Control of a handling machine

Abstract

The invention relates to a handling machine (1) comprising sensors (16, 18) configured to measure an extension amplitude of the handling arm and an angle of inclination of the handling arm (6) with respect to a horizontal plane or with respect to the main body (2) of the handling machine, and a control unit (10) configured to: determine a cut-off threshold value as a function of the extension amplitude and the angle of inclination of the handling arm (6), such that the cut-off threshold value is an increasing function of an effective distance (ℓ) between the second end of the handling arm (6) and the tilting axis, in which the effective distance (ℓ) represents a distance projected onto a horizontal axis or onto a longitudinal axis of the main body, stop a movement of the handling arm in response to a detection that the instability signal is greater than the cut-off threshold value.

Description

technical field

[0001] The invention relates to the field of handling machines, in particular a handling machine of the type comprising a main body, a telescopic handling arm mounted on said main body and movable in rotation about a horizontal axis of rotation, the axis of rotation being located on a first end of the handling arm, a second end of the handling arm being configured to receive a load to be handled, actuators configured to raise and lower the handling arm about the axis of rotation, and to extend and retract the handling arm in a longitudinal direction of said handling arm, and a tilt detector configured to produce a signal representative of a tilting moment applied to the main body about a tilting axis of said handling machine. Technological background

[0002] For a handling machine of the aforementioned type, regulations require that the user be provided with a load chart that defines the permissible positions of the handling arm for different transported masses. Regulations also require stability tests to be performed by placing the handling machine, with the transported mass, on an inclined plane whose angle increases instability. During these stability tests, the handling machine must be stable in all positions permitted by the load chart.

[0003] Using an inclined plane increases the machine's tendency to tip over compared to horizontal operation. This is done to incorporate safety margins into the load chart, ensuring that operating the machine within the load chart's limits does not endanger the user. The increased tendency to tip over caused by the inclined plane affects the various elements contributing to the total tipping moment to varying degrees. In particular, because the center of gravity of the mass carried at the end of the handling arm is higher than the center of gravity of the handling arm itself, the inclined plane amplifies the tipping moment contribution generated by the mass carried at the end of the handling arm to a greater extent than the tipping moment contribution generated by the handling arm itself.In other words, the load chart incorporates safety margins that take into account, to varying degrees, the two overturning moment contributions.

[0004] It is known to generate a signal representing the instability of the handling machine by means of a strain gauge placed on the axle opposite the transported mass, i.e., on the rear axle for a machine carrying a load overhanging at the front. It is known to provide a stability control system configured to compare the stability signal to a cutoff threshold and to interrupt any movement of the handling arm that increases the machine's instability as soon as the stability signal crosses the cutoff threshold. To set such a cutoff threshold, it is necessary to establish a safety margin relative to the machine's actual stability limit, particularly due to the response time of the stability control system and the inertial forces that may result from interrupting the movement. These inertial forces have, for example, been described in EP3431435A1. Summary

[0005] The instability signal generated by the strain gauge is incapable of distinguishing between the tipping moment contribution caused by the mass carried at the end of the handling arm and the tipping moment contribution caused by the handling arm itself. Applying a safety margin to the cutoff threshold therefore limits the sum of the two contributions but cannot limit each contribution separately. This results in a difficulty in providing a stability control system that guarantees the machine's operational safety while allowing the handling arm to move through all the positions permitted by the load chart. This difficulty stems in particular from the fact that the load chart takes into account the two tipping moment contributions to varying degrees.

[0006] In practice, it is observed that the lower the mass of the load, the more the tipping moment contribution generated by the handling arm is overrepresented in the instability signal, compared to the contribution actually taken into account in the stability tests, which leads to a cut-off of the movement by the stability control system increasingly further from the limits recorded in the load chart, and therefore a degradation of performance.

[0007] One idea underlying this invention is to provide a handling machine that allows for a wider range of use of the handling arm without risking the machine tipping over. Another idea underlying the invention is that the mass of the load can be taken into account, without being explicitly measured, by combining the instability signal with a measurement of the effective overhang of the load.

