NZ538885A - Weighing device for excavator payloads - Google Patents
Weighing device for excavator payloadsInfo
- Publication number
- NZ538885A NZ538885A NZ538885A NZ53888505A NZ538885A NZ 538885 A NZ538885 A NZ 538885A NZ 538885 A NZ538885 A NZ 538885A NZ 53888505 A NZ53888505 A NZ 53888505A NZ 538885 A NZ538885 A NZ 538885A
- Authority
- NZ
- New Zealand
- Prior art keywords
- load
- compensating
- multiple link
- function
- chassis
- Prior art date
Links
- 238000005303 weighing Methods 0.000 title claims description 47
- 238000000034 method Methods 0.000 claims description 86
- 230000001133 acceleration Effects 0.000 claims description 71
- 230000000694 effects Effects 0.000 claims description 51
- 239000012530 fluid Substances 0.000 claims description 20
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- 230000033001 locomotion Effects 0.000 claims description 12
- 238000012544 monitoring process Methods 0.000 claims description 4
- 230000004044 response Effects 0.000 claims description 4
- 238000009420 retrofitting Methods 0.000 claims description 3
- 238000009795 derivation Methods 0.000 claims description 2
- 230000006870 function Effects 0.000 description 65
- 239000011159 matrix material Substances 0.000 description 15
- 238000004364 calculation method Methods 0.000 description 11
- 230000008859 change Effects 0.000 description 11
- 238000005259 measurement Methods 0.000 description 9
- 238000012360 testing method Methods 0.000 description 7
- 238000004891 communication Methods 0.000 description 5
- 239000003921 oil Substances 0.000 description 4
- 230000001186 cumulative effect Effects 0.000 description 3
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- 238000013213 extrapolation Methods 0.000 description 2
- 239000010720 hydraulic oil Substances 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 230000015654 memory Effects 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 102220539945 Ileal sodium/bile acid cotransporter_T11K_mutation Human genes 0.000 description 1
- 206010033307 Overweight Diseases 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
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- 230000009977 dual effect Effects 0.000 description 1
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G19/00—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups
- G01G19/08—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups for incorporation in vehicles
- G01G19/083—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups for incorporation in vehicles lift truck scale
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/26—Indicating devices
- E02F9/264—Sensors and their calibration for indicating the position of the work tool
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Mining & Mineral Resources (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Operation Control Of Excavators (AREA)
Abstract
A load estimating device for an excavator comprising a plurality of sensors measuring the relative angles between components of the lifting mechanism and one or more inclinometers and/or accelerometers measuring inclination of the machine, angular speed of rotation, etc.. A controller calculates lift factors from the sensor information, estimates a maximum payload for the machine in its present orientation and indicates this to the operator. The controller may also retain lift information for later reporting.
Description
538885
NEW ZEALAND PATENTS ACT, 1953
No: 538885 Date: 15 March 2005
COMPLETE SPECIFICATION
intellectual property office of n.z.
1 6 MAR 2006
RECEIVED
WEIGHING DEVICE FOR EXCAVATOR PAYLOADS
We, ACTRONIC LIMITED, a company duly incorporated under the laws of New Zealand of 8 Walls Road, Penrose, Auckland, New Zealand, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
FIELD OF THE INVENTION
The present invention relates to a devicc for making estimates of the weight of payloads lifted by an excavator.
DESCRIPTION OF THE PRIOR ART
It is important to be able to estimate the payload of an excavator to avoid the overfilling of vehicles. Over-filling may damage vehicles, may damage roadways and on public roadways can incur over-weight tines.
In a typical excavator there is a main chassis with the operators cab on it. A boom is coupled to the chassis by a pivotal joint. An actuator moves the boom relative to the chassis. A "stick" is attached to the end of the boom by another pivotal joint. A second actuator moves the stick relative to the boom. A bucket is attached to the end of the stick by a further pivotal joint. A third actuator moves the bucket relative to the stick. In use the bucket carries 15 the payload.
A variety of ways to make weight measurements on an excavator payload exist. Some techniques, however, are limited by the requirement of a stationary machine to make an accurate measurement of the payload.
US patent 6,518,519 describes a system which estimates loads including when the 20 machine is operating on an inclined surface. However this system requires detailed prior knowledge of the machine geometry and precisely calibrated force measurements for the actuators. Accordingly this device is not suitable to retrofitting to a variety of machines, and is not adaptable to changes in the performance of an individual machine. For example from repairs or modification.
3B6 of Italy manufacture a weighing system designed for use on excavators.
Documentation supplied with this system describes how the excavator should be on level ground and stationary when weight measurements are made.
Weighing systems designed for other types of machines (such as wheel loaders) are sometimes applied to cxcavators. These systems limit machine operation (such as remaining 30 stationary and/or on level ground.
BRIEF DESCRIPTION OF THE INVENTION
It is an object of the present invention to provide a load estimating device for excavator payloads which at least goes some way toward overcoming the above disadvantages or which will at least provide the industry with a useful choice.
In a first aspect the present invention may broadly be said to consist of a weighing device for use with a load lifting machine having a multiple link lifting ami connected at one end to the machine chassis, said chassis being capable of slewing while lifting, said device comprising:
means for determining lift forces applied between said arm and said chassis; 10 means for determining a load estimate as a function of said lift forces and the relative link positions of said multiple link arm, and at least one of:
means for compensating for acceleration forces on said multiple link lifting arms by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of arm lift acceleration, measured lift speed and the relative link positions of said 15 multiple link arms;
means for compensating for slew rate by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of measured slew rate and the relative link positions of said multiple link arm; and means for compensating for inclination of the machine chassis in a plane parallel with 20 the plane of movement of said multiple link arm by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of measured inclination and the relative link positions of said multiple link arm.
According to a further aspect of the invention said device includes both said means for compensating for slew rate and said means for compensating for inclination. 25 According to a further aspect of the invention said includes both said means to compensate for acceleration forces and said means for compensating for slew rate.
According to a further aspect of the invention said device includes both said means for compensating for acceleration forces and said means for compensating for inclination.
According to a further aspect of the invention said device includes said means for 30 compensating for acceleration forces said means for compensating for slew rate and said means for compensating for inclination.
According to a further aspect of the invention said device includes means for displaying the compensated load estimate to an operator of the excavator.
According to a further aspect of the invention said means for display includes a screen, and means for driving said scrccn to display said estimated load.
According to a further aspect of the invention said device includes means for accumulating a total load value over a series of lifts, and said means for driving said screen 5 causes said screen to display said estimated load and said total load.
According to a further aspect of the invention said device includes a user input interface, and means for resetting said means for accumulating a total load in response to a predetermined entry on said user interface.
According to a further aspect of the invention said device is for fitting to excavators 10 having a hydraulic actuator operating between said ami and said chassis, said means for determining lift forces measures hydraulic pressures, and said device includes means for compensating for fluid pressure changes due to fluid flow rate by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of lift speed.
According to a further aspect of the invention said means for compensating for fluid 15 pressure changes due to fluid flow rate uses a function of lift speed and the position of said first link of said ami.
According to a further aspect of the invention said means for estimating a load calculates an estimate more than once at intervals during a single lift, and determines an estimated load as a derivative of this plurality of estimates.
According to a further aspect of the invention said means for compensating for slew wherein said means for compensating for slew includes slew offset means for compensating for the effect on lift forces due to centripetal forces operating on the multiple link arm, and slew factor means for compensating for the effect on lift forces due to centripetal forces operating on the load being lifted.
According to a further aspect of the invention said slew offset means derives a compensation offset value to be applied against said lift forces, said value being a function of said slew rate and the relative positions of the links in said multiple link arm.
According to a further aspect of the invention said slew offset function is proportional to the square of the slew rate and is a function of the height of the ccntre of mass of the 30 unloaded arm above the plane of rotation of the slewing chassis passing through the connection between said first link of said arm and said chassis, and proportional to the radius from the axis of rotation of the slewing chassis to the centre of mass of the unloaded arm, for the instantaneous relative positions of the links in the multiple link arm.
According to a further aspect of the invention said slew factor means deriving a compensation factor to be applied against said estimated load, said factor being a function of said slew rate and the position of the centre of mass of the load.
According to a further aspect of the invention the centre of mass of the load is determined from the relative positions of the links in said multiple link ami.
According to a further aspect of the invention said slew factor function is proportional to the square of the slew rate and a function of the height of the centre of mass of the load earned by the arm above the plane of rotation of the slewing chassis passing through the connection between said first link of said ann and said chassis, and proportional to the radius from the axis of rotation of the slewing chassis to the centre of mass of the load, for the instantaneous relative positions of the links in the multiple link ann.
According to a further aspect of the invention said means for compensating for tilt, wherein said means for compensate for tilt includes tilt offset means for compensating for the effect on lift forces due to gravity forces operating on the multiple link arm, and tilt factor means for compensating for the effect on lift forces due to gravity forces operating on the load being lifted.
