TECHNICAL FIELD The present disclosure relates to a vehicle seat assembly and particularly, but not exclusively, to a vehicle seat comprising a vibration dampening function. Aspects of the invention relate to a vehicle seat assembly, to a vehicle seat control module and to a vehicle. BACKGROUND

There is a growing demand for improving the comfort of drivers of vehicles, especially in the premium segment of the automotive industry. The ride quality of a vehicle is influenced by a number of elements, one important factor of which is a vehicle seat's ability to appropriately insulate the driver from road induced vibrations.

Known vibration mitigation methods and systems are configured towards marine, military and ground working machines and comprise the suspension of a vehicle seat assembly at the interface between the seat chassis and the vehicle floor. Such methods and systems tend to be bulky, as a result of articulation mechanisms used to provide the seat suspension. As a result, such known systems and methods tend to be quite power hungry and are difficult to package in smaller vehicles.

The present invention has been devised to mitigate or overcome at least some of the above-mentioned problems.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a vehicle seat assembly comprising: a chassis; a base assembly comprising a seat cushion, the base assembly being mounted to the chassis; an actuator disposed within the seat cushion and arranged to impart an impulse to the seat cushion in response to a control signal received from a control module. The present invention provides a vehicle seat assembly in which an active force element in the form of an actuator is disposed within the seat cushion of the vehicle seat. Positioning the actuator within the seat cushion reduces the mass that the actuator needs to act upon in order to impart an impulse to an occupant of the seat since vertical acceleration is only required to account for the cushion and the occupant. In contrast to prior systems the entire vehicle seat assembly is not acted upon and it is not required to install complicated and bulky suspension systems. The vehicle seat assembly of the present invention is therefore easier to package and requires less power to be effective. The vehicle seat assembly may comprise a vehicle sensor, the vehicle sensor being arranged to output sensor data relating to ride characteristics of the vehicle to the control module.

The vehicle seat assembly may comprise the control module. The control module may comprise: an input arranged to receive vehicle sensor data relating to ride characteristics of the vehicle; a processor arranged to determine a control signal in dependence on the received sensor data, the control signal being configured for the actuator within the seat cushion of the vehicle seat assembly and being arranged to mitigate against seat vibrations; and an output arranged to output the control signal to the actuator.

The control module may be arranged to filter out large amplitude vibrations above a predetermined threshold within the received sensor data such that the control module does not output a control signal in response to large vehicle movements. Filtering out large amplitude vibrations may avoid the actuator becoming saturated with control signals that exceed its operational parameters.

The vehicle sensor may comprise an accelerometer for detecting acceleration of the base assembly, the accelerometer being arranged to output accelerometer data to the control module. The accelerometer may be arranged to detect accelerometer data in a direction perpendicular to the plane of the seat cushion.

In addition to generating a control signal to mitigate against seat vibrations the control module may be arranged to general a control signal for generating warning signals to vehicle occupants. Warning signals may comprise one or more warning signal types selected from: a tyre pressure low warning signal; a lane departure warning; blind spot warning; driver alert warning. Each warning signal type is associated with a different haptic feedback profile. For example, haptic feedback profiles of the warning signals may comprise pulsed warning signals (i.e. the actuator may be arranged to impart a pulsed signal to the seat cushion); high frequency vibrations and low frequency vibrations. Additionally the control module may be arranged to send an audible signal to loudspeakers within the vehicle to generate audible warnings to accompany the haptic feedback signals.

The control module input may be arranged to receive sensor data from one of more vehicle sensors selected from: tyre pressure sensor; vehicle camera.

The control module input may be arranged to receive a notification signal from a further vehicle control unit in response to which the warning signal is generated.

The actuator may comprise one of: a piezoelectric actuator; a hydraulic actuator; an electric actuator; a magneto-rheological damper; an electro-rheological damper; a pneumatic actuator; an electro active polymeric actuator.

According to another aspect of the invention there is provided a vehicle seat control module for a vibration control system within a vehicle seat assembly, the module comprising: an input arranged to receive vehicle sensor data relating to ride characteristics of the vehicle; a processor arranged to determine a control signal in dependence on the received sensor data, the control signal being configured for an actuator within a seat cushion of the seat and being arranged to mitigate against seat vibrations; an output arranged to output the control signal to the actuator.

The control module may be arranged to impart vibrations to the seat cushion up to the saturation point of the actuator. Alternatively, the control module may be arranged to filter out large amplitude vibrations above a predetermined threshold such that the control module does not output a control signal in response to large vehicle movements, e.g. when passing over a pothole. The present invention extends to a vehicle comprising one or more vehicle seat assemblies in accordance with the above aspects of the invention The control module as described above comprising an electrical input for receiving one or more signals each indicative of a value of the vehicle sensor and comprising an electronic memory device electrically coupled to the electronic processor and having instructions stored therein, the control module being arranged such that the processor is configured to access the memory device and execute the instructions stored therein such that it is operable to detect that the vehicle is experiencing ride vibrations based on the value(s) of the vehicle sensor; and command the actuator by generating and outputting a control signal. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which: Figure 1 is a schematic illustration of a vehicle incorporating a vehicle seat in accordance with an embodiment of the present invention;

Figure 2 shows a perspective view of the vehicle seat comprised in the vehicle of Figure 1 ;

Figure 3 shows a section through the vehicle seats shown in Figure 1 and 2 in accordance with an embodiment of the present invention; and Figure 4 is a schematic illustration of a control module according to an embodiment of the present invention.

