SE528100C2 - Vehicle gear change method, by measuring parameter associated with movement of point on vehicle chassis relative to part of suspension - Google Patents

Abstract

The gear change method comprises the following steps: (1) measuring at least one parameter (z) associated with a movement of a predetermined point on the vehicle chassis relative to a predetermined part of the wheel suspension; (2) comparing the measured parameter with predetermined values for the same parameter; and (3) controlling output depending on this comparison in order to reduce movement of the driver's seat in the vertical direction.

Description

20 25 30 528 100 A possible solution appears from DE 101 23 653-A1, which describes a wheel suspension with active suspension. However, this solution requires the installation of a number of special components, which in addition to increasing complexity and service needs entail extra costs and increased vehicle weight. An active suspension of this kind usually uses sensors that measure and software that calculates how the tethering is to be controlled to achieve a certain effect. It does not compensate for variations in manufacturing tolerances and aging of components in the system.

US5832399 discloses a comfort-enhancing system where comfort reduction, due to change in acceleration in the longitudinal direction of the vehicle, is mitigated. In this arrangement, the longitudinal acceleration is measured, after which an evaluation is made of the measured values. Depending on the measured values, parameters that affect said acceleration are then controlled in such a way that the travel clutch control, torque reduction during shifting and motor torque control. felt more comfortable. Cold Item Mentioned Parameters The present invention aims to solve the above-mentioned problems by providing a method and a system which uses considerable equipment on the vehicle in a manner which can reduce said movement to a desired level.

This is done without increasing complexity, weight or cost, and requires only a minor adaptation of the software in the vehicle's electronic control system for application in a vehicle.

A system according to the invention will be insensitive to variations in manufacturing tolerances and aging of components, and will provide the desired set response during the life of the vehicle.

DISCLOSURE OF THE INVENTION The above-mentioned problems are solved by a method of motor control, according to claim i, and a system for carrying out the method, according to claim 11.

The invention relates to a method and a system for engine control with feedback from a predetermined part of the vehicle's tethering system. The system is preferably, but not necessarily, intended to be applied during a shifting process, when the vehicle and its driver's seat "sit" and "rise" due to the torque transmitted to the drive wheels, as described above. . The torque will also cause a certain simultaneous rotation of the chassis around the longitudinal axis of the vehicle. With the help of the feedback, you can determine which comfort is desired or change speed that is allowed for different vehicle combinations. An advantage of the system is that the value set is obtained regardless of varying manufacturing tolerances in the fiswing system, fising system age, or other factors. The system according to the invention adapts to changes or aging of the suspension and provides the same response throughout the vehicle's lifetime.

The required calculations can be performed by at least one electronic control unit, e.g. the vehicle's transmission control unit.

According to a first embodiment, the invention relates to a method for regulating at least one engine in a vehicle in connection with a shifting operation in a gearbox mounted between the engine and the vehicle's driving wheels, which vehicle comprises a frame and at least four wheels whose axles are connected to the frame by a in a wheel suspension included fi suspension system. The gearbox is preferably but not necessarily an automated mechanical transmission, also called AMT (automated mechanical transmission). The method preferably, but not necessarily, relates to the regulation of output motor torques and suitably comprises the following steps: - measuring at least one parameter related to a movement of a predetermined part on the vehicle frame relative to a predetermined point in the wheel suspension, - comparison between a measured value for said parameter and a first predetermined value for said parameter, - adjusting said output torque in dependence on said comparison in order to reduce the movements of the driver 's seat at least in the vertical direction. 10 15 20 25 528 100 r - The control unit further controls components in the chassis if it senses that the engine control performed does not give the desired result, or will not be sufficient.

Such a component may be an active tethering unit in the vehicle tethering system. The active suspension unit can be a hydraulically controlled damper. which in a first embodiment can be regulated if the measured value exceeds the first predetermined value after regulation of the motor. In this case, the movement between frame and wheels is limited primarily by means of motor control, whereby the active suspension is regulated secondarily. In this case, the active suspension can be controlled at the same time as the engine regulation is started, but with a gradually increasing effect. The active tethering can be regulated to maximum power as the motor control will not be sufficient to prevent the upper limit value from being exceeded.

After the comparison of said values, a signal is generated related to the movement of the vehicle frame if the measured value exceeds the first predetermined value. The signal is used to regulate the torque delivered to the gearbox.

