Stepping Motor Vector Control with Encoder Error Correction
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Solution Overview
Problem
Stepping motors in image forming apparatuses, such as copiers and printers, face uncontrollable states due to load torque exceeding output torque during synchronization control, leading to potential paper jams and increased power consumption and noise, and vector control requires accurate rotor position detection which can be compromised by sensor abnormalities like dirty encoders.
Innovation Solution
A motor control apparatus that continues vector control by correcting the rotational position of the rotor based on abnormal pulse signals from position detection sensors, ensuring the deviation between the determined and target positions approaches zero, thus maintaining efficient motor driving without entering an uncontrollable state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If synchronization control is used for the stepping motor, then the control structure is simple and does not require position detection sensors, but the motor enters step-out state when load torque exceeds output torque, causing uncontrollability and paper jams
Solution Approach 1:
The patent replaces the mechanical synchronization control method with an electronic control system that uses a position detection sensor (encoder) to detect rotor position. This substitution enables vector control, which calculates optimal driving currents based on actual rotor position, allowing the motor to maintain controllability under varying load conditions while preserving simplicity through automated electronic control.
Solution Approach 2:
The patent implements feedback control by using the position detection sensor to continuously monitor the rotor position and feeding this information back to the control unit. The control unit adjusts the driving current based on the detected position and load conditions, preventing step-out state and ensuring reliable operation. This closed-loop feedback mechanism resolves the contradiction by maintaining controllability without significantly increasing system complexity.
2Reliability
If margin current is added to prevent step-out state, then motor controllability is maintained, but power consumption increases and motor noise increases due to excessive torque
Solution Approach 1:
The patent implements dynamic current control where the driving current is continuously adjusted based on the actual rotor position and load torque requirements. The control unit calculates the optimal current magnitude and phase angle in real-time, ensuring the motor generates exactly the torque needed without excessive current. This dynamic adjustment maintains controllability while minimizing power consumption and noise.
Solution Approach 2:
The patent changes the control parameters from fixed synchronization control to variable vector control, where the current magnitude and phase angle are continuously modified based on rotor position and load conditions. This parameter optimization allows the motor to operate efficiently across different load scenarios, preventing step-out without applying excessive torque that would increase power consumption and noise.
3Reliability
If vector control is used to prevent step-out and optimize power consumption, then motor controllability is maintained and power efficiency improves, but position detection sensors are required which can become dirty and cause abnormalities
Solution Approach 1:
The patent implements abnormality detection and correction mechanisms that anticipate and compensate for encoder errors before they cause motor失控. The control unit monitors the encoder signals for abnormalities such as missing pulses or inconsistent readings, and when detected, it corrects the rotor position estimation using alternative calculation methods. This beforehand cushioning approach maintains vector control benefits while mitigating the impact of sensor contamination.
Solution Approach 2:
The patent uses feedback from the position detection sensor combined with abnormality detection to maintain reliable control. When the encoder becomes dirty or produces abnormal signals, the control unit detects these abnormalities through feedback monitoring and switches to correction modes that estimate rotor position using motor current and voltage information. This feedback mechanism ensures continuous reliable operation despite sensor contamination.
4Power
If encoder signals are used for vector control, then efficient torque generation is achieved, but missing pulses or abnormal signals cause errors in rotational position determination, leading to unstable motor operation
Solution Approach 1:
The patent implements multiple layers of feedback to ensure accurate rotor position detection. The control unit continuously monitors encoder pulses and compares them with expected values based on motor operating conditions. When abnormalities such as missing pulses are detected through feedback, the system activates correction algorithms that recalculate the rotor position using motor electrical characteristics, ensuring accurate position information is always available for efficient torque generation.
Solution Approach 2:
The patent introduces an intermediary correction mechanism between the encoder and the vector control calculation. When encoder signals are abnormal, this intermediary layer detects the error and provides corrected position information to the control algorithm. This intermediary acts as a buffer that maintains measurement precision even when the primary sensor becomes unreliable due to contamination or other issues.
Data Source
AI summary
A motor control unit performs driving control for a stepping motor by using vector control, and detects a rotational position θ of a rotor of the stepping motor, the rotational position θ being required for vector control, by using a position detection unit, based on a pulse signal that is output from an encoder. The motor control unit determines whether or not there is an abnormality in the pulse signal output from the encoder. Upon determining that there is an abnormality in the pulse signal, the motor control unit corrects a detection value of the position θ of the rotor of the stepping motor so as to compensate an error caused by the abnormality in the pulse signal.