GB2529996A - Payload weighing apparatus and method - Google Patents

Abstract

Calculating a payload weight of a load holder, such as a bucket or shovel on an excavation device or mechanical digger or loading machine. An angle measuring apparatus is in communication with weighing module (100) which calculates payload weight. The loading machine comprising an arm (7) and a load holder (8) pivotally mounted at a distal end of said arm (7). A measuring apparatus comprises an ultrasonic sensor (18) located at a distance from a pivot point (8b) between the load holder (8) and the arm (7) and it is configured determine the distance between the sensor (18) and the pivot point (8b). The remote ultra-sonic measurement aspect of the system is more reliable than electrical or optical devices would be in a dirty, muddy or wet environment.

Description

PAYLOAD WEIGHING APPARATUS AND METHOD

This invention relates generally to apparatus configured to weigh a load and, more particularly but not necessarily exclusively, to apparatus configured to weigh a payload of a loading machine such as a wheeled excavator/material handling machine or wheeled loading shovel, for example.

Off-road machines, such as, for example, loaders, are typically used to transport a payload material, such as, for example, rock, sand, dirt, or gravel, from one location to another. According to a particular work cycle, the loader may use a work tool, such as a bucket, to capture a portion of the payload material and transfer the captured portion of material to another location. Alternatively, a work cycle may include use of the loader to fill a larger payload capacity machine, such as a haulage truck, which is used to transport the material. According to these work cycles and others, it may be desirable to calculate the weight, or mass, of the payload material that is moved within or transported from a work site. This payload weight or mass calculation may be used to evaluate efficiency, productivity, and profitability of the A typical excavator comprises a chassis on a carriage comprising tracks and a cab for housing the controls of the excavator. An operator can sit in the cab and control the excavator. The chassis can slew or rotate relative to the carriage. A boom extends from the chassis, the angle of which can be controlled by a hydraulic ram extending between the chassis and the boom. A stick is connected to the boom by a pivotable joint and can be arranged at various angles relative to the boom by a hydraulic ram. A bucket or other load holder is provided for scooping or grabbing, holding, transporting and dumping material or other payload. The load holder is connected to the stick by a pivotable joint, and a hydraulic ram enables the angle between the bucket and the stick to be varied as required. An operator can sit in the cab and operate the controls to alter the geometry of the boom, stick and load holder in order to manipulate the load holder and its payload in the desired manner. The boom and stick are generically termed as "linkages". The boom, stick and holder combination may be termed a lifting linkage.

The excavator also has a number of sensors to determine parameters for calculating a weight estimation. Typically, there is provided a first sensor for measuring the angle between the boom and the chassis, a second sensor, located at the pivot point between the boom and the stick, for measuring the relative angle between the boom and the stick, and a third sensor for measuring the relative angle between the load holder and the stick. The third sensor, hereinafter referred to as the bucket angle sensor (although it will be appreciated that aspects of the present invention may be used in relation to a loading machine having a load holder other than a bucket), is located at, or as near as possible to, the pivot point between the load holder and the stick. There is further provided at least one fourth sensor for measuring the tilt of the chassis, and pressure sensors on the hydraulic actuator. It will be appreciated that other sensors may also be provided for providing additional angle and/or pressure measurements. Each of the sensors is connected via a cable to a weighing module.

A weighing module samples each of the sensor signals received via the respective cables and a computer program running in the weighing module applies a known algorithm to calculate (or estimate) weight. Data representative of the calculated/estimated payload weight value is fed to a user unit within the cab and displayed to the user on a screen.

However, the cable connecting the bucket angle sensor to the weighing module is required to extend along the length of the stick, alongside the hydraulic ram, as well as the length of the boom, in order to be connected to the weighing module, which is typically located at a convenient location on the chassis. Problems arise due to movement of the hydraulic ran and stick, which can cause the bucket sensor cable to become damaged and/or disconnected during use of the excavator.

The present invention seeks to alleviate this issue, and provides, in a first aspect, load holder angle measuring apparatus for a payload weight calculation system in a device comprising a stick and a load holder pivotally mounted at a distal end of said stick, the apparatus comprising an ultrasonic sensor located at a distance from a pivot point between said load holder and said stick and configured to generate a signal representative of a distance between said sensor and said pivot point.

In accordance with a second aspect of the present invention, there is provided a method measuring an angle between a load holder pivotally mounted at a distal end of a stick, the method comprising generating an ultrasonic signal at a sensor point on or adjacent said stick and directing said signal toward a pivot point between said load holder and said stick, receiving ultrasonic energy reflected from said pivot point and generating an electronic signal representative of the distance between said sensor point and said pivot point.