The control is preferably made in connection with accelerator and / or accelerator when driving with the accelerator pedal and / or with a cruise control connected.

The control can also be done in connection with a shifting process in a gearbox arranged between the engine and the driving wheels of the vehicle.

According to the invention, the control unit can be arranged to regulate the outgoing motor torque during the part of the shifting operation when the driveline is made torqueless before changing the gearbox in the gearbox. The control unit can also regulate the output motor torque during the part of the shifting operation when the gearbox is reloaded with torque after changing the gearbox in the gearbox. If the movement of the frame relative to the wheel suspension changes too quickly, the system can take measures to limit the movement, which increases comfort and / or reduces discomfort for the driver. i 10 15 20 25 30 528 100 The measurement of said parameter can be performed in a number of different ways using permanent or retrofitted equipment. Preferably, the measurement is performed by means of a continuous level measurement system between the vehicle frame and the wheel suspension. Such a system comprises one or more position sensors, which are used to measure, for example, the ground clearance of the vehicle for the purpose of raising or lowering the vehicle while driving, or for raising and lowering a tractor in connection with coupling and uncoupling of trailers.

Other ways of measuring the position of the frame relative to the wheel suspension may include a position sensor in at least one shock absorber in the suspension system, a strain sensor in at least one leaf cap, or a pressure sensor in at least one pressurized air bellows in the suspension system.

The measurement of said parameter can be performed continuously by a control unit.

By feedback of the measured parameter, the engine torque can be regulated to either limit said movement to prevent an upper predetermined limit being exceeded while a shifting process with subsequent throttle (or engine braking) is in progress. Measurement and control of said parameter can of course be programmed to be performed continuously only during a switching procedure.

As the shifting process nears its end, after the driver or system has shifted up through a number of gears and the vehicle approaches the desired cruising speed, the measured parameter, for example the distance between frame and wheels, will decrease to stabilize at a constant cruising speed at one level mainly original value in the case of a stationary vehicle. corresponding to the parameter The above-mentioned first predetermined value can be adjustable between at least two pre-programmed levels. Conveniently, the driver can set the system in a first position for comfort, whereby large, rapid ut eruptions during shifting can be prevented or limited by regulating the engine. A second mode can be performance, whereby the system is completely or partially disconnected when the driver knows that high engine power will be required to achieve the desired power, for example in connection with starting and upshifting on an uphill slope with a heavily loaded vehicle. Such pre-programmed levels can be stored in a control unit and include information on the above-mentioned predetermined values and upper limit values related to the measured parameter.

Preferably, regulation of delivered torque from the engine to the gearbox takes place, depending on the measured parameter, only if the regulation does not adversely affect the drivability of the vehicle. If the control unit senses that a desired control of the engine can cause the vehicle to stop, or if it would lead to an unnecessary wear of, for example, the clutch, the control unit can choose to temporarily prioritize the control.

According to an above-described embodiment of the invention, the control of delivered torque from the engine to the gearbox is controlled in dependence on said measured parameter to counteract that the measured value of said parameter exceeds said predetermined limit value.

According to a second alternative embodiment, said active kan can be regulated if the measured value exceeds a second predetermined value, between the first predetermined value and the upper limit value. In this case, the movement between frame and wheels is limited in a first step by means of motor control, whereby the active suspension is regulated in a second step. The second step is activated only when the measured value exceeds the second predetermined value, in order to prevent the upper limit value from being exceeded.

Said active components can be controlled simultaneously with the control of the engine, in order to limit a vertical component of the movement between the wheel suspension and the frame, or controlled individually, in order to counteract the simultaneous rotation of the chassis around the longitudinal axis of the vehicle.

According to a second alternative embodiment, the control unit can control one or more additional adjustable chassis components in the vehicle. For example, an adjustable anti-roll bar can be adjusted if the measured value exceeds the first predetermined value after adjusting the motor. An anti-roll bar of this type will primarily counteract the torsional torque to which the chassis is subjected. As stated above, an adjustable chassis component can alternatively be adjusted if the measured value exceeds a second predetermined value after control of the engine.

It is also possible to let the control unit simultaneously control both the active suspension and one or more additional adjustable chassis components.