According to a further aspect of the invention said tilt offset means derives a compensation offset value to be applied against said lift forces, said value being a function of said inclination and the relative positions of the links in said multiple link arm.
According to a further aspect of the invention said tilt offset function is a function of the inclination and proportional to the displacement of the centre of mass of the unloaded arm from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link ami.
According to a further aspect of the invention said tilt factor means derives a compensation factor to be applied against said estimated load, said factor being a function of said inclination and the relative positions of the links in said multiple link arm.
According to a further aspect of the invention said tilt factor function is a function of the inclination and proportional to the displacement of the centre of mass of the load from the connection of said first link to said chassis in the plane of rotation passing through said connection for the instantaneous relative positions of the links in the multiple link arm.
According to a further aspect of the invention said means for estimating the load includes offset means for estimating the effect on lift forces due to gravity forces operating on
the multiple link arm, and factor means for relating lift forces due to gravity forces operating on the load being lifted to the actual load.
According to a further aspect of the invention said offset means derives an offset value to be applied against said lift forces, said value being a function of the relative positions of the 5 links in said multiple link arm.
According to a further aspect of the invention said offset function is proportional to the displacement of the centre of mass of the unloaded arm from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link ann. 10 According to a further aspect of the invention said factor means derives a factor to be multiplied with the adjusted lift forces to determine an estimated load, said factor being a function of the relative positions of the links in said multiple link ann.
According to a further aspect of the invention said factor function is proportional to the displacement of the centre of mass of the load from the connection of said first link to said 15 chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link ann.
According to a further aspect of the invention said means for compensating for acceleration forces, wherein said means for compensating for acceleration forces includes means for compensating the acceleration forces on the multiple link arm and the load being 20 lifted.
According to a further aspect of the invention said compensating means preferably uses a common compensating factor for the combined load and multiple link ann.
According to a further aspect of the invention said acceleration compensating factor is a function of the instantaneous relative positions of the multiple link ami, and the acceleration 25 of the arms.
According to a further aspect of the invention said acceleration of the multiple link arm is determined by calculating the first differential of the speed of the multiple link ann.
According to a further aspect of the invention said acceleration of the multiple link arm is determined by sensing with an accelerometer located on said first link of said multiple 30 link ann, sensing acceleration on an axis tangential to the movement of said accelerometer with lifting of said ann.
According to a further aspect of the invention said device includes calibration means for prompting the operator of the excavator to perfonn predetennined excavator actions,
monitoring sensor signals, calculating calibration data from the sensor signals, and recording the calibration data for use by said means for determining a load estimate.
According to a further aspect of the invention a function involving the relative positions of the links of said arm uses, at least in part, a look-up table of values corresponding with different relative link position combinations.
According to a further aspect of the invention said function interpolates between lookup table values for link position combination as closest to the instantaneous position combination.
According to a further aspect of the invention said calibration means stores said calibration data in said lookup tables.
According to a further aspect of the invention said device comprising a controller including a microcomputer with an input interface receiving data from a plurality of sensors, an output interface including at least a display driver, a user input interface for receiving operator commands, said microcomputer executing a software program that implements said means for determining lift forces, said means for determining a load estimate, said means for compensating for slew rate, said means for compensating for inclination, and said means compensating for acceleration.
In a further aspect the present invention may broadly be said to consist in a system for retrofitting to excavators, for allowing an operator to estimate a load raised by the excavator in an individual lift or in a series of individual lifts, said system including a device as described in one or more of the above paragraphs, a plurality of sensors for providing input defining (or enabling derivation of) the raw lift forces, the relative positions of at least the first two links in a multiple link arm of the excavator, slew rate, and inclination, and means for providing outputs of said sensors to an input interface of said device.
In a still further aspect the present invention consists in a method for estimating load weight for use with a load lifting machine having a multiple link lifting arm connected at one end to the machine chassis, said chassis being capable of slewing while lifting, said method comprising:
determining lift forces applied between said arm and said chassis;
determining a load estimate as a function of said lift forces and the relative link positions of said multiple link arm, and at least one of:
compensating for acceleration forces on said multiple link lifting arms by modifying said determined lift forces, or by directly modifying said load estimate, according to a
function of arm lift acceleration, measured lift speed and the relative link positions of said multiple link arms;
compensating for slew rate by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of measured slew rate and the relative link positions of said multiple link arm; and compensating for inclination of the excavator chassis in a plane parallel with the plane of movement of said multiple link arm by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of measured inclination and the relative link positions of said multiple link arm.
According to a further aspect of the invention said method includes both compensating for slew rate and compensating for inclination.
According to a further aspect of the invention said method includes both compensating for acceleration forces and compensating for slew rate.
According to a further aspect of the invention said method includes both compensating for acceleration forces and compensating for inclination.
According to a further aspect of the invention said method includes compensating for acceleration forces, compensating for slew rate and compensating for inclination.
According to a further aspect of the invention said method includes displaying the compensated load estimate to an operator of the excavator.
According to a further aspect of the invention said method includes accumulating a total load value over a series of lifts, and displaying said estimated load and said total load.
According to a further aspect of the invention said method includes resetting said accumulated total load in response to a predetermined user entry.
According to a further aspect of the invention said method includes determining lift forces from measured hydraulic pressures, and compensating for fluid pressure changes due to fluid flow rate by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of lift speed.
According to a further aspect of the invention said method uses a function of lift speed and the position of said first link of said ann fluid pressure changes due to fluid flow rate.
According to a further aspect of the invention estimating a load includes calculating an estimate more than once at intervals during a single lift, and detennining an estimated load as a derivative of this plurality of estimates.
According to a further aspect of the invention said method includes compensating for slew by compensating for the effect on lift forces due to centripetal forces operating on the
multiple link ann, and compensating for the effect on lift forces due to centripetal forces operating on the load being lifted.
According to a further aspect of the invention said method includes deriving a compensation offset value to be applied against said lift forces as a function of said slew rate 5 and the relative positions of the links in said multiple link arm.
According to a further aspect of the invention said offset value is derived as proportional to the square of the slew rate and is a function of the height of the centre of mass of the unloaded arm above the plane of rotation of the slewing chassis passing through the connection between said first link of said ami and said chassis, and proportional to the radius 10 from the axis of rotation of the slewing chassis to the centre of mass of the unloaded ami, for the instantaneous relative positions of the links in the multiple link arm.
According to a further aspect of the invention said method includes deriving a compensation factor to be applied against said estimated load as a function of said slew rate and the centre of mass of the load.
According to a further aspect of the invention said method includes determining the centre of mass of the load from the relative positions of the links in said multiple link arm.
According to a further aspect of the invention said slew compensation factor is derived as a function is proportional to the square of the slew rate and a function of the height of the centre of mass of the load carried by the arm above the plane of rotation of the slewing 20 chassis passing through the connection between said first link of said arm and said chassis, and proportional to the radius from the axis of rotation of the slewing chassis to the centre of mass of the load, for the instantaneous relative positions of the links in the multiple link arm.
According to a further aspect of the invention said method includes compensating for tilt by compensating for the effect on lift forces due to gravity forces operating on the multiple 25 link arm, and compensating for the effect on lift forces due to gravity forces operating on the load being lifted.
According to a further aspect of the invention said method includes deriving a compensation offset value to be applied against said lift forces as a function of said inclination and the relative positions of the links in said multiple link arm.
According to a further aspect of the invention said tilt offset value is derived as a function of the inclination and is proportional to the displacement of the centre of mass of the unloaded ami from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link arm.
According to a further aspect of the invention said method includes deriving a compensation factor to be applied against said estimated load as a function of said inclination and the relative positions of the links in said multiple link arm.
According to a further aspect of the invention said compensation factor is derived as a 5 function of the inclination and proportional to the displacement of the centre of mass of the load from the connection of said first link to said chassis in the plane of rotation passing through said connection for the instantaneous relative positions of the links in the multiple link arm.
According to a further aspect of the invention said method includes estimating the
effect on lift forces due to gravity forces operating on the multiple link ann, and relating lift forces due to gravity forces operating on the load being lifted to the actual load.
According to a further aspect of the invention said method includes deriving an offset value to be applied against said lift forces, as a function of the relative positions of the links in said multiple link arm.
According to a further aspect of the invention said offset value is derived as proportional to the displacement of the centre of mass of the unloaded arm from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link ann.
According to a further aspect of the invention said method includes deriving a factor to be multiplied with the adjusted lift forces to determine an estimated load, said factor being a function of the relative positions of the links in said multiple link ann.
According to a further aspect of the invention said factor is derived as proportional to the displacement of the centre of mass of the load from the connection of said first link to said
chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link arm.
According to a further aspect of the invention said method includes compensating for acceleration forces includes by compensating for the acceleration forces on the multiple link arm and the load being lifted.
According to a further aspect of the invention compensating for acceleration forces uses a common compensating factor for the combined load and multiple link arm.
