Achieving an L2 string stable one vehicle look-ahead platoon with heterogeneity in time-delays

A methodology is proposed to design stabilising and robust fixed-order decentralised controllers for heterogeneous vehicular platoons with Cooperative Adaptive Cruise Control (CACC). We consider Linear Time Invariant (LTI) models with constant time-delays at state, input and output. The closed-loop systems of (identical) local controllers and...

Impact of time-variant turbulence behavior on prediction for adaptive optics systems

For high-contrast imaging systems, the time delay is one of the major limiting factors for the performance of the extreme adaptive optics (AO) sub-system and, in turn, the final contrast. The time delay is due to the finite time needed to measure the incoming disturbance and then apply the correction. By predicting the behavior of the...

Implications for contrast as a result of the wind vector and non-stationary turbulence

In an adaptive optics (AO) system, finite time delays contribute a relatively large amount to the overall wavefront error. The temporal error, due to the time delays, adds to the speckle halo which is visible in the science plane of a high contrast imaging (HCI) instrument. The halo limits the inner working angle, preventing HCI from probing...

Padé approximation of delays in CACC-controlled string-stable platoons

Cooperative Adaptive Cruise Control (CACC) improves road throughput by employing intervehicle wireless communications. The inherent communication time delay significantly limits the minimum inter-vehicle distance in view of string stability. Applying a Padé approximation leads to a model with a rational transfer function, which allows many...

In-line height profiling metrology sensor for zero defect production control

Contemporary production systems of mechanical precision parts show challenges as increased complexity, tolerances shrinking to sub-microns and yield losses that must be mastered to the extreme. More advanced automation and process control is required to accomplish this task. Often a solution based on feedforward/feedback control is chosen...

Phased-Array Antenna Beam Squinting Related to Frequency Dependency of Delay Circuits

Practical time delay circuits do not have a perfectly linear phase-frequency characteristic. When these delay circuits are applied in a phased-array system, this frequency dependency shows up as a frequency dependent beam direction (“beam squinting”). This paper quantifies beam squinting for a linear one-dimensional phased array with equally...

Underwater detection, classification and localisation: Improving the capabilities of towed sonar arrays

The end of the Cold War and the collapse of the Warsaw pact have resulted in a change of operational theatre for the naval forces of the North Atlantic Treaty Organisation (NATO). In particular, the focus of Anti Submarine Warfare forces has shifted from tracking Soviet nuclear ballistic missile submarine in the deep waters of the Atlantic ocean...

Localisation Performance of Passive Sonar for Self Protection Against Fast Craft

Assets at sea are vulnerable to attacks from fast craft relying on the effect of surprise. These threats are not necessarily stealthy but leave a very limited time of reaction to the platform at risk. Early detection of the approaching vessel provides an opportunity for the attacked ship to react in time. Accurate localisation of the threat...

Approximate realization of valve dynamics with time delay

This paper describes the model identification of control valve dynamics with a time delay. An experimental set-up is used to perform both frequency response and step response measurements on the control valve. An approximate realization algorithm and a new time delay estimation method are applied on the experimental data. The results illustrate...

Photonic true time delay beamformer demonstrator for a radio astronomical array antenna