Object Detection System Using Positive Pressure Teach Cycle
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Solution Overview
Problem
Vacuum nozzles used in robotic machines often cause small objects to 'jump' during the teaching cycle, leading to incorrect height measurements and subsequent pick and place errors when attempting to lift very small items like WLCSP, SOT, and DFN components.
Innovation Solution
The system employs a low-pressure blow-off (positive pressure) during the teach cycle, using an air sensor to detect pressure changes at the nozzle tip as it contacts the object, allowing accurate height measurement without lifting the object, and features a self-calibrating detection algorithm to account for variations in atmospheric pressure and nozzle conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum (negative pressure) is used to lift small objects during teaching cycle, then objects can be held against the nozzle for movement, but very small objects may jump up to the nozzle before contact, causing incorrect height measurements
Solution Approach 1:
The patent inverts the pressure approach by using positive pressure (blow-off) instead of negative pressure (vacuum) during the teaching cycle. This reversal prevents the object jumping issue while maintaining reliable object interaction, as the positive pressure pushes the object rather than pulling it, eliminating the premature contact problem that causes measurement errors
Solution Approach 2:
The system performs a preliminary teaching cycle using positive pressure to accurately determine object height and position before switching to vacuum mode for actual pick-and-place operations. This preliminary action with inverted pressure ensures correct height measurement is obtained first, preventing subsequent operational errors
2Ease of operation
If vacuum is used during teaching cycle, then objects can be lifted and positioned, but height measurement becomes incorrect due to object jumping
Solution Approach 1:
The patent applies pressure inversion during the teaching phase, using positive pressure to push objects onto the nozzle surface rather than vacuum pulling them. This maintains ease of object manipulation while eliminating the jumping behavior that compromises pick and place precision in subsequent operations
Solution Approach 2:
The patent segments the operation into two distinct phases: teaching cycle using positive pressure for accurate height measurement, and execution phase using vacuum for reliable object lifting. This segmentation allows each phase to use the optimal pressure mode for its specific function, maintaining both operational ease and manufacturing precision
3Measurement precision
If manual adjustments are made to compensate for atmospheric pressure and nozzle variations, then measurement accuracy can be maintained, but system complexity and operator training requirements increase
Solution Approach 1:
The system performs self-calibration during the teaching cycle, automatically compensating for atmospheric pressure variations, nozzle size differences, and flow rate changes. This self-service approach maintains measurement precision without requiring manual adjustments or specialized operator training, reducing system complexity
Solution Approach 2:
The system incorporates feedback mechanisms where the air sensor continuously monitors pressure or flow changes during the teaching cycle, and the control algorithm automatically adjusts based on this feedback to compensate for environmental and component variations, maintaining precision without manual intervention
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 method prevents object jumping, enhances accuracy in height measurement, reduces operator training, and improves the overall precision of pick and place operations for small objects, minimizing errors and increasing machine yield.
Implementation Method 1
An air sensor detects pressure or flow changes at the nozzle tip. A rise in pressure or drop in flow is detected as the nozzle makes contact with the object
Data Source
AI summary
An object detection system utilizes a teach cycle performed with a low-pressure blow-off (i.e. positive pressure) instead of vacuum (negative pressure). During the teach operation, the positive pressure is enabled and the nozzle is lowered to the object. An air sensor detects pressure or flow at the nozzle tip. A rise in pressure or drop in flow is detected as the nozzle makes contact with the object (i.e. just before or just after actual physical contact is made). The height of the object is stored as the taught height to be used subsequently in repetitive operations by the machine. This teaching method is particularly useful for very small objects because the positive pressure does not lift the object.