Technical Field

This disclosure is directed towards determining the relative orientation of two members of an articulated work machine utilising inertia sensors by referencing the output from inertia sensors mounted on the members to one another. Background

Articulated work machines, including articulated trucks with bodies, articulated trucks with ejector mechanisms, articulated wheel loaders and the like, typically comprise a first frame (such as a tractor) and a second frame (such as a trailer) connected to one another via an articulation joint. The articulation joint enables the frames to roll and yaw relative to one another. Articulated work machines are commonly employed during construction and excavation and may be operated on uneven terrain. As a result, one of the frames may be positioned at an unsafe roll and/or yaw angle and may cause the entire machine to turn over.

Alternatively, if the articulated machine has an open container, such as a bucket or body mounted on one of the frames, any materials held in the open container may fall out when one of the frames is positioned above certain roll and/or yaw angle thresholds.

Furthermore, since the roll and yaw angles of one frame are independent of the other frame, the operator may be unaware of the angles at which the frame in which he/she is not located are orientated. The operator may, therefore, be unaware that part of the articulated vehicle is at an unsafe roll and/or yaw angle or may have tipped over.

In many articulated vehicles one of the frames , usually the trailer, may have a body which is movable relative to the frame. One example is a tipping body which can be raised off the trailer chassis to tip out the contents. Currently a switch signal is used to warn the operator that the body is raised off the trailer chassis and provides the operator with information regarding the number of body raise cycles per predefined time interval, e.g. a working shift. With the current arrangement the angle of the body cannot be determined. One method of preventing tip over of an articulated vehicle is to measure the angle of the vehicle and provide a warning to the operator when the roll and/or yaw angles of the vehicle are approaching unsafe threshold values, above which the vehicle will tip over. US-B-5825284 discloses one such method. The vehicle described therein comprises a tractor and a trailer, the trailer comprising a frame attached to an axle. One sensor is attached to the frame to detect the roll angle of the frame and a second sensor is attached to the axle to detect the roll angle of the axle. The difference between these two roll angles is utilised to determine the angle between the frame _^ and the axle and thereby calculate the roll moment of the vehicle. A display is then used to indicate to the operator if the roll moment is sufficient such that the vehicle may roll over.

Articulated work machines may also comprise a member such as a body for holding material which can be tipped about a pivot point to empty any material held therein. When the body is tipped, the centre of gravity of the frame to which the body is attached may be raised further from the ground. As a result, the threshold values of the roll and/or yaw angles at which the frame tips over may change, and the frame may be more prone to tipping over.

US-B-5742228 discloses a system for detecting the roll and pitch of a tipper truck which comprises a tipper body. One or more level sensors, such as clinometers, are attached to the tipper body. The sensors detect the lateral level (i.e. roll angle) of the tipper truck and the longitudinal level (i.e. pitch angle) of the tipper body. A processor utilises the outputs of the one or more sensors to determine the risk of the tipper truck overturning and then display such a risk to an operator.

However, US-B-5742228 and US-B-5825284 do not disclose a means by which the orientation of one frame of an

articulated work machine can be determined in relation to the other frame .

Summary

The disclosure therefore provides an articulated work machine comprising; a first frame; a second frame comprising a body and a chassis, the body pivotally connected to the chassis; the first and second frames being connected by a coupling and being movable relative to each other in at least one direction; a first multi-axis inertia sensor attached to the first frame providing an output relating to the position of the first frame; a second multi-axis inertia sensor attached to the body providing an output relating to the position of the body; and a controller which compares the outputs of the first and second multi-axis inertia sensors to calculate the position of the body and the first frame relative to each other.