According to a further aspect of the invention said method includes deriving said acceleration compensating factor as a function of the instantaneous relative positions of the multiple link arm, and the acceleration of the arms.
According to a further aspect of the invention said method includes determining said acceleration of the multiple link ann by calculating the first differential of the speed of the multiple link arm.
According to a further aspect of the invention said acceleration of the multiple link 5 arm is determined by sensing with an accelerometer located on said first link of said multiple link ann, sensing acceleration on an axis tangential to the movement of said accelerometer with lifting of said arm.
According to a further aspect of the invention said method includes calibrating by prompting the operator of the excavator to perfonn predetennined excavator actions, 10 monitoring sensor signals, calculating calibration data from the sensor signals, and recording the calibration data.
According to a further aspect of the invention said method includes deriving offset values and compensation factor values involving the relative positions of the links of said arm includes, at least in part, looking up a table of values corresponding with different relative link 15 position combinations.
According to a further aspect of the invention deriving offset values and compensation factor values includes interpolating between lookup table values for link position combination as closest to the instantaneous position combination.
According to a further aspect of the invention said method includes storing calibration 20 data in said lookup tables.
In a still further aspect the invention consists in a weighing device for use with a load lifting machine having a multiple link lifting arm connected at one end to the machine chassis, said chassis being capable of slewing while lifting, said device comprising:
an input interface for receiving data from at least one sensor on said load lifting 25 machine a computer connected with said input interface,
a program executable by said computer, said program implementing a method as set forth in any one or more of the above paragraphs.
This invention provides an improved method of payload measurement system which 30 compensates for the dynamic rotational (slew) movement of the machine, and also any tilt the machine may be on. This allows measurements to be made while the machine is slewing, thus avoiding time wastage. And also when the machine is tilted by unstable ground, which is often the in-use scenario.
To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and arc not intended to be in any sense limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic drawing of the load estimating device and its associated sensors including illustration of the location of the sensors on a typical excavator.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figure 1, the load estimating device according to the present invention is intended for fitting to a typical excavator.
The typical excavator has a walking frame for mobility 70. The walking frame 15 typically has wheels or tracks on either side. Attached to the top of the frame is a slewing ring 80. The main chassis of the excavator is attached to the top of the slew ring and is driven by one or more pinion gears. This allows the driver to rotate the chassis on top of the walking frame. A drivers cab 90 is typically located at the front of the chassis. An engine bay and counterweight are generally located at the rear of the chassis. Typical excavators operate 20 using a hydraulic drive system. An internal combustion engine drives a pump to maintain a supply of hydraulic fluid at an elevated pressure. This hydraulic fluid is selectively applied to a variety of actuators for manipulating the lifting arm of the excavator, and for slewing the chassis and driving the wheels or tracks.
The load manipulating ami is generally a series of articulated members with one or 25 more actuators operating across each joint. A main boom 110 is attached to the front of the chassis and pivots about its connection to the chassis. Typically on large excavators the boom pivots about one axis, parallel to the front of the chassis. A hydraulic actuator 120 controls the rotation of the boom about its pivot point. Typically the actuator is connected between the chassis, some distance from the pivot point of the boom, to a position near the midpoint of the 30 boom. A further large member, referred to as the stick 130, is attached to the end of the boom by another pivoting joint. The stick moves in the same plane as the boom. The angle of the stick relative to the boom is controlled by another hydraulic actuator 140.
The load carrying device is attached to the end of the stick. The load carrying device is typically a bucket 150. The bucket can rotate by means of a pivotal joint where the rotation
is again controlled by a hydraulic actuator 160. The bucket holds the payload to be weighed. The bucket may scoop in toward the chassis - a backhoe - or may scoop away from the chassis - a shovel. Other load carrying devices are sometimes used. For example grab type attachments or large electromagnets.
The load estimating device of the present invention generally comprises a plurality of sensors that sense machine operating conditions, and an input/output (I/O) 170 controller that receives outputs of the sensors and operates a program embedded into a microcontroller 180 that calculates an estimated payload based on the sensor signals. The controller has a display 190 in the cab with the operator and provides immediate payload feedback to the operator, such as current load weight and a cumulative total load for a series of loading events. This is useful where the operator is loading a truck and a level of accuracy is required for greatest safe efficiency.
A first sensor 10 is attached over (or as close as possible to) the pivot point between the boom and chassis. The first sensor constantly outputs a pulse width modulated (PWM) signal that corresponds to the angle between the boom and chassis. The same information represented by this signal could be derived in other ways, for example from the extension of the actuator operating between the boom and chassis, or it may be an available output of the control system of the excavator.
A second sensor 20 is attached over (or as close as possible to) the pivot point between the boom and stick. This sensor constantly outputs a PWM signal that corresponds to the relative angle between the boom and the stick. Again, the information represented by this signal could be derived in other ways, for example from the extension of the actuator operating between the boom and stick, or it may be an available output of the control system of the excavator.
A first tilt sensor 50 is located directly over the centre of rotation of the chassis. The tilt sensor 50 may be, for example, a pendulum sensor. The tilt sensor constantly outputs a PWM signal which corresponds to the inclination angle or tilt of the machine, for example as a result of working on unstable or uneven ground. Other forms of inclinometer or accelerometer could be used as an alternative.
A second tilt sensor 60 (or accelerometer) is located on the machine chassis, some distance from the centre of rotation. The tilt sensor 60 could, for example, be a pendulum sensor. This sensor constantly outputs a PWM signal that corresponds to the inclination angle of the whole machine, and any rotational motion of the chassis. As the chassis rotates the pendulum sensor will experience a centripetal force directly related to the angular speed of
rotation. The difference between the outputs of the first and second tilt sensors is directly related to the rotation speed of the chassis - the slew rate. Many other ways of determining the slew rate are also possible. For example the slew rate may be a direct output of the excavator controller, or the sensor could involve a large size rotary encoder.
An accelerometer 65 is located on the boom approximately half way between the boom pivot 10 and the stick pivot 20. This sensor is orientated so its sensitive axis is tangent to the direction of boom rotation referenced to the main boom pivot. For example, the sensitive axis may be aligned with axis 75 in figure 1. This sensor constantly outputs a PWM signal corresponding to the magnitude of acceleration forces experienced by the boom 10 structure during lifting.
As an alternative to the accelerometer the controller can calculate acceleration from the output of the boom angle sensor. The rotational acceleration of the boom is calculated as the second differential of the boom angle from the boom angle sensor. This places a requirement on the resolution offered by the boom angle sensor. A calculation can be made 15 with as few as three reference points, but more reference points are required for accurate calculations. Preferably the boom angle sensor has at least six, and most preferably fifteen or more reference positions.
Two pressure sensors are mounted on the hydraulic actuator that controls the pivoting of the boom relative to the chassis. The sensors arc fitted to "tee-off points on both the lift 20 and return pressure lines for the cylinder. The first sensor 40 measures the pressure on the lift side of the actuator. The second sensor 30 measures the pressure on the return side of the actuator.
The pressure sensors arc a transducer system which constantly outputs a pair of signals, each directly related to the hydraulic oil pressures on each side of the actuator. Where 25 the actuator is not a hydraulic actuator other approaches to determining the actuation force would be necessary. For example electrical current measurements may be suitable for an electrical actuator, or the forces could be measured more directly using a straingauge or loadcell.
The control unit 220 located in the cab receives the signals from each of the sensors 30 (Boom Angle, Stick/boom Angle, Tilt 1, Tilt 2, Boom Acc, Pressure 1, Pressure 2). The control unit includes a microcontroller 180 and an I/O interface 170. The input interface samples each of the sensor signals sequentially. A program running in the microcontroller applies an algorithm to make the final payload weight measurement. The input interface also receives input from a user keypad 200. The controller outputs feedback to a screen for the
operator, and may also output data through a data communications interface or comm-port. The comm-port may allow for remote transmission, either one way or two way - for example using a radio modem, RS232 or USB.
The program running on the microcontroller is operable in at least two modes. In a 5 setup and calibration mode the program prompts the operator through at least one of a series of activities. The program monitors the sensor readings during these activities and calculates data values that represent the particular performance of the machinc to which the device is fitted. These calibration data values arc then saved into the microcontrollers onboard memory 230. The calibration process is described in more detail below for each of the factors that are 10 used by the program in the main load estimation function. In an operating mode the program monitors the sensor readings to discern load lift events.
When the boom begins to rise the program acquires a number (for example ten) of boom angle samples to make an accurate deduction of the boom speed. This is performed by differentiating the past ten boom positions to obtain the angular speed of the boom. The 15 importance of boom speed relates to its effect on the pressure difference between the lift side and return side of the main actuator. This effect, and how it may be compensated for, is described in more detail below.
