Method and sensor device for vehicle operation based on wheel torque

Abstract

The disclosure relates to a method of operating a vehicle based on wheel torque. According to a first aspect, the present disclosure presents a method for operating a vehicle including a driveline. The method comprises determining S2 a twist of one or more shafts of the driveline based on angular positions of the one or more shafts at different points along the driveline. The method further comprises estimating S3 a wheel torque of one or more wheels arranged on a driven axle 11 of the vehicle based on the determined torsion and a stiffness constant representative of a characteristic of the one or more axles 11a, 11b between the different points, and using S7 the estimated wheel torque when operating the vehicle. The disclosure also relates to a corresponding sensor device 200 and a computer program, and a vehicle comprising said sensor device.

Description

Technical Field

[0001] The present disclosure relates to a method for operating a vehicle based on wheel torque. The present disclosure also relates to a corresponding sensor device and a computer program, and a vehicle comprising the sensor device. Background Art

[0002] Traditionally, torque control of the powertrain is based on an estimated torque of the engine output shaft, which can be calculated based on the power consumed (such as electricity) or the fuel consumed. However, in battery electric vehicles (where there is less damping in the powertrain due to the lack of mechanical components such as the engine, gearbox, clutch), it is important to take into account the increased stiffness to avoid oscillations and poor powertrain torque performance. For example, vibrations may cause unnecessary stress on different powertrain parts and thus reduce powertrain life. In general, this problem is more significant in more efficient modern transmission systems, such as electric transmission systems that lack a gearbox, because the reduced friction in the transmission system increases the risk of oscillations. This is particularly important for vehicles in extreme applications (such as construction vehicles or mining vehicles).

[0003] By making wheel speed signals from the braking system and other axle sensors directly accessible in real time to the torque controller (often called an inverter), some of the oscillations and performance degradation in the oscillations can be reduced. However, further improvements are needed in this area. Summary of the invention

[0004] The object of the present disclosure is to alleviate at least some of the disadvantages of the prior art. In particular, the object is to provide a method for eliminating nonlinearities in a powertrain. These and other objects are at least partially achieved by methods and sensor devices according to the independent claims and by embodiments according to the dependent claims.

[0005] According to a first aspect, the present disclosure provides a method for operating a vehicle including a drive train. The method includes determining the torsion of one or more shafts of the drive train based on the angular position of one or more shafts at different points along the drive train. The method also includes estimating the wheel torque of one or more wheels arranged on a driven axle of the vehicle based on the determined torsion and a stiffness constant representing the characteristics of the one or more shafts between the different points, and using the estimated wheel torque when operating the vehicle. By estimating the wheel (angular) position rather than the wheel speed, the wheel torque can be calculated directly. The estimated wheel torque can be used in various applications to improve vehicle efficiency, comfort and quality.

[0006] In some embodiments, the method includes measuring the angular position using an angular position sensor arranged along the driven wheel axle, and wherein the determining includes determining the torsion of the driven wheel axle based on the angular displacement between the measured angular positions. By measuring the torsion of the driven wheel axle, an accurate estimate of the wheel torque can be made.

[0007] In some embodiments, the measurements are performed continuously while the vehicle is operating.By continuously monitoring the angular position of the shafts of the drive train, performance can be continuously optimized and defects detected.

[0008] In some embodiments, the angular position is provided by a plurality of first sensors arranged to measure the angular position of the wheels arranged on the driven axle and at least one second sensor arranged to measure the angular position at the differential gear arranged centrally at the driven axle. This is one example of how the angular position sensors can be arranged along the driven axle.

[0009] In some embodiments, at least one second sensor is arranged to measure the angular position of the drive gear and / or the angular position of the side gears of the differential gear.Thus, the angular position sensor may be arranged to measure various angular positions within the differential gear.

[0010] In some embodiments, the determining includes: determining the torsion of the entire driven wheel axle based on the difference between the observer angle and the angular position of the driving gear of the differential gear when the differential gear is open, wherein the observer angle is an average of the angular positions of the right wheel and the left wheel arranged at opposite ends of the driven wheel axle; and estimating the wheel torques of the left and right wheels based on the combined stiffness constant of the entire driven wheel axle and the torsion of the entire driven wheel axle. In this way, the wheel torque can be estimated based on the torsion of the entire differential using only three angular position sensors.

[0011] In some embodiments, the method includes determining the torsion of one side of the driven axle, and estimating the wheel torque of one or more wheels arranged on one side based on the stiffness constant of the one side of the driven axle and the torsion of the one side. Thus, alternatively, the torsion may be estimated at one side of the driven axle at a time. Thus, as an example, the torsion at the left side of the driven axle may be estimated first, and then the torsion of the right side of the driven axle may be estimated.

[0012] In some embodiments, the method includes determining the torsion of one side based on the difference between the angular position of the wheel arranged at one side and the angular position of the drive gear when the differential gear is closed. Thus, if the differential is closed, the torque is estimated separately for each side.

[0013] In some embodiments, the method includes determining the torsion of one side based on the difference between the angular position of the wheel arranged at one side and the angular position of the side gear of the differential gear at one side. In this way, the wheel torque can be estimated for one side of the driven axle.

