Conduit Reaction Force Tendon Tension Sensor
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Solution Overview
Problem
Existing tendon tension measurement techniques in robotic hands face challenges due to limited space and insensitivity of strain gauge sensors, and commercially available load cells are too large for robotic applications, making accurate tendon tension feedback difficult to achieve.
Innovation Solution
A tendon tension sensor that utilizes conduit reaction forces by mounting a cylindrical strain gauge element and a force member to the conduit through which the tendon is threaded, allowing the strain gauge to measure the reaction force caused by tendon tension, with additional features like symmetrical scallop portions and off-centered pillars for enhanced signal strength and temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If strain gauge sensors are used to measure tendon tension, then the sensor can be compact, but the measurement precision is insufficient due to small tensile forces in robotic applications
Solution Approach 1:
The patent introduces a strain gauge element as an intermediary component that is not directly attached to the tendon but rather measures the reaction force on the conduit. This mediator approach allows indirect measurement of tendon tension through conduit reaction forces, solving the problem of insufficient sensitivity while maintaining compact size.
Solution Approach 2:
The patent replaces the direct mechanical strain measurement approach with a force reaction measurement approach. Instead of measuring tendon strain directly, the system measures the reaction force exerted by the conduit on the strain gauge element, which provides better measurement sensitivity for small forces.
2Measurement precision
If load cells are used to measure tendon tension, then the measurement precision is improved, but the device becomes too large for robotic arm housing
Solution Approach 1:
The patent segments the measurement system into separate functional components: the conduit through which the tendon passes, the strain gauge element that measures reaction force, and the force member that transmits the force. This segmentation allows for a compact overall design while maintaining measurement precision.
Solution Approach 2:
The patent transitions from measuring tendon tension directly along the tendon axis to measuring the reaction force perpendicular to the tendon path through the conduit. This dimensional change allows for a more compact sensor configuration that fits within robotic arm constraints.
3Ease of operation
If tendon tension is measured directly, then the measurement location is straightforward, but the sensor installation is difficult due to limited space and tendon movement
Solution Approach 1:
The conduit serves as an intermediary structure that is stationary and easier to access than the moving tendon. By measuring the reaction force on the conduit rather than directly on the tendon, the system achieves both ease of sensor installation and accurate tension measurement.
Solution Approach 2:
The conduit naturally provides the reaction force that the strain gauge element measures. The system utilizes the existing structural elements (conduit and tendon interaction) to provide the measurement signal, eliminating the need for complex sensor installation on the moving tendon.
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
This approach provides an accurate and compact method to measure tendon tension, overcoming the limitations of previous techniques by using conduit reaction forces to predict tendon tension with increased accuracy and space efficiency.
Implementation Method 1
A strain gauge is mounted to the strain gauge element and measures the reaction force when tension on the tendon causes the strain gauge element to be pushed against the force member.
Data Source
AI summary
A technique that determines the tension in a tendon using a conduit reaction force applied to an end of a conduit through which the tendon is threaded. Any suitable tendon tension sensor can be employed that uses the conduit reaction force for this purpose. In one non-limiting embodiment, the tendon tension sensor includes a cylindrical strain gauge element and a force member mounted to an end of the conduit. The force member includes a cylindrical portion having a bore and a plate portion, where the cylindrical portion is inserted into a bore in the strain gauge element. The tendon is threaded through the strain gauge element and the force member. A strain gauge is mounted to the strain gauge element and measures the reaction force when tension on the tendon causes the strain gauge element to be pushed against the force member.