Patent GB-555476-A (GB)
Title: Improvements in and relating to remote control systems
IPC: G05D3/18
Filed: 1940-07-17
Abstract: 555,476. Remote control systems. AGABALTIC RADIO AKTIEBOLAG. July 17, 1940, No. 11801. Convention date, Sept. 6, 1939. [Class 40 (i)] In a system of the kind in which movement of the transmitter brings about a condition of unbalance at the receiver at which a motor automatically restores. balanced conditions and at the same time moves the object to be controlled, hunting is prevented by a retarding means which is under the joint control of a quantity dependent on the extent of the disagreement between the transmitter and receiver and a quantity which depends on the speed of the receiver motor. The invention is described with reference to systems of the kind in which the transmitter sends out a current of a frequency characteristic of its position and the receiver automatically tunes itself to this frequency. In one arrangement, Fig. 1 (not shown), a brake is actuated by a current derived from a generator driven by the receiver motor in series with the load resistance of a diode valve which rectifies a current derived from the incoming signal and having an amplitude inversely proportional to the discrepancy in position between the transmitter and receiver. In a similar arrangement, Fig. 3 (not shown), the composite current is used to excite the field of the receiver motor, which is driven by a Ward-Leonard generator controlled by the error-detector, so that as the position of co-incidence is approached its speed is reduced and its torque increased. In another system, Fig. 2, the control shaft is clutched to a constantly-running motor by one or other of two magnetic clutches 59, 60 according to the direction in which it is to be driven. The effectiveness of these clutches-depends on the current through them and this current depends (a) on the voltage applied to the grids of the tubes 12, 13 in accordance with the extent of disagreement in position of the transmitter and receiver, (b) on the bias applied to these grids by a tachometer generator 67 geared to the receiver motor, this bias depending jointly on the speed of the motor and the excitation of the field winding 78 which depends on the disagreement in frequency between the received signal and the tuning of the receiver, being small for large disagreements and vice versa. The field winding 82 of the driving motor also is excited more strongly near the position of coincidence to reduce its speed and increase its torque. As a result of these arrangements, the. control shaft cannot exceed a definite speed for any given set of conditions owing to the release of the operative clutch by the action of the generator 67 in opposition to the voltage in 52 or 51 and the energization of the other clutch to some extent to act as a brake. The speed is thus gradually reduced as the position of coincidence is approached. In another arrangement, Fig. 4, the control shaft adjusts an. auxiliary condenser 96 in addition to the main tuning condenser 4. This condenser is across the tuned circuit in series with a valve 95 the impedance of which is varied in accordance with the speed of the control motor by a generator 27. By this means the tuning of the receiver arrives at the condition corresponding to agreement in position of the transmitter and receiver before such agreement has actually been achieved, the point at which this occurs depending on the speed of the receiver motor owing to the effect of a generator 27 in reducing the impedance of valve 95. As the speed of the motor falls, the impedance of the valve rises and the condenser 96 is rendered ineffective by the time the true position of correspondence is reached. Before the position is reached, the receiver tuning, owing to the effect of the auxiliary condenser 96 may pass the condition of coincidence whereupon the other field winding of the motor is energized and the motor acts as a brake. Reference has been directed by the Comptroller to Specification 503,127.