[0014] In some embodiments, the method includes determining a stiffness constant based on the size and material of one or more shafts of the drive train between different points. Thus, the stiffness constant can be calculated based on knowledge of the material and shape of the shaft.

[0015] In some embodiments, the method includes determining the stiffness constant in a test environment by applying a predetermined torque to one or more shafts of the drive train and measuring the resulting angular displacement of the ends of the one or more shafts. Thus, the stiffness constant may also be revealed experimentally.

[0016] In some embodiments, the use includes operating the vehicle and / or diagnosing the vehicle based on the estimated wheel torque.Thus, there are many applications in which the estimated wheel torque can be used.

[0017] In some embodiments, the use includes controlling the engine to apply drive torque on the driven axle based on the estimated wheel torque.Thereby, performance and comfort can be optimized.

[0018] In some embodiments, control is performed based on one or more of comfort criteria, tear / wear criteria, performance criteria. Thus, various criteria may be applied to wheel torque to achieve various advantages.

[0019] In some embodiments, the control includes increasing or decreasing the drive torque when the wheel torque approaches zero, so that a rapid zero crossing is achieved. Thus, oscillations in the driveline can be avoided.

[0020] In some embodiments, the method includes estimating the damping of a gearbox of the vehicle by comparing the determined wheel torque to the drive torque of the engine. The damping may be used to diagnose the gearbox.

[0021] In some embodiments, the method comprises controlling the drive torque applied by the engine when changing gears based on the estimated damping of the gearbox.Thereby, wear and oscillations can be avoided.

[0022] In some embodiments, the method includes estimating a drive torque of an engine of a vehicle; measuring a wheel speed of a wheel of a driven axle using a wheel speed sensor;

[0023] And wherein the use includes estimating the efficiency of the vehicle's powertrain based on the drive torque of the vehicle's engine, the measured wheel speed and the estimated wheel torque of the driven axle. Therefore, the estimated wheel torque can be used to evaluate the power efficiency of the vehicle.

[0024] In some embodiments, the use includes estimating the slip of one or more wheels of the driven axle at a plurality of separate time points; and estimating the tire-road friction coefficient c by analyzing the slip for different estimated wheel torques τ. Thus, the estimated wheel torques can be used to estimate the friction between the wheels and the surface on which the vehicle stands or drives.

[0025] According to a second aspect, the present disclosure relates to a sensor arrangement for operating a vehicle comprising a drive train. The sensor arrangement comprises an angular position sensor and a control arrangement. The angular position sensor is arranged to measure the angular position of one or more shafts of the drive train at different points along the drive train.

[0026] The control device is configured to: determine the windup of one or more shafts of the driveline based on the angular positions provided by a plurality of angular position sensors; estimate the wheel torque of one or more wheels arranged on the driven axle based on the determined windup and a stiffness constant of the driven axle representing the characteristics of the one or more shafts between the angular position sensors; and use the estimated wheel torque when operating the vehicle. In further embodiments, the control device is configured to perform the method according to any one of the embodiments of the first aspect.

[0027] According to a third aspect, the present disclosure relates to a vehicle comprising the sensor arrangement of the second aspect.

[0028] According to a fourth aspect, the present disclosure relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to perform the method according to the first aspect.

[0029] According to a fifth aspect, the present disclosure relates to a computer-readable medium comprising instructions, which, when executed by a computer, cause the computer to perform the method according to the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The drive train of the vehicle is shown as seen from above.

[0031] Figure 2 The torsion of a shaft of the drive train is shown.

[0032] Figure 3 The driven axle is shown.

[0033] Figure 4 The differential gear is shown.

[0034] Figure 5 is a flow chart of the proposed method according to the first aspect.

[0035] Figure 6 The steps of using the estimated wheel torque are shown in more detail ( Figure 5 An example implementation scheme of ).

[0036] Figure 7 A control device configured to carry out the method is shown.

[0037] Figure 8 The correlation between rear axle torque and slap risk is shown.

[0038] Fig. 9 Some example friction coefficients that can be determined using wheel torque are shown. DETAILED DESCRIPTION

[0039] The proposed technique is based on the realization that wheel torque can be directly calculated by measuring the continuous angular position of the wheel of the driven axle, rather than the wheel speed, and comparing the wheel angle with other angles in the drive train. In other words, a good estimate of wheel torque can be obtained based on the angular difference at one or more parts of the drive train with well-known stiffness.

[0040] The estimated wheel torque can be used, for example, as a feedback signal to a torque controller (also called an inverter) of the electric machine of the powertrain. By allowing the inverter to control directly toward the angular position of the wheel or wheel torque, disturbances (torsion) and nonlinearities in the powertrain can be eliminated. In addition, the inventors have realized that the estimated wheel torque can be used for other purposes to achieve other effects.

[0041] Now refer to Figures 1 to 7 Describe the proposed technique. Figure 1 A powertrain of a vehicle is shown in which the proposed technique for operating a vehicle may be implemented.A vehicle may include a device for transportation in a broad sense, and may be, for example, a bus, a truck or other similar manned or unmanned vehicle.

