Electric Machine Torque Control for Smooth Vehicle Braking
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Solution Overview
Problem
Existing methods for controlling electric machine torque in vehicles fail to effectively prevent sudden torque fluctuations during braking, leading to reduced driving safety and comfort due to jerky movements and undesirable accelerations.
Innovation Solution
A method involving multiple high-pass and low-pass filters to differentiate and integrate speed gradients, ensuring dynamic control of setpoint torque by comparing output values from these filters, thereby preventing undesirable torque generation and improving damping during braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single high-pass filter is used to differentiate speed, then torque fluctuations can be reduced, but sudden accelerating torque during braking cannot be prevented
Solution Approach 1:
The patent divides the single filtering operation into multiple sequential filtering stages. The detected speed is first differentiated by a first high-pass filter, then limited to positive values, and then differentiated again by a second high-pass filter. This segmentation allows the system to progressively filter out harmful torque fluctuations while preventing sudden accelerating torque during braking operations.
2Ease of operation
If multiple filtering operations are applied to reduce torque fluctuations, then driving comfort improves, but the system complexity increases
Solution Approach 1:
The patent combines multiple filtering operations (two high-pass filters and one low-pass filter) into a unified control algorithm that processes speed signals through a coordinated sequence of operations. By merging these filtering functions into an integrated control strategy rather than separate physical components, the system achieves improved driving comfort while managing overall system complexity through software-based implementation.
3Stability of the object's composition
If the detected speed is differentiated multiple times to improve speed control, then rotational speed fluctuations are dampened, but undesirable torque generation during braking occurs
Solution Approach 1:
The patent applies preliminary anti-action by using the limited positive speed values from the first high-pass filter as an input to the second high-pass filter. This preliminary processing step prevents negative speed gradients from propagating through the filtering system, thereby preemptively blocking the generation of undesirable accelerating torque during braking operations before they can occur.
Solution Approach 2:
The patent introduces an intermediary element - the limiter that constrains speed values to only positive gradients - between the first and second high-pass filters. This intermediary component acts as a mediator that selectively allows only beneficial speed changes to pass through while blocking harmful negative gradients, thus preventing undesirable torque generation during braking.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for operating an electric machine (2) for a vehicle (3). A target torque of the electric machine (2) is regulated during a driving process depending on a detected time-dependent rotational speed of the electric machine (2). In the process, the detected rotational speed is differentiated by means of a first high-pass filter (5) over time, the detected rotational speed is then differentiated again over time in a limited manner to positive rotational speed values and using a second high-pass filter (8), and the target torque is regulated depending on the output value of the second high-pass filter (8).