Deceleration of motor vehicle by means of electric machine
By determining the momentum of the vehicle and precisely controlling the deceleration torque, the problem of inaccurate deceleration of foot-operated motor vehicles under skidding conditions is solved, achieving reliable electric drive deceleration control, reducing stopping distance and avoiding oscillation, and possessing advantages of low wear and energy recovery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BAYERISCHE MOTOREN WERKE AG
- Filing Date
- 2024-12-13
- Publication Date
- 2026-05-08
AI Technical Summary
Existing technologies make it difficult to precisely control the deceleration of pedal-powered motor vehicles during slippage, resulting in longer stopping distances and difficulty in controlling oscillations, especially when it is slow or decelerating rapidly, making it difficult to accurately determine the stationary state.
By determining the momentum of the motor vehicle, the deceleration direction and torque are determined based on the momentum. The electric drive motor provides the deceleration torque, and the deceleration torque is precisely controlled by sensors and a mass estimator to prevent the drive wheels from rotating in the opposite direction.
It achieves precise deceleration control under slip conditions, ensuring reliable braking of motor vehicles, reducing stopping distance, avoiding control oscillations, and making full use of the advantages of low wear and energy recovery of electric drive.
Smart Images
Figure CN122003336A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to slowing down motor vehicles using an electric motor. More particularly, this invention relates to slowing down pedal-powered motor vehicles using an electric drive motor. Background Technology
[0002] A pedal-powered vehicle includes a motor acting on the drive wheels of the vehicle. The pedal-powered vehicle can be decelerated by providing a torque that induces a decelerating force on the drive wheels via a drive motor. This torque can be controlled according to the rotational speed of the drive wheels, such that the torque is zero when the rotational speed of the drive wheels drops to zero and the pedal-powered vehicle comes to a standstill. Since conventional sensors used to determine the rotational speed of the drive wheels only provide information about the speed of rotation and not about the direction of rotation, the rotational speed of the drive motor can be alternatively calculated and used for control. The rotational speed and direction of rotation of the drive motor can be determined, for example, by means of sensors or provided by field-oriented control.
[0003] If slippage exists between the drive wheels and the ground, it may be impossible to accurately determine the speed of the pedal-powered vehicle, and especially its stationary state. Slippage can occur particularly during rapid deceleration and / or at low speeds. Therefore, the drive wheels may, for example, rotate in the opposite direction while the pedal-powered vehicle continues to move forward, causing the drive wheels to rotate forward first and the pedal-powered vehicle to accelerate briefly rather than decelerate. The stopping distance of the pedal-powered vehicle can thus be increased. In certain situations, the control may begin to oscillate, potentially adversely affecting the control of the pedal-powered vehicle. Summary of the Invention
[0004] The objective of this invention is to provide an improved technique for braking a motor vehicle using an electric drive mechanism. This invention addresses this objective through the subject matter of the independent claims.
[0005] A motor vehicle includes drive wheels that roll on the ground and an electric drive motor acting on the drive wheels. A method for decelerating a moving motor vehicle includes the steps of: determining the momentum of the motor vehicle; determining a deceleration direction based on the momentum; 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 the drive motor shaft and the ground; and controlling the drive motor to provide the deceleration torque.
[0006] The proposed method involves deriving the vehicle's speed from its momentum to improve deceleration control. Momentum can be reliably and accurately determined, especially when the vehicle has a predetermined minimum speed below which slippage is more likely during deceleration. Deceleration torque can be controlled more precisely, particularly in its direction. Even if the deceleration torque acting on the drive wheels is large enough to cause them to rotate against the vehicle's direction of travel, oscillations can be prevented. This provides the driver with reliable and precise braking technology. The advantages of deceleration using electric drive systems can be fully utilized, such as lower wear, the possibility of recovering kinetic energy from the vehicle, and lower emissions due to wear.
[0007] The speed of a motor vehicle can be determined based on the rotational speed of the electric drive motor and the effective leverage. The effective leverage can be determined based on the circumference of the drive wheels and the reduction ratio effective between the drive wheels and the drive motor. The rotational speed of the drive motor can be determined by sensors or provided by the drive motor's control unit.
[0008] Alternatively, the vehicle's speed can be determined using speed sensors on the drive wheels. Preferably, the drive wheel speed is determined while the torque achieved by the drive motor is below a predetermined threshold to facilitate slip-free operation of the drive wheels. Alternatively, speed sensors can be used on the non-drive wheels of the vehicle to determine speed. Speed can also be determined in other ways, such as using a GNSS-based positioning system (e.g., GPS, Galileo, or GLONASS).
