GB2553265B

GB2553265B - Oscillation controller and control method

Info

Publication number: GB2553265B
Application number: GB1610822.7A
Authority: GB
Inventors: Owen Simon; Richards Karl
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2016-06-21
Filing date: 2016-06-21
Publication date: 2019-08-14
Anticipated expiration: 2036-06-21
Also published as: DE112017003063T5; WO2017220313A1; GB201610822D0; GB2553265A

Description

OSCILLATION CONTROLLER AND CONTROL METHOD

TECHNICAL FIELD

The present disclosure relates to an oscillation controller. Particularly, but not exclusively, the invention relates to an oscillation controller for controlling oscillation of at least one wheel of a vehicle. Aspects of the invention relate to a controller, to a system, to a vehicle and to a method.

BACKGROUND

Out of balance vehicle wheels cause a variety of issues for vehicles, regardless of the cause, which might be, for example, soiling of the wheel. Soiling of the wheel includes situations wherein a deposit of material becomes attached non-uniformly to the wheel at one position unevenly, causing the wheel to be unbalanced. The material might be, for example, ice, mud or some other deposit. In cold weather conditions, a wheel may become soiled with a block of ice. During wet weather, for example, a vehicle wheel may become soiled with mud when operating on muddy terrain. Generally, soiling of a vehicle wheel may be less of a problem if the material is deposited in a substantially uniform thickness around the circumference of the wheel. However, at least some of the deposit may melt or fall off, for example during harsh braking, leaving a non-uniform deposit on part of the wheel. The non-uniform deposit, which may have a mass of, for example, 50-500g, is an eccentric weight on the wheel, resulting in imbalance of the wheel.

As the unbalanced wheel rotates, it oscillates; the unbalanced wheel is repeatedly displaced vertically due to the extra weight attached to the wheel forcing the whole wheel assembly up and down. Vibrations from wheel oscillation of this nature may be transmitted to the structure of the vehicle. Such vibrations are noisy, unpleasant and uncomfortable, as they are felt by the vehicle occupants in the cabin. Generally, oscillation of a front wheel is felt significantly through the steering wheel, whilst oscillation of a rear wheel is felt through the whole vehicle.

It is an aim of the present invention to address disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a controller, a system, a vehicle, a method and computer software as claimed in the appended claims.

According to an aspect of the invention, there is provided a wheel oscillation controller for a vehicle, configured to mitigate an out of balance wheel, the controller comprising: input means for receiving one or more signals indicative of oscillation of at least one wheel of the vehicle; processing means for determining whether the oscillation of the at least one wheel exceeds an oscillation limit; and output means to provide a signal to control an adaptive suspension damper associated with the at least one wheel to reduce the oscillation of the at least one wheel, wherein said signal to control the adaptive suspension damper is a signal configured to variably adapt the adaptive suspension damper throughout a rotation of the at least one wheel. An advantage of this aspect is that wheel oscillation can be adaptively controlled to mitigate the effects of an out of balance wheel.

In some embodiments, there is provided a controller as described above, wherein: said input means for receiving one or more signals indicative of oscillation of at least one wheel of the vehicle comprises an electronic processor having an electrical input for receiving said one or more signals; and an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, wherein said processing means for determining whether the oscillation of the at least one wheel exceeds an oscillation limit comprises the electronic processor being configured to access the memory device and execute the instructions stored therein such that it is operable to detect whether the at least one wheel exceeds an oscillation limit based on the one or more signals.

In some embodiments, a vehicle may comprise a plurality of adaptive suspension dampers, each adaptive suspension damper individually associated with a wheel of the vehicle. Each adaptive suspension damper can be individually controlled. Alternatively, two or more of the adaptive suspension dampers can be controlled concurrently, such as according to the same control signal. Advantageously, this enables more specific adaptation of the adaptive suspension dampers.

In an embodiment, said signal to control the adaptive suspension damper is a signal configured to control a stiffness of the adaptive suspension damper in response to the oscillation of the wheel. In this way, the rise and fall of the wheel may advantageously be controlled to reduce or remove the effects of an out of balance wheel.

In an embodiment, said signal is configured to control the stiffness of the adaptive suspension damper at a frequency corresponding to the oscillation of the wheel. This advantageously enables synchronous adaptation of the adaptive suspension damper with wheel oscillation.

In an embodiment, said adaptive damper is a dashpot system having a magnetorheological fluid and magnetic means for applying a magnetic field across the magnetorheological fluid to control a viscosity of the magnetorheological fluid, and said magnetic field is dependent on the signal provided by the output means. Advantageously, the magnetorheological dampers allow for quicker adaptive response to the signal provided by the output means than other suspension means.

Optionally, the one or more signals indicative of wheel oscillation comprise a wheel signal indicative of wheel speed relative to input torque and wherein said processing means is configured to compare said signal with an expected relationship between wheel speed and input torque to determine whether the oscillation of the at least one wheel exceeds the oscillation limit. This advantageously enables accurate determination of whether the oscillation of the at least one wheel exceeds the oscillation limit.

In some embodiments, said one or more signals may comprise a signal received from a stability control system (SCS). Alternatively, the wheel speed signal may be obtained otherwise than from the SCS. Advantageously, the one or more signals may comprise any one or more of a variety of signals, received from a variety of sources.

Optionally, the controller is configured to determine which wheel of a plurality of wheels of the vehicle is oscillating by comparing a frequency of wheel oscillation relative to a steering angle of the vehicle. This provides the advantage of more specific control of the adaptive suspension damper for a specific wheel.