[0042] A vehicle consists of many electrical systems and subsystems. However, for simplicity, Figure 1 Only some of the parts of a vehicle associated with the proposed technology are shown in FIG. The powertrain includes an engine 14 and a drive train 100, or transmission system. The drive train 100 is basically a mechanical system within a vehicle that connects the vehicle's engine 14 with wheels 15. The drive train 100 shown includes a driven axle 11, a gearbox 12, a differential gear 13, a plurality of sensors 16, and a control device 10.

[0043] The driven axle 11 in this context refers to the axle of the driven wheels of the vehicle. The driven axle 11 comprises one or more shafts, here a left shaft 11a and a right shaft 11b. In the example shown, the driven axle 11 is a split axle, in which a differential gear 13 is arranged between the two axle halves.

[0044] The differential gear 13 is a device that allows power from an engine 14 to be transferred to a pair of drive wheels 15. The gearbox 12 is arranged to transfer energy from the engine 14 and is used to increase or decrease torque when reducing or increasing speed. The engine 14 is an electric motor here, but it should be understood that the proposed technology can be used for any type of engine.

[0045] The angular position sensor 16 is an electromechanical device that measures mechanical rotation and converts it into an electrical signal. The angular position sensors 16a, 16b are arranged to measure the angular position of one or more shafts of the transmission system 100 at different points along the transmission system 100. When the shaft of the transmission system rotates around the axis of rotation, the angular position refers to the rotational orientation of the shaft relative to a specified reference position. The angular position is expressed as the amount of rotation in radians (degrees, turns) around the axis of rotation required to change to the reference position. For example, the angular position is measured by a gear sensor with a specific reference position.

[0046] Angular displacement refers to the difference between two angular positions. Angular displacement is a vector quantity, which means that the angular displacement has a magnitude and a direction associated with it. For example, a gear sensor is used that is arranged on the shaft of the transmission 100. The gear sensor can, for example, include two Hall effect sensors, a rare earth magnet and appropriate evaluation electronics. The magnetic field of the magnet is modulated by the target tooth passing by. This modulation is recorded by the Hall sensor, converted into a square wave signal by the comparator stage, and amplified at the driver stage. The signal also includes additional position information about the position of the gear in the cycle, such as one or more long pulse indications caused by one or more long teeth on the gear positioned at a predetermined position on the gear. By continuously measuring the angular position, a new reference point can be introduced for part of the transmission or the entire transmission when the coupling in the transmission may change when necessary.

[0047] In the example shown, the angular position sensors 16a, 16b are arranged along the driven axle 11 , but in some embodiments, the angular position sensors 16a, 16b are arranged along other axes of the driveline 100 , such as closer to the engine 14 .

[0048] The control device 10 is configured to carry out the proposed method for operating a vehicle. Figure 7 The control device 10 is described in more detail in . The control device 10 and the angular position sensors 16a, 16b form the proposed sensor device 200 for operating a vehicle.

[0049] The proposed technique estimates wheel torque based on measuring the torsion of the driven wheel axle 11. Torsion occurs when the ends of the axle rotate at different speeds. In a completely rigid driven wheel axle 11, the two ends would rotate synchronously. However, because the shafts 11a, 11b are somewhat elastic,

[0050] In practice there will be an angular difference, albeit very small, between the ends of the shafts 11a, lib.Thus, driveline twist is caused by twisting of the shafts of the driveline caused by, for example, engine or brake torque. Figure 2 The torsion of the shafts 11a, 11b of the driven axle 11 is shown. The angular difference a between the ends 101 of the driven axle 11 is the torsion caused by the torque applied to the respective ends, by friction or braking torque on one side and engine torque on the other side.

[0051] Figure 3 Shown in more detail Figure 1 The driven wheel axle 11 of the transmission system 100 in the differential gear 13. The driven wheel axle 11 includes two shafts 11a, 11b arranged on each side of the differential gear 13. An angular position sensor (not shown) is arranged along the driven wheel axle 11. The angular position sensor is arranged to measure the angular position at different points 101 (represented as a (left wheel), b (right wheel), co (center observer), cl (center-left), cr (center-right)) along the driven wheel axle 11. Point 101 is usually arranged close to the end of each shaft 11a, 11b. Therefore, the angular position sensor is arranged to measure the angular position at points 101a, 101b close to the outer ends of the shafts 11a, 11b where the wheels 15 are arranged. In other words, a plurality of first sensors 16a are arranged to measure the angular position α of the wheels 15 arranged on the driven wheel axle 11. L , α R In other words, measure the angular position α of the left wheel L and the angular position of the right wheel α R It will be understood that this means that the angle is measured at the wheel 15 or close to the connection between the axle and the wheel 15 .

[0052] Furthermore, the angular position sensor is arranged to measure the angular position at one or more points 101c-r, 101c-l, 101c-o close to the inner end of the shaft 11a, 11b, such as the angular position at the differential gear 13. In other words, at least one second sensor (not shown) is arranged to measure the angular position α at the differential gear 13 arranged centrally at the driven wheel shaft 11. C .

