Abstract: Operating device for the cover of a sliding and lifting sunroof of a motor vehicle having a desired value transmitter and an actual value transmitter for controlling the sliding sunroof function and the lifting roof function via an actuator that is part of a control circuit. By the control circuit, the desired value signal supplied by the desired value transmitter and corresponding to the respective desired position of the cover selected is compared with an actual value signal of the actual value transmitter corresponding to the respective actual position of the cover to cause the cover position to be adjusted until the actual cover position matches that desired. The operating element of the desired value transmitter is mounted, to slide for producing for a sliding of the cover, and to swing for producing a cover tilting-out movement.

Abstract: A servo for driving a control linkage in a radio controlled model includes a motor, a gear train coupled to the motor, an output shaft coupled to the gear train to which to couple a control linkage, a position sensor coupled to the output shaft for producing a signal indicative of output shaft position for feedback control purposes, and a slip clutch between the gear train and the output shaft for at least partially inhibiting the transmission of a transient force from the output shaft back to the gear train.

Abstract: A motorized window blind actuator including input means for receiving regulated voltage and first variable reference voltage signal. A motor having an output shaft which connects to the window blinds to open and close the window blinds is controlled by a controller/driver component. A transducer is operatively associated with the output shaft of the motor to assist in producing a second voltage reference signal which is related to the actual position of the motor output shaft, and in turn related to the actual position of the slats of the window blind. The first voltage reference signal is related to the desired setting and position of the window blind. First and second voltage reference signals are continually compared. If they are sufficiently different, the motor is directed by the controller/driver to adjust the window blinds until signals are sufficiently the same, or, until the output shaft of the motor hits physical limits which cause an over current situation resulting in stoppage of the motor.

Abstract: The present invention provides an apparatus for controlling operation of a fluid control valve. In the preferred embodiment, the present invention operates a hydraulic control valve to operate a hydraulic apparatus. The control system of the present invention permits the pre-selected adjustable control of the acceleration and speed of movement of the apparatus to be controlled. Additionally, the control system permits the selection of pre-determined movement limits within which the operation of the hydraulic apparatus may be contained. The control apparatus also senses the amount of actuation of the control valve.

Abstract: A fail-safe electronic position monitoring system for a motor is specifically described in a flame safeguard system. The same fail-safe system could be used more generally in any type of positional monitoring system using a potentiometer. The potentiometer and its wiper are monitored by a microcomputer which has stored in its memory a profile of at least three critical parameters. The parameters are a low voltage parameter, a high voltage parameter, and a parameter that deals with the rate of the voltage level change. The rate voltage level change includes monotonocity function.

Abstract: An electropneumatic position regulator having a current/pressure transducer has, as electric input, at least one coil (11) fed with a current (setting signal), as well as a permanent magnet (16) whose relative position is variable as a function of the current for the adjustment of a nozzle/impact-plate arrangement (17, 18) of a pneumatic system. The position regulator serves for a pneumatic setting device (23) which has a stroke output and is connected with the nozzle/impact-plate arrangement. The position regulator furthermore comprises a position report device with an electric path transmitter (31) which is connected to the stroke output (32) of the setting device (23). The report signal from the electric path transmitter (31) is fed back to the electric input (coil 12) of the current/pressure transducer.

Abstract: An adjustment and dialogue device, more particularly for speed variators comprises potentiometers for adjusting the operating parameters of the variator, a unit displaying these parameters, an advance knob for successively displaying these parameters, a processor whose inputs are connected to the advance knobn and to the potentiometers via a converter and whose outputs are connected to the display unit, and a support being one part of a printed circuit control card located in a casing whose front face has a removable part which can be opened by the user.

Abstract: An apparatus for actuation of a setting element has a desired value transmitter and an actual value transmitter for the deflection of the setting element from a rest position. The apparatus includes an electronic controller, particularly for a motor vehicle, wherein the deflection of the setting element is proportional to an electric current fed to the element by the controller. An operating mode of the controller is provided by which a signal emanating from the desired value transmitter is converted into a current proportional to a desired value.

Abstract: This invention relates to an automatic universal head for operating a motor on the basis of set information and automatically controlling the controlled mode of the universal head to a state conforming to the set information. In this invention, when the universal head control based on the set information is not executed for some reason or other, the power supply to the motor is automatically inhibited in a predetermined time after the universal head control is started.