In an exemplary embodiment, wherein pivoting of said load holder is effected by an actuator provided between said stick and said pivot point, the ultrasonic sensor may be mounted on a non-moving housing of said actuator.

In one embodiment, the actuator may comprise a hydraulic actuator, comprising a piston mounted for linear movement within a housing, a distal end of the piston being communicably coupled to said pivot point, wherein the ultrasonic sensor is mounted on the housing and configured to direct an ultrasonic signal toward said pivot point. In this case, the sensor may be configured to generate an electronic signal representative of the length of extension of the piston relative to the housing.

In one embodiment, the apparatus may be configured to generate a correction factor to match the output of said ultrasonic sensor to that of at least one other sensor provided in respect of said loading machine.

The present invention extends to a payload weighing system for a loading machine comprising a boom, a stick pivotally mounted to said boom and a load holder pivotally mounted to said stick, the weighing system comprising a plurality of sensors, at least one of said sensors comprising an ultrasonic sensor for generating an electronic signal representative of a relative angle between said boom and said stick or between said stick and said load holder.

In an exemplary embodiment, in which pivoting of said load holder is effected by a hydraulic actuator mounted between said stick and a pivot point between said stick and said load holder, the ultrasonic sensor is mounted on or adjacent to a non-moving housing of said actuator, at a distance from said pivot point.

The present invention extends still further to a weighing module for use in the payload weighing system defined above, the weighing module comprising one or more processors configured to receive electronic signals from said ultrasonic sensor and at least one other sensor located on or in relation to said loading machine, and perform an algorithm for calculating a weight value representative of a payload weight of said machine.

Whilst the invention has been described above, it extends to any inventive combination of features set out above or in the following description. Although illustrative embodiments of the invention are described in detail herein with reference to the accompanying drawings] it is to be understood that the present invention is not limited to these precise embodiments. As such, many modifications and variations will be apparent to practitioners skilled in the art. Furthermore, it is contemplated that a particular feature described either individually or as part of an embodiment can be combined with other individually described features, or parts of other embodiments, even if the other features or embodiments make no mention of the particular feature. Thus, the invention extends to such specific combinations not already described.

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of an excavator in which an exemplary embodiment of the present invention can be used to measure the weight of a payload; Figure 2 is a schematic diagram illustrating principal components of a payload weighing system according to an exemplary embodiment of the present invention; and Figure 3 is a schematic diagram illustrating only the load holder sensor portion of the system of Figure 2.

An exemplary embodiment of the invention relates to a method for calculating an estimation of the weight of a payload in a load holder of an excavator during a lift sequence. A first embodiment of the present invention also relates to an apparatus for carrying out the method. The apparatus comprises a processor and inputs for receiving signals from sensors. It optionally comprises the sensors themselves. The apparatus could be adapted to be retro-fitted to an excavator for enabling the calculation of a weight estimation of a payload. This enables payload weight estimation to be carried out in accordance with the invention in relation to an existing excavator that does not have any weight calculation functionality. Alternatively, the apparatus could be incorporated/built into an excavator at manufacture time. In the preferred embodiment, weight estimations can be output to a user as they operate the excavator in the normal manner.

Figure 1 shows an excavator 1 in schematic form. It comprises a chassis 2 on a carriage comprising tracks or other conveying means 3 and a cab 4 for housing the controls of the excavator. An operator can sit in the cab and control the excavator 1.

The chassis can slew or rotate relative to the carriage. A boom 5 extends from the chassis 2, the angle of which can be controlled by a hydraulic ram 6 extending between the chassis 2 and the boom 5. A stick 7 is connected to the boom by a pivotable joint and can be arranged at various angles relative to the boom by a hydraulic ram 9. A load holder 8 is provided for scooping or grabbing, holding, transporting and dumping material or other payload. Preferably the load holder is a bucket or grapple. Alternatively, it could be any other type of holding means for holding or retaining a payload, such as an electromagnet. The load holder 8 is connected to the stick 7 by a pivotable joint, and a hydraulic ram 10 enables the angle between the bucket and the stick to be varied as required. An operator can sit in the cab 4 and operate the controls to alter the geometry of the boom 5, stick 7 and load holder 8 in order to manipulate the load holder and its payload in the desired manner. The boom 5 and stick 7 are generically termed as linkages". The boom 5, stick 7 and holder 8 combination may be termed a lifting linkage.

Referring to Figure 2 of the drawings, the excavator also has a number of sensors to determine parameters for calculating a weight estimation. These sensors can form part of the existing excavator, or can be retro-fitted to the excavator as part of the first embodiment of the invention.

