Method and device for stabilizing a two-wheeled or three-wheeled vehicle during regenerative braking

Abstract

The invention relates to a method for stabilizing a wheel (104) of a two-wheeled or three-wheeled vehicle (100) during recuperation, wherein a scaling factor (118) for a recuperation torque (112) of a drive motor (106) of the wheel (104) is read from a recuperation characteristic curve (120) using a rotational speed gradient (116) of the drive motor (106) during recuperation, and the recuperation torque (112) is set using the scaling factor (118) in order to stabilize the wheel (104).

Description

Methods and apparatus for stabilizing two-wheeled or three-wheeled vehicles during regeneration. Technical Field

[0001] The present invention relates to a method and a corresponding device for stabilizing the wheels of a two-wheeled or three-wheeled vehicle during regeneration. Background Technology

[0002] When one or more wheels of a vehicle lose traction, the vehicle loses control. For example, the wheels may lock up and lose traction during braking. They may then only transmit lateral steering forces with very limited capacity.

[0003] To prevent this, vehicles can be equipped with an anti-lock braking system (ABS). The ABS uses speed sensors at the wheels to monitor wheel speed and, for example, manipulates pulsed releases of individual wheel brakes to allow the initially locked wheels to regain acceleration and road grip.

[0004] In electrically driven vehicles, efforts are made to apply electric braking in as many situations as possible to recover electrical energy. Electric braking can be referred to as regenerative braking. During electric braking, the vehicle's drive wheels are braked via a drive motor. Even during regenerative braking, it is possible to lock the braked wheels. This is particularly suitable for two-wheeled or three-wheeled vehicles, such as scooters and rollers. Summary of the Invention

[0005] Against this backdrop, the present invention utilizes the solutions described herein to introduce a method and a corresponding apparatus for stabilizing the wheels of a two-wheeled or three-wheeled vehicle during regeneration, according to the independent claims, and finally introduces a corresponding computer program product and a machine-readable storage medium. Advantageous modifications and improvements to the solutions described herein are derived from the specification and are described in the dependent claims.

[0006] In two-wheeled or three-wheeled vehicles with electric drive systems, electric motors that are directly coupled to the wheels are typically used. Through direct coupling, the rotational speed of the electric motor directly follows the rotational speed of the coupled wheel. Because the control electronics used to operate the electric motor monitor the current position of the rotor, the current acceleration or deceleration of the rotor is also known.

[0007] Advantages of the present invention.

[0008] An advantageous embodiment of the invention provides anti-lock braking functionality in electrically driven two-wheeled or three-wheeled vehicles without the need for wheel-mounted speed sensors. This functionality can be achieved at low additional cost by eliminating the need for additional sensing devices.

[0009] A method is proposed for stabilizing the wheels of a two-wheeled or three-wheeled vehicle during regeneration, wherein a scaling factor for the regeneration torque of the drive motor used for wheel regeneration is read from the regeneration characteristic curve, and the regeneration torque is set using the scaling factor to stabilize the wheels or the vehicle.

[0010] The conception of embodiments of the present invention can be considered primarily as being based on the concepts and understandings described below.

[0011] Two-wheeled or three-wheeled vehicles can be electrically driven scooters. These vehicles can be constructed using simple components and manufactured inexpensively. The drive motor can be a hub motor or an electric motor centrally located in the vehicle's chassis. The drive motor can be coupled to the wheels via a fixed gear ratio. The drive motor can drive and brake the wheels, that is, accelerate and decelerate them. During regeneration, the wheels are decelerated by the regenerative torque applied by the drive motor, and the drive motor acts as a generator to produce current from the vehicle's kinetic energy. The regenerative torque is the torque of the drive motor in the opposite direction to the vehicle's motion. The degree of braking of the vehicle can be set by the regenerative torque.

[0012] The speed gradient can be a measure of deceleration, i.e., the degree to which the wheels decelerate during braking. When the speed gradient increases suddenly, i.e., the wheels decelerate very rapidly, there is a high probability that the wheels will begin to lock. To prevent locking, the regenerative torque can be reduced. The regenerative torque can be reduced using a scaling factor. The scaling factor can be multiplied by the initially desired regenerative torque. The scaling factor can have values ​​between zero and one. The regenerative torque can be reduced periodically. For example, the regenerative torque can be reduced accordingly for 30 to 50 milliseconds or for the duration of wheel lockup. The regenerative torque can then be increased again and the process can be restarted.

