WO2006106296A1

WO2006106296A1 - Methods of load and axle measurement

Info

Publication number: WO2006106296A1
Application number: PCT/GB2006/001055
Authority: WO
Inventors: Geoffrey Mountain
Original assignee: Pm Group Plc
Priority date: 2005-04-04
Filing date: 2006-03-23
Publication date: 2006-10-12
Also published as: GB2424961A; GB0506796D0

Abstract

A method of measuring the centre of gravity of a payload of a vehicle comprising the steps of (a) providing a vehicle having a chassis and a payload; (b) providing a plurality of load cells between chassis and payload; (c) measuring the total load measured by all the load cells to give the total payload mass (d) calculating the total moment of the payload about a fiducial axis by multiplying the mass measured by each load cell by its perpendicular distance from the axis and totalling the result; (e) dividing the total moment by the total payload weight to determine the perpendicular distance of the payload centre of gravity from the fiducial axis.

Description

METHODS OFLOAD AXD AXLEMEASUREMENT

The present invention, relates to methods of load and axle measurement and apparatus for performing such measurement. More particularly, but not exclusively the present invention relates to a method of measurement axle loading for a vehicle. The present invention also relates to a method of measuring the tipping of the body of a tipping vehicle and an apparatus for performing such a method. The present invention also relates to a method of measuring the centre of gravity of a payload of a vehicle and an apparatus for performing such a method. The present invention also relates to a method of measuring the tipping stability of a vehicle and an apparatus for performing such a method.

Systems for weighing vehicle loads are known. In known analogue systems the load measuring cells are placed between the vehicle chassis and body. The analogue signals from the individual cells are combined to give an indication of the vehicle payload. By manipulating the data received from the load cells however more information can be obtained.

Accordingly in a first aspect, the present invention provides a method of measuring the centre of gravity of a payload of a vehicle comprising the steps of

(a) providing a vehicle having a chassis and a payload;

(b) providing a plurality of load cells between chassis and payload; (c) measuring the total load measured by all the load cells to give the total payload mass

(d) calculating the total moment of the payload about a fiducial axis by multiplying the mass measured by each load cell by its perpendicular distance from the axis and totalling the result; (e) dividing the total moment by the total payload weight to determine the perpendicular distance of the payload centre of gravity from the fiducial axis. The method according to the invention allows the accurate measurement of the centre of gravity of the vehicle payload. By correctly positioning the centre of gravity of the payload one can reduce vehicle running costs and wear on the vehicle components.

Preferably, the method is performed about two non-parallel fiducial axes.

The two fiducial axes can be co-planar.

Preferably, the two axes are parallel to the plane of the chassis.

Preferably, the two axes are orthogonal.

Alternatively, the method can be performed about at least three axes.

Preferably, the three axes are non co-planer, preferably orthogonal.

Preferably, at least one fiducial axis passes through at least one, preferably two load cells.

In a further aspect of the invention there is provided an apparatus for determining the centre of gravity of a payload of a vehicle, the apparatus comprising a plurality of load cells adapted to be positioned between payload and vehicle chassis; and control means adapted to receive load measurements from the load cells and to determine the centre of gravity by the method according to claim 1.

Preferably, the apparatus further comprises display means for displaying the position of the centre of gravity.

Preferably, the apparatus further comprises warning means for providing a warning, preferably an audible warning, if the centre of gravity of the payload is outside one or more predetermined limits. In a further aspect of the invention there is provided a method of measuring the tipping stability of a vehicle comprising the steps of

(a) providing a vehicle comprising a chassis and a payload, the chassis having a known predetermined weight; (b) providing a plurality of load cells between the chassis and payload;

(c) measuring the total mass measured by all the load cells to give the total payload mass

(d) calculating the total moment about a fiducial axis by multiplying the mass measured by each load cell by its perpendicular distance from the axis and totalling the result;

(e) dividing the total moment by the total vehicle mass to determine the distance of the vehicle centre of gravity from the fiducial axis

(f) producing an alarm if the centre of gravity fall outside a predetermined range.

The method of the invention has the advantage that the vehicle operator is given advanced warning when the vehicle is approaching a point of tipping instability, improving user safety.

