hydraulic pump (9)
Implementation Method 2
the wheels increase in ground contact pressure since the force that raises the bucket works upon the vehicle body as the counteraction from the object. As the ground contact pressure of the wheels increases, maximum frictional force between the wheels and the ground surface increases, so that when the bucket is being raised, occurrence of wheel slip tends to be reduced
Data Source
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Figure 5~6
AI summary
This invention includes a hydraulic pump (9), a working implement (107) having a lift cylinder (13) driven by a hydraulic fluid supplied from the hydraulic pump (9), an operating device (104) for operating the working implement (107), a traveling motor (7) for driving wheels, and a main controller (100). When the lift cylinder (13) fails to operate despite an extending instruction being imparted to the lift cylinder (13) via the operating device (104), the main controller (100) reduces a limit value for an increase rate of a torque required in the traveling motor (7) to a value smaller than that applied when the lift cylinder (13) operates. With this configuration, occurrence of wheel slip during lifting of an object to be carried can be reduced.