Patent Application
20220024740
The present invention relates to a controller for a working machine including a load handling apparatus, and a working machine including such a controller.
Working machines including a load handling apparatus typically include a front and a rear axle supporting a body on which the load handling apparatus is mounted. Wheels are normally coupled to the front and rear axles, the wheels being configured to engage the ground and permit movement of the working machine across the ground.
The load handling apparatus includes, for example, an extendable lifting arm moveable by one or more actuators with respect to the working machine body. The lifting arm includes a load carrying implement to carry a load such that a load carried by the load carrying implement can be moved with respect to the body by the lifting arm.
Movement of the load produces a moment of tilt about an axis of rotation of one of the front or rear axles. Alternatively, a moment of tilt may be induced about another axis where, for example, stabilizers are used to stabilise the body relative to the ground during load handling operations.
Extension of the lifting arm in a forwards direction, particularly when carrying a load, induces a moment of tilt about the axis of rotation of the front axle. As a result the portion of the working machine (and load) weight supported by the rear axle decreases.
In order to ensure that the working machine does not rotate about the front axle to such an extent that the wheels coupled to the rear axle are lifted from the ground surface (i.e. to ensure that the working machine does not tip), a controller prevents or restricts further movement of the lifting arm when the load on the rear axle reduces to a threshold level. An example of a working machine including such a controller to prevent tipping can be found in EP 1,532,065.
The lifting arm is typically moved using a hydraulic actuator under the control of a machine operator. Hydraulic fluid is provided by a hydraulic pump which is driven by the engine of the working machine. The controller restricts the movement of the lifting arm by controlling a valve which restricts the supply of hydraulic fluid to the hydraulic actuator as the tipping threshold approaches, overriding any control input from the machine operator. Once the tipping threshold is reached, the controller prevents further movement of the lifting arm by diverting hydraulic fluid away from the hydraulic actuator into a tank. The working machine engine runs constantly while the working machine is in operation meaning that the hydraulic pump is always running as well, even if the flow of hydraulic fluid is being restricted or the hydraulic fluid is being diverted into the tank—this is not particularly efficient.
The present inventions seeks to provide a means to prevent tipping with improved efficiency.
An aspect of the present invention provides a controller for use with a working machine, the working machine comprising:
Directly controlling an electrical drive element (such as an electric motor driven hydraulic pump or an electric actuator) provides a more efficient way to control the speed and movement of the load handling apparatus to avoid tipping rather than by restricting or diverting hydraulic fluid from a hydraulic pump that is always running off the engine. For example, rather than having a hydraulic pump still running when movement of the electrically driven actuator assembly has been stopped because a value of the tilt signal has reached a tilt threshold, there is no need to drive the electrical drive assembly, saving energy. It is particularly advantageous for electric working machines which do not have an engine running constantly to power a hydraulic pump and where energy savings help to preserve battery life.
The control signal may be configured to reduce the speed of the electrical drive element as the value of the tilt signal approaches the tilt threshold.
The control signal may be configured to prevent (stop) movement of the electrically driven actuator assembly when the value of the tilt signal reaches or exceeds the tilt threshold. The control signal may be configured to prevent movement of the electrically driven actuator assembly which would cause the value of the tilt signal to reach or exceed the tilt threshold (i.e. preventing any movement that would increase the risk of the working machine tipping).
The control signal may be configured so that when the value of the tilt signal reaches or exceeds the tilt threshold, the control signal allows movement of the electrically driven actuator assembly in one or more directions which would cause the value of the tilt signal to reduce below the tilt threshold (i.e., so that the load handling apparatus can be freely moved in one or more directions that reduces the risk of the working machine tipping). When moving the hydraulic actuator in one or more directions that reduces the value of the tilt signal below the tilt threshold (i.e., in one or more directions that reduces the risk of the working machine tipping), the speed of the hydraulic pump may be increased to increase the supply of hydraulic fluid to the hydraulic actuator. In this way, restrictions imposed on the hydraulic actuator as the tilt threshold was approached may be progressively lifted as the hydraulic actuator backs away from the tilt threshold.
The electrically driven actuator assembly optionally comprises an electric linear actuator and the electrical drive element comprises the electric linear actuator.
