Control system for controlling torque distribution

Abstract

Aspects of the present invention relate to a control system for controlling torque distribution between a first axle (110) and a second axle (120) in a vehicle (100), the control system including one or more controllers. The control system is configured to detect whether the vehicle is operating over limit and to detect the vehicle speed. When the vehicle is operating over limit and the vehicle speed is below a first speed threshold, the torque distribution is controlled to reduce the over-limit operating torque to the first axle and increase the over-limit operating torque to the second axle. The vehicle may be a hybrid vehicle including an internal combustion engine (ICE) (201), a belt integrated starter generator (B-ISG) (205), and an electric rear axle drive (ERAD) (204).

Description

Technical Field

[0001] This disclosure relates to a control system for controlling torque distribution in a vehicle. Aspects of the invention relate to control systems, vehicles, methods, and computer software for controlling torque distribution. Background Technology

[0002] It is known that internal combustion engines can provide negative engine torque under certain conditions. In the context of this application, negative engine torque is the torque required to apply force to decelerate a vehicle. This is most common when driving (not stationary) and in gear, where the driver demands less drive torque than is needed to provide vehicle acceleration or maintain vehicle speed. This is known as overrun torque. The drive torque demanded by the driver is typically based on the position of the accelerator pedal and the vehicle speed.

[0003] On low-friction or soft surfaces, excessive operating torque supplied to the drive wheels of a vehicle may be sufficient to produce undesirable slippage on these drive wheels. The object of this invention is to address one or more of the disadvantages associated with the prior art. Summary of the Invention

[0004] The present invention provides, in various aspects and embodiments, control systems, methods, vehicles and computer software as follows.

[0005] According to one aspect of the present invention, a control system for controlling torque distribution between a first axle and a second axle in a vehicle is provided. The control system includes one or more controllers, wherein the control system is configured to: detect whether the vehicle is operating beyond its limits; detect the vehicle speed; wherein, when the vehicle is operating beyond its limits and the vehicle speed is below a first speed threshold, the torque distribution is controlled to reduce the over-limit operating torque to the first axle and increase the over-limit operating torque to the second axle.

[0006] When a vehicle is traveling on a soft surface or terrain, the change in torque distribution allows the vehicle to reduce the buildup of material wedges in front of the wheels. This is particularly advantageous at low speeds when the vehicle is stationary, as it improves the vehicle's ability to restart after stopping.

[0007] Optionally, the device may include the control system described above, wherein the first axle is the front axle and the second axle is the rear axle. Alternatively, the device may include the control system described above, wherein the vehicle travels rearward, and the first axle is the rear axle while the second axle is the front axle.

[0008] Optionally, the device may include the aforementioned control system, which includes: detecting whether the vehicle is on an off-road surface; and adjusting the reduction of the over-limit operating torque to the first axle and the increase of the over-limit operating torque to the second axle based on the detected off-road surface.

[0009] Optionally, the device may include the aforementioned control system, which includes: determining the vehicle deceleration rate; and adjusting the reduction of the over-limit operating torque to the first axle and the increase of the over-limit operating torque to the second axle according to the determined vehicle deceleration rate.

[0010] Measuring the deceleration rate can provide an indication of surface softness and slope. These offer the advantage that torque distribution can be modified under appropriate conditions.

[0011] Optionally, the device may include the control system described above, wherein the amount of increase in over-limit operating torque on the second shaft depends on the amount of decrease in over-limit operating torque on the first shaft.

[0012] Controlling torque distribution without significantly affecting the overall deceleration of the vehicle is beneficial. This can be achieved by removing torque from one axle and adding a similar amount to another. Small imperfections may be beneficial in compensating for additional surface drag or gradient.

[0013] Optionally, the device may include the control system described above, wherein the increase in over-limit operating torque on the second axle is the same as the decrease in over-limit operating torque on the first axle. Alternatively, the device may include the control system described above, wherein if the vehicle's tilt angle exceeds a threshold, the decrease in over-limit operating torque to the first axle is greater than the increase in over-limit operating torque to the second axle.

[0014] Optionally, the device may include the control system described above, wherein the amount of overrun torque on the first shaft is reduced by applying drive torque to the first shaft using one or more of a B-ISG, C-ISG, or any motor incorporated into the first shaft arrangement.

[0015] Optionally, the device may include the control system described above, wherein the over-limit operating torque to the second shaft is caused by regenerative braking and / or friction braking from the motor.

[0016] Hybrid power systems can be beneficially used for torque distribution. For example, the electrical energy generated by the ERAD can be used to drive the B-ISG.

[0017] Optionally, the device may include the control system described above, wherein the reduction of the overrun torque to the first axle and the increase of the overrun torque to the second axle depend on a vehicle speed below a first speed threshold.

[0018] Soft surfaces behave differently depending on driving speed. Applying torque distribution is beneficial at lower speeds when necessary, but unnecessary at higher speeds where a wedge of soft material won't form in front of the wheel. Different surface conditions and moisture content result in different speeds at which material wedges may form, thus potentially requiring different torque distributions or speed thresholds.

[0019] Optionally, the device may include the control system described above, wherein the first speed threshold depends on a vehicle mode selected from grass-gravel-snow (GGS), sand, mud and ruts, and rock.

[0020] Optionally, the device may include the control system described in the preceding two paragraphs, wherein, for GGS mode, the first speed threshold is between 0 kph and 70 kph, for sand mode, the first speed threshold is between 0 kph and 50 kph, for mud and rut modes, the first speed threshold is between 0 kph and 55 kph, and for rock mode, the first speed threshold is between 0 kph and 30 kph.

