08-16-2017, 10:24 PM
physics working model on anti collision device
The Anti-Collision Device (ACD) is a self-acting microprocessor-based data communication device designed and developed by Konkan Railway.
When installed on locomotives (along with an auto-braking unit - ABU), guard vans, stations and level-crossing gates (both manned and unmanned), the network of ACD systems prevents high-speed collisions in mid-sections, station areas and at level-crossing gates.
The ACD uses both radio frequency and Global Positioning System (GPS) through satellites, whereby a train is automatically brought to a halt if the track ahead is not clear. The train starts braking 3 kms ahead of a blockade.
The ACD Network is a Train Collision prevention system invented by Rajaram Bojji and patented by Konkan Railway Corporation Limited (a public-sector undertaking of the Ministry of Railways, Government of India). ACDs have knowledge embedded intelligence. They take inputs from GPS satellite system for position updates and network among themselves for exchanging information using their data radio modems to take decisions for timely auto-application of brakes to prevent dangerous 'collisions', thus forming a 'Raksha Kavach' (meaning a '(Train) Safety shield').
ACDs fitted (both in locomotive and guard's van of a train) act as a watchdog in the dark as they constantly remain in lookout for other train bound ACDs, within the braking distance required for their relative speeds. They communicate through their radios and identify each other. If they happen to find themselves on the same track and coming closer to each other, they automatically restrain and stop each other, thereby preventing dangerous head-on and rear-end collisions.
Loco ACD of a train also applies brakes to reduce the train speed either to 15 km/h if on approach it receives a message from other train bound ACD that has stopped in a block section on adjacent track (and driver of that train has yet not communicated that things are 'Normal') or to bring the train to a stop if train bound ACDs of other train are radiating 'train parted' message thereby preventing dangerous side collision that may occur due to infringement of adjacent track by a stopped or a 'parted' train, respectively.
ACD trials have recently been concluded successfully in Southern Railway. Further implementation on Indian Railway is awaited.
ACD Deficiencies[edit]
The ACD system is based on GPS based positioning and track detection. This had its inherent problems as with the GPS- Standard Positioning GPS service or Coarse acquisition (Precision positioning is only available in US for military use) the best possible horizontal accuracy is 10 m. This is inadequate for detection of rail tracks separated by a distance of 10 15 feet. ACD does not even have DGPS (Differential GPS that gives an accuracy close to 2.5m ) and hence had errors in track detection using their patented Deviation Count Theory that worked in block sections but failed in station sections. The result was erratic braking that disrupted train movements and proved to be ineffective.[1]
Another design different to ACD was patented in 2001, named "Railway Collision Avoidance System" by an Indian inventor, Indranil Majumdar from Calcutta who was awarded the Texas Instruments Analog Design Challenge 2001 for this design and the patent granted in 2007.[2] The design ruled out GPS as it was a 3rd party system (US based) and suggested track based sensors similar to RFID (Radio Frequency Identification Device) or Balise (similar to the EuroBalise). The design didn't receive much attention as the inventor had no railway background. However, the design concepts were eventually reflected in the TCAS design first released in 2008.
After seven or eight years of problems with the ACD system, RDSO, Lucknow drafted the Train Collision Avoidance System (TCAS) specs. with amendments that followed and finally in 2012, the Ver3.1.1 spec. has been released (after joint consultation with companies manufacturing signaling equipment for the Indian Railways). The ACD system though in use with the Indian Railways, has its inherent problems in Station Sections due to its design concept of using GPS for track detection that is not viable.
The High Level Safety Review Committee at Mumbai on 12/13 January 2012 at the Western Railway HQ were sceptic of the ACD effectivity and were unanimous of having TCAS developed, as an open architecture system that shall offer multi-vendor operability without attracting any royalty unlike the ACD which is proprietary.[3]
TCAS being developed by qualified companies (RDSO approved and manufacturing railway safety systems that includes, Kernex Microsystems, Medha Servo Drives Hyderabad, Invensys Bangalore, Siemens, HBL Power Systems Ltd Hyderabad and others) in India selected by RDSO through an Expression of Interest (EOI), shall be an Indian Train Protection System offering collision avoidance and also offer many functionalities of the European Train Control System that includes prevention of Signal Passing at Danger (SPAD), Movement Authority and Control, Critical Train Data Recorder, advance in cab display of signals, advance alerts and warnings from Station sections, uploading of running train data to a Central Train Management System over GSM-GPRS or other cellular networks.
TCAS has been selected for implementation and it is going to cost very heavy to Govt as per this news report there would be a cost of 10 L INR per kilometre