GB2583899A

GB2583899A - A method and system for testing vehicle brake performance

Info

Publication number: GB2583899A
Application number: GB1905454.3A
Authority: GB
Inventors: James Grogut David; Stephenson Shaun; Ian Henry Bulley Gary
Original assignee: Ryder Ltd
Current assignee: Ryder Ltd
Priority date: 2019-04-17
Filing date: 2019-04-17
Publication date: 2020-11-18
Also published as: GB201905454D0

Abstract

A method and system 21 for testing the performance of brakes includes determining a change in the value of a parameter caused by a deflection in the suspension when the vehicle is moving and the brakes are applied (e.g. measuring the pneumatic suspension pressure using a pressure sensor 23) and calculating brake performance based on this (e.g. calculating total brake force or calculating total brake effort). The system may be used to check the brakes of a heavy goods vehicle (HGV) trailer. The suspension pressure (e.g. in air springs 13 of the wheels; fig. 2) may be measured when the brakes are not applied and compared to the value when the brakes are applied in isolation (e.g. using a regulator to apply brakes at a predetermined level while the trailer is being dragged at a set constant speed). The brake performance calculator may be a handheld mobile computer (e.g. a mobile phone) and may use vehicle specific quantities in the calculation, e.g. axle number, axle weight, suspension geometry, this information being requested and communicated from a remote server.

Description

Intellectual Property Office Application No. GII1905454.3 RTM Date:6 September 2019 The following terms are registered trade marks and should be read as such wherever they occur in this document: Driver and Vehicle Standards Authority DVSA Intellectual Property Office is an operating name of the Patent Office www.gov.uk/ipo A METH D AND SYSTEM FOR TESTING VEHICLE BRAKE PEFFORMANCE.

The present invention relates to a method and system for testing automotive vehicle brake performance. Particularly but not exclusively, the present invention relates to a method and system for testing brake performance of a heavy goods vehicle (HGV), specifically foundation brakes of a trailer of a HGV.

There is an almost global requirement for road vehicles to undergo inspection to ensure that they and their component systems are operating both correctly and safely. Typically, these inspections are required to be undertaken at least annually to ensure that the vehicle is operating within tolerable limits as prescribed by the jurisdictional authority of relevance. For instance, in the United Kingdom it is required for road vehicles over three years old to undergo a Ministry of Transport (MOT) test to ensure that the vehicle is safe and roadworthy up to the standards set by the Driver and Vehicle Standards Authority (DVSA).

In the case of heavy goods vehicles (HGVs), the DVSA requires testing to be carried out annually after first registration of the HGV to ensure the HGV is operating safeiy and within fixed operational limits, and in its guide to roadworthiness the DVSA recommends that certain HGV systems (e.g. braking system) be tested more frequently, e.g. quarterly. HGV operators may additionally impose on themselves more regular testing and inspections at set intervals throughout the course of a year.

One such vehicle system that is required to be tested to ensure it is operating correctly, and within safe and tolerable limits, is the braking system of a vehicle. It will be appreciated that the brakes of a vehicle are of crucial importance to the proper and safe operation of a vehicle.

Brake testing, in particular brake testing of HGVs, often requires the use of a roller brake tester. Roller brake testers usually comprise electric motors, rollers and brake force transducers. During testing, a vehicle's wheels are set on the rollers and the rollers are driven into rotation by virtue of the motors, which in turn drive the wheels of the vehicle into rotation. Once the wheels of the vehicle are rotating at the desired speed, measurements of the maximum brake force applied by each of the vehicle's brakes are measured by applying the vehicle brakes. The force produced by application of the vehicle's brakes induces a corresponding reaction force on the rollers. The transducer measures the reaction force on the electric motors. This measured reaction force, which is measured for each wheel and thus for each brake, corresponds to the maximum braking force applied by each brake and thus gives a measure of the performance of each brake. By summing the maximum braking force measured for each brake, the brake performance of a particular axle or the vehicle as a whole may also be calculated.

Roller brake testers are typically in-ground systems, whereby the rollers, motors and transducers are built integrally into the ground and are thus immobile and stationary. Therefore, it is required for the vehicle to be brought to the roller brake tester in order to have the necessary test of brake performance earned out This is inconvenient for all vehicle users as it requires a user to bring their vehicle to a test centre with a roller brake tester in order to have the necessary test of the brakes carried out. This leads to the vehicle being off the road and out of operation, The need to bring a vehicle to a roller brake tester for testing is also associated with a significant and detrimental environmental impact in view of he emissions of air pollutants and greenhouse gases that result from the fuel consumption of driving the vehicle to the roller brake tester.

The requirement of taking a vehicle to a test centre comprising a roller brake tester is particularly undesirable for HGV operators. As mentioned above, HGVs require more testing throughout the year as compared to smaller and/or noncommercial vehicles. Therefore, comparatively HGVs Will be out of operation and off the road more frequently. Moreover, the increased frequency of testing of HGVS will lead to an increase in emissions of air pollutants and greenhouse gases, and thus an increase in the detrimental impact to the environment These disadvantages are only further amplified for HGVs in that, test centres having the capabilities of testing vehicles of the dimensions of a HGV are relatively small in number and have limited numbers of staff qualified for carrying out the necessary testing of HGVs. Therefore, HGV operators may be required to travel long distances in order to reach a test centre capable of canying out the requisite brake testing of their respective HGVs, and there may be long wait times for testing at said test centres in view of the limited staffing. The additional travelling to and waiting for availability at such test centres leads to the HGVs being undesirably out of operation and leads to a larger detrimental impact on the environment.

