Vehicle control system with advanced tire monitoring

A control system (11) for a vehicle (10) includes vehicle dynamics sensors (35-47) providing a vehicle dynamics signal. Tire monitoring system sensors (20) in each wheel generate tire signals including temperature, pressure and acceleration data. A controller (26) communicates with the tire monitoring system sensors (20) and at least one vehicle dynamics sensor, and generates a roadway surface condition estimation value as a function of the multi-axis acceleration data of the tire signals. The roadway surface condition estimation value is transmitted to a suspension control system (33) to adjust the vehicle suspension characteristics in response to the roadway surface condition estimation value.

TECHNICAL FIELD

The present invention relates generally to vehicle control systems and tire monitoring systems. More particularly, the present invention is related to vehicle control systems incorporating advanced tire monitoring for comfort and convenience.

BACKGROUND

Tire pressure monitoring may soon become a standard feature on vehicles. Current tire pressure monitoring sensors, however, have limited functionality, and are not capable of discerning coordinate acceleration data for a wheel. Conventional tire pressure sensors provide pressure and temperature sensing along with data processing and wireless communication of such data. Most also include a movement detection device such as switch or piezoelectric device that activates upon a radial acceleration. The movement detection devices “wake” the sensor to initiate data transmission, while saving battery life while the wheel is not moving.

Advanced tire monitoring sensors (ATMS) are currently being developed. Besides traditional pressure and temperature data, ATMS include coordinate acceleration data for the associated wheel. This is accomplished with micro-electro-mechanical system (MEMS) accelerometers. Such devices have advantages in terms of robustness, and the ability to provide a linear output response to acceleration. Multiple MEMS are also contemplated to provide multi-axis (coordinate) acceleration data for the associated wheel.

ATMS provide the potential to vehicle manufacturers to offer new or enhanced capabilities in vehicle systems. The present disclosure is directed toward providing improved vehicle comfort and convenience systems utilizing ATMS.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a system for a vehicle including a tire sensor located within each wheel of the vehicle and generating a tire signal comprising pressure, temperature and multi-axis acceleration data. The system also includes at least one vehicle dynamics sensor providing a vehicle dynamics signal, such as the vehicle speed and braking. Further, a controller communicates with the tire sensor and the at least one vehicle dynamics sensor. The controller, in response to the vehicle dynamics signal, generates a roadway surface condition estimation value as a function of the multi-axis acceleration data of the tire signal, and transmits the roadway surface condition estimation value to at least one vehicle system controller. The system controller can be a suspension control system.

The controller generates the roadway surface condition estimation value as a function of the tire signal by comparing frequency and amplitude response characteristics of the tire signal to stored frequency and amplitude response characteristics indicative of different roadway surfaces. An indicator can signal to the vehicle operator the roadway surface condition estimation value.

The suspension control system can include any one of an active suspension component for altering suspension geometry, a pneumatic cylinder adapted to adjust vehicle ride height, an adjustable suspension damper, or a central tire inflator adapted to adjust tire inflation. Thus, when the roadway surface condition estimation value indicates a rough surface, the suspension control system is adapted to soften the vehicle suspension characteristics. Conversely, when the roadway surface condition estimation value indicates a smooth surface, the suspension control system stiffens the vehicle suspension characteristics.

In another aspect of the invention, the roadway surface condition estimation value dictates a first suspension value used to adjust the suspension system accordingly. A user selected second suspension value may also be included. When a user-selected second suspension value is present, the suspension control system adjusts the vehicle suspension characteristics as a function of the first and second suspension values. In one example, the suspension control system adjusts the vehicle suspension characteristics according to the second suspension value when the first and second suspension values are compatible, and adjusts the vehicle suspension characteristics according to the first suspension value when the first and second suspension values are incompatible. In this way, the user-selected value controls unless the road surface conditions indicate that ride and handling can be improved by modifying the suspension. This may be done to avoid the suspension components “bottoming out” (contacting hard stops), for example.

In another embodiment, the system mitigates rear wheel hop. The system includes a tire sensor located within each wheel of the vehicle and generating a tire signal comprising pressure, temperature and multi-axis acceleration data; at least one vehicle dynamics sensor providing a vehicle dynamics signal; a brake system for applying a braking torque to each of the vehicle wheels in response to a brake signal; and a controller communicating with the tire sensor and the at least one vehicle dynamics sensor. In response to the vehicle dynamics signal, controller generates the brake signal as a function of the multi-axis acceleration data of the tire signal, and transmits the brake signal to the brake system. The controller can generate the brake signal by comparing frequency and amplitude response characteristics of the rear tire signals, to frequency and amplitude response characteristics of the front tire signals to determine a rear wheel hop event. To mitigate the rear wheel hop event, braking maneuvers can be performed.

The embodiments of the present invention provide several advantages. One advantage provided by an embodiment of the present invention is a suspension control system that is capable of obtaining tire pressure and wheel acceleration knowledge and adjusting suspension control functions accordingly to improve vehicle ride and handling.

The present invention itself, together with further objects and attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION

In the following figures, the same reference numerals will be used to identify the same components. The present invention may be used in conjunction with vehicle control systems including a yaw stability control (YSC) system, roll stability control (RSC) system, lateral stability control (LSC) system, integrated stability control (ISC) system, or a total vehicle control system for achieving desired vehicle performance. The present invention is also described with respect to an integrated sensing system (TSS), which uses a centralized motion sensor cluster such as an inertial measurement unit (IMU) and other available, but decentralized, sensors. Although a centralized motion sensor, such as an IMU, is primarily described, the techniques described herein are easily transferable to using the other discrete sensors.

In the following description, various operating parameters and components are described for several constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting.

