Device and method for actuating a motor of an electric bicycle
Patent Information
- Application Number
- EP2024715199
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-04-03
- Filing Date
- 2024-03-28
- Publication Date
- 2026-02-11
Smart Images
Figure EP2024058655_10102024_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] title
[0003] Device and method for controlling a motor of an electric bicycle
[0004] State of the art
[0005] The present invention relates to a method and a device for controlling a motor of an electric bicycle.
[0006] Electric bicycles, especially pedelecs, provide motor assistance based on the torque applied by the rider. This torque is detected by a torque sensor. To ensure safe operation, motor assistance is only enabled when certain conditions are met. This is necessary to prevent the motor from rotating without the rider's consent due to disrupted or faulty sensor signals. The starting process is particularly important here. This must be reliably detected based on various sensor signals so that full motor assistance can be enabled.
[0007] In current pedelecs, rider torque is usually measured via a torque sensor. Motor assistance is only enabled when rider torque exceeds a threshold and another signal is detected, indicating a move-off request. This plausibility check, for example, with a second sensor, is necessary to ensure that the move-off request is reliably detected.
[0008] This additional signal can be the rider's cadence, which is recorded via a cadence sensor. However, this has the disadvantage that there is often a large amount of free travel during the rider's pedaling before motor assistance kicks in. For example, a cadence sensor operates with 36 teeth, which allows for a free travel of up to 10° before a cadence is detected and motor assistance can be provided.
[0009] Alternatively, a second signal is often used to check whether there is acceleration in the direction of travel, which is detected, for example, using an acceleration sensor. Forward acceleration must be detected before motor assistance is enabled. However, this can also occur when the bike is facing downhill, which is why the threshold values for detecting acceleration are often set high so that the acceleration can be reliably attributed to a starting motion. However, such acceleration values are often not reached when starting slowly or starting on an incline.
[0010] Reed contacts arranged on the frame of the electric bicycle are also often used to detect the movement of magnets, i.e. magnets arranged, for example, on a spoke of the bicycle. If such a magnet passes the reed contact, a speed pulse is generated. The motor assistance is only activated, for example, when such a speed pulse is detected. In the worst case, however, this can only occur after a full rotation of the wheel, which leads to a delay in the motor assistance. It is also not clear to the rider when the assistance is provided, since the position of the magnet is unknown at the time the bicycle is intended to start, and thus the angle to be covered until the reed contact is passed is random.
[0011] Regardless of the aforementioned conditions, however, it is always necessary for the rider's torque to exceed a certain threshold in order to meet the conditions for releasing the motor torque. The necessary second condition does not cover cases where, for example, a rider does not apply the necessary force to move the pedelec on a slope. In such a case, neither a positive rider cadence, forward acceleration, nor a speed pulse occurs.
[0012] Disclosure of the invention The device according to the invention for controlling a motor of an electric bicycle comprises a control unit which is configured to control the motor of the electric bicycle in a first operating mode, wherein in the first operating mode the motor is controlled such that no motor torque is provided by the motor, and to control the motor of the electric bicycle in a second operating mode, wherein in the second operating mode the motor is controlled such that at least briefly a motor torque is provided by the motor. The control unit is configured to switch from the first operating mode to the second operating mode when a first condition and a second condition are met.The first condition is met when a rider torque applied by a bicycle rider to the bicycle pedals is detected that exceeds a predefined first threshold. The second condition depends on a temporal profile of the rider torque, a motor speed, and / or a user input.
[0013] The method according to the invention for controlling a motor of an electric bicycle comprises controlling the motor of the electric bicycle in a first operating mode, wherein in the first operating mode the motor is controlled such that no motor torque is provided by the motor, controlling the motor of the electric bicycle in a second operating mode, wherein in the second operating mode the motor is controlled such that motor torque is provided by the motor at least briefly, and switching from the first operating mode to the second operating mode when a first condition and a second condition are met. The first condition is met when a rider torque exerted by the rider of the bicycle on the pedals of the bicycle is detected, which lies above a predefined first threshold value.The second condition depends on a temporal progression of the driver torque, an engine speed and / or a user input.
