Vehicle dynamics: From motorsports to customized driving
Race car–inspired suspension, steering, and braking features have evolved vehicle dynamics in today’s car. The future holds a more customizable car with the help of electronics.
The concept of vehicle dynamics has not only shaped the way a car drives on a fundamental level, but also has indirectly made consumers aware and more willing to spend for comfort and handling when choosing a car. The concept of vehicle dynamics has not only shaped the way a car drives on a fundamental level, but also has indirectly made consumers aware and more willing to spend for comfort and handling when choosing a car. Premium OEMs have been the champions of developing cars with more improved vehicle dynamics, by showcasing this “art” at famous auto shows. What initially was associated with being glamorous and “too high-tech” to the common man looking for a more utilitarian car has been made reachable in the past few years and has even become a factor in buying a car. All about driving pleasure Vehicle dynamics is the process of creating an optimal combination of the sprung mass (vehicle body), the suspension, and the unsprung mass (tire, brakes, etc.) to offer optimal ride handling and comfort to a car’s driving dynamics. However, vehicles dynamics actually originated from the study of the effect of external excitations on the working of the car. The overall concept behind vehicle dynamics comprises the following aspects: • Vehicle control and handling: Lateral and transverse handling and longitudinal and vertical dynamics of the car while driving. This includes how the car responds to driver demands during driving. • Stability and vehicle comfort: Vehicle vibration and longitudinal tire force while driving. This functions to isolate the driver from external disturbances. • Safety: Factoring human driving behavior during braking, cruising, turning, etc. Combined, these factors drive the “driving pleasure” that vehicle dynamics target in varying degrees based on the vehicle segment, customer type, and market. For instance, Europe’s stint with vehicle dynamics has been a long-standing one, with automakers such as BMW and Mercedes-Benz pushing the envelope. European automakers have not only focused on offering more content per vehicle, but also delivering the desired braking, handling, and steering attributes to their models. However, North America has largely opted for cars with bigger engines and larger cabins, while the vehicle dynamics factor is not as significant as the other factors in the vehicle buying decision. For instance, there is a difference between the Volkswagen (VW) Passat sedan produced in Europe on the MQB platform and the one in North America, which is produced on the same platform as its previous versions. According to media reports, the cornering abilities of the ones produced in Europe on the MQB platform are much better than its North American cousin, indicating that the European version has a more adaptive and tunable suspension. High-performance SUV/sedan: The automotive industry’s oxymoron Previously, there was a fine line between a luxury car, which majorly focused on comfort and premium feel, and a performance car, which focused more on sportiness and vehicle dynamics. However, this line has started to blur as customers, spoilt for choice, opt for cars with a focus on both comfort and vehicle dynamics. Case in point—the high-performance sedan or performance sport utility vehicle (SUV), a concept that is an oxymoron of sorts since it brings together two seemingly opposing driving features. A key example is the Mercedes-Benz AMG S63 Coupe 4MATIC+. The Mercedes-Benz S-Class sedan is the finest model in its class, offering the MAGIC BODY CONTROL suspension with the CURVE function. According to the company, the body tilts to the inside of the turn by up to 2.65 degrees, thereby reducing the centrifugal forces on the passenger while turning. However, with the AMG GLC 63 S 4MATIC+ SUV, the automaker combines this luxury with performance and improved vehicle dynamics by offering a 4.0L twin-turbo V8 engine. The front bumpers are sportier and have a larger intake with more aerodynamic sculpting. The automaker takes inspiration from motorsports, offering typical AMG steering wheel buttons for race car–specific driving dynamics functions and an optional AMG Driver’s package for a maximum speed of up to 280 kilometers per hour (km/h). Other examples include the Lamborghini URUS SUV, as well as the Audi SQ7, which is the performance version of the Audi Q7 SUV. Impact of motorsports technologies in chassis and subcomponents • Chassis o Multimaterial chassis using high-tensile-strength steel and even carbon fiber in many cases, such as the BMWi3 (carbon fiber chassis is even used in hypersonic planes) • Disc brakes o Originally premiered by Porsche for the 24 Hours of Le Mans o Enabled fast braking without locking the steering o Seen in mass markets in the 1980s due to their road safety aspect o Switched from steel disc rotors to lighter, more heat-resistant ceramic versions, such as the ones produced by Brembo • Adaptive suspension o Sensors aligned with the suspension feed data into an onboard computer to adapt suspension to road undulations. Some of the most dominant semiactive suspensions today include ZF’s CDC, Tenneco’s CVSA, and thyssenkrupp’s DampTronic systems. • Steering o Power steering evolving with tuned steering control for hard, soft, sport, and custom steering feel; early electric power steering (EPS) systems felt slightly disconnected, and some even described it as “wooden”. However, the likes of the