[0008] To this end, the invention proposes a handling machine of the aforementioned type, further comprising: sensors configured to measure the extension amplitude of the handling arm and the tilt angle of the handling arm relative to a horizontal plane or relative to the main body of the handling machine, and a control unit configured to: determine a cut-off threshold value based on the extension amplitude and the tilt angle of the handling arm, such that the cut-off threshold value becomes less restrictive when an effective distance between the second end of the handling arm and the tilt axis increases, in which the effective distance represents a distance projected onto a horizontal axis or onto a longitudinal axis of the main body, stop a movement of the handling arm in response to a detection that the signal representing the tilting moment has crossed the cut-off threshold value.

[0009] Thanks to these features, the instability signal is processed differently depending on the effective overhang distance to which it corresponds. This allows the load mass to be taken into account, which—all other things being equal—is lower the greater the effective distance. In other words, this minimizes the effect of the handling arm's mass. Using an increasing, and therefore more permissive, cutoff threshold as the effective distance increases thus compensates for the overrepresentation of the tipping moment contribution generated by the handling arm when the load mass is low.

[0010] According to another aspect of the invention, a control method is proposed for a handling machine comprising a main body, a telescopic handling arm mounted on said main body and rotatable about a horizontal axis of rotation, the axis of rotation being located on a first end of the handling arm, a second end of the handling arm being configured to receive a load to be handled, and actuators configured to raise and lower the handling arm about the axis of rotation, and to extend and retract the handling arm in a longitudinal direction of said handling arm, said method comprising: to receive, from a tilt detector, an instability signal representative of a tilting moment applied to the main body around a tilting axis of said handling machine, to receive, from sensors, measurement signals representing an extension amplitude of the handling arm and an angle of inclination of the handling arm with respect to a horizontal plane or with respect to the main body of the handling machine, to determine a cut-off threshold value as a function of the extension amplitude and the angle of inclination of the handling arm, such that the cut-off threshold value becomes less restrictive as an effective distance between the second end of the handling arm and the tilting axis increases, in which the effective distance represents a distance projected onto a horizontal axis or onto a longitudinal axis of the main body,to stop the movement of the handling arm in response to the detection that the signal representing the tipping moment has crossed the cutoff threshold value.

[0011] The control process can be executed by a control unit included in the handling machine.

[0012] According to advantageous embodiments, such a machine or process may have one or more of the following characteristics.

[0013] According to one embodiment, the signal representing the tipping moment is an instability signal, and the cutoff threshold value is an increasing function of the effective distance between the second end of the handling arm and the tipping axis, the movement of the handling arm being stopped in response to a detection that the instability signal is greater than the cutoff threshold value.

[0014] An increasing function is defined as a function that is not constant over its entire domain and that does not decrease. An increasing function may be strictly increasing. An increasing function may be constant over ranges of effective distance values. An increasing function may include step-like portions over ranges of effective distance values ​​and / or strictly increasing portions over ranges of effective distance values, including linear portions over ranges of effective distance values.

[0015] In one embodiment, the cutoff threshold value has at least one first value when the effective distance is within a first range of values ​​less than a predetermined distance, and at least one second value greater than the first value when the effective distance is within a second range of values ​​greater than the predetermined distance. In another embodiment, the cutoff threshold value takes on yet other values ​​when the effective distance is outside the first and second ranges of values.

[0016] The tilt detector can be made in different ways. According to one embodiment, the main body is mounted on wheels carried by axles, the axis of rotation being transverse to the main body, and the tilt detector includes an extensometer arranged at an axle opposite to the second end of the handling arm.

[0017] The actuators of the handling machine can be made in different ways. According to one embodiment, the actuators include a lifting actuator, for example of the hydraulic or electric type, connected on one side to the handling arm and on the other side to the main body and is configured to move the handling arm in rotation around the axis of rotation in order to perform upward and downward movements.

[0018] According to one embodiment, the handling arm comprises a plurality of deployable segments and the actuators comprise one or more extension actuators, for example of the hydraulic type, each extension actuator being arranged between two or more segments configured to deploy or retract the handling arm.

[0019] The sensors can be implemented in many ways. In one embodiment, the sensors include an angle sensor configured to measure the tilt angle of the handling arm relative to a horizontal plane or to the main body of the handling machine. The angle sensor can be arranged at the axis of rotation. The angle sensor can be an inclinometer.