Furthermore, roller brake testing of HGVs, under best practice (e.g, as set out in the DVSAs Guide to Roadworthiness), should be carried out whilst the trailer of the HGV is loaded so as to get an indication regarding the braking performance of the HGV in a loaded state. Loading and unloading a trailer of a HGV before and after roller brake testing is particularly time consuming, which is disadvantageous as it leads to an increase in the overall length of the roller brake test, resulting in further downtime of the HGV.

In an attempt to overcome some or these drawbacks associated with in-ground roller brake testers, in particular the issues of immobility, mobile roller brake testers have been employed. However, tnese mobile roller brake testers tend to be cumbersome, difficult to transport and time consuming to set-up. Consequently, the drawbacks of vehicles being undesirably out of operation and of a detrimental environmental impact are not fully addressed by mobiie roller brake testers.

Additionally, the need to load and unload a trailer of a HGV before and after testing also remains with mobile roller brake testers. Further, as is the case for in-ground roller brake testers, there are relatively few mobile roller brake testers with the capabilities of testing HGVs. Moreover, mobile roller brake testers typically do not offer the same level of accuracy with regard to brake performance measurements that the in-ground roller brake testers provide, Alternative systems to roller brake testers have also been employed in the art to measure braking performance of a vehicle. One such category of systems involve the use of a decelerometer. Such systems involve placing a device comprising a decelerometer, for instance a Tapley Brake Test Meter, into a vehicle.

To carry out the required braking test, the vehicle is then driven at a set, predetermined speed. Subsequently the brakes of the vehicle are applied. Upon application of the brakes, the vehicle will decelerate at a magnitude proportional to the braking force of the vehicle. Thus, by measuring this deceleration with the device comprising the decelerometer, the braking force and thus the braking performance of the vehicle can be calculated, It will be appreciated that decelerometer brake test systems provide benefits in terms of mobility and cost that roller brake testers do not.

However, there are certain drawbacks associated with systems reliant on deceierometers. Firstly, the decelerometer only gives an indication of the braking performance of the vehicle as a whole. However, many vehicles comprise component modules that are each individually responsible for part of the braking performance of the vehicle. For instance, in many HGVS, such as those comprising full draw bar trailers, centre axle trailers and semi-trailers, both the tractive vehicle and the trailer are in part responsible for the braking performance of the vehicle. For such vehicles, decelerometer based systems are not suitable for testing the braking performance because systems comprising a decelerometer provide no indication as to the braking performance of the component modules (e.g. tractive vehicles and trader) per se, but rather only provide an indication of the braking performance of the vehicle (e.g. FIGV) as a whole. This is hence why various jurisdictional authorities (e.g. the DVSA) often only approve the use of decelerometer based brake test systems for rigid vehicles (i.e. those not comprising a trailer component).

Moreover, decelerometer based brake test systems do not directly test braking performance (as is the case in the roller brake testers discussed above).

The tests carried out using decelerometer based systems are experimentally predictive. The results of such experimental tests may be affected by a great number of other variables other than merely the braking performance of the vehicle. As such, the results produced from decelerometer based brake test systems are often less reliable and accurate than those produced by, for instance, roller brake testers.

Therefore, a system and method for measuring braking performance, in particular braking performance of trailers of FIGVs, that provide advantages in terms of mobility, reliability and accuracy are desired.

According to a first aspect of the invention, there is provided a method of testing the performance of brakes of an automotive vehicle having a suspension, the method comprising the steps of determining a change in value of a parameter caused by a deflection in the suspension when the vehicle is moving and the brakes are applied; and calculating the performance of the brakes based on the change in value of the parameter.

The method of the first aspect allows the performance of brakes to be tested by determining a change in the value of a parameter of the suspension. Thus the suspension itself acts as an indicator of braking performance. An inherent parameter of the suspension is used to determine the braking performance, and thus in the method of the first aspect there is no requirement to determine a change in a parameter of an external means (such as deflection of a roller in a roller brake tester as discussed above) in order to determine braking performance. The method of the first aspect allows the vehicle itself to act as its own test equipment in order to test brake performance, and thus the reliance and requirement on and for additional testing equipment (such as a roller brake tester andlor a decelerometer based system) is reduced. As such, the method of the first aspect provides distinct advantages in respect of mobility over the prior art systems, in particular roller brake testers, since it largely eliminates the need for external testing equipment.

The reduced reliance on external testing equipment provided by the method of the first aspect also results in a reduced amount of vehicle down time as compared to methods known from the prior art that are reliant on external testing equipment, such as roller brake testers, which are associated with significant vehicle down time.

The detrimental impact on the environment associated with prior art methods is also significantly reduced by the method of the first aspect, particularly in view of the improved mobility and thus the reduced travel requirements

associated with prior art methods.

Furthermore, by determining a change in value of a parameter that is proportional to the braking performance of the vehicle, the method of the first aspect is made both more reliable and accurate than experimentally predictive methods such as those that employ decelerorneters as discussed above.

The performance of the Drakes that is calculated by the method of the first aspect may be the total brake force applied by the brakes of the vehicle. Alternatively and/or additionally, the performance of the brakes to be calculated by the method may be the brake effort of the vehicle.

The method of the first aspect may be used to test the performance of the brakes of any automotive vehicle having a suspension, For instance, the method may be used to test the performance of the brakes of a car, a motorcycle, a light commercial vehicle, a rigid commercial vehicle, a bus, an agricultural vehicle, etc. In embodiments, the method is used to test the performance of the brakes of a heavy goods vehicle (HGV).

In particular, the method of the first aspect may be used to test the performance of the brakes of a trailer of a HGV, the HGV also comprising a tractive vehicle having brakes. For instance, the method of the first aspect be used to test the performance of foundation brakes of a trailer of a hiGV. The trailer of the HGV may be a full draw bar trailer, a centre axle trailer or a semi-trailer.

