Resolver Zero Offset Correction Using Back-EMF Phase Angle
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Solution Overview
Problem
The existing methods face challenges in accurately correcting the initial zero position deviation between a permanent magnet synchronous motor and a resolver, leading to unstable motor speed regulation due to friction resistance and cogging torque, which complicates the alignment of the rotor's zero position with the resolver's zero position.
Innovation Solution
A method and system that involve driving the rotor at a constant speed, acquiring counter electromotive forces, calculating the space vector phase angle and rotation angle, and manually adjusting the resolver's position using a specific formula until the installation deviation meets precision requirements, thereby correcting the initial zero position deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct current is applied to stator winding to position rotor at zero position, then initial zero position can be detected, but friction resistance and cogging torque prevent complete alignment causing error angle
Solution Approach 1:
The patent applies preliminary action by driving the rotor to rotate at a constant speed before performing position detection. This dynamic state eliminates the influence of friction resistance and cogging torque that exist in static conditions, allowing for more accurate detection of the space vector phase angle and subsequent correction of the installation deviation between motor and resolver zero positions.
Solution Approach 2:
The patent changes the operational parameter from static DC positioning to dynamic constant-speed rotation. By operating the motor in a dynamic state with AC excitation, the system overcomes the limitations of static friction and cogging torque, enabling more reliable measurement and correction of the zero position deviation.
2Measurement precision
If manual adjustment of resolver position is performed to correct installation deviation, then zero position alignment improves, but adjustment complexity and time consumption increase
Solution Approach 1:
The patent implements feedback by calculating the installation deviation Δθ based on the difference between the space vector phase angle θ1 (from counter electromotive force) and the resolver rotation angle θ2. This quantitative feedback value directly guides the manual adjustment process, allowing operators to make precise corrections rather than trial-and-error adjustments, thereby reducing adjustment time while improving alignment accuracy.
Solution Approach 2:
The system performs self-diagnosis by automatically calculating the installation deviation value and providing it to the operator. This self-service approach eliminates the need for complex alignment procedures or specialized tools, as the system itself provides the correction information needed for rapid adjustment.
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 allows for precise correction of the initial zero position deviation between the motor and resolver, enhancing the stability and accuracy of motor speed regulation by aligning the rotor's position with the resolver's zero position effectively.
Implementation Method 1
Because of the special design of the rotor, a secondary coupling varies sinusoidally as an angle position varies. In a case where the rotor of the resolver rotates with the motor synchronously and an alternating-current excitation voltage is applied to the primary excitation winding, inductive potentials are generated in the two secondary output windings
Implementation Method 2
When a direct current is applied to a stator winding of the motor, a constant magnetic field is generated on the axis of the winding
Implementation Method 3
a constant magnetic field and the magnetic field of the permanent magnet rotor attract the rotor to a same position
Data Source
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AI summary
A method and a system for correcting an initial zero offset, said method comprising: obtaining, by means of calculating a back electromotive force of a stator of a permanent magnet synchronous motor, a corresponding space vector phase angle θ1 (S12); and then acquiring, according to a position of a rotator of a resolver, a rotation angle θ2 of the resolver (S13); calculating, according to a formula, an installation offset Δθ of the resolver (S14); and finally, adjusting, according to the precision requirement, the position of the resolver (S15). Said method is easy to operate, being capable of correcting an initial zero offset between the permanent magnet synchronous motor and the resolver.