[0014] The control unit is, for example, a digital processing unit, which receives the information acquired by the electric bicycle's sensors. For example, the control unit is connected to a torque sensor, which detects the torque exerted by the bicycle rider on the bicycle's pedals. Further preferably, the control unit is connected to a speed sensor, which detects the motor speed. Further preferably, the control unit is connected to an input unit, via which a user input can be detected.
[0015] The motor of the electric bicycle is designed to support the drive of the electric bicycle, i.e., to provide motor assistance. In the first operating mode, the motor is controlled in such a way that no assistance is provided for driving the electric bicycle. For example, no supply voltage is supplied to the motor.
[0016] In the second operating mode, the motor is controlled in such a way that a motor torque is provided by the motor for at least a short time. This is advantageous because in the second operating mode it is already known that motor assistance is desired by a cyclist. The motor assistance can therefore either be provided based on the torque applied by the cyclist, or it can be checked whether further conditions are met before longer-term motor assistance is provided. For example, in the second operating mode the motor torque is only provided for a short time to check whether the motor is blocked or can rotate. If the motor is blocked, i.e. cannot rotate, the control unit preferentially switches back to the first operating mode.
[0017] The first condition is met when a rider torque exerted by the bicycle rider is detected that lies above a predefined first threshold. This means that the torque sensor detects sufficient rider torque to indicate intentional pedaling by the bicycle rider. The first condition ensures, among other things, that unintentional minor loads on a bicycle pedal or an unwanted deviation of an output signal from the torque sensor from a zero value are not interpreted as a start-up request. Furthermore, minor errors or inaccuracies in the measurement signal of the torque sensor do not lead to an unintentional start-up. The second condition depends on the temporal progression of the rider torque, the motor speed of the motor, and / or a user input.This means that the temporal progression of the rider torque, the motor speed and / or the user input are evaluated, and the second condition is met when the temporal progression of the rider torque, the motor speed and / or the user input exhibits a certain characteristic. These parameters, on which the second condition depends, have in common that they indicate a desire by the rider of the electric bicycle for motor assistance, even if the rider is unable to move the bicycle pedals, for example, because their strength is insufficient on a slope. It should be noted that the motor speed is recorded when checking the second condition, but the rotation of the motor is not caused by the motor itself, since it does not provide any motor torque in the first operating mode.This means that the rotation of the motor, which results in the motor speed, is caused by a movement of the electric bicycle, for example by rolling backwards on a slope.
[0018] The second condition can be formulated in such a way that it depends on a combination of the said parameters, in particular depends on the time course of the driver torque and the engine speed, the time course of the driver torque and the engine speed, the time course of the driver torque and the user input or depends on the engine speed and the user input.
[0019] The subclaims show preferred developments of the invention.
[0020] Preferably, the second condition depends on the temporal progression of the driver torque and is fulfilled when the temporal progression of the driver torque exhibits a predefined characteristic. Thus, the temporal progression of the driver torque does not only consider an instantaneous value of the driver torque, as is possible, for example, in the context of the first condition, but rather the driver torque is considered over time. This yields additional information. For example, it can be detected whether the driver of the electric bicycle is performing a continuous action that indicates a desire for assistance from the motor.
[0021] Preferably, the temporal profile of the driver torque has the predefined property if the detected driver torque is greater than a second threshold value over a predefined period of time, a gradient of the detected driver torque is greater than a third threshold value, and / or an integral over the temporal profile of the detected driver torque over a predefined time interval is greater than a fourth threshold value. The second threshold value can thus be used to define how long the driver must maintain a driver torque so that a conclusion can be drawn about their desire for motor assistance. The second threshold value is preferably greater than the first threshold value or greater than or equal to the first threshold value. More preferably, the second threshold value is equal to the first threshold value.Based on the third threshold, it is possible to define how dynamically the rider must act on the bicycle pedals in order to determine whether motor assistance is desired. By using the integral and the fourth threshold, a system is created in which either a comparatively short application of high rider torque or a comparatively long application of a relatively low rider torque leads to the fulfillment of the second condition and thus to motor assistance. The aforementioned predefined properties can be combined with one another. For the second condition to be fulfilled, either two or all of the aforementioned predefined properties must be present.
