Method and apparatus for optimal control of driving torque for smooth ride over uneven road

Abstract

This application provides a method and apparatus for optimal control of drive torque to achieve smooth driving on uneven roads. It includes using the vehicle's acceleration value and jerk constraints to calculate pitch motion reduction objective functions, longitudinal acceleration reduction objective functions, and jerk reduction objective functions, and weights are reflected in these objective functions to calculate the final drive torque and apply it to the vehicle, thereby reducing pitch motion, longitudinal acceleration, and jerk.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2021-0149911, filed on November 3, 2021, with the Korean Intellectual Property Office under 35 U.SC §119(a), the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0003] This invention relates to the control of a vehicle's drive system, and more specifically to a technique for optimal control of drive torque to achieve smooth driving on uneven roads (such as roads with bumps or depressions). Background Technology

[0004] When a vehicle travels over uneven roads (e.g., with bumps, potholes, etc.), unintended pitch motion and longitudinal acceleration are added to the vehicle's sprung mass, thus reducing ride comfort. Here, "sprung mass" is a term primarily used to model vehicle load and refers to the upper part of the vehicle (i.e., where people sit). On the other hand, the lower body structure is referred to as unsprung mass.

[0005] According to relevant technologies, in order to minimize the vertical displacement of the sprung mass, specific active suspensions of the vehicle are mainly used in an attempt to improve ride comfort.

[0006] For example, Korean Patent Publication No. 10-1997-0069430 (November 7, 1997) reports a specific leveling device for a vehicle, wherein, in order to detect road surface conditions with bumps, an actuator operates based on a signal transmitted from a road sensor installed under the vehicle body to open or close a leveling valve for controlling compressed air. An air spring that adjusts the vehicle height by controlling the compressed air of the leveling valve is installed between the vehicle body and the axle to prevent damage to the lower part of the vehicle body due to bumps and to absorb and mitigate impacts from the road surface, thereby improving passenger ride comfort. Summary of the Invention

[0007] Traditionally, the only way to mitigate vertical undulations (pitch motion) that occur when a vehicle travels over uneven roads has been through proportional gain control (P control). However, we have found that, in addition to pitch motion, vehicles traveling over uneven roads or surfaces are significantly affected by longitudinal acceleration and jerk.

[0008] In one aspect, the present invention aims to provide a control method and apparatus that improves ride comfort by reducing longitudinal acceleration and jerk, as well as pitch motion that occurs when driving over uneven roads.

[0009] To improve ride comfort by reducing pitch (pitch motion) changes that occur when a vehicle drives over bumps or indentations, it is possible to keep pitch motion at zero. In particular, in front-wheel-drive vehicles, this is achieved by generating drive torque in the direction opposite to increasing or decreasing pitch.

[0010] Therefore, while controlling pitch motion, ride comfort is adjusted and improved by appropriately adjusting the vehicle's longitudinal acceleration and jerk. For example, if the vehicle's front nose is raised (entering a bump or exiting a depression), torque is generated in the opposite direction of the vehicle's travel to control the front nose that is being lowered; conversely, if the vehicle's front nose is lowered (exiting a bump or entering a depression), torque is generated in the vehicle's travel direction to control the front nose that is being raised.

[0011] To execute this control, based on optimal control, the objective functions for reducing pitch motion, longitudinal acceleration, and jerk are calculated using the vehicle's acceleration and jerk constraints. Weights are reflected in these objective functions to calculate the final drive torque, which is then applied to the vehicle to reduce pitch motion, longitudinal acceleration, and jerk.

[0012] In one aspect, a method is provided for optimal or enhanced control of drive torque for driving on uneven roads or surfaces, the method comprising the steps of: a) calculating a set of torque candidates based on an estimated pitch angular velocity; b) generating a pitch motion reduction objective function based on the set of torque candidates; c) estimating a set of vehicle acceleration candidates corresponding to the set of torque candidates generated in step a); d) generating a longitudinal acceleration reduction objective function by integrating predetermined acceleration constraints and the estimated set of vehicle acceleration candidates; e) estimating a jerk candidate set by calculating a current acceleration value obtained from a sensor together with the vehicle acceleration candidate set estimated in step c); f) generating a jerk reduction objective function by integrating predetermined jerk constraints and the jerk candidate set; and g) selecting the candidate with the minimum value in the objective function and determining the drive torque corresponding to the selected candidate.

[0013] In some aspects of the preferred method, in step b), the pitch reduction objective function is generated inversely proportional to the magnitude of the drive torque candidate set, so that the pitch reduction objective function gradually decreases as the magnitude of the drive torque increases.

[0014] In an additional aspect of the preferred method, in step d), the longitudinal acceleration reduction objective function is generated proportionally to the size of the candidate group of drive torques, so that the longitudinal acceleration reduction objective function gradually increases with the increase of the magnitude of the drive torque.