Abstract: A position transmitter which can be incorporated in a pneumatic-pneumatic or electro-pneumatic converter, and which readily provides for calibration between a zero position and a maximum position of a device to be actuated by the converter. The invention also provides a virtually non-interacting zero and span or full scale adjustment, for ease of calibration.

Abstract: A device for preventing a motor from being locked comprises a position indicator for indicating a position to be moved in response to rotation of the motor, a position detector for detecting the position being moved in response to rotation of the motor, a servo control unit for supplying a current to the motor so that an output signal from the position detector will be equalized with an indication by the position indicator, a stop detector for detecting stoppage of the motor in response to a differential of the output signal from the position detector, and a cutoff control unit for cutting off the current supplied from the servo control unit to the motor in response to an output signal from the stop detector.

Abstract: An automatically balancing type pen recorder, which is compact in size and is highly reliable in operation, comprises an integral servo unit formed of a single printed circuit board which incorporates therein a pen carriage and an automatic balancing mechanism adapted to move a recording chart in a direction perpendicular to the direction of feed of the chart, in response to the magnitude of a measuring signal.

Abstract: A device for controlling the output speed of a motor of a ring spinning machine, a ring twisting machine and the like in case of replacing travelers of such machines includes a speed setter for the motor and a potentiometer which is operatively connected with the speed setter to limit the output speed of the motor for allowing breaking in of replaced travelers. The potentiometer is further coupled with a speeding-up unit which is e.g. a stepper motor and which over a selected period of time increases the limited output speed to the normal operating level by automatically resetting the slider of the potentiometer from one end position to another end position.

Abstract: A control system for controlling the rotation of a rotary mechanism such as a propeller housing in a Z-type propulsion apparatus is provided. A command signal and a feedback signal both relating to the rotation of the rotary mechanism are compared with each other. And a control signal which varies at a predetermined inclination is generated when the command and feedback signals differ in amplitude from each other. And a drive unit rotates the rotary mechanism in accordance with the control signal.

Abstract: A temperature control device used in an automobile air conditioner system includes a potentiometer for detecting the opening amount of an air-mix door. The potentiometer is tapped and includes at least one auxiliary resistance connected in parallel with a resistance element of the potentiometer.

Abstract: A motor driving circuit apparatus for use in a motor actuator for actuating, for example, a valve between two limit positions, having a control means for inputting a driving control signal for the motor, a sensor adapted to output a signal corresponding to the position of the actuator, and a comparator section adapted to compare the input through the control means and the output from the sensor, the comparator being adapted to produce an output signal in accordance with which the motor is driven and controlled. The motor driving circuit apparatus comprises a differentiation circuit for differentiating the output of the comparator section and a timer section adapted to be controlled by the output from the differentiation circuit, wherein the driving control of the motor by the output of the comparator section is conducted only within a predetermined period of time in accordance with the output from the timer section.

Abstract: A load positioning system with gravity compensation has a servo-motor (12), position sensing feedback potentiometer (38) and velocity sensing tachometer (42) in a conventional closed-loop servo arrangement to cause lead screw (14) and ball nut (20) to vertically position load (22). Gravity compensating components comprise the DC motor (32), gears (34) and (36), which couple torque from motor (32) to the lead screw (14), and constant-current power supply (37). The constant weight of the load (22) applied to the lead screw (14) via the ball nut (20) tends to cause the lead screw (14) to rotate, the constant torque of which is opposed by the constant torque produced by motor (32) when fed from the constant-current source (37). The constant current is preset as required by potentiometer (54) to effect equilibration of the load (22) which thereby enables the positioning servo-motor (12) to "see" the load (22) as weightless under both static and dynamic conditions.

Abstract: A motor-driven rotary actuator includes an electric drive motor adapted to be configured for providing one of a plurality of output torques. A power transmission is coupled to the drive motor and includes a rotatable output shaft and drive elements adapted to be formed of disparate materials selected for transmitting one of the output torques. An electric controller is coupled to the motor for providing rotation positioning control of the output shaft in response to digital command signals.

Abstract: A numerically controlled motor provides a drive at a rate which is proportional to rotation of an independently driven shaft. In addition, the ratio of such rate to such rotation can be varied by a control circuit by which, in response to each pulse supplied by an encoder on said shaft, an incremental value, corresponding to an analogue signal supplied by a potentiometer to an A-D converter, which converts said signal to said value, is supplied to an accumulator, which sums the successively supplied increment values and, at a predetermined cumulative value, "overflows", such "overflow" supplying a drive signal to the n.c. motor. The potentiometer is manually set by an operator to vary the increment value and thus the frequency of "overflow" in relation to shaft rotation. The control circuit also enables "reverse" and "fast forward" drive to the motor independently of the shaft.

