A drive system equipped with a control device for controlling the electric drive unit using active short-circuit in the event of a failure.

Abstract

The present invention relates to a drive system for an electric bicycle (F), comprising: a drive shaft (1) for applying driving force to drive the electric bicycle (F) by human power; an output shaft (2) for transmitting the driving force to the wheels (112) of the electric bicycle (F); at least one electric motor (11, 12) for generating assist force by external power; a gear shift (15) for connecting the drive shaft (1) to the output shaft (2) and transmitting the assist force to the output shaft (2); and a control device (8) for controlling at least one electric motor (11, 12). The control device receives at least one fault signal (f s In response to this, the system is configured to control at least one electric motor (11, 12) using an active short circuit before switching to a no-load state.

Description

[Technical Field]

[0001] The proposed solutions relate particularly to drive systems for electric bicycles. [Background technology]

[0002] In a drive system for an electric bicycle, which includes at least one electric motor for generating assist force operated by an external power source, it is known that at least one electric motor is switched to a no-load state in response to at least one fault signal. Therefore, if a safety-critical fault is detected and as a result reliable control of, for example, the level of assist force generated by at least one electric motor is no longer possible, it is necessary to switch at least one electric motor to a no-load state, i.e., a safe state. [Overview of the project] [Problems that the invention aims to solve]

[0003] However, immediately and abruptly switching at least one electric motor to a no-load state in response to a detected fault can completely startle a rider of an electric bicycle. In particular, this can lead to the sudden disappearance of the resistance the rider experiences when pedaling the electric bicycle, which was previously provided by at least one electric motor. The immediate switch to a no-load state may feel to the electric bicycle rider as if the drive chain had broken on a conventional bicycle. Depending on the current riding conditions, such an immediate switch to a no-load state of at least one electric motor could lead to injury to the electric bicycle rider. [Means for solving the problem]

[0004] In this respect, the proposed solution is intended to provide an improvement.

[0005] The proposed drive system for electric bicycles comprises at least the following: A drive shaft that applies the driving force to propel an electric bicycle using human power. Output shaft for transmitting driving force to the wheels of an electric bicycle. At least one electric motor for generating an assist force operated by an external power source, A transmission that connects the drive shaft and the output shaft and transmits assist force to the output shaft, and A control device for controlling at least one electric motor, configured to control at least one electric motor using an active short circuit in response to at least one fault signal before the control device switches at least one electric motor to an unloaded state.

[0006] The proposed solution is based on the fundamental idea that, in the event of a fault electronically notified by at least one fault signal, at least one electric motor in the drive system is first controlled at least once using an active short circuit, rather than immediately switching it to an unloaded, i.e., safe state. This maintains resistance in the drive shaft for the duration of the active short circuit in at least one electric motor, although it may be lower than the situation before the fault signal was generated. This allows the electric bicycle rider to continue to feel that resistance through the pedals connected to the drive shaft via the crank. Thus, the risk of rider injury (e.g., from a fall) can be reduced compared to an abrupt switch to an unloaded state.

[0007] Control using active short circuits has the additional advantage that it can be performed even when the hardware is only minimally functional, and therefore remains feasible even in the case of safety-critical faults indicated by at least one fault signal. Furthermore, in the case of control using active short circuits, the possibility of at least one electric motor further accelerating the rotor (shaft) driven by that electric motor is eliminated. Therefore, in the case of control using active short circuits, at least one electric motor can no longer provide assist force to rotate the drive shaft.

[0008] Furthermore, it has been observed that when at least one electric motor is activated using an active short circuit, vibrations that can be felt and / or heard by the electric bicycle rider may occur in the housing of the drive unit of the drive system that houses the electric motor, depending on the circumstances. In this way, the electric bicycle rider can be further informed of the occurrence of a fault (in addition to potentially outputting an alarm to the control unit of the drive system) tactilely and / or audibly. As a result, the electric bicycle rider will be drawn to the fault event, which typically results in the rider reducing the force with which they pedal. Therefore, the electric bicycle rider will no longer be startled by the subsequent switching of the electric motor to an unloaded state.

