The DØ experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DØ.

This paper presents a comprehensive model for piezoceramic actuators (PAs), which accounts for hysteresis, non-linear electric field and dynamic effects. The hysteresis model is based on the widely used general Maxwell slip model, while an enhanced electro-mechanical non-linear model replaces the linear constitutive equations commonly used. Further on, a linear second order model compensates the frequency response of the actuator. Each individual model is fully characterized from experimental data yielded by a specific PA, then incorporated into a comprehensive 'direct' model able to determine the output strain based on the applied input voltage, fully compensating the aforementioned effects, where the term 'direct' represents an electrical-to-mechanical operating path. The 'direct' model was implemented in a Matlab/Simulink environment and successfully validated via experimental results, exhibiting higher accuracy and simplicity than many published models. This simplicity would allow a straightforward inclusion of other behaviour such as creep, ageing, material non-linearity, etc, if such parameters are important for a particular application.Based on the same formulation, two other models are also presented: the first is an 'alternate' model intended to operate within a force-controlled scheme (instead of a displacement/position control), thus able to capture the complex mechanical interactions occurring between a PA and its host structure. The second development is an 'inverse' model, able to operate within an open-loop control scheme, that is, yielding a 'linearized' PA behaviour. The performance of the developed models is demonstrated via a numerical sample case simulated in Matlab/Simulink, consisting of a PA coupled to a simple mechanical system, aimed at shifting the natural frequency of the latter.

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