Work Vehicle Drive Control System Slippage Prevention
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Solution Overview
Problem
Existing drive control systems for work vehicles struggle to quickly increase drive power on the contact area, especially when inclined, leading to repetitive switching between two-wheel and four-wheel drive modes, causing slippage and damage during turning and inclines.
Innovation Solution
A drive control system that includes a steering angle detection unit, high-speed detection unit, start detection unit, shift operation detection unit, engine revs change detection unit, target revs detection unit, and actual revs detection unit, which prioritize transitioning to a high-speed drive state during over-steering and other conditions to prevent slippage and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive mode is switched from two-wheel drive to four-wheel drive when slip ratio exceeds a threshold, then slippage is eliminated and drive power is increased, but the switching response is delayed and hunting occurs on slopes
Solution Approach 1:
The control system performs preliminary action by switching to four-wheel drive mode before slippage actually occurs. When the slip ratio exceeds a first threshold, the system proactively switches drive modes in advance, preventing slippage from developing fully. This eliminates the delay associated with waiting for slippage to occur before responding.
Solution Approach 2:
The system implements feedback control by continuously monitoring the slip ratio and using it to adjust drive mode decisions. The slip ratio serves as a feedback signal that triggers mode switching when it exceeds the first threshold, creating a closed-loop control system that responds dynamically to actual driving conditions and prevents hunting on slopes.
2Reliability
If the drive mode switches automatically based on slip ratio, then slippage is reduced, but repetitive switching (hunting) occurs when inclined
Solution Approach 1:
The system uses feedback control with the slip ratio as the control signal. By continuously monitoring slip ratio and comparing it against the first threshold, the system makes informed decisions about mode switching. This feedback mechanism prevents hunting by ensuring switches occur only when truly necessary, based on actual slip conditions rather than transient fluctuations.
Solution Approach 2:
The system changes the parameter used for mode switching decision-making. Instead of using a second threshold that causes hunting, the system switches to using the first threshold based on slip ratio, which provides more stable and reliable control. This parameter change fundamentally resolves the hunting problem by using a more appropriate control variable.
3Ease of operation
If the work vehicle turns in two-wheel drive mode, then turning is achieved, but damage occurs to the contact area
Solution Approach 1:
The system applies preliminary anti-action by detecting when the work vehicle is turning and proactively preventing contact area damage before it occurs. When a turn is detected, the control system switches to four-wheel drive mode in advance, which distributes the mechanical load more evenly and prevents the excessive stress that would otherwise damage the contact area during turning maneuvers.
Data Source
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AI summary
A drive control system for a work vehicle is provided with a power transmission device that drives front wheels and rear wheels, a request determination unit, and a drive mode control unit. The power transmission device has a drive mode switching mechanism that performs drive mode switching between a four-wheel drive mode in which drive power is transmitted to front wheels and rear wheels and a two-wheel drive mode in which drive power is transmitted to only the rear wheels. The request determination unit determines a necessity for an increase in drive power on a contact area of the work vehicle, and outputs an increase request based on the determination result. The drive mode control unit outputs a drive mode switching request for switching to the four-wheel drive mode to the drive mode switching mechanism, in response to output of the increase request.