[0009] The mass of a motor vehicle can be determined using a mass estimator, which, for example, assesses how the vehicle's speed changes when a known acceleration is introduced. Optionally, the uphill or downhill gradient of the road on which the vehicle is traveling can be considered. Since the mass of a motor vehicle typically does not change significantly during travel, multiple such determinations can be performed during travel and processed together.
[0010] When momentum is below a predetermined threshold, the deceleration force can be reduced below the desired deceleration. In other words, when the speed of the pedal-powered vehicle is below the corresponding threshold, the deceleration force can be reduced. If the momentum is above the threshold, the desired deceleration and the deceleration force can correspond to each other. The desired deceleration represents a force that always extends against the speed of the pedal-powered vehicle, and the deceleration force is controlled in the same direction.
[0011] Further preferably, the reduction occurs linearly with respect to momentum. When the momentum of the vehicle is within a range around zero, as determined by a threshold, the closer the momentum is to zero, the smaller the deceleration force can be. When the momentum is zero, the deceleration force is also zero. Conversely, when the momentum is outside this range, the deceleration force can achieve the full desired deceleration. Preferably, the control sign of the deceleration force is correct, i.e., a negative sign when the momentum is positive and a positive sign when the momentum is negative. Thus, the vehicle can be precisely electrically braked to a standstill.
[0012] The reduction need not necessarily follow a linear function. In another embodiment, the reduction is determined in relation to a predetermined characteristic curve of momentum. The characteristic curve can describe any curve. Typically, the characteristic curve is symmetrical about the zero momentum point and extends monotonically. The characteristic curve can be determined, for example, experimentally, to achieve effective and precise deceleration in the range close to rest.
[0013] In one implementation, the characteristic curve has a numerical range between -1 and 1, and can be used to determine the deceleration force from the desired deceleration. This determination can be performed simply using linear algebra or based on a family of characteristic curves.
[0014] In another implementation, the value of the deceleration force can be upwardly limited to a predetermined value. A similar characteristic curve can be used here, the numerical range of which can be absolutely defined. The deceleration torque can be controlled such that it lies within a range between the characteristic curve and the horizontal axis. The deceleration expectation—whose value exceeds the characteristic curve, taking into account the effective momentum—can be limited to the value of the characteristic curve. If the momentum is positive, the deceleration torque can be maintained greater than a negative value and less than zero; if the momentum is negative, the deceleration torque can be maintained less than a positive value and greater than zero. If the momentum is zero, the deceleration torque can also be zero. Due to the possible sign variation of the momentum, this control can also be referred to as minimum-maximum control.
[0015] The driving torque can be determined such that a stationary motor vehicle is held on an uphill or downhill slope of the ground. The driving torque can act in opposition to the sliding force and prevent the motor vehicle from rolling away.
[0016] In one implementation, a holding force is determined to keep the vehicle stationary on an uphill or downhill slope. The holding force can be determined based on the mass of the vehicle and the gradient of the uphill or downhill slope. The holding force can be applied to the deceleration force.
[0017] In another embodiment, the characteristic curve is vertically shifted by a value such that the characteristic curve has a positive value when the momentum is zero in the case of an uphill slope, or a negative value when the vehicle is on a downhill slope.
[0018] In yet another embodiment, a family of characteristic curves is provided to determine the appropriate torque controlled by the drive motor based on the degree of momentum and the slope of the uphill or downhill section.
[0019] Furthermore, the change in momentum of the motor vehicle can be determined based on at least one force acting on the motor vehicle along the direction of motion. This allows for a more refined determination of the dynamic effects on the momentum. The force may in particular include one of the following: driving force generated by a drive motor, frictional force generated by a friction brake, rolling resistance, air resistance, and sliding force.
[0020] Each force can be determined individually using an attached sensor or an estimator based on other values. The motor vehicle may include multiple drive motors, which can be considered individually, and the electric drive motor may constitute one of the multiple drive motors.
[0021] The current momentum can be determined based on the determined momentum and the change in momentum. Specifically, the determined momentum can be low-pass filtered and the change in momentum can be high-pass filtered. Preferably, the time constants of the two filters are equal.
[0022] The current momentum can be determined using a complementary filter based on the determined momentum and the determined change in momentum. This allows for the rapid and accurate determination of the vehicle's current momentum, and enables improved control of the drive unit to perform the described deceleration.