[0021] Optionally, the device may include the control system described above, wherein the reduction of the overrun torque to the first axle and the increase of the overrun torque to the second axle depend on the vehicle deceleration rate.

[0022] Optionally, the device may include the aforementioned control system, wherein the over-limit operating torque increase on the second axle is performed only when the vehicle deceleration rate is higher than 0.3 g and / or the vehicle speed is lower than 10 kph.

[0023] Optionally, the device may include the aforementioned control system, wherein the reduction of the overrun torque to the first shaft and the increase of the overrun torque to the second shaft depend on the humidity of the off-road surface.

[0024] Optionally, the device may include the aforementioned control system, wherein when creep occurs, the reduction of the over-limit operating torque to the first axis and the increase of the over-limit operating torque to the second axis are stopped.

[0025] According to another aspect of the present invention, a vehicle including the above-described control system is provided.

[0026] According to another aspect of the present invention, a method for controlling torque distribution between a first axle and a second axle in a vehicle is provided, the method comprising: detecting whether the vehicle is operating beyond its limits; detecting the vehicle speed; and when the vehicle is operating beyond its limits and the vehicle speed is below a first speed threshold, controlling the torque distribution to reduce the over-limit operating torque to the first axle and increase the over-limit operating torque to the second axle.

[0027] According to another aspect of the present invention, computer software is provided, which is configured to perform the above-described method when executed.

[0028] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples, and alternatives set forth in the foregoing paragraphs, in the claims, and / or in the following description and drawings, and in particular their various features, may be adopted independently or in any combination. That is, all embodiments and / or features of any embodiment may be combined in any manner and / or combination, unless such features are incompatible. The applicant reserves the right to amend any originally filed claim or accordingly file any new claim, including the right to modify any originally filed claim to incorporate any feature dependent on and / or incorporated into any other claim, even though it was not initially claimed in this manner. Attached Figure Description

[0029] One or more embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

[0030] Figure 1 A schematic diagram of a vehicle according to an embodiment of the present invention is shown in a side view;

[0031] Figure 2 An embodiment of the powertrain arrangement according to the present invention is shown;

[0032] Figure 2A Examples of graphs showing vehicle coasting speed versus time during overrunning operations on various surfaces are shown.

[0033] Figure 3 It shows the use of Figure 2 Example control system of the power system shown;

[0034] Figure 4A A graph showing the torque of the front axle motor during vehicle deceleration when the vehicle is traveling on a soft surface, and an example control strategy of an embodiment of the present invention are shown.

[0035] Figure 4B A graph showing the front axle engine torque during vehicle deceleration when the vehicle is traveling on a soft surface, and an example control strategy of an embodiment of the present invention are shown.

[0036] Figure 4C The diagram illustrates the rear axle motor torque or brake torque during vehicle deceleration when the vehicle is traveling on a soft surface, along with an example control strategy based on an embodiment of the invention; and

[0037] Figure 5 It shows the control Figure 2 The example control flowchart of the power system is shown below. Detailed Implementation

[0038] This document describes a method for controlling torque distribution in a vehicle according to an embodiment of the present invention, with reference to the accompanying drawings.

[0039] Figure 1 A vehicle 100 according to an embodiment of the present invention is shown. The vehicle 100 has a first axle 110 and a second axle 120, for example, each axle has two wheels. In another embodiment, the vehicle may have more than two axles, which may provide the vehicle with, for example, six or eight wheels or more.

[0040] In this specification, the torque applied to the shaft refers to the torque at the wheel, which includes any braking torque other than the driving torque or over-limit operating torque from the engine or motor.

[0041] Figure 2 It shows the installation Figure 1 The powertrain 200 in the vehicle according to an embodiment of the present invention. The powertrain 200 shown has an engine 201 connected to an electric motor 202, which is connected to a transmission 203. The transmission 203 in this embodiment is a FWD transmission, which can distribute torque to a first shaft 110 and to the front wheels 214, 215 via a differential (not shown) and a shaft drive shaft assembly 210.

[0042] Motor 202 is a crank-integrated starter-generator (C-ISG) 202, which is a crankshaft-connected motor located between engine 201 and transmission 203. The C-ISG may have a clutch to allow the engine to stop while the C-ISG provides drive torque to the transmission. Disengaging the clutch allows the engine to provide drive torque to both the transmission and the C-ISG. In this mode, the C-ISG can provide additional torque or use some engine torque to charge the battery. A starter-generator (B-ISG) 205 is also shown, which is typically a smaller motor mounted on the engine and connected to the engine via a drive belt from the B-ISG to the engine crankshaft pulley. In this embodiment, both C-ISG 202 and B-ISG 205 are shown, but other embodiments may have only a C-ISG or a B-ISG. In other embodiments, the motor may be incorporated into either the gearbox 203 arrangement (not shown) or the shaft drive shaft component 210.

[0043] In this embodiment, the second axle 120 fitted to the vehicle may include an electric rear axle drive (ERAD) 204, a drive shaft assembly 211, and rear wheels 216, 217. Since there is no physical connection between the first axle 110 and the second axle 120, the ERAD 204 can provide positive or negative electric drive torque through the second axle 120 and can operate independently of the first axle 110. In another embodiment, a physical connection may exist between the first and second axles provided by a driveshaft and a center differential arrangement (not shown), which is a conventional way to provide four-wheel drive (4x4) transmission capability.

