Undercarriage control system

An apparatus and method for controlling the undercarriage of a vehicle with means for adjusting vehicle parameters, such as, for example, the spring travel or the spring constant, in accordance with computed control signals. A signal receiving means receives signals from the environment of the vehicle and converts the signals into environmental signals. A signal processing means determines vehicle-related data from the environmental signals and a computing means computes the control signals for the vehicle control system with the aid of the vehicle-related data.

BACKGROUND OF THE INVENTION
 The invention concerns a device and a method for controlling the
 undercarriage of a vehicle with means for the adjustment of undercarriage
 parameters, such as, for example, the spring travel or the spring
 constant, in accordance with computed control signals. The invention is
 suitable for use in motor vehicles, particularly for use in passenger
 vehicles.
 Undercarriage control systems have been used increasingly in passenger
 vehicles during recent years to enhance the comfort and safety of these
 vehicles. Such an undercarriage control system permits, for example, an
 adjustable damping characteristic or leveling control of the vehicle body
 independently of vehicle loading, in order to adapt the undercarriage to
 different road conditions.
 Undercarriage control systems are classified according to their control
 characteristic as passive, adaptive, semiactive and active. An overview of
 the various control characteristics is provided in R. Kallenbach et al.,
 Optimierung des Fahrzeugverhaltens mit semiaktiven Fahrwerkregelungen
 [Optimization of vehicle behavior by means of semiactive undercarriage
 control systems], VDI [Verein Deutscher Ingenieure; Association of German
 Engineers] Reports No. 699, 1988, pp. 121-135. The technical complexity of
 undercarriage control systems and their resultant cost depends on the
 desired control characteristic, and generally increase continuously from
 passive to active undercarriage control. The cited document describes in
 particular the optimization of vehicle behavior by means of semiactive
 undercarriage control systems, which offer a marked cost advantage over
 active undercarriage control systems.
 A modern concept of undercarriage control is described in W. Schramm et
 al., "A high-performance concept for active undercarriage control with
 reduced energy demand," ATZ Automobiltechnische Zeitschrift 94 (1992), pp.
 392-403. In particular, this article introduces a new concept for
 semiactive undercarriage control, consisting of a fully load-bearing
 hydropneumatic suspension with actuators in a shutoff-cylinder
 arrangement.
 The sensing devices currently used in undercarriage control consist of
 travel sensors that determine the spring travel of the undercarriage at
 each axle, preferably at each wheel. From the present standpoint, optimum
 measurement acquisition would require measurement of the spring travel at
 each wheel suspension. Despite this high technical complexity and the
 associated high cost, due in particular to the use of a large number of
 sensors and a high available computation speed, as well as the provision
 of high-performance hydraulic, pneumatic and/or electrical final control
 elements to achieve a high control speed, the prior art undercarriage
 control systems are unable to achieve optimal and sufficiently rapid
 detection of all the situations that can arise during driving.
 From digital image processing, methods and algorithms are known that can be
 used to identify at least partly preestablished structures and patterns in
 complex images and to filter them out of these images. Such methods can be
 used, for example, in medical technology for the automatic recognition of
 cancer cells in tissue specimens.
 From automotive measurement technology, methods of distance measurement are
 known, for example involving the use of electromagnetic waves in various
 frequency ranges. In addition, modern navigational systems can be used in
 motor vehicles to furnish data regarding position and/or traffic flow.
 The problem underlying the invention is to provide a device and a method
 for controlling the undercarriage of a motor vehicle that ensures a high
 degree of driving safety and driving comfort. In particular, the
 undercarriage control system should react quickly and optimally to all
 existing and immediately impending driving situations. Furthermore, the
 technical complexity and the associated production, installation and
 operating costs should be as low as possible.
 SUMMARY OF THE INVENTION
 The problem is solved, in a device for controlling the undercarriage of a
 vehicle, via means for the adjustment of vehicle parameters, such as, for
 example, the spring travel or the spring constant, in accordance with
 computed control signals, in that the device includes: signal receiving
 means for receiving signals from the environment of the vehicle and
 converting the signals into electrical environmental signals, signal
 processing means for determining vehicle-related data from the
 environmental signals, and computing means for computing the control
 signals for the undercarriage control system with the aid of the
 vehicle-related data. The signals from the environment of the vehicle can
 be either optical signals, for example in the form of images of the
 environment, electromagnetic signals from the environment, or radio
 signals from the environment, for example terrestrial or
 satellite-transmitted radio signals. Correspondingly, the signal receiving
 means can include, for example, a camera for receiving images, a radio
 antenna, or the like.
