CONTROL METHOD FOR CONTROLLING AN EXCAVATOR AND EXCAVATOR COMPRISING A CONTROL UNIT IMPLEMENTING SUCH A CONTROL METHOD

Abstract

A control method includes the steps of: providing an excavator including: several movable members configured to move parts of the excavator, one actuating set comprising several actuators, among which at least one electric actuator, one or more static brakes movable between: i) a locking position and ii) an unlocking position, a command device to receive commands from an operator, a control unit to control the actuators and the static brakes based on command signals. The control method further includes: a reception step for receiving a command signal, an actuation check step to check whether the command signal requires the control unit to actuate an actuator of the actuating set, and if yes, an unlocking step wherein the control unit releases the static brakes of the actuating set.

Claims

1. A control method, for controlling an excavator, the control method including a step of: providing an excavator including at least: several movable members, each movable member being configured to move at least a part of the excavator, at least one actuating set comprising at least two actuators, the at least two actuators including at least one electric actuator, each actuator being configured to actuate at least one of the movable members, at least one static brake movable between: i) a locking position where the at least one static brake locks the at least one electric actuator, and ii) an unlocking position where the at least one static brake unlocks the at least one electric actuator, a command device configured to receive commands from an operator and to generate command signals based on the commands, a control unit configured to receive the command signals and to control the actuators and the at least one static brake based on the command signals, the control method further including at least: a reception step wherein the control unit receives a command signal, an actuation check step wherein the control unit checks whether the command signal requires the control unit to actuate at least one actuator belonging to the at least one actuating set, and in case the command signal requires the control unit to actuate an actuator belonging to the at least one actuating set, an unlocking step wherein the control unit controls the at least one static brake so that the at least one static brake moves towards its unlocking position.

2. The control method according to claim 1, wherein the control unit controls the at least one static brake so that the at least one static brake moves towards its unlocking position within less than 500 milliseconds, preferably within less than 100 milliseconds.

3. The control method according to claim 1, wherein the at least one actuating set comprises at least two electric actuators, wherein the excavator includes at least two static brakes, each static brake being movable between: i) a respective locking position where the static brake locks a respective electric actuator, and ii) a respective unlocking position where the static brake unlocks the respective electric actuator, and wherein, during the unlocking step, the control unit controls each static brake so that each static brake moves towards its respective unlocking position.

4. The control method according to claim 1, wherein the actuators belonging to the at least one actuating set are configured to cooperate in order to generate a combined motion of at least one of the movable members.

5. The control method according to claim 4, further including an actuation step wherein the control unit actuates at least two actuators belonging to the at least one actuating set when the command signal requires the control unit to actuate the at least two actuators belonging to the at least one actuating set.

6. The control method according to claim 1, wherein the at least one electric actuator is selected in the group consisting of a linear electric actuator and a rotational electric actuator.

7. The control method according to claim 1, wherein the at least one electric actuator includes a respective electric motor, and wherein, during the unlocking step, the control unit energizes the electric motor.

8. The control method according to claim 7, wherein, during the unlocking step, the control unit energizes the electric motor of the at least one electric actuator before the at least one static brake moves towards its respective unlocking position.

9. The control method according to claim 7, wherein, during the unlocking step, the control unit energizes the electric motor of the electric actuator substantially during a period where the at least one static brake moves towards its respective unlocking position.

10. The control method according to claim 9, wherein, during the unlocking step, the control unit energizes the electric motor of the at least one electric actuator progressively as the at least one static brake moves towards its respective unlocking position.

11. The control method according to claim 7, wherein, during the unlocking step, the control unit energizes the electric motor so as to actuate the at least one electric actuator belonging to the at least one actuating set.

12. The control method according to claim 7, wherein, during the unlocking step, the control unit energizes the at least one electric motor so as to maintain in a static position the at least one electric actuator.

