AIR SUSPENSION SWITCH FOR A VEHICLE

Abstract

Control system (14) for a suspension height adjustment mechanism of a vehicle (12), wherein the suspension height adjustment mechanism (50, 52, 54, 56) comprises a front suspension height adjustment mechanism (50, 52) at a front end (68) of the vehicle and a rear suspension height adjustment mechanism (54, 56) at a rear end (70) of the vehicle, wherein the control system (14) is configured to control the suspension height adjustment mechanism (50, 52, 54, 56) in response to user-generated control signals to: increase the height of at least the rear end (70) of the vehicle to a first predetermined vehicle height corresponding to a high trailer hitch height (90); and decrease the height of at least the rear end of the vehicle (70) to a second predetermined vehicle height corresponding to a low trailer hitch height (92), wherein both the first and second predetermined vehicle heights are accessible from one or more other vehicle heights that differ from the first and second predetermined heights;and wherein reducing the vehicle height from the high trailer hitch height (90) to the low trailer hitch height (92) comprises the control system controlling the suspension height adjustment mechanism (50, 52, 54, 56) such that the height of the front end (68) of the vehicle is reduced less than the height of the rear end (70) of the vehicle; ; wherein the control system is configured to control the rear suspension height adjustment mechanism (54, 56) and the front suspension height adjustment mechanism (50, 52) such that the height of the rear end (70) of the vehicle is adjusted before the height of the front end (68) of the vehicle.

Description

TECHNICAL AREA

[0001] The present disclosure relates to an air suspension switch for a vehicle and in particular, but not exclusively, a switch installed in the trunk of a vehicle. Aspects of the invention relate to a control system, a suspension system, a vehicle comprising a control system or a suspension system, a method for controlling a suspension height adjustment mechanism, a control device for controlling a suspension height adjustment mechanism, and a non-volatile, computer-readable storage medium. STATE OF THE ART

[0002] It is known to provide vehicle suspension systems that can be configured to achieve a range of predefined vehicle ride heights. These systems can be operated via one or more manual switches on a vehicle console and be accessible from the driver's position, allowing a user to select the suspension setting most suitable for their driving style or the type of terrain the vehicle is traveling on. Such suspension settings might include, for example, a normal ride height, an off-road ride height, and an access height.

[0003] With these known systems, the ability to adjust the vehicle's suspension is often only available to the user when seated in the driver's or front passenger's seat, and the available ride heights are limited to a range of preset heights. Some vehicles partially accommodate these limitations and offer limited ride height adjustment functionality when the vehicle is parked and the user is outside the cabin.

[0004] The available vehicle ride heights in such systems often include a normal height and a loading height, and the user has the option to lower the vehicle ride height from the normal height to the loading height, for example, to facilitate access to the rear cargo area of ​​the vehicle. However, this functionality is limited, so the user can usually only select one of two preset vehicle ride heights. A "Raise" switch is used to access a higher ride height when the vehicle is at a lower height, and a "Lower" switch is used to access the lower ride height when the vehicle is at the higher ride height.

[0005] The DE 10 2004 008 928 A1 refers to a driver assistance system for coupling a trailer hitch on the vehicle with a counterpart on the trailer.

[0006] There remains a need to provide a vehicle suspension system with increased functionality and greater flexibility for the user. The present invention was developed to minimize or overcome at least some of the aforementioned problems. BRIEF SUMMARY OF THE INVENTION

[0007] According to one aspect of the present invention, a control system is provided for a vehicle's suspension height adjustment mechanism, wherein the suspension height adjustment mechanism comprises a front suspension height adjustment mechanism at a front end of the vehicle and a rear suspension height adjustment mechanism at a rear end of the vehicle. The control system is configured to control the suspension height adjustment mechanism in response to user-generated control signals to: increase the height of at least the rear end of the vehicle to a first predetermined vehicle height corresponding to a high trailer hitch height; and decrease the height of at least the rear end of the vehicle to a second predetermined vehicle height corresponding to a low trailer hitch height.Both the first and second preset vehicle heights are accessible from one or more other vehicle heights that differ from the first and second preset heights. Reducing the vehicle height from the high trailer hitch height to the low trailer hitch height involves the control system adjusting the suspension height adjustment mechanism so that the height of the front end of the vehicle is reduced less than the height of the rear end.

[0008] A user-operated system that allows access to high and low trailer hitch heights provides easy access to at least two predefined vehicle heights. Advantageously, the user can operate the input device so that the vehicle is at a suitable height for coupling or uncoupling a trailer, or for facilitating access to the vehicle's rear cargo area. Additionally, the high and low trailer hitch heights can be accessed from any number of other vehicle heights, allowing the user to maintain a constant trailer hitch height regardless of the vehicle's starting height.

[0009] Advantageously, the control system can be configured to control the suspension height adjustment mechanism to reduce the height of the front end of the vehicle by an amount that depends on the direction of the headlight beam.

[0010] In response to a user-generated control signal to raise the rear of the vehicle to the first preset height, the control system is optionally configured to determine a target rear height to which the rear suspension height adjustment mechanism raises the rear of the vehicle. This target rear height is determined relative to a front starting height. In this case, the target rear height can be determined using a lookup table.

[0011] Raising and lowering the vehicle height can involve controlling the suspension height adjustment mechanism to pivot a longitudinal axis of the vehicle around a point offset forward from a front axle. Pivoting a vehicle's longitudinal axis around a point offset forward from a front axle can involve controlling the suspension height adjustment mechanism to pivot a vehicle's longitudinal axis around a point offset downward and forward from the front axle. Alternatively, pivoting a vehicle's longitudinal axis around a point offset forward from a front axle can involve controlling the suspension height adjustment mechanism to pivot a vehicle's longitudinal axis around a point offset upward and forward from the front axle.

[0012] A longitudinal axis of the vehicle can be pivoted around the point furthest from the vehicle where light from the vehicle's headlights falls on the ground. Advantageously, pivoting the longitudinal axis around this point prevents a beam of light from the headlights from being raised to an impermissible height when the suspension is lowered or raised, thus preventing the possibility of third parties being dazzled by the headlights during vehicle height adjustments. The control system can further comprise one or more input devices capable of generating a user-generated control signal. These one or more input devices can include a manually operated input device that can be installed in the vehicle's trunk. The one or more input devices can optionally include a manually operated remote input device, such as...A key fob for locking / unlocking the vehicle, a custom-designed remote control, or an app running on a mobile device such as a smartphone or smartwatch. Alternatively or additionally, the one or more input devices may include a manually operated input device that can be installed in the vehicle's cabin.