Once the boom speed has been calculated the program calculates the payload weight for each new set of samples. In the preferred embodiment of the present invention a new set 20 of samples is taken approximately 25 times each second. The program then calculates the final payload estimate as an average of some or all of the calculated estimates obtained between when the boom begins to rise and some later time, for example when the boom slows down significantly or stops. This final estimate is displayed to the excavator operator in the cab. The system will begin to average the samples after the boom has rised through a 'boom 25 minimum height' trigger point, which is a preset position of the boom. The program preferably allows the operator of the excavator to reset the trigger point at any time.
As well as displaying the estimated load for the present lift, the program may compute a cumulative total over a number of lifts, may record the load estimate for the lift together with data indicating the time or location or an identifier of the operator or vehicle being 30 loaded. The program may allow the operator to enter identifiers for the material type or for the vehicle being loaded. The program preferably allows the operator to reset the cumulative total to indicate the end of a particular loading sequence, for example a change of truck receiving the load.
Load estimating calculation
The overall weight calculation formula implemented by the program executed by the microcomputer is as follows:
Pd = Filter (PL-k.PR)
W = (((Pd - ZSP)* SBA) - Z - ZSL - Ztlt) * S * SSL * Sjlt
Where:
Estimated load weight Pressure Lift
Ratio of return pressure effective are to lift pressure effective area Pressure Return Filtered Pressure difference Zero offset
Zero offset from Lift Speed Compensation Zero offset from Slew Compensation Zero offset from Tilt Compensation Span factor
Span factor from Slew Compensation Span factor from Tilt Compensation Span factor from Acceleration Compensation
Note: When the arms are lifted at constant speed, SBa is equal to 1, and the other calibration functions simplify accordingly.
Filter Function to provide a digital filter on the measured values (FIR)
Each of the offsets and factors in this overall function relies on calibration for the machine to which the device is fitted. The calibration requirements for each of the offsets and factors are described in more detail with the description of that offset or factor. In practise, the calibration steps are all conducted at the time of commissioning the load estimating device for 30 a particular excavator. The program may allow the calibration procedure to be repeated as necessary over the life of the machine. The calibration is described here in relation to a series of lookup tables. The values for the tables are derived in the calibration procedure. This ensures that the values are accurate for the particular machine in question and for the particular installation of the device. However with accurate installation of the device and its
W Pl k
Pr Pd Z
Zsp ZsL Ztlt S
SsL
Stlt
Sba
sensors the calibration values for machines of the same model would be substantially identical and could perhaps be preloaded into the controller. In practise a better result may be obtained through the calibration procedure. Furthermore the calibration is described with reference to lookup tables. For at least some of the offsets and factors the lookup table may be replaced by 5 a custom derived function that can be used to derive equivalent values to the valves that may be interpolated from the lookup tabic data.
In the preferred embodiment the calibration data is stored in separate data arrays and obtained by calibration in separate steps. However other embodiments of the invention may combine the data into combinational tables, or curve fitting formulae. In addition, the 10 individual calibration steps may be combined in various combinations.
£ SPAN ACCELERATION COMPENSATION FACTOR (SBA)
This value is a function of the current boom and stick position. This value relates a component of the lift force to the boom acceleration at the time of measurement. The force 15 component resulting from boom acceleration depends on the boom and stick positions as these affect the moment of inertia of the ann and load. In the referred embodiment, the acceleration factor, Sba, is calculated as:
Sba=1/((Ab*CBA)+1)
In which:
Sba= Span factor from Acceleration Compensation Ab Boom Acceleration
CBa Boom Acceleration Compensation factor which is calculated as:
CBa = K-ba S/So
Where: Kba = a stored constant
S = span factor at current boom and stick positions So = span factor at current boom position but minimum stick position
The Arm (Boom) acceleration is preferably measured by calculating the first differential of the ami rotation speed. Alternatively it can be measured directly by the means of one or more accelerometer sensors mounted on the ann.
Alternatively Cba may be determined from a lookup table of values accessed by current boom and stick position.
The constant Kba is calculated during calibration of the system. A series of movements of the arms arc made with varying acceleration. The forces measured when the 5 arms are subjected to various accelerations are compared to determine the constant. Alternatively a lookup tabic can be generated for the Cba variable using the same method
ZERO OFFSET (Z)
At any given boom and stick position, a certain pressure is required to lift the 10 unloaded arm (boom, stick, bucket and associated apparatus). This pressure varies with both boom and stick positions. A table (matrix) of zero offsets is generated to define the pressure required to lift an empty bucket. The Zero or Offset values are used to correct for the pressures required to lift the excavator arms and empty bucket.
In this section we are calculating the value of 'Z' for the main load estimation 15 function. SI to S6 and B1 to B6 are six different predetermined stick and boom positions respectively that index a lookup table of integers.
B1 B2 B3 B4 B5 B6
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52
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54
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Zero OFFSET Matrix
To calibrate the table the excavator is operated on level ground and without slewing.
The boom is operated through at least six lifts with the stick held in the six different positions. The lifts are carried out with an empty bucket. The calibration value for each position is calculated when the boom and stick are at the respective locations as:
Value = Pd - Zsp.
In use, to calculate Z for a live lift, a value is calculated for the actual boom and stick positions using values extracted from the table. The value is calculated by interpolating between the four values that are associated with the closest predetermined boom and stick positions (SI to S6 and B1 to B6).
SPAN FACTOR (S)
The Span values are used to implement the relationship between a change in pressure (from the offset / zero values) and a load weight. At any given boom and stick position, there is a direct relationship between change in payload weight and lift pressure. However the relationship changes with the positions of the boom and stick. A table (matrix) of gain factors is generated to define the relationship between changes in pressure and changes in weight, for a range of boom / stick positions.
In this section we are calculating the value of "S' for the main load estimation function. SI to S6 and B1 to B6 are the six different predetermined stick and boom positions respectively and index a lookup table of integers
B1 B2 B3 B4 B5 B6
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52
53
54
55
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SPAN FACTOR Matrix
To calibrate the table the excavator is operated on level ground and without slewing. The boom is operated through at least six lifts with the stick held in the six different positions. A load of known weight (Test Weight) is held in the bucket. The calibration value for each position is calculated when the boom and stick are at the respective locations as:
Value = Test Weight / (Pd - Z - Zsp)
In use, to calculate S for a live lift, a value is calculated for the actual boom and stick positions using values extracted from the table. The value is calculated by interpolating
between the four values that are associated with the closest predetermined boom and stick positions (SI to S6 and B1 to B6).
LIFT SPEED COMPENSATION (ZSP)
The load is moving when weighing occurs. If the load is moving then so are the hydraulic lifting cylinders and so in turn is the hydraulic oil through the lift and return hosing and valves. This flow of oil causes pressure drops. Whether the pressure drops impact on estimation accuracy depends on where these pressure drops occur. In general, the faster the lift, the greater the pressure drops. In non-hydraulic systems a lift speed compensation may be 10 unnecessary, or an alternative compensation may be required for lift speed.
This variable pressure with lift speed will result in a variable weight display unless some form of compensation is applied. In a dual transducer system (where lift and return pressure are both measured), the major portion of the speed variable pressure has been removed. However a small portion does remain and must be compensated for. 15 The lift speed effects are primarily an offset effect. This means that the effect is independent of load in the bucket. The relationship between lift speed and pressure drop is nonlinear. The relationship is poorly defined and cannot be easily modelled. The pressure drop depends on if the flow is laminar or turbulent. In practice, the flow through the pipes and valves is a mixture of both and is temperature and speed dependent. For this reason in the 20 preferred implementation of the present invention a calibrated lookup table is used.
The relationship between boom speed and oil flow varies during the lift (as the mechanical advantage changes). In addition there may not be a linear relationship between boom rotation and sensor rotation. Accordingly for the present implementation the boom sensor speed vs. oil speed relationship is determined at several points (e.g. at the same boom 25 positions other calibrations are done at).
Two tables are required; the first relates the rate of change of the boom position sensor output to the linear speed of the cylinder (and therefor the flow rate of the hydraulic fluid). This first table would be unnecessary in an implementation where the actuator extension or fluid flow rate is sensed directly. An example table of values would be:
Boom Pos B1 B2 B3 B4 B5 B6
Speed Norm 1.00 1.02 1.04 1.07 1.11 1.20
The second table gives a series of values defining a speed vs. pressure offset relationship. An example table of values would be:
Seq
Speed
Compensation
Return Shift
1
6.1
105
2
.0
7
87
3
12.5
3
121
4
.4
17
108
17.9
24
150
6
21.0
In the above tables:
"B1 - B6' are the predetermined boom positions;
"Speed Norm' values are a normalisation factor between the apparent lift speed from the position sensor at any given boom position and cylinder speed (related to the first boom position);
'Speed' is the normalised speed (effectively the rate of change of the sensor output normalised back to the equivalent rate of change of sensor output if the boom was at boom position Bl);
"Compensation' is the change in the mixed pressure (A-D counts) between each speed step; and
'Return Shift' is the change in return line pressure (A-D counts) between each speed step.
