METHOD AND SYSTEM FOR CONTROLLING AN ELECTRIC BICYCLE

Abstract

A method and a system for controlling an electric bicycle are proposed, and the method for controlling the electric bicycle according to an embodiment of the present disclosure includes: detecting a pedal speed and a wheel speed; generating a wheel torque command by applying a wheel speed parameter to a difference between a wheel speed command generated by multiplying the pedal speed by a gear ratio and the wheel speed; generating a pedal torque command by applying a pedal speed parameter to the difference between the wheel speed command and the wheel speed; controlling a motor based on the wheel torque command; and controlling a generator based on the pedal torque command.

Description

[0001] This application claims the benefit of and priority to Korean Patent Application No. 2024-0016696, filed on February 2, 2024, the entire disclosures of which are incorporated herein by reference.

[0002] The present disclosure relates to a method and system for controlling an electric bicycle. More specifically, the present disclosure relates to an electric bicycle control method and system that improves pedal feel by controlling pedal speed according to a pedal speed parameter provided separately from a wheel speed parameter in a chainless electric bicycle powered by a motor.

[0003] An electric bicycle (including electric cargo bikes (E-Cargo)) either assists a person or propel the electric bicycle by controlling a motor with electricity. The PAS (Pedal Assistance System) system uses the power of a motor to assist a person pedaling to propel the wheels, while the throttle system propels the wheels solely through the power of the motor when a throttle is applied. In addition, there is also an electric bicycle equipped with a PAS (throttle valve) and a throttle lever, which supports both the PAS and throttle systems.

[0004] Generally, a chainless electric bicycle detects the speed at which the operator pedals and controls the motor speed proportionally to the pedal speed. Since the pedal is not connected by a chain, there is no load, so the generator (alternator) connected to the pedal is controlled to generate a pedal load similar to that of a chain-operated bicycle. By controlling the pedal load depending on the electric bicycle's speed, the user can experience a pedal feel similar to that of a chain-operated bicycle.

[0005] In the prior art, when generating a pedal feel, an engine torque is generated by rotating the pedal, and the pedal feel is generated based on the engine torque.

[0006] In this prior art method, the pedal feel becomes heavier when the pedal speed is greater than the wheel speed, and the pedal feel becomes lighter when the pedal speed is less than the wheel speed.

[0007] However, in this case, if the pedal feel is generated based on the wheel speed, for example, when the pedal is depressed hard, there is a problem that pedal slippage may occur in which the pedal is depressed too hard due to the weak pedal reaction force, which is uncomfortable for the driver.

[0008] The object is therefore to propose a method and a system for controlling an electric bicycle that creates a riding feel more similar to that of a bicycle with a chain in a chainless electric bicycle and also prevents pedal slippage so that the rider has a stable pedal feel.

[0009] Publication WO 2015 / 128818 A1 discloses a drive system in which a typical chain power transmission system is replaced by an electric motor driven by a generator. The generator is connected via a transmission mechanism, for example, to the pedals of a human-operated bicycle. These can be directly connected or energy storage devices can be interposed. The generator is configured to add a controllable counter torque to the operation of the transmission mechanism. The pedals drive the generator at a generator speed, with the energy generated in the generator depending on the counter torque. The generator is controlled with an input reference R that depends on the generator angular velocity and the device speed.

[0010] Publication US 2009 / 0 095 552 A1 describes a bicycle with at least one drive wheel, a motor connected to the drive wheel, an energy storage device for powering the motor, a control device for controlling the motor, and a pedal crank. To improve the bicycle's handling characteristics, the pedal crank is movable independently of the drive wheel and is connected to a braking device that applies a resistance torque to the rotation of the pedal crank. The resistance torque of the braking device is controlled by the control device.

[0011] Publication US 2023 / 0 373 590 A1 describes a boost mode of an electric bicycle that enables safe operation of the electric bicycle while providing necessary acceleration force by preventing sudden acceleration not intended by the user by doubly determining the user's intention when rapid acceleration is required, such as when starting off or overtaking an electric bicycle.

[0012] Publication DE 10 2022 211 073 A1 describes a drive device for an electric bicycle. It comprises a generator; a power generation circuit electrically connected to the generator; a drive circuit electrically connected to the power generation circuit; a motor electrically connected to the drive circuit; and a control device electrically connected to the drive circuit. The control device is configured to control the drive circuit to limit a drive current supplied to the motor based on the output power of the power generation circuit.

[0013] According to the invention, the above-mentioned object is achieved by a method and a system according to the independent claims.

[0014] The present disclosure is intended to solve the above-mentioned problems of the prior art, and an object of the present disclosure is to provide a method and system for controlling an electric bicycle, which make it possible to perform the control suitable for each system by providing the pedal speed controller suitable for the pedal system separately from the wheel speed controller that controls the acceleration performance of the electric bicycle.

[0015] Another object of the present disclosure is to provide a method and system for controlling an electric bicycle that provides stable pedal feel regardless of the characteristics of the electric bicycle by controlling the pedal feel using a pedal speed parameter.

[0016] However, the technical problem to be achieved by the embodiments of the present disclosure is not limited to the technical problems described above, and other technical problems may also exist.

[0017] The inventive method for controlling electromobility in the form of an electric bicycle comprises: detecting a pedal speed and a wheel speed; receiving a difference between a wheel speed command or target value, which is generated by multiplying the pedal speed by a gear ratio, and the wheel speed with a wheel speed controller and with a pedal speed controller separate from the wheel speed controller; generating a wheel torque command or target value by applying a wheel speed parameter to the difference between a wheel speed command or target value and the wheel speed with the wheel speed controller; generating a pedal torque command by applying a pedal speed parameter to the difference between the wheel speed command and the wheel speed with the pedal speed controller; controlling a motor based on the wheel torque command; and controlling a generator based on the pedal torque command.