[0044] ERAD 204 may include a motor capable of providing positive or negative torque to the transmission assembly and an optional differential that directs torque through the rear axle assembly 211 and then to the wheels 216, 217. The transmission assembly may be a single-speed or multi-speed transmission. In the illustrated embodiment, ERAD 204 may have a motor, transmission gear reducer, and differential output integrated into a single unit. The output to wheels 216, 217 via drive shaft assembly 211 is shown.

[0045] exist Figure 2 In the embodiments described herein, the first shaft 110 and the second shaft 120 can be driven independently, and the torque distribution in each shaft is separate. In this example embodiment, the first shaft 110 drives the front axle, but in other embodiments it could drive the rear axle. The output of engine 201 is connected to the input of C-IMG 202, the output of C-IMG 202 is connected to the input of transmission 203, and the output of transmission 203 is connected to the front axle drive shaft assembly 210 via a differential (not shown). The front axle drive shaft assembly 210 is connected to wheels 214 and 215.

[0046] This front axle arrangement has three possible torque sources: engine 201, C-IMG 202, or B-ISG 205. The following description will focus on the use of C-IMG 202 as a torque source, but B-ISG 205 can assist or interchangeably replace the torque provided by C-IMG 202.

[0047] The C-IMG 202 can provide positive or negative drive torque to the first axle 110 to move the vehicle forward or backward, respectively. An optional clutch (not shown) between the C-IMG 202 and the engine allows the engine output to be disconnected from the C-IMG input, which allows the engine to be disconnected from the torque path and allows only electric drive from the C-IMG 202.

[0048] Figure 2The arrangement also allows for the supply of either positive or negative drive torque from engine 201 to the front axle 110. Positive drive torque is a product of the driver's demand for positive drive torque using the throttle, while negative drive torque is caused by frictional losses within the engine and some reduction in the driver's throttle demand experienced during engine over-limit operation. Engine over-limit operation occurs when, during driving (non-stationary) and gear engagement, the driver's demand for drive torque is less than the drive torque required to provide vehicle acceleration or maintain vehicle speed. The level of over-limit operating torque is a result of frictional and pumping losses in the engine when reduced throttle demand is present. Engine 201 can drive either positive or negative torque to the input of C-IMG 202, which is then transmitted to the output of C-IMG 202 and then via transmission 203, through the differential (not shown), into the drive axle assembly 210 and to the wheels.

[0049] The torque in the front axle 110 can be provided by the engine 201, the C-IMG 202, or a combination of the engine 201 and the C-IMG 202. A second embodiment may include an integrated starter-generator (B-ISG) 205, which can drive the front axle 110 by adding positive or negative torque to the engine. Engine torque can also be provided to the C-IMG 202 or the B-ISG 205 to supply charge to the battery or vehicle electrical system.

[0050] Under certain driving conditions and on soft surfaces such as sand, gravel, shale, soil, mud, and rock, a vehicle's forward movement may be hindered because the wheels or axles may sink into the ground. This can be exacerbated by uncontrolled torque input, leading to surface deformation.

[0051] For example, Figure 2 The vehicle described has a conventional engine connected to the front axle. Assuming the driver is not using the throttle, this engine has a certain amount of over-limit operating braking torque acting on the front axle. In high-friction surface environments, such as... Figure 2 The vehicle in this configuration may be propelled solely by the rear axle 120. In this example, the vehicle is propelled via ERAD 204, which can provide the positive motor torque required by the driver and, if needed, can also provide simulated engine over-limit negative torque. This is especially relevant when encountering road surfaces with lower surface friction, such as... Figure 2The vehicle described herein will enable both axles to provide drive torque, thereby providing vehicle stability in a four-wheel drive mode. This recognition of surface conditions can be confirmed by the driver selecting a vehicle mode or by the vehicle's automatic selection mode. In this configuration, when drive torque is provided from both axles, the vehicle can only provide overrun torque via the first axle connected to the internal combustion engine due to friction and pumping losses from the internal combustion engine. In this case, the engine is the sole source of overrun braking, and the overrun torque will act only on the front axle because there is no mechanical connection between the front and rear axles. This overrun braking is caused by the engine's natural friction and pumping losses and serves as a negative deceleration torque for the vehicle. At low speeds, this deceleration torque acting on the wheel associated with the first axle may begin to deform the road surface at the point of contact with the tire, creating a deformable material wedge in front of the wheel. When the vehicle is stationary, this material wedge in front of the wheel may increase the rate of deceleration of the front axle and may cause problems the next time the vehicle attempts to move away. Material wedges can be used as obstacles to vehicle movement because they form a material barrier that the wheels need to overcome or drive over in order to move the vehicle.

[0052] Even when the driver's throttle input is very low, excessive operating torque can still occur. For example, a driver might use a throttle input of 50 Nm of engine combustion torque at a speed where the engine friction torque is -80 Nm. In this case, the vehicle's net deceleration torque is -30 Nm.

[0053] In an alternative implementation, the engine provides drive via a drive shaft to the rear axle and an electric axle drive to the front axle. In this configuration, the same control methods can be applied to distribute torque between the axles in the opposite direction to that described previously. Therefore, at high speeds, torque distribution may reach the rear, and when the vehicle decelerates below a threshold, the C-IMG may reduce the over-operation torque on the rear axle. The front axle drive can then provide the over-operation torque to compensate for the torque reduction of the C-IMG. As previously mentioned, the B-ISG can provide the functionality of the C-IMG.

