GB2540359A

GB2540359A - Engine drive control

Info

Publication number: GB2540359A
Application number: GB1512210.4A
Authority: GB
Inventors: John Hennion Duncan; Bizzarri Davide
Original assignee: McLaren Automotive Ltd
Current assignee: McLaren Automotive Ltd
Priority date: 2015-07-13
Filing date: 2015-07-13
Publication date: 2017-01-18
Anticipated expiration: 2035-07-13
Also published as: GB2540359B; GB201512210D0

Abstract

A vehicle 10 comprising: a power source or engine 12 capable of driving the vehicle; at least one drive wheel 14; a drivetrain 13 coupled between the power source and the drive wheel to transfer drive generated by the power source to the at least one drive wheel, the drivetrain having a lash-width being the rotational travel between where the drivetrain is capable of transmitting drive in one rotational direction and where the drivetrain is capable of transmitting drive in the opposite rotational direction; and a power source controller or ECU 18 configured to: control the power source in response to a throttle input and a drive demand adjustment to suppress torsional oscillations in the drivetrain; calculate a drivetrain lash-condition indicating the rotational position of the drivetrain within the lash-width; and calculate the drive demand adjustment in dependence on the drivetrain lash-condition. The vehicle may also comprise a means to determine a first and second torsional velocity which can be used to indicate the drivetrain is about to or is undergoing lash crossing. The actual drive demand adjustment may be calculated based on multiple drive demand adjustments based on different lash-conditions.

Description

ENGINE DRIVE CONTROL

This invention relates to a vehicle comprising a power source controller, and a power source controller for suppressing torsional oscillations in the drivetrain of the vehicle. A vehicle such as an automobile has a number of wheels, typically four. At least one of those wheels is typically driven by a power source. Normally, an automobile is driven by at least two of those wheels; those wheels being driven by the power source. The driven wheels can be coupled to the power source by a drivetrain. This drivetrain will generally comprise a gearbox to permit the drive wheels to be driven at a range of speeds greater than the standard speed range of the power source. The drivetrain may also comprise a differential to split the drive originating from the power source, potentially via the gearbox, to drive more than one wheel.

The drivetrain typically exhibits torsional compliance meaning that, when the power source produces a torque to rotate the drive wheels via the drivetrain, the drivetrain can twist in the drive direction during its torque transmission between the power source and the drive wheels. This torsional compliance typically results from two sources: lash in the gearing present in the drivetrain, and the elastic response of the drivetrain to twisting.

The drivetrain can comprise one or more meshed gears. These meshed gears may be found in the gearbox, differential and any other power transmission device present in the drivetrain. Typically these meshed gears will be configured to have an amount of lash between their forward and reverse drive states. I.e. an amount of rotational travel between the position where the meshed gears can transmit drive in one direction and the position where the meshed gears can transmit drive in the opposite direction. Lash may be present in the system to permit gears to be engaged and disengaged smoothly and also to reduce wear on the contact surfaces of the gears. The lash of the meshed gears can be combined together to give the amount of lash that is present in the drivetrain for a particular configuration of the power transmission devices present within the drivetrain. The lash of the drivetrain can therefore be the amount of rotational travel of one end of the drivetrain relative to the other end of the drivetrain between the position where the drivetrain can transmit drive in one direction and the position where the drivetrain can transmit drive in the opposite direction. The amount of lash may alter depending on the particular configuration of the power transmission devices present within the drivetrain, for instance the gearbox may use fewer gears when in one drive mode than another and so the total lash may be reduced, alternatively different drive modes may use gears that have different amounts of lash.

The drivetrain also typically exhibits elasticity which means that, when the power source produces a torque to rotate the drive wheels via the drivetrain, the drivetrain can twist in the drive direction during its torque transmission between the power source and the drive wheels. It will be appreciated that the torque transmission may be from the power source to the drive wheels, i.e. when the power source is producing a positive torque to drive the drive wheels, or from the drive wheels to the power source, i.e. when the power source is producing a negative torque to retard the drive wheels. Therefore the drivetrain can twist in two rotational directions depending on the torque generated by the power source.