The invention also relates to a system for regulating output torque in at least one engine for driving a vehicle, which vehicle comprises a frame and at least four wheels whose axles are connected to the frame by means of a suspension system included in a wheel suspension, and a preferably, but not necessarily , automated gearbox mounted between the engine and at least a pair of driving wheels, whereby control of the engine takes place during a shifting operation in the gearbox. The vehicle further comprises a measuring device arranged to measure at least one parameter related to a movement of a predetermined point on the vehicle frame relative to a predetermined part in the wheel suspension. At least one electronic control unit is arranged to continuously regulate the output torque in dependence on said measured parameter by means of a feedback of said sensor in order to reduce vehicle movements at least in the vertical direction.

The control unit may be arranged to compare a measured value and a predetermined value stored in the control unit for said parameter, the control unit being arranged to regulate the counter torque as a function of the frame movement relative to the wheel suspension if the measured value exceeds the predetermined value.

According to one embodiment, said parameter is a distance between said points, which distance can be measured by a level sensor. The level sensor is preferably arranged between the frame and the wheel suspension. Alternatively, a position sensor arranged in a shock absorber in the vehicle's suspension system can be used. The parameter can also be estimated by measuring the air pressure in the air bellows of the suspension, or by means of strain gauges on one or more of the blades of the suspension.

The control unit is arranged to regulate the delivered torque to the gearbox in dependence on said signal so that said measured value does not exceed a predetermined, maximum limit value.

In all embodiments, it applies that all the above-mentioned predetermined values are related to a measured basic value. This basic value can be determined at one or preferably at fl times, both at a stationary vehicle or at speed while driving, preferably when the torque in the driveline is close to zero. The basic value can compensate for the current vehicle weight and the load distribution on the vehicle. In this way, the system also becomes relatively insensitive to differences in manufacturing tolerances or to the aging of individual components.

All predetermined values and limit values can also vary with regard to vehicle type, with / without turntable, tractor wheel base, vehicle combination e.g. tractor with / without trailer, and the like. These values can preferably be pre-programmed in the control unit from the manufacturer, but could also be set by a forwarder. The latter can allow individual variations and adaptation to odd or new types of vehicle combinations. lLeX.

The method according to the invention is primarily aimed at use when shifting between gears with a large gear ratio (low gears) because the torque on the drive wheels becomes large on these gears. This applies to both positive and negative engine torques. It is possible to have different sets of limit values for positive and negative motor torques.

The method and system can also be adapted for use in connection with - starting from a standstill for a vehicle with an automated gearbox. In this case, the starting process can be divided into two phases, where a first phase means that the vehicle must be raised to a speed corresponding to the engine speed. When the clutch begins to be applied, the driveline will be torqueed. To avoid unnecessary wear in the clutch and gearbox, the torque must be increased 10 15 20 25 528 100 9 controlled. The transmitted torque will increase gradually until the speed of the vehicle corresponds to the engine speed.

The second phase begins at the time when the clutch no longer slips, which in principle means that the driveline is connected and that the engine speed can be further increased to increase the vehicle's speed. As soon as the second phase has begun, the method can be applied, whereby the movement of the cab and thus the driver's seat can be damped.

It is also conceivable to connect the system to a measurement of the road slope and / or the load of the vehicle. On uphill slopes, the control unit's predetermined first and second values as well as upper limit values can be compensated with regard to slope and / or load. It may also be possible to disconnect the system if the slope of the road exceeds certain values, to avoid stops on steep uphill slopes and to achieve maximum effect when braking engines on steep descents.

The method for controlling the output torque of a motor according to the invention can be performed by executing a computer program in at least one data processor arranged in at least one control unit. within the framework of the invention, the method can be realized by means of one or your control units in the vehicle.

An inventive computer program includes program code for, with a device arranged in the vehicle, measuring in a predetermined manner at least one parameter related to a movement of a predetermined part of the vehicle frame relative to a predetermined point in the wheel suspension, comparing a measured value and a first predetermined value for said parameter, generating a signal related to the movement of the vehicle frame if the measured value exceeds the first predetermined value, and using the signal for regulating delivered torque to the gearbox, when programs are executed by at least one data processor integrated in or connected to one or more of the vehicle controllers. The inventive computer program may be stored on a medium readable by a computer system integrated in the device. This medium may be, for example, a data disk, a preferably portable memory module, a CD or the like. This can be advantageous, for example, when the software is to be downloaded to the vehicle in production and / or when the software in the vehicle is to be updated. The software can be updated, for example, at regular service occasions or, if desired, directly by a customer or freight forwarder.