[0018] The generation of the pedal torque command is thus carried out by a different controller than the one in which the wheel torque command is generated.

[0019] Furthermore, generating the wheel torque command may include: receiving the difference between the wheel speed command or target value and the wheel speed; generating a first wheel torque value by adding a value of the difference between the wheel speed command or target value and the wheel speed, multiplied by a proportional gain coefficient according to the wheel speed parameter, to a value obtained by integrating the difference between the wheel speed target value and the wheel speed and multiplying by an integral gain coefficient according to the wheel speed parameter; generating a second wheel torque value by differentiating the difference between the wheel speed command and the wheel speed and then multiplying by a moment of inertia of the wheel; and generating a wheel torque command by adding the first wheel torque value and the second wheel torque value.

[0020] In addition, the proportional gain coefficient according to the wheel speed parameter can be proportional to the moment of inertia of the wheel.

[0021] In addition, the moment of inertia of the wheel can be determined based on the weight of the electric bike, the number of motors or the size of the wheel.

[0022] Furthermore, generating the first wheel torque value may include performing anti-windup control to limit an output value by controlling an integral value when integrating the difference between the wheel speed command or target value and the wheel speed.

[0023] Further, controlling the motor may include detecting a drive current of the motor; generating a motor torque control current based on the difference between the wheel current command and the drive current of the motor; and applying the motor torque control current to the motor.

[0024] Furthermore, generating the pedal torque command or target value may include: generating a first pedal torque value by adding a value of the difference between the wheel speed command or target value and the wheel speed, multiplied by a proportional gain coefficient according to the pedal speed parameter, to a value obtained by integrating the difference between the wheel speed command or target value and the wheel speed and multiplying by an integral gain coefficient according to the pedal speed parameter; generating a second pedal torque value by differentiating the difference between the wheel speed command or target value and the wheel speed and then multiplying by a moment of inertia of the pedal;and generating a pedal torque command by adding the first pedal torque value and the second pedal torque value and multiplying by an assist ratio.;

[0025] In addition, the proportional gain coefficient can be proportional to the moment of inertia of the pedal according to the pedal speed parameter.

[0026] In addition, the moment of inertia of the pedal can be determined based on the characteristics of the pedal, regardless of the weight of the electric bicycle, the number of motors or the size of the wheel.

[0027] Furthermore, the first pedal torque value can be generated by controlling the continuous integration of the difference between the wheel speed command or setpoint and the wheel speed.

[0028] Further, controlling the generator may include: detecting a drive current of the generator; generating a pedal current command based on the pedal torque command; and generating a generator torque control current based on the difference between the pedal current command and the drive current of the generator and applying the generator torque control current to the generator.

[0029] The system according to the invention for controlling electromobility in the form of an electric bicycle comprises: a pedal speed sensor configured to detect a pedal speed; a wheel speed sensor configured to detect a wheel speed; a motor current sensor configured to detect a drive current of a motor; a generator current sensor configured to detect a drive current of a generator; a control device configured to control the electric bicycle; a wheel actuator configured to control the motor;and a pedal actuator configured to control the generator, the controller comprising: a wheel speed controller configured to receive the difference between the wheel speed and the wheel speed command and to generate a wheel torque command by applying a wheel speed parameter to the difference between the wheel speed and the wheel speed command, which is generated by multiplying the pedal speed by the gear ratio; and a pedal speed controller separate from the wheel speed controller, configured to receive the difference between the wheel speed and the wheel speed command or target value and to generate a pedal torque command by applying a pedal speed parameter to the difference between the wheel speed command and the wheel speed.

[0030] Furthermore, the wheel speed controller may be configured to: generate a first wheel torque value by adding a value of the difference between the wheel speed command and the wheel speed, multiplied by a proportional gain coefficient according to the wheel speed parameter, to a value obtained by integrating the difference between the wheel speed command and the wheel speed and multiplying it by an integral gain coefficient according to the wheel speed parameter; generate a second wheel torque value by differentiating the difference between the wheel speed command and the wheel speed and then multiplying it by a moment of inertia of the wheel; and generate a wheel torque command by adding the first wheel torque value and the second wheel torque value.

[0031] In addition, the wheel speed controller may be configured to perform anti-windup control to limit an output value by controlling an integral value when integrating the difference between the wheel speed or target value and the wheel speed.

[0032] Furthermore, the pedal speed controller may be configured to: generate a first pedal torque value by adding a value of the difference between the wheel speed command or target value and the wheel speed, multiplied by a proportional gain coefficient according to the pedal speed parameter, to a value obtained by integrating the difference between the wheel speed target value and the wheel speed and multiplying it by an integral gain coefficient according to the pedal speed parameter; generate a second pedal torque value by differentiating the difference between the wheel speed command and the wheel speed and then multiplying it by a moment of inertia of the pedal; and generate a pedal torque command by adding the first pedal torque value and the second pedal torque value and multiplying it by an assist ratio.

[0033] In addition, the moment of inertia of the pedal can be determined based on the characteristics of the pedal, regardless of the weight of the electric bicycle, the number of motors or the size of the wheel.

[0034] In addition, the pedal speed controller may be configured to generate the first pedal torque value by continuously integrating the difference between the wheel speed command and the wheel speed.

[0035] Furthermore, the control device may comprise: a wheel torque controller configured to generate a wheel current command based on the wheel torque command generated by the wheel speed controller; and a pedal torque controller configured to generate a pedal current command based on the pedal torque command generated by the pedal speed controller.