[0053] Figure 4The angular sensor placement at the differential gear is shown in more detail. The differential gear includes a drive gear 13a or crown gear, and a housing 13e connected thereto. The drive gear 13a is driven by a differential input shaft 13f. The differential also includes a differential pinion 13c arranged on a differential pin 13d, wherein the differential pin 13d is connected to the differential housing 13e. The differential gear 13 includes a left side gear and a right side gear, the left side gear being mounted on the left shaft 11a for common rotation, and the right side gear being mounted on the right shaft 11b for common rotation. Differential gears are well known in the art and therefore will not be described in detail.

[0054] In order to measure the angular position at the inner ends of the shafts 11a, 11b of the driven wheel axle 11, the angular position sensor should be arranged to measure the angular position of a part of the differential that rotates at the same speed as the ends of the shafts, or at least a known relationship between the speeds is required. If the differential gear 13 is locked, the drive gear 13a and the side gears 13b will all rotate at the same speed. Therefore, in this case, the angular position sensor 16 can be arranged to measure the angular position α of the drive gear 13a of the differential gear 13 C and / or the angular position α of the side gear 13b CL , α CR However, if the differential is open, it is a bit more complicated and there are different options as will be described below.

[0055] Now refer to Figure 3 and Figure 4 The estimation of wheel torque based on the angular position of one or more shafts 11a, 11b of the driveline 100 at different points 101 along the driveline 100 is described in more detail. In this example, sensors are arranged at the wheels 15 and at the differential 13. However, it must be understood that other sensor placements are possible. However, it is generally desirable to measure as close to the wheels 15 as possible.

[0056] Based on the assumption that the mass of the shafts 11a, 11b and the friction in the differential gear 13 are negligible, the torque applied at / by the ends of the shafts for a stationary situation can be calculated, where the torque is equal at both ends of the respective shafts. More specifically, Hooke's law (Equation 1) can be applied, which gives that the torque τ required to wind up the shaft is proportional to the angular displacement α.

[0057] τ=k*α (1)

[0058] The proportionality constant (referred to herein as the stiffness constant k) is based on the characteristics, such as size and material, of the one or more axes 11a, 11b between the points 101 at which the displacement α is measured. The stiffness constant k (often referred to as the elastic constant) represents the elastic behavior of the object (here the body between the points at which the angular position is measured).

[0059] Therefore, for a locked differential, the angular position α of the drive gear 13a is C The angular position α of one of the side gears 13b is CL , α CR are the same because they all rotate at the same speed. Therefore, for a locked differential there is only one center angle, denoted α for simplicity. C .

[0060] For a locked differential gear 13 having only one center point 101c, equation (2) can be used to estimate the wheel torque:

[0061] τ x =k rax *(α x -α c ) (2)

[0062] Since the input torque is not evenly distributed between the wheels 15, but depends on the friction on the wheels 15, a torque τ must be applied to the left and right wheels separately. L , τ R Estimates.

[0063] For an open differential, the torque is evenly split between the two shafts 11a, 11b. Therefore, the rotational speed of the side gear 13b will depend on the friction torque applied to the wheels 15. Therefore, the angle within the differential will change based on the change in resistance between the wheels 15.

[0064] One option is to use two angular position sensors 16, one at each side gear 13a. In other words, it is possible to use the angular position α of the wheel 15 arranged at one side (L or R) based on the angular position α of the wheel 15 arranged at one side (L or R). L , α R and the angular position α of the side gear 13a of the differential gear 13 at one side (L or R) CL , α CR to calculate the twist on one side (left L or right R) of the driven axle 11. The wheel torque can then be estimated for one side using equation (3), and it can be assumed that the torque on the other wheel 15 is the same.

[0065] τ x =k rax *(α x -α cX ) (3)

[0066] Alternatively, the observer angle α representing the two axes O It can be defined by equation (4). Observer angle α O is the angular position α of the right wheel arranged at the opposite end of the driven wheel shaft 11 Rand the angular position α of the left wheel L In other words, the observer angle represents the average twist of the shafts 11a, 11b.

[0067] α O =(α L -α R ) / twenty four)

[0068] Due to the parallel coupling of the shafts 11a, 11b in the differential gear, the wheel torque can then be estimated based on the torsion of the entire driven wheel shaft 11. Due to the parallel coupling, the proportionality constant (herein referred to as the stiffness constant k) of the entire driven wheel shaft 11 will then correspond to the sum of the individual shafts 11a, 11b, see equation (5).

[0069] k ra =k raL +k raR (5)

[0070] Hooke's law can then be applied to the entire axle to estimate the wheel torque T applied to each of the wheels 15 using equation (6) L,R, .

[0071] τ L,R =k ra *α O (6)

[0072] Figure 5 is a flow chart of a proposed method for operating a vehicle including a transmission system 100 according to the first aspect. The method is performed by a control device 10 ( Figure 1 and Figure 7 ) is executed, and the control device can be arranged on the vehicle and / or outside the vehicle. The control device 10 is, for example, an ECU of an inverter that controls the torque of the engine 14. The method is usually executed in a continuous manner when operating the vehicle 1.

