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Supervised Operator Systems (SOS)
Most commonly used on elevating work platforms, the SOS is a special-purpose remote control system that allows a Supervisor to take control of a machine if the Operator is injured or disabled, or his controller is damaged. Furthermore, the Supervisor always has a fail-safe STOP control available at all times in case he sees a hazard that the operator does not.
Working  on  live  overhead  power  lines  requires the use of HV insulated booms on EWPs. Typically, the boom itself contains a fibreglass section separating the boom from the chassis. Controlling the machine from the basket presents some difficulties, because it is not possible to run any electrical  cables  from  the  base  to  the  basket, as this would compromise the insulation. In the past, the most common way to build the basket control system was with pilot hydraulics – i.e. levers in the basket would control a low-pressure hydraulic  system,  requiring  expensive  maintenance  and  providing  very  limited  safety  performance. Due to the potential hazards of working on  live  power  lines,  in  most cases the  operators of these EWPs require the presence of a safety observer. The observer’s role is to render assistance should the operator in the basket be injured, trapped, or otherwise incapable, and to be aware of hazards that may not be seen by the operator. While the EWP may be fitted with manual controls on the deck of the truck, these are inaccessible in the event of a common emergency – a fallen power line. In this case, the observer cannot approach the truck due to the danger of electric shock. What is needed in this case, is for the observer to have a secondary means of control.
The Problem
Autec designed a solution allowing the EWP to safely operate in these conditions. The Autec SOS solution comprises: - An Operator transmitter used by the operator in the basket - A Supervisor  transmitter used by the supervisor on the ground - A special-purpose receiver capable of communicating with both transmitters simultaneously. How it works: - The Supervisor transmitter must always be turned ON, started and in-range in order to use the EWP - When the Operator is to control the machine normally the switch on the Supervisor transmitter is in the “Observe” position. The basket operator starts his transmitter, and drives the machine normally. - When in “Observe” mode, the controls on the Supervisor transmitter are ignored – with the exception of the STOP which is always active. In the event of an emergency, either the Operator in the basket, or the Supervisor on the ground can stop the system. - If the machine is unable to be controlled from the basket because of an injury to the operator, a fault, or any other reason, the Supervisor on the ground can switch from “Observe” to “Take Control”. This activates all of the controls on that transmitter and allows him to drive the machine to a safe place. Note that this disables all of the basket operator’s controls, including the STOP. Valve Spool Monitoring The receiver is optionally available with feedback inputs that allow it to monitor hydraulic spools for correct operation. The system suits valve types that indicate only out-of-neutral condition, as well as those that report direction of movement. In the latter case, the receiver can monitor for wrong-direction faults as well as unexpected-motion faults. Technical: The Autec B/O system is based on a TÜV Functional Safety certified architecture whose main features are: - Redundant architecture on both Transmitter and Receiver sub-systems - STOP function compliant with PL e/Cat. 4 (ISO 13849-1) and SIL 3 (IEC 62061) - UMFS (Unintended Movement From Standstill) function compliant with PL d/Cat. 3 (ISO 13849-1) and SIL 2 (IEC 62061) - Radio communication protected against errors with Hamming Distance>15 and     Probability of Undetected Errors below 10-15 (Integrity Level 3 - IEC 60870-5) - Extensive Environmental, EMC, Automotive, Mechanical testing - Production process includes functional testing inside climatic chambers for 100% of the boards. Available with the FJR and FJM series transmitters
The solution