[0054] Figure 2A An example graph 600 of a vehicle coasting speed versus time during overrunning on various surfaces is shown. The term coasting describes the deceleration curve of a vehicle on a flat surface, where the brakes and throttle are applied at zero and the gearbox is in the appropriate gear. The decelerating forces acting on the vehicle are aerodynamic drag, wheel rolling friction, transmission losses, and engine overrunning. Figure 2A A comparison of the skid curves for various example surfaces, such as asphalt 610, wet grass 620, mud 630, and sand 640, is shown. From Figure 2AIt can be observed that mud 630 and sand 640 cause the vehicle to decelerate more quickly. This graph does not show the input of creep torque provided as part of the inherent mass of the automatic gearbox. Typically, a wheel experiencing negative overrunning torque during deceleration on a low-friction surface or soft surface structure begins to experience wheel slippage, and this wheel slippage is part of a mechanism in which a material wedge begins to form in front of the wheel during deceleration. For example, asphalt surface 610 will have a slip deceleration curve, where there will be very little surface resistance due to the high stiffness of the surface. Mud 630 and sand 640 show slip curves that are gradually faster than those of asphalt 610, indicating a higher resistance surface where there is a greater tendency to form a material wedge in front of the wheel during deceleration, which can cause the deceleration rate to increase with the size of the wedge.

[0055] When the surface is wet or very soft, material wedges may form in front of the wheel, increasing slippage between the wheel and the surface. Applying excessive operating torque to the wheel will further increase slippage and the size of the formed wedges. This will result in higher surface resistance.

[0056] Vehicle 100 is equipped with a throttle system 220 and a device for detecting the throttle position, such as a potentiometer connected to the vehicle control unit (VCU) 226. The vehicle is also equipped with a braking system 222 capable of operating a hydraulic braking system. Furthermore, the braking system 222 is connected to the VCU 226, which can request torque from the C-IMG 202 and ERAD 204.

[0057] VCU 226 communicates with engine 201, C-IMG 202, B-ISG 205 and ERAD 204, and can dynamically request positive or negative torque from these units as needed.

[0058] Vehicle 100 may be equipped with a 3-axis or 6-axis accelerometer 224, which can detect acceleration and deceleration and determine vehicle speed from wheel speed sensors or traction motor speed resolvers. The VCU, using known calculation methods, can also determine the vehicle's tilt and yaw motion.

[0059] Figure 3 It shows the use of Figure 2The example control system of the powertrain shown is illustrated. The vehicle control unit (VCU) 226 communicates with the engine control unit (ECU) 410 and can request engine torque from the engine 201 when needed by the throttle system 220. The VCU 226 communicates with the C-IMG 202 control unit 420 and can request positive or negative torque from the C-IMG 202. The VCU 226 communicates with the B-ISG 205 control unit 430 and can request positive or negative torque from the B-ISG 205. The VCU 226 communicates with the ERAD 204 control unit 400 and can request positive or negative torque from the ERAD 204. Figure 3 The image shows an off-road mode selector 450, which can select vehicle off-road modes such as sand, mud and ruts, snow, and grass / gravel / snow. The off-road mode selector 450 communicates with the VCU 226 to allow the driver to indicate the type of surface they intend to drive on. The vehicle can also have an "automatic" mode, which is automatically selected by the vehicle based on the surface it is traveling on or a predicted surface it will travel on. The selected driving mode can determine the torque distribution between the front axle 110 and the rear axle 120 in a manner best suited to the surface.

[0060] In this context, a vehicle is considered off-road when at least one front wheel and at least one rear wheel are traveling on and in contact with any surface other than asphalt or concrete. This could occur when sand is blown across an asphalt road or when the driver places both wheels on the shoulder.

[0061] Although Figure 3 The physical implementation of the control system is shown, but the control functions performed can be distributed across different architectures. Controllers can be combined or distributed, and can employ several different networks to perform the same functions. Similarly, control software functions can be performed in different controllers with available processing power, storage space, and / or network communication. For example, the VCU is shown as a separate controller, but the functions performed by the VCU can be implemented in the ECU, thus eliminating the need for a separate VCU.

[0062] Combination Figure 4A , Figure 4B and Figure 4C A possible motor torque distribution control method is shown, which can alleviate the problem of building deformable material wedges in front of one or more wheels during vehicle deceleration, for example, on sand. Figure 4A , Figure 4B and Figure 4CEach of them shares the same timeline because the motor torque distribution control method needs to be coordinated between the front axle 110 and the rear axle 120.

[0063] Figure 4A The diagram shows the torque of the B-ISG motor during vehicle deceleration when the vehicle is traveling on a soft surface. During deceleration, the vehicle passes through various speed thresholds, such as Sp1, Sp2, Sp3, and Sp4, which triggers various control responses. At various points during the control strategy, the front axle motor torque will change to example levels of FMT1, FMT2, FMT3, and FMT4 depending on the driving conditions.

[0064] Figure 4B A graph showing the front axle torque is displayed. This is the engine torque (not shown) and... Figure 4A The sum of the B-ISG torques. Between Sp1 and Sp3, the engine provides -100 Nm of overrun torque. Typically, when the vehicle comes to a stop after SP4, the engine overrun torque shifts to provide crawl torque at FET4 (if crawling is provided).

