FR2498268A1 - ELECTRO-HYDRAULIC ROBOT POSITIONING SYSTEM - Google Patents

Abstract

AN ELECTRO-HYDRAULIC CONTROL INCLUDES A CLOSED LOOP HYDRAULIC SYSTEM WITH A DISCHARGE SIDE AND A RETURN SIDE. AN ALTERNATIVE PUMP 50 DRIVES HYDRAULIC FLUID UNDER PRESSURE THROUGH THE SYSTEM AND ONE OR MORE HYDRAULIC ACTUATORS 60, 62 ARE ACTUATED BY THE HYDRAULIC PRESSURE OF THE SYSTEM TO PERFORM USEFUL WORK. A 58 VALVE ARRANGEMENT DIRECTS THE HYDRAULIC FLUID BETWEEN THE PUMP AND THE DISCHARGE SIDE OF THE CONTROL SYSTEM ALSO THE MOVEMENT OF THE HYDRAULIC ACTUATORS IN ACCORDANCE WITH THE PARTICULAR OPERATION TO BE CARRIED OUT ON A PART. AN ACCUMULATOR 82 AT THE RETURN SIDE OF THE SYSTEM MAINTAINS A PREDETERMINED MINIMUM PRESSURE THEREIN AND COMPENSATES FOR VARIATIONS IN THE VOLUME OF THE HYDRAULIC FLUID AT BOTH SIDES OF THE SYSTEM WHICH OCCUR WHEN CERTAIN OF ITS COMPONENTS ARE ACTIONED.

Description

1. The present invention relates to electro-

  improved hydraulics intended primarily for use with robots of a type comprising

  one or more part actuating elements.

  The robot described in the United States patent

  of America No. 3,406,837 of October 22, 1968 is a robot ty-

  spike with which the system of the present invention can

to be used.

  In short, the control system of the present invention comprises a plurality of hydraulic actuators, each intended to be actively connected to a part actuating means of the robot and capable of operating in

  walks so as to give different movements to the element

  or to the parts actuator elements. More specific

  a closed-loop hydraulic circuit includes

  both the discharge and return sides are connected to the ac-

  hydraulic actuators, and a pre-actuator

  ference through an appropriate speed reducer

  property is connected to the piston of a power cylinder re-

  linked itself to a part of the hydraulic circuit to which it

  belongs, and works as a hydraulic pump to drive

  ner the hydraulic fluid in the circuit. A means of cla-

  reversing pet mounted in the hydraulic circuit between the cylinder and the hydraulic actuators directs the fluid

  hydraulic during pumping always towards the pressure side

  2. load the circuit and the control valves mounted in the

  circuit operating in association with the actuators -

  hydraulics control the operation of the latter in response to certain system operating conditions so that the hydraulic actuators can be main-

  held stationary or be selectively operated, indi-

  by vacuum and in a predetermined order to move the part actuation means of the robot in accordance with a predetermined program. An appropriate means such

  a piston type accumulator is connected to the side

  turn the hydraulic circuit to maintain a pressure

  predetermined hydraulic pressure within the circuit and

  to take into account variations in the quantity of hy-

  hydraulics in the return side of the system occurring in

  works for one reason or another, for example following

  the displacement of the hydraulic actuators.

  An important object of the present invention is an electro-hydraulic servo control system for robots.

  and the like which is more efficient than

  vo existing and which operates at sensitive sound levels

significantly lower.

  Another object of the present invention is a system

  electro-hydraulic servo control valve that works

  by positive displacement of the hydraulic fluid in the system

  teme, which is capable of producing relatively pressure

  high in the hydraulic part of the system so as to

  secure controllable movements with precision and ease

  of the parts for actuating the robot part and in which the pressure can be easily regulated by a

  selective operation of the servo actuator.

  Another object of the present invention is a

  electro-hydraulic servo control system of the above type

  tee above in which the temperature of the hydraulic fluid

  that in the system remains relatively low as a result of the

  lack of turbulence in the rest position, particularly

  typical of hydraulic vane type pumps used

  generally read in existing systems.

3.

  More particularly, the control system using

  vo of the present invention is provided for positioning a mechanical load during manipulation by the robot at

  by means of a robot actuator in response to digital commands

  risk. The system is specifically designed to use a contactless digital tree encoder in conjunction with a control logic circuit to develop position information back. A circuit said

  Completely symmetric oxide-metal semiconductor CMOS

  can be used in the control unit to reduce power consumption and clearance

  heat. The mutual relationship between the various components

  system health is such that the connection can be simple by limiting the order of orders to a minimum number of entries. Control orders can be generated by computer, by digital control logic

  or by closing electro-mechanical contacts. The action-

  electromechanical servo neur for the system preferably includes a permanent magnet, a DC motor, a speed measuring tachometer and a shaft encoder giving position information,

  as well as an amplifier and an external power supply.

  These components constitute a means of positioning

  full system and action item (s)

robot part.

