Drift stabilization system and method for vehicle and trailer reverse assist system when trailer is backing up in a straight line

Abstract

A trailer reverse assist system includes a coupler angle detection sensor for detecting a zero degree angle of a trailer relative to a vehicle. A drift controller receives a signal from a vehicle dynamic sensor. The drift controller is electrically connected to a trailer reverse assist module. When the vehicle reverses the trailer on an intended straight implied path, and because the coupler angle sensor that detects the zero degree angle is not fully calibrated based on the signal from the vehicle dynamic sensor, the drift controller estimates the distance the trailer has drifted from the straight intended path, and provides a drift correction signal to the trailer reverse assist module in a closed-loop feedback manner for modifying the value of the zero degree angle and thereby causing adjustment of the steering system to realign the trailer toward the straight implied path without manual steering intervention.

Description

Technical Field

[0001] The present invention relates to a vehicle trailer reverse assist system, and more particularly to a drift stabilization system and method for real-time control and correction of trailer drift when the trailer moves in reverse on an implied straight path. Background Art

[0002] Reversing a vehicle with a trailer attached is a non-trivial and counter-intuitive process that often frustrates consumers and presents challenges when trying to maneuver a trailer into a tight spot. Drivers are often confused as to which way to turn the vehicle's steering wheel to achieve a desired change in the trailer's direction. Recently added Trailer Reverse Assist (TRA) type features remedy this situation by allowing the driver / operator to simply steer the trailer along with the vehicle when backing up. However, Figure 1 During straight-line reverse of the trailer 12, the control system in the vehicle 10 with the trailer reverse assist function enabled is susceptible to small errors that may cause the trailer 12 to drift significantly from the implied / intended / desired reverse direction. Figure 2 , this drift must be periodically and manually adjusted by the driver and is a significant inconvenience as it interrupts the smooth and intuitive operation of the system. Figure 2 In the figure, the Y scale is enlarged for clarity of description.

[0003] Therefore, there is a need to provide a system and method that removes such drift and enables real-time updates to the calibration of a TRA-type system to further mitigate drift. Summary of the invention

[0004] The purpose of the present invention is to meet the needs involved above. According to the principle of the present embodiment, the purpose is achieved by providing a trailer reverse assist system, which is used for straight-line reversing of a vehicle with a trailer connected to the vehicle via a coulper. The vehicle has a steering system and a vehicle dynamic sensor for detecting vehicle operating parameters. The system includes a coupler angle detection sensor, which is constructed and arranged to detect a zero-degree angle of the trailer relative to the vehicle. The trailer reverse assist module is constructed and arranged to receive signals from the vehicle dynamic sensor and the coupler angle detection sensor. The trailer reverse assist module is associated with the steering system and is used to cause a change in the steering of the vehicle while reversing the trailer on an intended straight implied path. The drift controller is constructed and arranged to receive signals from the vehicle dynamic sensor. The drift controller is electrically connected to the trailer reverse assist module. When the vehicle is backing up a trailer on an intended straight implied path, and because the coupler angle sensor that detects the zero degree angle may not be perfectly calibrated based on signals from the vehicle dynamic sensors, the drift controller is constructed and arranged to 1) estimate the distance the trailer has drifted from the straight intended path, and 2) provide a drift correction signal to the trailer reverse assist module in a closed-loop feedback manner for modifying the value of the zero degree angle and thereby causing adjustment of the steering system to realign the trailer toward the straight implied path without manual steering intervention.

