Transit Door Obstruction Detection via Position-Dependent Current Thresholds
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Solution Overview
Problem
Existing systems for detecting obstructions in transit vehicle passenger doors are inadequate as they fail to accurately differentiate between normal operation and obstruction, leading to potential damage or safety issues due to inconsistent torque and mechanical variations.
Innovation Solution
A method involving the recording of motor current profiles versus door position, establishing acceptable current increases for each position, and comparing real-time current to these thresholds to detect potential obstructions, with the system utilizing a brushed DC motor and rotary encoder to control the door operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing obstruction detection systems are used with fixed torque thresholds, then the system structure remains simple, but the measurement precision of obstruction detection deteriorates due to inability to differentiate normal operation variations from actual obstructions
Solution Approach 1:
The patent applies dynamics by transitioning from fixed torque thresholds to dynamic, position-dependent current thresholds. The system records motor current profiles at multiple door positions during normal operation, establishing a baseline for each position. During operation, the system compares real-time current against position-specific thresholds, allowing the detection criteria to adapt dynamically to the door's mechanical variations at different positions, thereby improving obstruction detection accuracy without requiring overly complex additional hardware
Solution Approach 2:
The patent applies preliminary action by pre-recording motor current profiles during a setup phase before actual door operation. The system stores acceptable current ranges for each door position based on normal operation characteristics. When the door operates subsequently, obstruction detection relies on comparing real-time measurements against these pre-established profiles, enabling accurate detection without real-time complex calculations or additional sensors
2Reliability
If torque is limited to a maximum value in existing systems, then motor safety is improved, but the productivity of door operation deteriorates due to inconsistent torque application and mechanical variations
Solution Approach 1:
The patent applies local quality by implementing position-specific current thresholds instead of a uniform maximum torque limit. The system records acceptable current ranges at multiple discrete door positions and applies appropriate thresholds locally at each position during operation. This allows the motor to operate with optimal torque at each position for efficient door movement, while still preventing excessive torque that could cause damage, thereby maintaining both reliability and productivity
Solution Approach 2:
The patent applies parameter changes by varying the torque threshold parameter based on door position rather than maintaining a constant maximum value. The system adjusts the acceptable current threshold dynamically according to the door's position in its travel range, matching the mechanical requirements at each position. This enables efficient door operation with appropriate torque levels while maintaining safety through position-aware monitoring
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
Effectively identifies door obstructions by adjusting current thresholds based on door position and mechanical conditions, preventing damage by cutting off power to the motor when excessive current is detected, thus ensuring safe and reliable door operation.
Implementation Method 1
a brushed direct current electrical motor
Data Source
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AI summary
A method of detecting an obstruction of a passenger door on a public transit vehicle comprising the steps of: recording the profile of the actuator (motor) current vs. door position following initiation of an opening or closing of the door; based on the recorded profile of actuator current vs. door position acceptable increase in motor current for one or more discrete positions following initiation of opening or closing the door indicative of no obstruction; and comparing an instant current profile to the acceptable increase and indicating a potential door obstruction if the current exceeds the acceptable increase.