[0013] The scaling factor can be applied when the vehicle speed is greater than the stable speed. It can be deactivated when the vehicle speed is less than the walking speed. The stable speed is greater than the walking speed. Speed ​​hysteresis can be defined by the walking speed and the stable speed. Speed ​​hysteresis helps avoid unstable states near activation or deactivation speeds. The walking speed can be, for example, 4 km / h or less. The stable speed can be, for example, 8 km / h or more. The walking speed and stable speed can differ from each other by at least 2 km / h, preferably at least 4 km / h. The scaling factor can be applied when the vehicle speed increases from 7 km / h to 8 km / h, as per the mentioned exemplary values, and can be deactivated when the vehicle speed decreases from 5 km / h to 4 km / h.

[0014] When using vehicle speed, a regenerative characteristic curve can be selected from the family of regenerative characteristic curves. When using speed gradient, a scaling factor can be read from the selected regenerative characteristic curve. The family of regenerative characteristic curves can include multiple regenerative characteristic curves for different vehicle speeds. An adapted regenerative characteristic curve can be used based on the vehicle speed. Therefore, the response characteristics of the method described here can be optimized based on speed.

[0015] The vehicle's speed can be read from its satellite navigation system. The satellite navigation system can also be a component of a mobile device coupled to the vehicle. Specifically, the scooter can be activated via a mobile device for payment purposes, thus providing a direct speed signal.

[0016] Alternatively, a dedicated speed sensor for the vehicle can be used to provide a speed signal representing the vehicle's speed.

[0017] Vehicle speed can also be derived from the drive motor's rotational speed. This is based on the fixed gear ratio of the direct drive system, which couples rotational speed with vehicle speed. The rotational speed can be provided by the drive motor's control electronics via an interface.

[0018] The rotational speed can be determined using the angle signal from the drive motor. The drive motor is typically equipped with a rotor position sensor. The control electronics of the drive motor can manipulate the rotor of the drive motor by adjusting its position. The angle signal can be provided and directly captured by the rotor position sensor. The rotational speed can be obtained by differentiating the angle signal.

[0019] It can derive the speed gradient from the speed. It can differentiate the speed to obtain the speed gradient.

[0020] The regeneration characteristic curve can be stored as a series of grid points (Stüützstellen) in a table. To read the scaling factor, interpolation can be performed between the grid points. The table occupies relatively little storage space. Interpolation can produce intermediate values ​​with sufficiently high accuracy. For example, linear interpolation can be performed between two grid points.

[0021] The method can be executed, for example, in software or hardware, or in a hybrid form consisting of software and hardware, such as in a controller.

[0022] The solution described herein further implements a device constructed for performing, controlling, or implementing the steps of a variation of the method described herein in a corresponding apparatus.

[0023] The device can be an electrical device having: at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, and at least one interface and / or communication interface for reading in or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a so-called system-ASIC, or a microcontroller, for processing sensor signals and outputting data signals based on the sensor signals. The storage unit can be, for example, flash memory, EPROM, or magnetic storage. The interface can be configured as a sensor interface for reading sensor signals from a sensor and / or configured as an actuator interface for outputting data signals and / or control signals to an actuator. The communication interface can be configured for wirelessly and / or wiredly reading in or outputting data. The interface can also be, for example, a software module existing near other software modules on a microcontroller.

[0024] It is also advantageous to have a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium, such as semiconductor memory, hard disk storage or optical memory, and for performing, implementing and / or manipulating the steps of a method according to one of the embodiments described above, especially when the program product or program is implemented on a computer or device.

[0025] It should be noted that some of the features and advantages of the present invention are described herein with reference to different embodiments. Those skilled in the art will recognize that the features of the controller and method can be combined, adapted, or interchanged in a suitable manner to implement other embodiments of the invention. Attached Figure Description

[0026] Embodiments of the invention are described below with reference to the accompanying drawings, which should not be construed as limiting the invention.

[0027] Figure 1 shows a diagram of a vehicle having a device for stabilization according to one embodiment;

[0028] Figure 2 shows a flowchart of another implementation of the stabilization method according to one embodiment;

[0029] Figure 3 shows a diagram illustrating the driving conditions according to one embodiment; and

[0030] Figure 4 shows a detailed diagram of the driving conditions according to one embodiment.

[0031] The accompanying drawings are schematic only and are not to scale. The same reference numerals in the drawings denote the same or equivalent features. Detailed Implementation

[0032] Figure 1 illustrates a vehicle 100 having a stabilization device 102 according to one embodiment. Device 102 is configured to implement the methods described herein. The vehicle 100 is a two-wheeled vehicle with a direct electric drive. The vehicle 100 can be, for example, a scooter. The vehicle 100 can also be a tricycle. During the electric braking process, i.e., regeneration, device 102 stabilizes the drive wheels 104, i.e., the rear wheels of the vehicle 100 in the illustrated case. During regeneration, the kinetic energy of the vehicle 100 is converted into electrical energy using a generator-type drive motor 106 of the vehicle 100 and stored in the energy storage of the vehicle 100. The drive motor 106 is here a central motor and is coupled to the wheels 104 via a fixed gear ratio. Alternatively, the drive motor 106 can also be implemented as a wheel-side motor integrated into the wheels 104.

