FR2645846A1 - DEVICE FOR MONITORING THE POSITION AND OSCILLATIONS OF A SUSPENDED LOAD DURING TRANSFER THROUGH A LIFTING APPARATUS - Google Patents

Abstract

Device for controlling automatically the position and the oscillations of a suspended load during its transportation by a lifting device, comprising: - at least one guide means on which moves a translationally moveable carriage, actuated by a motor, to which is hooked a cable (or a rod) from the other end of which is suspended the load to be transported; - at least one position sensor, - an angle sensor, arranged on the carriage, characterised in that it comprises: - a first control loop comprising: . a first comparator (22> . a proportional corrector (23> . a second so-called position control loop, comprising: . a second comparator (20> . a proportional and integral corrector (21> - an adder (24). Application to any transportation of a suspended load requiring special conditions.

Description

AUTOMATIC CONTROL DEVICE FOR THE POSITION AND

  OSCILLATION1S OF A SUSPENDED LOAD DURING TRANSFER

USING A LIFTING APPARATUS.

  The present invention relates to a device for automatically controlling the position and oscillations of a suspended load during its transfer, in particular

by means of a hoist.

  The invention can be adapted to gear of the

  variety of types, such as for example

  cranes, cranes or cranes. Handling

  a load by a hoist

  It is desirable to cushion the load as completely as possible in order to be able to deposit the load without difficulty in a specific location. In addition, in the context of handling environmentally hazardous loads, it is desirable to transfer said charges in a relatively short time and above all,

  taking care that these remain in a separate plan.

perfectly stable and vertical.

  Currently, only crane operators with long experience manage to achieve a relatively relative stabilization of the oscillations of the load. However, these stabilizations are not satisfactory because they

  usually ask for time to get them.

  Rigid masts or telescopic mats integral with a mobile carriage in translation have also been used. However, this type of installation is expensive and cumbersome, because it involves the development of a volume located above the carriage to allow

  the passage of the mast. So, if this achievement is satis-

  technically, on the other hand, it is not

  not compatible with adequate mass industrialization

to any situation.

  It has also been proposed to guy the load by means of symmetrical inclined cables. This guying proves to be long and tedious to set up, and is

  therefore not suitable for repetitive charge transfer.

  In the French patent FR-A-2,399,378, it was proposed

  a load anti-sway device of the type in question, in which the transfer member undergoes sinusoidal acceleration laws determined. However,

  if this law is valid for a given period, that is

  - ie for a given cable length, on the other hand,

  it is not adapted to a variation of the so-called

cable.

  In the French patent application FR-A-2,598,141, a system controlled in a minimum time was described. In this system, the load is accelerated in both directions to compensate for sway. In fact, we do not deal with oscillations during the transfer, but only at the start and finish. As already said,

  these oscillations are unacceptable for certain

  in particular in the context of the environment

and the safety of the staff.

  The present invention aims to overcome these drawbacks

  vantages. It proposes a servo device for transferring quickly and with small oscillations a suspended load comprising:

  at least one guiding means on which

  a movable carriage in translation actuated by a motor, which is hooked a cable (or rod) at the other end of which (of which) is suspended said load to be transferred;

  at least one position sensor for detecting

  keep the position of the truck in relation to

  determined point, and to provide a so-called positive

corresponding to this marking.

  The present invention is characterized in that said device comprises: an angular sensor disposed on the carriage, intended to measure the value of the angle formed by the cable or the rod relative to the vertical, and to provide

  a so-called angular signal corresponding to this measurement.

  re; a first servocontrol loop comprising: a first comparator intended to provide the angular difference between the angular signal thus determined and an angular value of

  predetermined reference, by means of a model

  the reference, depending on the destination

  load and speed of transmission.

the desired section;

  a proportional corrector for multi-

  fold the gap thus determined by a

aunt fixed in advance;

  a second servo-control loop known as a posi-

  comprising: a second comparator for providing the difference between the position signal and a

  predefined theoretical reference position

  born by the same reference model, based on the same data; a proportional and integral corrector intended on the one hand, to multiply said gap by a predetermined constant and on the other hand, to integrate said gap with respect to time over a predetermined interval; a summator, respectively connected to the output of the proportional corrector, the proportional and integral corrector and an amplifier for amplifying the value of the reference speed, also determined by means of said reference model, according to the same data, the said summator being intended to summon

  values from these outputs to deliver a

  general capable of operating the control motor of the truck.

