49 says. “It’s not enough to make sure it will survive 300,000 km in the best of conditions, but the worst-case realistic conditions as well.” This means exposing the RE-100 to the kind of shock loads that would be generated when hitting a large pothole or striking a kerb, along with extremes of temperature. “You go down to -40 C a number of times. You assume it will see that number of very low temperatures in its life, and some high temperatures too,” he says. “We’re close to completion.” Development has been done and deals signed with lead customers for delivery this year. Testing is an ongoing process, however, and is principally focused on new-use cases. “We’re still finding different applications and vehicles that these motors might be used in, which may throw up new testing requirements for us,” Lambert says. Looking further ahead, Protean is looking for optimising tweaks that will improve efficiency. “That may mean changing components or tuning how we are using those components to ultimately give our customers the best possible solution from a range, efficiency and cost point of view,” Lambert adds. “Doing all of this in the wheel is very hard, but our advantage is that we have been doing it for 15 years and we have understood the issues,” says Lambert. Broadly, solving these issues involves providing protection for inherently delicate components and engineering the rest to be as tough as they can be. He explains: “Where you’re designing something from scratch, you design it to be as robust as possible, and when we’re buying something in and integrating it – typically in the electronics – it’s more about ruggedising it as much as possible. What you don’t want is components falling off the PCB, so the vibration becomes quite a severe design constraint. You have got to work with your suppliers to make sure they can build assemblies that will be suitable for the application.” Complexities arise as components of varying sizes made from different materials can resonate in response to different forcing frequencies, and understanding this is crucial. “You can narrow it down by looking at the high-risk items and anything with a high mass or a high moment as a result of where it is being vibrated from, particularly if it is sticking out from its support and could resonate loose,” Lambert says. “Again, we know where to look and what sorts of mitigations to put in place.” Because the RE-100 has independent drives for each wheel, it must meet a higher Automotive Safety Integrity Level (ASIL), as defined under the ISO 26262 standard, than would a conventional e-axle with a single motor, transmission, differential and inverter. “As soon as you have those independent drives for each wheel, you are in ASIL-D territory, so your starting point is always going to be the most stringent automotive functional-safety level,” Lambert says. “Working with the industry, particularly with our OEM customers and BEDEO, to understand how the motors are integrated into the vehicle helps us a lot in developing our safety strategy for the motors.” An important element of the safety strategy relates to how the motors are integrated into the vehicle’s electronic stability programme. Protean has built demonstrator vehicles to study the impact of torque vectoring and traction control, for example, in highperformance applications, and Lambert says these read across well to the more prosaic world of commercial vehicles. “Understanding how those things work at the limit of grip on highperformance vehicles helps us to design a safer commercial vehicle,” he says. “The advantage of in-wheel motors is that they can respond very quickly, compared to an e-axle.” (The company quotes a response time for the Pd18 4250 of 2 ms.) “They don’t have the compliance and twist in the shafts that go to the wheels, so the only real constraint on how quickly we can impact the torque delivered to the road is the flex in the tyre itself.” Accelerated testing The RE-100 is designed for a service life of 300,000 km or 15 years, and Protean is going through a rigorous, accelerated life testing programme to ensure it meets that requirement. “It’s accelerated, but it still takes weeks and months, and it is harsh testing that takes in all the edge cases as well,” he E-Mobility Engineering | March/April 2024 The external rotor also serves as the protective outer casing of the motor and incorporates a patented, dynamic seal technology that minimises friction and keeps contaminants out (Image courtesy of Protean) Protean van conversion | EVD
RkJQdWJsaXNoZXIy MjI2Mzk4