According to another aspect of the invention, there is provided a vehicle comprising the controller as hereinabove described.

According to another aspect of the invention, there is provided a wheel oscillation control method for a vehicle, the method comprising: receiving one or more signals indicative of oscillation of at least one wheel of the vehicle; determining whether oscillation of the at least one wheel exceeds an oscillation limit; controlling an adaptive suspension damper associated with the at last one wheel to reduce the oscillation of the at least one wheel, wherein controlling the adaptive suspension damper comprises variably adapting the adaptive suspension damper throughout a rotation of the at least one wheel. In this way, wheel oscillation can advantageously be adaptively controlled to mitigate the effects of an out of balance wheel. The controller can advantageously control the level of vibration and noise transmitted to the vehicle cabin, providing a comfortable environment for any vehicle occupant(s).

In an embodiment, said controlling comprises controlling stiffness of the damper in response to the oscillation of the wheel. In this way, the rise and fall of the wheel may advantageously be controlled to reduce or remove the effects of an out of balance wheel.

Optionally, said controlling comprises controlling the stiffness of the adaptive suspension damper at a frequency corresponding to the oscillation of the wheel. This advantageously enables synchronous adaptation of the adaptive suspension damper with wheel oscillation.

In an embodiment, the adaptive suspension damper comprises a magnetorheological damper and said controlling comprises applying, removing, increasing, reducing or maintaining a magnetic field across the damper to modify the stiffness of the damper, in response to the oscillation of the wheel. Advantageously, modifying the stiffness of the damper minimises transmission to the vehicle cabin of vibrations resulting from wheel oscillation. The magnetorheological dampers advantageously allow for quicker adaptive response to the signal provided by the output means than other suspension means.

Optionally, the one or more signals indicative of wheel oscillation comprise a wheel signal indicative of wheel speed relative to input torque and wherein said method comprises comparing said signal with an expected relationship between wheel speed and input torque to determine whether the oscillation of the at least one wheel exceeds the oscillation limit.

The method may comprise determining which wheel of a plurality of wheels of the vehicle is oscillating by comparing a frequency of wheel oscillation relative to a steering angle of the vehicle. This provides the advantage of enabling more specific control of the adaptive suspension damper for a specific wheel.

In an embodiment, when the oscillation of the wheel exceeds a first threshold value, said controlling comprises controlling the adaptive suspension damper to reduce the oscillation of the wheel to below the first threshold value. This advantageously provides control of wheel oscillation with respect to a maximum level of allowable oscillation.

In an embodiment, when the oscillation of the wheel is above said first threshold value and above a second threshold value, said controlling comprises controlling the adaptive suspension damper to maintain or increase the oscillation of the wheel above the first threshold value. Advantageously, by maintaining or increasing oscillation of the wheel when the oscillation of the wheel is above said second threshold value, the issue of an out of balance wheel may be brought to the attention of vehicle occupant(s).

Optionally, when the oscillation of the wheel is above the first threshold value, the method includes notifying a user of the same. This advantageously increases safety, by providing the user with valuable information that they otherwise may not have been aware of.

According to another aspect of the invention, there is provided a vehicle comprising means for implementing the method as hereinabove described.

According to yet another aspect of the invention, there is provided computer software which, when executed by a computer, is arranged to perform the method as hereinabove described.

Optionally the computer software is stored on a computer-readable medium.

Optionally, the computer-readable medium is non-transitory. The computer software may be tangibly stored on a computer-readable medium.

Optionally, there is provided a processor arranged to implement the computer software.

According to still another aspect of the invention, there is provided a processor arranged to implement the method as hereinabove described.

According to yet another aspect of the invention, there is provided a wheel oscillation control system for a vehicle, the system comprising: receiving means for receiving one or more signals indicative of oscillation of at least one wheel of the vehicle; processing means for determining whether the oscillation of the wheel exceeds an oscillation limit and outputting a signal in dependence thereon; and adaptive damping means for adaptively controlling the oscillation of the wheel in dependence on the signal. In this way, wheel oscillation can be adaptively controlled to mitigate the effects of an out of balance wheel.

In some embodiments, there is provided a system as described above, wherein: said receiving means for receiving one or more signals indicative of oscillation of at least one wheel of the vehicle comprises an electronic processor having an electrical input for receiving said one or more signals; and an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, wherein said processing means for determining whether the oscillation of the at least one wheel exceeds an oscillation limit comprises the electronic processor being configured to access the memory device and execute the instructions stored therein such that it is operable to detect whether the at least one wheel exceeds an oscillation limit based on the one or more signals.

According to another aspect of the invention, there is provided a vehicle comprising the system as hereinabove described.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a method according to an embodiment of the invention;

Figure 2 is a wheel oscillation controller according to an embodiment of the invention;

Figure 3A is a schematic side view of a vehicle wheel having a deposit thereon, with the deposit in a 12 o’clock position;

Figure 3B is a schematic side view of a vehicle wheel having a deposit thereon, with the deposit in a 3 o’clock position;

Figure 3C is a schematic side view of a vehicle wheel having a deposit thereon, with the deposit in a 6 o’clock position;

Figure 3D is a schematic side view of a vehicle wheel having a deposit thereon, with the deposit in a 9 o’clock position;

Figure 4 is a schematic plan view of a vehicle according to an embodiment of the invention;

Figure 5 is a plot showing a relationship between wheel oscillation and time during operation of a vehicle having an eccentric weight on one of its wheels;

Figure 6 shows a method according to an embodiment of the present invention;

Figure 7 is a wheel oscillation controller according to an embodiment of the present invention;

Figure 8 is a plot showing a line indicative of a relationship of expected electric machine (EM) speed over time, as compared with a line indicative of detected EM speed over time, for a wheel having an eccentric weight thereon; and

Figure 9 is a vehicle according to an embodiment of the present invention.

