NZ562752A - Weight calculation for lifted payloads using compensation of intrinsic rig losses - Google Patents

Abstract

A method for determining weight of a payload lifted by a rig of a load lifting machine and an apparatus for use with a load lifting machine comprising a rig for lifting a payload are disclosed. The apparatus comprises one or more sensors or one or more inputs for coupling to one or more sensors and a processor coupled to the one or more sensors or inputs. The one or more sensors or the one or more inputs receive one or more raise parameters being or indicative of force or pressure required to raise the rig during a compensation lift; one or more lower parameters being or indicative of force or pressure required to lower the rig during a compensation lift, and one or more lift parameters being or indicative of force or pressure required to lift the payload using the rig. The processor is adapted to calculate the weight of the payload using the lift parameters and a coefficient that compensates for intrinsic losses in the rig. The coefficient is determined based on the difference between the raise parameter(s) and lower parameter(s). Also disclosed is the load lifting machine comprising a rig for lifting a payload, at least one sensor attached to the rig to measure one or more parameters being or indicative of force or pressure required to raise or lower the rig, and a processor coupled to the sensor, the processor adapted to receive one or more raise parameters being or indicative of force or pressure required to raise the rig during a compensation lift, receive one or more lower parameters being or indicative of force or pressure required to lower the rig during a compensation lift, receive one or more lift parameters being or indicative of force or pressure required to lift the payload using the rig, calculate the weight of the payload using the lift parameters and a coefficient that compensates for intrinsic losses in the rig. The coefficient is determined based on the difference between the raise parameter(s) and lower parameter(s).

Description

Received at IPONZ 30 March 2010 NEW ZEALAND PATENTS ACT, 1953 No: 562752/565545 Date: 23 October 2007/29 January 2008 COMPLETE SPECIFICATION WEIGHT CALCULATION COMPENSATION We, ACTRONIC LIMITED, a New Zealand company of 45 Patiki Road, Avondale, 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: Received at IPONZ 5 October 2010 FIELD OF THE INVENTION The present invention relates to compensation for friction and/or other losses in weight calculation of payloads being lifted by a load lifting machine.

BACKGROUND TO THE INVENTION Load lifting machines are used to lift, carry and shift payloads. Typically load lifting machines can take the form of ftont-end loaders, back-end loaders, excavators, dust bin loaders and the like. The payload is typically crushed stone, sand, debris, rubbish or other solid objects that need to be lifted and moved.

It is often desirable to determine the weight of a payload being Lifted in a load lifting machine. For example, the weight being transported by a dump truck needs to determine to ensure the truck meets weight restrictions. One way of doing this is by calculating the weight of the individual payloads being loaded into a dump-truck as the load lifting machine fills the truck.

Apparatus exist for determining the weight of a payload being lifted by a load Lifting machine. Such apparatus typically look at the pressure of hydraulic fluid in hydraulic actuators as the payload is being lifted by operating the load lifting machine rig. The difficulty with such apparatus is that they are prone to inaccuracy. This is because the base their calculations on assumptions regarding the 20 characteristics of the load lifting machine rig. Often characteristics such as friction are not taken into account.

It is desirable to provide improved accuracy when calculating weight of payloads being lifted by load lifting machines.

SUMMARY OF THE INVENTION The object of the present invention is to provide a load lifting machine, method and/or apparatus for determining the weight of a payload. This will typically be the payload being lifted by a front-end loader or similar load lifting machine.

In one aspect the invention can be broadly said to consist of a method implemented in a processor for determining weight of a payload lifted by a rig of a load lifting machine comprising: receiving one or more raise parameters being or indicative of force or pressure required to raise the rig during a compensation lift, receiving one or more lower parameters being or indicative of force or pressure required to lower the rig during a compensation lift, Received at IPONZ 28 March 2011 3 receiving one or more lift parameters being or indicative of force or pressure required to lift the payload using the rig, calculating the weight of the payload using the lift parameters and a coefficient that compensates for intrinsic losses in I he rig, and wherein the coefficient is determined based on the difference between the raise parameter(s) and lower parameter^).

Preferably the rig comprises one or more actuators to raise and lower the rig, wherein applied by one or more of the actuators while raising the rig during a compensation lift, the one or more lower parameters are or are indicative of force or pressure existing in or applied by one or more of the actuators while lowering the rig during a compensation lift, and the one or more lift parameters are or are indicative of force or pressure existing in or 15 applied by one or more of the actuators to lift the payload using the rig.

Preferably the method further comprising: receiving one or more first speed parameters being or indicative of the speed of the rig while the rig is raised during a compensation lift, receiving one or more second speed parameters being or indicative of the speed of the rig while the rig is being lowered during a compensation lift, wherein the coefficient is also based on the difference between the first and second speed parameters.

Preferably the weight of the payload is calculated using: outputting information to indicate the weight on a user interface, the one or more raise parameters are or are indicative of force or pressure existing in or Weight = ((Lift * (1 - C)) — (k * Return) - Zero) * Span, wherein: Lift is the lift pressure in the hydraulic cylinder when a payload lift is performed, Return is the return pressure in the hydraulic cylinder when a payload lift is performed, k is the rod bore mixing ratio, Zero is the normal calibration 2ero, Span is the normal calibration span, C forms the compensation coefficient for friction and/or other losses.

Preferably the method further comprising: Received at IPONZ 5 October 2010 r — ~ ~ >2u ^'^2d P»+Pu where Pltl is the Lift Pressure in the hydraulic cylinder as arms are raised during a compensation lift 5 P2u is the Return Pressure in the hydraulic cylinder as arms are raised during a compensation lift, Pld is the Lift Pressure in the hydraulic cylinder as arms are lowered during a compensation lift, P2d is the Return Pressure in the hydraulic cylinder as arms are lowered during a 10 compensation lift, k is the Rod Bore mixing ratio.

Preferably the weight of the payload is calculated using: Weight = ((Lift * (1 - C)) - (k * Return) - Zero - C*n* j V |) * Span wherein: lift is the lift pressure in the hydraulic cylinder when a payload lift is performed, Return is the return pressure in the hydraulic cylinder when a payload lift is performed, k is the rod bore mixing ratio, Zero is the normal calibration zero, Span is the normal calibration span, | V [ is the speed of the rig, C and/or n form the compensation coefficient for friction and/or other losses. 25 Preferably the method further comprising: c = PI.-Pu+k(Pu-Pj Pu*Pu+«W+KI) and wherein, -.p2/)+c^,-;i,) " = ~ ~ Received at IPONZ 5 October 2010 where Plu is the Lift Pressure in the hydraulic cylinder as arms are raised during a compensation lift P2u is the Return Pressure in the hydraulic cylinder as arms are raised during a compensation 5 lift, Pld is the Lift Pressure in the hydraulic cylinder as arms are lowered during a compensation lift, P2d is the Return Pressure in the hydraulic cylinder as arms are lowered during a compensation lift, k is the Rod Bore mixing ratio, Vu is the Boom Speed as arms are raised during a compensation lift, Vd is the Boom Speed as arms are lowered during a compensation lift, Pi; is the Lift Pressure as arms are raised at idle during a compensation lift, Pa is the Return Pressure as arms are raised at idle during a compensation Eft, 15 Plfis the Lift Pressure as arms are raised at full throttle during a compensation lift, P2f is the Return Pressure as arms are raised at full throttle during a compensation lift, V, is the Boom Speed as arms are raised at idle during a compensation lift, and Vf is the Boom Speed as arms are raised at full throttle during a compensation lift.

In yet another aspect the invention can be said to broadly consist in a load lifting machine comprising: a rig for lifting a payload, at least one sensor attached to the rig to measure one or more parameters being or indicative of force or pressure required to raise or lower the rig, and 25 a processor coupled to the sensor, the processor adapted to: receive one or more raise parameters being or indicative of force or pressure required to raise the rig during a compensation lift, receive one or more lower parameters being or indicative of force or pressure required to lower the rig during a compensation lift, receive one or more lift parameters being or indicative of force or pressure required to lift the payload using the rig, calculate the weight of the payload using the lift parameters and a coefficient that compensates for intrinsic losses in the rig, wherein the coefficient is determined based on the difference between the raise parameter(s) 35 and lower parameter(s).

