OHT Carrier Lifting Force Control for Variable Load Handling
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Solution Overview
Problem
In semiconductor fabrication, existing automated conveying systems face challenges in efficiently transporting workpieces between processing instruments while minimizing power consumption and preventing damage due to varying weights and abnormal locking conditions.
Innovation Solution
A conveying system with an overhead hoist transport vehicle that calculates and adjusts a minimum lifting force based on the weight of the carrier, number of workpieces, and vertical distance, and includes a sensor to detect abnormal circumstances, preventing damage and optimizing energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed lifting force is applied to all carriers, then the conveying system can lift any carrier, but power consumption increases and damage may occur to lightly-loaded carriers
Solution Approach 1:
The lifting force is made dynamic rather than fixed. The system determines the actual weight of each carrier and adjusts the lifting force accordingly, allowing the force to vary based on the specific carrier being lifted. This resolves the contradiction by enabling reliable lifting of all carriers while minimizing power consumption for lightly-loaded carriers.
Solution Approach 2:
The lifting force parameter is changed from a constant value to a variable value based on carrier weight. By measuring or determining the actual weight of each carrier and adjusting the lifting force parameter accordingly, the system achieves both reliable lifting and reduced power consumption.
2Reliability
If a high lifting force is applied to prevent damage from abnormal locking, then carrier safety improves, but power consumption increases and normal carriers may be damaged
Solution Approach 1:
The lifting force becomes a dynamic parameter adjusted in real-time based on carrier conditions. By determining the actual weight of each carrier and applying only the necessary lifting force, the system protects carriers from abnormal locking damage without applying excessive force that could harm normal carriers.
Solution Approach 2:
The system incorporates feedback mechanisms to detect abnormal locking conditions and adjust the lifting force accordingly. By monitoring carrier status and providing feedback to the control system, the lifting force can be optimized to prevent damage from abnormal locking while avoiding harm to normal carriers.
3Reliability
If the conveying system lifts every carrier with maximum force, then all carriers can be transported safely, but energy efficiency deteriorates
Solution Approach 1:
The lifting force parameter is optimized by changing from a maximum fixed value to a dynamically adjusted value based on actual carrier weight. This allows the system to maintain safe transportation of all carriers while significantly improving energy efficiency by avoiding unnecessary application of maximum force to lightly-loaded carriers.
Solution Approach 2:
The conveying system determines the actual weight of each carrier and uses this information to self-adjust the lifting force. By making the system self-aware of the carrier load through weight determination, it can optimize energy usage while maintaining safe transportation.
Data Source
AI summary
A method for operating a conveying system is provided. An overhead hoist transport (OHT) vehicle is provided, wherein the OHT vehicle includes a gripping member configured to grip and hold a carrier, and a receiver configured to receive a signal. The signal is transmitted to the receiver of the OHT vehicle. The OHT vehicle is moved toward the carrier, and the carrier is gripped by the gripping member of the OHT vehicle. A lifting force is determined based on a weight of a carrier, a number of workpieces in the carrier, or a vertical distance between the OHT vehicle and the carrier, and the lifting force is applied to the carrier.