[0036] Furthermore, the wheel actuator may be configured to control the motor by applying a motor torque control current based on the difference between the wheel current command and the sensed drive current of the motor, and the pedal actuator may be configured to control the generator by applying a pedal torque control current based on the difference between the pedal current command and the sensed drive current of the generator.

[0037] The means for achieving the object described above is merely exemplary and should not be construed as limiting the present disclosure. In addition to the exemplary embodiments described above, further embodiments may be included in the drawings and the following detailed description.

[0038] According to the above-described means for achieving the object of the present disclosure, it is possible to provide an electric bicycle control method and system that can control the electric bicycle by applying the parameter(s) suitable for each system by incorporating a pedal speed controller provided separately from a wheel speed controller into a chainless electric bicycle.

[0039] Moreover, according to the above-described means for achieving the object of the present disclosure, it is possible to provide a method and system for controlling the electric bicycle that can improve the pedal feel by preventing the pedal slip phenomenon by which the pedal is depressed due to the weak pedal reaction force, providing the same pedal feel regardless of the characteristics of the vehicle.

[0040] However, the effects achievable with the present disclosure are not limited to the effects described above, and other effects may also occur. Fig. 1 is a flowchart showing a method of controlling an electric bicycle according to an embodiment of the present disclosure. Fig. 2A is a flowchart specifically showing the step of generating a wheel torque command in the method of controlling the electric bicycle according to the embodiment of the present disclosure, and Fig. 2B is a flowchart specifically showing the step of controlling a motor according to the wheel torque command in the method of controlling the electric bicycle according to the embodiment of the present disclosure. Fig. 3A is a flowchart specifically showing the step of generating a pedal torque command in the method of controlling the electric bicycle according to the embodiment of the present disclosure, and Fig. 3B is a flowchart specifically showing the step of controlling a generator according to the pedal torque command in the method of controlling the electric bicycle according to the embodiment of the present disclosure. Fig. 4 is a control block diagram schematically showing a system for controlling an electric bicycle according to the embodiment of the present disclosure. Fig. 5 is a structural diagram schematically showing the configuration of the electric bicycle including the electric bicycle control system according to the embodiment of the present disclosure. Fig. 6 is a circuit diagram specifically showing a wheel speed controller and a pedal speed controller in the structure of the electric bicycle including the electric bicycle control system according to the embodiment of the present disclosure.

[0041] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the embodiments. However, the present disclosure may be embodied in many different forms and is not limited to the embodiments described herein. Similar parts are designated by similar reference numerals throughout the present disclosure.

[0042] When a part is “connected” to another part, it is not only “directly connected,” but also “electrically connected” to another element in between, including cases where they are “indirectly connected.”

[0043] When this disclosure refers to a member being “on,” “over,” “below,” or “under” another member, this includes not only the case where it is in contact with the other member, but also the case where another member is between the two members.

[0044] When a part “contains” a particular component, it does not mean that it excludes other components, but rather that it may contain other components unless otherwise stated.

[0045] Various embodiments of the present disclosure generally relate to a method and system for controlling an electric bicycle to achieve stable pedal feel by controlling pedal feel using pedal speed parameters suitable for a pedal system in a chainless electric bicycle.

[0046] Fig. 1 is a flowchart showing a method of controlling an electric bicycle according to an embodiment of the present disclosure.

[0047] With reference to Fig. 1, the method for controlling the electric bicycle according to the present embodiment includes detecting the pedal speed and the wheel speed S100. Thus, the pedal speed is detected by a pedal speed sensor, and the wheel speed is detected by a wheel speed sensor.

[0048] Next, a step of generating a wheel torque command S200 is performed by applying a wheel speed parameter to the difference between the wheel speed command generated by multiplying the pedal speed by the gear ratio and the wheel speed.

[0049] In this wheel torque command generation step S200, a predetermined wheel speed parameter will be applied to generate a wheel torque command. A specific embodiment of the wheel torque command generation step in which the wheel speed parameter(s) is / are applied is described in the description of Fig. 2A is explained in more detail.

[0050] Furthermore, according to the present embodiment of the present disclosure, a step of generating a pedal torque command is performed by applying a pedal speed parameter to the difference between the wheel speed command generated by multiplying the pedal speed by the gear ratio and the wheel speed (S300).

[0051] In this pedal torque command generation step S300, a predetermined pedal speed parameter is applied to generate a pedal torque command. A specific embodiment of the pedal torque command generation step in which the pedal speed parameter(s) is / are applied is described in the description of Fig. 3A is explained in more detail.

[0052] Furthermore, according to an embodiment of the present disclosure, a step of controlling the motor based on the generated wheel torque command S400 and a step of controlling the generator based on the generated pedal torque command S500 are performed.

[0053] According to this embodiment of the present disclosure, in a chainless electric bicycle, a pedal torque command is generated by applying the pedal speed parameter, which is provided separately from the wheel speed parameter, to the difference between the wheel speed command and the wheel speed. Therefore, it is possible to achieve pedal feel by generating the pedal torque command optimized for the control behavior of the electric bicycle's pedal system.

[0054] Fig. 2A is a flowchart specifically showing the step of generating a wheel torque command in the method of controlling the electric bicycle according to the embodiment of the present disclosure.

[0055] Referring to Fig. 2A, step S200 for generating the wheel torque command may include inputting the difference between the wheel speed command Nw* and the wheel speed Nw (S210), generating a first wheel torque value T1* by adding a value of the difference between the wheel speed command Nw* and the wheel speed Nw, multiplied by a proportional gain coefficient or P gain Kp1 according to the wheel speed parameter, to a value obtained by integrating the difference between the wheel speed command Nw* and the wheel speed Nw and multiplying by an integral gain coefficient or I gain Ki1 according to the wheel speed parameter (S220), generating a second wheel torque value Ta1 by differentiating the difference between the wheel speed target value Nw* and the wheel speed Nw and then multiplying by an inertia moment of the wheel J1 (S230),and generating a wheel torque command Tw* by adding the first wheel torque value T1* and the second wheel torque value Ta1 (S240).