[0022] Preferably, the second condition depends on the motor speed of the motor and is met when the motor speed of the motor is below a predefined fifth (negative) threshold, wherein the motor speed of the motor is caused by the bicycle rolling backwards and is thus negative. The motor speed is positive when the motor rotates in a direction used to propel the bicycle. The motor speed is negative when the motor rotates in a direction caused by the bicycle rolling backwards. By checking whether the motor speed of the motor is above a predefined fifth threshold, it is detected that the electric bicycle is rolling backwards when the motor assistance is desired.This typically occurs when a cyclist does not exert enough power to accelerate the bike uphill on a slope.
[0023] Further preferably, the second condition is dependent on the user input and is fulfilled when a user performs a predefined input via an input unit. Thus, it is advantageous if a user performs any predefined action through which the user can consciously communicate that motor assistance is desired.
[0024] The input unit is preferably a button, and the user input is pressing the button for a predefined period of time. Such a button is preferably located on the handlebars of the electric bicycle. The button can also be implemented digitally, for example, on a touchscreen.
[0025] More preferably, the second condition to be fulfilled or a combination of second conditions to be fulfilled is selected depending on a current driving situation, which is determined based on recorded sensor data. For example, sensors of the electric bicycle determine whether the electric bicycle is on a slope. If this is the case, the second condition can be optimized for this situation. For example, the second condition is selected such that it depends on the gradient of the detected driver torque and the duration that the detected driver torque is above the first threshold value. Thus, a situationally optimized second condition can be selected, which increases driving comfort depending on the current driving situation.
[0026] Preferably, the control unit is configured to determine in the second operating mode whether the motor torque provided by the motor results in movement of the motor, and to switch to the first operating mode if the motor torque provided by the motor does not result in movement of the motor, and to switch to a third operating mode if the motor torque provided by the motor results in movement of the motor. This prevents the motor from providing continuous assistance that does not result in movement of the electric bicycle but could lead to overheating of the motor.
[0027] It is also advantageous if the control unit is configured to control the motor of the electric bicycle in the third operating mode such that the motor torque is provided depending on the rider torque. Thus, it is advantageous if a regular riding mode is provided after a test to determine whether the motor is blocked.
[0028] Short description of the drawings
[0029] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:
[0030] Figure 1 is a representation of an electric bicycle with a device according to the invention for controlling a motor, and
[0031] Figure 2 shows a flow diagram of a method according to the invention for
[0032] Controlling a motor of an electric bicycle.
[0033] Embodiments of the invention
[0034] Figure 1 is a schematic representation of an electric bicycle 10, for example a pedelec, which comprises a device 1 according to the invention for controlling a motor 2 of the electric bicycle 10. The device 1 executes the method 100 according to the invention for controlling the motor 2 of the electric bicycle 10, with an exemplary flowchart of the method 100 being shown in Figure 2.
[0035] The device 1 comprises at least one control unit 3 configured to execute the method 100. A motor speed sensor 4, which is a component of the device 1 or provides information thereto, is arranged on the motor 2 of the electric bicycle 10. Furthermore, a rider torque sensor 5, which is a component of the device 1 or provides information thereto, is arranged on the electric bicycle 10.
[0036] The control unit 3 is configured to control the motor 2 of the electric bicycle. The control unit 3 is configured to control the motor 2 at least in a first operating mode 101 and in a second operating mode 102. In the embodiment described here, the control unit 3 is further configured to control the motor 2 of the electric bicycle 10 in a third operating mode 104 and in a fourth operating mode 107. Depending on the current operating mode, the motor 2 of the electric bicycle 10 is controlled in different ways.
[0037] With reference to Figure 2, the motor 2 is initially controlled in the first operating mode 101. In the first operating mode 101, the motor 2 is controlled such that no assistance for driving the electric bicycle 10 is provided by the motor 2. In this case, no motor torque is provided by the motor 2. The first operating mode 101 is thus a mode that typically occurs when the electric bicycle 10 is stationary and no motor assistance is desired by the user.