The software update can also be done via a connection, for example via the Internet or a wireless network, to a server where the software is stored.

Thus, the above-mentioned computer program product may be stored as program code on a computer readable medium, or alternatively be directly loadable into an internal memory of a computer, which computer program product comprises computer programs for performing the above method when said computer program on the computer program product is executed on the computer.

In all of the above embodiments, however, the driver must in certain critical situations receive the response he expects. For example, a full swing on the accelerator pedal when starting a heavy vehicle on a steep hill must also give full throttle to the engine, whereby any other chassis components may be used to dampen the driver's movement. -In a corresponding manner, the system should be able to be disconnected and provide access to full power for engine braking in certain critical situations, for example if the driver acts on the brake pedal while the vehicle is engine braking.

DESCRIPTION OF THE DRAWINGS The invention will be described in more detail in the following, with reference to exemplary embodiments shown in the accompanying schematic drawings, in which Figure 1 shows a schematic side view of a tractor; Figure 2 shows a diagram illustrating the vertical deflection of the driver's seat over a number of gear changes; 10 15 20 25 30 528 100 11 Figure 3 shows a diagram illustrating the vertical deflection of the driver's seat over a changeover process; PREFERRED EMBODIMENTS Figure 1 schematically shows a side view of a tractor V (trailer not shown) and the forces to which it may be subjected during a thrust after shifting from a lower to a higher gear. Kraftema F, resp. F; on the front of the vehicle resp. rear wheels 1, 2 correspond to the total weight mg of the weight of the tractor and the weight of the trailer on the turntable 3. When applied, the rear drive wheels 2 act against a ground with a force Fa, which is counteracted by the force M x corresponding to the mass and acceleration of the trailer. During acceleration, these forces cause a torque around the driving rear wheel 2 which causes the vehicle cab and thus the driver's seat to rise a distance z (pitch), which during heavy acceleration and / or heavily loaded trailer can be experienced as uncomfortable by the driver. In addition to this movement, the vehicle's engine will apply a torque to a driveline running from the engine via a gearbox to a rear axle that drives the rear wheels 2. This torque causes a simultaneous rotation of the vehicle's chassis around its longitudinal axis x (roll), whereby the combined the effect is that one front corner of the cab will be raised more than the other corner. A vehicle according to the invention is preferably equipped with a control unit with at least two settings. In connection with Figure 2 are settings corresponding to "Performance". without regulation, and "Comfort". with regulation, to be described.

Figure 2 shows a diagram illustrating the vertical deflection of the driver's seat in relation to a predetermined point in the wheel suspension over a number of gear changes for an automated gearbox. From start S, a start is made from a first gear, whereby the stroke z initially increases relatively sharply from a zeroed starting position until the engine reaches a torque requested by the driver. When the requested torque is reached, the rash will stabilize at this level, after first exceeding it. At the time when the driver or the vehicle's control electronics consider it appropriate to engage a higher gear, the next shifting process is initiated. The gearbox then starts a torque deduction in order to be able to change gears in the gearbox. The torque reduction means that the driver's impact z decreases rapidly. The driver's seat's own moment of inertia means that the result z passes the zeroed starting position and temporarily becomes negative. When changing gears in the gearbox has been carried out, at times A, B, the stroke z will again increase relatively sharply from the zeroed starting position until the engine reaches the torque requested by the driver and the stroke stabilizes, as described above. As can be seen from Figure 2, the reading for the next level will be slightly lower, as shown by the difference Az. This is because the gear ratio in the gearbox has changed and the torque on the vehicle's drive wheel will be lower for each higher gear selected in the gearbox for one and the same engine torque. Without regulation, the driver's seat will thus perform relatively strong movements at each shift. In order to reduce the movement of the driver 's seat, the delivered torque of the engine can be controlled with respect to a relative movement between a predetermined point on the vehicle frame and a predetermined part in the wheel suspension of the vehicle. According to a first embodiment, at least one signal from a constant level measurement system is used. The vertical position of the driver's seat, z, is estimated using the information from the level measurement system and is used to regulate the engine torque. When applied, the stroke z increases from a zeroed basic value until it reaches a first predetermined value z1, which is shown in Figure 3. The information from the level measurement system can be the suspension stroke at each wheel. The vertical movement z of the driver's seat can in such cases be estimated with the aid of the information about the suspension travel at the wheel closest to the driver's seat.

