What is “Skyactiv-Vehicle Architecture,” Mazda’s structural technology next-generation vehicles?
-Taking maximum advantage of the human body’s inherent ability to balance itself, in our quest for the further evolution of our principle of Jinba-ittai (oneness of horse and rider).-
Mazda’s goal is to provide the “joy of driving.” This is not the kind of exhilaration and sense of speed that comes from sudden changes in acceleration, like the thrill of riding a roller coaster.
In scenes of everyday driving, such as commuting to work, going shopping, or taking long drives with your family, like handling a well-used tool, your car will move, turn, and stop just the way you want it to. You can feel the car’s response and it will make you want to keep on driving. By combining the human body’s natural movements with the car’s motion, your fellow occupants will also naturally sense the motion of the car and feel reassured. That car that captured your heart at first sight, that made you want to keep gazing at the way it changes constantly with the surrounding scenery and the light. It will make you will want to drive again.
It is the sense of total satisfaction of the heart that owning such a car gives you and that you feel when you drive it wherever you want to go, and spend time with your car. That is the “joy of driving” that Mazda aims to achieve.
To make that happen, our development team have consistently pursued Jinba-ittai, in which the wishes of the driver and the motion of the car are at one with each other and you can drive safely and securely just the way you want. In its quest for this ideal, Mazda pursued the development with an intensified focus on car making based on its human-centered design philosophy.
By comprehensively refining its existing Skyactiv platform all the way down to its most basic functions, Mazda has succeeded in the development of its next-generation Skyactiv-Vehicle Architecture platform. Along with the next-generation engine, Skyactiv-X, Skyactiv-Vehicle Architecture will be adopted in next-generation Mazda vehicles to be released in 2019 and beyond.
Coordination as the overall structure of the vehicle
The aim of the Skyactiv-Vehicle Architecture development was to take the human body’s ability to balance itself unconsciously when walking and to make it possible to exercise that same ability while occupying the vehicle. Occupants will be able to sense the motion of the car just as naturally and unconsciously as when they are walking. This will achieve the “joy of driving” through the ultimate Jinba-ittai driving experience, by taking maximum advantage of the inherent ability of the human body and offering a more comfortable, less tiring ride for all occupants.
To make this happen, we focused less on the individual systems of the car platform, and more on making the individual elements, from the seats that occupants sit in to the car body, chassis, and tires, coordinate with each other as the overall structure, or architecture, of the vehicle. This development has been pursued with organic interaction. In this edition, we will look at the concepts behind Skyactiv-Vehicle Architecture.
What is the ideal state of the human body when it is walking?
When humans walk, they unconsciously take advantage of the flexibility of the spine to create an axis in the direction of forward motion. That axis forms the basis for balancing the body. At Mazda, we call this the “Progression axis.”
Based on this progression axis, the body moves the pelvis and upper body in opposite directions and uses small changes in posture and muscles, to control the body’s center of gravity efficiently and maintain a dynamic balance with limited movement of the head. Even when overcoming changes in direction and uneven surfaces, the body moves smoothly and continuously, with no wavering of that progression axis.
It is the body unconsciously exercising its ability to balance itself that makes this possible. This ability is one of the most advanced of the human body’s inherent abilities.
There are two key points to maintaining this basic state. One is the fact that the pelvis is in an upright position that maintains the spine’s natural “S” curve. The other is the fact that the reactive force from the ground is transferred smoothly from the legs to the pelvis and the pelvis itself moves regularly and continuously.
The development team wondered how those key points could be translated to cars. What would they need to do to create the ideal condition in which the car’s occupants to exercise the body’s same inherent ability to balance itself as when they are walking? The following two points provided the answer.
- ・To be able to sit in the seat in a way that kept the pelvis upright to maintain the spine’s natural “S” curve.
・Instead of the human body’s legs, the car will transfer the force from the road surface smoothly to the pelvis, allowing the pelvis to move continuously and smoothly.
The aim of the Skyactiv-Vehicle Architecture platform was to take maximum advantage of this ability of the human body to balance itself.
Advances in individual technology
Next, we will look at the main technologies developed for the Skyactiv-Vehicle Architecture that incorporated these concepts.
・ Seat – Maintaining the spine’s “S” curve –
The latest findings in human research have been incorporated in the seat’s structure to ensure a seated posture that keeps the pelvis upright, so the spine’s S curve is maintained.
The shape and hardness of the seat have been redesigned to support the lumbar vertebra to prevent the pelvis from leaning backward and to wrap around the thorax center*1, to maintain the S curve of the spine. Stand-alone adjustment of the thigh area has also been achieved, to offer all customers their ideal driving posture.
On top of this, the rigidity of the seat’s internal structure has been increased so that the load is transferred from the sprung mass to the human body in a straight line.
*1 The thorax center is where the upper body’s center of gravity is located. It has a major impact on the whole body’s center of gravity.
・ Body – Transmitting inputs without delay –
By connecting the car body in the front-to-back direction as well as the top-to-bottom and left-to-right directions, thus creating a multi-directional ring structure, four-wheel diagonal rigidity has been increased and inputs are transmitted without delay. This has enabled a 30% reduction in input delay from the front to the diagonal rear, so the car’s motion is better able to conform to the natural movement of the human body.
Left: Previous vehicle frame; Right: Skyactiv-Vehicle Architecture
While analyzing force flow, the frame (red sections) has been positioned effectively from the viewpoint of increasing four-wheel diagonal rigidity.
・ Chassis – Smooth input from unsprung mass –
Force input from the road surface is transferred to the car body via the suspension. Skyactiv-Architecture involved redesigning the chassis, moving away from the conventional notion of changing the size of the energy transferred to the sprung mass toward a concept of making the energy transfer to the sprung mass smoother over time.
The suspension’s front-to-rear support rigidity, tires, arms, springs, and dampers interact with each other in turn along a time line, to adjust the suddenness of the spring’s movements. Another change was making the top and bottom springs of the tire soft instead of hard, to take advantage of the tire rubber’s inherent vibration absorption and damping functions.
This development also actively used G-vectoring control for load transfer during steering, generating grip force in the tires without delay, to achieve smoother input.
・ Further advances in NVH
Providing a quiet space is an important factor in maximizing the human body’s inherent abilities. Skyactiv-Vehicle Architecture has also achieved major advances in NVH*2.
The development team researched the mechanisms by which humans perceive sound, focusing not only on the volume, but also on how sound changes over time and the direction it comes from. This information was used to attenuate the vibration energy in the car body. Placing the attenuation nodes and bonds in effective positions on the platform has resulted in better NHV performance.
*2: Noise Vibration Harshness. Refers to the noise, vibration, and ride quality of the vehicle.
This article has presented a brief, if slightly difficult, overview of Skyactiv-Vehicle Architecture.
When Mazda’s new-generation vehicles are launched, be sure to take a test drive.
■ Video: Mazda Human-Centric Development SKYACTIV-VEHICLE ARCHITECTURE
■ Video: The Art of Human-Centricity