DETAILED DESCRIPTION

Figure 1 illustrates a wheel oscillation control method 100 according to an embodiment of the invention. The method 100 is for adaptively reducing oscillation of at least one wheel of a vehicle, as will be explained.

An embodiment of the method 100 will be explained with reference to Figure 2, which illustrates a wheel oscillation control means 200 according to an embodiment of the invention. The wheel oscillation control means 200 may be a wheel oscillation controller 200. The controller 200 comprises input means 202, for receiving one or more signals 201 indicative of wheel oscillation, processing means 204 to determine wheel oscillation and output means 206 output a signal to control an adaptive suspension damper associated with the wheel responsive to said determined wheel oscillation. In some embodiments, a vehicle may comprise a plurality of adaptive suspension dampers, each adaptive suspension damper individually associated with a wheel of the vehicle. Each adaptive suspension damper can be individually controlled. Alternatively, two or more of the adaptive suspension dampers can be controlled concurrently, such as according to the same control signal.

The input means 202 may comprise an electronic processor, such as formed by one or more processing devices, having at least one electrical input for receiving said one or more signals 201 indicative of wheel oscillation. Said one or more signals may comprise a signal received from a stability control system (SCS). The signal 201 may comprise one or more signals indicative of wheel speed relative to torque input. For example a first signal may be indicative of wheel speed and a second signal indicative of torque applied to said wheel. It will be appreciated that the wheel speed signal may be obtained otherwise than from the SCS. Said one or more signals may additionally or alternatively comprise a signal received from a sensing means associated with a suspension system of the vehicle, such as a signal indicative of deflection of a suspension damper associated with the wheel. The sensing means may comprise one or more sensing devices arranged to monitor deflection of the suspension damper, or a mechanical component of the suspension, associated with the wheel.

Said processing means 204 may comprise an electronic memory device electrically coupled to an electronic processor, the electronic memory device having instructions stored therein, such that said processing means 204 is operable to determine wheel oscillation based on the one or more signals 201. The electronic processor may be the same processor as that of the input means 202 described above, or may be an additional processor. Said processing means 204 may alternatively be provided in the form of one or more processing devices for operatively executing computer-executable instructions, wherein the instructions may be stored in a computer-readable medium, such as a data storage means 208. The computerexecutable instructions may implement an embodiment of the method 100 illustrated in Figure 1. In some embodiments, the processing means 204 is configured to determine 106 whether the oscillation of the at least one wheel exceeds one or more predefined oscillation values, based on the at least one signal 201 received by the input means 202.

Step 102 of the method 100 comprises receiving data indicative of a wheel parameter. In some embodiments, said receiving 102 includes determining the wheel parameter. The wheel parameter is indicative of oscillation of at least one wheel of the vehicle. As described above, a vehicle wheel may become soiled by a non-uniformly distributed deposit on the wheel. The deposit may be attached to a portion of the wheel such as a rim or tyre of the wheel. The deposit acts as an eccentric weight on the wheel causing an imbalance of the wheel, consequently resulting in wheel oscillation. It will be understood that wheel oscillation comprises vehicle movement of the wheel as the wheel rotates. The frequency of the wheel oscillation depends on, inter alia, the circumferential position of the weight on the wheel at any given point of time, a speed at which the vehicle is moving and dimensions of the wheel. The severity of the wheel oscillation is dependent on the amount of weight the wheel is out of balance, i.e. on the mass of the deposit on the wheel. Referring to Figures 3A-3D, as the vehicle wheel 300 rotates in direction 304 through positions A, B, C and D, so too does the deposit 302. With each rotation, the unbalanced wheel 300 is repeatedly displaced vertically due to the extra weight on the wheel 300 forcing a wheel assembly including the wheel and hub carrier, brake etc. up and down. As the wheel 300 rotates and the deposit 302 moves from a “12 o’clock” position shown in Figure 3A through a “3 o’clock” position, shown in Figure 3B to a “6 o’clock” position shown in Figure 3C, the wheel speed increases, relative to input torque applied to the wheel, due to the downward force of gravity acting on the deposit 302 on the wheel 300. As the deposit 302 then moves from the “6 o’clock” position shown in Figure 3C, through a “9 o’clock” position shown in Figure 3D, back to the “12 o’clock” position shown in Figure 3A, the wheel speed decreases, relative to input torque received from the engine (not shown), due to the downward force of gravity acting on the deposit 302 on the wheel 300. In general, the input signal 201 indicative of wheel speed, such as obtained from the SCS, is highly accurate and can be obtained in real-time. Generally, the largest component of vertical force on the wheel due to the weight occurs when the weight is in the 3 o’clock position (Figure 3B) and the 9 o’clock position (Figure 3D). The fluctuations in wheel speed relative to torque input therefore provide, in some embodiments, a signal indicative of wheel oscillation. It will be appreciated that an indication of torque applied to the wheel may be obtained from a motive system of the vehicle i.e. indicative of a desired torque applied to the wheel by one or both of a motor or engine of the vehicle.

