Deceleration of a motor vehicle by means of an electric machine

Abstract

A motor vehicle (105) comprises a drive wheel (115), which rolls on an underlying surface (120), and an electric drive machine (110), which acts on the drive wheel (115). A method (200) for decelerating the travelling motor vehicle (105) comprises steps of determining (215, 225) momentum of the motor vehicle (105); determining (245) a deceleration direction on the basis of the momentum; determining (240) a deceleration force on the basis of a deceleration request (125); determining (255) a deceleration torque (130) on the basis of the deceleration direction, the deceleration force and an effective lever between an axis of rotation of the drive machine (110) and the underlying surface (120); and actuating (255) the drive machine (110) in order to provide the deceleration torque (130).

Description

[0001] -2508 DE 1 Deceleration of a motor vehicle by means of an electric machine The present invention relates to the deceleration of a motor vehicle by means of an electric machine. In particular, the invention relates to the deceleration of a motorcycle by means of an electric drive machine. A motorcycle comprises an electric machine which acts on a drive wheel of the motorcycle. The motorcycle can be decelerated by providing a torque to the drive wheel by means of the drive machine, which torque causes a deceleration force. The torque can be controlled as a function of a rotational speed of the drive wheel, so that the torque becomes zero when the rotational speed of the drive wheel drops to zero and the motorcycle comes to a standstill.Since a conventional sensor for determining the speed of the drive wheel only provides information about the rotational speed and not about the direction of rotation of the drive wheel, the speed of the prime mover can be converted accordingly and used for control purposes. The speed and direction of rotation of the prime mover can be determined, for example, using a sensor or provided by a field-oriented control system. If there is slippage between the drive wheel and the ground, the driving speed of the motorcycle and, in particular, its standstill cannot be precisely determined. Slippage can occur particularly during sharp deceleration and / or at low driving speeds. For example, the drive wheel can rotate backward while the motorcycle is still moving forward, so that the drive wheel can initially turn forward again and the motorcycle can be briefly accelerated instead of decelerated.This can increase the stopping distance of the motorcycle. Under certain circumstances, the steering may begin to oscillate, which may impair control of the motorcycle. -2508 DE 2 An object underlying the present invention is to provide an improved technique for braking a motor vehicle using an electric drive motor. The invention solves this problem by means of the subject matter of the independent claims. A motor vehicle comprises a drive wheel that rolls on a surface and an electric drive motor that acts on the drive wheel.A method for decelerating a moving motor vehicle comprises the steps of determining an impulse of the motor vehicle; determining a deceleration direction based on the impulse; determining a deceleration force based on a desired deceleration; determining a deceleration torque based on the deceleration direction, the deceleration force, and an effective lever between a rotational axis of the drive motor and the ground; and controlling the drive motor to provide the deceleration torque. It is proposed to derive the driving speed of the motor vehicle from its impulse in order to be able to control the deceleration more effectively. The impulse can be determined reliably and precisely, particularly if the motor vehicle has a predetermined minimum speed, below which increased slip can occur during deceleration.The deceleration torque can be controlled with improved precision and, in particular, with correct direction. Even if the deceleration torque acting on the drive wheel is so great that the drive wheel rotates opposite to the direction of travel of the motor vehicle, control oscillation can be prevented. A driver of the motor vehicle can be provided with reliable and precise braking technology. The advantages of deceleration using the electric drive motor can be utilized, for example, low wear, the possibility of recuperating the vehicle's kinetic energy, or low emissions due to abrasion. -2508 DE 3 The driving speed of the motor vehicle can be determined based on the speed of the electric drive motor and the effective lever.The effective lever can be determined based on a circumference of the drive wheel and a valid reduction ratio between the drive wheel and the prime mover. The speed of the prime mover can be determined by means of a sensor or provided by a control device of the prime mover. Alternatively, the driving speed of the motor vehicle can also be determined by means of a speed sensor on the drive wheel. It is preferred that the drive wheel speed is determined while an amount of torque converted by the prime mover is below a predetermined threshold in order to promote slip-free running of the drive wheel. Alternatively, a speed sensor on a non-driven wheel of the motor vehicle can be used to determine the speed.The speed can also be determined in other ways, for example using a GNSS-based positioning system such as GPS, Galileo, or Glonass. The mass of the motor vehicle can be determined using a mass estimator, which, for example, evaluates how the speed of the motor vehicle changes when a known acceleration is initiated. Optionally, an incline or decline of a road being traveled can be taken into account. Since the mass of the motor vehicle generally does