[0005] According to another aspect of the embodiment, a method for reversing a trailer along a straight implied path using a vehicle is provided. The vehicle has a steering system, a trailer reverse assist module associated with the steering system for causing a change in the vehicle's steering when reversing the trailer, and a vehicle dynamics sensor for detecting a vehicle operating parameter. The method includes detecting a zero-degree angle of the trailer relative to the vehicle. The trailer reverse assist module determines whether the detected zero-degree angle is substantially 0 degrees. The trailer reverse assist module receives a signal from the vehicle dynamics sensor. The method provides a drift controller electrically connected to the trailer reverse assist module. The drift controller also receives a signal from the vehicle dynamics sensor. When the vehicle is reversing the trailer with the intention of moving the trailer along a straight implied path, and when the trailer reverse assist module determines that the relative trailer angle is substantially 0 degrees and because the zero-degree angle is not perfectly detected based on the signal from the vehicle dynamics sensor received by the drift controller, the drift controller estimates the distance that the trailer has drifted from the straight implied path. In a closed-loop feedback manner, the drift controller provides a drift correction signal to the trailer reverse assist module to modify the value of the zero degree angle and thereby cause adjustment of the steering system to realign the trailer toward a straight implied path without manual steering intervention.

[0006] Other objects, features and characteristics of the present invention, as well as the method of operation and the function of the related elements of structure, the combination of parts and the economy of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention will be better understood from the following detailed description of preferred embodiments of the present invention when read in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, and wherein:

[0008] Figure 1 is a view of a conventional vehicle equipped with a trailer and TRA system during straight line reverse showing drift from the intended path.

[0009] Figure 2 yes Figure 1 0026] Figure 2 is a view of a conventional vehicle, trailer and TRA system showing periodic operator correction points used to realign a drifting trailer toward a target position.

[0010] Figure 3 is a diagram of an embodiment of a trailer reverse assist system showing the angle at the coupler or hitch between the vehicle and the trailer being zero.

[0011] Figure 4 is a schematic illustration of a trailer reverse assist system for controlling vehicle steering and thus the drift of a trailer during its straight-line reverse maneuvering, according to an embodiment.

[0012] Figure 5 It is shown Figure 4 Schematic view of the trailer reverse assist module and the input of the drift controller.

[0013] Figure 6 is a diagram illustrating application of an exponential path correction algorithm for steering a trailer toward an implied path.

[0014] Figure 7 Shown in Figure 6 The exponential path correction algorithm used Figure 5 The aTan module of the drift correction module.

[0015] Figure 8 is a flow chart of method steps of an embodiment. DETAILED DESCRIPTION

[0016] refer to Figure 3, a trailer reverse assist (TRA) system, generally indicated at 14, is shown for assisting a vehicle 10' in reversing a trailer 12 coupled thereto via a coupler or hook 15. The vehicle 10' includes a trailer reverse assist (TRA) module 16, preferably of the type disclosed in U.S. Pat. No. 9,248,858 B2, the contents of which are hereby incorporated by reference into this specification. Figure 4 As best shown in FIG. 1 , the TRA module 16 is an electronic control unit (ECU) that includes or is connected to a separate vehicle steering module 20 . In this embodiment, the steering wheel module 20 is shown as part of the TRA module 16 . A coupler angle detection sensor 21 and an input device 23 are connected to the TRA module 16 . The sensor 21 and the input device 23 may already be existing components and incorporated into the vehicle 10 ′. For example, the input device 23 may be a joystick controller used with a navigation / information system. The sensor 21 may be used to measure a coupler or hook angle that represents the relative angle between the vehicle and the trailer. The sensor 21 may be one or more sensors that measure the relative distance between the vehicle 10 ′ and the trailer 12 and use the varying distance to calculate the hook angle. The sensor(s) 21 may use horizontal or vertical features on the trailer 12 in the distance measurement. In this embodiment, the sensor 21 is a camera, preferably a camera that is already installed in the vehicle 10 ′, such as a backup camera. The camera 21 may capture images, and image analysis may be used to calculate the hook angle. Distinguishing marks 25 may be established on the trailer 12 and captured by the camera 21 for analysis.

