Secure operation of a vehicle combination

Abstract

A computer-implemented method of determining a torque limit for an operating state of a first vehicle combination, the vehicle combination comprising a tractor unit and at least one trailer unit, the method comprising simulating a plurality of operating states of one or more second vehicle combinations, wherein each operating state is based on one or more operating parameters associated with a physical characteristic of the one or more second vehicle combinations, one or more parameters associated with an operating environment of the one or more second vehicle combinations, and one or more parameters related to a driving scenario of the one or more second vehicle combinations; classifying each of the simulated operating states as safe or unsafe; receiving an unsimulated operating state of the first vehicle combination; and determining a torque limit for the unsimulated operating state based on the simulated operating state.

Description

Technical Field

[0001] The present disclosure relates to safe operation of a vehicle combination. In particular, the present invention relates to determining a torque limit of a combination of at least two vehicle units in different operating states. Background Art

[0002] The total global carbon emissions of humanity have been growing exponentially over the past few decades. They are expected to continue to grow in the coming years. In 2020, the road transport sector (which includes heavy-duty trucks used in the construction, logging and refrigeration industries) is estimated to account for 5% of total global CO2 emissions and 30% of total transport sector CO2 emissions. Therefore, research into battery electric vehicles (BEVs) is a hot topic in the heavy-duty vehicle industry, as they are an environmentally sustainable alternative to internal combustion engines running on fossil fuels. Several companies in the heavy-duty truck industry are aiming to reach a level in the near future where they only sell and produce trucks that use electricity as the main source of propulsion.

[0003] One of the many issues with battery-powered heavy-duty trucks is their ability to maintain as long a driving range as trucks powered by fossil fuels. Current BEV trucks are able to achieve a driving range sufficient for short-distance deliveries in urban areas of cities and industrial areas. However, for long-distance deliveries, existing electric trucks may require multiple time-consuming recharging to complete the entire trip.

[0004] One solution to extend the vehicle's driving range is to add more batteries, thereby increasing the total on-board energy capacity. If batteries are installed on the trailer of a tractor-trailer combination, an electric motor can also be installed so that the trailer can serve as a propulsion supplement for the vehicle. This makes it possible to use electric trailers on both tractors with internal combustion engines and BEV tractors. In addition, conventional heavy truck trailers are usually equipped with pneumatic brakes to stop the vehicle safely and promptly. Electric trailers can also recharge the batteries through regenerative braking, thus preventing energy from being wasted through mechanical braking systems.

[0005] However, the introduction of a propulsion element on the trailer affects the stability of the vehicle combination in certain operating conditions, compared to the conventional setup where the vehicle combination is towed only by the tractor. Therefore, further knowledge is needed to understand whether safe driving can be ensured when the trailer accelerates or decelerates the vehicle combination. Summary of the invention

[0006] The present disclosure attempts to solve the above mentioned problems by providing a method for determining how to use an electric trailer for propulsion in a vehicle combination in a safe manner. The present disclosure focuses on the use of a multi-unit vehicle combination where different units can be used as propulsion units. This allows for the analysis of unconventional propulsion strategies, such as propelling the vehicle combination solely by the battery and electric motor of the electric trailer.

[0007] Safe driving is defined as the vehicle combination not being in any of a set of predefined unsafe modes. A set of requested forces and moments (from the physical driver or the autonomous system) and additional parameters such as the road profile and the longitudinal speed of the vehicles can then be used to determine the safe operating envelope (SOE) of the vehicle combination. SOEs have been well studied in the aviation industry. However, their research in the heavy vehicle sector is limited.

[0008] The present disclosure uses parameters of the operating state of the vehicle combination to determine which user inputs will produce safe vehicle motion and which will not. This can be defined by torque limits that ensure safe driving in different operating states. This enables the use of an electric trailer for propulsion to increase the driving range of a BEV truck while ensuring that unsafe vehicle behavior is avoided during normal driving conditions.

[0009] According to one aspect, a computer-implemented method for determining a torque limit for an operating state of a first vehicle combination is provided, the vehicle combination comprising a tractor unit and at least one towed unit, the method comprising simulating a plurality of operating states of one or more second vehicle combinations, wherein each operating state is based on one or more operating parameters related to physical characteristics of the one or more second vehicle combinations, one or more parameters related to an operating environment of the one or more second vehicle combinations, and one or more parameters related to a driving scenario of the one or more second vehicle combinations; classifying each of the simulated operating states as safe or unsafe; receiving an unsimulated operating state of the first vehicle combination; and determining a torque limit for the unsimulated operating state based on the simulated operating state.

[0010] Optionally, simulating a plurality of operating states comprises using a nonlinear high-fidelity mathematical transport model. Optionally, the one or more operating parameters associated with the physical characteristics of the specific second vehicle combination include the geometry of the second vehicle combination, the number of axles of the tractor unit, the distance between the axles of the tractor unit, the number of axles of the at least one towing unit, the distance between the axles of the at least one towing unit, the number of motion support devices of the tractor unit, the number of motion support devices of the at least one towing unit, the cornering stiffness on the tires of the tractor unit, the cornering stiffness on the tires of the at least one towing unit, the inertia of the tractor unit about the yaw axis, the inertia of the at least one towing unit about the yaw axis, the peak torque output of the electric motor on the tractor unit, the peak torque output of the electric motor on the at least one towing unit, the axle load on at least one axle of the tractor unit, and the axle load on at least one axle of the at least one towing unit. Optionally, the one or more parameters associated with the operating environment of the specific second vehicle combination include at least one of a road profile and a road surface friction coefficient. Optionally, the one or more parameters related to the driving scenario of the specific second vehicle combination include at least one of the longitudinal speed of the tractor unit, at least one articulation angle between consecutive units, the total applied torque on the tractor unit, the total applied torque on the at least one towing unit, the longitudinal coupling force at each coupling point, and the lateral coupling force at each coupling point.