Preferably, the fiducial axis is orthogonal to a contact line extending between two points of contact of the vehicle with the ground.

The alarm can be produced if the centre of gravity is proximate to either of the points of contact.

Preferably, the alarm is produced if the distance between the centre of gravity and a point of contact is less than 20%, preferably less than 10% of the distance between the points of contact.

The method can be performed about at least two fiducial axes determine the position of the centre of gravity within a plane. -A- The two axis can be parallel to the ground.

Preferably, the axes are orthogonal.

Preferably, the position of the centre of gravity is compared to the vehicle footprint comprising the area defined by lines extending between the points of contact of the vehicle with the ground and the alarm is sounded if the centre of gravity is proximate to an edge of the footprint.

In a further aspect of the invention there is provided an apparatus for determining the tipping stability of a vehicle comprising a plurality of load cells adapted to be positioned between payload and vehicle chassis; and control means adapted to receive load measurements from the load cells and to measure the tipping stability according to the method of claim 12.

Preferably, the apparatus further comprises alarm means, the alarm means being adapted to provide at least one of a visual or audible alarm.

In a further aspect of the invention there is provided a tipping vehicle comprising a chassis and a body for carrying a payload; lifting means extending between the chassis and the body adapted to lift the body with respect to the chassis between up and down positions; a chassis support connected to the chassis and adapted to bear at least a portion of the weight of the body when in the down position; at least one load cell connected in series with the lifting means between the chassis and the body; and control means connected to the load cell and adapted to produce an alarm if the load measured by the load cell exceeds a predetermined limit.

The vehicle according to the invention has the advantage that it provides a warning if the vehicle body is accidentally raised during use. Preferably, the control means is adapted to produce an alert if the load measured by the load cell exceeds the load measured by the load cell when the load is in the down position by a determined amount.

The body can be pivo tally connected to the chassis proximate to the end of the body.

The lifting means can be connected to the body remote from the pivot, preferably proximate to the end of the body opposite the pivot.

In a further aspect of the invention there is provided a method of measuring the tipping of the body of a tipping vehicle comprising the steps of:

(1) providing a tipping vehicle comprising

(a) a chassis and a body for carrying a payload;

(b) lifting means extending between the chassis and the body adapted to lift the body with respect to the chassis between up and down positions; (c) a chassis support connected to the chassis and adapted to bear at least a portion of the weight of the body when in the down position;

(d) at least one cell connected in series with the lifting means between the chassis and the body; and

(e) control means connected to the load cell and adapted to produce an alarm if the load measured by the load cell exceeds a predetermined limit;

(2) measuring the load by means of the load cell;

(3) comparing the measured load to a predetermined value and producing a alarm if the measured load exceeds the predetermined value.

In a further aspect of the invention there is provided a method of calculating axle loading for a vehicle comprising the steps of

(a) providing a vehicle comprising a chassis and a payload, the chassis being supported by first and second axles;

(b) providing a plurality of load cells between chassis and payload; (c) measuring the total mass of the payload;

(d) calculating the total moment of the payload about a fiducial axis parallel to the axles by multiplying the mass measured by each load cell by its perpendicular distance from the axis and totalling the result; (e) dividing the total moment by the total payload mass to determine the perpendicular distance of the payload centre of gravity from the fiducial axis;

(f) calculating the load on the second axle by multiplying the total mass of the payload by the distance of the payload centre of mass from the first axle and dividing the result by the distance between the axles. The method according to the invention has the advantage that one can directly calculate the loading on each axle so ensuring the loading is within safety limits. This also reduces running costs and wear on the vehicle.

Preferably, the method can comprise the further step of calculating the load on the first axle by multiplying the total mass of the payload by the distance of the payload centre of mass from the second axle and dividing the result by the distance between the axles.

Preferably, the empty vehicle axle load is added to the measured axle load.

The second axle can be an imaginary axle comprising third and fourth real axles and arranged at the mid-point therebetween, and the method further comprises the step of calculating the loads on the third and fourth axles from the simultaneous equations:

A₃

= 1 +

2 and

+ - A

where A₂, A₃ and A₄ are the loads on the second third and fourth axles, X₂ is the distance between the centre of mass of the payload and the imaging second axle; and k₂ is a known constant.