[0020] Alternatively, the angle sensor can be mounted on a moving part coupled to the handling arm. Such a sensor can be configured to determine the actuation stroke of the lifting actuator.

[0021] In another example, the sensors include a first inclinometer mounted on the main body and a second inclinometer mounted on the handling arm. The angle of inclination of the handling arm relative to the main body is therefore obtained by subtracting the measurements from the two inclinometers.

[0022] In one embodiment, the sensors include a length sensor configured to measure the extension amplitude of the handling arm. The length sensor can be arranged on one or more segments of the handling arm and configured to measure the distance between the segment(s) and the main body.

[0023] Alternatively, the length sensor can be mounted on a moving part coupled to the handling arm. Such a sensor can be configured to determine the actuation stroke of the extension actuator(s).

[0024] According to one embodiment, the handling machine further comprises a demand element actuable by an operator to generate a movement request signal, the control unit being configured to cause the movement of the handling arm in response to the movement request signal.

[0025] The motion request signal can be generated in various ways. In one embodiment, motion request detectors can be implemented by one or more sensors mounted on a control lever or knob. These sensors can include, but are not limited to, switches, potentiometers, or Hall effect sensors, and are connected to the control unit. Specifically, the control unit can be configured to determine a signal from the request element corresponding to a movement to be performed by the handling machine, such as a lowering, lifting, extending, or retracting movement of the handling arm.

[0026] In one embodiment, a signaling device is installed in the handling machine and configured to display or emit a warning signal if the instability signal is close to or above the cutoff threshold. The warning signal may be audible and / or visual. The signaling device may be a display located in a cabin of the handling machine intended for use by a handling machine operator. Alternatively, or in addition, the signaling device may be an alarm located in the cabin and configured to emit the warning signal.

[0027] In particular, the control unit is configured to control the signaling means to display or emit the warning signal.

[0028] The cut-off threshold values ​​can be implemented in various ways. In one embodiment, the cut-off threshold values ​​and their corresponding effective distances are predetermined, particularly based on the geometry of the handling arm and the main body, and are stored beforehand in onboard memory of the handling machine. In another embodiment, the cut-off threshold values ​​can be implemented as correction coefficients that depend on the effective distances and must be multiplied by a nominal threshold value.

[0029] In one embodiment, the handling machine comprises a plurality of stabilizing feet configured to be extended or retracted from the main body, and the cut-off threshold values ​​vary depending on whether or not said stabilizing feet are extended. In another embodiment, it is the correction coefficients that vary depending on whether or not said stabilizing feet are extended.

[0030] Such a handling machine can notably be made in the form of a telescopic arm forklift. Brief description of the figures

[0031] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings. There figure 1is a schematic representation of a material handling machine. figure 2 is a representation of a tilt detector that can be implemented in the handling machine of the figure 1 . There figure 3 is a schematic representation of a calibration curve that can be implemented in the handling machine of the figure 1 . There figure 4 is a graphical representation of cut-off threshold values ​​that can be implemented in the handling machine of the figure 1 according to a first example. The figure 5 is a schematic representation of a control process that can be implemented by the handling machine of the figure 1 . There figure 6 is a graphical representation of cut-off threshold values ​​that can be implemented in the handling machine of the figure 1 according to a second example. Description of the implementation methods

[0032] In the figure 1A material handling machine 1, which is shown here as a telescopic handler, is depicted. The material handling machine 1 comprises a chassis 2 supported on the ground by means of a front axle carrying front wheels 3 and a rear axle 4 carrying rear wheels. The material handling machine 1 includes a telescopic handler arm 6 mounted on the chassis 2 at one end and rotatable about an axis of rotation 7 transverse to the chassis 2. The handler arm 6 includes a load-carrying tool 14 articulated to a second end of the handler arm 6 by the linkage 15 and configured to carry a payload 9. In the example shown, the load-carrying tool 14 is a fork, but other tools can be used, for example, a bucket.