Received at IPONZ 5 October 2010 Preferably the tig comprises one or mote actuators to raise and lower the rig, wherein the one or more raise parameters are or are indicative of force or pressure existing in or applied by one or more of the actuators while raising the rig during a compensation lift, the one or more lower parameters are or are indicative of force or pressure existing in or 5 applied by one or more of the actuators while lowering the rig during a compensation lift, and the one or more lift parameters are or are indicative of force or pressure existing in or applied by one or more of the actuators to lift the payload using the rig.

Preferably the load lifting machine further comprising 10 at least one sensor attached to the rig to measure one or more parameters being or indicative of the speed of the rig while the rig is raised or lowered during a lift, wherein the processor is further adapted to: receive one or more first speed parameters being or indicative of the speed of the rig while the rig is raised during a compensation lift, receive one or more second speed parameters being or indicative of speed of the rig while the rig is being lowered during a compensation lift, wherein the coefficient is also based on the difference between the first and second speed parameters.

Preferably the weight of the payload is calculated using: Weight — ((Lift * (1 - C)) — (k * Return) - Zero) * Span, wherein: Lift is the lift pressure in the hydraulic cylinder when a payload lift is performed, Return is the return pressure in the hydraulic cylinder when a payload lift is performed, k is the rod bore mixing ratio, Zero is the normal calibration zero, Span is the normal calibration span, C forms the compensation coefficient for friction and/or other losses.

Preferably the load lifting machine as defined further comprising C-Pi« ~Pid ~LP2„ +kAd Pu, +PW where Received at IPONZ 5 October 2010 Plu is the Lift Pressure in the hydraulic cylinder as arms are raised during a compensation lift P2u is the Return Pressure in the hydraulic cylinder as arms are raised during a compensation lift, Pld is the Lift Pressure in the hydraulic cylinder as arms are lowered during a compensation lift, P2d is the Return Pressure in the hydraulic cylinder as arms are lowered during a compensation lift, k is the Rod Bore mixing ratio.

Preferably the weight of the payload is calculated using: Weight = ((Lift * (1 - C)) — (k * Return) — Zero - C*n* j V |) * Span wherein: Lift is the lift pressure in the hydraulic cylinder when a payload Hft is performed, Return is the return pressure in the hydraulic cylinder when a payload lift is performed, k is the rod bore mixing ratio, Zero is the normal calibration zero, Span is the normal calibration span, | V | is the speed of the rig, C and/or n form the compensation coefficient for friction and/or other losses.

Preferably the load lifting machine as defined further comprising: 9r f _ u ~ P\d + k{P2d ~ P2u ) k,->Pu+4v*\+K\) and wherein, n= WJM ~ where Plu is the Lift Pressure in the hydraulic cylinder as arms are raised during a compensation lift Received at IPONZ 5 October 2010 P2ll is the Return Pressure in the hydraulic cylinder as arms are raised during a compensation Hft, Pld is the Lift Pressure in the hydraulic cylinder as arms are lowered during a compensation Hft, P2d is the Return Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, k is the Rod Bore mixing ratio, Vu is the Boom Speed as arms are raised during a compensation Hft, Vd is the Boom Speed as arms are lowered during a compensation Hft, Pi; is the Lift Pressure as aims are raised at idle during a compensation Hft, P2i is the Return Pressure as arms are raised at idle during a compensation Hft, Plf is the Lift Pressure as arms are raised at full throttle during a compensation Hft, P2f is the Return Pressure as arms are raised at fuH throtde during a compensation Hft, V; is the Boom Speed as arms are raised at idle during a compensation Hft, and 15 Vf is the Boom Speed as arms are raised at full throttle during a compensation Hft.

In another aspect the invention can be said to broadly consist in an apparatus for use with a load Hfting machine comprising a rig for Hfting a payload comprising: one or more sensors or one or more inputs for coupling to one or more sensors that receive: 20 one or more raise parameters being or indicative of force or pressure required to raise the rig during a compensation Hft, one or more lower parameters being or indicative of force or pressure required to lower the rig during a compensation Hft, and one or more Hft parameters being or indicative of force or pressure required to Hft 25 the payload using the rig, and a processor coupled to the one or more sensors or inputs, the processor adapted to: calculate the weight of the payload using the Hft parameters and a coefficient that compensates for intrinsic losses in the rig, wherein the coefficient is determined based on the difference between the raise parameter(s) and lower parameters).

Preferably the rig comprises one or more actuators to raise and lower the rig, wherein the one or more raise parameters are or are indicative of force or pressure existing in or appHed by one or more of the actuators while raising the lig during a compensation Hft, Received at IPONZ 5 October 2010 the one or more lower parameters are or are indicative of force or pressure existing in or applied by one or more of the actuators while lowering the rig during a compensation lift, and the one or more lift parameters are or are indicative of force or pressure existing in or applied by one or more of the actuators to lift the payload using the rig.

Preferably the apparatus as defined further comprising the one or more sensors or one or more inputs for coupling to one or more sensors also receive: one or more parameters being or indicative of the speed of the rig while the rig is raised or lowered during a Eft, and the processor is further adapted to: receive one or more first speed parameters being or indicative of the speed of the rig while the rig is raised during a compensation Eft, receive one or more second speed parameters being or indicative of speed of the rig while the rig is being lowered during a compensation Eft, wherein the coefficient is also based on the difference between the first and second speed parameters.

Preferably the weight of the payload is calculated using: Weight — ((Lift * (1 - C)) — (k * Return) - Zero) * Span, wherein: Lift is the Eft pressure in the hydrauEc cylinder when a payload Eft is performed, Return is the return pressure in the hydrauEc cylinder when a payload Eft is performed, k is the rod bore mixing ratio, Zero is the normal calibration zero, Span is the normal caEbration span, C forms the compensation coefficient for friction and/or other losses.

Preferably the apparatus as defined further comprising: C = ^>1" ~ +^-P2d where Received at IPONZ 5 October 2010 Plu is the Lift Pressure in the hydraulic cylinder as arms are raised during a compensation lift P2u is the Return Pressure in the hydraulic cylinder as arms are raised during a compensation lift, Pld is the Lift Pressure in the hydraulic cylinder as arms are lowered during a compensation 5 lift, P2d is the Return Pressure in the hydraulic cylinder as arms are lowered during a compensation lift, k is the Rod Bore mixing ratio.

Preferably the weight of the payload is calculated using: Weight = ((Lift * (1 - C)) — (k * Return) - Zero — C*n* | V |) * Span wherein: Lift is the lift pressure in the hydraulic cylinder when a payload lift is performed, Return is the return pressure in the hydraulic cylinder when a payload lift is performed, k is the rod bore mixing ratio, Zero is the normal calibration zero, Span is the normal calibration span, | V | is the speed of the rig, C and/or n form the compensation coefficient for friction and/or other losses.

Preferably the apparatus as defined further comprising: oc r< _ P\u ~ + M/jrf ~ P2u ) and wherein, n= wm where Plu is the Lift Pressure in the hydraulic cylinder as arms are raised during a compensation lift Received at IPONZ 5 October 2010 In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such 20 external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

The term "comprising" as used in this specification means "consisting at least in part of'. Related 25 terms such as "comprise" and "comprised" are to be interpreted in the same manner.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are 30 mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will be described with reference to the following drawings of which: Figure la is a schematic diagram of a generic loading hfting rig Received at IPONZ 5 October 2010 Figure lb is a schematic diagram of a load lifting machine, Figure 2 is a schematic diagram of a rig in raised and lowered positions.