The vertical movement z of the driver 's seat can also be estimated with the help of the information on all tethering positions together with the vehicle's geometric configuration, such as wheelbase, track gauge, position of the measuring devices and the position of the driver' s seat. In other cases, with other information from the level measurement system, the vertical movement z of the driver's seat can be estimated in a similar manner by means of information on the geometric configuration of the vehicle together with its' corrosion characteristics. A standard 10 15 20 25 30 528 100 13 configuration is a vehicle with leaf suspension at the front and air suspension at the rear, where level information is only available for the rear wheel suspension.

An output signal representing the stroke z can also be obtained from a pressure sensor in at least one of the air bellows of the vehicle. A curve for pressure over time would essentially be an inversion of the curve in Figure 2. The deflection can also be measured by means of a strain gauge on at least one of the vehicle's leaf springs, or by a position sensor on a conventional or active shock absorber.

At the stroke z1, a feedback control of the motor torque is started as a function of the stroke z. The measurement of the stroke takes place continuously, whereby the torque is controlled so that the stroke does not exceed an upper limit value 23. This limit value can be set by the driver Comfort".

The limit value 23 is thus the reading that limits the maximum torque output.

Depending on the level at which this limit value is set, regulation may in some cases be required for all gears, while a higher level only requires regulation at certain low gears.

When the driver or system indicates that a higher gear should be engaged, a torque deduction is generated again. By reducing the torque more slowly than normal, it is possible to avoid an estimate of a negative result at the end of the torque deduction. By feedbacking the stroke to the motor control, the stroke can be controlled down to zero at the same time as the torque reduction is completed or almost completed. Of course, this control may only slightly extend the time required for the shift process.

This steering gives the driver improved comfort, with only a slightly impaired acceleration caused by the control. Regulation of comfort for the driver will cease if the result of the regulation with respect to the signal would adversely affect the drivability of the vehicle.

According to a second embodiment, an output signal corresponding to a change speed is used for the movement of the driver's seat. As can be seen from Figure 3, this can be illustrated as the slope dzldt of the curve representing the variation of the rash over time. Similar to the stroke z, the engine torque can be controlled so that the amount of the change speed dz / dt does not become too large. By continuously measuring the change rate and feedback thereof, the delivered torque can be controlled so that a set upper limit value of dz / dt is not exceeded. In the same way, the delivered torque can be controlled before a torque deduction so that another limit value for dz / dt is not exceeded.

The torque deduction can also be controlled so that the result z does not become negative.

According to a further alternative embodiment of the invention, which can be applied to all of the above embodiments, is to let the control unit control additional components if it senses that the motor control being performed does not give the desired result, or will not be sufficient. An example is a vehicle with an active suspension unit in the vehicle's tethering system, which unit can consist of a hydraulically controlled damper. According to one embodiment, the active damper can be regulated if the measured value exceeds the first predetermined value z1 after control of the motor. In this case, the movement between frame and wheels is limited in the first place by means of motor control, whereby the active fi suspension is regulated in the second place.

The active suspension is controlled at the same time as the engine control is started, but with a gradually increasing effect. The active kan-suspension can be regulated to maximum power when the control unit senses that the motor control will not be sufficient to prevent the upper limit value from being exceeded.

According to an alternative embodiment, said active suspension can be regulated if the measured value exceeds a second predetermined value 22, between the first predetermined value 21 and the upper limit value 23. In this case the movement between frame and wheels is limited in a first step by means of motor control, wherein the active suspension is regulated in a second step. The second step is activated only when the measured value exceeds the second predetermined value 22, in order to prevent the upper limit value z; exceeded. According to an alternative embodiment, said active suspension can be regulated if the measured value dz / dt exceeds a predetermined value at torque application and exceeds a second predetermined value at torque deduction.

Said active components can be controlled simultaneously with the control of the engine, in order to limit a vertical component of the movement between the wheel suspension and the frame, or controlled individually on opposite sides of the vehicle, in order to counteract the simultaneous rotation of the chassis around the vehicle's longitudinal axis. In a preferred embodiment, the function is divided so that measurement of the parameter is made in the control unit connected to the vehicle's suspension system and the control of the engine torque is controlled by the control unit of the transmission.

The invention should thus not be considered to be limited to the embodiments described above, but a number of further variants and modifications are conceivable within the scope of the appended claims.