Referring toFIG. 1, an automotive vehicle10with a control system of the present invention is illustrated with the various forces and moments thereon. Vehicle10has front right (FRW) and front left (FLW) wheel/tires12aand12band rear right (RRW) wheel/tires12cand rear left (RLW) wheel/tires12d, respectively. The vehicle10may also have a number of different types of front steering systems14aand rear steering systems14b, including having each of the front and rear wheels12a,12b,12cand12dconfigured with a respective controllable actuator, the front and rear wheels12having a conventional type system in which both of the front wheels12a,12bare controlled together and both of the rear wheels12c,12dare controlled together, a system having conventional front steering and independently controllable rear steering for each of the wheels12cand12d, or vice versa. Generally, the vehicle10has a weight represented as Mg at the center of gravity of the vehicle10, where g=9.8 m/s2and M is the total mass of the vehicle10.

The control system11has an active/semi active suspension system, and may include rollover mitigation and prevention systems, which include and/or comprise of, an active steering system, a deployable lateral stability system, inwardly mounted wheel assemblies, and other related devices such as known in the art. The control system11may also be used with or include an anti-roll bar, or airbags or other safety devices deployed or activated upon sensing predetermined dynamic conditions of the vehicle10.

The control system11is in communication with a sensing system16. The sensing system16may have many different active and passive sensors including the sensor set typically found in a roll stability control or a rollover control system (including lateral accelerometer, yaw rate sensor, steering angle sensor and wheel speed sensor which are equipped for a traditional yaw stability control system) together with a roll rate sensor and a longitudinal accelerometer. The sensing system16may also includes object detection sensors, which aid in the detection of an imminent rollover obstacle. The various sensors will be further described below and are shown with respect toFIGS. 2 and 4.

The sensors may also be used by the control system11in various determinations such as to determine a lifting event, determine a height and position of a mass, etc. Wheel speed sensors can be mounted at each corner of the vehicle and generate signals corresponding to the rotational speed of each wheel. The rest of the sensors of the sensing system16may be mounted directly on the center of gravity of the vehicle body, along the directions x, y, and z shown inFIG. 1. As those skilled in the art will recognize, the frame from b1, b2, and b3is called a body frame22, whose origin is located at the center of gravity of the car body, with the b1corresponding to the x axis pointing forward, b2corresponding to the y axis pointing off the driving side (to the left), and the b3corresponding to the z axis pointing upward. The angular rates of the car body are denoted about their respective axes as ωxfor the roll rate, ωyfor the pitch rate and ωzfor the yaw rate. Calculations may take place in an inertial frame24that may be derived from the body frame or chassis22as described below.

The angular rate sensors and the accelerometers may be mounted on the vehicle car body along the body frame directions b1, b2and b3which are the x-y-z axes of the sprung mass of the vehicle.

The longitudinal acceleration sensor is mounted on the car body located at the center of gravity, with its sensing direction along b1axis, whose output is denoted zx. The lateral acceleration sensor is mounted on the car body located at the center of gravity, with its sensing direction along b2axis, whose output is denoted as ay.

FIG. 1depicts a road frame system r1r2r3that is fixed on the driven road surface, where the r3axis is along the average road normal direction computed from the normal directions of the four-tire/road contact patches.

Referring now toFIG. 2, a block diagrammatic view of an advanced tire monitoring system ATMS (18) for a vehicle10in accordance with an embodiment of the present invention is shown. The control system11includes a controller25. The controller may be a controller for estimating a roadway surface condition and modifying a suspension characteristic in response to the estimated roadway surface conditions. Examples of such comfort and convenience control systems CCS25are described below. The control system11utilizes tire status information gathered from the advanced tire monitoring system ATMS18in operation of the controller25. The ATMS18provides tire pressure, tire temperature and acceleration data to the control system25. A sample advanced tire monitoring system is described in detail with respect toFIGS. 2 and 3. A sample comfort and convenience control system is described with respect toFIG. 4. Logic routines for different comfort and convenience functions are described with respect toFIGS. 5 through 10.

The control system11includes one or more controllers. The controllers may be part of the advanced tire monitoring system18, the convenience control system25, or may be a stand-alone controller. The convenience control system25may be coupled to other control systems to respond to safety, comfort or convenience events as detected by the logic routines and ATMS18. Such control systems could include a brake control system that is used to actuate brakes; a suspension control system for activating suspension components to mitigate the effect of a detected event; a steering control system to likewise mitigate a detected event; active and passive safety control systems; a central tire inflation system, and the like. Control events related to safety, comfort or convenience may be indicated to a vehicle occupant via an indicator90.

Several of the stated control systems are shown and described with respect toFIG. 4. Therein, the control system11is illustrated in further detail having a controller26, a passive safety system27-30, multiple active systems31-34, various vehicle status sensors and driver or vehicle operator input sensors20and35-47. The passive system27includes object detection devices or sensors28, collision detection sensors29, and various passive countermeasures30. The active systems may include a brake control system31, a steering control system32, a suspension control system33, and a drivetrain control system34. Based upon inputs from the sensors, the convenience control system25may operate the safety device51. Further, although it is shown as a safety device51, it also activates the comfort and convenience features discussed herein, because several of the mechanisms provide dual roles in improving passenger comfort and mitigating safety-relate events.

The controllers described herein may be microprocessor based such as a computer having a central processing unit, memory (RAM and/or ROM), and associated input and output buses. The controllers may be application-specific integrated circuits or may be formed of other logic devices known in the art. The controllers may each be a portion of a central vehicle main control unit, an interactive vehicle dynamics module, a restraints control module, a main safety controller, a control circuit having a power supply, combined into a single integrated controller, or may be a stand-alone controller as shown.