Figure 3 is a block diagram of a weight calculation apparatus, Figure 4 is a flow diagram of operating a load lifting machine with weight calculation 5 apparatus, Figure 5 is a flow diagram of a weight calculation method conducted by software, Figure 6 is an example of a typical front-end loader that may utilise the invention, Figure 7 is a schematic diagram of a hydraulic actuator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention is described generally in relation to a generic loading rig shown in Figure la. This provides an overview of the invention. The rig 1 comprises a lifting arm 2 adapted to lift a payload 3, for example by way of a bucket or other loading holding means. The lifting arm 2 is moveable around a pivot 6a, which allows for lifting and lowering of the load 3 as shown by the 15 arrow. The arm 2 is moved by way of an actuator 5. This might be, for example, a hydraulic actuator with a cylinder and a ram that extends from and retracts in to the cylinder. Extending the ram lifts the arm 2 and payload 3, while retracting the ram lowers the arm 2 and payload 3. The actuator 5 can pivot as required around pivot 6b. The rig could be used by any type of machinery that is intended to raise and lower a payload 3.

The invention allows for calculation of the weight of the payload 3. Traditional methods for calculating load weight are inaccurate. The applicants have determined that this is at least partially due to the presence of friction and/or other losses present and/or occurring in the payload lifting rig during a Hft. Further, the degree of friction varies throughout operation, due to the rig "warming 25 up". The friction within the hydraulic cylinders of the rig is a function of pressure, temperature and in some cases, speed. Pressure primarily varies with load, but can also vary (due to changes in return line pressure) with pressures caused by other hydraulic equipment. The traditional methods of payload weight calculation cannot account for losses due to friction and the like. The present invention provides for an improved weight calculation of a payload by compensating for these 30 losses.

In general, the force required to raise the payload 3 is equal to the force caused by gravity acting on the payload mass, plus any losses. The force required to support the payload while it is being lowered is equal to the force caused by gravity acting on the mass, minus any losses. This can be 35 written as: Filing - M.g + Fj^uj, (1) Received at IPONZ 5 October 2010 ^Lowering ^Vo^.Dov.il (^) where; ^Raising Force required raising the load M Mass of the load g Gravitational Constant Fj^u Force required to overcome losses (such as friction) while raising the load FLowering Force required to support the load while lowering F, os;Doi,,,. Force caused by losses (such as friction) while lowering the load By rearranging and combining (1) and (2) we get; F - F = F + F f3"i Riasmg x LossUp Lowering LossDown V / which in turn becomes; F - . - F = F + F f4^i Kjasmg Lowering LossUp LossDown \ / If now define a new parameter, being the mean of the up and down losses; FLoss (^LossUp ^J.oS/iDov.'n) / ^ (^) We get; F - F = 7 * F Rjasing Lowering Loss \yj Thus, the difference between the force required to raise a given load and the force required to support the same load as it is lowered is equal to twice the mean losses (due to friction or other 30 effects).

This fundamental principle can be used to determine a parameter that is indicative of the losses in a mechanical system. These losses are typically primarily caused by friction of bearings or other rubbing surfaces. The friction is a function of the load applied to said bearings or surfaces. The 35 losses could be due to other factors also. By measuring the friction (and other) losses at any given load, we are able to predict the friction (and other) losses for other applied loads.

Received at IPONZ 5 October 2010 This concept can be applied to a range of applications where weight calculation of a payload being lifted by lifting rigs is required. A preferred embodiment of the invention is shown in Figure lb in which the weight calculation is implemented in respect of a load lifting machine 10. A load lifting 5 machine can be a front-end or wheel loader, back-end loader, excavator, rubbish bin loader or any other loading machine that can lift payloads using a lifting rig. The preferred embodiment relates to a front-end (or wheel-loader), although the invention should not be considered to be restricted to such a machine.

The front-end loader 10 comprises a main body 11 that can be manoeuvred by conveying apparatus such as wheels 12 or continuous tracks. The main body comprises the engine (not shown) for manoeuvring and operating the front-end loader 10 along with the necessary hydraulics system. The front-end loader 10 also comprises a cab or other driver location 13 mounted on the top of the main body 11. A driver can operate the front-end loader 10 from this position. The front-end loader 15 comprises a payload lifting rig 14 attached to the front of the body 11. The rig comprises a load holder 15 for holding a payload and one or more lift arms 16 (one is visible) for attaching the load holder to the main body 11. The load holder 15 can take the form of a bucket, grapple, forks, electromagnet, shovel or other attachment for holding a load. In Figure lb, a bucket is shown. The arms 16 are pivotally connected to the bucket 15 and main body 11 to enable manoeuvring of the 20 bucket up and down. A shown in Figure 2, the bucket can be moved to a raised position 2a, or a lowered position 2b via the arm 16. This enables debris and other objects to be scooped up and then lifted by operation of the arms.

A hydraulic or other actuator 17 is attached to the body 11 and arm 16 in order to operate the rig to 25 hft a payload. In this particular case shown in Figure lb, there is a hydraulic actuator 17 coupled between the main body and the arm 16 to raise and lower the arm. The hydraulic actuator comprises a cylinder 18a, and a ram 18b that extends from and retracts into the cylinder 18a under the influence of hydraulic fluid. A lift is performed by extending the ram 18b from the hydraulic cylinder 18a to push the lift arm 16 in an upwards direction pivoting on the central pivot 7 on the 30 body of the machine. This puts the rig in the raised position 2a in Figure 2. The rig can be lowered 2b by retracting the ram 18b into the hydraulic cylinder 18a. This moves the hft arm 16 in a downwards direction pivoting on the central pivot 7. Additional hydraulic actuators (not shown) could be provided between the arm 16 and the bucket 15. Such actuators could be manipulated to tilt the bucket 15, as required. The hydrauEc actuator 17 is operated by the hydraulic system in the 35 main body 11, under the control of an operator in the cab 13.

Received at IPONZ 5 October 2010 The front-end loader 10 also comprises components to determine the weight of a payload in the bucket 15. To do so, one or more sensors 20 are placed on or in the hydraulic actuator 17 to measure the pressure of the hydraulic fluid. More particularly each sensor can sense or measure a parameter being or being indicative of, hydraulic fluid pressure in the cylinder 18a of the hydraulic 5 actuator 17. This parameter is, or is indicative of, a force or pressure applied by the actuator to the rig or a force or pressure existing in the actuator (such as fluid pressure). In a preferred embodiment, hydraulic fluid pressure is measured by the sensors, although other sensing could take place. For example, a force sensor could measure a parameter that is indicative of a force or pressure applied by the actuator to the rig, or a force or pressure existing in the actuator. The 10 sensors can also measure the speed and/or velocity of the rig as it is raised/lowered. These sensor measured parameters are termed "Hft parameters" when they relate to the output of the sensors while the actuators are performing a lift. The sensor(s) pass signals/data back to a main unit 19 that utilizes the parameters from the sensors to calculate or otherwise determine a payload weight. The calculated weight can then be communicated to the operator in the cab 13, via a screen or other 15 output device 4.

The front-end loader 10 also comprises one or more position sensors 9 to determine the position of the arm 16. This allows weight calculation to be triggered at an appropriate time during the lift. These sensors might also measure speed and/or velocity of the rig as it is raised/lowered. The 20 sensors 9 can be placed in any suitable location, for example on or near the pivot 7. This enables the arm 16 position to be determined by its rotation. The position information is fed back to the main unit 19.

It will be appreciated that Figure lb shows a generic rig for exemplary purposes, and that an actual 25 rig of a front-end loader or other load lifting machine might differ. For example, a rig might comprise multiple arms, and one or more hydraulic actuators to operate each arm.

