Steering angle estimation device and method by differential braking, and computer-readable storage medium storing

Abstract

The invention discloses an apparatus and a method for estimating a steering angle based on differential braking, and a non-transitory computer-readable storage medium storing a program for executing the method. A steering angle estimation device based on differential braking according to one aspect of the present invention may include: a memory that stores an estimation model that has at least one coefficient and specifies a relationship between a differential braking force of a vehicle and a steering angle of free rolling front wheels of the vehicle; and a processor that inputs test data including a plurality of different differential braking forces and steering angles generated when each differential braking force is applied to the estimation model and determines the coefficients of the estimation model.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2024-0001603 filed on January 4, 2024, in the Korean Intellectual Property Office, and Application No. 10-2023-0084153 filed on June 29, 2023, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a steering angle estimation device and method based on differential braking, and a non-transitory computer-readable storage medium storing a program for executing the method. More specifically, it relates to a steering angle estimation device and method based on differential braking, and a non-transitory computer-readable storage medium storing a program for executing the method, which can be used to implement differential braking control to cope with vehicle steering system failures. Background Art

[0004] Recently, cars are not just a means of transportation, but also a personal mobile space for drivers, and various future technologies are being developed and applied. In this regard, the space management efficiency and control performance are improved through the vehicle chassis system of the by-wire method.

[0005] Under this trend, vehicle steering systems are also changing. For example, an electric signal type intelligent steering system, namely a steer-by-wire (SbW) system, is also being actively researched and developed. This system performs steering by transmitting the driver's steering intention through electric signals without requiring a mechanical connection between the steering wheel operated by the driver and the wheels of the vehicle. However, there is a problem with this system, that is, once a fault such as a communication barrier occurs, the driver will have no device to operate the steering.

[0006] Patent document: Korean authorized patent No. 1229126 "Steering control system of steer-by-wire system", authorized on January 28, 2013. Summary of the invention

[0007] The present invention is proposed to solve the above-mentioned problems. The purpose of the present invention is to provide a steering angle estimation device and method based on differential braking, and a non-temporary computer-readable storage medium storing a program for executing the method, which estimates the steering angle of a vehicle when differential braking is performed, so as to assist the steering force through the vehicle's differential braking when the vehicle's steering system fails.

[0008] Another object of the present invention is to provide a steering angle estimation device and method based on differential braking, and a non-transitory computer-readable storage medium storing a program for executing the method, which accurately estimates the steering angle of the front wheels based on differential braking when the front wheels of a vehicle are in a free rolling state.

[0009] The objects of the present invention are not limited to the above objects, and other objects not mentioned will be clearly understood by those skilled in the art to which the present invention pertains through the following description.

[0010] According to one aspect of the present invention, a steering angle estimating device based on differential braking, a memory, storing an estimation model having at least one coefficient and specifying the relationship between the differential braking force of a vehicle and the steering angle of a free-rolling front wheel of the vehicle; and a processor, inputting test data including a plurality of different differential braking forces and the steering angle generated when each differential braking force is applied into the estimation model and determining the coefficient of the estimation model.

[0011] According to the steering angle estimating device based on differential braking according to one aspect of the present invention, the differential braking force may be determined by a difference between a brake pressure of a left front wheel of the vehicle and a brake pressure of a right front wheel of the vehicle.

[0012] The steering angle estimation device based on differential braking according to one aspect of the present invention can be represented by the following first mathematical formula, and has J δ 、b δ and k δ As the coefficient,

[0013] The first mathematical formula:

[0014]

[0015] Among them, δ″ f represents the front wheel steering angular acceleration, δ′ f represents the front wheel steering angular velocity, δ f represents the front wheel steering angle, Indicates the left front wheel brake pressure. represents the right front wheel brake pressure, and W represents the vehicle's wheelbase.

[0016] According to a steering angle estimation device based on differential braking according to one aspect of the present invention, the test data includes n (n is a natural number greater than or equal to 3) different differential braking forces and the steering angle generated when each differential braking force is applied, and the processor can determine the J using the following second mathematical formula: δ 、b δ and k δ .

[0017] The second mathematical formula:

[0018]

[0019] According to a steering angle estimation device based on differential braking according to one aspect of the present invention, the processor may determine the J by a least square method. δ 、b δ and k δ .

[0020] According to the steering angle estimating device based on differential braking according to one aspect of the present invention, the speed of the vehicle is divided into a plurality of speed intervals, and the coefficient of the estimation model may be determined according to each of the plurality of speed intervals.

[0021] According to the steering angle estimating device based on differential braking according to one aspect of the present invention, the size of the speed interval can be set to 10 km / h.

