Control method for controlling a movable member of an excavator and excavator comprising a control unit implementing such a control method

• US 10,633,824 B2
• Filed: 04/03/2015
• Issued: 04/28/2020
• Est. Priority Date: 04/03/2015
• Status: Active Grant

• Current Assignee: Volvo Construction Equipment AB (Volvo AB)
• Original Assignee: Volvo Construction Equipment AB (Volvo AB)
• Inventors: Bruyere, Lilian, Nedjimi, Ahcene, Savoye, Francois, Caillieret, Roger
• Primary Examiner(s): Hilgendorf, Dale W
• Application Number:
  US15/563,629
• Publication Number:
  US 20180072281A1
• Time in Patent Office: 1,852 Days
• CPC Class Codes: B60T 1/062 acting on transmission parts
• CPC Class Codes: B60T 13/748 acting on electro-magnetic brakes combined with fluid-pressure brake systems B60T13/667
• CPC Class Codes: B60T 2201/022 Collision avoidance systems
• CPC Class Codes: B60T 7/22 initiated by contact of vehicle, e.g. bumper, with an external object, e.g. another vehicle , or by means of contactless obstacle detectors mounted on the vehicle
• CPC Class Codes: B60T 8/17616 Microprocessor-based systems
• CPC Class Codes: B66C 13/105 electrical
• CPC Class Codes: B66C 13/30 Circuits for braking, traversing, or slewing motors
• CPC Class Codes: E02F 3/425 Drive systems for dipper-arms, backhoes or the like
• CPC Class Codes: E02F 9/128 Braking systems
• CPC Class Codes: E02F 9/2029 Controlling the position of implements in function of its load, e.g. modifying the attitude of implements in accordance to vehicle speed control for hydraulic or pneumatic drives E02F9/2203, E02F9/2221 and E02F9/2253 take precedence
• CPC Class Codes: E02F 9/2033 Limiting the movement of frames or implements, e.g. to avoid collision between implements and the cabin sub-groups of E02F3/431 of E02F3/435 take precedence; for turntables E02F9/123
• CPC Class Codes: E02F 9/2083 Control of vehicle braking systems
• CPC Class Codes: E02F 9/2095 Control of electric, electro-mechanical or mechanical equipment not otherwise provided for, e.g. ventilators, electro-driven fans control of hydraulic driven equipment E02F9/22
• CPC Class Codes: E02F 9/2221 Control of flow rate; Load sensing arrangements E02F9/2203 take precedence over E02F9/2221

Abstract

A control method controls a movable member of an excavator including a movable member holding a load, an actuator with electric motor and static brake, a control unit and a motion sensor unit. The static brake and electric motor generate respectively an upper threshold brake force and an upper threshold motor force. An immobilization operation provides that the static brake generates the upper threshold brake force and the electric motor is stopped. A slippage detection operation provides that the control unit detects whether an electric actuator is moving despite the static brake. If the electric actuator is moving, a motor energizing operation provides that the electric motor generates a motor force equal or superior to upper threshold brake force in a direction opposite to the slippage direction. After energizing the motor, a brake release operation provides that the control unit releases the static brake.

Claims

1. A control method, for controlling a movable member of an excavator, the control method including a step of:

providing the excavator including at least;

the movable member configured to hold a load when the excavator is in service,

an electric actuator configured to actuate the movable member, the electric actuator comprising;

i) an electric motor which is reversible and which is configured to apply a motor force on the electric actuator, and ii) a static brake configured to generate a brake force so as to brake the electric actuator,

a control unit configured to control, the electric motor and the static brake, and

a motion sensor unit configured to detect a motion of the electric actuator and to send motion signals to the control unit,

wherein the static brake is configured to generate an upper threshold brake force and the electric motor is configured to generate an upper threshold motor force, the upper threshold brake force being inferior to the upper threshold motor force, and

wherein the control method includes at least;

performing an immobilization step wherein the control unit controls the static brake to generate the upper threshold brake force,

performing a slippage detection step wherein the control unit checks the motion signals in order to detect whether the electric actuator is moving in a slippage direction despite the static brake generating the upper threshold brake force,

in case the control unit detects that the electric actuator is moving in the slippage direction, performing a motor energizing step wherein the control unit controls a power supply to the electric motor so that the electric motor generates a motor force substantially equal or superior to the upper threshold brake force in a direction opposite to the slippage direction, and

after start of the motor energizing step and in case the electric motor generates a non null motor force, performing a brake release step wherein the control unit releases at least partially the static brake.