A first sensor 11 is attached over (or as close as possible to) the pivot point between the boom 5 and chassis 2. The first sensor 11 constantly outputs a signal that corresponds to the angle between the boom and chassis. The information represented by this signal could be derived in several different ways, as will be apparent to a person skilled in the art, 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. However, the present invention is in no way intended to be limited in this regard.

A second sensor 12 is attached over (or as close as possible to) the pivot point between the boom and stick. This sensor constantly outputs a signal that corresponds to the relative angle between the boom and the stick. Again, the information represented by this signal could be derived in several different ways, as will be apparent to a person skilled in the art, 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. However, the present invention is in no way intended to be limited in this regard.

A third sensor 18 is attached to the outer body of the hydraulic ram 9. The sensor 18 is an ultrasonic sensor which is arranged and configured to emit an ultrasonic signal 1 Ba in the direction of the pivot point Sb between the load holder 8 and the stick 7. The purpose of the ultrasonic sensor 18 is to measure the extension of the hydraulic ram 10, i.e. the by measuring the distance of the sensor 18 from the pivot point Sb, which is directly proportional to the relative angle between the load holder 8 and the stick 7. Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to an object. It will be appreciated that ultrasonic sensors are known, and any known type of ultrasonic sensor can be used for this purpose in the present invention.

Referring additionally to Figure 2 of the drawings, a first tilt sensor 13 is optionally located directly over the centre of rotation of the chassis. The tilt sensor may be, for example, a pendulum sensor. The tilt sensor constantly outputs a 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. One or more further tilt sensors 1 3b may be provided on the chassis for measuring, for example, slew rate of the chassis.

Two pressure sensors 14, 15 are mounted on the hydraulic actuator that controls the pivoting of the boom relative to the chassis. The sensors are fitted to "tee off' points on both the lift and return pressure lines for the cylinder. The first sensor 15 measures the pressure on the lift side of the actuator. The second sensor 14 measures the pressure on the return side of the actuator.

The pressure sensors are a transducer system which constantly outputs a pair of signals, each directly related to the hydraulic oil pressures on each side of the actuator. These can be used to determine torque. Where 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 strain gauge or load cell.

Cables 11 b, 1 2b, 1 3b, 1 4b, 1 Sb and 1 8b connect each of the respective sensors 11, 12, 13, 14, 15 and 18 to a weighing module 100, samples each of the sensor signals received via the respective cables lib, 12b, 13b, 14b, 15b, lab anda computer program running in the weighing module applies a known algorithm to calculate (or estimate) weight. Data representative of the calculated/estimated payload weight value is fed to a user unit 102 within the cab and displayed to the user on a screen.

Thus, referring to Figure 3 of the drawings, which shows the load holder sensor 18 in isolation, the cable 1 8b feeding the sensor, and carrying signals back to the weighing module, only needs to extend along an upper portion of the stick and does not need to extend alongside the moving portion of the hydraulic ram 9, thereby reducing the potential for the cable 1 8b to become damaged or disconnected during normal operation of the excavator.

Some algorithms for calculating or estimating the payload weight using the measurement signals are known, and the present invention is not necessarily intended to be limited in this regard. However, a novel example will now be described in further detail, for completeness.

Thus, a requirement for the system described above might be to achieve accurate compensation at nominal bucket angles. Such angles are, for example, +1- 25° from bucket level. Changing the bucket angle from level with the ground can create a large error, sometimes up to 10% with a tilt of 20° (from level), thus a table of corrections is created, based on angle from bucket level.

Up to, say, three methods might be required, depending on the design of attachment used: * Lifting the Bucket as if it full of water. The bucket has to remain level during the lift. (Measuring the angle of the bucket with reference to ground) * Lifting the Bucket, but with the bucket only being level at the weighing point, but being level at different Dipper Positions. (Measuring the angle of the bucket with reference to the Boom) * Fixed Bucket position. (Measuring the angle of the bucket with reference to the Dipper Arm or "stick') As a secondary function to bucket angle compensation, there is the option to have a "weighing inhibition function" if the angle of the bucket is out of position from a set weighing point, in which case an alarm may be caused to sound during weighing if the bucket is not in the chosen weighing position (+1-50) The following list of bucket factors may be displayed to a user via the control unit in the cab of the machine: Bucket Sensor Mode -this provides two options in accordance with an exemplary embodiment of the present invention: 1. Inhibit only: bucket position must be maintained at this point within +1-5°. If not, the bucket alarm will sound. No weight compensation is provided in this mode, it simply inhibits weighing until the bucket is in the correct position.

2. Compensation: the system compensates for the angle of the bucket. In this case, no inhibit function is required, and no alarm will sound.

