Method, computer program and control unit for accelerating a motor vehicle with acceptable wear on the vehicle clutch

Abstract

Method carried out in a powertrain control unit (110) to accelerate a motor vehicle (V) from an initial speed (v0) to a desired speed (v t ) to accelerate while a clutch (125) in the vehicle (V) is gradually engaged, the procedure comprising: Obtaining a set of input parameters (v0, v t , m, F e , L), and Controlling the vehicle (V) so that it accelerates from the initial to the desired speed, based on the set of input parameters characterized by Determine, in a processing circuit (112) of the control unit (110), a minimum acceleration (a min ), which is needed to achieve the desired speed (v t ) with acceptable wear on the clutch (125), whereby the minimum acceleration (a min) is determined based on the set of input parameters that define a driving resistance (F e ) for the vehicle (V), a weight (m) of the vehicle (V), a maximum amount of energy (L) that can be absorbed by the clutch (125), and a speed difference (Δv) between the initial and the desired speed (v0, v t ) includes, and Generating a control signal (S ctrl ), which is configured to control a powertrain (120) in the vehicle (V) to cause the vehicle (V) to accelerate from the initial speed (v0) to the desired speed (v t ) at least as fast as specified by the minimum acceleration (a min ) accelerated.

Description

TECHNICAL FIELD

[0001] The invention generally relates to an automatic cruise control system for motor vehicles. More specifically, the present invention relates to a method for accelerating a motor vehicle, a powertrain control unit implementing the present method, and a vehicle including the powertrain control unit. The invention also relates to a computer program product and a non-volatile data carrier. BACKGROUND

[0002] In autonomous vehicles, it is common practice to accelerate relatively quickly from a standstill to minimize wear on the vehicle's clutch. However, if the vehicle is carrying passengers, such acceleration may be perceived as unpleasant by the passengers. A smoother acceleration would be preferable. However, this causes greater wear on the clutch and makes it difficult to determine appropriate clutch maintenance intervals.

[0003] US 2013 / 0281260 A1 discloses systems and methods for assisted direct launch control. One exemplary method varies engine torque, forward clutch engagement pressure, and wheel brake pressure during launch of a vehicle in response to a longitudinal vehicle gradient to improve launch performance.

[0004] WO 2010 / 047652 A1 describes a method for controlling the speed of an engine of a motor vehicle with an automatic transmission upon engagement of a clutch of the vehicle when the vehicle is started. The method comprises: - requesting a desired clutch torque; - determining a current clutch torque of the clutch and a closing rate for the clutch upon engagement; - determining a dynamic torque increase required to provide the increase in engine speed required when the clutch is engaged at the closing rate; - determining, based on parameters including the current clutch torque and the dynamic torque increase, a necessary engine torque to achieve the requested clutch torque; - Determining from the necessary engine torque for the engine a necessary engine speed to achieve the requested clutch torque; - Increasing the engine speed to the required engine speed if the required engine speed is greater than a predetermined engine speed.

[0005] DE 10 2014 216 973 A1 discloses a method for limiting the amount of energy lost in a friction clutch drivingly coupling an engine to a transmission, in which a target engine speed is set and the engine is controlled based on the set target engine speed. The target engine speed is not fixed, but rather variable based at least in part on the engagement state of the clutch to smoothly transition the engine speed to the speed of an input to the transmission. When the clutch is engaged, the target engine speed converges with a transmission input speed to a value slightly above the transmission input speed.

[0006] DE 601 13 517 T2 discloses a method and arrangement for indicating clutch slip in a manually controlled friction clutch in a vehicle with a manually controlled mechanical transmission, comprising a device for calculating a value representing the energy released in the clutch based on an expression for the engine torque and the clutch slip, and devices for generating an attention signal when the calculated released energy exceeds a certain predetermined level. The invention is characterized by: a device for at least substantially continuously calculating the relationship between the engine speed and the vehicle speed, a device for detecting the temporal change in the value of this relationship, and devices for indicating the occurrence and non-occurrence of clutch slip and its magnitude using the detected change.