 The device according to the invention offers the advantage that
 vehicle-related data are determined by the reception of signals from the
 environment of the vehicle and can be taken into account in the
 computation of the control signals for the undercarriage control system,
 so that the undercarriage control system no longer need rely solely on the
 measurement values determined directly on the vehicle, such as spring
 travel or spring deflection rate, in computing and adjusting the
 undercarriage parameters, but can also adjust--with foresight, so to
 speak--to immediately impending driving situations. On the one hand, this
 increases driving safety; on the other, it also nevertheless increases the
 reaction time available to the undercarriage control system, thereby
 lowering the requirements with regard to both computation speed and
 regulating speed. The lower requirements regarding computation speed can
 advantageously be utilized to achieve higher accuracy of computation, and
 thus higher driving safety. The lower requirements with regard to
 regulating speed, for example the requirement that the hydraulic,
 pneumatic or electrical final control elements provide appropriate spring
 pressure, permit the use of final control elements of smaller size, lower
 weight and lower power consumption. The device according to the invention
 further permits a high increase in driving safety, since the signal
 receiving means is able to detect imminent cornering or braking even
 before the driver of the vehicle reacts to the impending event.
 Furthermore, it is advantageous that devices already present in the
 vehicle can be used for the signal receiving means, for example a radio
 receiving antenna that is already on hand for the radio, or the data from
 a navigation system already present in the vehicle.
 A particular embodiment of the invention is characterized by means for
 measuring transient vehicle-specific data, such as, for example,
 instantaneous speed or weight distribution, these transient
 vehicle-specific data being taken into account by the computing means in
 computing the control signals. This embodiment has the advantage the
 undercarriage control system can be optimized by the measurement and
 consideration of transient vehicle-specific data, thereby increasing
 driving safety. Transient vehicle-specific data are, for example,
 instantaneous speed, engine speed, transmission step, tuning angle of the
 steering wheel, weight, and weight distribution. It is advantageous if a
 number of these transient vehicle-specific data, such as speed, are
 already being measured routinely in the vehicle. In this way the cost of
 determining these data and using them for undercarriage control is,
 advantageously, low.
 In a particular embodiment of the invention, the signal receiving means is
 formed by image receiving means for receiving images of the environment of
 the vehicle, and the signal processing means determines the road-related
 data through the use of digital image processing methods and algorithms.
 This embodiment has the advantage that the image receiving means delivers
 very relevant road-related data, particularly for imminent processes
 within the undercarriage control system. For example, the image receiving
 means, in association with digital image processing, can measure the
 lateral path of the driving lane immediately in front of the vehicle. In
 conjunction with transient vehicle-specific data, such as, for example,
 instantaneous speed and instantaneous turning angle of the steering wheel,
 the undercarriage control system can advantageously determine impending
 changes in the driving situation well in advance. In addition, it is
 advantageous if the image receiving means is able to determine not only
 static conditions, but also dynamic processes taking place in the area in
 front of the vehicle, such as a preceding vehicle that is braking, or an
 object moving toward the road from the side, such as a child moving toward
 the road. The device according to the invention thus offers the advantage
 that the undercarriage control system can prepare for the immediately
 impending braking process of the vehicle, and, for example, can counteract
 "dipping" of the vehicle by appropriate variation of the undercarriage
 parameters, for example the spring constant in the front axle.
 According to a further particular embodiment of the invention, the image
 receiving means is positioned in a high position inside the vehicle,
 preferably between the rear-view mirror and the windshield, the image
 receiving means comprising a camera, preferably a CMOS (Complementary
 Metal Oxide Semiconductor) image sensor or a CCD (Charged Coupled Devices)
 camera. This high position of the image receiving means has the advantage
 that the image receiving means has a good overview of the area in front of
 the vehicle, and thus a good overview of the path of the road and the road
 conditions. It is further advantageous that with the image receiving means
 positioned between the rear-view mirror and the windshield in the vehicle
 interior, the field of view of the image receiving means is still located
 in an area that is swept by the windshield wiper blades. This ensures that
 the image receiving means will function reliably even under rainy
 conditions. It is further advantageous that the use of a CMOS image sensor
 or a CCD camera enables the image receiving means to have a small
 structural shape and low weight, so that it can readily be installed in
 the vehicle interior.