[0015] In a further aspect of the preferred method, in step e), the magnitude of the objective function is increased in the region above the acceleration constraint.

[0016] In another aspect of the preferred method, in step f), the objective function is generated proportionally to the size of the candidate group of drive torques, so that the jerk reduction objective function gradually increases as the magnitude of the drive torque increases.

[0017] As discussed, the method and system appropriately include the use of a controller or processor. Therefore, in the above method, the method may include the following steps: a) calculating a torque candidate set via the controller based on an estimated pitch angular velocity; b) generating a pitch motion reduction objective function via the controller based on the torque candidate set; c) estimating a vehicle acceleration candidate set corresponding to the torque candidate set generated in step a) via the controller; d) generating a longitudinal acceleration reduction objective function via the controller by integrating predetermined acceleration constraints and the estimated vehicle acceleration candidate set; e) estimating a jerk candidate set via the controller by calculating a current acceleration value obtained from a sensor and the vehicle acceleration candidate set estimated in step c); f) generating a jerk reduction objective function via the controller by integrating set jerk constraints and the jerk candidate set; and g) selecting the candidate with the minimum value in the objective function via the controller and determining the drive torque corresponding to the selected candidate.

[0018] In another embodiment, a vehicle is provided that includes devices or systems as disclosed herein.

[0019] The configuration and operation of the present invention will become clearer through the specific embodiments described below with reference to the accompanying drawings. Attached Figure Description

[0020] The above and other objects, features and advantages of the present invention will become more apparent to those skilled in the art from the detailed description of exemplary embodiments of the invention with reference to the accompanying drawings, in which:

[0021] Figure 1 This is a schematic diagram illustrating the control of ride comfort according to the present invention;

[0022] Figure 2 This is a logic flowchart of the method for controlling ride comfort according to the present invention;

[0023] Figure 3 This is a block diagram of a device for controlling ride comfort according to the present invention;

[0024] Figure 4 yes Figure 2 The control logic flowchart of the modified control logic embodiment;

[0025] Figure 5This is a diagram showing the simulation results of pitch motion for a sports utility vehicle (SUV) and a sedan;

[0026] Figure 6 This is a diagram showing the results of pitch motion simulations based on the old control, the new control, and no control.

[0027] Figure 7 This is a graph showing the simulation results of longitudinal acceleration based on the application of the old control and the technology of this invention;

[0028] Figure 8 This is a graph showing the simulation results of jerk adjustments based on the old control and the application of the present invention's technology; and

[0029] Figure 9 This is a graph showing the simulation results of wheel input torque based on the application of the old control and the technology of this invention. Detailed Implementation

[0030] It should be understood that the term "vehicle" or "of a vehicle" or other similar terms as used herein include motor vehicles in general, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, water vehicles including various boats and vessels, aircraft, etc., and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other vehicles powered by alternative fuels (e.g., fuels derived from resources other than petroleum). As described herein, a hybrid vehicle is a vehicle with two or more power sources, such as a vehicle that has both gasoline and electric power.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this disclosure. The singular forms “a,” “an,” and “the” as used herein are intended to also include the plural forms unless the context clearly indicates otherwise. These terms are intended only to distinguish one component from another, and they do not limit the nature, order, or sequence of the constituent components. It will be further understood that the terms “comprises” and / or “comprising,” as used herein, specifically describe the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term “and / or” includes any and all combinations of one or more associated listed items. Throughout this specification, unless explicitly stated otherwise, the word “comprises” and variations such as “comprises” and / or “comprising” will be understood to mean including the stated elements, but not excluding any other elements. Furthermore, the terms “unit,” “person,” “device,” and “module” described in this specification refer to a unit for performing at least one function and operation, and may be implemented by hardware components or software components and combinations thereof.

[0032] Although the exemplary embodiments are described as using multiple units to perform exemplary processes, it is understood that the exemplary processes may also be performed by one or more modules. Additionally, it is understood that the term controller / control unit refers to a hardware device including a memory and a processor, specifically programmed to perform the processes described herein. The memory is configured to store modules, and the processor is specifically configured to execute said modules to perform one or more processes, which will be further described below.

[0033] Furthermore, the control logic of this disclosure can be embodied in a non-transitory computer-readable medium containing executable program instructions that are executed by a processor, controller, or similar device. Examples of computer-readable media include, but are not limited to, ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium can also be distributed across a network-coupled computer system so that it is stored and executed in a distributed manner, for example, via a telematics server or controller area network (CAN).

[0034] Unless otherwise specified or apparent from the context, as used herein, the term "approximately" is understood to mean within the normal tolerance range in the field, such as within 2 standard deviations of the mean. "Approximately" can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless the context otherwise requires, all numerical values ​​provided herein are modified by the term "approximately".

