Dependability of machine system - usable characteristics

The subject of this paper deals with dependability of machine systems base on selected usable characteristics. In the subsystem man-machine and environment, determined tasks are carried out. The sequence of activity is following: man handles machine, which in turn makes the environment deliver desired reaction, e.g. processing or transportation. A machine and desired reaction of environment will recognize the positive effect of above activities as carrying out of set task. It is also of utmost importance that the man and machine's impact on environment is efficient and harmless. Therefore the selection of an adequate machine and its operator to carry out the given task is crucial. The circumstances considered as undesired for task implementation are identified as hazard to man and machine. Within the endangered man - machine and environment subsystem, we can distinguish following phases in the machine degradation process: worthy, partially worthy, partially unworthy, critically unworthy and totally unworthy. The selection of adequate means towards achieving set goals is considered important, and, subsequently, the description of selected machine and human (as operator and decision maker) attributes has been undertaken. The basic attributes of man and machine complex are: adequacy, dependability, safety, durability and effectiveness. Adequacy, described as common machine property, turns out to be a collection of four attributes: functionality, configurability, coverage, and programmability. Reliability, on closer inspection, as a combined property of man -machine complex, is described by four attributes: reliability, redundancy, faultlessness and availability. Safety, as a man - machine - environment property is described by a collection of five attributes: protectionability, hazardousness, harmlessness, safeguardability and deleteriousness. Durability as a machine property can be described by five attributes: strength, refractoriness, maintainability, supportability and serviceability. Effectiveness as a man - machine system property is described by four attributes: efficiency, capability, economically and managementability. It is acceptable to assume that the attributes mentioned above can be of use when selecting machines for outdoor exploitation and facilitating of selected tasks. Particular significance is in the relations between basic attributes of the man - machine - environment subsystem, namely: dependability is the starting point for safety and effectiveness, durability assures dependability, safety and effectiveness, adequacy guarantees a successful outcome of all named attributes of man - machine system.