Secrets of GM’s Active Aero Program Revealed by Michael Accardi April 5, 2017April 7, 2017 Share Comments Thread A large batch of patent documents reveal General Motors is working on an active aerodynamic system which could feature across multiple applications. In the early ‘60s Enzo Ferrari once famously proclaimed aerodynamics were for people who couldn’t build engines, fast forward 50 years and it’s amazing how wrong “il Grande Vecchio” was. Recently, as displacement has become highly demonized and computational fluid dynamics created a utopic engineering playground, aerodynamic dependency has proliferated; first on the race track and now on the road. Arguably, engineers of high end performance metal enjoy even greater creative freedom than their race department counterparts–who despite their obsessive quest for more downforce and less drag are chained to rulebooks which ban active or adjustable aerodynamics mainly on the grounds of cost. GMI has come across eight (8) patent documents published last week which depict several different subsystems which in theory will combine to create a highly adaptable active aerodynamic system which adjusts to best optimize performance based on several steady streams of information provided to the system’s CPU. The key to good active aerodynamics isn’t just information, but information about what is happening between a set of parameters. Significant to GM’s active aero program is a “method for diagnosing the aerodynamic system and verifying downforce estimation using a force sensor.” Effectively the force sensor is tasked with determining target downforce values for acceleration, braking and cornering events based on vehicle speed and what exactly the driver is asking the car to do. The force sensor also determines maximum possible downforce values under acceleration, braking and cornering and contrasts them with an optimal target value in order to determine a preferred front/rear distribution of downforce which would theoretically be controlled by a movable front splitter and an adjustable rear wing. Complimenting the force sensor, GM has a method for “verifying downforce estimation based on electric motor current.” Here GM is once again contrasting the expected downforce acting on the car’s aerodynamic elements with the actual downforce acting on said elements as determined by the electrical current used by the electric motor to move the wing and splitter. Based on the language in the document, GM may even be considering cutting the front splitter in half, “the front spoiler assembly may further include a first, left winglet and a second, right winglet,” this could theoretically move applied downforce laterally across the nose of the car for better turn in or mid-corner stability. Another subsystem patented is a “method and apparatus for controlling vehicle tractive effort,” which is a fancy way of saying using downforce to minimize wheelspin. GM’s method determines the coefficient of surface friction at each wheel based on vehicle speed, wheel slip, and torque applied which then determines how much downforce should be distributed. Because the active aerodynamic system is capable of applying downforce to just one of the wheels in order to control wheelspin GM could be foreshadowing future all-wheel drive applications. The document does mention the potential for integration of electric all-wheel drive– the mythical mid-engine Corvette has long been rumored to feature electric driven front-wheels, this is very possibly the first official hint of such a system–however it could also be GM engineers casting the widest possible net. In order to verify the aerodynamic effect on ride and handling GM has subsequently designed a subsystem which measures the actual dynamic output of the active aero system through a network of sensors mounted on the body which will calculate yaw rate, wheel speed, ambient airflow, current steering angle which will partially inform the CPU’s decision to modulate the electric actuators and motors that control the splitter, wing, air dam, diffuser and grille shutters. While the vehicle, its operating condition and surrounding environment are integral to delivering optimized downforce, there is a second half to the relationship; what does the driver want? Car’s equipped with GM’s active aero system will feature a controller which is in constant communication with steering, throttle and brake inputs in order to generate a feedforward signal–seemingly a composite of past and current behavior–which forecasts what the driver will want from the car before the driver wants it. This could be an evolution of Jeff Trush’s excellent work on the 10-speed automatic’s performance algorithms which understands and adjusts for what the car is doing based on lateral acceleration and driver inputs. Lastly, GM didn’t just patent the subsystems, but also a “sensor based closed loop control of active aerodynamic elements” which allows the subsystems to communicate with one another: “a controller or control system this is in communication with numerous systems and components throughout the vehicle via wired or wireless communication protocols.” What we’re looking at here isn’t a system designed for one single specific application, but a system of subsystems that could and should be deployed across GM’s Camaro, Corvette and V-series performance brands. It would be logical to assume we won’t see GM’s active aero system in full bloom until the mid-engine Corvette makes its debut within the next year or so; but much like GM’s other high profile development work expect the technology to trickle down as it matures.