Force Sensor Overload Protection via Compliant Spacer
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Solution Overview
Problem
Existing human-machine interfaces with force sensors are costly due to the need for robust components to prevent overloading, which increases the overall cost without effective overload protection mechanisms.
Innovation Solution
A human-machine interface design that includes a gimbal assembly, a gimbal interface rod, a force sensor mount, and spacers or flexible O-rings to maintain a circumferential gap until a predetermined user input force is reached, engaging the force sensor mount with the gimbal interface rod to prevent sensor overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the force sensor mount is made robust to prevent overload, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
A compliant member (flexible O-ring or elastomeric spacer) is introduced as an intermediary between the force sensor mount and the gimbal interface rod. This compliant member acts as a mechanical limiter that engages at a predetermined force threshold, preventing overload transmission to the force sensors while using inexpensive, easily manufactured materials.
Solution Approach 2:
The design changes the mechanical parameter of the force sensor mount by introducing a compliant member with specific force-deflection characteristics. The compliant member is designed to deflect freely under normal operating forces but engages to limit further deflection when a predetermined force threshold is reached, thereby protecting the force sensors from overload without requiring a robustly designed force sensor mount.
2Reliability
If a circumferential gap is maintained between the force sensor mount and gimbal interface rod, then overload protection is achieved, but device complexity increases
Solution Approach 1:
The compliant member serves as a simple intermediary component that fills the circumferential gap between the force sensor mount and gimbal interface rod. This single component provides the overload protection function without requiring complex mechanisms, maintaining simplicity while achieving reliability.
Solution Approach 2:
The force sensor mount is segmented into two functional zones: an inner region with a circumferential gap for normal operation and an outer region that engages with the gimbal interface rod when overload occurs. The compliant member bridges these zones, allowing free movement under normal conditions while providing mechanical limitation under overload conditions.
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
The design provides cost-effective overload protection for force sensors while allowing full application of user input forces, preventing sensor overload and maintaining system functionality without increasing costs.
Implementation Method 1
The flexible O-rings are disposed between and engage the portion of the gimbal interface rod and the force sensor mount. The flexible O-rings are configured to maintain the circumferential gap between the force sensor mount and the gimbal interface rod until a predetermined user input force is supplied to the user interface whereupon the force sensor mount engages the portion of the gimbal interface rod.
Implementation Method 2
The force sensors are coupled to the force sensor mount. Each force sensor is configured to sense at least a portion of the user input force supplied to the user interface and supply a force signal representative thereof.
Data Source
AI summary
A human-machine interface includes a user interface, a gimbal assembly, a gimbal interface rod, a force sensor mount, and a spacer. The gimbal assembly is coupled to the user interface. The gimbal interface rod is coupled to and extends from the gimbal assembly. The force sensor mount is coupled to the user interface and to the gimbal assembly, is configured to have a plurality of force sensors coupled thereto, and surrounds a portion of the gimbal interface rod and is spaced apart therefrom to define a circumferential gap. The spacer is disposed between and engages the portion of the gimbal interface rod and the force sensor mount, and is configured to maintain the circumferential gap between the force sensor mount and the gimbal interface rod until a predetermined user input force is supplied to the user interface whereupon the force sensor mount engages the gimbal interface rod.