US3205618A

US3205618A - Remote control system for toy automobiles

Info

Publication number: US3205618A
Application number: US288258A
Authority: US
Inventors: Heytow Solomon
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-06-17
Filing date: 1963-06-17
Publication date: 1965-09-14
Anticipated expiration: 1982-09-14

Description

Sept. 14, 1965 s. HEYTOW 3,205,618

REMOTE CONTROL SYSTEM FOR TOY AUTOMOBILES Filed June 17, 1963 2 Sheets-Sheet 1 A WORN/LY Sept. 14, 1965 s. HEYTOW 3,205,618

REMOTE CONTROL SYSTEM FOR TOY AUTOMOBILES Filed June 17, 1963 2 Sheets-Sheet 2 H 7 Rim M H26 55 I y me 6 4 r- T- 5, B V INVENTOR.

50A O/MON HEYTO W United States Patent 3,205,618 REMOTE CONTRGL @YSTEM lFtOR TOY AUTUMGBILES Solomon Heytow, 7900 Sunuyhrae Ave., Canoga Park, Calif. Filed Tune 17, 1963, Ser. No. 288,258 4 Claims. (Ci. 46244) This invention relates to remote control systems, and more particularly to such a system in which both the speed and steering of a free-running object are remotely controlled.

Although the system of the invention is applicable to the remote control of any steerable and/or speed-controllable movable object, it will be described with reference to a toy automobile, although it is to be clearly understood that it is not to be limited thereto and may be applied to other mobile toys and even full-size vehicles.

Heretofore, various toy automobile devices and systems have been available to the public. The majority of them have been electrically or electronically operated, so far as speed control and acceleration are concerned. However, in the majority of such systems, steering of the automobile has not been under the control of the operator. They have, for the most part, run on a track, much in the manner of a toy train, or between fences or the like which serve to define a definite, predetermined pathway for the automobile. Relatively recently, at least one system has been introduced in which a toy automobile has a limited amount of steerability. However, even in that system, the automobile is held captive with respect to the track on which it runs, and its steerability is limited to approximately one inch on either side of the center of the track. Such toys, because of the severely limited number of functions under the control of their operator, quickly lose their appeal for a child. Furthermore, they are generally not conveniently portable because of their fixed track, and cannot easily be disassembled and taken from place to place.

The present invention obviates the disadvantages of toy automobile systems heretofore known. It provides a system in which one or more toy automobiles are completely under the control of one or more operators with respect to acceleration, speed, right and left steering, and forward or reverse direction of travel. The roadbed on which the automobile or automobiles run may be easily rolled up and transported from place to place. The sys tem is electronically controlled through the use of low voltages which present no safety hazard whatever, even for small children. Furthermore, the system is rugged and relatively troublefree, since it embodies solid state elements, and is as inexpensive to manufacture as its somewhat sophisticated design permits.

Briefly, in the system of the present invention, one or more vehicles run on a roadbed from which they receive control signals, which control the acceleration and speed of the vehicles, their steering, and their direction of travel. The vehicles are completely free and completely maneu verable, so long as they remain on the roadbed. The roadbed may be of any desired size which is conveniently portable (in the case of a toy), such as four by eight feet, or a similar size. The roadbed is made of a very thin material than can be easily rolled, so that its size does not radically atfect its portability.

The system of this invention is based on the concept that signals of two different types may be simultaneously provided to a movable object, such as a toy automobile, through a single transmission medium. Specifically, in one embodiment direct current (DC) signals are provided to control the speed and forward or reverse direction of travel of the toy automobile, and alternating current (A.C.) variable frequency signals are. provided to control its degree of steering, right or left.

In another embodiment, A.C. signals control all functions of the automobile, so that by employing signals of various frequencies a plurality of automobiles may be individually controlled on one roadbed at the same time. These signals are picked up by the toy automobile or automobiles from the roadbed on which they run. The roadbed comprises a plurality of strips of conductive material with alternate strips being electrically connected together and insulated from adjacent strips. The toy automobiles are each provided with a plurality of brushes so arranged that, at all times, no less than two brushes are contacting two adjacent strips, respectively. Thus, control signals and power are coupled to the automobiles continuously to control their movements.