[0023] Determining the time constant based on the driving state of the motor vehicle can be advantageous. Thus, the time constant can be determined, for example, based on driving speed, longitudinal acceleration, tilt position, or road gradient.
[0024] According to another aspect of the invention, a device for decelerating a motor vehicle as described herein includes: A device for determining the momentum of the motor vehicle; a first interface for obtaining a deceleration expectation; a second interface for controlling the drive unit; and a processing device. The processing device is configured to: determine a deceleration direction based on the momentum; determine a deceleration force based on the deceleration expectation; determine a deceleration torque based on the deceleration direction, the deceleration force, and an effective lever between the drive unit's shaft and the ground; and control the drive unit to provide the deceleration torque.
[0025] The processing device is preferably configured to perform the methods described herein, either partially or completely. For this purpose, the processing device can be implemented electronically and, for example, includes an integrated circuit, a programmable logic module, or a programmable microcomputer. The method can be implemented in a configuration form or as a computer program product having program code modules 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.
[0026] According to yet another aspect of the invention, a motor vehicle includes the device described herein. The motor vehicle can be driven wholly or partially by the electric drive motor. The motor vehicle may have one or more tracks; in a particularly preferred embodiment, the motor vehicle includes a motorcycle, a motorized scooter, or a similar single-track two-wheeled vehicle. The described technology can help the driver maintain balance in the single-track motor vehicle at the moment of stopping and prevent lateral tipping. Attached Figure Description
[0027] The invention will now be described in detail with reference to the accompanying drawings, wherein: Figure 1 Showing the equipment mounted on the motor vehicle; Figure 2 A flowchart illustrating the method is shown; and Figure 3 An example variation curve is shown. Detailed Implementation
[0028] Figure 1 The device 100 mounted on a motor vehicle 105 is shown. The motor vehicle 105 is configured here, for example, as a pedal-powered motor vehicle, especially as a motorcycle; however, other embodiments are also possible. Figure 1 For clarity, only the rear section of the motor vehicle 105 is shown. The motor vehicle 105 includes an electric drive motor 110 that acts on drive wheels 115. A transmission may be provided for this purpose, achieving a predetermined reduction ratio between corresponding rotational movements. The drive wheels 115 support the motor vehicle 105 relative to the ground 120. When the motor vehicle 105 is in motion, the drive wheels 115 typically roll on the ground, although slippage may occur in the direction of travel.
[0029] To decelerate a moving motor vehicle 105, a deceleration expectation 125 can be determined, provided, for example, by the driver of the motor vehicle 105 or by systems onboard the motor vehicle 105, such as safety systems or driving stability systems. The drive motor 110 can then be manipulated to provide a deceleration torque 130 on the drive wheels 115, the deceleration torque being suitably tailored to achieve the deceleration expectation. During deceleration, the kinetic energy of the motor vehicle 105 can be converted into electrical energy and either received in an energy storage device or released as heat. The deceleration force has a predetermined value and is set opposite to the longitudinal movement of the pedal-operated motor vehicle 105. The deceleration torque 130 is achieved by the drive motor 110 and acts as a deceleration force on the motor vehicle 105 via the drive wheels 115.
[0030] Device 100 includes a processing unit 135, a first interface 140 for acquiring a deceleration expectation 125, and a second interface 145 for controlling a drive unit 110. It is proposed that the deceleration torque 130 be controlled based on the momentum of the vehicle 105. For this purpose, the processing unit 125 can be configured to determine the momentum based on the speed and mass of the vehicle 105. The speed can be determined, for example, based on sensor signals from wheel speed sensors 150 at the drive wheels 115, and the mass of the vehicle 105 can be determined using a mass estimator 160. The mass estimator 160 can also be implemented by the processing unit 135, and preferably determines the mass based on the observed relationship between the driving force or deceleration force and acceleration. An approximate estimation of the mass, for example, with an accuracy of approximately ±15%, may be sufficient for the present purpose.
[0031] Momentum is further determined or estimated through different approaches, with a first approach particularly effective at tracking low-frequency changes in momentum and a second approach particularly effective at tracking high-frequency changes. The first approach can determine momentum based on travel speed and mass, while the second approach can determine speed changes based on one or more forces acting along the travel direction. Different forces can be detected individually or in groups and processed together. This processing can be performed using complementary filters.
[0032] Figure 2 Showing according to Figure 1 A flowchart of a method 200 for decelerating a motor vehicle 105 is provided. In step 205, the mass of the motor vehicle 105 can be estimated. This step can be performed periodically or event-controlled multiple times during the movement of the motor vehicle 105, and multiple determined values can be calculated together, for example, by averaging. The determined mass can also be incorporated into other determinations or controls onboard the motor vehicle 105.
