Lockable Differential Control Using Slip and Operating Parameters
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Solution Overview
Problem
Existing differential locking systems in off-highway machines are inefficient due to manual operation, leading to undue wear on tires and other components, and require complex control systems to manage wheel slip effectively, often failing to optimally control differential locking and unlocking based on multiple operating parameters.
Innovation Solution
A method and system that monitor operating parameters other than wheel slip to proactively lock and unlock differentials, using an electronic controller to determine machine operating modes and adjust differential states based on sensed parameters such as ground speed, articulation angle, and transmission torque, allowing for proactive differential locking before wheel slip occurs and unlocking when conditions improve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual differential locking is used, then the operator can control when locking occurs, but the operator becomes distracted from other controls and may not engage or unlock at appropriate times, causing undue wear on tires and components
Solution Approach 1:
The system uses sensors to automatically detect wheel slip conditions and controls the differential lock engagement and disengagement without operator intervention. The controller monitors wheel speed sensors and automatically actuates the differential lock when slip is detected, and releases it when slip ceases, making the system self-regulating based on actual operating conditions
Solution Approach 2:
The system continuously monitors wheel speed through sensors and provides feedback to the controller. When the controller detects wheel slip through this feedback mechanism, it automatically engages the differential lock. When wheel slip stops, the system receives feedback and automatically disengages the lock, creating a closed-loop control system that responds dynamically to changing conditions
2Productivity
If selective braking mechanism is used to address wheel slip, then torque can be returned to the non-slipping wheel, but brake component wear increases and complex control systems are required
Solution Approach 1:
The patent extracts the differential locking function from the complex selective braking system and implements it as a separate, simpler mechanism. Instead of using the braking system to control torque distribution, the patent uses a dedicated differential lock that mechanically couples the wheels, eliminating the need for complex brake control logic while achieving the same productivity benefit
Solution Approach 2:
The patent replaces the mechanical braking system with a mechanical differential locking mechanism. Instead of using brake force to prevent wheel slip, the system uses a mechanical lock to directly couple the differential wheels, substituting a simpler mechanical solution for a more complex brake-based control system
3Ease of operation
If conventional lockable differentials are manually operated, then the operator can engage the lock when wheel slip begins, but this causes undue wear on tires and other drive train components
Solution Approach 1:
The system performs preliminary action by continuously monitoring wheel speed and detecting slip conditions before they become severe. The automatic control system engages the differential lock at the first sign of wheel slip, preventing the slip from causing excessive tire and component wear, rather than waiting for the operator to notice and respond
Data Source
AI summary
A method of operating a machine having a lockable differential includes monitoring a first operating parameter indicative of wheel slip, and monitoring a second operating parameter different from the first parameter, the method further including controlling locking and unlocking of the differential responsive to the second operating parameter. A machine is provided having an electronic controller including software control logic for controlling locking and unlocking of a differential, the electronic controller being configured to lock the differential where the machine is in an operating mode where wheel slip is likely, such as a digging/dozing mode. Satisfaction of criteria for locking may be recognition by the controller of a predetermined pattern of sensor inputs corresponding with a likely wheel slip condition, or actual slip detection.