Working equipment with electrically powered hydraulically operated arm arrangement

Abstract

Working equipment including a hydraulically movable arm arrangement for a crane, an electric motor, a hydraulic pump, and a pump controller. An equipment controller is arranged to determine a maximum flow limit from the pump in dependence of a comparison of a current limit received from a battery system and a current consumption monitored by the pump controller, and to compare the determined limit with required flow of hydraulic fluid from the pump needed to move the movable arm arrangement in accordance with operating signals, and if the result does not fulfil a rule of a set of fluid control rules, the controller adapts the operating signals to reduce flow of hydraulic fluid to at least one of a plurality of actuators according to a rule of a set of adaptation rules, such that at least one rule of the set of fluid control rules is fulfilled.

Claims

1. A working equipment comprising: a hydraulically movable arm arrangement for a crane, at least one electric motor arranged to be powered by a battery system, at least one hydraulic pump arranged to be operated by the at least one electric motor, and a pump controller configured to control the electric motor and/or the hydraulic pump, and to monitor the current consumption of the at least one electric motor; a plurality of actuators, arranged to be operated by hydraulic fluid discharged from the at least one hydraulic pump and further arranged to move the hydraulically movable arm arrangement during a working assignment, wherein the battery system has an associated available current limit that decreases as the at least one electric motor powers the at least one hydraulic pump to operate the actuators to move the hydraulically movable arm arrangement, and an equipment controller configured to control movement of the movable arm arrangement by generating operating signals controlling a flow and/or pressure of hydraulic fluid to the plurality of actuators, and to receive a battery condition signal comprising a presently available current limit from the battery system, wherein the equipment controller is further configured to monitor the required flow of hydraulic fluid from the at least one hydraulic pump needed to move the movable arm arrangement in accordance with the operating signals, characterized in that the equipment controller is configured to dynamically adapt to decreases in the available current limit of the battery system in that the equipment controller is arranged to determine a maximum flow limit of the hydraulic fluid from the at least one hydraulic pump in dependence of a comparison of the presently available current limit received from the battery system and the monitored current consumption by the pump controller, wherein, the equipment controller is configured to compare said determined maximum flow limit with a required flow of hydraulic fluid from the at least one hydraulic pump needed to move the movable arm arrangement in accordance with the operating signals, and if the result of the comparison does not fulfil at least one rule of a set of fluid control rules, the equipment controller is configured to adapt the operating signals to reduce the flow of hydraulic fluid to at least one of the plurality of actuators according to at least one rule of a set of adaptation rules, such that at least one rule of said set of fluid control rules is fulfilled.

2. The working equipment according to claim 1, wherein, if the monitored current consumption is larger than the current limit, the maximum flow limit of the hydraulic fluid is set to a value corresponding to said current limit.

3. The working equipment according to claim 1, wherein said set of fluid control rules comprises at least one of: the required flow of hydraulic fluid is lower than said received maximum flow limit; the required flow of hydraulic fluid is at least 5-15% lower than said received maximum flow limit.

4. The working equipment according to claim 1, wherein said set of adaptation rules comprises at least one of: a scaling down rule comprising generating operating signals to reduce the flow of hydraulic fluid to the plurality of actuators by a preset reduction factor; a priority rule comprising generating operating signals to reduce the flow of hydraulic fluid to the plurality of actuators according to a priority list where actuators having higher priority have no or low reduction and actuators having lower priority have high reduction.

5. The working equipment according to claim 1, wherein the pump controller is further configured to control the operation of the electric motor and/or the hydraulic pump to make available the required flow or corresponding pressure of hydraulic fluid from the pump.

6. A working equipment system comprising a working equipment according to claim 1, wherein the battery system includes a battery, a sensor system for measuring parameters related to a battery condition of the battery, and a battery controller configured to generate the battery condition signal comprising the presently available current limit for the battery in response to the measured parameters related to the battery condition.

7. The working equipment system according to claim 6, wherein the battery controller is further arranged to generate an alert signal in response to the measured parameters related to the battery condition indicating a malfunction state of the battery, and the equipment controller is further arranged to determine the maximum flow limit of the hydraulic fluid from the pump to a predetermined alert level in response of receipt of the alert signal from the battery controller.