[0007] US 2018 / 0148058 A1 discloses a vehicle speed control system comprising a vehicle acceleration mechanism manually movable between a plurality of positions, a sensing arrangement configured to sense the position of the vehicle acceleration mechanism and generate an output signal indicative of the position of the vehicle acceleration mechanism, a vehicle speed controller configured to establish a speed of the vehicle as a function of the sensed position of the manually controllable vehicle acceleration mechanism and use the output signal as an input speed control signal.Furthermore, the vehicle speed controller is further configured to be operatively activated by a user to operate one of a clutch unit, drive unit, and service brake, wherein, when the vehicle speed controller is operatively activated by the user to use the output signal as an input speed control signal, the vehicle speed controller is further configured to be operated by the user to control the speed of the vehicle through actuation of one of the clutch unit, drive unit, and service brake, allowing the user to manually control the speed of the vehicle as a function of the position of the vehicle acceleration mechanism. A method for controlling the speed of a vehicle by a vehicle speed control system is also provided.

[0008] DE 20 2014 002 546 U1 discloses a computer program comprising computer code suitable for executing a method for controlling an engine torque request for an internal combustion engine of a motor vehicle, the vehicle also comprising a clutch, the method performing the following steps when the vehicle is started during the time interval in which the clutch is not fully engaged: - calculating an engine speed target value as a function of a position of an accelerator pedal, - calculating an engine torque that enables the engine speed target value to be reached, - if an estimated clutch temperature is within a predetermined range, learning and adapting a clutch curve using a position of the clutch pedal as an input parameter and a clutch torque that the clutch can transmit as an output parameter, - performing a clutch pedal position prediction,- Calculating a clutch torque value based on the clutch curve with the predicted clutch pedal position as input parameter, - Limiting an engine torque request to the clutch torque increased by a calibration parameter.,

[0009] Thus, various solutions are known for controlling motor vehicles so that they accelerate automatically. However, there is still no method that ensures that the clutch does not experience excessive wear. SUMMARY

[0010] An object of the present invention is therefore to provide an improved solution for accelerating a motor vehicle to a desired speed while gradually engaging the clutch so that the clutch can be fully engaged at a desired speed.

[0011] According to one aspect of the invention, this object is achieved by a method executed in a powertrain control unit, the method involving the acceleration of a motor vehicle from an initial speed, for example from a stationary position, to the desired speed. A set of input parameters is obtained in the powertrain control unit; and based on the set of input parameters, the control unit controls the vehicle to accelerate from the initial to the desired speed. In particular, a processing circuit in the control unit determines a minimum acceleration necessary to reach the desired speed with acceptable wear for a clutch in the vehicle.The minimum acceleration is determined based on the set of input parameters, which includes a driving resistance for the vehicle, a weight of the vehicle, a maximum amount of energy absorbable by the clutch, and a speed difference between the initial and target speeds. A control signal is generated configured to control a drivetrain in the vehicle to cause the vehicle to accelerate from the initial speed to the target speed at least as fast as specified by the minimum acceleration.

[0012] This method is advantageous because it not only ensures that no more than an acceptable amount of energy is absorbed by the clutch, but also allows clutch wear to be predicted very precisely. Consequently, a clutch maintenance schedule can be created with the utmost accuracy.

[0013] According to one embodiment of this aspect of the invention, the minimum acceleration is determined in relation to the driving resistance and in a quadratic relationship with the speed difference.

[0014] The minimum acceleration is preferred, a min , determined as: amin=Fe2LΔv2−m, where F e the driving resistance is, L is the maximum amount of energy that can be absorbed by the clutch with respect to the acceptable wear, Δv is the speed difference between the initial and the target speed, and m is the weight of the vehicle.

[0015] Therefore, an acceleration value can be calculated that represents a constant speed increase from the initial to the target speed and ensures that the clutch does not experience unnecessary wear.

[0016] According to another embodiment of this aspect of the invention, the maximum amount of energy absorbable by the clutch is either a constant number or a variable parameter. In the former case, the constant number is set to an empirically verified value for the specific clutch; and in the latter case, the parameter is determined based on a current clutch temperature, a clutch maintenance interval, and / or a fuel consumption condition. Therefore, the minimum acceleration can be calculated with even greater precision.

