The present invention relates to trailer sway mitigation. More specifically, the invention relates to the use of ultrasonic or radar sensors in trailer sway mitigation.
Towing a trailer behind a vehicle often presents stability problems for both the vehicle and the trailer. Trailers tend to oscillate or sway back and forth in a lateral direction when being pulled behind a vehicle. The oscillations can be caused by a number of circumstances including excessive driving speed and severe changes in direction. For example, an operator of the vehicle may swerve to yield to a vehicle merging from a freeway ramp. The quick swerving movement is transferred to the trailer and the trailer may begin to oscillate. Without proper damping, the oscillations may continue to increase in magnitude. If the oscillations are not decreased, the vehicle and trailer may become unstable.
Some methods have been developed to dampen and substantially decrease the frequency and magnitude of trailer oscillations in order to bring the vehicle and trailer back to a stable operating condition. For example, trailer sway mitigation (“TSM”) in vehicles is described in U.S. patent application Ser. No. 11/503,875, filed on Aug. 11, 2006 (which is incorporated herein by reference). However, many current methods of trailer-sway mitigation use sensors that only detect vehicle characteristics. The position and oscillatory action of the trailer is not measured directly. As a result, current methods are subject to error, such as false activation when no trailer is present. In addition, the accuracy of the current methods is low because the actual trailer position and oscillatory behavior is estimated with no method for confirming the accuracy of the estimation.
The present invention provides a method of mitigating trailer sway by providing a direct and accurate measurement of the distance from a rear end of the vehicle to the trailer and providing the accurate measurements to an electronic control unit that implements the trailer sway mitigation. Thus, the method is only activated when the trailer is present. Furthermore, the method is more accurate because the actual trailer distances are measured and used as inputs to the method.
In one embodiment, the invention provides a method of controlling a vehicle and a trailer. The vehicle has a front and a rear end, and the trailer is coupled to the rear end. The method includes sensing a plurality of vehicle characteristics, sensing a distance between the vehicle and the trailer with a sensor positioned on the rear end of the vehicle, determining an oscillatory action of the trailer based on the sensed distance, and applying a braking force on at least one wheel of the vehicle in response to the oscillatory action.
In another embodiment, the invention provides a system for controlling a vehicle and a trailer. The vehicle has a front end and a rear end, and the trailer is coupled to the rear end. The system includes a plurality of vehicle characteristic sensors, at least one distance sensor, and an electronic control unit (“ECU”). Each of the plurality of vehicle characteristic sensors is configured to output a sensor signal. The distance sensor is coupled to the rear end of the vehicle and senses a distance between the rear end and the trailer and output a signal indicative of the sensed distance. The ECU receives the sensor signals and the distance signal, and determines a plurality of target characteristics based on the sensor signals. The ECU compares the sensor signals to the target characteristics and produces an error signal based on the comparison. A braking force is applied to the wheels of the vehicle in response to the error signal.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
The vehicle 10 includes a plurality of sensors that provide information to the ECU 28. The sensors include a steering angle sensor 32, an engine torque sensor 34, a wheel speed sensor corresponding to each wheel 36A, 36, 36C, and 36D, a brake-system master cylinder pressure sensor 38, a lateral acceleration sensor 40, a yaw rate sensor 42, a right distance sensor 44, and a left distance sensor 46. Of course, in other embodiments, the vehicle 10 could include more or less sensors. The vehicle 10 defines a longitudinal vehicle axis 48.
A trailer 50 is coupled to the rear end of the vehicle by a hitch 52. The trailer 50 includes a front end 54, rear end 56, right side 58, left side 60, and four wheels 62A, 62B, 62C, and 62D. The front wheels 62A and 62B are coupled to a front axle 64, and the rear wheels 62C and 62D are coupled to a rear axle 66. Trailers with more or less axles can be used with embodiments of the invention. The trailer 50 also has a longitudinal trailer axis 68 and rear taillights that operate in response to operator input from the vehicle 10 such as braking and turn signals. Unlike the vehicle 10, the trailer 50 does not include an electronic control unit.