[0056] This step of generating the wheel torque command can be performed by a proportional-integral-derivative (PID) controller.

[0057] The difference (Nw*-Nw) between the wheel speed setpoint Nw* and the wheel speed Nw can also be called an error, which can be controlled so that the value of the error is 0, that is, the wheel speed follows the wheel speed setpoint.

[0058] For this purpose, in step S210, the difference between the wheel speed command value Nw* and the wheel speed Nw may be input, and in step S220, the first wheel torque value T1* may be generated by adding the value of the difference between the wheel speed command value Nw* and the wheel speed Nw, multiplied by the proportional gain coefficient Kp1 according to the wheel speed parameter, to the value obtained by integrating the difference between the wheel speed command value Nw* and the wheel speed Nw and multiplying by the integral gain coefficient Ki1 according to the wheel speed parameter.

[0059] The first wheel torque value T1* can be determined, for example, by the following equation. T1*=Kp1×(Nw*−Nw)+Ki1∫(Nw*−Nw)dt

[0060] The proportional gain coefficient Kp1 can be proportional to the wheel's moment of inertia J1, corresponding to the wheel speed parameter. Furthermore, the proportional gain coefficient (Kp1) can also be proportional to the wheel speed parameter, corresponding to a vehicle acceleration frequency (a frequency suitable for the engine system). The vehicle acceleration frequency (control bandwidth) can be, for example, approximately 0.1 to 0.35 Hz.

[0061] Meanwhile, the moment of inertia of the wheel J1 can have a value determined based on the weight of the electric bicycle, the number of motors, or the size of the wheel. For example, if the weight of the electric bicycle is heavy, the moment of inertia of the wheel J1 may become large, and accordingly, the proportional gain coefficient Kp1 corresponding to the wheel speed parameter may also have a large value.

[0062] In addition, the proportional gain coefficient Kp1 and the integral gain coefficient Ki1 can be set according to the wheel speed parameter, allowing for a low response speed (low response gain) while taking into account the characteristics of the electric bicycle. By controlling the wheel speed according to the proportional gain coefficient Kp1 and the integral gain coefficient Ki1, which allow for such a low response speed, rapid acceleration of the electric bicycle can be suppressed and a smooth acceleration feeling can be achieved.

[0063] When generating the first wheel torque value T1*, when integrating the difference between the wheel speed command value Nw* and the wheel speed Nw, an anti-windup control can be performed, which limits an output value by controlling / regulating the integral value.

[0064] If the error (the difference between the wheel speed setpoint and the wheel speed) is continuously integrated, excessive force may be transmitted to the actuator due to the error accumulation, which may cause vibration or unintended acceleration of the electric bicycle. Therefore, anti-windup control can effectively promote the riding stability of the electric bicycle by limiting the power of the wheel actuator through control of the integral value, thus reducing the accumulated errors over time.

[0065] In step S230, the difference between the wheel speed command value Nw* and the wheel speed Nw can then be differentiated and then multiplied by the moment of inertia of the wheel J1 to generate the second wheel torque value Ta1. The second wheel torque value Ta1 calculated in this way can be referred to as the forward compensation torque caused by the wheel acceleration.

[0066] This second wheel torque value Ta1 can be determined, for example, by the following equation. Ta1=(Nw*−Nw)d / dt×J1×gain1

[0067] In other words, the forward compensation torque of the wheel can be determined by differentiating the difference between the wheel speed command value Nw* and the wheel speed Nw and then multiplying it by the moment of inertia of the wheel J1 and a gain value gain1.

[0068] Subsequently, the wheel torque command Tw* can be generated by adding the first wheel torque value T1* and the second wheel torque value Ta1 (S240). Furthermore, the motor can be controlled according to the wheel torque command Tw*.

[0069] Fig. 2B is a flowchart specifically showing the step of controlling a motor according to the wheel torque command in the method of controlling the electric bicycle according to the embodiment of the present disclosure.

[0070] Referring to Fig. 2B, the step of controlling the motor S400 may include detecting a drive current of the motor S410, generating a wheel current command iw* based on the wheel torque command Tw* S420, and generating and applying a motor torque control current iw based on the difference between the wheel current command iw* and the drive current of the motor S430.

[0071] Here, the detection of the drive current of the motor may be performed by a motor current sensor, and the wheel current command iw* for driving the motor may be calculated from the wheel torque command Tw* previously generated in step S200, and the motor may be controlled by applying the motor torque control current iw so that the drive current of the motor follows the wheel current command iw*.

[0072] Fig. 3A is a flowchart specifically showing the step of generating a pedal torque command in the method of controlling the electric bicycle according to the embodiment of the present disclosure.

[0073] Referring to Fig. 3A, step S300 for generating the pedal torque command may comprise inputting the difference between the wheel speed command Nw* and the wheel speed Nw (S310), generating a first pedal torque value T2* by adding a value of the difference between the wheel speed command value Nw* and the wheel speed Nw, multiplied by a proportional gain coefficient Kp2 according to the pedal speed parameter, to a value obtained by integrating the difference between the wheel speed command value Nw* and the wheel speed Nw and multiplying by an integral gain coefficient Ki2 according to the pedal speed parameter (S320), generating a second pedal torque value Ta2 by differentiating the difference between the wheel speed command value Nw* and the wheel speed Nw and then multiplying by a moment of inertia of the pedal J2 (S330),and generating a pedal torque command Tp* by adding the first pedal torque value T2* and the second pedal torque value Ta2 and multiplying by an assist ratio AL (S340).