  The present invention will be well understood during

  the following description made in conjunction with the drawings

  attached in which: Figure 1 is a block diagram of a servo control system according to the present invention;

  Figure 2 is a schematic view of a means of ac-

  servo actuator which is part of the

  command of Figure 1, representing more particular-

  how the electro-hydraulic actuator

  lique proceeds to pump the hydraulic fluid into the

  hydraulic circuit, and also representing a plura-

  lity of hydraulic actuators incorporated into a part of the 4. circuit connected to the part actuation means with which the robots of the type involved in the present invention are conventionally equipped; Figure 3 is a schematic representation of the hydraulic circuit which constitutes part of the electro-hydraulic actuator means shown in Figure 2; and Figure 4 is a schematic representation

  in greater detail of the electric servo drive means

  tro-hydraulic for hydraulic motors that make

  operate the robot part actuating elements.

  Firstly in connection with FIG. 4, we have

  shown a conventional reversible servo motor 10, with

  continuous rant, which comprises a drive shaft 12 connected to an externally threaded shaft 14 by a coupler

  16. The motor 10 and the shaft 14 are kept stationary.

  res in the longitudinal direction in an appropriate way or

  classic, but the shaft 12 and the screw 14 as well as the

  connecting beam 16 are mounted so that they can rotate freely. In this regard, it will be observed that the tree 14 is

  shown here as being supported by a pair of pa-

  liers 18 and 20 located at a certain distance from each other

  be. A nut 22 is engaged in the screw 14 and is fixed by screws 24 to a suitable carriage 26, which is in turn supported in sliding by bearings 28 and 30 on a guide rod 32 itself mounted in supports

extremes-34 and 36.

  When running, the rotation of the motor 10 has ef-

  fet to drive the screw 14, which causes the displacement of the nut 22 either to the right or to the left of

  the figure according to the direction of rotation of the screw. Preferably

  rence, the screw 14 and the nut 22 are in the form

  of a conventional ball nut so as to minimize the re-

  friction resistance braking the movement of the nut on the shaft, as well as the losses of movement between these

  two elements. The carriage 26 moves on the guide rod.

  dage 32 at the same time as the nut 22. It will appear that 5. the preceding mechanism is capable of animating the nut 22 and the carriage 26 with a back and forth movement on the shaft 14 and that it thus acts as a means of transmitting movement

  of rotation of the drive shaft 12 of the motor in

  alternating rectilinear carriage 26 as well as in

  speed driver generally represented by the reference

  ce 37 so as to move the carriage at a speed

  stroke slower than the motor drive shaft 12.

  Mounted on the carriage 26 with which it is mo-

  bile, there is a support 38 having the general shape of a

  U whose two arms 40 and 42 are connected to the two parts

  ties 44 and 46 of the rod of a piston 48 with double rod which

  is mounted so as to be animated by a back-and-forth movement

  comes in a fixed cylinder 50. From the above, it will easily appear that the support 38 moves with the carriage 26 and at the same speed as the latter and that, during its movement, it actuates the piston 48

  to animate it back and forth in the cylinder

  dre 50. In Figure 4, the parts just discussed

  tion are shown in solid lines, the piston 48 being

  located approximately in the middle of its interior race

  cylinder 50. The extreme position of the support 38

  on the left of figure 4 is represented in 38a and its po-

  extreme position on the right of this figure in 38b. The race

  support 38 to the right and to the left is com-

  commissioned in normal operation by a representative controller

  schematically felt in 200 in FIG. 1 according to the

  instructions from a computer shown in 192, and the extent

  due to the course of the support is adjusted according to the requirements of the particular situation by modification of the computer program. However, it is envisaged that the piston 48 does not move over the total distance allowed by the cylinder 50 and two limit switches 52 and 54 are placed in the actuator control circuit 10 so as to reverse its direction of rotation to have security in the event of too large a stroke,

  the support 38 coming for one reason or another in connection

  6. tact with limit switches 52 and 54 to

  the extreme limit of its course in one direction or the other.

  The piston 48 and the cylinder 50 define

  seems a pump 55 which constitutes a part of a closed loop hydraulic circuit in which conduits 56 and 57 extending at the opposite ends of the cylinder 50 make it possible to communicate the chambers of the cylinder situated on each side of the piston 48 with an arrangement with valves or valve circuit shown schematically in

  58 in figure 4. The circuit 58 directs the hy-

  pump 55 to hydraulic actuators and 62 of one or more movable part actuators which constitute a part of a robot or the like as described above. As suggested, it is expected that the

  electro-hydraulic control system of this in-

  vention is used with a mechanical robot and that the hydraulic actuators are connected to one or more moving parts of the device such as, for example, a

workpiece transfer arm.

  The hydraulic actuator 60 shown here at half

  tre illustration is a rotary actuator comprising a cylinder 64 in which is mounted a rotary shaft 66 in the axial direction. A fixed radial fin 68 extending from the cylinder 64 towards the shaft 66 separates the cylinder into two chambers 70 and 72, and a fin 74 fixed to the shaft 66 with which it rotates and extending radially towards

  the cylinder drives the shaft and, whatever the par-

  attached robot, move it either in the direction of

  clockwise either counterclockwise

  watch faces according to whether one of the chambers 70, 72 is connected to the discharge side of the hydraulic circuit by

the valve circuit 58.