Figure 3 shows an apparatus 21 in accordance with one embodiment of the invention that could be used to calculate or otherwise determine a weight of a payload in a front-end loader. The apparatus 30 21 can be retrofitted to an existing front-end loader or incorporated into a new front-end loader, such as that shown in Figure lb. The apparatus 21 comprises a processor 22 that runs a weight calculation program 23 or algorithm. The processor 22 is or can be coupled to one or more sensors 20 attached to the actuator 17 on the lifting rig 14. Preferably, the sensors 20 are pressure sensors that detect the hft and return hydraulic fluid pressures in the actuators 17 they are attached to. Any 35 suitable number of sensors could be used. In a preferred embodiment, there is at least one sensor 20 attached to at least one of the actuators 17 of the rig, although a sensor 20 is not necessarily Received at IPONZ 5 October 2010 required for each actuator 17. Each sensor can sense or measure a lift parameter as described earlier. Preferably, this parameter is, or is indicative of, the lift pressure and return pressure of hydraulic fluid in the respective hydraulic actuator as a lift is made. The Uft pressure is the pressure of hydraulic fluid at the base of the cylinder that is forcing the ram to extend out of the hydraulic 5 cylinder. The return pressure is the hydraulic fluid pressure at the rod end of the cylinder.

The processor 22 can receive the measured lift parameters (i.e. lift and return pressures) from the one or more sensors 20. It operates the program 23, which utilizes the lift parameters and calculates the weight of the payload being lifted. This can be done as the hft is being performed. 10 Alternatively, the weight can be determined at a later point in time. Preferably, the weight is calculated based on lift parameters that are determined at a trigger point during the lift. The trigger point might be some position the arm moves through between the lowered position 2b of the rig and the raised position of the rig 2a. The trigger point will be detected by the sensor 9. Preferably, the trigger point is when the arm 16 is clear of the stockpile being moved, and when the arm is 15 about or above horizontal. Other trigger points could be used, however.

The determined weight is then communicated to the operator, for example via a screen or display 25. Alternatively, the weight might be calculated from lift parameters taken at various points, or continuously throughout the lift. The apparatus 21 also comprises a user interface for operating the 20 apparatus 21.

The processor 22 can also determine the intrinsic losses in the rig as the rig is lifted. These are primarily caused by friction, although can be due to other losses also. It does this by receiving Hft parameters from the sensors 20 during a compensation Hft. The compensation Hft involves a raising 25 and lowering of the rig. The difference in the measured parameters from the up and down movements provide an indication of losses. This can be used to compensate for losses during an actual weight calculation Hft. The rest of the specification will refer to the losses as being friction, as these are the predominant loss. However, it should be remembered that other losses might be present, which can be compensated for by the present invention. Again, the Hft parameter is or is 30 indicative of the Hft pressure and return pressure of hydrauHc fluid in the respective hydrauHc actuator as a Hft is made. This parameter is or is indicative of a force or pressure apphed by the actuator to the rig, or a force or pressure existing in the actuator.

The processor 22 can determine a (friction) compensation coefficient based on the Hft parameters 35 taken from a compensation Hft. This coefficient can be used to at least partially compensate for intrinsic friction and/or other losses in the rig 14 when calculating a payload weight. More Received at IPONZ 5 October 2010 particularly, during an actual lift, the processor receives lift parameters. From these lift parameters, and the previously calculated compensation coefficient, the processor 22 can use the program 23 to calculate a weight of the payload, in which friction of the rig 14 has at least been partially compensated for. This provides for a more accurate determination of weight.

The program 23 in the processor 22 calculates or otherwise determines the weight of a payload using a program which is created to carry out weight calculations that compensate for friction.

A typical (existing) weight algorithm (for each trigger point) is: Weight = (Lift - (k * Return) - Zero) * Span (7) Where: Lift is the filtered Hft pressure interpolated at a trigger point during a payload Hft. 15 Return is the filtered return pressure interpolated at a trigger point during a payload Hft. k is the rod bore mixing ratio, which is A2/A , (as seen in Figure 7 that is the ratio of the bore cross-sectional area to the rod end cross-sectional area).

Zero is the normal caHbration zero.

Span is the normal caHbration span.

The program 23 in the processor 22 of the present invention uses a modified to equation (7), which compensates for friction. There are two embodiments. A first embodiment utiHses the difference in friction during up and down Hfts to determine a compensation coefficient. A second embodiment further utiHses velocity to refine the compensation for better accuracy.

Embodiment 1 In the first embodiment, the program 23 implements the foHowing modified version of equation (7) 30 which the inventors have devised.

Weight = ((Lift * (1 - C)) - (k * Return) - Zero) * Span (8) Flere, CC' is the compensation coefficient for friction and/or other losses. 'C5 is updated each time 35 the compensation function is performed. It is calculated by; Received at IPONZ 5 October 2010 18- P\ P] j k-P? + k.P-,, Ui l_tf £ii Id /q\ ~ P + P rht + r\d Plu is the lift pressure -as the hft arms of the rig are raised in a compensation Hft, P2u is the return pressure as the Hft arms are raised in a compensation Hft, P1d is the Hft pressure as the Hft arms are lowered in a compensation Hft, P2d is the return pressure as the Hft arms are lowered in a compensation Hft, The Hft and return pressures mentioned in respect of equations 7 to 9 relate to the pressures (and more particularly the Hft parameters) measured by one or more sensors 20 on an actuator 17 operating a Hft arm 16. It is possible that such parameters could be obtained from further sensors 10 attached to one or more further Hft arms. In this case, the received parameters could be processed and used to create a representative parameter for use in equations 7 to 9.

The value of 4C' should be able to be common for aH trigger points.

The derivation of equation 9 is set out in Appendix A.

Span and Zero are the main two parameters that define the relationship between weight and Hft pressure (force). The Zero parameter is the pressure (or force) required to Hft the empty bucket due to the inherent mass of the rig. Thus, if you subtract the Zero fluid pressure of the pressure 20 required to Hft the arms, bucket and any given load, the remainder should be the pressure required for just the payload part.

The Span parameter indicates the relationship between change in pressure and change in load. For example, if an extra 500PSI was required to Hft a load of 1000kg, then the Span factor would be £2'. 25 Thus if we saw a pressure of 600PSI (above the cZero' pressure value), we would know the load is 600 x 2 = 1200kg.

Zero and Span parameters are determined during initial caHbration, usuaHy at the time of installing or configuring the weight calculation apparatus. This is determined by Hfting a known test weight. 30 They may be updated from time to time (perhaps yearly), or whenever required.

The appHcants have determined that one of the causes of inaccuracies in weight calculation for load Hfting machines is the intrinsic friction within the Hfting rig 14. Friction is present in each of the moving joints, (typicaHy around 11 bearing sets) and in the internal friction of the hydraulic Hft Received at IPONZ 5 October 2010 cylinders 18a. As the hfting machine 10 warms up, and as ambient conditions change, this friction changes, in turn causing errors in weight calculation.

Some of the error due to friction can be compensated for by "zeroing" which is a typical technique 5 used by rig operators. Zeroing compensates for build up of debris or other matter in the bucket 15 of the rig 14, which results in inaccurate weight calculation. This can be carried out periodically. However, as the applicants have determined, since friction is primarily a "gain" or "sensitivity" effect, standard zeroing has only a partial impact, typically one third. Further, friction within the hydraulic cylinders 18a is a function of pressure and temperature. The applicants have determined 10 that pressure primarily varies with load but can also vary (due to changes in return line pressure) with pressures caused by other hydrauHc equipment.

Embodiment 2 In the second embodiment, the program 23 implements the foHowing modified version of equation 15 (7) which the inventors have devised. Here, a velocity component is included when calculating weight. In effect, a compensation coefficient that includes velocity considerations is used to compensate for friction.

Here 'C' and 'n' are the compensation coefficients for friction and/or other losses. They are updated each time the 'Zero' function is performed (as described below).

CC' is calculated by: Weight = ((Lift * (1 - C)) - (k * Return) - Zero - C*n* | V |) * Span (80 C (9') and, 'n' is calculated by: n (9") Where Received at IPONZ 5 October 2010 Pld is the Lift Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, P2d is the Return Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, k is the Rod Bore mixing ratio, Vu is the Boom Speed as arms are raised during a compensation Hft, Vd is the Boom Speed as arms are lowered during a compensation lift, Pi: is the Lift Pressure as arms are raised at idle during a compensation Hft, P2l is the Return Pressure as arms are raised at idle during a compensation Hft, 10 Plf is the Lift Pressure as arms ate raised at full throttle during a compensation Hft, P2f is the Return Pressure as arms are raised at full throttle during a compensation Hft, V, is the Boom Speed as arms are raised at idle during a compensation Hft, Vf is the Boom Speed as arms are raised at fuH throttle during a compensation Hft, and | V | is the Boom Speed in either up or down direction.