[0035] The advantages and features of the present invention, as well as methods for implementing them, will become apparent from the exemplary embodiments described in detail with reference to the accompanying drawings. However, the invention is not limited to the embodiments described below, but may be embodied in various other forms. The embodiments are provided only to fully disclose the invention and to fully inform those skilled in the art of its scope, and the invention will be defined by the claims. Furthermore, the terminology used herein is for explaining the embodiments and not limiting the invention. Unless otherwise stated, the singular form includes the plural form in this specification. Moreover, the terms "comprising," "including," etc., used herein to describe components, steps, operations, and / or elements do not exclude the presence or addition of one or more other components, steps, and / or elements.

[0036] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In describing the embodiments, well-known structures or functions will not be described in detail, as they may unnecessarily obscure the understanding of the invention.

[0037] Reference Figure 1 An overview of the ride comfort control according to the present invention is provided.

[0038] When a vehicle travels over uneven roads (such as roads with bumps and depressions), pitch motion changes (sag and dive). To improve ride comfort, pitch motion needs to be kept zero (0). In this invention, in a front-wheel-drive vehicle, pitch motion is counteracted by generating vehicle torque in the direction opposite to the direction that increases or decreases pitch motion. Furthermore, while controlling pitch motion, ride comfort is adjusted and improved by appropriately adjusting the vehicle's longitudinal acceleration and the degree of jerk.

[0039] Furthermore, if the front nose of the vehicle is raised (e.g., into a bump or out of a depression), a driving torque (i.e., braking torque) is generated in the direction opposite to the vehicle's travel direction to control the front nose of the vehicle being lowered. Conversely, if the front nose of the vehicle is lowered (e.g., out of a bump or into a depression), a driving torque (i.e., acceleration torque) is generated in the vehicle's travel direction to control the front nose of the vehicle being raised.

[0040] exist Figure 1In section ①, the control situation generates front-wheel drive acceleration torque in the vehicle's direction of travel to raise the vehicle's front nose, and this control is required when clearing bumps, as in section ③. Additionally, section ② generates front-wheel braking torque in the direction opposite to the vehicle's direction of travel to lower the vehicle's front nose, and this control is required when entering bumps, as in section ④.

[0041] Unlike bumps, control is executed in the opposite direction to that described above when there are depressions. Therefore, the following description will primarily focus on control for bumps.

[0042] Figure 2 This is a flowchart of the ride comfort control logic according to the present invention, and Figure 3 This is a block diagram of a device according to the present invention for controlling ride comfort by determining drive torque.

[0043] First, the abbreviations used in the following description will be introduced.

[0044] Estimate pitch or estimate pitch motion. Estimate pitch angular velocity

[0045] v x Longitudinal velocity, a x Longitudinal acceleration Estimate longitudinal acceleration, Longitudinal acceleration target constraint

[0046] Longitudinal acceleration target constraint

[0047] Twhl,cand: Candidate group of driving torques applied to the wheels; Twhl: Final driving torque.

[0048] u: control input, u * Optimal control input

[0049] k u Candidate sets of proportional gain used to calculate drive torque

[0050] J, J(x, u): Objective function or cost function

[0051] J θ The objective function for reducing pitch motion, J a The objective function for reducing longitudinal acceleration, J jerk The objective function for reducing jerk is denoted by . Each of these can be calculated using the following equation.

[0052]

[0053]

[0054]

[0055] w1 and w2: Weights of the objective function (corresponding to acceleration reduction and jerk reduction, respectively).

[0056] Reference Figure 2 and Figure 3 An optimal control method and apparatus for improving ride comfort according to the present invention will be described. This will be discussed in the main description. Figure 2 While describing the method and process, add... Figure 3 Description of the device.

[0057] 1. Generate candidate sets of drive torque based on the estimated vehicle pitch angular velocity.

[0058] The pitch rate estimation unit 11 can calculate the estimated pitch rate of the vehicle using various known methods. Furthermore, the drive torque candidate group generation unit 22 generates a drive torque candidate group based on the estimated pitch rate calculated by the pitch rate estimation unit 11.

[0059] As described above, the objective of this invention is to select the most suitable drive torque that minimizes the cost function through optimal control. To this end, the drive torque candidate generation unit 22 first needs to generate candidates for drive torques that can be generated by the vehicle. For example, in cases where positive torque is required to reduce pitch motion, torques that can be generated by the controller are periodically divided and preset. In this case, since control needs to be performed in the direction of reducing pitch motion, the estimated pitch angular velocity is used... The torque candidate set k is obtained by multiplying by a certain gain (proportional gain control). u It is set. For example, suppose P controls candidate group k. u If set as a vector [0, 200, 400, 600, 800, 1000, ..., 2000, 2200], then the torque candidate group... Depend on OK. In this example, the proportional gain has been defined as ranging from 0 to 2200, with intervals of 200 (a total of 12 dimensions of vectors). Considering the limitations of the drive system and the range of estimated pitch angular velocities, the maximum proportional gain selected for the candidate group has been set (approximately 8000), and considering the amount of data, the interval (dimensionality of the vector) has been selected (approximately 20).