Abstract: An operating system for movable parts for the selective closing or exposing of openings, especially for sliding roofs and sliding/lifting roofs of motor vehicles. The operating mechanism has a motor drive for the movable part and an actuating member for starting the drive, if required. In order to facilitate, especially, the bringing of the movable part into intermediate positions, the actuating member is developed as a desired-value transmitter for the position of the movable part, and the drive is part of a control circuit which compares the position selected at the desired-value transmitter with the actual position of the movable part and adjusts the movable part until the deviation has become zero.

Abstract: Automatic high insulation switch with low consumption level and small overall dimensions. The switch is associated with an apparatus for measuring very low currents (10.sup.-7 to 10.sup.-14 amperes) comprising an amplifier controlled by an input field effect transistor. The invention aims to switch on the amplifier's very high value resistors with the aid of magnetically controlled, flexible reed interrupters or switches, actuated by a permanent magnet, which is itself controlled by a conventional servomechanism having a motor and a potentiometer controlled by a microprocessor. Other interrupters ensure the protection of the transistor. The invention is more particularly used for measuring currents supplied by ionization chambers.

Abstract: A motor-driven rotary actuator includes an electric drive motor adapted to be configured for providing one of a plurality of output torques. A power transmission is coupled to the drive motor and includes a rotatable output shaft and drive elements adapted to be formed of disparate materials selected for transmitting one of the output torques. An electric controller is coupled to the motor for providing rotation positioning control of the output shaft in response to digital command signals.

Abstract: A circuit arrangement for controlling the action of an adjusting device, in particular of a patient chair, which comprises, as target value indicator, a digital-analog converter (1) and, as actual value indicator controllable by the adjusting device, a potentiometer (2), which receives an equalized feed voltage which serves to operate the digital-analog converter, and which is connected via a branch (13) to a comparator unit (12), whose other input is connected to output (8) of the digital-analog converter (1), and which controls the adjusting device (31, 32, 33). According to this circuit design, the digital-analog converter (1), and the potentiometer (2), form a Wheatstone bridge of which one diagonal is supplied with a single feed voltage, while the other diagonal contains the comparator unit (12).

Abstract: A circuit for controlling the rotation angle of a motor by comparing an output signal from angle setting means with the detection result from a potentiometer means which detects the rotation angle of the motor while the motor is driven in response to the output signal from the angle setting means which has: a first potentiometer for detecting the rotation angle of the motor; a second potentiometer for detecting another rotation angle at a phase different from that of the first potentiometer; an interval selecting means for selecting one of a plurality of interval signals in response to the output signal from the angle setting means; a potentiometer selecting means for selecting one of the output signals from the first and second potentiometers in response to the output signal from the interval selecting means; a compensating signal generating means for generating an offset compensating signal for compensating for an offset between a selected signal from the potentiometer selecting means and the output signal

Abstract: A control system for positioning an implement using a power steering unit. Instead of connecting a rotary spool of the power steering unit with a steering wheel, the rotary spool is connected with a DC motor through reduction gears. An angular displacement of a control lever is detected by an angular position detector and an angular displacement of an implement is detected by another angular position detector. Signals from both detectors are fed into a comparator which is connected with an amplifier for rotating the DC motor in either direction in response to signals therefrom.

Abstract: The invention relates to a mechanism wherein a relative rotary angle of a driving motor is detected by use of an encoder, and, if an error occurs in a servo control action when the driving motor is servo-controlled in accordance with a deviation value of the relative rotary angle from a desired rotary angle of the driving motor, then the servo control action is brought to an emergency stop. A potentiometer for detecting an absolute rotary angle of the driving motor is connected to a rotary shaft of the driving motor and said emergency stop is effected when a difference between said absolute rotary angle and said relative rotary angle exceeds a preset tolerance value, so that an error in the servo control action can be reliably prevented.

Abstract: A drive mechanism comprising a power driven screw (16) and a nut means (17) co-operating with the screw includes a device for the correction of backlash prevailing between the screw and the nut means. The correction takes place electronically by modification of two pulse trains (A, B) which are generated by a pulse generator (19) which is synchronized with the movement of the screw. From the two pulse trains information as to position and direction of movement is derived for a movable unit (11), which is connected to the nut means and which, for instance, can be a printing unit in a printer or a typewriter. A measured or estimated value of the backlash is digitally stored with a resolution of one quarter of the period of the pulse trains. This resolution is four times the smallest distance through which the movable unit can be moved.

