E-Mobility Engineering 015 l EMotive Scarab off-road truck dossier l In Conversation: Giulio Ornella l Hall effect and magnetic sensors focus l Challenge of batteries for heavy-duty EVs l Alpha Motor Corporation digest l Automated charging insight l HVAC systems focus
Dossier | EMotive Scarab off-road truck “In the final stages we will be going through everything with a fine-tooth comb in terms of FEA, working out if there are areas where we have to put in extra strengthening, perhaps changing a radius here and there on the chassis where we have laser-cut parts. There will certainly be some tidying up at the end.” Traction control and active suspension As each airbag/spring can have its pressure increased and decreased individually by the electrically driven compressor, they form the basis of a kind of active suspension system that can be used for advanced functions including traction control, ride height adjustment and potentially ride levelling, all of which are currently in development or under consideration. “At the moment we are looking at doing everything with a single ride height, although we can add an adjustment capability,” Williams says. “I don’t yet know whether we will go for a dynamic ride height or a passive system with on-road/off-road settings that the system would maintain regardless of load.” He explains that the left and right sides of each axle could be linked pneumatically to manage body roll. “It is not something we are doing now, but there is no reason why we couldn’t with the systems we have on board. The master controller can easily look at wishbone angle to determine the ride height, and change the air pressure in the springs to adjust the height accordingly.” The air suspension could also help maximise grip and traction, he says. If there is a loss of tractive effort from an individual wheel because it is slightly off the ground, the system can add pressure to that wheel’s air spring to push the wheel down for firmer contact with the ground. “This is all part of our thought process, and as we progress through the trials period we will go through that and see if we need it,” he says. “Having individual motors, one per wheel, gives us good control of our traction. Using the master controller, we can monitor and control each wheel station individually and, when we detect a loss of traction, we can change wheel speeds and apply braking where needed to restore it. With the adjustable pressure in the air suspension we can enhance that capability significantly. “We can also determine axle loads through our airbag pressures, so we can calculate how much mass we have on each wheel station. We have encoders in the motors to show their rotational position, we have ABS sensors, and we have individual control of each motor and its service brake. “Although there is still a lot of work to be done on testing the traction control, we are giving the system all the sensors and feedback it needs to gain that full control over each wheel station. The master controller will know where each wheel is within its range of vertical travel and steering angle, how fast it is This electrically driven hydraulic pump and its fluid reservoir serve the power steering and role equipment. In the production version it will be relocated to a space under the cab (Author’s photo) 26 Autumn 2022 | E-Mobility Engineering
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