[0038] In the second operating mode 102, the motor 2 is controlled by the control unit 3 in such a way that a motor torque is provided by the motor 2 at least briefly.
[0039] The control unit 3 must make a decision as to when a change 103 from the first operating mode 101 to the second operating mode 102 should occur. This change should occur when it is determined that motor assistance from the motor 2 is desired by a rider of the electric bicycle 10. It is a challenge here to ensure that no unwanted movements of the pedals result in motor assistance being provided, as this would lead to unwanted movement of the electric bicycle 10. At the same time, the aim is to detect the desire for assistance from the motor 2 as quickly as possible, but also as reliably, so that the electric bicycle 10 exhibits dynamic riding behavior. This is achieved by the device 1 in that a change from the first operating mode 101 to the second operating mode 102 occurs when two conditions are met.The control unit 3 thus checks whether the parameters defined by a first condition and the parameters defined by a second condition are present, and in response to the presence of these parameters defined by the conditions, a change 103 occurs from the first operating mode 101 to the second operating mode 102.
[0040] The first condition is met when a driver torque applied by the rider of bicycle 10 to the pedals of bicycle 10 is detected that exceeds a predefined first threshold. For this purpose, for example, an output signal of the driver torque sensor 5 is compared with a comparison value predefined by the first threshold, and if the measured driver torque exceeds the first threshold, the first condition is met. For example, the first threshold could be set to 12.5 Nm, and the first condition is met when the rider of the electric bicycle 10 exerts a driver torque that exceeds this 12.5 Nm.
[0041] The second condition ensures, among other things, that motor torque is not yet provided by motor 2 when a comparatively high driver torque is unintentionally applied. This can be the case, for example, if a move-off procedure fails, for example because the driver slips off the pedal or if the driver merely rests their leg on the pedal. It also ensures that minor errors and inaccuracies in the sensor signal are not falsely identified as the driver's request to move off. The second condition should be used to reliably detect a request for motor assistance, regardless of the existing driving or terrain situation. Fast detection of the second condition is desirable so that motor assistance is provided quickly when the driver requests it.This is important, for example, when starting uphill, as a lack of motor support could cause the bike to roll backwards.
[0042] Below, various options for designing the second condition are listed. These can be combined with one another, and each of these example second conditions depends on a temporal progression of the driver torque, an engine speed of engine 2, or a user input.
[0043] The second condition is designed, for example, in such a way that it depends on the temporal course of the driver torque and is fulfilled when the temporal course of the driver torque has a predefined property.
[0044] The predefined property is, for example, that the detected driver torque is greater than a second threshold value over a predefined period of time. The second threshold value is greater than the first threshold value of the first condition. Thus, the second threshold value is preferably selected in a range between 50 Nm and 100 Nm, for example, 80 Nm. Thus, the driver torque detected by the driver torque sensor 5 must be above the second threshold value for an applicable time in order for the second condition to be met. The applicable time is preferably selected in a range between 30 ms and 400 ms, for example, 200 ms.
[0045] The predefined property is, for example, that a gradient of the detected rider torque is greater than a third threshold value. Thus, a gradient of a torque signal from rider torque sensor 5 must be above the third threshold value over an applicable time period. The applicable time period is preferably selected in a range between 30 ms and 400 ms, for example, 200 ms. The third threshold value is preferably selected in a range between 50 Nm / s and 500 Nm / s, for example, 200 Nm / s. In this way, it is prevented, for example, that a slow increase in rider torque leads to the fulfillment of the second condition and motor assistance from motor 2. This covers, for example, situations in which the rider rests on the pedal without starting off or in which a bicycle is held in position on a slope by rider torque.In addition, this would prevent the error case of a slow drift in the sensor signal.
[0046] The predefined property is, for example, that an integral over the temporal progression of the detected driver torque over a predefined time interval is greater than a fourth threshold. This means that the integrated driver torque signal, which is detected by the driver torque sensor 5 and integrated over an applicable time, must be above the fourth threshold. Mathematically, this means that the result of the following term is compared with the fourth threshold:
[0047] Where ti is the applicable time and Mdriver(t) is the driver torque over time.