The torsion and/or lash in the drivetrain can store energy provided by the torque of the power source and/or drive wheels. When the power source transitions between being a torque producer and a torque consumer the drivetrain may transition between being twisted up and/or in a forward drive lash state, where the gears lash against the drive side of the gears, and twisted down and/or in a reverse drive lash state, where the gears lash against the idle side of the gears. This transition can lead to vibrations in the drivetrain as the stored energy causes the over-twisting of the drivetrain which then unwinds, which in an undamped state can lead to oscillations between an undertwisted and over-twisted state of the drivetrain. These vibrations are commonly known as jerk in the drive of the vehicle.

Conventional systems to combat drivetrain jerk monitor the rotational speed of the power source. The raw rotational speed of the power source can be high pass filtered and then compared to historic power source speeds to work out a correction to the power source speed that can aid in damping of the bumps and oscillations in the drive train caused by a change in torque of the power source. There is the potential for lag in the response of such a system due to the use of historic engine speed data that may not be relevant to current torque delivery conditions of the power source.

An alternative system is described in US 4,713,763, this models the drivetrain of a vehicle as having two flywheels joined by a drive shaft. The first flywheel is taken to be the engine flywheel and the second flywheel represents the vehicle mass. The document describes that there can be a difference between the angular velocity of the first flywheel relative to the second flywheel and that there can be an angle of twist on the drive shaft between the two flywheels. The angle of twist is caused by the torque being transmitted via the drive shaft. The angle of twist of the drive train is used, together with any difference in the angular velocity of the two flywheels, to regulate the fuel injection of the engine to modify the torque of the engine to supress the vibrations in the drive train.

There is potential for these systems to over adjust the torque delivery of the power source to damp the potential vibrations in the drivetrain which can reduce the amount of torque available from the power source to drive the vehicle. This reduction can have an impact on the performance of the power source which can lower the efficiency of the vehicle, and also the performance of the vehicle. This is particularly important in high performance vehicles where high power and torque delivery with good response times in particularly important. These systems can also reduce the responsiveness of the power source which is, again, undesirable.

There is therefore a need for an alternative power source control system for a vehicle that can damp drivetrain vibrations.

According to a first aspect of the present invention there is provided a vehicle comprising: a power source capable of driving the vehicle; at least one drive wheel; a drivetrain coupled between the power source and the drive wheel to transfer drive generated by the power source to the at least one drive wheel, the drivetrain having a lash-width being the rotational travel between where the drivetrain is capable of transmitting drive in one rotational direction and where the drivetrain is capable of transmitting drive in the opposite rotational direction; and a power source controller configured to: control the power source in response to a throttle input and a drive demand adjustment to supress torsional oscillations in the drivetrain; calculate a drivetrain lash-condition indicating the rotational position of the drivetrain within the lash-width; and calculate the drive demand adjustment in dependence on the drivetrain lash-condition.

The drivetrain may comprise a plurality of drivetrain configurations, each drivetrain configuration having a respective lash-width, and the power source controller being configured to calculate the drivetrain lash-condition indicating the rotational position of the drivetrain within the lash-width of the current drivetrain configuration. Each drivetrain configuration may have a different drive ratio between the end of the drivetrain coupled to the power source and the end of the drivetrain coupled to the drive wheel.

The drive demand adjustment may be an actual drive demand adjustment, and the power source controller may be configured to control the power source in response to the throttle input and the actual drive demand adjustment, and the power source controller may be further configured to calculate a first drive demand adjustment and a second drive demand adjustment and calculate the actual drive demand adjustment based on the first drive demand adjustment, second drive demand adjustment and the drivetrain lash-condition.

