Interstory drift measurement is a critical parameter for determining earthquake damages in civil engineering structures. It can be measured using global positioning systems (GPS), accelerometers, LVDTs, and so forth. Each of these methods has limitations in terms of accuracy, cost, installation, and so on. In this study, a novel, laser-based in situ interstory drift measurement setup is proposed and tested on a shake table on which the laser sensors were mounted in the frame to measure interstory drift without any reference frame. The in situ measurements are compared with measurements from reference lasers, which are mounted on a frame separate from the structure.

Sensorless position signal can be obtained from the charge inflow to the piezoelectric actuator or effective capacitance variation due to stroke. However, the first technique imposes sophisticated hardware requirement and it is prone to drift due to current offset. The latter is limited to slow operations. In this note, a hybrid position observer is used to fuse these two self-sensing signals to obtain a high quality position signal which compensates for both creep (slow operations) and rate-dependent hysteresis (fast operations). Experimental results are presented to demonstrate the performance of the observer.

Background: Optical coherence tomography (OCT) is a leading ocular imaging modality, known for delivering high-resolution volumetric morphological images. However, conventional OCT systems are limited by their narrow field-of-view (FOV) and their reliance on scattering contrast, lacking molecular specificity. Methods: To address these limitations, we developed a custom-built 105^∘ ultra-widefield polarization-diversity OCT (UWF PD-OCT) system for assessing various retinal and choroidal conditions, which is particularly advantageous for visualizing peripheral retinal abnormalities. Patients with peripheral lesions or pigmentary changes were imaged using the UWF PD-OCT to evaluate the system’s diagnostic capabilities. Comparisons were made with conventional swept-source OCT and other standard clinical imaging modalities to highlight the benefits of depolarization contrast for identifying pathological changes. Results: The molecular-specific contrast offered by UWF PD-OCT enhanced the detection of disease-specific features, particularly in the peripheral retina, by capturing melanin distribution and pigmentary changes in a single shot. This detailed visualization allows clinicians to monitor disease progression with greater precision, offering more accurate insights into retinal and choroidal pathologies. Conclusions: Integrating UWF PD-OCT into clinical practice represents a major advancement in ocular imaging, enabling comprehensive views of retinal pathologies that are difficult to capture with current modalities. This technology holds great potential to transform the diagnosis and management of retinal and choroidal diseases by providing unique insights into peripheral retinal abnormalities and melanin-specific changes, critical for early detection and timely intervention.

Piezoelectric actuators are often modeled as a lumped mass system in the mechanical domain and as a capacitive element in the electrical domain. Based on a real-time capacitance measurement, it is observed that the piezoelectric capacitance is a function of voltage. This leads to a modification of the traditional piezoelectric actuator model where the capacitance is usually considered constant. A voltage-dependent capacitance term is introduced in the constitutive equations in the electrical domain, and it is demonstrated that this term satisfies a power balance. Then, a novel parameter identification technique is proposed for the modified constitutive equations. The advantage of this identification technique lies in its simplicity that requires only a single experiment to identify all pertinent model parameters. In addition, the hysteresis voltage is conveniently extracted from the applied voltage for a large frequency range. In comparison to the traditional parameter identification procedure and electromechanical models, the proposed technique along with the modified model provides an improved fitting of the parameters. The new model and its identification technique can be applied to sensorless position control applications where exact models are the basis for robust control system designs.