Whilst testing the performance of the brakes of a trailer of a HGV, the method may further comprise the step of isolating a level valve of the trailer. Isolating the level valve may prevent any additional changes in the value of the parameter during testing other than those caused by a deflection in the suspension when the vehicle is moving and the brakes are applied. -6 -

Whilst testing the performance of the brakes of a trailer of a HGV, the brakes of the trailer may be applied in isolation from other brakes within the HGV, such as those in the tractive vehicle This allows for the performance of the brakes of the trailer of the HGV to be measured in isoiation of the brakes of the tractive vehicle without any contribution from the brakes of the tractive vehicle affecting the calculated performance, Thus, the method of the first aspect may be suitably used to test the braking performance of HC3Vs and other non-rigid vehicles.

It is typical in the art to measure braking performance as a function of the level or amount to which the brakes of a vehicle are applied. Therefore, during testing of the performance of the brakes of the vehicle, the brakes may be applied to a predetermined, set level. In applying the brakes to a predetermined, set level, the calculated brake performance can be determined as a function of the level to which the brakes are applied.

The predetermined, set level of the brakes may be selected to ensure that the brakes of the vehicle do not lock during testing.

The brakes of the vehicle may be any type of vehicle brake as is known in the art. Optionally, the brakes are pneumatic brakes. The pneumatic brakes may be applied to a predetermined, set level by applying a set, control pressure to the brakes. The predetermined, set pressure may be from 0 bar to 10 bar, optionally from 0 bar to 5 bar, further optionally from 0 bar to 2 bar, and may for instance be 1.8 bar.

A set pressure applied to pneumatic brakes of the vehicle may be applied by means of a regulator. The regulator may be connected to the pneumatic brakes and to a source of compressed air. The regulator may regulate the supply of compressed air from the compressed air source to the brakes at the set pressure, The use of a regulator may be particularly advantageous when testing the performance of the brakes of HGV trailers comprising /Pneumatic brakes given that such trailers will typically already have the necessary connection points allowing for easy and simple connection of the regulator to the pneumatic brakes of the trailer.

For instance, the regulator may be connected to a brake line and a supply line of a brake system of the trailer. The trailer brake system may be any known type of trailer brake system. The regulator may supply compressed air to the brake line of the trailer without supplying the brakes of the tractive vehicle of the HGV and/or without applying the brakes of the tractive vehicle. Therefore, the brakes of the trailer may be applied in isolation of the brakes of the tractive vehicle. -7 -

The use of a regulator may also be particularly advantageous when testing the performance of pneumatic brakes of partly loaded or unloaded HGV trailers. This is because the brake pressure during testing can be regulated based on the weight of the load of the trailer.

A HGV comprising a trailer having pneumatic brakes may additionally comprise a compressor, usually within its tractive vehicle. Therefore, in embodiments, the compressor of the HGV may be connected to the regulator as a source of compressed air.

The method of the first aspect may be for testing the performance of brakes of an automotive vehicle having any known type of suspension. For instance, the suspension may be a mechanical suspension system. The mechanical suspension system may comprise a mechanical spring, optionally a plurality of mechanical springs. The parameter may be a change in position of a portion of the mechanical spring.

Alternatively, the suspension may be a pneumatic suspension. It will be appreciated that pneumatic suspensions are more typical in heavier, larger automotive vehicles, such as HGVs to which the method of the first aspect is optionally applied.

The suspension may be a trailing arm suspension, The pneumatic suspension may comprise an air spring. The parameter may be a pressure in the pneumatic suspension, e.g. a pressure in the air spring. The pneumatic suspension may be supplied by a compressor. In embodiments where the vehicle is a HGV, the suspension may be supplied by a compressor in a tractive vehicle of the HGV. The compressor that supplies the pneumatic suspension may be the same compressor as the compressor that supplies compressed air to the pneumatic brakes of the HGV.

The method of the first aspect may comprise the step of placing a sensor into communication with the suspension of the vehicle. The step of placing the sensor into communication with the suspension of the vehicle optionally occurs prior to the step of determining a change in value of the parameter. The sensor may measure a value of the parameter.

In embodiments where the suspension is a pneumatic suspension, the sensor may be a pressure sensor configured to measure a pressure in the pneumatic suspension. The pressure sensor may be configured to connect -8 -test point of the pneumatic suspension to measure a pressure in the pneumatic suspension system.

Alternatively, in embodiments where the suspension is a pneumatic suspension, the sensor may be placed into communication either through a wired connection or wirelessly, with an electronic control unit (ECU) of the vehicle, the ECU in turn being in communication with the suspension of the vehicle, The ECU may communicate the pressure in the pneumatic suspension to the sensor.

In embodiments where the suspension is a mechanical suspension system, the sensor may be a position sensor configured to measure a position of the mechanical suspension.

The method of the first aspect may comprise the step of measuring a value of the parameter when the brakes are not applied. The step of measuring a value of the parameter when the brakes are not applied may take place whilst the vehicle is stationary. The method may additionally or alternatively include the step of measuring a value of the parameter when the vehicle is moving and the brakes are applied. The step of determining a change in value of a parameter may comprise determining the change between the value of the parameter when the brakes are not applied and the value of the parameter when the vehicle is moving and the brakes are applied.

