35 “Then, we use controlled testing cases to tune the algorithms for the best results during normal driving scenarios. Optimising localisation for fine motor control just depends on having an accurate, closed-loop feed of sensor data on what’s around Robobus at any given time. The aforementioned sub-5 cm object contour error helps in that regard.” Energy levels The battery pack integrates cells based on LiFePO4 cathode chemistries for the voltage and thermal stability (hence safety, particularly for passenger-carrying applications) that these are espoused for. The pack outputs power over a 400 V bus, electrically matching the e-motor and its inverter, and it carries up to 173 Ah of energy, making for approximately 69.2 kWh. Its BMS hardware and software – including charging control software – are also developed and supplied by CATL, with battery management largely isolated from the MU to avoid burdening the latter with unnecessary monitoring and analytics. The one battery parameter continually monitored by the MU is state of charge, so the Robobus knows when it is running low enough on energy to merit a recharge (though route planning and analysis should prevent this happening before the end of a working day). “And, of course, if some health or performance parameter should shift far out of line, the BMS transmits an error code to the MU, and depending on the severity of the error and the location of Robobus, the vehicle will respond by stopping or pulling over to a safe location for passengers to disembark,” Liu adds. Cabin systems The design of each subsystem in the cabin, including lighting, air conditioning and door control, was allocated to different specialists among WeRide’s team. Each subsystem was then planned and drawn out individually, with the air conditioning developed through blueprinting of the system of air vents and fans, calculations of power requirements, and selections and placements of the compressors, noise-control parts, radiators, temperature and humidity sensors, and other components. In the case of the infotainment screen, a 21 in (53.34 cm) LCD interface was chosen and integrated towards the front portion of the cabin’s ceiling. Safety systems chosen inside the cabin also include seatbelt sensors (with alerts triggered when passengers have not fastened theirs) and cameras monitoring the interior for incidents; for instance, altercations, medical alerts such as passenger heart attacks, or personal belongings being forgotten. Each specialist was responsible for developing the software needed for running their portion of the cabin, including algorithms for controlling the air conditioning, the infotainment functions and the doors. The latter of these runs on the MU, intertwined with the self-driving algorithm, to ensure the doors automatically open and close only at specified destinations, and only when the vehicle has stopped. Buttons are also installed and connected with the MU for either pedestrians or passengers to activate the doors themselves at stops. “Then, according to each cabin specialist’s planning documents, a verification stage followed in which the various cabin subsystems were integrated together into the vehicle design and simulated to gauge how well they worked together,” Liu says. “That, followed by vehicle prototype tests, ensured there weren’t emergent issues, like EMI buildups between subsystems, uncomfortable noise levels for passengers, or resonances affecting the reliability of mechanical components like compressors or door motors. “And, before either vehicle version left the factory for real-world trials and demonstrations, the project team conducted a joint review of every subsystem and function to verify if each one was acceptable from the point of view of pedestrians, passengers, fleet managers and engineers. If everything passes from all those perspectives, the product can go to market.” Vehicle connectivity A dual-redundant 4G radio system is installed on Robobus for consistent, uninterrupted remote safety monitoring, as well as teleoperation, if needed. To enhance the consistency of communications, WeRide has developed its own multipass UDP solution, which enables multiple telecoms providers to be used, with the 4G system continuously monitoring and selecting whichever carrier seems to provide the Uncrewed Systems Technology | October/November 2024 The 400 V, LFP battery pack and its BMS are integrated at the rear of the cabin, rather than in the floor, allowing for a very low floor and ride height
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