PMSM Controller Angle Correction for Step-Out Prevention
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Solution Overview
Problem
Permanent magnet synchronous motors experience synchronization loss and reduced torque due to delays in estimating the rotational speed and magnetic pole position, especially during acceleration, which can lead to step-outs, and existing solutions either increase manufacturing costs or impair responsiveness.
Innovation Solution
A controller for permanent magnet synchronous motors that includes a speed estimating portion, magnetic pole position estimating portion, step-out presuming portion, and correction portion to correct the estimated angle based on the target and estimated speeds, preventing step-outs by adjusting the current to the windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotational speed is increased during acceleration, then the productivity is improved, but the synchronization is lost and step-out occurs due to delay in estimating the rotational speed and position of magnetic poles
Solution Approach 1:
The invention performs preliminary correction of the estimated angle by adding a correction amount calculated from the difference between target speed and estimated speed. This preliminary action compensates for the inherent delay in speed estimation before it causes synchronization loss, allowing the system to maintain reliability during high-speed acceleration.
Solution Approach 2:
The invention implements a feedback mechanism where the estimated speed is continuously compared with the target speed, and the difference (error) is used to calculate a correction amount that is added to the estimated angle. This feedback loop dynamically adjusts the angle estimation to compensate for delays, preventing step-out during acceleration.
2Force
If the current command value is increased to compensate for torque reduction, then the force is improved, but the manufacturing cost increases due to higher upper limit of settable range
Solution Approach 1:
The invention changes the parameter of estimated angle by adding a correction amount derived from speed difference, rather than simply increasing the current command value. This parameter change compensates for torque reduction caused by angle delay without requiring higher current limits, avoiding increased manufacturing costs.
Solution Approach 2:
The invention replaces the mechanical approach of increasing current magnitude with a control algorithm that corrects the angle estimation. Instead of relying on higher mechanical/electrical capacity (higher current limits), the system uses computational correction to maintain torque, avoiding the need for more expensive driving circuit components.
3Reliability
If the upper limit of current settable range is raised to prevent step-out, then the reliability is improved, but the device complexity increases due to changing components of driving circuit
Solution Approach 1:
The invention uses feedback from speed estimation to dynamically correct the angle, maintaining synchronization reliability without modifying the driving circuit. The correction amount is calculated based on the difference between target and estimated speeds, creating a software-based solution that avoids hardware complexity.
Solution Approach 2:
The invention changes the control parameter (estimated angle) through computational correction rather than modifying hardware parameters (current limits, circuit components). This parameter change approach maintains reliability while keeping the driving circuit simple and cost-effective.
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 controller effectively prevents step-outs by accurately estimating and correcting the magnetic pole position, maintaining torque and reducing the likelihood of synchronization loss during acceleration without increasing manufacturing costs.
Implementation Method 1
a speed estimating portion (24), the magnetic pole position estimating portion (25), each estimates, based on the current flowing through the armature, a rotational speed of the rotor, and a position of magnetic poles of the rotor
Implementation Method 2
an alternating current is fed to the windings to cause a rotating magnetic field, which rotates the rotor synchronously therewith
Data Source
AI summary
A method for controlling a permanent magnet synchronous motor having a rotor using a permanent magnet, the rotor rotating by a rotating magnetic field caused by a current flowing through an armature is provided. The method includes: presuming, based on a target speed and an estimated speed that is an estimated value of a rotational speed of the rotor, whether or not a step-out occurs; correcting, when it is presumed that a step-out occurs, an estimated angle that is an estimated value of a position of magnetic poles of the rotor; and controlling, based on a post-correction estimated angle that is the estimated angle after the correction, a current flowing through the armature to cause the rotating magnetic field rotating at the target speed.