Patent GB-1263878-A (GB)
Title: Automatic steering systems
Inventor: KAWADA SHIN-ICHI
IPC: G05D1/02
Filed: 1970-02-04
Abstract: 1,263,878. Automatic steering system for ships. TOKYO KEIKI K.K. Feb.4, 1970 [Feb.8, 1969(2)], No.5291/70. Heading G3R. An automatic steering system for a ship and which effects proportional and differential operations comprises means for automatically increasing the rate time of the steering system when a value - obtained by adding a signal corresponding to deviation between the actual heading of the ship and a set course to a rate value of the signal - exceeds a certain value, thereby to prevent overshoot of the ship during course change. In Fig.2 the actual heading # e.g. from a gyro compass and the set course #i are compared in an adder 1 (e.g. a differential gear) and a value significant of deviation ## is converted by an angular signal generator 2 (e.g. a potentiometer) to a D.C. voltage E1 proportional to the deviation. This voltage E 1  = K 1 ## is applied to the input of an analogue computer 4 and is added to a rate signal transmitted through R 2  C at an input terminal j of an operational amplifier 5. A further signal significant of the rudder order angle # and produced by a power unit 8 is converted into an electric signal by a converter 9 and fed via Rf 1  to be also added at terminal j . The signal amplified by amplifier 5 is applied as negative feedback via R 7 , cancelling the input signal. Since the gain of amplifier 5 is high the input j is normally held at zero potential and the output E 0  of the amplifier is exactly proportional to the difference between the input via R 1 , R 2 , C and the rudder angle signal through Rf 1 . A controller 7 which operates the hydraulic power unit 8 for the rudder, remains in a neutral position when E 0  is zero. If, however E 0  has a positive or a negative value, the power unit 8 is controlled until E 0  becomes zero thus producing the rudder angle #. If the feedback circuit including Rf 1  and circuit 11 is purely resistive the angle # is always proportional to the deviation ## and also to its rate value so that the system performs proportional and differential operations. Such would be the case in Fig.3, for low rudder angles and values of the voltage E 2  when voltage Vx is insufficient to break down Zener diodes D z . However for larger rudder angles and values of E 2  when Vx exceeds the Zener voltage a capacitor Ca receives current via Rf 2  causing a volt drop thereacross so that the voltage across Rf 1  is delayed in phase compared with the case when Ca is inaperature. It is demonstrated mathematically that the rate time is thereby caused to increase and angular acceleration control is added to the auto steering system, further preventing the ship from overshooting in the case of automatic course change and control for maintainance of the set course is achieved. In an embodiment, Fig.7 (not shown) an additional capacitor (Cf) is inserted between Rf 2  and line 10 whereby non-linear rate operation is achieved. Fig. 9 (not shown) illustrates an alternative to the Zener diodes for a 'dead zone' facility. Alternative circuits Figs.4, 5 and 6 (not shown) give similar operational results as Fig.3, while Fig.8 (not shown) is a modification of Fig.4 (not shown) and includes the additional capacitor (Cf)