The lookup table is generated in a 'Lift Speed Compensation Calibration' part of the calibration process. Lift speed compensation calibration is typically carried out prior to other calibration steps as the compensation value, Zsp, features in calculation of the other offsets and factors. The first table may be calibrated by one or more lifts at a constant cylinder speed. The second table may then be calibrated by a series of lifts at different constant lift speeds across a range of possible lift speeds for the machine in question.
In use the speed compensation offset Zsp is calculated for each lift. The speed is calculated as described earlier.
- Any lift with a speed less than the lowest in the table results in a compensation value of zero.
- Any lift with a speed between the minimum (speed 1) and maximum (speed 6) has a compensation value calculated by linear interpolation between the values from the table corresponding to the bounding predetermined speeds.
- A lift speed above the maximum (speed 6) has a compensation value 5 calculated by extrapolating the slope between speed 5 and speed 6.
- A lift with a speed greater than 20% higher than that recorded for speed 6 is rejected. The program will display a user alert, such as 'Lift Speed too high!" or similar. No weight is recorded.
SLEW EFFECTS
The rotational speed of the machine affects the lift pressure for a given load. This is due to the centripetal forces generated on the arm/bucket structures and the load itself. Depending on the physical configuration at any given time, the lift pressure may either increase or decrease with slewing (or not be effected at all).
The centripetal force on the structure and load is dependent on the acceleration they arc under:
a, = co2.r
Where:
ac Acceleration to Angular Velocity (rad / s)
r Radius to Centre of Mass of object rotating
The torque generated on the arm is dependent on the elevation (angle from the horizontal) and the linear distance of the line between the pivot between the boom and chassis and the centre of mass of the whole arm assembly and load.
In the described embodiment the angular velocity values (co) used in the following discussions are derived from the two tilt sensors. The rotational speed (co) is calculated by 30 taking the tangent of the additional angle induced by the centripetal force in the pendulum sensor located away from the centre of rotation of the chassis, multiplying by the gravitational constant, and dividing by the distance between this tilt sensor and the centre of rotation of the chassis. In other implementations the slew rate may be found more directly.
Regardless of filtering of the various sensor signals, all data must remain time synchronised.
Slew Offset (ZSL)
At any given boom and stick position, the effect of slew oil lift pressure is directly proportional to the square of the angular velocity. In the preferred embodiment of the present invention the program uses a calibrated lookup table to derive values compensating for the effect of the excavator structure on lift pressure at varying slew rates. The values stored in the table are normalised to a nominal slew rate. Values in the Slew Offset Matrix are integers. A simple matrix is used to relate how the lift pressures changes as a function of the effect of slew on the empty bucket.
In this section we are calculating the value of 'Zsl' for the main load estimation function. SI to S6 and B1 to B6 are the six different predetermined stick and boom positions respectively and index a lookup table of integers
B1 B2 B3 B4 B5 B6
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Slew Offset Matrix
To calibrate the table the excavator is operated on level ground. The boom is operated through at least six lifts with the stick held in the six different positions. The lifts are made with no load in the bucket. The lifts are made while slewing. The calibration value for each position is calculated when the boom and stick are at the respective locations as:
Value = (Pd - Z - ZSP) * (Vnom / co2)
Where;
Vnom Constant (effectively angular velocity all values are normalised to)
co2 Angular velocity at the point the on the lift where pressures recorded
In use, to calculate Zsl for a live lift, a position dependant value is calculated for the actual boom and stick positions using values extracted from the table. The value is calculated by interpolating between the four values that are associated with the closest predetermined boom and stick positions (S1 to S6 and B1 to B6).
The value extracted from the table must be de-normalised to a compensation value for the angular velocity at which the weight data was measured. This is calculated as
'y
Zsl = Interpol ated Value * (or / Vnom)
Slew Factor (Ssl)
At any given boom and stick position, the effect of slew on lift pressure is directly proportional to the square of the angular velocity. For this reason the values stored in the table will be normalised to a nominal speed value. Values in the Slew Factor Matrix are scale factors.
A slew span look-up table is used to relate how, for a given load, the effect of slew rate on lift pressure changes as a function of the boom and stick positions. The calculation of the effect of slew due to the load is very similar to effect due to the arm structure. The primary difference is the effect on the load is a scale factor rather than offset.
In this section we are calculating the value of 'Ssl' for the main load estimation function. SI to S6 and B1 to B6 are the six different predetermined stick and boom positions respectively and index a lookup table of integers
B1 B2 B3 B4 B5 B6
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52
53
54
55
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Slew Factor Matrix
To calibrate the table the excavator is operated on level ground. The boom is operated through at least six lifts with the stick held in the six different positions. The lifts are made
with a known load (Test Weight) in the bucket. The lifts are made while slewing. The calibration value for each position is calculated when the boom and stick are at the respective locations as:
Value = Test_Weight / ((Pd - Z - Zsp - ZSl) * S) * (Vnom / or)
Where;
Vnom Constant (effectively angular velocity all values are normalised to)
or Angular velocity at the point the on the lift where pressures recorded
Test Weight Entered test weight value, or value measured not slewing
In use, to calculate Ssl for a live lift, a position dependant value is calculated for the actual boom and stick positions using values extracted from the table. The value is calculated by interpolating between the four values that are associated with the closest predetermined boom and stick positions (SI to S6 and B1 to B6).
The value extracted from the table must be de-normalised to a compensation value for 15 the angular velocity at which the weight data was measured. This is calculated as
Ssl = 1 + (Interpolated Value * (co2 / V„om))
TILT EFFECTS
The ann and bucket structure may be considered to act as a single mass at some angle from the pivot point. When gravity acts on the mass, this generates a moment (torque) around the pivot that the hydraulic cylinder(s) must counteract. This moment is directly proportional to 'd\ the horizontal distance between the arm pivot point and the centre of mass of the ann structure. Ld! is in turn proportional to the cosine of the angle to horizontal.
The fore and aft inclination of the machine (direction observed relative to the chassis,
in a plane parallel with the plane of movement of the ann) will affect the weight calculations. Inclination of the machine will have an impact due to the arm and bucket structure, as well as due to the load.
When the machine tilts forward and back, the distance "d1 changes. The torque
countered by the actuator lift force changes proportionally. The effect tilt has on apparent weight will depend on the angle from the pivot to the equivalent mass. When the angle is close to zero (ann horizontal) the effect will be minimum, the greater the angle of the ann, the greater the influence tilt will have. This is because the relationship between angle and'd' is a cosine function of the angle and the mass.
As an example, the following table illustrates the effect on "d" for a 10° backward tilt.
Angle to Mass "d" original "d" tilted (+10°) Change % change
0° 5m 4.925m -0.075m -1.5%
40° 3.830m 3.214m -0.616m -16.1%
The effect of the 10° backward tilt is much greater when the arm is vertical rather than horizontal.
In the main function our controller uses to estimate load the tilt effect on the ann and 10 bucket structure are compensated for by an offset (Ztit). The tilt effect from the load in the bucket is compensated by factor Sttt that changes proportionally to the change in 'd\ In each case separate offsets or factors are provided for forward tilt and backward tilt.
The tilt effect is not directly proportional to angle. As described in the relationship above, it is a trigonometric function depending on the initial conditions of angle to centre of 15 mass. Consequently the calibration for tilt compensation theoretically requires multiple angles of machine tilt in order to generate compensation values.
Tilt Offset (Ztlt)
At any given boom and stick position, the effect of tilt on the offset is a function of tilt 20 angle. There may be minor variations between the tilt of the machine between each calibration lift. For this reason the values stored in the table are normalised to a nominal tilt value.
In this section we are calculating the value of 'Ztlt' for the main load estimation function. For each ann configuration (the various stick vs boom positions used in other calibration steps) we must determine the effect of tilt. SI to S6 and B1 to B6 are the six 25 different predetermined stick and boom positions respectively, and index a lookup table of integers.
B1 B2 B3 B4 B5 B6
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Tilt Offset Matrix
To calibrate the table the excavator is operated without slewing. The chassis is oriented so that the machine is level in a side to side direction, but tilted in the fore and aft direction. The boom is operated through two lifts; one with the stick in the first position, and 5 the second with the stick in the last position (position eight). The remaining values in the table are predicted according to the previous relationships between the different stick positions in the offset matrix (Z). The lifts are made with no load in the bucket. The tilt value for the offset matrix is recorded and a calibration value for the each position is calculated when the boom and stick are at the respective locations as:
Value = (Pd - Z - ZSP) * (Tnom / Tmcasua.d)
Where;
Tnom Constant (angle all values are normalised to)
Tmeasured Measured tilt at the point of the lift where pressures recorded
In use, to calculate Ztlt for a live lift, a position dependant value is calculated for the actual boom and stick positions using values extracted from the table. The value is calculated by interpolating between the four values that are associated with the closest predetermined
boom and stick positions (SI to S6 and B1 to B6).