  In other words, the present invention is

  characterized in that the load transfer device is provided with two servo loops connected on the one hand to sensors respectively measuring the angle formed by the cable or the rod relative to the vertical and the position of the carriage , and on the other hand to the organ of

  control of the motor actuating the carriage, the servo-

  based on the values determined by a reference model taking into account the speed

  desired and load transfer point.

  According to the present invention, the reference values

  rence determined by the so-called reference model, namely the angular position, the speed and the position, come from the following law: r = e "(lo + vt) + 2ve '+ go oe, 6' and 8" designate angle, angular velocity and angular acceleration, respectively, g means the acceleration of gravity, lo the initial length of the cable (or rod), v the constant speed of variation of the cable length (or the stem), and r

the acceleration of the carriage.

  In a particular case of the present invention, for which the length of the pendulum defined by the load does not vary, the reference values determined by the reference model come from the following law: r = e "lo + ge Advantageously, in practical: - the trolley is mobile in direction on a first

  rectilinear guide means, itself mobile in transla-

  on a second rectilinear guide means, coplanar

  in a direction perpendicular to that of said first guide means, said second guide means being actuated by means of a motor also controlled by means of two control loops (in

  position and angle) of the same nature as those

  described for the movement in direction, the

  service being a function of a reference model which is specific to said engine; - the carriage is mobile on a traveling crane; - The carriage is movable in a radial movement on a first guide means, itself movable in rotation by means of a rotational member, actuated by means of a motor also controlled by means of a servo-control loop. function of a reference model which is also proper to it;

  - the carriage is movable along the horizontal arrow

zontal of a crane;

  the servo calculations are carried out approximately

  twenty times per second by means of a calibration

digital ass.

  The way in which the invention can be realized and the benefits derived therefrom will emerge more clearly from

  examples of implementation which follow, given as

  dicative but not limiting, in support of the figures

  secured. Figure 1 shows a transfer trolley

guided by a unidirectional rail.

  FIG. 2 represents the same carriage that can move in two different directions and

  coplanar, such as a traveling crane.

  Figure 3 is a diagram showing the displacement

  the load plan by means of an overhead crane, in

according to the present invention.

  FIG. 4 shows a crane equipped with its load that can also move in at least two

  different directions and coplanar.

  FIG. 5 is a graph showing, with respect to each other, the characteristic curves of the acceleration, speed, angle and position communicated to the carriage respectively according to the reference model in accordance with FIG. invention for a fixed length of the pendulum defined by the load, corresponding to the

initial length l1.

  Figure 6 is a diagram of the function principle

  ment and servo the device according to the invention.

  Figure 7 is a schematic diagram of the deter-

  reference values by means of the model of

  reference according to the present invention.

  Figure 8 is a graph representing two

  curves facing each other correspondingly

  the angular variation and the position of the load as a function of time, the length of which varies during the transfer, the hoisting apparatus to which

  suspended the load being controlled according to the invention.

tion.

  Figures 9 and 10 show a corresponding curve.

  to the acceleration signal provided by the reference model to the hoisting apparatus to which the load is suspended, in which, respectively, the length of the pendulum constituted by the load varies until the end of the

  transfer, or is stopped before the end of it.

  The device according to the invention is all

  first be described in the case of a correct displacement

  unidirectional line of a load (5) (see Figure 1), suspended by means of a cable (4) to a carriage (1). The carriage (1) moves on rails (2) by means of a motor not shown. The carriage (1) further comprises a winding cylinder (3) capable of varying the

height of the load (5).

  The motor causing the displacement of the carriage (1) is a variable speed motor, whose speed is controlled by a device commonly called "electronic speed variator", on which a speed reference defined by a voltage applied between two points is applied. , said voltage being proportional

at this speed.

  During the displacement, the suspended load (5) has an angular deflection 8 with respect to the vertical. In a very well-known way, the theory gives as value of the period oscillations:

T = 2T4

  \ rg o g is the acceleration of gravity and 1 the length

of the pendulum.

  The carriage (1) has a not shown angular sensor, located in the vertical plane defined by the movement, and intended to measure the angle e. This angular sensor of the potentiometer type is well known for

this application.

  The device according to the invention also has

  a sensor of the actual position of the truck on

  the rails (2) with respect to a pre-existing position

  determined. This sensor, not shown, can be constituted

  killed by a rack secured to the rails (2), on

  which engages a digital coder in solidarity with the

  riot (1). In this way, the actual position of the trolley

  is precisely defined and known instantly.