8. A method of a working equipment comprising: a hydraulically movable arm arrangement for a crane, at least one electric motor arranged to be powered by a battery system, at least one hydraulic pump arranged to be operated by the electric motor, and a pump controller configured to control the at least one electric motor and/or the hydraulic pump, and to monitor the current consumption of the at least one electric motor; a plurality of actuators, arranged to be operated by hydraulic fluid discharged from the at least one hydraulic pump and further arranged to move the hydraulically movable arm arrangement during a working assignment, wherein the battery system has an associated available current limit that decreases as the at least one electric motor powers the at least one hydraulic pump to operate the actuators to move the hydraulically movable arm arrangement, and an equipment controller configured to control movement of the movable arm arrangement by generating operating signals controlling a flow and/or pressure of hydraulic fluid to the plurality of actuators, and to receive a battery condition signal comprising a presently available current limit from the battery system arranged to power the at least one electric motor, wherein the method comprises: monitoring, by the equipment controller, the required flow of hydraulic fluid from the at least one pump needed to move the movable arm arrangement in accordance with the operating signals, characterized in that the method further comprises: dynamically adapting to decreases in the available current limit of the battery system by determining, by the equipment controller, a maximum flow limit of the hydraulic fluid from the at least one pump in dependence of a comparison of the current limit received from the battery system and the monitored current consumption by the pump controller, comparing, by the equipment controller, said determined maximum flow limit with a required flow of hydraulic fluid from the at least one pump needed to move the movable arm arrangement in accordance with the operating signals, and if the result of the comparison does not fulfil at least one rule of a set of fluid control rules, the method comprises adapting the operating signals to reduce the flow of hydraulic fluid to at least one of the plurality of actuators according to at least one rule of a set of adaptation rules, such that at least one rule of said set of fluid control rules is fulfilled.

9. The method according to claim 8, wherein, if the monitored current consumption is larger than the current limit, the maximum flow limit of the hydraulic fluid is set to a value corresponding to said current limit.

10. The method according to claim 8, wherein said set of fluid control rules comprises at least one of: the required flow of hydraulic fluid is lower than said received maximum flow limit; the required flow of hydraulic fluid is at least 5-15% lower than said received maximum flow limit.

11. The method according to claim 8, wherein said set of adaptation rules comprises at least one of: a scaling down rule comprising generating operating signals to reduce the flow of hydraulic fluid to the plurality of actuators by a preset reduction factor; a priority rule comprising generating operating signals to reduce the flow of hydraulic fluid to the plurality of actuators according to a priority list where actuators having higher priority have no or low reduction and actuators having lower priority have high reduction.

12. The method according to claim 8, comprising controlling, by the pump controller, the operation of the at least one electric motor and/or the hydraulic pump to make available the required flow or corresponding pressure of hydraulic fluid from the at least one hydraulic pump.

13. The method according to claim 8, comprising determining, by the equipment controller, the maximum flow limit of the hydraulic fluid from the at least one hydraulic pump to a predetermined alert level in response of receipt of an alert signal in response to a battery condition indicating a malfunction state of a battery in said battery system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block diagram schematically illustrating the working equipment, and the working equipment system according to the present invention.

(2) FIG. 2 is flow diagram illustrating the method according to the present invention.

DETAILED DESCRIPTION

(3) The working equipment, the working equipment system, and the method of operating the working equipment, will now be described in detail with references to the appended figures. Moreover, the items and the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

(4) The present invention is preferably applicable on a hydraulically operated crane that may comprise a crane pillar rotatable around a vertical axis. A first boom may be attached to the crane pillar and may be lifted relative the crane pillar. A second boom may further be provided that may be an extendible telescopic boom attached to the first boom. A hydraulically operated working tool is advantageously arranged, e.g. at a tip of the telescopic boom. Movements of one or many of these various parts are normally hydraulically operated.

(5) With references to FIG. 1, a working equipment 2 is provided that comprises a hydraulically movable arm arrangement 4. Examples of such a working equipment may be a crane or a hooklift or other working equipment mounted to a truck. It may further be a working equipment in the form of a vehicle such as a forklift.

