A high-resolution and large force-range load cell by means of nonlinear cantilever beams

• Published in: Precision engineering Vol. 43; pp. 241 - 256
• Main Authors: Kluger, Jocelyn M., Sapsis, Themistoklis P., Slocum, Alexander H.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.2016
• Subjects: Assembly; Cantilever; Cantilever beams; High resolution; Hysteresis; Load cells; Mathematical analysis; Nonlinear load cell; Nonlinearity; Springs; Stiffening; Cantilever; Nonlinear load cell; High resolution
• ISSN: 0141-6359; 1873-2372
• DOI: 10.1016/j.precisioneng.2015.08.003

•We describe a nonlinear load cell with high resolution over a large force range.•Force nonlinearity is implemented by cantilevers that contact rigid surfaces.•Experiments demonstrate the load cell properties.•We fabricate the load cell as a monolithic part for reduced assembly cost. In the present work, we describe a nonlinear stiffening load cell with high resolution (the ability to detect 1% changes in the force) that can function over a large force range (5 orders of magnitude), and exhibit minimal hysteresis and intrinsic geometric protection from force overload. The stiffening nature of the load cell causes its deflection and strain to be very sensitive to small forces and less sensitive to large forces. High stiffness at high forces prevents the load cell from over-straining. We physically implement the nonlinear springs with cantilever beams that increasingly contact rigid surfaces with carefully chosen curvatures as more force is applied. We analytically describe the performance of the load cell as a function of its geometric and material parameters. We also describe a method for manufacturing the mechanical component of the load cell out of one monolithic part, which decreases hysteresis and assembly costs. We experimentally verify the theory for two load cells with two different sets of parameters.