  In order to limit the oscillations of the load

  hanged (5) during the transfer while performing it at a predetermined bearing speed by the operator, the actuating motor of the carriage (1) is doubly enslaved. The actual position measured as before

  described, is compared to a specific reference position

  mined using a reference model that will be described

  later. The difference obtained in a comparison

  (20) is then subjected to a treatment at the level of

  a proportional and integral corrector (21). This treatment

  in the known way, on the one hand to multi-

  bend the difference thus obtained by a predetermined constant

  It is a function of the characteristics of the system, and on the other hand, to add to this value the integral with respect to the time of said positional deviation, the output signal of said corrector (21) being of the form: K, (pos. ref.pos.range) + K2 {t (pos.ref.- actual pos.) dt

  o K, and K2 denote the said predetermined constants

  born. Similarly, the actual measured value of angle 8 that

  form the suspended load with the vertical, is also

  compared by means of a comparator (22) with a

  reference angle also determined by means of the model

  the reference. The angular deviation thus determined undergoes a treatment in a proportional corrector (23). The

  treatment followed in the proportional corrector con-

  is a simple multiplication by a predetermined constant also depending on the characteristics of the

  system of the value of the said gap.

  The two values thus determined,

  correctors (23) and (21) are added together in a

  mateur (24) at a third value corresponding to the

  reference speed from the reference model, la-

  what is previously multiplied by a constant

in the amplifier (25).

  The signal from the summator (24) is then converted into an analog signal by means of a digital converter (not shown) and transferred to the actuating motor of the carriage (1). The two loops

  enslavement are thus fully described.

  Advantageously, the comparators (20,22)

  as well as the two correctors (21,23) and the amplification

  (25), as well as the summator (24) and the conversion

  digital weaver, are concentrated in the same electronic processing card. The said card is

  managed by means of a microprocessor capturing the measurements

  angle and actual position as well as

  servo some twenty times a second. In this way, the possible oscillations of the load are rigorously controlled and immediately compensated

  by said servo loops.

  The same device is applied as part of a plan transfer. As can be seen in Figure 2, the carriage (1) moves in the direction (Y) on the rails (2), the latter moving themselves in translation (X) coplanar and perpendicular to the direction (Y) of the carriage (1). The rails (2) integral with each other are

  guided on straight rails (6).

  The device according to the invention involves a

  displacement of the load in a vertical plane,

  shown in Figure 3. In this way, the movement

  of the charge results from the component of two

  in translation, on the one hand, in the direction of another

  share. The operator himself defines the speeds in

  bind for each of the movements V. and V ,. According to the spaces to be traversed Px and P., the respective times Px / vx and P, / Vy. are not necessarily equal. The slowest motion imposes its law on the resulting motion and in fact, the speed of the second is adjusted to achieve the movement at the same time and thus have a synchronization of the two movements which results in a movement located in a vertical plane. Going through

  the starting and ending points of the load.

  The two movements according to (X) and (Y) are independent

  and virtually decoupled, especially for the assertion

  other than that speeds are cal-

  beforehand in order to obtain a displacement according to

  a fixed vertical plane containing the two points of de-

  part and destination of the load.

  This results in two laws of simul-

  tended, one along the X axis, the other along the Y axis.

  each corresponds to a reference model and an asser-

  vissement. The microprocessor performs the calculations for both at each time period, that is, about twenty times per second. In this way, there are two control loops for each of the two components of the movement, respectively a position control loop in combination with a position sensor, and an angular control loop in association with an angular sensor. So there are finally four

servo loops.

  In this embodiment, the angular sensors

  are located in two perpendicular planes, namely one defined by the vertical plane of translation,

  and the other by the vertical plane of direction.

  In another embodiment, the device is suitable for transferring a suspended load to a crane (see FIG. 4). In known manner, the movements of a crane are respectively radial along the bearing beam (10) and circular around its pivot axis (11). As in the two previous cases, the displacement of the load is carried out according to a vertical plane, of the position P. located at the distance R. of the pivot axis, and forming an angle a, with respect to the axis of reference OX, at a position P2, distant from the pivot axis (11) by a distance R2, forming with

  the reference axis OX an angle a2. In this way, this

  placement in a straight line requires first to calculate in the Cartesian space OX-OY the equation of the said straight line, to determine in projection on the axes

  OX-OY the laws of motion with reference models

  this and servos as before, and then retransform the Cartesian equations into equations

  polar respectively corresponding to the cir-

  eyelike and radial movement. In fact, the microproces-

  therefore simply performs an additional step

  of Cartesian coordinate transformation in coordi-

  Polar data using an appropriate converter. It will be described now in more detail the

  reference model according to the present invention.