Raising and lowering the rig arms at fuH throttle means that the hydrauHc valve is fuHy open and the engine is run at maximum RPM. Raising and lowering the rig arms at idle means that the hydrauHc valve is fuUy open and the engine is run at idle speed. Plu P2l. Plri and P2d can be measured at any suitable engine speed.

The value of CC' and/or £n' should be able to be common for aU trigger points.

Equations 9' and 9" can be combined together to produce: \Vr\-nK+rJ+n+\yM-Py) () In this embodiment a weighing method of measuring up and down and/or up at idle and up at full throttle.

The Hft and return pressures mentioned in respect of equations 7, 8' and 9'-9"' relate to the pressures (and more particularly the Hft parameters) measured by one or more sensors 20 on an actuator 17 operating a Hft arm 16. It is possible that such parameters could be obtained from further sensors attached to one or more further Hft arms. In this case, the received parameters could be processed and used to create a representative parameter for use in equations 7 to 9.

The coefficients C and n of this embodiment can provide more accuracy in the weight measurement that the compensation coefficient in the first embodiment. This is because velocity of the rig Received at IPONZ 5 October 2010 movement is also taken into account. Velocity of the rig can affect friction. The coefficients ate scaling factors that are proportional to pressure and velocity The value of 'C' and 'n' should be able to be common for all trigger points.

The derivation of equations 9' to 9'" is set out in Appendix B.

Use of the coefficients and equations in both embodiments The equations above (for embodiments 1 and 2) compensate for friction. The remainder of the 10 description relates to use of any embodiment (such as those above) where some type of compensation coefficient is determined. This may be the compensation coefficient C of the first embodiment, or the compensation coefficients C, n (or C*n) of the second embodiment. The singular term "Compensation coefficient" can be taken to refer both C and n jointly. Recalculation of the compensation coefficient can occur periodically by carrying out compensation lifts 15 periodically. The compensation lifts are carried out as and when required to update the compensation coefficient. Each time an updated compensation coefficient is calculated, it is used in the weight calculation for each subsequent payload Hft. This compensates for changing friction in the front-end loader rig throughout the day. Once a payload weight is calculated, this can be communicated to the operator via a screen or display 25.

Figure 4 shows operation of the front-end loader 10 in accordance with an embodiment of the invention. At the beginning of operation of the front-end loader 10 the operator can conduct a zeroing function, step 40, in the normal way known to those skiHed in the art. This compensates for leftover debris or other matter in the bucket. This is normaUy done by Hfting up the rig and 25 measuring the weight prior to the actual Hft.

The operator can then conduct a compensation (caHbration) Hft, step 41, in order to enable the processor 22 to determine a compensation coefficient to compensate for friction in the Hfting rig 14 during weight calculation. The compensation Hft, step 31, comprises the operator Hfting the rig 14 30 and then lowering the rig 14 again. Preferably this is done without a payload in the bucket 15. The zeroing Hft could form part of the compensation Hft, as the zeroing Hft just requires an upwards Hft. However, the compensation Hft could be a separate Hft. As the rig 14 is Hfted, the Hft pressure on one or more of the hydrauHc actuators 17 is measured by one or more sensors 20 attached to those actuators 17. The return pressure is also received by the same or different sensor 20. As the rig 14 35 is lowered, the Hft pressure and return pressure are also measured by the sensor 20, and received by the processor as a Hft parameters, step 42. Once the compensation Hft is formed, the processor uses Received at IPONZ 5 October 2010 the received lift parameters from die sensors to calculate a compensation coefficient using the program 23. The compensation coefficient is calculated in accordance with equation 9 or 9'-9"', as appropriate depending on which embodiment is being used, step 43.

Alternatively the 'Zero' lift or operation and the compensation lift can be combined into the same operation.

The operator can then operate the front-end loader 10 to Hft an actual payload as and when required, step 44. When an actual Hft takes place the operator wiH Hft the rig 14 from a lowered 10 position 2b to the raised position 2a. At some point during the movement, the Hft pressure and return pressure in one or more of the hydrauHc cylinders 18a measured and passed to the processor as Hft parameters, step 45. The sensors 20 may be measuring continuously, or only at a trigger point. Preferably the processor 22 only uses the received Hft parameters at a trigger point. The trigger point wiH be a position of the rig at any suitable point between the lowered position 2b and raised 15 position 2a. The processor 22 then uses the program 23 to calculate the weight of the payload, step 46. To do so, the program implements equation 8 (or 8' if using the compensation of embodiment 2), and uses the Hft parameters measured/received during the actual Hft, and the compensation coefficient determined from the last performed compensation Hft. The inputs of the sensors are used as the parameters of the equations implemented by the software 23 The calculated weight is then output to the screen or other output device, step 17. The operator can carry out numerous Hfts and obtain their weight in the same manner, steps 44-48. However, periodicaUy the operator can carry out another compensation Hft as and when required, steps 48 and 41. The operator can conduct a compensation Uft optionaHy between every actual payload Hft. 25 Alternatively, a pre-select mode could be operated. In that mode, the operator presses a compensation key on the apparatus and then conducts a compensation Hft, when required.

TypicaHy in this mode, the operator would carry out a compensation Hft periodicaUy throughout the day based on when it seems Hkely that the intrinsic friction in the rig may have changed and therefore the compensation coefficient needs updating. For example, as the environment and/or 30 the front-end loader's 10 temperature rises, the operator might decide to carry out another compensation Hft. Alternatively or in addition, the operator may carry out compensation lifts at specified times, or a specified number of times throughout the day. The compensation Hfts can be carried out based on experience of the operator and operating procedures. The compensation coefficient function can be turned off, thereby setting the friction coefficient at zero.

Received at IPONZ 5 October 2010 It is not essential for the compensation Hft to be carried out prior to an actual hft, although it is preferable. The compensation Hft could be carried out after the payload Hft.

While in one embodiment the compensation coefficient can be determined at the time of receiving 5 the compensation Hft parameters, in an alternative it is possible to simply store these parameters and use them at the same time as calculating the weight from the actual Hft parameters, step 53.

Figure 5 shows operation of the software 23 in the processor 22. The program 23 is normally in a wait cycle, step 50. In this state, the program waits to receive Hft parameters. These are the Hft 10 parameters that are received by the processor 22 from the sensors 20 either during a compensation Hft or actual Hft. At step 51, if the program 23 receives parameters, it then determines if these are from a compensation Hft or an actual Hft, step 52. It can do this from some prompt from the processor 22, for example from user input indicating the type of Hft, or some automatic signal from the front-end loader 10 that determines the type of Hft. If the received parameters relate to a 15 compensation Hft, then the program 23 determines or calculates a compensation coefficient, step 55, and then stores this coefficient step 56. The program then goes back into the wait cycle, steps 50, 51. At step 52, if the program determines that the received parameters are from an actual Hft, then the program 23 calculates the weight of the payload from the received parameters, and from the previously calculated compensation coefficient, step 53. The program then outputs information that 20 indicates the weight, which can be displayed by the processor 22 in the display, step 54. After outputting the weight information the program 23 goes back into the wait cycle steps 50, 51. While in one embodiment the compensation coefficient can be determined at the time of receiving the compensation Hft parameters, in an alternative it is possible to simply store these parameters and use them at the same time as calculating the weight from the actual Hft parameters, step 53.