DETAILED DESCRIPTION

A vehicle 100 (also labelled as V in Figure 1 ) incorporating a vehicle seat assembly 1 in accordance with an embodiment of the present invention is schematically shown in Figure 1 . The vehicle V in the illustrated arrangement is an automobile, but the vehicle seat assembly 1 could be used in other types of vehicle V. In the illustrated arrangement, the vehicle seat assembly 1 is the right hand seat in the vehicle V. The vehicle V has a reference frame comprising a longitudinal axis X, a transverse axis Y and a vertical axis Z in a direction perpendicular to the page.

As shown in Figure 2, the vehicle seat assembly 1 comprises a squab (backrest) assembly 2 and a base assembly 3. The squab assembly 2 comprises a padded squab 4 mounted to a support assembly 5. The base assembly 3 comprises a seat cushion 6 supported on a seat cushion pan (not shown in Figure 2) mounted to a chassis 7. The squab assembly 2 is pivotally mounted to the base assembly 3 and pivots about a pivot axis (not shown). The chassis 7 is slidably mounted to a pair of parallel rails 8 fixedly mounted to a floor of the vehicle V. A headrest 16 is located at the top of the squab assembly 2.

Figure 3 shows a section through the vehicle seat assembly 1 of Figures 1 and 2. Like reference numbers are used to denote like features.

The seat cushion 6 is located on a seat cushion pan 20. The seat cushion 6 comprises an upper portion 22 and a lower portion 24 which are separated from one another to define a volume 26. The volume 26 may be filled with, for example, a foam element or some other structural support element such as the force element 28 shown in Figure 3. (It is noted that for clarity only a single force element 28 is shown in the figure though in reality there may be a plurality of such elements between the upper and lower portions (22, 24) of the seat cushion 6). The upper portion 22 of the seat cushion 6 comprises a support plate element 30 upon which is mounted an accelerometer 32.

The force element 28 is in communication with the support plate element 30 at one end and the seat cushion pan 20 at its other end. The force element 28 represents a passive (static) force element such as a seat spring.

The vehicle seat assembly 1 also comprises an actuator 34 which is an active force element within the seat cushion 6. The actuator 34 is in communication with the support plate element 30 and the seat cushion pan 20. In Figure 3 the actuator is shown located within the volume 26. It is noted that the actuator 34 may be located in other parts of the seat cushion, for example the upper portion 22 or attached directly to the support plate element 30. The vehicle seat assembly 1 also comprises a control module 36 (labelled as the active seat control module in Figure 3). The control module comprises an input 38 for receiving accelerometer data from the accelerometer 32 and an output 40 for outputting control signals to the actuator 34. The actuator 34 may comprise any convenient actuator device such as a piezoelectric actuator; a hydraulic actuator; an electric actuator; a magneto-rheological damper; an electro-rheological damper; a pneumatic actuator; or, an electro active polymeric actuator. In use, the force element 28 sustains an occupant's weight and provides a measure of vibration control by virtue of the natural damping effect that such a seat spring provides.

The accelerometer 32 is arranged to measure vertical acceleration of the seat cushion 6 during a vehicle journey (i.e. acceleration in the direction of axis Z) and to output this acceleration data to the control module 36. The control module 36 is arranged to process the received accelerometer data and to generate a control signal for the actuator 34 to dampen the vibrations arising as a result of the ride of the vehicle. The control module 32 may be arranged to filter out large amplitude seat movements as the actuator 34 may not have a large displacement capacity. Such a filtering function would avoid the actuator performance becoming saturated. In addition to reducing vibrations experienced by the seat occupant, the vehicle seating assembly, according to embodiments of the present invention, may supply additional stimuli to the seat cushion for a number of reasons.

For example, the control module may receive data indicating that a driver is becoming drowsy and may output a control signal that generates a warning series of vibrations in the seat cushion.

Similarly, haptic feedback may be provided to the vehicle driver (and other occupants of the vehicle) for a range of driving conditions, such as low tyre pressure, lane departure, another vehicle in the vehicle's blind spot. In one arrangement different haptic feedback may be used for each driving condition so that, for example, a regular step input may be used to inform the driver that one of the tyres has a low pressure warning, an intermittent low frequency vibration may be used to alert the driver over a lane departure and an intermittent high frequency vibration may be used to alert the driver that there is another vehicle in their blind spot.

Figure 4 shows the input to the control module 36 in more detail. Like numerals are used to denote like features. It is noted that some or all of the following sensor inputs may be received at the control module 36 depending on the particular set up within the vehicle (e.g. in some arrangements the control module may be configured to mitigate ride vibrations using only data from the accelerometer 32. In other arrangements, a wider range of sensor data may be used to detect and mitigate more sources of seat vibration and to provide additional stimuli to the vehicle occupants). The input 38 of the control module 36 may receive sensor data from a range of different sources that are indicative either of vibrations arising from ride motion of the vehicle or are required to provide the additional stimuli noted above. As shown in Figure 4, the input 38 of the control module 36 may receive vehicle sensor data 42 relating to the vehicle's motion. Sensor data in this category of data may include one or more of: speed data; pitch/roll rates; vertical acceleration data; wheel acceleration; pressure data from vehicle tyre sensors; image data from one or more on- board cameras, radar data etc.

As described above in relation to Figure 3, sensor data may be received from an accelerometer 32 within the vehicle seat assembly. Driver assistance data 44 such as driver alertness indications, lane departure warnings may also be received from an on-board advanced driver assistance system (ADAS)(not shown).

Received sensor data (32, 42, 44) may be processed by a processor 46 within the control module 36 which is running suitable control software 48 to generate control signals for the actuator 34.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.