  The hydraulic actuator 62 is an actuator of different shape which comprises a cylinder 76 enclosing a piston 78 mounted so as to be driven back and forth with a piston rod 80 extending from one end of the cylinder . Typical use of 7. hydraulic actuator 62 in robots of the type including

  it was discussed above would be that the rod 80 action-

  does a moving part of the robot in an alternating movement

  tif. The mobile part of the robot which has been discussed with regard to the two hydraulic actuators 60 and

  62 can constitute the same set or two different sets

  famous. In the robot object of the patent of the United States of America naked 3.406. 837 mentioned above, the transfer arm with elevation and rocking movement having in this patent the reference 70 constitutes a typical arrangement of part actuator of the type represented here in and 62. The arm 70 is provided for lifting and swing a vacuum vase shown in 74 in the patent and, in adapting the control system of the present invention to the patented device, an ordinary mechanic

  can easily attach the piston rod 80 of the action-

  hydraulic neur to the arm 70 or to one of its adjustment members so as to cause the arm to be raised, and it

  will also be easy for an ordinary fi-

  fix the shaft 66 of the hydraulic actuator 60 to the arm 70 or to one of its auxiliary members so as to give

  a rotation or rocking movement on the arm. However

  However, in connection with the above, it will appear easy-

  ment that, while a pair of actuators driven in a rotary and reciprocating motion are shown here by way of example, any number of actuators or combinations of actuators of any type may be used in the system of the present invention and it is also contemplated that the system will be used in any environment or situation where such circuits

command have their utility.

  During operation, the piston 48 of the pump 55 drives the hydraulic fluid under a relatively high pressure in the closed-loop hydraulic circuit during the

  two piston strokes. Thus, when the piston 48 comes off

  place to the left of Figure 4, it forces the fluid 8.

  pressurized hydraulics to enter line 56.

  By cons, when the piston 48 moves to the right of Figure 4, the pressurized hydraulic fluid is entrained-in line 57. It is important for the operation of the electrohydraulic control system

  of the present invention that the hydraulic circuit with bou-

  closed key has a discharge side where the hydraulic fluid

  that flows to the part actuators, shown

  here as an example in 60 and 62, and that the hy-

  hydraulics has a return side where the hydraulic fluid

  is routed from the actuators to the pump.

  It is also important that the com-

  Mande of the present invention comprises an accumulator used to maintain a predetermined minimum pressure in the return line of the hydraulic circuit and to compensate for the variations in volume of the hydraulic fluid in the line which occur when piston actuators of the type shown in 62 are used. In this

  regard, a piston type accumulator 82 is shown

  tee as being connected to the return side of the hydraulic circuit

  only via a line 84. The accumulator 82 comprises a cy-

  lindre 86 in which is mounted a floating piston 88 li-

  sharply. Hydraulic fluid from the return side of the circuit can flow freely in line 84 to enter the part of cylinder 86 located above

  piston 88 and out of it, so that the fluid is

  Vant in the upper part of the cylinder 86 is subjected to the same pressure as the fluid located in the return side of the circuit. An inert gas such as nitrogen or the like is supplied from an appropriate source by a

  inlet pipe 90 to the part of cylinder 86 located above

  below the piston 88. The gas pressure in the lower part of the cylinder 86 can vary as a function of the pressure of the hydraulic fluid in the return side of the hydraulic circuit. A gas pressure of around 3.5 bar is suitable in most cases, but it will appear

  easily than for a particular installation the pres-

9.

  be significantly higher for the purpose of maintaining

  nir the piston 88 in a substantially middle position inside the cylinder 86 so that the gas from the cylinder

  serve as a shock absorber on which the piston 88 is supported when

  that the hydraulic pressure increases in the circuit and which

  pushes the piston to the top of the cylinder when the

  The hydraulic fluid in the circuit decreases.

  In the control system shown in FIG. 4, the hydraulic fluid goes from the valve circuit 58 to the part actuator 60 or circulates in the other direction,

  opposite sides of the fixed fin 68 passing through the

  picks 92 and 94, and this takes place independently of the

  culation of the fluid towards the actuator 62 or coming from the latter. Likewise, the hydraulic fluid flows from circuit 58 to actuator 62 or returns therefrom via lines 96 and 98 situated on opposite sides of piston 78 independently.

  of the actuator 60. It is envisaged that in operation the circuit

  baked with valves 58 works so as to connect selectively-

  ment the discharge side of the hydraulic circuit to one or other of the lines 92 and 94 which supply the actuator 60. Similarly, it is envisaged that the valve circuit 58 operates so as to convey the hydraulic fluid from the discharge side of the circuit to the actuator 62 selectively via one or the other of the

  lines 96 and 98. Obviously, if a hydraulic fluid

  that at high pressure is supplied to the actuator 60 via line 92 while line 94 is connected to the side

  return of the hydraulic circuit, the movable fin 74 is released

  will place counterclockwise inside the cylinder 64 as seen in the drawings, and if the relatively high pressure hydraulic fluid is supplied to the cylinder 64 on the other side of the fixed fin 68 in similar circumstances, the movable fin 74 will move clockwise. In the supposed US patent robot installation