The value extracted from the table must be de-normalised to a compensation value for the inclination (TnK.asureci) at which the weight data was measured. This is calculated as
Zjlt = InterpolatedValue * (T11K.asureJ / Tnoin)
This compensation assumes that tilt angles remain in a range where the tilt effect is effectively linear, for example less than 30 (degrees). The controller may be programmed to provide a user alert if the measured tilt is outside this range.
Tilt Factor (STlt)
In this section we are calculating the value of 'Sti.t for the main load estimation function. For each arm configuration (the various stick vs boom positions used in other calibration steps) we must determine the effect of tilt and load on the lift pressure. SI to S6
and B1 to B6 are the six different predetermined stick and boom positions respectively and index a lookup table of integers.
At any given boom and stick position, the effect of tilt on the lift pressure is a function of tilt angle. There may be minor variations between the tilt of the machine between each 5 calibration lift. For this reason the values stored in the table are nonnalised to a nominal tilt value. Values in the Tilt Factor Matrix are scale factors (preferably integers).
B1 B2 B3 B4 B5 B6
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Tilt Factor Matrix
To calibrate the table the excavator is operated without slewing. The chassis is oriented so that the machine is level in a side to side direction, but tilted in the fore and aft direction. The boom is operated through two lifts; and with the stick in the first position, and the second with the stick in the last position (position eight). The remaining values in the table are predicted according to the previous relationships between the different stick
positions in the gain matrix (S). The lifts are made with a known load (Test Weight) in the bucket. The calibration value for each position is calculated when the boom and stick are at the respective locations as:
Value = Test Weiglit / ((Pd - Z - ZSp - ZSl) * S) * (Tnom / Tmcasured)
Where;
T110111 Constant (angle all values are normalised to)
Tmcasured Measured tilt at the point of the lift where pressures recorded
In use, to calculate Sjlt for a live lift, a position dependant value is calculated for the actual boom and stick positions using values extracted from the table. The value is calculated
by interpolating between the four values that are associated with the closest predetermined boom and stick positions (SI to S6 and B1 to B6).
The value extracted from the table must be de-normalised to a compensation value for the inclination (Tmcasurcti) at which the weight data was measured. This is calculated as
Stlt = 1 + (InterpolatedJValue * (Tmcasurcd / Tnom))
There is an interaction between tilt and slew rate. Slew rate has an effect in line with the plane of rotation of the machine. Tilt is a gravity referenced effect. On flat ground, these 10 will be at 90° to each other and there will be no noticeable interaction. The interaction should be small for up to moderate slopes (for example about 1.5% for 10°).
In the program executed by the microcomputer, calculation of each of the offsets and factors for the main load estimation function is organised as a separate function. Each lookup table is maintained as a data structure, retained in non-volatile storage (such as hard-disk or 15 flash-ram), and loaded into memory when the program is operating. The main operating program for performing the load estimation, and for guiding and performing the calibration is also retained in non-volatile storage. At least the relevant parts of the program are loaded into short term memory as needed.
Each lookup table is described above in relation to a system where the boom angle and 20 stick angle are each sensed at six defined angular positions. For more accurate analysis a greater position resolution may be used. For example the applicant presently prefers a resolution of fifteen boom angle positions and eight stick angle positions. The greater resolution is particularly useful in allowing more accurate estimation of boom acceleration.
With the greater angle resolution each lookup table is preferably expanded to include 25 values for each possible position combination. However calibration may be conducted using only a sample of positional combinations in the manner discussed above, with the remaining entries in the table being filled by interpolation or extrapolation. Of course these parts of each table may be replaced by interpolation or extrapolation functions used in real time to derive the required value from the calibration values that are taken.
The input interface and output interface of the device may include a data communication network interface, with some or all of the sensor modules, display modules and user interface being network enabled. The communications network may be, for example, a CANBUS network. Alternatively the input interface could be particularly adapted to receive line level signals from the sensors in either digital (for example PWM) or analogue
form, and whether in hardware only or in combination of hardware and software, extract data from said inputs.
The program may be executed on a computer device on the excavator. Alternatively the sensor data may be transmitted to a remote computing device, and the calculated load data may be transmitted back to a display device on the excavator.
The load calculation may be performed by a single computing device. Alternatively elements of the calculation may be made on separate computers in communication. For example the compensation factors may be calculated on a computing device located on the excavator which also includes program to facilitate the calibration process. This may transmit compensation factor data to another computer, local or remote, which calculates the estimated load.
For this reason, "device'' as used in the appended claims shall be taken to include a plurality of physically separate modules acting in concert.
In the case of each computer the program may be implemented in software or hardware as desired. For example elements of the calculations may be implemented in programmable logic devices. As a further example, processing of data input signals may be partially or completely undertaken in software. In part these choices will follow choice of communication method between the sensors and the computing device.
Available choices for aspects of implementation, such as those described above, may vary over time. Persons skilled in the art will understand a range of implementation options available at any time and may choose to implement the invention within that range without departing from the intended scope of the patent.
Claims (78)
1. A weighing device for use with a load lifting machine having a multiple link lifting arm connected at one end to the machine chassis, said chassis being capable of slewing while lifting, said device comprising: means for determining lift forces applied between said ann and said chassis; means for determining a load estimate as a function of said lift forces and the relative link positions of said multiple link ann, and at least one of: means for compensating for acceleration forces on said multiple link lifting arms by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of ann lift acceleration, measured lift speed and the relative link positions of said multiple link arms; means for compensating for slew rate by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of measured slew rate and the relative link positions of said multiple link ann; and means for compensating for inclination of the machine chassis in a plane parallel with the plane of movement of said multiple link arm by modifying said detennined lift forces, or by directly modifying said load estimate, according to a function of measured inclination and the relative link positions of said multiple link ami.
2. A weighing device as claimed in claim 1 wherein said device includes both said means for compensating for slew rate and said means for compensating for inclination.
3. A weighing device as claimed in claim 1 wherein said device includes both said means to compensate for acceleration forces and said means for compensating for slew rate.
4. A weighing device as claimed in claim 1 wherein said device includes both said means for compensating for acceleration forces and said means for compensating for inclination.
5. A weighing device as claimed in claim 1 wherein said device includes said means for compensating for acceleration forces said means for compensating for slew rate and said means for compensating for inclination. -32-
6. A weighing device as claimed in any one of claims 1 to 5 wherein said device includes means for displaying the compensated load estimate to an operator of the excavator.
7. A weighing device as claimed in claim 6 wherein said means for display includes a 5 screen, and means for driving said screen to display said estimated load.
8. A weighing device as claimed in claim 7 wherein said device includes means for accumulating a total load value over a series of lifts, and said means for driving said screen causes said screen to display said estimated load and said total load. 10
9. A weighing device as claimed in claim 8 wherein said device includes a user input interface, and means for resetting said means for accumulating a total load in response to a predetermined entry on said user interface. 15
10. A weighing device as claimed in any one of claims 1 to 9 wherein said device is for fitting to excavators having a hydraulic actuator operating between said arm and said chassis, said means for determining lift forces measures hydraulic pressures, and said device includes means for compensating for fluid pressure changes due to fluid flow rate by modifying said dctennincd lift forces, or by directly modifying said load estimate, according to a function of 20 lift speed.
11. A weighing device as claimed in claim 10 wherein said means for compensating for fluid pressure changes due to fluid flow rate uses a function of lift speed and the position of said first link of said arm. 25
12. A weighing device as claimed in any one of claims 1 to 11 wherein said means for estimating a load calculates an estimate more than once at intervals during a single lift, and determines an estimated load as a derivative of this plurality of estimates. 30
13. A weighing device as claimed in any one of claims 1 to 12 including said means for compensating for slew wherein said means for compensating for slew includes slew offset means for compensating for the effect on lift forces due to centripetal forces operating on the multiple link ann, and slew factor means for compensating for the effect on lift forces due to centripetal forces operating on the load being lifted. -33 -
14. A weighing device as claimcd in claim 13 wherein said slew offset means derives a compensation offset value to be applied against said lift forces, said value being a function of said slew rate and the relative positions of the links in said multiple link ann. 5
15. A weighing device as claimed in claim 14 wherein said slew offset function is proportional to the square of the slew rate and is a function of the height of the centre of mass of the unloaded ami above the plane of rotation of the slewing chassis passing through the connection between said first link of said arm and said chassis, and proportional to the radius 10 from the axis of rotation of the slewing chassis to the centre of mass of the unloaded ami, for the instantaneous relative positions of the links in the multiple link arm.
16. A weighing device as claimed in any one of claims 13 to 15 wherein said slew factor means deriving a compensation factor to be applied against said estimated load, said factor 15 being a function of said slew rate and the position of the centre of mass of the load.
