Patent GB-1401651-A (GB)
Title: Vehicle control system
IPC: B61L23/00
Filed: 1972-06-12
Abstract: 1401651 Vehicle control system GENERAL SIGNAL CORP 12 June 1972 [14 June 1971] 27248/72 Heading B7N In a control system for vehicles moving on a predetermined path, e.g. hovercraft confined to a fixed track, the track is divided into blocks by loop conductors 20 carrying speed limit and speed command signals for the vehicles and by markers 23 responsive to a lead magnet 28 on a vehicle V 1  as it enters a block and to a rear magnet 28<SP>1</SP> as it leaves the preceding block. With the vehicle in block C, marker 23 has actuated occupancy detector 24 which provides an output to the speed selection units 25 of the preceding four blocks. In addition the detector 24 provides an output to OR gates 26 in its own block C and in the block D in advance which provides outputs to gate amplifiers 27 supplying speed control signals from the respective speed selection units to the loops defining the blocks. Two speed control signals are provided in each block-a speed limit signal (AVP) and a speed command signal (AVO), the former being determined by the braking capacity of the emergency brake system of the vehicle which when applied brings the vehicle to a stop before it can enter an occupied block and the second being determined by the normal vehicle braking system. The speed limit signals are signals at frequency F1 (low), F2 (medium) and F1 and F2 (high) and the speed command signals are F2+F3 (low), F1+F2 (medium) and F1+F2+ F3 (high). The speed signals are picked up by antenna 40 on the vehicle and applied to modulation detector 43 which provides the speed limit and command signals to speed control 44 which governs the running speed of the vehicle. The limit signal and an output from tachometer 47 indicating actual speed is applied to an overspeed unit 45 which holds off emergency braking if the actual speed does not exceed the limit. In view of the importance of the comparison between actual speed and speed limit, two comparators are provided one performing the comparison whilst the other is under test. Operation of the emergency braking can be held off by brake assurance unit accelerometer 48 when speed is above the limit but is being correctly reduced by the normal braking system of the vehicle. When the vehicle has stopped at a station as signalled by motion detector 45 and has been de-levitated as signalled by unit 53, a berth tone generator emits a signal via loop 55 which when received in a berthing pick up loop causes the generation of a signal at a doors open frequency which is picked up by antenna 40 and after demodulation operates the door control 46. At certain stations magnetic identification readers are provided for reading the vehicle identification 70. This information is signalled to a central control which provides route information to the vehicle through the vehicle berthing loop and this is picked up on the vehicle by antenna 40 and applied via the demodulator 43 to route selector 72 which feeds this route informat on to shift register 74. As the vehicle approaches a track switch the last digit of the route information is transmitted by unit magnet 75 to sensor 75A and the switch is set accordingly. On passing the switch read contact 76 picks up a signal from apparatus 76A on the track which moves the register one position so that the condition of the second digit can be read in advance of the next track switch. Information on malfunctions on the vehicle, vehicle identity, &c., are transmitted to the wayside by a communication system including transceiver 81. The polarity of the magnets carried by the vehicle for co-operation with the markers 23, which are bi-stable switches, is arranged N-S on the lead magnet and S-N on the rear magnet so that the marker switches to a second state when passed by the first magnet and back to a first state when passed by the second. The occupancy of a block is cleared when a vehicle completely enters the next block ahead thereof or when the vehicle has completely entered the next block ahead and its front with the leading magnet has also entered the block in advance of the next block.