  In the different stages of calculation that will follow, we will assimilate the suspended load to a simple pendulum

of mass m.

  g represents the acceleration of gravity; lo the initial length of the pendulum; v the constant speed of variation of the length of the load support; e the angle of the cable with the vertical;

  r the acceleration of the point P representing the chain

  riot. The pendulum theory, sufficiently well known not to be further developed here, makes it possible to arrive at LAGRANGE's theory with the following expression: ## EQU1 ## where the symbols 'and' represent respectively the first derivative and the second derivative of the variable

  corresponding to time.

  The angle e with respect to the vertical remaining

  weakly, it is reasonable to linearize this equation with respect to e: 21'e '+ the "+ ge = r The variation of 1 is assumed to be linear from lo, so we can write: 1 = lo. + vt d finally, the following expression: e "(lo + vt) + 2ve '+ ge = r (Q) which corresponds to a variable linear differential equation. In the simplest case where the length of the pendulum remains constant, and using the transform

  from LAPLACE to solve the previous equation, we find

  ve for a constant acceleration r, the oscillation period T of the pendulum is equal to: T = 2 \ g These different results are listed in figure 5 in which the curve I represents the constant acceleration r, the curve It represents the variation of the speed, the curve III represents the variation of the angle and finally, the curve IV that of the position and this, for different phases, respectively

  phase A of speed up, phase B which corresponds to

  a step corresponding to the maximum speed, and

  the phase C corresponding to the descent in speed. Lake-

  r is constant for a time T equal to the pendulum period and the deceleration of the same value for the same duration. In fact, the other three curves II, III and IV are deduced. As we can see, for a constant acceleration, the rise in speed

  is linear. On the other hand, when the acceleration stops

  eg, we get a speed stop. Similarly, the deceleration

  ration being constant, we observe a descent of

  symmetrical pitch relative to the climb.

  The position curve is obtained by simple inte-

  that of speed versus time.

  The value of the angle is a sinusoidal function of time, which vanishes during the bearing and becomes symmetrical during deceleration from its

  value during the acceleration phase.

  For each movement, the operator sets the system data which are: the predetermined value of the step speed of the carriage; - the length of the pendulum;

  - the coordinates of the arrival point.

  These three data make it possible to calculate the three

  references as a function of time, respectively the

  of the carriage v, the deflection angle e and the posi-

  In fact, the law is thus perfect-

  defined by this reference model. If the clock

  is perfect, correctly identified, if the engine action-

  the trolley does not have a dynamic and that its gain is

  equal to 1, and in the absence of disturbance, the

  The real pendulum is that of the reference model.

  However, because of the observed and measured differences between reality and theory, we associate with the model a servo, whose operating principle is

shown in Figure 6.

  The enslavement applied to the motor makes it possible

  check the values defined by the reference model to arrive at a zero angular deflection at the point of arrival of the load by correcting the differences between the theory and the reality. In addition, the effects of possible disturbances are also attenuated, for example oscillations of the departure during the taking of

  unforeseen load and shocks during transfer.

  As already said, the microprocessor performs the various calculations about 20 times per second in order to readjust each time the speed reference value.

of the cart.

  Servoing at the end of the movement is maintained

  until the position is reached with the tolerance

  required and that the oscillation be cushioned for

  reach a maximum value within the required tolerance.

  In the general case where the length of the pendulum is

  variable, for example to avoid an obstacle, the assertion

  This remains the same, but the reference model is slightly more complex. The starting point becomes the equation seen above referenced 5: e "(lo + vt) + 2ve '+ ge = r (Q) The principle of the command is to generate an acceleration law r such that the behavior of the pendulum

  constituted by the load is that of the pendulum of lon-

  constant lo. It then becomes possible to use

264-5846

  the device described in the case of the control of a pendulum of constant length. The variable linear terms are then compensated by generating a command of the type: r = Tp + compensation terms

  the term Tp will be defined later.

  The terms of compensation are functions of the variation of the length 1 of the pendulum and make it possible to

  transform the pendulum of variable length into a

* dule of constant length lo whose period is: T = 2ng The compensation terms are taken from the reference model already used in the case of the constant-length pendulum, this model thus giving e '=. f, e "= f

by drifting 8.f.

