Motor Control Apparatus Rotor Position Estimation via Induced Voltage Sampling
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Solution Overview
Problem
Existing motor control systems that estimate rotor position without sensors face challenges in maintaining stable operation, especially at varying load torques and moment of inertia, leading to rotor deceleration, noise influence, and desynchronization due to periodic zeroing of motor current, which affects torque output and control system switching.
Innovation Solution
The system acquires induced voltage information by sampling motor voltage at least twice when all phases are turned off and estimates rotor position based on this information, allowing for stable operation without rotor speed dropping near zero, and reduces noise influence by selecting optimal data points for estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all switching devices of the three-phase inverter are turned off at arbitrary timing to measure terminal voltage, then rotor position estimation can be performed, but the motor torque is not outputted during the zero current period causing rotor deceleration
Solution Approach 1:
The patent applies preliminary action by performing terminal voltage measurement during the current zero period before the rotor speed drops to zero. By carefully timing the measurement to occur during the zero current period when the rotor speed is still sufficiently high, the system obtains accurate terminal voltage data for rotor position estimation without suffering from the adverse effects of rotor deceleration to zero speed.
2Measurement precision
If terminal voltage is measured after predetermined time from turn-off of switching devices, then measurement can be performed, but rotor speed may drop near to zero making noise influential and correct rotor position cannot be estimated
Solution Approach 1:
The patent applies preliminary action by performing terminal voltage measurement during the current zero period before the rotor speed drops to zero. By carefully timing the measurement to occur during the zero current period when the rotor speed is still sufficiently high, the system obtains accurate terminal voltage data for rotor position estimation without suffering from the adverse effects of rotor deceleration to zero speed.
Solution Approach 2:
The patent uses feedback by monitoring the current period and rotor speed to determine the optimal timing for terminal voltage measurement. The measurement is performed during the current zero period when the rotor speed is still sufficiently high, ensuring that the induced voltage amplitude is large enough to overcome noise and enable accurate rotor position estimation.
3Loss of information
If measurement is made four times per revolution, then rotor position information can be acquired, but detection frequency cannot be increased easily due to predetermined time requirement
Solution Approach 1:
The patent applies preliminary action by performing terminal voltage measurement during the current zero period before the rotor speed drops to zero. By carefully timing the measurement to occur during the zero current period when the rotor speed is still sufficiently high, the system obtains accurate terminal voltage data for rotor position estimation without suffering from the adverse effects of rotor deceleration to zero speed.
4Productivity
If control system is switched from position sensor-less control with periodic current zeroing to another system at high speed, then detection frequency increases, but torque output becomes discontinuous and shock occurs
Solution Approach 1:
The patent applies preliminary action by performing terminal voltage measurement during the current zero period before the rotor speed drops to zero. By carefully timing the measurement to occur during the zero current period when the rotor speed is still sufficiently high, the system obtains accurate terminal voltage data for rotor position estimation without suffering from the adverse effects of rotor deceleration to zero speed.
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 enables reliable rotor position estimation and stable motor operation across varying load conditions, preventing desynchronization and improving torque output consistency.
Implementation Method 1
induced voltage information of the motor is acquired by sampling at least twice the motor voltage
Data Source
Figure 1
Figure 2(1)~2(5)
Figure 3
AI summary
In a motor control apparatus, apparatus all switching devices (UP, UN, VP, VN, WP, WN) of all phases of an inverter (3) are kept fixed at OFF in accordance with a value of an all-OFF control pulse signal Poff outputted by a pulse generator (12, 15). The pulse generator (15) generates at least twice a pulse causing an induced voltage detection signal Pdet to change to an H level. A terminal voltage of a motor (5) is inputted in accordance with the value of the induced voltage detection signal Pdet. Data of the sampling round in which amplitude of the induced voltage signal is great and the signal is not in saturation is selected from the data so inputted and a rotor position is estimated.