The step of measuring a value of the parameter when the vehicle is moving and the brakes are applied may be carried out whilst the vehicle is moving at a constant speed. This can ensure that a variation in speed of the vehicle is not a factor that affects the calculated brake performance The constant speed may be from 0 mph to 20 mph, optionally 0 mph to 10 mph. For instance, the constant speed may be 5 mph, The vehicle may be driven at the constant speed, and thus the method of the first aspect may comprise the step of driving the vehicle at a constant speed. Alternatively, the vehicle may be towed to the constant speed, and thus the method of the first aspect may comprise the step of towing the vehicle at a constant speed.

in some embodiments, wherein the brakes to be tested are the brakes of a trailer of a HGV, the trailer may be towed at a constant speed by a tractive vehicle of the HGV.

The method of the first aspect may be carried out on the brakes of a fully loaded vehicle. For instance, where the automotive vehicle is a HGV the trailer of the HGV may be fully loaded. Alternatively, the automotive vehicle may only be partly loaded or unloaded. For instance, where the automotive vehicle to be tested is a HGV, the trailer may only be partly loaded or unloaded.

According to a second aspect of the invention, there is provided a system for testing the performance of brakes of an automotive venicle having a suspension, the system comprising. a measuring device configured to measure a parameter of the suspension, and a brake performance calculator or computing unit configured to calculate the performance of the brakes based on a change in value of the parameter caused by a deflection in the suspension of the vehicle when the vehicle is moving and the brakes are applied.

The system of the second aspect of the invention provides largely similar advantages in respect of mobility, reliability, accuracy and reduced detrimental environmental impact that the first aspect of the invention provides. In particular, because the system of the second aspect is configured to calculate performance of the brakes of the vehicle based on an inherent parameter of the suspension of the vehicle, the vehicle itself acts as part of the testing equipment to calculated brake performance. Consequently, the reliance and requirement for additional testing equipment (e.g. roller brake testers) in order to test the braking performance of an automotive vehicle is significantly reduced by the system of the second aspect. Thus the system of the second aspect is made significantly more mobile, less costly, and less cumbersome than prior art systems (e.g. roller brake testers and decelerorneter based systems).

Moreover, as the system of the second aspect is configured to calculate brake performance based on an inherent parameter of the suspension of the vehicle, the system can more accurately and reliably determine the braking performance of a vehicle as compared to prior art systems, e.g. decelerometer based systems.

The system of the second aspect as described above or in the following statements may be used for carrying out the method of the first aspect as set out in the preceding statements.

The measuring device of the second aspect may be configured to measure a value of the parameter when the brakes are not applied and/or when the vehicle is stationary. The measuring device may be configured to measure a value of the parameter when the vehicle is moving and the brakes are applied. The brake performance calculator or computing unit may be configured to determine the change in value of the parameter based on the value of the parameter when the -10 -vehicle is moving and the brakes are applied as compared to the value of the parameter when the brakes are not applied and/or when the vehicle is stationary.

The performance of the brakes that is determined by the system of the second aspect may be the total brake force and/or brake effort of the brakes as discussed above in relation to the first aspect.

The system may be configured for testing the performance of the brakes of any of the vehicle types discussed in relation to the first aspect. In particular, the system may be configured for testing the performance of the brakes of a heavy goods vehicle (HGV), optionally the system may be configured for testing the performance of the brakes of a trailer of a HGV, in particular the performance of foundation brakes of a trailer of a HGV.

The system may be for testing the brake performance of brakes of an automotive vehicle having a trailing arm suspension.

The system may be for testing the brake performance of brakes of an automotive vehicle having a pneumatic suspension. In embodiments where the suspension is pneumatic, the parameter may be a pressure of the suspension, e.g. a pressure in an air spring. Alternatively, the system may be for testing the brake performance of brakes of an automotive vehicle having a mechanical suspension system.

The system of the second aspect may comprise a regulator. The regulator may be in accordance with the regulator discussed above in relation to the first aspect of the invention.

The measuring device may be a pressure sensor or a position sensor. The pressure sensor or position sensor may be configured for use as discussed above in relation to the first aspect of the invention. For instance, the sensor may be a pressure sensor in embodiments for testing the brake performance of brakes of an automotive vehicle having a pneumatic suspension. Alternatively, the sensor may be a position sensor in embodiments for testing the brake performance of brakes of an automotive vehicle having a mechanical suspension.

Alternatively, in embodiments for testing the brake performance of brakes of an automotive vehicle having a pneumatic suspension the sensor may be configured to be placed into communication, either through a wired connection or wirelessly. with an electronic control unit (ECU) of the vehicle, the ECU in turn being in communication with the suspension of the vehicle, The ECU may communicate the pressure in the pneumatic suspension to the sensor.

The brake performance calculator may be a device comprising a proces For instance, the brake performance calculator may be a handheld computer device, e.g a tablet or a mobile phone.

The brake performance calculator or cornputing unit may e configured to use vehicle specific quantities, e.g. dimensions and variables of the vehicle, in order to calculate the performance of the brakes. The dimensions of the vehicle may include a number of axles of the vehicle, a number of brakes of the vehicle, a suspension geometry, a total axle weight of the vehicle anti/or a diameter of an air spring of the vehicle. The variables of the vehicle may include a pressure of a brake chamber of the pneumatic brakes of the vehicle as a function of a pressure supplied to a brake line of the vehicle and as a function of a load of the vehicle. The system of the second aspect may comprise a remote server in communication with the brake performance calculator or computing unit. The remote server may comprise data relating to vehicle specific quantities of a plurality of vehicles. The brake performance calculator or computing unit may be configured to send a request for the data relating to the vehicle specific quantities of the vehicle to the remote server. The remote server, upon receipt of the request may be configured to identify the data relating to the vehicle specific quantities of the vehicle and to transmit the data relating to the vehicle specific quantities of the vehicle to the brake performance calculator or computing unit.