Range Rover Evoque were the first few to keep the hydraulic feel of the steering despite sporting an EPS. Electronics allow for customization of vehicle dynamics While the concept of personalizing dynamics may beg the argument of whether vehicle dynamics can actually be customized for driving pleasure and for precision, performance driving, electronics are expected to offer certain benefits, particularly as the automotive industry looks on to an autonomous horizon apart from alternate propulsions. Engineers of today’s car are already pushing the mechanical componentry to its physical limits. Therefore, electronics open up new avenues to further stretch the mechanical limitations to derive increased driving stability and safety. This is particularly visible in the supercar segment. Electronics will be particularly useful as more assistance systems creep their way into the vehicle. With important autonomous driving navigation technologies and road-sensing systems defining what the future car may offer, it is important that they communicate with physical components, such as the suspension, steering, and braking systems. Here is where sensors, actuators, and electronic control units (ECUs) assist the vehicle in reaching utmost comfort and safety by personalizing vehicle dynamics. For instance, with navigation systems leading the way in most premium cars, interconnected steering, braking, and suspension systems communicate to offer a comfortable ride for the passengers, particularly at turns, when the car slows down and turns. This real-time data exchange between connected vehicles will enable prediction of the surroundings—the traffic situation or the road surface or both—and adapt the systems to them. A classic precursor to this function is the adaptive cruise control (ACC). The system uses a vehicle’s surround sensors to detect the front vehicle, calculate its speed, and maintain a desired distance with the help of the brake system and the engine. Meanwhile, the dynamic drive assistance system allows for small spurts of systematic braking at high speeds to maintain a safe distance from the front car. As these and other significantly advanced technologies are developed, they will also focus on the noise, vibration, and harshness (NVH) aspect to further enhance ride comfort and handling. However, the argument remains—what is sporty and high performance to one may be too much for daily driving for another. Meanwhile, offering a seamless ride through enhanced vehicle dynamics might make driving enthusiasts feel that the ride is overdone and lacks physical feel and connection with the road. It would be interesting to see how tuned vehicle dynamics fulfil the need for customized road feel in the future. Torque vectoring A consequence of racing technology has been the development of torque vectoring, positively impacting the lateral dynamics of a car during, for example, braking and steering at turns. Electronic stability program or control (ESP/ESC) is a key example of how electronics have managed to evolve torque vectoring for more complex component systems of today’s car. Depending on the driving and road conditions, speed, and predefined system settings, torque vectoring allows for a tuned and balanced ride that avoids both understeer and oversteer, even at high speeds of sports and race cars. This has also helped in enhancing safety during crash avoidance maneuvers and improved balance during hard braking. According to a recent white paper by Bosch, current network architectures are reaching their limit in terms of pushing the boundaries of vehicle dynamics. The company suggests that the solution is “an electronics architecture where parts of the software are relocated from the chassis control unit to the electric-motor management system”. The company further explains, “The results of this are shorter transmission paths, faster switching times, and therefore a highly sensitive and precise torque-vectoring function.” In any case, the key result of involvement of electronics is the emergence of driving modes. Comfort mode, sporty mode, and a less visible chauffeur mode all indicate that electronics not only optimize vehicle dynamics and thereby safety, but also improve them. However, some may find that this is being done at the cost of driving feel. Platform sharing helps Platform modularity has played some role in striking the correct vehicles dynamics balance at the volume car segment. For instance, both the Audi SQ7 SUV and Q7 SUV are based on the same MLB platform (as is the URUS). However, the SQ7 is both performance- and comfort-focused and thus has different vehicle dynamics compared with the Q7, which is mostly a luxury SUV. Audi does this with the help of not just an upgraded powertrain but adaptive suspension settings, in the form of modes. The SQ7 has a DYNAMIC chassis mode that allows the car’s air suspension to lower the body, and the engine becomes bass-heavy to offer a more petrol, V8-like feel. Moreover, due to the tuned suspension and steering, the SUV hardly rolls or understeers. On the other hand, the adaptive air springs and active roll stabilization system soften the suspension when “lowering” the DYNAMIC mode, thus creating a relatively more comfortable ride. Additionally, the rear wheel steering makes it easy to park the vehicle as well. Therefore, the consumer is offered the comfort and luxury of a premium SUV and the ability to handle a track day. According to the IHS Markit forecast, the MLB platform is expected to parent 13% of VW Group’s models in 2019. The following table shows the volumes for different chassis components under the MLB platform: