The Perfect Balance of Drivability and Ride Comfort: Going beyond Components to Design a System that Represents Driving The Perfect Balance of Drivability and Ride Comfort: Going beyond Components to Design a System that Represents Driving

The Spirit of Monozukuri—12 The Spirit of Monozukuri—12
The Story Behind the Development of the Damping Force Control System (Adaptive Variable Suspension) The Story Behind the Development of the Damping Force Control System (Adaptive Variable Suspension)

Variable Dampers Set the Standard for Premium Cars to Offer a Flexible Riding Sensation Variable Dampers Set the Standard for Premium Cars to Offer a Flexible Riding Sensation

Dampers, also called shock absorbers, are amongst the indispensable automotive parts that determine ride comfort. The positioning of a vehicle when on the road depends on how well its dampers and springs work, and this determines whether you have a comfortable ride and how well your car performs. These components are of such importance that auto racing enthusiasts say that having your dampers and springs properly set up can be the winning factor that brings glory to your team.

Setting the damper and springs hard to brace the car during quick cornering results in loss of comfort, meaning you feel the bumpy road conditions more directly. If your setup is too soft, driving performance drops. Since the early days of the automobile, finding the optimal balance between performance and comfort has been the ultimate goal for suspension engineers dealing with shock absorbers.

The adaptive variable suspension (AVS) mechanism came as a means of achieving this goal. A variable damper uses the electric current flowing into a variable damping force valve with linear solenoids to control internal oil flow. The less oil allowed to flow, the greater the force the damper creates. Alternately, with more oil it requires less force to move. Commonplace dampers are capable of only fixed damping force. What is desired here is variable damping force. Variable dampers lower the damping force for a smooth ride when the road surface is rough and bumpy, and increase damping force when agility is required. In short, the way the dampers work (i.e., how they create damping force) changes with each passing moment to best adapt to road conditions. This is how the AVS functions.

Adjusting damping force was by no means a new concept. Back in the 1980’s Toyota had already launched vehicles which featured AVS. However, it was only available on some high-end models due to the complexity and manufacturing cost of the mechanism. Eventually, European premium automotive brands began to rapidly expand their offerings that came with variable dampers, enabled by recent advancements in electronic control technology. Domestic car brands followed suit.

It was in 2012, amid this trend, when Aisin was approached by Toyota, which was in search of “a new adaptive variable suspension system to represent the next generation” for use in new models set to hit the market around 2014. Selected Aisin, perceivably because of the variety of technologies it engages in, making it better suited to develop a system of this scale. There were a number of damper manufacturers available, but the automotive giant.

Learning along the way: Developing a New Dynamical Control Theory Learning along the way: Developing a New Dynamical Control Theory

While being acknowledged for engineering capability was an honor, Aisin had no expertise in developing dampers or their accessories.

“We had to start right from the beginning with ‘What is a damper?’” recalls one project member. A member from System Control adds, “In early meetings, I had no clue what the definitions were for the technical terms the Toyota people used and it felt like a communication crisis. Vehicle movement was expressed by a series of equations that I had never seen or heard of.”

The team was lacking in know-how. Nonetheless, they were required not only to create a new mechanism, but also to analyze data with account for noise and vibration after the shock absorber was onboard. No in-house data existed on how the noise from solenoids for damping force adjustment travels and is heard by the driver. What seemed even more daunting was the fact that they had to develop metrics to determine that noise level from scratch. Mechanism analysis and establishing a method to measure operating noise—both were done in parallel. One more thing was required—digging deep to understand the fundamentals of vehicle mechanics. Motorsports experts joined the team.

The project that one member calls “the hardest of my entire carrier as an engineer” went on steadily bit by bit. Efforts bore fruit in the form of dynamical control theory to let a single sensor deal with the relative speed between sprung and unsprung with reliable accuracy. Published in an academic journal, the new technology using the theory received the 2018 Asahara Science Award from the Society of Automotive Engineers of Japan.

The control system for adjusting damping force was finalized and hit the market as a component of the damper equipped to new Lexus models launched in 2014. “We were proud of having done everything we could.” The damping force system that featured what were then cutting-edge technologies was welcomed and well received across the industry, and adopted by other automotive brands.


He continued, “The project was far from over. We continued working to develop better damping force systems.”

For the team, the success in being installed on a new vehicle model was just the first milestone. They went on to create what they call the second generation.