The brake performance calculator or computing unit may be configured to send an identifier of the vehicle to, e.g. a registration number, as part of the request for the data relating to the vehicle specific quantities of the vehicle. The remote server may be configured to identify the data relating to the vehicle specific quantities of the vehicle based on the identifier.

Where the remote server does not comprise the data relating to the vehicle specific quantities of the vehicle, the remoter eerier may be configured to transmit to the brake performance calculator or computing unit that the data relating to the vehicie specific quantities of the vehicle is not available. The brake performance calculator or computing unit may display the unavailability of the data relating to the vehicle specific quantities of the vehicle to the user.

Certain embodiments 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 representation of a typical heavy goods vehicle (HGV) to which embodiments of the present invention are applicable; -12 -Figure 2 is a schematic side view of a wheel and suspension system of a trailer of the HGV of Figure 1; Figure 3 depicts a system in accordance with an embodimen of the invention being used to test the brake performance of a HGV trailer; Figure 4 shows a brake regulator in accordance with embodiments of the invention; and Figure 5 shows a graph of brake effort of a HGV trailer plotted against pressure applied to pneumatic brakes of the trailer Figure 1 shows a HGV 1, the HGV 1 comprising a tractive vehicle 3 and a trailer 5. The tractive vehicle 3 is releasably connected to the trailer 5 in an articulated, flexible (i.e. non-rigid) manner. As such, as is known in the art, the tractive vehicle 3 may be driven in isolation of the trailer 5 or in combination therewith.

The tractive vehicle 3 comprises two axles 7A, each axle comprising a plurality of wheels 9A, the left outermost of which being the only visible wheel 7A in Figure 1. Each axle 7A is connected in a known manner to a chassis (not shown) of the tractive vehicle 3. The trailer 5 comprises three axles 76, each axle comprising a plurality of wheels 9B, the left outermost of which being the only visible wheel in Figure 1. Each axle 78 of the trailer 5 is connected to a chassis (not shown) of the trailer 5 in a known manner. It will be appreciated that, whilst depicted as having three and two axles 7A, 76 respectively, the tractive vehicle 3 may comprise a larger number of axles, for instance three, four or five axles, whilst the trailer may comprise a fewer or greater number of axles, for instance 2, 4, 5 or 6 axles.

The trailer, and the tractive vehicle 3 as depicted in Figure 1 each comprise brakes (not shown) such that both the trailer 5 and the tractive vehicle 3 are responsible for the braking of the HGV 1 when connected. The brakes of the trailer 5 are pneumatic brakes as are known in the art.

Figure 2 shows an enlarged schematic side view of one of the wheels gB of the trailer 5. The wheel 98 is connected to the axle 78 in a known rotatable fashion. Connected to the axle 78 is a suspension system 11 associated with wheel 98. it will be appreciated that the trailer 5 comprises a plurality of suspension systems 11, typically one suspension system 11 associated with each wheel 98 of the trailer 5. However, this is not required and the trailer 5 may comprise more or fewer suspension systems 11 than wheels 98. Each suspension -13 -system 11 comprised in the trailer 5 is substantially identical to that described below with reference to Figure 2.

The suspension system 11 depicted in Figure 2 is a pneumatic suspension system 11, comprising a spring hanger 15 and an air spnng 13. The spring hanger 15 is connected to the chassis (not shown) of the trailer 5 at a first end, which is an upper end as depicted in Figure 2. Similarly, the air spring 13 is connected to the chassis of the trailer Sat a first end, which is an upper end as depicted in Figure 2.

Both the air spring 13 and the spring hanger 15 are connected at their respective second ends (respective lower ends as shown in Figure 2) to a connecting member 17. As shown in the Figure, the connecting member 17 is a substantially horizontal member. The connection of the spring hanger 15 to the connection member 17 is typically proximate a first end 17A of the connecting member 17, whilst the connection of the air spring 13 to the connecting member 17 is typically proximate a second end 17C of the connecting member 17, the first and second ends 17A, 17C being spaced from one another along the primary axis of the connecting member 17.

The connecting member 17 is positioned above the axle 7B such that an underside of the connecting member 17 contacts the axle 7B at a midpoint 17B of the connecting member 17 at a position between the first end 17A and second end 178 of the connecting member 17. The contact between the axle 7B and the connection member 17 at the midpoint 17B provides a suspension pivot point between the first end 17A and the second end 178, and thus provides a fulcrum positioned between the connection points of the spring hanger 15 and the air spring 13 with the connecting member 17. The suspension pivot point is positioned at a height h above the ground.

The air spring 13 has a diameter D and is formed from flexible bellows. The air spring 13 is in communication with a compressor comprised in the tractive vehicle 3. The compressor is configured to supply compressed air to the air spring 13 to inflate its bellows and thereby expand the air spring 13.

The connection of the spring hanger 15 to both the chassis of the trailer 5 and the connecting member 17 provides a counterbalance to the air spring 13 about the suspension pivot point, whereby the moment applied to the connecting member 17 by the air spring 13 about the axle 78 (said moment being eoual to the force applied by the air spring 13 to the connecting member multiplied by the distance b of the air spring 13 from the suspension pivot point) is equal to the -14 -moment applied to the connecting member 17 by the spring hanger 15 about the axle 7E8 (said moment being equal to the force applied by the spring hanger 15 to the connecting member multiplied by the distance a of the spring hanger 15 from the suspension pivot point). This counterbalance ensures that the air spring 13 is maintained between the axle 78 and the chassis of the trailer 5.

