Relative heading estimation under constant disturbances for Unmanned Aerial Vehicles

Relative state estimation is an important component in multi-vehicle applications in GPS-denied environments. In this paper, we consider relative head- ing estimation between two Unmanned Aerial Systems (UAS). We examine observability properties of relative states between the two UAS in the presence of constant disturbances. We assume that UAS 2 measures UAS 1’s position in its own frame. We first present observability conditions of the relative states when UAS 1 maintains a constant heading rate and a constant airspeed under the disturbance. We next establish state observability properties when UAS 1 is tracking a stationary ground target using a feedback control. In this case, the heading rate is non-constant. We design an extended Kalman filter (EKF) and conduct simulations to demonstrate its effectiveness in estimating the relative states.

Fig.1. Relative Heading Estimation without disturbances
Fig. 2. Relative Heading Estimation with disturbances i.e., wind.
Authors: Asad N. Awan, He Bai (IEEE American Control Conference, Seattle, USA 2017)
Observability properties of relative state estimation with bearing-only measurements

We consider the problem of relative position and heading estimation between two Drone vehicles. We assume that one vehicle, say vehicle 2, is equipped with a monocular camera sensor to obtain bearing measurements of vehicle 1. We investigate global observability properties of this problem when the linear speeds and the angular velocities of both vehicles are constant. We establish observability conditions when the velocity information of vehicle 1 is communicated to vehicle 2. We also illustrate unobservable scenarios when both vehicles are cruising or orbiting. We further prove that the relative state is observable without communication between the vehicles, if vehicle 1 and 2 are orbiting and cruising, respectively. When both vehicles are orbiting, we develop conditions on the angular velocities of the vehicles to ensure observability.

Authors: Asad Nisar Awan, He Bai (IEEE Conference on Decision and Controls, Melbourne, Australia 2017)
Planning for Mitigation of Variability in Renewable Energy Resources using Temporal Complementarity

Many regions in the world exhibit temporal complementarity of solar and wind energy. In such regions, during certain time periods, when more solar energy is present, lesser amount of wind energy is available and vice-verse. The motivation of this work is to develop a general planning methodology for the integration of these variable renewable energy (VRE) resources in smart power grids, while exploiting temporal complementarity to minimize the supply demand mismatch. We develop an appropriate analytical framework to determine the total investment needed in such VRE resources and the fraction of the total investment in each resource. A multivariate optimization problem is formulated and an optimal algorithm is developed to determine these parameters. To test the proposed methodology, a case study is developed for a region in Northern Ireland. In this region, based on the historical data of past 10 years and using daily average wind and solar capacity factors, we determine the Pearson correlation coefficient, which turns out to be -0.34, showing a sufficient degree of complementarity (anti-correlation) between solar and wind energy. Planning parameters are determined for different load profiles in our case study. General conclusion of the work is that once the temporal complementarity of solar and wind energy resources is exploited, the net supply variability is significantly reduced in microgrids. However, the total investment costs also increases, which is offset by the savings in the storage costs. In addition, reduced variability also leads to a reduction in storage losses, emissions losses, dispatch losses, fuel costs and network congestion.


Authors: Aamir Hussain Chughtai; Naveed Ul Hassan; Chau Yuen (IEEE Innovative Smart Grid Technologies, Singapore 2018)
Random PWM Quiets Noise And Reduces Emissions In Three-Phase Inverter Applications

RPWM signals for three-phase inverters can be generated using different techniques and usually expensive DSPs and FPGAs are used in industrial applications to achieve the desired results. In this article, a suitable RPWM generation technique for three-phase inverter applications using a low-cost CMIC has been outlined. Through appropriate simulations and experimental results, it has been established that the proposed technique is functional and the SLG46620 IC provides sufficient resources to carry out the intended results.

Authors: Aamir Hussain Chughtai, Muhammad Saqib; Publisher:
Random Pulse Width Modulation for Three-Phase Inverter Applications

Conventional Pulse Width Modulation (PWM) methods for driving three phase inverters have been found to produce some undesirable effects in industrial applications like the production of acoustic noise, radio interference, and mechanical vibration. Traditionally, these problems are solved by employing separate filters that can filter out the predetermined harmonic content and mitigate electromagnetic interference. In such applications, Random Pulse Width Modulation (RPWM) has been found much more effective than traditional methods as it inherently spreads the harmonic content over a wide range hence reducing the unwanted effects in three phase inverter fed systems. This application note provides details of RPWM signal generation for driving three phase inverters using the SLG46620 CMIC.

Author: Aamir Hussain Chughtai; Publisher: Dialog Semiconductor
Serial Line Coding Converters

Because of its efficiency, serial communication is common in many industries. Usually, standard protocols like UART, I2C or SPI are used for serial interfaces. However, in many industrial applications, dedicated or customized serial protocols may be very desirable. Some customized serial protocols are based on standard line codes, and conversion to custom can be simplified. This app note details using the Dialog SLG46537 CMIC for several line code conversion examples. In this way, line code customization can be achieved in an inexpensive and easy way.

Author: Aamir Hussain; Publisher: Dialog Semiconductor
Traffic Signal Controller

In this app note a traffic controller that can manage traffic passing through the intersection of a busy main street and a lightly used side street was implemented using a Dialog GreenPAK SLG46537. The scheme is based on an ASM that ensures the traffic signals sequence requirements are met. The behavior of the design was verified by several LEDs and an Arduino UNO microcontroller. The results verified that the design objectives were met. The key advantage of using the Dialog product is to obviate the need of discrete electronic components and microcontroller to build the same system.

The existing design can be extended by adding an input signal from a push button for passage of pedestrian looking to cross the busy street. The signal can be passed to an OR gate along with signal from the side vehicle input sensor to trigger the first state change. However, to ensure safety of the pedestrian now there is an additional requirement of some minimum time to be spent in the fourth state. This can easily be accomplished using another timer block. The green and red signals on the side street traffic signal can now also be fed to the side pedestrian signals on the side street.

Author: Aamir Hussain; Publisher: Dialog Semiconductor