System for predictive chassis control for an off-road utility vehicle

[0001] This application claims the benefit of International Patent Application PCT/EP2016/055852, filed Mar. 17, 2016, which claims priority to German Application Ser. No. 102015205210.9, filed Mar. 23, 2015, the disclosures of which are hereby expressly incorporated by reference in their entirety.

[0002] The present disclosure relates to a system for predictive chassis control for an off-road utility vehicle.

[0003] A system for predictive chassis control are known, in particular, from the automobile industry. For instance, a system for optimizing the handling of a motor vehicle equipped with an adaptive chassis is disclosed in German patent application DE 10 2012 017 118 A, in which a topographical profile of a roadway surface situated ahead in the direction of travel is captured for the purpose of predicting a motion behavior to be expected of the motor vehicle. The system further adapts a damping behavior of the chassis and looks ahead on the basis of the motion behavior to be expected. The capture of the roadway surface situated ahead is undertaken by using imaging sensors such as, for example, a laser scanner, a mono camera, or a stereo camera. Due to the image processing to be carried out, the known system can only be realized with significant technical effort.

[0004] It is therefore desirable for a simplified system for predictive chassis control for an off-road utility vehicle.

[0005] In one embodiment of the present disclosure, a system for predictive chassis control for an off-road utility vehicle includes a wheel-spring device which is controllable with respect to a damping characteristic or suspension characteristic, a sensor means for ascertaining a force profile of a disturbance acting on the wheel-spring device by reason of a condition of a ground surface to be driven along, a navigation means for ascertaining a current geoposition of the off-road utility vehicle in the form of associated position data, and also a memory unit in which a control unit saves the force profile brought about by reason of the disturbance, or a quantity derived therefrom, inclusive of the position data corresponding thereto, as an associated data pair. The control unit detects by continuous reconciliation of the current geoposition, made available by the navigation means, of the off-road utility vehicle with the saved position data, an imminent renewed crossing of the disturbance and adapts the damping characteristic or suspension characteristic, on the basis of the saved force profile or on the basis of the quantity derived therefrom, by pilot control of the wheel-spring device in such a manner that an influence of the disturbance on the wheel-spring device is at least partly compensated.

[0006] The system takes advantage of the circumstance, typical of the agricultural sector, for example, that in the case of field cultivation one and the same point of the field or of peripheral access paths and access areas is driven across repeatedly at comparatively short time-intervals by reason of a large number of successive cultivation steps. The storage of the data pairs therefore makes it possible to perform a mapping of the disturbances and to provide for improving the ride comfort as well as the ground contact of the off-road utility vehicle by appropriate pilot control of the wheel-spring device. The mapped disturbances in this case ultimately represent the condition or qualities of the ground surface being driven along as regards ground irregularities, undulations, furrows, potholes and such like.

[0007] The off-road utility vehicle may be, for example, an agricultural tractor equipped with a front axle having individual wheel suspension so that a total of two of the wheel-spring devices are provided. For each of the two wheel-spring devices a wheel-specific ascertainment and storage of associated data pairs can be undertaken. Deviating from this, the agricultural tractor may also exhibit a sprung swing axle, in which case the ascertainment of the data pairs is then carried out not in wheel-specific manner but in axle-oriented manner.

[0008] The wheel-spring device is of conventional design and includes a hydraulic spring strut which extends between a wheel suspension link, swivel-mounted on a vehicle chassis, or an axle body of the swing axle, on the one hand, and a linking point provided on the vehicle chassis on the other hand. A hydraulic piston partitions a hydraulic cylinder encompassed by the hydraulic spring strut into an annular chamber and a piston chamber. The annular chamber and the piston chamber communicate with one another via a throttle valve which is adjustable with respect to its resistance to flow so that the damping characteristic of the hydraulic spring strut can be varied. A pressure control valve further permits an adaptation of the working pressure and hence of the suspension characteristic of the hydraulic spring strut. Both the throttle valve and the pressure valve exhibit associated electrically controllable adjusting elements which permit the control unit to influence the resistance to flow or the working pressure of the hydraulic spring strut for the purpose of adapting the damping characteristic or suspension characteristic.

[0009] It should be noted that use of the system is not restricted to the agricultural sector; rather, this system can be employed just as well also in road construction or the like.

[0010] The derived quantity may be a category allocated to the respective disturbance. By categorizing the disturbance, it is possible for the data-processing effort in connection with the drive of the wheel-spring device to be reduced further in which connection categories such as “driving along an uneven ground”, “driving along an undulating ground”, “driving across a deep furrow”, “fast driving across a pothole”, “slow driving across a pothole” are conceivable. The existence of a certain category in this connection can be ascertained by the control unit on the basis of an amplitude and frequency analysis of the captured force profile. The assessment of the speed of locomotion of the off-road utility vehicle is undertaken in a known manner by evaluating the wheel speeds captured by means of associated wheel-speed sensors.