[0011] Optionally, classifying each of the simulated operating states as safe or unsafe comprises determining an outcome of a driving maneuver defined by the operating state. Optionally, the method comprises classifying the operating state as unsafe if the outcome of the driving maneuver is an unsafe mode, the unsafe mode comprising at least one of a deviation of the vehicle combination, a folding of the vehicle combination, a swinging of the at least one towed unit, or a rollover of the vehicle combination. Optionally, the method comprises classifying the operating state as safe if the outcome of the driving maneuver is not an unsafe mode.

[0012] Optionally, the method comprises determining torque limits for the plurality of operating states of the second vehicle combination to provide a safe operating envelope for the second vehicle combination. Optionally, the method further comprises validating the determined torque limits using data from actual driving of the second vehicle combination.

[0013] Optionally, receiving the unsimulated operating state of the first vehicle combination comprises receiving the operating state of the unsimulated vehicle combination and / or receiving the unsimulated operating state of the simulated vehicle combination. Optionally, the unsimulated operating state comprises at least one of a coefficient of friction of a road surface, a longitudinal speed of the tractor unit, an articulation angle between consecutive units, a total applied torque on the tractor unit, a total applied torque on the at least one towing unit, a longitudinal coupling force at each coupling point, and a lateral coupling force at each coupling point for the unsimulated operating state.

[0014] Optionally, determining the torque limit for the unsimulated operating state comprises determining the closest simulated operating state. Optionally, determining the torque limit for the unsimulated vehicle combination comprises interpolating between two similar simulated vehicle combination operating states. Optionally, the method comprises applying the determined torque limit to a total propulsion load of a plurality of motion support devices of the tractor unit and / or the at least one towed unit. Optionally, the plurality of motion support devices comprises a plurality of electric motors.

[0015] According to another aspect, a computer readable medium having stored thereon instructions which, when executed by one or more processors, cause the method steps to be performed is provided.

[0016] Generally, unless otherwise clearly defined herein, all terms used in the claims should be interpreted according to their ordinary meanings in the art. All references to "a / an / the element, device, part, means, step, etc." will be interpreted as referring to at least one instance of the element, device, part, means, step, etc., unless otherwise clearly stated. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless clearly stated. Other features and advantages of the present invention will become apparent when studying the attached claims and the following description. The technician will appreciate that, without departing from the scope of the present invention, the different features of the present invention may be combined to form embodiments other than the embodiments described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Exemplary embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which:

[0018] Figure 1 An exemplary vehicle combination is shown;

[0019] FIG. 2A to FIG. 2D Unsafe behavior patterns of vehicle combinations are shown;

[0020] Figure 3 An example unit coordinate system for modeling a vehicle combination is shown;

[0021] Figure 4 The forces, angles, moments and dimensions defined for each element on the modeled vehicle combination are shown;

[0022] Figure 5 All forces acting on each element in the model are shown;

[0023] Figure 6 An exemplary road profile for simulating an operating state of a vehicle combination is shown;

[0024] Figure 7 A visualization of the safe operating envelope is shown;

[0025] Figure 8 is a flow chart of a method for determining a torque limit that describes an operating state of a vehicle combination; and

[0026] Fig. 9 is a block diagram illustrating an exemplary computer system in which embodiments of the present disclosure may be implemented. DETAILED DESCRIPTION

[0027] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, the embodiments are provided by way of example so that the disclosure will be thorough and complete and the scope of the invention will be fully conveyed to those skilled in the art. Therefore, it should be understood that the present invention is not limited to the embodiments described herein and shown in the accompanying drawings; rather, those skilled in the art will recognize that many changes and modifications may be made within the scope of the appended claims. Throughout the specification, the same reference numerals refer to the same elements.

[0028] Figure 1 An exemplary vehicle combination 10 of the type contemplated in the present disclosure is shown. The vehicle combination 10 includes a tractor unit 12 and at least one trailer unit 14. The tractor unit 12 is typically the front-most unit in the vehicle combination and includes a cab for the driver (including steering controls, dashboard display, etc.). Typically, the tractor unit 12 is used to provide propulsion power for the vehicle combination 10. At least one trailer unit 14 is typically used to store cargo being transported by the vehicle combination. At least one trailer unit 14 can be a truck, trailer, dolly, etc. At least one trailer unit 14 can also provide propulsion for the vehicle combination 10. For example, the trailer unit 14 can include one or more electric motors configured to drive one or more axles or individual wheels of the trailer unit 14. A trailer unit 14 without a front axle is called a semitrailer.

[0029] The vehicle combination 10 can be defined by the physical characteristics of the individual units, such as the geometry of each unit and the entire combination, the number of axles on each unit, the distance between the axles on each unit, the number of motion support devices (e.g., including electric motors, mechanical service brakes, and steering actuators) on each unit, the cornering stiffness on the tires of each unit, the inertia of each unit about the yaw axis, the peak torque output of the electric motors on each unit, and the axle loads on the axles of each unit.

