The control electronics used in WAP5 and WAG9 is called MICAS-S2 — Micro Computer Automation System Series 2 — a process-oriented, distributed control system optimised for electric traction vehicles. It comprises devices for signal input/output, signal processing, and communication systems exchanging data between bus stations (control units), plus a man-machine interface and aids for planning/commissioning/maintenance. MICAS-S2 is mainly used on locomotives, multiple-unit trains, tramways, and trolley buses; thanks to its modularity it adapts to varied requirements.
Real 3-Level Hierarchical Architecture
| Real Level | Real Function |
|---|---|
| Train control level | Coordinates/controls several similar traction vehicles (multiple traction), interfaces to brake systems etc. Converts driver's commands (e.g. set speed) into commands for individual vehicles, passed to the vehicle control level. |
| Vehicle control level | Responsible for ALL vehicle functions — converts commands from both train-control level and the driver into actions (contactor control, EP valves etc.), gives feedback on important events/operating states. Automatically reacts to events during operation so the driver can concentrate on observing track/signals. |
| Drive control level | Receives the set tractive-effort value from vehicle control level and controls the power converters so motors deliver the required torque. |
Real System Characteristics
- Internationally standardised data transfer per IEC TC9 WG22 (Train Communication Network, MICAS Vehicle Bus, Train Bus). Data between up to 62 vehicles can be exchanged via the Train Bus, controlling one or several traction vehicles (multiple traction commuter train); it flexibly adapts to train-configuration changes, and mixed trains with vehicles lacking a Train Bus interface are possible.
- MICAS Vehicle Bus is optimised for real-time process-value transfer via cyclic broadcast, with real cycle times possible between 1ms and 1024ms; up to 127 devices can connect to one bus, with high noise immunity from fibre-optic cable linking. The Parallel bus (AMS-Bus) controls input/output devices in subracks.
- Drive control electronics dynamically controls asynchronous motors via stator-flux-oriented torque control (direct and indirect self-control), giving maximum adhesion utilisation, optimum comfort, and minimum wear — with universal application from heavy goods trains to fast passenger trains.
- Other real characteristics: self-diagnosis of all devices with centralised processing (fault-tolerance degree widely adaptable to availability/safety needs); simple configuration/programming via the 'Mic Tools' software package; uniform software/data-transfer interface; MICAS Vehicle Bus access for commissioning/maintenance; third-party electronic-module integration into a MICAS-S2 installation; extensive electromagnetic-interference protection.
Real Programming & Diagnosis Concept
Software for MICAS-S2 splits into 3 real groups: (1) operating-system firmware, independent of application; (2) user programs for project-specific control tasks (control, diagnosis, visualisation) — written in FUPLA (Function Block Language), a graphic-symbol-based programming tool that keeps process-automation programs simple to write, test, and document; (3) Mic Tools — programs for planning installations, writing project-specific software, testing, commissioning, and maintenance.
As part of the distributed control system, MICAS-S2 diagnosis has a decentralised structure: diagnostic messages produced by process computers transmit to the diagnostic computer, which runs an expert system evaluating/storing incoming messages. Special FUPLA function blocks produce diagnostic messages — programmers define which disturbances trigger a message. The expert system's reaction to a message is programmed via ADL (Action Diagnostic Language), which can weigh earlier messages or current operating states to reach an appropriate conclusion — possibly resulting in a message to the driver. The diagnostic computer passes the message to the Visualisation Controller (Vico), which transmits it to the alphanumeric display in the driver's cab. Because the diagnostic computer is NOT involved in process control, the system can run without it, and — since it has no influence on vehicle-safety-critical functions — redundancy isn't required for it.
Real Mechanical Design
Control-electronics modules use the 6U double-height Eurocard format (6U = 233.35 × 220mm). Subracks are configured/manufactured/wired in different widths per project need, holding one or several processors, input/output boards, bus couplers, and one or more power supplies; they're usually integrated into shielded cases for EMI protection. Process signals connect via front connectors — almost exclusively common DB9, DB15, and DB25 type connectors per DIN 41652.
Real Worked Example — Pantograph Control on WAP5/WAG9
The vehicle control scheme in WAP5/WAG9 integrates MICAS-S2 software with conventional hardware (relays, auxiliary contactors etc.). Detailed schematics are in real ABB drawing No. 3EHP 281105 (hardware); the software specification is in real ABB document No. 3EHP 541681. Control software logic is organised as 'function groups', each comprising FUPLA-written functional segments; the pantograph-control circuit (real ABB doc 3EHP541891, 'Design FG 31 — Pantograph Control') is used as the worked example of how hardware and software integrate.
- Rotary pantograph-selection switch has 3 real positions: 'I' (pantograph above Cab1 selected), 'AUTO' (pantograph above the inactive cab auto-selected — MCE only controls selection in this position; in 'I'/'II' the selected pan is independent of MCE), 'II' (pantograph above Cab2 selected). The spring-loaded raise/lower switch itself has 3 positions: 'UP' (raise, spring-loaded), 'O' (neutral), 'DN' (lower, spring-loaded).
- Each pantograph pan is monitored by a real pressure switch. With VCB open: after the driver's raise command, if pan air pressure isn't OK within 20 seconds, a fault message displays and VCB stays disabled. With VCB closed: on low pressure at a raised pan, after a 2-second delay VCB opens and a priority-1 fault message displays — this delay is settable during commissioning.
- The pan can never be lowered automatically just because catenary voltage exceeds the upper line-voltage limit — the driver must always be able to lower the pan in any situation without risk of loco damage, and can raise it at any speed (except in a neutral section). The MCE can override a driver's 'pan up' command with 'pan down' only via specific de-energising paths: key switch in 'O', emergency stop pushbutton, or fatal mode of MCE (loco dead).