[0013] An input to the control system can therefore be configured to receive user-generated control signals from multiple input devices. Providing multiple input devices allows the user to control the suspension height adjustment mechanism from more than one location around the vehicle. The user can choose to operate the multiple input devices in combination, accessing a first vehicle height via a first input device and a second vehicle height via a second input device. The control system can include an input device in the form of a switch.

[0014] In one embodiment, the control system can include an input device with a first selector switch that is operational to control the suspension height adjustment mechanism to increase the height of at least the rear end of the vehicle. Optionally, the input device can include a second selector switch that is operational to control the suspension height adjustment mechanism to decrease the height of at least the rear end of the vehicle.

[0015] If the input device includes a first selector switch and / or a second selector switch, the control system can be configured to continuously raise or lower at least the rear of the vehicle for the duration of continuous operation if the first selector switch and / or the second selector switch is continuously activated. This functionality can prevent unintentional operation of the suspension height adjustment mechanism and thus prevent a potential entrapment situation in which an object becomes trapped under the vehicle. Furthermore, this functionality can help the user prevent the vehicle body or doors from touching the ground. The first selector switch and / or the second selector switch can be activated by pressing it.

[0016] In one example, it is possible to control the suspension height adjustment mechanism to access a continuum of vehicle heights. A specific height within this continuum can be activated by deactivating the first selector switch and / or the second selector switch.

[0017] The control system can still be configured to adjust the vehicle height to access a third preset vehicle height, which corresponds to a standard trailer hitch height. The first and second selector switches can be operational simultaneously to adjust the vehicle height to this third preset vehicle height.

[0018] A high towbar height can refer to a towbar height that is between approximately 80 mm and 100 mm higher than the standard towbar height. A low towbar height can refer to a towbar height that is between approximately 60 mm and 80 mm lower than the standard towbar height.

[0019] According to the invention, the control system is further configured to control the rear suspension height adjustment mechanism and the front suspension height adjustment mechanism in such a way that the height of the rear end of the vehicle is adjusted before the height of the front end of the vehicle.

[0020] The control system can be configured to provide feedback to the user when the vehicle height reaches a predefined level. Advantageously, the control system can be configured to at least temporarily halt the raising or lowering process when the vehicle height reaches a predefined level.

[0021] The specified vehicle height can include the low trailer hitch height, the high trailer hitch height, or the normal coupling head height.

[0022] According to another aspect of the invention, a suspension system for a vehicle is provided, wherein the suspension system comprises a control system according to a previous aspect of the invention.

[0023] According to another aspect of the invention, a vehicle is provided, wherein the vehicle comprises a control system or a suspension system according to a previous aspect of the invention.

[0024] According to a further aspect of the invention, a method for controlling a vehicle's suspension height adjustment mechanism is provided, wherein the method comprises controlling the suspension height adjustment mechanism in response to user-generated control signals to: increase the height of at least one rear end of the vehicle to a first predetermined vehicle height corresponding to a high trailer hitch height; and decrease the height of at least the rear end of the vehicle to a second predetermined vehicle height corresponding to a low trailer hitch height. Both the first and the second predetermined vehicle heights are accessible from one or more other vehicle heights that differ from the first and second predetermined heights.The procedure further includes controlling a front suspension height adjustment mechanism at the front end of the vehicle and controlling a rear suspension height adjustment mechanism at the rear end of the vehicle. Reducing the vehicle height from the high trailer hitch height to the low trailer hitch height involves controlling the suspension height adjustment mechanism so that the height of the front end of the vehicle is reduced less than the height of the rear end of the vehicle.

[0025] According to another aspect of the invention, a control device for controlling a vehicle's suspension height adjustment mechanism is provided. The control device comprises an electronic processor with an electrical input for receiving: a first user-generated signal indicating a user selection of a first predefined vehicle height corresponding to a high trailer hitch height; and a second user-generated signal indicating a user selection of a second predefined vehicle height corresponding to a low trailer hitch height. The control device includes an electronic storage device that is electrically coupled to the electronic processor and in which commands are stored.The processor is configured to access the memory device and execute the instructions stored therein, enabling it to: control the suspension height adjustment mechanism in response to the first user-generated control signal to raise the height of at least one rear end of the vehicle to the first preset vehicle height, and control the suspension height adjustment mechanism in response to the second user-generated control signal to lower the height of at least one rear end of the vehicle to the second preset vehicle height. Both the first and second preset vehicle heights are accessible from one or more other vehicle heights that differ from the first and second preset heights.In response to the second user-generated signal, the processor controls a front suspension height adjustment mechanism at the front end of the vehicle and controls a rear suspension height adjustment mechanism at the rear end of the vehicle, so that the height of the front end of the vehicle is reduced less than the height of the rear end of the vehicle.

[0026] According to a further aspect of the invention, a non-volatile, computer-readable storage medium is provided on which instructions are stored which, when executed by one or more electronic processors, cause the one or more electronic processors to execute a method according to a preceding aspect of the invention.

[0027] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples, and alternatives presented in the preceding paragraphs, in the claims, and / or in the following description and drawings, and in particular their individual features, may be considered independently of one another or in any combination. This means that all embodiments and / or features of any embodiment may be combined in any way and / or in any combination, provided that these features are not incompatible.The applicant reserves the right to amend any originally filed patent claim or to file any new patent claim accordingly, including the right to amend any originally filed patent claim to depend on and / or incorporate any feature of any other patent claim, even if it was not previously claimed in this manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] One or more embodiments of the invention are now described by way of example only with reference to the accompanying drawings, which show: Fig. 1 a schematic top view of a vehicle having a vehicle suspension system of an embodiment of the invention; Fig. 2 a side view of a vehicle, including the vehicle's suspension system made of Fig. 1, which depicts the vehicle at off-road vehicle height, normal vehicle height and access vehicle height; Fig. 3 a view of a switch of the vehicle suspension system installed in the trunk Fig. 1; Fig. 4 a side view of a vehicle, including the vehicle's suspension system made of Fig. 1, which represents a high trailer hitch height and a low trailer hitch height of the vehicle; Fig. 5 a side view of a vehicle, including the vehicle's suspension system made of Fig. 1, each representing: a starting vehicle height corresponding to the normal vehicle height; and a target trailer hitch height corresponding to the vehicle's low trailer hitch height; Fig. 6. A side view of a vehicle, including the vehicle's suspension system. Fig. 1, each representing: a starting vehicle height corresponding to the access vehicle height; and a trailer coupling target height corresponding to the low trailer coupling height; Fig. 7 a side view of a vehicle, including the vehicle's suspension system made of Fig. 1, each representing: a starting vehicle height corresponding to the normal vehicle height; and a target trailer hitch height corresponding to the high trailer hitch height; Fig. 8 a side view of a vehicle, including the vehicle's suspension system made of Fig. 1, each representing: a starting vehicle height corresponding to the off-road vehicle height; and a target trailer hitch height corresponding to the high trailer hitch height; and Fig. 9 a side view of a vehicle, including the vehicle's suspension system made of Fig. 1, each representing: a starting vehicle height corresponding to the off-road vehicle height; a target trailer hitch height corresponding to the low trailer hitch height; and a subsequent target trailer hitch height corresponding to the high trailer hitch height. DETAILED DESCRIPTION

