The three primary functions of force sensors are to detect:
- Force from an applied load
- Rate of change of a force load over time
- Presence of pressure or contact
They can monitor forces to ensure safe operating conditions and detect force thresholds during operation. The following scenarios are examples of how flexible force-sensing resistors (FSRs) are being used today.
Industry: Consumer Products, Musical Instruments
Product type: Sensor-based musical instruments
Inserting a force sensor below the strings of a violin or the keys of a piano can measure finger pressure and posture to improve musical technique and pedagogy. FSRs can be used to detect problems with muscle tension or posture while holding the instrument that could lead to early fatigue or problems like carpal tunnel.1 The sensors open new opportunities for performance analysis and smart instruments that can give feedback about the player’s pressure, stiffness, and finger position. Additionally, sensor-based musical instruments show promise in electronic instruments with more parameters that can substantially enhance the expressivity of the traditional instruments by adding new parameters and show pressure patterns that are, until today, undetectable.2
Industry: Medical Devices
Product type: Orthopedic implants
Force sensors have been implemented in “smart” knee implants. The sensors can compare the peak force values during walking, running, climbing stairs, cycling, and other physical activities.3 The data gathered from the sensors is helpful for improving the design of orthopedic implants to ensure they hold up to the body’s force requirements. Furthermore, the information enables doctors to diagnose the lifetime of the implant, load distribution of the bone, and understand the implant’s yield strength to predict mechanical fracture before it occurs.
Force sensors can detect the compression force between the edges of the implant plate and bone surface. The measurements collected may be used to provide a baseline for the engagement of the plate with the bone immediately following implantation, and subsequent measurements may then be compared to the baseline to determine whether the plate has remained in place or needs adjustment. The ideal case is wherein the compression force between plate and bone remains fixed for the duration that the implant is installed.
Product type: Centripetal force sensor
Force sensors are also used in automobiles to monitor centripetal force during turns to improve driver safety. The data can be used to extrapolate the road adhesion of the tires while a vehicle is driving. A turn angle sensor, velocity sensor, and force sensor have been combined in automobile systems to determine a vehicle’s centripetal force. As the moving vehicle begins to turn, the centripetal force of the vehicle keeps the vehicle in a circular path. Friction between the wheel and the road surface keeps the vehicle in the turn. However, at a certain velocity, the inertia acting on the vehicle will exceed the centripetal force required to keep the vehicle in the turn and the wheels will begin to slip away from the direction of the turn, creating a potentially dangerous condition. The force sensor system can alert the driver or take automatic action to reduce the centripetal force and improve vehicle stability. More recently, these sensors can give real-time feedback to the driver via IoT integration.
Not only can force sensors be embedded in medical devices, consumer products, and automobiles, but can also be applied to robotics, industrial applications, aerospace, and other industries.
Find more information on our SensoForce, flexible force-sensing resistor here.
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- T. Grosshauser. Low force pressure measurement: Pressure sensor matrices for gesture analysis, stiffness recognition and augmented instruments. In S. G. Volpe, A. Camurri, editor, 8th International Conference on New Interfaces for Musical Expression NIME08, 2008.
- A. Hadjakos. Sensor-Based Feedback for Piano Pedagogy, PhD Thesis. PhD thesis, Technischen Universitat Darmstadt, 2011.
- Ledet, Eric H, et al. “Smart Implants in Orthopedic Surgery, Improving Patient Outcomes: a Review.” Innovation and Entrepreneurship in Health, U.S. National Library of Medicine, 19 Sept. 2018, www.ncbi.nlm.nih.gov/pmc/articles/PMC6145822/.
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Ariadna is a junior at Cornell University studying Materials Science and Engineering. She is a staff writer for The Cornell Daily Sun and a member of the Nanoscale Materials for Energy Lab.