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Design Overview
The aerospace industry has employed fly-by-wire concepts successful for many years, and AEVITŪ "drive-by-wire" systems have followed this idea closely since 1986. In "by-wire" systems, the direct mechanical control of a machine is replaced by an electronic one.For example, it means that the movements made by the driver with the steering Input Device (joystick, yoke, wheel, etc.), is not transmitted mechanically via the steering column, through to the steering rack, and then to the front wheels as in conventional control. Instead, the driver's physical movement on the steering Input Device , is sensed and converted into a digital electronic signal that is transmitted to intelligent Drive Modules that in turn command intelligent Electromechanical Servos to steer the front wheels. The same method of control is applied to the braking and acceleration of the vehicle.
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Reliance on Human Factors for Redundancy
This simple phrase is the key to understanding the safety concept of Primary Controls (steering and braking) in most conventional vehicles we have driven for decades. To understand this, let's discuss the conventional methods used.
Conventional steering controls have a steering shaft connected to a steering rack/box that in turn changes the steering angle of the front wheels. The steering system is hydraulic and/or electrically power assisted, which allows the driver to easily turn the wheels while driving. The hydraulic and/or electric power assist system is a "single point failure" , which means that in the event that this assist system fails, for whatever single reason, i.e. (hose, pump, belt, battery, cable, sensor, etc.), the driver is required to recognize the situation and provide the greatly increased physical strength necessary to overcome this large mechanical requirement. You can demonstrate this to yourself in your own vehicle in most cases, by attempting to turn your steering wheel without the engine running and/or the lectric assist motor disconnected.
Conventional Brake controls have a similar method of a mechanical pedal connected to a rod that actuates the hydraulic master brake cylinder. The brakes are also hydraulic, pneumatic, or electric power assisted to enable the driver to easily apply the brakes with their foot. However, like the steering, these assist systems are "single point failures". Safety standards dictate that a vehicle must have a diminished, but acceptable stopping distance if this situation occurs, but the driver must recognize the situation and provide the 120 lbs. of force necessary in this test. Safety standards also dictate that in the event of a single hydraulic failure (broken brake line), the vehicle must have a diminished, but acceptable stopping distance if this situation occurs, but the driver must recognize the situation and provide the additional pedal travel necessary to stop the vehicle. Total hydraulic failure requires the use of the mechanical park brake circuit to stop the vehicle. Have you ever tried to stop your vehicle without power assist or with a broken brake line?
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Safety Critical Design:.... AEVITŪ
AEVITŪ involves much more than merely replacing hydraulic and mechanical systems by an electric motor or making adaptations to the transmission, brakes and steering column. AEVITŪ is, and needs to be......... (a) Intelligent and (b) Redundant (multiple safety backups). Keep in mind that conventional controls require that the driver (a) Recognize (intelligence), and provide (b) heightened Physical skills (redundancy) in the event of single point failures. The average driver typically will not respond correctly in time when these conventional failures occur, due to the panic feeling associated with a "Stiff" feeling steering wheel or brake pedal, or a brake pedal that suddenly travels to the floor. Many drivers do not have the physical ability to turn the wheel or push the brake pedal in the absense of power assist. AEVITŪ had to address these "human factors" for it to be the safety critical design alternative that it is.
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 | | | Click for typical AEVITŪ Cockpit | | | |
For instance, the AEVITŪ electromechanical brake, steering, and acceleration controls provide information about the force exerted, travel distance, and so on. With AEVITŪ, you are connected to these Primary Controls (braking/accelerating, steering) by-wire, and cannot "physically sense" failures of these systems. Therefore, AEVITŪ has to sense and respond automatically in milliseconds, with multiple backup safety routines.
Another key is that all the AEVITŪ control systems, whether for the brakes, acceleration or steering, remain linked to the relevant original vehicle stability management, antilock brake controllers, and the engine's ECU functions. In other words, AEVITŪ is passive to the original vehicles sub-systems, and does not alter the original intent of these systems. As the technology of these OEM subsystems change, AEVITŪ interface to these subsystems will also change.
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 | | Click for typical AEVITŪ Cockpit | | |
When you sit in the driver's seat, you always have to adapt the position of your arms and legs to the car's basic controls, pedals, and steering wheel. AEVITŪ drive-by-wire technology, has made it possible to radically rethink the man-car interface and the car's interior architecture. No more pedals or steering wheel, because now the steering, accelerator, brakes, and transmission are all controlled by- wire. And inside, <AEVITŪ equipped cars have created living space unhampered by the usual restrictions to freedom of position and movement. Thanks to this technology, auto designers have been able to redefine the interior environment and radically rethink how drivers interact with their car and the external environment. The absence of a steering column not only is viewed as considerably safer in the event of an accident, but also creates a constraint-free instrument panel that has an uncomplicated, clean and relaxing look.
Those parts of the AEVITŪ control system that interface with people, cannot merely be switches. All Input Devices (ID's) incorporated in the control system, must ensure drivers have the sensation of what is happening, and the virtual feeling of car driving has to be retained. The Input Devices integrate the accelerator, braking and steering functions as manual joystick, lever, miniature wheel, or yoke controls. The center console or dash sections host all the other Secondary Controls required by the driver. Buttons used to change gears, lights, windscreen wipers, audio equipment, heating and air-conditioning are within easy reach of the driver's hands, or can be voice activated with VIC.
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