Downhill Speed Control Reference Speed Dynamics
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Solution Overview
Problem
Heavy vehicles often experience inefficient fuel economy and increased braking on downhill gradients due to excessive speed control, leading to potential speeding fines and unnecessary braking, as the set speed for downhill speed control systems is typically set higher than the cruise control speed to account for gravity, resulting in prolonged braking and reduced kinetic energy utilization.
Innovation Solution
A method for governing the reference speed of a downhill speed control system to allow an increased reference speed at the end of a downhill gradient, utilizing simulated future speed profiles and tachograph infringement rules to maximize kinetic energy utilization without risking speeding fines, by coordinating with cruise control systems like Scania Active Prediction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the set speed for downhill speed control is set higher than cruise control speed to account for gravity, then the vehicle can maintain adequate speed on downhill gradients, but this results in prolonged braking and reduced kinetic energy utilization
Solution Approach 1:
The reference speed for downhill speed control is made dynamic by allowing it to temporarily exceed the set speed at the end of downhill gradients based on simulated future speed profiles. The system transitions from a static reference speed equal to set speed to a dynamic reference speed that adapts to terrain conditions, enabling kinetic energy recovery while maintaining safety margins during actual downhill descent.
Solution Approach 2:
The system performs preliminary simulation of future speed profiles before allowing increased reference speed. By predicting the vehicle's speed trajectory using topographic information and ignoring downhill speed control effects in the simulation, the system proactively identifies opportunities to increase reference speed before they arise, enabling kinetic energy recovery without risking speed limit infringements.
2Use of energy by moving object
If the reference speed is increased at the end of downhill gradient to maximize kinetic energy utilization, then fuel economy improves, but this risks exceeding speed limits and incurring fines
Solution Approach 1:
The system uses feedback from simulated future speed profiles to dynamically adjust the reference speed. By continuously monitoring the simulated speed trajectory against speed limit infringement rules and tachograph guidelines, the system provides feedback that prevents reference speed increases that would result in speeding fines, while still maximizing kinetic energy utilization within safe boundaries.
Solution Approach 2:
The reference speed parameter is changed based on multiple factors including simulated future speed profiles, topographic information, and tachograph infringement rules. The system adjusts this parameter dynamically, increasing it to maximize kinetic energy recovery while simultaneously considering speed limit constraints and infringement risks, thereby optimizing fuel economy without incurring fines.
3Reliability
If the downhill speed control system brakes the vehicle to maintain set speed, then speed control is maintained, but this leads to unnecessary braking and increased fuel consumption
Solution Approach 1:
The system transitions from maintaining a static reference speed equal to the set speed to using a dynamic reference speed that varies with terrain conditions. By allowing the reference speed to exceed the set speed at the end of downhill gradients when simulation indicates safety, the system reduces unnecessary braking while maintaining reliable speed control during actual downhill descent, thereby reducing fuel consumption without sacrificing control reliability.
4Loss of energy
If the set speed is set above the infringement speed to allow for speed variations, then the vehicle can utilize kinetic energy, but this increases the risk of logging infringements on the tachograph
Solution Approach 1:
The system performs preliminary simulation of future speed profiles to identify safe opportunities for increasing reference speed. By using topographic information and simulating the vehicle's speed trajectory while ignoring downhill speed control effects, the system proactively determines when kinetic energy utilization is safe, allowing the vehicle to exit downhill gradients with higher speed and maximize kinetic energy recovery without risking tachograph infringements.
Solution Approach 2:
The system uses feedback from simulated future speed profiles and tachograph infringement rules to dynamically adjust the reference speed. By continuously monitoring whether the simulated speed trajectory would result in infringements, the system provides feedback that prevents unsafe reference speed increases, thereby enabling kinetic energy utilization while maintaining reliability in infringement avoidance.
Data Source
Figure 1a~1b
Figure 2a
Figure 2b
AI summary
The present invention provides a system for governing a reference speed vref_dhsc for a downhill speed control system in a vehicle in connection with a downhill gradient. The system comprises a simulation unit which is arranged to simulate at least one future speed profile vsim for an actual vehicle speed over a section of road in front of the vehicle. This simulation is based on topographic information. The system also comprises an establishing unit that is arranged to establish whether the reference speed vref_dhsc is to be allocated the increased reference speed vref_dhsc_schwung. This establishment is based on a comparison of the simulated future speed profile vsim with a permitted magnitude of the increased reference speed vref_dhsc_schwung and/or with an infringement speed vs1. The system also comprises an allocation unit, arranged to allocate the value of the increased reference speed Vref_dhsc_schwung to the reference speed vref_dhsc if this has been established.