  America No. 3,406,837 previously discussed

  ment by way of example, the fin 74 has the effect of tilting the transfer arm 70 of this patent either to the right or to the left depending on its direction of movement. Likewise, in this installation, the piston 78 and its rod 80 advance or retreat in the cylinder 76 depending on whether a high pressure hydraulic fluid is introduced through the line 96 or through the line 98. However, whatever in itself, the displacement of the piston rod can be used either to raise or to lower the transfer arm 70 represented in this patent by a

  appropriate handling of the valve of circuit 58 which controls

  the flow of hydraulic fluid to lines 96 and 98.

  Figure 2 shows a semi-

  connectable to the system shown in Figure 4 but intended for

  serve three hydraulic actuators shown diagram-

  matically at 100, 102 and 104, which are all actuators of the piston type shown at 62 in FIG. 4. In addition, in FIG. 2, each actuator on 100, 102 and 104

  is shown schematically as being connected to ac-

  separate part holders 106, 108 and 110, respectively.

  In the modified control system of Figure 2, relatively high pressure hydraulic fluid is supplied

  alternately to the valve circuit 112 by conduits

  tes 56 and 57 as in the case described above in the present invention. In addition, the circuit 112 is modified to take account of the three hydraulic actuators 100,

  102 and 104. Furthermore, the two control systems

  presented in figures 2 and 4 are identical and work

in the same way.

  We will now refer to Figure 3 which

  schematically shows a typical circuit of valves 112 for three room actuators. It will appear easily

  on reading the detailed description of circuit 112

  how this can be changed to give an agency-

  ment such as the arrangement shown in 58 of FIG. 4 which only serves the two hydraulic actuators 60 and

  62. Similarly, it is believed that it will also appear at the

11.

  description of circuit 112 how it can be modified

  trusted to service just about any number or type of hydraulic actuators that would be

  normally involved in a robot mechanism or dis-

  similar positive. More particularly, the valve circuit 112 comprises a solenoid valve 114 having orifices

  116 and 118 to which the two lines are connected

  tes 56 and 57. The valve 114 also has two ports.

  these outlet 120 and 122 to which are connected conduits

  tes 124 and 126. In a certain position of the reel of

  valve, through channels 128 and 130 connect the ori

  inlet ports 116 and 118 to the respective outlet openings

  tifs 120 and 122. In another position of the coil, channels 132 and 134 connect the inlet ports 116 and 118 to the outlet ports 122 and 120, respectively, so as to maintain the flow of hydraulic fluid in the pipe. 124; that is to say that the flow is always carried out from the valve 114 in the direction of valves 138, 140 and 142 which serve the hydraulic actuators 100, 102

  and 104. The valve 114 represented here is of a conventional type.

  that the coil moves to the left, i.e.

  towards the position shown, by excitation of a solenoid

  of 136 and de-energization of a solenoid 137 in order to connect line 56 to line 124 and line 57 to line 126 via channels 128 and, respectively, and where the coil moves to the right by excitation of the solenoid 137 and de-excitation of the solenoid 136, which has the effect of connecting the pipe 56 to the pipe 126 and the pipe 57 to the pipe 124

  through channels 132 and 134, respectively.

  In practice, the solenoids 136 and 137 are connected to the service

  vomitor 10 in electrical circuits comprising

  appropriate control devices and control devices

  rust which position the valve 114, as shown

  tee in figure 3, when the piston 48 of the pump moves

  this to the left of FIG. 2 and which position the valve 12 with the channels 132 and 134 corresponding with the conduits 56, 126 and 57, 124, respectively, when the piston 48 moves to the right. So driving

  124 always supplies high pressure hydraulic fluid

  sion to actuators 138, 140 and 142 in any direction

  displacement of the piston 48. Furthermore, as appears

  later, the hydraulic fluid in line 126 will always flow from the control valves 138, 140

  and 142 to pump 55. In this regard, as indicated above

  cédément, it is important that the accumulator 82 is always

  days connected to the return side of the closed-loop hydraulic circuit which will now be described, and it will be observed that the line 84 leaving the accumulator is here connected to the

liquid return line 126.

* The three hydraulic actuators 100, 102 and

  104 are served by three-position solenoid valves

  Sections 138, 140 and 142, respectively. The pipes of

  discharge and return 124 and 126 are connected to the conduits

  the main hydraulics 144 and 146, respectively, and the latter are connected to the valves 138, 140 and 142 by respective pairs of pipes 148, 150; 152, 154 and 156, 158. The hydraulic fluid coming from the valves 138, 140 and 142 goes into the hydraulic actuators 100, 102 and 104 and returns therefrom by respective pairs of

  lines 160, 162; 164, 166 and 168, 170 (Figure 2).