[0029] Fig. Figure 1 shows a schematic representation of a vehicle suspension system 10 of a vehicle 12. The vehicle suspension system 10 comprises a control system in the form of a suspension control system 14, which includes a suspension control module (SCM) 16. The SCM 16 is connected to a first input device in the form of a user control module installed in the trunk, including a switch 18 installed in the trunk. The SCM 16 is further connected to a second input device in the form of a control module or a switch 20 installed in the cabin, as well as to a front valve assembly and a rear valve assembly, corresponding to a front axle 22 and a rear axle 24 of the vehicle 12, respectively. The front valve assembly includes a front right angle valve 26 and a front left angle valve 28.Similarly, the rear valve arrangement comprises a rear right angle valve 30 and a rear left angle valve 32. The vehicle suspension system 10 further comprises an air compressor pump 34, which has an external motor and an air reservoir 36. In one embodiment, air enters the vehicle suspension system 10 via an inlet silencer 38, which is in fluid communication with the compressor pump 34. The compressor pump 34 supplies air to components of the vehicle suspension system 10 at high pressure, with the air flowing from an outlet of the compressor pump and through an air dryer 40. The compressor pump 34 is further connected to a main outlet valve 42, the main outlet valve being controlled, in conjunction with a pilot outlet valve 44, by the venting of the system. The air expelled from the main outlet valve 42 flows through an outlet 46.

[0030] The air reservoir 36 serves as a compressed air storage tank, with the airflow from the reservoir controlled via a reservoir valve 48. The front corner valves 26, 28 and rear corner valves 30, 32 are each in fluid communication with a suspension height adjustment mechanism of the vehicle suspension system 10. The suspension height adjustment mechanism comprises four air spring assemblies: a first air spring assembly 50 corresponding to the right side of the front axle 22 of the vehicle 12; a second air spring assembly 52 corresponding to the left side of the front axle 22 of the vehicle 12; a third air spring assembly 54 corresponding to the right side of the rear axle 24 of the vehicle 12; and a fourth air spring assembly 56 corresponding to the left side of the rear axle 24 of the vehicle 12.The SCM 16 is still configured to communicate with a front right height sensor 58, a front left height sensor 60, a rear right height sensor 62 and a rear left height sensor 64, with each height sensor 58, 60, 62, 64 being provided near the respective air spring assembly 50, 52, 54, 56.

[0031] The SCM 16 is configured to receive user-generated control signals from the trunk-mounted switch 18 and the cabin-mounted switch 20, and to control adjustments to the vehicle height 12 in response to these user-generated control signals. Such adjustments are controlled by communication between the SCM 16 and the valves of the vehicle suspension system 10. The front right corner valve 26 and the front left corner valve 28 are configured to control the airflow to the first and second air spring assemblies 50 and 52, respectively. The rear right and rear left corner valves 30 and 32 are configured to control the airflow to the third and fourth air spring assemblies 54 and 56, respectively. The corner valves 26, 28, 30, 32 are further arranged to regulate the airflow in an opposite direction to remove excess air from the air spring assemblies 50, 52, 54, 56.

[0032] To supply air to one or more of the air spring assemblies 50, 52, 54, 56, the SCM 16 communicates with the reservoir valve 48 and the corresponding angle valve(s) 26, 28, 30, 32 of the vehicle suspension system 10 to open the valves and allow air to flow from the reservoir valve 36 and the respective air spring assembly 50, 52, 54, 56. Compressed air from the compressor pump 34 is then used to refill the reservoir 36. Alternatively, the SCM 16 can control the lifting of the vehicle by communicating with the compressor pump 34 and configuring it to drive compressed air through the system while the corresponding angle valve(s) 26, 28, 30, 32 is / are opened.

[0033] To vent one or more of the air spring assemblies 50, 52, 54, 56, the SCM 16 communicates with the pilot exhaust valve 44 and the corresponding angle valves 26, 28, 30, 32 to open the valves. Opening the pilot exhaust valve 44 forces the air through the main exhaust valve 42 and through the exhaust valve 46 to the outside, expelling the air from the vehicle suspension system 10.

[0034] The vehicle 12 has a chassis 66, which forms the main load-bearing structure of the vehicle 12. It is understood that the chassis 66 of the vehicle 12 can be in the form of a frame that is separate from a body of the vehicle 12. Alternatively, the vehicle can be constructed using a shell-type design, with the vehicle body being the main structural component of the vehicle 12. It is understood that the invention described herein is applicable to a vehicle 12 in shell-type construction or to a vehicle of any other suitable configuration, as well as to a vehicle 12 with a separate frame and body.

[0035] The chassis 66 comprises a front end 68, corresponding to the front axle 22 of the vehicle 12, and a rear end 70, corresponding to the rear axle 24 of the vehicle 12. Each height sensor 58, 60, 62, 64 of the vehicle suspension system 10 provides the SCM 16 with a signal indicating the instantaneous height of the chassis 66 at the position of the respective height sensor 58, 60, 62, 64. The height sensors 58, 60, 62, 64 are configured to communicate continuously with the SCM 16, so that the SCM 16 is supplied with real-time information about the height of the chassis 66 at the right and left sides of the front and rear axles 22, 24 of the vehicle 12. The height of the chassis 66 on the right and left sides of axles 22 and 24 is measured from a wheel hub corresponding to the respective side of axle 22 and 24 and a reference point on the vehicle body. The reference point can be a point directly above the wheel hub.Alternatively, the chassis height 66 can be a relative measure, calculated as the difference between this instantaneous height measurement and the same measurement taken when the vehicle is at a reference height.

[0036] The user can operate the suspension system 10 via the switch 20 installed in the cabin and the switch 18 installed in the trunk. In one embodiment, the cabin-installed switch 20 consists of a switch positioned on a center console within the cabin of the vehicle 12, the switch being operable by the user to select a setting from a discrete number of predefined settings of the suspension system 10. More generally, the Fig. 1 to 3, such suspension settings may include: Normal 72, based on a standard vehicle height where the vehicle suspension system 10 has been optimized for on-road use; Offroad 74, based on an increased vehicle height compared to Normal 72, for improved ground clearance when the vehicle 12 travels over uneven terrain; and Access 76, based on a lower vehicle height relative to Normal 72, for easier loading of the vehicle and for easier entry and exit of the occupants.