13. The control method according to claim 3, wherein, during the unlocking step, the control unit energizes the electric motor so as to actuate the at least one electric actuator belonging to the at least one actuating set, wherein, during the unlocking step, the control unit energizes the at least one electric motor so as to maintain in a static position the at least one electric actuator, and wherein, during the unlocking step, the control unit energizes both: at least one electric motor so as to actuate at least one of the electric actuators, and the remaining electric motors of all of the electric actuators belonging to the at least one actuating set in order to maintain in a static position the electric actuators.

14. The control method according to claim 13, wherein, during the unlocking step, the control unit energizes all the electric motors so as to actuate all of the electric actuators belonging to the at least one actuating set.

15. The control method according to claim 1, wherein the control unit comprises a memory for storing at least a dataset containing data identifying each actuator belonging to the at least one actuating set.

16. The control method according to claim 1, further comprising a cab, wherein each one of the movable members is selected from the group consisting of a tool configured to work on a site, an arm configured to move the tool, a boom configured to move the arm, an offset member configured to offset the boom, a drive member configured to displace the cab with respect to a site ground and a blade configured to partially lift the cab.

17. The control method according to claim 16, wherein the movable members include a tool configured to work on a site and an arm configured to move the tool, wherein the at least one actuating set comprises a tool actuating set, the tool actuating set including at least a tool actuator configured to drive the tool and an arm actuator configured to drive the arm, and wherein the at least one static brake includes at least a tool static brake configured to lock the tool actuator and an arm static brake configured to lock the arm actuator.

18. The control method according to claim 17, wherein the movable members further include a boom configured to move the arm, wherein the tool actuating set further includes a boom actuator configured to drive the boom, and wherein the static brakes further include a boom static brake (36) configured to lock the boom actuator.

19. The control method according to claim 18, wherein the movable members further include an offset member configured to offset the boom, and wherein the tool actuating set further includes an offset actuator configured to drive the offset member, and wherein the static brakes further include an offset static brake configured to lock the offset actuator.

20. The control method according to claim 1, further comprising a cab, wherein the movable members further include a blade configured to partially lift the cab and a drive member configured to displace the cab, wherein the at least one actuating set comprises a cab actuating set, the cab actuating set including at least a blade actuator configured to drive the blade and a drive actuator configured to drive the drive member, and wherein the at least one static brake includes at least a blade static brake configured to lock the blade actuator and a drive static brake configured to lock the drive member.

21. The control method according to claim 20, wherein the drive member comprises at least two drive devices including a right track drive device configured to impart a translation to a right part of the excavator and a left track drive device configured to impart a translation to a left part of the excavator, and wherein the cab actuating set is configured to actuate both the right track drive device and the left track drive device.

22. The control method according to claim 2, wherein the movable members further include a swing member configured to swing the cab, wherein the cab actuating set further includes at least a swing actuator configured to drive the swing member, and wherein the static brakes include at least a swing static brake configured to lock the swing actuator.

23. The control method according to claim 1, further including a lock check step wherein the control unit checks whether the at least one electric actuator is currently locked, wherein the control unit performs the unlocking step in case the at least one electric actuator is currently locked.

24. The control method according to claim 1, wherein the excavator further includes several position sensors, each position sensor being configured to detect the position of a respective electric actuator and to send position signals to the control unit, the control unit being further configured to determine the position of each one of the electric actuators based upon the position signals.

25. The control method according to claim 24, wherein each position sensor is an encoder coupled with an electric actuator.

26. The control method according to claim 1, wherein the control unit further comprises at least one timer for counting at least one predetermined period as from the start of the reception step, and wherein, after the predetermined period has elapsed without the control unit receiving any further command signal, the control unit controls the at least one static brake so as to move the at least one static brake towards its respective locking position.

27. The control method according to claim 1, wherein the excavator further comprises at least one temperature sensor configured to measure the temperature of the at least one electric actuator and connected to the control unit, the control method further including a cooling step wherein, in case the temperature exceeds a predetermined temperature threshold, the control unit controls the at least one static brake so as to move the at least one static brake towards its respective locking position.