In view of the arrangement of each of the suspension systems 11 comprised in the trailer 4, when compressed air, by means of the compressor in the tractive vehicle 3, is supplied to the air springs 13 in each suspension system 11, the chassis of the trailer 5 is raised from each connecting member 17 and thus each axle 78. This raising of the chassis of the trader 5 from the axles 78 provides a cushioned support to the chassis and thus the trailers, and thereby provides suspension to the trailer 5 when being driven as part of the HGV 1.

In a condition where the HGV 1 is moving (being driven) and the brakes of the HGV 1 (both the brakes of the tract vs vehicle 3 and the trailer 5) are applied, a brake force BF is applied to each of the wheels 9A, 9B of the HGV 1 in a direction opposed to its direction travel. This brake force BF is applied to each of the wheels 9A, 98 at their contact point C with the ground 19. The brake force BF applied to the wheels 9A, 98 is transferred to the chassis of the HGV I (that is both the chassis of tne tractive vehicle 3 and the trailer 5) and to the suspension systems of the HGV 1, including suspension systems 11 comprised in the trailer. The transfer of said brake force to the trailer 5 causes a deflection in the suspension system 11, in particular a deflection in the air spring 13, that is proportional in magnitude to the total braking force BTotal, which is equal to the sum of the brake force BE over all of the wheels 9A, 98 of the HGV 1. Thus, by determining a deflection in suspension system 11 when the HGV 1 is moving and the brakes are applied, or rather by determining a change in value of a parameter caused by a deflection in the suspension 11 when the HGV is moving and the brakes are applied it is possible to calculate the total braking force &rota: applied by the brakes, and thus the brake effort and braking performance as detailed below.

Figure 3 shows a system 21 according to an embodiment of the invention being used to test the brakes of the HGV 1. As shown in Figure 3, the system 21 is specifically being used to test the performance of the foundation brakes of the trailer 5 in isolation of the tractive vehicle 3. The isolation of the brakes of the trailer 5 will be described in more detail below with reference to Figure 4.

-15 -The system 21 comprises a pressure sensor 23. The pressure sensor 23 is connected to a test point of the suspension system 11 that is in communication with a pressure in an interior of the air spring 13 such that it can measure (detect) the pressure within the air spring 13. The system 21 further comprises an output device 27 in communication with the sensor 23 via a cable 25. The output device 27 receives the pressure measurements that are detected by the sensor 23 and displays them to a user.

To measure and calculate the total brake force Eimial applied by the brakes of the trailers in isolation of the brake force applied by the brakes of the tractive vehicle 3, the brakes of the trailer 5 must be applied in isolation of the brakes of the tractive vehicle 3 such that the total braking force Brotai applied during testing is a result of the brakes of the trailer 5 only This is achieved by means of a regulator 31 as depicted in Figure 4. The regulator 31 connects to a brake line 33 of the trailer 5 via a first input line 35. The regulator 31 also connects to a supply line 37 of the trailer 5 via a second input line 39. The first and second input lines 37, 39 connect to an air compressor within the tractive vehicle 3 and act as a conduit for compressed air to both the brake iine 33 and the supply line 37. This compressor is the same compressor to the compressor that supplies air to the air springs 13.

The magnitude of the pressure of the compressed air supplied through the brake line 33 determines a level to which the pneumatic brakes of the trailer 5 are applied, whilst the supply of compressed air to the supply line 37 provides the necessary suppiy of compressed air to apply the pneumatic brakes to said level. This type of trailer brake system is known in the art and will not be described further here.

The regulator 31 regulates the pressure of the compressed air incoming from the compressor to a set pressure Pr, and applies this set pressure to the brake line 33 of the trailer such that the pneumatic brakes of the trailer 5 may be applied to a predetermined, set level. Thus, the regulator 31 is used to apply the brakes of the trailer 5 to a predetermined, set level by controlling the supply of pressure thereto.

Further, as the input lines 37, 39 connect the compressor in the tractive vehicle 3 directly to the brakes in the trailer 5, there is no requirement for the brake pedal in the cab of the tractive vehicle 3 to be pressed in order to supply the brakes in the trailer 5 with the necessary compressed air to be applied. Therefore, the brakes of the trailer 5 can be applied in isolation of the brakes of the tractive vehicle 3 in the cab of the tractive vehicle 3 (which would additionally be applied in a scenario where the brake pedal is pressed).

The testing of the brake performance of the brakes of the trailer 5 begins with a measurement of the pressure in the air spring 23 whilst the HGV 1 is stationary. This pressure is detected by the sensor 23 in communication with one of the air springs 13 in the trailer and is displayed by the output device 27 to a user. The pressure detected by the sensor 23 whilst the HGV 1 is stationary is representative of the weight on the trailer axle, and thus the load of the trailer 5.

Once the stationary pressure measurement has been recorded by the user, the brakes of the trailer 5, by means of the regulator 31, are applied to a predetermined, set level. For instance, 1.8 bar of pressure may be supplied by the regulator 31 to the brake line of the trailer 5. After the brakes of the trailer 5 have been applied, the trailer 5 is then dragged forward at a predetermined, set speed (e.g. 5 mph) by the tractive vehicle 3 for a short, predetermined period of time (e.g. 5 seconds) The predetermined level that the brakes are applied to is less than a level that would cause the brakes to lock at the predetermined speed and can be selected/regulated based on the load of the trailer.

As the trailer 5 is towed by the tractive vehicle 3 at the predetermined, set speed, the pressure sensor 23 continuously monitors the pressure within the air spring 13. During the short, predetermined period of time, the output device 27 displays the pressure detected by the pressure sensor 23 to a user and saves the maximum pressure recorded whilst the trailer 5 is dragged. Once the short, predetermined period of time has elapsed, the output device 27 displays the maximum pressure recorded.

