Printer Controller Using Motor Current to Prevent Head Damage
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Solution Overview
Problem
Inkjet printers face issues with erroneous interruption of printing due to incorrect velocity detection by encoders, leading to unnecessary stops and potential damage from head-sheet contact, caused by stained or flawed scales in linear or rotary encoders.
Innovation Solution
A printer system with a controller that uses feedback control to adjust the carriage motor's velocity based on accurate detection of reference marks by the encoder, setting thresholds for overshoot and undershoot to differentiate between actual head-sheet contact and encoder abnormalities, preventing unnecessary interruptions and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the printer uses feedback control based on encoder velocity detection to prevent head-sheet contact, then head protection is improved, but false interruptions occur due to scale staining or flaws causing incorrect velocity readings
Solution Approach 1:
The patent introduces an intermediary verification mechanism by detecting changes in motor current as an additional indicator of head-sheet contact. Instead of relying solely on encoder velocity readings, the system uses current consumption patterns as a mediator to confirm whether velocity deviations are caused by actual contact or encoder errors, thereby resolving the contradiction between protection reliability and measurement accuracy
Solution Approach 2:
The patent enhances the feedback control system by adding a second feedback loop that monitors motor current consumption. This dual-feedback approach allows the system to cross-validate velocity data with current data, distinguishing between genuine contact events and false alarms caused by scale contamination, thus maintaining both head protection and accurate detection
2Reliability
If the printer interrupts printing when detected velocity is lower than target velocity to prevent head damage, then head safety is improved, but productivity decreases due to unnecessary interruptions from encoder errors
Solution Approach 1:
The patent uses motor current consumption as an intermediary variable to verify whether velocity deviations warrant interruption. By introducing this mediator, the system can distinguish between velocity drops caused by head-sheet contact (requiring interruption) and those caused by encoder scale issues (not requiring interruption), thereby maintaining productivity while ensuring head safety
Solution Approach 2:
The patent changes the decision-making parameters from relying solely on velocity threshold to using a combination of velocity deviation and current consumption thresholds. This parameter transformation allows the system to maintain safety while reducing false interruptions, as both parameters must indicate contact before triggering an interruption, thus preserving printing continuity
3Device complexity
If the printer uses a single velocity threshold for interruption detection, then the control logic is simple, but it cannot distinguish between encoder errors and actual head-sheet contact
Solution Approach 1:
The patent transforms the single-parameter velocity threshold control into a two-parameter control system combining velocity deviation and motor current consumption. This parameter expansion enables reliable distinction between encoder errors and actual contact events, as the system now evaluates both kinematic (velocity) and energetic (current) indicators before making interruption decisions
Solution Approach 2:
The patent makes the control system multi-functional by using the motor current sensor to serve dual purposes: monitoring both velocity control feedback and contact detection. This universal use of current data allows the system to maintain relatively simple hardware while achieving reliable contact detection accuracy through multiple functions from the same sensor
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
The solution effectively prevents printer head damage and reduces erroneous interruptions by accurately distinguishing between head-sheet contact and encoder errors, ensuring continuous operation and maintaining print quality.
Implementation Method 1
a sensor configured to detect the reference marks formed on the scale while moving relative to the scale
Implementation Method 2
the controller is configured to perform liquid discharging to control the head to discharge the liquid from the nozzles toward a recording medium while performing feedback control of the carriage motor based on velocity information
Data Source
AI summary
A printer includes a head having nozzles, a carriage with the head mounted thereon, a carriage motor to move the carriage along a scanning direction, an encoder including a scale having reference marks formed thereon along a particular direction, and a sensor to detect the reference marks while moving relative to the scale along with movement of the carriage along the scanning direction, and a controller configured to perform liquid discharging to control the head to discharge liquid from the nozzles toward a recording medium while performing feedback control of the carriage motor based on velocity information such that the carriage moves at a target velocity along the scanning direction, the velocity information representing a carriage velocity based on detection results of the sensor, and interrupt the liquid discharging when the carriage velocity exceeds an overshoot threshold higher than the target velocity during the liquid discharging.