Crosshead Collision Braking in Material Testing Systems
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Solution Overview
Problem
Material testing systems often experience collisions due to operator error, leading to potential damage to the testing frame, load cells, fixtures, and specimens, as existing systems lack effective collision detection and mitigation mechanisms.
Innovation Solution
The implementation of a collision mitigation apparatus that uses a control processor to detect collisions by analyzing force and displacement measurements, applying a braking force via actuators to quickly stop moving components, thereby reducing the likelihood of damage. This system distinguishes between loaded and free motion to prevent unnecessary braking and adjusts braking duration based on collision severity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If collision mitigation apparatus is implemented with control processor and actuators, then collision detection and mitigation capability is improved, but device complexity increases
Solution Approach 1:
The control processor is designed to perform multiple functions: it controls the actuator for normal operation, detects collisions by monitoring force and displacement data, and triggers mitigation actions. This multi-functionality reduces the need for separate dedicated collision detection hardware, thereby improving reliability while limiting the increase in device complexity.
2Object-affected harmful factors
If braking force is applied to stop moving components quickly, then damage risk is reduced, but false braking during normal operation may occur
Solution Approach 1:
The control processor continuously monitors force and displacement data from sensors during actuator operation. By analyzing this feedback data, the system can distinguish between normal operational forces and abnormal collision forces, enabling accurate collision detection while preventing false braking during legitimate testing procedures.
Solution Approach 2:
The collision detection threshold and mitigation response are dynamically adjusted based on the current operational state. The control processor evaluates whether the actuator is in loaded motion (during testing) or free motion (positioning), and only triggers mitigation during free motion when a collision is detected, thereby preventing false braking while maintaining protection capability.
3Speed
If collision detection is performed continuously, then collision detection speed is improved, but energy consumption increases
Solution Approach 1:
The control processor performs collision detection at periodic intervals by continuously monitoring force and displacement data during actuator operation. This periodic monitoring approach ensures rapid collision detection while managing energy consumption by processing data at appropriate intervals rather than requiring constant high-power processing.
Data Source
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AI summary
An example material testing system includes: a crosshead configured to be actuated to transfer testing force to a test specimen during a material test; an actuator configured to actuate the crosshead and to apply the testing force to the crosshead; a force sensor configured to measure force applied by the crosshead to the specimen; and a control processor configured to: determine a reference force range based on a first force measurement from the force sensor in response to initiation of movement of the crosshead; and in response to a second force measurement by the force sensor that is outside of the reference force range, controlling the actuator to apply a braking force to the crosshead.