[0033] Regeneration is triggered, for example, by actuating the brake lever 107 of the vehicle 100, and in particular, a braking signal 108 proportional to the force applied to the brake lever 107 is sent to the controller 110 of the drive motor 106. In response to the braking signal, a regenerative torque 112 is pre-applied to the rotor 109 of the drive motor 106 via the controller 110, and a braking torque 114 is applied to the wheel 104 coupled to the drive motor 106. The vehicle 100 decelerates.

[0034] When the braking torque 114 is too large, or when the coefficient of friction of the ground beneath wheel 104 is too small, wheel 104 loses its traction on the ground and begins to lock. When wheel 104 locks, it is almost impossible to transfer lateral guiding force from wheel 104 to the ground. This causes wheel 104 and ultimately the entire vehicle 100 to become unstable.

[0035] To overcome this situation, in the solution described here, when using the rotational speed gradient 116 of the regenerative drive motor 106, or rotor 109, a scaling factor 11g for the regenerative torque 112 is read from the regenerative characteristic curve 120. The scaling factor 11g is output to the controller 110 to stabilize the wheel 104. The controller 110 reduces the regenerative torque 112 according to the scaling factor 118.

[0036] Wheel 104 requires a short period of time to stabilize. After, for example, 30 to 50 milliseconds, or after the duration of wheel lockup, the regenerative torque 112 is increased again and the process is repeated.

[0037] In one embodiment, the drive motor 106 is an asynchronous motor, and the speed gradient 116 is inferred from the speed 122 of the drive motor 106. For example, the speed 122 can be provided via a speed signal 124 from the controller 110.

[0038] In one embodiment, the drive motor 106 is a synchronous motor, and the rotational speed 122 is inferred from the angle signal 126 of the drive motor 106. The angle signal 126 is generated by a rotor position sensor 128 of the drive motor 106. The controller 110 uses the angle signal 126 to energize the windings of the drive motor 106. If the drive wheel or brake disc is equipped with a rotational speed signal sensor, then that same sensor can also be used to determine the rotational speed gradient 116.

[0039] In one embodiment, a regeneration characteristic curve 120 is selected from a family of regeneration characteristic curves 132 when using a vehicle speed 130 of vehicle 100. Then, a scaling factor 118 is read from the selected regeneration characteristic curve 120 when using a speed gradient 116.

[0040] The vehicle speed 130 can be provided, for example, by the GPS device 134 or the tachometer 136 of the vehicle 100. Alternatively, since the drive motor 106 is coupled to the wheel 104 via a fixed gear ratio, the vehicle speed 130 can be directly derived from the rotational speed 122.

[0041] In one embodiment, the family of regeneration characteristic curves 132 has multiple columns. In each column, the regeneration characteristic curve 120 is stored as a series of grid points. Here, each grid point is stored in a cell of the family of regeneration characteristic curves 132. Each cell is defined by a value pair consisting of vehicle speed 130 and rotational speed gradient 116. The value of the grid point is stored in the cell. The values ​​of the grid points between cells are interpolated with respect to the intermediate values ​​of vehicle speed 130 and rotational speed gradient 116.

[0042] Figure 2 shows a flowchart of another implementation of the stabilization method according to one embodiment. This method can be implemented, for example, on the device 102 shown in Figure 1. Here, in the case of using speed hysteresis 200, it is determined whether the scaling factor 118 read from the regeneration characteristic curve 120, when using the rotational speed gradient 116 or the rotor's angular acceleration, is used to limit the regeneration torque.

[0043] The vehicle speed 130 is evaluated using speed hysteresis effect 200. Here, when the vehicle speed 130 is greater than the upper limit of speed hysteresis effect 200, logic value 202 switches from "No" to "Yes". The upper limit can be referred to as the stable speed 204. When the vehicle speed 130 is less than the lower limit of speed hysteresis effect 200, logic value 202 switches from "Yes" to "No". The lower limit can be referred to as the walking speed 206.

[0044] When the logical value 202 is "Yes", a scaling factor of 118 is used. When the logical value 202 is "No", a scaling factor of 118 is not used.