The electrical drive element may comprise an electric motor, such as a motor that generates rotational motion (to drive a mechanical assembly in the linear actuator which converts the rotational motion into linear motion) or a linear motor.
The electrically driven actuator assembly optionally comprises a hydraulic actuator and an electrically driven hydraulic pump configured to provide hydraulic fluid to the hydraulic actuator, wherein the electrical drive element comprises the electrically driven hydraulic pump and wherein the control signal is configured to control the electrically driven hydraulic pump to control a supply of hydraulic fluid to the hydraulic actuator based on the value of the tilt signal relative to the tilt threshold.
The control signal may be configured to control the electrically driven hydraulic pump to restrict (for example, reduce) the supply of hydraulic fluid to the hydraulic actuator in order to restrict movement of the load handling apparatus based on the value of the tilt signal relative to the tilt threshold.
The control signal may be configured to control the electrically driven hydraulic pump to restrict the supply of hydraulic fluid to the hydraulic actuator in order to restrict movement of the load handling apparatus by indicating a reduction in the speed of the hydraulic pump.
The control signal is optionally configured to stop the electrically driven hydraulic pump based on the value of the tilt signal reaching or exceeding the tilt threshold to substantially prevent the supply of hydraulic fluid to the hydraulic actuator in order to prevent a movement of the load handling apparatus which would increase the value of the tilt signal above the tilt threshold (i.e., preventing any movement that would increase the risk of the working machine tipping).
The control signal is optionally configured so that, when the value of the tilt signal reaches or exceeds the tilt threshold, the control signal causes the electronically driven hydraulic pump to supply hydraulic fluid to the hydraulic actuator only so that the hydraulic actuator can be moved in one or more directions which reduces the value of the tilt signal below the tilt threshold (i.e., so that the load handling apparatus can be freely moved in one or more directions that reduces the risk of the working machine tipping). When moving the hydraulic actuator in one or more directions that reduces the value of the tilt signal relative to the tilt threshold (i.e., one or more directions that reduce the risk of the working machine tipping), the speed of the hydraulic pump may be increased to increase the supply of hydraulic fluid to the hydraulic actuator.
The controller is further optionally configured to receive a load orientation signal representative of an orientation of the load handling apparatus with respect to a reference orientation, the tilt threshold being dependent on the load orientation signal.
The load orientation signal may represent an angle of the load handling apparatus with respect to the reference orientation.
The reference orientation may be one of: gravity; a horizontal level; and an orientation of the load handling apparatus relative to an orientation of the working machine.
The controller may further be configured to receive a stabilizer signal representative of whether one or more stabilizers of the working machine are deployed, and the tilt threshold is further dependent on the stabilizer signal.
The tilt signal optionally represents the load on an axle of the working machine.
A second aspect of the present invention provides a control system incorporating a controller according to the first aspect of the present invention.
A third aspect of the present invention provides a working machine incorporating a controller according to the first aspect of the present invention or a control system according to the second aspect of the present invention.
The working machine may further comprise a body and a load handling apparatus.
The load handling apparatus may comprise a lifting arm, the lifting arm being at least pivotable with respect to the working machine body.
The lifting arm may be pivotable about a substantially transverse axis of the working machine and the lifting arm extends substantially parallel to a longitudinal axis of the working machine.
The lifting arm may be pivotable about a location between a longitudinal mid-point of the body and a rear of the body.
The lifting arm is optionally telescopic.
The lifting arm may have a fixed orientation in a vertical plane with respect to the body.
A load handling implement may be mountable to the lifting arm forward of the body.
The working machine optionally further comprises a ground engaging propulsion structure to permit movement thereof over the ground.
The ground engaging propulsion structure may be electrically propelled.
The working machine may further comprise an electrical energy store configured to provide electrical energy to the actuator assembly, and optionally to propel the working machine.
The electrical energy store may comprise a battery, and/or a capacitor and/or a fuel cell.
The working machine may further comprise one or more stabilizer legs.
The actuator assembly optionally comprises a hydraulic actuator and an electrically driven hydraulic pump.
The electrically driven hydraulic pump may comprise an electric motor and the working machine comprises an independent electric steering motor and/or an independent electric traction motor.
The actuator assembly optionally comprises an electric actuator.