[0011] The sensor means may be a pressure sensor for capturing a working pressure existing in a hydraulic spring strut of the wheel-spring device. From the working pressure captured by sensor means, the control unit ascertains the force acting on the wheel-spring device as well as the profile thereof over time, taking as a basis the known piston cross-section of the hydraulic spring strut.

[0012] It should be noted at this point that the ascertainment of the force profile may also be undertaken by using an acceleration sensor assigned to the wheel-spring device, in which case the acceleration sensor measures a vertical acceleration arising on the vehicle chassis in the region of the wheel-spring device.

[0013] Moreover, the navigation means may be a satellite-aided GPS navigation system. For the purpose of increasing the accuracy of the position data made available by the GPS navigation system, the latter may also take the form of a so-called real-time navigation system operating in accordance with the RTK (real-time kinematic) method. The mode of operation of said method is based on carrier-phase measurements of received GPS satellite signals, whereby correction data having an accuracy within the centimeter range are transmitted to the GPS navigation system in real time from a stationary reference station which, for example, has been installed at the edge of a field to be cultivated. As a general rule, a GPS navigation system of such a type is present, in particular, in the case of agricultural tractors having autonomous steering so that the cost-effective concomitant use thereof is possible.

[0014] In this connection there is the possibility that the control unit deletes the data pair saved in the memory unit upon expiration of a predetermined storage-time. For this purpose, the data pair can be provided with a time-stamp by the control unit, the storage-time that begins with the setting of the time-stamp having been predetermined in such a manner that an erroneous drive of the wheel-spring device by reason of significant changes in the condition of the ground surface being driven along that have occurred in the meantime can be largely ruled out.

[0015] In addition, a variable presetting of the storage-time by the control unit as a function of the meteorological conditions is conceivable. Accordingly, the storage-time should be shortened appropriately if considerable changes in the condition of the ground surface being driven along are to be expected by reason of heavy rain, storms or the like. The meteorological data required for this purpose can be received by means of, for example, a VHF radio located in the off-road utility vehicle, and made available to the control unit.

[0016] Additionally or alternatively, the control unit can update the data pair saved in the memory unit upon renewed crossing of the disturbance, particularly in the case where said control unit establishes that by reason of changes in the condition of the ground surface being driven along that have occurred in the meantime, the influence of the disturbance on the wheel-spring device is only being compensated inadequately. Whether this is the case is detected by the control unit by evaluation of the force profile ascertained in this respect upon renewed crossing of the disturbance.

[0017] The control unit can additionally transmit the data pair to a central database for the purpose of storage, in which case the transmitted data pairs can be made available in mapped and anonymized form to further users. Conversely, a reception of the data pairs transmitted to the central database by other users is also conceivable.

[0018] In the simplest case, the transmission can be undertaken in wireless manner by means of a GSM network, for which purpose the control unit communicates with the central database via a GSM interface.

[0021] The system 10 is an integral part of an off-road utility vehicle which is not represented in any detail and which in the present case is an agricultural tractor equipped with a front axle 12 having individual wheel suspension. The front axle 12 exhibits steerable front wheels 14 to which wheel-spring devices 16 which are controllable with respect to their damping characteristic or suspension characteristic are assigned. For reasons of clarity, only one of the wheel-spring devices 16 has been reproduced in the FIGURE. This device is supplied by means of a compressor 18 with hydraulic fluid from a central reservoir 20 of a hydraulic system of the agricultural tractor.

[0022] The wheel-spring device 16 is of conventional design and exhibits a hydraulic spring strut 22 which extends between a wheel suspension link 26, which is swivel-mounted on a vehicle chassis 24, and a linking point 28 provided on the vehicle chassis 24.

[0023] A hydraulic piston 30 partitions a hydraulic cylinder 32 encompassed by the hydraulic spring strut 22 into an annular chamber 34 and a piston chamber 38 connected to a membrane reservoir 36. The annular chamber 34 and the piston chamber 38 communicate with one another via a throttle valve 40 which is adjustable with respect to its resistance to flow. A pressure control valve 44 taking the form of a 4/3-way valve 42, with a blocking central position, further permits an adaptation of the working pressure. Both the throttle valve 40 and the pressure control valve 44 exhibit associated electrically controllable adjusting elements 46, 48, so that the resistance to flow or the working pressure of the hydraulic spring strut 22 and hence the damping characteristic or suspension characteristic of the wheel-spring device 16 can be influenced by a control unit 50.

[0024] A sensor means 54 taking the form of a pressure sensor 52 serves for capturing the working pressure existing in the piston chamber 38 of the hydraulic spring strut 22. From the operating pressure captured by sensor means, the control unit 50 ascertains the force acting on the wheel-spring device 16 as well as the profile F(t) thereof over time t, taking as a basis the known piston cross-section of the hydraulic spring strut 22.

