Electric Machine Efficiency Control for Endurance Braking
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Solution Overview
Problem
Heavy-duty vehicles face challenges in endurance braking due to the limited energy absorption capability of their energy storage systems (ESS) and brake resistors, leading to potential brake fading and the need for over-dimensioning components.
Innovation Solution
A method is implemented in a vehicle control unit to dynamically regulate the output energy of the electric machine (EM) during braking, matching the energy absorption capabilities of the ESS. This involves configuring the power loss level or efficiency level of the EM based on the ESS's energy absorption capability and the amount of regenerated energy during braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the electric machine operates at high efficiency to maximize regenerative braking energy recovery, then energy efficiency is improved, but the energy absorption capability of the ESS may be exceeded causing brake fading
Solution Approach 1:
The patent implements dynamic efficiency control of the electric machine during regenerative braking. The control system continuously adjusts the EM efficiency level based on real-time monitoring of ESS state of charge, temperature, and energy absorption capability. This dynamic adjustment allows the system to optimize energy recovery while preventing ESS saturation, thereby maintaining reliable braking capability throughout the braking event.
Solution Approach 2:
The patent employs a feedback control mechanism where the vehicle control unit continuously monitors ESS parameters (state of charge, temperature, energy absorption capability) and adjusts the EM efficiency level accordingly. This closed-loop feedback ensures that regenerative braking operates within the ESS absorption limits, preventing brake fading while maximizing energy recovery when conditions permit.
2Reliability
If additional braking systems or over-dimensioned energy storage systems are installed to support prolonged endurance braking, then braking reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the operational parameters of the existing electric machine by dynamically adjusting its efficiency level during braking events. Instead of adding hardware, the system modifies the EM's operating characteristics (efficiency, power loss level) based on ESS capability. This parameter-based control enables prolonged endurance braking using the existing system architecture, avoiding the need for additional braking systems or over-dimensioned ESS.
3Loss of energy
If the electric machine operates continuously at maximum efficiency, then energy recovery is maximized, but component overheating occurs reducing lifespan
Solution Approach 1:
The patent implements periodic modulation of the electric machine's efficiency level during regenerative braking. Rather than sustaining maximum efficiency continuously, the system varies the efficiency level in response to thermal conditions and ESS capability, allowing periodic thermal management while maintaining effective energy recovery. This periodic action prevents sustained overheating while preserving braking performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method extends the endurance capability of heavy-duty vehicles by optimizing the energy usage during braking, reducing the need for additional braking systems and minimizing component overheating, thus maintaining energy efficiency and prolonging the lifespan of vehicle components.
Implementation Method 1
The electric machine may then act as a generator which converts the kinetic energy from the vehicle into electrical energy
Implementation Method 2
Surplus energy from regenerative braking can be fed to a brake resistor where it is converted into heat
Data Source
AI summary
A method performed in a vehicle control unit for controlling an electric machine (EM) of a heavy-duty vehicle, wherein the heavy-duty vehicle comprises an energy storage system (ESS) connected to the EM, the method comprising obtaining an energy absorption capability of the ESS, determining an amount of regenerated energy by the EM during braking, and configuring an efficiency level of the EM in dependence of the energy absorption capability of the ESS relative to the amount of regenerated energy by the EM during braking.