[0037] By positioning the switch in one of the predefined positions, the user can select a suspension setting adapted to their needs or to the terrain on which the vehicle 12 is traveling. Such settings as described here are known and can be manually selected by the user. Alternatively or additionally, the vehicle suspension system 10 can be automatically adjusted if certain conditions are met. For example, the vehicle suspension system 10 can automatically reduce the vehicle height from off-road height 74 to normal height 72 if a measured vehicle speed exceeds a predefined vehicle speed threshold.

[0038] In one example, the off-road height 74 typically corresponds to a vehicle height where both the front end 68 of the chassis 66 and the rear end 70 of the chassis 66 are positioned 40 mm above their respective positions at normal height 72. The access height 76 typically refers to a vehicle height where both the front end 68 of the chassis 66 and the rear end 70 of the chassis 66 are positioned 50 mm below their respective positions at normal height 72. Other suspension settings may be available, such as a second off-road height 74, where the vehicle 12 is raised relative to the off-road height 74 for use in wading and extreme off-road driving.

[0039] The trunk-mounted switch 18 is positioned in a rear cargo area of ​​the vehicle 12 and provides the user with additional functionality to the cabin-mounted switch 20. Access to the rear cargo area is via a rear tailgate 78 of the vehicle 12, and the trunk-mounted switch 18 is only operational when the rear tailgate 78 is open. Alternatively, a switch can be positioned near a rear passenger door of the vehicle 12, allowing the user to operate the switch from a position on the side of the vehicle 12. The trunk-mounted switch 18 includes two options or buttons 80, 82, each of which can be selected by the user to access a separate function of the air suspension assemblies 50, 52, 54, 56.

[0040] A first option, or first button 80, can be used to access a first function of the air spring assemblies 50, 52, 54, 56 to raise the vehicle suspension height while the first button 80 is pressed and held continuously. A second option, or second button 82, can be used to access a second function of the air spring assemblies 50, 52, 54, 56 to lower the vehicle height while the second button 82 is pressed and held continuously. By simultaneously pressing and holding both buttons 80 and 82, the vehicle height is effectively "reset," adjusting the front end 68 and the rear end 70 of the chassis 66 so that the vehicle height corresponds to the normal height 72.The first button 80 typically represents an "upward arrow" 84, and the second button typically represents a "downward arrow" 86, so that the user can easily predict how the vehicle 12 will respond to the selection of a button 80, 82 of the switch 18 installed in the trunk.

[0041] By operating switch 18 installed in the trunk, the user can choose to access a range of predefined target vehicle heights in addition to the normal height 72. As in Fig. As shown in Figure 4, the nominal vehicle heights correspond to the nominal trailer hitch heights of a trailer hitch or coupling head 88 of the vehicle. In particular, the SCM 16 is configured to control the air spring assemblies 50, 52, 54, 56 of the vehicle suspension system 10 to access a high trailer hitch height, or a high coupling head height 90, and a low trailer hitch height, or a low coupling head height 92. The user may choose to access the high coupling head height 90 to facilitate attaching a trailer to the vehicle 12. Alternatively, the user may wish to access the high coupling head height 90 to manipulate the position of an attached trailer to facilitate loading or unloading the trailer or to level the trailer on uneven terrain.The low coupling head height of 92 can be selected if the user wishes to make loading and unloading the rear cargo space of the vehicle 12 easier, or if the user wishes to make uncoupling an attached trailer easier.

[0042] The normal height corresponds to a normal trailer coupling height or normal coupling head height 72, where the front end 68 of the chassis 66 is in a reference position of 0 mm and the rear end 70 of the chassis 66 is in a reference position of 0 mm, measured by the front and rear height sensors 58, 60, 62, 64 respectively (shown in Fig. 1) The reference value of 0 mm is used here as a reference against which all other chassis heights are compared. Any other suitable reference value can be assigned to the height of the front and rear ends 68, 70 of the chassis 66 at the normal coupling head height 72.

[0043] The high coupling head height 90 corresponds to a coupling head height that is between approximately 80 mm and 100 mm higher than the standard coupling head height 72. Specifically, with the high coupling head height 90, the coupling head 88 is 95 mm higher than the standard coupling head height 72. The low coupling head height 92 corresponds to a coupling head height that is between approximately 60 mm and 80 mm lower than the standard coupling head height 72. In particular, with the low coupling head height 92, the coupling head 88 is 70 mm lower than the standard coupling head height 72.

[0044] Regarding the Fig. 1 to 4, the SCM 16 can calculate an instantaneous coupling head height from the real-time height data provided by the height sensors 58, 60, 62, 64 of the vehicle suspension system 10. The SCM 16 uses the height data together with the dimensions relating to the vehicle 12 to calculate the instantaneous coupling head height using trigonometry. When a button 80 or 82 of the switch 18 installed in the trunk is selected, the SCM 16 determines the target coupling head height. Specifically, if the user selects the first button 80 of the switch 18 installed in the trunk, the SCM 16 determines the target coupling head height as the high coupling head height 90. Conversely, if the user selects the second button 82 of the switch 18 installed in the trunk, the SCM 16 determines the target coupling head height as the low coupling head height 92.

[0045] The SCM 16 is configured to control vehicle height adjustments so that a longitudinal axis of the vehicle 12 can pivot about a point offset forward from the front axle 22 of the vehicle 12. Selecting the first button 80 of the switch 18 located in the trunk pivots a longitudinal axis of the vehicle 12 about a point offset forward and downward from the front axle 22 of the vehicle 12. Selecting the second button 82 of the switch 18 located in the trunk pivots the longitudinal axis of the vehicle 12 about a point offset upward and forward from the front axle 22 of the vehicle 12. The vehicle height adjustments are controlled to prevent the headlight beams of the vehicle 12 from dazzling other road users.

[0046] The SCM 16 is configured to minimize the movement of the front end 68 of the chassis 66 in response to a target coupling head height, whereby the height of the front end 68 of the chassis 66 is only adjusted to achieve acceptable headlight alignment and to protect other road users from glare. This reduces the time required to adjust the vehicle suspension system 10 and minimizes the air resources needed to actuate the air springs 50, 52, 54, 56 of the vehicle suspension system 10 to achieve the target coupling head height. Reducing the height adjustment at the front end 68 of the chassis 66 also prevents entrapment situations in which an object becomes trapped under the front end of the chassis 66 during operation of the vehicle suspension system 10.Reducing these height adjustments can also prevent the lower surface of the vehicle 12 from being lowered onto a rock or other road surface formation, thus avoiding damage to the vehicle 12.