(6) The movable arm arrangement may comprise one or many hydraulically moveable booms, telescopic booms, and hydraulically actuated working tools, e.g. grapples, hydraulic hooks or brick grabs mounted on a boom tip.

(7) At least one electric motor 6 is arranged to be powered by a battery system 8, and at least one hydraulic pump 10 is arranged to be operated by the electric motor 6, which is indicated by an arrow. The electric motor may be a speed controlled electric motor having variable or fixed speed. Also other types of electric motors are applicable herein provided they can be operated to control a hydraulic pump.

(8) The hydraulic pump may be a fixed pump and/or a variable displacement pump, and if many pumps are used, a mixture of fixed pumps and variable displacement pumps may be applied. Also other types of hydraulic pumps are applicable herein.

(9) The working equipment also comprises a pump controller 12 configured to control the electric motor 6 and/or the hydraulic pump 10, and to monitor the current consumption 13 of the at least one electric motor 6, and also to monitor various parameters 23 of the hydraulic pump 10. The electric motor and the hydraulic pump may form an integrated unit or form separate parts.

(10) A plurality of actuators 14 are arranged to be operated by hydraulic fluid discharged from the at least one hydraulic pump 10 and further arranged to move the movable arm arrangement 4 during a working assignment. This is schematically indicated by arrows from the actuators 14, and the pump 10 via the actuators 14, to the arm arrangement 4. The actuators may comprise hydraulic cylinders, to and from which the hydraulic fluid is controlled by hydraulic valves. By controlling an hydraulic valve the piston side chamber of a cylinder may e.g. be filled with hydraulic fluid pushing the piston and causing a piston rod to e.g. move a boom of a crane. In the schematic of FIG. 1, the actuators 14 further comprise these hydraulic valves. Operating signals 18a controlling the flow and/or pressure of hydraulic fluid to the plurality of actuators 14, may hence be received and executed by the hydraulic valves.

(11) The working equipment comprises an equipment controller 16 configured to control movement of the movable arm arrangement 4 by generating the operating signals 18, which in FIG. 1 are indicated as different operating signals 18a, 18b, 18c, and 18d. The operating signal 18a is configured to control the flow of hydraulic fluid to hydraulic controlling valves controlling the flow of hydraulic fluid to or from the plurality of actuators 14. The operating signal 18b is applied to the pump controller 12 that in its turn controls the electric motor 6 by operating signal 18c, and/or the hydraulic pump 10 by operating signal 18d, to control the flow of hydraulic fluid (or corresponding pressure) generated by the pump 10. The at least one pump 10 is hydraulically connected to the various actuators by hydraulic connection means such as pipes and hoses in accordance with generally applied techniques.

(12) The equipment controller 16 and the pump controller 12 are illustrated as separate units. However, it may also be possible that these controllers are realized as an integrated unit, or that the equipment controller 16 and/or pump controller 12 are distributed on a plurality of units. These controllers have the necessary processing capacities, communication capabilities, and all other functions required to perform their respective task.

(13) The equipment controller 16 is configured to receive a battery condition signal 20 comprising a presently available current limit from the battery system 8 which is arranged to power the at least one electric motor 6. The electric power to be supplied to the electric motor is schematically illustrated in FIG. 1 as a block arrow.

(14) The battery system 8 is not part of the working equipment, but is included in the working equipment system which will be discussed below. However, it comprises a battery 24, e.g. a battery pack, for supply of current, and further a battery controller 28 and battery sensors 26. By using input from the battery sensors the battery controller is configured to measure e.g. cell voltages and cell temperatures to determine the battery health. Based on the battery's health condition, the battery controller calculates a current limit for the battery pack. The current limit represents the present discharge that can be made from the battery pack without drastically shortening the lifetime of the battery. That is one standardized method for the supplier to provide a lifecycle guarantee for the battery. The battery controller outputs the current limit in ampere, and optionally also error and/or warning alerts, e.g. if the electric motor should be stopped based on the condition of the battery.

