Recently, New York City has been seriously discussing modernizing its aging subway system which would be a huge cost to taxpayers and a monumental effort, according to the NY Times . Amtrak has recently had multiple major accidents that ended in loss of life for a variety of reasons. Adding technology solutions to improve both systems can be an enormous help, but might it be time to begin considering an advanced technology system of distance travel like Elon Musk’s Hyperloop idea? Granted, we are about 10 years from such a deployment, but there can be huge benefits with this type of system regarding speed and safety with modern electronics technology.

Let’s take a look at one example of a Hyperloop prototype development effort and you can judge for yourself. I have been intimately involved in the Arizona State University AZLoop project, right across town from where I live. This team finished in the top eight among 35 finalist teams this past August at the SpaceX facility in California. ASU graduate Josh Kosar was the co-leader of the team and a robotics engineer and he has been guiding me through their design process with each visit to speak with their team. The project co-lead was ASU graduate Lynne Nethken, a mechanical engineer. Let’s take a look at their amazing design efforts.

The AZLoop team was among the top teams in points after a week of testing, but they were not in the final-three race to determine the winner—the German WARR team, who reached a top speed of 201 mph. This did not dampen their spirits nor did it lessen their enormous technical accomplishments.

Figure 1 Here is the US/Canadian team Paradigm pod on the SpaceX test track in California about to enter the pressurized vacuum tube during the competition (Image courtesy of Charlie Leight/ASU Now)

Here in the Phoenix, Arizona area, 103 graduate and undergraduate students, faculty advisors, and industry advisors collaborated in a massive effort to develop an economical, sustainable, and scalable pod for the SpaceX Hyperloop transit system concept started by Elon Musk. The students came from Arizona State University (ASU), Embry-Riddle Aeronautical University, Northern Arizona University (NAU), and the Thunderbird School of Global Management, ranging from freshmen to PhDs, in a multi-discipline effort that spans engineering, science, mathematics, and business disciplines. The 10 faculty advisors are versed in propulsion, levitation, electrical, dynamics, modeling, controls, and other disciplines, and the 11 industry advisors represent various engineering and business sectors.

These are some of the most talented students in Arizona dedicated to making the Hyperloop a reality. Every member of AZLoop is required to contribute a minimum of 10 hours per week, each student driven by the recognition that the SpaceX Hyperloop Pod Competition is a collaborative and unique opportunity to revolutionize the world through innovation in transportation.

Figure 2 The AZLoop team with their pod at SpaceX (Image courtesy of Charlie Leight/ASU Now)

I met some members of this talented team at the ASU campus recently and could feel the excitement, dedication, and anticipation of new discoveries and techniques in their quest to have the winning design to make this a better world. This team has now advanced their design from the original 1,300 team designs to a select few 24 teams with incredibly advanced designs. Learn more in the following video:

The team’s ability to work smoothly across the multiple disciplines that make this design a success, have greatly impressed me. I saw no evidence of showmanship or trying to upstage another team member or group. There was a genuine comradeship among all those I have met, as well as an air of excitement and anticipation of what they will be doing to make this system function at its highest level to meet the need for one of the next generation’s means of transportation for mankind. It was a true atmosphere of professionalism, technical prowess, and a vibrant search for solutions that is rarely seen in recent times. As an example, see the following video which shows the propulsion and software teams of AZLoop collaborating.

In this article, I will primarily be highlighting the electronics and magnetics of the design, but will also give a good overview of all the key systems incorporated into this complex design.

After initial acceleration from the SpaceX pusher, the pod is accelerated by an onboard compressed air system for propulsion.

The levitation system consists of arrays of Neodymium permanent magnets which allow the pod to achieve levitation at approximately 5 m/s. Aluminum wheels with polyurethane rims support the pod at low speeds.

In the braking system, magnetic eddy current brakes initially slow the pod from maximum velocity to approximately 5 m/s, at which point contact friction pads take over to bring the pod to a complete stop. The aluminum wheels with polyurethane rims ride along the test track rail to provide lateral stability to the pod.

The competition pod is electrically powered using Lithium Ion batteries. The main electrical supply contains 264 Wh of LiFePO4 batteries with peak capability of 6.7 KW. A backup power supply will be available for emergency scenarios.

Industrial-grade programmable automation controllers (PACs) are used to monitor the sensors and actuators, which ensures safety and system performance during the pod’s run. An industrial-grade inertial measurement unit (IMU) and digital-signal processor (DSP) are used for the pod’s strap-down inertial navigation. Multiple laser and optical sensors provide active tuning for the pod’s navigation system.

Ten shape iterations were tested using an ANSYS computational fluid dynamics (CFD) tool to minimize both the coefficients of drag and lift. The results were observations in which the coefficient of drag ranged from 0.21 to 2.95 for an air velocity of 150 m/s, finally settling on design 10. The final design has a drag coefficient of 0.26 at an air velocity of 200 m/s.

The Embry-Riddle Aeronautical University wind tunnel was set up to replicate the track environment and measure drag forces on the pod (Figure 3 ).