[0022] According to the steering angle estimating device based on differential braking according to one aspect of the present invention, the maximum value of the plurality of mutually different differential braking forces in the test data may be set to 60 bar or less.

[0023] According to the steering angle estimating device based on differential braking according to one aspect of the present invention, the test data may all be obtained in a state where a scrub radius of the vehicle is set to be positive.

[0024] According to the steering angle estimating device based on differential braking according to one aspect of the present invention, the test data may all be obtained in a state where a scrub radius of the vehicle is set to negative.

[0025] According to another aspect of the present invention, a steering angle estimation method based on differential braking is provided, comprising: a memory storing an estimation model having at least one coefficient and specifying the relationship between the differential braking force of a vehicle and the steering angle of a free-rolling front wheel of the vehicle; and a processor inputting test data including a plurality of different differential braking forces and the steering angle generated when each differential braking force is applied into the estimation model and determining the coefficient of the estimation model.

[0026] According to the steering angle estimating method based on differential braking according to one aspect of the present invention, the differential braking force may be determined by a difference between a left front wheel braking pressure of the vehicle and a right front wheel braking pressure of the vehicle.

[0027] According to a steering angle estimation method based on differential braking according to one aspect of the present invention, the estimation model is represented by the following first mathematical formula, and may have Jδ 、b δ and k δ As the coefficient,

[0028] The first mathematical formula:

[0029]

[0030] Among them, δ″ f represents the front wheel steering angular acceleration, δ′ f represents the front wheel steering angular velocity, δ f represents the front wheel steering angle, Indicates the left front wheel brake pressure. represents the right front wheel brake pressure, and W represents the vehicle's wheelbase.

[0031] According to a steering angle estimation method based on differential braking according to one aspect of the present invention, the test data includes n (n is a natural number greater than or equal to 3) different differential braking forces and a steering angle generated when each differential braking force is applied, and in the step of determining the coefficient of the estimation model, the processor may determine the J using the following second mathematical formula: δ 、b δ and k δ .

[0032] The second mathematical formula:

[0033]

[0034] According to a steering angle estimation method based on differential braking according to one aspect of the present invention, the processor may determine the J by a least square method. δ 、b δ and k δ .

[0035] According to the steering angle estimation method based on differential braking according to one aspect of the present invention, the speed of the vehicle is divided into a plurality of speed intervals, and the coefficient of the estimation model may be determined according to each of the plurality of speed intervals.

[0036] According to the steering angle estimation method based on differential braking according to one aspect of the present invention, the size of the speed interval can be set to 10 km / h.

[0037] According to the steering angle estimating method based on differential braking according to one aspect of the present invention, the maximum value of the plurality of mutually different differential braking forces in the test data may be set to 60 bar or less.

[0038] According to the steering angle estimating method based on differential braking according to one aspect of the present invention, the test data can be obtained when the scrub radius of the vehicle is set to positive, or the test data can be obtained when the scrub radius of the vehicle is set to negative.

[0039] According to still another aspect of the present invention, a non-transitory computer-readable storage medium is provided according to an aspect of the present invention, wherein the program includes at least one instruction for executing a steering angle estimation method based on differential braking. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and other objects, features and advantages of the present invention will become more apparent to those skilled in the art by describing in detail exemplary embodiments of the present invention with reference to the accompanying drawings.

[0041] Figure 1 1 is a diagram showing a configuration of a steering angle estimating device based on differential braking according to an embodiment of the present invention.

[0042] Figure 2 FIG. 1 is a diagram showing a configuration of a vehicle capable of estimating a steering angle based on differential braking by a steering angle estimating device based on differential braking according to an embodiment of the present invention.

[0043] Figure 3 FIG. 1 is a diagram for explaining a scrub radius in relation to a steering angle estimating device based on differential braking according to an embodiment of the present invention.

[0044] Figure 4 1 is a diagram showing an example of test conditions related to acquisition of test data input to a steering angle estimating device based on differential braking according to an embodiment of the present invention.

[0045] Figure 5 The present invention is based on a steering angle estimation device based on differential braking according to an embodiment of the present invention. Figure 4 This is a graph showing the results of estimating the steering angle using test data acquired under the test conditions.

[0046] Figure 6 1 is a diagram showing another example of test conditions related to acquisition of test data input to the steering angle estimating device based on differential braking according to an embodiment of the present invention.

[0047] Figure 7 The present invention is based on a steering angle estimation device based on differential braking according to an embodiment of the present invention. Figure 6 This is a graph showing the results of estimating the steering angle using test data acquired under the test conditions.

