What is the performance that appeals to human dynamic sensibilities?What is the direction of setting the goal?

It may be boring for science people, but I will continue to orient a little more.For example, if you think about the exercise of traveling 600km on the Shinkansen in 2 hours, I think that the outline of dynamic Kansei engineering becomes clearer.

In this case, only the simple numbers "600km" and "2 hours" are shown, but when you connect them with the word "move", you instantly divide them to "300km / h". You will imagine the movement.In other words, we are deriving a new concept of "velocity" by comparing two physical quantities.As a result, you will be able to compare speed with other vehicles.This example is too routine to be realized, but I remember that finding new relationships between various physical quantities is very important for both general physics and our Kansei engineering. Put it down please.
So, let's go further with that work.The speed of 300km / h in this case is just an average speed, not a passenger's feeling.

The actual Shinkansen does not always run at 300km / h, but its speed changes over time, such as acceleration from the time of departure and deceleration when the vehicle is stopped.Therefore, in order to investigate the movement of the Shinkansen from the perspective of dynamic Kansei engineering, it seems necessary to get closer, expand the squares of time, and observe the details of the changes.The purpose is to discover "the degree to which the speed changes with time".So what should we do to do that?Divide by "time" again.That is a new physical quantity called "acceleration".The unit may be "km / h / h", but in order to see more detailed changes, it is usually calculated in seconds and "m / s".²It is written as.
Looking at the actual performance curve here, the speed rises in a gentle curve, maintains the maximum speed, and then descends in a staircase pattern.How does the change in velocity, that is, the magnitude of acceleration, change in this case?It doesn't have to be an exact number, so imagine what kind of curve it will be.And think about how it affects the dynamic sensibilities of the passengers.Then, try drawing the ideal acceleration curve for the Shinkansen.What happens?
Of course, Shinkansen drivers are not in a position to "enjoy driving."Safe transportation of passengers is our greatest mission, and passengers will not expect to feel acceleration.Therefore, this is just a dynamic sensibility for the Shinkansen, and our position of "enjoying driving" should be a very different conclusion.But the basic idea is the same.Here is the entrance to dynamic Kansei engineering.


Changes in exercise over time

In the previous lecture, I mentioned that dynamic sensibility can be defined as "how to feel movement", but it seems that it is necessary to think more strictly when it comes to this point.
For example, when considering the roll when turning, the size of the roll angle at the cornering limit alone is not enough to examine the dynamic sensitivity.When rotating a steady circle at a constant speed, the roll is constant, so a certain balance is maintained, and it is emotionally stable regardless of the size of the roll angle.Rather, the problem is the angular velocity and acceleration to get there.In other words, the object of dynamic sensibility is not just "movement", but "change in movement" over time.

And, in my sense, human sensibilities even more delicately feel the "change" of "change."For example, jerk (the change in acceleration is calculated by dividing the acceleration by time).This is a bit confusing, but it shows how the "degree of change in velocity (acceleration)" changes with time.
For example, when an airplane takes off, it gradually increases the engine output and starts gliding.Then, instead of a constant acceleration, you will feel your body pressed harder against the seat until you reach a higher acceleration and takeoff speed.In other words, you are feeling the change in acceleration (jerk).Therefore, it may be better to modify the definition of dynamic sensibility a little and go as far as "how to feel the change in movement".
I think that our dynamic sensibilities are shaken not only by physical quantities but also by their changes and processes of change.


Meaning of further "differentiating" changes

To summarize the above, the driver's dynamic sensibility may be evaluated by feeling the change in movement.Therefore, how the change changes with time and input ... Further differentiation is required.Differentiation here is simply division.To explain a little technically, the vertical axis is a physical quantity, and the horizontal axis is, for example, the slope of the tangent line at the time of the graph line of the non-stationary change amount when time is taken.Now you can see the "change in movement".Then, if you plot this change on the vertical axis, take time on the horizontal axis, and differentiate it again, it may be a little difficult to attach, but now you can see the "change in change".To give an example, the degree of slope of the tangent line (differentiated value) at a certain time when the velocity is taken on the vertical axis as shown in the figure below is the acceleration.Jerk is the result of further differentiating the acceleration over time.Compared to the velocity (distance / time) graph, you can see that the process of motion change becomes clearer with each derivative.