The constant K can be calculated by making direct measurements of A₃ and A₄ for the vehicle in empty and loaded states.

The first axle can be an imaginary axle comprising fifth and sixth real axles, the first axle being arranged at the mid-point therebetween and the method further comprising the step of calculating the loads on the fifth and sixth axles from the simultaneous equations

— l ₌ l + _L and

A₆ k_x

A₁ = A₅ + A₆

where A₁, A₅, A₆ are the loads on the first, fifth and sixth axles;

X₁ is the distance between the centre of mass of the payload and the imaginary

first axle; and k_x is a known constant.

Preferably, the vehicle is a refuse vehicle having a packer plate and an ejector plate, wherein the method further comprises the step of moving the ejector plate towards the front of the vehicle when the load on the rear axle exceeds a predetermined limit.

Preferably, the method further comprises the step of disabling the compactor plate when the ejector plate reaches the front of the vehicle. Preferably, the compactor plate is disabled when the vehicle payload exceeds a predetermined limit.

The present invention will now be described by way of example only and not in any limitative sense, in which figure 1 shows a vehicle in side cross section showing a method according to the invention; figure 2 shows a vehicle in rear cross section showing a method according to the invention; figure 3 shows a vehicle in rear cross section showing a method according to the invention; figure 4 shows a vehicle in side cross section including a body raising detection means according to the invention; figures 5 to 7 show vehicles in side cross section showing the axle loading measuring method according to the invention; figure 8 shows a refuse vehicle in side cross section embodying an axle loading measurement method according to the invention; and figure 9 shows apparatus suitable for carrying out the methods according to the invention.

Shown in figure 1 is a vehicle in cross section. The vehicle comprises a chassis and body on the chassis. Positioned between the body and chassis are a plurality of load cells.

When the position of the cells on the vehicle is known (9) the moment produced by the front cell pair (4a,b) around an arbitrary fixed reference axis (8) can be calculated as the total load on the front cells (2) multiplied by the distance of the cells from the reference point (9).

Likewise the moment produced by the rear cells is the load on the rear cells (3) multiplied by their distance (11) from the reference (8).

If more than 4 cells are used their moment is calculated in the same manner. Measuring the load on all cells allows the calculation of the total payload weight (1). All cell moments are summed and with the vehicle in equilibrium they must match the moment produced from the payload around the reference axis.

i.e. (l) x (10) = [(2) x (9)] + [(3) x (H)]

AU elements in the above equation are known other than (10). By dividing the total cell moment by the payload weight (1) the position of the front to rear centre of gravity (10) is calculated.

Le. (10) = {[(2) x (9)] + [(3) x (l l)]} / (l)

Figure 2 - vehicle rear view. The process is repeated viewed at 90 degrees to above around a reference axis though the centre of the vehicle (12).

i.e. The moment (anti-clockwise) produced by the rear cells = [(3b) x (15)] - [(3a) x (14)]

Likewise the moment produced by the front and any other cells is calculated. Again for the vehicle in equilibrium the total cell moment must match the payload moment [(1) x (13)] and so the position to the left to right centre of gravity (13) can be calculated.

The distance of the centre of gravity from the vehicle centre can then be expressed as a percentage error based on the width of the load carrying area,

i.e. % loading error = (13) x 100 / (45)

Where (45) is the distance from the centre of the vehicle to edge of the loading area. The data can then be displayed to the operator in a graphical form such as a bar-graph.

e.g.

Loading Error

43% L [] R

Shown in figure 3 is a vehicle in rear cross section on unlevel ground. The body (7) is raised the left to right centre of gravity (18) of the vehicle moves towards the edge of the vehicle. In the extreme case where the centre of gravity extends beyond a point of support, i.e. a wheel (17), the vehicle is unstable and will tip over.

Knowing the payload weight (1) and its left to right centre of gravity (13) from section 1 (payload distribution) above, and also the total vehicle weight (46) the position of the vehicle centre of gravity (18) can be calculated.

Vehicle centre of gravity (18) = Payload weight (I) x body centre of gravity (13)

Total vehicle weight (46)

The point of instability being when the centre of gravity equals or exceeds a point of support

i.e. (18) >= (19).