The invention shall now be described, by way of example only, with reference to the accompanying drawings, in which:
The working machine 1 has a ground engaging propulsion structure comprising a first axle A1 and a second axle A2, each axle being coupled to a pair of wheels (two wheels 4, 5 are shown in
At least one of the first and second axles A1, A2 may be coupled to the working machine body 2 by a pivot joint (not shown) located at substantially the centre of the axle such that the axle can rock about a longitudinal axis of the working machine 1—thus, improving stability of the working machine 1 when moving across uneven ground. It will be appreciated that this effect can be achieved in other known manners.
A load handling apparatus 6, 7 is coupled to the working machine body 2. The load handling apparatus 6, 7 may be mounted by a mount 9 to the working machine body 2. The load handling apparatus 6, 7 includes a lifting arm 6, 7. The lifting arm 6, 7 may be a telescopic arm having a first section 6 connected to the mount 9 and a second section 7 which is telescopically fitted to the first section 6. The second section 7 of the lifting arm 6, 7 is telescopically moveable with respect to the first section 6 such that the lifting arm 6, 7 can be extended and retracted.
Movement of the first section 6 with respect to the second section 7 of the lifting arm 6, 7 may be achieved by use of an extension actuator 8 which may be a double acting hydraulic linear actuator or an electric linear actuator. One end of the extension actuator 8 is coupled to the first section 6 of the lifting arm 6, 7 and another end of the extension actuator 8 is coupled to the second section 7 of the lifting arm 6, 7 such that extension of the extension actuator 8 causes extension of the lifting arm 6, 7 and retraction of the extension actuator 8 causes retraction of the lifting arm 6, 7. As will be appreciated, the lifting arm 6, 7 may include a plurality of sections: for example, the lifting arm 6, 7 may comprise two, three, four or more sections. Each arm section may be telescopically fitted to at least one other section.
The lifting arm 6, 7 can be moved with respect to the working machine body 2 and the movement is preferably, at least in part, rotational movement about the mount 9 (about pivot B of the lifting arm 6, 7). The rotational movement is about a substantially transverse axis of the working machine 1, the pivot B being transversely arranged. Rotational movement of the lifting arm 6, 7 with respect to the working machine body 2 is achieved by use of at least one lifting actuator 10 coupled, at one end, to the first section 6 of the lifting arm 6, 7 and, at a second end, to the working machine body 2. The lifting actuator 10 is a double acting hydraulic linear actuator, but may alternatively be single acting, or an electric linear actuator.
A load handling implement 11 may be located at a distal end of the lifting arm 6, 7. The load handling implement 11 may include a fork-type implement which may be rotatable with respect to the lifting arm 6, 7 about a pivot D, this pivot also being transversely arranged. Other implements may be fitted such as shovels, grabs etc. Movement of the load handling implement 11 may be achieved by use of a double acting linear hydraulic actuator (not shown) coupled to the load handling implement 11 and the distal end of the section 7 of the lifting arm 6, 7 or an electric linear actuator.
Off-highway working machines 1 such as those according to the present invention are configured to transport loads L over uneven ground, i.e. with a load held by the load handling implement 11, an operator controls the propulsion structure to move the entire working machine with the load from one location to another. This may be contrasted with working machines such as mobile cranes and roto-telehandlers in which a boom is pivotable about both a lateral and an upright axis—i.e. the boom can slew relative to a working machine body on a turret or turntable—as well as pivot upwards about the lateral axis. Such working machines may be driven to a particular location and are immobilised on four or more stabilizer legs to lift the wheels or other propulsion means entirely off the ground, and to ensure the upright slew axis is absolutely vertically aligned. From that fixed location the working machine will move a load from one location to another location using movements of the boom about the lateral and upright axes. As such, different stability considerations apply to working machines in which a boom can also move about an upright axis. Therefore different safety legislation, and consequently different safety systems, are employed on such working machines.
When the working machine 1 lifts a load L supported by the load handling implement 11, the load L (and implement 11) will produce a moment about an axis of the working machine 1 which causes the working machine to tend to tilt about that axis. The moment is, therefore, referred to herein as a moment of tilt. In the depicted example, this axis of the working machine 1 about which the working machine 1 is likely to tilt is axis C—i.e. about the first (or front) axle A1. If the lifting arm 6, 7 is stopped suddenly when the lifting arm 6, 7 is carrying a heavy load L and/or moving a load L at high speed, the inertia may be sufficient to cause the working machine to tip.
