—This technical note addresses the problem of transforming a single-input–single-output discrete-time system into the extended observer form, which comprise a linear time-invariant observable component, and a nonlinear injection term, which depends on the input, output, and their forward shifts up to a finite order. Intrinsic necessary and sufficient conditions are provided for obtaining the extended observer form via a parametrized state transformation. The conditions are formulated directly in terms of the state equations and do not rely on input–output equations as in the earlier papers. Further, an algorithm for obtaining the required transformation is presented. Unlike the existing results on observer forms, the results are not restricted to reversible systems but to more general submersive systems, i.e., to systems, which are reversible via static state feedback.

Tactile Internet (TI) envisions communicating haptic sensory information and kinesthetic feedback over the network and is expected to transfer human skills remotely. For mission-critical TI applications, the network latency is commonly mandated to be between 1-10 ms, due to the sensitivity of human touch, and the packet delivery ratio to be 99.99999%, failing which can lead to catastrophic outcomes. However, with humans-in-the-loop, their dexterity and adaptability to varying responses to stimuli under different network conditions, measuring the performance of a TI session only with latency and packet losses are insufficient and presents an incorrect representation of the experience of the TI application. To develop an objective measure of the quality of TI sessions, we propose a framework that models TI applications as networked control systems, including humans-in-the-loop. We derive a closed-form expression for measuring the difference between the application performance in ideal and non-ideal network conditions. Based on Weber’s law of Just Noticeable Difference, we provide a metric called TIM to estimate the impact of the network on haptic feedback. We implemented TIM on multiple applications on a TI testbed to show that our approach is feasible and TIM strongly follows real subjective measurements. Further, we propose a channel compensation spring based on TIM, to alleviate the network conditions’ negative effects. We demonstrate the efficacy of the channel compensation spring in improving the user experience. We also present implementation notes for TI application developers.

This paper addresses the problem of transforming a single-input single-output discrete-time system into the extended observer form which comprises a linear observable component and a nonlinear injection term depending on the input, output and their forward shifts up to a finite order. The necessary and sufficient conditions for the existence of the extended observer form are provided in terms of vector fields. The algorithm is presented to find a parametrised state transformation necessary to transform the system into the extended observer form. The obtained results are applicable also in case of non-reversible systems.

In this letter, we present Hermes - a novel, low-cost, wireless, batteryless, energy harvesting system for aerial vehicles for sensing wind speed and Angle of Attack (AoA) concurrently. Hermes comprises a set of piezoelectric films which flutter due to incoming wind and the characteristics of this aeroelastic flutter are utilized for determining the wind speed and AoA of the head-wind. Note that in our work we restrict the notion of flutter to high frequency oscillations due to incoming air flow. Hermes consists of five piezoelectric flags that are mounted on rigid clamps specifically placed at different angles. We designed Hermes to maximize the sensing performance and energy harvesting capability simultaneously, without compromising either accuracy or harvesting efficiency. Our current prototype can harvest the power of 440 $\mu$W on average. Over a wide range AoA from $-10^{\circ }$ to $30^{\circ }$, the estimation of the wind speed is within 0.7 km/h error with 90% probability, and AoA error is within $1.2^{\circ }$ with 90% probability. Since Hermes necessitates no wires and batteries and is a low-cost sensor, it is well suited for a range of UAVs, gliders, and aircraft, which require flexible sensor placement and do not require new wiring, which is often complex in aircraft. Hermes is the first of its kind that exploits piezoelectric energy harvesting to simultaneously sense AoA and wind speed. This work is expected to open up new avenues for interdisciplinary research on embedded computing devices for aerospace applications.