28. An excavator including at least: several movable members, each movable member being configured to move at least a part of the excavator, at least one actuating set comprising at least two actuators, the at least two actuators including at least one electric actuator configured to actuate at least one of the movable members, at least one static brake movable between: i) a locking position where the at least one static brake locks the at least one electric actuator, and ii) an unlocking position where the at least one static brake unlocks the at least one electric actuator, a command device configured to receive commands from an operator and to generate command signals based on the commands, a control unit configured to receive the command signals and to control the actuators and the at least one static brake based on the command signals, the control unit being further configured to perform at least: a reception step wherein the control unit receives a command signal, an actuation check step wherein the control unit checks whether the command signal requires the control unit to actuate an actuator belonging to the at least one actuating set, and in case the command signal requires the control unit to actuate an electric actuator belonging to the at least one actuating set, an unlocking step wherein the control unit controls the at least one static brake so that the at least one static brake moves towards its unlocking position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0107] The features and advantages of the present invention will also appear upon reading the following description in view of the appended drawings, which represent, as non-limiting examples, an embodiment of an excavator arm according to the invention.

[0108] The following detailed description of several embodiments of the invention is better understood when read in conjunction with the appended drawings. However, the invention is not limited to the specific embodiments disclosed herewith.

[0109] FIG. 1 is a schematic side view of an excavator according to one aspect of the invention;

[0110] FIG. 2 is a schematic perspective view of the excavator of FIG. 1;

[0111] FIG. 3 is a schematic side view of an electric actuator belonging to the excavator of FIG. 1; and

[0112] FIG. 4 is a flow chart illustrating a control method according to one aspect of the invention for controlling the excavator of FIG. 1.

DETAILED DESCRIPTION

[0113] FIG. 1 illustrates an excavator 1 according to one aspect of the invention. In the example of FIG. 1, excavator 1 is a mechanical shovel. Excavator 1 includes a cab 50, for accommodating an operator, and several movable members, in particular:

[0114] a tool 2 configured to work on a site,

[0115] an arm 4 configured to move tool 2,

[0116] a boom 6 configured to move arm 4, [0117] an offset member 7 configured to offset boom 6, so as to rotate boom 6 substantially about a vertical axis,

[0118] a swing member 8 configured to swing cab 50,

[0119] a drive member 10 configured to displace swing member 8 with respect to a site ground, and [0120] a blade 9 configured to partially lift cab 50 and drive member 10, in order to immobilize cab 50 while excavator 1 is excavating the ground.

[0121] Each movable member 2, 4, 6, 8, 10 is configured to bear and move a respective part of excavator 1. When excavator 1 is in service, tool 2 moves itself, arm 4 moves tool 2, boom 6 moves arm 4, swing member 8 moves boom 6 and drive member 10 moves swing member 8. Drive member 10 can include a right track drive device 10.1 and a left track drive device 10.2, as visible on FIG. 2.

[0122] Tool 2 and arm 4 can be linked by an articulation, e.g. a hinge, which allows at least a rotation of tool 2 relative to arm 4. Arm 4 and boom 6 can be linked by an articulation, e.g. a hinge, which allows at least a rotation of arm 4 relative to boom 6. Boom 6 and offset member 7 can be linked by an articulation, e.g. a hinge, which allows at least a rotation of boom 6 relative to offset member 7. Swing member 8 and drive member 10 can be linked by an articulation, e.g. a hinge, which allows at least a rotation of swing member 8 relative to drive member 10. Swing member 8 is configured to swing cab 50 about a swing axis Z8 which is substantially vertical when excavator 1 lies on a horizontal site H.

[0123] For the movable member 2, 4, 6, 8, 10 to move a respective part of excavator 1, excavator 1 further includes several actuating sets, each actuating set comprising at least two electric actuators configured to actuate at least one of the movable members 2, 4, 6, 8, 10.

[0124] The actuating sets can comprise a tool actuating set 20.1, which herein includes:

[0125] a tool actuator 22 configured to drive tool 2,

[0126] an arm actuator 24 configured to drive arm 4, [0127] a boom actuator 26 configured to drive said boom 6, and

[0128] an offset actuator 27 configured to drive said offset member 7.

