Sensorless Motor Startup Control with Pre-Set Excitation Current
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Solution Overview
Problem
In sensorless motor control systems, switching from forced commutation control to sensorless control can result in unstable rotor position and speed detection due to excessive narrowing of coil current, leading to motor activation instability.
Innovation Solution
A motor control apparatus that sets a non-zero command value for excitation current before switching from forced commutation control to sensorless control, ensuring a stable coil current and preventing excessive reduction, thereby maintaining motor stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the control method is switched from forced commutation control to sensorless control when rotation speed becomes equal to or greater than predetermined speed, then the motor can operate in sensorless mode, but coil current may be excessively narrowed by feedback control leading to unstable rotor position and speed detection
Solution Approach 1:
The invention applies preliminary action by setting the excitation current command value to a predetermined value greater than 0 before switching from forced commutation control to sensorless control. This preemptive setting ensures that when sensorless control begins, sufficient excitation current is already present to maintain stable rotor position and speed detection, preventing the excessive narrowing of coil current that would otherwise occur.
2Speed
If feedback control is performed in sensorless control immediately after switching, then control response is improved, but coil current is excessively narrowed causing unstable detection of rotor position and speed
Solution Approach 1:
The invention sets the excitation current command value to a predetermined value greater than 0 in advance, before feedback control in sensorless mode begins. This preliminary action ensures that when feedback control starts operating, the excitation current is already at an appropriate level, preventing excessive narrowing and maintaining stable measurement of rotor position and speed while still achieving rapid control response.
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 stabilizes the estimation of rotor position and speed, preventing motor activation failures by maintaining an effective coil current value during the transition from forced commutation to sensorless control.
Implementation Method 1
a stop position of a rotor is detected by using a property in which an inductance value of a coil of a motor changes in accordance with the stop position of the rotor
Implementation Method 2
the motor control apparatus can detect a rotation position (rotation phase) and rotation speed of the rotor by induced voltage occurring in the coil
Data Source
AI summary
A motor control apparatus includes: a current supply unit configured to supply coil current to a plurality of coils of a motor by controlling, based on a first command value of excitation current and a second command value of torque current, voltage to be applied to the plurality of coils; a first setting unit configured to set the first command value; a second setting unit configured to set the second command value; and a control unit configured to use first control in starting of rotation of a rotor of the motor, and switch control to second control after rotation speed of the rotor becomes greater than predetermined speed. The first setting unit is further configured to set a value greater than 0 as the first command value before the control unit switches control from the first control to the second control.