Robustness through redundancy
To ensure robustness, multiple ways to maintain performance, specifically ways to maintain performance during stress or non standard conditions is important. In essence the design needs to ensure the ability to withstand force, to have a toughness built into the system.
While there are multiple ways to improve robustness a common solution is to achieve it through redundancy of control mechanisms and components. The benefit proper redundancies have over simply a tougher or stronger solution is that it can withstand a greater variety of issues, if implemented correctly.
As a simple example we'll take a look at the braking system of a bike as an example to see what "good looks like"...
Key design choices affecting redundancy are:
A possible weakness in this design is that all three systems depend on tyre friction to stop the bike. Note that a helmet that protects the riders head is not a redundancy, although great for resilience and allowing the rider to recover from an event such measures should be considered a complement to redundancy.
Most systems are vastly more complex and may need to support interaction of multiple persons at the same time and have a much higher number of system dependencies. The greater the complexity the more important that proper redundancy thinking is applied to avoid a fragile system.
From a design perspective it is also important that there are events when redundancy become less meaningful. If your system is solving a convenience problem it might not make sense to have redundancy for losing electricity since several life supporting systems will have priority until power returns.
While there are multiple ways to improve robustness a common solution is to achieve it through redundancy of control mechanisms and components. The benefit proper redundancies have over simply a tougher or stronger solution is that it can withstand a greater variety of issues, if implemented correctly.
As a simple example we'll take a look at the braking system of a bike as an example to see what "good looks like"...
The quick summary of the brake systems available here are:
- Rear wheel brake, via the pedals
- Rear wheel brake, via handle brake
- Front wheel brake, via handle brake
Key design choices affecting redundancy are:
- Variation of components used: Pedals and chain are complemented by handles and wires lowering risk of a total failure to all of the sub systems.
- Flexibility of operation: Hands and/or feet can be used offering great flexibility for the rider in case of injury to a specific limb.
- Few single points of failure by having low dependency between sub systems.
A possible weakness in this design is that all three systems depend on tyre friction to stop the bike. Note that a helmet that protects the riders head is not a redundancy, although great for resilience and allowing the rider to recover from an event such measures should be considered a complement to redundancy.
Most systems are vastly more complex and may need to support interaction of multiple persons at the same time and have a much higher number of system dependencies. The greater the complexity the more important that proper redundancy thinking is applied to avoid a fragile system.
From a design perspective it is also important that there are events when redundancy become less meaningful. If your system is solving a convenience problem it might not make sense to have redundancy for losing electricity since several life supporting systems will have priority until power returns.
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