[0009] In a modified embodiment, the control device of the drive system is configured to control at least one electric motor using an active short circuit for a predetermined period of time in response to at least one fault signal before switching to an unloaded state. Accordingly, the control device stores the period of time during which the active short circuit is maintained after the occurrence of at least one fault signal. For example, this period is within the range of one second.

[0010] Alternatively, the control device may be configured to control at least one electric motor in a control sequence in response to at least one fault signal. This sequence includes a first control using an active short circuit followed by a first switch to a no-load state, followed by at least one further control using an active short circuit followed by at least one further switch to a no-load state. Thus, in a variation of such an embodiment, at least one electric motor is initially switched to a no-load state only temporarily during at least two operations with an active short circuit before the final switch to a no-load state occurs last and the at least one electric motor is held in that no-load state. The transition between the phase with an active short circuit and the no-load state may, additionally, make the electric bicycle operator more sensitive to the occurrence of a fault scenario and prepare for the final switch to and holding of the at least one electric motor in a no-load state.

[0011] In this context, it may be advantageous if a predetermined time period for a first control with an active short circuit is longer than a second time period for at least one further control with an active short circuit. For example, in a control sequence, if a first phase in which at least one electric motor is driven with an active short circuit is alternated with a second phase in which at least one electric motor is switched to an unloaded state (until the end of the control sequence in which at least one electric motor is finally switched to an unloaded state is reached), the length of the first phase can become shorter over time, and in particular, continuously shorter.

[0012] When a first phase and a second phase, each lasting for a predetermined period, are periodically switched, the proportion of the first phase in which the active short circuit is activated can decrease over time, particularly continuously. By decreasing the proportion of the first phase over time, the resistance, and therefore the reaction force, that the electric bicycle rider can feel with the pedals can be continuously reduced before the resistance completely disappears when at least one electric motor is switched to an unloaded state.

[0013] In principle, the first and second phases may alternate over a predetermined total time period before finally switching to a no-load state. For this purpose, the control device is configured to control at least one electric motor in alternating first and second phases for a predetermined total time period in response to at least one error signal.

[0014] The duration of the switch between the first and second phases, until the system finally switches to a no-load state in response to at least one fault signal, may, in principle, depend on whether the rate at which the first phase, in which at least one electric motor is controlled by active short-circuiting, decreases over time has decreased to a threshold. Therefore, control using active short-circuiting terminates when the length of the first phase, which decreases over time, reaches a threshold, for example, zero.

[0015] The control device may be configured to periodically control at least one electric motor using an active short circuit via a control pulse. Thus, the control device is configured to generate a pulsed short circuit for at least one electric motor. This includes, for example, a modification of the above embodiment in which the phase involving the control of the active short circuit is shortened, and in which the control device is configured to reduce the degree of drive ("duty cycle") of the control pulse over time during the control sequence. For example, the duration of the control pulse, and thus its proportion of the period, can be reduced at least every three or two periods. Alternatively, the period of the control pulse may be reduced continuously, and therefore immediately with each subsequent control pulse.

[0016] In a modification of one embodiment, the control device is further configured to control at least one electric motor using an active short circuit only if at least one additional criterion is met. This additional criterion may relate, for example, to the operating parameters of the drive system. Therefore, it has been found that in certain driving conditions, controlling at least one electric motor using an active short circuit may be disadvantageous. Thus, in a modification of a particular embodiment, it may be advantageous to first check whether at least one additional criterion is also met before performing an active short circuit in response to at least one fault signal. If necessary, the operation by an active short circuit in response to at least one fault signal is performed with a time delay, specifically, only if at least one additional criterion is also met. The satisfaction of the corresponding criterion can be detected, for example, electronically.