Bucket Weighing Position -indicates the point at which the bucket will weigh without causing an inhibit alarm. Used only when the above-mentioned Inhibit mode is selected.

Bucket Position Calculation -enables the type of calculation for measuring the bucket angle to be selected. In this exemplary embodiment, there are three types: -With Ground: (Bucket raw sig*Bucket Sig Gain Factor)+Dipper Sig)+(Boom/i 5)+(Chassis/i.5) -With Boom: (Bucket raw Sig*Bucket Sig Gain Factor)+Dipper Sig -With Dipper (Stick): (Bucket raw Sig*Bucket Sig Gain Factor) Note: (Boom/iS) and (Chassis/iS) are calculations used in order to balance the boom and chassis 120° signals with the 180° dipper sensor signal.

Bucket Zero Point -Combined signal that is calculated when the bucket is level. The signals used to calculate this factor are dependent on the above-mentioned Bucket Position Calculation setting.

Bucket Signal Gain Factor -The multiplier to balance" the difference between the bucket signal and the dipper (stick) sensor signal, i.e. if the bucket signal is half of the dipper over the same angle change, the factor is "2" to balance the gain outputs (calculated from the Inclinometer sequences which will be described in more detail later).

Bucket Angle Compensation Factor -The compensation factor to correct the pressure calculation (after all other corrections) in respect of the bucket angle from level.

The signal from the ultrasonic sensor installed on the hydraulic cylinder is non-linear compared with the angle change of the bucket. For simplicity, the signal should ideally be a linear relationship. Also, the signal does not match that of the dipper arm and boom (varies between machines). Therefore, the system according to this exemplary embodiment provides a routine to solve this, to create a known true bucket sensor angle.

Thus, the algorithm may include the following calibration sequence: (Set) Dipper to mm Level bucket to ground Log Dipper sig and Bucket Raw sig (Set) Dipper to max Level bucket to ground Log Dipper sig and Bucket raw Sig From these logged points, the Bucket Signal Gain Factor can be calculated: Bucket Signal Gain Factor = -1 *(Bucket raw Sigmax Dipper -Bucket raw Sigmin Dipper) Next, the Bucket Zero Point is calculated: Dipper to mid point Level bucket to ground Log Dipper signal + Bucket Signal + Boom + Chassisx This gives a temporary store of pressure points.

Bucket Zero Point: If Bucket Position calculation with Ground is set use calculation: (Bucket raw Sig * Bucket Sig Gain Factor) i-Dipper Sig-'-(Boom/1.5)-'-(Chassisx/1.5) If Bucket Position calculation with Boom is set use calculation: (Bucket raw Sig * Bucket Sig Gain Factor) i-Dipper Sig If Bucket Position calculation with Dipper is set use calculation: (Bucket raw Sig * Bucket Sig Gain Factor) Once the ultrasonic sensor output has been corrected to match the output of the dipper sensor, the true angle of the bucket at any dipper position is known. A routine can then be used to calibrate the effect of load centre effects due to the bucket angle changing: With a half full bucket Boom to horizontal, Dipper midway, Bucket Level (bucket must be within 3 degrees of level) Temporarily save static live pressure when user presses ok' Open up bucket to +25°, stop Temporarily save bucket angle and static live pressure -save to a temporary table Bucket Compensation factor = Live Pressure Out -Live Pressure Level (i.e Combined Bucket Sig out -Combined Bucket Sign Level) Notes: the Combined bucket signal is dependent on the Bucket Position Calculation set (e.g With Ground, with Boom or with Dipper); Live pressure is based on the normal static weighing calculation.

The following calculation may be used to provide correction when weighing in use (after segment corrections): Corrected pressure -(Bucket Angle Comp Factor*(Combined Bucket Angle -Bucket Zero Point) It will be apparent to a person skilled in the art that modifications and variations can be made to the described embodiment of the invention without departing from the scope of the present invention as claimed. For example, whilst the present invention has been described above in relation to a wheeled excavator or similar material handling machine, it is equally applicable for use in measuring receptacle position for a weigh transfer compensation system in a wheeled loading shovel or the like.