  If the valve circuit is designed to serve only two hydraulic actuators such as the actuators shown in 60 and 62 in FIG. 4, the

  main lines 144 and 146 terminate at the lines

  valves 152 and 154. In this case, the

  three-position valve 138 serves the hydraulic actuator

  lique 60 via the lines 92 and 94 and the three-position valve 140 the hydraulic actuator 62 via the lines 96 and 98. Similarly, if the

  valve circuit is provided to serve three actions-

  hydraulic nors such as the actuators shown in

  , 102 and 104 of Figure 2, the supply lines

  13. main tion 144 and 146 terminate at lines 156 and 158. In the latter case, the three-position valves 138, 140 and 142 serve the hydraulic actuators 100, 102 and 104 respectively. On the other hand, if the valve circuit were to serve more than three hydraulic actuators

  the main lines 144 and 146 would be extended

  due as shown in 172 in Figure 3, and would be

  even connected to other hydraulic actuators.

  The three solenoid valves 138, 140 and 142 have

  identical construction and operation and one of-

  detailed description of the single valve 138 will therefore be sufficient. As shown in the figure, valve 138 has inlet ports 174 and 176 which are connected to lines 148 and 150, respectively, and outlet ports 178 and 180 which are connected to lines 160 and 162. valve 138 has a through position shown schematically at 182, an inversion position shown schematically at 184, and a

  intermediate blocking position shown diagrammatically-

  in 186. Balancing springs generally represented

  generally in 185 and 187 normally maintain the coil in the intermediate blocking position. A solenoid

  located at one end of the valve 138, when it is ex-

  cited, has the effect of moving the coil to the crossing position shown in the figure and a solenoid 188 located at the other end of the valve 138, when it is

  excited, has the effect of moving the coil towards the posi-

  inversion tion 184. As in the case of the valve 114, the solenoids 188 and 190 are provided to be electrically connected and locked in a conventional manner to

  appropriate control means which program the function

  valve 138, 140 and 142 in accordance with the mechanical operating conditions of the action-

  part and the robot of which they are part.

  In the case of the three-position valve 138 which serves the hydraulic actuator 100 and the actuator

  Exhibit 106 (Figure 2), it will be readily apparent that, when

  14. that it is in the normal locking position 186, the supply of hydraulic fluid to the actuator 100

  is cut and the actuator 106 stationary. But when

  that the valve 138 is in position 182, a high pressure hydraulic fluid comes from the reversing valve 114, passes through the lines 124, 148 and 160 to reach the lower part of the hydraulic actuator in order to bring back its piston back and raise the actuator 106. During the backward movement of the actuator piston 100, the hydraulic fluid located in the

  - upper part of this actuator circulates in the con-

  pick 162, the three-position valve 138, the lines, 126 and 57 to return to the pump 55. On the other hand, when the three-position valve 138 is in the

  reversal position 184 and that the valve 114 is position-

  born as shown in figure 3, the hydraulic fluid with high

  pressure from valve 138 goes to the top

  actuator 100 passing through line 162 so as to advance the piston in the actuator

  hydraulic 106 and lower this actuator.

  In connection with the above, it will easily be seen that the three-position valves 138, 140 and 142 operate in the same way to control the operation of their respective actuators 100, 102 and 104 and therefore the part actuators 106, 108 and 110. It will also be noted that the three-way valves

  positions 138, 140 and 142 can be positioned selected

  individually so as to actuate their respective actuators of part 106, 108 and 110 either in

  the crossing position, ie in the reverse position

  sion and that it can be run in either

  position of the main valve 114. In addition, each valve

  pet in three positions 138, 140 and 142 can be selectively held individually in the locking position so as to maintain its respective actuator

  part in the stationary state for a predetermined period of time

  born, whatever work performed by other ac-

15. keepers.

  From the above, it can be seen that the agency

  cement of valves shown here permanently allows

  constant control and command of the part actuators

  ce and the selective operation of the part actuators according to a predetermined program. This is made

  possible by the control system of this invention

  tion which supplies the hydraulic circuit with fluid from the pump 55 in a relatively constant manner and under a relatively high pressure at all times of the

  servomotor operation 10. Starting the servomotor

  vomitor 10, and therefore the movement of the nut

  drag 22 and piston 48 can be ordered with

  precision within extremely narrow limits. This

  in turn puts individual control of the movement of

  room actuators 106, 108 and 110 within limits

  also very narrow, at least in part, because the high pressure hydraulic fluid which implements the part actuators is supplied by a closed loop system. The whole system works with a minimum

  noise and gives off relatively little heat.

  In addition, the need for pre-heating and

  cooling positive, which are normally born

  dealers in hydraulic systems of the type involved here, is eliminated. Hydraulic fluid temperature

  of the circuit remains relatively low due to the absence of

  this turbulence in the system at rest.