[0065] Figure 4C The graphs shown are of the rear axle torque derived from either the brake application or the rear axle motor torque, or both the brake application and the rear axle motor torque. The example control strategy will now be described using all three graphs (4A, 4B, and 4C).

[0066] In this implementation, the vehicle may be positioned on off-road surfaces such as sand, gravel / snow, soil, mud, and ruts. As the vehicle decelerates, some or all of the wheels may deform the surface and accumulate a wedge-like material in front of the wheels. While the vehicle typically moves along the surface with minimal resistance at high speeds and with inertia, it may sink into the surface as it decelerates. Furthermore, during deceleration, the material wedge can accumulate more rapidly and at higher vehicle speeds due to the negative torque encountered at the wheels. This negative torque and the low-friction surface cause the drive wheels to rotate slower than the vehicle speed. This wheel slippage (or under-rotation) allows the soft surface to accumulate in front of the drive wheels, rather than allowing the drive wheels to roll over the top of the wedge. At low vehicle speeds, this excessive running torque tends to push any soft off-road surface in front of the wheels, rather than causing the wheels to roll over the surface, resulting in the formation of a material wedge in front of the wheels. Additionally, if the vehicle is traveling in the forward direction and is decelerating, weight is transferred from the rear wheels to the front wheels, which tends to push the front wheels further into the off-road surface. This effect exacerbates the problem of material wedges accumulating in front of the wheels, a situation that occurs on the front axle when engine overload torque flows through it. As another example, if the vehicle has an engine-driven rear axle, the rear axle will act as an axle that may tend to form material wedges accumulating in front of the rear wheels during overload deceleration.

[0067] Once the vehicle stops, this material wedge-shaped structure can create resistance to the vehicle's departure and may also cause the vehicle to decelerate faster than the driver intends to stop as indicated by the required braking pressure. We are seeking ways to mitigate this problem by controlling the torque distribution within the vehicle during deceleration.

[0068] Figure 4A , Figure 4B and Figure 4C An example method for wheel torque control is described to counteract material wedges that accumulate during deceleration, for example, on sand. The deceleration conditions can be zero throttle requirement, zero driver braking request, and... Figure 4A At speed point Sp1, the forward vehicle speed can be 30 kph. The wheel torque distribution at Sp1 is FET1 = -100 Nm and RT1 = 0 Nm, which is the net negative overrun deceleration torque applied to the front axle, which is -100 Nm. In this case, the overrun torque is only experienced on the front axle, and the vehicle moves reasonably fast so that the overrun torque does not cause material to accumulate in front of the front wheels. As at speed point Sp1, the rear axle does not experience overrun torque.

[0069] Since no throttle is applied, the vehicle will decelerate to speed point Sp2 due to frictional resistance from the wheel surfaces and excessive operating torque resulting from engine pumping losses. Speed ​​point Sp2 can be 20 kph. At speed point Sp2, the torque distribution in the front axle 110 and rear axle 120 changes, resulting in a front axle motor torque FMT2 = 50 Nm. This positive torque is applied directly to the engine by the B-ISG (or alternatively, C-IMG), resulting in a front axle torque FET2 = -50 Nm. The B-ISG torque inputs a positive torque value to the internal combustion engine (ICE), partially offsetting the -100 Nm pumping and frictional losses, resulting in a total front axle torque of -50 Nm in this case. Simultaneously, the rear axle torque changes to RT2 = -50 Nm. Therefore, at speed point Sp2, the net vehicle torque is -100 Nm, with -50 Nm on the front axle 110 and -50 Nm on the rear axle 120. It should be noted that the B-ISG torque delivered by the electric motor in this example can also be delivered by allowing the supply of combustible fuel and air to the ICE. This "fuel" state of the engine can be configured to provide some or all of the positive torque as described in this example, thereby counteracting some or all of the excessive operating torque on the ICE power (front) axle.

[0070] Moving to a speed point Sp3, which is likely around 15 kph, the axle torque distribution changes again to FET3 = 0 Nm and RT3 = -100 Nm. Therefore, applying -100 Nm to the rear axle via the brakes or ERAD results in an overrun torque of -100 Nm for the vehicle. The 0 Nm applied to the front axle (a combination of 100 Nm B-ISG torque and -100 Nm ICE torque) provides the vehicle's desired deceleration torque, which reduces material buildup at the front contact point of the front wheels and also allows the front wheels to roll over some or all of the material wedges in front of the front wheels on the front axle.

[0071] Move to a speed point Sp4, which is likely around 7 kph, and Sp4 is also the speed point at which the "creep" function can begin to generate positive drive torque. Figure 4B At torque FET4, "creep" is indicated as an automatically requested engine torque to transmit forward motion within the vehicle, a common feature in most vehicles equipped with automatic transmissions. When VCU 226 receives a creep torque indication, VCU 226 can subsequently cancel the method of controlling torque distribution within the vehicle as described in this invention, since modes may be incompatible, and creep torque can be adjusted as follows: Figure 4B The crawl function can be initiated at any time within the marked area 1, but it is known that, depending on the accumulation of surface wedges, the vehicle's tilt and weight, and other vehicle inputs, the crawl function can be initiated at other times not shown in Z1. Figure 4A and Figure 4C As shown, at speed Sp5, when crawling, FMT5 = 0 Nm, FET5 = 20 Nm, and RT5 = 20 Nm. Depending on the drive mode, crawling can be provided by the front axle, the rear axle, or both. For example, a stop-start system can request the ICE to disconnect and crawling to be provided by the rear axle. Conversely, if the traction battery has a low state of charge, the ICE can continue operating and provide crawling torque. In low-friction conditions, crawling torque from both axles may be preferred. This torque will be transmitted to provide the driver with seamless crawling functionality. As long as it does not interfere with the torque transmission desired by the driver, the introduction of crawling torque can be transmitted on one axle while pressure modification is completed on the other axle. The crawling torque transmission on the ERAD can be... Figure 4C The creep function is introduced at any point in region 2 (Z2) shown, but it is known that the creep function can be initiated at other times not shown in Z2, depending on surface wedge buildup, vehicle tilt and weight, and other vehicle inputs. Therefore, due to the creep torque functionality, there is a net acceleration torque, but the method of controlling torque distribution in the vehicle as described in this invention can be cancelled.