Claims (18)

10 15 20 25 528 100 16 PATENT REQUIREMENTS A method of controlling output torque from at least one vehicle engine for propelling a vehicle, said vehicle comprising a frame and at least four wheels (1, 2) whose axles are connected to the frame by a suspension system included in a wheel suspension, characterized in that the method comprises the following steps: - measuring at least one parameter (z) related to a movement of a predetermined point on the vehicle frame relative to a predetermined part of the wheel suspension, - comparison between said measured parameter (z) and a predetermined value for said parameter (z1, 22, za), - regulation of said output elements in dependence on said comparison in order to reduce the movements of the driver 's seat at least vertically, - an active suspension in the vehicle's dr suspension system is regulated and / or an adjustable chassis component in the vehicle is adjusted, in parallel or after regulation of outgoing engine torque in order to reduce the movements of the driver 's seat at least vertically. Method according to claim 1, characterized in that said regulation is made in connection with accelerator and / or accelerator when driving with accelerator pedal and / or cruise control. Method according to claim 1, characterized in that said regulation is made in connection with a shifting process in a gearbox arranged between the engine and the driving wheels of the vehicle (2). 4. A method according to claim 3, characterized in that the control unit regulates the output motor torque during the part of the shifting operation when the driveline is made torqueless before changing the gearbox in the gearbox. 10 15 20 25 30 528 100 17 5. A method according to claim 3, characterized in that the control unit regulates the outgoing motor torque during the part of the shifting operation when the gearbox is re-loaded with torque after changing the gearbox in the gearbox. Method according to claim 1, characterized in that regulation of delivered torque to the gearbox in dependence on the said comparison only takes place if the regulation does not adversely affect the drivability of the vehicle. Method according to claim 1, characterized in that the measurement of said parameter (z) is performed continuously to check that the measured parameter value does not exceed the predetermined value (21, 22. za) after the regulation of the output motor torque. Method according to claim 1, characterized in that the regulation of the outgoing motor number of the gearbox in dependence on said comparison is controlled to prevent the measured parameter value (z) from exceeding the predetermined value (zj, 22, 23). Method according to any one of the preceding claims, characterized in that said measured parameter is a rate of change of the distance between a predetermined point on the wheel suspension. framework and a predetermined part of Method according to any one of the preceding claims, characterized in that said predetermined value is adjustable between at least a first and a second pre-programmed level. System for regulating output torque from at least one vehicle engine for driving a vehicle with a frame and at least four wheels (1, 2) whose axles are connected to the frame with a suspension system included in a wheel suspension, the system comprising at least one control unit for continuous regulating the output torque of the engine based on a requested torque, sensor for measuring at least one parameter (z) related to a movement of a predetermined point on the vehicle frame relative to a predetermined part in the wheel suspension characterized in that the control unit is arranged by a feedback of said sensor 10 15 20 25 528 100 18 continuously regulate the output torque in dependence on said measured parameter (z) in order to reduce the movements of the driver 's seat at least in the vertical direction. and that the control unit is arranged to control in parallel or after the regulation of the outgoing engine torque an active suspension arranged in the vehicle in the vehicle's suspension system and / or a chassis component arranged in the vehicle in order to reduce driver movements at least vertically. System according to claim 12, characterized in that said parameter (z) is a distance between said point and said part, which distance is measured by position sensors belonging to shock absorbers in the tethering system or level sensors arranged between the frame and the wheel suspension or pressure sensors arranged in a compressed air bellows in the air suspension system. . System according to claim 12, characterized in that the control unit is arranged to regulate the output torque in dependence on said parameter (z) so that said measured parameter does not exceed a predetermined value (z1, 22, 23). 14. A system according to any one of claims 12 to 15, characterized in that the control unit is arranged to perform said control in connection with gas deduction and / or throttle application at cruise control. accelerator and / or A system according to any one of claims 12 to 15, characterized in that the control unit is arranged to perform said control in connection with a shifting process in a gearbox arranged between the engine and the driving wheels of the vehicle (2). A computer program comprising program code for performing the method of claim 1, when said computer program is executed on a computer. A computer program product comprising program code stored on a computer readable medium for performing the method of claim 1, when said computer program is executed on the computer. 528 100 19 A computer program product directly loadable into an internal memory of a computer, the computer program product comprising computer programs for performing the method of claim 1, when said computer program product is executed on the computer.