Other features and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a fragmentary perspective view of a toy automobile in place on a roadbed constructed in accordance with the teachings of the invention:

FIG. 2 is a fragmentary diagrammatic plan view showing the roadbed on which the vehicle runs;

FIG. 3 is a bottom diagrammatic view of a toy automobile or other vehicle showing the arrangement of the electrical brushes carried thereby;

FIG. 3(a) is an elevational view of a typical brush;

FIG. 4 is a schematic diagram of a power supply for the system;

FIG. 5 is a schematic diagram of a steering control circuit for the vehicle;

FIG. 6 shows schematically a modified steering mechanism; and

FIG. 7 is a schematic diagram of a modified speed control circuit for the vehicle.

As previously noted, the system of the invention will be described with reference to a toy automobile system, although it is certainly not limited to such an application. Therefore, FIG. 1 illustrates a toy automobile 10 in place on a roadbed 11. The roadbed 11 is constructed of a plurality of

strips

12a, 12b, 12c, 13a, 13b, and 130, made of an electrically conductive material, with adjacent strips insulated from each other by conventional means.

As best seen in FIG. 2, the roadbed 11 comprises a plurality of strips 12a 12m and 13a 1311, with the strips 12 being electrically connected together and the strips 13 being electrically connected together. As previously noted, the strips 12 and 13 are electrically insulated from each other. The roadbed may be constructed of separate strips of copper or like conductive material, preferably of uniform width, interdigitally arranged, with alternate strips electrically connected by means of wires, or it may be constructed as shown in FIG. 2 with alternate strips and their connection being integrally formed. In the case of a roadbed for a toy, the strips 12 and 13 may conveniently be of the order of one to two inches wide and one or two mils thick. They may be cemented or otherwise mounted on an insulating backing material, and an insulating tape such as Mylar may be used to cover the edges of adjacent strips and the opening therebctween, if desired.

As best seen in FIGS. 2 and 3, the toy automobile 10 is provided with a plurality of electrical brushes 14a-14e, which extend from its underside and make contact with the strips 12 and 13 of the roadbed. The brushes 14 may be made of conventional material and may be of virtually any desired configuration. Of course, they are insulated from each other and from the body of the automobile. In practice, it has been found that brushes formed as small coil springs, such as shown in FIG. 3a,

serve well and cause minimal wear on the roadbed. Of course, either end of the brush may be used to contact the roadbed, but it is obvious that less wear on the roadbed will result if the rounded end of the brush is so used.

A plurality of more than two brushes are utilized so that when the automobile is oriented in all ways with respect to the strips 12 and 13 of the roadbed there is at least one brush contacting a strip 12 and at least one brush contacting a strip 13. It has been found that the minimum number of brushes 14 required to meet the foregoing condition is five. They are preferably arranged as shown in FIGS. 2 and 3 in the form of two opposed equilateral triangles with one brush being common to both triangles. As shown,

brushes

14a, 14b, and 14c form one equilateral triangle, and

brushes

14c, 14d, and 142 form another equilateral triangle. The spacing of the brushes from each other is, of course, dependent on the size of the toy and the widths of the roadbed strips 12 and 13. The principal requirements is that, at no time, can the automobile be so positioned that all brushes contact the same roadbed strip. Thus, the brushes 14a and 14b (and the

brushes

14d and 14a), forming bases of the triangles, must be spaced apart by a distance greater than the width of any of the roadbed strips, so that when the brush 14c is contacting the strip 13a, for example, the brushes 14a and 14b are respectively contacting the strips 12a and 12b. The particular brush arrangement is not critical, the equaliteral triangle aranngement being shown as merely exemplary, so long as the foregoing criterion is met.

FIG. 4 shows, in schematic form, a power supply for the system of the invention. The power supply illustrated provides direct current (D.C.) power for driving and for controlling the acceleration and speed of the automobile as well as alternating current (A.C.) power for controlling the steering of the automobile. As shown, the power supply comprises a transformer 20 having a primary winding 20a and a secondary winding 2%. The primary winding 20a is connected through a switch 21 to a connector 22 for insertion into a con ventional household power circuit (not shown). It desired, an indicator light 23 may be connected across the primary winding 20a to show when the system is energized.

The secondary winding 20b of the transformer 20 is connected into a full-wave rectifier circuit comprising two

diodes

24 and 25 and a capacitor 26, with a diode being connected to each end of the secondary winding. The capacitor 26 is connected between a center tap of the winding and one end of the winding, in this case, the bottom end, to which the cathodes of both diodes are connected. Thus, the charge built up across the capacitor 26 is positive at the bottom and negative at the top, as shown in FIG. 4.