The power source controller may be configured to calculate the actual drive demand adjustment as the first drive demand adjustment when the drivetrain lash-condition indicates the rotational position of the drivetrain is near the middle of the lash-width; and calculate the actual drive demand adjustment as the second drive demand adjustment when the drivetrain lash-condition indicates the rotational position of the drivetrain is near the end of the lash-width. The power source controller may be configured to calculate the actual drive demand adjustment as the first drive demand adjustment when the drivetrain lash-condition indicates the rotational position of the drivetrain is approaching the middle of the lash-width; and calculate the actual drive demand adjustment as the second drive demand adjustment when the drivetrain lash-condition indicates the rotational position of the drivetrain is approaching the end of the lash-width. The power source controller may be configured to calculate the actual drive demand adjustment as the first drive demand adjustment when the drivetrain lash-condition indicates the rotational position of the drivetrain is at the middle of the lash-width; and calculate the actual drive demand adjustment as the second drive demand adjustment when the drivetrain lash-condition indicates the rotational position of the drivetrain is at the end of the lash-width.

The power source controller may be configured to calculate the actual drive demand adjustment based on the first drive demand adjustment and second drive demand adjustment in proportion to the drivetrain lash-condition.

The vehicle may comprise a first drivetrain sensor configured to measure a first angular velocity of the drivetrain at a first position on the drivetrain, and a second drivetrain sensor configured to measure a second angular velocity of the drivetrain at a second position on the drivetrain, and wherein the power source controller may be configured to calculate a torsion velocity of the drivetrain in dependence on the first angular velocity and the second angular velocity.

The drivetrain may have at least one drive ratio between the first and second positions and the power source controller may be configured to calculate the torsion velocity of the drivetrain in dependence on the current drive ratio of the drivetrain. The power source controller may be configured to calculate the torsion velocity by adjusting one of the first angular velocity and the second angular velocity by the drive ratio and taking the difference between the adjusted angular velocity and the other of the angular velocities. The power source controller may be configured to calculate a torsion velocity for the drivetrain, and determine a lash-crossing event in dependence on the torsion velocity.

The throttle input may indicate the driver-requested power source drive level, and the power source controller may be configured to determine a lash-crossing event in dependence on the driver-requested engine drive amount indicating that the power source should transition between a drive producer and a drive consumer. The power source controller may be configured to initiate control of the power source, in response to a throttle input and a drive demand adjustment, in response to the lash-crossing event indicating a change in direction of the drivetrain lash-condition.

The present invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

Figure 1 shows a schematic diagram of a vehicle.

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

The present invention relates to a vehicle that comprises a power source. The power source is capable of driving the vehicle. In other words, the power source is capable of providing motive power to the vehicle. The vehicle also comprises at least one drive wheel and a drivetrain coupled between the power source and the drive wheel. The drivetrain is configured to transfer drive and/or torque generated by the power source to the at least one drive wheel. The drivetrain has a lash-width associated with it. The lash-width being the amount of rotational travel between where the drivetrain is capable of transmitting drive in one rotational direction and where the drivetrain is capable of transmitting drive in the opposite rotational direction. The rotational travel can be embodied by the drivetrain twisting under torsion from the power source at one end and the drive wheel at the other end.

The vehicle also comprises a power source controller that is configured to supress torsional oscillations in the drivetrain. The power source controller controls the power source in response to a throttle input and a drive demand adjustment. The drive demand adjustment providing the adjustment to the drive demand associated with the throttle input at a given time required to suppress the torsional oscillations. The power source controller is configured to calculate the drive demand adjustment in dependence on a drivetrain lash-condition, which is calculated by the power source controller as indicating the rotational position of the drivetrain within the lash-width.