Claims (10)

1. CLAIMS1. Load holder angle measuring apparatus for a payload weight calculation system in a loading machine comprising a stick and a load holder pivotally mounted at a distal end of said stick, the apparatus comprising an ultrasonic sensor located at a distance from a pivot point between said load holder and said stick and configured to generate a signal representative of a distance between said sensor and said pivot point.
2. 2. Apparatus according to claim 1, for a loading machine in which pivoting of said load holder is effected by an actuator provided between said stick and said pivot point, wherein the ultrasonic sensor is mounted on a non-moving housing of said actuator.
3. 3. Apparatus according to claim 2, for a loading machine in which the actuator comprises a hydraulic actuator comprising a piston mounted for linear movement within a housing, a distal end of the piston being communicably coupled to said pivot point, wherein the ultrasonic sensor is mounted on the housing and configured to direct an ultrasonic signal toward said pivot point.
4. 4. Apparatus according to claim 3, wherein the sensor is configured to generate an electronic signal representative of the length of extension of the piston relative to the housing.
5. 5. Apparatus according to any of the preceding claims, configured to generate a correction factor to match the output of said ultrasonic sensor to that of at least one other sensor provided in respect of said loading machine.
6. 6. A method measuring an angle between a load holder pivotally mounted at a distal end of a stick, the method comprising generating an ultrasonic signal at a sensor point on or adjacent said stick and directing said signal toward a pivot point between said load holder and said stick, receiving ultrasonic energy reflected from said pivot point and generating an electronic signal representative of the distance between said sensor point and said pivot point.
7. 7. A payload weighing system for a loading machine comprising a boom, a stick pivotally mounted to said boom and a load holder pivotally mounted to said stick, the weighing system comprising a plurality of sensors, at least one of said sensors comprising an ultrasonic sensor for generating an electronic signal representative of a relative angle between said boom and said stick or between said stick and said load holder.
8. 8. A payload weighing system according to claim 7, for a loading machine in which pivoting of said load holder is effected by a hydraulic actuator mounted between said stick and a pivot point between said stick and said load holder, wherein the ultrasonic sensor is mounted on or adjacent to a non-moving housing of said actuator, at a distance from said pivot point.
9. 9. A weighing module for use in the payload weighing system according to claim 8, the weighing module comprising one or more processors configured to receive electronic signals from said ultrasonic sensor and at least one other sensor located on or in relation to said loading machine, and perform an algorithm for calculating a weight value representative of a payload weight of said machine.
10. 10. Load holder angle measuring apparatus substantially as herein described with reference to the accompanying drawings.AMENDMENTS TO CLAIMS HAVE BEEN FILED AS FOLLOWSCLAIMS1. A payload weight calculation apparatus comprising a load holder angle measuring apparatus communicably coupled to a weighing module configured to calculate a weight value representative of a payload weight in respect of a loading machine comprising an arm and a load holder pivotally mounted ata distal end of said arm, the load holder angle measuring apparatus comprising an ultrasonic sensor located at a distance from a pivot point between said load holder and said arm and configured to generate a distance signal representative of a distance between said sensor and said pivot point and provide said distance signal, or data representative thereof, to said weighing module for use in said calculation of said weight value.2. Apparatus according to claim 1, wherein said load holder angle measuring 14') apparatus is configured to generate, using said distance signal, data representative of a relative angle between said arm and said load holder and provide said data to said weighing module for use in said calculation of said weight value.N3. Apparatus according to claim 1 or claim 2, for a loading machine in which pivoting of said load holder is effected by an actuator provided between said arm and said pivot point, wherein the ultrasonic sensor is mounted on a non-moving housing of said actuator.4. Apparatus according to any of claims 1 to 3, wherein said arm comprises a boom, and said load holder is pivotally mounted at a distal end of said boom.5. Apparatus according to claim 2, for a loading machine in which the actuator comprises a hydraulic actuator comprising a piston mounted for linear movement within a housing, a distal end of the piston being communicably coupled to said pivot point, wherein the ultrasonic sensor is mounted on the housing and configured to direct an ultrasonic signal toward said pivot point.6. Apparatus according to claim 5, wherein the sensor is configured to generate an electronic signal representative of the length of extension of the piston relative to the housing.7. Apparatus according to any of the preceding claims, configured to generate a correction factor to match the output of said ultrasonic sensor to that of at least one other sensor provided in respect of said loading machine.8. Apparatus according to any of the preceding claims, comprising a plurality of sensors for generating data for use by said weighing module in said calculation of said weight value, at least one of said sensors comprising an ultrasonic sensor for generating said electronic signal representative of a relative angle between said arm and said load holder. IC)9. A method of calculating a payload weight in a loading machine comprising an arm and a load holder pivotally mounted at a distal end of said arm, the method comprising generating an ultrasonic signal at a sensor point on or adjacent said arm and directing said signal toward a pivot point between said load holder and said arm, receiving ultrasonic energy reflected from said pivot point, and providing data representative of the distance between said sensor point and said pivot point to a weighing module configured to use said data to calculate a weight value representative of a payload weight of said machine.1O.A payload weight calculation apparatus substantially as herein described andlor with reference to the accompanying drawings.