[0033] In step 210, the travel speed of the vehicle 105 can be determined. This can be done, for example, by evaluating the signal from the wheel speed sensor 155 or the speed signal from the controller of the drive unit 110. Alternatively, the speed can be determined, for example, by means of a receiver for navigation signals used in a global navigation satellite system or by means of an optical system for detecting the surrounding environment. The travel speed can be continuously or periodically re-determined.
[0034] In step 215, the momentum of the vehicle 105 can be determined based on the determined travel speed. The low-pass component of the momentum can be determined using a low-pass filter. In this TP Tkomp It is a low-pass filter function, wherein the low-pass filter function has a time constant T komp For independent variable Perform low-pass filtering. The low-pass component is stable over the long term and reflects slow changes in momentum.
[0035] In parallel, in step 220, the driving speed of the vehicle 105 and therefore the force acting on it, which is either an acceleration force or a braking force, can be determined. The force can be determined individually or in groups. For this determination, sensors can be scanned and / or processing can be performed. One or more of the following forces can be determined, for example: - The driving or braking force F of one or more motors mot One of the motors may be a drive motor 110; - The deceleration force F of the friction brake of motor vehicle 105 brems ; - Rolling resistance F rol ; - Air resistance F aero ; - The sliding force F caused by the uphill or downhill slope of the ground at 120 degrees. hang .
[0036] When there is a large dead time in the implementation of the driving torque in the system, it is advantageous to estimate the motor driving force F of the drive motor 110 by substituting the actual motor torque with the set motor torque. mot .
[0037] Based on the force, the momentum change of the motor vehicle 105 can be determined in step 225. The momentum change can be high-pass filtered so that only the component with a predetermined lowest frequency is considered. Vehicle momentum p TP High-pass component p HP It was identified as:
[0038] Here, HP Tkomp It is a high-pass filter function, wherein the high-pass filter function has a time constant Tkomp For the independent variable ( High-pass filtering is performed on F(t)dt. The high-pass filter function is HP. Tkomp It can be alternatively written as HP Tkomp (x) = x - TP Tkomp (x). Therefore:
[0039] When the PT1 stage is used as the low-pass filter function, the equation can be further simplified to:
[0040] It is important to note that the low-pass filter function TP in step 225... Tkomp Time constant T komp It should be compared with the high-pass filter function HP in step 215. Tkomp Time constant T komp They are of the same magnitude so that the low-frequency components of momentum change can be determined based on velocity as much as possible and the high-frequency components can be determined based on force as much as possible.
[0041] In step 230, the first and second momentum changes can be combined, preferably using a complementary filter. The vehicle momentum p is determined using the complementary filter. komp The final conclusion is:
[0042] The deceleration expectation 125 can be determined or detected in step 235. In step 230, an increase or decrease, or adjustment, can be determined based on momentum. For this purpose, a predetermined function can be used, which provides a predetermined adjustment to the current momentum. The adjustment can include a minimum or maximum value.
[0043] In step 245, the deceleration force can be determined based on momentum. The deceleration torque can then be determined based on the effective reduction ratio and the circumference of the drive wheel 115 and controlled at the drive unit 110.
[0044] Figure 3 Exemplary adjustments that can be determined in step 230 are shown. The first adjustment 305 is relative and is characterized by a first characteristic curve 310. The second adjustment 315 is absolute and is shown by characteristic curve 320. The two figures illustrate the momentum of the vehicle 105 in the horizontal direction, with zero momentum at the origin of the coordinate system.
[0045] In relative adjustment 305, coefficients are plotted vertically, which can be between -1 and +1. The first characteristic curve 310 is substantially Z-shaped and extends through the origin. Below a predetermined (negative) momentum, the value of the first characteristic curve 310 is one, and above a predetermined (positive) momentum, it is negative one. The numerical values are the same for the momentum boundaries. In the region between these values, the characteristic curve 310 extends linearly. A non-linear relationship is given in another embodiment.
[0046] For a given momentum of motor vehicle 105, the value of the first characteristic curve 310 can be determined, and the deceleration expectation 125 can be multiplied by this value to determine the deceleration force.