[0072] As the vehicle speed decreases at SP4, the vehicle's overrun torque moves away from the rear axle 120 and returns to the front axle 110. This allows the rear wheels in this example to roll and sit on top of any wedges of surface material that have accumulated in front of the rear axle wheels when the vehicle stops due to the full overrun torque transmitted by these wheels.

[0073] Depending on the surface slope and vehicle speed, torque distribution may not be as described in this embodiment, and many factors may need to be considered to achieve control over torque distribution. These factors may include known wheel and tire sizes, tire pressures, track width, and vehicle weight, among other inputs. If, for example, the second axle has wider tires than the first axle, or if the second axle is significantly lighter, such as in the case of an unloaded pickup truck, then all the steps required to activate this function may not be necessary.

[0074] When the vehicle lacks a creep function or when the surface resistance torque is higher than the creep torque, the vehicle will reach a standstill (0 kph) as shown at positions P1, P2, and P3 in SP5. Apart from the creep torque function, which is not part of the proposed invention, there will be no negative or positive torque transmitted to shafts 110 and 120. Therefore, FMT5 = 0 Nm, FET5 = 20 Nm, and RT5 = 20 Nm. It is known that when the creep torque is insufficient to enable the motor to rotate with its torque request, the motor will prevent the torque request from being executed, which prevents heat buildup and conserves energy. Since the motor can respond to changes in drive torque request faster than the ICE, there is no significant performance loss when the driver requests additional torque.

[0075] In this example, the proposed method for controlling torque distribution in a vehicle stops at a speed point Sp4 (e.g., 7 kph). However, depending on the surface, the selected off-road mode, or the vehicle's surroundings, the invention may stop at other speeds.

[0076] Although Figures 4A to 4C Sp4 illustrates torque control that reverts to front axle overrun in one scenario, but alternative torque distributions may exist to achieve the optimal stopping position of the wheels on soft surfaces.

[0077] Torque variation can include a hybrid function that controls the rate at which torque variation is transmitted at each step, making the change imperceptible to the driver or other vehicle occupants.

[0078] On a vehicle moving forward, the torque distribution strategy described above redistributes torque away from the front wheels 214, 215, which are most likely to form a material wedge in front of the wheels, to the rear wheels. This maintains a consistent net deceleration torque distribution for the vehicle. As the vehicle speed decreases, the net deceleration torque can vary in a manner similar to other vehicles, but the balance of the negative deceleration torque distribution shifts rearward toward the rear axle. All vehicles experience deceleration caused by overrun braking, and the amount of braking typically depends on the speed of the running engine, the selected gearbox gear, the final drive ratio, and the friction pumping losses at that engine speed. The proposed control strategy does not affect the vehicle's net negative deceleration torque, and in this way, the driver will not feel any difference in vehicle deceleration due to torque redistribution. The invention does not preclude modification of the total overrun torque if necessary. Similarly, vehicle deceleration on soft surfaces may differ due to the torque distribution of the invention, as material does not accumulate in front of the wheels, which has the benefit of overrun behavior being closer to the driver's expectations based on experience with overrun on hard surfaces.

[0079] In another embodiment, if the vehicle is traveling backwards, the leading wheels will be the rear wheels 216, 217 on the rear axle 120, and the control distribution will be reversed. For example, if the vehicle is traveling in reverse, the leading wheels 216, 217 will be driven in reverse by the ERAD 204, and the rear wheels will be driven in reverse by the engine 201 and / or C-IMG 202 and / or B-ISG 205. If the vehicle is traveling in reverse, the over-running torque of the engine 201 may still be problematic for the front axle 110 because the engine operation can still generate torque during reverse travel, which will cause material wedges to accumulate on wheels 214, 215 in front of them. To reduce or prevent such material wedges, the over-running torque of the engine (in reverse) can still be offset by the C-IMG 202 and / or B-ISG 205 generating counter-torque. The ERAD will provide torque to compensate for the B-ISG or C-IMG torque.

[0080] In some implementations, the surface over which the vehicle travels affects the VCU 226 control strategy. Figure 5 In the example implementation described herein, starting at step 500, VCU 226 determines the surface on which the vehicle is traveling at step 510, and the proposed torque distribution method applies only when the vehicle is traveling on certain surfaces. The method of torque distribution control may depend on the off-road mode detected or selected by the driver at step 505. For example, VCU 226 may determine that the wheels on the vehicle are slipping intermittently by observing wheel speed signals, and thus VCU 226 may determine that the vehicle is on a soft surface. Alternatively, the driver may manually operate the off-road mode selection via a switch, push button, or other input device to select “Auto,” GGS, Sand, Rock, Dynamic, Mud, and Ruts. “Auto” is an automatic terrain response selection that allows VCU 226 to automatically select the most suitable terrain mode when VCU 226 recognizes that the vehicle is on a surface of a given type. Automatic terrain recognition uses a number of inputs from vehicle sensors to detect surface type and friction level, including but not limited to wheel speed sensors, GPS, lateral and longitudinal acceleration signals, pitch, heave, and yaw signals, and environmental inputs such as temperature and air pressure. These can be inputs to the VCU 226, which will allow it to select the most suitable terrain mode based on the best available modes of terrain GGS, sand, rock, dynamics, mud, and ruts to maximize traction. The control method can also be a combination of multiple selection criteria from other control charts.