Referring again to Figures 3A-3D, depending on the position of the deposit 302 on the wheel 300, as the deposit 302 approaches each of the 12 o’clock and 6 o’clock positions, a suspension damper (not shown) associated with the wheel 300 is correspondingly deflected. The suspension damper may be part of, or communicable with, the suspension system mentioned above. Deflection of the suspension damper therefore provides to the input means 202, in some embodiments, a signal 201 indicative of wheel oscillation.

One or more signals indicative of deflection of the suspension damper may be used as a primary indicator of wheel oscillation. Alternatively, or additionally, one or more signals indicative of wheel speed may be used as a secondary proof of wheel oscillation.

In some embodiments, the input means 202 may receive said one or more signals 201 directly or indirectly from a sensing means, such as a sensor, for example. Turning now to Figure 4 and using the above example of fluctuating wheel speed relative to input torque, the controller 200 may receive a signal from a sensor 400a, 400b, 400c, 400d which may be arranged on an axle 402, 404 of the vehicle. At least one of the sensors 400a, 400b, 400c, 400d may at least temporarily be associated with the wheel 300a having an eccentric weight 302 thereon. In the embodiment illustrated in Figure 4, four sensors 400a, 400b, 400c, 400d are provided, each sensor corresponding to each wheel 300a, 300b, 300c, 300d, respectively.

Although wheel speed relative to torque input, and suspension deflection are hereinbefore described as signals 201 indicative of wheel oscillation, this description is not intended as providing an exhaustive list and other such signals 201 indicative of wheel oscillation may be used by embodiments of the invention to determine wheel oscillation.

Referring again to Figures 1 and 2, the method 100 comprises a step of determining wheel oscillation 104 based on the determined wheel parameter. In some embodiments, the processing means 204 of the controller 200 uses as an input the wheel parameter into one or more algorithms capable of determining wheel oscillation 104. For example, where the determined wheel parameter is wheel speed, the algorithm may comprise comparing the wheel speed with torque applied to the wheel. The algorithm may comprise comparing the relationship between the determined wheel speed relative to torque input with an expected relationship between wheel speed relative to torque input. As described above, wheel speed fluctuates relative to applied torque when an eccentric weight is acting on a wheel and consequently wheel oscillation is derivable from such comparisons.

In another example, where the determined wheel parameter is deflection of a suspension damper associated with a wheel, the algorithm may comprise comparing determined deflection with one or more expected deflection patterns.

After determining wheel oscillation 104, the processing means 204 is then arranged to determine whether the wheel oscillation is acceptable 106. In some embodiments, this is determined by comparing the determined wheel oscillation with at least one predefined value. The predefined value may be indicative of a maximum value of acceptable oscillation.

If step 106 concludes that wheel oscillation is acceptable, such as being less than the maximum value the method 100 comprises repeating steps 102 and 104. If the determined wheel oscillation is not deemed acceptable, such as by being equal to or greater than the maximum value, the output 206 of the controller 200 provides a signal 207 to adapt 108 the adaptive suspension damper (not shown) associated with the wheel 300. Said adapting 108 includes modifying and/or maintaining stiffness of the adaptive suspension damper in response to wheel oscillation. Said modifying includes stiffening or softening the damper in response to wheel oscillation. Indeed, the adaptive suspension damper can be adapted in real time, by adjusting a stiffness of the adaptive suspension damper per the frequency of wheel oscillation, for example. Said adapting 108 may be variable throughout wheel rotation and may comprise any combination, cycle or pattern of increasing, decreasing or maintaining the stiffness of the adaptive suspension damper within a single revolution of the wheel 300. Said frequency of wheel oscillation differs depending on the circumferential position of the weight 302 on the wheel 300 at any point of time and consequently, different modifications to the stiffness of the adaptive suspension damper may be used for different circumferential positions of the weight 302. For example, said stiffness may be variably increased or decreased to transmit more or less vibration to the vehicle cabin, respectively, throughout each revolution of the wheel. The adapting may be applied additional to a control of the damper applied to control movement of the wheel on terrain, such as a road or off-road surface.

Said adapting 108 may be matched with frequency of wheel oscillation such that the adapting 108 is synchronous with wheel oscillation. In that case, the processing means 204 may additionally account for steering rate and steering angle. The adaptive suspension damper may also be adjusted per the direction of the wheel 300 and may be synchronised with wheel direction, as described above. In this way, the adaptive suspension damper can be synchronised by the processing means 204 to adapt suspension in dependence on the one or more signals 201. In some embodiments, steps 102, 104, 106 and, if required, step 108, are repeated 112, optionally continuously throughout operation of the vehicle.

In some embodiments, the adaptive suspension damper may comprise a dashpot system having a magnetorheological fluid and a pair of opposed electromagnets about the magnetorheological fluid. Each adaptive suspension damper of the vehicle may be individually controlled. Alternatively, two or more of the adaptive suspension dampers may be controlled concurrently. The electromagnets are arranged to apply, remove, modify or maintain a magnetic field across the magnetorheological fluid to cause particulates within the fluid, which might be, for example, iron filings, to align to a more or lesser extent. The viscosity of the magnetorheological fluid and consequently the stiffness of the adaptive suspension damper may therefore be controlled by applying, removing, modifying or maintaining a magnetic field across the magnetorheological fluid. The adaptive suspension damper is configured to operate in dependence on a signal from the output 206 of the controller 200, so as to adapt the viscosity of the magnetorheological fluid in dependence on whether determined wheel oscillation 104 is acceptable 106.