Abstract: Controller for an antenna rotator having a rotatable member on which is mounted an antenna to be rotated to various headings. Switching circuitry selectively energizes a motor in the rotator to rotate the member in either of two, opposite directions. Antenna headings are user selectable and pre-programmable, the controller including control circuitry for accepting pre-programmed headings entered from a keyboard, storing the pre-programmed headings and retrieving headings. Users can select a pre-programmed heading or enter a new heading via the keyboard, the control circuitry controlling the motor switching circuitry to rotate the antenna to the selected heading. Circuitry is also provided to energize a brake solenoid in the rotator to, in the absence of jamming or binding, release the brake.

Abstract: A device for the electric control of the speed of an automotive vehicle having a guide signal transmitter developed as settable memory, having a comparison element fed with the guide signal and a vehicle-speed signal, having a control amplifier which is arranged behind the comparison element and gives off a set signal to a setting drive for the displacement of a throttle valve which controls the air-fuel mixture of an internal combustion engine, having a position indicator coupled with the throttle valve apparatus and having a guide signal transmitter developed as settable memory. A comparator for comparing the set signal with a feedback signal given off by the position indicator is provided, the output value of which sets the guide signal transmitter at such a large guide signal that the position of the throttle valve at an end of the setting process, which has been determined during the setting by a driver, is established by the set signal.

Abstract: This invention relates to a circuit arrangement and the associated mechanism for slaving the angles of rotation of the slats of a plurality of centrally controlled sun or window blinds. The driving motor of each blind is provided with current via a corresponding operational amplifier and related circuit. The motor operates the slats to achieve balance between an input control voltage and a voltage depending on the angular position of the slats. An automatic version in which the control voltage is generated by a photoelectric sensor and several circuit variations are shown.

Abstract: The profile measurement control comprises a potentiometer adjustable by means of a lever. The voltage tapped-off the potentiometer is attenuated via a resistance network proportional to the radius of the base circle disc and additionally via an encoding switch and a voltage attenuating circuit when a certain pre-selected diagram length transmission or translation is exceeded. Thus a voltage is always supplied to the drive motor driving a generating carriage or slide which ensures for an optimum paper feed rate when the lever is located to engage a stop. Hence, the lever can be always adjusted to engage the stop without the preselected diagram length translation or the radius of the selected base circle disc having to be taken into account. Consequently, the measuring rate during series testing of gear profiles can be considerably increased.

Abstract: A controller for operating devices adapted for motor control, such as dampers, valves and the like in a heating, ventilating and air conditioning (HVAC) system interfaces with a serial link which may carry control signals for operating a multiplicity of controllers on a time division multiple access (TDMA) basis has digital circuitry responsive to the control signals which translates them into digital signals which are stored between access times. Two series connected pluralities of resistors define, between their opposite ends and their junction points, a potentiometer which is variable by normally open and normally closed contacts which individually are connected across each resistor in each of the pluralities. The switches are operated in response to the digital signals so as to vary the resistance presented by the potentiometer between the opposite ends thereof and the junction.

Abstract: An electronically controlled apparatus for controllably positioning pneumatic actuators includes, in a first embodiment, first means for selectively flowing compressed fluid to the actuator and valve means for selectively exhausting compressed fluid from the actuator. An electronic control panel is adapted to receive digital command signals from a computerized controller and is coupled to the first means and to the valve means for actuation thereof in response to the command signals. Means are included for isolating electrical switching transients from the controller.In a second preferred embodiment, the positioner also includes transducer means for generating a feedback signal representative of the position of the actuator piston assembly. A third preferred embodiment is similar to that of the second embodiment and incorporates a control adapted to receive analog rather than digital command signals. An optional high limit pressure switch may be used with any embodiment.

Abstract: A remote controller is disclosed for controlling the throttle, brake and steering mechanism of a conventional motor vehicle, with the remote controller being particularly advantageous for use by severely handicapped individuals. The controller includes a remote manipulator which controls a plurality of actuators through interfacing electronics. The remote manipulator is a two-axis joystick which controls a pair of linear actuators and a rotary actuator, with the actuators being powered by electric motors to effect throttle, brake and steering control of a motor vehicle adapted to include the controller. The controller enables the driver to control the adapted vehicle from anywhere in the vehicle with one hand with minimal control force and range of motion. In addition, even though a conventional vehicle is adapted for use with the remote controller, the vehicle may still be operated in the normal manner.