Figure 1 illustrates a vehicle 10. The vehicle comprises a body 11. The vehicle has a power source 12. The power source 12 provides mechanical drive, via a drivetrain 13, to one or more drive wheels 14 of the vehicle. The drivetrain 13 may comprise one or more transmission devices, such as a gearbox 15 and differential 16 as illustrated in Figure 1. The drivetrain 13 may also comprise one or more driveshafts, shown in figure 1 as 17a to 17d. Driveshafts 17a, 17b may couple the power source 12 to the one or more power transmission devices 15, 16 to provide mechanical drive to those devices. Driveshafts 17c, 17d may couple a power transmission device 16 to the drive wheels 14. As illustrated in figure 1, the power source 12 is coupled to the gearbox 15 by a first driveshaft 17a, the gearbox 15 is coupled to the differential 16 by driveshaft 17b and differential 16 is coupled to one or more drive wheels by driveshafts 17c and 17d. Whilst the gearbox 15 and differential 16 are illustrated as two devices in figure 1, it will be appreciated that they may be combined in to one power transmission device. Gearbox 15 may be releasably coupled to the power source by one or more clutches. The clutch(es) can independently engage and disengage the drive from engine 12 to gearbox 15 and the other components of the drivetrain 13 located along the drivetrain 13. These clutches may be comprised in gearbox 15. The clutches and gearbox may be configured as a dual-clutch transmission 15 (DCT).

In this example the vehicle 10 has an internal combustion engine (ICE) 12. However, the vehicle could alternatively be driven by other power sources. For example, it could be a hybrid vehicle in which an ICE is supplemented by another power source such an electric motor, or it could be an electric only vehicle. In each case the power source can be controlled to alter the torque that is provided by the power source.

Within the body is a seat 21 for a driver. When a driver is sat in the seat 21 he can reach a throttle pedal 22 with his foot. The throttle pedal is pivotable about its rearmost end relative to the body of the vehicle. Its forward end is biased upwardly by spring 23 to an uppermost position where it hits a stop, and can be pressed down by the driver’s foot to a lowermost position where it hits another stop. The pedal is thus constrained to be movable only between the uppermost position (“0%”) and the lowermost position (“100%”). A position detector 24 is attached to the pedal and senses the angle of deflection of the pedal. It will be appreciated that other throttle controls could be used instead of the throttle pedal 22 to gather the target drive demand from the engine requested by the driver. For instance, the vehicle could comprise a hand operated control as a throttle control.

The operation of the engine 12 is regulated by an ECU 18. The ECU comprises a processor 19 and a non-volatile memory 20. The memory stores a set of program instructions that are executable by the processor, and reference data such as look-up tables that can be referenced by the processor in response to those instructions. The processor may be configured to operate in accordance with a computer program stored in non-transitory form on a machine readable storage medium. The computer program may store instructions for causing the processor to perform the determination step and/or the control and/or the calculation in the manner described herein.

The ECU is coupled to the position detector 24 to receive from it the detected position of the throttle pedal. The ECU is coupled to the engine to receive from it data relating to the operation of the engine, such as current RPM and inlet air temperature, and to transmit to the engine control information that will regulate the operation of the engine. That control information could, for example, include the amount of fuel and/or air to be charged in each inlet stroke, valve and ignition timings and turbo boost level.

The program instructions stored by the memory define a mechanism whereby the ECU can determine a set of output parameters for controlling the engine in response to a set of input parameters it has received and/or computed. In the present example, the ECU follows a two-stage process to determine the output parameters. First, in response to at least some of the input parameters (including throttle position and a representation of throttle direction) the ECU determines a target drive demand from the engine. The drive demand can conveniently be a torque demand, but it could be expressed in other ways such as power demand or fuel burned per unit time. Second, using a pre-stored model of the behaviour of the engine the ECU determines the outputs needed to cause the engine to satisfy that drive demand. It then transmits those outputs to the engine to cause the engine to behave in accordance with the computed drive demand. These stages are repeated frequently: typically 20 or more times per second, to generate a series of output values reflecting up-to-date input values.

Whilst the vehicle above is described as being powered by an internal combustion engine (ICE), as noted the vehicle could be driven in another way. For example it could be a hybrid vehicle in which an ICE is supplemented by another power source such as an electric motor, or it could be an electric only vehicle. In each case the ECU can control the power source, or each power source, to arrange that it or they in combination provide the desired drive in response to throttle position

The current RPM of the engine may be provided to the ECU 18 by a first drivetrain sensor 25. The first drivetrain sensor 25 may be configured to measure the current RPM of the power source 12. The first drivetrain sensor 25 may be an engine crank position sensor. The engine crank position sensor measures the time taken for a point on the crank to rotate 360 degrees back to a starting position. This duration can be used to calculate the current power source speed. The ECU 18 may be coupled to the first drivetrain sensor 25 to receive from it the detected power source revolution speed.