[0048] Figure 8 is a sequence diagram of a steering angle estimation method based on differential braking according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] Embodiments of the present invention will be described in detail below so that those skilled in the art to which the present invention belongs can easily implement the embodiments. The present invention can be implemented in a variety of different forms and is not limited to the embodiments described herein. In order to clearly describe the present invention, parts not related to the description are omitted in the accompanying drawings, and the same or similar parts are represented by the same reference numerals throughout the specification.

[0050] The words and terms used in the specification and claims should not be restrictively interpreted as their ordinary meanings or dictionary meanings, but should be interpreted as meanings and concepts consistent with the technical spirit of the present invention in accordance with the principle that the inventor is able to define terms and concepts to best describe his invention.

[0051] In the specification, it should be understood that terms such as “including” or “having” are intended to specify the existence of the features, numbers, steps, operations, components, parts or their combinations described in the specification, and do not exclude the possibility of the existence or addition of one or more other features, numbers, steps, operations, components, parts or their combinations.

[0052] Figure 1 1 is a diagram showing a configuration of a steering angle estimating device based on differential braking according to an embodiment of the present invention. Figure 2 FIG. 1 is a diagram showing a configuration of a vehicle capable of estimating a steering angle based on differential braking by a steering angle estimating device based on differential braking according to an embodiment of the present invention.

[0053] According to an embodiment of the present invention, a steering angle estimation device 10 based on differential braking can estimate the steering angle of the vehicle 100 during differential braking using an estimation model and test data obtained for input into the estimation model. The estimation model specifies changes in the steering angle according to the differential braking force when the vehicle 100 is traveling.

[0054] Reference Figure 1 According to an embodiment of the present invention, a steering angle estimating device 10 based on differential braking may include a memory 11 and a processor 12 .

[0055] The memory 11 stores the estimation model. The estimation model has at least one coefficient and specifies the relationship between the differential braking force of the vehicle 100 and the steering angle of the free-rolling front wheels of the vehicle 100.

[0056] The memory 11 may include at least one of a semiconductor device-based storage medium (e.g., random access memory (RAM), read-only memory (ROM), flash memory, etc.), a magnetic medium (e.g., a hard disk, a floppy disk, a magnetic tape), an optical recording medium (e.g., a compact disk read only memory (CD-ROM), a digital video disk (DVD), etc.), and a magneto-optical medium (e.g., a floppy disk). Of course, the memory 11 may have different hardware configurations.

[0057] Reference Figure 2 The vehicle 100 includes a vehicle body 110 and a left front wheel W connected to the vehicle body 110. FL , right front wheel W FR , left rear wheel W RL , right rear wheel W RR In addition, the vehicle 100 may further include a steering system 120. For example, the steering system 120 may be configured as a steer-by-wire system. Of course, the type of the steering system 120 is not limited to the steer-by-wire system, and the steering system 120 may also be configured as an electric power steering (EPS) in which an electric motor provides auxiliary steering force.

[0058] When the vehicle 100 is traveling, the front wheels may be in a free rolling state. FL and right front wheel W FR For example, when the steering system 120 of the vehicle 100 fails and cannot steer the vehicle 100 according to the driver's steering wheel operation, the left front wheel W FL and right front wheel W FR Can be in free scrolling state.

[0059] When the left front wheel W of the vehicle 100 FL and right front wheel W FR In the free rolling state, if differential braking is applied to the vehicle 100, a front wheel steering angle is generated between the wheels (tires) of the vehicle 100 and the ground. In this regard, the vehicle 100 may include a braking system 130 capable of performing differential braking control, which is capable of applying differential braking control to the left front wheel W. FL and right front wheel W FRProduces different braking forces.

[0060] When the steering system 120 of the vehicle 100 fails and the left front wheel W of the vehicle 100 is FL and right front wheel W FR In the free rolling state, if the brake system 130 is properly controlled for differential braking based on the steering wheel operation information of the driver of the vehicle 100, the steering force of the vehicle 100 can be prevented from being completely lost. FL and right front wheel W FR In free-rolling mode, steering can be performed using differential brake control.

[0061] For such a steering based on differential braking, the estimation model specifies the change of the front wheel steering angle according to the differential braking force. The differential braking force may be the left front wheel W of the vehicle 100. FL The braking pressure is related to the right front wheel W of the vehicle 100. FR The difference between the brake pressures is determined.

[0062] The estimation model can represent the change of the front wheel steering angle according to the differential braking force as a second-order system model. In one embodiment of the present invention, the estimation model is configured as the following first mathematical formula, and can have J δ 、b δ and k δ As the coefficient,

[0063] The first mathematical formula:

[0064]

[0065] Among them, δ″ f represents the front wheel steering angular acceleration, δ′ f represents the front wheel steering angular velocity, δ f represents the front wheel steering angle, Indicates the left front wheel brake pressure. represents the right front wheel brake pressure, and W represents the vehicle's wheelbase.