  Another feature of the control system

  of electro-hydraulic of the present invention is its faci-

  incorporation into a larger system which can

  be controlled so as to give automatic operation

  only under the direction of a computer using means and techniques well known to those skilled in the art. As shown diagrammatically in FIG. 1, the reference 192 designates a computer having a closed loop connection

  represented in 194 and 196 with an interface 198 to which

  the is in turn connected to the reversible servo motor with

16.

  continuous 10 through a de-control unit

  the and amplification 200 as indicated in 202, 204 and

  206, 208. As described above, the motor 10 comprises

  te a direct drive mechanical connection 210 with the mechanism for converting rotation into linear movement 37 which reduces the speed of the drive shaft of the

  motor and actuates pump 55 in an alternating movement

  tif as indicated in 212. Control devices and

  speed and motion control, such as a tacho

  meter 213 and an encoder or resolution device 215,

  are mechanically driven by the motor 10, as re-

  presented in 218 and 220, and are in turn electrically connected to the control and amplification unit

  , as shown in 222 and 224, to provide an in-

  return training on speed and position to the uni-

  motor control tee so that the stroke of the

  tone of the pump and the position of the piston inside the pump cylinder can be regulated in accordance with system conditions. The connections between the pump 55

  and the valve circuit 112 are shown diagrammatically

  only in 56 and 57 in Figure 1, and the hy-

  hydraulics shown at 60 and 62 in Figure 4 and

  , 102 and 104 in Figure 2 - shown schematically -

  only in FIG. 1, and designated collectively by the reference 214. The hydraulic connections between the valve circuit 112 and the hydraulic actuators 214 are shown diagrammatically at 216 and 218. The movements

  hydraulic actuators 214 are controlled by

  suitable position sensors such as limit switches or the like. It is envisaged that each hydraulic actuator will be individually served by its own position detector or set of detectors

  and, for the present description, it is assumed that the ac-

  hydraulic actuators represented schematically and collectively at 214 in FIG. 1 include the

  three hydraulic actuators 100, 102 and 104 of the

  gure 2. To this end, three position detectors or sets 17. of detectors 226, 228 and 230 are shown here, a detector being provided by hydraulic actuator 100, 102 and 104. The connections between the position detectors

  226, 228 and 230 and their respective hydraulic actuators

  tifs are represented schematically in 232, 234 and 236. The position detectors 226, 228 and 230 are also electrically connected, as generally represented in 238, to the interface 198, and the latter is connected in turn, as indicated in 240 , to the solenoids of the control valves 114, 138, 140 and 142, as shown in

figure 3.

  In operation, the servomotor 10 is programmed by

  the computer 192 so as to animate the piston 48 with a movement

  vement back and forth in the middle part of the cylinder 50, the length of the piston stroke being determined in the environment shown here by way of example by special conditions of movement of the actuators 106, 108 and 110 of the robot , and for the execution of the operation, the interface 198 translates the control signals coming from the computer and sends it information in return. For example, if the program requests the operation of the

  servomotor 10 for a period corresponding to 300 pulses

  continuous wave sions, it sends the appropriate instructions

  requested for this purpose, and the interface 198 establishes the direction of the

  servo motor controller and outputs a 300 pulse train

  via driver 202, then verify that the controller has returned a signal "executed" by the

  conductor 204. Interface 198 also translates data

  born from position detectors by the conduc-

  tor 238 in a form that can be understood by the computer

  192. This implies an analog-digital conversion.

  if the position sensors 226, 228 and 230 are

  potentiometer type detectors, or it was born

  stop counting the pulses if the detectors are decoders. The interface 198 is also used to convert the coded signals from the computer into voltage levels in

  alternating current and transmits these voltages through

  18 o diary of the conductor 240 to the solenoid valves 138, 140 and 142 appropriate so as to establish the desired dispatch of

  hydraulic fluid to actuators 100, 102 and 104.

  The complete system represented in figure 1 presents a possibility of program for the configuration of the

  individual implementation of the movement of the main axes

  room actuators in a robot, for example. A positive driving force for the robot movement is provided by the hydraulic fluid in such a way that the speed and extent of the movement in each case can be precisely controlled, and the precision of the

  movement necessary for precise positioning of a part

  this by the part actuators which constitutes a part of the robot mechanism is particularly well ensured by the direct current servomotor and by the conversion of the rotary movement into linear movement carried out by the speed reducer 37, the pump 55 and the combination of these two devices, as well as their unique association with the servomotor 10, since the latter can be controlled with precision by the computer 192 for

  that the pump piston 48 is driven by a movement of

  back and forth inside cylinder 50 in response to a mid

  croprocessor which receives feedback on the position, speed and volume of oil from the electrohydraulic control system. The device 55, when coupled to a direct current servomotor of the type shown in 10, transforms the torque of the shaft

  of the motor in fluid pressure in a particular way

  highly efficient and easily controllable for moving the robot actuators. In addition, the unique correlation between the mechanism for converting rotational movement into

  linear movement represented in 37 and the part mechanism

  pump base shown in 55 allows minute control

  pump movement piston 48 inside the

  cylinder 50 and its normal positioning at the media part-

  ne of the cylinder, or near this part so that one has the assurance of a complete displacement of the mechanisms 19. of the robot part actuators during the stroke of the piston. This is particularly important when a control system of the type described here is called upon to make

  operate a robot mechanism, since the

  middle tie of the pump cylinder 50 represents the useful zone of the piston stroke. When the piston 48 is too close to one or the other end of the cylinder, complete steps in the movement of the robot cannot

  to be obtained. Thus, the micro-

  computer must cycle the servo motor

  operating pump 55 forwards and backwards so

  Less that the movement of the pump piston 48 is maintained

  near the middle part of the pump cylinder 50.

