| 摘要 |
<p>1285557 Automatic speed control TRACKED HOVERCRAFT Ltd 8 Oct 1969 [18 July 1968] 34336/68 Heading G3R A speed control system for a vehicle propelled by a three-phase linear induction motor, includes means for generating a modified demand speed signal arranged to change at a limited rate. This signal is compared with an actual speed signal, and the resulting error signal is used to determine the firing angles of a thyristor regulator in the motor supply. In the system described, the vehicle is a tracked hovercraft having a speed control lever 18, Fig. 5. A demanded speed signal is fed on a line 38 to a saturable operational amplifier 39 followed by a limiter 40. The signal then passes through an integrator 41 which produces a modified demand speed signal which is fed back to the amplifier 39 input and also to a speed control circuit 35, shown in more detail in Fig. 2. In use, a rapid change in the demand signal on line 38 causes the amplifier 39 to saturate so that the integrator 41 integrates at a fixed rate resulting in uniform acceleration of the craft until the demanded speed is attained. Referring to Fig. 2, the modified demand signal is compared with an actual speed signal in a device 20, the resulting error signal being passed to an operational amplifier 23 and then to the firing circuit 24 of a thyristor regulator 25 arranged in the input to the linear motor 28. The thyristor firing angles are thus adjusted until the motor drives the vehicle at the required speed. If the error signal changes polarity, the output of amplifier 23 reverses and the thyristor gating pulses disappear. The motor current now decays, and when it reaches zero a logic circuit 30 receives a signal which, together with a polarity change signal from a comparator 32, causes a circuit 22 to reverse the polarity of the input to amplifier 23, and a circuit 26 to reverse two of the supply input phases. The motor 28 thus produces reverse thrust.</p> |