[0081] At step 515, over-limit operation is detected by checking the engine torque graph, ECU 410, or by detecting, for example, the absence of a detected throttle input 220. VCU 226 then determines at step 520 whether the vehicle is operating beyond its limits, and if the answer is yes, VCU 226 proceeds to step 530.

[0082] In some implementations, vehicle speed is a factor influencing the VCU 226 control strategy. Figure 5 In the example implementation described, VCU 226 determines the vehicle speed at step 530, and the proposed torque distribution method applies only when the speed is below a threshold. The speed threshold can depend on the off-road mode detected or selected by the driver. For example, in Dynamic mode, the speed threshold can be between 0 kph and 80 kph; in Grass Gravel Snow (GGS) mode, the speed threshold can be between 0 kph and 70 kph; in Sand mode, the speed threshold can be between 0 kph and 50 kph; in Mud and Ruts mode, the speed threshold can be between 0 kph and 55 kph; and in Rock mode, the speed threshold can be between 0 kph and 30 kph. For each mode, the speed threshold can also be varied based on the vehicle's tilt and whether the terrain is wet or dry.

[0083] In some implementations, the vehicle's deceleration rate is a factor influencing the VCU 226 control strategy and the method of controlling torque distribution within the vehicle. Figure 5 In the example implementation described in B, VCU 226 determines the vehicle's deceleration rate at step 540, and the proposed torque distribution method applies only if the deceleration rate is greater than a threshold. The deceleration rate threshold can depend on the off-road mode detected or selected by the driver. For example, for GGS, the deceleration rate threshold can vary between 0.9 and 0.2g limits; for sand, it can vary between 0.9 and 0.15g limits; for mud and ruts, it can vary between 0.9 and 0.2g limits; or for rock mode, it can vary between 0.9 and 0.05g limits. Other limits can be applied and can be varied depending on the vehicle's tilt and whether the terrain is wet or dry.

[0084] Figure 5 A control method for operation according to an exemplary embodiment of the present invention is illustrated. Step 500 is the start of the control sequence and can be initiated when the vehicle ignition is turned on. Step 500 can turn on all controllers and initiate communication between all controllers 400, 410, 420, 430 and 226.

[0085] Other control structures can be applied.

[0086] At step 510, VCU 226 uses off-road detection device 505 to determine whether the vehicle is off-roading. If the vehicle is determined to be off-roading, VCU moves to step 520, where VCU determines whether over-limit operation detection device 515 has detected that the vehicle engine 201 is operating beyond its limits. If VCU determines that the engine 201 is operating beyond its limits, VCU 226 moves to step 530, where VCU determines whether vehicle speed detection device 525 has detected that the vehicle speed is below a threshold. If VCU 226 determines at step 530 that the vehicle speed is below the threshold, VCU 226 moves to step 540, where it checks the calculated deceleration rate device 545 and determines whether the vehicle's deceleration rate is greater than a threshold. If the vehicle's deceleration rate exceeds a threshold, VCU 226 moves to the next step, whereby VCU 226 instructs C-IMG 202 and / or B-ISG 205 to increase the torque on the first axle 110 and instructs ERAD 204 to decrease the torque on the second axle 120.

[0087] If the analysis is negative at any of the steps 510, 520, 530, or 540, the VCU 226 controller returns to step 510 to repeat the process.

[0088] In this implementation, the vehicle may be positioned on a slope where the amount of overrun torque on the first axle can be determined and how the amount of braking torque on the second axle can be controlled. For example, if the vehicle is traveling forward on a steep uphill slope, the vehicle's center of gravity (COG) may shift to the rear of the vehicle. In this example, a reduced downward force on the first (front) axle 110 and an increased downward force on the second (rear) axle 120 may mean that the traction limits of the first and second axles may have changed. For example, if the downward force on the axle decreases, the amount of torque that a given wheel can transmit to the ground will decrease, and vice versa; if the downward force on the axle increases, the amount of torque that a given wheel can transmit to the ground will increase.

[0089] In this example, the method of controlling torque distribution in a vehicle may need to take into account the change in axial downforce distribution caused by vehicle tilt, otherwise there is a risk of wheel slippage and loss of traction.

[0090] If the vehicle's tilt angle exceeds a threshold, the amount of positive torque to the first axle can be reduced by a greater amount than the amount of torque reduced on the second axle. This takes into account changes in weight distribution within the vehicle and the downforce available on each axle of the wheels to ensure no loss of traction. For example, if the vehicle moves forward on a slope, the COG will move backward within the vehicle, reducing the downforce on the front axle and increasing the downforce on the rear axle. This will reduce the amount of available traction on the front axle and increase the amount of available traction on the rear axle.

[0091] In this implementation, the vehicle speed determines when to activate the method for controlling torque distribution within the vehicle. For example, above a certain speed threshold, the torque distribution within the vehicle may remain unchanged relative to a normal vehicle, but when the vehicle decelerates below the speed threshold, the method for controlling torque distribution within the vehicle is activated and the torque distribution is changed.