Abstract: A transducer for generating a feedback signal representative of the position of a movable member includes a signal generating mechanism for providing an electrical feedback signal representative of the position of the movable member. The signal generating mechanism includes a first shaft portion having a first longitudinal centerline and a drive mechanism having a shaft member coupled in driving engagement to the first shaft portion. The drive mechanism is adapted to be cable connected to one of a plurality of movable members having maximum travel spans different one from the other. The shaft member has a shaft longitudinal centerline which is concentric with the first centerline, the centerlines defining a first axis. An alignment mechanism is coupled to the drive mechanism and the signal generating mechanism and permits limited movement of the first axis with respect to a reference axis. The alignment mechanism thereby isolates the signal generating mechanism from misalignment reaction forces.

Abstract: A decoder decodes and accurately scales so-called "tribit" servo signals after the receipt of only one tribit pattern without the use of A.G.C. by storing the peak values of the position indicating pulses the capacitors in first and second peak-and-hold circuits and thereafter discharging both capacitors with the same time constant, activating a sample-and-hold circuit to hold the value of the output of a difference amplifier at the instant when the output of a summing amplifier falls below a predetermined value.

Abstract: In a numerical control unit capable of driving a motor at a feed speed designated by a feed speed-designation dial, there are provided a potentiometer for generating a DC voltage proportional to the amount that a feed speed-designation knob is turned and an AD converter for converting the DC voltage output from the potentiometer into a digital quantity, the AD converter output being read out by a main processor section. The circuit construction can be markedly simplified as compared with the conventional circuit construction employing a voltage-controlled variable oscillator.

Abstract: A control circuit for an antenna rotator includes a difference amplifier which develops a motor drive signal of both positive and negative polarity for rotation of a DC motor in both clockwise and counterclockwise directions. A feedback loop circuit for control of the motor is provided by a sensor of antenna position, the sensor being coupled between the antenna and the amplifier. Friction in a gear train coupling the motor to the antenna isolates the circuit from wind induced vibrations of the antenna.

Abstract: A feedback system is disclosed for use in a remote control linear actuator device including a pair of actuator members that are relatively linearly displaceable by a motor, which feedback system includes a mounting bracket connected with one of the actuator members, a slide bar connected with the mounting bracket for linear movement by the other actuator member in a direction parallel with the direction of relative movement of said actuator members, and a rotary member operable by the slide bar to supply a feedback signal to the motor that is a function of the relative positions of the actuator members.

Abstract: The present invention provides an automatic control system for position following and reciprocating motion of a controlled object. By using a specially designed controlling switch, and a pair of variable resistor for varying the position of the demanding object, the position of the controlled object and its motion pattern may be controlled. Using the automatic control system of the present invention, the motion characteristics of best deceleration rate for the controlled object may be obtained. And the automatic system of the present invention may improve the disadvantages of the conventional position control device contributes a perfectly ideal automatic control for the motor-operated or hydraulically-operated mechanism.

Abstract: To render the mixing relationship of mixed actual pulling force signals and actual positioning signals independent of the level of the respective individual signals, and thus avoid resetting of a manual positioning command element (7) upon change of respective relationships of pulling force and position, for example depth of furrow of a plough upon change of soil consistency, the force signal is normalized or rendered of equal value with respect to the position signal, preferably in accordance with predetermined events, such as change in the positioning command element, sensing of excessive pulling force, or the like, so that the normalized force signal and the actual position signal will be in balance, and relative change thereof in the mixer will not cause uncontrolled change in the position of the load, for example the plough, without resetting of the command element (or, conversely, require resetting of the command element upon change in relationship of the mixed signals).

Abstract: A control circuit for stopping a spindle at a predetermined rotational position, of the type having a position sensor for producing a zero volt signal when a specified point on the spindle arrives at the predetermined rotational position, and for producing a voltage which is positive or negative when the specified point on the spindle is in the vicinity of the predetermined rotational position on either the left or right side thereof. The control circuit includes an orientation control circuit for stopping the spindle drive motor when the output signal from the position sensor attains the value of zero volts, thereby stopping the specified point on the spindle at the predetermined rotational position. The control circuit further includes a position adjustment circuit for adjusting the rotational position, of the specified point on the spindle, at which the output signal from the position sensor crosses the zero volt line.