[0017] The steering module 20 includes a processor circuit 22 that is constructed and arranged to actively change the direction of the front axle wheels 24 ( Figure 3 ) without the vehicle driver giving a corresponding input through the vehicle steering wheel 18. The steering wheel angle is detected by a sensor 26 and the steering angle is changed via an actuator 28 coupled to a steering system 27, such as by using a shaft 29 connected to the steering wheel 18 to provide torque to the steering wheel. The shaft 29 can be considered to be part of the steering wheel 18. The steering module 20 may also include the ability to additionally steer the rear axle wheels. Reference Figure 4 Based on signals 32 obtained from conventional vehicle dynamic sensors 34 (e.g., wheel rotations, and / or distance traveled and steering wheel angles obtained from sensor 26), user requested steering signals 35 from input device 23, and observed trailer orientation signals 37 obtained from sensor 21, processor circuit 22 calculates corrective actions to be taken and initiates steering actuator 28 via steering output signals 30 to steer vehicle 10' and trailer 12 accordingly. Note that steering wheel angle sensor 26 may be considered part of the vehicle dynamic sensors.

[0018] When the user provides input to the TRA module 16 for reversing in a straight line with the trailer 12 aligned (trailer angle is approximately 0 degrees relative to the vehicle axis A), the vehicle 10' is expected to act as if there is no trailer attached to it and reverse in a straight line with the driver holding the steering wheel 18 straight. The TRA module 16 works well for its intended purpose, but in reality, this 0 degree angle is not maintained because the trailer 12 tends to swing to one side due to small imperfections in the alignment of the system. A conventional TRA module 16 for reversing in a straight line involves vehicle steering in an attempt to maintain a trailer angle sensor 21 reading of zero degrees. When the reported value of the 0 degree trailer angle (due to inaccurate detection by the sensor 21) is not perfectly calibrated, this is equivalent to connecting the trailer 12 to the vehicle 10' with a small angle error and then reversing. When this occurs, the vehicle 10' gradually turns and follows the trailer 12. As discussed above with respect to Figure 1 and Figure 2 It is noted that, as a result, the reverse direction deviates slightly from the implied straight-line path.

[0019] According to this embodiment, a drift controller 30 is provided as part of or preferably connected to the TRA module 16 to mitigate drift of the trailer 12 during straight-line reverse. As noted above, the vehicle 10' has a steering wheel angle sensor 26, and the vehicle can also detect the distance traveled by each road wheel individually (via sensor 34). Given this data, an estimate can be determined as to how far the vehicle or trailer is from the implied straight-line path (the imaginary line connecting the starting position and the desired final position). This estimate can be considered a path deviation estimate. This path deviation estimate can be used to instruct the steering wheel module 20 to apply torque to the steering wheel via the actuator 28 to bring the vehicle or trailer back onto the implied path. This can be referred to as drift correction.

[0020] refer to Figure 4 and Figure 5 In this embodiment, the drift controller 30 uses signals 32 obtained from vehicle dynamic sensors 34 (e.g., sensing vehicle operating parameters such as wheel rotation and / or distance traveled, where the steering wheel angle is obtained from sensor 26) to estimate the path deviation or offset of the trailer 12 and propose a new path (heading angle) that closes the accumulated path error without user intervention. Thus, as Figure 5 As best shown in FIG. 1 , the drift controller 30 receives the same precision vehicle dynamics input signals 32 used to drive the TRA module 16. These input signals 32 are sufficient to estimate the deviation of the position and orientation of the vehicle 10' from its initial straight position. This deviation is then used as feedback to control the TRA module 16 to cause the vehicle 10' to realign the trailer 12 back to its original path.

[0021] The drift controller 30 may be any type of controller that sends a drift correction signal 40 as an input to the TRA module 16 for controlling the steering module 20 to cause changes to the steering system 27. The drift correction module 38 may also be employed to recalibrate or modify the value of the zero relative trailer angle in the TRA module 16. For example, the drift correction module 38 may employ proportional control feedback to the TRA module 16 so that a stable (balanced value) correction to the TRA module is obtained during maneuvers. The angle sensor 21 may be recalibrated (by permanently subtracting the correction from the angle sensor). Once this is done, the TRA module 16, and therefore the steering module 20, will be driven exponentially back to zero offset.

