Evaluation and Design of Displacement-Amplifying Compliant Mechanisms for Sensor Applications

Displacement-amplifying compliant mechanisms (DaCMs) reported in literature are widely used for actuator applications. This paper considers them for sensor applications that rely on displacement measurement, and proposes methods to evaluate and design such mechanisms. The motivation of this work is to increase the sensitivity of a micromachined capacitive accelerometer and a minute mechanical force sensor using DaCMs. A lumped spring-mass-lever (SML) model, which effectively captures the effects of appending a DaCM to a sensor, is introduced. This model is a generalization of the ubiquitously used spring-mass model for the case of an elastic body that has two points of interest—an input and an output. The SML model is shown to be useful in not only evaluating the suitability of an existing DaCM for a new application but also for designing a new DaCM. With the help of this model, we compare a number of DaCMs from literature and identify those that nearly meet the primary problem specifications. To obtain improved designs that also meet the secondary specifications, topology and size-optimization methods are used. For the two applications considered in this paper, we obtain a few new DaCM topologies, which are added to the catalog of DaCMs for future use. The spring-mass-lever model, the evaluation and design methods, and the catalog of DaCMs presented here are useful in other sensor and actuator applications.