Abstract: A proportional solenoid actuated servo system and associated drive circuitry are disclosed in which a pair of oppositely acting coils of the solenoid are connected in series across a floating power supply with the center point between the coils grounded. The voltages produced at the power supply terminals are differentially controlled relative to ground by voltage control means which responds to position command and armature position feedback signals. The force exerted by the armature is controlled by a power control signal which varies the voltage difference between power supply terminals.

Abstract: Solar energy system incorporating a dirigible motor-driven collector and an electronic sensor for turning the collector to follow the sun. The collector is turned progressively during the day to occupy successive positions during predetermined time periods in which it collects solar energy most efficiently, at the end of the day automatically returning the solar collector to its initial, morning position. The system is controlled by an arrangement which is composed largely of a novel combination of commercially available units, thereby cutting its cost and increasing its reliability.

Abstract: The device comprises for each window an electric driving motor and a selector which is adapted to ensure the selective supply of current to the motor, in one direction or the other, through a control circuit acting on a supply source. The supply source is of the type capable of delivering at least two distinct energy levels. The control circuit comprises means for applying to an input of the supply source an energy level control signal which produces, as a function of the position of the selector, the application of a torque to the motor when raising the window which is higher than the torque applied when descending the window.

Abstract: In a multi-channel recording instrument, the reference signal of each channel is floating from the ground level. Therefore, one each isolated power supply means must be provided for each channel. However, when the error signal for each channel is transmitted through a photo-coupler, the circuit after the photo-coupler can be isolated from the biasing voltage of the reference signal, and a common power supply can be used for all the stages after the photo-couplers, including servo-motor drivers, of all the channels. This reduces the size and cost of the power supplies as a whole. The non-linear character of the photo-coupler does not cause a positioning error, since the photo-coupler is in the servo-loop having a sufficiently large gain.

Abstract: An actuator for use in the nature of a servomotor, having means for providing a signal indicative of the position of a mechanical linkage member. A feedback signal source voltage is alternately connected to a feedback signal lead by switch means which are carried by the mechanical linkage member of the actuator. Variable resistance means can be inserted between the voltage source and the feedback signal lead to provide a plurality of feedback signal voltages, each of which indicates a different position of the actuator linkage member.

Abstract: Method and device of servo-controlling a rotating workpiece in relation to a member such a tool capable of translational motion along a system of two mutually perpendicular axes as a function of a desired rate of transit of the periphery of said workpiece past said tool, in which a tangent to said periphery is determined and the tool is slaved to the displacement of said tangent parallel to itself, while the angular position of said workpiece is determined and the speed of the tool is varied along its system of axes as a function of said displacement of the tangent. Application to the automatic welding of odd pieces.

Abstract: A bracket for an electrical servo actuator wherein said servo actuator (10) is mounted on a support arm (12) which is allowed to pivot on a bolt (14) through a fixed mounting bracket (16). The actuator is pivotally connected to the end of the support arm by a bolt (18) which has an extension (24) allowed to pass through a slot (26) in the fixed mounting bracket. An actuator rod (34) extends from the servo actuator to a crank arm (32) which turns a control shaft (36). A short linear thrust of the rod pivots the crank arm through about 90.degree. for full-on control with the rod contracted into the servo actuator, and full-off control when the rod is extended from the actuator. A spring (28) is connected at one end to the fixed mounting bracket and at the other end to the extension (24) of the bolt (18) connecting the actuator to the support arm.

Abstract: A direction and speed control system for a steerable locomotive having independent speed controls for two driving rollers, in which, where C.sub.D and C.sub.G are speed control signals for the two rollers, .alpha. is a steering angle of a steerable support, which may be a mere skid or a driving roller and C.sub.max is a maximum speed control value, there are three operational networks which generate signals F.sub.1, F.sub.2 and F.sub.3 given by C(1-K.sub.1 tan .alpha.), C(1+K.sub.1 tan .alpha.) and C.sub.max (1-K.sub.1 .vertline. tan .alpha..vertline.)/(1+K.sub.1 .vertline. tan .alpha..vertline.), comparators which receive C.sub.max and F.sub.1 and C.sub.max and F.sub.2 respectively and output terminals fed in parallel, through gating circuits controlled by the comparators, by the first and third networks and by the second and third networks respectively.