[0073] The method may be implemented as a computer program including instructions, when the program is executed by a computer (e.g., the control device 10 ( Figure 7 ) when executed by a processor in the computer program, these instructions cause the computer to implement the method. According to some embodiments, the computer program is stored in a computer-readable medium (e.g., a memory or a CD) comprising instructions, and when executed by a computer, these instructions cause the computer to implement the method.

[0074] As explained above, the wheel torque is estimated based on a stiffness constant representing the characteristics of one or more shafts 11a, 11b of the drive axle 11. The stiffness constant can be obtained in a variety of ways. The stiffness constant can then be preconfigured in the vehicle, such as in the memory 102 of the control device 100 ( Figure 7) pre-configured. This can be done during manufacture or at a later point in time. There can be one stiffness constant that represents the characteristics of the entire axle, or there can be multiple stiffness constants that represent various parts of the axle. The method is described here for the driven wheel axle 11, but it must be understood that the method can be carried out for several axles in parallel, such as a driven bogie axle.

[0075] One method of obtaining the stiffness constant is to calculate the stiffness constant based on the size and material of the shaft. In some embodiments, the method includes determining the S0 stiffness constant based on the size and material of one or more shafts 11a, 11b of the transmission system 100 between different points 101.

[0076] Another possibility is to simply perform a stress test in which the shaft is wound in a controlled environment. The stiffness constant can then be calculated based on the angular displacement caused by the known torque. If many vehicles use the same shaft design, this test experiment can be performed once and the same value can be used for several vehicles. In other words, in some embodiments, the method includes determining the S0 stiffness constant in a test environment by applying a predetermined torque to one or more shafts of the powertrain 100 and measuring the resulting angular displacement of the ends of the one or more shafts.

[0077] In an initial step of the proposed method, the control device 10 obtains angular measurement data, i.e. sampled sensor values, from angular position sensors 16a, 16b arranged at different points 101 along the transmission system 100. The angular measurement data indicates the angular position sensed by the sensors 16a, 16b. In the example in this article, the position sensors 16a, 16b are arranged along the driven wheel axle 11, but other deployments are also possible. However, the closer the angular position sensors 16a, 16b are placed to the wheel 15, the better the expected accuracy. In other words, in some embodiments, the method includes measuring the angular position of one or more shafts 11a, 11b of the S1 transmission system 100 using angular position sensors 16a, 16b arranged along the transmission system, and in particular along the driven wheel axle 11.

[0078] The angular position of the transmission system 100 can be monitored in a continuous manner, such as in real time. In other words, in some embodiments, the measurement S1 is performed continuously while the vehicle is operating. For example, the angular position is continuously sampled at certain intervals. Thus, the winding of the driven wheel axle can be studied in a continuous manner, such as in real time.

[0079] The idea is based on the recognition that, as explained above, the measured angular position can be used to determine the wheel torque. In other words, the method comprises determining S2 the winding of one or more shafts 11a, 11b of the drive train 100 based on the angular position of the one or more shafts 11a, 11b at different points 101 along the drive train 100. For example, determining S2 comprises determining the angular displacement α between the measured angular positions based on the angular displacement α between the measured angular positions. Δ To determine the torsion of the driven wheel shaft 11.

[0080] Hooke's law can then be used to estimate the wheel torque on one or more of the wheels of the vehicle. Thus, the method comprises estimating S3 the wheel torque τ of one or more wheels 15 arranged on a driven axle 11 of the vehicle 1 based on the determined wind-up α and a stiffness constant k representative of the characteristics of the one or more shafts 11a, 11b between different points 101.

[0081] The torsion may be determined for the entire axle, such as for the entire driven axle 11, or for individual portions of the driven axle 11, such as for the left and right axles 11a and 11b. Alternatively, the torsion of other portions of the driven axle may be determined.

[0082] In one exemplary embodiment, the estimation S3 of the wheel torque is based on a joint calculation of the torsion of the entire axle with an open differential as explained above. In other words, in these embodiments, the determination S2 comprises, when the differential gear 13 is open, calculating the wheel torque based on the observer angle α O and the angular position α of the drive gear 13a of the differential gear 13 C The difference between the two determines S2, the torsion of the entire driven wheel shaft 11. As explained above, the observer angle α O is the angular position α of the right wheel arranged at the opposite end of the driven wheel shaft 11 R and the angular position α of the left wheel L Then, based on the combined stiffness constant k of the entire driven wheel shaft 11 ra and the torsion of the entire driven wheel shaft 11, the wheel torque τ of the left and right wheels is estimated S3.

[0083] In other example embodiments, the estimation S3 of the wheel torque is based on the torsion of a portion of the driven axle 11, such as for the left and right sides of the differential gear 13, respectively. In other words, in these embodiments, the determination S2 includes determining the torsion of one side of the driven axle 11. Then, based on the stiffness constant k of one side raL k raR and the torsion of one side (left or right) of the driven wheel axle 11, the wheel torque τ of one or more wheels arranged on one side is estimated S3.