[0074] This step of generating the pedal torque command can also be performed by a proportional-integral-derivative (PID) controller.

[0075] First, the difference between the wheel speed command value Nw* and the wheel speed Nw may be input in step S310, and in step S320, the first pedal torque value T2* may be generated by adding the value of the difference (Nw*-Nw) between the wheel speed command value Nw* and the wheel speed Nw, multiplied by the proportional gain coefficient Kp2 according to the pedal speed parameter, to the value obtained by integrating the difference between the wheel speed command value Nw* and the wheel speed Nw and multiplying by the integral gain coefficient Ki2 according to the pedal speed parameter.

[0076] The proportional gain coefficient Kp2 corresponding to the pedal speed parameter can be a value independent of the proportional gain coefficient Kp1 corresponding to the wheel speed parameter, and the integral gain coefficient Ki2 corresponding to the pedal speed parameter can also be a value independent of the integral gain parameter Ki1. The proportional gain coefficient Kp2 corresponding to the pedal speed parameter and the integral gain coefficient Ki2 corresponding to the pedal speed parameter can each be a parameter suitable for the pedal system.

[0077] The first value of the pedal torque T2* can be determined, for example, by the following equation. T2*=Kp2×(Nw*−Nw)+Ki2∫(Nw*−Nw)dt

[0078] The proportional gain coefficient Kp2 can be proportional to the pedal moment of inertia J2, corresponding to the pedal speed parameter. Furthermore, the proportional gain coefficient Kp2 can also be proportional to the pedal feel frequency (a frequency suitable for the pedal system) corresponding to the pedal speed parameter. For example, the pedal feel frequency (the control bandwidth) can be approximately 0.3 to 0.5 Hz.

[0079] However, the moment of inertia of the pedal J2 can be determined independently of the weight of the electric bicycle, the number of motors or the size of the wheel and is based on the characteristics of the pedal (the inertia of the pedal itself).

[0080] In addition, the proportional gain coefficient Kp2 and the integral gain coefficient Ki2 corresponding to the pedal speed parameter can have values ​​that enable high response speed (high response gain) while taking into account the characteristics of the pedal system. That is, Kp2 can have a larger value than Kp1, and Ki2 can have a larger value than Ki1. By controlling the pedal speed according to the proportional gain coefficient Kp2 and the integral gain coefficient Ki2, which enable such a high response speed, it is possible to create a pedal feel suitable for the pedal system and also achieve a pedal feel similar to that of a bicycle with a chain.

[0081] Meanwhile, in the step of generating the first pedal torque value T2*, unlike the step of generating the first wheel torque value, the anti-windup control may not be performed, and it may be controlled such that the difference between the wheel speed command value and the wheel speed is continuously integrated.

[0082] In this way, in the generation of the pedal torque command, unlike the generation of the wheel torque command, since the continuous integration is performed without the anti-windup control (continuous error accumulation), the phenomenon that the pedal is over-depressed (pedal slippage) during strong operation due to the weak pedal reaction force can be prevented, and it is possible to generate a pedal feel more similar to that of a bicycle with a chain.

[0083] Meanwhile, for example, if the error value, which is the difference between the wheel speed setpoint or command and the wheel speed, is less than 0 (Nw*-Nw < 0), overshoot can be prevented by initializing the accumulated errors of the integrator. This can prevent unnecessary pedal feel during slow pedal rotation, thereby suppressing the side effects of continuous integration.

[0084] In step S330, the difference between the wheel speed command or target value Nw* and the wheel speed Nw can then be differentiated and then multiplied by the moment of inertia of the J2 pedal to generate a second pedal torque value Ta2. The second pedal torque value Ta2 calculated in this way can be referred to as the forward compensation torque caused by the pedal acceleration.

[0085] This second pedal torque value Ta2 can be determined, for example, by the following equation. Ta2=(Nw*−Nw)d / dt×J2×gain2

[0086] In other words, the forward compensation torque of the pedal can be determined by differentiating the difference between the wheel speed command Nw* and the wheel speed Nw and then multiplying it by the moment of inertia of the pedal J2 and a gain value gain2.

[0087] Subsequently, the pedal torque command or target value Tp* can be generated by adding the first pedal torque value T2* to the second pedal torque value Ta2 and then multiplying it by the assist ratio AL (S340). This assist ratio (or assist level) is an adjustable value, and depending on the set assist ratio, the pedal torque command Tp* can be greater or less than the resulting value (T2* + Ta2) according to the pedal speed parameter. Therefore, it is possible to make the pedal feel lighter or heavier depending on the user's intention.

[0088] Fig. 3B is a flowchart specifically showing the step of controlling a generator according to the pedal torque command in the method of controlling the electric bicycle according to the embodiment of the present disclosure.

[0089] Referring to Fig. 3B, the step of controlling the generator S500 may include detecting a drive current of the generator (S510), generating a pedal current command ip* based on the pedal torque command Tp* (S520), and generating and applying a generator torque control current ip based on the difference between the pedal current command ip* and the drive current of the generator (S530).

[0090] In this case, the detection of the drive current of the generator can be performed by a generator current sensor, and the pedal current command ip* for driving the generator can be calculated from the pedal torque command Tp* previously generated in step S300, and the generator can be controlled by applying the generator torque control current ip so that the drive current of the generator follows the pedal current command ip*.

[0091] According to the above-described embodiment of the present disclosure, in generating the pedal torque command, the pedal torque command is generated based on the pedal speed parameter provided separately from the wheel speed parameter, whereby the pedal torque command is generated independently of the wheel torque command, and thus it is possible to generate a pedal feel suitable for the pedal system.