[0017] In a modified embodiment, the control device is configured to control at least one electric motor using an active short circuit only when the rotational speed of at least one electric motor exceeds a threshold. Such a configuration has proven particularly advantageous in a drive system comprising first and second electric motors, wherein the transmission includes at least one planetary transmission, and the gear ratio is adjustable using the first and second electric motors. In such a drive system, the torque generated by the first electric motor is transmitted at least partially to the output shaft. In normal operation, the second electric motor supports the driver torque, which is applied by the driver and therefore by human operation, resulting from the applied driving force. It is this second electric motor that ensures the resistance that the driver of the electric bicycle can feel with the pedals in normal operation. Depending on the driving conditions, the second electric motor drives its (second) rotor shaft for rotation in the positive rotational direction (corresponding to the forward rotation of the second electric motor) or the opposite negative rotational direction. For example, if a failure occurs that ultimately switches the electric motor to an unloaded state, and it is detected that the second rotor shaft of the second electric motor is rotating in the opposite negative direction, the active short circuit will not be performed initially. Instead, it will first wait until the direction of rotation changes and therefore the measurement signal indicating the rotation of the second rotor becomes positive at this point (and thus exceeds the threshold of 0). Only when this additional criterion is met will the active short circuit be performed for the first time, and therefore, for example, the control sequence described above will begin. For example, in the case of an electric drive system that is no longer fully functioning correctly, if the second rotor shaft is accelerated in the positive direction for a relatively short time by the human power applied to the drive shaft by the electric bicycle rider, then at the time of the failure, even if there is initially a negative rotational speed due to the current driving conditions, the rotational speed of the second rotor shaft will change from a negative value to a positive value after a short time.

[0018] As a rule, it can be stipulated that the control device comprises a B6 bridge circuit for controlling at least one electric motor. Such a B6 bridge circuit comprises, for example, six MOSFETs.

[0019] In particular, one or more fault signals that trigger the switching of at least one electric motor to the no-load state can notify, for example, that the position of the rotor (rotor shaft) of at least one electric motor can no longer be detected and / or specified, and / or that the necessary phase current measurement is no longer available in the field orientation control of at least one electric motor by the control device. Correspondingly, when an error is detected electronically, active commutation of at least one electric motor is no longer possible, so at least one electric motor must be switched to a completely no-load state, i.e., a safe state, in any case. The proposed solution can be used particularly in such cases of failure.

[0020] The proposed solution also relates to a method for controlling the drive system of an electric bicycle. In this case, at least the following are provided in the drive system. A drive shaft for applying a driving force for driving the electric bicycle by human power, An output shaft for transmitting the driving force to the wheels of the electric bicycle, At least one electric motor for generating an assist force actuated by external power, and, A transmission provided for connecting the drive shaft and the output shaft and transmitting the assist force to the output shaft.

[0021] In the proposed control method, here, it is stipulated that, before switching to the no-load state, at least one electric motor is controlled (at least once) using an active short circuit in response to at least one fault signal.

[0022] Embodiments of the proposed control method can be implemented using embodiments of the proposed drive system. Accordingly, the advantages and features described above and below for modifications of embodiments of the proposed drive system also apply to modifications of embodiments of the proposed control method, and vice versa.

[0023] Furthermore, a computer program product is proposed that, when executed by at least one processor of a control device for a drive system of an electric bicycle equipped with an electric drive unit, includes instructions causing the at least one processor to execute a modified embodiment of the proposed control method. Thus, the at least one processor may be part of a control device implemented together with the control device, which is configured to control at least one electric motor using an active short circuit in response to at least one fault signal before switching to a no-load state. [Brief explanation of the drawing]

[0024] The attached drawings illustrate examples of possible embodiments of the proposed solution. These include: [Figure 1] A 2D design proposal for the electric drive unit of the proposed drive system embodiment is shown. [Figure 2] A schematic side view of an electric bicycle equipped with the proposed drive system is shown. [Figure 3] An example of a B6 bridge circuit for the control device of the present invention is shown. [Figure 4] This example shows a control sequence in which the degree of control over pulse short circuits decreases over time, resulting in alternating phases of control by active short circuits that gradually shorten and phases in which the electric motor drive is switched to a no-load state that gradually lengthen. [Figure 5] A flowchart of an embodiment of the proposed control method is shown. [Modes for carrying out the invention]

