Resolver Offset Diagnosis via d-q Axis Current Comparison
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Solution Overview
Problem
Existing electric motor systems with resolvers face challenges in accurately determining the mutual positioning of the rotor and stator, leading to potential anomalies that can cause reduced torque, unexpected vehicle movements, and even motor failures due to unrecognized changes in the resolver offset during operation.
Innovation Solution
A diagnostic method is implemented to verify the correctness of the resolver offset by applying sinusoidal voltage pulses in specific configurations and analyzing the resulting currents on the motor's axes, determining the phase relationship and amplitude to identify any deviations from the predetermined offset, thereby ensuring accurate angular position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resolver offset is determined at production and stored in memory, then the angular position determination is established for normal operation, but the system cannot detect modifications to the offset that occur during operation, leading to control errors
Solution Approach 1:
The patent applies preliminary action by establishing a baseline resolver offset value during production and storing it in memory before normal operation. This predetermined offset serves as a reference for later diagnostic comparisons, allowing the system to detect any deviations that occur during operation without requiring continuous recalibration.
Solution Approach 2:
The patent implements feedback through a diagnostic method that continuously monitors the resolver offset during operation by comparing current angular position measurements against the predetermined offset stored in memory. When discrepancies are detected, the system generates diagnostic information to alert operators, creating a closed-loop feedback mechanism that enhances system reliability.
2Device complexity
If the motor operates without continuous offset verification, then the system simplicity is maintained, but anomalies in rotor position can cause reduced torque, unexpected movements, and motor failures
Solution Approach 1:
The patent extracts the offset verification function as a separate diagnostic procedure that operates independently from the main motor control loop. By isolating the offset detection logic into a specific diagnostic routine using existing resolver signals and memory storage, the patent adds safety verification without significantly increasing overall system complexity.
Solution Approach 2:
The patent enables self-service by utilizing the existing resolver and control unit resources to perform offset diagnostics without requiring additional external measurement equipment. The control unit uses its own internal memory and processing capabilities to verify the resolver offset, making the system self-diagnosing and reducing external dependencies.
3Productivity
If the resolver offset modification is not detected, then the system operates with the stored predetermined offset, but the incorrect angular position determination causes erroneous torque control and potential motor damage
Solution Approach 1:
The patent prepares the system in advance by storing the correct offset value in memory during production, enabling rapid detection and correction of offset modifications during operation. This preliminary setup allows the system to maintain productivity by quickly identifying and addressing anomalies before they cause significant damage.
Solution Approach 2:
The patent provides beforehand cushioning by implementing a diagnostic safety net that detects offset modifications before they can cause catastrophic motor failures. The continuous monitoring and diagnostic information generation create a protective mechanism that alerts operators to potential issues, allowing for preventive maintenance and avoiding severe consequences.
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 method allows for the detection of offset modifications in real-time, preventing motor control errors, ensuring safe and efficient vehicle operation by confirming the correct angular position and minimizing risks associated with incorrect torque application.
Implementation Method 1
The resolver comprises an excitation winding through which a sinusoidal excitation current flows, and two stationary windings in electrical phase quadrature. The mobile part set in rotation induces in the fixed windings an e.m.f. composed of two components: a first component of transformer-type origin, due to the variations in an excitation voltage
Implementation Method 2
The sine and the cosine of the angular position of the mobile part modulate in amplitude the carrier with an angular frequency ω present on the winding excitation. From the voltage signals at ends of the fixed windings, by demodulation, it is possible to obtain an estimate of the angle
Data Source
Figure 1~2
Figure 1~2
Figure 3a~3b
AI summary
A method is described for the diagnosis of the offset of the resolver of an electric machine, comprising acquiring a predetermined offset of a resolver associated with the electric machine; in a first transient, supplying an excitation current to the phases of the electric machine so as to determine the injection of an exploring excitation current on an axis d of minimum reluctance of the electric machine, in which the position of axis d is determined as a function of the predetermined offset of the resolver; in a second and in a third transient, respectively, supplying an excitation current to the phases of the electric machine so as to determine the injection of an exploring excitation current on the axis d of the electric machine, in which the position of the axis d is determined as a function of a offset of the resolver modified by a predetermined amount of deviation, in excess, respectively in defect with respect to the predetermined offset of the resolver. As a consequence of the excitation current, a current established on the axis d of minimum reluctance and a current established on an axis q in phase quadrature with respect to the axis of minimum reluctance are determined. The correctness of the offset of the resolver is diagnosed if the current established on the axis d in the first transient is higher than the current established on the axis d in the second or third transient, and if the current established on the axis q in the first transient is lower than the current established on the axis q in the second or third transient. An error in the offset of the resolver is diagnosed if the current established on the axis d in the first transient is lower than the current established on the axis d in the second or third transient, or if the current established on the axis q in the first transient is higher than the current established on the axis q in the second or third transient.