[0092] Fig. 4 is a control block diagram schematically showing a system for controlling an electric bicycle according to the embodiment of the present disclosure.

[0093] Furthermore, Fig. 5 is a structural diagram schematically showing the structure of the electric bicycle including the electric bicycle control system according to the embodiment of the present disclosure. In Fig. 5 Np stands for the pedal speed, GR for the gear ratio, Nw for the wheel speed, Nw* for the wheel speed command or setpoint, Tw* for the wheel torque command or setpoint, Tp* for the pedal torque command or setpoint and AL for the assistance ratio, iw* for the wheel current command or setpoint, iw for the motor torque control current, ip* for the pedal current command or setpoint and ip for the generator torque control current.

[0094] As in the Fig. 4 and Fig. 5, the system for controlling an electric bicycle 100 according to the embodiments of the present disclosure includes a wheel speed sensor 111 configured to detect the wheel speed, a motor current sensor 112 configured to detect the drive current of the motor, a pedal speed sensor 113 configured to detect the pedal speed, a generator current sensor 114 configured to detect the drive current of the generator, a controller 120 configured to control the electric bicycle, a wheel actuator (WA) 130 configured to control the motor 200, and a pedal actuator (PA) 140 configured to control the generator 300.

[0095] Furthermore, the control device 120 includes a wheel speed controller 121 configured to generate the wheel torque command Tw* by applying the wheel speed parameter to the difference between the wheel speed command Nw* generated by multiplying the pedal speed Np by the gear ratio GR and the wheel speed Nw, and a pedal speed controller 123 configured to generate the pedal torque command Tp* by applying the pedal torque parameter to the difference between the wheel speed command Nw* and the wheel speed Nw.

[0096] Furthermore, the control device 120 may include a wheel torque controller 122 configured to generate the wheel current command iw* based on the wheel torque command Tw* generated by the wheel speed controller 121, and a pedal torque controller 124 configured to generate the pedal current command ip* based on the pedal torque command Tp* generated by the pedal speed controller 123.

[0097] Meanwhile, the wheel actuator (WA) 130 can control the motor 200 by applying the motor torque control current iw generated based on the difference between the wheel current command iw* and the detected drive current of the motor, thereby rotating the wheel 210 mechanically connected to the motor 200.

[0098] Furthermore, the pedal actuator (PA) 140 can control the generator 300 by applying the generator torque control current ip based on the difference between the pedal current command ip* and the sensed generator drive current, thereby controlling the pedal feel of the pedal (ePedal) 310.

[0099] According to the electric bicycle control system 100 with the above configuration, the pedal speed controller 123, which is separate from the wheel speed controller 121, can control the pedal feel by applying the pedal speed parameters appropriate for the pedal system. Thus, it is possible to provide the same pedal feel regardless of the vehicle's characteristics (weight, wheel size, number of motors, motor type, etc.).

[0100] Fig. 6 is a circuit diagram specifically showing a wheel speed controller and a pedal speed controller in the structure of the electric bicycle including the electric bicycle control system according to the embodiment of the present disclosure.

[0101] As in Fig. 6, both the wheel speed controller 121 and the pedal speed controller 123 may be a PID (proportional-integral-derivative) controller according to the embodiments of the present disclosure.

[0102] As described above, the wheel speed controller 121 can receive the difference between the wheel speed command or target value and the wheel speed (Nw*-Nw), generate the first wheel torque value T1* by adding a value of the difference between the wheel speed target value and the wheel speed (Nw*-Nw) multiplied by the proportional gain coefficient Kp1 according to the wheel speed parameter to a value obtained by integrating the difference between the wheel speed target value and the wheel speed (Nw*-Nw) and multiplying it by the integral gain coefficient Ki1 according to the wheel speed parameter, generate the second wheel torque value Ta1 by differentiating the difference between the wheel speed target value and the wheel speed (Nw*-Nw) and then multiplying it by the moment of inertia of the wheel J1, and generate the wheel torque command Tw* by adding the first wheel torque value T1* and the second wheel torque value Ta1.

[0103] The moment of inertia of the wheel J1 can be determined based on the weight of the electric bicycle, the number of motors or the size of the wheel.

[0104] In addition, the wheel speed controller 121 may also include an anti-windup control (AW) and control the integral value when integrating the difference between the wheel speed setpoint or command and the wheel speed (Nw*-Nw) so that the output value is limited.

[0105] In addition, the pedal speed controller 123 may receive the difference between the wheel speed command value and the wheel speed (Nw*-Nw), generate the first pedal torque value T2* by adding a value of the difference between the wheel speed command value and the wheel speed (Nw*-Nw) multiplied by the proportional gain coefficient Kp2 according to the pedal speed parameter, with a value obtained by integrating the difference between the wheel speed command value and the wheel speed (Nw*-Nw) and multiplying by the integral gain coefficient Ki2 according to the pedal speed parameter,generate the second pedal torque value Ta2 by differentiating the difference between the wheel speed command value and the wheel speed (Nw*-Nw) and then multiplying it by the pedal inertia moment J2, and generate the pedal torque command Tp* by adding the first pedal torque value T2* and the second pedal torque value Ta2 and multiplying it by the assist ratio AL.

[0106] The moment of inertia of the pedal J2 can be determined based on the characteristics of the pedal, regardless of the weight of the electric bicycle, the number of motors or the size of the wheel.

[0107] In addition, the pedal speed controller 123 can generate the first pedal torque value T2* by continuously integrating the difference between the wheel speed target and the wheel speed (Nw*-Nw). This can reduce the phenomenon of pedal slippage when the pedal is pressed hard and improve pedal feel.

[0108] However, if the difference between the wheel speed command and the wheel speed (Nw*-Nw) is less than 0, the integral value can be initialized to prevent overshoot.