[0022] Figure 6 A simple first order exponential path planner is shown. The controller 38 constructs a smooth path that converges to the desired path and can be easily interpreted as a steering command to the TRA module 16 and does not involve excessive back and forth motion of the steering wheel 18. Therefore, the proportional controller 38 related to the heading angle correction per unit offset translation has an exact analytical solution and is an exponential path. Reference Figure 7 , the controller 38 applies an inverse tangent function 42 which converts the slope to an angle. The trailer heading should be –atan(trailer offset error*K), and the trailer angle sensor 21 may have its 0 degree calibration value adjusted by exactly that amount.

[0023] Any closed-loop control scheme may be applied to correct the errors mentioned above. One example embodiment of estimating the position of vehicle 10' is to track the LEFT and RIGHT rear wheel displacements combined with the steering wheel angle signal from sensor 26 via signal 32, and a constant steering ratio and a constant wheelbase. Thus, for example, referring to Figure 8 , showing the steps for implementing the method of the embodiment. In step 44, at the beginning of the routine, the path deviation is assumed to be 0 and the heading angle is also assumed to be 0, where the vehicle orientation is assumed to be along a straight implied path. In step 46, the TRA 16 determines whether the user input is 0.0 and whether the trailer angle (from sensor 21) is substantially 0.0. If not, the routine returns to step 44, but if so, in step 48, the drift controller 30 ( Figure 5 ) For example, the path offset is calculated as follows:

[0024] = Steering wheel angle / steering ratio

[0025] = Average of the rear wheel displacements since the previous step

[0026]

[0027]

[0028] Offset = Offset + Offset

[0029] .

[0030] In step 46, the drift correction signal 40 from the drift controller 30 is fed back to the TRA module 16 to recalibrate or modify the zero relative trailer angle value in the TRA module 16. Therefore, there is a new offset every cycle. Figure 5 The above calculations are performed in a processor circuit or path deviation estimator 36 of the controller 30 , as shown in , and the results are input to a drift correction module 38 and then to the TRA module 16 .

[0031] Thus, when the user provides active input, the TRA module 16 operates as normal, and the new system 14 overrides the normal operation of the TRA module 16 and enables a more precise path following feature to reverse the vehicle in a perfectly straight line. Thus, the drift controller 30 is employed to perform the following operations:

[0032] Detects the value of mechanical misalignment,

[0033] Using feedback loops to compensate for mechanical misalignment, and

[0034] Make sure to steer the vehicle back onto the implied straight path.

[0035] There are many different ways to achieve similar feedback results. Figure 8 Step 48 calculates the offset of the center of the rear axle of the vehicle 10'. Another approach is to calculate the distance offset of different points on the vehicle 10' or points on the trailer 12 (e.g., the center of the axle on the trailer). Note that velocity measurements can be used instead of displacement measurements. Yaw rate can also be used. All four conventional wheel sensors can be used. Because the steering ratio is generally not constant, a more accurate relationship of the steering system and wheel slip and geometry can be used to improve the estimate.

[0036] The operations and algorithms described herein may be implemented as executable code within the processor circuit 22 and path deviation estimator 38 as described, or stored on a separate computer or machine readable non-transitory tangible storage medium, which is performed based on the execution of the code by a processor circuit implemented using one or more integrated circuits. Example implementations of the disclosed circuits include hardware logic implemented in a logic array such as a programmable logic array (PLA), a field programmable gate array (FPGA), or implemented by mask programming of an integrated circuit such as an application specific integrated circuit (ASIC). Any of these circuits may also be implemented using software-based executable resources that are executed by a corresponding internal processor circuit such as a microprocessor circuit (not shown), and implemented using one or more integrated circuits, wherein the execution of the executable code stored in the internal memory circuit causes the (one or more) integrated circuits implementing the processor circuit to store application state variables in the processor memory, thereby creating executable application resources (e.g., application instances) that perform the circuit operations as described herein. Therefore, the term "circuitry" as used in this specification refers to hardware-based circuitry implemented using one or more integrated circuits and including logic for performing the described operations, or software-based circuitry including a processor circuit (implemented using one or more integrated circuits) including a reserved portion of a processor memory for storing application state data and application variables modified by the execution of executable code by the processor circuit. For example, the memory circuit may be implemented using non-volatile memory such as a programmable read-only memory (PROM) or EPROM and / or volatile memory such as DRAM, etc.