[0060] 2. Based on the candidate estimation of driving torque and the objective function related to pitch motion reduction

[0061] The pitch reduction objective function generation unit 21 receives drive torque candidates generated by the drive torque candidate group generation unit 12 and generates an objective function related to pitch motion (or pitch) reduction. The objective function is modeled as a proportional relationship between drive torque and pitch reduction. In this case, since pitch reduction becomes more favorable with increasing drive torque, the objective function is determined to be inversely proportional to the magnitude of the drive torque candidate group, thereby making the objective function J... θ It gradually gets smaller.

[0062] More specifically, the objective function related to pitch reduction is Furthermore, this equation is the same as the one described in the abbreviation above. The objective function is generated as the reciprocal of the square of the candidate set of driving torques. This is done because J θ The value is set to a smaller value to respond to an increase in drive torque, as the pitch reduction effect increases with increasing drive torque. Furthermore, the square is used to calculate positive numbers. For example, in the previous example, if the drive torque candidate group... for and If the value is 0.05, then J can be calculated using the equation. θ =0.0001*[infinity, 11.111, 2.7778, 1.2346, 0.6944, 0.4444, 0.3086, 0.2268, 0.1736, 0.1372, 0.1111, 0.0918].

[0063] 3. Estimate the current pitch value based on the estimated pitch angular velocity.

[0064] Integrator 31 estimates the current pitch value by integrating the estimated pitch rate calculated by pitch rate estimation unit 11. In this case, it is determined whether the control according to the invention is input (activated) or terminated (completed) (32), and the pitch value estimation operation is reset (initialized) each time control is input.

[0065] A detailed description is provided below. To estimate longitudinal acceleration, it is necessary to estimate the current pitch motion value. This operation is a current pitch value estimation operation. For this purpose, the estimated pitch angular velocity is integrated in integrator 31 to estimate the pitch value (pitch motion value). However, in this invention, pitch estimation is not always performed, but only when the vehicle passes over a bump (and in the case of a depression), and the control operation according to the invention is activated (input control). Thereafter, when it is determined that the vehicle has completely passed over the bump, the control is terminated, and the estimation of abnormal pitch is also terminated. Therefore, it is necessary to initialize (reset) the pitch estimation at each input after the control is terminated to start the integration from the initial pitch value (i.e., zero (0)). This is to reduce pitch estimation errors caused by vehicle acceleration / deceleration during driving on flat ground, uphill, or downhill.

[0066] 4. Determine the target constraints for longitudinal acceleration and jerk.

[0067] Before generating the objective function related to longitudinal acceleration reduction and the objective function related to jerk reduction, the objective constraint determination unit 41 determines the objective constraints for longitudinal acceleration and jerk.

[0068] Specifically, when pitch motion is excessively reduced using the control method according to the invention, a large acceleration is generated. To prevent this, the objective constraint is set to prevent longitudinal acceleration from becoming excessive. In other words, as the magnitude of the drive torque increases, reducing vehicle longitudinal acceleration becomes unfavorable, and the objective constraint is determined to generate an objective function proportional to the size of the candidate set of drive torques, such that the associated objective function J... a (Related to longitudinal acceleration) gradually increases (the same applies to the objective constraint for jerk). In the region above the acceleration constraint according to design intent, the magnitude of the objective function is intentionally increased to exclude it from the candidates for optimal control input.

[0069] For example, when the acceleration is greater than 2.943 m / s² 2 At this point, the driver will feel very uncomfortable. Therefore, in order to implement control and avoid acceleration exceeding this value, a longitudinal acceleration target constraint can be set.

[0070] 5. Estimation of candidate acceleration (longitudinal acceleration) sets and generation of objective functions related to longitudinal acceleration reduction.

[0071] By receiving the drive torque candidate set generated by the drive torque candidate set generation unit 12 and the pitch motion value estimated by the integrator 31, the longitudinal acceleration reduction correlation objective function generation unit 51 estimates the longitudinal acceleration candidate set and generates the acceleration correlation objective function. In this case, acceleration is estimated using longitudinal vehicle dynamics together with the longitudinal acceleration sensor 52 (e.g., a G-sensor) installed in the vehicle. To generate the objective function, the acceleration target constraint determined by the target constraint determination unit 41 is referenced.

[0072] The acceleration candidate set is the longitudinal acceleration estimated based on the drive torque candidate set. The acceleration candidate set is defined as follows.