[0030] exist Figure 1 In the example of , the tractor unit 12 includes a plurality of tractor axles 16, and the towing unit 14 includes a plurality of trailer axles 18. At least one of the axles on each unit may be a driven axle, meaning it is coupled to a propulsion system to drive the vehicle combination 10 forward. The propulsion system may include a conventional propulsion system coupled to the drive axle of the tractor unit 12, and / or an electric motor coupled to the drive axle of the tractor unit 12 or the towing unit 14. For example, the three tractor axles 16 may include two driven tractor axles 20, and the three trailer axles 18 may include two driven trailer axles 22. The units may be specified by existing axle combinations. Figure 1 In the example shown, the vehicle combination 10 comprises a “6x4” tractor unit 12 and a “6x4” trailer unit 14, which means that each unit has six wheels, four of which are driven wheels.

[0031] Although three tractor axles 16 and three trailer axles 18 are shown, it should be understood that any suitable number of axles may be provided on the tractor unit 12 and at least one towing unit 14. It should also be understood that any number of the tractor axles 16 and / or trailer axles 18 may be drive axles, including zero (i.e., one of the units may include at least one drive axle while the other does not). In addition, additional towing units 14 may be provided that are interconnected. This results in vehicle combinations of different types and names.

[0032] In order to classify the movements of the vehicle combination 10, an appropriate definition of what is considered safe is required. This is done by first listing some predetermined unsafe behavior patterns. These can be summarized in FIG. 2A to FIG. 2D The four possible modes are shown in .

[0033] Figure 2A The figure shows the deviation caused by understeering. Specifically, the front axle of the tractor unit 12 slips, while the rest of the vehicle combination 10 does not slip, resulting in deviation due to understeering. Figure 2BThe folding is shown when the wheels of the tractor unit 12 slip. Specifically, the wheels on the two rear axles of the tractor unit 12 slip, while the wheels on the trailer unit 14 do not slip, thereby causing the folding. Figure 2C The trailer sway is shown due to wheel slippage of the towing unit 14. Specifically, the wheels on the towing unit 14 slip, while the wheels on the tractor unit 12 do not slip, resulting in the trailer swaying. Figure 2D A vehicle rollover is shown due to the tractor unit 12 and / or the trailer unit 14 tipping over.

[0034] Figures 3 to 5 An example of how the dynamics of a vehicle combination 10 can be modeled is shown. In order to describe the motion and dynamics of the different vehicle units, it is necessary to define coordinate systems and the global forces acting on them. For this purpose, the international standard ISO 8855 for road vehicles is used.

[0035] like Figure 3 As shown, X V,i , Y V,i and Z V,i is a unit coordinate system, where i ϵ {1, 2, … n}, where the tractor unit 12 is unit number 1, and the numbers of the trailer units 14 increase sequentially. n is the total number of units of the vehicle combination 10.

[0036] like Figure 4 As shown, forces, angles, moments and dimensions are defined for each unit i on the vehicle combination 10. If unit i is the first unit of the vehicle, the connection point i-1 is ignored along with all related dimensions. If unit i is the last unit of the vehicle, the connection point i+1 is ignored along with all related dimensions. For the sake of clarity, the connection points of the front and rear of consecutive units are shown separately. However, in the model and in reality they coincide with each other. Local force F x,i and F y,i The total longitudinal and lateral forces on the element are defined by their origin at the element's center of gravity. Similarly, the accelerations and moments on each element are defined in the same coordinate system as the local forces on each element. The world coordinate system in which the vehicle moves is defined by the coordinates express.

[0037] Figure 4 The total force shown can be decomposed into all the forces acting on each unit, which includes the forces acting on each wheel, the joint forces, and the combined forces caused by air resistance and rolling resistance. Figure 5 The index "V" indicates the force acting on the element, excluding external forces such as joint forces and resultant forces. xV,i 、F yV,i and M zV,i For representing and collecting Figure 5 All longitudinal and lateral tire forces are shown in . The longitudinal force is divided into the force F generated by the electric motor xV,I,em and the force F generated by the service brake xV,I,sb Each element has a coordinate frame at each joint point in order to correctly transform forces between elements.

[0038] In order to determine how to use an electric trailer for propulsion in a vehicle combination in a safe manner, it is proposed to simulate the operating states of different vehicle combinations to determine the SOE of the vehicle combination. To simulate the movement of the vehicle combination, a nonlinear high-fidelity mathematical transport model is used. The Volvo Group has developed models for different tractor-trailer unit combinations, which can be used to simulate the vehicle combination 10. The model has been validated in publications such as "Alidation of VTM model oftractor 4x2 with semi-trailer using winter test results from arjeplog 2111w11p2685", P. Sundström and L. Laine, Engineering Report ER-624557, Department of Applied Mechanics, Chalmers University of Technology, 2012; and "Heavy vehicle braking using friction estimation for controller optimization", B. Westerhof and D. Kalakos, Master's thesis, Chalmers University of Technology, Gothenburg, Sweden, 2017. It should be understood that other models can also be used to simulate the operating states of different vehicle combinations.