2. The control method according to claim 1, wherein, during the motor energizing step, the control unit controls the power supply to the electric motor so that the electric motor generates a motor force that is superior to 80% to 100%, of the upper threshold brake force.

3. The control method according to claim 1, further including at least:

after completion of the brake release step, performing a motion detection step wherein the control unit checks the motion signals in order to detect whether the electric actuator keeps moving in the slippage direction,

in case the electric actuator is moving in the slippage direction, performing a check step wherein the control unit checks whether the electric motor is generating a motor force equal or superior to the upper threshold motor force, and

in case the electric motor is generating the motor force equal or superior to the upper threshold motor force, performing an overload relief step wherein the control unit controls the electric motor to generate the upper threshold motor force.

4. The control method according to claim 3, further including:

in case the electric motor is generating a motor force inferior to the upper threshold motor force, performing an incremental step wherein the control unit increases the motor force,

performing a loop step wherein the motion detection step, an overload check step, the overload relief step and/or the incremental step are repeated until the electric actuator remains motionless during a predetermined period, and

in case the electric actuator has stopped moving during the predetermined period, performing the immobilization step.

5. The control method according to claim 4, wherein the control unit further comprises a timer for counting the predetermined period, and wherein the predetermined period ranges from 1 s to 5 s.

6. The control method according to claim 1, wherein the control unit performs the motor energizing step in case the motion signals present a predetermined condition, for instance in case an amplitude of the motion signals supersedes a predetermined motion threshold.

7. The control method according to claim 1, wherein, during the motor energizing step, the control unit controls the power supply to the electric motor so that the electric motor generates a motor force ranging between 100% and 120% of the upper threshold brake force.

8. The control method according to claim 1, wherein the upper threshold motor force ranges between 100% and 300% of the upper threshold brake force.

9. The control method according to claim 1, wherein the upper threshold brake force can range between 33% and 99% of a maximum brake force.

10. The control method according to claim 1, wherein the upper threshold brake force corresponds to a predetermined overload limit.

11. The control method according to claim 10, wherein the predetermined overload limit is set as a function of the mechanical strength of the movable member.

12. The control method according to claim 11, wherein the predetermined overload limit ranges between 25% and 80% of the mechanical strength of the movable member.

13. The control method according to claim 1, wherein the movable member 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, a swing member configured to swing the boom, a drive member configured to displace the swing member with respect to a site ground and an offset member.

14. The control method according to claim 1, wherein the motion sensor unit includes a motion sensor selected from the group consisting of an encoder coupled with the electric actuator, a motion detector and a system comprising at least two position sensors which are configured to cooperate in order to generate motion signals.

15. The control method according to claim 1, wherein the electric actuator is selected in a group consisting of linear electric actuators and rotational electric actuators.

16. An excavator including at least:

a movable member configured to hold a load when the excavator is in service,

an electric actuator configured to actuate the movable member, the electric actuator comprising;

i) an electric motor which is reversible and which is configured to apply a motor force on the electric actuator, and ii) a static brake configured to generate a brake force so as to brake the electric actuator,

a control unit configured to control the electric motor and the static brake,

a motion sensor unit configured to detect a motion of the electric actuator and to send motion signals to the control unit,

wherein the static brake is configured to generate an upper threshold brake force and the electric motor is configured to generate an upper threshold motor force, the upper threshold brake force being inferior to the upper threshold motor force, and

wherein the control unit is further configured to;

perform an immobilization step wherein the control unit controls the static brake to generate the upper threshold brake force,

perform a slippage detection step wherein the control unit checks the motion signals in order to detect whether the electric actuator is moving in a slippage direction despite the static brake generating the upper threshold brake force,

in case the control unit detects that the electric actuator is moving in the slippage direction, perform a motor energizing step wherein the control unit controls a power supply to the electric motor so that the electric motor generates a motor force substantially equal or superior to the upper threshold brake force in a direction opposite to the slippage direction, and

after start of the motor energizing step and in case the electric motor generates a non null motor force, perform a brake release step wherein the control unit releases at least partially the static brake.