[0073]

[0074] Here, m represents the vehicle mass, and r dyn C represents the rolling radius of the wheel. r1 and C r2 V represents the rolling resistance coefficient. x C represents the longitudinal vehicle speed, ρ represents the air density, and C represents the longitudinal vehicle speed. d This represents the air drag coefficient, and A F This indicates the area of ​​the front of the vehicle.

[0075] Furthermore, the objective function related to pitch motion reduction is shown below and has been described in the abbreviated explanation.

[0076]

[0077] The objective function described above is generated as an estimated longitudinal acceleration from the candidate set of driving torques. The square root. This is done in response to an increase in the driving torque value, which will... a The value is set to a relatively large value because the magnitude of the acceleration increases with the driving torque. The square is used to calculate positive numbers, and the square root is used to adjust the overall magnitude of the objective function. Furthermore, acceleration constraints are set to prevent the acceleration from increasing to a certain value. The above applies when the acceleration is greater than the target acceleration. At that time, J a It is set to a very large value (i.e., penalty). For example, when The expression is [0, 0.1, 0.25, 0.4, 0.55, 0.7, 0.9, 1.1, 1.4, 1.7, 2.1, 2.7] and... When the value is 1.962, if the penalty is set to 10 6 Then, J can be calculated from the equation. a= [0, 0.1, 0.25, 0.4, 0.55, 0.7, 0.9, 1.1, 1.4, 1.7, 10] 6 10 6 ].

[0078] 6. Estimation of candidate jerk sets and generation of objective functions related to jerk reduction

[0079] The jerk reduction-related objective function generation unit 61 estimates a jerk candidate group from the current acceleration candidate group generated in the jerk reduction-related objective function generation unit 51, and generates a jerk-related objective function. In this case, wheel speed sensors 62 installed in the vehicle are used to perform jerk estimation. To generate the objective function, the jerk target constraints determined by the target constraint determination unit 41 are referenced.

[0080] In this operation, since the decrease in jerk becomes unfavorable as the magnitude of the driving torque increases, the objective function is determined to be proportional to the size of the candidate set of driving torques, such that the objective function J... jerk Gradually increasing. As designed, the size of the objective function is intentionally increased in the region above the jerk constraint to exclude it from the candidates for optimal control input.

[0081] This will be described in detail. The jerk candidate set is an estimate of the jerk that will occur when drive torque is applied under the current vehicle conditions. These jerk estimates are generated by dividing the difference between the estimated longitudinal acceleration candidate set and the current acceleration obtained from the G-sensor by the sampling time (0.01 seconds). That is, the estimated jerk is calculated as follows: Here, a x，curr T represents the acceleration of the current state. s This indicates the controller's sampling time, which is 0.01 seconds. Furthermore, the jerk candidate group is defined as follows.

[0082]

[0083] When implementing the control of this invention, ride comfort will decrease when large jerk occurs. To treat this as an objective function, the square root of the estimated acceleration is set as the objective function. Furthermore, as with longitudinal acceleration, very large jerk should be avoided to prevent deterioration of ride comfort. Therefore, when jerk occurs within jerk constraints... When above, a penalty will be imposed, and therefore the objective function J will be affected. jerk It is designed to be very large. For example, if the current acceleration is a x，curr =0.1, then the estimated longitudinal acceleration vector And the penalty = 106 And accelerate the candidate group Furthermore, the jerk objective function J jerk =[10, 0, 15, 10] 6 10 6 10 6 10 6 10 6 10 6 10 6 10 6 10 6 ].

[0084] 7. Operations to determine the final objective function

[0085] The final objective function determination unit 71 calculates the final objective function as a linear sum of the three objective functions mentioned above. The final objective function is given by J = J θ +w1J a +w2J jerk Okay. Here, w1 and w2 are weights, and it means that when the final objective function is determined, increasing w1 can suppress the increase in longitudinal acceleration, and increasing w2 can suppress the increase in jerk. Depending on the relative magnitudes of w1 and w2, the contribution effects on the control of longitudinal acceleration and jerk can be applied differently. Details of the weights will be described below.

[0086] 8. Determine weights based on control intent.

[0087] Before the final objective function is determined by the final objective function determination unit 71, the weight determination unit 72 can determine the weights of constants or variables by considering the importance of the objective functions for pitch reduction, longitudinal acceleration, and jerk. For example, an increase in the weight w1 of the acceleration objective function reflects the designer's intention to suppress acceleration increase, and an increase in the weight w2 of the jerk objective function reflects the designer's intention to suppress jerk increase. These weights can be set as constants or variables.