Figure 3 The wind tunnel at Embry-Riddle Aeronautical University (Image courtesy of Embry-Riddle Aeronautical University, Prescott, AZ)

The Reynold’s number was used and the velocity of the air in the tunnel was modified according to the scaled-down pod prototype size. The Reynold’s number for the two environments was equated and the relation between the velocity of the air and the characteristic length of the pod was obtained.

The final design chose four fixed arrays of permanent magnets at each corner of the pod. This design was chosen to increase stability in pitch and roll at high speeds, greater than 5 m/s, while levitating. Wheels are actually used at low speeds since there would be small magnetic forces at speeds below 5m/s.

Magnetic forces are induced by alternating poles created by velocity over the conductive aluminum surface. Test runs saw the pod accelerate at a rate of 19.61 m/s2 which brought the pod to a speed of 5 m/s in only 0.76 seconds. At that speed of 5 m/s and higher, the pod levitation height is 0.012m above the track (Figure 4 ).

  Figure 4 A view from the top of the Levitation Assembly which flanks the braking assembly. (Image courtesy of Reference 1)

The primary levitation mechanism is designed with four Halbach arrays (Figure 5 ).

Figure 5 A Linear Halbach Array (Image courtesy of Sunlase.com)

Each Halbach array contains five 0.254 m3 Neodymium N52 permanent magnets. These types of magnets exhibit a high magnetic flux which allows for levitation speeds above 5 m/s.

The magnets not only maintain the pod’s levitation, but help contribute to braking during a power loss. They also help contribute to stability in attitude, pitch, and roll (Figure 6 ).

  Figure 6 Simulation results from Vizimag 3.18 showing the magnetic field lines for the Halbach Array (Image courtesy of Reference 1)

A rigorous analysis of the levitation system performance was done via mathematical modeling. Some assumptions that were taken are listed here:

Let’s look at the model equations:

Figure 7 Model equation (Image courtesy of Reference 1)

Where the geometry of the Linear Halbach Array was as follows:

Figure 8 Geometry of the Linear Halbach Array (Image courtesy of Reference 1)

The primary braking system consists of three pairs of eddy current brakes (in blue in Figure 9 ) which are non-contact since they only use the opposing forces of the eddy currents generated by the moving magnets to decelerate. These brakes are applied at high speed and slow the pod down for the secondary contact brakes (in red in Figure 9 ) to take over for a complete stop. The secondary brakes are also redundant, braking in the event of a primary system malfunction. Safety functions like this were an important part of the design, and a necessary condition in the SpaceX challenge (Figure 9 ).

Figure 9 The complete pod braking system is composed of ten modules: eddy current brakes (in blue) and friction brakes (in red). (Image courtesy of Reference 1)

The competition pod was powered via compressed air in conjunction with Lithium Polymer batteries. The main electrical power has 264 Wh of LiFePO4 batteries with a peak capability of 6.7 kW. The batteries are A123’s ANR26650M1-B cells. A 24 VDC system mains was set up via the batteries with eight cells in series. To attain the needed 50A maximum load needs, four rows of eight batteries were placed in parallel.

There was also a reserve power supply which powers the electronics systems in the case of a primary power failure. This is composed of 264 Wh of batteries as well.

The battery system can supply power for 30 runs with an estimated run time duration of 32 seconds.

Figure 10 The electrical power system (Image courtesy of Reference 1) Click to enlarge

The Orion BMS was chosen to keep the batteries in their safe operating range as well as to balance the battery cell voltages.

In order to convert the 24VDC battery system to the needed system voltages, switched mode power supplies (SMPS) were used. There were two converters:

The electronic controller system architecture can be seen in Figure 11 .

Figure 11 Electronic system controller architecture diagram (Image courtesy of Reference 1)

  Figure 12 Power system block diagram (Image courtesy of Reference 1) Click to enlarge

The pod controllers are a Siemens Automation product. These programmable automation controllers (PACs) incorporate in their design, redundancy, high-speed processing, protocol standardization, and are easy to use. 

The CPU for each controller was chosen because of the speed and I/O requirements in the system.

Figure 13 Additional modules are added to the main controller module in order to accommodate the input and output signals listed in these charts. (Image courtesy of Reference 1)

Figure 14 Location of sensors in the pod (Image courtesy of Reference 1)

Sensors and actuators went through a rigorous screening process for their respective use in the pod depending upon range and sensitivity requirements and the function it would support.

Part 2 of this series will cover the various sensor and actuator selections for each system in the pod for areas such as propulsion, levitation, braking, communication/navigation, power systems and dynamics. We will also delve into the navigation and communication system electronics, look at some of the modelling tools and techniques used in this design, and discuss the full-scale model design with passenger cabin, luggage compartment, and the final design for their Hyperloop pod.

Figure 15 Here are some of the brightest young minds in our engineering future. (Image courtesy of Reference 1)

Steve Taranovich is a senior technical editor at EDN with 45 years of experience in the electronics industry.

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