[0066] In the estimation model, the wheelbase W of the vehicle represents the distance between the wheels of the vehicle. More specifically, the wheelbase W of the vehicle refers to the left front wheel W of the vehicle 100. FL With right front wheel W FR The distance between the left front wheel W FL With right front wheel W FR The distance between the left front wheel and FL The center C1 and the right front wheel W FR The distance d between the center C2 of the left front wheel W FL The center C1 and the right front wheel WFR The center C2 can be determined based on the tire.

[0067] In the estimation model, the left front wheel brake pressure Refers to the longitudinal force acting on the left front wheel WFL due to differential braking. Left front wheel brake pressure can be based on the left front wheel W applied to the vehicle FL The braking pressure is calculated using the torque factor of the effective radius.

[0068] Right front wheel brake pressure Refers to the differential braking acting on the right front wheel W FR Longitudinal force. Braking pressure of right front wheel can be based on the right front wheel W applied to the vehicle FR The braking pressure is calculated from the torque coefficient of the effective radius.

[0069] In the estimation model, the front wheel steering angular velocity δ′ f This can be achieved by adjusting the front wheel steering angle δ f In addition, the front wheel steering angular acceleration δ″ f It can be obtained by adjusting the front wheel steering angular velocity δ′ f Obtained by differentiation.

[0070] The processor 12 inputs test data including a plurality of differential braking forces different from each other and a steering angle generated when each differential braking force is applied to the estimation model and determines the coefficient of the estimation model.

[0071] The processor 12 may be a hardware unit in a computer that performs calculations and controls. For example, the processor 12 may include at least one arithmetic logic unit (ALU) and a processing register.

[0072] Once the coefficients J of the imputed model are determined δ 、b δ and k δ , the steering angle for a given arbitrary differential braking force can be calculated by the estimation model. FL , W FR In the free-rolling state, the differential braking force required to obtain the desired steering angle can be derived by the estimation model.

[0073] The J as the coefficient of the estimated model δ 、b δ and kδ The estimation can be performed based on the test data of the vehicle. More specifically, the coefficient J as the estimation model can be determined by the front wheel steering angle test data of the differential braking force obtained under various conditions. δ 、b δ and k δ .

[0074] The test data includes a plurality of different differential braking forces and a steering angle generated when each differential braking force is applied. That is, the test data may include a plurality of different differential braking forces applied to the vehicle 100 and a steering angle generated by the front wheels of the vehicle in a free rolling state when the corresponding differential braking forces are applied.

[0075] For example, the test data may be obtained through testing (based on simulation software, model-based design platform, etc.). More specifically, the test data may be obtained by driving the vehicle 100 according to the designed test logic (scenario).

[0076] At this time, the control input information and state information of the vehicle 100 including the differential braking force and the steering angle can be acquired in real time through communication with the vehicle steering system 120 or the braking system 130. For example, the communication can be performed in a Controller Area Network Flexible Data-Rate (CANFD) manner.

[0077] On the other hand, when the steering system 120 is an electric power steering system (EPS), the steering angle can be obtained by a steering angle sensor (SAS) of the steering system 120. In addition, when the steering system 120 is a wire steering system, the steering angle can also be obtained based on position information of a driving mechanism (e.g., a rack) that provides steering force to the wheels of the vehicle.

[0078] In one embodiment of the present invention, the test data includes n different (n is a natural number greater than 3) differential braking forces and the steering angle generated when each differential braking force is applied. The processor 12 can determine the J using the following second mathematical formula: δ 、b δ and k δ .

[0079] The second mathematical formula:

[0080]

[0081] In the second mathematical formula, when the matrix consisting of the front wheel steering angular acceleration, the front wheel steering angular velocity and the front wheel steering angle obtained from the test data is A, the coefficient J of the estimation model is δ 、b δ and k δ When the matrix composed of is x and the vector matrix related to the differential braking force on the left side of the second mathematical formula is B, x can be expressed as the following third mathematical formula.

[0082] The third mathematical formula:

[0083] x=(A T A) -1 A T B

[0084] The processor 12 can determine the J by regression analysis. δ 、b δ and k δ More specifically, the processor 12 may determine the J by the least square method. δ 、b δ and k δ .

[0085] When the i-th row (i is a natural number greater than 1 and less than n) of matrix A is represented as A i , the i-th row of matrix B is represented by B i When , the processor 12 can obtain the vector matrix x that minimizes the following fourth mathematical formula.