[0017] According to yet another embodiment of this aspect of the invention, the driving resistance in turn includes: a road gradient factor, an air resistance parameter, and / or a rolling resistance parameter. This enables a dynamic and high-quality allocation of the driving resistance. This also allows the minimum acceleration to be determined more appropriately.

[0018] According to yet another embodiment of the present aspect of the invention, the target speed is a maximum speed at which the clutch is fully engaged. In other words, the clutch can be fully engaged at a speed below the target speed. This results in even less clutch wear, but likely also in somewhat less comfort for any passengers in the vehicle.

[0019] According to a further aspect of the invention, the object is achieved by a computer program containing instructions which, when executed on at least one processor, cause the at least one processor to carry out the method described above.

[0020] According to yet another aspect of the invention, the object is achieved by a non-volatile data carrier containing such a computer program.

[0021] According to yet another aspect of the invention, the above object is achieved by a powertrain control unit suitable for inclusion in a vehicle for accelerating the vehicle from an initial speed to a desired speed while gradually engaging the clutch in the vehicle. The powertrain control unit is configured to obtain a set of input parameters and, based thereon, to control the vehicle to accelerate from the initial to the desired speed. A processing circuit in the control unit is specifically configured to determine a minimum acceleration required to reach the desired speed with acceptable wear on the clutch.The minimum acceleration is determined based on the set of input parameters, which includes a driving resistance for the vehicle, a weight of the vehicle, a maximum amount of energy absorbable by the clutch, and a speed difference between the initial and target speeds. The processing circuit is further configured to generate a control signal configured to control the vehicle to accelerate from the initial speed to the target speed at least as fast as specified by the minimum acceleration. The advantages of this control unit, as well as its preferred embodiments, are apparent from the above description with reference to the proposed method.

[0022] According to yet another aspect of the invention, the object is achieved by a vehicle comprising the proposed control unit for detecting errors in a driver assistance system of the vehicle.

[0023] Further advantages, advantageous features and applications of the present invention will become apparent from the following description and the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will now be described in more detail with reference to preferred embodiments disclosed as examples and the accompanying drawings. In the drawings: Fig. Figure 1 schematically shows a vehicle in an initial position when traveling at an initial speed and at a later time when traveling at a target speed; Fig. 2 is a block diagram of a powertrain control unit according to an embodiment of the invention; and Fig. 3 shows the general method according to the invention using a flow chart. DETAILED DESCRIPTION

[0025] On the left side Fig. 1 schematically shows a motor vehicle V in an initial position when it is traveling at an initial speed v0. On the right-hand side, the vehicle V is shown at a later time when it is traveling at a target speed v t Typically, the initial speed v0 is zero; and for a heavy motor vehicle, such as a truck or a bus, the target speed v t by the idle speed of the engine and the currently selected gear. However, according to the invention, any other values ​​of the initial speed v0 and the target speed v tequally conceivable, as long as v t > v0.

[0026] The vehicle V has a drive train that is Fig. 1 by reference numeral 120. The drivetrain 120 includes the drivetrain components of the vehicle V between the transmission and the differential. The drivetrain 120 may thus include a drive shaft and a drive joint.

[0027] Fig. 1 also symbolically shows a clutch 125 in the vehicle V, i.e., a mechanical device configured to engage and disengage power transmission from the drive shaft of the engine to a driven shaft of the drive train 120.

[0028] The vehicle V further includes a powertrain control unit 110 which, based on a control signal S ctrl configured to cause the vehicle V to accelerate from an initial speed v0 to a target speed v taccelerates while the clutch 125 is gradually engaged. To this end, the powertrain control unit 110 is configured to obtain a set of input parameters on the basis of which the acceleration is controlled.