[0033] The handling arm 6 is rotatable by means of a cylinder 8 connected to the chassis 2 and to the handling arm 6. The handling arm 6 comprises at least two segments 61 and 62 deployable by means of an extension cylinder, not shown, arranged between the at least two segments 61 and 62.

[0034] Another actuator, not shown, is arranged to change the orientation of the load-carrying tool 14 around a transverse axis of rotation relative to the frame 2.

[0035] The handling machine 1 further includes an actuation demand element 12 configured to manually control the handling arm 6, enabling the handling arm 6 to be raised and lowered and deployed and retracted.

[0036] The handling machine 1 also includes position detectors configured to produce a signal relative to a position of the handling arm 6, in particular an angle of inclination of the handling arm 6 relative to the chassis 2 and an extension length of the handling arm 6.

[0037] The position detectors include, for example, a first sensor 18 located at the axis 7 and arranged to measure the tilt angle of the handling arm 6. The first sensor 18 produces a signal representative of the tilt angle of the handling arm 6 relative to the frame 2. The position detectors also include, for example, a second sensor 16 located at the extension cylinder and arranged to measure the stroke of the extension cylinder. The second sensor 16 produces a signal representative of the extension length of the handling arm 6.

[0038] There figure 1The diagram shows the handling arm 6 carrying the payload 9 in a high, retracted position (solid line) and in several lower, more extended positions (dashed line). The static tipping moment exerted by the handling arm 6 and the payload 9 in the forward direction increases as the overhang increases, because its position decreases towards the horizontal and / or because the length of the handling arm 6 increases.

[0039] The position sensors allow the control unit 10 to determine a measurement of the overhang in the form of an effective distance between the machine's tilt axis and the second end of the handling arm carrying the load. This effective distance can be defined in various ways. In the example shown, it is the distance ℓ between the base of the front wheel 3 and the ground projection of a reference point A chosen on the handling arm 6. In the example shown, the reference point A corresponds to the linkage 15, but other choices are possible.

[0040] The handling machine 1 further includes a tipping detector 11 configured to produce a signal representative of a tipping moment applied to the chassis 2 around a tipping axis, located here at the front axle 3. Stabilizing feet 5 can optionally be deployed to lift the front axle, in which case the stabilizing feet 5 define the tipping axis.

[0041] In one embodiment shown on the figure 2 , the tipping detector 11 is arranged at the rear axle 4.

[0042] In the figure 2The rear axle 4 of the handling machine 1 comprises two wheel support arms 60 carrying rear wheels 62. Each wheel support arm 60 includes an extensometer 61, for example in the form of a strain gauge, configured to measure an elastic deformation of the wheel support arm 60, for example a bending deformation of the wheel support arm 60, in particular a change in length between two spaced points on the wheel support arm 60. The measurement signals from the extensometers 61 can be used to form the signal representing the tipping moment, for example as the average of the two measurement signals. Alternatively, it is possible to use a single extensometer 61 to produce the signal representing the tipping moment. Preferably, the rear axle 4 is connected to the frame 2 by means of a pivot 66 with a longitudinal axis passing through a central portion 65 of the axle.

[0043] There figure 3 illustrates a calibration curve to calibrate the signal representing the tipping moment in the form of an IS instability signal which increases when the machine approaches a forward longitudinal tipping situation and decreases when it moves away from it.

[0044] On the ordinate, we have represented the residual mass at the rear MRA which is the mass which would be weighed by a scale placed under the rear wheels 62. Subject to the linearity defects of the extensometers 61, the measurement signals of the extensometers 61 vary linearly with MRA.

[0045] The x-axis represents the IS instability signal. The IS instability signal can be calibrated with two measurement points.

[0046] For the first measurement point, a standardized load is placed on the load-carrying tool 14, and the handling arm 6 is placed in a fully lowered and retracted position. The handling machine 1 is in a very stable state corresponding to a certain positive value of MRA. The instability signal IS is then assigned the value 0.

[0047] For the second measurement point, the handling arm 6 is placed in a sufficiently extended position so that the handling machine 1 tilts longitudinally forward. The rear axle 4 is then no longer in contact with the ground. The instability signal IS is then assigned a positive value Smax, which corresponds to a zero value of MRA. Between the two measurement points, a linear law is applied to generate the instability signal IS from the measurement signals of the extensometers 61.