The distance of the vehicle centre of gravity (18) from the vehicle centre (12) can then be expressed as a percentage based on the width of the vehicle,

i.e. % instability = (18) x 100 / (19)

Where (19) is the distance from the centre of the vehicle to wheel. The data can be displayed to the operator in a graphical form such as a bar graph.

e.g.

Instability

43% L [] R

By knowing its degree of instability the system can then warn of an approaching unstable condition before the vehicle actually becomes unstable.

Shown in figure 4 is a tipping vehicle in cross section. On tipping vehicles it is possible that a driver can accidentally operate the hydraulic ram (20), and so the body (7) will rise without his knowledge leading to a dangerous situation.

The ram (20) for lifting the body (7) is mounted on the front pair of cells (4a, 4b). When the body (7) is fully down it rests on the chassis body supports (21) and so very little load is applied to the front cells.

Once the vehicle starts to tip the body clears the chassis supports (21) and the front load cells (4a, 4b) see their full share of the payload.

With the vehicle body fully down resting on the chassis supports (21) the reduced load (2a, 2b) is applied to the front ram cells (4a, 4b) is recorded.

The system will warn the driver of a body up condition when the measured load (2a, 2b) on the front ram cells (4a, 4b) exceeds the body down state load plus a fixed threshold (K).

i.e. Body up if [(2a) + (2b)] >= [(2a) + (2b)]_down + K

Although traditional methods allow the total vehicle weight to be calculated regulations specify limits for individual axle loads. It is possible that a vehicle can still be within its maximum gross weight but be overloaded on one or more axles.

Be calculating the actual load on the axles the system can warn the driver of an axle overload condition.

Figure 5 shows a two axle vehicle. The payload and its centre of gravity are calculated as previously described.

Viewing moments around an axis (26) running through the front axle gives the payload moment = payload weight (1) x distance from front axle (24). The moment produced by the rear axle is the load on the axle (23) x the distance of the rear axle front the front axle [(24) + (25)] .

In equilibrium the moments must equal,

i.e. (1) x (24) = (23) x [(24) + (25)]

As all elements other than (23) are known, so it can be calculated.

The process is repeated viewing moments around the rear axle position (27) to give

(1) x (25) = (22) x [(24) + (25)] where (22) is the load on the front axle.

Shown in figures 5 to 7 are multicode vehicles in side cross section showing the axle load measurement method according to the invention.

As before all elements other than (22) are known, so it can be calculated.

The empty vehicle axle weights are input to the system at installation. The total axle weights are then calculated as the sum of the empty state axle weight plus the axle loading due to payload calculated above. Figure 6 shows three axle vehicle the rear two axles (28) and (29) are grouped together to form one imaginary axle. The imaginary axle is position (30) is the centre point of the two rear axle positions (34) and (35). The imaginary axle load (33) is the sum of the two rear axle loads (31) and (32).

The ratio of the two rear axle loads (31) and (32) has a linear relationship with distance (36) of the payload centre of gravity from the imaginary axle position (30).

i.e. (31) / (32) = 1 + (36) / Kr

Where Kr is a constant relating to the rear axle pair.

At the time of calibration axles loads (31) and (32) are recorded for both empty and full states.

The position of the centre of gravity (36) can then be calculated as in section 1 and so the parameter of Kr can then be derived for that specific vehicle be rearranging the above equation to give,

(36)

Kr = -

(31)/(32) -l

In use the payload and its centre of gravity are measured as in section 1. The method shown above for the two axle vehicle is then used to calculate the loads on the front and the imaginary axle.

Once the imaginary axle is known it is split between the rear axle using the equation

(31) / (32) = 1 + (36) / Kr

hi an alternative method the imaginary axle load is divided into two equal portions to determine the individual axle loads. Figure 7 shows a four axle vehicle. The same method used on the three axle system is used to also group the front pair of axles into 1 front imaginary axle. The front imaginary axle is position (41) is the centre point of the two front axle positions (40) and (42). The front imaginary axle load (41) is the sum of the two front loads (37) and (38).

The ratio of the two front axle loads is given by a similar linear equation as the rear

(38) / (37) = 1 + (43) / Kf

Where Kf is a constant relating to the front axle pair.