The pressure in the air springs 13 whilst the trailer 5 is dragged by the tractive vehicle 3 will increase as compared to the pressure in the air spring 13 whilst the HGV 1 is stationary. This increase in pressure is caused by the deflection in the chassis of the trailer 5 and thus the suspension systems 11 as a reaction to the total braking force Brae applied as a result of application of the brakes of the trailer 5. This in turn causes a deflection in the air springs 13 that decreases a volume of each air spring 13 and thus an increase in the pressure therein. Therefore, by calculating this increase in pressure, in particular the maximum increase in pressure, the maximum braking force Brae, of the trailer 5 can be calculated based on the deflection in the suspension system 11.

-17 -In the embodiment of the system depicted in Figure 3, the maximum braking force of the trailer 6-rots' is calculated by virtue of a handheld computer device (not shown). The user inputs both the pressure measured in the air spring 13 measured whilst the HGV 1 was stationary and the maximum pressure measured in the air spring 13 whilst the trailer was dragged. The handheld device then calculates the total braking force Brow of the trailer in accordance with equation 1): 1) Beutat(N) = (P2 --Pe) x 100,000 x ( * ) a+b zx.:ive) X NoA x NoB Where P2 is the maximum pressure (in bar) recorded whilst the trailer 5 was towed, P1 is the pressure On bar) in the air spring 13 measured whilst the HGV 1 was stationary, iv 1 is the area (in m2) of the air spring 13, a*b is the eixit5th)) * h suspension 11 geometry, NoA is the number of trailer axles 7B, and NoB is the number of brakes per axle 7B. The factors of 100,000 and 1000 present in equation 1) are to convert the pressures from units of bar to units of Pa and to convert the diameter D of air spring 13 from units of mm to units of m respectively.

The suspension geometry aij---! factors in the effect that the height h of the suspension pivot point, the distance b of the air spring 13 from the suspension pivot point and the distance a of the spring hanger 15 from the suspension pivot point have on the forces acting about the suspension pivot point.

With regard to the suspension geometry riEtb, the diameter D of the air spring 13, the number of axles NoA of the trailer 5, and the number of brakes NoB per axle 7B of the trailer, these dimensions of the trailer can all be input manually to the handheld computer device by the user in order to calculate the total braking force Brea; of the trailer. However, the handheld device is also able to obtain these dimensions of the trailer by communicating with a remote server that comprises data relating to the dimensions of a plurality of vehicles and trailers. In this scenario, the user inputs the registration number of the trailer 5 to the handheld device and then instructs the handheld device to retrieve the data relating to the dimensions of the trailer 5. The handheld device then sends a request for the data relating to the dimensions of the trailer 5 to the remote server. The remote server, upon receipt of the request, identifies the data relating to the dimensions of the trailer 5 and then transmits the data to the handheld device. The handheld device -8 -can then calculate the total braking force B-rwa, absent the need for input of the dimensions of the trailer.

If the remote server does not comprise data relating to the dimensions of the trailer 5, then the remote server transmits that no such data is available to the handheld device. The handheld computer device can then display to the user that the data relating to the dimensions of the trailer is unavailable and can request that the user input the dimensions manually in order to calculate the total braking force Brow' of the trailer 5.

The total brake braking force arotai of the trailer from equation 1) is output in units of N; however the handheld device also calculates and outputs the total braking force to the user in units of kg, as is more typical in the art, by virtue of the following equation: 2) B70t6/(k9) Where g is the acceleration due to gravity, with a value of 9.80665 ms Since the testing of the total Drake force is carried out at a set pneumatic brake pressure Pm, the handheld device is also able to calculate a deceleration of the trailer 5 as a function of the pressure PNA of the air applied to the pneumatic brakes of the trailer 5, commonly termed the brake effort BFff. This brake effort BEff of the trailer 5 is another measure of the braking performance of the trailer that can be derived from the brake force Bmta; and is a typical measure used by the jurisdictional authorities of relevance (e.g. the DVSA in the UK) of brake performance to ensure the brakes are operating within safe and tolerable limits.

Figure 5 shows a graph of brake effort of a trailer BEff plotted against pressure Pm applied to the pneumatic brakes of a vehicle, such as brakes of a trailer of a HGV. A first line 41 and a second line 43 are plotted on the graph of Figure 5. These lines are specifically relevant to trailers of HGVs and define the braking performance that HGV trailers must meet in the UK as regulated by the DVSA. The first line 41 sets a lower limit of the brake effort BEff that is required to be achieved by the brakes of a HGV trailer at a given brake pressure P,, whilst the second line 43 sets an upper limit of the brake effort BEff that is required to be achieved by the Drakes of a HGV trailer at a given brake pressure Pr,, The space 45 defined between the first 41 and second 43 lines is termed the braking corridor.

-19 -The brake effort of a trailer of a HGV, such as trailer 5, is required to fall within the braking corridor in order for the braking performance of the trailer to be deemed safe.

From Figure 5, it can be seen that at a braking pressure Pm of 7.5 bar a minimum brake effort BM of 0.45 (45 %) and a maximum brake effort Beffof 0.65 (65%) is required in order for a trailer to adhere to the DVSA's requirements of brake performance. Using these requirements of brake performance as set out by the DVSA as a benchmark, the handheld device of the system 21 calculates the brake effort BEr of the trailers at a brake line pressure of 7.5 bar by virtue of equation 3): 3) Buf -gramKkg)a:e.

TMW

Where BTotai(kg) is the total braking force Brotaiof the trailer 5 in units of kg as calculated in equation 2), TAW is the total mass on the axles 7B of the trailer 5 and E is an extrapolation factor. The extrapolation factor E maps the total braking force BTotal of the trailer 5 onto the braking corridor at a brake line pressure of 7.5 bar and is calculated by the handheld device using equation 4).

