Tham khảo tài liệu 'anatomy of a robot part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 126 CHAPTER FOUR N components are necessary for the successful operation of the system the designers add one more system hence the terminology N 1. If one of the N components fails the spare component will take up the slack and the overall system will keep running. If however a second component fails before the broken one is repaired then the system fails. The calculations for MTTF and availability are somewhat complex in a case such as this. For further information see the following sites categories engineering manufacturing html home home Done properly availability goes up quite high but at the price of a single extra component. Repair is basically instantaneous except for the case where two or more components fail at the same time. It s therefore wise to make the repair to broken units as rapidly as possible. This too increases the availability. COMPONENTS Another way to increase the MTTF of a system is to avoid unreliable components. The Bellcore component tables list the failure rates of many different types of components. Without the tables in front of me I ll list the components I remember as having high failure rates. These are components we should avoid in the design and construction of the robot. Connectors Connectors of all sorts are lower-reliability parts. Every single pin on every connector must be counted. Connectors generally work by spring pressure. A bent piece of metal pushes on another piece of metal and thus excludes gas and dirt. Often a wiping action is made as the connection is made. The following problems can make connectors fail. Contaminants If we have too many contaminants or gases are not excluded corrosion can creep into the connection and ruin it. Currents In addition if high currents move over the contacts they can corrode from too much heat. Vibration Movement can cause contacts to break open interrupting signals. Operator error Service