[0039] All electric motors are modeled as low pass filters that filter the requested torque for each electric motor. The low pass filter is used to model the response time of the electric motor, which will appear as a time delay during the simulation. Each wheel connected to the electric motor will receive the requested torque, but with a slight time delay. The torque and power of the electric motors are limited. The low pass filter adds a delay d1 to the requested torque with a time constant (e.g., 0.01 seconds for the electric motors). The transfer function used to model the electric motors of both the tractor unit 12 and the trailer unit 14 is as follows:

[0040] Similarly, the transfer function for the time delay d2 for the mechanical service brake is set to a slightly longer delay, for example 0.1 seconds for the electric motor:

[0041] During the construction of the SOE, the motors on each axle on all units can be considered so that both wheels on each axle have the same torque when accelerating or decelerating. It can also be assumed that the power output of each motor is proportional to the speed of the motor.

[0042] Since the vehicle combination 10 is simulated, there is no physical driver controlling its speed or heading. Therefore, a mathematical driver model is required to control the vehicle combination 10. The driver model consists of two subsystems: a speed controller and a path follower.

[0043] During the simulation process, a speed controller is used to control propulsion. The speed controller enables the vehicle combination 10 to automatically accelerate, decelerate and maintain the requested speed throughout the simulation process. The speed controller used is a PID controller, as described in Equation 3. Since the controller is used to maintain the requested speed, it will act on the error between the requested speed and the current speed of the vehicle. That is, . in are constants that are appropriately chosen to tune the controller for the simulation.

[0044] The speed controller calculates the total requested propulsion force needed to achieve the requested speed. In the event that not all axles are driven, the force is proportionally distributed between the drive axles 20, 22. Each drive axle 20, 22 is assigned a force proportional to the axle load relative to the total axle load of the drive axles of the unit. Finally, the speed controller outputs the requested wheel torque and the total requested acceleration. The wheel torque is obtained by multiplying the requested force with the corresponding wheel radius, and the acceleration is obtained by dividing the total force by the total mass of the vehicle. Depending on the application in the simulation, both torque and acceleration can be useful.

[0045] There are also some system limitations that can be considered in the speed controller modeling. First, the total propulsion force output by the controller cannot exceed the total force that the electric motors can produce. Second, the force distributed to each wheel cannot exceed the maximum friction available. This limitation is implemented to prevent the vehicle from losing traction.

[0046] A path follower is required to adjust the steering angle of the vehicle to follow the desired path. This is handled by a PID controller that acts on the lateral distance error between the center of the front-most axle and the desired path. To obtain the distance between the center of the axle and the desired path, the velocities of the axles specified in the world coordinate system are used. These velocities are then expressed as velocities in the path's coordinate system, where represents the longitudinal distance traveled, and Represents the lateral displacement relative to the path. The coordinate system is transformed from the world coordinate system to the road's coordinate system using a rotation matrix.

[0047] in is the velocity in the world coordinate system, and is the corresponding speed in the path's coordinate system. The rotation angle or vehicle heading specified in the world coordinate system By the angular velocity of the path Integrate to calculate:

[0048] in is the curvature of the path, is the travel length of the path The lateral velocity obtained in the path coordinate system is Describes the speed at which the front axle of the vehicle deviates from the path. The integration gives the lateral distance between the center of the axle and the path, which is the input to the PID controller. The controller outputs the requested steering angle according to the following equation: :

[0049] in are constants that are appropriately chosen to tune the controller for the simulation.

[0050] The longitudinal air resistance acting on vehicle combination 1+ is calculated as follows:

[0051] in is estimated to be 1, A is set to be the frontal area of ​​the tractor unit 12, and Set to normal temperature and pressure of air. Rolling resistance is based on the The rolling resistance torque estimate is obtained by where i represents the vehicle unit, j represents the axle on the unit, and s represents the side of the axle (left or right). Together with the tire radius on the vehicle, each rolling resistance is related as follows:

[0052] where n is the number of cells, and is the number of axles on unit i. Therefore, the total resistance of each unit becomes:

[0053] like Figure 6As shown, the road profile is defined as a simulated test track. In this example, the track starts with a straight path of 20 m, followed by a r The track ends at another 20 m long straight. A 15 m transition section is added between the straight and the turn to avoid large vehicle motion jitters caused by large instantaneous differences in road curvature. In this example, the path has no inclines, dips or crowns and consists of one lane. It should be understood that return Different road profiles with different straight paths, turning angles, turning radii, inclines, cambers, and lane selections can be implemented.

[0054] The simulated vehicle combination 10 starts on a road at a set cruising speed, which is controlled by a speed controller. The controller applies sufficient torque on the drive axle of the tractor unit 12 to keep the vehicle at the set speed. Any oscillations in the vehicle state caused by the transition between the initial straight and the curve must be eliminated. Therefore, the vehicle combination 10 is driven halfway on the track and the cruise controller acts on the tractor unit 12. The speed controller is then disconnected, leaving the vehicle combination 10 to roll without any applied torque. Immediately after disconnection, a fixed constant torque T is applied to each wheel on the two front axles of the towing unit 14. No traction control or slip control is used here to limit the torque applied to the wheels.

[0055] In order for the SOE to manage all the scenarios that the vehicle combination 10 may be in, data from a large number of different simulations is required. Many parameters affect the trajectory of the vehicle combination through a bend. For example, the radius of the bend, the speed of the vehicle combination 10, and the friction coefficient all play an important role when considering the movement of the vehicle combination 10 and how it handles the bend. Therefore, simulation data for many possible combinations of these parameters is needed to understand how the vehicle combination behaves.