[0084] If the differential gear is locked, only one angular position sensor 16 can be used to estimate the wheel torque of the two wheels 15. Therefore, in some embodiments, the method includes, when the differential gear is closed, based on the angular position α of the wheel arranged at one side. L , α R and the angular position α of the drive gear 13a C The difference between the two determines the torsion of one side. In this case, the angular position α of the drive gear 13a is C is equal to the angular position of any of the side gears 13b. Therefore, only one sensor is required. Although an estimate must be made for each wheel, when the differential 13 is locked, the torque is not evenly divided by the differential.

[0085] If the differential gear 13 is open, two sensors arranged centrally on the driven wheel axle are required to determine the torsion on the left and right sides, respectively, since the wheels 15 may rotate at different speeds depending on the friction. In the example shown, a sensor arranged to measure the angular position α of the corresponding side gear 13 b is used. CL , α CR In these embodiments, the determination S2 comprises determining the angular position α of the wheels arranged at one side. L , α R and the angular position α of the side gear 13a of the differential gear 13 at one side C The torsion of one side is determined by the difference between α and α, as explained above. Then, based on the angular position α of the wheel arranged at one side, L , α R and drive gear α C The angular position α L The difference between the values ​​of τ and τ is used to estimate S3 the wheel torque τ of one or more wheels arranged on one side.

[0086] Further measurements and estimates may be performed for use in conjunction with wheel torque for various purposes. In some embodiments, the method includes estimating S4 the drive torque of the vehicle engine 14. For example, the drive torque of an electric engine is estimated based on the applied voltage and the drawn current. The power of an internal combustion engine may be estimated based on the injected fuel.

[0087] In addition to wheel torque, wheel speed is usually measured. If gear sensors are arranged at the wheels, they can also be used to measure wheel speed. In some embodiments, the method includes measuring S5 the wheel speed of the wheel 15 of the driven wheel axle 11 using a wheel speed sensor 6. In addition, the wheel speed of the freewheeling wheel can also be measured.

[0088] In some embodiments, the method comprises estimating at a plurality of individual points in time the slip S6 of one or more wheels 15 of the driven axle 11. For example, the slip is measured by comparing the wheel speeds of the driven wheel and the freewheeling wheel.

[0089] The estimated wheel torque can then be used for a variety of different applications. In other words, the method includes using the wheel torque τ estimated in S7 when operating the vehicle. In other words, the wheel torque can be used to perform one or more actions or activities related to the vehicle. For example, the operation of the vehicle and / or the diagnosis of the vehicle is based on the estimated wheel torque τ.

[0090] Figure 6 The steps of using the wheel torque τ estimated by S7 when operating the vehicle are shown in more detail. In a first example embodiment, the wheel torque is used to optimize comfort, tear and performance associated with propelling the vehicle. In other words, in some embodiments, the use includes controlling S7a engine to apply drive torque on the driven wheel axle 11 based on the estimated wheel torque. This is typically done using an inverter that controls the torque of the engine 14. Various criteria can be defined to optimize, for example, comfort, tear and performance. For example, by allowing the inverter to control directly towards the wheel position, such as in autonomous driving, better driving precision can be achieved.

[0091] Additionally, vibrations in the driveline 100 may occur when internal torque in the powertrain changes sign / direction, such as during tip-in / tip-out (i.e., when starting to push or releasing the accelerator pedal). Internal torque depends on friction, and therefore many factors will affect vibrations. However, internal torque can be summarized by monitoring the rear axle torque corresponding to the wheel torque. Figure 8 The correlation between the rear axle torque and the risk of slapping is shown as a dashed area 81 corresponding to the wheel torque associated with the risk of vibration. Through torque control, one can limit the time that the applied torque (shown by curve 82) is within the dashed area 81 to mitigate the slapping that causes comfort issues, in which dashed area there is a risk of slapping. This basically means that when the rear axle torque approaches this area, the engine torque should be adjusted to pass through this area as quickly as possible. This means that oscillations in the powertrain can be damped and offset to provide a truly seamless / smooth acceleration experience and also improve performance. In other words, in some embodiments, control S7a of the engine is performed based on comfort and / or performance criteria. In some embodiments, control S7a includes increasing or decreasing the drive torque when the wheel torque approaches zero, so that a rapid zero crossing is achieved.

[0092] The estimated wheel torque can also be used to avoid driving conditions that impose unnecessary stress on different powertrain parts and thus reduce the life of the powertrain. This is particularly important for vehicles in extreme applications (such as construction vehicles or mining vehicles). In case of large deviations between the angular positions at different points along the drive train, the stresses are generally high. Under certain combinations of wheel torque, gear, temperature, wheel speed, etc., a tearing risk may occur. Criteria can be defined to avoid this situation. In other words, in some embodiments, the control S7a of the engine is performed based on a tear / wear criterion.