The system 20 includes a tilt sensor 22 configured to sense a parameter which is representative of a moment of tilt of the working machine 1 about an axis. The tilt sensor 22 is further configured to issue a signal to a controller 24 such that a moment of tilt of the working machine about an axis can be determined.
The tilt sensor 22 may include a strain gauge coupled to an axle A1, A2 of the working machine 1. The tilt sensor 22 may include a load cell located between the working machine body 2 and an axle and configured to sense the load (or weight) on the axle. The tilt sensor 22 may be coupled to or otherwise associated with the second (or rear) axle A2. The tilt sensor 22 may include several sensors which sense different parameters and use these parameters to generate a signal such that a moment of tilt of the working machine 1 can be determined. The tilt sensor 22 may take other forms, as will be appreciated, such as by monitoring fluid pressure in one or more actuators, or utilising strain gauges located on the load handling apparatus.
The controller 24 receives a tilt signal from the tilt sensor 22 representative of a moment of tilt of the working machine 1. The controller 24 may be any suitable microprocessor type controller and the signals may be transmitted by any suitable wired or wireless communication system or protocol, such as via a CAN bus of the working machine 1.
In this embodiment, an orientation sensor arrangement 14 (see
The orientation sensor arrangement 14 is further configured to issue a signal to the controller 24 representative of an orientation (hereinafter and orientation signal) of at least a portion of the load handling apparatus 6, 7 with respect to the reference orientation H, G or the machine body 2. With reference to
Thus, to counteract this issue, one measure is to require a greater threshold load on the second axle A2 to provide a suitable safety margin in all operating conditions. However such a safety margin may be excessive in positions Y and Z, and so the machine 1 may be prevented from carrying out operations that are safe in these positions if such a threshold is present. As such the productivity of the machine for carrying out certain operations may be reduced.
In an embodiment (see
When the signal representative of an orientation of the load handling apparatus 6, 7 indicates that the load handling apparatus 6, 7 is in a second orientation with respect to horizontal ground H or the machine body 2, the controller compares the signal representative of the moment of tilting with the second threshold value TV2. The controller 24 may then issue a signal or command to restrict or substantially prevent a movement of the load handling apparatus 6, 7 if, for example, the signal representative of the moment of tilting is close to or is approaching the second threshold value TV2.
In an embodiment, the first and second threshold values TV1 and TV2 are selected dependent on the orientation of the load handling apparatus 6, 7. A single threshold value may apply to several different orientations of the load handling apparatus 6, 7. The threshold values may be proportional to or substantially proportional to an orientation of the load handling apparatus 6, 7 with respect to the reference orientation or the machine body. The proportional or substantially proportional dependency of the threshold value on the orientation of the load handling apparatus 6, 7 may be limited to a range of orientations of the load handling apparatus 6, 7 or may be over the entire range of permitted or possible orientations of the load handling apparatus 6, 7.
In an embodiment, there is a plurality of threshold values each with a respective load handling apparatus orientation associated therewith. The threshold values and associated load handling apparatus orientations may be stored in a lookup table which can be accessed by the controller 24.
In an embodiment, the load sensor arrangement senses the weight on the second (or rear) axle A2 of the machine 1. In this example embodiment, a typical load on the second axle of the machine 1 is 4000 kg to 6000 kg. A first threshold value for the controller 24 is selected to be about 1000 kg for lifting arm angles with respect to the horizontal (with the machine in an typical orientation) of less than about 30° (or less than about 20°-25° in another example), a second threshold value is selected to be about 3500 kg for lifting arm angles with respect to the horizontal of greater than about 45° (or greater than about 40° in another example). The threshold value for any angles between these angles (e.g. between 30° and 45° in one example) may be proportional or substantially proportional to the angle such that there is a substantially linear progression of the threshold value for a given angle from the first to the second threshold value between the specified angles (e.g. between 30° and 45° in one example).