[0129] The electric actuators 22, 24, 26 and 27 belonging to the tool actuating set 20.1 can be configured to cooperate in order to generate a combined motion of an assembly formed by tool 2, arm 4, boom 6 and offset member 7.

[0130] The tool actuator 22 can have two telescopic parts which are mounted in a telescopic arrangement and which may be displaced lengthwise by a non illustrated electric motor so as to vary the length of tool actuator 22. A mechanism links the two telescopic parts of the tool actuator 22 in order to convert a rotary motion of the electric motor in a linear relative displacement of the two telescopic parts. Such a mechanism can be of the roller screw type.

[0131] Likewise, the arm actuator 24 and boom actuator can have telescopic parts displaceable by means of a rotational electric motor and of a roller screw.

[0132] The actuating sets can further comprise a cab actuating set 20.2, which herein includes:

[0133] a swing actuator 28 configured to drive said swing member 8,

[0134] a blade actuator 29 configured to drive said blade 9, and

[0135] a drive actuator 30 configured to drive said drive member 10.

[0136] Swing member 8 can comprise a rotating platform bearing cab 50.

[0137] Blade 9 comprises a main blade and two legs which are articulated to a substructure of cab 50, as visible on FIG. 2. Drive member 10 can comprise either a caterpillar track or wheels for driving excavator 1.

[0138] The actuators 28, 29 and 30 belonging to the cab actuating set 20.2 can be configured to cooperate in order to generate a combined motion of an assembly formed by swing member 8 and drive member 10.

[0139] The electric actuators can be formed by linear electric actuators. The electric actuators include respective electric motors. Electric power can be supplied to the electric motors by a non illustrated electric accumulator which can for instance be mounted on a chassis of excavator 1. The electric accumulator can store 15 kWh of energy and supply current at a 600 V tension. A DC/DC converter can supply each electric motor with current at a suitable tension. Electric motors in turn supply mechanical power to the electric actuator.

[0140] Excavator 1 further includes several static brakes, each static brake is movable between: i) a non illustrated locking position where the static brake locks one electric actuator, and ii) a non illustrated unlocking position where the static brake unlocks the electric actuator. In other words, each static brake is configured to lock one of the electric actuators 22, 24, 26, 27, 28, 29, 30.

[0141] The static brakes can include a tool static brake 32 configured to lock tool actuator 22, an arm static brake 34 configured to lock arm actuator 24, a boom static brake 36 configured to lock boom actuator 26 and an offset static brake 37 configured to lock offset actuator 27.

[0142] Tool static brake 32 is movable between: i) a non illustrated locking position where tool static brake 32 locks tool actuator 22, and ii) a non illustrated unlocking position where tool static brake 32 unlocks tool actuator 22. Likewise, arm static brake 34 and boom static brake 36 have their respective locking and unlocking positions to lock arm 24 and boom 26.

[0143] Besides, the static brakes can include a swing static brake 38 configured to lock swing actuator 28, a blade static brake 39 configured to lock blade actuator 29, a drive static brake 40 configured to lock drive actuators.

[0144] Excavator 1 further can include cab 50 configured to accommodate the operator and a command device 52 configured to receive commands from the operator. Command device 52 can for instance comprise a joystick or handle remotely connected to a control unit 54.

[0145] The command device 52 is further configured to generate command signals based on said commands. The command signals can be transmitted from command device 52 to control unit 54 either by a wire or wirelessly by radiowaves.

[0146] Excavator 1 further includes the control unit 54 configured to receive the command signals from command device 52. Control unit 54 is further configured to control, based on said command signals, the electric actuators 22, 24, 26, 27, 28, 30 and the static brakes 32, 34, 36, 37, 38, 39, 40. Control unit 54 can comprise a memory 56 for storing a dataset containing data identifying each electric actuator 22, 24, 26, 27, 28, 29, 30 belonging to the tool actuating set 20.1 and to the cab actuating set 20.2. Besides, memory 56 can store another dataset containing data identifying each static brake 32, 34, 36, 37, 38, 39, 40 and its respective electric actuator.