The disclosure also provides a method of determining the relative position of members of an articulated work machine, the articulated work machine comprising; a first frame to which a first multi-axis inertia sensor is

attached; a second frame comprising a body and a chassis, the body pivotally connected to the chassis; a second multi- axis inertia sensor being attached to the body; the first and second frames being connected by a coupling and being movable relative to each other in at least one direction,- the method comprising the steps of: comparing the outputs of the first and second multi-axis inertia sensors to calculate the position of the body and the first frame relative to each other. By way of example only, embodiments of an apparatus and method for the detection of the orientation of the frames of an articulated work machine are now described with reference to, and as shown in, the accompanying drawings.

Brief Description of the Drawings

Figure 1 is a side elevation of one embodiment of an articulated work machine of the present disclosure; Figure 2 to 9 illustrate the pitch and roll angles of the first and second frames of the articulated work machine; and

Figure 10 is flow diagram illustrating the decision steps of the warning system.

Detailed Description

The present disclosure is generally directed towards an apparatus and method for determining the orientation of at least two members of an articulated work machine and their orientation relative to each other. Inertia sensors are attached to two members of the articulated work machine and the output of each inertia sensor is referenced to either the output of the other inertia sensor or a calibrated position parameter, to calculate the orientation of each member in reference to the orientation of the other member.

Figure 1 illustrates an embodiment of an articulated . work machine 10 of the present disclosure. Although the illustrated articulated work machine 10 is an articulated tipper truck, the articulated work machine 10 may be any type of articulated work machine. The articulated work machine 10 comprises a first frame 11 in the form of a tractor unit, attached to a second frame 12, in the form of a trailer unit, by a coupling 13.

The coupling 13, which may be an articulation joint, may allow each of the frames 11, 12 to be orientated at a different yaw and/or roll angle to the other frame 12, 11. The yaw angle of the first frame 11 may be different to the yaw angle of the second frame 12 about an axis of

articulation 14. The articulated work machine 10 may be steered by adjusting the yaw angle of the first and second frames about the axis of articulation 14 utilising

actuators, for example hydraulic cylinders, suitably

attached to each of the frames 11, 12 on either side of the coupling 13.

The articulated work machine 10 may further comprise driving means. The driving means comprise ground engaging means 15 in contact with ground 16. The ground engaging means 15 may be, for example, tracks and/or wheels which enable the machine 10 to move along the ground 16, and the articulated work machine 10 may comprise any number of ground engaging means 15. The driving means may further comprise a power unit (not shown) which drives at least one of the ground engaging means 15 to move the articulated work machine 10 along the ground 16. The power unit may be of any suitable type, such as an internal combustion engine, a micro-turbine or an electric motor. In one embodiment, the power unit is situated in/on one of the frames 11, 12 and the coupling 13 transfers power from the power unit to ground engaging means 15 attached to the other frame 12, 11. Therefore, the ground engaging means 15 is/are operably connected to, i.e. receives power from, the power unit. In a further embodiment, all of the ground engaging means 15 of the articulated work machine 10 are operably connected to the power unit .

The second frame 12 may comprise a member, such as an dump (or ejector) body 17 adapted to carry a load, and which is pivotally attached to a chassis 23 at a pivot point. The second frame 12 comprises a tipping system 24 which, when activated, causes the body 17 to rotate about the pivot from a "body down" position into a "body up" position 25, which is a tipping position with one end of the body 17 raised upwardly from the chassis 23 and the other end of the body 17 lowered relative to the chassis 23. The tipping system 24 may be any suitable system, such as, for example, a

hydraulic system with one or more hydraulic actuators connected between the body 17 and the chassis 23, a

mechanical system or an electric system. As the tipping system 24 rotates the body 17 to the body up position 25, the body 17 ejects any materials or load from the body 17. The body 17 may be any type of container and may be open at the top, fully enclosed or partially enclosed. The body 17 may comprise a gate or door which opens to allow the load or material to be tipped out as the body 17 is rotated into the tipping position 25.

One frame, for example the first frame 11 as

illustrated in Figure 1, may comprise an operator cabin 22 housing the controls for the machine 10.