  The rise of the load begins at the same time as the translation of the carriage, but because this rise can end either during the speeding up of the carriage, during the landing, or even during the deceleration, five different cases can occur. to present oneself

  for which the above equation is written differently

  is lying. The following example illustrates a particular case of

  variation in length of the pendulum, but it is well

  tense that we can generalize this type of calculation to

  any type of length variation.

  1 / During the speeding up of the carriage and while the length of the pendulum varies with a speed v, the control equation becomes:

r = "e.f.vt + 2v '=. + rp-

  for t 5 T or t t, t. representing the time of

  variation of the length of the pendulum.

  Equation n then becomes: -e "lo + ge = 1x in the case where '= $' =. Z and e8" = = 2 / During the setting of the carriage speed and after the variation of the length of the pendulum (if this one is different from lo), the command becomes: r = e "=. (l - lo) + TE for t_. t ET and 1, final length of the pendulum in Equation Q then becomes:

e "10o + ge = Tp if 8" = =.

  3 / During the landing and whatever the variation

  If the length of the pendulum varies with a speed v ', the control is given by: r = e "=. f. v't + 2v'e '= ú + e "= o0 (l. lo) + Ti after translation of the time origin in t = td,

  start of deceleration time.

  The equation Q which is worth in this case: 8 "(l1 + v't) + 2v'e '+ ge = r then becomes: e" 1o + go = 1. if O "= e", ._ and e = '= .e / During the deceleration of the carriage and while the variation of the length of the pendulum is stopped in: t = td + t' and that it is equal to lo + vt. + v't '., the command is given by: r = e, ",,. (vt. + v't'.) + T the equation Q then becomes: e" 1o + ge = Ts if eOf = The position reached at the end of the trajectory is given by the double integral of r. From the result of this calculation, just choose the constant r. so that the position reached at the end of the trajectory is that desired. For example: if v = V from 0 to t. with T. = T. and v '= -V from td to t'. + td with t '. = T. we show that: Tp _ V = f.max T + V (cos2TT - 1) g T For T. = T or T ,. > T, there is no change from the constant length pendulum: TP = Vmx

T

  The reference model corresponds to the one represented

  Figure 7, which summarizes the five cases

  tories previously, and for which the functions f

  and h depend on the situation considered to be

  be the table below, in which v denotes the rate of rise of the pendulum, that is to say the rate of decrease of the length of the pendulum, and v 'its speed

downhill.

  interval t function f function h 0 Ot te. vt 2v t_ S t T 1 - lo O t 5 t td 0 0 td tetd + t '. 1. + v '(t + td) 2v' t, + t'.5tEtd + T vt. + v't '0 The functions f and h are respectively homogeneous

  to a length and a speed, which multiplied

  by an angular acceleration e "and a speed

  angle, then become homogeneous at a

  lération. The following expression, schematized in FIG. 7, then constitutes the compensation terms mentioned above, associated with the value of: h.8 '+ fO ": compensation terms Thus, according to FIG. reference for a linear pendulum of length lo (30) determines the values 8 =, m, '1..f and e "= f. The modules (31) and

  (32) respectively determine the values of the

  h and f, depending on the different phases of the

  load transfer. The functions f and h thus de-

  are then multiplied respectively to "= Z, and e '=., the expressions thus obtained being then summed and added to the value of rp by means of an adder (33), the said value of zp being calculated beforehand according to the destination position

of the charge.

  In this way, the output signal of the summator (33) corresponds to the value of r, ie to the signal

  acceleration communicated to the load, through

  of the lifting device. The value of r is correct

  averaged 20 times per second, in order to

  on the one hand, any possible disturbances

  tible to intervene during transfer, and secondly, according to the different phases of transfer. The signal r is successively integrated twice, by means of the integrators (34) and (35), in order to give

  the values of v = .f and the reference position.

  Advantageously, all the integrators

  and summers is integrated within the same microproces-

  calculating the reference model.

  FIG. 8 shows an example

  - the consequence of the enslavement on the oscilla-

  angle as a function of time in the form of a curve. In order to better reflect the different phases of the transfer, the curve representative of the position is also shown next to this curve.

  the load during its transfer as a function of time.

  There are clearly three successive phases

  sive, respectively corresponding to the acceleration at the beginning of the transfer, generating a relatively small amplitude oscillation (the ordinate scale is graduated in radians), said amplitude being rapidly damped by means of the servocontrol. We then move on

  at a phase of almost negligible oscillations, cor-

  responding to the phase at landing speed. Then a new

  the phase of greater inverse amplitude, corresponding to

  when deceleration occurs. The point of destination of the load is then reached. In fact, there is a

  additional phase, following the passage of the

  by the final position, during which it is

  subjected to the servitude described above, so that

  to dampen the residual oscillations.