[0047] The height of the front end 68 of the chassis 66 and the height of the rear end 70 of the chassis 66 are therefore adjusted in various stages in most height adjustment scenarios. The SCM 16 is equipped with an algorithm for calculating a target front height for the front end 68 of the chassis 66 and a target rear height for the rear end 70 of the chassis 66 in response to a user's selection of a coupling head target height. The algorithm is configured to achieve the coupling head target height in such a way as to minimize the adjustment of the first and second air spring assemblies 50, 52. The SCM 16 is thus able to calculate a target rear height using trigonometry.

[0048] to calculate the dependence on the coupling head target height and a front target height, whereby the front target height is selected such that the movement of the front end 68 of the chassis 66 is minimized.

[0049] Alternatively, the SCM 16 can use a lookup table from which the front target height and the rear target height can be extracted as a function of a front starting height and a rear starting height of the chassis 66, measured by the height sensors 58, 60, 62, 64 of the vehicle suspension system 10. The lookup table is created offline during a calibration process before the vehicle 12 is used. When a button 80, 82 of the switch 18 installed in the trunk is selected, the SCM 16 enters the coupling head target height as well as the front and rear starting heights into the lookup table, extracting the corresponding front and rear coupling head heights.

[0050] For the low coupling head height 92, the lookup table includes front and rear target heights for every possible combination of chassis starting heights, with the target values ​​achieving a coupling head height 70 mm below the normal coupling head height 72. Similarly, the lookup table for the high coupling head height 90 includes front and rear target heights for every possible combination of chassis starting heights, with the target values ​​achieving a coupling head height 95 mm above the normal coupling head height 72. The vehicle suspension system 10 is therefore configured so that the user can adjust the vehicle height to achieve the specified coupling head target heights from any vehicle starting height.

[0051] Fig. Figure 5 represents the operation of the vehicle suspension system 10 in use. In the scenario of Fig. 5. The vehicle 12 was parked at its normal height 72, and the user intends to lower the rear of the vehicle 12 70. In this case, upon exiting the vehicle 12 and opening the tailgate 78, the user selects the second button 82 of the switch 18 installed in the trunk to access the second function of the air suspension assemblies 50, 52, 54, 56 and lower the vehicle 12.

[0052] Selecting the second button 82 of the switch 18 installed in the trunk causes the switch 18 installed in the trunk to send a user-generated control signal to the SCM 16. Upon receiving the user-generated control signal, the SCM 16 determines the coupling head target height to be 70 mm below the normal coupling head height 72, calculating a corresponding front target height and rear target height using any previously described means.

[0053] The SCM 16 is configured to simultaneously command the lowering of the front end 68 of the chassis 66 and the rear end 70 of the chassis 66. The SCM 16 then transmits a signal to the rear valve assembly, the front valve assembly, and the pilot exhaust valve 44 of the vehicle suspension system 10, allowing compressed air to flow from all four air spring assemblies 50, 52, 54, 56 of the vehicle suspension system 10. The air flows from the air spring assemblies 50, 52, 54, 56 and through the angle valves 26, 28, 30, 32 of the front and rear valve assemblies. A small amount of air flows through the pilot exhaust valve 44 and activates the main exhaust valve 42. Essentially, all of the air is then routed through the main exhaust valve 42 and out through the outlet 46. The air exiting the air spring assemblies causes the air spring assemblies to contract and the front end 68 and the rear end 70 of the chassis 66 to be lowered.

[0054] The user-generated control signal is continuously transmitted to the SCM 16 while the second button 82 is selected, so that with button 82 pressed, the vehicle 12 continues to lower to the low coupling head height 92. The height sensors 58, 60, 62, 64 continue to transmit height data to the SCM 16, and a feedback loop is established, with the SCM 16 maintaining the rear valve assembly in a state to expel air from the rear air spring assemblies 54, 56 while the rear end 70 of the chassis 66 is above the rear setpoint height.

[0055] Similarly, the front valve assembly is held in a position to expel air from the front air spring assemblies 50, 52 while the front end 68 of the chassis 66 is above the front nominal height. The chassis 66 is slightly lowered at the front end 68 to achieve acceptable headlight alignment. The front end 68 of the chassis 66 experiences a smaller vertical displacement relative to the rear end 70 of the chassis 66, so that at the low coupling head nominal height 92, the vehicle 12 is inclined towards the front of the vehicle 12, as shown in Fig. Figure 5 shows that when the signals from the height sensors 62 and 64 indicate that the low coupling head height 92 has been reached, the SCM 16 terminates the signals to the front and rear valve assemblies, thus preventing further movement of the front end 68 and the rear end 70 of the chassis 66, respectively. Once the SCM 16 determines that both the front and rear target heights have been reached, the SCM 16 configures the pilot exhaust valve 44 to close.

[0056] In one embodiment, the SCM 16 can receive signals from a Light Control Module (LCM) of the vehicle 12. The LCM can be configured to inform the SCM 16 about the status of the vehicle 12's headlights. If the signals indicate that the headlights are in an "OFF" state, the chassis 66 does not need to be lowered at the front end 68 to achieve acceptable headlight alignment. Therefore, in this situation, the SCM 16 can be configured to inhibit the lowering of the front end 68 of the chassis 66, thereby minimizing the operation of the air suspension assemblies 50, 52, 54, 56.

[0057] Fig. Figure 6 describes the operation of the vehicle suspension system 10 in the event that the user decides to lower the vehicle 12 when the vehicle 12 is parked at access height 76, at which the front end 68 and the rear end 70 of the chassis 66 are each 50 mm below their respective positions at normal height 72. Since the front starting height at access height 76 is lower than the front starting height at normal height 72, the rear end 70 of the chassis 66 must be lowered to a lower rear target height with respect to the scenario of Fig. 5 lowered to achieve the low coupling head height of 92.

[0058] As described above, the SCM 16 transmits a signal to the angle valves 30, 32 of the rear valve assembly of the vehicle suspension system 10 and to the pilot exhaust valve 44 to configure the rear valve assembly to release air from the third and fourth air spring assemblies 54, 56. The third and fourth air spring assemblies 54, 56 retract, and the rear end 70 of the chassis 66 is lowered until the rear setpoint height is reached. The rear setpoint height is lower than the rear setpoint height corresponding to a normal vehicle takeoff height, but the required displacement of the rear end 70 of the chassis 66 to achieve the low coupling head height 92 is smaller. Therefore, the lowering of the rear end 70 is insufficient to cause an impermissible headlight alignment, and no adjustment is required at the front end 68 of the chassis 66.

[0059] Alternatively, the front end 68 and the rear end 70 of the chassis 66 can be lowered sequentially, with the rear end 70 being lowered to the rear target height before the front end 68 being lowered to the front target height, as calculated by the SCM 16.

