A somewhat unconventional idea, which is particularly close to my heart, because it has the potential to save lives and health.
And it should be easier to implement technically and legally as driver assistance systems of (semi-) autonomous vehicles, because with the wheel brake, the driver remains the agent in charge.
English version: 06/29/2015, German version: 04/16/2014
Novel way of actuation of the service brake for cars, trucks, etc., which should lead to a reduction in the overall stopping distance with emergency braking
It is supposed to avoid accidents or mitigate the severity of the accident.
Service braking via the "Wheel Brake" is also possible.
In an emergency stop you lose valuable time by taking the foot from the accelerator and put it on the brake pedal, which leads to an unnecessarily long stopping distance.
In addition, there is a danger that the driver in the hustle and bustle of an emergency (shock) catches their foot behind the brake pedal and so there is no braking at all.
The steering wheel gets a new function: by applying force with one or both hands on the steering wheel rim you can always slow down the car without any delay, as long as at least one hand grasps the steering wheel rim.
This feature provides an additional braking option, ie the brake pedal and everything else that goes with it, will remain as it is!
For detection of pressure forces on the steering wheel rim mechanical, hydraulic or pneumatic methods are imaginable.
The method described here provides for the use of piezoelectric films, as they were used in space (ESA) to measure the forces at work on the wings of the space shuttle Hermes or for crash tests (Volkswagen) for recording the transactions on impact eg.
This method provides the most benefits, because as you can see from the examples mentioned, piezoelectric films are highly resistant. In addition, they are very thin, pliable and also very temperature-resistant and non-aging.
They produce a small electrical voltage analogous to mechanical pressure exerted on it, which can be amplified, processed, and used for controlling actuators. Such actuators already exist. They are used in disabled rebuilt vehicles which are equipped with electronic brake pedals and / or electronic brake rings (before or behind the wheel). The company "Continental" offers "brake by wire" systems.
To implement this new braking method and to integrate it in an actual vehicle, here are some detailed considerations that still need to be supplemented and specified during the planning,
calculation, implementation and testing phase:
The piezoelectric films should be applied around the steering wheel rim (below or within the foam casing) in the form of individual segments in the dimension of a few square centimeters, and in such a way that on the driver-facing side and on the rear side of the steering wheel rim separated from one another and independently queryable sensors are attached.
The signal processing control logic should launch a brake only when the threshold values of the front and the rear sensors both are exceeded. This is to ensure that if the driver supports (or pulls) themselves against with one hand (or both hands), for example, to change the seating position, it does not come to an unwanted braking. Only when pressure is applied to opposing sensors, that is, when a squeezing of the steering wheel rim is applied, the values measured by the sensors are included in the calculation of the desired braking force.
Further, it should be determined whether individual thresholds (below which there should be no braking) are required for different drivers, or if a general threshold value can be specified for all drivers.
The same applies to the maximum pressure value, which then should correspond to the maximum braking force.
Also, a characteristic curve needs to be defined that specifies the resulting brake force, for the event that the driver additionally stepped on the brake pedal during the braking via the steering wheel.
When a steering wheel braking is in progress a gas shut-off must take place, because it could happen that the driver (because of the shock situation) keeps their foot on the accelerator.
A new acceleration may then only be possible after the accelerator pedal has reached the zero position.
Signal submission from the steering wheel sensors to the control unit must be designed with redundancy, for example, by two collector ring contact sets that are independent from each other. Or one collector ring contact set plus an alternate submission mode. Both ways must constantly be checked by the control device for proper operation and any failure must be displayed without the chance to be acknowledged by the driver (in that case the system has to be checked / repaired by a professional car service station).