[0092] Speed ​​thresholds can be approximately 10 kph, 5 kph, or within a speed range depending on driving conditions. Speed ​​point thresholds sp1, sp2, sp3, and sp4 are merely examples, and these values ​​may vary depending on the surface the vehicle is driving on or the terrain response pattern the vehicle is in.

[0093] For example, a sandy surface can be considered softer than a dense gravel surface, and although both surfaces may experience material buildup in front of the wheel during overrun braking, the sandy surface can form material wedges more quickly, and the speed thresholds (Sp1, Sp2, Sp3, Sp4) will be higher than those of the dense gravel surface.

[0094] In this implementation, the rate at which the vehicle decelerates during over-limit braking can determine when to initiate a method for controlling torque distribution within the vehicle. For example, if the vehicle decelerates rapidly, this may indicate a soft surface (similar to sand) and the absorption of rolling energy due to increased frictional losses at the wheels. If the controller detects that the deceleration rate exceeds a deceleration threshold, it initiates a method for controlling torque distribution within the vehicle.

[0095] Vehicle deceleration can be measured via an onboard accelerometer 224 or by monitoring the output of wheel speed sensors. Deceleration can be measured in meters per second squared or "g", where 1 g equals 9.81 meters per second squared.

[0096] One method for controlling wheel torque in a vehicle is, for example, to offset the amount of negative engine overrun torque on the first axle by increasing the positive torque on the first axle, and to reduce torque on the second axle only when the vehicle deceleration rate is above 0.3 g and / or the vehicle speed is below 10 kph.

[0097] The vehicle will have a controllable braking system on each axle, which can be electric, electromechanical, or hydraulic (not shown).

[0098] It will be understood that various changes and modifications can be made to the invention without departing from the scope of this application.

Claims

1. A control system for controlling torque distribution between a first axle and a second axle in a vehicle, the control system comprising one or more controllers, wherein, The control system is configured to: The system detects whether the vehicle is operating beyond its limits. Operating beyond the limits is defined as a situation where the driving torque requested by the driver is less than the driving torque required to provide vehicle acceleration or maintain vehicle speed. Detect vehicle speed; Specifically, when the vehicle is operating beyond its limits and its speed is below a first speed threshold, the torque distribution is controlled to reduce the over-limit operating torque to the first axle and increase the over-limit operating torque to the second axle. Specifically, the over-limit operating torque on the second shaft is increased based on the amount by which the over-limit operating torque on the first shaft is reduced.

2. The control system according to claim 1, wherein, The control system is configured to: Detect whether the vehicle is on an off-road surface; and The over-limit operating torque to the first axle is reduced and the over-limit operating torque to the second axle is increased based on the detected off-road surface.

3. The control system according to claim 1 or claim 2, wherein, The control system is configured to: Determine the vehicle deceleration rate; and The over-limit operating torque to the first axle and the over-limit operating torque to the second axle are adjusted according to the determined vehicle deceleration rate.

4. The control system according to any of the preceding claims, wherein, The amount by which the over-limit operating torque on the second shaft increases is the same as the amount by which the over-limit operating torque on the first shaft decreases.

5. The control system according to any one of claims 1 to 3, wherein, When the vehicle's tilt angle exceeds a threshold, the decrease in the over-limit operating torque to the first axle is greater than the increase in the over-limit operating torque to the second axle.

6. The control system according to any of the preceding claims, wherein, The amount of overrun torque on the first shaft is reduced by applying drive torque to the first shaft using one or more of a B-ISG, C-ISG, or any motor incorporated into the first shaft arrangement.

7. The control system according to any of the preceding claims, wherein, The excessive operating torque to the second shaft is caused by regenerative braking and / or friction braking from the motor.

8. The control system according to any of the preceding claims, wherein, The reduction in the overrun torque to the first axle and the increase in the overrun torque to the second axle depend on the vehicle speed being below the first speed threshold.

9. The control system according to any of the preceding claims, wherein, The first speed threshold depends on the vehicle mode selected from GGS, sand, mud and ruts, and rock.

10. The control system according to any of the preceding claims, wherein, The reduction in overrun torque to the first axle and the increase in overrun torque to the second axle depend on the vehicle deceleration rate.

11. The control system according to any one of claims 2 to 10, wherein, The reduction in overrun torque to the first axle and the increase in overrun torque to the second axle depend on the humidity of the off-road surface.

12. The control system according to any of the preceding claims, wherein, When crawling occurs, the reduction of the over-limit operating torque to the first axis and the increase of the over-limit operating torque to the second axis are interrupted.

13. A vehicle comprising a control system according to any of the preceding claims.

14. A method for controlling torque distribution between a first axle and a second axle in a vehicle, the method comprising: The system detects whether the vehicle is operating beyond its limits. Operating beyond the limits is defined as a situation where the driving torque requested by the driver is less than the driving torque required to provide vehicle acceleration or maintain vehicle speed. Detect vehicle speed; and When the vehicle is operating beyond its limits and the vehicle speed is below a first speed threshold, the torque distribution is controlled to reduce the over-limit operating torque to the first axle and increase the over-limit operating torque to the second axle, wherein the over-limit operating torque on the second axle is increased according to the amount of reduction in the over-limit operating torque on the first axle.

15. A computer software product configured to perform the method of claim 14 when run.

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