[0025] Figure 2 shows an electric bicycle F having a drive system comprising an electric drive unit 10. The electric bicycle F has a frame 110, which, in this example, includes a top tube, a down tube, and a seat tube, and the drive unit 10 is fixed in the intersection region of the seat tube and the down tube. Part of the drive unit 10 is a control device 8 and a sensor device 115. The electric motors 11 and 12 of the drive unit 10 (see Figure 1) are controllable via the control device 8, in particular to predetermine the level of assist force generated by external power operation to drive the electric bicycle F. The sensor device 115 is provided to acquire the rotational speed of the drive shaft (pedal shaft) 1 of the drive unit 10 by sensor. For this purpose, the sensor device 15 may include a rotational speed sensor, which can measure the rotational speed of the pedal shaft 1. The driving force to drive the electric bicycle F can be applied to the drive shaft 1 by the human power operation of the driver of the electric bicycle F, via a pair of pedal cranks 1A connected to the drive shaft 1 and the pedals provided thereon. If necessary, the sensor device 115 may be provided to acquire the torque input to the drive shaft 1 by manual operation, and may be configured, for example, using a torque sensor and / or a position sensor.

[0026] The output element of the drive unit A, for example, a hollow output shaft 2 (see Figure 1) supported coaxially with the pedal shaft 1, is connected to the rear wheel 112 of the electric bicycle F via a belt or chain 213 as a power transmission member, in order to drive the electric bicycle F. A wheel sensor 114 is assigned to this rear wheel 112, for example, to determine the speed of the electric bicycle F. Of course, the wheel sensor 114 may be provided on the front wheel 111 of the electric bicycle F instead.

[0027] The drive system of the electric bicycle F further includes an operating unit 102. In Figure 2, the operating unit 102 is fixed, for example, in the area of ​​the handlebars of the electric bicycle F and is typically connected to the control device 8 of the drive unit 10 via one or more cables. User input is obtained through the operating unit 102 and can be used to control the drive unit 10. For example, the operating unit 102 includes at least one display for notifying the user of the electric bicycle F of the following: The current operating status of drive unit F (for example, with respect to the set assist level), The charge state of the energy storage device 9 (including, for example, at least one (rechargeable) battery) that supplies electrical energy to the drive unit 10, and / or A set gear ratio that defines the gear ratio at which the drive torque input to the drive shaft 1 by human operation is transmitted to the output shaft 2 of the drive unit 10.

[0028] Figure 1 shows a 2D design proposal of the drive unit 10 of Figure 2, which includes two electric motors 11 and 12.

[0029] The drive unit 10 has a drive shaft 1 and an output shaft 2, both of which are rotatably supported within the housing 25 of the drive unit 10. The drive shaft 1 passes through the housing 25 and is connected to a crank 1A on each side, through which the driver of the electric bicycle F can apply driving force by manual operation. The output shaft 2 protrudes from the housing 25 on only one side and is connected from there to a sprocket or a toothed belt pulley to drive the rear wheel 112 of the electric bicycle F.

[0030] The drive unit 10 includes a first electric motor 11 having a first rotor shaft 3 and a second electric motor 12 having a second rotor shaft 4. The two electric motors 11 and 12 communicate via a control device 8 to form an electric continuously variable transmission. The control device 8 is also connected to an energy storage device 9. Therefore, the output shaft 2 can also be driven purely electrically via the first electric motor 11. The energy storage device 9 can also be used as a regenerative energy storage device when braking force flows into the drive unit 10 at the output shaft 2.

[0031] The drive shaft 1, output shaft 2, and two rotor shafts 3 and 4 are connected via a multi-stage planetary transmission 15 having multiple gear stages with a first degree of freedom and at least one planetary gear stage 16 with a second degree of freedom. Here, the gear stages are configured as spur gear stages. However, toothed belt gear stages are also conceivable. In this example, the three-axis planetary gear stage 16 comprises a sun gear 17, a ring gear 18, and a planetary carrier 19 having multiple planetary gears 20 supported by planetary gear bolts.

[0032] The elements of the drive unit 10 are, in this example, distributed across three shaft rows 21, 22, and 23, all arranged parallel to each other within the installation space defined by the housing 25. The drive shaft 1, the output shaft 2, and the second rotor shaft 4 of the second electric motor 12 are arranged coaxially in the first shaft row 21. The three-axis planetary gear stages 16 of the multi-stage planetary transmission 15 are located in the second shaft row 22. The first rotor shaft 3 of the first electric motor 11 is located in the third shaft row 23. In the first shaft row 21, the outer (hollow) output shaft 2 surrounds the inner drive shaft 1 on one side of the housing 25, and the second rotor shaft 4 surrounds the drive shaft 1 on the other side of the housing 25.