Referring again toFIG. 2, the advanced tire monitoring system18monitors the air pressure, temperature and multi-axis accelerations for a right front tire12a, a left front tire12b, a right rear tire12c, and a left rear tire12d. Each tire12a-12dhas a respective tire ATMS sensor20a-20d, each of which has a respective antenna19a-19d. Each tire12a-12dis positioned upon a corresponding wheel.

A fifth tire or spare tire12eis also illustrated having an ATMS sensor20eand a respective antenna19e. Although five wheels are illustrated, the tire status of various numbers of wheels may be monitored. For example, the present invention applies equally to vehicles such as pickup trucks that have dual wheels for each rear wheel. Also, various numbers of wheels may be used in a heavy-duty truck application having dual wheels at a number of locations. Further, the present invention is also applicable to trailers and extra spares.

Each tire12may have a respective initiator23a-23epositioned within the wheel wells adjacent to the tire12. Initiator23generates a low frequency RF signal initiator and is used to initiate a response from each wheel so that the position of each wheel may be recognized automatically by the advanced tire monitoring system18. Initiators23are coupled directly to the advanced tire monitoring system18. In commercial embodiments where the position programming is done manually, the initiators may be eliminated.

The controller comprising the ATMS18may be microprocessor based controller having a programmable CPU that may be programmed to perform various functions and processes including those set forth herein. Controller has a memory18aassociated therewith. Memory18amay be various types of memory including ROM or RAM. The memory is used to store various thresholds, calibrations, tire characteristics, wheel characteristics, serial numbers, conversion factors, temperature probes, spare tire operating parameters, and other values needed in the calculation, calibration and operation of the advanced tire monitoring system18. For example, memory may contain a table that includes the sensor identification. Also, the warning status of each of the tires may also be stored within the table.

The ATMS18is also coupled to a transceiver80. Although the transceiver80is illustrated as a separate component, the transceiver80may also be included within ATMS18. The transceiver80has an antenna associated therewith. The antenna is used to receive pressure, temperature and multi-axis acceleration information from tire ATMS sensors20a-20e. One transceiver may be used for all of the tire ATMS sensors20, or a front and rear transceiver may be used, or dedicated transceivers may be used, each in communication with the ATMS18. The ATMS18performs preprocessing before placing the tire data on the vehicle communications bus (CAN) or other digital protocol for transmission to the convenience control system25.

In the example shown, the convenience controller25is also coupled to a plurality of sensors81and other measurement and control systems such as an IMU82. The sensors81may include a barometric pressure sensor, an ambient temperature sensor, an object detection sensor, a speed sensor, a brake pedal sensor, a throttle position sensor, steering wheel position sensor, and an ignition sensor. Sensor data may also be provided such as suspension position and loading. Of course, various other types of sensors may be used. A barometric pressure sensor generates a barometric pressure signal corresponding to the ambient barometric pressure. Thus, barometric pressure compensation may be used, but is not required in the calculation for determining the pressure within each tire12. The ambient temperature signal corresponding to the ambient temperature and may also be used to generate a temperature compensated pressure profile. The sensor data81may also be preprocessed before being communicated to the convenience control system25.

The inertial measurement unit (IMU)82contains inertial sensors for detecting vehicle yaw, pitch and roll. This data is communicated to the convenience control system25(when used as part of a safety control system) in order to determine whether a rollover event exists. This data can also act to initiate the ATMS18when a potential for rollover exists, or indicate that data collection from the ATMS sensors20is desirable.

Safety, comfort and convenience devices are generally indicated at51. Safety devices may include restraints components such as seat mounted side airbags or side curtain airbags, seat belt pretensioners, deployable trim panels and the like. To prevent or mitigate a rollover event, safety devices51may also include vehicle lateral support systems, wheel sets or active suspension components. Comfort and convenience devices may include suspension components such as active bushings or linkages and, pneumatic or hydraulic cylinders. They may also include a centralize tire inflator for changing the amount of tire pressure at each of the tires12.

Control system25may also be coupled to an indicator90. The indicator90may include a video system, an audio indicator, a heads-up display, a flat-panel display, a telematic system, a dashboard indicator, a panel indicator, or other indicator known in the art. In one embodiment of the present invention, the indicator90is in the form of a heads-up display and the indication signal is a virtual image projected to appear forward of the vehicle10. The indicator90provides a real time image of the target area to increase the visibility of the objects during relatively low visible light level conditions without having to refocus ones eyes to monitor an indication device within the vehicle10. Indicator90may provide some indication as to the operability of the system such as confirming receipt of a signal such as a calibration signal or other commands, warnings, and controls. Indicator90may also alert the vehicle operator with respect to tire pressure data, a safety event, or a comfort or convenience event.

Referring now also toFIG. 3, a schematic view of an advanced tire monitoring system (ATMS) sensor20in accordance with an embodiment of the present invention is shown. The ATMS sensor20is illustrated mounted to a rim of a vehicle wheel12inside the tire. The sensor has a transmitter/receiver or transceiver83. The transmitter/receiver83is coupled to antenna19for transmitting information to transceiver80. The transmitter/receiver83may be used to receive an activation signal from an initiator23located at each wheel, if an initiator is used in the particular application. The sensor circuit20may have various information such as a serial number memory84, a pressure sensor85for determining the pressure within the tire, a temperature sensor86for determining the temperature within the tire, and a motion detector in the form of a multi-axis accelerometer87. Preferably, the accelerometer87is a MEMS device. The accelerometer may be used to activate the advanced sensing system. The initial message is referred to as a “wake” message, meaning the sensor sensing circuit is now activated to send its pressure transmissions and the other data.