The capacitor 26 is connected across a current amplifier circuit comprising a PNP transistor 27, whose collector is connected to the top of the capacitor 26 and whose base is connected through an inductance 28 and a Zener diode 29 to the bottom of the capacitor 26. A resistor 30 is connected between the collector and base of the transistor 27. The Zener diode serves to provide a substantially constant voltage on the base of the transistor 27, and the resistor 30 acts to maintain the base of the transistor slightly negative with respect to the emitter. The inductor 28 offers an impedance to AC. in the base circuit of the transistor.

The emitter of the transistor 27 from which the output voltage is taken, is connected to a parallel combination of a capacitor 31 and a variable resistor 32, the latter serving to control the output voltage of the supply and thus acting as a speed control or throttle for the automobile energized by the power supply. As will be hereafter explained in detail, the variable resistor 32 may be eliminated and replaced by a throttle control carried by the automobile and energized by an alternating current signal. As shown, the output voltage appears between two

output terminals

33 and 34, which are connected to the roadbed strips 12 and 13, respectively. In the preferred embodiment, the circuit constants are so chosen that the maximum output voltage between the

terminals

33 and 34 is approximately 15 volts. Thus, the voltage utilized presents no safety hazard even to small children.

The A.C. signals for controlling the steering of the automobile are provided by an astable or free-running multivibrator 35, whose output signals are connected through a capacitor 36 to the base of the transistor 27. Since the emitter-collector current of a transistor is proportional to the base voltage, the DC. output voltage of the transistor 27 will have an AC. voltage from the multivibrator superimposed on it.

The multivibrator 35 may be of conventional, well known design which provides a variable frequency output signal of the order of one or two volts amplitude, peakto-peak. A large amplitude signal from the multivibrator is not utilized in order to prevent distortion; the signal is amplified in the automobile before it is used for control purposes. In a conventional multivibrator, as contemplated by the invention, the frequency of its ouput signal is generally controlled by varying the time constant of its feedback path. Therefore, a variable resistor 35' is shown in FIG. 4 to represent the frequency-controlling element of the oscillator. Preferably, the frequency of the multivabrator 35 is variable over a narrow range of frequencies, such as from two to four kilocycles or from four to six kilocycles.

FIG. 4 also shows another multivibrator 37 having a different frequency range from the multivibrator 35. The second multivibrator 37 may be used to control the steering of another automobile on the same roadbed with the first automobile, or it may be utilized vto control the acceleration and speed of the first automobile, as will be later explained. Of course, if a plurality of automobiles are run from the same power supply simultaneously, they will all operated at the same speed unless each is provided with its own internal throttle, as will be described here inafter. Although only two

multivibrators

35 and 37 are shown in FIG. 4, it is to be understood that a greater number may be utilized. In a preferred embodiment of the invention, two multivibrators are provided for each automobile being operated, with all of the multivibrators having different, mutually exclusive (not overlapping), frequency ranges, which provides individual speed and steering control for each automobile being run.

FIG. 5 is a schematic diagram of one embodiment of the drive means and steering means carried by each automobile. Each electrical brush 14a-14e of the automobile, which contacts the roadbed (FIGS. 2 and 3), is connected to two oppositely-poled diodes 40a and 40b, with the cathodes of the diodes 40a being connected together and the anodes of the diodes 40b being connected together. The cathodes of the diodes 40a are connected to the anodes of the diodes 40b through a series circuit comprising a capacitor 41 and the primaries of two audio frequency discriminators, shown generally by the

numerals

42 and 43.

The audio discriminators 42-and 43 include

transformers

44 and 45, respectively, of a type known in the art as cup cores. The

transformers

44 and 45 have loosely coupled primary and secondary windings, with their half-turn primary windings connected in series with the capacitor 41 between the diodes 40a and 40b.