The ECU 18 may also be coupled to a second drivetrain sensor 26. The second drivetrain sensor 26 may be configured to measure the current wheel speed of one or more drive wheels 14. The second drivetrain sensor 26 may measure the time taken for one revolution of the driveshaft 17c that is connected to one or more drive wheels. The second drivetrain sensor 26 or the ECU 18 may use this to calculate the current wheel speed using a known wheel size. In this way, the ECU 18 may be coupled to the second drivetrain sensor 26 to receive from it the detected drive wheel revolution speed.

More generally, the first drivetrain sensor 25 may be configured to measure the (first) angular velocity at a first position on the drivetrain 25 and the second drivetrain sensor 26 may be configured to measure the (second) angular velocity at a second position on the drivetrain 25. The current angular velocity at each of the two positions is reported to the ECU 15. This reporting may occur frequently, for instance many times per second.

The first angular velocity and second angular velocity may be used by the ECU 18 to calculate a drive demand adjustment to the current drive demand of the engine 12. The drive demand adjustment being calculated to reduce or remove drivetrain oscillations caused by drivetrain torsional compliance.

The first angular velocity and second angular velocity may be processed by the ECU 18 to derive the relative rotational motion of the second position relative to the first position. As discussed above, the drivetrain 25 exhibits torsional compliance and so at any given moment there may be a difference in the relative rotational motion, or relative angular velocity, between the two positions on the drivetrain 25. This difference is due to the drivetrain twisting-up or twisting-down relative to the rotational direction of the drivetrain 25 and movement across any lash present in the drivetrain at that moment. As mentioned above, there may be power transmission devices 15, 16 comprising gearing to alter the rotational velocity of the drivetrain 13 across the power transmissions device 15, 16. Therefore, the ECU 18 may be configured to process the difference in relative angular velocity to include a correction for the gear ratios present in the power transmission devices between the first position and the second position. The relative angular velocity between the two positions on the drivetrain, once corrected for any gear ratio across that part of the drivetrain, gives the velocity at which the drivetrain is twisting-up or twisting-down, or in other words the velocity of the torsion in the drivetrain. This relative angular velocity can be usefully referred to as the torsion velocity of the drivetrain between the first position and the second position because it provides the speed, and direction, at which the drivetrain is twisting.

The ECU 18 may be configured to receive an input parameter from the gearbox 15 which is the current drive gear of the gearbox 15. The ECU 18 can use the current drive gear of the gearbox 15 to calculate the gear ratio across the drivetrain 13. The ECU 18 may calculate the current gear ratio across the drivetrain 13 by referring to a look-up table of gear ratios for the different drive gears of the gearbox 15. The lookup table may be stored in memory 19. The other power transmission devices, such as a differential 16, may have a fixed gear ratio.

The ECU 18 is configured to calculate the drive demand adjustment in dependence on the torsion velocity of the drivetrain. The ECU 18 may be configured to calculate drive demand adjustments in dependence on the torsion velocity of the drivetrain to reduce, supress and/or inhibit oscillations in the torsion velocity. The ECU 18 may be configured to calculate the difference between the measured torsion velocity and a desired torsion velocity and use a predetermined proportion of that difference to calculate the drive demand adjustments. The predetermined proportion may be a predetermined correction factor. This correction factor may be a proportional gain. The desired torsion velocity may be calculated dynamically or may be a fixed value. The fixed value may be zero, i.e. the ECU 18 is configured calculate drive demand adjustments to move the torsion velocity towards zero.

It has been identified that the drivetrain exhibits a different response to the drive demand adjustments depending on the lash condition of the drivetrain.