[0088] Specifically, the importance of each objective function is determined based on the controller designer's intent. For example, some vehicle models may focus on reducing pitch motion, while others may generate a large amount of pitch motion, but conversely, may focus on minimizing longitudinal acceleration. Therefore, the weight determination unit 72 is used to adjust the control of pitch motion, longitudinal acceleration, and jerk according to the concept and design intent of the vehicle model.

[0089] The term "importance" used here refers to "the degree of consistency with the vehicle or vehicle model concept and the designer's intent." For example, when reducing pitch motion alone is important, weights w1 and w2 can be set to zero (0). Then, even with large accelerations and jerks, pitch motion reduction performance can be guaranteed. Furthermore, since the designer does not need to consider jerk, when only pitch motion reduction and longitudinal acceleration reduction are important, only weight w1 is increased, and w2 is set to 0. Moreover, in this case, to more aggressively reduce longitudinal acceleration than to reduce pitch motion, when the initially set weight value w1 is increased, longitudinal acceleration is suppressed (however, pitch motion performance will conversely deteriorate to some extent). Finally, to reduce pitch motion, reduce longitudinal acceleration, and reduce jerk, both weights w1 and w2 need to be considered.

[0090] Here, the weights can be determined through appropriate adjustments in simulation and experimentation. Furthermore, the weights w1 and w2 can be determined as constants or variables.

[0091] 9. Determination of the objective function for minimizing the final driving torque

[0092] Finally, this involves determining the drive torque used to propel the vehicle's wheels. Here, an objective function minimization algorithm 73 is used to determine the final drive torque value that minimizes the determined final objective function. To do this, firstly, drive torque candidates with the minimum final objective function can be selected, and the final drive torque amount can be determined from the selected candidates.

[0093] This will be described in detail. First, the concept of "optimal control" used in this invention will be briefly described using the formulation of linear optimal control theory.

[0094] Optimal control is a control technique that yields an optimal solution when all conditions cannot be simultaneously improved. By setting a cost function J as the control objective, the control input u is determined to minimize the cost function over the entire control cycle. An example of optimal control theory is presented below.

[0095]

[0096] As described above, the cost function to be minimized (i.e., the objective function described above in this invention) is defined, and the control input (the driving torque applied to the wheels in this invention) that minimizes the cost function is obtained for each control cycle. According to optimal control theory, the smaller the cost function, the better the control that satisfies the control intent. This invention applies this concept to traffic control along uneven roads (such as roads with bumps and depressions).

[0097] To better understand, the process of selecting the drive torque at a certain point in time, according to the control method described above according to the present invention, will be used as an example. The following explanation is a comprehensive summary of the examples exemplified in each of the above operations.

[0098] When the drive torque candidate group for and When the value is 0.05, According to the calculation of the equation, J θ =0.0001*[infinity, 11.111, 2.7778, 1.2346, 0.6944, 0.4444, 0.3086, 0.2268, 0.1736, 0.1372, 0.1111, 0.0918]. Furthermore, according to the formula, when... When the '[0, 0.1, 0.25, 0.4, 0.55, 0.7, 0.9, 1.1, 1.4, 1.7, 2.1, 2.7]' , The value is 1.962, and the penalty is set to 10. 6 Then J a = [0, 0.1, 0.25, 0.4, 0.55, 0.7, 0.9, 1.1, 1.4, 1.7, 10] 6 10 6 Furthermore, when the current acceleration a x，curr When = 0.1, the estimated longitudinal acceleration vector a x，curr = [0, 0.1, 0.25, 0.4, 0.55, 0.7, 0.9, 1.1, 1.4, 1.7, 2.1, 2.7], And the penalty = 10 6 accelerometer candidate group Furthermore, the jerk objective function J jerk =[10, 0, 15, 106, 10 6 10 6 10 6 10 6 10 6 10 6 10 6 10 6 ].

[0099] Assume the weight w1 = 5e -4 and w2 = 2e -4 The control is configured to take into account pitch motion, longitudinal acceleration, and jerk, and the final objective function is calculated as J = J θ +w1J a+w2J jerk And therefore J = [infinity, 0.0012, 0.0034, 200.0003, 200.0004, 200.0005, 200.0006, 200.0007, 200.0008, 200.0009, 700, 70].

[0100] The optimal drive torque input u* that minimizes J is found in the control input (u, candidate set of drive torques) and is therefore adopted as the second control input with a minimum value of 0.0012. The optimal drive torque is then determined to be 10.

[0101] In this way, the objective function is obtained for each control cycle, and the minimum value is obtained to determine the optimal drive torque corresponding to the minimum value.