not change significantly during a journey, many such determinations can be made during a journey and processed together. The deceleration force can be reduced below the desired deceleration if the impulse is below a predetermined threshold. In other words, the deceleration force can be reduced if the driving speed of the motorcycle is below a corresponding threshold.If the magnitude of the impulse is above the threshold value, the desired deceleration and the deceleration force can correspond. The desired deceleration represents a force that always runs counter to the driving speed of the motorcycle, and the deceleration force is controlled in the same direction. More preferably, the reduction occurs linearly over the impulse. If the impulse of the motor vehicle is within a range around zero determined by the threshold value, the deceleration force can be smaller the closer the impulse is to zero. If the impulse is zero, the deceleration force is also zero. If, on the other hand, the impulse lies outside the range, the deceleration force can implement the entire desired deceleration. The deceleration force is preferably controlled with the correct sign, i.e. with a negative sign if the impulse is positive, and with a positive sign if the impulse is negative.In this way, the motor vehicle can be precisely braked electrically to a standstill. The reduction does not necessarily have to follow a linear function. In a further embodiment, the reduction is determined with respect to a predetermined characteristic curve via the impulse. The characteristic curve can describe any curve. Typically, the characteristic curve is point-symmetrical with respect to an impulse of zero and is monotonic. The characteristic curve can, for example, be determined experimentally in order to achieve effective and precise deceleration in the near-standstill range. In one embodiment, the characteristic curve has a value range between - ^1 and 1 and can be used to determine the deceleration force from the desired deceleration. The determination can easily be made using linear algebra or on the basis of a characteristic map. In another embodiment, the amount of the deceleration force can be upper limited to a predetermined amount.A similar characteristic curve can be used, the value range of which can, however, be specified absolutely. The deceleration torque can be controlled so that it lies in a range between the characteristic curve and the horizontal axis. A deceleration request whose magnitude – taking into account an applicable pulse – exceeds the characteristic curve can be limited to the value of the characteristic curve. If the pulse is positive, the deceleration torque can be kept greater than a negative value and less than zero; if the pulse is negative, the deceleration torque can be kept less than a positive value and greater than zero. If the pulse is zero, the deceleration torque can also be zero. Because of the possible change in sign of the pulse, this type of control can also be called min-max control.The drive torque can be determined such that the stationary motor vehicle is held on a slope or incline of the ground. The drive torque can counteract a downhill force and prevent the motor vehicle from rolling away. In one embodiment, a holding force is determined in order to hold the motor vehicle at a standstill on the incline or decline. The holding force can be determined as a function of a mass of the motor vehicle on the basis of the degree of the slope or incline. The holding force can be effected in addition to the deceleration force. In another embodiment, the characteristic curve is shifted vertically by an amount such that the characteristic curve has a positive value at an impulse of zero if there is an incline, or a negative value if the motor vehicle is on a decline.In yet another embodiment, a characteristic map is provided to determine a suitable torque, which is controlled by the drive engine, based on the degree of the impulse and the incline or decline. -2508 DE 6 Furthermore, a change in the impulse of the motor vehicle can be determined on the basis of at least one force acting on the motor vehicle in the direction of movement. This allows a dynamic influence on the impulse to be determined more effectively. The force can in particular comprise one of a driving force caused by a drive motor, a friction force caused by a friction brake, a rolling resistance force, an air resistance force, and a downhill force. Forces can be determined individually using an associated sensor or estimator on the basis of further values.The motor vehicle can comprise several drive motors, which can be considered individually, and of which the electric drive machine can be one. A current pulse can be determined based on the determined pulse and the pulse change. For this purpose, in particular, the determined pulse can be low-pass filtered and the pulse change can be high-pass filtered. The time constants of both filters preferably correspond to one another. A current pulse can be determined using a complementary filter based on the determined pulse and the determined pulse change. In this way, the current pulse of the motor vehicle can be determined quickly and precisely, and the drive machine can be controlled more effectively in order to carry out the described deceleration. It can be advantageous to determine the time constant as a function of a driving state of the motor vehicle.For example, the time constant can be determined as a function of a driving speed, a longitudinal acceleration, an incline, or a road gradient. According to a further aspect of the present invention, a device for decelerating a motor vehicle described herein comprises: -2508 DE 7 a device for determining an