Similarly, you can differentiate rotational motions such as rolls and yaws.The point is to magnify the changes in movement like slow motion and identify the factors that affect human sensibilities.This is because "performance that appeals to human dynamic sensibilities" lurks there.


Driver acceptance and expectations for change

A car is an object that constantly moves by repeatedly accelerating and decelerating and steering.Therefore, it is always accompanied by dynamic changes.Even if you are cruising on the highway at 100km / h, there are stimuli to dynamic sensibilities such as changes in behavior due to external factors such as unevenness of the road surface and the influence of crosswinds, and the feeling of vehicle speed felt from the entire vehicle. Exists.

However, in terms of driver acceptability to such dynamic changes, drivers will often be able to to some extent naturally accept it.However, when dynamic changes occur suddenly and greatly, human beings are also sensitive to danger as living things, so they feel scared.It can be said that its acceptability has an inevitable limit.It is basically the same for changes in behavior that correspond to driving operations, not changes due to disturbance.
For drivers who want to enjoy driving, it can be said that there is a positive expectation for the movement of the car for their driving operation. We have defined the car as an enlargement function of the body.It may be said that modern cars have advanced development technology, and most cars meet the expectations of drivers to some extent.However, as soon as we set the goal of "enjoying driving more actively," the acceptance and expectations of dynamic sensibilities will go a long way.
Therefore, in the development of sports cars, changes in the behavior of cars that exceed general acceptance are, of course, limited, but they are required at a higher level.Ideally, the reaction on the car side should match the driver's expectations.Which level is the sweet spot for the supposed driver?Goal setting in dynamic Kansei engineering is the key to finding the correct answer.I think it is a synonym for pursuing "Jinba Ittai".


The idea of ​​"optimization of transient characteristics"

I think that the absolute performance in steady driving probably does not make much sense for dynamic Kansei engineering.The problem is the process of change that appears in the behavior of the car as a result of the driver's accelerator, brake and steering maneuvers.Especially, the timing of the change is important.The connection is called "transient characteristics".If this is not properly seasoned, I think that you will not be able to enjoy the satisfaction of dynamic sensibilities such as driving fun and happiness.
In a certain area, the degree of change is constant, and the so-called "linear characteristics" are required.Then, when the driver aims for some change, he / she realizes the expected dynamic change at an exquisite timing, without a sudden feeling, so as to be close to the driving operation.Furthermore, it smoothly returns to an appropriate stable state ...Without such a series of connections, it cannot be said to be a sufficient characteristic for dynamic sensibility.I think that the so-called "safety", that is, the fusion of maneuverability and stability, is the sum of such transient characteristics.
We have already talked about acceptability and expected value, but if we explain it in an easy-to-understand event, it is so-called initial responsiveness.If it's too dull, you'll get bored, and if it's too sharp, you'll be over-acceptable and even scared.It means that the transient characteristics are not optimized.Since this is an area of ​​evaluation based on human sensibilities, I think it is difficult to convert it into data and simulate it in terms of automobile engineering.Dynamic Kansei Engineering is to evaluate this based on the sensibilities of actual driving and to improve its technical skills, and I believe that it is the goal of tuning.
Needless to say, the behavior of a car is not determined solely by the performance of a single part.Rather, it generally depends on the basic packaging and the combined work of many components.Even if the design of individual parts is scrutinized, the ideal dynamic sensitivity performance cannot be achieved.The goal of dynamic Kansei engineering is to analyze the process of change in various driving situations, elucidate the factors, and adjust the connection of a series of changes, that is, the transient characteristics according to the driver's sensitivity. ..

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By now, you should have an overview of the idea of ​​"dynamic Kansei engineering".From the next time, I will talk about the main physical quantities that affect the dynamic sensibility and the related mechanisms individually and concretely.It's a difficult world of theory, but it's worth knowing, so please do your best to get along.

We also want our readers to ride in as many different situations as possible in a large number of cars that are said to have good performance.Then, the experience value such as "This characteristic of this car was good. The stability performance of that car is excellent." Is taken into the brain as a memory.Efforts to improve one's driving skills are also essential.This is because it is necessary to increase the "acceptability and expected value" of the driver in order to correctly evaluate the dynamic sensitivity performance of the car.I believe that the collaboration of theory and practice is the best guide for your tuning.