Intelligent braking systems for public service escalators

Public service escalators are characterised by carrying large numbers of passengers and as acting as part of the main route within railways and terminal stations. High safety factors are used in sizing their braking system to prevent the risk of runaway situations. This presents the hazard of passenger falls or even avalanche passenger falls when spurious stops take place. It is estimated that 2.5% of all escalator stops lead to passenger falls. Closed loop feedback braking systems can control the value of acceleration and jerk as well as the stopping distance. This paper discusses the design, implementation and testing of an intelligent braking system on a public service escalator. It outlines the aspects of the hardware and software FMEA (failure modes and effects analysis), the use of appropriate feedback devices, control algorithms and braking system hardware. Results are discussed that illustrate the success of the system in reducing stopping variations caused by changes in load. The paper concludes by showing test results that correlate the stopping characteristics of an escalator with the probability of passenger falls. Based on those results it proposes the optimum stopping curve characteristics to minimise passenger falls and meet requirements laid down by standards.