impulse of the motor vehicle; a first interface for detecting a deceleration request; a second interface for controlling the drive engine; and a processing device.The processing device is configured to determine a deceleration direction based on the impulse; to determine a deceleration force based on a deceleration request; to determine a deceleration moment based on the deceleration direction, the deceleration force, and an effective lever between a rotational axis of the drive machine and the ground; and to control the drive machine to provide the deceleration moment. The processing device is preferably configured to partially or completely carry out a method described herein. For this purpose, the processing device can be embodied electronically and comprise, for example, an integrated circuit, a programmable logic module, or a programmable microcomputer. The method can be implemented in the form of a configuration or as a computer program product with program code means for the processing device.The configuration or the computer program product can be stored on a computer-readable data carrier. Features or advantages of the method can be transferred to the device, or vice versa. According to yet another aspect of the present invention, a motor vehicle comprises a device described herein. The motor vehicle can be driven exclusively or partially by means of the electric drive motor. The motor vehicle can have one or more tracks; in a particularly preferred embodiment, the motor vehicle comprises a motorcycle, a scooter, or a similar single-track two-wheeler. The described technology can assist a driver in keeping the single-track motor vehicle balanced when stopping and in preventing it from tipping sideways.-2508 DE 8 The invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 shows a device on board a motor vehicle; Figure 2 shows a flow diagram of a method; and Figure 3 illustrates exemplary processes. Figure 1 shows a device 100 on board a motor vehicle 105. The motor vehicle 105 is designed here, for example, as a motorcycle, in particular as a motorbike, but other embodiments are also possible. For the sake of clarity, Figure 1 shows only a rear section of the motor vehicle 105. The motor vehicle 105 comprises an electric drive machine 110 which acts on a drive wheel 115. For this purpose, a transmission can be provided which implements a predetermined reduction between corresponding rotary movements. The drive wheel 115 supports the motor vehicle 105 with respect to a ground 120.When the motor vehicle 105 is moving, the drive wheel 115 typically rolls on the ground 120, whereby slippage may occur in the direction of travel. To decelerate the moving motor vehicle 105, a deceleration request 125 can be determined, which is provided, for example, by a driver of the motor vehicle 105 or by a system on board the motor vehicle 105, for example a safety or driving stability system. The drive motor 110 can then be controlled to provide a deceleration torque 130 to the drive wheel 115, which implements the deceleration request as appropriately as possible. During deceleration, kinetic energy of the motor vehicle 105 can be converted into electrical energy and either stored in an energy storage device or released as heat. The deceleration force has a predetermined magnitude and opposes a longitudinal movement of the motorcycle 105.The deceleration torque 130 is converted by the drive engine 110 and acts as a deceleration force on the motor vehicle 105 via the drive wheel 115. The device 100 comprises a processing device 135, a first interface 140 for detecting the deceleration request 125; and a second interface 145 for controlling the drive engine 110. It is proposed to control the deceleration torque 130 as a function of an impulse from the motor vehicle 105. For this purpose, the processing device 125 can be configured to determine the impulse based on a speed and a mass of the motor vehicle 105. The speed can be determined, for example, based on a sensor signal from a wheel speed sensor 150 on the drive wheel 115, and the mass of the motor vehicle 105 can be determined using a mass estimator 160.The mass estimator 160 can also be implemented by the processing device 135 and preferably determines the mass with respect to an observed relationship between a driving or decelerating force and an acceleration. An approximate estimate of the mass, for example, accurate to approximately ±15%, can be sufficient for the present purposes. The momentum is further preferably determined or updated using different methods, with a first method being particularly good at reproducing a low-frequency change in the momentum and a second method being particularly good at reproducing a high-frequency change. The first method can determine the momentum based on the driving speed and the mass, and the second method can determine a change in speed based on one or more forces acting in the direction of travel. Different forces can be recorded individually or in groups and processed together.Processing can be carried out using a complementary filter. -2508 DE 10 Figure 2 shows a flow diagram of a method 200 for decelerating a motor vehicle 105 according to Figure 1. In a step 205, a mass of the motor vehicle 105 can be estimated. This step can be carried out periodically or event-controlled, even multiple times during a journey with the motor vehicle 105, and several determinations can be offset against one another, for example by forming an average. The determined mass can be included in further determinations or controls on board the motor vehicle 105. In a step 210, a driving speed of the motor vehicle 105 can be determined. For this purpose, for example, a signal from the wheel speed sensor 155 or