[0102] When the expected reduction in jerk effect is slightly smaller, w2 can be reduced more significantly. In this case, for example, when the weight is controlled at w1 = 5e... -4 and w2 = 2e -5 When the objective function is calculated, the final objective function is J = J θ +w1J a +w2J jerk And thus we obtain J = [infinity, 0.0012, 0.0007, 20.0003, 20.0003, 20.0004, 20.0005, 20.0006, 20.0007, 20.0009, 520, 520]. In this case, the optimal control input is adopted as... The third control input has a minimum value of 0.0007. Therefore, the final drive torque is determined to be 20. Thus, it can be seen that the control intent changes according to the values ​​of w1 and w2.

[0103] Figure 4 yes Figure 2 The illustrated modified embodiment of weight determination logic 8. Compared to SUVs, sedan passenger vehicles have greater pitch motion due to their lower body and lower center of gravity (see...). Figure 5 In particular, when driving on flat ground after passing over a large bump (or depression), pitching motion will occur additionally once or twice. Figure 5 The simulation results show the pitch motion of an SUV and a sedan driving at 30 km / h sequentially over a long bump, a long depression, and a short bump. The pitch motion of the passenger car (sedan) is generally greater than that of the SUV, and in particular, it can be confirmed that pitch motion occurs additionally even after 8 seconds (sec) after escaping the bump in the road segment and reaching flat ground.

[0104] In order to apply this invention, the characteristics of passenger vehicles have been taken into consideration, such as... Figure 4 As shown, during the weight determination process of weight determination unit 72, additional control routines are executed in response to the additional pitch motion after passing over a bump (or depression). As a supplement, sub-operations 81 to 83 are added according to... Figure 2 Operation 8 (Weight Determination) of the control flow diagram in the embodiment.

[0105] First, by integrating Figure 2 The estimated pitch value in operation 3 and the signal calculated for control input determine whether the current vehicle has passed over a bump (or depression) and then reaches flat ground (81).

[0106] An index is calculated to determine whether control should be executed after escaping a bump, and thus determines whether additional control (further control) should be executed after escaping a bump (82). The execution of additional control is determined by combining the estimated pitch rate value, the control input / off (ON / OFF) signal, and the control end time. A certain amount of time needs to be maintained after the estimated pitch rate exceeds a certain value, and this is executed when passing over a bump or depression, and after all control has ended. Specific values ​​and times are adjusted through experiments and simulations.

[0107] When additional controls are determined, the weights are adjusted so that, in sections where one or two additional pitch movements occur (after escaping a bump), pitch movement is suppressed more than longitudinal acceleration and jerk suppression (83). This is performed after weight adjustment. Figure 2 8. Operation of the control method. Weight adjustment and reference. Figure 2 and Figure 3 The descriptions are the same. That is, Figure 4 Operation 83 of the embodiment and Figure 2 Operation 8 (determining weights based on control intent) is the same.

[0108] Figures 6 to 9 These are simulation results used to demonstrate the improvements of the ride comfort control technology according to the present invention compared to related technologies.

[0109] Figure 6 The diagram illustrates pitch motion according to conventional control, the new control of this invention, and no control, in a scenario where an SUV is traveling at 30 km / h sequentially over a longer (or wider) bump, a wider depression, and a shorter (or narrower) bump.

[0110] Figure 7 The longitudinal acceleration is shown under the same scenario, based on the old control and the new control.

[0111] Figure 8 The accelerator is shown in the same scene, based on the old control and the new control.

[0112] Figure 9 The diagram shows the wheel input torque under the old and new controls in the same scenario.

[0113] Based on the above simulations, compared with related technologies (proportional gain control), this technology (optimal control) has the following characteristics.

[0114] The control technology according to the present invention limits, for example Figure 9 The control input torque shown is used to prevent longitudinal acceleration from increasing beyond the specified value. Figure 7 A certain level as shown. Furthermore, it can be prevented by, for example... Figure 8 The acceleration shown increases rapidly to improve ride comfort. However, it can be seen that pitch motion reduces performance as... Figure 6 The figure shows a decrease.

[0115] These results are due to the inverse relationship between pitch reduction, longitudinal acceleration, and jerk reduction. That is, pitch reduction performance deteriorates significantly when the magnitude of longitudinal acceleration and jerk is greatly reduced, and deteriorates less when the magnitude of longitudinal acceleration and jerk is slightly reduced. Figure 2 and Figure 4 In operation 7 of the control flow diagram, the degree can be adjusted while changing the weight.

[0116] In controls based on related technologies (e.g., proportional gain control (or P control)), effective control for reducing pitch motion can be implemented, but the amplitudes of longitudinal acceleration and jerk become quite large, thereby compromising ride comfort. On the other hand, according to the present invention, control that takes into account overall ride comfort can be implemented, thus controlling longitudinal acceleration and jerk and reducing pitch motion occurring when driving over uneven roads. According to the present invention, the reduction in ride comfort caused by longitudinal acceleration and jerk, which are not considered in related technologies, can be effectively improved.