(15) The equipment controller 16 is further configured to monitor the required flow of hydraulic fluid from the a least one pump 10 needed to move the movable arm arrangement 4 in accordance with the operating signals 18. The monitoring may be based on signals from pressure or flow sensors in the hydraulic system, signals from the hydraulic valves governing the operation of the hydraulics actuators, the operating signals 18 or from user input received from the operator of the working equipment describing wanted movements of the movable arm arrangement 4. Thus, the monitoring is based upon information in an actuator condition signal 21 received from the actuators, a signal 17 received from the pump controller 12, and from a current consumption 13 monitored by the pump controller, and various parameters 23 from the hydraulic pump 10. The required flow of hydraulic fluid from each hydraulic function may be estimated based on the above in combination with known dimensions and features of the hydraulic actuators.

(16) The equipment controller 16 is arranged to determine a maximum flow limit of the hydraulic fluid from the at least one pump in dependence of a comparison of the current limit received from the battery system 8 and the current consumption 13 monitored by the pump controller 12.

(17) And then, the equipment controller 16 is configured to compare the determined maximum flow limit with the required flow of hydraulic fluid from the at least one pump 10 needed to move the movable arm arrangement 4 in accordance with the operating signals.

(18) If the result of the comparison does not fulfil at least one rule of a set of fluid control rules, the equipment controller 16 is configured to adapt the operating signals 18, i.e. one or many of operating signals 18a, 18b, 18c, and 18d, to reduce the flow of hydraulic fluid to at least one of the plurality of actuators 14 according to at least one rule of a set of adaptation rules, such that at least one rule of said set of fluid control rules is fulfilled.

(19) According to one embodiment, if the monitored current consumption 13 is larger than the current limit, the maximum flow limit of the hydraulic fluid is set to a value corresponding to the current limit. The value corresponding to the current limit, is the value of the hydraulic fluid flow if the current limit of the battery is applied. The flow value corresponding to the current limit of the battery may be estimated using a known relationship from calibrations and/or theory. A value may be calculated or fetched from a table of stored values; stored values may e.g. be further processed using interpolation techniques.

(20) As an alternative, the maximum flow limit may be lowered step-wise in one or many preset intervals until the current consumption is lower than the current limit.

(21) According to another embodiment, the set of fluid control rules comprises at least one of: the required flow of hydraulic fluid is lower than the received maximum flow limit; the required flow of hydraulic fluid is at least 5-15% lower than the received maximum flow limit.

(22) According to another embodiment, the set of adaptation rules comprises at least one of: a scaling down rule comprising to generate operating signals 18 to reduce the flow of hydraulic fluid to the plurality of actuators 14 by a preset reduction factor, e.g. 10%, 20%, 30%, etc.; a priority rule comprising to generate operating signals 18 to reduce the flow of hydraulic fluid to the plurality of actuators 14 according to a priority list where actuators having higher priority have no or low reduction and actuators having lower priority have high reduction;

(23) Naturally, these rules may be combined, e.g. a highly prioritized telescope boom may be controlled to move at a lower speed.

(24) In still another embodiment, the pump controller 12 is further configured to control the operation of the electric motor 6 and/or the hydraulic pump 10 to make available the required flow of hydraulic fluid from the pump.

(25) This may be achieved by the pump controller by receiving information of required flow of hydraulic fluid from the equipment controller. Depending on the configuration of the hydraulic system and the choice of pump, the pump may be arranged to control the pressure of the hydraulic fluid instead of the flow. The equipment controller or the pump controller may then estimate a pressure corresponding to the required flow for the pump. As an alternative, the pump controller is configured to ascertain that the electric motor 6 and/or the hydraulic pump 10 maintain the pressure of the hydraulic fluid that is dependent on, and governed by, the operation of the actuators.

(26) The present invention also relates to a working equipment system 22 which will be described with references to FIG. 1. The working equipment system 22 comprises a working equipment according to the above description, and it is here referred to that description. In addition the system 22 comprises, as described above, a battery system 8 including a battery 24, a sensor system 26 for measuring parameters related to a battery condition of the battery, and a battery controller 28 configured to generate a battery condition signal 20 comprising the presently available current limit for the battery in response to the measured parameters related to the battery condition. The battery system 8 has been described above in relation to the description of the working equipment, and it is referred to that description. The battery system 8 may be provided with a standard interface including a specific communication protocol defining e.g. the format of the battery condition signal.