[0056] During the simulation, the longitudinal velocity is used for each simulated vehicle combination 10 , the friction coefficient between the tire and the road , Curve radius and applied trailer torque T. The coefficient of friction is limited by its definition as the ratio of the friction force resisting motion to the normal force between the surface and the object. The speed of the vehicle combination may be capped, such as the standard speed limit for heavy goods vehicles (>3.5 tonnes) without trailers on motorways and expressways (25 m / s in Sweden). Longitudinal speed It is also limited by the maximum theoretical speed during a turn without slipping due to centripetal acceleration:

[0057] The total torque T applied to the trailer is limited by the longitudinal slip limit between the four driving wheels of the trailer and the road:

[0058] in is the total torque applied to the drive wheels of the hitch unit 14 in the x direction relative to its own coordinate system, and r2 is the radius of the wheels on the hitch unit 14. The longitudinal slip limit is considered only for the axle load of the drive axle 22.

[0059] Many different articulation angles are covered in the SOE by simulating different scenarios at different radii on the test track. The simulations can be performed using any suitable radius. In one example, simulations were performed using a radius ranging from 10 m to 100 m.

[0060] To summarize, in one example, the limits of the parameters that make up the SOE can be constrained as follows:

[0061] T is the torque applied at each wheel, so the limit is set to When a torque is applied to the towed unit 14 in the simulation, the current articulation angle must be measured. and coupling forces. These can be difficult to measure due to the large shudders that occur in the vehicle combination 10 when torque is applied mid-track. The average of the last 30% of measurements before torque is applied is used to approximate. any fluctuations.

[0062] The coupling force is affected by the torque applied on the trailer, which in turn is delayed by the transfer function in equation 1. Similar to when approximating the articulation angle, once the full torque of the towed unit 14 has been applied to the vehicle combination 10, further measurements are required to reach a sufficiently stable coupling force value. Therefore, the coupling force is averaged, for example between 1 and 2 seconds after the torque is first applied to the towed unit 14. If the vehicle combination 10 is unable to move for 2 seconds or more after the torque is applied, the average is taken until the end of the simulation. However, this increases the risk of uncertainty and inaccuracy in the coupling force estimate.

[0063] Each individual simulation run generates a data point in the SOE. All generated data points contain relevant data from their corresponding simulation. There are several ways to define data points. One method is to record the torque T applied to each drive wheel of the trailer unit 14 and the friction coefficient between the tire and the road. , Radius of the curve and the longitudinal speed of the tractor unit 12 Since these variables may change throughout the simulated curve, they are recorded when the trailer unit torque is first applied. This results in a 4-dimensional SOE that takes into account both the vehicle state and the environmental parameters.

[0064] The 4D SOE is only reliable if the towed units 14 handle all the propulsive forces and the road radius is known. However, since the dynamics of the vehicle combination 10 will vary depending on which units are used for propulsion, a more flexible definition of the SOE is needed to cover different propulsive distributions. Therefore, the SOE must contain additional parameters related to the state of the vehicle. By including the longitudinal coupling forces in the SOE and lateral connection force , a relationship between the units can be established, which allows force limitations to be applied to different unit combinations in different simulated vehicle combinations 10. In addition, since the radius of the road is difficult to measure and is not always a reliable measure of the attitude of the vehicle combination 10, the current articulation angle Instead of the road radius, it is easier to measure and better describes the difference in yaw angle between the tractor and trailer. Therefore, the parameter defining the SOE is instead chosen to be .

[0065] This way of representing SOE is more general because it is 6-dimensional and the coupling forces allow for a certain degree of disturbance handling. For example, when the tractor unit 12 brakes, or when strong winds push the trailer unit 14, the coupling forces will be affected, so these disturbances will also be taken into account.

[0066] The 6-dimensional SOE can be visualized by first viewing it as a set of 3D spaces clustered in a 2D space. Figure 7 In SOE, the parameters and are considered the least variable of the five parameters of SOE, which is why they were chosen to make up the 2D space. For each data point in the plane, there exists a 3D space consisting of the remaining parameters. Specifying all of the first five parameters then gives the corresponding applied torque T for a particular data point, which represents the last dimension.

[0067] The resolution of the SOE increases with the number of simulations and the data points generated. It is desirable to have a very high resolution SOE because it allows more accurate identification of unsafe scenarios and finding more appropriate torque limit recommendations. In contrast, using a large SOE will require more computational resources to find the nearest safe data points. In order to obtain a SOE that covers all relevant states of the vehicle, suitable parameter limits are used, such as those illustrated in Equation 15.

[0068] Each data point is classified as safe or unsafe according to the results of the corresponding simulation. As discussed above, unsafe behaviors can be summarized into four possible modes: deviation of the vehicle combination, folding of the vehicle combination, swinging of at least one trailer unit, or overturning of the vehicle combination.

[0069] like Figure 2A As depicted, when the lateral displacement of the center of the front axle of the tractor unit 12 from the center of the lane exceeds half the width of a single lane, an unsafe behavior caused by deviation is considered to have occurred. The width of the lanes on highways near rural areas in Sweden is at least 3.25 meters. Therefore, in one example, the threshold for deviation is set to 1.75 m.