[0060] The Fig. 7 and Fig. Figure 8 describes the operation of the vehicle suspension system 10 in the event that the user chooses to use the switch 18 installed in the trunk to raise the vehicle height from normal height 72 or off-road height 74. By raising the rear end 70 of the chassis 66, the vehicle height decreases towards the front end 68 of the chassis 66, thus maintaining the headlight beam in an acceptable alignment. Raising the vehicle 12 to achieve the high coupling head height 90 from normal height 72 or off-road height 74 therefore only requires adjusting the height of the rear end 70 of the chassis 66, while the front end 68 of the chassis 66 remains at the starting front height.

[0061] In the scenario of Fig. 7. The user selects the first button 80 of the switch 18 installed in the trunk and triggers a user-generated control signal to be transmitted to the SCM 16. The SCM 16 simultaneously transmits a signal to the rear right corner valve 30 and the rear left corner valve 32 of the vehicle suspension system 10 and to the reservoir valve 48 to configure the vehicle suspension system 10 to allow compressed air to flow from the air reservoir 36 to the third and fourth air spring assemblies 54 and 56. The compressed air injection expands the third and fourth air spring assemblies 54 and 56, and the rear end 70 of the chassis 66 is raised from its normal height 72.When the signals from the height sensors 62, 64 indicate that the target height for the rear end 70 of the chassis 66 has been reached, the SCM 16 terminates the signal transmission to the angle valves 30, 32 of the rear valve assembly and to the reservoir valve 48, further movement of the rear end 70 of the chassis 66 is prevented and the coupling head 88 is determined to lie at the high coupling head height 90.

[0062] In the event that the user selects the first button 80 when the vehicle is at off-road height 74, essentially the same process is performed. In the scenario of Fig. However, the front starting height is higher than that corresponding to a normal vehicle height of 72. Therefore, to achieve the high coupling head height of 90, the rear target height must be higher than that set by the SCM 16 if the vehicle 12 is to be lifted from the normal height of 72.

[0063] After the vehicle height has been adjusted to facilitate coupling and uncoupling a trailer or access to the rear cargo area, the user may wish to reset the coupling head height. In this case, the user can simultaneously press and hold both the first button 80 and the second button 82 of the trunk-mounted switch 18 to actuate the vehicle suspension system 10 and return to the normal coupling head height 72. With both buttons 80 and 82 of the trunk-mounted switch 18 selected simultaneously, the SCM 16 sends a signal to the angle valves 30 and 32 of the rear valve assembly and / or the angle valves 26 and 28 of the front valve assembly, as appropriate. The airflow to the air spring assemblies 50, 52, 54, and 56 is controlled to raise or lower the chassis to achieve the front setpoint height and the rear setpoint height of 0 mm.As previously described, when the vehicle 12 is lowered, the SCM 16 transmits a signal to the pilot exhaust valve 44 so that air can escape from the system. Conversely, when raising the vehicle, the SCM 16 transmits a signal to the reservoir valve 48 to allow the flow of compressed air to the corresponding air spring assemblies 50, 52, 54, 56.

[0064] As mentioned above, the SCM 16 continues to control the air suspension assemblies while one or both buttons 80, 82 of the trunk-mounted switch 18 are pressed and held continuously to cause movement to the coupling head setpoint height. However, the user may wish to hold the coupling head 88 at an intermediate position between two of the coupling head setpoint heights. This is particularly likely when the user is attempting to hitch a trailer to the vehicle 12, as the high coupling head height 90 may not be the optimal height for all trailer dimensions and configurations. The user may also wish to adjust the vehicle height incrementally to allow time to assess the most suitable coupling head height or to manipulate the trailer's position when loading and unloading.

[0065] In this case, the user can release the selected button(s) 80, 82 of the switch 18 installed in the trunk before the target vehicle height is reached. Referring again to Fig. 5. The user can first select the second button 82 to configure the vehicle suspension system 10 to lower the chassis 66. The user can then choose to release the second button 82 at any time, with the rear and front valve arrangements configured by the SCM 16 to prevent further airflow to or from the vehicle's air spring assemblies 50, 52, 54, 56.

[0066] Upon release of the second button 82, the SCM 16 determines the height of the rear end 70 of the chassis 66, measured by the rear height sensors 62, 64 of the vehicle suspension system 10. The SCM 16 then calculates the difference between the determined height of the rear end 70 of the chassis 66 and the rear target height, where the rear target height corresponds to the low coupling head height 92. The calculated difference is applied to the front target height, so that the SCM 16 controls the first and second air spring assemblies 50, 52 to adjust the front end 68 of the chassis 66 until the front end 68 is at least as close to the front end target height as the rear end 70 is to the rear end target height. It is understood that the suspension control system 14 can be configured to perform this function only when the chassis 66 is raised.Alternatively, the suspension control system 14 can be configured to perform this function when the chassis 66 is either lowered or raised.

[0067] Configuring the SCM 16 to inhibit further movement of the chassis 66 upon release of the second button 82 allows the user to react to potential entrapment situations and prevent the possibility of an object becoming trapped under the vehicle 12. In one embodiment, after the front end of the chassis 66 has been lowered, the SCM 16 is further configured to raise the front end 68 of the chassis 66 to the front starting height in response to the subsequent selection of the first button 80 of the switch 18 installed in the trunk.

[0068] With an exemplary reference to Fig.In a first step, the user may have chosen to lower the vehicle 12 from the off-road height 74 to access the low coupling head height 92, thereby lowering the front end 68 of the chassis 66 to a first front target height. Subsequently, by selecting the first button 80 of the switch 18 installed in the trunk, the SCM 16 determines a second front target height as the front starting height, corresponding to the off-road height 74. In a next step, the SCM 16 calculates a rear target height, which, in combination with the second front target height, achieves the high coupling head height.

[0069] Essentially the same process is carried out if the chassis 66 is first lowered from the normal vehicle height 72 before the first button 80 of the switch 18 installed in the trunk is selected. In this case, the front end 68 of the chassis 66 is raised again to the front starting height, which corresponds to a normal vehicle height 72.

[0070] The SCM 16 is configured to first instruct the lifting of the rear end 70 of the chassis 66 before lifting the front end 68 of the chassis 66. Such a movement is quickly visible to the user, who is located at the rear of the vehicle 12, and as such gives the user the assurance that the vehicle 12 is responding to their request.

[0071] A similar functionality can also be available if the height of the vehicle 12 has been increased beforehand, if necessary. For example, if the rear end 70 of the chassis 66 is significantly raised, the tilt of the vehicle 12 towards the rear end 70 may reduce the available space under the front end 68 of the chassis 66. In this case, when the first button 80 is subsequently selected, the SCM 16 can be configured to raise the front end 68 of the chassis 66 according to the tilt of the vehicle 12, thus avoiding potentially undesirable situations at the front end 68. This functionality can be made available to the user automatically. Alternatively, the user can choose to activate the functionality by interacting with a human-machine interface (HMI) in the vehicle cabin.

