EC Motor Control Unit Emergency Torque Compensation
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Solution Overview
Problem
Electronically commutated electric motors with defective semiconductor switches experience reduced or complete loss of mechanical power and braking torque, leading to increased steering effort in vehicles equipped with servo steering systems.
Innovation Solution
The control unit of the electric motor incorporates semiconductor switches that can short or connect with low impedance, allowing the motor to compensate for defects by using stored rotation energy and adjusting control patterns to maintain torque production, even with a defective switch, thereby reducing braking torque and ensuring continued operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor switch in the power output stage becomes defective (shorted or connected with low impedance), then the electric motor loses mechanical power and produces braking torque, but the steering system requires increased steering effort
Solution Approach 1:
The patent detects the defective semiconductor switch and converts the harmful braking torque effect into beneficial operation by switching to an emergency control pattern. The control unit identifies the defect and reconfigures the power output stage to use remaining functional switches, transforming a failure state into a degraded-but-functional operating state that eliminates braking torque while maintaining steering assistance.
2Reliability
If the control unit disconnects the stator from the power output stage using a relay upon detecting a defect, then the system protects itself from damage, but the electric motor can no longer emit torque and steering assistance is completely lost
Solution Approach 1:
The patent implements a dynamic response strategy where the control unit does not immediately disconnect the stator upon detecting a defect. Instead, it first identifies the specific defective switch, then selectively activates only the functional switches in the power output stage. This dynamic reconfiguration maintains torque emission capability while protecting the system, avoiding the complete disconnection that would occur with a simple relay-based approach.
Solution Approach 2:
The patent applies local quality by treating each semiconductor switch independently in the power output stage. When one switch is detected as defective, the control unit specifically deactivates only that switch while keeping other switches operational. This localized response allows the motor to continue producing torque using remaining functional switches, rather than completely disconnecting the stator as would occur with a blanket relay disconnection approach.
3Reliability
If the stator coil associated with a defective semiconductor switch permanently produces a magnetic field due to the shorted switch, then the stator can no longer be sufficiently influenced in the defect angle range, but the rotor can use stored rotation energy to overcome the defect angle range
Solution Approach 1:
The patent employs preliminary action by detecting the defective semiconductor switch before the rotor enters the problematic defect angle range. The control unit identifies the defect and pre-configures the emergency control pattern, ensuring that when the rotor approaches the angle range where the defective switch would cause issues, the control strategy is already in place to manage the situation. This allows the rotor to smoothly overcome the defect angle range using stored rotation energy without sudden control disruptions.
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 solution enables the electric motor to maintain torque production and reduce braking torque, ensuring smooth vehicle steering without increased steering effort, even with defective semiconductor switches, by utilizing stored energy and adaptive control patterns.
Implementation Method 1
The control unit is designed to control the stator such that the stator can produce a magnetic rotating field in order to rotate the rotor
Implementation Method 2
the rotor can use stored rotation energy to overcome the defect angle range of the rotor revolution which corresponds to the defective semiconductor switch
Data Source
AI summary
The invention relates to an electronically commutated electric motor. The electric motor comprises a stator, and a rotor, in particular a permanent-magnetic rotor. The electric motor further comprises a control unit connected to the stator. The control unit is designed to actuate the stator such that the stator can generate a magnetic rotating field for rotationally moving the rotor. According to the invention, the control unit of the electric motor is provided with a power output stage having semiconductor switches. Subject to the low-resistance, or short-circuited, semiconductor switch of the power output stage, in particular as a result of defect, the control unit is designed to actuate the stator for generating the rotating field such that during a complete rotor revolution, the rotor can provide a mechanical output, or in the operational mode, a braking torque of the electric motor caused by the defect is reduced, or completely neutralized, by the low-resistance, or short-circuited, semiconductor switch.