[0147] FIG. 3 illustrates the tool electric actuator 22. Tool actuator 22 includes a generally cylindrical actuator body 22.1, a rotational electric motor 22.2 with magnetic coils 22.3, a static brake 22.4 and a position sensor 22.5. Position sensor 22.5 can be of the encoder type.

[0148] Power supply to the rotational electric motor 22.2 is performed through a power cable 22.6. Rotational electric motor 22.2 rotates around a rotation axis Z22.2.

[0149] In service, control unit 54 sends its control signals to tool actuator 22 via a signal cable 22.7. Likewise, position sensor 22.5 sends its feedback signals to control unit 54 via signal cable 22.7.

[0150] In service, the output torque of rotational electric motor 22.2 moves a screw rod 22.8. Tool electric actuator 22 actuates the screw rod 22.8 which delivers mechanical power to the tool 2.

[0151] Static brake 22.4 has a disk which can rotate with the rotational electric motor 22.2 and which bears braking pads configured to rub against a friction surface attached to actuator body 22.1. Alternatively, a static brake could be located on the electric motor, on a gear or on the screw.

[0152] FIG. 2 illustrates a control method 100 according to another aspect of the invention, for controlling excavator 1 when it is in service. Control method 100 includes a reception step 102 wherein control unit 54 receives a command signal. Such a command signal is usually generated by the command device 52 upon command by the operator sitting in cab 50.

[0153] In case (Yes) the control unit 54 receives such a command signal, control method 100 performs an actuation check step 104. During actuation check step 104 the control unit 54 checks whether the command signal requires the control unit 54 to actuate at least one electric actuator belonging to an actuating set, say the tool actuating set 20.1 or the cab actuating set 20.2.

[0154] The operator sitting in cab 50 can command the tool actuating set 20.1. For instance, the operator may request for a movement using the command device 52, which can include a joystick, a button, a roller, a pedal and/or a lever. The operator's request can be for a position, a speed, a power or a torque. For instance, the operator's request can be for speed. When the command device 52 is at rest the speed request is null, when the command device 52 is displaced the speed request depends on the amplitude of displacement of the command device 52 as from its rest position.

[0155] In case (Yes) the command signal requires the control unit 54 to actuate an electric actuator belonging to the tool actuating set 20.1 or to the cab actuating set 20.2, control unit 54 performs an unlocking step 105 where control unit 54 controls tool, arm and boom static brakes 32, 34 and 36 so that tool, arm and boom static brakes 32, 34 and 36 move towards their respective unlocking positions. In other words, the control unit 54 releases all the static brakes 32, 34, 36, 37 or 38, 39, 40 from locking all the electric actuators 22, 24, 26, 27 or 28, 29, 30 which belong respectively to the tool actuating set 20.1 or to the cab actuating set 20.2.

[0156] For instance, in case (Yes) the command signal requires the control unit 54 to actuate the tool actuator 22, which belongs to the tool actuating set 20.1, the control unit 54 performs the unlocking step 105 so that tool static brake 32, arm static brake 34 and boom static brake 36 move towards their respective unlocking positions. Thus, control unit 54 releases all the tool, arm and boom static brakes 32, 34 and 36 from locking all the electric actuators 22, 24 and 26 which belong to the tool actuating set 20.1.

[0157] When the command signal requires control unit 54 to actuate at least two electric actuators belonging to the tool actuating set 20.1, the control unit 54 can actuate two or three electric actuators belonging to the tool actuating set 20.1. For instance, the command signal may require control unit 54 to actuate the tool actuator 22 and the arm actuator 24 concomitantly when the motion required for the tool 2 has an amplitude which is too large for being reached by the sole tool actuator 22.

[0158] Control unit 54 controls tool static brake 32, arm static brake 34 and boom static brake 36 so that tool static brake 32, arm static brake 34 and boom static brake 36 move towards their respective unlocking positions within approximately 50 milliseconds.