[0072] Therefore, the movement of the front end 68 of the chassis 66 can be initiated by three means during the operation of the vehicle suspension system 10. Either: by selecting the second button 82 of the switch 18 installed in the trunk; when the rear end 70 of the chassis 66 has reached the target height for the rear end for a specific coupling head target height; or by releasing a button 80, 82 of the switch 18 installed in the trunk before the rear target height is reached.

[0073] In one embodiment, the user has the option of using a remote input device, such as a key fob assigned to the vehicle 12, to operate the vehicle's suspension system. As is typical, the key fob includes buttons that allow the user to, among other things, lock the vehicle 12 and control the opening of the tailgate 78. For example, the key fob may have a first button to activate the vehicle 12's hazard warning lights, a second button to open the vehicle 12's tailgate 78, a third button to unlock the vehicle 12, and a fourth button to lock the vehicle 12. The key fob can be automatically configured to operate the vehicle's suspension system 10 when the first button is selected. Alternatively, the user may choose to activate the key fob to control the vehicle's suspension system 10 by entering a command into the vehicle 12's HMI.

[0074] When the key fob is activated, the first and second buttons of the key fob can be selected simultaneously by the user to access the second function of the vehicle 12, thereby lowering the vehicle 12. The first and third buttons of the key fob can be selected simultaneously to access the first function of the vehicle 12, raising the vehicle 12. The first and fourth buttons of the key fob can be selected simultaneously to reset the vehicle 12 to its normal coupling head height 72. Such functionality is useful if the switch 18 installed in the trunk is inaccessible, for example, if a bicycle carrier is mounted on the rear of the vehicle 12. In one embodiment, the hazard warning lights of the vehicle 12 must be switched on in order to access the suspension functionality via the key fob.

[0075] The SCM 16 can be configured to allow operation of the vehicle suspension system 10 only when the air pressure in reservoir 36 is sufficient to reverse the operation. Such a measure protects against a situation in which the vehicle 12 has been lowered to achieve the low coupling head height 92, but the air pressure available to the air spring assemblies 50, 52, 54, 56 is insufficient to subsequently raise the vehicle 12. To provide the user with a visual indication of the status of the vehicle suspension system 10, one or more of the switches 18, 20 can include an indicator. For example, the indicator can be in the form of LEDs located near the trunk-mounted switch 18, with a green LED illuminated when the suspension system 10 is operable via the trunk-mounted switch 18, and a red LED illuminated when the user is not permitted to operate the vehicle suspension system 10.

[0076] As described above, the height of the chassis 66 is controlled independently at each axle 22, 24. It is understood that the height of the chassis 66 can optionally be controlled at each wheel, since each corner valve 26, 28, 30, 32 corresponds to a separate air spring assembly 50, 52, 54, 56 of the vehicle suspension system 10. When a button 80, 82 of the switch 18 installed in the trunk is selected, the SCM 16 determines a front right target height, a front left target height, a rear right target height, and a rear left target height and configures the corner valves 26, 28, 30, 32 to control the airflow to each of the respective air spring assemblies 50, 52, 54, 56 in order to achieve the low or high coupling head height 92, 90 as required.

[0077] Determining the front right, front left, rear right, and rear left target heights may depend in part on a calculated average front target height and a calculated average rear target height. The front right and front left target heights may be calculated to achieve the average front target height, and analogously, the rear right and rear left target heights may be calculated to achieve the average rear target height. As described above with respect to the front-end and rear-end target heights, the average front and rear target heights may be set to achieve the coupling head target height. The use of average target heights may account for situations where the vehicle is parked on uneven ground.

[0078] The front and rear axles 22, 24 of the vehicle can be physical, fixed axles connecting the front and rear wheels of the vehicle, respectively. Alternatively, the terms ‘front axle’ 22 and ‘rear axle’ 24 can refer to a pair of front wheels and a pair of rear wheels, each wheel of the wheel pairs being in an independent suspension arrangement.

[0079] As described above, by selecting the first button 80 of the switch installed in the trunk, the vehicle suspension system 10 can be configured to allow compressed air to flow from the air reservoir 36 to the third and fourth air spring assemblies 54 and 56, thus raising the rear end 70 of the chassis 66. Alternatively, selecting the first button 80 can configure the vehicle suspension system 10 to release air from the first and second air spring assemblies 50 and 52, while simultaneously allowing compressed air to flow to the third and fourth air spring assemblies 54 and 56. In this way, the rear end 70 of the chassis 66 is raised, while the front end 68 of the chassis 66 is lowered. Such functionality can enable the vehicle to reach the high coupling head height 90 more quickly.

[0080] It is noted that the switch 20 installed in the cabin may be configured alternatively or additionally to access the low coupling head height 92 and / or the high coupling head height 90, with the low coupling head height 92 and / or the high coupling head height 90 being provided as preset settings on the center console scale. Likewise, it is noted that the switch 18 installed in the trunk may be configured alternatively or additionally to access the access vehicle height 76 and / or the off-road vehicle height 74.

[0081] In practice, the user might want to use the cabin-mounted switch 20 in combination with the trunk-mounted switch 18 to operate the vehicle suspension system 10. For example, the user might choose to access the low coupling head height 92 by operating the cabin-mounted switch 20 before adjusting the coupling head height 88 to couple a trailer to the vehicle 12 using the trunk-mounted switch 18. The trunk-mounted switch 18 allows the user to fine-tune the coupling head height 88 from a position at the rear of the vehicle 12. Similarly, the user might want to uncouple the trailer using the trunk-mounted switch 18 to move the vehicle 12 forward to release the coupling head 88, and then raise the vehicle height to normal height 72 using the cabin-mounted switch 20.

[0082] The vehicle suspension system 10 described herein is an "open" system. It is understood that the invention is also applicable to a "closed" suspension system in which a compressor pumps air from an air reservoir into air spring assemblies. When the vehicle is lowered, the compressor is switched to pump air from the air spring assemblies and back into the air reservoir.

[0083] Many modifications can be made to the above examples without deviating from the scope of the present invention as defined in the attached claims.