17. A weighing device as claimed in claim 16 wherein the centre of mass of the load is determined from the relative positions of the links in said multiple link arm. 20
18. A weighing device as claimed in claim 17 wherein said slew factor function is proportional to the square of the slew rate and a function of the height of the centre of mass of the load carried by the ami above the plane of rotation of the slewing chassis passing through the connection between said first link of said arm and said chassis, and proportional to the radius from the axis of rotation of the slewing chassis to the centre of mass of the load, for the 25 instantaneous relative positions of the links in the multiple link ann.
19. A weighing device as claimed in any one of claims 1 to 18 including said means for compensating for tilt, wherein said means for compensate for tilt includes tilt offset means for compensating for the effect on lift forces due to gravity forces operating on the multiple link 30 ami, and tilt factor means for compensating for the effect on lift forces due to gravity forces operating on the load being lifted. - 34- 10 15 30
20. A weighing device as claimed in claim 19 wherein said tilt offset means derives a compensation offset value to be applied against said lift forces, said value being a function of said inclination and the relative positions of the links in said multiple link ann.
21. A weighing device as claimed in claim 20 wherein said tilt offset function is a function of the inclination and proportional to the displacement of the centre of mass of the unloaded ann from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link arm.
22. A weighing device as claimed in any one of claims 19 to 21 wherein said tilt factor means derives a compensation factor to be applied against said estimated load, said factor being a function of said inclination and the relative positions of the links in said multiple link arm.
23. A weighing device as claimed in claim 22 wherein said tilt factor function is a function of the inclination and proportional to the displacement of the centre of mass of the load from the connection of said first link to said chassis in the plane of rotation passing through said connection for the instantaneous relative positions of the links in the multiple 20 link arm.
24. A weighing device as claimed in any one of claims 1 to 23 wherein said means for estimating the load includes offset means for estimating the effect on lift forces due to gravity forces operating on the multiple link ami, and factor means for relating lift forces due to 25 gravity forces operating on the load being lifted to the actual load.
25. A weighing device as claimed in claim 24 wherein said offset means derives an offset value to be applied against said lift forces, said value being a function of the relative positions of the links in said multiple link arm.
26. A weighing device as claimed in claim 25 wherein said offset function is proportional to the displacement of the centre of mass of the unloaded arm from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link arm. -35-
27. A weighing device as claimed in any one of claims 24 to 26 wherein said factor means derives a factor to be multiplied with the adjusted lift forces to determine an estimated load, said factor being a function of the relative positions of the links in said multiple link ann. 5
28. A weighing device as claimed in claim 27 wherein said factor function is proportional to the displacement of the centre of mass of the load from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link arm. 10
29. A weighing device as claimed in any one of claims 1 to 28 including said means for compensating for acceleration forces, wherein said means for compensating for acceleration forces includes means for compensating the acceleration forces on the multiple link arm and the load being lifted. 15
30. A weighing device as claimed in claim 29 wherein said compensating means preferably uses a common compensating factor for the combined load and multiple link arm.
31. A weighing device as claimed in claim 30 wherein said acceleration compensating 20 factor is a function of the instantaneous relative positions of the multiple link arm, and the acceleration of the arms.
32. A weighing device as claimed in any one of claims 29 to 31 wherein said acceleration of the multiple link arm is determined by calculating the first differential of the speed of the 25 multiple link ann.
33. A weighing device as claimed in any one of claims 29 to 31 wherein said acceleration of the multiple link arm is determined by sensing with an accelerometer located on said first link of said multiple link ann, sensing acceleration on an axis tangential to the movement of 30 said accelerometer with lifting of said arm.
34. A weighing device as claimed in any one of claims 1 to 33 wherein said device includes calibration means for prompting the operator of the excavator to perform predetermined excavator actions, monitoring sensor signals, calculating calibration data from -36- the sensor signals, and recording the calibration data for use by said means for determining a load estimate.
35. A weighing device as claimed in claim 34 when dependant on any one of claims 5 11,14, 18, 19 to 23,25 to 28 and 31 to 33 wherein a function involving the relative positions of the links of said arm uses, at least in part, a look-up table of values corresponding with different relative link position combinations.
36. A weighing device as claimed in claim 35 wherein said function interpolates between 10 lookup table values for link position combination as closest to the instantaneous position combination.
37. A weighing device as claimed in claim 35 wherein said calibration means stores said calibration data in said lookup tables. 15
38. A weighing device as claimed in any one of claims 1 to 37 said device comprising a controller including a microcomputer with an input interface receiving data from a plurality of sensors, an output interface including at least a display driver, a user input interface for receiving operator commands, said microcomputer executing a software program that 20 implements said means for determining lift forces, said means for determining a load estimate, said means for compensating for slew rate, said means for compensating for inclination, and said means compensating for acceleration.
39. A system for retrofitting to excavators, for allowing an operator to estimate a load 25 raised by the excavator in an individual lift or in a series of individual lifts, said system including a device as claimed in any one of claims 1 to 38, a plurality of sensors for providing input defining (or enabling derivation of) the raw lift forces, the relative positions of at least the first two links in a multiple link ann of the excavator, slew rate, and inclination, and means for providing outputs of said sensors to an input interface of said device. 30
40. A method for estimating load weight for use with a load lifting machine having a multiple link lifting ann connected at one end to the machine chassis, said chassis being capable of slewing while lifting, said method comprising: -37- determining lift forces applied between said arm and said chassis; determining a load estimate as a function of said lift forces and the relative link positions of said multiple link arm, and at least one of: compensating for acceleration forces on said multiple link lifting arms by modifying 5 said determined lift forces, or by directly modifying said load estimate, according to a function of arm lift acceleration, measured lift speed and the relative link positions of said multiple link arms; compensating for slew rate by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of measured slew rate and the relative 10 link positions of said multiple link ann; and compensating for inclination of the excavator chassis in a plane parallel with the plane of movement of said multiple link ann by modifying said detennined lift forces, or by directly modifying said load estimate, according to a function of measured inclination and the relative link positions of said multiple link arm. 15
41. A method as claimed in claim 40 wherein said method includes both compensating for slew rate and compensating for inclination.
42. A method as claimed in claim 40 wherein said method includes both compensating for 20 acceleration forces and compensating for slew rate.
43. A method as claimed in claim 40 wherein said method includes both compensating for acceleration forces and compensating for inclination. 25
44. A method as claimed in claim 40 wherein said method includes compensating for acceleration forces, compensating for slew rate and compensating for inclination.
45. A method as claimed in any one of claims 40 to 44 wherein said method includes displaying the compensated load estimate to an operator of the excavator. 30
46. A method as claimed in claim 45 wherein said method includes accumulating a total load value over a series of lifts, and displaying said estimated load and said total load. - 38 -
47. A method as claimed in claim 46 wherein said method includes resetting said accumulated total load in response to a predetermined user entry.
48. A method as claimed in any one of claims 40 to 47 wherein said method includes 5 determining lift forces from measured hydraulic pressures, and compensating for fluid pressure changes due to fluid flow rate by modifying said determined lift forces, or by directly modifying said load estimate, according to a function of lift speed.
49. A method as claimed in claim 48 using a function of lift speed and the position of said 10 first link of said arm fluid pressure changes due to fluid flow rate.
50. A method as claimed in any one of claims 40 to 49 wherein estimating a load includes calculating an estimate more than once at intervals during a single lift, and determining an estimated load as a derivative of this plurality of estimates. 15
51. A method as claimed in any one of claims 40 to 50 including compensating for slew by compensating for the effect on lift forces due to centripetal forces operating on the multiple link ann, and compensating for the effect on lift forces due to centripetal forces operating on the load being lifted. 20
52. A method as claimed in claim 51 including deriving a compensation offset value to be applied against said lift forces as a function of said slew rate and the relative positions of the links in said multiple link arm. 25
53. A method as claimed in claim 52 wherein offset value is derived as proportional to the square of the slew rate and is a function of the height of the centre of mass of the unloaded arm above the plane of rotation of the slewing chassis passing through the connection between said first link of said arm and said chassis, and proportional to the radius from the axis of rotation of the slewing chassis to the centre of mass of the unloaded arm, for the 30 instantaneous relative positions of the links in the multiple link arm.
54. A method as claimed in any one of claims 51 to 53 including deriving a compensation factor to be applied against said estimated load as a function of said slew rate and the centre of mass of the load. -39-
55. A method as claimed in claim 54 including determining the centre of mass of the load from the relative positions of the links in said multiple link arm. 5
56. A method as claimed in claim 55 wherein said slew compensation factor is derived as a function is proportional to the square of the slew rate and a function of the height of the centre of mass of the load earned by the arm above the plane of rotation of the slewing chassis passing through the connection between said first link of said ami and said chassis, and proportional to the radius from the axis of rotation of the slewing chassis to the centre of 10 mass of the load, for the instantaneous relative positions of the links in the multiple link arm.