Figure 6 shows an example of a front-end loader 10 that could utiHze a weight calculation apparatus that compensates for friction. Such a front end front-end loader comprises a body 60, cab 61 and wheels 62. It also comprises a Hfting rig 63 that has a bucket 64 that can be manoeuvred by two Hfting arms (65a, 65b). The Hfting arms are manoeuvred by hydrauHc actuators 66, of which one is 30 shown. Sensors can be placed to measure the fluid pressure in the hydrauHc actuator (not shown). The bucket is pivotably attached to one end of the arms 65a, 65b and can be pivoted by way of a linkage system 67 that is operated by a third central hydrauHc actuator 68.

An embodiment of the invention can be provided or implemented on any loading machine that 35 utihzes a Hfting rig with hydrauHc actuators, or other similar actuators. The invention could be also apphed to a rope shovel machine operated by electric motor actuators, whereby the difference of Received at IPONZ 5 October 2010 forces during a compensation lift could be calculated to compensate for losses in a weight calculation. The machinery shown in Figures 1 and 4 and the particular geometry of the hfting rigs are shown by way of example only. The invention could be applied to a range of different lifting rigs with different geometries. An embodiment of the invention could also comprise a load Hfting 5 machine comprising an apparatus for payload weight measurement that compensates for friction. An embodiment of the invention also comprises a method of operating such a machine or apparatus. An embodiment of the invention also comprises a method of calculating payload weight that comprises compensating for friction.

In an alternative embodiment, it is possible to measure the forces on the lifting rig using force sensors. A compensation coefficient could be determined in a similar manner by utilizing the output from force sensors during a compensation Hft.

It wiH be appreciated that more than one sensor 20 can be used, if necessary. Preferably at least one 15 sensor is used on each hydrauHc cylinder 18a. However, more than one sensor could be used on each hydrauHc cylinder to provide further accuracy or other benefits. Alternatively, one or more sensors might be provided on only one of the hydrauHc actuators. For example, in some Hfting rig embodiments, the hydrauHc actuators used are fluidly coupled such that the pressures in each are relatively similar. In this case sensors ate only required on one actuator.

The preferred embodiment of the invention could comprise a newly constructed front-end loader with the weight calculation and compensation abiHty constructed into the front-end loader.

Alternatively an apparatus 21 can be provided that can be retrospectively fitted to a front-end loader 25 10.

Further, an apparatus could be in the form of a processor 22 that is coupled to existing sensors 20 on a front-end loader 10 that already has an existing weight calculation apparatus. This enables an existing system to be updated, utihzing the existing sensors 20.

Yet farther, an existing weight calculation apparatus 21 could be upgraded by updating the software 23 in the processor to calculate a compensation coefficient, and to use this in determining a more accurate weight calculation.

It wiH be appreciated that while Figure 3 shows the apparatus 21 comprising a screen 25, processor 35 22 and sensors 20, it is not necessary for the apparatus to comprise aH of these. The apparatus 21 might just comprise the processor, or just the processor and screen. The sensors 20 do not Received at IPONZ 5 October 2010 necessarily form part of the apparatus 21 per se, as these may already exist on a machine to which the apparatus 21 is retro-fitted. In this case the processor 22 would be coupled to the existing sensors 20.

In general terms, it will be appreciated that the invention could comprise or be provided on any front-end loader 10 that comprises a Hfting rig and uses hydrauHc 17 or other similar type actuators.

In a further embodiment, a temperature sensor could be added to the rig 14. This could provide the advantage of aUowing auto-tuning functionaHty to tune the values of the faction coefficient between 10 compensation Hfts. The additional temperature sensor might have a use in diagnostics also. A service person might be able to relate changes in weight to a change in temperate of any given component, such as hydrauHc oil, bearing or the like which could provide advantages.

Received at IPONZ 5 October 2010 APPENDIX A Equation 9 can be derived as follows, with reference to Figure 7, which shows a schematic diagram of a hydrauHc cylinder with a ram extending from the cylinder. The cylinder has a cross-sectional area At and the rod side of the piston has a cross-sectional area A2. Alf A2 are the Hft and return side areas, respectively. Further, there is a first base-end pressure Pl3 which is the Hft pressure. P; creates a force that points in the direction shown by arrow A. There is a pressure P2) the return pressure, which exists in the rod-end of the cylinder. P2 creates a force that points in the direction shown by arrow. F0 is the force output of cylinder, which is the difference between the two opposing forces A, B. This is calculated form F=P1A1-P2A2. Ff is the friction force (friction within cylinder) Now, F0^(P1.AX)-(P2.A2)-Ff when cyclinder extending, and F0^(PVAX)-(P2.A2) + Ff (10) when cylinder retracting, and Ff = CJ\ (11) where equation 10 is an approximation, and (12) A rewriting these, we get Bore2 -Rod2 (13) Bore2 and F0 =P]-k.P1-C.P] (14) = Pv(l-C)-k.P2 when cylinder extending, and Received at IPONZ 5 October 2010 27 - F0 = i> -k.P2+C.P} = Pv{\ + C)-k.P2 when cylinder retracting.

In the above, the units have been ignored. This is done in the real system, as pressures are in A-D counts, the dimensions unit less.

So that just leaves finding 'C' the compensation coefficient. This is a unit less constant representative of the friction coefficient of the cylinder. Conveniendy this will also be close to representing the friction coefficient of the bearings. The value of k.P2 is minor error.

In operation, to find 'C the same load is raised and lowered. If friction is fully compensated for, the effective Force (F) should be the same for up and down.

Fvp = (15) Pu .(1 - C) - k.P2v = Pld .(1 + C) - k.Pld (16) -Plu.(l-C) + P,d.(l + C) = -k.P2t, +k.P2d (17) C-{P\U + P\d) = P\u ~ P\u ~ k.P2u + k.P2d (18) Therefore, P\u ~Pld -k-Plu +k-P2d itt Id Zu ' 2a (m P + P rls Where Plu is the Lift Pressure in the hydrauHc cylinder as arms are raised during a compensation Hft, P2u is the Return Pressure in the hydrauHc cylinder as arms are raised during a compensation Hft, Pld is the Lift Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, P2d is the Return Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, k is the Rod Bore mixing ratio.

So, in summary, the sequence is: 1. Hft the arms up (smoothly), record pressures at trigger point(s), Received at IPONZ 5 October 2010 2. lower the arms down (smoothly), record pressures at trigger point(s) 3. calculate 'C'.

The load is theoretically not too important. The value of 'C' does alter slightly with load. This could 5 imply that it is better to determine '(.? with a full load rather than empty. However early practical testing has shown that the measurements are much more repeatable (less bounce) with an empty bucket rather than full.

Received at IPONZ 5 October 2010 APPENDIX B Equations 9', 9" can be derived as follows, with reference to Figure 7, which shows a schematic diagram of a hydrauHc cylinder with a ram extending from the cylinder. The cylinder has a cross-sectional area A! and the rod side of the piston has a cross-sectional area A2. At, A2 are the Hft and return side areas, respectively. Further, there is a fkst base-end pressure Pl9 which is the Hft pressure. Pj creates a force that points in the direction shown by arrow A. There is a pressure P2, the return pressure, which exists in the rod-end of the cylinder. P2 creates a force that points in the direction shown by arrow. F0 is the force output of cylinder, which is the difference between the two opposing forces A, B. This is calculated form F=P1A1-P2A2. Ff is the friction force (friction within cylinder) Where; Pi,P2 Aj, A2 F0 Ff Lift and Return pressures (respectively) Lift and Return side areas (respectively) Force Output of cylinder Friction force (friction within cylinder) Now, F0 = (P\A\ )-(P2A2)-Ff (20) when the cylinder is extending, and F0 = {PxAl)~~{P2A2) + Ff (21) when the cylinder is retracting, and Ff=CPl (11) or, Ff = CPX + Cn\v\ (22) Which is an approximation based on separate research.

