Compliant mechanisms have received considerable amount of interest in the design of systems having bistable behavior, following a dwell motion, impact motion as well as bio-inspired mechanisms. As technology advances it brings the opportunity to manufacture compliant mechanisms using additive manufacturing with new materials. Compliant mechanisms incorporating flexible links and flexure segments creates motion through the deflection of its flexible links rather than the relative motion between two links as appear in traditionally designed rigid mechanisms. They provide several advantages such as fewer number of links required to build the mechanisms, no friction, no backlash and high precision and high performance compared to their rigid-body counterparts. Despite the advantages, modeling and design of compliant mechanisms are challenging, and require design and modeling experience. Finite element method provides an accurate solution considering the material nonlinearities.  Common modeling methods such as Elliptic integral solution and pseudo rigid body modeling is applicable to simple flexible link geometries such as fixed-fixed, pinned-pinned and small length flexure hinges. If the complexity in the design increases, as expected deriving the mathematical model of compliant mechanism becomes more challenging.

This paper presents the informative process of modeling of compliant mechanisms using MATLAB Simscape. Simscape is the modeling environment analyzing both rigid and flexible systems using either the blocks provided in the library or the CAD models imported from modeling software. We present the modeling of four compliant mechanisms: dwell, five bar, translational and hopping mechanisms. Once the cad model of a system is imported into Simscape, the flexible links or flexure segment on each example system is replaced by its equivalent lumped parameter block.  Compliant dwell mechanism is comprised of a rail, two pinned-pinned flexible links, slider, rigid crank and a DC motor. The second mechanism is a fully compliant five bar mechanism incorporating large deflecting flexures and actuated by two servo motors. The objective is to control the trajectory of the tip position. Third example models a bio-inspired translational compliant mechanism driven by servo motors and comprised of three sliders connected by single piece designed 2 rigid arm-flexure hinge linkages mimicking the motion of a caterpillar. The last example is the modeling of a compliant hopping robot consisting of two pairs of gears; one pair is attached to the motor and the other pair allows the bottom links to rotate at same angular velocity in opposite directions. Rigid and flexible links on each example system are 3D printed using polylactic acid (PLA) and polyethylene terephthalate glycol (PETG) filaments. MATLAB Simscape modeling outputs are validated through experimental setups for each system.


Modeling of Compliant Mechanisms in MATLAB Simscape

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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