[0109] According to the wheel speed controller 121 and the pedal speed controller 123 of the electric bicycle structure according to the above-described embodiments of the present disclosure, it is controlled to generate a torque command (wheel torque command or pedal torque command) suitable for each system (the motor system or the pedal system) by applying different parameters to the same input value (Nw*-Nw). Accordingly, it is possible to optimize the control for each system performance.

[0110] As explained above, according to the embodiments of the present disclosure, the pedal torque command or target value is generated using pedal parameters appropriate for the pedal system. Therefore, it is possible to provide an electric bicycle control method and system that can generate a pedal feel similar to that of a bicycle with a chain and prevent pedal slippage, thereby producing a more stable pedal feel.

[0111] Furthermore, according to the embodiments of the present disclosure, by generating the pedal torque command using the pedal speed controller which is separated from the wheel speed controller according to the present invention, it is possible to generate the same pedal feel regardless of factors such as the weight of the electric bicycle, the size of the wheel, the number of motors and the motor type, and furthermore, the pedal feel can be adjusted differently according to the rider's preference. 100 System for controlling an electric bicycle 111 Wheel speed sensor 112 Motor current sensor 113 Pedal speed sensor 114 Generator current sensor 120 Control device 121 Wheel speed controller 122 Wheel torque controller 123 Pedal speed controller 124 Pedal torque controller 130 Wheel actuator (WA) 140 Pedal actuator (PA) 200 engine 210 wheel 300 Generator (alternating current machine) 310 Pedal S100 Detection of pedal speed and wheel speed S200 Generation of wheel torque command S210 Input of difference between wheel speed command and wheel speed S220 Generation of first wheel torque value S230 Generation of second wheel torque value S240 Generate wheel torque command S300 Generate pedal torque command S310 Input of difference between wheel speed command and wheel speed S320 Generation of first pedal torque value S330 Generation of second pedal torque value S340 Generate pedal torque command S400 Controlling the engine S410 Detecting the motor drive current S420 Generation of wheel current command S430 Generating and applying motor torque control current S500 Controlling the generator S510 Detecting the generator drive current S520 Generate pedal current command S530 Generating and applying generator torque control current AL support ratio gain1 gain value gain2 gain value GR gear ratio Np pedal speed Nw wheel speed Nw* Wheel speed command ip generator torque control current ip* pedal current command iw Motor torque control current iw* wheel current command J1 Moment of inertia of the wheel J2 Moment of inertia of the pedal Ki1 integral gain coefficient Ki2 integral gain coefficient Kp1 proportional gain coefficient Kp2 proportional gain coefficient T1* first wheel torque value T2* first pedal torque value Ta1 second wheel torque value Ta2 second pedal torque value Tp* Pedal torque command Tw* Wheel torque command