  The particular arrangement and correlation between parts in the control of the pump 55 also allow the coupling of optical encoders or equivalent means to the

  servomotor 10, as shown in 220, so as to

  der to a feedback to the processor on the orientation in position, and a tachometer can be similarly coupled to the servomotor, as shown

  in 218, to provide a speed signal for the orienta-

  tion in speed of the workpiece actuation mechanism of the

  bot. As the computer 192 controls the direction of circulation

  tion of the hydraulic fluid, as well as the volume of fluid moving in the closed-loop hydraulic circuit,

  flow control means can also be

  connected to the outlet lines of the pump 55, so that

  provide feedback to the computer on the vi-

  tesse of the fluid for purposes of orientation of the volume.

  The present invention is not limited to the examples

  ples of realization which have just been described, it is on the contrary susceptible of modifications and variants

  which will appear to those skilled in the art.

-2498268

20.

Claims (14)

  1 - Electro-hydraulic control system for a robot of a type comprising part actuation means, characterized in that it comprises - a closed-loop hydraulic circuit having.   one side of fluid discharge and one side of fluid return   of; - a means of pumping hydraulic fluid to   the discharge side of the circuit with simultaneous reception   born from hydraulic fluid from the return side, and   - a plurality of hydraulic actuators   actively linked to the discharge and return sides of the hydraulic circuit by means of   individually controlled valve designed to be re-   linked to the part actuation means so as to put   these implement the valve means which can be activated   independently operated to move the actuating means selectively in either of two directions or to keep the means stationary actuation.   2 - Independent closed loop hydraulic circuit   in an electro-hydraulic control system for a robot of a type comprising part actuating means, characterized in that it comprises: - a pair of separate driving means through which a hydraulic fluid circulates in the circuit and comprising a plurality of means for   hydraulic motor, each having a cylinder and an action-   neur mobile in this cylinder which is thus divided into separate chambers,   - the driving means being connected to cham-   respective bres of hydraulic motor means and allows   both the circulation of hydraulic fluid between the hydraulic motor means; - at least one of the hydraulic motor means comprising a drive motor means and this drive motor means capable of operating to proceed 21. to the pumping introduction of the hydraulic fluid at a relatively high pressure alternatively in the driving means, - another hydraulic motor means comprising a driven motor means which can be implemented by   fluid pressure from the drive motor means   so as to operate the means of action   part of the robot, - a main valve means connected to the driving means between the drive motor means and the driven motor means which can be used to always direct the hydraulic fluid coming from the drive motor means towards one of the driving means for supplying the driven motor means, after which, the other driving means between the main valve means and the driven motor means returns the hydraulic fluid by means of drive, - a control valve means connected to the driving means between the main valve means and the means   motor driven to control the flow of hydraulic fluid   lique going to or from the driven motor means, and   - an accumulator means connected to the connection means   return line between the main valve means and the   motor means driven to maintain a minimum pressure   minimum predetermined in the hydraulic circuit and capable of operating so as to take account of variations in the quantity of hydraulic fluid in the discharge and return sides of the hydraulic circuit due to operation hydraulic motor means.   3 - Hydraulic circuit according to claim 2, characterized in that it comprises an actuator means, a   speed reducer means driven by the ac means   actuator, and in that the drive motor means comprises a cylinder and a piston mounted so as to be driven back and forth in the cylinder, the piston having rods extending through the two 22 .   ends of the cylinder which are connected by means of reduc- speed sensor.   4 - Hydraulic circuit according to claim   2, characterized in that it comprises a servomotor with neck-   continuous rant comprising a drive shaft which is   connected by means of drive motor.   - Hydraulic circuit according to claim 2,   characterized in that the actuator of the drive motor means   drag in the form of a reciprocating piston, and in that the circuit comprises a reversible direct current servomotor comprising a rotary drive shaft, and a   speed reduction means comprising a connection   dragged with the servo motor shaft and a connection   dragging with the piston of the drive motor means   ment, this speed reduction means being able to function   so as to transform the rotational movement of the ser-   vomitor in alternative piston stroke.   6 - Hydraulic circuit according to claim 2,   characterized in that the actuator of the drive motor means   drag in the form of a reciprocating piston and in this   that the circuit includes a reversible servo motor with   continuous rant comprising a rotary drive shaft,   and a speed reduction means comprising a screw   drag connected to the servo motor drive shaft   and a carriage connected to the piston of the drive motor means   provided with a nut means which can move linearly rement on the drive screw.   7 - Hydraulic circuit according to claim 2, characterized in that the actuator of the drive motor means has the form of a reciprocating piston, and in that   that the circuit includes a reversible servo motor with   continuous rant comprising a rotary drive shaft, and a means which can be actuated by the servomotor   to transform the rotational movement of the drive shaft   dragging the servomotor in reciprocating motion drive motor means.   