[0070] like Figure 2B As shown, the folding situation is achieved by utilizing the lateral sliding of the tractor unit 12 and the trailer unit 14 and the articulation angle between the units. The definition of a folding vehicle stipulates that the rear axle of the tractor unit 12 should lose traction, while the axle of the trailer unit 14 should maintain traction. Therefore, the lateral slip of the rear axle of the tractor unit 12 will be high, while the lateral slip of the trailer unit 14 will be low. Based on simulation experience, the threshold value α for lateral slip is selected as

[0071] where index 12 and 22 represent the second axle of the first unit and the second unit, respectively. The thresholds were chosen empirically in simulations. In addition, to further define the folding, the hinge angle Since folding only poses a danger to the vehicle if the tractor and trailer collide with each other, use As additional conditions for defining folding. When all three thresholds are met, folding is considered to have occurred.

[0072] like Figure 2C As shown in , the definition used for trailer sway is similar to that for folding. The main difference is that the tractor maintains traction while the trailer does not. Therefore, the threshold for lateral slip is reversed; α 12 > 0.4 and α 22 < 0.8. The threshold for the hinge angle between units is set to .

[0073] The last unsafe behavior (such as Figure 2D The vehicle rollover shown includes a scenario where the vehicle rolls over. The threshold used is only for a roll angle of 90° for the tractor unit 12 or the trailer unit 14.

[0074] Scenarios that are not included in the unsafe behavior are considered safe. The first safe scenario is when the simulated vehicle combination 10 successfully drives all the way through the simulated test track. It is also possible that the vehicle combination 10 brakes to a complete stop without fully completing the track. Both scenarios are considered safe because they do not encounter any unsafe scenarios.

[0075] The classified data points then provide the SOE for the simulated vehicle combination 10. The idea of ​​the SOE is to limit the driver's input to ensure safe driving of a specific vehicle combination 10. More specifically, by reading and analyzing the current state of the vehicle combination 10, the SOE can be used as a reference to predict whether the driver's request will result in a safe vehicle movement. The goal is to create a point in the SOE with the current or future state of the vehicle combination 10 and find a similar existing point that is classified as safe. When such a point is found, the corresponding applied torque T associated with the point is set to the limit of the driver's input. The determined torque T can then be verified using data from actual driving of the vehicle combination.

[0076] The unsimulated state of the vehicle combination 10 may be an unsimulated state of the vehicle combination 10 and / or a simulated state of the vehicle combination 10 having operating parameters different from the simulated state. The unsimulated state is defined by certain current or future parameters of the state (e.g., the same parameters that define the SOE). Specifically, the unsimulated operating state may be defined by the road surface friction coefficient. , the longitudinal speed v of the tractor unit x,1 , the hinge angle between consecutive units , the total applied torque T on the tractor unit, the total applied torque T on the at least one towing unit, the longitudinal coupling force at each coupling point , and the lateral connection force at each connection point is defined by at least one of .

[0077] The received unsimulated state is then applied to the SOE to determine if it is safe, or to determine the torque limit that makes it safe. To ensure that the SOE does not output limits that could result in unsafe driving (i.e., too much or too little torque request), some assumptions are made. Assume that the smaller , larger v x,1 , larger and larger absolute values ​​of T, either alone or in combination, will create more difficult driving scenarios, thus increasing the likelihood of unsafe driving.

[0078] Using the state of the vehicle as a reference, a SOE algorithm (e.g., Algorithm 1 included as an attachment) can find similar data points of equal or greater difficulty level that have been classified as safe. The algorithm does this by methodically filtering out all points that correspond to easier driving scenarios. In order not to limit the performance of the vehicle while also including enough data points for the filtered subset, a small range of selected values ​​for each parameter is used based on the assumptions made previously:

[0079] in is the set of friction coefficients used in the SOE. The algorithm of the SOE will find all safe data points corresponding to the current state of the vehicle, including nearby points based on the assumptions in equations 18 to 20. Only a subset of the entire SOE is retained, and the nearest neighbor method of Euclidean distance is used to find the safe data point closest to the current state. The torque corresponding to the data point is taken as the maximum positive and negative applicable torque of the trailer and T The system limit is returned.

[0080] When implemented in a control system, the SOE works similarly to a lookup table. The state of the vehicle is used as a reference for the first five parameters of the SOE: . These values ​​may be obtained from sensors on the vehicle combination 10, or may be estimated. These parameters determine the corresponding torque limit T. Since the SOE is non-linear, for a single vehicle combination 10 no interpolation between existing points is performed, as this could lead to incorrect assumptions about whether the state is safe or not. Since only safe points in the SOE are of interest when restricting the vehicle combination 10, unsafe points are removed from the SOE to reduce the number of points to be processed, thereby reducing the calculation time of the SOE.

[0081] Algorithm 1 shows the concept of how the SOE can limit the input torque, expressed in pseudo code. The last index of the variables from the current state of the vehicle combination 10 is "s" and the last index of the variables belonging to the SOE is "e".

[0082] The torque limits of unsimulated vehicle combinations can also be determined by interpolating between points in the SOE. For example, the SOE may be based on the simulation of two different vehicle combinations: a 6x4 tractor unit with a 6x6 trailer unit, and a 6x4 tractor unit with a 6x2 trailer unit. There will be data points where the operating conditions are identical except for the number of wheels on each unit. It is then desirable to evaluate a vehicle combination with a 6x4 tractor unit and a 6x4 trailer unit. Since the average number of driven trailer wheels for the simulated vehicle combinations included in the envelope is 4 (one with 6 and one with 2), it can be assumed that the torque limit of the vehicle combination with 4 driven trailer wheels is the average of the torque limits of the simulated vehicle combinations. If there are no simulated data points for a similar vehicle combination that exactly corresponds to the unsimulated state, filtering and nearest neighbor methods can be used to identify suitable points, as discussed above.