[0045] The method described, and the equipment used to implement it, especially in technically simple vehicles such as scooters (where significant cost pressures often prevent the use of more expensive ABS systems), enables the execution of sufficient ABS functionality during regeneration in many cases without requiring significant additional hardware.

[0046] In other words, this paper introduces an electric motor ABS for two-wheeled and three-wheeled vehicles.

[0047] In the realm of personal mobility, electric and hybrid vehicles are becoming increasingly popular. This is particularly true for electrically powered two-wheeled and three-wheeled vehicles, especially in China, India, and ASEAN countries. A similar trend is emerging in Europe, with a growing number of startups and manufacturers offering electrically powered two-wheelers and three-wheelers. All of these electric vehicles refer to those that, during braking, can convert the vehicle's kinetic energy into electrical energy through the proper control of an electric motor and store it in a so-called traction battery. This process is known as regenerative braking.

[0048] In driving physics, regeneration describes the braking process. Wheel locking occurs during braking on wet or slippery roads. Wheel locking is a crucial effect in driving dynamics. For this reason, ABS and / or ESP have been legal requirements for passenger cars for many years. These legal requirements do not apply to many two-wheeled or three-wheeled vehicles, especially outside of Europe where such systems are generally not legally required. Furthermore, the cost of such safety systems (ABS, ESP) is prohibitively high compared to the total cost of an electric two-wheeler. Therefore, an ABS-derived solution is introduced here, which uses the rotational speed signal of an electric motor to achieve "ABS-like" functionality for electric two-wheelers or three-wheelers.

[0049] In the case of two-wheeled or three-wheeled vehicles, the electric drive motor is a so-called stroke motor (= hub motor), whose speed is directly proportional to the vehicle speed. Other motor designs, so-called central motor designs, use one or more belts or a transmission mechanism to connect the electric motor and the drive wheel.

[0050] In classic ABS, wheel speed is determined by wheel speed sensors and used to correctly operate the ABS. High-precision angle signals are needed to control the electric motor. The electric motor's speed can be calculated or determined by mathematically differentiating the angle signal. The electric motor's speed can be used not only in hub-driven systems but also in drives with a central motor to predict drive wheel lock-up during regeneration. If potential drive wheel lock-up is detected, regeneration can be immediately terminated (i.e., electric braking) to avoid dangerous situations in driving dynamics.

[0051] First, the rotational speed of the electric motor is determined from the angle signal obtained from the rotor position sensor. Then, using the same or similar algorithm, the so-called speed gradient, i.e., the change in the electric motor speed over time, is derived from the rotational speed of the electric motor. In particular, the change in rotational speed, i.e., the speed gradient, can be used as an indicator of the upcoming locking of the wheels.

[0052] A combination of rotational speed and rotational speed gradient can generate a matrix, from which the reduction in regeneration can be calculated or determined. Here, such a matrix, or family of regeneration characteristic curves, can be, for example, as shown in Figure 1.

[0053] Figure 1 shows the signal chain from the angle signal to the rotational speed and rotational speed gradient. As an additional illustration, a family of 3D regenerative characteristic curves and the limitation on the regenerative torque are shown in the figure.

[0054] Here, for example, with a rotational speed of 2000 rpm and a rotational speed gradient of -700 rpm / s, a scaling factor of "1" is obtained from the family of characteristic curves. By multiplying this factor by the regenerative torque, a "restricted" regenerative torque is thus obtained, which in this case is the same as the initial regenerative torque.

[0055] For a speed signal of 1000 rpm and a speed gradient signal of -1500 rpm / s, the scaling factor is "0". In this case, the "restricted" regenerative torque is equal to 0. Therefore, regeneration is turned off.

[0056] In the embodiment shown in Figure 2, the electric motor ABS is activated only at speeds exceeding a predefined range. This activation can be controlled, for example, using a hysteresis characteristic curve. Such a hysteresis characteristic curve allows for very robust control of the activation and deactivation of the electric motor ABS, without continuous back-and-forth fluctuations between activated and deactivated states.

[0057] If the vehicle speed is below the lower limit of the hysteresis effect, the "No" path is activated in the switch following the hysteresis effect, and the scaling factor for regeneration is set to 1, thus deactivating the electric motor ABS. Conversely, if the vehicle speed is above the upper limit of the hysteresis effect, the "Yes" path of the switch is activated, and the scaling factor for regeneration is obtained from the regeneration characteristic curve, which can take a value between 0 and 1 depending on the motor's speed gradient or angular acceleration.

[0058] Here, for example, with a speed gradient of -700 rpm / s, a scaling factor of "1" is obtained from the family of characteristic curves. By multiplying this factor by the regenerative torque, a "restricted" regenerative torque is thus obtained, which in this case is the same as the initial regenerative torque.