Each of the transceiver83, memory84, pressure sensor85, temperature sensor86, and motion sensor87are coupled to a power source such as a battery88. The battery88may be a long-life battery capable of lasting the life of the tires. In another aspect, the battery may be omitted, or have a substantially smaller capacity. An energy scheme using an RF field generated by an antenna on the vehicle, such as antenna181, can be used to power the sensor circuit20. This is generally indicated inFIG. 3by the RF signal path in both sensor circuit20and transceiver circuit80. A self-generating energy scheme may also be used wherein the device20scavenges energy from the rotational movement of the tires. Such schemes may permit continuous sensor data transmission and/or longer sensor life when equipped with a battery supply.

A sensor function monitor89in the form of a microcontroller core or state machine, for example, may also be incorporated into ATMS sensor20circuit. The sensor function monitor89generates an error signal when various portions of the ATMS circuit are not operating or are operating incorrectly. Also, sensor function monitor may generate a signal indicating that the circuit is operating normally. The ATMS function monitor microcontroller89can locally pre-process the sensor data streams prior to wireless delivery to the vehicle transceiver. It also provides a supervisory function to control the overall operation of the sensor including processing, diagnostics and error detection.

The transceiver80in communication with the ATMS sensor20, similarly includes a power source, transmitter/receiver device, microcontroller and antenna. It also includes an interface for the vehicle communications bus (CAN bus). Thus, each ATMS sensor20communicates wirelessly with the controller18for at least a portion of its communication path. The transceiver80receives either the raw sensor data or the pre-processed sensor data from the tire sensors and communicates with the ATMS18for further processing with defined algorithms.

An advantage of the ATMS sensors20just described is that it provides temperature and pressure data for each tire, as well as x, y and z acceleration data for each tire. This acceleration data is generated much more directly than vehicle acceleration data generated by conventional IMU sensing systems. Traditional IMU systems determine roll, pitch and yaw above the vehicle suspension. Thus, signal propagation is delayed and/or modified with other stimuli and transfer functions because of the distance of the signal source, i.e., what is occurring at the contact patches of the tires or to the tires themselves. The ATMS sensors20of the present invention reduce the signal propagation path and latency because they are distributed very close to the road surface and other inputs, such as objects impacting the tires. The ATMS sensors20allow data signals directly from the relevant tire/wheel. Items such as road surface characteristics, impacts and/or obstacles, tire defects, wheel defects and suspension defects can all be monitored by signature analysis of the wheel data provided by the ATMS sensors20.

Referring toFIG. 4, a block diagrammatic view of a convenience control system25in accordance with an embodiment of the present invention is shown. The convenience control system25may consist of a rollover stability controller RSC56, as shown. It can also be a stand-alone system receiving input from only the ATMS sensors20and a limited number of other sensors. In this example, however, the convenience control system monitors many sensor inputs, including inputs from ATMS sensors20located at each wheel/tire of the vehicle. Front right (FR) and front left (FL) wheel/tires12aand12band rear right (RR) wheel/tires12cand rear left (RL) wheel/tires12d, respectively, are shown and may be part of a vehicle, such as the vehicle10. The vehicle may also have a number of different types of front steering systems and rear steering systems, including having each of the front and rear wheels configured with a respective controllable actuator, the front and rear wheels having a conventional type system in which both of the front wheels are controlled together and both of the rear wheels are controlled together, or a system having conventional front steering and independently controllable rear steering for each of the wheels or vice versa.

The convenience control system25includes the controller or integrated sensing system (ISS)26, which signals the safety device51, the suspension control49, the engine/transmission controller123and the brake controller60in response to information received from the ATMS18, and the sensor cluster50. In other application, as described below, the ISS26may only indicate to the vehicle operator a sensed condition, without taking any other active measures to alter the sensed condition.

The controller26as well as the suspension control49, the brake controller60, and the engine/transmission controller123may be microprocessor based such as a computer having a central processing unit, memory (RAM and/or ROM), and associated input and output buses. The controllers26,49,60, and123may be application-specific integrated circuits or may be formed of other logic devices known in the art. The controllers26,49,60, and123may each be a portion of a central vehicle main control unit, an interactive vehicle dynamics module, a restraints control module, a main safety controller, a control circuit having a power supply, combined into a single integrated controller, or may be a stand-alone controller as shown. The controllers26,49,60, and123may be configured to be mounted and located within a vehicle dashboard or vehicle panel or in some other location on the vehicle10.

The controllers and devices in communication with the ISS26are described below. Thereafter, the inputs to the ISS26are described.

Referring toFIG. 4, a passive safety system may be in communication with the controller or ISS26. The passive safety system27includes collision detection sensors29, object detection sensors28, and passive countermeasures30. The object detection sensors28monitor the environment around the vehicle10and generate object detection signals upon detection of an object. The object detection sensors28may be infrared, visible, ultrasonic, radar, active electro-magnetic wave-ranging, or lidar based, a charged-coupled device, a series of photodiodes, or in some other form known in the art. Wave-ranging devices may include radar, lidar, stereo camera pairs, 3-D imagers, with active infrared illumination, or other wave-ranging devices known in the art. Vision sensors may refer to robotic cameras or other visual imaging cameras. The wave-ranging sensors and the vision sensors may be monocular or binocular and may be used to obtain height, width, depth, range, range rate, angle, and any other visual aspect information. Monocular cameras may be used to obtain less accurate and less reliable range and range rate data as compared to binocular cameras. The object detection sensors28may also be in the form of an object indicator. The object detection sensors28may be in various locations on the vehicle and any number of each may be utilized. The object detection sensors may also include occupant classification sensors (not shown). With respect to tripped rollover events, object detection sensors28detect objects which may cause a tripped rollover.