a speed signal from a control system of the drive engine 110 can be evaluated.Alternatively, the speed can be determined, for example, using a receiver for navigation signals from a GNSS or using an optical system for scanning the environment. The driving speed can be redetermined continuously or periodically. In a step 215, the momentum of the motor vehicle 105 can be determined on the basis of the determined driving speed. By low-pass filtering, a low-pass component ^^^^^^ = ^^^^^^^^^^^^^^(^^ ∗ ^^) of the momentum can be determined. TPTkomp is a low-pass filter function which low-pass filters the argument (v * m) with the time constant Tkomp. The low-pass component is long-term stable and reflects slow changes in the momentum. In parallel, in a step 220, forces can be determined that act on the driving speed of the motor vehicle 105 and are thus acceleration or braking forces. The forces can be determined individually or in groups.For the determination, a sensor can be scanned and / or processing can be performed. For example, one or more of the following forces can be determined: -2508 DE 11 - a driving force or braking force Fmot of one or more motors, one of which can be formed by the drive engine 110; - a deceleration force Fbrems of a friction brake of the motor vehicle 105 - a rolling resistance force Froll; - an air resistance force Faero; - a slope force Fhang due to a gradient or incline of the ground 120. If there are long dead times in the conversion of the drive torque in the system, it can be advantageous to estimate the motor drive force ^^mot of a drive motor 110 based on a desired engine torque instead of an actual engine torque. On the basis of the forces, a change in momentum of the motor vehicle 105 can be determined in a step 225.The pulse change can be high-pass filtered to consider only components that have a predetermined minimum frequency. A high-pass component pHP of the vehicle pulse pTP is determined as ^^^^^^ = ^^^^^^^^^^^^^^(∫^^ (^^)^^^^). Here, HPTcomp is a high-pass filter function that high-pass filters the argument (∫^^ (^^)^^^^) with the time constant Tcomp. The high-pass filter function HPTcomp can alternatively be written as ^^^^^^^^^^^^^^(^^) =^^ − ^^^^^^^^^^^^^^(^^). This gives:^^^^^^ = ∫^^ (^^)^^^^ − ^^^^^^^^^^^^^^(∫^^ (^^)^^^^).If a PT1 element is used as the low-pass filter function, this equation can be further simplified to -2508 DE 12 ^^^^^^ = ^^^^^^^^^^ ∗ ^^^^^^^^^^^^^^(^^).It should be noted that the time constant Tcomp of the low-pass filter function TPTcomp in step 225 should be just as large as the time constant Tcomp of the high-pass filter function HPTcomp in step 215 in order to determine low-frequency components of the pulse change based solely on the speed and high-frequency components based solely on the forces. In a step 230, the first and second pulse changes can be combined, for which purpose a complementary filter is preferably used. The vehicle pulse pcomp determined using the complementary filter is then ultimately obtained as: ^^^^^^^^ = ^^^^^^ + ^^^^^^. The deceleration request 125 can be determined or sampled in a step 235. In a step 230, an increase or decrease or an adjustment can be determined based on the pulse. For this purpose, a predetermined function can be used which provides a predetermined adjustment for an existing pulse.The adjustment can comprise a minimum amount or a maximum amount. In a step 245, the deceleration force can be determined based on the impulse. From this, a deceleration torque can be determined based on an applicable gear ratio and a circumference of the drive wheel 115 and controlled on the drive machine 110. Figure 3 shows exemplary adjustments that can be determined in step 230. A first adjustment 305 is relative and represented by a first characteristic curve 310. A second adjustment 315 is absolute and represented by a characteristic curve 320. Both representations show an impulse of the motor vehicle 105 in a horizontal direction with the impulse zero at the coordinate origin. In the relative adjustment 305, a factor is plotted in the vertical direction, which can be between -1 and +1. The first characteristic curve 310 is essentially Z-shaped and runs through the origin.Below a predetermined (negative) impulse, a value of the first characteristic curve 310 is one, and above a predetermined (positive) impulse, it is minus one. The values ​​of the limits for the impulses are equal. In a range between these values, the characteristic curve 310 is linear. In another embodiment, a non-linear relationship exists. For a given impulse of the motor vehicle 105, a value of the first characteristic curve 310 can be determined, and the desired deceleration 125 can be multiplied by this value to determine the deceleration force. In the absolute adaptation 315, a deceleration moment 255 is plotted in the vertical direction. An area between the second characteristic curve 320 and the horizontal axis is considered the permissible range. By means of the adaptation 315, the amount of the deceleration moment 255 can be limited to a predetermined value depending on the current impulse of the motor vehicle 105.The limiting occurs in the positive direction if the pulse is negative, and in the negative direction if the pulse is positive. The deceleration torque Mverz can be determined as follows: -2508 DE 14 if ^^(^^^^^^^^,^^^^^^^^^^^^)(^^) <0 The function min(^^1, ^^2) returns the smaller of the two arguments ^^1, ^^2, while max(^^1, ^^2) returns the larger of the two arguments. The minimum-maximum limiting torque ^^deceleration,^^^^^^^^^^^^(^^) can, for example, be derived from the impulse using the characteristic curve 320 shown. A differently shaped characteristic curve 320 can also be used.