Capacitors

46 and 47 are respectively connected across the secondary windings of

transformers

44 and 45 to tune each discriminator. The

audio discriminators

42 and 43 are tuned to different frequencies, which frequencies depend on the frequency range of the multivibrator in the power supply to which they are to respond. For example, if the multivibrator 35 (FIG. 4) has a frequency range of from two to four kilocycles, the

discriminators

42 and 43 would be tuned to two and four kilocycles, respectively,

or vice versa. Another automobile, which is responsive to a different multivibrator, would have its discriminators respectively tuned to the upper and lower frequencies of the range over which its control multivibrator operates, and so on. Various types of discriminators may be utilized, and the invention is not limited to the use of any particular type.

The secondary windings of the

transformers

44 and 45 are connected in series between the bases of two

PNP transistors

48 and 49, which act as amplifiers in a conventional manner. The emitters of the

transistors

48 and 49 are respectively connected through

load resistors

52 and 53 to a tap between the secondary windings of

transformers

44 and 45, to which the cathodes of the diodes 40a are also connected. The collectors of the

transistors

43 and 49 are respectively connected to the collectors of another pair of

PNP transistors

54 and 55, which provide another stage of amplification.

The emitters of the

transistors

54 and 55 are connected to the juncture of the

resistors

52 and 53, and their bases are biased by being respectively connected to the emitters of the

first stage transistors

48 and 49.

Capacitors

56 and 57 are respectively connected between the emitters and collectors of the

transistors

54 and 55 to provide voltage and current smoothing.

Steering of the automobile is controlled by a solenoid 60 having a pair of actuating windings 62 and 63 and a core or armature 64 that is preferably a permanent magnet. The armature 64 is mechanically connected by conventional linkages 64' to the front wheels 65 of the toy automobile, so that as the armature moves in one direction the automobile is steered to the left and as the armature moves in the other direction the automobile is steered to the right. Of course, the degree of steering is controlled by the amount of movement of the armature. As mentioned, the linkages 64' are conventional and may be of types such as shown in U.S. Patents 1,856,991 of Franklin, 2,661,070 of Ferrill, In, or 2,993,299 of Dingee, Jr., et al.

The windings 62 and 63 are connected in series between the collectors of the

transistor amplifiers

54 and 55, and the juncture of the windings is connected to the negative side of the capacitor 41. Thus, if more current flows through the winding 62 than through the winding 63, the armature 64 will move upwardly (as shown in FIG. 5), and if the opposite condition prevails, the armature will move downwardly.

The speed and acceleration of the automobile is controlled by the voltage provided to a DC. motor 66, which is connected across, the capacitor The motor 66 is conventionally connected through a gear train 67 to the rear wheels 68 of the automobile. As the resistance of the variable resistor 32 in the power supply (FiG. 4) is varied, the current through the motor 66 is varied and thus the speed of the automobile is varied. If desired, a conventional reversing switch 70 may be provided to reverse the direction of current through the motor 66 and permit the automobile to be backed up.

For purposes of explaining the operation of the control circuitry, assume that the steering control multivibrator 35 (FIG. 4) has a variable frequency range of from two to four kilocycles and that the audio discriminators 42 and 4-3 (FIG. 5) are respectively tuned to two and four kilocycles. If now the frequency control resistor 35 of the multivibrator is so adjusted that the multivibrator output frequency is two kilocycles, the output of the discriminator 42 will be much greater than the output of the discriminator 43. This causes the transistor-

amplifiers

48 and 54 to conduct much more heavily than the transistor-

amplifiers

49 and 55, thus causing more current to flow through the winding 62 than through the winding 63 and the armature 64 to be moved a maximum amount in one direction. On the other hand, if the output frequency of the multivibrator is four lrilocycles, the transistor-arnplifiers 49 and 55 will conduct most heavily and the armature 64 will be moved a maximum amount in the other direction. Of course, as the output frequency of the multivibrator varies between its limits, the armature 64 is moved by varying amounts depending upon the relative outputs of the

discriminators

42 and 43 to provide complete steering control of the automobile.

FIG. 6 illustrates diagrammatically another type of solenoid, which may be used instead of the solenoid 60 shown in FIG. 5. As shown in FIG. 6, a solenoid may be used, which has four

actuating windings

76, 77, 73, and 79, and an armature 86. The armature 86 is connected to the mechanical steering mechanism and the wheels 65 of the automobile in the same fashion as the armature 64 of FIG. 5.

T he windings 76 and 77 are connected in series, as are the windings 73 and 79, and the two series circuits are connected in series between the collectors of the transistor-

amplifiers

54 and 55 by means of leads S1 and 82, respectively. The juncture of the

windings

76 and 78 may be connected to the negative side of the capacitor 41 by means of a lead 83.