The collision detection sensors29are used to detect a collision and more particularly, a side collision. The collision detection sensors29may also be located anywhere on the vehicle10and generate collision detection signals in response to a collision. The collision detection sensors29may include sensors that are used as vehicle status sensors, such as the yaw rate sensor35, the lateral acceleration sensor39, and the longitudinal acceleration sensor40. The collision detection sensors29may also be in the form of an accelerometer, a piezoelectric sensor, a piezo-resistive sensor, a pressure sensor, a contact sensor, a strain gage, or may be in some other form known in the art.

The passive countermeasures30may include internal air bag control, seatbelt control, knee bolster control, head restraint control, load limiting pedal control, load limiting steering control, seatbelt pretensioner control, external air bag control, pedestrian protection control, and other passive countermeasures known in the art. Air bag control may include control over front, side, curtain, hood, dash, or other type of airbags known in the art. Pedestrian protection may include a deployable vehicle hood, a bumper system, or other pedestrian protective devices.

The brake control system31can also be in communication with the ISS controller26. The brake control system31includes the brake controller60that actuates front vehicle brakes62aand62band rear vehicle brakes62cand62d. The vehicle brakes62are associated with the wheels12a-12d. The brakes62may be independently actuatable through the brake controller60. The brake controller60may control the hydraulic system of the vehicle10. Of course, electrically actuatable brakes may be used in the present invention. The brake controller60may also be in communication with other safety systems such as an antilock brake system64, a yaw stability control system66and a traction control system68.

The steering control system32, which may also communicate with the ISS controller26, can include a number of different types of front and rear steering systems including having each of the front and rear wheels12a-12dconfigured with respective controllable adjusting elements55A-D. The wheels12may be controlled together or individually. The ISS controller26may control the position of the front right wheel adjusting element55A, the front left wheel adjusting element55B, the rear left wheel adjusting element55D, and the right rear wheel adjusting element55C. Although as described above, two or more of the adjusting elements may be simultaneously controlled. For example, in a rack-and-pinion system, the two wheels coupled thereto are simultaneously controlled. Based on the inputs from sensors35-47and from the ATMS18, the ISS controller26controls the steering position and/or braking of the wheels. Thus, with respect to the steering control system32, the adjusting elements55permit directional control of the particular wheel.

The controller26may also communicate with the suspension control system33. The suspension control system33includes the suspension control49, the suspension48, and the suspension adjusting elements55A-55D (FRSP, FLSP, RRSP, RLSP) that are associated with each wheel12. The suspension control49and adjusting elements55A-55D may be used to adjust the suspension48to prevent rollover. The adjusting elements55A-55D may include electrically, mechanically, pneumatically, and/or hydraulically operated actuators, adjustable dampers, or other known adjustment devices, and are described below in the form of actuators. The adjusting elements55may allow for active modification of the suspension response or geometry. For example, they may comprise active dampers. The adjusting elements55may also be bushings which can electronically decouple the sway bar associated with a wheel to enhance suspension articulation. Another example is a bushing comprising magnetorheological fluid and oil allowing it to articulate within the wheel joint to alter suspension geometry and/or the wheel's NVH characteristics. In a further example, the suspension components55may be pneumatic cylinders. The suspension control system33may also operate to adjust the tire pressure with central tire inflation capability. For instance, the tire pressure may be lowered to traverse softer road conditions. This feature can be used in response to a road surface characteristic detection as described below, or a low tire pressure signal.

The controller26may also be in communication with the drivetrain control system34. The drivetrain control system34includes an internal combustion engine120or other engine known in the art. The engine120may have a throttle device142coupled thereto, which is actuated by a foot pedal144. The throttle device142may be part of a drive-by-wire system or by a direct mechanical linkage between the pedal144and the throttle device142. The engine controller123may be an independent controller or part of the controller26. The engine controller123may be used to reduce or increase the engine power. While a conventional internal combustion engine is contemplated, the vehicle10could also be powered by a diesel engine or an electric engine or the vehicle could be a hybrid vehicle utilizing two or more types of power systems.

The drivetrain system34also includes a transmission122, which is coupled to the engine120. The transmission122may be an automatic transmission or a manual transmission. A gear selector150is used to select the various gears of the transmission122. The gear selector150may be a shift lever used to select park, reverse, neutral, and drive positions of an automatic transmission. Of course, in the case of electric vehicles, electric motors may replace the conventional engine/transmission setup shown in this example.

Safety device51may control one or more passive safety countermeasures such as airbags30or a steering actuator55A-D at one or more of the wheels12a,12b,12c,12dof the vehicle. The safety device51may also operate the suspension control/tire inflator49as described above.

A lateral support system70may also be in communication with the convenience controller26, either directly or through the safety device51. The lateral support system70is adapted to mitigate tripped rollover events. It can include a deployable set of linkages and one or more arms, which each have a wheel set attached to the outwardly extending end thereof. The inward end of the arm is attached to a deploying mechanism. In normal driving conditions the wheels sets are not in contact with the driving surface. The lateral support system70may also or alternatively include laterally deployable airbags. The airbags are also outwardly deployed to prevent or mitigate a tripped rollover. The airbags may be deployed from any location on the vehicle10and any number of airbags may be utilized.

Indicator90may also be in communication with the convenience controller26directly, or indirectly though the safety device51. It may be used to indicate to a vehicle operator various vehicle-related and status information.

In this example, the controller26receives numerous inputs to aide in determining vehicle dynamic conditions. For example, it may determine whether a rollover event is in progress or is imminent. The controller26may include a signal multiplexer50that receives the signals from the sensors20and35-47. In this example, the signal multiplexer50provides the signals to a roll stability control (RSC) feedback control command56which is part of the convenience controller25. As mentioned above, however, the convenience system could be implemented with many fewer sensor inputs and, indeed, may only receive input from ATMS sensors20to determine the roadway surface conditions and other convenience functions described below.

