Active safety
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In engineering, active safety systems are systems which can be activated in response to a safety problem or abnormal event. Such systems could be activated either by a human operator, automatically by a computer driven system, or even mechanically. In nuclear engineering, active safety contrasts to passive safety in that it relies on operator or computer automated intervention, whereas passive safety systems rely on the laws of nature to make the reactor respond to dangerous events in a favourable manner.
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[edit] Examples
- The computer operated control rods in a nuclear power station provide an active safety system, whereas a fuel which produces less heat at abnormally high temperatures constitutes a passive safety feature.
- The seat belts of a modern car are attached to a mechanical device which prevents the seatbelt from being rapidly extended in the case of a collision.
- Many buildings have interconnected fire alarms that can be triggered manually by pushing a button or breaking a glass plate attached to sensors.
[edit] Automotive Sector: Blurred defintions
In the automotive sector the term 'active safety' has traditionally referred to systems that help prevent accidents. For example, good visibility from the vehicle can be considered a component of active safety (the term Primary Safety is also used). This compares with passive safety (or Secondary Safety), which include features that may help mitigate the severity of accidents. However, a new generation of safety features that operate automatically, in response to sensor signals that give an understanding of the vehicle's state, are also being referred to as active safety systems. These systems, such as ABS, ESC, brake assist, traction control, VSC, VDIM and seat belt pre-tensioning are active in the sense that they invoke an action in order to improve safety. The confusion comes because this can include systems such as seat belt pre-tensioning which would be considered active because they take action in an accident, even though their role in mitigating the accident's effect would have traditionally seen them classed as passive safety systems. Here, a useful separation may be achieved by considering those systems and design elements that are relevent up to the moment of impact contribute to the 'active safety', and those which are called upon and affect the system performance from the moment of impact contribute to the 'passive safety'.
[edit] Active Safety Features in Automobiles, some examples:
Contributors to active safety of a motor vehicle, accident avoidance:- good visibility from driver's seat, low noise level in interior, legibilty of instrumentation and warning symbols, head up displays, good chassis balance and handling, good grip, ABS braking, ESP Chassis assist, all wheel drive, secure luggage and passengers (cannot interfere with vehicle or driver) etc.
[edit] Passive Safety Features in Automobiles, some examples:
Contributors to passive safety of a motor vehicle, accident limitation, minimisation of outcome:- Passenger safety cell, deformation zones, seat belts, loadspace barrier-nets, air-bags, laminated glass, correctly positioned fuel tanks, fuel pump kill switches etc.
