Tractor-Trailer Braking Control With CVT Speed Demand Balancing
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Solution Overview
Problem
Work machines with CVT powertrains face issues in maintaining speed under varying loads, particularly when towing trailers with diverse braking systems, leading to potential jack-knifing due to inconsistent braking efforts between the tractor unit and trailer.
Innovation Solution
A method and control system that adjusts the braking effort of a tractor unit by increasing motive force through enhanced braking modes, using operator input to enhance speed demand and adjust transmission ratios to balance braking forces between the tractor unit and trailer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tractor unit applies standard braking effort, then the braking system is simple to operate, but the trailer may out-brake the tractor unit leading to jack-knifing and loss of control
Solution Approach 1:
The braking system dynamically adjusts the braking effort applied to the tractor unit based on real-time conditions including trailer braking status, vehicle speed, and load. The control system continuously monitors whether the trailer is out-braking the tractor unit and automatically modulates the tractor's brake force to maintain balanced braking distribution, preventing jack-knifing while adapting to varying operational conditions.
Solution Approach 2:
The system implements feedback control by monitoring the relative braking effort between tractor unit and trailer through sensors that detect brake pressure, vehicle deceleration, and coupling forces. This feedback information is fed to the control system which adjusts the tractor's braking effort in real-time to maintain stable braking balance and prevent lateral motion of the trailer.
2Power
If the tractor unit increases engine speed to maintain power delivery, then more power is readily available, but fuel efficiency decreases and noise and pollution increase
Solution Approach 1:
The CVT system dynamically adjusts the transmission ratio to optimize engine operating points during braking and power delivery. During braking events, the system allows engine speed to reduce naturally while maintaining adequate power delivery through optimized gear ratios. During acceleration, the CVT selects transmission ratios that keep the engine operating in efficient fuel consumption regions while still delivering required power, thereby improving fuel efficiency without sacrificing power capability.
3Use of energy by moving object
If the tractor unit uses a fixed transmission ratio, then the transmission system is simpler, but the engine cannot operate at optimal speeds under varying loads
Solution Approach 1:
The continuous variable transmission system continuously varies the transmission ratio based on engine load, vehicle speed, and driver demand. The control system monitors engine operating conditions and adjusts the CVT ratio to maintain the engine at optimal operating points for fuel efficiency and power delivery. This dynamic adaptation allows the engine to operate efficiently across a wide range of loads without requiring complex multi-speed gearboxes or frequent manual shifting.
Solution Approach 2:
The system changes the transmission ratio parameter continuously rather than in discrete steps. The CVT mechanism allows smooth variation of the gear ratio to optimize engine operating conditions. During braking, the transmission ratio is adjusted to allow engine speed to reduce appropriately. During acceleration, the ratio is optimized for power delivery. This continuous parameter adjustment maintains engine efficiency while adapting to varying operational demands.
Data Source
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AI summary
The invention relates in one aspect to a method for controlling the braking effort of a tractor unit (10) relative to the braking effort of a trailer (17) being towed by the tractor unit, the method comprising: activating an enhanced braking mode in the tractor unit; receiving a braking command from an operator input device whilst in the enhanced braking mode; increasing a tractor unit speed demand on the tractor unit whilst receiving the braking command; applying the brakes to the trailer and tractor unit, wherein the braking effort applied to the tractor unit is reduced relative to the trailer due to the increased speed demand. In another aspect the invention relates to a tractor unit (10) configured to tow a trailer (17).