A hydraulic pump 26 supplies hydraulic fluid to at least the hydraulic actuators 8, 10 which controls movement of the load handling apparatus 6, 7. The hydraulic pump 26 is driven by an electric motor 25. The electric motor 25, hydraulic pump 26 and one or more of the actuators 8, 10 can be considered to be an electrically driven actuator assembly. The electric motor 25 can be considered to be an electrical drive element of the electrically driven actuator assembly.
The controller 24 is configured to issue a control signal to control the electric motor 25 of the hydraulic pump 26 to control the supply of hydraulic fluid to the hydraulic actuators 8, 10 based on the demand of an operator based on their input from an operator control 13, as well as the tilt signal and optionally the orientation signal. For example, the control signal may cause the electric motor 25 to stop if the tilt signal indicates that a tilt threshold is exceeded, despite there being a demand from the control 13 for a particular movement of the load handling apparatus 6, 7 to occur.
Stopping the electric motor 25 driving the hydraulic pump 26 substantially prevents the supply of hydraulic fluid to the hydraulic actuators 8, 10 which prevents movement of the load handling apparatus 6, 7 which could cause the tilt threshold to be exceeded and risk tipping the working machine 1. Similarly, the control signal may restrict the electric motor 25 in some way such as causing the electric motor 25 to operate at a reduced speed (for example, slower than the desired velocity that is input by a working machine operator) when the tilt signal indicates that that the tilt threshold is approaching. This may prevent a sudden stop of the load handling apparatus 6, 7 when the tilt threshold is reached, where the inertia of such a sudden stop could lead to the working machine 1 tipping.
Therefore, the controller 24 is able to control the speed of the electric motor 25 driving the hydraulic pump 26, and stop it if necessary. This is more efficient than running the hydraulic pump constantly and restricting/diverting the flow of hydraulic fluid.
The relationship between the maximum permitted speed of operation of an actuator and an associated threshold value TV1 and TV2 may be controlled according to a predetermined relationship stored in the controller 24. The relationship may be a proportional relationship. The relationship may be directly proportional or proportional in accordance with a trigonometric function (such as a tangential function) or other mathematical relationship, for example. In an embodiment, the maximum permitted speed may be zero at the threshold value and may increase in direct proportion to the value of rear axle load in excess of the threshold value. For example, if the threshold value is 1000 kg, the maximum permitted lowering speed of the load handling apparatus at a rear axle load of 1200 kg is double that at 1100 kg. The maximum speed may be in terms of angular velocity or linear velocity of the load handling apparatus 6, 7 or it may be the angular velocity of the electric motor 25 or linear velocity of the actuator. The speed may be measured directly, for example, by sensing motor rotation or derived indirectly from another parameter.
In an embodiment, restricting or substantially preventing a movement of the load handling apparatus 6, 7 includes restricting or substantially preventing a movement of the load handling apparatus 6, 7 in one or more directions that present a risk of the machine tipping. However, movement of the load handing apparatus 6, 7 may be allowed or derestricted in one or more directions that reduce the risk of the machine tipping. For example, the controller 24 may be configured to issue a control signal to control the electric motor 25 of the hydraulic pump 26 to supply hydraulic fluid to the hydraulic actuator 8 and/or hydraulic actuator 10 based on an input from an operator control 13 which indicates a desire to move the hydraulic actuator 8 and/or hydraulic actuator 10 in a direction that reduces the tilt signal below the tilt threshold. The controller 24 may also lift speed restrictions as the tilt signal moves away from the tilt threshold.
In the instance that a demand is received from operator control 13 to move a first hydraulic actuator in a direction that reduces the tilt signal below the tilt threshold but to move a second hydraulic actuator in a direction that increases the tilt signal above the tilt threshold, the controller 24 may issue a control signal which permits the first hydraulic actuator to move while preventing or restricting the second hydraulic actuator from moving. This may be done in the case when each hydraulic actuator has a separate hydraulic pump 26 by controlling the hydraulic pump 26 individually, or in the case where there is only a single hydraulic pump 26 by controlling a valve to restrict or divert the supply of hydraulic fluid to the second actuator.
In an embodiment in which the load handling apparatus 6, 7 includes a lifting arm 6, 7, restricting or substantially preventing a movement of the lifting arm 6, 7 may prevent lowering of the arm 6, 7 to reduce the risk of the machine tipping but may allow movement of the lifting arm 7 in a direction that reduces the risk of the machine tipping, such as raising and/or retraction of the lifting arm 7.
