Electric Drive Inverter Torque Limiting for Slip-Controlled Braking
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Solution Overview
Problem
Existing systems for controlling electric drives in vehicles, particularly commercial vehicles, fail to optimize the interaction between electric drives and friction brakes, leading to suboptimal recuperation and braking performance.
Innovation Solution
A method for torque-based operation of an inverter in an electric drive system, where the inverter adjusts its operation based on an adjusted rpm limit calculated by a controller, ensuring optimal torque distribution and coordination with the friction brake system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric drive is operated with slip-control to improve recuperation and braking performance, then the recuperation efficiency and braking performance are improved, but the coordination complexity between the electric drive and the braking system increases
Solution Approach 1:
The patent merges the control functions of the electric drive and friction brake system into a unified slip-control mechanism. The controller coordinates both systems based on slip conditions, allowing them to work together seamlessly rather than independently. This integration resolves the complexity issue by providing a hierarchical control structure where slip conditions dictate the operation of both systems.
Solution Approach 2:
The control system dynamically adjusts the operation mode between electric drive and friction brakes based on real-time slip conditions. The system transitions between different control states (electric drive only, combined operation, friction brake only) depending on the slip magnitude and vehicle conditions, enabling adaptive optimization of recuperation efficiency while managing coordination complexity through condition-based control strategies.
2Measurement precision
If the electric drive is used for braking control to improve precision and dynamics, then the braking precision and response dynamics are improved, but the system stability may be compromised without proper coordination
Solution Approach 1:
The patent implements feedback control by continuously monitoring slip conditions and adjusting the braking torque accordingly. The controller uses real-time slip measurements to regulate the electric drive torque and friction brake application, ensuring that braking precision is maintained while system stability is preserved through closed-loop control. This feedback mechanism prevents excessive slip and ensures stable operation during regenerative braking.
Solution Approach 2:
The system changes operational parameters (torque limits, slip thresholds, control modes) based on vehicle conditions and slip states. By dynamically adjusting these parameters, the system maintains high braking precision when conditions permit while ensuring stability through conservative parameter selection during critical situations. The controller modifies torque commands and control strategies according to the current operational context.
3Reliability
If the friction brake controller deactivates the electric drive in stability-critical situations to ensure stability, then the system stability is maintained, but the recuperation potential is lost
Solution Approach 1:
Instead of completely deactivating the electric drive in stability-critical situations, the system dynamically adjusts its operation mode. The controller allows the electric drive to continue operating within modified torque limits and adjusted slip thresholds, enabling partial recuperation even during stability-challenged conditions. This dynamic approach replaces the binary on/off control with continuous adaptation, maintaining stability while preserving energy recovery opportunities.
Solution Approach 2:
The controller modifies operational parameters (torque commands, slip limits, control gains) during stability-critical situations rather than completely disabling the electric drive. By adjusting these parameters within safe operating boundaries, the system maintains stability while allowing the electric drive to continue contributing to energy recuperation. This parameter-based control enables fine-tuned optimization of both stability and energy recovery.
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
This approach enhances the stability and efficiency of vehicle braking, allowing for effective recuperation and improved control over slip conditions, thereby optimizing the use of both electric and friction brakes.
Implementation Method 1
detection of an actual rpm of the electric drive by the inverter
Implementation Method 2
inverter with an internal inverter controller, an electric machine
Implementation Method 3
friction brake device 30
Data Source
AI summary
A method is for torque-based operation of an inverter of an electric drive of a vehicle, in particular a commercial vehicle. The electric drive is set up for regenerative braking. A control unit is connected to the inverter and different from the inverter and is for controlling a friction brake device and/or the electric drive. The method includes: measuring an actual rpm of the electric drive via the inverter; ascertaining a rpm limit determined based on a target rpm for a wheel which is able to be driven by the electric drive via the controller; determining an updated rpm limit as a function of the rpm limit and the actual rpm via the controller; and, operating the inverter at a reduced torque based on the updated rpm limit.