There is no turning back from the rise of the electric vehicle. The automotive industry is shifting away from combustion technology at a rate of speed not witnessed before, pushed by environmental issues, government legislation and the need to change how we power personal mobility.
EVs aren’t a perfect technology yet. There are still, for example, issues surrounding recharging – both the speed at which it can be done and the available infrastructure – but the seeds have been sown. Engineers are working to smooth out the transition from combustion to electric, and there are three technologies that could be key to this process.
Solid-state batteries
You can’t mention EVs without discussing battery technology. At present most electric vehicles rely on one of the many chemistry make-ups that fall under the lithium-ion umbrella and use liquid electrolytes.
But though the technology is becoming cheaper per kilowatt hour, able to supply a significant amount of range from a single charge, it’s unlikely to be the technology that truly democratises EVs. The industry is looking at solid-state lithium batteries to achieve that.
Solid-state batteries, as the name suggests, use solid electrolytes, which are demonstrably safer and support greater energy density, opening the door to larger capacities and greater vehicle ranges.
The technology hasn’t been perfected yet. The lithium metal anodes that are frequently used in solid-state batteries are prone to trigger the growth of dendrites which can produce undesirable side effects that reduce a battery’s lifespan and safety.
But work continues, with firms including Samsung, research bodies such as the Faraday Institution and start-up manufacturers such as Fisker looking to develop and introduce the technology to the market.
In-wheel motors
Motor technology is arguably the most mature component of an electric vehicle, with decades of development behind it.
Motors are highly efficient, simple (compared to the many moving parts of a combustion engine), and able to produce vast amounts of power and torque, meaning they can be scaled easily depending on application.
Current logic means they are usually integrated centrally, but there are firms that think that shifting them into the wheels would be a better fit, especially as we look at commercial vehicle applications and move into an age of autonomous vehicles where interior design could be shifted to a more social layout.
There are still many arguments as to why in-wheel motors aren’t a good idea, unsprung mass being one, but there are notable benefits. Protean Electric has demonstrated the technology’s manoeuvrability advantages, with a system that offers a limitless 360° steering capability.
The steering capability is possible because of a rotating interface that sits above the corner module’s main arm. The top of the rotating interface is fixed to the vehicle; the lower interface is fixed to the module arm. The electric steering-by-wire unit is located above the interface, so that the axis points to the bottom of the wheel.
From the lower rotational interface, control cables for the motor, hydraulics, and pneumatic ride height controls are channelled down the module arm and are connected to a second static interface within the hub and into the wheel motor unit. As the arm module rotates through 360°, the full component set rotates with it. As a result, the connections and cables are not twisted or stressed. So in urban environments, for delivery vehicles or autonomous taxi pods, in-wheel electric motors could offer a flexibility that centrally placed motors may not be able to.
P4 electric drives
Cost reduction is incredibly important for OEMs if they want to begin the process of shifting people from combustion engine vehicles to EVs. Using a P4 electric drive architecture could be critical. P4 systems integrate the inverter and electric motor into a compact transmission module that applies torque to the axle, sending it directly to the wheels, and can recover energy directly under braking.
The integrated approach saves money, and makes offering either front-wheel drive or all-wheel drive far simpler and more cost-effective. Tier One supplier GKN estimates that by 2026 annual production of P4 electric drive systems will reach around 13m units, and most of the growth in e-mobility in Europe and China over the next decade will be powered by P4 systems. Of these, single-speed set-ups are expected to account for 94% of volumes.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.