Turning now to Figure 5, line 506 shows a relationship between wheel oscillation 502 and time 504 during operation of a vehicle having an eccentric weight on at least one of its wheels. In some embodiments, the controller 200 may or may not adapt the adaptive suspension damper associated with the at least one wheel, depending on whether the determined wheel oscillation exceeds any one of one or more predefined threshold values. For example, it might be that, throughout each full revolution of the wheel, wheel oscillation less than a first threshold value, T1 508 is acceptable and no control owing to wheel oscillation needs to be made to the adaptive suspension damper. Said adapting 108 of the adaptive suspension damper in that scenario may therefore be “maintain operation” which may comprise operating the damper according to a selected suspension control operation according to terrain and/or driving conditions. If the damper is a dashpot system having a magnetorheological fluid, as described above, said adapting 108 may be “maintain magnetic field across the magnetorheological fluid so as to maintain viscosity of the magnetorheological fluid”.

However, if the determined wheel oscillation, at any point throughout a full revolution of the wheel, is of a value above the first threshold value T1 508, then said adapting 108 may be to “adjust stiffness of the adaptive suspension damper”, so as to mitigate the problem of wheel oscillation. If the damper is a dashpot system having a magnetorheological fluid, as described above, said adapting 108 in that scenario may be “adjust, apply or remove a magnetic field about the magnetorheological fluid so as to increase or decrease the viscosity of the magnetorheological fluid”. In this way, the adaptive damper can be controlled to counter vertical movement of the vehicle caused by the deposit on the wheel to reduce or remove the effects of the imbalance. It may be that said adapting 108 comprises, throughout each revolution of the wheel, variable adjustments to viscosity of the magnetorheological fluid and consequently, damper stiffness, in dependence on wheel oscillation. Said adjustments to viscosity may be matched in response to frequency of wheel oscillation and/or wheel direction.

In some embodiments, it may be desirable not to reduce wheel oscillation, at least for a period of time. For example if a deposit of a considerable mass has soiled a vehicle wheel, it may be desirable to allow the vibrations to be transmitted to the vehicle structure, so as to bring the issue to the attention of one or more vehicle occupants. Referring still to Figure 5, if the determined wheel oscillation exceeds a second threshold value, T2 510, said adapting 108 in that scenario may comprise “maintain operation”. If the damper is a dashpot system having a magnetorheological fluid, as described above, said adapting 108 may be “maintain magnetic field across the magnetorheological fluid so as to maintain viscosity of the magnetorheological fluid”. Alternatively, in scenarios where it is desirable to bring wheel oscillation to the attention of the vehicle occupant(s), said adapting 108 may comprise stiffening the adaptive suspension damper, so as to purposely transmit vibrations to the vehicle structure. In some embodiments, wherein wheel oscillation is brought to the attention of the vehicle occupant(s) by taking no action as described above, if the vehicle continues to be operated by the driver, for perhaps at least a predefined length of time, said adapting 108 may further comprise deliberately stiffening the adaptive suspension damper so as to purposely increase the transmission of vibrations to the vehicle structure. This may encourage vehicle occupant(s) to stop, vacate the vehicle and attend to the cause of wheel oscillation, for example, remove material deposited on the wheel.

Optionally, the method 100 may also include a step of explicitly alerting the driver 110 as to the imbalance of the wheel 300 in addition to, or alternative to the processes described above. This may be done by means of the output means 206 providing a signal 209 to an output means such as an output device 210 so as to display an alert on a dashboard or multimedia screen inside the vehicle and/or to sound an alarm. In addition or alternative to displaying and/or sounding an alarm, the method 100 may include a step (not shown) of providing information to the driver, informing them of a wheel imbalance issue. This may include, in some embodiments, advising the driver to visit a garage in order to have the problem investigated by an automotive professional. The method 100 may also include a step (not shown) of advising the driver to exit the vehicle and remove the deposit. If the vehicle is in mud and ruts terrain (M+T TR) mode, the method 100 may include a step (not shown) of advising the driver that one of the wheels of the vehicle wheel likely has a mud deposit thereon and advising the driver to vacate the vehicle to remove the mud.

In some embodiments, the method 100 may additionally include a step (not shown) of determining which wheel of the vehicle is oscillating i.e. is out of balance. Returning now to Figure 4, whilst four sensors 400a, 400b, 400c, 400d are illustrated, each sensor corresponding to a respective wheel 300a, 300b, 300c, 300d, in other embodiments, there may be only one sensor provided on each axle 402, 404 of the vehicle. In that case, it may not be immediately clear which vehicle wheel associated with the axle is out of balance. Specifically, the method 100 may include the step of determining (not shown) which of the two wheels on the axle 402 or 404 is out of balance. This step may be performed before adapting 108 the adaptive suspension damper associated with the wheel determined as being out of balance. As a vehicle is cornering, the wheel speeds of each wheel 300a, 300b on an axle 402 adjust to the radius of the curve, resulting in a difference in wheel speed between the wheel on the inside of the curve and the wheel on the outside of the curve. If one of the wheels has an eccentric weight 302 acting thereon and consequently is out of balance, then the detected difference in wheel speed between the outside wheel and the inside wheel will be higher than or lower for at least a part of each revolution of the vehicle wheel than an expected difference in wheel speed between the outside and inside wheels, depending on which wheel 300a, 300b the eccentric weight is deposited.