[0029] Now, with reference to Fig. Figure 2 shows a block diagram of the powertrain control unit 110 according to one embodiment of the invention. The powertrain control unit 110 is preferably implemented in one or more so-called ECUs (electronic control units) in the vehicle V, wherein these ECUs exchange data and instructions with other units, sensors, and actuators in the vehicle V via a CAN (control unit network) bus or an analog internal communication network.

[0030] The powertrain control unit 110 includes a processing circuit 112 and a non-volatile data storage medium 114 communicatively connected to the processing circuit 112. The non-volatile data storage medium 114, in turn, includes a computer program product 115 containing software for carrying out the method described below when executed by the processing circuit 112. In response to control by the software, the processing circuit 112 is specifically configured to maintain a minimum acceleration a min required to reach the desired speed v t with an acceptable wear for the clutch 125 when starting at the initial speed v0.

[0031] As clutch 125 is used, i.e., engaged and disengaged, it suffers a certain amount of physical deterioration. More specifically, during the process of engaging clutch 125, such as when starting from a standstill or in conjunction with a gear shift, various surfaces within clutch 125 rub against each other to gradually transfer more power to the drivetrain and thus achieve comfortable and safe operation of the vehicle. Depending on the degree of friction between the surfaces, clutch 125 suffers a greater or lesser degree of physical deterioration. For the purposes of the present disclosure, the term acceptable wear is intended to define how much of this friction can be tolerated so as not to cause excessive wear on clutch 125 while still achieving comfortable and safe operation of the vehicle.

[0032] The processing circuit 112 determines the minimum acceleration a min based on the set of input parameters, which in turn determines a driving resistance F e for the vehicle V, a weight m of the vehicle V, a maximum amount of energy L that can be absorbed by the clutch 125, and a speed difference Δv between the initial and the target speed v0 and v t This means that if the initial velocity v0 is zero, the velocity difference Δv will be equal to the desired velocity v t . The maximum amount of energy L that can be absorbed by the clutch 125 can essentially be expressed by how much heat can be dissipated through the clutch 125. As discussed below, this energy can be represented either by a constant number or by a dynamic parameter.

[0033] The driving resistance F eis composed of any external causes that have a decelerating effect on the movement of the vehicle V. Consequently, the driving resistance Fe may include a road gradient factor (i.e., a measure of a gradient or slope), an air resistance parameter, and / or a rolling resistance parameter.

[0034] After reaching the minimum acceleration a min determined, the processing circuit 112 generates the control signal S ctrl , which is configured to control the vehicle V to accelerate from the initial speed v0 to the target speed v t at least as fast as the minimum acceleration a min In other words, a faster acceleration than the minimum acceleration a min acceptable.

[0035] Accordingly, according to one embodiment of the invention, the desired speed v tthe highest speed at which the clutch 125 should be fully engaged. This means that from the point of view of clutch wear, it is equally acceptable for the clutch to be fully engaged at any speed below the target speed v t is fully indented.

[0036] Preferably, the processing circuit 112 is configured to determine the minimum acceleration a min in relation to the driving resistance F e and in a quadratic relationship with the speed difference Δv. More precisely, the minimum acceleration a min be determined as: amin=Fe2LΔv2−m, where F e the driving resistance is, L is the maximum amount of energy that can be absorbed by the clutch 125, Δv is the speed difference between the initial speed v0 and the desired speed v t is, and m is the weight of the vehicle V.

[0037] According to one embodiment of the invention, the processing circuit 112 is configured to treat the maximum amount of energy L absorbable by the clutch 125 either as a constant number or as a dynamic parameter.

[0038] If the maximum amount of energy L that can be absorbed by the clutch 125 is considered a constant number, this number is preferably set to an empirically verified value that takes the clutch design into account. Generally, this means that for a large and relatively robust clutch, L will be comparatively high; and vice versa for a smaller and less robust clutch.

[0039] If the maximum amount of energy L that can be absorbed by the clutch 125 is considered a dynamic parameter, this parameter may in turn be determined based on a current temperature of the clutch 125, a service interval for the clutch 125, and / or a fuel consumption condition. For example, if the current temperature of the clutch 125 is already relatively high, L is set to a slightly smaller number than if the clutch temperature had been lower. The service interval for the clutch 125 may influence the maximum amount of energy such that L can typically be set to a higher value for a clutch with shorter service intervals than for an identical clutch with less frequent service opportunities. The fuel consumption condition may influence the maximum amount of energy such that a lower allowable fuel consumption increases L, and vice versa.