Restricting or substantially preventing a movement of the load handling apparatus 6, 7 is intended to seek to reduce the risk of the machine tipping by preventing or restricting a movement which would otherwise tip—or risk tipping—the machine 1. The use of a threshold value TV1 TV2 which is dependent on an orientation of the load handling apparatus 6, 7 is intended to seek to avoid restricting movement of the load handling apparatus 6, 7 based on a demand from an operator via the controls 13 needlessly, when there is little or no risk of tipping the machine 1 or moving out of safety limits.
The controller 24 may operate according to an algorithm which enables the controller to ignore transient changes of loading sensed by the sensor as a result of changing machine dynamics or of reaction to initial lift arm movements.
The electric motor 25 driving the hydraulic pump is separate from an electric motor M which propels the working machine 1 and separate from any electric steering motor S. Therefore, the controller 24 is able to independently control the speed of the electric motor 25 driving the hydraulic pump 26 to prevent tipping, without adversely affecting propulsion or steering.
The tilt threshold value(s) for a particular working machine will be dependent on the working machine characteristics. For example, the tilt threshold may be dependent on the geometry of the working machine, the mass of the working machine, the geometry and mass of the load handling apparatus 6, 7. Further, for working machines in which the load handling apparatus 6, 7 is telescopically extendible, a given angular velocity will result in a differing x and y component of linear velocity dependent upon the extension of the load handling apparatus. As such an extension sensor (not shown) may also signal the controller 24 and the controller 24 may adjust the threshold value according to the extension. The threshold values are selected in an attempt to prevent tipping of the working machine during operation.
The working machine 1 may include one or more stabilizers S which may be extended (deployed) or retracted from the working machine body 2. The or each stabilizer S preferably extends from a part of the working machine body 2 which is towards the load handling implement 11 of the working machine 1. There are preferably two stabilizers S and each stabilizer is preferably located adjacent to a wheel which is coupled to the first (or front) axle.
The or each stabilizer S is configured to be extended such it makes contact with a ground surface (as depicted in broken lines in
For working machines 1 of the teachings it is typically not required for there to be further stabilizers adjacent to or rearward of the rear axle. This is because such stabilizers would not offer an appreciable increase in forward stability and there is typically no requirement for rearward stability since the load would not ordinarily placed in a position where it overhangs a rear of the working machine.
In other words, an optimal forward stability can be achieved by the front of the working machine being supported on the stabilizer(s) S and the rear of the working machine is supported on the wheels 5 mounted to axle A2.
If the working machine 1 includes one or more stabilisers S, then the controller 24 may be further configured to receive a signal from a stabiliser sensor 28, the signal being representative of whether or not the or each stabiliser has been deployed. If the or each stabiliser S has been deployed, then the threshold values used by the controller 24 may be different from those which are used without the or each stabiliser S deployed. The controller 24 may include a first set of threshold values for when the or each stabiliser S is not deployed and a second set of threshold values for when the or each stabiliser S is deployed. The threshold values used when the or each stabiliser S is deployed may be higher than the threshold values used for corresponding orientations of the load handling apparatus 6, 7 when the or each stabilizer S is not deployed.
The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the teachings in diverse forms thereof. It will be appreciated that numerous changes may be made within the scope of the present teachings.
For example, although the working machine 1 has been described in terms of having an electric motor E for propulsion, the working machine could be propelled with a conventional (e.g. diesel) engine where the separate electric motor 25 driving the hydraulic pump 26 still allows for independent control of the hydraulic pump 26, which provides improved efficiency over running the hydraulic pump 26 constantly from the conventional engine. Further, other forms of electrically driven actuator assemblies may be employed. For example, linear electric motors may be employed or electric motors connected to leadscrew, ball screw, rack and pinion, cable, chain, belt or other gear arrangements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1902826.5 | Mar 2019 | GB | national |
| 1902827.3 | Mar 2019 | GB | national |
| 1903399.2 | Mar 2019 | GB | national |
| 1904474.2 | Mar 2019 | GB | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16806985 | Mar 2020 | US |
| Child | 17493656 | US |