The controller26takes advantage of the information provided by the advanced tire monitoring sensors20described above, as well as the traditional vehicle dynamics sensors35-47in monitoring for potential rollover events and other vehicle and roadway dynamics. Thus, the acceleration data, temperature data and pressure data for each wheel is analyzed in various safety schemes described in further detail with respect toFIGS. 5 through 10. Heretofore, control systems have not considered coordinate acceleration data at each wheel. Rather, such vehicle and roadway data was only determined by means such as conventional IMU units, typically with reference to the body center frame, and located above the suspension line of the vehicle.

Briefly, the vehicle status sensors35-47may include the yaw rate sensor35, the pitch rate sensor36, the roll rate sensor37, the vertical acceleration sensor38, lateral acceleration sensor39, longitudinal acceleration sensor40, the speed sensor41, the steering wheel angle velocity sensor42, the steering angle (of the wheels or actuator) position sensor43, the suspension load sensor44, the suspension position sensor45, the accelerator/throttle signal generator46, and the brake pedal/brake signal generator47. It should be noted that various combinations and sub-combinations of the sensors may be used. The steering wheel angle sensor42, the accelerator/throttle signal generator46, and the brake pedal/brake signal generator47are considered driver input sensors, since they are associated with a pedal, a wheel, or some other driver input device. Depending on the desired sensitivity of the system and various other factors, not all the sensors35-47may be used in a commercial embodiment. These sensors may be used in a conventional rollover stability control scheme, if the vehicle is so equipped, as in this example. One example of a rollover stability control scheme using such sensors, as well as an advanced tire monitoring system is disclosed in U.S. patent application Ser. No. 11/693,131, which is incorporated by reference herein. In the comfort and convenience schemes discussed below, however, the control method is based on feedback from the ATMS18alone, or in combination with only one or a few other sensor inputs such as the driver input and vehicle speed. Thus, the remaining sensors35-47are only included for completeness, and may only act as confirmatory sensors to the detected condition based on the ATMS18data.

The vehicle dynamic sensors35-40may be located at the center of gravity of the vehicle10. Those skilled in the art will recognize that the sensors may also be located off the center of gravity and translated equivalently thereto.

FIG. 5is a logic flow diagram illustrating a method of operating a control system of a vehicle in accordance with an embodiment of the present invention providing roadway surface condition estimation. Although the following steps are described primarily with respect to the embodiments ofFIGS. 1-4, they may be modified and applied to other embodiments of the present invention, including vehicle embodiments wherein less than all sensors35-47are included. Indeed, in this example, only an ATMS sensor20at each wheel and vehicle speed data are analyzed.

In general terms, the roadway surface condition estimation scheme detects the type of road surface being traversed by the vehicle, and actively adjusts vehicle sub-systems accordingly to improve the ride comfort and/or vehicle handling. Roadway surfaces are differentiated by an analysis of the tire acceleration signals provided by the ATMS sensor20at each wheel. Rough road surfaces such as dirt roads exhibit higher acceleration signal and spectral content, i.e., acceleration frequency components, in the X and Z axis as compared to smooth road surfaces such as asphalt roads. On this basis, roadway surfaces can be detected, and suspension and/or tire adjustments can be made to improve vehicle ride and handling. Other road surface conditions can also be discerned such as ice, water, gravel, snow, etc.

Referring toFIG. 5, in step200, tire signals are generated, which are indicative of the current tire pressure, temperature and multi-axis accelerations within each tire of the vehicle. This information is provided by the advanced tire monitoring system sensors20. Steps202,204and206preprocess the data generated by the ATMS sensors20. In the block202the data is segmented and parsed into discrete time windows and transformed from the time domain into the frequency domain using the Fourier Transform (FT) techniques. Alternate embodiments may use other frequency transformation techniques such as wavelet transformation techniques to transform the time domain data into its frequency domain representation. In block206the signal amplitude-time data is parsed into discrete time windows and signal amplitude vs. time table is generated for each time window for each of the sensor data as shown inFIG. 6. The generated tables are used in the subsequent algorithm blocks and are compared to known stored road surface conditions tables to determine the current road surface conditions. In block204a signal magnitude vs. frequency table is generated for each time window as shown inFIG. 7. The generated tables are used in the subsequent algorithm blocks and are compared to known stored road surface conditions tables to determine the current road surface conditions. As mentioned above, because the data is generated inside each tire for the vehicle, the signature profiles of the sensor data provide direct insight into what each tire is experiencing while it contacts the road surface. This data is generated much more directly than vehicle acceleration data generated by conventional IMU sensing systems because traditional IMU systems determine roll, pitch and yaw and coordinate accelerations above the vehicle suspension. The ATMS sensors20eliminate signal propagation through the suspension, and provide a clearer “view” of the vehicle dynamics.

The preprocessed ATMS sensor data is then analyzed according to roadway surface condition estimation criteria in step208. A more detailed explanation of the roadway surface condition estimation criteria is provided in the example ofFIG. 8. In this example, the ATMS sensor signals are compared to stored sensor frequency response signatures and stored amplitude/time response signatures from block210.

The robustness of the system can be improved further by combining a wheel slip analysis with the ATMS data analysis. For example, the longitudinal wheel slip of a given wheel can be determined according to:
S=(wr/v)−1  (1)
wherein w is the wheel's angular velocity, r is the radius of the tire, and v is the linear wheel/tire velocity. This slip value can then be compared to sensed ATMS data to confirm the roadway surface condition estimation.

