1Antenna Simulation for Commercial Unmanned Aerial Vehicles and Wireless Networks in a Warehouse Environment //

Antenna Simulation for Commercial Unmanned Aerial Vehicles and Wireless Networks in a Warehouse Environment

/ Special Air DeliveryUsing commercial UAVs for shipping packages to a consumer’s doorstep — particularly attractive for last-mile delivery service — ensures speedy delivery, resulting in a timelier and improved customer experience. This automated delivery by UAVs will rely less on manpower and transportation infrastructure, leading to significant cost savings.

Retail giants, multinational technology companies and tech startups are experimenting with small commercial UAVs for delivering packages in multiple international locations. Organizations involved in this effort need to solve many engineering problems in various stages of the delivery process to make this technology work. Ansys 3-D physics simulations offer solutions to many of these engineering problems with full-physics simulations predicting the performance, reliability and safety of delivering a package to a client’s doorstep. Simulations can also assist in developing algorithms necessary for this automated and unmanned paradigm.

Major technology corporations and automakers envision a future of self- driving cars, commercial UAVs and advanced wireless devices connecting to the next generation of high speed wireless services with 5G networks. These 5G networks of the future are expected to operate in the millimeter wave band of the wireless spectrum, where blockage and diffraction effects due to buildings and obstacles are pronounced: Communicating through and around these obstacles will pose significant RF link performance challenges. Therefore, 5G networks in the future will require a higher density of distributed MIMO antennas and base stations, making adoption of high-frequency electromagnetic and multiphysics simulation tools necessary for driving further innovation and containing development costs.

Commercial unmanned aerial vehicles (UAVs) show great promise in applications spanning transportation and delivery, entertainment, agriculture, telecommunications and defense. The transportation and delivery industries show great early promise to bring the revolutionary gains of the Industrial Internet of Things (IIOT) to bear on low-cost and efficient package delivery. This white paper explores diverse communications and engineering problems involving commercial UAVs for delivering consumer merchandise, and describes solutions from Ansys to these manifold problems. The focus is on antenna-enabled systems in warehouses, as well as wireless connectivity and performance issues expected along a UAV’s flight path.

Ansys tools can be used for modeling realistic scenarios of UAV-delivery in an urban environment, providing valuable data to the companies involved in regulated and restricted UAV-flight technology testing. Physical system testing requires significant investment in equipment, prototypes, time and manpower. Companies can use Ansys multiphysics solutions to ensure product and system development cost reductions, and enable innovations of these technologies through high-fidelity simulations.

WHITE PAPER

Figure 1. Delivering a package by a commercial UAV.

2Antenna Simulation for Commercial Unmanned Aerial Vehicles and Wireless Networks in a Warehouse Environment //

/ A Cable-Free World Makes the Antenna a Critical ComponentWith Ansys, users can create or import virtual prototypes of UAVs, robots, self-driving tractors, RF systems, electronic equipment and large scale environments, and simulate the electromagnetic behavior and interaction of the various devices. Antennas are one of the most important components in these complex systems; wireless network interoperability relies heavily on them. Antenna performance is strongly influenced by an antenna’s host platform and its environment. For instance, a warehouse is a large and complex electromagnetic environment with many wireless devices, electronic systems and pieces of equipment dispersed among its inventory of goods. Obstacles like metal shelves, reinforced walls and warehouse robots may reflect RF signals, creating multipath interference and signal blockage. A suboptimal choice for the location of an antenna on a mobile platform or at a base station can lead to unintended signal blockage, affecting the radio system’s ability and reliability to communicate. Deliveries in a warehouse environment involve a host of physics ranging from electromagnetics, electromechanical and RF to mechanical and thermal — all of which potentially couple in the real world. Aerodynamic considerations through fluid dynamic simulations such as the impact of wind pressure and wind speed on the UAV can also be evaluated in a multiphysics Ansys simulation platform.

For all these reasons, it’s critical to simulate UAVs and the system antennas upon their platforms and within their operating environment before liftoff with the package.