In some embodiments, the controller 200 comprises a means for storing data concerning determined wheel oscillation (not shown), which data can later be accessed by the driver, or by an automotive professional, for example, during servicing. Said means for storing data concerning determined wheel oscillation may be the data storage means 208 described above, or may be an additional memory component of the controller 200, or a memory component of another system which may be of the vehicle or remote storage. Said means for storing data concerning determined wheel oscillation may also store information about levels of acceptable wheel oscillation, such as threshold values, T1, T2.

An embodiment of the method 600 will now be explained with reference to Figure 6 and Figure 7, which illustrate a wheel oscillation control method 600 and a wheel oscillation controller 700, according to another embodiment of the invention. The controller 700 comprises input means 702, said input means for receiving one or more signals 701 indicative of wheel oscillation, processing means 704 to determine wheel oscillation and output means 706 to adjust operation of an electric machine (EM) (not shown) associated with the wheel so as to reduce wheel oscillation. The EM may provide motive force to one or more of the vehicle wheels, such as including the wheel having at least temporarily the eccentric deposit.

Said input means 702 may comprise an electronic processor, such as formed by one or more processing devices, having at least one electrical input for receiving said one or more signals 701 indicative of a value of wheel oscillation. Said one or more signals may comprise a signal received from the EM associated with the wheel, such as a signal indicative of current supplied to the EM or power required to transmit torque to the associated wheel, for example. It will be appreciated that the wheel speed signal may be obtained otherwise than from the EM such as from a wheel speed sensor. Said one or more signals may additionally or alternatively comprise a signal received from a sensing means associated with a suspension system of the vehicle, such as a signal indicative of deflection of a suspension damper associated with the wheel. The sensing means may comprise one or more sensing devices arranged to monitor deflection of the suspension damper or a mechanical component of the suspension associated with the wheel.

Said processing means 704 may comprise an electronic memory device electrically coupled to an electronic processor. The electronic memory device has instructions stored therein, such that said processing means 704 is operable to determine wheel oscillation based on the one or more signals 701. The electronic processor may be the same processor as that of the input means 702 described above, or may be an additional processor. Said processing means 704 may alternatively be provided in the form of one or more processing devices for operatively executing computer-executable instructions, wherein the instructions may be stored in a computer-readable medium, such as a data storage means 708. The computerexecutable instructions may implement an embodiment of the method 600 illustrated in Figure 6. In some embodiments, the processing means 704 is configured to determine 706 whether the oscillation of the at least one wheel exceeds one or more predefined oscillation values, based on the at least one signal 701 received by the input means 702.

Step 602 of the method 600 comprises receiving data indicative of a wheel parameter. In some embodiments, said receiving 602 includes determining the wheel parameter. The wheel parameter is indicative of oscillation of the at least one wheel of the vehicle. During normal vehicle operation, the EM applies a given torque to a wheel 300 with which it is associated. The torque applied at any point in time may vary in dependence on a driver input. When the vehicle wheel is soiled with a deposit acting as an eccentric weight, the power required to rotate the wheel reduces and increases depending on the position of the deposit, due to the additional weight of the deposit on the wheel. The speed of the EM is consequently affected and fluctuates with the fluctuations in power required to rotate the wheel. Figure 8 is a plot 800 showing a line 802 indicative of expected EM speed 806 vs time 808, as compared with line 804 indicative of detected EM speed 806 vs time 808 for a wheel having an eccentric weight thereon. A signal indicative of required power and/or a signal indicative of current supplied to the EM may therefore provide to the input means 702, in some embodiments, a signal 701 indicative of wheel oscillation.

Referring still to Figures 6 and 7, after a wheel parameter has been determined 602, the method 600 comprises a step of determining wheel oscillation 604 based on the wheel parameter. In some embodiments, processing means 704 of the controller 700 uses as an input the determined wheel parameter into one or more algorithms capable of determining wheel oscillation 604. For example, where the determined wheel parameter is current supplied to the EM associated with the wheel, at least one of the one or more algorithms compares the current supplied to the EM, with an expected current to be supplied to the EM for a given operational setting. Where the determined wheel parameter is power required to rotate the wheel, at least one of the one or more algorithms compares this with expected power required to rotate the wheel rotating at a given speed. Consequently wheel oscillation is derivable from such comparisons.

In another example, where the determined wheel parameter is deflection of a suspension damper associated with a wheel, at least one of the one or more algorithms compares determined deflection with expected deflection patterns.

After determining wheel oscillation 604, the processing means 704 then determines whether the wheel oscillation is acceptable 706. In some embodiments, this is determined by comparing the determined wheel oscillation with at least one predefined wheel oscillation value. The predefined value may be indicative of a maximum value of acceptable oscillation. If step 606 concludes that wheel oscillation is acceptable, the method 600 comprises repeating steps 602 and 604. If the determined wheel oscillation is not deemed acceptable, the output 706 of the controller 700 provides a signal 707 to adapt 608 operation of the EM associated with the wheel 300. Said adapting 608 may be variable throughout wheel rotation and may comprise any combination, cycle or pattern of modifying and/or maintaining the EM operation within a single revolution of the wheel 300. Said frequency of wheel oscillation may differ depending on the circumferential position of the weight 302 on the wheel 300 at any point of time and consequently, different modifications to EM operation are required for different circumferential positions of the weight 302.

Said adapting 608 may be matched with frequency of wheel oscillation such that said adapting 608 is synchronous with wheel oscillation. In that case, the processing means 704 may additionally account for steering rate and steering angle. Said adapting 608 may also be per the direction of the wheel 300 and may be synchronised with wheel direction. In this way, EM operation can be synchronised with the processing means 704 to adapt operation in dependence on the one or more signals 701. Indeed, EM operation can be adapted in real time, by adjusting EM operation per the frequency of wheel oscillation, for example. In that case, the processing means 704 may additionally account for steering rate and steering angle. In some embodiments, steps 602, 604, 606 and, if required, step 608, are repeated 612, optionally continuously throughout operation of the vehicle.