[0086] The fourth mathematical formula:

[0087]

[0088] It has been confirmed that the coefficient of the estimation model is different for each speed interval of the vehicle 100. That is, the estimation model can be determined differently for each speed interval of the vehicle 100. Therefore, the speed of the vehicle 100 can be divided into a plurality of speed intervals, and the coefficient of the estimation model can be determined according to each of the plurality of speed intervals. For example, the size of the speed interval is set to 10 km / h.

[0089] On the other hand, when the front wheels of the vehicle 100 are in a free rolling state, the front wheel steering angle generated when differential braking is applied is related to the scrub radius. That is, the front wheel steering angle generated when differential braking is applied when the front wheels of the vehicle 100 are in a free rolling state may have different forms depending on whether the scrub radius is positive or negative.

[0090] Figure 31 is a diagram for explaining a scrub radius in relation to a steering angle estimation device based on differential braking according to an embodiment of the present invention. Figure 3 The scraping radius R is defined as the distance between the intersection of the vertical center line A1 of the tire T of the vehicle wheel and the road surface G and the intersection of the kingpin center line A2 of the vehicle and the road surface G.

[0091] At this time, when the intersection of the vertical centerline A1 of the tire T and the kingpin centerline A2 is located above the road surface G, the scraping radius R has a negative value ( Figure 3 (a)). When the intersection of the vertical centerline A1 of the tire T and the kingpin centerline A2 is below the road surface G, the scraping radius R has a positive value ( Figure 3 (b)).

[0092] Hereinafter, for the acquisition of test data, the scrape radius R may be set to a positive value or a negative value. At this time, when the hardware limitation of the test vehicle makes it difficult to adjust the kingpin inclination of the vehicle, the kingpin offset (lateral offset at center) of the test vehicle may be adjusted. A spacer may be used to adjust the kingpin offset of the test vehicle.

[0093] Figure 4 1 is a diagram showing an example of test conditions related to acquisition of test data input to a steering angle estimating device based on differential braking according to an embodiment of the present invention. Figure 4 A test condition for acquiring test data including a steering angle according to differential braking of a vehicle is shown, wherein a scrub radius of the vehicle is set to be greater than 0, that is, set to be positive.

[0094] Reference Figure 4 In one embodiment of the present invention, the test data can be obtained when the scrub radius of all vehicles 100 is set to be positive.

[0095] Reference Figure 4 (a), the differential braking input can limit the driver's operation, and the test can be repeated based on a sine waveform. At this time, the maximum value of the multiple different differential braking forces in the test data can be set to less than 60 bar. That is, the maximum braking pressure of the front and rear wheels can be fixed to a level (horizontal) of about 60 bar at which no slip occurs, which is converted into torque, about 2520 Nm for the front wheel and about 1272 Nm for the rear wheel.

[0096] As an example, it is possible to perform four tests of two 4-second and 8-second cycles for the right break pressure and the left break pressure in the direction of differential braking. In addition, it is possible to perform at least 2 to 3 cycles for each test. In addition, the value can be extracted in units of 0.01 seconds.

[0097] Reference Figure 4 (b) The vehicle speed range is set to 60-70 km / h. At this time, the cruise control function can be activated to keep the vehicle under test at the corresponding speed. Figure 4 The multiple other speed intervals other than the speed interval shown in (b) are performed as described above. Figure 4 Repeat the test described in (a).

[0098] Figure 5 The present invention is based on a steering angle estimation device based on differential braking according to an embodiment of the present invention. Figure 4 This is a graph showing the results of estimating the steering angle using test data acquired under the test conditions.

[0099] Reference Figure 5 It can be confirmed that when an estimation model to which an estimation coefficient is applied for a speed range of 60 to 70 km / h of a vehicle with a scrape radius set to positive is used, an estimated value of the steering angle based on differential braking estimated by the estimation model (estimated wheel angle) follows well the actual measured value of the steering angle based on differential braking (measured wheel angle).

[0100] For example, in one embodiment of the present invention, for a vehicle speed range of 60 to 70 km / h with a scratch radius set to be positive, the J as a coefficient of the estimation model may be δ 、b δ and k δ They are respectively determined to be 54750, 7087, and 377981. Of course, this is just an example, and the specific coefficient values ​​may vary depending on the vehicle type, etc.

[0101] Figure 6 1 is a diagram showing another example of test conditions related to acquisition of test data input to the steering angle estimating device based on differential braking according to an embodiment of the present invention. Figure 6 A test condition for acquiring test data including a steering angle according to differential braking of a vehicle is shown, wherein a scrub radius of the vehicle is set to be less than 0, that is, set to be negative.