As noted, the trailer 50 may begin to oscillate when towed and the oscillation may affect the vehicle 10. The vehicle operator may respond to the oscillation by steering or pressing a brake pedal in an attempt to compensate for movement of the vehicle 10. The operator may over-steer and may lose control of the vehicle.
The vehicle 10 includes a trailer sway mitigation (“TSM”) function to increase the stability of the vehicle 10 when towing the trailer 50, the logic of the TSM function is illustrated in
In general terms, the TSM increases the stability of the vehicle 10 by causing the brakes (or, more broadly, wheel torque) to be controlled in a specified manner. Symmetric and asymmetric braking (or, more broadly, torque control) is applied to the vehicle wheels 20 to dampen trailer oscillations. Symmetric braking forces are applied equally to the vehicle wheels typically all four wheels (or the two front wheels or the two rear wheels). Asymmetric braking forces are applied unequally to one or more of the wheels. For example, a braking force may be applied to only the front right wheel (or only the rear right, or both right wheels). Then, a similar barking force may be applied to only the front left wheel (or only the rear left, or both left wheels). Various asymmetric braking may be carried out until trailer oscillations decrease.
The ESC module 70 determines a gain value K based on the vehicle speed and vehicle yaw rate. As shown on
ψ(t)=f(lws) Equation 1
The right distance sensor 44 and the left distance sensor 46 are mounted on the rear end 14 of the vehicle 10 and are spaced from each other. As illustrated, the right sensor 44 is a distance l1 from the longitudinal axis 48 and the left sensor 46 is a distance l2 from the longitudinal axis 48. The distances l1 and l2 do not change and the values of l1 and l2 (in meters) are stored in a memory of the ECU 28.
During operation, the target trailer position is calculated. For example, when the operator turns the steering wheel, the target trailer position, defined by a target trailer sway angle θso(t), is determined based on the steering angle input lws using Equation 2.
θso(t)=K*ψ(t) Equation 2
The target trailer sway angle θso(t) describes the relationship between the longitudinal vehicle axis 48 and the longitudinal trailer axis 68. When the trailer 50 is in line with the vehicle 10, then the longitudinal vehicle axis 48 and the longitudinal trailer axis 68 are parallel to each other and θ(t) is equal to zero degrees.
The right target distance d1so(t) and the left target distance d2so(t) are calculated using Equation 3. The right target distance d1so(t) is the distance from the rear end 14 of the vehicle 10 adjacent the right sensor 44 to the front end 54 of the trailer 50. Similarly, the left target distance d2so(t) is the distance from the rear end 14 of the vehicle 10 adjacent the left sensor 46 to the front end 54 of the trailer 50, along a line that is substantially parallel to the longitudinal vehicle axis 48. If a line 76 parallel to the rear end 14 of the vehicle 10 is extended and a line parallel 78 to the front end 54 of the vehicle 50 is extended, the lines intersect at a point 80. The angle between the lines 76 and 78 is equal to the trailer sway angle θ(t). The length l(t) is defined as the distance from the left sensor 46 to the point 80, as illustrated in
The actual right distance d1(t) and the actual left distance d2(t) are determined by analyzing the signals produced and received by the right and left distance sensors 44 and 46. The right and left distance sensors 44 and 46 can be ultrasonic sensors, radar sensors, or the like. The right distance sensor 44 emits a signal 82 in the direction of the trailer 50. At least a portion of the signal 82 is reflected back toward the right sensor 44 and the sensor determines the right distance d1(t) based on the amount of elapsed time. The left distance sensor 46 emits a signal 84 in the direction of the trailer 50 and determines the amount of time for the signal 84 to reach the front end of the trailer 54 and reflect back to the left distance sensor 46.
After the target right and left distances d1so(t) and d2so(t) are calculated and the actual right and left distances d1(t) and d2(t) are received from the distance sensors, a right error signal ε1(t) 86 and a left error signal ε2(t) 88 are calculated using Equations 4 and 5, respectively.