[0048] The second condition, like the first condition, can thus be derived from the measured driver torque provided by the driver torque sensor 5. However, the second condition must meet stricter criteria than the first condition.
[0049] Depending on potentially occurring error patterns of the driver torque sensor 5, which could, for example, lead to the triggering of the first condition, the previously mentioned options for the second condition can also be combined to prevent an unwanted switch to the second operating mode. In an exemplary implementation, the driver torque must be above 12.5 Nm to fulfill the first condition, and the torque gradient must be above the third threshold of 200 Nm / s for a period of 200 ms. In particular, this combination covers the case of impulsive dynamic acceleration on inclines. According to this example, it is therefore also advantageous if the second condition is only fulfilled when the gradient of the detected driver torque is above the third threshold for a predefined period.The high threshold value and the specific signal curve (strongly increasing torque) reduces the risk of incorrect triggering of the motor assistance.
[0050] Alternatively or additionally, the second condition depends on the motor speed of the motor 2, which is detected by the speed sensor 4. The second condition is preferably met when the motor speed of the motor 2 is below a predefined fifth negative threshold. When the electric bicycle 10 is moved backwards, the entire drive train also rotates backwards. The drive train comprises the rear wheel, the pinion set, the chain, the chainring, the pedals (only in systems without driver freewheel) and the motor 2 of the electric bicycle. This movement can be detected by a rotor position sensor of the motor, which is used, for example, as a speed sensor 4. This case occurs, for example, when the rider of the electric bicycle 10 attempts to start up a hill but does not apply sufficient rider torque to set the electric bicycle 10 in forward motion.Instead, the electric bicycle 10 rolls backward, and the motor 2 also rotates backward. If the motor speed of the motor 2 is below an applicable negative threshold, in this case the fifth threshold, the second condition is met. The motor speed of the motor 2 considered in the second condition is caused by the bicycle 10 rolling backward.
[0051] Alternatively or additionally, the second condition depends on the user input. The second condition is met, for example, when a predefined input is made by a user via an input unit. The predefined input is, for example, pressing a button for a predefined period of time. The second condition can be the triggering of a (dedicated) button 6, i.e. a button, on a control element of the electric bicycle 10. This can be a singular event. This means that the button 6 is pressed briefly once, or the button must remain pressed for an applicable period of time for the second condition to be met. In the second case, the button 6 can be assigned multiple functions, whereby, for example, the button for switching up an assistance mode is also used as an input unit for the method according to the invention.Direct support by the electric motor 2, which is triggered by pressing the button 6, is also advantageous here.
[0052] As already explained, the second conditions listed here as examples can be combined with each other. A second condition can therefore consist of several subconditions.
[0053] Preferably, the second condition to be met or the combination of second conditions to be met is selected depending on the current riding situation, which is determined based on recorded sensor data. Thus, the previously described activation of the motor assistance in a system can be triggered, for example, by means of a specific combination of second conditions, and this only occurs when a slope of the electric bicycle 10 is detected by a position sensor.
[0054] If the second condition is met, the control unit switches to the second operating mode 102. In the second operating mode 102, the motor
[0055] 2, in the embodiment described here, individual torque pulses are provided, wherein it is detected whether the motor 2 is rotating when the torque pulses are provided. This is determined by means of the motor speed sensor 4, which detects the motor speed of the motor 2. If the temporary provision of the motor torque in the second operating mode 102 does not result in rotation of the motor 2, the control unit switches back to the first operating mode 101, since it can be assumed that the motor 2 is blocked. This switch back takes place in a switch step 106 according to Figure 2.
[0056] If, however, it is determined that the briefly provided motor torque results in movement of motor 2, a changeover step 105 is initiated from the second operating mode 102 to a third operating mode 104. In the third operating mode 104, the motor 2 is controlled by the control unit 3 such that the motor torque is provided depending on the rider torque. The rider torque is detected by the rider torque sensor 5 and, using an associated algorithm, is converted into a requested motor torque, which is then provided by the motor 2. In the third operating mode 104, typical regular operation of the electric bicycle 10 occurs.
