Analysis and optimization of a compliant mechanism-based digital force/weight sensor

Digital force/weight sensors have some advantages over their analog counterparts. This paper describes the optimization and implementation of a novel digital force/weight sensor that uses a thickness-shear quartz crystal resonator (QCR) and a unique compliant mechanism. The compliant mechanism consists of eight flexure hinges and is used to fix the sensitive QCR and transfer the measured force. Advantages of such a sensor include inherent digital output, high resolution, high reliability, and low cost. Due to the complex structure and the multivariables of the compliant mechanism, conventional trial methods are inefficient in determining the dimensions. To solve this problem, an optimization method has been developed by employing rigid-body model, finite element method, and nonlinear programming techniques. Experimental results show that it is more efficient than trial methods in optimizing complex compliant mechanism-based sensors. This method can be used as a generic method for optimizing force sensors using compliant mechanisms, to obtain the desired specifications.