Vehicle Speed Shift Optimization Using Energy-Based State Costs
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Solution Overview
Problem
Conventional methods for determining an optimal speed and gear shift profile for motor vehicles require high computing effort and resources due to non-linear equations of motion, especially when considering force balances and energy changes.
Innovation Solution
The method determines state change costs based on specific energy changes, using a linear model to approximate fuel mass flow and energy changes, reducing computational complexity and resource requirements by considering kinetic and potential energy changes together, and storing pre-calculated energy changes for efficient look-up during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods using non-linear equations of motion and force balances are used to determine optimal speed and gear shift profile, then accuracy of the optimization is improved, but computational effort and resource usage increase significantly
Solution Approach 1:
The patent transforms the physical model parameters from force-based variables (tractive force, braking force, driving resistance) to energy-based variables (kinetic energy, potential energy). This parameter transformation simplifies the mathematical relationships while preserving the physical accuracy needed for optimal gear shift determination.
Solution Approach 2:
The patent replaces the mechanical force balance approach with an energy balance approach. Instead of solving non-linear differential equations based on forces, the system uses energy conservation principles where the change in mechanical energy (kinetic + potential) equals the work done by non-conservative forces, resulting in simpler algebraic equations that are computationally more efficient.
2Reliability
If force balance with non-linear equations of motion is applied to calculate state transitions, then comprehensive physical factors are considered, but storage capacity and processing power requirements increase
Solution Approach 1:
The patent changes the fundamental parameters from force components (F = ma, F_friction, F_drag) to energy components (E_kinetic = 1/2mv², E_potential = mgh). This transformation reduces the complexity of the equations of motion from second-order non-linear differential equations to first-order energy balance equations, maintaining physical comprehensiveness while improving computational efficiency.
Solution Approach 2:
The patent pre-calculates and stores energy-related parameters (kinetic energy at different speeds, potential energy changes over elevation profiles) before the optimization process. This preliminary preparation reduces the real-time computational burden during actual gear shift optimization, allowing faster processing without sacrificing accuracy.
Data Source
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AI summary
The invention relates to a device and a method for determining an optimal speed and associated gear shift profile of a motor vehicle, to be automatically set on a preceding road segment, with respect to predetermined target criteria. The method comprises defining (S10) a discrete search space (10) that specifies possible profiles of driving states (14) of the motor vehicle (1) along a preceding road segment (12), wherein a driving state (14) is defined by a speed and the associated gear of the motor vehicle (1). The method further comprises defining (S20) state change costs for possible driving state transitions within the search space and defining (S30) an optimal profile (17) of the driving states (14) within the defined search space (10) for the preceding road segment (12) with respect to the determined state change costs.The method is characterized by the fact that for each driving state (14) within the search space (10), a kinetic energy of the vehicle is determined (S21), and that an energy change is determined for each possible driving state transition within the search space (S23), where the energy change indicates a change in the vehicle's energy during a transition between two driving states. The state change costs are then determined as a function of the determined energy changes (S24).