Phase Angle Detection System for Motor Transmission Units
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Solution Overview
Problem
Existing rotary encoders struggle to accurately detect the position of a rotor of an electric motor when installed on the output axis of a transmission unit that changes the motor's rotation speed.
Innovation Solution
A phase angle detection system using a first sensor to detect a specific phase angle and a second sensor to measure rotation, combined with an arithmetic processing unit to calculate an estimated absolute angle of the rotor, compensating for detection errors based on rotational direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a rotary encoder is provided on the output axis of a transmission unit to detect rotation, then the transmission unit can change the rotation speed of the electric motor, but it becomes difficult to detect the position of the rotor of the electric motor using the Z pulse output by the rotary encoder
Solution Approach 1:
The patent introduces a phase angle detection system that acts as an intermediary between the rotary encoder on the transmission output axis and the motor control system. This system calculates the motor's absolute angle by combining the encoder's position data with the transmission ratio information, effectively mediating the measurement gap created by the transmission unit's speed changing capability
Solution Approach 2:
The patent replaces direct mechanical coupling between the rotary encoder and motor shaft with a computational approach. Instead of mechanically linking the encoder to the motor rotor, the system uses arithmetic processing to calculate the motor's absolute angle from the transmission output axis measurements, substituting mechanical directness with mathematical computation
2Device complexity
If a single sensor is used to detect phase angle, then the device complexity is reduced, but the detection accuracy deteriorates due to rotational direction-specific deviations
Solution Approach 1:
The patent changes the parameter of deviation compensation by storing different deviation values in a lookup table corresponding to different rotational directions. The system selects the appropriate deviation value based on the detected rotation direction, effectively adapting the single sensor's output to maintain high accuracy without adding more sensors
Solution Approach 2:
The patent performs preliminary action by pre-calculating and storing deviation values for different rotational directions in advance. When the motor rotates, the system simply retrieves the pre-computed deviation value corresponding to the current rotation direction, avoiding real-time complex calculations and maintaining fast response with high accuracy
Data Source
AI summary
A phase angle detection system according to one aspect of the embodiment detects a phase angle of an electric motor in a drive system provided with a transmission unit that changes a rotation speed of the electric motor. The phase angle detection system includes a first sensor, a second sensor, and an arithmetic processing unit. The first sensor outputs a first signal for detecting at least a specific phase angle of a rotor of the electric motor. The second sensor outputs a second signal capable of detecting an amount of rotation of an output axis of the transmission unit. The arithmetic processing unit calculates, with an amount of deviation included in a result of the detection of a specific phase angle by the first signal defined for each rotational direction of the electric motor in advance, an estimated value of an absolute angle of the rotor of the electric motor using the amount of deviation of the first signal determined by a rotational direction of the electric motor, a result of the detection of the first signal, and the second signal.