8 - Hydraulic circuit according to claim 2, 23. characterized in that it comprises a plurality of means   driven motor each having a cylinder and an action-   neur mobile in the cylinder, and in that the means of   discharge line is connected to the cylinder of each mo-   motor yen driven to one side of the actuator located in the cylinder, and in that the return line means is connected to the cylinder of each means driven to   the other side of the actuator located in the cylinder.   9 - Hydraulic circuit according to claim   8, characterized in that it comprises a plurality of mo-   control valve yen, with one valve means per   driven motor means, each check valve means   control being actively connected to a motor means   respective driven and capable of operating individually   so as to selectively connect the connection means   discharge line to the cylinder of its engine means   respective dragged to either side of the cylinder actuator or to completely block the flow of hydraulic fluid to the cylinder, as a result of which the driven motor means can be selectively actuated individually and successively according to a predetermined order. - Electro-hydraulic control for a robot of a type comprising a movable part actuating element, characterized in that it comprises   - at least one hydraulic actuator means   with individual rooms separated by an element   ment of movable actuator, this actuator element being provided to be connected to the part actuation element in order to operate the latter; - a reversible direct current servomotor, - a stationary cylinder normally filled with hydraulic fluid, - a double rod piston mounted so as to be driven back and forth in the cylinder, - a means driven by the connected servo motor   active way to the piston so that it slides   ci in one direction or the other inside the cylinder 24. as a function of the direction of rotation of the engine, and   - a closed loop hydraulic system comprising   both discharge and return sides connected to the stationary cylinder at opposite sides of the piston and to respective chambers of the hydraulic actuator means at the sides   opposite the movable actuator element.   11 - Electro-hydraulic control according to the resale   dication 10, characterized in that it comprises a flow direction change valve means connected to the discharge and return sides of the hydraulic system which can operate so as to establish communication between the stationary cylinder at one or the other. on the other side of the double rod piston and one or the other of the chambers of the means hydraulic actuator.   12 - Electro-hydraulic control according to the resale   dication 10, characterized in that it comprises a piston type accumulator means connected to the return side of the   hydraulic system to ensure relative pressure   constant in the hydraulic system and to take into account variations in the volume of the hydraulic fluid in the system due to the actuation of the movable actuator element. 13 -Electro-hydraulic control for a robot of a type comprising movable means for actuating a part,   characterized in that it includes -   - a plurality of hydraulic actuators for   before operating individually so as to provide   different movements predetermined by the means of action   part, each hydraulic actuator comprising   pressure chambers separated by an ac element   movable actuator designed to be actively associated with the part actuation means and connected to them, - an electric reversible drive motor,   - an engine cylinder normally filled with fluid hydraulic,   - a piston mounted so as to be driven by a   alternately in the cylinder defining individual pressure chambers 25. at its opposite sides, - a connecting means driven by the engine actively connected to the piston to slide the latter   in one direction or the other depending on the direction of rotation engine, and   - a normal closed loop hydraulic system -   filled with hydraulic fluid and through which the hydraulic fluid passes between the engine cylinder   and hydraulic actuators, this hydraulic system   bearing discharge and return sides connected to the chambers   pressure cylinder of the engine cylinder and to the indi-   hydraulic pressure actuators, and a   valve means to always connect the chamber under pressure   sion in which the piston moves to the discharge side of the hydraulic system and to block the flow of hydraulic fluid to the hydraulic actuators or to selectively connect the discharge side of the system to the chamber   under pressure on either side of the action element-   mobile neur of each hydraulic actuator.   14 - Electro-hydraulic control as claimed   cation 13, characterized in that the drive motor   is a DC servo motor.   - Electro-hydraulic control as sold   cation 13 or claim 14, characterized in that   the connecting means comprises a speed reducer.   16 - Electro-hydraulic control as claimed   cation 13, characterized in that the drive motor is a direct current servo motor comprising a rotary drive shaft, and in that the connecting means comprises a mechanism for transforming a movement of   rotation in linear motion connecting the motor shaft of the vomiting piston.   17 - Electro-hydraulic control as claimed   cation 13, characterized in that the drive motor is a direct current servo motor comprising a rotary drive shaft, and in that the connecting means   includes a screw-type speed reduction mechanism 26.   ball comprising a threaded shaft having a driven connection   born with the actuator drive shaft, a nut   can be moved forward and backward on the threaded shaft in operation   tion of the direction of rotation of the drive shaft, and a carriage connected to the nut with which it can move   provided with a drive link with the piston and   before operating in motion so as to animate a movement   reciprocating this piston in the cylinder, after which there is an alternating pumping of the hydraulic fluid between the cylinder on the opposite sides of the piston and the side   hydraulic system discharge.   18 - Electro-hydraulic control as per   vendications 13 or 17, characterized in that the means of   valve includes a plurality of control valves associated with   actively active with the plurality of hy-   for controlling the flow of hydraulic fluid   and can be activated selectively and individually   duel following a predetermined order to confer their   respective movements to the part actuation means.