[0047] In the absolute adjustment 315, the deceleration torque 255 is plotted in the vertical direction. The area between the second characteristic curve 320 and the horizontal axis is considered the allowable range. With the help of adjustment 315, the value of the deceleration torque 255 can be limited to a predetermined value based on the current momentum of the vehicle 105. The limit is applied in the positive direction when the momentum is negative, and in the negative direction when the momentum is positive. Deceleration torque M verz It can be determined as follows:
[0048] The function min(x1, x2) outputs the smaller of the two independent variables x1 and x2, while max(x1, x2) outputs the larger of the two independent variables. Minimum and maximum limiting torque M verz,MinMax(p) For example, momentum can be derived using the characteristic curve 320 shown. Characteristic curves 320 of other shapes can also be used.
[0049] List of reference numerals:
[0050] 100 devices
[0051] 105 Motor vehicles
[0052] 110 drive unit
[0053] 115 drive wheels
[0054] 120 Ground
[0055] 125 Deceleration Expectation
[0056] 130 deceleration torque
[0057] 135 Processing Unit
[0058] 140 First Interface
[0059] 145 Second Interface
[0060] 150 Wheel Speed Sensor
[0061] 155 Quality Estimator
[0062] 200 methods
[0063] 205 Estimating Mass
[0064] 210 Determine the speed
[0065] 215 Determining the change in momentum based on velocity
[0066] 220 Certainty
[0067] 225 Determining Momentum Change Based on Force
[0068] 230 Complementary Filter
[0069] 235 Determine the expected deceleration
[0070] 240 Determine reduction / adjustment
[0071] 245 Controlling deceleration torque
[0072] 305 First Adjustment (Relative)
[0073] 310 First characteristic curve
[0074] 315 Second Adjustment (Absolute)
[0075] 320 Second characteristic curve
Claims
1. A method (200) for decelerating a moving motor vehicle (105) by means of an electric drive motor (110), the electric drive motor acting on drive wheels (115) of the motor vehicle (105) rolling on the ground (120), wherein the method (200) comprises the following steps: - Determine the momentum of the motor vehicle (105) described in (215, 225); - Determine the deceleration direction (245) based on the momentum; - Determine the (240) deceleration force based on the deceleration expectation (125); - Determine (255) the deceleration torque (130) based on the deceleration direction, the deceleration force, and the effective lever between the shaft of the drive unit (110) and the ground (120); and Control (255) the drive (110) to provide the deceleration torque (130).
2. The method (200) according to claim 1, wherein, If the momentum is below a predetermined threshold, the deceleration force is reduced to below the deceleration expectation (125).
3. The method (200) according to claim 2, wherein, The reduction occurs linearly with respect to the momentum.
4. The method (200) according to claim 2, wherein, The reduction is determined in relation to a predetermined characteristic curve of momentum.
5. The method (200) according to any one of the preceding claims, wherein, The value of the deceleration force is limited upward to a predetermined value.
6. The method (200) according to any one of the preceding claims, wherein, The deceleration force is thus determined so that the stationary motor vehicle (105) is kept on an uphill or downhill slope.
7. The method (200) according to any one of the preceding claims, wherein, The momentum change of the motor vehicle (105) is determined based on at least one force acting on the motor vehicle (105) along the direction of motion.
8. The method (200) according to claim 7, wherein, The force includes one of the following: driving force generated by a drive motor, frictional force generated by a friction brake, rolling resistance, air resistance, and downward force.
9. The method (200) according to any one of claims 7 or 8, wherein, The current momentum is determined based on the determined momentum and the change in momentum.
10. The method (200) according to claim 9, wherein, The determined momentum is low-pass filtered, and the change in momentum is high-pass filtered; wherein the time constants of the two filters are equal to each other.
11. The method (200) according to claim 10, wherein, The time constant (230) is determined based on the driving status of the motor vehicle (105).
12. The method (200) according to claim 10 or 11, wherein, The current momentum is determined (230) based on the determined momentum and the determined momentum change using a complementary filter.
13. A device (100) for decelerating a moving motor vehicle (105) by means of an electric drive motor (110), the electric drive motor acting on drive wheels (115) of the motor vehicle (105) rolling on the ground (120), wherein the device comprises: - Device (135) for determining the momentum of the motor vehicle (105); - First interface (140) for obtaining deceleration expectation (125); - A second interface (145) for controlling the drive (110); - Processing device (135), which is configured to: The deceleration direction is determined based on the momentum. The deceleration force is determined based on the deceleration expectation (125); Based on the deceleration direction, the deceleration force, and the effective lever between the shaft of the drive unit (110) and the ground (120), the deceleration torque (130) is determined; and The drive motor (110) is controlled to provide the deceleration torque (130).
14. A motor vehicle (105) comprising the device (100) according to claim 13.