[0093] Wheel torque can also be used to estimate the damping of the gearbox 12. The damping of the gearbox 12 can be determined by comparing the wheel torque and the torque before the gearbox 12, such as by the engine torque. When the components of the gearbox 12 wear, the damping may increase. Therefore, the gearbox can be diagnosed based on the wheel torque. In other words, in some embodiments, using S7 includes diagnosing the damping of the gearbox 12 of the S7b vehicle by comparing the determined wheel torque and the driving torque of the engine (estimated in step S4).

[0094] It is also often desirable to change gears without torque in the drive train. Today, this is usually done when the engine torque is zero. However, there is a risk that the friction in the gearbox 12 drags around the motor. For example, the damping of the gearbox is estimated by comparing a wheel torque of 900Nm and an engine torque of 1000Nm. The damping is therefore 100Nm. When changing gear, an engine torque of 100Nm should be applied to achieve zero torque on the rear axle. In other words, in some embodiments, the method includes controlling the drive torque applied by the engine 15 based on the estimated damping of the gearbox 12 when changing gear.

[0095] The estimated wheel torque can also be used to diagnose components of the powertrain 100. In some embodiments, the power at the wheel can be calculated based on the estimated wheel torque in combination with the measured wheel speed (step S5). The difference between this power and the input power (i.e., the DC current / voltage of the EV and the fuel consumption of the internal combustion engine) shows the real-time efficiency of the entire powertrain. This efficiency can be used to ensure that certified powertrain performance is met, similar to the on-board diagnostic OBD monitor currently used. This may be important because powertrain efficiency may be the subject of future CO2 emissions requirements and other legislation.

[0096] The real-time efficiency of the powertrain 100 can be presented to the driver, for example as an input similar to today's OBD. This may be a legal requirement for future vehicles / powertrains. In other words, in some embodiments, using S7 includes estimating S7c the efficiency of the powertrain of the vehicle based on the drive torque of the vehicle's engine 14 (estimated in step S4), the measured wheel speed (estimated in step S5) and the estimated wheel torque of the driven axle 11.

[0097] As a further example, the friction between the surface and the wheel can be estimated by measuring the slip of the driven axle in combination with the torque of the driven axle (step S6). Compared with deriving the wheel torque from the engine 14, this method will give more accurate results because there is no need to consider as many uncertainties for this method.

[0098] Furthermore, reduced efficiency can be used as an indication that something is malfunctioning in the powertrain 100. In other words, wear, tear, or other errors can be detected by studying the changes in the powertrain efficiency over time. This can also be a safety measure, because if a large amount of energy generated by the electric motor does not go to the wheels, this difference may be converted into heat somewhere in the powertrain 100, which may lead to fatal errors over time. Therefore, if the powertrain efficiency falls below a safe threshold, there may be a warning indicating that the vehicle should be taken to a service station immediately.

[0099] Another possible use relates to the estimation of the friction coefficient of the wheel. As is well known, the friction between the surface and the wheel 15 can be estimated by measuring the slip of the wheel 15 arranged on the driven axle (step S6) and in combination with the estimated wheel torque of the driven axle 11. Today, friction is usually measured based on the wheel torque derived from the engine 14. However, by using the proposed method for estimating wheel torque, the wheel force can be calculated, which gives the possibility of estimating the friction coefficient more accurately and in real time. This is certainly important during acceleration, but it may be more important as a traction control input to an autonomous vehicle. In other words, in some embodiments, using S7 includes estimating the tire-road friction coefficient S7d by comparing the slip at various points in time (estimated in step S6) with the estimated wheel torque of the wheel of the driven axle 11. Fig. 9 An example of how the coefficient of friction may be estimated based on measurements 91 of slip (x-axis) and estimated torque (y-axis) at various points in time is shown. Fig. 9In the embodiment, two sets of measurements m1, m2 are recorded and plotted as different theoretical friction curves μ. Therefore, by measuring the slip for different estimated wheel torques τ (such as at different time points) (step S6), a matching friction coefficient μ can be found. In other words, in some embodiments, using S7 includes estimating the tire-road friction coefficient S7d by analyzing the slip for different estimated wheel torques τ.

[0100] Figure 7 A control device 10 configured to implement the proposed method for operating a vehicle is shown in more detail. In some embodiments, the control device 10 is a "unit" in a functional sense. Thus, in some embodiments, the control device 10 is a control device comprising several physical control devices that operate together. The control device can be arranged on board the vehicle and / or at least partially outside the vehicle.

[0101] The control device comprises a processor 104 and a memory 102. The control device 10, or more specifically the processor 104 of the control device 10, is configured to cause the control device 10 to perform all aspects of the method described above and below. This is usually accomplished by running a computer program code P stored in a data storage device or memory 102 in the processor 104 of the control device 10. The memory 102 may also be configured to store various relevant parameters, such as standards for driving torque and stiffness constants for controlling the transmission system 100.

[0102] The control device 10 may further include a communication interface 103 for communicating with other control units of the vehicle (eg, via an ECU) and / or with an external system, such as an off-board server.

[0103] More specifically, the control device 10 is configured to determine the winding of one or more shafts of the drive train based on the angular positions provided by the plurality of angular position sensors 16a, 16b.