The determined roadway surface condition estimation is then broadcast to other vehicle subsystems. This may include safety modules such as the active/passive safety systems, ABS, RSC, or integrated vehicle dynamics controller. By broadcasting the roadway surface conditions, these other systems can then optimize their performance based upon the sensed roadway surface. For instance, if a rollover event is declared, but the roadway surface conditions are not optimal (for example, slippery conditions), the thresholds that are used in activating or initiating interventions may be adjusted, scaled, opened, or relaxed, to alter intervention timing. In such situations, earlier interventions may be desired. In another example of broadcasting, a pre-arm signal for safety-related countermeasures based upon the ATMS data may be generated. Pre-arming would be appropriate for the roll stability control system as well as the restraints control system. The brake pressure applied during any intervention or countermeasure may also be modified as a result of the roadway surface estimation. For instance, the brake pressure may be tiered based on the contact patch conditions at each tire: full range or maximum brake pressure range, a reduced range or brake pressure limiting range, and an inactive range or brake pressure prevented range. When the contact patch surface roughness is estimated to be high or greater than or equal to a first surface roughness threshold value, the control system may apply a brake pressure up to a maximum threshold. In those cases, the full range brake control functions are maintained. When the surface roughness estimate of a tire of concern is in the reduced range or between a first roadway surface roughness threshold TPT1and a second roadway surface roughness threshold TPT2, the control system may apply a reduced or limited brake pressure, which is less than that which would normally be applied. In the reduced range the amount that the brake pressure is limited is gradually or progressively increased. This increase may be linear, may be nonlinear, or may result using some other relationship. When the roadway surface roughness estimate of a tire of concern is less than or equal to the second threshold TPT2, the control system is prevented from applying brake pressure. Although the control system is prevented from applying a brake pressure, brake pressure may be applied manually by a vehicle operator. In another embodiment, the control system can override the manual brakes and limits or prevents manual brake pressure.

Optionally, in step213, the tire pressure may be changed in response to the detected roadway surface condition and/or merely on a low or high tire pressure indication. This may be accomplished by the central tire inflation device49(FIG. 4), if the vehicle is so equipped. Thus, if the tires are at a lower than normal pressure, and the roadway surface is hard, the tire should be inflated to reduce the potential for tire de-beading, de-treading, or other tire damage associated with low pressure driving. Similarly, the tires may be maintained or put in a low pressure state to improve soft road condition handling (sand, loose gravel). When the vehicle encounters a hard surface for sufficient length of time, the ATMS18would indicate the roadway surface condition, and the tires could be inflated to a more appropriate pressure.

In step214, the control system may also indicate via an indicator, such as the indicator90(FIG. 4), to a vehicle operator the roadway surface condition and/or the status of each tire. The control system may indicate that a tire pressure is low and the extent thereof. This information may also be stored, viewed, and downloaded for future review and/or evaluation. The viewing and downloading may be to an offboard or offsite system. The control system may also indicate to a vehicle operator that active tasks are being performed and the status of the vehicle. This indicated information may also be stored, viewed, and downloaded for future review and/or evaluation. The viewing and downloading may be to an offboard or offsite system.

The above tasks may be performed via any one or more of the herein mentioned controllers, control systems, stability control systems, or the like.

The above-described steps are meant to be illustrative examples; the steps may be performed sequentially, synchronously, simultaneously, or in a different order depending upon the application.

Referring now toFIG. 8, a logic flow diagram illustrating one particular method of ATMS sensor-based roadway surface condition estimation in accordance with an embodiment of the present invention is shown. This process is one example of the roadway surface condition estimation as called for in step208ofFIG. 5. Of course, this example may be modified and applied to other embodiments of the present invention.

The routine starts at steps216and218by determining whether the vehicle is moving or braking. If the vehicle is moving, but not braking, the logic continues. Otherwise, no roadway surface condition is estimated in step220.

The sensed tire data from steps202,204and206as described above, is then compared to stored values from information block210in step222. The stored Fourier response may comprise a lookup table of sensor signatures, each indicative of a roadway surface condition at various speeds. If the current frequency response characteristic matches any stored frequency response characteristic at the same vehicle speed indicative of a particular roadway surface condition in step224, the logic continues to step226. Otherwise, no roadway surface condition is estimated in step220.

If a roadway surface condition match exists for the sensed ATMS data, step226begins the process of determining which roadway surface has been estimated. This continues through N stored roadway surface signatures, as shown in step228. If the first tested roadway surface condition matches the sensed data, it is broadcast to the other vehicle subsystems in step230, as described above. The confidence level of the roadway surface condition estimation can be determined from the closeness of the match and/or by confirmatory calculations of wheel slip as discussed above. Further, if the system has a high confidence level regarding the declared roadway surface condition in step232, and it is deemed useful driver information, it may be indicated to the vehicle operator, as in step214. Again, for each of N stored roadway conditions, similar steps are indicated at236,238and240.

FIG. 9is a logic flow diagram illustrating a method of operating a control system of a vehicle in accordance with an embodiment of the present invention providing active suspension control. Although the following steps are described primarily with respect to the embodiments ofFIGS. 1-4, they may be modified and applied to other embodiments of the present invention, including vehicle embodiments wherein less than all sensors35-47are included. Indeed, in this example, only ATMS sensor20data at each wheel and the vehicle speed data are analyzed.

In general terms, the active suspension scheme detects the type of road surface being traversed by the vehicle, and actively adjusts the vehicle suspension to improve the ride comfort and/or vehicle handling. Roadway surfaces are differentiated by an analysis of the tire/wheel acceleration signals provided by the ATMS sensor20at each wheel, as described above. Rough road surfaces such as dirt roads exhibit higher acceleration signal and spectral content, i.e., acceleration frequency components, in the X and Z axis as compared to smooth road surfaces such as asphalt roads. On this basis, roadway surfaces can be detected, and suspension and/or tire adjustments can be made to improve vehicle ride and handling. Additionally, if the vehicle is equipped with operator-selectable handling, the desired vehicle handling can be incorporated into the active suspension scheme.