 In a further particular embodiment of the invention, the image processing
 means determines the pitch angle of the vehicle. This is advantageous
 because it permits automatic leveling control of the vehicle in its
 longitudinal direction. Correspondingly, it is also possible to determine
 the roll angle or the yaw angle of the vehicle in relation to the road and
 to the radius of a curve that is to be negotiated.
 The invention further includes an operating method for controlling the
 undercarriage of a vehicle in accordance with the device described
 hereinabove, and the use of signals from the environment of a vehicle,
 particularly images of the environment, to compute control signals for a
 vehicle undercarriage control system. The advantages of this method
 correspond to the advantages cited hereinabove in reference to the device
 according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT
 FIG. 1 shows a vehicle 101 with the undercarriage control system according
 to the invention, in particular with a camera 102. The vehicle 101 is
 traveling along the street 110 in direction 103 and is at distance 104
 from a curve 111 with the radius 105. The camera 102, as the image
 receiving means or signal receiving means, converts the received signals
 into electrical environmental signals. A signal processing means in the
 vehicle 101 uses the electrical environmental signals to determine the
 distance 104 from the curve 111 and the radius 105 of the curve 111. The
 speed of the vehicle 101 could also be determined from the received image
 data. On the basis of the vehicle speed, the distance 104 to the curve and
 the radius 105 of the curve 111, the undercarriage control system
 according to the invention determines the vehicle parameters that must be
 set to ensure safe and comfortable negotiation of the curve. Also included
 in the calculation of the vehicle parameters are other data, which are, in
 the example shown, the electromagnetic signals transmitted by a
 transmitter 106 and reflected by the environment and received by a
 receiver 107. The transmitter and the receiver can be, for example,
 microwave-based radars or laser-based systems operating particularly in
 the infrared range. The electromagnetic signals permit conclusions
 regarding objects on the road or preceding vehicles. Further, the
 environmental temperature determined by means of a temperature sensor 108
 is also taken into account in the calculation of the vehicle parameters.
 FIG. 2 depicts the entire vehicle control system according to the
 invention. The camera 102 receives the signals from the environment of the
 vehicle and converts these signals into electrical environmental signals
 211. The signal processing means 201 uses these electrical environmental
 signals 211 to determine the vehicle-related data 212. Computing means 202
 compute the control signals 213 for the undercarriage control system 203
 with the aid of the vehicle-related data 212. The undercarriage control
 system 203 converts the control signals 213 into corresponding hydraulic,
 pneumatic or electrical control signals, which are relayed through
 corresponding leads 204 to the active undercarriage components 205. The
 environmental signals 211 are preferably electrical in nature, but, like
 the vehicle-related data 212 and the control signals 213, can also be of a
 different type, for example they can be transmitted optically via a
 fiberoptic cable. In the exemplary embodiment depicted, the undercarriage
 control system 203 also takes signals from the speed sensor 206 and
 signals from a measurement-value receiver 207 into account in determining
 the turning angle of the steering wheel. These two transient
 vehicle-specific parameters are cited solely as examples, and can be
 supplemented as needed by further transient vehicle-specific data, such as
 engine speed, transmission step, weight, or weight distribution. The
 transient vehicle-specific parameters 206, 207 can alternatively or
 additionally be made available to the computing means 202 for signal
 processing or can be taken into account by the computing means 202.
 FIG. 3 is a cross section along the longitudinal axis of the vehicle. In
 this example, the camera 102 is disposed comparatively high in the vehicle
 interior, behind the windshield, in such a way that it has a good "view"
 of the traffic in the direction of travel of the vehicle and also is still
 located within the radius of action of the wiper blades of the vehicle
 101. The camera 102 is fixedly attached to the vehicle 101. The optical
 axis 103 of the camera 102 forms an angle .beta. with a horizontal axis
 104 of the vehicle 101. The image processing means according to the
 present invention determines the angle .alpha. formed by the optical axis
 103 of the camera 102 and the plane 105 of the road. Since angle .beta. is
 invariable and is known to the control system, the difference between the
 known angle .beta. and the measured angle .alpha. can be used to determine
 the pitch angle of the vehicle 101.
 The camera 102 can be, for example, a CMOS image sensor or a CCD camera. In
 the case of a CMOS image sensor, it is advantageous to provide a
 characteristic curve whose slope decreases with increasing luminous
 intensity. It is particularly useful to provide a logarithmic
 characteristic curve.
 It is further possible to use a plurality of optionally synchronized
 cameras, in particular with different settings, e.g. different focal
 lengths.