Duplex Scanner Closed-Loop Feedback Control for Stepper Motor Reliability
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Solution Overview
Problem
Conventional open-loop controlled stepper motors in scanners face issues such as loss of step-synchronism, motor stall, high operating temperature, vibration, noise, and low scanning speed, which are inadequate for high rotational speeds, high loads, and high scanning speeds.
Innovation Solution
A duplex scanner design incorporating two scanning modules, a transmission mechanism, and a power source that outputs feedback signals, controlled by a processing unit to maintain synchronization and optimize scanning speed and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an open-loop controlled stepper motor is used to drive the transmission mechanism, then the device complexity is reduced and ease of manufacture is improved, but the reliability deteriorates due to loss of step-synchronism and motor stall at high rotational speeds
Solution Approach 1:
The patent introduces a feedback-controlled power source that receives feedback signals from an encoder attached to the transmission mechanism. This closed-loop control system continuously monitors the position and speed of the transmission mechanism, adjusting the drive signals to maintain accurate synchronization even at high rotational speeds, thereby resolving the reliability issue while maintaining manufacturing feasibility
Solution Approach 2:
The patent replaces the traditional open-loop stepper motor control system with an electrically-controlled power source that uses electromagnetic or electrostatic actuation. This substitution enables precise control through electrical feedback signals rather than mechanical step commands, eliminating step-loss issues while keeping the overall device complexity manageable
2Productivity
If the stepper motor operates at high rotational speed to increase scanning speed, then the productivity is improved, but the reliability worsens due to motor stall and loss of step-synchronism
Solution Approach 1:
The feedback-controlled power source continuously receives position and speed information from the encoder, allowing it to dynamically adjust drive parameters to maintain reliable operation at high scanning speeds. The system can detect approaching stall conditions and preemptively adjust torque or speed profiles to prevent motor failure
Solution Approach 2:
The patent implements dynamic control of the transmission mechanism where the power source adjusts operational parameters in real-time based on feedback signals. This includes variable speed control, adaptive torque management, and real-time position correction, enabling the system to maintain reliability across varying scanning speed requirements
3Force
If the stepper motor operates in full step state to maintain maximum holding torque, then the force is improved, but the object-generated harmful factors worsen due to high vibration and noise
Solution Approach 1:
The feedback-controlled power source implements micro-stepping or partial-stepping sequences that use periodic, graduated activation of motor phases rather than abrupt full-step transitions. This creates smoother torque delivery with reduced vibration and noise while maintaining adequate holding torque through controlled phase sequencing
Solution Approach 2:
The patent changes the operational parameters of the power source by using variable pulse widths, adjusted current levels, and modified switching frequencies based on feedback signals. These parameter adjustments allow the system to maintain necessary torque while operating in lower-vibration modes that reduce noise and mechanical stress
4Force
If the open-loop controlled stepper motor is operated under fully powered state to maintain maximum holding torque, then the force is improved, but the use of energy worsens resulting in high operating temperature
Solution Approach 1:
The feedback-controlled power source applies partial powering strategies where only the necessary motor phases are activated at any given time, rather than all phases being fully powered continuously. The system adjusts current magnitude and duration based on actual load requirements and feedback signals, maintaining adequate torque while significantly reducing overall power consumption and heat generation
Data Source
AI summary
A duplex scanner comprising a first scanning module, a second scanning module, a transmission mechanism, a power source and a control processing unit is provided. The first scanning module scans a front side of a to-be-scanned document and captures a front side image of the to-be-scanned document. The second scanning module scans a back side of the to-be-scanned document and captures a back side image of the to-be-scanned document. The transmission mechanism moves the to-be-scanned document relatively to the first scanning module and the second scanning module. The power source outputs at least a feedback signal while driving the transmission mechanism. The control processing unit receives a scan command and accordingly controls the power source to drive the transmission mechanism. The control processing unit receives the feedback signal and accordingly controls the first scanning module and the second scanning module to proceed duplex scan.