  FIGS. 9 and 10 show as curves two acceleration signals r provided

  to the lifting device and resulting from the treatment

  described above, on the one hand, in the case where the duration of variation of the length of the pendulum defined by the load corresponds to that of the transfer, and secondly, in the case where this duration is less than the duration of transfer . As can be seen, in the first case, during the acceleration and deceleration phases, the corresponding signals are generally symmetrical, the phase

  constant speed generating of course a zero signal.

  On the other hand, in the second case, for which the variation of the length of the pendulum is interrupted

  during the deceleration phase, the appearance

  a bearing in the signal r, corresponding to the signal applied in the case of a pendulum of length

  constant, as shown in Figure 5.

  Thus, the device according to the invention makes it possible to obtain systematic stabilization and

  rapid oscillation and other disturbances

  tible to cause oscillations during the trans-

  of a suspended charge. The double servo both angular deflection and position is therefore

  particularly suitable for any load transfer

  hanging, especially in the context of activities requiring special precautions, such as for example the nuclear industry, etc.

Claims (7)

  1 / Device for automatic control of the posi-   and oscillations of a suspended load during its transfer by a hoisting apparatus comprising: - guiding means (2,6) on which moves a carriage (1) movable in translation actuated by a motor, which is hung a cable (4) (or a rod) at the other end of which (from which) is suspended the charge to be transferred (5); a position sensor, intended to permanently mark the position of the carriage (1) with respect to a given point and to supply a so-called position signal corresponding to this marking, characterized in that it comprises: an angular sensor, disposed on the carriage (1), for measuring the value of the angle e that forms the   cable (or rod) in relation to the vertical and   a so-called angular signal corresponding to this measurement.   re; a first servo loop comprising:   a first comparator (22) for   the angular difference between the angular signal   thus determined and an angular value   predetermined reference point by means of a   reference model, depending on the   determination of the load (5) and the desired translation speed; a proportional corrector (23) for multiplying the difference thus measured by a predetermined constant;   a second servo-control loop known as a posi-   comprising: a second comparator (20) for providing the difference between the position signal and a   predefined theoretical reference position   born by the same reference model, based on the same data; a proportional and integral corrector (21) for, on the one hand, multiplying said deviation by a predetermined constant and, on the other hand, integrating said deviation with respect to time over an equally predetermined interval; an adder (24), respectively connected to the   output of the proportional corrector (231   portionnal and integral (21) and amplifier (25)   intended to amplify the value of reference speed   this also determined by the so-called reference model.   according to the same data, said summator (24) being intended to sum the values from these outputs to deliver a signal able to actuate the   motor (26) for controlling the carriage (1).   2 / Servo-control device according to larevendica-   1, characterized in that the reference values determined by the reference model, namely the angular position, the speed and the position, are derived from the following law: r = e "(lo + vt) + 2ve ' + ge by successive integration, oe, e 'and e "designate   the angle, the angular velocity and the   angular celeration, g denotes the acceleration of gravity, lo the initial length of the cable (or rod), v the speed of variation of the length of the cable   (or rod), and r acceleration of the carriage.   3 / servo device according to the claim   2, characterized in that the length of the pendulum   defined by the load is constant, the reference values   the reference model determined by the reference model   following the following law: r = e8 "o + ge 4 / Servo-control device according to one of the   Claims 1 and 2, characterized in that the carriage   (1) is movable in a direction on a first means of guiding   rectilinear tread (2), itself movable in translation on a second rectilinear guide means (6), coplanar but in a direction perpendicular to that of said   first guide means, said first means of guiding   being operated by means of a motor also   served by means of two servo loops respec-   in position and angle, depending on a model   the reference of its own.   5 / servo device according to the claim   4, characterized in that the carriage (1) is movable on an overhead crane.   6 / servo device according to the claim   1, characterized in that the carriage (1) is movable in translation on a first guide means, itself rotatable by means of a rotational member, actuated by means of a motor also controlled by the intermediate two servo loops according to a reference model which is also clean.   7 / Servo-control device according to the claim   6, characterized in that the carriage (1) is movable   along the horizontal arrow (10) of a crane.   8 / Servo-control device according to one of   preceding claims, characterized in that the   servo calculations are performed around twenty   times per second, by means of a numerical computation than.