/ Antenna-Enabled Systems in a Warehouse EnvironmentAs an example of an Ansys solution to maintain operational efficiency in a warehouse, imagine a customer choosing an air delivery option for their online order. The online retail company relays the order to a centralized server or a central control unit in a warehouse. The server communicates with the robots, wireless devices and equipment through a triple-band antenna at 900 MHz, 2.45 GHz, and 5.8 GHz. Ansys HFSS combined with Ansys EMIT can simulate these antennas and radios in their local environments to predict and optimize their performance across — and even between — the various operating bands. These simulations provide insights into the directions in which the antennas radiate and the quality of the RF link coupling, and help in addressing electromagnetic compatibility (EMC) issues related to the centralized server. The server finds the correct warehouse location of the package and automatically conveys this information to a robot near the package. The robot’s RFID tag reader operating at 900 MHz locates and reads the RFID tag identifier of the package and communicates this ID to the network via its 5.8 GHz communication system. Once the robot fetches the package from the shelf, it transports the package and Figure 2. HFSS simulation of a wireless warehouse environment. places it on to the conveyor belt (see Figure 4). An RFID reader system mounted next to the conveyor belt scans the product RFID tag as it passes by, verifying that the correct product is selected and on its way to the customer. The reader communicates information over the same 5.8 GHz link to a nearby printer, which then prints a shipping label for the package. This label is affixed on the package by a pick and place robot, and the package continues its journey to the UAV delivery staging location at the end of the belt conveyor system.

Potential Wireless Systemsin a Warehouse Frequency Bands

RFID systems 13.56 MHz, 433 MHz, 915 MHz, 2.45 GHz, 6-8 GHz

WiFi, Access Points, routers,base stations 2.4-2.5 GHz, 5.725-5.875 GHz

WiMAX USB Modems, base station, backhaul, etc. 2.5 GHz, 3.5 GHz, 5.8 GHz

Global Positioning Systems 1575.42 MHz

Central Warehouse Control Unit 2.4 GHz, 5.8 GHz, 900 MHz

Handheld radios or walkie talkies 446 MHz

Table 1. Wireless networks in a warehouse and their frequency bands.

Figure 3. Warehouse with electronic equipment, robots and centralized server (or wireless control unit).

3Antenna Simulation for Commercial Unmanned Aerial Vehicles and Wireless Networks in a Warehouse Environment //

The simulated RF electric fields and currents induced in the conveyor structures and RFID reader system for the belt conveyor system and printer are shown in Figure 4. A UAV communicating with the warehouse control server over a separate 2.4 GHz communication network receives a signal to pick up the package and take off for delivery. Once outside the warehouse, the UAV receives navigation information through a GPS L1 link at 1575.42 MHz. The product location and delivery process in the warehouse involves more than 15 antennas and radio systems, each of which are simulated and optimized in Ansys HFSS. The behavior of the physical wireless links over the scale of the warehouse (and beyond) are efficiently evaluated using the asymptotic shooting and bouncing ray (SBR) solver in Ansys HFSS SBR+. This tool rapidly solves antenna installation and antenna-to-antenna coupling issues with great accuracy in problems ranging from hundreds to even tens of thousands of wavelengths in size. This naturally extends the capability of Ansys HFSS simulations to solve complete antenna systems and environments with dimensions spanning over five orders of magnitude.

/ Meeting the Antenna Challenge for UAVsEngineering design challenges increase in complexity as the UAV soars into the sky with the package on-board. The UAV itself is equipped with multiple antennas — a GPS antenna at 1575.42 MHz, a Wi-Fi antenna operating at 2.45 GHz for communication within the warehouse and an antenna for communicating in the outside environment during its flight path at 5.8 GHz. There is limited room on the UAV for siting these antennas, and the location of each antenna causes interactions with the UAV’s structure and potentially with the other antenna and radio systems — a behavior known as RF co-site interference. A bad antenna location could result in an RF blindness at some angles, which in turn, could result in a broken control link at some point during delivery. Potential interaction with a variety of payloads should also be considered, particularly with payloads containing metallic objects that can reflect or passively redistribute RF energy. The siting of each antenna on the UAV combined with a model for the radio must account for the RF co-site interference potential between the RF systems. Figure 5 illustrates an Ansys HFSS simulation of the performance of the wireless systems antennas on the UAV.

After sorting out the wireless environment issues and eliminating radio frequency interference (RFI) issues, the UAV can take off for delivery. The UAV CAD models can also be leveraged to look at its performance in mechanical and fluid dynamics domains, such as the aerodynamic performance of the UAV on its flight path through an urban environment, using Ansys multiphysics simulation.

The UAV simulated using Ansys solutions can withstand a maximum force of 2 N exerted by winds blowing at a rate of 35 knots (approximately 40 miles per hour). Ansys AIM and Ansys CFD can be used to predict air flow streamlines and contour plots throughout the city representing wind pressures, patterns and direction.

Ansys CFD can analyze UAV propellers under acceleration to visualize dynamic pressure fields. Ansys CFD calculates velocity swirling strength, which is a measure of turbulence, along the UAV’s path, and predicts regions of high turbulence. CFD analyses can also predict unsteady forces in regions where the UAV undergoes high turbulence. In simulations of the basic weather conditions above, the velocity and pressure fields change with time, but the forces on the UAV do not exceed the limit of 2 N. Ansys solutions offer accurate and reliable information modeling for designing UAVs, evaluating what-if scenarios and mitigating issues in the UAV’s flight path. All this simulation effort leads to successful, timely delivery of your package through expedited design, verification and risk reduction.