[0033] Four gear stages 31-34, configured as spur gear stages, are used to kinematically connect the elements of the drive unit 10, which are distributed across three shaft rows 21, 22, and 23 and housed within the housing 25. The drive shaft 1 on the first shaft row 21 is connected to the first connecting shaft 5 on the second shaft row 22 via the first spur gear stage 31. The output shaft 2 on the first shaft row 21 is connected to the second connecting shaft 6 on the second shaft row 22 via the second spur gear stage 32. The second rotor shaft 4 of the second electric motor 12 on the first shaft row 21 is connected to the third connecting shaft 7 on the second shaft row 22 via the third spur gear stage 33. This third connecting shaft also supports the sun gear 17. The first rotor shaft 3 of the first electric motor 11 on the third shaft row 23 is connected to the ring gear 18 of the planetary gear stage 16 on the second shaft row 22 via the fourth spur gear stage 34. In the second shaft row 22, the first connecting shaft 5 is connected to the planetary carrier 19, the second connecting shaft 6 is connected to the ring gear 18, and the third connecting shaft is connected to the sun gear 17 of the planetary gear stage 16. The first rotor shaft 3 of the first motor 11 is connected to the ring gear 18 and therefore to the output shaft 2, so the drive unit 10 shown as an example has an output-side power split.

[0034] The first spur gear stage 31 increases the rotational speed of the drive shaft 1 to, for example, the absolute rotational speed of the first connecting shaft 5, which is approximately three times greater. The first connecting shaft 5 is connected to the second connecting shaft 6 via the planetary gear stage 16. The rotational speed of the second connecting shaft 6 is transmitted to the rotational speed of the output shaft 2, for example, approximately 30% lower, by the gear ratio of the second spur gear stage 32.

[0035] Figure 1 shows five arrangement planes 35, 36, 37, 38, and 39, whose numbers increase as you move along the axial direction 30. The axial direction 30 refers to the direction from where the output shaft 2 exits the housing 25 toward the interior of the housing 25. In Figure 1, it can be seen that the second spur gear stage 32 is located in the first arrangement plane 35, the planetary gear stage 16 and the fourth spur gear stage 34 are located in the second arrangement plane 36, which is offset from and parallel to the first arrangement plane 35 in the axial direction 30, the first spur gear stage 31 is located in the third arrangement plane 37, which is similarly offset from the second arrangement plane 36 in the axial direction 30, the third spur gear stage 33 is located in the fourth arrangement plane 38, which is similarly offset from the third arrangement plane 37 in the axial direction 30, and the two electric motors 11 and 12 are located in the fifth arrangement plane 39, which is similarly offset from the fourth arrangement plane 38 in the axial direction 30.

[0036] The planetary gear stage 16 and the fourth spur gear stage 34 can be positioned in the same second alignment plane 36 because the gear of the fourth spur gear stage 34 on the second shaft row 22 has a larger pitch circle radius than the ring gear 18 of the three-axis planetary gear stage 16. As a result, the ring gear 18 has space inside this gear of the fourth spur gear stage 34 in the second alignment plane 36.

[0037] This axial arrangement of spur gears 31, 32, 33, and 34 near the planetary gear stage 16 on the second shaft row 22, combined with the distribution of drive elements to the three shaft rows 21, 22, and 23 shown in the figure, results in an extremely compact multi-stage planetary transmission 15.

[0038] In the first arrangement plane 35 having a second spur gear stage 32, a freewheel 40, for example in the form of a clamp-type freewheel, is positioned between the drive shaft 1 and the output shaft 2. The freewheel 40 allows the drive shaft 1 to be directly connected to the output shaft 2, especially at the maximum gear ratio. The freewheel 40 also functions, on the one hand, as overload protection for the drive unit 10, and on the other hand, to ensure the basic mechanical function of the drive unit 10 in the event of electrical system problems (e.g., voltage drop) or control / regulation problems (e.g., caused by failure of one or more sensors of the sensor device 115).