[0040] In summary and with reference to the flow chart in Fig. 3, the general method according to the invention for accelerating a motor vehicle from an initial speed to a desired speed while gradually engaging the clutch of the vehicle will now be described.

[0041] A first step 310 checks whether a set of input parameters has been received in the form of: a driving resistance for the vehicle, a weight of the vehicle, a maximum amount of energy absorbable by the clutch, and a speed difference between the initial and target speed. If the set of input parameters has been received, a step 320 follows; otherwise, the process returns in the loop and remains at step 310.

[0042] In step 320, a minimum acceleration is determined, i.e., the smallest constant speed increase from the initial speed to the target speed. The minimum acceleration is determined based on the set of input parameters, for example, in relation to the driving resistance, and in a quadratic relationship with the speed difference.

[0043] Thereafter, in a step 330, a control signal is generated that is configured to control a drive train in the vehicle to cause the vehicle to accelerate from the initial speed to the desired speed at least as fast as specified by the minimum acceleration.

[0044] The process then returns to step 310 in the loop.

[0045] All process steps and any subsequence of steps that are related to the above Fig.3 can be controlled by means of at least one programmed processor. Furthermore, although the embodiments of the invention described above with reference to the drawings comprise a processor and processes executed in at least one processor, the invention thus also covers computer programs, and in particular computer programs on or in a carrier suitable for practicing the invention. The program may be in the form of source code, object code, an intermediate source of code and object code, such as in partially compiled form, or in any other form suitable for use in implementing the inventive process. The program may be either part of an operating system or a separate application. The carrier may be any entity or device capable of carrying the program.For example, the carrier may comprise a storage medium such as a flash memory, a ROM (read-only memory), for example a DVD (Digital Video / Versatile Disk), a CD (Compact Disc), or a semiconductor ROM, an EPROM (erasable programmable read-only memory), an EEPROM (electrically erasable programmable read-only memory), or a magnetic recording medium such as a floppy disk or a hard disk. Furthermore, the carrier may be a transferable medium such as an electrical or optical signal that can be transported via an electrical or optical cable, or via radio, or via other means. If the program is embodied in a signal that can be transported directly via a cable or other device or means, the carrier may consist of such a cable, device, or means.Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being suitable for executing or being used in executing the processes in question.

[0046] The term "comprises / comprising," when used in this specification, is intended to imply the presence of specified features, integers, steps, or components. However, the term does not preclude the presence or addition of one or more additional features, integers, steps, or components, or groups thereof.

[0047] The invention is not limited to the embodiments described in the figures, but can vary freely within the scope of the claims.