[0057] The method shown in Figure 2 further preferably comprises a motor blocking protection for protecting the motor 2 in the event of a blockage after a release of the motor support and an operation of the control unit 3 in the third operating mode 104. Thus, the control unit
[0058] 3, for example, switches to a fourth operating mode 107 if a blockage of the motor 2 occurs in the third operating mode 104. In this case, in the fourth operating mode 107, the motor torque of the motor 2 is continuously reduced until the blockage is removed. This prevents overheating of the motor 2. If the blockage is removed, the control unit 3 switches back to the third operating mode 104 in a switching step 109.
[0059] If a request for motor assistance is no longer required, regardless of whether the control unit 3 is in the third operating mode 104 or in the fourth operating mode 107, the control unit 3 returns to the first operating mode 101 in a respective changeover step 110, 111.
[0060] In addition to the above description, explicit reference is made to the disclosure of Figures 1 and 2.
Claims
Claims 1. Device (1) for controlling a motor (2) of an electric bicycle (10), comprising a control unit (3) which is designed to: - to control the motor (2) of the electric bicycle (10) in a first operating mode, wherein in the first operating mode the motor (2) is controlled such that no motor torque is provided by the motor (2), and - to control the motor (2) of the electric bicycle (10) in a second operating mode, wherein in the second operating mode the motor (2) is controlled such that a motor torque is provided by the motor (2) at least briefly, - wherein the control unit (3) is configured to switch from the first operating mode to the second operating mode when a first condition and a second condition are met, - wherein the first condition is met when a driver torque exerted by a driver of the bicycle (10) on the pedals of the bicycle (10) is detected which is above a predefined first threshold value, and - wherein the second condition is dependent on a time profile of the driver torque, an engine speed of the engine (2) and / or a user input.
2. Device according to claim 1, wherein the second condition depends on the time course of the driver torque and is fulfilled when the time course of the driver torque has a predefined property.
3. Device according to claim 2, wherein the time course of the driver torque has the predefined property when: • the detected driver torque is greater than a second threshold value over a predefined period, • a gradient of the detected driver torque is greater than a third threshold, and / or • an integral over the time course of the recorded driver torque over a predefined time interval is greater than a fourth threshold value.
4. Device according to one of the preceding claims, wherein the second condition depends on the engine speed of the engine (2) and is met when the engine speed of the engine (2) is below a predefined fifth negative threshold value, wherein the engine speed of the engine (2) is caused by the bicycle (10) rolling backwards.
5. Device according to one of the preceding claims, wherein the second condition depends on the user input and is fulfilled when a predefined input is made by a user via an input unit.
6. The device according to claim 5, wherein the input unit is a button, and the user input is an actuation of the button for a predefined time.
7. Device according to one of the preceding claims, wherein the second condition to be fulfilled or a combination of second conditions to be fulfilled is selected depending on a currently existing driving situation which is determined based on detected sensor data.
8. Device according to one of the preceding claims, wherein the control unit (3) is arranged to - to determine in the second operating mode whether the motor torque provided by the motor (2) results in a movement of the motor (2), and - to switch to the first operating mode when the motor torque provided by the motor (2) does not result in any movement of the motor (2), and - to switch to a third operating mode when the motor torque provided by the motor (2) results in a movement of the motor (2).
9. Device according to claim 8, wherein the control unit (3) is configured to control the motor (2) of the electric bicycle (10) in the third operating mode such that the motor torque is provided depending on the rider torque.
10. A method (100) for controlling a motor (2) of an electric bicycle (10), comprising: - controlling (101) the motor (2) of the electric bicycle (10) in a first operating mode, wherein in the first operating mode the motor (2) is controlled such that no motor torque is provided by the motor (2), - controlling (102) the motor (2) of the electric bicycle (10) in a second operating mode, wherein in the second operating mode the motor (2) is controlled such that at least briefly a motor torque is provided by the motor (2), and - Switching (103) from the first operating mode to the second operating mode when a first condition and a second condition are met, wherein the first condition is met when a driver torque exerted by a driver of the bicycle (10) on the pedals of the bicycle (10) is detected which lies above a predefined first threshold value, and wherein the second condition is dependent on a temporal profile of the driver torque, an engine speed of the engine (2) and / or a user input.