[0159] During unlocking step 105, control unit 54 can energize the electric motors of all of the electric actuators belonging either to the tool actuating set 20.1 or to the cab actuating set 20.2. For instance, control unit 54 can energize these electric motors before the corresponding static brakes 32, 34, 36, 37, 38, 39 and/or 40 have arrived at their respective unlocking position. Once their electric motors get energized, the electric actuators 22, 24, 26, 28, 29 or 30 can hold the loads in lieu of the static brakes 32, 34, 36, 37, 38, 39 or 40.

[0160] Thus, if the command signal or a further command signal requires the control unit 54 to also move the arm 4, then the start of the motion of the arm 4 will not induce backlash, bump nor vibrations through the components of the excavator 1, thus improving the operator's comfort and increasing the service life of the components of the excavator 1.

[0161] Otherwise, in case (No) the control unit 54 does not receive a command signal, then the control unit 54 starts a timer 58 plus further, non illustrated timers, which belong to the excavator 1 and which are configured to count several predetermined periods, for instance 10 seconds. Excavator 1 can comprise several timers, for instance at least one timer per actuating set (20.1, 27).

[0162] Then control unit 54 performs a timer check step 108:

[0163] 10) if said predetermined period has not elapsed, then the control unit 54 lies in a waiting state 110 until timer 58 reaches the end of said predetermined period;

[0164] 12) after said predetermined period has elapsed whereas the control unit 54 has not received any command signal (Yes), the control unit 54 performs a locking step 112 during which the control unit 54 actuates all the static brakes 32, 34, 36, 37, 38, 39, 40 so as to lock all the electric actuators belonging to an actuating set, either the tool actuating set 20.1 or the cab actuating set 20.2.

[0165] The control method 100 can further include a lock check step wherein control unit 54 checks whether all the electric actuators 22, 24, 26 or 28, 29, 30 belonging respectively to the tool actuating set 20.1 and/or to the cab actuating set 20.2 are currently locked. In other words, control unit 54 checks whether all the static brakes 32, 34, 36, 37 or 38, 39, 40 are in their respective locking position. In case the lock check step is positive (Yes), control unit 54 can perform the unlocking step 105.

[0166] After the unlocking step 105, control unit 54 can perform a motion request check step 114 in order to check: (Yes) whether the motion requested by the operator can be effected by actuating only one electric actuator or instead (No) whether the motion requested by the operator requires the actuation of more than one electric actuator of the actuating set, e.g. the tool actuating set 20.1.

[0167] In case (Yes) the motion requested by the operator involves only one electric actuator, in a steady step 116, control unit 54 keeps actuating the first electric actuator already moving, without actuating a second electric actuator.

[0168] In case (No) the motion requested by the operator involves two or more electric actuators, in an actuation step 118, control unit 54 can actuate a second electric actuator belonging to the same actuating set as the first electric actuator already moving. The second electric actuator is actuated in proportion of the requested motion. Thus, the second electric actuator and the first electric actuator move concomitantly or consecutively to move a part of the excavator 1.

[0169] For instance, in case (No) the motion requested by the operator involves tool actuator 22 and arm actuator 24, whereas only tool actuator 22 is moving, control unit 54 can, in the actuation step 118, actuate arm actuator 24 concomitantly to tool actuator 22 so as to move tool 2.

[0170] Furthermore, excavator 1 can further include several position sensors. Each position sensor can be configured to detect the position of a respective electric actuator and to send position signals to control unit 54. Control unit 54 can be further configured to determine the position of each one of the electric actuators based upon said position signals. For instance, each position sensor can be an encoder coupled with a respective electric actuator.

[0171] The control method 1 can be performed continuously or recursively as long as the excavator 1 is in service. In other words, control method 1 can be performed as a loop.

[0172] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the appended drawings. Instead, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

[0173] For instance, according to a non illustrated embodiment, the excavator can include an actuating set comprising an hydraulic actuator and several electric actuators. The control method can be implemented on such an excavator.

[0174] Likewise, according to a non illustrated embodiment, in addition to one or several actuating set(s) comprising only electric actuators (no hydraulic actuators) as here-above mentioned, the excavator can comprise one or several hydraulic actuators, controlled individually apart from the electric actuators. The control method can be implemented on such an excavator.