ε1(t)=d1(t)−d1so(t) Equation 4
ε2(t)=d2(t)−d2so(t) Equation 5
A summing node 90 sums the error signals 86 and 88 calculated by the ESC using Equations 4 and 5 and outputs the sum (controller input) 92 to a proportional-integral-derivative (PID) controller 94. The ESC sensors 32, 34, 36, 38, 40 and 42 also provide outputs 96 that are filtered using a bandpass filter 98 and are provided to the PID controller 94. The PID controller 94 uses the error signal 92 and the filtered ESC sensor outputs 100 to produce a control signal 102 that is provided to a hydraulic unit 104. The hydraulic unit 104 produces an output 106 to apply symmetric braking, asymmetric braking, or both to the vehicle 10. The process is repeated until the trailer oscillations are below a predetermined threshold value.
The output 106 of the hydraulic unit 104 also depends upon an analysis of certain thresholds, including (1) θ(t) converges to θso(t), i.e. |θ(t)−θso(t)|<3° and
If the absolute value of the difference between the actual or measured sway angle θ(t) and the target sway angle θso(t) is greater than three (3) degrees, braking is applied. Symmetric braking is applied when
Asymmetric braking is applied when
If the actual sway angle θ(t) is negative, braking is applied to the left wheels. If θ(t) is positive, braking is applied to the right wheels.
The distance sensor 114 is positioned adjacent the hitch 130 and is aimed toward the trailer 128 along a line substantially parallel to the longitudinal vehicle axis 126. The logic of
The target distance dso(t) is calculated using Equation 6.
d0 is the distance between the vehicle and the trailer when θ=0 (i.e., the trailer is aligned with the vehicle). The ESC module 70 receives the sensed distance d(t) and compares the sensed distance d(t) to the target distance dso(t) to determine an error signal ε(t) using Equation 7.
ε(t)=d(t)−dso(t) Equation 7
The error signal 92 is used by the PID controller 94 to determine whether to apply symmetric braking, asymmetric braking, or both to the wheels. The control signal 102 produced by the PID controller 94 is provided to the hydraulic unit 104 to apply braking force to the wheels of the vehicle 112. Thus, trailer oscillations are decreased and the stability of both the vehicle 112 and the trailer 128 is increased.
Thus, the invention provides, among other things, a method of controlling a vehicle and a trailer using a trailer sway mitigation control system. Various features and advantages of the invention are set forth in the following claims.
Number | Name | Date | Kind |
---|---|---|---|
3908782 | Lang et al. | Sep 1975 | A |
4023863 | Sisson et al. | May 1977 | A |
4023864 | Lang et al. | May 1977 | A |
4034822 | Stedman | Jul 1977 | A |
4232910 | Snyder | Nov 1980 | A |
RE30550 | Reise | Mar 1981 | E |
4254998 | Marshall et al. | Mar 1981 | A |
4275898 | Muste Llambrich | Jun 1981 | A |
4697817 | Jefferson | Oct 1987 | A |
4706984 | Esler et al. | Nov 1987 | A |
4850249 | Kirstein | Jul 1989 | A |
5011170 | Forbes et al. | Apr 1991 | A |
5022714 | Breen | Jun 1991 | A |
5029948 | Breen et al. | Jul 1991 | A |
5139374 | Holt et al. | Aug 1992 | A |
5333940 | Topfer | Aug 1994 | A |