[0083] Figure 8 is a flow chart of a method 100 for determining a torque limit for an operating state of a first vehicle combination 10 comprising a tractor unit 12 and at least one towed unit 14. The method may be a computer-implemented method.

[0084] In step 102, multiple operating states of one or more second vehicle combinations 10 are simulated. Simulating multiple operating states may include using a nonlinear high-fidelity mathematical transportation model, as discussed above. Each operating state is based on one or more operating parameters related to the physical characteristics of one of the second vehicle combinations 10, one or more parameters related to the operating environment of the second vehicle combination 10, and one or more parameters related to the driving scenario of the second vehicle combination 10. In order to build a robust SOE, multiple different vehicle combinations in multiple different operating states may be simulated.

[0085] The one or more operating parameters related to the physical characteristics of the second vehicle combination 10 include at least one of the geometry of the second vehicle combination 10, the number of axles 16 of the tractor unit 12, the distance between the axles 16 of the tractor unit 12, the number of axles 18 of the at least one towing unit 14, the distance between the axles 18 of the at least one towing unit 14, the number of motion support devices of the tractor unit 12, the number of motion support devices of the at least one towing unit 14, the cornering stiffness on the tires of the tractor unit 12, the cornering stiffness on the tires of the at least one towing unit 14, the inertia of the tractor unit 12 about the yaw axis, the inertia of the at least one towing unit 14 about the yaw axis, the peak torque output of the electric motor on the tractor unit 12, the peak torque output of the electric motor on the at least one towing unit 14, the axle load on the at least one axle 16 of the tractor unit 12, and the axle load on the at least one axle 18 of the at least one towing unit 14. The one or more parameters related to the operating environment of the second vehicle combination include the road profile and the road surface friction coefficient The one or more parameters related to the driving scenario of the second vehicle combination include the longitudinal speed v of the tractor unit x,1 , at least one articulation angle between consecutive units , the total applied torque T1 on the tractor unit, the total applied torque on the at least one towing unit , longitudinal connection force at each connection point , transverse connection force at each connection point at least one of .

[0086] At step 104, each of the simulated operating states is classified as safe or unsafe. Classifying each of the simulated operating states as safe or unsafe includes determining the result of a driving maneuver defined by the operating state, and if the result of the driving maneuver is an unsafe mode, the operating state is classified as unsafe. Unsafe modes include deviation of the vehicle combination, folding of the vehicle combination, swinging of at least one towing unit, or overturning of the vehicle combination. If the result of the driving maneuver is not an unsafe mode, the operating state is classified as safe. A torque limit can be determined for each of the plurality of simulated operating states to provide a safe operating envelope for the second vehicle combination. The determined torque limit can be verified using data from actual driving of the second vehicle combination.

[0087] At step 106, an unsimulated operating state of the first vehicle combination 10 is received. The unsimulated state may be an operating state of the unsimulated vehicle combination, or an unsimulated operating state of a simulated vehicle combination. That is, the first vehicle combination and the second vehicle combination may be different or the same. The unsimulated operating state of the first vehicle combination is characterized by the road surface friction coefficient , the longitudinal speed v of the tractor unit x,1 , the hinge angle between consecutive units , the total applied torque T on the tractor unit, the total applied torque T on the at least one towing unit, the longitudinal coupling force at each coupling point , and the lateral connection force at each connection point at least one of .

[0088] At step 108, a torque limit for an unsimulated operating state is determined based on the simulated operating state. This may be accomplished by determining the nearest simulated operating state, for example using a nearest neighbor method using Euclidean distance. For an unsimulated vehicle combination, this may be accomplished by interpolating between operating states of two simulated (second) vehicle combinations that are similar to the first vehicle combination.

[0089] The determined torque limit may be applied to the total propulsion load of the plurality of motion support devices of the tractor unit 12 and / or at least one towed unit 14 of the first vehicle combination. The plurality of motion support devices may include a plurality of electric motors configured to drive axles of the vehicle combination 10.

[0090] Fig. 9 900 in which embodiments of the present disclosure may be implemented. The example shows a computer system 900 that can be used in whole, in part, or with various modifications to provide the functionality of the disclosed system. For example, the computer system 900 can control various functions including, by way of example only, simulating, determining, classifying, receiving, and the like.

[0091] The illustrated computer system 900 includes hardware elements that can be electrically coupled via a bus 990. The hardware elements can include one or more central processing units 910, one or more input devices 920 (e.g., a mouse, keyboard, etc.), and one or more output devices 930 (e.g., a display device, a printer, etc.). The computer system 900 can also include one or more storage devices 940. For example, the storage device 940 can be a disk drive, an optical storage device, a solid-state storage device (such as a random access memory ("RAM") and / or a read-only memory ("ROM")), which can be programmable, flash-updatable, and / or the like.

[0092] The computer system 900 may further include a computer-readable storage medium reader 950, a communication system 960 (e.g., a modem, a network card (wireless or wired), an infrared communication device, a Bluetooth™ device, a cellular communication device, etc.), and a working memory 980, which may include RAM and ROM devices as described above. In some embodiments, the computer system 900 may also include a processing acceleration unit 970, which may include a digital signal processor, a dedicated processor, etc.