As discussed above, the drivetrain may comprise one or more meshed gears that can each be configured with an amount of lash between their drive surfaces. These lash amounts for each gear can be combined to give the lash amount of the drivetrain between the first and second positions. The drivetrain therefore has an amount of rotational travel between the position where the drivetrain is capable of transmitting drive in one direction and the position where the drivetrain is capable of transmitting drive in the opposite direction. The rotational travel can be expressed as the rotational angle between the two drive transmission directions. This rotational travel can be expressed in radians. The rotational travel may be the lash-width of the current configuration of the drivetrain 13. The lash condition can therefore be described as whether the drivetrain is currently capable of transmitting drive.

When the drivetrain is mid-lash, and thus not capable of transmitting drive, the power source is, in effect, disconnected from the load generated by the drive wheels. It has been identified that this means that the power source is much more responsive during this period to drive demand adjustments. This may mean, for instance, that a smaller amount of drive demand adjustment is required during this intermediate period to mean that drive is smoothly taken up when the drivetrain approaches a rotational position where it can transmit drive. I.e. a post-lash position. Therefore, different levels of drive demand adjustments can be used during the periods where the drivetrain 13 is undergoing a lash-crossing, and the periods where the drivetrain 13 is transmitting drive between the power source 12 and the drive wheels 14.

The ECU 18 can therefore be configured to detect a lash-crossing period for the drivetrain, and in response to this lash-crossing period calculate the drive demand adjustment in dependence on a different predetermined correction factor. There may be a predetermined correction factor for when the drivetrain is capable of transmitting drive (drivetrain in-contact position) and another predetermined correction factor for when the drivetrain is not capable of transmitting drive (drivetrain non-contact position). The ECU 18 may be configured to use both predetermined correction factors during a lash-crossing period in proportion to the position across the lashcrossing.

The ECU 18 may determine that the drivetrain 13 is predicted to undergo a lashcrossing using one or more of the following parameters: - The ECU 18 can be configured to store, in memory 19, a lash-width for each configuration of the drivetrain 13. For instance, as discussed above, the drivetrain may comprise a gearbox 13 and so there may a different lash-width for the drivetrain 13 depending on the particular gear radio that is selected by the gearbox 13. The lash-width may comprise the angular rotation of the drivetrain to move from being capable of transmitting drive in one direction to being capable of transmitting drive in the other direction. The lash-width(s) may be configurable by the ECU 18, for example, because over time the gears in the drivetrain may wear and the lash-width increase. Therefore, the ECU 18 may be able to detect the end points of the lash-width (the positions where significantly greater resistance is provided by the drivetrain against the drive of the power source) and thus reconfigure the lash-width(s) in response to this determination. - The torsion velocity of the drivetrain 13. The torsion velocity may be used to determine a change in direction of the torsion on the drivetrain 13, by virtue of a change in direction of the torsion velocity. The change in direction of the torsion indicates that the drivetrain 13 is about to, or is undergoing, a lashcrossing. - The driver demanded engine drive amount. This may be the target drive demand calculated by the ECU 15 in response to input parameters including the throttle position. This is can be calculated by the ECU 15 as discussed above in dependence on input provided by a driver-operated throttle control 22. The driver demanded engine drive amount may be calculated by the ECU 15 as a driver demanded engine torque.

The ECU 18 may be configured to detect a drivetrain lash-crossing in response to the driver-requested engine drive demand crossing zero. The engine drive demand crossing zero may indicate that the engine is now required to provide torque or power to the drivetrain 13, and thus the drive wheels 14, to drive the wheels. Alternatively, that the engine is now required to consume torque or power from the drivetrain, and thus the drive wheels, to provide engine-braking. The engine drive demand crossing zero may be described as the engine drive demand transitioning between a positive and negative drive demand.

