Elevator Brake Drag Detection Using Motor Torque Comparison
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Solution Overview
Problem
Existing elevator systems face challenges in detecting a dragging brake, which can lead to increased friction, heating, and wear due to the brake not fully disengaging during normal operation, potentially causing the brake to fail in holding the elevator cab when motor power is not supplied.
Innovation Solution
A system and method that utilizes a motor drive to generate torque reference values, compare current feedback signals, and use position feedback to detect when a braking surface does not fully disengage, identifying a dragging brake by comparing torque differences to predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the holding brake is adjusted to apply stronger braking force for safety, then the brake holding capability is improved, but the brake may not fully disengage during normal operation causing dragging
Solution Approach 1:
The system continuously monitors motor torque during operation and compares it against expected torque values. When torque exceeds a threshold indicating the brake is not fully disengaged, the system generates an alarm signal to alert operators of the dragging brake condition, enabling timely intervention.
Solution Approach 2:
The patent replaces mechanical brake adjustment mechanisms with an electrical detection system that uses motor torque measurement and comparison logic to identify dragging brake conditions, eliminating the need for manual mechanical adjustments.
2Reliability
If the brake is adjusted to ensure full engagement for safety, then the holding reliability is improved, but the brake may not fully release causing friction and heating during operation
Solution Approach 1:
The system uses continuous torque monitoring during motor operation to detect abnormal torque increases that indicate brake dragging. When the measured torque exceeds the threshold, the system triggers an alarm to alert operators of the overheating risk caused by incomplete brake disengagement.
3Ease of manufacture
If manual brake adjustment procedures are used during commissioning, then initial brake performance can be optimized, but the brake may go out of adjustment over time requiring repeated manual interventions
Solution Approach 1:
The patent replaces manual mechanical brake adjustment and inspection procedures with an automated electrical detection system that continuously monitors brake performance through torque measurement. This eliminates the need for repeated manual adjustments and inspections, reducing maintenance time and labor requirements.
Solution Approach 2:
The system performs self-diagnosis by automatically detecting dragging brake conditions through torque monitoring and comparison, eliminating the need for manual inspection and adjustment by operators, thereby reducing maintenance time and improving system autonomy.
4Force
If the brake is set to apply high friction force for safe stopping, then the stopping capability is improved, but the brake surfaces experience excessive wear during normal operation
Solution Approach 1:
The system monitors motor torque during operation to detect when the brake is not fully disengaged. By continuously measuring torque and comparing it against thresholds, the system identifies dragging brake conditions that cause excessive wear and triggers alarms to alert operators, enabling timely correction before significant wear occurs.
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 detects a dragging brake by measuring torque variations, preventing excessive heating and wear, and ensuring the brake properly disengages, thereby maintaining elevator safety and efficiency.
Implementation Method 1
A first value of torque generated by a motor operatively connected to a motor drive is determined when a holding brake in a drive train between the motor and a load controlled by the motor is initially released
Implementation Method 2
A spring applies a force against a brake member, such as brake pads, which, in turn, engage the rotating member of the elevator drive train
Implementation Method 3
A spring applies a force against a brake member, such as brake pads
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A system and method for detecting a brake dragging during normal operation of a motor monitors torque at zero speed and at constant speed. For an inertial system acted upon by gravity, a value of torque required to maintain zero speed is approximately the same as a value of torque required to maintain operation at a constant speed. In an exemplary, elevator system, a motor drive determines the torque required to maintain zero speed operation of an elevator cab after a holding brake opens and before it begins controlling the motor to rotate. The motor drive again determines the torque required to maintain a constant speed and compares this value to the value of torque required to maintain zero speed. If the difference between the two values of torque is greater than a predefined threshold, then the motor drive determines that the brake is dragging and sets an error message.