Claims

[1] Control system (14) for a suspension height adjustment mechanism of a vehicle (12), wherein the suspension height adjustment mechanism (50, 52, 54, 56) comprises a front suspension height adjustment mechanism (50, 52) at a front end (68) of the vehicle and a rear suspension height adjustment mechanism (54, 56) at a rear end (70) of the vehicle, wherein the control system (14) is configured to control the suspension height adjustment mechanism (50, 52, 54, 56) in response to user-generated control signals to: increase the height of at least the rear end (70) of the vehicle to a first predetermined vehicle height corresponding to a high trailer hitch height (90); and decrease the height of at least the rear end of the vehicle (70) to a second predetermined vehicle height corresponding to a low trailer hitch height (92), wherein both the first and second predetermined vehicle heights are accessible from one or more other vehicle heights that differ from the first and second predetermined heights;and wherein reducing the vehicle height from the high trailer hitch height (90) to the low trailer hitch height (92) comprises the control system controlling the suspension height adjustment mechanism (50, 52, 54, 56) such that the height of the front end (68) of the vehicle is reduced less than the height of the rear end (70) of the vehicle; wherein the control system is configured to control the rear suspension height adjustment mechanism (54, 56) and the front suspension height adjustment mechanism (50, 52) such that the height of the rear end (70) of the vehicle is adjusted before the height of the front end (68) of the vehicle. [2] Control system (14) according to claim 1, wherein the control system is configured to control the suspension height adjustment mechanism (50, 52, 54, 56) to reduce the height of the front end (68) of the vehicle by an amount which depends on the direction of the headlight beam. [3] Control system according to claim 1, wherein, in response to a user-generated control signal to increase the height of the rear end (70) of the vehicle to the first predetermined height, the control system is configured to determine a target height of the rear end to which the rear suspension height adjustment mechanism (54, 56) increases the height of the rear end of the vehicle, the rear target height being determined as a function of a front starting height. [4] Control system according to claim 3, wherein the target height of the rear end is determined by means of a lookup table. [5] Control system according to one of the preceding claims, further comprising one or more input devices (18, 20) capable of generating a user-generated control signal, wherein the one or more input devices comprise a first selector switch (80) capable of controlling the suspension height adjustment mechanism (50, 52, 54, 56) to increase the height of at least the rear end (70) of the vehicle, and a second selector switch (82) capable of controlling the suspension height adjustment mechanism to decrease the height of at least the rear end (70) of the vehicle, wherein, during continuous operation of the first selector switch (80) and / or the second selector switch (82), the control system is configured to continuously raise or lower at least the rear end (70) of the vehicle for the duration of the continuous operation. [6] Control system according to claim 5, wherein the suspension height adjustment mechanism (50, 52, 54, 56) is controllable to access a continuum of vehicle heights, wherein a specific height within this continuum can be selected by terminating the operation of the first selector switch (80) and / or the second selector switch (82). [7] Control system according to one of the preceding claims, further configured to adjust the vehicle height to a third predetermined vehicle height corresponding to a normal trailer hitch height. [8] Control system according to claim 7, when dependent on claim 5, wherein the first and the second selector switches (80, 82) are simultaneously operable to adjust the vehicle height to the third predetermined vehicle height. [9] Control system according to one of the preceding claims, wherein raising and lowering the vehicle height comprises controlling the suspension height adjustment mechanism (50, 52, 54, 56) to pivot a longitudinal axis of the vehicle about a point offset forward from a front axle (22) of the vehicle. [10] Control system according to claim 9, wherein pivoting a vehicle longitudinal axis about a point offset forward from a front axle (22) of the vehicle comprises controlling the suspension height adjustment mechanism (50, 52, 54, 56) to pivot a vehicle longitudinal axis about a point offset downwards and forwards from the front axle (22) of the vehicle. [11] Control system according to claim 9, wherein pivoting a vehicle longitudinal axis about a point offset forward from a front axle (22) of the vehicle comprises controlling the suspension height adjustment mechanism (50, 52, 54, 56) to pivot a vehicle longitudinal axis about a point offset upward and forward from the front axle (22) of the vehicle. [12] Vehicle comprising a control system according to any one of claims 1 to 11. [13] Method for controlling a suspension height adjustment mechanism (50, 52, 54, 56) of a vehicle (12), the method comprising: Controlling the suspension height adjustment mechanism (50, 52, 54, 56) in response to user-generated control signals to: raise the height of at least one rear (70) end of the vehicle to a first predetermined vehicle height corresponding to a high trailer hitch height (90); and lower the height of at least the rear (70) end of the vehicle to a second predetermined vehicle height corresponding to a low trailer hitch height (92), wherein both the first and second predetermined vehicle heights are accessible from one or more other vehicle heights that differ from the first and second predetermined heights; wherein the method further comprises: controlling a front suspension height adjustment mechanism (50, 52) at a front end (68) of the vehicle and controlling a rear suspension height adjustment mechanism (54, 56) at the rear end (70) of the vehicle, wherein reducing the vehicle height from the high trailer hitch height (90) to the low trailer hitch height (92) comprises: controlling the suspension height adjustment mechanism (50, 52, 54, 56) such that the height of the front end (68) of the vehicle is reduced less than the height of the rear end (70) of the vehicle; and wherein the method further comprises controlling the rear suspension height adjustment mechanism (54, 56) and the front suspension height adjustment mechanism (50, 52) so that the height of the rear end (70) of the vehicle is adjusted before the height of the front end (68) of the vehicle. [14] Control device for controlling a suspension height adjustment mechanism (50, 52, 54, 56) of a vehicle, the control device comprising: an electronic processor with an electrical input for receiving: a first user-generated signal indicating a user selection of a first predefined vehicle height corresponding to a high trailer hitch height (90); and a second user-generated signal indicating a user selection of a second predefined vehicle height corresponding to a low trailer hitch height (92); an electronic storage device that is electrically coupled to the electronic processor and contains instructions stored therein, where the processor is configured to access the storage device and execute the instructions stored therein, so that it is operational: to control the suspension height adjustment mechanism (50, 52, 54, 56) in response to the first user-generated control signal to increase the height of at least one rear end (70) of the vehicle to the first preset vehicle height, and to control the suspension height adjustment mechanism (50, 52, 54, 56) in response to the second user-generated control signal to decrease the height of at least the rear end (70) of the vehicle to the second preset vehicle height, wherein both the first and the second preset vehicle height are accessible from one or more other vehicle heights that differ from the first and second preset heights;and wherein, in response to the second user-generated signal, the processor controls a front suspension height adjustment mechanism (50, 52) at a front end (68) of the vehicle and controls a rear suspension height adjustment mechanism (54, 56) at the rear end (70) of the vehicle, such that the height of the front end (68) of the vehicle is reduced less than the height of the rear end (70) of the vehicle; and; to control the rear suspension height adjustment mechanism (54, 56) and the front suspension height adjustment mechanism (50, 52) so that the height of the rear end (70) of the vehicle is adjusted before the height of the front end (68) of the vehicle. [15] Non-volatile, computer-readable storage medium on which instructions are stored which, when executed by one or more electronic processors, cause the one or more electronic processors to execute the method according to claim 13.

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