/ The Radio EnvironmentJust as it’s crucial for the antennas to perform well, the associated radio systems must also function efficiently so that many radio systems in the warehouse operate without experiencing RF co-site Interference. Ansys EMIT is optimal for investigating RF co-site interference in large environ- ments like a warehouse, and involving many co-located RF and wireless systems. Wherever RF co-site interference potential is identified, EMIT can quickly evaluate co-site mitigation techniques. The 3-D antenna and wireless link simulation results from Ansys HFSS can be exported to Ansys EMIT. EMIT’s built-in libraries of radios and components can simulate the entire wideband RF coupling environment from radio to radio, and learn how well the network devices will perform. For rapid insight, a scenario matrix in EMIT (see figure 7) gives a color-coded view to quickly understand which wireless platforms experience potential interference.

Figure 4. Electric field on the belt, RFID reader system in preparation for packaging.

Figure 5. Impressed RF current density plot on a UAV due to an active wireless system antenna.

Figure 6. Wind pressure streamlines in an urban environment modeled by Ansys AIM.

4Antenna Simulation for Commercial Unmanned Aerial Vehicles and Wireless Networks in a Warehouse Environment //

Each square in the matrix indicates interactions between transmitters and receivers comprising the RF systems. Victim RF receivers with desensitiza- tion or saturation events — at any channel, either in-channel or outside the channel — are represented by red squares. Co-channel, adjacent channel, transmitter intermodulation products, broadband noise and other inter- ference types are diagnosed and mitigated in EMIT. Interaction diagrams denote the root cause and the signal path traversed by any of these interference issues that are preventing the co-existence of wireless systems.

Interference issues due to unintentional emitters like handheld radios can be difficult to diagnose. A warehouse supervisor may use a handheld radio operating in the 446 MHz UHF band to communicate with other workers. Virtual prototypes of the supervisor and handheld radios are placed in the warehouse model with Ansys HFSS simulations to develop the antenna radiation models; HFSS SBR+ then characterizes the link between the antennas as influenced by the warehouse environment. These models are combined with radio and component models in EMIT to yield simulations that predict the impact of emitters in the environment on the automated warehouse control wireless system. Ansys EMIT can quickly identify these problems before deployment and offer rapid evaluation of mitigation strategies, such as filters for harmonic or intermodulation product suppression, higher isolation in an RF switch or employing an amplifier with higher linearity to eliminate the interference.

/ ConclusionSimulation tools from Ansys can greatly accelerate the design of these new delivery systems by predicting and avoiding potential reliability or failure issues prior to deployment. Ansys provides the multidomain physics analysis tools to shorten the design effort, reduce prototype cycles and consider environment interactions that would be very difficult or impossible to construct for physical test and evaluation.

Electronic simulation tools from Ansys can mitigate the unique RF propagation issues in electrically large environments and help create solid wireless links for all associated systems. Developing an interference-free RF environment creates more business efficiencies and helps to serve customers better by eliminating lost time and cost applied to solving network or link outages, or potentially lost UAV vehicles and deliveries. Finally, Ansys can help technology innovators to effectively exploit the promise of future 5G wireless protocols through powerful modeling and simulation capabilities in order to ensure smooth product integration into the next generation wireless landscape.

/ References1. A. Sligar, M. Raju, M. Commens, L. Williams, “Ansys HFSS for Antenna Simulation” – White Paper.

2. S. Carpenter, M. Raju, M. Commens, “An Integrated Workflow for Simulating Installed Antenna and RF System Performance on Airborne Platforms” – White Paper.

3. M. Raju, S. Carpenter, M. Commens, “Simulate Installed Antenna and RF Cosite Issues with EM Tools” – Technical Article in Microwaves & RF.

4. S. Rousselle, M. Miller, A. Sligar, “Complex antenna system simulation uses EM software.” – Technical Article in Defense Electronics.

5. “Clarity from Above,” -- a PwC White Paper.

/ AuthorsLaila Salman (Ph.D.), Manohar Raju, Shawn Carpenter, Matthew Commens (Ph.D.).

Figure 7: EMIT scenario matrix identifies systems with RF Interference (red squares), low margin for RF Interference (yellow squares) and low RF Interference potential (green squares).

Figure 8. Analysis of co-site RFI issues in EMIT showing fully mitigated RF co-site interference potential.

5Antenna Simulation for Commercial Unmanned Aerial Vehicles and Wireless Networks in a Warehouse Environment //

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