[0104] The control device 10 is also configured to estimate the wheel torque τ of one or more wheels 15 arranged on the driven wheel axle 11 based on the determined torsion α and the stiffness constant k of the driven wheel axle 11, represent the characteristics (such as shape, size and material) of one or more shafts 11a, 11b between the angular position sensors 16a, 16b, and use the estimated wheel torque τ when operating the vehicle.

[0105] The terminology used in the description of the embodiments as illustrated in the accompanying drawings is not intended to be limiting of the described methods, control apparatus or computer programs. Various changes, substitutions and / or alterations may be made without departing from the embodiments of the present invention as defined in the appended claims.

[0106] As used herein, unless otherwise expressly stated, the term "or" should be interpreted as a mathematical OR, i.e., as an inclusive disjunction, and not as a mathematical exclusive or (XOR). In addition, the singular forms "a", "an" and "the" should be interpreted as "at least one", and therefore may also include multiple entities of the same type, unless otherwise expressly stated. It should also be understood that the terms "include", "comprise" and / or "contain" specify the presence of stated features, actions, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, actions, integers, steps, operations, elements, components and / or their groups. A single unit such as a processor can implement the functions of several items listed in the claims.

Claims

1. A method for operating a vehicle comprising a drive train (100): - determining (S2) the winding of one or more shafts (11a, 11b) of the drive train (100) based on the angular position of the one or more shafts (11a, 11b) at different points (101) along the drive train (100), - estimating (S3) a wheel torque (τ) of one or more wheels (15) arranged on a driven axle (11) of the vehicle based on the determined winding (α) and a stiffness constant (k) characteristic of the one or more axles (11a, 11b) between the different points (101), - using ( S7 ) the estimated wheel torque (τ) when operating the vehicle.

2. The method of claim 1, wherein the method comprises: - measuring (S1) the angular position using an angular position sensor (16a, 16b) arranged along the driven wheel shaft (11), and wherein the determining (S2) comprises determining the angular displacement (α) between the measured angular positions based on the angular displacement (α) between the measured angular positions. Δ ) to determine (S2a) the torsion of the driven wheel shaft (11).

3. The method according to claim 1 or 2, wherein the measuring (S1) is performed continuously while operating the vehicle.

4. A method according to any one of the preceding claims, wherein the angular position is determined by a sensor arranged to measure the angular position (α) of a wheel (15) arranged on the driven axle (11). L ,α R ) and a plurality of first sensors (16a) arranged to measure an angular position (α) of a differential gear (13) centrally arranged at the driven wheel shaft (11). C ) is provided by at least one second sensor (16b).

5. The method according to claim 4, wherein the at least one second sensor (16b) is arranged to measure the angular position (α) of the drive gear (13a) of the differential gear (13). C ) and / or the angular position (α) of the side gear (13b) CL ,α CR ).

6. The method according to any one of the preceding claims, wherein the using (S7) comprises: - controlling (S7a) the engine to apply a driving torque on the driven wheel axle (11) based on the estimated wheel torque.

7. The method according to claim 6, wherein the controlling (S7a) comprises increasing or decreasing the drive torque when the wheel torque approaches zero so that a rapid zero crossing is achieved.

8. Method according to any of the preceding claims, wherein said using (S7) comprises estimating (S7b) a damping of a gearbox (12) of the vehicle by comparing said determined wheel torque with a driving torque of said engine 14.

9. A method according to any one of the preceding claims, comprising: - estimating the driving torque (S4) of the engine (14) of the vehicle, - measuring (S6) the wheel speed of the wheel (15) of the driven axle (11) using a wheel speed sensor (6), and Wherein said using (S7) comprises estimating (S7c) the efficiency of a powertrain of said vehicle based on the driving torque of an engine (14) of said vehicle, the measured wheel speed and said estimated wheel torque of said driven axle (11).

10. The method according to any one of the preceding claims, wherein the using (S7) comprises: - estimating the slip (S5) of one or more wheels (15) of the driven axle (11) at a plurality of individual points in time, and - Estimating the tire-road friction coefficient c by analyzing the slip for different estimated wheel torques τ ( S7d ).

11. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to perform the method as claimed in any one of claims 1 to 10.

12. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 10.

13. A sensor device (200) for operating a vehicle comprising a powertrain (100), the sensor device (200) comprising: - angular position sensors (16a, 16b) arranged to measure the angular position of one or more shafts of the drive train (100) at different points (101) along the drive train (100), - a control device (10), the control device being configured to: determining the winding of the one or more shafts of the drive train (100) based on the angular positions provided by the plurality of angular position sensors (16a, 16b), estimating a wheel torque (τ) of one or more wheels (15) arranged on the driven wheel axle (11) based on the determined torsion (α) and a stiffness constant (k) of the driven wheel axle (11) representative of the characteristics of one or more shafts (11a, 11b) between the angular position sensors (16a, 16b), • Using the estimated wheel torque (τ) when operating the vehicle.

14. The sensor arrangement (200) according to claim 20, wherein the sensor arrangement (200) is configured to perform the method according to any one of claims 2 to 10.

15. A vehicle comprising a sensor device (200) according to claim 13 or 14.

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