Again Kf is derived at time of calibration by rearranging the above equation

(43)

Kf =

(38)/(37) - l

Shown in figure 8 is a refuse vehicle employing an axle load measuring method according to the invention.

When waste is collected in a refuse vehicle it is compressed by a packer plate (44) against the ejector plate (47). The compaction pressure is set by the hydraulic pressure of the ejector plate ram (48). As the vehicle is filled the refuse is compressed until it reaches • the set pressure, at which point the ejector plate moves towards the front of the vehicle.

The optimum compression of the waste depends on the waste type (household waste, green waste etc). The weighing system has control over the hydraulic pressure of the ejector plate. The vehicle operator is able to select a waste type on the indicator, the system will control the ejector plate pressure to optimise payload.

With the ejector plate and payload both located near the rear of the vehicle it is relatively easy to overload the rear axles. By calculating the vehicle axle weights the system will move the ejector plate towards the front when to it nears a maximum rear axle weight. When the vehicle nears its maximum payload the compactor plate (44) is disabled to prevent further loading causing an overload condition.

Show in figure 9 is an apparatus for performing the methods according to the invention. The apparatus comprises a plurality of load cells adapted to be positioned between the chassis and the body. The load cells are connected to a control means. The control means receives measurements from the local cells and performs the necessary calculations. The results of the calculations are displayed by display means, typically positioned within the vehicle cab.

Claims

CLAMS

1. A method of measuring the tipping stability of a vehicle comprising the steps of

2. A method as claimed in claim 1, wherein the fiducial axis is orthogonal to a contact line extending between two points of contact of the vehicle with the ground.

3. A method as claimed in claim 2, wherein the alarm is produced if the centre of gravity is proximate to either of the points of contact.

4. A method as claimed in claim 3, wherein the alarm is produced if the distance between the centre of gravity and a point of contact is less than 20%, preferably less than

10% of the distance between the points of contact.

5. A method as claimed in claim 1, wherein the method is performed about at least two fiducial axes determine the position of the centre of gravity within a plane.

6. A method as claimed in claim 5, wherein the two axis are parallel to the ground.

7. A method as claimed in either of claims 5 or 6, wherein the axis are orthogonal.

8. A method as claimed in any one of claims 5 to 7, wherein the position of the centre of gravity is compared to the vehicle footprint comprising the area defined by lines extending between the points of contact of the vehicle with the ground and the alarm is sounded if the centre of gravity is proximate to an edge of the footprint.

9. An apparatus for determining the tipping stability of a vehicle comprising a plurality of load cells adapted to be positioned between payload and vehicle chassis; and control means adapted to receive load measurements from the load cells and to measure the tipping stability according to the method of claim 1.

10. An apparatus as claimed in claim 9, further comprising alarm means, the alarm means being adapted to provide at least one of a visual or audible alarm.

11. A method of calculating axle loading for a vehicle comprising the steps of

(a) providing a vehicle comprising a chassis and a payload, the chassis being supported by first and second axles; (b) providing a plurality of load cells between chassis and payload;

(c) measuring the total mass of the payload;

(f) calculating the load on the second axle by multiplying the total mass of the payload by the distance of the payload centre of mass from the first axle and dividing the result by the distance between the axles.

12. A method as claimed in claim 11 comprising the further step of calculating the load on the first axle by multiplying the total mass of the payload by the distance of the payload centre of mass from the second axle and dividing the result by the distance between the axles.

13. A method as claimed in either of claim 11 or 12 wherein the empty vehicle axle load is added to the measured axle load.

14. - A method as claimed in claim 11, wherein the second axle is an imaginary axle comprising third and fourth real axles and arranged at the mid-point therebetween, and the method further comprises the step of calculating the loads on the third and fourth axles from the simultaneous equations:

A₄ K₂ and

A₃ + A₄ — A₂

where A₂, A₃ and A₄ are the loads on the second third and fourth axles,

X₂ is the distance between the centre of mass of the payload and the imaging second axle; and k₂ is a known constant.

15. A method as claimed in claim 30, wherein the constant K is calculated by making direct measurements of A₃ and A₄ for the vehicle in empty and loaded states.