[0002] -2508 DE 15 Reference numerals 100 Device 105 Motor vehicle 110 Drive machine 115 Drive wheel 120 Surface 125 Deceleration request 130 Deceleration moment 135 Processing device 140 First interface 145 Second interface 150 Wheel speed sensor 155 Mass estimator 200 Method 205 Estimate mass 210 Determine speed 215 Determine momentum change according to speed 220 Determine forces 225 Determine momentum change according to forces 230 Complementary filter 235 Determine deceleration request 240 Determine lowering / adaptation 245 Control deceleration moment 305 First adaptation (relative) 310 First characteristic curve 315 Second adaptation (absolute) 320 Second characteristic curve

Claims

-2508 DE 16 claims 1. Method (200) for decelerating a moving motor vehicle (105) by means of an electric drive machine (110) which acts on a drive wheel (115) of the motor vehicle (105) which is rolling on a surface (120), the method (200) comprising the following steps: - determining (215, 225) an impulse of the motor vehicle (105); - determining (245) a deceleration direction on the basis of the impulse; - determining (240) a deceleration force on the basis of a deceleration request (125); - determining (255) a deceleration torque (130) on the basis of the deceleration direction, the deceleration force and an effective lever between a rotational axis of the drive machine (110) and the surface (120); and - controlling the (255) drive motor (110) to provide the deceleration torque (130). 2.Method (200) according to claim 1, wherein the deceleration force is reduced below the desired deceleration (125) if the impulse is below a predetermined threshold value.

3. Method (200) according to claim 2, wherein the reduction occurs linearly over the impulse.

4. Method (200) according to claim 2, wherein the reduction is determined with respect to a predetermined characteristic curve over the impulse.

5. Method (200) according to one of the preceding claims, wherein an amount of the deceleration force is limited upwards to a predetermined amount. -2508 DE 17 6. The method (200) according to one of the preceding claims, wherein the deceleration force is determined such that the stationary motor vehicle (105) is held on an uphill or downhill slope.

7. The method (200) according to one of the preceding claims, wherein a change in momentum of the motor vehicle (105) is determined on the basis of at least one force acting on the motor vehicle (105) in the direction of movement.

8. The method (200) according to claim 7, wherein the force comprises one of a drive force caused by a drive motor, a friction force caused by a friction brake, a rolling resistance force, an air resistance force, and a downhill force.

9. The method (200) according to one of claims 7 or 8, wherein a current momentum is determined on the basis of the determined momentum and the change in momentum. 10.Method (200) according to claim 9, wherein the determined pulse is low-pass filtered and the pulse change is high-pass filtered; wherein time constants of both filters correspond to one another.

11. Method (200) according to claim 10, wherein the time constant is determined (230) as a function of a driving state of the motor vehicle (105).

12. Method (200) according to claim 10 or 11, wherein a current pulse is determined (230) by means of a complementary filter on the basis of the determined pulse and the determined pulse change.

13. Device (100) for decelerating a moving motor vehicle (105) by means of an electric drive machine (110) which is connected to a. -2508 DE 18 drive wheel (115) of the motor vehicle (105) which rolls on a surface (120), the device comprising the following: - a device (135) for determining an impulse of the motor vehicle (105); - a first interface (140) for detecting a deceleration request (125); - a second interface (145) for controlling the drive machine (110); - a processing device (135) which is configured to: - determine a deceleration direction based on the impulse; - determine a deceleration force based on a deceleration request (125); - determine a deceleration moment (130) based on the deceleration direction, the deceleration force and an effective lever between a rotational axis of the drive machine (110) and the surface (120); and - to control the drive motor (110) to provide the deceleration torque (130).

14. Motor vehicle (105) comprising a device (100) according to claim

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