[0102] Reference Figure 6 In one embodiment of the present invention, the test data may be obtained when the scrub radius of all vehicles 100 is set to negative.

[0103] Reference Figure 6 (a), the differential braking input can limit the driver's operation, and the test can be repeated based on a sine waveform. At this time, the maximum value of the multiple different differential braking forces in the test data can be set to less than 60 bar. That is, the maximum braking pressure of the front and rear wheels can be fixed to about 60 bar at a level where no slip occurs, which is converted into torque, about 2520 Nm for the front wheel and about 1272 Nm for the rear wheel.

[0104] As an example, it is possible to perform four tests of two 4-second and 8-second cycles for the right break pressure and the left break pressure in the direction of differential braking. In addition, it is possible to perform at least 2 to 3 cycles for each test. In addition, the value can be extracted in units of 0.01 seconds.

[0105] Reference Figure 6 (b) The vehicle speed range is set to 60-70 km / h. At this time, the cruise control function can be activated to keep the vehicle under test at the corresponding speed. Figure 4 The multiple other speed intervals other than the speed interval shown in (b) are performed as described above. Figure 4 Repeat the test described in (a).

[0106] Figure 7 The present invention is based on a steering angle estimation device based on differential braking according to an embodiment of the present invention. Figure 6 This is a graph showing the results of estimating the steering angle using test data acquired under the test conditions.

[0107] Reference Figure 7 It can be confirmed that when an estimation model to which an estimation coefficient is applied for a speed range of 60 to 70 km / h for a vehicle in which the scrape radius is set to negative is used, an estimated value of the steering angle based on differential braking estimated by the estimation model (estimated wheel angle) follows well the actual measured value of the steering angle based on differential braking (measured wheel angle).

[0108] For example, in one embodiment of the present invention, for a vehicle speed range of 60 to 70 km / h in which the scraping radius is set to be negative, the J as a coefficient of the estimation model may be δ 、b δ and k δ They are determined to be -46698, -89501, and -396572 respectively. Of course, this is just an example, and the specific coefficient values ​​may vary depending on the vehicle type, etc.

[0109] The steering angle estimation device 10 based on differential braking according to an embodiment of the present invention has been described in detail above. Next, a steering angle estimation method based on differential braking according to an embodiment of the present invention will be described.

[0110] Figure 8 is a sequence diagram of a steering angle estimation method based on differential braking according to an embodiment of the present invention.

[0111] The steering angle estimation method S10 based on differential braking according to an embodiment of the present invention may be executed by the steering angle estimation device 10 based on differential braking according to an embodiment of the present invention. Figure 8 , the steering angle estimation method S10 based on differential braking according to an embodiment of the present invention may be performed as follows.

[0112] First, the memory 11 stores an estimation model S11 having at least one coefficient and defining the relationship between the differential braking force of the vehicle and the steering angle of the free-rolling front wheels of the vehicle. The estimation model may have at least one coefficient and define the relationship between the differential braking force of the vehicle 100 and the steering angle of the free-rolling front wheels of the vehicle 100.

[0113] The estimation model is represented by the following mathematical formula and can have J δ 、b δ and k δ as the coefficient.

[0114] The first mathematical formula:

[0115]

[0116] Among them, δ″ f represents the front wheel steering angular acceleration, δ′ f represents the front wheel steering angular velocity, δ f represents the front wheel steering angle, Indicates the left front wheel brake pressure. represents the right front wheel brake pressure, and W represents the vehicle's wheelbase.

[0117] The variables and coefficients of the estimation model shown in the first mathematical formula are the same as those described with respect to the steering angle estimation device 10 based on differential braking according to an embodiment of the present invention. Therefore, a detailed description thereof will be omitted.

[0118] Next, the processor 12 inputs test data including a plurality of differential braking forces different from each other and a steering angle generated when each differential braking force is applied into the estimation model and determines the coefficient S12 of the estimation model. The processor 12 can estimate the steering angle of the vehicle 100 during differential braking using the test data obtained for input into the estimation model.

[0119] Once the coefficients J of the imputed model are determined δ 、b δ and k δ , the steering angle for a given arbitrary differential braking force can be calculated by the estimation model. FL , W FR In the free-rolling state, the differential braking force required to obtain the desired steering angle can be derived by the estimation model.

[0120] The J as the coefficient of the estimated model δ 、b δ and k δ The estimation can be performed based on the test data of the vehicle. More specifically, the coefficient J as the estimation model can be determined by the front wheel steering angle test data of the differential braking force obtained under various conditions. δ 、b δ and k δ .

[0121] The test data includes n different (n is a natural number greater than 3) differential braking forces and the steering angle generated when each differential braking force is applied. The processor 12 can determine the J by using the following second mathematical formula δ 、b δ and k δ .