In some embodiments, said step 608 of adapting EM operation comprises modulating torque applied to a wheel 300 having a deposit 302 thereon in response to detected wheel oscillation. Referring again to Figures 3A-3D, 6 and 7, said adapting step 608 comprises reducing torque applied to the wheel as the deposit 302 “falls”, moving from the 12’oclock position (Figure 3A) through the 3 o’clock position (Figure 3B) to the 6 o’clock position (Figure 3C). The application of reduced torque, relative to applied torque during normal operation, counteracts the acceleration of the wheel 300 that is caused by the deposit 302 on the wheel 300. As the deposit 302 “rises”, moving from the 6 o’clock position (Figure 3C), through the 9 o’clock position (Figure 3D) back to the 12 o’clock position (Figure 3A), said adapting step 608 comprises increasing torque applied to the wheel 300, to counteract the deceleration of the wheel 300 that is caused by the deposit 302 on the wheel 300. The EM is configured to receive a signal from the output 706 of the controller 700, so as to modulate torque applied to the wheel associated therewith, as described above.

Turning again to Figure 5, line 506 shows a relationship between wheel oscillation 502 and time 504 during operation of a vehicle with an eccentric weight on at least one of its wheels. In some embodiments, the controller 700 may or may not adapt EM operation 608, depending on whether the determined wheel oscillation exceeds any one of one or more threshold values. For example, it might be that, throughout each full revolution of the wheel, wheel oscillation less than a first threshold value, T1 508 are acceptable and no adjustment needs to be made to the adaptive suspension damper. Said adapting 608 of EM operation in that scenario may therefore be “maintain EM operation”. However, at any point throughout a full revolution of the wheel, if the determined wheel oscillation is of a value above the first threshold value T1 508, then said adapting 608 might be “modulate torque from EM applied to wheel in dependence on detected wheel oscillation”, so as to mitigate the problem of wheel oscillation. It may be that said adapting 608 comprises, throughout each revolution of the wheel, variable adaptations to EM operation in dependence on wheel oscillation. Said adaptations may be matched in response to frequency of wheel oscillation and/or wheel direction.

In some embodiments, it may not be desirable to reduce wheel oscillation. For example if a deposit of a considerable mass has soiled a vehicle wheel, it may be desirable to allow the vibrations to be transmitted to the vehicle cabin so as to bring the issue to the attention of the vehicle occupants. Referring still to Figure 5, if the determined wheel oscillation exceeds a second threshold value, T2 510, said adapting 608 in that scenario may comprise “maintain EM operation”. Alternatively, in scenarios where it is desirable to bring wheel oscillation to the attention of vehicle occupants, said adapting 608 may comprise controlling applied torque, so as to purposely transmit vibrations to the vehicle structure. In some embodiments, wherein wheel oscillation is brought to the attention of the vehicle occupant(s) by transmitting vibrations to the vehicle structure, as described above, if the vehicle continues to be operated by the driver, for perhaps at least a predefined length of time, said adapting 608 may further comprise controlling applied torque so as to purposely increase the transmission of vibrations to the vehicle structure. This may encourage vehicle occupant(s) to stop, vacate the vehicle and attend to the cause of wheel oscillation, for example, remove material deposited on the wheel. Optionally, the method 600 may also include a step (not shown) of explicitly alerting the driver 610 as to the imbalance of the wheel 300, in addition to, or alternative to the processes described above. This may be done by means of the output 706 providing a signal 709 to an on board computer 710 so as to display an alert on a dashboard or multimedia screen inside the vehicle and/or to sound an alarm. In addition or alternative to displaying and/or sounding an alarm, the method 600 may include a step (not shown) of providing information to the driver, informing them of a wheel imbalance issue. This might additionally include, in some embodiments, advising the driver to visit a garage in order to have the problem looked at by an automotive professional. The method 600 may also include a step (not shown) of advising the driver to exit the vehicle and remove the deposit. If the vehicle is in mud and ruts terrain (M+T TR) mode, the method 600 may include advising the driver that a vehicle wheel likely has a mud deposit thereon and advising the driver to vacate the vehicle and remove the mud.

In some embodiments, EM feedback may be used to confirm which wheel of a plurality of wheels of the vehicle is out of balance. This is particularly applicable to a vehicle having only one EM per axle, rather an individual Ems associated with each wheel. When a vehicle is cornering, frequency of oscillations in EM speed signal change, depending on whether the left or right wheel on an axle 620 is out of balance. For example, in a right hand bend, if the outside wheel is the wheel having the imbalance issue, then the frequency of oscillation of the EM speed signal will increase relative to the vehicle speed at a fixed ratio steering angle. If the inside wheel is the wheel having the imbalance issue, then the frequency of oscillation of the EM speed signal will reduce relative to vehicle speed. In some embodiments, the method 100 or the method 600 may include a step (not shown) of mitigating effect on steering input caused by an out of balance wheel. When one or more wheels of a vehicle is out of balance, such as due to a deposit thereon acting as an eccentric weight, this can affect steering of the vehicle. For example, when a front wheel is out of balance, vibrations due to the oscillating wheel are transmitted to the steering column, resulting in vibration or chatter felt on the steering wheel by a driver. In some embodiments, the method 100 or the method 600 include providing an input to a steering servomechanism of the vehicle to mitigate steering input as the deposit moves to the 3 o’clock and 9 o’clock positions shown in Figures 3B and 3D, respectively.