[0093] Computer-readable storage media reader 950 may also be connected to computer-readable storage media, which together (and optionally, in combination with storage device 940) comprehensively represent remote, local, fixed and / or removable storage devices plus storage media for temporarily and / or more permanently containing computer-readable information. Communication system 960 may allow data to be exchanged with the above-mentioned networks, systems, computers and / or other components.

[0094] The computer system 900 may also include software elements, shown as currently located in the working memory 980, including an operating system 988 and / or other code 984. It should be understood that alternative embodiments of the computer system 900 may have numerous variations that differ from the above-described embodiments. For example, custom hardware may also be used, and / or specific elements may be implemented in hardware, software (including portable software, such as applets), or both. In addition, connections may be made to other computing devices, such as network input / output and data acquisition equipment.

[0095] The software of the computer system 900 may include code 984 for implementing any or all of the functionality of the various elements of the architecture described herein. For example, software stored on and / or executed by a computer system such as the system 900 may provide the functionality of the disclosed system. Methods implemented by software on some of these components have been discussed in detail above.

[0096] Appendix: Algorithm 1 uses the safe operating envelope to limit T

[0097]

Claims

1. A computer implemented method of determining a torque limit for an operating state of a first vehicle combination, the vehicle combination comprising a tractor unit and at least one towed unit, the method comprising: Simulating a plurality of operating states of the one or more second vehicle combinations, wherein each operating state is based on: one or more operating parameters related to physical characteristics of the one or more second vehicle combinations, one or more parameters related to the operating environment of the one or more second vehicle combinations, and one or more parameters related to a driving scenario of the one or more second vehicle combinations; classifying each of the simulated operating states as safe or unsafe; receiving an unsimulated operating state of the first vehicle combination; as well as A torque limit for the non-simulated operating condition is determined based on the simulated operating condition. 2 . The computer-implemented method of claim 1 , wherein simulating a plurality of operating states comprises using a nonlinear high-fidelity mathematical transport model.

3. A computer-implemented method according to claim 1 or 2, wherein the one or more operating parameters related to the physical characteristics of the specific second vehicle combination include at least one of the geometry of the second vehicle combination, the number of axles of the tractor unit, the distance between the axles of the tractor unit, the number of axles of the at least one towing unit, the distance between the axles of the at least one towing unit, the number of motion support devices of the tractor unit, the number of motion support devices of the at least one towing unit, the cornering stiffness on the tires of the tractor unit, the cornering stiffness on the tires of the at least one towing unit, the inertia of the tractor unit about the yaw axis, the inertia of the at least one towing unit about the yaw axis, the peak torque output of the electric motor on the tractor unit, the peak torque output of the electric motor on the at least one towing unit, the axle load on at least one axle of the tractor unit, and the axle load on at least one axle of the at least one towing unit.

4. A computer-implemented method according to any preceding claim, wherein the one or more parameters relating to the operating environment of the particular second vehicle combination include at least one of a road profile and a road surface friction coefficient.

5. A computer-implemented method according to any preceding claim, wherein the one or more parameters associated with the driving scenario of the specific second vehicle combination include at least one of the longitudinal speed of the tractor unit, at least one articulation angle between consecutive units, the total applied torque on the tractor unit, the total applied torque on the at least one towed unit, the longitudinal coupling force at each coupling point, and the lateral coupling force at each coupling point.

6. A computer-implemented method according to any preceding claim, wherein classifying each of the simulated operating states as safe or unsafe comprises determining an outcome of a driving maneuver defined by the operating state.

7. A computer-implemented method according to claim 6, comprising classifying the operating state as unsafe if the result of the driving maneuver is an unsafe mode, wherein the unsafe mode includes at least one of deviation of the vehicle combination, folding of the vehicle combination, swinging of at least one towing unit, or rollover of the vehicle combination.

8. A computer-implemented method according to claim 6 or 7, comprising classifying the operating state as safe if the result of the driving maneuver is not an unsafe mode.

9. A computer implemented method according to any preceding claim, comprising determining torque limits for the plurality of operating states of the second vehicle combination to provide a safe operating envelope for the second vehicle combination.

10. A computer implemented method according to any preceding claim, further comprising validating the determined torque limit using data from actual driving of the second vehicle combination.

11. A computer-implemented method according to any preceding claim, wherein receiving the unsimulated operating state of the first vehicle combination comprises receiving an unsimulated operating state of a vehicle combination and / or receiving an unsimulated operating state of a simulated vehicle combination.

12. A computer-implemented method according to any preceding claim, wherein the unsimulated operating conditions include at least one of a road surface friction coefficient, a longitudinal speed of the tractor unit, an articulation angle between consecutive units, a total applied torque on the tractor unit, a total applied torque on the at least one towed unit, a longitudinal coupling force at each coupling point, and a lateral coupling force at each coupling point for the unsimulated operating conditions.

13. A computer implemented method according to any preceding claim, wherein determining the torque limit for the unsimulated operating state comprises determining a closest simulated operating state.

14. A computer implemented method according to any preceding claim, wherein determining the torque limit for the unsimulated vehicle combination comprises interpolating between operating states of two similar simulated vehicle combinations.

15. A computer implemented method according to any preceding claim, further comprising applying the determined torque limit to a total propulsion load of a plurality of motion support devices of the tractor unit and / or the at least one towed unit.

16. The computer-implemented method of claim 15, wherein the plurality of motion support devices comprises a plurality of electric motors.

17. A computer readable medium having stored thereon instructions which, when executed by one or more processors, cause the method steps of any one of claims 1 to 16 to be performed.

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