[0122] The second mathematical formula:

[0123]

[0124] In the second mathematical formula, when the matrix consisting of the front wheel steering angular acceleration, the front wheel steering angular velocity and the front wheel steering angle obtained from the test data is A, the coefficient J of the estimation model is δ 、b δ and k δ When the matrix composed of is x and the vector matrix related to the differential braking force on the left side of the second mathematical formula is B, x can be expressed as the following third mathematical formula.

[0125] The third mathematical formula:

[0126] x=(A T A) -1 A T B

[0127] In addition, the processor 12 can determine the J by regression analysis. δ 、b δ and k δ More specifically, the processor 12 may determine the J by the least square method. δ 、b δ and k δ .

[0128] When the i-th row (i is a natural number greater than 1 and less than n) of matrix A is represented as A i , the i-th row of matrix B is represented by B i When , the processor 12 can obtain the vector matrix x that minimizes the following fourth mathematical formula.

[0129] The fourth mathematical formula:

[0130]

[0131] At this time, the speed of the vehicle is divided into a plurality of speed intervals, and the coefficient of the estimation model can be determined according to each of the plurality of speed intervals. For example, the size of the speed interval can be set to 10 km / h.

[0132] In addition, the maximum value of the plurality of different differential braking forces in the test data may be set to be less than 60 bar. The maximum braking pressure of the front and rear wheels may be fixed to about 60 bar, which is a level at which no slip occurs.

[0133] In addition, the test data are all obtained in a state where the scrub radius of the vehicle is set to be positive, or the test data are all obtained in a state where the scrub radius of the vehicle is set to be negative.

[0134] In addition, in the acquisition of the test data and the determination of the estimation model, the contents described about the steering angle estimation device 10 based on differential braking according to an embodiment of the present invention can be faithfully applied to the steering angle estimation method S10 based on differential braking according to an embodiment of the present invention.

[0135] On the other hand, the present invention further provides a non-transitory computer-readable storage medium, on which is stored a program for executing the steering angle estimation method based on differential braking. Specifically, the present invention may provide a non-transitory computer-readable storage medium, on which is stored a program, the program including at least one instruction for executing the steering angle estimation method based on differential braking.

[0136] At this time, it may include not only the machine code generated by the compiler, but also the high-level language code executable by the computer. In addition, the recording medium may include a hardware device configured to store and execute program commands such as magnetic media (Magnetic Media) such as hard disks, floppy disks and tapes, optical media (Compact Disk Read Only Memory, CD-ROM), optical recording media (Optical Media) such as digital video disks (Digital Video Disk, DVD), magneto-optical media (Magneto-Optical Media) such as floptical disks (Floptical Disk), read-only memory (ROM), random access memory (RAM), flash memory, etc.

[0137] When the coefficients of the estimation model are determined according to the present invention, the estimation model with the determined coefficients can be loaded into an electronic control unit (ECU) of a vehicle. When the wheels of such a vehicle are in a free-rolling state, the steering intention of the driver of the vehicle can be identified based on the operation information of the steering wheel, and the estimation model can be used to perform differential braking control to obtain the steering angle desired by the driver.

[0138] Furthermore, according to the present invention, there is no need to provide an additional sensor for the differential brake control of the vehicle, and thus the fail over performance of the steering system can be effectively improved.

[0139] Furthermore, the present invention may improve the fail over performance of steering systems that have no physical connection between the steering wheel and the wheels of the vehicle by operating using only electrical signals (eg, steer-by-wire systems).

[0140] According to the above configuration, a steering angle estimation device and method based on differential braking according to one aspect of the present invention, and a non-transitory computer-readable storage medium storing a program for executing the method provide a steering angle value estimated based on differential braking so that when a vehicle steering system fails, the steering of the vehicle can be assisted by differential braking.

[0141] According to an aspect of the present invention, a steering angle estimation device and method based on differential braking, and a non-transitory computer-readable storage medium storing a program for executing the method, can provide an accurate estimation value of the steering angle of the front wheels based on differential braking when the front wheels of a vehicle are in a freerolling state.

[0142] It should be understood that the effects of the present invention are not limited to the above-mentioned effects, and include all effects inferable from the inventive configuration described in the detailed description of the present invention or the claims.

[0143] Although the embodiments of the present invention have been described, the spirit of the present invention is not limited by the embodiments set forth in the specification. As long as those skilled in the art understand the spirit of the present invention, they can easily propose other embodiments within the scope of the same spirit by adding, changing, deleting or adding components, but this is also included in the scope of the spirit of the present invention.