[0117] Although the present invention has been described with reference to exemplary embodiments thereof, those skilled in the art will understand that various modifications and changes can be made without departing from the spirit or essential characteristics of the invention. Therefore, it should be understood that the above embodiments are exemplary in all respects and not restrictive.

Claims

1. An optimal control method for drive torque to achieve smooth driving on uneven roads, the method comprising the following steps: a) Calculate the torque candidate group based on the estimated pitch angular velocity; b) Generate a pitch reduction objective function based on the torque candidate set; c) Estimate the vehicle acceleration candidate set corresponding to the torque candidate set generated in step a); d) Generate a longitudinal acceleration reduction objective function by integrating predetermined acceleration constraints and the estimated candidate set of vehicle accelerations; e) Estimate the jerk candidate group by calculating the current acceleration value obtained from the sensor and the vehicle acceleration candidate group estimated in step c); f) Generate an accelerometer reduction objective function by combining the set accelerometer constraints and the accelerometer candidate group; as well as g) Select the candidate with the minimum value in the objective function and determine the driving torque corresponding to the selected candidate.

2. The method according to claim 1, wherein, In step b), the pitch motion reduction objective function is generated inversely proportional to the magnitude of the drive torque candidate set, such that the pitch motion reduction objective function gradually decreases as the magnitude of the drive torque increases.

3. The method according to claim 1, wherein, In step d), the longitudinal acceleration reduction objective function is generated proportionally to the size of the drive torque candidate group, such that the longitudinal acceleration reduction objective function gradually increases as the magnitude of the drive torque increases.

4. The method according to claim 1, wherein, In step d), the magnitude of the objective function is increased in the region above the acceleration constraint.

5. The method according to claim 1, wherein, In step f), an objective function is generated proportionally to the size of the candidate group of driving torques, such that the jerk reduction objective function gradually increases as the magnitude of the driving torque increases.

6. The method according to claim 1, wherein, In step f), the magnitude of the objective function is increased in the region above the jerk constraint.

7. The method according to claim 1, wherein, Step g) also includes applying the weights to the objective function calculated in steps b), d), and f).

8. The method according to claim 7, wherein, When applying the weights, a first weight related to longitudinal acceleration and a second weight related to jerk are applied.

9. A device for driving torque, the device comprising: The drive torque candidate group generation unit is configured to calculate torque candidate groups based on the estimated pitch angular velocity from the pitch angular velocity estimation unit; The pitch reduction objective function generation unit is configured to generate a pitch motion reduction objective function from the generated torque candidate set; An acceleration reduction objective function generation unit is configured to generate a longitudinal acceleration reduction objective function by estimating a vehicle acceleration candidate set and integrating a preset acceleration constraint with the estimated vehicle acceleration candidate set, wherein each of the vehicle acceleration candidate sets corresponds to one of the torque candidate sets generated by the drive torque candidate set generation unit. The jerk reduction objective function generation unit is configured to estimate a jerk candidate group by calculating the current acceleration value obtained from the longitudinal acceleration sensor and the estimated vehicle acceleration candidate group, and to generate a jerk reduction objective function by combining a preset jerk constraint and the jerk candidate group. as well as The final objective function determination unit is configured to select the candidate with the minimum value from the objective function and determine the drive torque corresponding to the selected candidate.

10. The apparatus according to claim 9, wherein, The pitch motion reduction objective function generation unit generates the pitch motion reduction objective function inversely proportional to the magnitude of the drive torque candidate group, such that the pitch motion reduction objective function gradually decreases as the magnitude of the drive torque increases.

11. The apparatus according to claim 9, wherein, The longitudinal acceleration reduction objective function generation unit generates the longitudinal acceleration reduction objective function in proportion to the size of the driving torque candidate group, such that the longitudinal acceleration reduction objective function gradually increases as the amplitude of the driving torque increases.

12. The apparatus according to claim 9, wherein, The longitudinal acceleration reduction objective function generation unit increases the magnitude of the objective function in the region above the acceleration constraint.

13. The apparatus according to claim 9, wherein, The jerk reduction objective function generation unit generates an objective function proportional to the size of the driving torque candidate group, such that the jerk reduction objective function gradually increases as the amplitude of the driving torque increases.

14. The apparatus according to claim 9, wherein, The acceleration reduction objective function generation unit increases the magnitude of the objective function in the region above the acceleration degree constraint.

15. The apparatus of claim 9, further comprising a weight determination unit configured to apply weights to target functions calculated in the pitch reduction target function generation unit, the acceleration reduction target function generation unit, and the jerk reduction target function generation unit.

16. The apparatus according to claim 15, wherein, The weight determination unit applies a first weight related to longitudinal acceleration and a second weight related to jerk to the objective function.

17. A vehicle comprising the means according to any one of claims 9 to 16.

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