In some embodiments, the controller 700 comprises a means for storing data concerning determined wheel oscillation, which data can later be accessed by the driver, or by an automotive professional, for example, during servicing. Said means for storing data concerning determined wheel oscillation may be the data storage means 708 described above, or may be an additional memory component of the controller 700. Said means for storing data concerning determined wheel oscillation may also store information about levels of acceptable wheel oscillation, such as threshold values, T1, T2.

Figure 9 illustrates a vehicle 900 according to an embodiment of the invention. The vehicle 900 comprises a wheel oscillation controller according to an embodiment of the invention for controlling oscillation of the wheel of the vehicle, as described above. Whilst Figure 9 illustrates a car, the skilled person will recognise that the controllers, systems and methods described and claimed herein may be applied to any vehicle where wheel oscillation could be present, such as a car, bike, train or plane, for example.

It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs that, when executed, implement embodiments of the present invention. Accordingly, embodiments provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine readable storage storing such a program. Still further, embodiments of the present invention may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Claims

1. A wheel oscillation controller for a vehicle, configured to mitigate an out of balance wheel, the controller comprising: input means for receiving one or more signals indicative of oscillation of at least one wheel of the vehicle; processing means for determining whether the oscillation of the at least one wheel exceeds an oscillation limit; and output means to provide a signal to control an adaptive suspension damper associated with the at least one wheel to reduce the oscillation of the at least one wheel, wherein said signal to control the adaptive suspension damper is a signal configured to variably adapt the adaptive suspension damper throughout a rotation of the at least one wheel.

2. The controller as claimed in claim 1, wherein said signal to control the adaptive suspension damper is a signal configured to control a stiffness of the adaptive suspension damper in response to the oscillation of the wheel.

3. The controller as claimed in claim 2, wherein said signal is configured to control the stiffness of the adaptive suspension damper at a frequency corresponding to the oscillation of the wheel.

4. The controller as claimed in any preceding claim, wherein said adaptive damper is a dashpot system having a magnetorheological fluid and magnetic means for applying a magnetic field across the magnetorheological fluid to control a viscosity of the magnetorheological fluid, and said magnetic field is dependent on the signal provided by the output means.

5. The controller as claimed in any preceding claim, wherein the one or more signals indicative of wheel oscillation comprise a wheel signal indicative of wheel speed relative to input torque and wherein said processing means is configured to compare said signal with an expected relationship between wheel speed and input torque to determine whether the oscillation of the at least one wheel exceeds the oscillation limit.

6. The controller as claimed in any preceding claim, wherein the controller is configured to determine which wheel of a plurality of wheels of the vehicle is oscillating by comparing a frequency of wheel oscillation relative to a steering angle of the vehicle.

7. A wheel oscillation control method for a vehicle, the method comprising: receiving one or more signals indicative of oscillation of at least one wheel of the vehicle; determining whether oscillation of the at least one wheel exceeds an oscillation limit; controlling an adaptive suspension damper associated with the at least one wheel to reduce the oscillation of the at least one wheel, wherein controlling the adaptive suspension damper comprises variably adapting the adaptive suspension damper throughout a rotation of the at least one wheel.

8. The method as claimed in claim 7, wherein said controlling comprises controlling stiffness of the damper in response to the oscillation of the wheel.

9. The method as claimed in claim 8, wherein said controlling comprises controlling the stiffness of the adaptive suspension damper at a frequency corresponding to the oscillation of the wheel.

10. The method as claimed in any of claims 7 to 9, wherein the adaptive suspension damper comprises a magnetorheological damper and said controlling comprises applying, removing, increasing, reducing or maintaining a magnetic field across the damper to modify the stiffness of the damper, in response to the oscillation of the wheel.

11. The method as claimed in any of claims 7 to 10, wherein the one or more signals indicative of wheel oscillation comprise a wheel signal indicative of wheel speed relative to input torque and wherein said method comprises comparing said signal with an expected relationship between wheel speed and input torque to determine whether the oscillation of the at least one wheel exceeds the oscillation limit.

12. The method as claimed in any of claims 7 to 11, comprising determining which wheel of a plurality of wheels of the vehicle is oscillating by comparing a frequency of wheel oscillation relative to a steering angle of the vehicle.

13. The method as claimed in any of claims 7 to 12, wherein, when the oscillation of the wheel exceeds a first threshold value, said controlling comprises controlling the adaptive suspension damper to reduce the oscillation of the wheel to below the first threshold value.

14. A method as claimed in any of claims 7 to 13, wherein when the oscillation of the wheel is above said first threshold value and above a second threshold value, said controlling comprises controlling the adaptive suspension damper to maintain or increase the oscillation of the wheel above the first threshold value.

15. A method as claimed in any of claims 7 to 14, wherein, when the oscillation of the wheel is above the first threshold value, the method includes notifying a user of the same.

16. A wheel oscillation control system for a vehicle, the system comprising a controller according to any one of claims 1 to 6; and adaptive damping means for adaptively controlling the oscillation of the wheel in dependence on the signal.

17. A vehicle comprising the controller of any of claims 1 to 6 and/or comprising the system of claim 16.

18. Computer software which, when executed by a computer, is arranged to perform a method according to of any of claims 7 to 15; optionally the computer software is stored on a computer-readable medium.