[0037] The foregoing preferred embodiments have been shown and described for the purpose of illustrating the structural and functional principles of the present invention and illustrating the method of using the preferred embodiments, and are subject to changes without departing from such principles. Therefore, the present invention includes all modifications contained within the spirit of the following claims.

Claims

1. A trailer reverse assist system for straight-line vehicle reverse of a trailer connected to the vehicle via a coupler, the vehicle having a steering system and a vehicle dynamics sensor for detecting vehicle operating parameters, the system comprising: a coupler angle detection sensor constructed and arranged to detect a zero degree angle of the trailer relative to the vehicle, a vehicle dynamics sensor constructed and arranged to obtain a signal regarding an operating parameter, the operating parameter comprising at least one of a steering wheel angle, a wheel rotation, and a distance traveled, a trailer reverse assist module constructed and arranged to receive signals from the vehicle dynamics sensor and the coupler angle detection sensor, the trailer reverse assist module being associated with the steering system for causing a change in the steering of the vehicle when backing up on an intended straight implied path, and a drift controller constructed and arranged to receive signals from the vehicle dynamics sensor, the drift controller being electrically connected to the trailer reverse assist module and comprising a proportional controller, wherein the proportional controller is constructed and arranged to provide a drift correction signal to the steering system to cause an adjustment of the steering to realign the trailer along the exponential path toward the straight implied path, Wherein when the vehicle is backing up a trailer on an intended straight implied path, and because the coupler angle sensor that detects the zero degree angle is not perfectly calibrated based on signals from the vehicle dynamic sensors, a drift controller is constructed and arranged to 1) estimate a distance the trailer has drifted from the straight implied path, and 2) provide a drift correction signal to a trailer reverse assist module in a closed-loop feedback manner for modifying the value of the zero degree angle and thereby causing adjustment of the steering system to realign the trailer toward the straight implied path without manual steering intervention.

2. The system of claim 1, wherein the coupler angle detection sensor is a camera.

3. The system of claim 1, further comprising a steering system, the steering system comprising: A steering module electrically connected to the trailer reverse assist module, steering wheel, Steering wheel angle sensor, and An actuator is electrically connected to the steering module and associated with the steering wheel such that based on the drift correction signal, the actuator provides torque to the steering wheel to change the steering wheel angle to move the trailer toward the straight implied path.

4. The system of claim 1, wherein the drift controller comprises: A path deviation estimator constructed and arranged to estimate a distance the trailer has drifted from a straight implied path, and a drift correction module constructed and arranged to provide a drift correction signal.

5. The system of claim 4, wherein the path deviation estimator is a processor circuit.

6. A method of backing a trailer along a straight implied path using a vehicle having a steering system, a trailer reverse assist module associated with the steering system for causing a change in the vehicle's steering when backing the trailer, and a vehicle dynamics sensor for detecting a vehicle operating parameter, the operating parameter including at least one of a steering wheel angle, a wheel rotation, and a distance traveled, the method comprising the steps of: Detecting the zero angle of the trailer relative to the vehicle, In the trailer reverse assist module, determining whether the relative trailer angle is substantially 0 degrees, The trailer reverse assist module receives a signal from a vehicle dynamic sensor, providing a drift controller electrically connected to the trailer reverse assist module, wherein the drift controller comprises a proportional controller and the drift correction signal causes an adjustment of the steering to move the trailer along the exponential path toward the straight implied path, receiving a signal from a vehicle dynamics sensor at a drift controller, and When the vehicle is reversing a trailer with the intent to move the trailer along a straight implied path, and when the trailer reverse assist module determines that the relative trailer angle is substantially zero degrees and the zero degree angle is not perfectly detected due to signals from the vehicle dynamics sensors received by the drift controller: in the drift controller to estimate how far the trailer has drifted from the straight implied path, and A drift correction signal is provided in a closed-loop feedback manner to the trailer reverse assist module to recalibrate the value of the relative trailer angle and thereby cause adjustment of the steering system to move the trailer toward a straight implied path without manual steering intervention.

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