Once a lash-crossing has been detected by the ECU 18, the lash-crossing can be calculated in dependence on the current lash-width of the drivetrain and the torsion velocity of the drivetrain. The ECU 18 can determine the position of the drivetrain through the lash-crossing independence on these two parameters. This can be calculated as the drivetrain rotating through the lash-width at the torsion velocity. The ECU 18 may be configured to output a lash-crossing factor indicating the position of the drivetrain relative to the non-contact position and the in-contact position. The non-contact position being the point where the drivetrain cannot transmit power and the incontact position being the point where the drivetrain can transmit maximum power. The ECU may be configured to calculate the lash-crossing factor in the range from zero to one. Zero may indicate the drivetrain is in the non-contact position and one may indicate the drivetrain is in the contact position, or vice-versa.

The ECU 18 may be configured to calculate the lash-crossing factor non-linearly with respect to the lash-width. The ECU 18 may be configured to use a lash-crossing map to output the lash-crossing factor in dependence on the position of the drivetrain across the lash-width. The ECU 18 may be configured to calculate the lash-crossing factor so that it approaches the in-contact position exponentially.

The lash-crossing factor can be used by the ECU 18 to calculate the drive demand adjustment. The ECU 18 may calculate the drive demand adjustment in dependence on the lash-crossing factor. The ECU 18 may be configured to calculate a first drive demand adjustment for the drivetrain non-contact position and a second drive demand adjustment for the drivetrain in-contact position. The ECU 18 can use a proportion of the first drive demand adjustment and second drive demand adjustment in dependence on the lash-crossing factor to calculate the actual drive demand adjustment.

The ECU 18 may calculate both the first drive demand adjustment and the second drive demand adjustment and then calculate a weighted sum of the first drive demand adjustment and the second drive demand adjustment in dependence on the lashcrossing factor.

In the case that the ECU is configured to calculate the lash-crossing factor in the range from zero to one, and zero indicates the drivetrain is in the non-contact position and one indicates the drivetrain is in the contact position. The ECU 18 may be configured to calculate the actual drive demand adjustment by summing the multiplication of the first drive demand adjustment by one minus the lash-crossing factor and multiplication of the second drive demand adjustment by the lash-crossing factor.

In the case that the ECU is configured to calculate the lash-crossing factor in the range from zero to one, and one indicates the drivetrain is in the non-contact position and zero indicates the drivetrain is in the contact position. The ECU 18 may be configured to calculate the actual drive demand adjustment by summing the multiplication of the first drive demand adjustment by the lash-crossing factor and multiplication of the second drive demand adjustment by one minus the lash-crossing factor.

It will be appreciated that the minus one in the above two cases could be replaced by the maximum value of the lash-crossing factor.

As discussed above, the ECU 18 may be configured to calculate the difference between the measured torsion velocity and a desired torsion velocity and use a predetermined proportion of that difference to calculate the drive demand adjustments. The predetermined proportion may be a predetermined correction factor. The first drive demand adjustment may be calculated in dependence on a first correction factor and the second drive demand adjustment may be calculated in dependence on a second correction factor. The first correction factor may be set to take in to account that the drivetrain produces less rotational resistance during the mid-part of the lashcrossing than when the drivetrain is in the in-contact position. Similarly, the second correction factor may be set to take in to account that the drivetrain produces more rotational resistance when the drivetrain is in the in-contact position relative to the non-contact position. The first and second correction factors may be first and second proportional gains. The first and second correction factors may be different.

This configuration is advantageous because the rotational inertia being controlled during lash crossing is different to that during in-contact operation. During a lashcrossing the main contribution to rotational inertia is provided by the engine inertia because the engine 12 is momentarily disconnected from the rest of the drivetrain. During in-contact operation, i.e. when power/torque is being transferred by the drivetrain from the power source to the drive wheels 14, the rotational inertia is provided by a combination of the engine rotational inertia, the drivetrain rotational inertia and the vehicle longitudinal inertia reflected in to the rotational domain. The vehicle longitudinal inertia being the inertia provided by the moving mass of the vehicle 10 which is transferred in to the rotational domain via the drive wheels 14 of the vehicle acting against the drive surface of the vehicle 10.

