Condition-based, auto-thresholded elevator maintenance

A method of determining when one or more specific maintenance recommendation message, each relating to a specific corresponding parameter of an elevator, should be generated, said method comprising:

• (a) monitoring conditions and/or events related to said parameter to determine any such conditions or events which are deemed notable with respect to elevator maintenance, and generating defect indications in response thereto;
• (b) in each of a series of sequential algorithm periods
• (i) recording the number of said defect indications generated;
• (ii) recording the number of operations of an elevator element related to said parameter;
• (iii) providing a defect rate indication as a ratio of the number of said defect indications to the related number of said operations for an algorithm period;
• (c) periodically generating an average defect rate indication from said number of defect indications and said number of operations recorded during a plurality of said periods including one or more periods prior to said each period;
• (d) in said each algorithm period
• (iv) generating a deviation indication in response to said average defect rate indication and said related number of operations;
• (v) generating an upper threshold indication in response to said average defect rate indication and said deviation indication;
• and
• (vi) selectively generating a maintenance flag indication, denoting that a maintenance recommendation message relating to said parameter should be generated, in response to at least one of (1) the number of said defect indications recorded in at least one of said periods exceeding the corresponding one of said upper threshold indications generated in said at least one period, and (2) said step (c) resulting in an upward adjustment of said average defect rate.