BC" (7.3 zsan BL, BC,"(Pn.,) is the pressure within brake chambers of the brakes of the trailer during testing whilst the test pressure Pi, is applied to the brakes. BCp(P",) is measured during testing using a pressure sensor in communication with an interior of the brake chamber. The measured value of BC,s,(Pm) is then input by the user to the handheld device.

BCp(7.5 bar) is the pressure within the brake chambers of the brakes of the trailer when the trailer is fully laden and 7.5 bar of pressure has been applied to the brake line. The value of BC(7.5 bar) may be obtained from a data plate of the trailer and can be input manually to the handheld device, or the value of BCp(7.5 bar) can be retrieved from the remote server by the handheld device in an automatic manner similar to described above in relation to the dimensions of the trailer. Once the values of BC,(7.5 bar) and Bp(P) have been made available to the handheld device, the handheld device calculates the extrapolation factor E by virtue of equation 4). Subsequently, the handheld device calculates and displays -20 -the results of equation 3) to the user, A result of brake effort BEff of between 0.45 and 0.65 will indicate that the brakes of the trailer 5 are operating at a safe level within the braking corridor). The handheld device will also explicitly indicate to the user whether the result of BEfi falls within the braking corridor (i.e. between the values of 0.45 and 0.65). This indication will be in the form of a pass or a fail message to the user. -21 -

Claims

Claims: 1. A method of testing the performance of brakes of an automotive vehicle having a suspension, the method comprising the steps or determining a change in value of a parameter caused by a deflection in the suspension when the vehicle is moving and the brakes are applied; and calculating the performance of the brakes based on the change in value of the parameter.
2. A method as claimed in claim 1, wherein the performance of the brakes is the total brake force and/or brake effort of the brakes
3. A method as claimed in claim 1 or 2, wherein the automotive vehicle is a heavy goods vehicle (HGV).
4. A method as claimed in claim 3, wherein the brakes of the HGV that are tested are the brakes of a trailer of the HGV.
5. A method as claimed in claim 4, wherein the brakes of the trailer are applied in isolation from all other brakes in the HGV.
6 A method as claimed in any preceding claim, wherein the brakes of the vehicle are applied to a predetermined level.
7. A method as claimed in claim 6, wherein the brakes of the vehicie are applied to the predetermined level by means of a regulator.
8. A method as claimed in any preceding claim, further comprising, prior to the step of determining a change in value of the parameter, placing a sensor into communication with the suspension of the vehicle, the sensor being configured to measure the parameter.
9. A method as claimed in any preceding claim, wherein the vehicle comprises pneumatic suspension.-22 -
10. A method as claimed in claim 9 wherein the parameter is a pressure in the pneumatic suspension.
11. A method as claimed in any preceding claim, further comprising: measuring a value of the parameter when the brakes are not applied; measuring a value of the parameter when the vehicle is oving and the brakes are applied; and wherein the step of determining a change in value of the parameter comprises determining the change between the value of the parameter when the brakes are not applied and the value of the parameter when the vehicle is moving and the brakes are applied.
12. A method as claimed in claim 11, wherein the step of measuring a value the parameter when the vehicle is moving and the brakes are applied is earned out whilst the vehicle is moving at a constant speed,
13. A system for testing the performance of brakes of an automotive vehicle having a suspension. the system comprising: a measuring device configured to measure a parameter of the suspension; and a brake performance calculator configured to calculate the performance of the brakes based on a change in value of the parameter caused by a deflection in the suspension of the vehicle when the vehicle is moving and the brakes are applied.
14. A system as claimed in claim 13, wherein: the measuring device is configured to measure a value of the parameter when the brakes are not applied; the measuring device is configured to measure a value of the parameter when the vehicle is moving and the brakes are applied; and the brake performance calculator is configured to determine the change in value of the parameter.-23 -
15. A system as claimed in claim 13 or 14, wherein the performance of the brakes is the total brake force and/or brake effort of the brakes.
16. A system as claimed in claim 13, 14 or 15, wherein the system is configured for testing the performance of the brakes of a heavy goods vehicle (HGV).
17. A system as claimed in can 16, wherein the system is confgured for testing the performance of the brakes of a trailer of the HGV
18. A system as claimed in any of claims 13 to 17, the system comprising a regulator configured to apply the brakes to a predetermined level.
19. A system as claimed in 18 when dependent on claim 17, wherein the regulator is configured to apply the brakes of the trailer to the predetermined level in isolation from all other brakes in the FiGV.
20. A system as claimed in any of claims 13 to 19, wherein the system is for testing the performance of brakes of an automotive vehicle having a pneumatic suspension, and wherein the parameter is a pressure in the pneumatic suspension.
21. A system as claimed in any of claims 13 to 20, wherein the brake performance calculator is configured to use vehicle specific quantities in order to calculate the performance of the brakes based on the change in value of the parameter.
22. A system as claimed in claim 21, the system comprising a remote server in communication with the brake performance calculator, the remote server comprising data relating to vehicle specific quantities of a plurality of vehicles; wherein the brake performance calculator is configured to send a request for data relating to the vehicle specific quantities of the vehicle to the remote server; and wherein the remote server, upon receipt of the request, is configured to identify the data relating to the vehicle specific quantities of the vehicle -24 -and to transmit the data relating to the vehicle specific quantities of the vehicle to the brake performance calculator,
23. A system as claimed in claim 22, wherein the brake performance calculator is configured to send an identifier of the vehicle to the server as part of the request for the data relating to the vehicle specific quantities of the vehicle; and wherein the remote server is configured to identify the data relating to the vehicle specific quantities of the vehicle based on the identifier.