[0059] For a speed gradient signal of -1500 rpm / s, a scaling factor of "0" is obtained. In this case, the "restricted" regenerative torque is equal to 0. Therefore, regeneration is shut off.

[0060] Figure 3 shows an embodiment for a driving condition with such an electric ABS having regenerative braking.

[0061] Figure 3 illustrates the driving conditions of the vehicle from Figure 1. The driving conditions are depicted using six graphs. These graphs have time intervals t from 0 seconds to 30 seconds plotted on their horizontal axes. The first graph plots the vehicle speed 130 on its vertical axis, thus depicting the speed change curve 300 for the driving conditions. The second graph plots the drive motor torque 302 on its vertical axis, thus depicting the torque change curve 304 for the driving conditions. The third graph plots tire acceleration 306 and vehicle acceleration 308 on its vertical axis. The third graph thus depicts two acceleration change curves 310 for the driving conditions. The fourth graph plots tire slip 312 on its vertical axis, thus depicting the slip change curve 314 for the driving conditions. The fifth graph plots the engine speed 122 on its vertical axis, thus depicting the engine speed change curve 316 for the drive motor. The sixth graph plots the engine speed gradient 116 on its vertical axis, thus depicting the engine speed gradient change curve 318 for the driving conditions.

[0062] Figure 4 shows a detailed illustration of the driving conditions according to one embodiment. The detailed illustration is also depicted using six graphs. The graphs have been plotted on their horizontal axis, showing the time t from 16.6 seconds to 17.6 seconds as shown in Figure 3.

[0063] The vehicle accelerates to 35 km / h and begins regeneration in 17 seconds. As can be seen in the enlarged view in Figure 4, the torque variation of the electric motor 304, due to its correlation with the speed gradient and speed, as well as the scaling factor already described, limits tire slip 312 to a value within the range of -0.015. A slip factor less than -0.2 can induce wheel lock-up very quickly.

[0064] If the regenerative torque of 112 is not limited, an unstable driving state will suddenly occur.

[0065] This type of electric ABS can be used on all electric two-wheelers and three-wheelers, maximizing the potential of recycling and bringing safe and enjoyable driving experience to electric scooters and rickshaws.

[0066] Finally, it should be noted that terms such as "having" or "comprising" do not exclude other elements or steps, and terms such as "an" or "a" do not exclude multiple. Reference numerals in the claims should not be considered restrictive.

Claims

1. A method for stabilizing the wheels (104) of a two-wheeled or three-wheeled vehicle (100) during regeneration, wherein, With the rotational speed gradient (116) of the regenerated drive motor (106) of the wheel (104) in use, the scaling factor (118) for the regenerated torque (112) of the drive motor (106) is read from the regeneration characteristic curve (120), and the regenerated torque (112) is set with the scaling factor (118) in order to stabilize the wheel (104). Accordingly, the scaling factor is used when the speed of the vehicle is greater than the upper limit of the speed hysteresis effect, and is not used when the speed of the vehicle is less than the lower limit of the speed hysteresis effect.

2. The method according to claim 1, characterized in that, in, The lower limit of the speed lag effect is the walking speed (206).

3. The method according to any one of the preceding claims, characterized in that, When using the vehicle speed (130) of the vehicle (100), the regeneration characteristic curve (120) is selected from the family of regeneration characteristic curves (132), and when using the speed gradient (116), the scaling factor (118) is read from the selected regeneration characteristic curve (120).

4. The method according to any one of claims 2 to 3, characterized in that, The vehicle speed (130) is read from the satellite navigation system (134) of the vehicle (100).

5. The method according to any one of claims 2 to 3, characterized in that, The vehicle speed (130) is derived from the rotational speed (122) of the drive motor (106).

6. The method according to claim 5, characterized in that, The rotational speed (122) is determined using the angle signal (126) of the drive motor (106).

7. The method according to any one of claims 5 to 6, characterized in that, The speed gradient (116) is derived from the speed (122).

8. The method according to any one of the preceding claims, characterized in that, The regeneration characteristic curve (120) is stored in a table as a series of grid points, wherein interpolation is performed between the grid points in order to read the scaling factor (118).

9. Equipment (102), of which, The device (102) is configured to implement, realize and / or manipulate the method according to any one of the preceding claims in a corresponding apparatus.

10. A computer program product configured to, when implemented, instruct a processor to implement, realize, and / or manipulate the method according to any one of claims 1 to 8.

11. A machine-readable storage medium having a computer program product according to claim 10 stored thereon.

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