[0048] The second measurement point is by no means a physical extremity of the handling machine 1. It simply corresponds to a very stable state. In other words, it is possible for the instability signal IS to reach negative values ​​during machine operation.

[0049] The handling machine 1 further includes a control unit 10 configured to receive signals from the tilt detector 11 and stop the movement of the handling arm 6 if the instability signal exceeds a cutoff threshold value. For example, the control unit 10 is configured to prevent or stop the movement of the handling arm 6 by cutting off the hydraulic flow supplying the cylinder 8 and / or the extension cylinder.

[0050] With reference to the figure 4We have shown a first example of the increasing relationship between the cutoff threshold value and the distance ℓ, which can be implemented by the control unit 10. Curve 20 represents the cutoff threshold value. For a distance ℓ less than a predetermined positive value ℓ0, the cutoff threshold value takes a first value S1. For a distance ℓ greater than the predetermined positive value ℓ0, the cutoff threshold value takes a second value S2 greater than S1.

[0051] There figure 6 represents a second example using the same references as the Fig. 4 Here, the cutoff threshold value increases linearly from the first value S1 to the second value S2 as the distance ℓ increases from 0 to the predetermined positive value ℓ0. Numerical example

[0052] In an example, Smax is assigned the value 130, S1 the value 105 and S2 the value 110 (arbitrary unit).

[0053] For a machine with a total mass of approximately 12 t and a lifting height greater than 17m, the predetermined positive value ℓ0 is greater than 7m for operation on wheels and greater than 8m for operation on stabilizers.

[0054] Deflections M1 and M2 qualitatively illustrate the operation of the stability control system implemented by control unit 10 during the handling of two different loads. Since the y-axis represents the tipping moment (via the instability signal IS) and the x-axis represents the overhang (via the distance ℓ), the slope of deflection M1 or M2 varies qualitatively with the mass of the load. Deflection M1 therefore corresponds to a heavier mass than deflection M2.

[0055] Arrows M1 and M2 illustrate a handling operation that tends to increase the overhang until the control unit 10 interrupts the movement of the handling arm 6 when the instability signal IS crosses the cutoff threshold. For the heavier mass, arrow M1 reaches the threshold value S1. But for the lighter mass, arrow M2 reaches the threshold value S2. The stability control system is therefore less restrictive for handling a lighter load, in that it allows positions closer to the tipping point (represented by the Smax value) to be reached than for a heavier load.

[0056] In the example of figures 2 to 4 And 6The signal representing the tipping moment is an IS instability signal that increases as the machine approaches a forward longitudinal tipping state. Other choices are possible. For example, if a tipping moment signal that varies like MRA (i.e., that decreases as the machine approaches a forward longitudinal tipping state) is used, the relationships between the different threshold values ​​must be reversed compared to those described for the IS instability signal.

[0057] The handling machine 1 includes a display 13 connected to the control unit 10 and configured to display a warning signal if the instability signal is close to or greater than the cutoff threshold value.

[0058] In all cases, the control unit 10 can be configured to implement a control process, as shown in the figure 5 .

[0059] The control method is used to stop the movement of the handling arm 6 in order to prevent the handling machine 1 from tipping over.

[0060] The process includes: a step 21 of determining the distance ℓ, a step 22 of determining the cut-off threshold value as a function of the distance ℓ, a step 23 of comparing the signal representing the tipping moment to the cut-off threshold value, a step 24 of stopping or preventing the movement of the handling arm 6 when the signal relating to the tipping moment has crossed the cut-off threshold value.

[0061] This process is, for example, executed iteratively at a certain clock rate according to the known technique.

[0062] According to one embodiment, the cut-off threshold value is preferably variable depending on whether or not the stabilizing feet 5 are deployed.

[0063] According to one embodiment, the stopping of the movement is preceded by a deceleration controlled by the control unit 10, for example according to the principles taught in JP3252006.

