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Pod “Lavinia Heisenberg”

«Lavinia Heisenberg» is the first full-scale prototype by Swissloop with a newly developed drive topology. The pod can transport up to 100 kg of additional payload on a standard Euro pallet. The newly developed linear switched reluctance motor (LSRM) enables a hybrid drive concept. In the first phase, the on-board coils operate as passive electromagnets, while a stationary booster integrated into the track provides the energy-intensive acceleration. In the second phase, the on-board drive system operates as a reluctance motor and no active elements are needed on the track. This means that long tracks can be built relatively inexpensively. In the final phase, a stationary booster can again be used for regenerative braking and optimize the efficiency of the overall system.

The new motor consists of 16 coils positioned between two tooth-shaped rails and is capable of generating acceleration forces of up to 0.5 g. The entire pod is 2.95 m long, 1.37 m wide and 1.12 m high (including the shell) and has a net weight of 224 kg. In addition, the pod is equipped with a variable pneumatic control pressure brake with disc springs to ensure safe braking under all circumstances. The inverter, which was adapted from «Simon Ammann», uses FPGA-based hysteresis control to switch the corresponding coils precisely and very reliably. The two detachable, autonomous battery boxes can accommodate up to 24 batteries, supply 400 V and provide peak currents of up to 400 A. We are proud to have developed all of our electronics by ourselves in the workshop.

A special track was developed for the new motor topology. The teeth in the middle segment are made from a ferromagnetic material.
The suspension supports the weight of the pod and absorbs disturbances through misalignment in the track while keeping the chassis as level as possible.
The newly developed switched reluctance motor supports a hybrid propulsion system, with trackside boosters for acceleration and passive scalable and cost-effective long-distance tracks during constant speed operation.
The stability ensures that the pod and especially the motor retain the correct position during acceleration and constant speed operation.
The pneumatic variable pressure brake uses disc springs to guarantee safe deceleration under any circumstances. The variable braking pressure permits controlled and smooth deceleration.
The aluminium-sandwich chassis with a ROHACELL® core provides mounting points for all subsystems. Further, the optimized design grants easy accessibility to all subsystem while making the best use of the new track interface.
A self-developed SiC-MOSFET inverter is used to power the coils of the motor, where each coil can be excited with up to 100 A. In total four modules, split up into two shielded boxes, are used to control the eight phases of the LSRM.
Most of the low-voltage electronics, including the vehicle and inverter control unit, are placed in a central shielded box and are connected with via the CAN system bus. Additionally, most of the sensors are connected to a dedicated sensor bus running through the whole pod.
In total 24 LiPo battery modules are placed in two battery boxes to provide currents up to 400 A with a voltage of 400 V. The two boxes are connected in parallel and are constantly monitoring the voltage and temperature of each cell.
After mounting the cargo plate, our new pod is capable of carrying up to 100 kg additional cargo on a standard EUR-pallet, fixated by two high-quality airline rails.
The carbon fibre shell provides additional protection, improves the aerodynamic behaviour of the pod and provides a platform to present our numerous invaluable partners. It was manufactured with carbon fibre using a wet lamination process.

“Lavinia Heisenberg” was developed by a team of 31 students with various backgrounds and from different universities throughout Switzerland. The core engineering team, consisting of only sixteen computer, electrical or mechanical engineers; designed, manufactured, assembled and tested the whole prototype during the ten-month season starting in September. The whole prototype is a complex system with numerous parts, all interacting with one another.

Electrical

The linear switched reluctance motor (LSRM) accelerates the vehicle by switching a pulsed direct current through the coils of the motor. When this happens at the right position on the track, the pod is always attracted to the teeth further forward, resulting in continuous forward motion. The motor consists of sixteen coils with a laminated core and is mounted on the underside of the chassis to achieve a low center of gravity. The inverter is the link between the batteries and the LSRM and regulates the current through the motor. 

The electrical systems are largely divided into two high-voltage and one low-voltage box. The high-voltage boxes each contain two power modules and are placed at the front and rear of the vehicle. The low-voltage box contains the vehicle and inverter controls as well as the low-voltage power supply and is located in the middle of the pod. The batteries are integrated into two battery boxes, one on each side of the prototype. The entire battery system consists of 24 lithium-polymer battery packs and has a nominal voltage of 400 V. These boxes contain additional electronics, including the battery management system (BMS), which is responsible for monitoring each individual battery cell. 

Further, the vehicle controller is responsible for the digital integration of the pod. This includes collecting data from the other systems and determining the state of the overall vehicle via the various sensors connected to one of the CAN-FD buses. The vehicle control system then takes action based on this collected data. It also establishes a wireless connection to the control software, from where manual control commands can be sent.

Mechanical

The chassis forms the structural framework of the vehicle. As such, it must withstand the forces applied to it and is made of an aluminum and foam sandwich structure. In addition, a carbon fiber reinforced plastic shell covers the prototype and cargo and improves aerodynamic performance. The suspension and stability system attached to the chassis provides the physical contact between the vehicle and the track. It not only ensures that the pod travels on the desired track, but also serves as protection against impacts due to bumps in the track. It consists of four pairs of wheels that limit the vertical and lateral movement of the chassis, and three additional pairs of wheels that limit the lateral movement of the motor independently of the rest of the pod. For the suspension of the chassis, mountain bike shock absorbers were used for the vertical suspension, and rubber torsion springs for the lateral suspension, while the motor is rigidly stabilized. 

Furthermore, the brakes ensure that the vehicle can come to a safe stop in all cases. The braking mechanism is controlled by a pneumatic system that provides the necessary braking energy. The braking force is generated by a pneumatic cylinder that presses the brake blocks onto the rail so that the pod is decelerated by mechanical friction. The system has a redundant design and sufficient braking force can always be guaranteed even in the event of unexpected failures. The disc springs used as redundancy are constantly compressed and are released even without power or air supply. In addition, the braking force can be regulated via a software controlled pressure regulator in the pneumatic system.

More information is provided in the Annual Report 2022!
Annual Report 2022

224

Weight

100

Cargo

2

Awards @ EHW

Lavinia Heisenberg

Prof. Lavinia Heisenberg is a researcher at ETH Zurich. Here she is particularly involved in gravitational physics, cosmology and computational astrophysics, for which she has received several awards. Her outstanding research and passion for physics make Professor Heisenberg the perfect choice to be the namesake of our new pod.

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