The articulated work machine 10 further comprises a first multi-axis inertia sensor 20 attached to the first frame 11 and a second multi-axis inertia sensor 21 attached to the body 17 mounted on the second frame 12. The sensor 20 may be attached to any part of the first frame 11 and this acts as the reference sensor. In the illustrated embodiment the second multi-axis inertia sensor 21 may be attached close to the pivoting point between the body 17 and the chassis 23. This enables the length of any wiring leading to the second multi-axis inertia sensor 21 from the chassis 23 to be reduced. The sensors 20, 21, may be any type of sensor which is capable of determining the pitch, yaw and/or roll angle of the members (i.e. first frame 11 and body 17 in the

illustrated example) , on which the sensor is positioned relative to the direction of gravitational acceleration. Each of the sensors 20, 21, may be, for example, an

inclination sensor, an accelerometer or a gyroscope, and may be of any type, for example, piezoelectric, capacitive, potentiometric , Hall effect, magnetoresistive ,

piezoresxstive or any type of microelectromechanical system (MEMS) .

These sensors generally comprise a "proof" mass. This mass moves relative to the frame of the sensor. That difference in movement between the frame and proof mass is related to its acceleration and can be measured in a variety of ways: capacitively, piezo-electrically, and piezo- resistively. A solid object's movement can be fully

described by measuring linear acceleration in the x, y, and z directions and angular velocity about the x, y, and z axes .

The work machine 10 further comprises an electronic controller (commonly known as an electronic control module or ECM) which controls various aspect of the work machine 10. The output signals from the sensors 20, 21 are

transmitted to the controller and used to calculate relative angles of the members to which the sensors 20,21 are

attached, e.g. the angle of the body 17 relative to the first frame 11. The calculations may relate to both fore and aft angles (in the lateral direction of the machine 10) and side to side (across the transverse direction of the machine 10) . This is described in more detail below.

In order for the load or materials to be ejected from the body 17 it may not be designed to move relative to the chassis 23, but may instead utilise an ejector mechanism. Ejector mechanisms are well known in the art, and typically comprise an ejector plate which slides horizontally from one end of the inside of the body 17 towards the other end (the ejection end) to push any load or materials out of the body 17. A hydraulic actuator or the like may be used to move the ejector plate towards the ejection end of the body 17.

In such an embodiment the first multi-axis inertia sensor 20 is again positioned on the first frame 11 and the second multi-axis inertia sensor 21 is attached to the body 17.

Industrial Applicability

Figures 2 to 9 illustrate some possible orientations of a work machine 10 and the relative angles of the first member (in this case the tractor (which forms the first frame 11) and the second member (in this case the body 17 mounted on the trailer chassis 23 of the second frame 12) using the embodiment of Figure 1. Essentially the relative body angle of the body 17 to the tractor is the absolute angle minus the tractor angle. This applies to both the pitch and the roll angles.

Figure 2 - the body 17 is in the body down position on the chassis 23 and the tractor and trailer 11,12 are in horizontal lateral alignment (i.e from one end of the tractor 11 to the opposing end of the trailer 12, which is shown by the arrow x) . The relative body pitch angle (x _x ) = tractor pitch angle (x ₂ ) = 0° as the absolute body angle (x ₃ ) is 0°.

Figure 3 - the body 17 is in the body down position and the tractor and trailer 11,12 are in lateral alignment, but at an angle to the horizontal in the x direction, so the relative body pitch angle (xi) = tractor pitch angle (x ₂ ) as the absolute body angle (x ₃ ) is 0°.

