MOTORS & DRIVES & CONTROLS
SECTION TITLE
identify the load-bearing structures. Battery packs can weigh up to 500kg, therefore ascertaining the sections of key load-bearing structures and simulating in FEA is critical. In the electrical and systems domain we must identify what systems we can communicate with, what we need to replace and what we can modify. In all situations we add a powertrain controller. Tis needs to interface with the driver controls, in some instances we need to update controls such as the throttle pedal.” Te modelling is a crucial part of the
process. Equipmake uses Matlab Simulink for simulation, typically modelled against known routes or industry standard duty cycles.
Te parts that are removed are checked
and serviceable items returned to the operator. Stevens notes, “As the converted fleet increases in numbers this can be a useful spares resource for the standard fleet.”
THE COMPLETE PACKAGE Stevens continues, “Te batteries on the Routemaster are particularly complicated from a packaging perspective. Tere are 5 separate packs in a variety of challenging shapes located under stairs, above wheel arches and so on. Typically Equipmake would use our standard battery pack. Fortunately we are used to dealing with multiple packs and they are connected to a Power Distribution Unit (PDU) of Equipmake’s own design. Tis incorporates
the controller and distributes the high voltage to the traction motor and auxiliary systems. “Equipmake do not build batteries from
cell level, but work with modules that in recent years have reached very competitive prices. Tis allows us to have flexibility of pack shape, but with a relatively short development time. We must however take care of crash loads and UNECE Regulation 100, which includes external conditions such as surviving a fire for a period of time.” Te drivetrain consists of Equipmake’s HTM-3500 motor. Tis is a 3,500RPM, 3,500Nm 400kW unit. In bus applications the peak power is not required, but double decker buses such as the Routemaster require the torque for fully-laden hill climbing. Tis motor can also be stacked in tandem to give 7,000Nm, such as required for fire truck applications. Stevens explains, “Te installation of the motor is often one of the simpler parts of the conversion. We position it where the gearbox output would typically be and drive the differential directly with what is often a custom-length driveshaft. After removing the engine and gearbox there is often space left over for batteries or other systems. Tis was certainly the case with the Routemaster.” Te motor is liquid cooled and weighs around 195kg. Due to its relatively flat shape it is often mistakenly thought to be axial flux, but it is a radial IPM (Interior Permanent Magnet) machine.
The prototype Routemaster bus is undergoing a mechanical makeover
Chief Development Engineer Jonathan
Stevens takes up story: “Te process begins with a strip down of the bus. Removed parts are weighed and the location noted so if possible the standard weight distribution can be adhered to, however the over riding requirement is vehicle and axle weight. In this particular bus we uprated the front axle as packaging prevented the old weight distribution being matched. We make extensive use of scanning, which we sub-contract. We often don’t have access to vehicle CAD and even when we do there is often variations in real life with buses. “Once we have the scanned data we
Driveability can be fine-tuned with a host of software parameters
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