Hydrostatic Transmission Control for Slope Roll-Back Prevention
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Solution Overview
Problem
Agricultural sprayers experience roll-back on sloped surfaces when the service brake is released, as the hydrostatic transmission takes time to ramp up sufficient speed to overcome downhill forces, potentially leading to vehicle instability and damage.
Innovation Solution
A system with a speed setting device and computing system that adjusts the transmission speed mapping to a roll-back speed mapping, allowing limited speed increase while the service brake is engaged, reducing the risk of roll-back when the brake is released.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmission speed is increased rapidly when the service brake is released, then the vehicle can overcome downhill forces more effectively, but the transmission and service brake may be damaged due to excessive force
Solution Approach 1:
The system performs preliminary action by ramping up the transmission output speed to a predetermined level while the service brake is still engaged, before the brake is released. This ensures the transmission is already at sufficient speed to overcome downhill forces when the brake releases, preventing roll-back without subjecting the brake to sudden high-speed forces that could cause damage
Solution Approach 2:
The system dynamically adjusts the transmission control based on service brake status. When the service brake is engaged, the transmission is allowed to ramp up speed; when the service brake is released, the transmission maintains or increases speed to prevent roll-back. This dynamic control optimizes both speed performance and component protection
2Strength
If the transmission is prevented from ramping up speed while the service brake is engaged, then the transmission and brake are protected from damage, but the vehicle experiences roll-back when the brake is released on sloped surfaces
Solution Approach 1:
The system performs preliminary speed buildup while the service brake is engaged, so that when the brake is released, the transmission is already at sufficient speed to prevent roll-back. This preliminary action ensures vehicle stability on slopes without compromising transmission or brake protection
Solution Approach 2:
The system uses feedback from service brake status to control transmission speed ramping. When the service brake is engaged, the transmission ramps up speed; when released, the transmission maintains speed to prevent roll-back. This feedback-based control resolves the contradiction between protection and stability
3Reliability
If the transmission speed is limited while the service brake is engaged, then component damage is prevented, but the vehicle cannot respond quickly to overcome downhill forces after brake release
Solution Approach 1:
The system performs preliminary speed buildup during the period when the service brake is engaged, so that when the brake is released, the transmission is already at the speed needed to overcome downhill forces immediately. This eliminates response delay while maintaining component reliability through controlled ramp-up rates
Solution Approach 2:
The system dynamically changes transmission speed limits based on service brake engagement status. When engaged, a controlled ramp-up rate is applied; when released, higher speeds are permitted immediately. This dynamic adjustment ensures both reliability and rapid response capability
Data Source
AI summary
An agricultural method for preventing roll-back of an agricultural vehicle may include receiving a roll-back prevention input from a speed setting device indicative of a command to increase the transmission speed of the hydrostatic transmission while a service brake of the agricultural vehicle is engaged. Further, the method may include adjusting a speed mapping for the speed setting device from a predetermined speed mapping to a roll-back speed mapping in response to the roll-back prevention input, with the roll-back speed mapping being associated with a reduced speed range. Additionally, the method may include determining a transmission control command associated with a current position of the speed setting device based on the roll-back speed mapping and controlling an operation of the hydrostatic transmission to adjust the transmission speed based at least in part on the transmission control command.