Using the above described techniques, the ECU 18 can smoothly adjust the drive demand adjustment during the lash crossing between the drive adjustment that is needed to control the rotational inertia mid-lash transition and the drive adjustment that is needed to control the drivetrain inertia post-lash crossing.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1. A vehicle comprising: a power source capable of driving the vehicle; at least one drive wheel; a drivetrain coupled between the power source and the drive wheel to transfer drive generated by the power source to the at least one drive wheel, the drivetrain having a lash-width being the rotational travel between where the drivetrain is capable of transmitting drive in one rotational direction and where the drivetrain is capable of transmitting drive in the opposite rotational direction; and a power source controller configured to: control the power source in response to a throttle input and a drive demand adjustment to supress torsional oscillations in the drivetrain; calculate a drivetrain lash-condition indicating the rotational position of the drivetrain within the lash-width; and calculate the drive demand adjustment in dependence on the drivetrain lash-condition.

2. A vehicle as claimed in claim 1, wherein the drivetrain comprises a plurality of drivetrain configurations, each drivetrain configuration having a respective lash-width, and the power source controller being configured to calculate the drivetrain lash-condition indicating the rotational position of the drivetrain within the lash-width of the current drivetrain configuration.

3. A vehicle as claimed in claim 2, wherein each drivetrain configuration has a different drive ratio between the end of the drivetrain coupled to the power source and the end of the drivetrain coupled to the drive wheel.

4. A vehicle as claimed in any preceding claim, wherein the drive demand adjustment is an actual drive demand adjustment, and the power source controller is configured to control the power source in response to the throttle input and the actual drive demand adjustment, and the power source controller is further configured to calculate a first drive demand adjustment and a second drive demand adjustment and calculate the actual drive demand adjustment based on the first drive demand adjustment, second drive demand adjustment and the drivetrain lash-condition.

5. A vehicle as claimed in claim 4, wherein the power source controller is configured to calculate the actual drive demand adjustment as the first drive demand adjustment when the drivetrain lash-condition indicates the rotational position of the drivetrain is near the middle of the lash-width; and calculate the actual drive demand adjustment as the second drive demand adjustment when the drivetrain lash-condition indicates the rotational position of the drivetrain is near the end of the lash-width.

6. A vehicle as claimed in claim 4 or 5, wherein the power source controller is configured to calculate the actual drive demand adjustment based on the first drive demand adjustment and second drive demand adjustment in proportion to the drivetrain lash-condition.

7. A vehicle as claimed in any preceding claim, the vehicle comprising a first drivetrain sensor configured to measure a first angular velocity of the drivetrain at a first position on the drivetrain, and a second drivetrain sensor configured to measure a second angular velocity of the drivetrain at a second position on the drivetrain, and wherein the power source controller is configured to calculate a torsion velocity of the drivetrain in dependence on the first angular velocity and the second angular velocity.

8. A vehicle as claimed in any preceding claim, wherein the drivetrain has at least one drive ratio between the first and second positions and the power source controller is configured to calculate the torsion velocity of the drivetrain in dependence on the current drive ratio of the drivetrain.

9. A vehicle as claimed in claim 8, wherein the power source controller is configured to calculate the torsion velocity by adjusting one of the first angular velocity and the second angular velocity by the drive ratio and taking the difference between the adjusted angular velocity and the other of the angular velocities.

10. A vehicle as claimed in any preceding claim, wherein the power source controller is configured to calculate a torsion velocity for the drivetrain, and determine a lash-crossing event in dependence on the torsion velocity.

11. A vehicle as claimed in any preceding claim, wherein the throttle input indicates the driver-requested power source drive level, and the power source controller is configured to determine a lash-crossing event in dependence on the driver-requested engine drive amount indicating that the power source should transition between a drive producer and a drive consumer.

12. A vehicle as claimed in claims 10 or 11, wherein the power source controller is configured to initiate control of the power source, in response to a throttle input and a drive demand adjustment, in response to the lash-crossing event indicating a change in direction of the drivetrain lash-condition.

13. A vehicle substantially as herein described with reference to the accompanying drawings.