5348331 | Hawkins | Sep 1994 | A |
5380072 | Breen | Jan 1995 | A |
5671982 | Wanke | Sep 1997 | A |
5707071 | Prestidge et al. | Jan 1998 | A |
5747683 | Gerum et al. | May 1998 | A |
5799745 | Fukatani | Sep 1998 | A |
5861802 | Hungerink et al. | Jan 1999 | A |
5964819 | Naito | Oct 1999 | A |
5986544 | Kaisers et al. | Nov 1999 | A |
6012780 | Duvernay | Jan 2000 | A |
6042196 | Nakamura et al. | Mar 2000 | A |
6074020 | Takahashi et al. | Jun 2000 | A |
6223114 | Boros et al. | Apr 2001 | B1 |
6272407 | Scholl | Aug 2001 | B1 |
6311111 | Leimbach et al. | Oct 2001 | B1 |
6324447 | Schramm et al. | Nov 2001 | B1 |
6349247 | Schramm et al. | Feb 2002 | B1 |
6438464 | Woywod et al. | Aug 2002 | B1 |
6446998 | Koenig et al. | Sep 2002 | B1 |
6450019 | Wetzel et al. | Sep 2002 | B1 |
6452485 | Schutt et al. | Sep 2002 | B1 |
6466028 | Coppinger et al. | Oct 2002 | B1 |
6476730 | Kakinami et al. | Nov 2002 | B2 |
6480104 | Wall et al. | Nov 2002 | B1 |
6494281 | Faye et al. | Dec 2002 | B1 |
6498977 | Wetzel et al. | Dec 2002 | B2 |
6501376 | Dieckmann et al. | Dec 2002 | B2 |
6516260 | Wetzel et al. | Feb 2003 | B2 |
6516925 | Napier et al. | Feb 2003 | B1 |
6522956 | Hecker et al. | Feb 2003 | B2 |
6523911 | Rupp et al. | Feb 2003 | B1 |
6553284 | Holst et al. | Apr 2003 | B2 |
6600974 | Traechtler | Jul 2003 | B1 |
6604035 | Wetzel et al. | Aug 2003 | B1 |
6636047 | Arlt et al. | Oct 2003 | B2 |
6655710 | Lindell et al. | Dec 2003 | B2 |
6668225 | Oh et al. | Dec 2003 | B2 |
6756890 | Schramm et al. | Jun 2004 | B1 |
6788190 | Bishop | Sep 2004 | B2 |
6873891 | Moser et al. | Mar 2005 | B2 |
6959970 | Tseng | Nov 2005 | B2 |
7114786 | Bess et al. | Oct 2006 | B2 |
7125086 | Tanaka et al. | Oct 2006 | B2 |
7204564 | Brown et al. | Apr 2007 | B2 |
7226134 | Horn et al. | Jun 2007 | B2 |
7272481 | Einig et al. | Sep 2007 | B2 |
7277786 | Stumpp et al. | Oct 2007 | B2 |
7301479 | Regan | Nov 2007 | B2 |
7302332 | Nenninger | Nov 2007 | B2 |
7394354 | Yu | Jul 2008 | B2 |
7401871 | Lu et al. | Jul 2008 | B2 |
7561953 | Yu | Jul 2009 | B2 |
7798263 | Tandy et al. | Sep 2010 | B2 |
7904222 | Lee et al. | Mar 2011 | B2 |
7917274 | Hackney et al. | Mar 2011 | B2 |
8010252 | Getman et al. | Aug 2011 | B2 |
8060288 | Choby | Nov 2011 | B2 |
20040021291 | Haug et al. | Feb 2004 | A1 |
20040246116 | Polzin | Dec 2004 | A1 |
20040249547 | Nenninger | Dec 2004 | A1 |
20050006946 | Traechtler | Jan 2005 | A1 |
20050065694 | Nenninger | Mar 2005 | A1 |
20050161901 | Ahner et al. | Jul 2005 | A1 |
20050206224 | Lu | Sep 2005 | A1 |
20060025896 | Traechtler et al. | Feb 2006 | A1 |
20060033308 | Waldbauer et al. | Feb 2006 | A1 |
20060125313 | Gunne et al. | Jun 2006 | A1 |
20060155457 | Waldbauer et al. | Jul 2006 | A1 |
20060204347 | Waldbauer et al. | Sep 2006 | A1 |
20060206253 | Yu | Sep 2006 | A1 |
20060229782 | Deng et al. | Oct 2006 | A1 |
20060273657 | Wanke et al. | Dec 2006 | A1 |
20070260385 | Tandy, Jr. et al. | Nov 2007 | A1 |
20080036296 | Wu et al. | Feb 2008 | A1 |
20080172163 | Englert et al. | Jul 2008 | A1 |
20080177454 | Bond et al. | Jul 2008 | A1 |
20080262686 | Kieren et al. | Oct 2008 | A1 |
