Advanced Actuators

One of the primary uses for compliant mechanisms is displacement amplification, particularly when coupled with smart materials actuators such as piezoelectric or shape memory alloy materials. Compliant mechanisms can produce significant amplification of small deflections, up to 60X in a compact, high-frequency system that does not rely on resonance to achieve desired displacement. This greatly extends the applicability of smart materials actuators, which by themselves are typically limited to small strains and correspondingly small deflections (10 µm - 1000 µm). By integrating a joint-less, backlash-free compliant mechanism with a smart materials actuator, the force and stroke can be tailored to suit specific needs.

We illustrate above how a compliant mechanism alters the force-displacement characteristic of a smart materials or conventional actuator or actuator. The compliant mechanism can increase the displacement (displacement multiplication), or increase the force (force multiplication). Using newly developed optimization techniques, it is possible to design compliant mechanisms that can achieve multiplication factors as high as 60 or more.

Application - Voice-Coil Actuator

A rapid prototype compliant displacement amplifier is mated to a linear voice coil actuator. The compliant mechanism can simultaneously provide rectilinear motion guidance while amplifying the force or displacement capability of the actuator. By exploiting low impedance motion amplification, it is possible to obtain large amplitude output motion at frequencies where the voice coil motor cannot directly produce the required motion alone. This device provides 20:1 amplification.

Application - Piezo Actuator

An array of 8 piezo stack actuators paired with 65X compliant displacement amplifiers is shown. Each actuator-amplifier weighs 17 grams and occupies 22.5 mm x 53 mm x 5 mm envelope. The actuator-amplifier can provide 4.1 N block force and 2.97 mm free-displacement. The first natural frequency of the system is 300 Hz. The performance capabilities of this actuator far exceed that of competing piezo-amplifier systems and bender-type configurations in terms of block force, stroke, and frequency capability - opening the door to new, compact, high-power actuation systems.