Adjustments to the suspension contemplated include modifying suspension dampers, ride height, and activating suspension bushings to modify suspension geometry and characteristics at the wheels. Active suspension dampers vary the amount of damping performance of the shock absorbers. They typically use megnetoreological fluids or pneumatic pressure to provide an extremely responsive change to damping performance. Most conventional suspension adjustment systems are “open loop” in that they rely upon operator input to adjust the suspension. In the example of the present invention, besides allowing open loop control, the system permits “closed loop” suspension control based on feedback from the ATMS18. Ride height can be modified by an active air suspension system which uses compressed air to control suspension response and vehicle ride height. Again, convention systems are largely open loop systems that only sense vehicle height, whereas the present system permits closed loop control with respect to ride height and roadway surface conditions. Other active suspension components include sway bars that can be electronically decoupled by bushings to provide enhanced suspension articulation. Such features could also be used to automatically correct wheel misalignment, which could also be sensed by the ATMS18.

Referring toFIG. 9, in step300, ATMS signals are generated, which are indicative of the current tire pressure and temperature within and multi-axis accelerations at each wheel/tire of the vehicle. This information is provided by the ATMS sensors20. Steps302,304and306preprocess the data generated by the ATMS sensors20. As mentioned above, because the data is generated inside each tire for the vehicle, the signature profiles of the sensor data provide direct insight into what each tire is experiencing while it contacts the road surface. This data is generated much more directly than vehicle acceleration data generated by conventional IMU sensing systems because traditional IMU systems determine roll, pitch and yaw and coordinate accelerations above the vehicle suspension. The ATMS sensors20eliminate signal propagation through the suspension, and provide a clearer “view” of the vehicle dynamics.

The preprocessed ATMS sensor data is then analyzed according to active suspension control criteria in step308. A more detailed explanation of the active suspension control is provided in the example ofFIG. 10. In this example, the sensor signals are compared to stored sensor frequency response signatures from block310and stored amplitude/time response signatures from block309.

If the vehicle operator has selected a desired driving characteristic for the vehicle, by way of a user selectable input, this could also be provided from block311. Such indicators may include “sport”, “normal” or “comfort” handling and ride characteristics for the vehicle.

In step312, the user-selected input311and active suspension control scheme308are used to actively tune the suspension to provide improved ride and handling. In one example, the vehicle is operated according to the user-selected ride setting, but actively adjusted based on the sensed road conditions. For instance, if the user selected a “sport” or “firm” ride characteristic, the perceived stiffness of the suspension would be softened upon detection of a rough road surface to alleviate any undesirable operator feedback or noise, vibration and Harshness.

The above-described steps are meant to be illustrative examples; the steps may be performed sequentially, synchronously, simultaneously, or in a different order depending upon the application.

Referring now toFIG. 10, a logic flow diagram illustrating one particular method of ATMS sensor-based active suspension control in accordance with an embodiment of the present invention is shown. This process is one example of the active suspension control as called for in step308ofFIG. 9. Of course, this example may be modified and applied to other embodiments of the present invention.

The routine starts at steps316and318by determining whether the vehicle is moving or braking. If the vehicle is moving, but not braking, the logic continues. Otherwise, no suspension characteristics are modified in step320.

The sensed tire data from steps302and304as described above, is then compared to stored values at the same vehicle speed from information block310in step322. The stored Fourier response may comprise a lookup table of sensor signatures, each indicative of a roadway surface condition. If the current frequency response characteristic is compatible with the operator-input suspension mode in step324, no suspension adjustment is made. Otherwise, if the selected suspension mode is incompatible or undesirable for the detected road condition (i.e., “firm” ride on a rough road), the suspension is adjusted accordingly in step326. The user-selected suspension mode is determined from block311.

In step328, the detected acceleration data, including the amplitude/time response characteristics of the ATMS data from block306is compared to stored amplitude/time response signatures at the same vehicle speed from block309. The user-selected ride mode from block311is also considered in block330. If the roadway surface condition-based suspension response matches the user-selected suspension mode, no changes are made. Otherwise, the suspension is adapted in step326as a function of the determined suspension setting according to the detected road surface conditions, taking into account the user-selected setting. As mentioned above, suspension adjustments can include modifying suspension dampers, ride height, and activating suspension bushings to modify suspension geometry and characteristics at the wheels. Further, any actions with regard to the suspension may be indicated to the vehicle operator, as before.

Thus, the suspension control system adjusts the vehicle suspension characteristics according to the user selected suspension value when the user-selected value and the detected road surface conditions are the compatible; and adjusts the vehicle suspension characteristics according to the detected road surface condition when the user-selected suspension value and detected road surface conditions are incompatible, such as a sports ride selection under estimated rough road conditions.

In another aspect of active suspension control, rear wheel hop mitigation may be included. Rear wheel hop occurs when one or typically, both rear wheels vertically and laterally jump from uneven road surfaces. Such occurrences are common on dirt roads and as a result of tar strips in concrete. Rear wheel hop can cause sudden lateral (sideways) rear vehicle movement leading to temporary vehicle instability or compromised control.

Rear wheel hop mitigation may be implemented as part of the active suspension control. During a rear wheel hop event, the rear wheels experience both a Z (vertical) and Y (lateral) acceleration which can be readily detected by the ATMS18. These signals will only be detected in the rear wheels with the exception of some Z axis acceleration component from the road surface. Thus, wheel signature profiles indicative of rear wheel hop can be stored as in blocks309and310and compared to the sensed wheel data from blocks302,304and306.

In response to a detected rear wheel hop event, step326can implement countermeasures to mitigate or prevent further wheel hop. Such countermeasures can include suspension adjustments, as mentioned above. Alternatively, or additionally, they may include reducing the engine power and/or braking the associated wheels.