Figure 4 - the body 17 is in the body up position and the tractor and trailer 11,12 are in horizontal lateral alignment, so the relative body pitch angle ( i) = absolute body angle ( ₃ ) - tractor pitch angle (x ₂ ) ;

Figure 5 - the body 17 is in the body up position and the tractor and trailer 11,12 are in lateral alignment at an angle to the horizontal, so the relative body pitch angle ( i) = absolute body angle (x ₃ ) - tractor pitch angle (x ₂ ) ;

Figure 6 - the body 17 is in the body down position and the tractor and trailer 11,12 are in horizontal transverse alignment (i.e. from one side of the tractor and trailer 11,12 to the opposing side which is shown by the arrow y) and horizontal lateral alignment, so the relative body pitch angle (x _x ) = tractor pitch angle (x ₂ ) as the absolute body angle (x ₃ ) is 0°. However the body 17 is tilted sideways relative to the frame 11, so the relative body roll angle (Zi) = absolute body angle (z ₃ ) as the tractor roll angle (z ₂ ) is 0°;

Figure 7 - the body 17 is in the body up position and is in lateral alignment with the trailer 23 so the body pitch angle ( i) = body angle (x ₃ ) - first frame pitch angle (x ₂ ) . However the trailer 23 is also tilted sideways relative to the tractor 11, so the relative body roll angle ( zi ) = absolute body angle (z ₃ ) as the tractor roll angle ( z ₂ ) is 0°.

Figure 8 - the body 17 is in the body down position and the tractor and trailer 11,12 are in lateral and transverse alignment, although the whole machine 10 is on a side slope, at an angle to the horizontal in the y direction, so the relative body pitch angle (x = tractor pitch angle (x ₂ ) as the absolute body pitch angle (x ₃ ) is 0°. The relative body roll angle ( z _x ) is 0° as the absolute body roll angle ( z ₃ ) is the same as the tractor roll angle ( z ₂ ) .

Figure 9 - the body 17 is in the body up position and the tractor and trailer 11,12 are in horizontal and lateral alignment, although the whole machine 10 is on a side slope, at an angle to the horizontal in the y direction so the relative body pitch angle (x = body angle (x ₃ ) - first frame pitch angle (x ₂ ) . The tractor 11, body 17 and the chassis 23 are all tilted at the same angle in the y

direction, so the relative body roll angle ( z _x ) is 0° as the absolute body roll angle ( z ₃ ) is the same as the tractor roll angle ( z ₂ ) .

This angle information may be utilized by the

controller in an algorithm, which allows the operator and manufacturer to set safety limits for the various angles. Figure 10 illustrates the decision steps which may be made by such an algorithm. Once the individual positions (angles) of the two members on which the sensors 20, 21 are mounted have been determined, the controller is able to calculate the relative angles between them. The calculation may be achieved by comparing the outputs of the two sensors 20,21 with each other, or with a calibrated position parameter. The actual and relative angles may then be compared to the preset limits for the various angles. In the event that certain of the preset limits are exceeded the controller may be programmed to disable the tipping system 24, to limit the body angle (x ₃ ) to which the body 17 can be tipped, limit the machine speed or gear selection, provide a warning or display or an emergency alert. These may include :-

- Body up

- Body raise angle

- The number of cycles in which the measured angles differ from each other in a defined time interval

- Relative angles of the first and second members with a warning of potential roll over if any of the angles exceed the preset limits

- Relative angles of the first and second members with a warning that the machine 10 is operating/tipping at an unsafe angle, for example on an unsafe side slope This information can thus be utilized by the controller to: -

- Reduce frame impact stresses by automatically

reducing cylinder pressure/flow when the body 17 is

approaching the down position

- Reduce cylinder stresses by automatically reducing cylinder flow when the body 17 is approaching the fully raised position

- Notify, via a suitable machine communication system, site management or the emergency services that a machine 10, or either member 11 or 17 has rolled. The apparatus and method of detecting the state of an articulated work machine can be used in a wide variety of work machines, which have articulated frames (tractor or trailer) and a member mounted on at least one of the frames (body) which can move relative to each other.

The use of multi-axis inertia sensors 20,21 allows for enhanced f nctionality over the prior art, i.e. roll over warning, warning against operating/ tipping on an unsafe side slop, and further provides installation, reliability and durability benefits. In particular the system provides improved information for the operator and improved safety.