Claims

[1] Method which is carried out in a powertrain control unit (110) for accelerating a motor vehicle (V) from an initial speed (v0) to a desired speed (v t ) while gradually engaging a clutch (125) in the vehicle (V), the method comprising: Obtaining a set of input parameters (v0, v t , m, F e , L), and Controlling the vehicle (V) to accelerate from the initial to the target speed based on the set of input parameters, characterized by Determining, in a processing circuit (112) of the control unit (110), a minimum acceleration (a min ) required to reach the desired speed (v t ) with an acceptable wear for the clutch (125), wherein the minimum acceleration (a min) is determined based on the set of input parameters, which includes a driving resistance (F e ) for the vehicle (V), a weight (m) of the vehicle (V), a maximum amount of energy (L) that can be absorbed by the clutch (125), and a speed difference (Δv) between the initial and the desired speed (v0, v t ), and Generating a control signal (S ctrl ) configured to control a drive train (120) in the vehicle (V) to cause the vehicle (V) to accelerate from the initial speed (v0) to the desired speed (v t ) at least as fast as specified by the minimum acceleration (a min ) accelerates. [2] Method according to claim 1, comprising determining the minimum acceleration (a min ): in relation to the driving resistance (F e ), and in a quadratic relationship with the speed difference (Δv). [3] Method according to claim 2, comprising determining the minimum acceleration (a min ) as: Fe2LΔv2−m, where F e the driving resistance is, L is the maximum amount of energy that can be absorbed by the clutch (125), Δv is the speed difference between the initial and the target speed, and m is the weight of the vehicle (V). [4] A method according to any one of the preceding claims, wherein (L) the maximum amount of energy that can be absorbed by the clutch (125): is a constant number or based on at least one of a current temperature of the clutch (125), a service interval for the clutch (125), and a fuel consumption condition. [5] Method according to one of the preceding claims, wherein the driving resistance (F e ) comprises at least one of: a road gradient factor, an air resistance parameter and a rolling resistance parameter. [6] Method according to one of the preceding claims, wherein the desired speed (v t ) is a maximum speed at which the clutch (125) is fully engaged. [7] Method according to one of the preceding claims, wherein the initial speed (v0) is zero. [8] A computer program product (115) loadable onto a non-volatile data carrier (114) communicatively connected to the processing circuit (112), the computer program product (115) comprising software for carrying out the method according to any one of claims 1 to 7 when the computer program product (115) is executed on the processing circuit (112). [9] A non-volatile data carrier (114) containing the computer program product (115) according to claim 8. [10] Powertrain control unit (110) adapted to be included in a motor vehicle (V) for controlling the vehicle (V) from an initial speed (v0) to a desired speed (v t ) while gradually engaging a clutch (125) in the vehicle (V), wherein the powertrain control unit (110) is configured to: Obtaining a set of input parameters (v0, v t , m, F e , L), and Controlling the vehicle (V) to accelerate from the initial to the target speed based on the set of input parameters, characterized by that the control unit (110) comprises a processing circuit (112) configured to: Determining a minimum acceleration (a min) required to reach the desired speed (v t ) with an acceptable wear for the clutch (125), wherein the minimum acceleration (a min ) is determined based on the set of input parameters, which includes a driving resistance (F e ) for the vehicle (V), a weight (m) of the vehicle (V), a maximum amount of energy (L) that can be absorbed by the clutch (125), and a speed difference (Δv) between the initial and the desired speed (v0, v t ), and Generating a control signal (S ctrl ) configured to control the vehicle (V) to accelerate from the initial speed (v0) to the target speed (v t ) at least as fast as the minimum acceleration (a min ) accelerated to the specified speed. [11] Powertrain control unit (110) according to claim 10, wherein the processing circuit (112) is configured to determine the minimum acceleration (a min ) to determine: in relation to the driving resistance (F e ), and in a quadratic relationship with the speed difference (Δv). [12] Powertrain control unit (110) according to claim 11, wherein the processing circuit (112) is configured to determine the minimum acceleration (a min ) to be determined as: Fe2LΔv2−m, where F e the driving resistance is, L is the maximum amount of energy that can be absorbed by the clutch (125), Δv is the speed difference between the initial and the target speed, and m is the weight of the vehicle (V). [13] Powertrain control unit (110) according to one of claims 10 to 12, wherein the processing circuit (112) is configured to either: Treating the maximum amount of energy (L) that can be absorbed by the coupling (125) as a constant number, or Determining the maximum amount of energy (L) absorbable by the clutch (125) based on at least one of a current temperature of the clutch (125), a service interval for the clutch (125), and a fuel consumption condition. [14] Drive train control unit (110) according to one of claims 10 to 13, wherein the driving resistance (F e ) comprises at least one of: a road gradient factor, an air resistance parameter and a rolling resistance parameter. [15] Powertrain control unit (110) according to one of claims 10 to 14, wherein the initial speed (v0) is zero. [16] Drive train control unit (110) according to one of claims 10 to 15, wherein the desired speed (v t ) is a maximum speed at which the clutch (125) is fully engaged. [17] Vehicle (V) comprising a drive train (120) and the drive train control unit (110) according to one of claims 10 to 15 for controlling the drive train (120).

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