[0064] Some of the elements shown, particularly the control unit, can be implemented in various forms, either individually or in a distributed manner, using hardware and / or software components. Usable hardware components include ASICs (Automatic System Integrated Circuits), FPGAs (Field Programmable Gate Arrays), and microprocessors. Software components can be written in various programming languages, such as C, C++, Java, or VHDL. This list is not exhaustive.

[0065] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0066] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0067] In claims, any reference sign in parentheses should not be interpreted as a limitation of the claim.

Claims

1. Handling machine (1) comprising: a main body (2), a telescopic handling arm (6) mounted on said main body and rotatable about a horizontal axis of rotation (7), the axis of rotation being located on a first end of the handling arm (6), a second end of the handling arm (6) being configured to receive a load to be handled, actuators (8) configured to raise and lower the handling arm about the axis of rotation, and to extend and retract the handling arm in a longitudinal direction of said handling arm, a tipping detector (11) configured to produce a signal representative of a tipping moment applied to the main body about a tipping axis of said handling machine, sensors (18,16) configured to measure the extension amplitude of the handling arm and the tilt angle of the handling arm (6) relative to a horizontal plane or relative to the main body (2) of the handling machine, and a control unit (10) configured to: determine a cut-off threshold value based on the extension amplitude and tilt angle of the handling arm (6), such that the cut-off threshold value (S1, S2) becomes less restrictive as the effective distance between the second end of the handling arm (6) and the tilt axis increases, where the effective distance (ℓ) represents a distance projected onto a horizontal axis or onto a longitudinal axis of the main body, stop (24) a movement of the handling arm in response to detection that the signal representing the tilting moment has crossed the cut-off threshold value.

2. Machine according to claim 1, wherein the signal representing the tipping moment is an instability signal (IS), and wherein the cut-off threshold value (S1, S2) is an increasing function of the effective distance (ℓ) between the second end of the handling arm (6) and the tipping axis, the movement of the handling arm being stopped in response to a detection that the instability signal (IS) is greater than the cut-off threshold value.

3. Machine according to claim 1 or 2, wherein the cut-off threshold value has at least a first value (S1) when the effective distance is in a first range of values ​​less than a predetermined distance and at least a second value (S2) greater than the first value when the effective distance is in a second range of values ​​greater than the predetermined distance.

4. Machine according to any one of claims 1 to 3, wherein the main body (2) is mounted on wheels carried by axles, the axis of rotation (7) being transverse to the main body, and the tilt detector comprises an extensometer (61) arranged at an axle (4) opposite the second end of the handling arm (6).

5. Machine according to any one of claims 1 to 4, further comprising a demand member (12) actuable by an operator to generate a movement request signal, the control unit (10) being configured to cause the movement of the handling arm in response to the movement request signal.

6. Control method for a handling machine (1) comprising a main body (2), a telescopic handling arm (6) mounted on said main body and rotatable about a horizontal axis of rotation (7), the axis of rotation being located on a first end of the handling arm (6), a second end of the handling arm (6) being configured to receive a load to be handled, and actuators (8) configured to raise and lower the handling arm about the axis of rotation, and to extend and retract the handling arm in a longitudinal direction of said handling arm, said method comprising: receiving from a tilt detector (11) a signal representative of a tilting moment (IS) applied to the main body about a tilting axis of said handling machine, receiving from sensors (16,18) measurement signals representing an extension amplitude of the handling arm and an angle of inclination of the handling arm (6) with respect to a horizontal plane or with respect to the main body (2) of the handling machine, determine a cut-off threshold value as a function of the extension amplitude and the angle of inclination of the handling arm (6), such that the cut-off threshold value (S1, S2) becomes less restrictive as an effective distance between the second end of the handling arm (6) and the tilting axis increases, in which the effective distance (ℓ) represents a distance projected onto a horizontal axis or onto a longitudinal axis of the main body, stop (24) a movement of the handling arm in response to a detection that the signal representing the tilting moment (IS) has crossed the cut-off threshold value.

7. Method according to claim 6, wherein the signal representing a tipping moment is an instability signal (IS), and wherein the cutoff threshold value is an increasing function of the effective distance between the second end of the handling arm (6) and the tipping axis, the movement of the handling arm being stopped in response to a detection that the instability signal (IS) is greater than the cutoff threshold value.

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