'

16. A method as claimed in either of claims 30 or 31, wherein the first axle is an imaginary axle comprising fifth and sixth real axles, the first axle being arranged at the mid-point therebetween and the method further comprising the step of calculating the loads on the fifth and sixth axles from the simultaneous equations

^{^}L - I ₊ ^L and A₆ k_λ

A₁ = A₅ + A₆ where A₁, A₅, A₆ are the loads on the first, fifth and sixth axles;

first axle; and k_x is a known constant.

17. A method as claimed in any one of claims 11 to 16, wherein the vehicle is a refuse vehicle having a packer plate and an ejector plate, wherein the method further comprises the step of moving the ejector plate towards the front of the vehicle when the load on the rear axle exceeds a predetermined limit.

18. A method as claimed in claim 17, wherein the method further comprises the step of disabling the compactor plate when the ejector plate reaches the front of the vehicle.

19. A method as claimed in either of claims 17 or 18, wherein the compactor plate is disabled when the vehicle payload exceeds a predetermined limit.

20. A method of measuring the centre of gravity of a payload of a vehicle comprising the steps of (a) providing a vehicle having a chassis and a payload;

(b) providing a plurality of load cells between chassis and payload;

(c) measuring the total load measured by all the load cells to give the total payload mass

(d) calculating the total moment of the payload about a fiducial axis by multiplying the mass measured by each load cell by its perpendicular distance from the axis and totalling the result;

(e) dividing the total moment by the total payload weight to determine the perpendicular distance of the payload centre of gravity from the fiducial axis.

21. A method as claimed in claim 20, wherein the method is performed about two non-parallel fiducial axes.

22. A method as claimed in claim 21 wherein the two fiducial axes are co-planar.

23. A method as claimed in claim 22, wherein the two axes are parallel to the plane of the chassis.

24. - A method as claimed in any one of claims 21 to 23 wherein the two axes are orthogonal.

25. A method as claimed in claim 20 wherein the method is performed about at least three axes.

26. A method as claimed in claim 25, wherein the three axes are non co-planer, preferably orthogonal.

27. A method as claimed in any one of claims 20 to 26, wherein at least one fiducial axis passes through at least one, preferably two load cells.

28. An apparatus for determining the centre of gravity of a payload of a vehicle, the apparatus comprising a plurality of load cells adapted to be positioned between payload and vehicle chassis; and control means adapted to receive load measurements from the load cells and to determine the centre of gravity by the method according to claim 20.

29. An apparatus as claimed in claim 28, further comprising display means for displaying the position of the centre of gravity.

30. An apparatus as claimed in either of claims 28 or 29, further comprising warning means for providing a warning, preferably an audible warning, if the centre of gravity of the payload is outside one or more predetermined limits.

31. A tipping vehicle comprising a chassis and a body for carrying a payload; lifting means extending between the chassis and the body adapted to lift the body with respect to the chassis between up and down positions; a chassis support connected to the chassis and adapted to bear at least a portion of the weight of the body when in the down position; at least one load cell connected in series with the lifting means between the chassis and the body; and control means connected to the load cell and adapted to produce an alarm if the load measured by the load cell exceeds a predetermined limit.

32. A tipping vehicle as claimed in claim 31, wherein the control means is adapted to produce an alert if the load measured by the load cell exceeds the load measured by the load cell when the load is in the down position by a determined amount.

33. A tipping vehicle as claimed in either of claims 31 or 32 herein the body is pivo tally connected to the chassis proximate to the end of the body.

34. A tipping vehicle as claimed in claim 33, wherein the lifting means is connected to the body remote from the pivot, preferably proximate to the end of the body opposite the pivot.

35. A method of measuring the tipping of the body of a tipping vehicle comprising the steps of:

(1) providing a tipping vehicle comprising (a) a chassis and a body for carrying a payload;

(b) lifting means extending between the chassis and the body adapted to lift the body with respect to the chassis between up and down positions;

(c) a chassis support connected to the chassis and adapted to bear at least a portion of the weight of the body when in the down position; (d) at least one cell connected in series with the lifting means between the chassis and the body; and

(e) control means connected to the load cell and adapted to produce an alarm if the load measured by the load cell exceeds a predetermined limit; (2) measuring the load by means of the load cell;