Claims

1. A steering angle estimation device based on differential braking, wherein: include: a memory storing an estimation model having at least one coefficient and defining a relationship between a differential braking force of a vehicle and a steering angle of a free-rolling front wheel of the vehicle; as well as A processor inputs test data including a plurality of differential braking forces different from each other and a steering angle generated when each differential braking force is applied to the estimation model and determines the coefficient of the estimation model.

2. The steering angle estimation device based on differential braking according to claim 1, wherein: The differential braking force is determined by a difference between a left front wheel brake pressure of the vehicle and a right front wheel brake pressure of the vehicle.

3. The steering angle estimation device based on differential braking according to claim 1, wherein: The estimation model is represented by the following first mathematical formula and has J δ 、b δ and k δ As the coefficient, The first mathematical formula: Among them, δ″ f represents the front wheel steering angular acceleration, δ′ f represents the front wheel steering angular velocity, δ f represents the front wheel steering angle, Indicates the left front wheel brake pressure. represents the right front wheel brake pressure, and W represents the vehicle's wheelbase.

4. The steering angle estimation device based on differential braking according to claim 3, wherein: The test data includes n different differential braking forces and a steering angle generated when each differential braking force is applied, and the processor determines the J by using the following second mathematical formula δ 、b δ and k δ , The second mathematical formula: n is a natural number greater than or equal to 3.

5. The steering angle estimation device based on differential braking according to claim 4, wherein: The processor determines the J by the least square method δ , b δ and k δ .

6. The steering angle estimation device based on differential braking according to claim 1, wherein: The speed of the vehicle is divided into a plurality of speed intervals, and the coefficient of the estimation model is determined according to each of the plurality of speed intervals.

7. The steering angle estimation device based on differential braking according to claim 6, wherein: The size of the speed interval is set to 10 km / h.

8. The steering angle estimation device based on differential braking according to claim 1, wherein: The maximum value of the plurality of mutually different differential braking forces in the test data is set to be 60 bar or less.

9. The steering angle estimation device based on differential braking according to claim 1, wherein: The test data are all obtained in a state where the scratch radius of the vehicle is set to be positive.

10. The steering angle estimation device based on differential braking according to claim 1, wherein: The test data are all obtained when the scratch radius of the vehicle is set to negative.

11. A steering angle estimation method based on differential braking, wherein: include: the step of storing an estimation model having at least one coefficient and defining a relationship between a differential braking force of a vehicle and a steering angle of a free-rolling front wheel of said vehicle, and The processor inputs test data including a plurality of differential braking forces different from each other and a steering angle generated when each differential braking force is applied to the estimation model and determines the coefficient of the estimation model.

12. The steering angle estimation method based on differential braking according to claim 11, wherein: The differential braking force is determined by a difference between a left front wheel brake pressure of the vehicle and a right front wheel brake pressure of the vehicle.

13. The steering angle estimation method based on differential braking according to claim 11, wherein: The estimation model is represented by the following first mathematical formula and has J δ , b δ and k δ As the coefficient, The first mathematical formula: Among them, δ″ f represents the front wheel steering angular acceleration, δ′ f represents the front wheel steering angular velocity, δ f represents the front wheel steering angle, Indicates the left front wheel brake pressure. represents the right front wheel brake pressure, and W represents the vehicle's wheelbase.

14. The steering angle estimation method based on differential braking according to claim 13, wherein: The test data includes n differential braking forces different from each other and a steering angle generated when each differential braking force is applied, and in the step of determining the coefficient of the estimation model, the processor determines the J using the following second mathematical formula: δ , b δ and k δ , The second mathematical formula: n is a natural number greater than or equal to 3.

15. The steering angle estimation method based on differential braking according to claim 14, wherein: The processor determines the J by the least square method δ 、b δ and k δ .

16. The steering angle estimation method based on differential braking according to claim 11, wherein: The speed of the vehicle is divided into a plurality of speed intervals, and the coefficient of the estimation model is determined according to each of the plurality of speed intervals.

17. The steering angle estimation method based on differential braking according to claim 16, wherein: The size of the speed interval is set to 10 km / h.

18. The steering angle estimation method based on differential braking according to claim 11, wherein: The maximum value of the plurality of mutually different differential braking forces in the test data is set to be 60 bar or less.

19. The steering angle estimation method based on differential braking according to claim 11, wherein: The test data are all obtained in a state where the scratch radius of the vehicle is set to be positive, or the test data are all obtained in a state where the scratch radius of the vehicle is set to be negative.

20. A non-transitory computer-readable storage medium, wherein: The non-transitory computer-readable storage medium stores a program, wherein the program includes at least one instruction for executing the steering angle estimation method based on differential braking of claim 11 .

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