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Smooth Driving, Like a Dolphin

The ancestors of the dolphin are said to have been dog or wolf-like animals measuring around 1.5 meters in length. They migrated from the land to the sea...

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2014/01/14

The ancestors of the dolphin are said to have been dog or wolf-like animals measuring around 1.5 meters in length. They migrated from the land to the sea at some point between 50 and 55 million years ago.

After this, every part of their bodies evolved to adapt them for life underwater. For example, the front paws evolved into fins, which could be used as brakes when swimming under the water and also to change the direction in which they were traveling. Their body hair also disappeared so they became streamlined, meaning the resistance from the water decreased and they could swim faster and more smoothly. The early dolphins also developed dorsal fins that then allowed them to swim steadily at high speeds.

To the eye, cars have not evolved in as big a way as dolphins. But internally, in the same way as dolphins have transformed themselves in order to be able to swim better, cars have also greatly evolved. Let’s look at Nissan’s new chassis control, which allows you to drive smoothly, intuitively, and comfortably.
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The fundamental capabilities of car are driving, turning and stopping. Nissan’s control technology offers drivers comfort and driving fun better than ever by making these three things as smooth as those of a living creature.
A car can change its direction and stop because its suspension, steering wheel and brakes are functioning. Together we call this the chassis. The chassis control we will look at is effective in three situations: braking, steering around a bend, and when passing over a poorly surfaced road.

Braking
Until now, it was the driver who adjusted the way he or she stepped on the brake pedal in order to stop smoothly in the target position. With the new chassis control system, by adding engine braking that corresponds to the driver’s braking, the effectiveness of the brake feels stronger and stopping becomes easier.

It’s also the same when decelerating as you go into a bend. Ordinarily for a driver, it is necessary here to adjust speed by stepping on the brake according to the size of the bend. With the new chassis system, though, the effect of the engine brake is adjusted based on how much the steering wheel is being turned and the speed of the vehicle. As a result, the amount and frequency of the driver having to brake is reduced and driving becomes more comfortable.


Going Around a Curve
Who hasn’t accelerated as you take a bend and enjoyed the feeling of the car going just where you want it to go? But actually, because of centrifugal force, at a bend the car will move to the outside, away from where intentioned.

By using various sensors, the car can detect when it is drifting to the outside of the curve and the brake will be automatically applied to the inner wheel. This is the same logic as for a rowing boat when you place just one oar in the water. You will create resistance and go in circles in that direction. In this way, the car will not pull to the outside and will travel along the trajectory you want.

The system works not only for when exiting a curve but for entering it too. If by mistake you drive into a bend at a high speed, the car body leans and both driver and passengers will feel alarmed. At such times, this system determines from the movement of the steering wheel and the speed that assistance is needed in controlling the vehicle. It then gently applies braking to each of the wheels, working to improve the steering. As a result, the drive is able to continue driving smoothly.

Skillful drivers, though, will not panic even if they take the curve with a little too much speed, and may not want the system to assist them and “meddle” with their driving. Based on the sensor data, the system can also distinguish differences in driver techniques and so it doesn’t engage when it detects support is not required.

Driving Over Uneven Surfaces
In a car suspension there are shock absorbers that will smooth any shaking from the top or bottom of the vehicle. If the shock absorbers are strong, there will be less shaking in the car body when the vehicle is passing over uneven road surfaces.

Nissan discovered something that wasn’t known until now, which is that if the brakes are applied, the shock absorbers are strengthened. From this it could develop technology that enhances the shock absorbers by braking if the system detects large bumps from changes in the number of times the wheels are turning, though the braking is not enough for the driver to notice.

The new system not only controls the brakes, but also the engine torque in order to smooth the shaking in the car. The electric Nissan LEAF also features motor control technology that implements engine control.

The technology controls the vehicle through extremely quick and minute adjustments of the engine torque. Torque increases when you step on the accelerator, and this causes the front of the vehicle to lift up. Taking your foot off the accelerator then decreases the torque, and the car will lower at the front. The system exploits this.

When it passes over a road with small bumps, the car will move up and down, but with the new system, this kind of pitching can always be determined from the speed of the wheels rotating. By very slightly increasing or decreasing the engine torque, the movement of the car can then be minimized.

The degree to which the engine torque is increased or decreased is extremely small, and the driver won’t feel anything strange. Due to this control technology, drivers have now become able to drive comfortably even over uneven roads.
Driving as Smoothly as a Dolphin
Actually, technology similar to this has existed for a long time. For example, many cars feature systems that curb the output of the engine or automatically apply the brake to one tire in order to stabilize the car.

We could say that this new chassis control technology is an evolved version of the previous control technology systems. However, there is one major difference: it doesn’t just work in extreme situations, but also helps when driving normally. It has evolved to help ensure safety and also now enhances the comfort of the driving experience.

In what has become known as Gray’s Paradox, the British zoologist Sir James Gray once speculated that for dolphins to be able swim at their speeds of around 50km/h, they should have seven times the muscle mass they actually have.

There are many theories as to why dolphins can swim so fast. One view has it that they are changing part of their body in order to reduce the friction from the water. In other words, they are becoming one with the current and controlling their bodies in order to swim faster. Even after they switched from living on land to the sea, dolphins are still evolving.

The new control system is also calculating what is going to happen from the sensors all over the car, and it then controls the engine and brakes so that the driver can have an experience that is fun and relaxing. It grasps the situation and surroundings, and controls the body functions in order to move more smoothly: just like a dolphin.