Application Examples

Sensor Mode (Fig. 1a+b)

• Vibration damping applications: good results can be achieved by combining a piezoelectric sensor with a servo-controller and having the sensor signal control an (external) damping mechanism.
• Structural Health Monitoring (SHM): DuraAct™ patch transducers can be used to monitor the functional and structural integrity; the patch transducers are either part of the structure itself, or embedded within it.
• Fast switching: DuraAct™ patch transducers provide fast response and long lifetime and are ideal actuators for these applications.

Actuator Mode (Fig. 2)

DuraAct™ patch transducers feature a very high bandwidth. In combination with suitable electronics (e.g. E-413.D2 from PI) they can be used as highdynamics positioners with submicron precision.

Structural Health Monitoring (Fig. 3)

Whole areas can be surveyed with an array of multiple modules attached to various points on the surface. Active monitoring, where some transducers are used as actuators while the others detect the waves they generate, is also possible. Faults in the structural material, like microcracks, are detected by comparing the signals with those from an undamaged system.

Adaptive Systems Use Both Sensors and Actuators

• Active Vibration Damping: A DuraAct™ patch transducer is used as high-precision sensor and high-performance actuator, simultaneously detecting and damping or eliminating undesirable vibrations in, for example, rotating components. The DuraAct™ sensor signal may be used as power supply for the same module, where it is fed back in with a phase shift. Multilayer ceramic designs make for higher efficiency.
• Profile or shape control: The sensor functionality is used to detect a deformation, and the actuator function to counteract it. The resulting shape control is highly precise, down to the submicron range.

Adaptronics
The use in adaptive structures exploits both the sensor and actuator functionality of the DuraAct™ patch transducer. As smart materials, they can adapt to varying environmental conditions like impact, bending or pressure. Adaptive materials are used in particular for vibration reduction in vehicles, and their use in mechanical engineering is growing.

Energy Harvesting (Fig. 4)

• DuraAct™ patch transducers can provide power for low-power electronics like sensors, making the development of autonomous systems possible. A special branch of Structural Health Monitoring
• (SHM) is Wireless Health Monitoring. Here, a DuraAct™ patch transducer can serve simultaneously as shape-control sensor and supply energy to a radio transmitter for remote data transfer. DuraAct™ patch transducers may replace other power supply solutions in existing applications.

Fig. 1a: Classical application of the direct piezo effect. Minute deformations of the substrate cause displacements in the DuraAct™ patch transducer and produce an electric current proportional to the motion. DuraAct™ transducers can detect deformations—like those caused by bending strain or pressure—very precisely, even at high frequencies.


Fig. 1b: The same operating mode can be used with an array of several modules.


Fig. 2: In actuator mode, DuraAct™ patch transducers use the inverse piezo effect: they contract when voltage is applied. Affixed to a substrate material, a DuraAct™ patch transducer acts as a bender


Fig. 3: Design principle for a health monitoring system: one DuraAct™ patch transducer is controlled by an electronic amplifier (actuator functionality) and induces vibrations in the substrate. An array of transducers detects the vibrations and transfers the signals to suitable control electronics. Comparison with the signal pattern from an undamaged system gives information concerning the condition of the substrate.


Fig. 4: The ability of DuraAct™ transducers to convert mechanical to electrical energy makes them ideal for satisfying power requirements of low-power electronics, and makes possible construction of energy-autonomous systems.
Profile or shape control: The sensor functionality is used to detect a deformation, and the actuator function to counteract it. The resulting shape control is highly precise, down to the submicron range