The advantage of utilizing a solenoid having four windings, such as the solenoid 75, is that the windings may be so wound and connected that they aid each other in moving the armature 80. In other words, ifcurrent flows from the lead 81 to the lead 83, the current through the winding 78 may push the armature while the current through the winding 79 pulls the armature. Thus, more force may be exerted on the armature than in the arrangement of FIG. 5 to more positively control the automobile steering. Alternatively, a servo motor may be utilized to steer the automobile.

As previously mentioned, each automobile may be provided with an internal throttle to control its acceleration and speed. A circuit for providing such control is shown in FIG. 7. Such an arrangement has several advantages. First, when the circuits of FIGS. 4 and 5 are utilized, the steering control is somewhat tied to the speed. That is, if the variable resistor 32 (FIG. 4) is adjusted for reduced speed of the automobile, the amount of current available to energize the solenoid 60 (FIG. 5) is similarly reduced. Therefore, at low speeds of operation, the steering control of the automobile is reduced. This is not true if the circuit of FIG. 7 is utilized; steering is completely independent of speed. Second, when using the arrangement of FIGS. 4 and 5, if a plurality of automobiles are being run simultaneously, all must run at the same speed. With the circuit shown in FIG. 7, the speed of each automobile may be individually controlled.

The circuit of FIG. 7, having power input terminals A and B, may be utilized to replace the motor 66 (FIG. 5) with the power input terminals A and B connected across the capacitor 41 to corresponding terminals A and B. The circuit includes another discriminator 90, comprising a cup core or transformer 91 and a capacitor 92 connected across the secondary of the transformer 91. The primary of the transformer 91, of course, is connected in the input circuit in series with the primaries of the

transformers

44 and 45 at any desired point, such as the point designated X. One end of the secondary of the transformer 91 is connected to the base of a PNP transistor 93 and the other end of the secondary is connected to input terminal A and through a resistor 94 to the transistor emitter. The collector of the transistor 93 is connected to the collector of another PNP transistor 95, whose emitter is connected to the bottom of the secondary winding of transformer 91 and to the terminal A. The base of the transistor 95 is connected to the emitter of the transistor 93, so that the

transistors

93 and 95 serve as conventional transistor-amplifiers.

A DC. motor 66, similar to the motor 66 in FIG. 5, is connected between the collector of the transistor 95 and input terminal B. As in FIG. 5, the motor 66' is connected through conventional gearing 67 to the drive wheels 68 of the automobile.

The speed discriminator 90 is tuned to a different frequency than the steering discriminators 42 and 43 (FIG. For example, if the

steering discriminators

42 and 43 are respectively tuned to two andfour kilocycles, the speed discriminator 90 might be tuned to siX kilocycles, and be under the control of another multivibrator, such as the multivibrator 37 shown in FIG. 4. If the output frequency of the multivibrator 37 is variable from six to eight kilocycles, the output of the

transistoramplifiers

93 and 95 would be maximal at six kilocycles and the motor 66' would run at full speed. Similarly, if the multivibrator output frequency is eight kilocycles, the motor would run at a very slow speed or be stopped entirely, if the transistor-95 is cut off. Of course, D.C. power must still be supplied by the power supply (FIG. 4) to energize the motor 66', with the variable frequency AC. power provided by the multivibrator 37 serving only to control the direct current through the motor.

It is apparent that virtually any desired number of vehicles may be simultaneously operated on the roadbed, with the speed and steering of eachIvehicle being controlled by individual multivibrators. Of course, all of the multivibrators must have separate, non-overlapping frequency ranges, and the discriminators in the vehicles must be tuned to respond to the proper multivibrators.

Summarizing briefly, it is now apparent that the invention provides a remote control system for a free-running, steerable object that incorporates complete control by electronic means of both the speed and steering of the object. The object may be powered by a low DC. voltage that is completely harmless to humans, and both its speed and steering may be controlled by very low voltage A.C. signals superimposed on the DC. voltage. A plurality of objects may be run simultaneously on a single roadbed under the individual control of a plurality of operators.