Claims

[1] A method for controlling an electric bicycle, comprising: Detecting (S100) a pedal speed (Np) and a wheel speed (Nw); Receiving a difference between a wheel speed command (Nw*) generated by multiplying the pedal speed (Np) by a gear ratio (GR) and the wheel speed (Nw) with a wheel speed controller (121); Receiving the difference between the wheel speed command (Nw*) and the wheel speed (Nw) with a pedal speed controller (123) separate from the wheel speed controller (121); Generating (S200) a wheel torque command (Tw*) by applying a wheel speed parameter to the difference between the wheel speed command (Nw*) and the wheel speed (Nw) with the wheel speed controller (121); Generating (S300) a pedal torque command (Tp*) by applying a pedal speed parameter to the difference between the wheel speed command (Nw*) and the wheel speed (Nw) with the pedal speed controller (123); Controlling (S400) a motor (200) based on the wheel torque command (Tw*); and Controlling (S500) a generator (300) based on the pedal torque command (Tp*). [2] The method of claim 1, wherein generating (S200) the wheel torque command (Tw*) with the wheel speed controller (121) comprises: Generating (S220) a first wheel torque value (T1*) by adding a value of the difference between the wheel speed command (Nw*) and the wheel speed (Nw), multiplied by a proportional gain coefficient (Kp1) according to the wheel speed parameter, with a value obtained by integrating the difference between the wheel speed command (Nw*) and the wheel speed (Nw) and multiplying by an integral gain coefficient (Ki1) according to the wheel speed parameter; Generating (S230) a second wheel torque value (Ta1) by differentiating the difference between the wheel speed command (Nw*) and the wheel speed (Nw) and then multiplying it by a moment of inertia of the wheel (J1); and Generating (S240) a wheel torque command (Tw*) by adding the first wheel torque value (T1*) and the second wheel torque value (Ta1). [3] A method according to claim 2, wherein the proportional gain coefficient (Kp1) corresponding to the wheel speed parameter is proportional to the moment of inertia of the wheel (J1). [4] The method according to claim 3, wherein the moment of inertia of the wheel (J1) is determined based on the weight of the electric bicycle, the number of motors or the size of the wheel. [5] The method according to claim 2, wherein generating (S220) the first wheel torque value (T1*) comprises performing anti-windup control to limit an output value by controlling an integral value when integrating the difference between the wheel speed command (Nw*) and the wheel speed (Nw). [6] Method according to one of claims 1 to 5, wherein controlling (S200) the motor (200) comprises: Detecting (S410) a drive current of the motor (200); Generating (S430) a motor torque control current (iw) based on the difference between the wheel current command (iw*) and the drive current of the motor (200) and applying the motor torque control current (iw) to the motor (200). [7] Method according to one of claims 1 to 6, wherein generating (S300) the pedal torque command (Tp*) with the pedal speed controller (123) comprises: Generating (S320) a first pedal torque value (T2*) by adding a value of the difference between the wheel speed command (Nw*) and the wheel speed (Nw), multiplied by a proportional gain coefficient (Kp2) according to the pedal speed parameter, with a value obtained by integrating the difference between the wheel speed command (Nw*) and the wheel speed (Nw) and multiplying by an integral gain coefficient (Ki2) according to the pedal speed parameter; Generating (S330) a second pedal torque value (Ta2) by differentiating the difference between the wheel speed command (Nw*) and the wheel speed (Nw) and then multiplying it by a moment of inertia of the pedal (J2); and Generating (S340) a pedal torque command (Tp*) by adding the first pedal torque value (T2*) and the second pedal torque value (Ta2) and multiplying by an assist ratio (AL). [8] A method according to claim 7, wherein the proportional gain coefficient (Kp2) corresponding to the pedal speed parameter is proportional to the moment of inertia of the pedal (J2). [9] The method according to claim 8, wherein the moment of inertia of the pedal (J2) is determined based on the characteristics of the pedal independently of the weight of the electric bicycle, the number of motors or the size of the wheel. [10] A method according to any one of claims 7 to 9, wherein generating (S320) the first pedal torque value (T2*) is performed by controlling the continuous integration of the difference between the wheel speed command (Nw*) and the wheel speed (Nw). [11] Method according to one of claims 1 to 5 and 7 to 10, wherein controlling (S500) the generator (300) comprises: Detecting (S510) a drive current of the generator (300); Generating (S520) a pedal current command (ip*) based on the pedal torque command (Tp*); and Generating (S540) a generator torque control current (ip) based on the difference between the pedal current command (ip*) and the drive current of the generator (300) and applying the generator torque control current (ip) to the generator (300). [12] System for controlling an electric bicycle, comprising: a pedal speed sensor (113) configured to detect a pedal speed (Np); a wheel speed sensor (111) configured to detect a wheel speed (Nw); a motor current sensor (112) configured to detect a drive current of a motor (200); a generator current sensor (114) configured to detect a drive current of a generator (300); a control device (120) configured to control the electric bicycle; a wheel actuator (130) configured to control the motor (200); and a pedal actuator (140) configured to control the generator (300), characterized by , that the control device (120) comprises: a wheel speed controller (121) configured to receive a difference between the wheel speed (Nw) and a wheel speed command (Nw*) generated by multiplying the pedal speed (Nw) by the gear ratio (GR), and to generate a wheel torque command (Tw*) by applying a wheel speed parameter to the difference between the wheel speed (Nw) and the wheel speed command (Nw*); and a pedal speed controller (123) separate from the wheel speed controller (121) and configured to receive the difference between the wheel speed (Nw) and the wheel speed command (Nw*) and to generate a pedal torque command (Tp*) by applying a pedal speed parameter to the difference between the wheel speed command (Nw*) and the wheel speed (Nw). [13] The system according to claim 12, wherein the wheel speed controller (121) is configured to generate a first wheel torque value (T1*) by adding a value of the difference between the wheel speed command and the wheel speed (Nw), multiplied by a proportional gain coefficient (Kp1) according to the wheel speed parameter, to a value obtained by integrating the difference between the wheel speed command (Nw*) and the wheel speed (Nw) and multiplying it by an integral gain coefficient (Ki1) according to the wheel speed parameter; to generate a second wheel torque value (Ta1) by differentiating the difference between the wheel speed command (Nw*) and the wheel speed (Nw) and then multiplying it by an inertia moment of the wheel (J1); and to generate a wheel torque command (Tw*) by adding the first wheel torque value (T1*) and the second wheel torque value (Ta1). [14] The system according to claim 13, wherein the wheel speed controller (121) is arranged to perform anti-windup control to limit an output value by controlling an integral value when integrating the difference between the wheel speed command (Nw*) and the wheel speed (Nw). [15] The system according to any one of claims 12 to 14, wherein the pedal speed controller (123) is configured to generate a first pedal torque value (T2*) by adding a value of the difference between the wheel speed command (Nw*) and the wheel speed (Nw), multiplied by a proportional gain coefficient (Kp2) according to the pedal speed parameter, to a value obtained by integrating the difference between the wheel speed command (Nw*) and the wheel speed (Nw) and multiplying it by an integral gain coefficient (Kp2) according to the pedal speed parameter; to generate a second pedal torque value (Ta2) by differentiating the difference between the wheel speed command (Nw*) and the wheel speed (Nw) and then multiplying it by a moment of inertia of the pedal (J2);and generate a pedal torque command (Tp*) by adding the first pedal torque value (T2*) and the second pedal torque value (Ta2) and multiplying by an assist ratio (AL); [16] The system of claim 15, wherein the moment of inertia of the pedal (J2) is determined based on the characteristics of the pedal independently of the weight of the electric bicycle, the number of motors, or the size of the wheel. [17] The system of claim 15 or 16, wherein the pedal speed controller (123) is configured to generate the first pedal torque value (T2*) by continuously integrating the difference between the wheel speed command (Nw*) and the wheel speed (Nw). [18] System according to one of claims 12 to 17, wherein the control device (120) comprises: a wheel torque controller (122) configured to generate a wheel current command (iw*) based on the wheel torque command (Tw*) generated by the wheel speed controller (121); and a pedal torque controller (124) configured to generate a pedal current command (ip*) based on the pedal torque command (Tp*) generated by the pedal speed controller (123). [19] The system of claim 18, wherein the wheel actuator (130) is configured to control the motor (200) by applying a motor torque control current (iw) generated based on the difference between the wheel current command (iw*) and the detected drive current of the motor (200), and the pedal actuator (140) is configured to control the generator (300) by applying a pedal torque control current generated based on the difference between the pedal current command (ip*) and the detected drive current of the generator (300).

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