Also, 40 i _ A2 _ Bore2 — Rod2 K — A, Bore (23) and, F'0 = PX -kP2 -CPX -Cn\V\ Received at IPONZ 5 October 2010 Received at IPONZ 5 October 2010 31 C(P„ +pu +«d^l + K|))=^.-Pu + *fe, -/>„,) (31) SO, c = P,.'Pu+k(P2d-P2h) pu+pu+wA+ To find 'n' a lift at idle and a lift at full throttle can be used, in which case: Pu(1 -O-kP2i -Cn\Vt\=P]f(l-C)-kP2f+ Cn\vf (9') (33) (34) so, n ■ P^-O-P^l-Q + ^-P,,) M) cr (9") CC can be found independently from *n' by combining the above two equations, we get: C = Piu + pu + PUt P] d+k{P2d Pj P]fa~c)~-pu(i-c)+k[p2i-p2f) cIC/l-KI) ■d^i+Ki) (35) so. c(\vf\-Y^Pu+^)+(W+Klk-PJ = |F/|-KlK-Pu +k(?u --PJH^I + KlR-pu + -Pifh (N-WK-P" +^^A,))-(i^i + Kfe/ 'Pu + *fe, -^/)) \Vf\-\V\lPu+Pu)AVM\V.\lPu-P>f) where P,u is the Lift Pressure in the hydraulic cylinder as arms are raised during a compensation hft P2u is the Return Pressure in the hydraulic cylinder as arms are raised during a compensation hft, Pld is the Lift Pressure in the hydrauHc cylinder as arms are lowered during a compensation 35 Hft, P2d is the Return Pressure in the hydrauHc cyHnder as arms are lowered during a compensation hft, Received at IPONZ 5 October 2010 k is the Rod Bore mixing ratio, Vu is the Boom Speed as arms are raised during a compensation hft, Vd is the Boom Speed as arms are lowered during a compensation Hft, Pi: is the Lift Pressure as arms are raised at idle during a compensation hft, 5 P2j is the Return Pressure as arms are raised at idle during a compensation Hft, Plf is the Lift Pressure as arms are raised at full throtde during a compensation Hft, P2f is the Return Pressure as arms are raised at full throttle during a compensation Hft, V; is the Boom Speed as arms are raised at idle during a compensation Hft, Vfis the Boom Speed as arms are raised at fuH throttle during a compensation Hft, and 10 |V| is the Boom Speed in either up or down direction.

So, in summary, the sequence for determining 'C' alone is: 1. Hft the arms up (smoothly), record pressures at trigger pointfs), 2. lower the arms down (smoothly), record pressures at trigger point(s), 15 3. calculate £C'.

For combined £C' and £n' the sequence is: 1, Hft the arms up (smoothly), record pressures at trigger point(s), 2. lower the arms down (smoothly), record pressures at trigger point(s), 3. Hft the arms up (smoothly) at idle, record pressures and speeds at trigger point(s), 4. Hft the arms up (smoothly) at full throttle, record pressures and speeds at trigger point(s), . calculate £C' and hence 'n'.

The load is theoretically not too important. The value of £C' does alter shghdy with load. This could 25 imply that it is better to determine 'C' with a full load rather than empty. However early practical testing has shown that the measurements are much more repeatable (less bounce) with an empty bucket rather than full.

When 'C' and £n' are both used rather than using four Hfts to perform a zero, the operation can be spHt into two separate steps of a 'C' zero and a speed zero that can alternately be performed. A £C' zero involves an up and down Hft, while a speed zero involves two up Hfts.

Received at IPONZ 28 March 2011

Claims (24)

CLAIMS We claim:

1. A method implemented in a processor for determining weight of a payload hfted by a rig of a load lifting machine, comprising: 5 receiving one or more raise parameters being or indicative of force or pressure required to raise the rig during a compensation hft, receiving one or more lower parameters being or indicative of force or pressure required to lower the rig during a compensation lift, receiving one or more hft parameters being or indicative of force or pressure required to hft 10 the payload using the rig, calculating the weight of the payload using the hft parameters and a coefficient that compensates for intrinsic losses in the rig, and outputting information to indicate the weight on a user interface wherein the coefficient is determined based on the difference between the raise parameter(s) 15 and lower parameters).

2. A method according to claim 1 wherein the rig comprises one or more actuators to raise and lower the rig, wherein the one or mote raise parameters are or are indicative of force or pressure existing in or 20 applied by one or more of the actuators while raising the rig during a compensation hft, the one or more lower parameters are or are indicative of force or pressure existing in or apphed by one or more of the actuators while lowering the rig during a compensation hft, and the one or more Hft parameters are or are indicative of force or pressure existing in or apphed by one or more of the actuators to hft the payload using the rig. 25

3. A method according to claim 1 or 2 further comprising: receiving one or more first speed parameters being or indicative of the speed of the rig while the rig is raised during a compensation hft, receiving one or more second speed parameters being or indicative of the speed of the rig 30 while the rig is being lowered during a compensation hft, wherein the coefficient is also based on the difference between the first and second speed parameters. 35

4. A method according to claim 1 or 2 wherein the weight of the payload is calculated using: Weight = ((Lift * (1 - C)) — (k * Return) - Zero) * Span, Received at IPONZ 5 October 2010 -34- wherein: Lift is the lift pressure in the hydraulic cylinder when a payload Hft is performed, Return is the return pressure in the hydrauHc cylinder when a payload Hft is performed, k is the rod bore mixing ratio, 5 Zero is the normal caHbration zero, Span is the normal caHbration span, C forms the compensation coefficient for friction and/or other losses.

5. A method according to claim 4 wherein 10 c — ~ ~ + k.P2d Pu+Pui where Plu is the Lift Pressure in the hydrauHc cylinder as arms are raised during a compensation Hft P2u is the Return Pressure in the hydrauHc cylinder as arms are raised during a compensation 15 Hft, Pld is the Lift Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, P2d is the Return Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, 20 k is the Rod Bore mixing ratio.

6. A method according to claim 3 wherein the weight of the payload is calculated using: Weight - ((Lift * (1 - C)) - (k * Return) - Zero - C*n* | V |) * Span 25 wherein: Lift is the Hft pressure in the hydrauHc cylinder when a payload hft is performed, Return is the return pressure in the hydrauHc cyHnder when a payload Hft is performed, k is the rod bore mixing ratio, Zero is the normal caHbration zero, 30 Span is the normal caHbration span, | V | is the speed of the rig, C and/or n form the compensation coefficient for friction and/or other losses. -35-

7. A method according to claim 7 wherein: Received at IPONZ 5 October 2010 5 and wherein, Q _ Plu Pld+k{P2d P2u) r„+r»+4vA+K I) n = c(KI-M) 10 where P,., is the Lift Pressure in the hydraulic cylinder as arms are raised during a compensation hft P2u is the Return Pressure in the hydraulic cylinder as arms are raised during a compensation hft, Pld is the Lift Pressure in the hydraulic cylinder as arms are lowered during a compensation 15 hft, P,^ is the Return Pressure in the hydraulic cylinder as arms are lowered during a compensation hft, k is the Rod Bore mixing ratio, Vu is the Boom Speed as arms are raised during a compensation hft, 20 Vd is the Boom Speed as arms are lowered during a compensation hft, P,; is the Lift Pressure as arms are raised at idle during a compensation hft, P2i is the Return Pressure as arms are raised at idle during a compensation hft, Plf is the Lift Pressure as arms are raised at full throttle during a compensation hft, P2f is the Return Pressure as arms are raised at full throttle during a compensation hft, 25 V. is the Boom Speed as arms are raised at idle during a compensation hft, and Vfis the Boom Speed as arms are raised at full throttle during a compensation hft.

8. A load lifting machine comprising: a rig for hfting a payload, 30 at least one sensor attached to the rig to measure one or more parameters being or indicative of force or pressure required to raise or lower the rig, and a processor coupled to the sensor, the processor adapted to: Received at IPONZ 5 October 2010 -36- receive one or more raise parameters being or indicative of force or pressure required to raise the rig during a compensation lift, receive one or more lower parameters being or indicative of force or pressure required to lower the rig during a compensation hft, 5 receive one or more hft parameters being or indicative of force or pressure required to hft the payload using the rig, calculate the weight of the payload using the hft parameters and a coefficient that compensates for intrinsic losses in the rig, wherein the coefficient is determined based on the difference between the raise parameter(s) 10 and lower parameter(s).