(27) In a further embodiment of the working equipment system 22 the battery controller 28 is further arranged to generate an alert signal 30 in response to the measured parameters related to the battery condition indicating a malfunction state of the battery 24. The alert signal 30 may be either a separate signal, or may be integrated in the battery condition signal 20. The equipment controller 16 is further arranged to determine the maximum flow limit of the hydraulic fluid from the pump 10 to a predetermined alert level in response of receipt of the alert signal 30 from the battery controller 28. The predetermined alert level is preferably considerably lower than the present maximum flow limit. In that case the adaptation rules may include one or many rules applicable when an alert signal has been received that may include to have a specific priority order of the actuators to be applied. Thus, the equipment controller may be configured to react to errors and warnings sent from the battery and limit the flow demand in all situations regardless of current consumption. In addition, an alarm signal may be generated to alert the machine operator that something is happening. The operator may then be recommended to e.g. park the working equipment.

(28) The present invention also relates to a method of a working equipment 2. The method will be described with references to the flow diagram shown in FIG. 2. The working equipment has been described in detail above and it is herein referred to that description.

(29) Thus, the working equipment 2 comprises a hydraulically movable arm arrangement 4 for a crane, and at least one electric motor 6 arranged to be powered by a battery system 8, at least one hydraulic pump 10 arranged to be operated by the electric motor 6, and a pump controller 12 configured to control the electric motor 6 and/or the hydraulic pump 10, and to monitor the current consumption 13 of the at least one electric motor 6.

(30) A plurality of actuators 14 are provided, arranged to be operated by hydraulic fluid discharged from the at least one hydraulic pump 10 and further arranged to move the movable arm arrangement 4 during a working assignment. An equipment controller 16 is also provided, configured to control movement of the movable arm arrangement 4 by generating operating signals 18 controlling the flow and/or pressure of hydraulic fluid to the plurality of actuators 14, and to receive a battery condition signal 20 comprising a presently available current limit from the battery system 8 arranged to power the at least one electric motor 6.

(31) The method comprises monitoring, by the equipment controller 16, the required flow of hydraulic fluid from the at least one pump 10 needed to move the movable arm arrangement 4 in accordance with the operating signals.

(32) The method further comprises determining, by the equipment controller 16, a maximum flow limit of the hydraulic fluid from the at least one pump in dependence of a comparison of the current limit received from the battery system 8 and the current consumption 13 monitored by the pump controller 12.

(33) Furthermore, the method comprises comparing, by the equipment controller 16, the determined maximum flow limit with the required flow of hydraulic fluid from the at least one pump 10 needed to move the movable arm arrangement 4 in accordance with the operating signals.

(34) If the result of the comparison does not fulfil at least one rule of a set of fluid control rules, the method comprises adapting the operating signals 18 to reduce the flow of hydraulic fluid to at least one of the plurality of actuators 14 according to at least one rule of a set of adaptation rules, such that at least one rule of said set of fluid control rules is fulfilled.

(35) If the monitored current consumption 13 is larger than the current limit, the maximum flow limit of the hydraulic fluid is preferably set to a value corresponding to the current limit.

(36) In a further embodiment, the set of fluid control rules comprises at least one of: the required flow of hydraulic fluid is lower than said received maximum flow limit; the required flow of hydraulic fluid is at least 5-15% lower than said received maximum flow limit.

(37) In still another embodiment, the set of adaptation rules comprises at least one of: a scaling down rule comprising to generate operating signals 18 to reduce the flow of hydraulic fluid to the plurality of actuators 14 by a preset reduction factor; a priority rule comprising to generate operating signals 18 to reduce the flow of hydraulic fluid to the plurality of actuators 14 according to a priority list where actuators having higher priority have no or low reduction and actuators having lower priority have high reduction,

(38) The method preferably comprises controlling, by the pump controller 12, the operation of the electric motor 6 and/or the hydraulic pump 10 to make available the required flow of hydraulic fluid from the pump.

(39) In still another embodiment the method comprises determining, by the equipment controller 16, the maximum flow limit of the hydraulic fluid from the pump 10 to a predetermined alert level in response of receipt of an alert signal 30 in response to a battery condition indicating a malfunction state of a battery 24 in the battery system 8. The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.