[0025] Additionally or alternatively, the ascertainment of the force profile F(t) is undertaken by using an acceleration sensor 56 assigned to the wheel-spring device 16, in which case the acceleration sensor 56 measures a vertical acceleration arising on the vehicle chassis 24 in the region of the wheel-spring device 16.

[0026] Moreover, a navigation means 60 taking the form of a satellite-aided GPS navigation system 58 is present. This navigation means serves for ascertaining a current geoposition of the agricultural tractor in the form of associated position data.

[0027] For the purpose of increasing the accuracy of the position data made available by the GPS navigation system 58, said system takes the form of a so-called real-time navigation system operating in accordance with the RTK (real-time kinematic) method. The mode of operation of said method is based on carrier-phase measurements of received GPS satellite signals, whereby correction data having an accuracy within the centimeter range are transmitted to the GPS navigation system 58 in real time from a stationary reference station 62 which, for example, has been installed at the edge of a field to be cultivated.

[0028] A disturbance 66 acting on the wheel-spring device 16 via the associated front wheel 14, depending upon the condition of the ground surface 64 being driven along, results in a corresponding temporal alteration of the working pressure existing in the piston chamber 38 of the hydraulic spring strut 22, or of the vertical acceleration arising on the vehicle chassis 24 in the region of the wheel-spring device 16. The force profile F(t) brought about in such a way by reason of the disturbance 66, inclusive of the position data corresponding thereto, is saved by the control unit 50 as a data pair in a memory unit 68. The ascertainment and storage of the data pairs are undertaken in this connection in wheel-specific manner for each of the two wheel-spring devices 16.

[0029] In the case where the agricultural tractor exhibits a sprung swing axle instead of a front axle 12 having individual wheel suspension, the ascertainment of the data pairs is undertaken not in wheel-specific manner but rather in axle-oriented manner.

[0030] According to an optional configuration of the system 10, instead of the ascertained force profile F(t) the control unit 50 saves a quantity derived therefrom in the memory unit 68. The derived quantity is a category allocated to the disturbance 66, in which connection, amongst other things, the categories “driving along an uneven ground”, “driving along an undulating ground”, “driving across a deep furrow”, “fast driving across a pothole”, “slow driving across a pothole” are provided. The presence of a certain category in this connection is determined by the control unit 50 on the basis of an amplitude analysis or frequency analysis of the ascertained force profile F(t). The assessment of the speed of locomotion of the agricultural tractor is undertaken in known manner by evaluation of the wheel speeds captured by means of associated wheel-speed sensors 70.

[0031] If the control unit 50 detects an imminent renewed crossing of the disturbance 66 by continuous reconciliation of the current geoposition of the agricultural tractor made available by the GPS navigation system 58 with the position data saved in the memory unit 68, the control unit adapts the damping characteristic or suspension characteristic of the wheel-spring device 16 on the basis of the force profile F(t) saved in the memory unit 68 or on the basis of the category allocated thereto by pilot control of at least one of the two adjusting elements 46, 48 in such a manner that the influence of the disturbance 66 on the wheel-spring device 16 is at least partly compensated.

[0032] In addition, the control unit 50 transmits the data pair to a central database 72 for the purpose of storage so that said data pair can be made available in mapped and anonymized form to further users 74, 76. The transmission is undertaken in wireless manner by means of a GSM network 78, for which purpose the control unit 50 is in communication with the central database 72 via a GSM interface 80. At the same time, said database permits a reception of data pairs that are transmitted to the central database 72 by the other users 74, 76.

[0033] The control unit 50 deletes the data pair saved in the memory unit 68 upon expiration of a predetermined storage-time. For this purpose, the data pair is provided with a time-stamp by the control unit 50. The storage-time that begins with the setting of the time-stamp is predetermined by the control unit 50 in such a manner that an erroneous drive of the wheel-spring device 16 by reason of significant changes in the condition of the ground surface 64 being driven along that have occurred in the meantime can be largely ruled out. In this connection, the storage-time lies within the range of a few days.

[0034] The presetting of the storage-time by the control unit 50 is undertaken variably. Accordingly, the storage-time is shortened appropriately if considerable changes in the condition of the ground surface 64 being driven along are to be expected by reason of heavy rain, storms or such like. The meteorological data required for this purpose are received by means of a VHF radio 82 located in the agricultural tractor, and made available to the control unit 50.

[0035] In addition, the control unit 50 updates the data pair upon renewed crossing of the disturbance 66 in the case where said control unit establishes that the influence of the disturbance 66 on the wheel-spring device 16 is only being compensated inadequately by reason of changes in the condition of the ground surface 64 being driven along that have occurred in the meantime. Whether this is the case is detected by the control unit 50 by evaluation of the force profile F(t) ascertained in this respect upon renewed crossing of the disturbance 66. At the same time, the data pair updated in such a way is provided with a new time-stamp by the control unit 50.

[0036] While embodiments incorporating the principles of the present disclosure have been described hereinabove, the present disclosure is not limited to the described embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.