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Steering Wheel and Telemetry

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Introduction

When we designed our steering wheel, we mainly thought about what the driver needs during the race. According to our necessity, we used an Agile approach: the “client”, our driver, has an active role in the software development and also in the design of the Steering Wheel.

Prototype

We started from a blank page, drawing with a pen the interface as a low fidelity prototype: here, the whole development team worked together attentively considering what the driver had to say. The next phase involved the high fidelity prototype: our designer concretized our idea through Illustrator which made things easier, mostly as we had the possibility to export the assets on Photoshop. In this way, the objects were easily manageable and ready-to-use in our UI, coded with C++.

The Framework used is Qt 5.10.1, being it the most used in Automotive industries. The result of our work is an eandearing interface composed of 6 tabs.

The thing that makes our Steering Wheel so unique is the assets, which are designed by us and inspired to the racing world — in particular to the racing game. We choose to use Raspberry Pi as target board, it made things easier when we had trouble during the development, the RPI has its own Shield designed by us to extend the GPIO and integrate CAN-BUS to communicate with the other boards of the vehicle.

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One of the most important choices to have the best HMI possible was to display the state of charge of the HV and LV and the state of the vehicle (IDLE, SETUP, RUN and STOP) from each tab as a frame, considering the UI. This is the most apparent change and this choice was very important during the development, because it determined the order of our work starting from the frame and going on only after with the tabs.

Steering Wheel Manifacture

Also regarding the case and the front panel they were design and produce by us.

  • Why the steering wheel has been redesigned from scratch:
    • ergonomics not good
    • not intuitive (buttons position & single central rotary switch)
    • materials not suitable for continuative use and stresses transmitted from steering system
    • low construction quality and assembly
    • ECU connection with flying cable not practical
  • Design:
    • project started on September 2017 form a white sheet of paper
    • evaluation of internal space needed for electronic components
    • quick release disconnect with integrated connector
    • requirements: mechanical strenght, ergonomics, material quality, assembly, aesthetics
    • gathering of driver’s feedback about position and ergonomics
    • continuous solutions implementation based on production technologies availability
  • Materials & Production methods (all components described below has been designed and produced in house):
    • main plate: carbon fiber prepreg T1000 with 1.5 mm internal core, autoclave cured and cutted with waterjet. Overall thickness 3 mm
    • paddles: carbon fiber prepreg T200, autoclave cured, 1.5 mm thick, cutted with waterjet
    • front mask: SLA (stereolithography) with Form 2 printer, Formlabs Black resin
    • rotary switches: MJF (Multi Jet Fusion) with HP Jet Fusion 3D 4200 printer, PA 12 powder, sandblasted and painted
    • hand grips: SLA with Form 2 printer, Formlabs Tough resin, structural epoxy resin bonding
    • back shell: aerospace-grade aluminium alloy (Ergal 7075), CNC milled from raw block of material
  • Future developments:
    • weight reduction
    • handgrips: driver’s imprint in modelling clay, 3D scanning and cad model generation

Tabs

  • How it works

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  • Errors Tab

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    The first one is called “Errors Tab”: through this, we can see if there are any critical errors on the car; if there is none, we can start the car and, later, we can stop it. These actions activate or deactivate the tractive system, so the starting procedure must be done every time before turning on the engine. The usefulness is in the fact that if there are errors and the driver doesn’t notice, the car won’t start.

  • Warnings Tab

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    The second one is called “Warnings Tab”, to see if there is any warning on the car. Unlike errors, warnings are not system critical and are there only to inform the driver if a certain sensor is not working properly. If there is a warning, the car can still turn on and if during the race a warning appears, the car will stay on. These values are updated every 500ms.

  • Status Tab

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    In the third tab we can see the status of the precharge, as well as the status of the inverters. We can also decide to turn an inverter on or off. This procedure must be done before going in ready-to-drive mode: if the inverters are off or cannot be started (which they are by default), the ready-to-drive mode won’t be enabled.

  • Racing Page

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    The fourth tab, also called “Racing Page”, is the most important one. From here, the driver can go in ready-to-drive mode by clicking the button in the top left corner. In the middle of the screen, the driver sees how many KW of power he’s requesting to the motors, while on the bottom he can see the motor map he is in. Motor maps are used to limit the power available, with map 1 being -20% (which means reverse), map 2 being 20%, map 3 being 40% and so on until 100%. The map can be changed before going in ready-to-drive. In this page the driver can also see the temperatures of the HV and LV batteries, as well as their voltage. This data is shown respectively in the bottom left and right of the screen. In the central part of the screen there are two more indicators, which show how much throttle and brake is applied at any given moment. At the top of the tab there is also an indicator which shows whether the control is on, if there is an error and if there is a warning. These indicators update every 500ms, just like in the other tabs.

  • Battery Tab

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    The fifth tab, also called “Battery Tab”, shows the status of the batteries: here is possible to see the minimum, average and maximum of temperature and voltage of HV and LV

  • Sensors Tab

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    The sixth tab is essentially sensors (APPS, BSE and STEER). Here, we can setup them with an interactive procedure staring from the MIN and ending with the MAX. It’s very important to us in order to remove the use of an external device for this procedure.

Conclusion

We consider our work not as a finished project, but as a good point to start from for the next year. The solution we developed allowed us to better comprehend QT and find some issues to solve and improve, as the time needed for the RPI to start. Considering the board, we want to move our code to something less amateur like an STM32.