57. A method as claimed in any one of claims 40 to 56 including compensating for tilt by compensating for the effect on lift forces due to gravity forces operating on the multiple link arm, and compensating for the effect on lift forces due to gravity forces operating on the load 15 being lifted.
58. A method as claimed in claim 57 including deriving a compensation offset value to be applied against said lift forces as a function of said inclination and the relative positions of the links in said multiple link arm. 20
59. A method as claimed in claim 58 wherein said tilt offset value is derived as a function of the inclination and is proportional to the displacement of the centre of mass of the unloaded ann from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in 25 the multiple link arm.
60. A method as claimed in any one of claims 57 to 59 including deriving a compensation factor to be applied against said estimated load as a function of said inclination and the relative positions of the links in said multiple link arm. 30
61. A method as claimed in claim 60 wherein said compensation factor is derived as a function of the inclination and proportional to the displacement of the centre of mass of the load from the connection of said first link to said chassis in the plane of rotation passing -40- through said connection for the instantaneous relative positions of the links in the multiple link ami.
62. A method as claimed in any one of claims 40 to 61 including estimating the effect on 5 lift forces due to gravity forces operating on the multiple link arm, and relating lift forces due to gravity forces operating on the load being lifted to the actual load.
63. A method as claimed in claim 62 including deriving an offset value to be applied against said lift forces, as a function of the relative positions of the links in said multiple link 10 arm.
64. A method as claimed in claim 63 wherein said offset value is derived as proportional to the displacement of the centre of mass of the unloaded ann from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said 15 connection for the instantaneous relative positions of the links in the multiple link arm.
65. A method as claimed in any one of claims 62 to 64 including deriving a factor to be multiplied with the adjusted lift forces to detennine an estimated load, said factor being a function of the relative positions of the links in said multiple link arm. 20 25
66. A method as claimed in claim 65 wherein said factor is derived as proportional to the displacement of the centre of mass of the load from the connection of said first link to said chassis in the plane of rotation of the slewing chassis passing through said connection for the instantaneous relative positions of the links in the multiple link arm.
67. A method as claimed in any one of claims 40 to 66 including compensating for acceleration forces includes by compensating for the acceleration forces on the multiple link ann and the load being lifted. 30
68. A method as claimed in claim 67 wherein compensating for acceleration forces uses a common compensating factor for the combined load and multiple link arm. -41 -
69. A method as claimed in claim 68 including deriving said acceleration compensating factor as a function of the instantaneous relative positions of the multiple link ann, and the acceleration of the arms. 5
70. A method as claimed in any one of claims 67 to 69 including determining said acceleration of the multiple link ann by calculating the first differential of the speed of the multiple link arm.
71. A method as claimed in any one of claims 68 to 70 wherein said acceleration of the 10 multiple link ann is detennined by sensing with an accelerometer located on said first link of said multiple link arm, sensing acceleration on an axis tangential to the movement of said accelerometer with lifting of said arm.
72. A method as claimed in any one of claims 40 to 71 including calibrating by prompting 15 the operator of the excavator to perfonn predetermined excavator actions, monitoring sensor signals, calculating calibration data from the sensor signals, and recording the calibration data.
73. A method as claimed in claim 72 wherein deriving offset values and compensation factor values involving the relative positions of the links of said arm includes, at least in part, 20 looking up a table of values corresponding with different relative link position combinations.
74. A method as claimed in claim 73 wherein deriving offset values and compensation factor values includes interpolating between lookup table values for link position combination as closest to the instantaneous position combination. 25
75. A method as claimed in claim 73 including storing calibration data in said lookup tables.
76. A weighing device for use with a load lifting machine having a multiple link lifting 30 arm connected at one end to the machine chassis, said chassis being capable of slewing while lifting, said device comprising: an input interface for receiving data from at least one sensor on said load lifting machine ; 5 <«. •/ ' . f ■•••'. v...* , a computer connected with said input interface, ! I 0 » " •> ( -42- a program executable by said computer, said program implementing a method as claimed in any one of claims 40 to 75.
77. A weighing device substantially as herein described with reference to the accompanying drawing.
78. A method of estimating a load weight substantially as herein described with reference to the accompanying drawing.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NZ538885A NZ538885A (en) | 2005-03-15 | 2005-03-15 | Weighing device for excavator payloads |
| PCT/NZ2006/000048 WO2006098645A1 (en) | 2005-03-15 | 2006-03-15 | Weighing device for excavator payloads |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NZ538885A NZ538885A (en) | 2005-03-15 | 2005-03-15 | Weighing device for excavator payloads |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| NZ538885A true NZ538885A (en) | 2006-10-27 |
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ID=36991943
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| NZ538885A NZ538885A (en) | 2005-03-15 | 2005-03-15 | Weighing device for excavator payloads |
Country Status (2)
| Country | Link |
|---|---|
| NZ (1) | NZ538885A (en) |
| WO (1) | WO2006098645A1 (en) |
Families Citing this family (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NZ555187A (en) * | 2007-05-15 | 2010-01-29 | Actronic Ltd | Weight estimation for excavator payloads |
| US8660758B2 (en) * | 2007-11-30 | 2014-02-25 | Caterpillar Inc. | Payload system with center of gravity compensation |
| US7912612B2 (en) * | 2007-11-30 | 2011-03-22 | Caterpillar Inc. | Payload system that compensates for rotational forces |
| EP2088407A1 (en) * | 2008-02-07 | 2009-08-12 | Tedea Huntleigh International Ltd. | Load indicating system |
| US7650252B2 (en) * | 2008-06-17 | 2010-01-19 | Caterpillar Trimble Control Technologies, Llc | Inclinometer measurement system and method providing correction for movement induced acceleration errors |
| GB2461273A (en) * | 2008-06-24 | 2009-12-30 | Seppo Haekkinen | Load monitoring system |
| DE102010050796A1 (en) * | 2010-10-23 | 2012-04-26 | Robert Bosch Gmbh | A method of determining the mass of cargo received in a tool of a front loader mounted on a vehicle |
| US8548689B2 (en) | 2010-11-23 | 2013-10-01 | Caterpillar Inc. | Implement induced machine pitch detection |
| WO2013027873A1 (en) * | 2011-08-24 | 2013-02-28 | Volvo Construction Equipment Ab | Method for controlling a working machine |
| US8924094B2 (en) | 2012-10-17 | 2014-12-30 | Caterpillar Inc. | System for work cycle detection |
| US8909437B2 (en) | 2012-10-17 | 2014-12-09 | Caterpillar Inc. | Payload Estimation system |
| US9091586B2 (en) | 2013-03-29 | 2015-07-28 | Caterpillar Inc. | Payload determination system and method |
| US9938692B2 (en) | 2016-01-04 | 2018-04-10 | Caterpillar Inc. | Wheel loader payload measurement system linkage acceleration compensation |
| US11009522B2 (en) | 2018-09-07 | 2021-05-18 | Caterpillar Inc. | Systems and methods for calibrating an acceleration sensor using a payload system |
| WO2021150893A1 (en) | 2020-01-24 | 2021-07-29 | Milwaukee Electric Tool Corporation | Zero-gravity hoist control |
| CN112097886A (en) * | 2020-09-21 | 2020-12-18 | 河南达正然智能科技有限公司 | Loader and high-precision weighing method thereof |
| US12012727B2 (en) * | 2020-11-06 | 2024-06-18 | Cnh Industrial America Llc | System and method for estimating the weight of a load carried by an implement of a work vehicle |
| CN113124972A (en) * | 2021-03-12 | 2021-07-16 | 中国航空工业集团公司西安飞行自动控制研究所 | Excavator material weighing method and system |
| CN114923554B (en) * | 2022-04-27 | 2023-06-20 | 株洲嘉成科技发展股份有限公司 | Self-adaptive weighing device and method for loader |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU648367B2 (en) * | 1991-01-10 | 1994-04-21 | Dresser Industries Inc. | A method for measuring the weight of a suspended load |
| JPH0610378A (en) * | 1992-06-26 | 1994-01-18 | Komatsu Ltd | Workload detection device for excavation and loading machine |
| DE59509448D1 (en) * | 1995-04-03 | 2001-08-30 | Ascorel Controle Et Regulation | Weighing method and lifting vehicle for carrying out the method |
| US6072127A (en) * | 1998-08-13 | 2000-06-06 | General Electric Company | Indirect suspended load weighing apparatus |
| JP3760731B2 (en) * | 2000-07-11 | 2006-03-29 | ソニーケミカル株式会社 | Bumped wiring circuit board and manufacturing method thereof |
| US8373078B2 (en) * | 2003-08-15 | 2013-02-12 | Siemens Industry, Inc. | System and method for load measuring by motor torque |
-
2005
- 2005-03-15 NZ NZ538885A patent/NZ538885A/en unknown
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2006
- 2006-03-15 WO PCT/NZ2006/000048 patent/WO2006098645A1/en active Application Filing
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| WO2006098645A1 (en) | 2006-09-21 |
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