9. A load hfting machine according to claim 8 wherein the rig comprises one or more actuators to raise and lower the rig, wherein the one or more raise parameters are or are indicative of force or pressure existing in or 15 apphed by one or more of the actuators while raising the rig during a compensation hft, the one or more lower parameters are or are indicative of force or pressure existing in or apphed by one or more of the actuators while lowering the rig during a compensation hft, and the one or more hft parameters are or are indicative of force or pressure existing in or applied by one or more of the actuators to lift the payload using the rig. 20

10. A load hfting machine according to claim 8 or 9 comprising at least one sensor attached to the rig to measure one or more parameters being or indicative of the speed of the rig while the rig is raised or lowered during a lift, wherein the processor is further adapted to: 25 receive one or more first speed parameters being or indicative of the speed of the rig while the rig is raised during a compensation Uft, receive one or more second speed parameters being or indicative of speed of the rig while the rig is being lowered during a compensation Uft, wherein the coefficient is also based on the difference between the first and second speed 30 parameters.

11. A load hfting machine according to claim 8 or 9 wherein the weight of the payload is calculated using: 35 Weight — ((Lift * (1 - C)) — (k * Return) - Zero) * Span, Received at IPONZ 5 October 2010 -37- wherein: Lift is the hft pressure in the hydrauhc cylinder when a payload hft is performed. Return is the return pressure in the hydrauhc cyhnder when a payload hft is performed, k is the rod bore mixing ratio, 5 Zero is the normal caHbration zero, Span is the normal caHbration span, C forms the compensation coefficient for friction and/or other losses. 10

12. A load Hfting machine according to claim 11 wherein q _ P\u P\d k.P2u + k.P2d +P\d where Plu is the Lift Pressure in the hydrauHc cylinder as arms are raised during a compensation Hft P2u is the Return Pressure in the hydrauHc cylinder as arms are raised during a compensation 15 Hft, Pld is the Lift Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, P2d is the Return Pressure in the hydrauHc cylinder as arms are lowered during a compensation Hft, 20 k is the Rod Bore mixing ratio.

13. A load Hfting machine according to claim 10 wherein the weight of the payload is calculated using: 25 Weight - ((Lift * (1 - C)) — (k * Return) — Zero - C*n* | V |) * Span wherein: Lift is the Hft pressure in the hydrauHc cylinder when a payload Hft is performed, Return is the return pressure in the hydrauHc cylinder when a payload Hft is performed, 30 k is the rod bore mixing ratio, Zero is the normal caHbration zero, Span is the normal caHbration span, | V j is the speed of the rig, C and/or n form the compensation coefficient for faction and/or other losses. 35

14. -38- A load Hfting machine according to claim 13 wherein: Received at IPONZ 5 October 2010 5 and wherein, c=-p„,-

15. An apparatus for use with a load hfting machine comprising a tig for Hfting a payload comprising: 30 one or more sensors or one or more inputs for coupling to one or more sensors that receive: one or more raise parameters being or indicative of force or pressure required to raise the rig during a compensation Hft, Received at IPONZ 5 October 2010 -39- one or more lower parameters being or indicative of force or pressure required to lower the rig during a compensation hft, and one or more hft parameters being or indicative of force or pressure required to hft the payload using the rig, 5 and a processor coupled to the one or more sensors or inputs, the processor adapted to: calculate the weight of the payload using the hft parameters and a coefficient that compensates for intrinsic losses in the rig, wherein the coefficient is determined based on the difference between the raise 10 parameter(s) and lower parameter(s).

16. An apparatus according to claim 15 wherein the rig comprises one or more actuators to raise and lower the rig, wherein the one or more raise parameters are or are indicative of force or pressure existing in or apphed by one or more of the actuators while raising the rig during a compensation hft, the one or more lower parameters are or are indicative of force or pressure existing in or apphed by one or more of the actuators while lowering the rig during a compensation hft, and the one or more hft parameters are or are indicative of force or pressure existing in or apphed by one or more of the actuators to Hft the payload using the rig.

17. An apparatus according to claim 15 or 16 wherein the one or more sensors or one or more inputs for coupling to one or more sensors also receive: one or more parameters being or indicative of the speed of the rig while the rig is raised or lowered during a hft, and the processor is further adapted to: receive one or more first speed parameters being or indicative of the speed of the rig while the rig is raised during a compensation Hft, receive one or more second speed parameters being or indicative of speed of the rig while the rig is being lowered during a compensation Hft, wherein the coefficient is also based on the difference between the first and second speed parameters. 35

18. An apparatus according to claim 15 or 16 wherein the weight of the payload is calculated using: 15 20 25 30 -40- Received at IPONZ 5 October 2010 Weight = ({Lift * (1 - C)) — (k * Return) - Zero) * Span, wherein: 5 Lift is the hft pressure in the hydrauhc cylinder when a payload hft is performed, Return is the return pressure in the hydrauhc cylinder when a payload Uft is performed, k is the rod bore mixing ratio, Zero is the normal caHbration zero, Span is the normal caHbration span, 10 C forms the compensation coefficient for friction and/or other losses.

19. An apparatus according to claim 18 wherein C = k-P2u +k.P2d P\u 15 where Pu is the Lift Pressure in the hydrauhc cylinder as arms are raised during a compensation Uft P2u is the Return Pressure in the hydrauhc cyhnder as arms are raised during a compensation Hft, Pld is the Lift Pressure in the hydrauHc cylinder as arms are lowered during a compensation 20 Hft, P2d is the Return Pressure in the hydrauHc cyhnder as arms are lowered during a compensation Hft, k is the Rod Bore mixing ratio. 25

20. An apparatus according to claim 17 wherein the weight of the payload is calculated using: Weight = ({Lift * (1 - C)) — (k * Return) — Zero - C*n* | V)) * Span wherein: 30 Lift is the Hft pressure in the hydrauhc cylinder when a payload Hft is performed, Return is the return pressure in the hydrauHc cylinder when a payload Hft is performed, k is the rod bore mixing ratio, Zero is the normal caHbration zero, Span is the normal caHbration span, 35 | V | is the speed of the rig, Received at IPONZ 5 October 2010 -41 - C and/or n form the compensation coefficient for friction and/or other losses.

21. An apparatus according to claim 20 wherein: P\u ~ d + k{P2d ~ P2u) c = p\u +p\d + +r« and wherein, 10 n = p,f-p,,+i'(p1,-plf)+c(pl,-plf) WPyti where Plu is the lift Pressure in the hydrauhc cyhnder as arms are raised during a compensation hft P2u is the Return Pressure in the hydrauhc cylinder as arms are raised during a compensation 15 hft, Pld is the Lift Pressure in the hydrauhc cyhnder as arms are lowered during a compensation hft, Pjj is the Return Pressure in the hydrauhc cyhnder as arms are lowered during a compensation hft, 20 k is the Rod Bore mixing ratio, Vu is the Boom Speed as arms are raised during a compensation hft, Vd is the Boom Speed as arms are lowered during a compensation hft, Pi; is the Lift Pressure as arms are raised at idle during a compensation hft, P2. is the Return Pressure as arms are raised at idle during a compensation hft, 25 Plf is the Lift Pressure as arms are raised at full throttle during a compensation hft, P2f is the Return Pressure as arms are raised at full throtde during a compensation hft, V; is the Boom Speed as arms are raised at idle during a compensation hft, and Vf is the Boom Speed as arms are raised at full throtde during a compensation hft. 30

22. A method for determining weight of a payload lifted by a rig of a load hfting machine substantially as herein described or shown in any one of figure 4 and figure 5. Received at IPONZ 5 October 2010 -42-

23. An apparatus for use with a load hfting machine comprising a rig for hfting a payload substantiaUy as herein described or shown in any one of figures la, lb and 3 or figures 6 and 7.

24. A load hfting machine substantiaUy as herein described or as shown in any one of figures la, 5 lb and 3 or figures 6 and7.