20090005932 | Lee et al. | Jan 2009 | A1 |
20090005946 | Futamura et al. | Jan 2009 | A1 |
20090093928 | Getman et al. | Apr 2009 | A1 |
20090105906 | Hackney et al. | Apr 2009 | A1 |
20090198425 | Englert | Aug 2009 | A1 |
20090210112 | Waldbauer et al. | Aug 2009 | A1 |
20090228182 | Waldbauer et al. | Sep 2009 | A1 |
20090306861 | Schumann et al. | Dec 2009 | A1 |
Number | Date | Country |
---|---|---|
1661392 | Aug 2005 | CN |
19964048 | Jan 2001 | DE |
10212582 | Sep 2003 | DE |
1477338 | Nov 2004 | EP |
1516792 | Mar 2005 | EP |
2402453 | Dec 2004 | GB |
2001191964 | Jul 2001 | JP |
2002243423 | Aug 2002 | JP |
2005132360 | May 2005 | JP |
2006000578 | Jan 2006 | WO |
2008021942 | Feb 2008 | WO |
Entry |
---|
U.S. Appl. No. 12/512,783, filed Jul. 30, 2009, Wu et al. |
Kimbrough, Scott, et al., “A Control Strategy for Stabilizing Trailers Via Selective Actuation of Brakes”, Dynamic Systems of Control Division (Publication) DSC, vol. 44, Transportation Systems, 1992, pp. 413-428, ASME 1992. |
“Automobiles”, 81 pages, Copyright 2004 by Marcel Dekker, Inc. |
Tamura, Kazuya, et al., “Autonomous Vehicle Control System of ICVS City Pal: Electrical Tow-bar Function”, Proceedings of the IEEE Intelligent Vehicles Symposium 2000, pp. 702-707, Dearborn (MI), USA, Oct. 3-5, 2000. |
Kimbrough, Scott, “Coordinated Braking and Steering Control for Emergency Stops and Accelerations”, American Society of Mechanical Engineers, Design Engineering Division (Publication) DE, vol. 40, Advanced Automotive Technologies, pp. 229-244, ASME 1991. |
Liebemann, E., et al., “Light Commercial Vehicles—Challenges for Vehicle Stability Control”, Robert Bosch GmbH, Chassis Systems Control, Germany, Paper No. 07-0269. |
Deng, Weiwen, et al., “Parametric Study on Vehicle-Trailer Dynamics for Stability Control”, SAE International, SAE Technical Paper Series, 2003-01-1321, 2003 SAE World Congress, Detroit, Michigan, Mar. 3-6, 2003. |
Kimbrough, Scott, et al., “A Brake Control Algorithm for Emergency Stops (Which May Involve Steering) of Tow-Vehicle/Trailer Combinations”, Proceedings of the American Control Conference, vol. 1, pp. 409-414, 1991. |
Chen, Chieh, et al., “Steering and Independent Braking Control for Tractor-Semitrailer Vehicles in Automated Highway Systems”, Proceedings of the 34th Conference on Decision and Control, New Orleans, LA, vol. 2, pp. 1561-1566, Dec. 13-15, 1995. |
Tseng, et al., “The Development of Vehicle Stability Control at Ford”, IEEE/ASME Transactions on Mechatronics, vol. 4, No. 3., pp. 223-234, Sep. 1999. |
Wu, Kevin, “Enhancement of Trailer Sway Mitigation by Using Trailer Brakes”, Trailer Sway Mitigation, Vehicle Dynamics Expo USA, 2008 Conference, Bosch TSM, Oct. 23, 2008. |
Wang, Guo-Lin, et al., “Breaking Stability Analysis of Car-Trailer”, Journal of Jiangsu University, Natural Science Edition, vol. 27, No. 2. pp. 130-132, Mar. 2006. |
PCT/US2007/075561 International Search Report and Written Opinion, 15 pages, dated Dec. 7, 2007. |
Office Action from the Japanese Patent Office for Application No. 2009-524739 dated Jul. 13, 2012 (Translation only, 2 pages). |
Number | Date | Country | |
---|---|---|---|
20110022282 A1 | Jan 2011 | US |