What is claimed is:

1. A remote control system for a steerable electric power driven object, comprising:

a roadbed for said object;

power supply means for supplying direct current to said roadbed to drive and steer said object;

first oscillator means for superimposing variable frequency alternating current speed control signals on I said direct current;

second oscillator means for superimposing variable frequency alternating current steering control signals on said direct current;

electric motor means carried by said object and in electrical circuit with said roadbed for driving said object;

electrically operable means carried by said object and in electrical circuit with said roadbed for steering said object;

first discriminator means carried by said object and responsive to said speed control signals for controlling said direct current supplied to said electric motor means; and

second discriminator means carried by said object and responsive to said steering control signals for controlling said direct current supplied to said means for steering said object to control steering thereof.

2. The system defined by claim 1, wherein said variable frequency speed control signals and said variable frequency steering control signals are of exclusive, nonoverlapping frequencies.

3. A remote control system for a plurality of steerable, electric power driven objects, comprising:

a roadbed for said objects;

power supply means for supplying direct current to said roadbed to drive and steer all of said objects;

a first plurality of oscillators for providing variable frequency signals, corresponding in number to said plurality of objects, for superimposing alternating current speed control signals on said direct current; a second plurality of oscillators for providing variable frequency signals, corresponding in number to said plurality of objects, for superimposing alternating current steering control signals on said direct current;

electric motor means carried by each said object for driving said object;

electrically operable means carried by each said object for steering said object;

first discriminators carried by each of said objects and responsive to a different one of said speed control signals for controlling said direct current supplied to said electric motor means; and

second discriminators carried by each of said objects and responsive to a diiferent one of said steering control signals for controlling said direct current supplied to said means for steering said object for controlling steering thereof.

4. The system defined byclaim 3, wherein an of said oscillators provide variable frequency signals of ditferent, non-overlapping frequency ranges.

References Cited by the Examiner UNITED STATES PATENTS 1,420,629 6/22 Hammond 24477 1,856,991 5/32 Franklin 46244 X 2,073,443 3/37 CardOza 104-149 2,661,070 12/53 Ferrill 104-149 2,717,557 9/55 Seytfer 104-149 2,743,678 1/56 Hibbard 104-152 2,858,773 11/58 Eldridge 104-149 2,872,879 a 2/59 Vierling 104149 2,993,299 7/61 Dingee et al. 104149 FOREIGN PATENTS 702,764 1/54 Great Britain. 938,174 1/56 Germany.

OTHER REFERENCES Teichmann, German application Serial No. T 9,423, printed Nov. 29, 1956.

BENJAMIN HERSH, Primary Examiner. KENNETH H. BETTS, A. HARRY LEVY, Examiners.

Claims

1. A REMOTE CONTROL SYSTEM FOR A STEERABLE ELECTRIC POWER DRIVEN OBJECT, COMPRISING: A ROADBED FOR SAID OBJECT; POWER SUPPLY MEANS FOR SUPPLYING DIRECT CURRENT TO SAID ROADBED TO DRIVE AND STEER SAID OBJECT; FIRST OSCILLATOR MEANS FOR SUPERIMPOSING VARIABLE FREQUENCY ALTERNATING CURRENT SPEED CONTROL SIGNALS ON SAID DIRECT CURRENT; SECOND OSCILLATOR MEANS FOR SUPERIMPOSING VARIABLE FREQUENCY ALTERNATING CURRENT STEERING CONTROL SIGNALS ON SAID DIRECT CURRENT; ELECTRIC MOTOR MEANS CARRIED BY SAID OBJECT AND IN ELECTRICAL CIRCUIT WITH SAID ROADBED FOR DRIVING SAID OBJECT; ELECTRICALLY OPERABLE MEANS CARRIED BY SAID OBJECT AND IN ELECTRICAL CIRCUIT WITH SAID ROADBED FOR STEERING SAID OBJECT; FIRST DISCRIMINATOR MEANS CARRIED BY SAID OBJECT AND RESPONSIVE TO SAID SPEED CONTROL SIGNALS FOR CONTROLLING SAID DIRECT CURRENT SUPPLIED TO SAID ELECTRIC MOTOR MEANS; AND SECOND DISCRIMINATOR MEANS CARRIED BY SAID OBJECT AND RESPONSIVE TO SAID STEERING CONTROL SIGNALS FOR CONTROLLING SAID DIRECT CURRENT SUPPLIED TO SAID MEANS FOR STEERING SAID OBJECT TO CONTROL STEERING THEREOF.