[0039] For the ease of assembly of the remaining elements of the drive system 10 and their support within the housing 25, the housing 25 has four housing components. The housing 25 consists of a main housing 26 connectable to or connected to the center land 27, a motor cover 28 connectable to or connected to the main housing 26 on the side of the fifth alignment plane 39, and a transmission cover 29 connectable to or connected to the main housing 26 on the side of the first alignment plane 35, through which the output shaft 2 protrudes from the housing 25.

[0040] The control device 8 of the electric drive unit 10 in Figures 1 and 2 includes a B6 bridge circuit 80 for controlling the first and second electric motors 11 and 12 in particular. Figure 3 shows an example of such a B6 bridge circuit with six MOSFETs, which is common in the prior art. In the event of a fault, the B6 bridge circuit 80 of the control device 8 can be turned off to switch the electric motors 11 and 12 to a safe and no-load state. Thus, for example, at least one fault signal f s This allows the control device 8 to be notified that a safety-critical fault has been detected in the drive unit 10. This can be done, for example, by sending a fault signal f sHowever, this includes the fact that at least one rotor position of rotors 3, 4 can no longer be acquired and / or determined by the sensor, or that the phase current measurement required for magnetic field direction control of the first and second electric motors 11, 12 is no longer available. In such a case, the control device 8 intends to switch the electric motors 11 and 12 to an unloaded state. However, at least one fault signal f s If the transition to a no-load state occurs immediately in response to the presence of this force, this leads to a sudden disappearance of the reaction force in the pedal fixed to crank 1A. The driver of electric bicycle F will then experience a sudden "free pedaling" sensation, similar to what would occur if the drive chain broke on a conventional bicycle.

[0041] To reduce the risk of injury to the driver of the electric bicycle F in the event of a failure of the electric motor drive unit, the control device 8 receives at least one fault signal f s In response, instead of immediately switching the electric motors 11 and 10 to a no-load state, the second electric motor 12 is configured to be controlled by an active short circuit at least once beforehand. During the duration of the active short circuit, a reaction force that can still be felt by the driver of the electric bicycle F can be generated on the pedals, so that the driver of the electric bicycle 1 does not suddenly spin freely. Control using an active short circuit also has the advantage that it can be implemented with hardware that still allows the active short circuit to function properly with minimal effort, and that the active short circuit does not lead to acceleration of the rotors 3 and 4. Furthermore, it can be observed that control using an active short circuit causes vibrations to be felt and heard in the housing 25 of the drive unit 10. This makes it possible for the drive unit 10 to immediately notify the driver of the electric bicycle F of the occurrence of a fault tactilely and audibly, so that the driver recognizes the fault and reduces the driving force applied to the drive shaft 1, especially the pedal crank 1A, at their own discretion.

[0042] To guide the driver of electric bicycle F to the final and definitive no-load state, fault signal f sIf such a condition exists, it may be advantageous not to control the second electric motor E2 only once by active short circuit for a predetermined period of time. Therefore, it is also possible to specify that a first phase in which control by active short circuit is performed and a second phase in which the electric motor drive is switched to an unloaded state are performed alternately. Over time, the first phase may be shortened in particular by a continuous manner.

[0043] Such a shortening of the first phase with active short circuit is shown as an example in Figure 4. For the control of the active short circuit, a pulse signal may be generated by the control device 8. The pulse width PW1 of the corresponding (first) control pulse decreases over time t through pulse width PW2 to pulse width PW3. Thus, the duty cycle decreases with time t. That is, the proportion of the first phase in the period T decreases with time. Thus, the ratio of the pulse duration for control by active short circuit to the period T decreases. When the duty cycle reaches 0, the electric motors 11 and 12 are maintained in an unloaded state.

[0044] In the diagram in Figure 4, for example, at least two control pulses having the same pulse width PW1 or PW2 are followed by a control pulse with a shorter pulse width PW2 or PW3. However, it is also possible to continuously decrease the pulse widths PW1, PW2, and PW3, and consequently the operating degree (duty cycle). That is, the pulse width of the subsequent control pulse is made shorter than the pulse width of the preceding control pulse. In that case, the control pulses shown by the dashed lines in Figure 4 are omitted.

[0045] It should be noted here that, for illustrative purposes only, Figure 4 shows only three control pulses having different pulse widths PW1, PW2, and PW3. Of course, in the control sequence of the control device 8, in which the first phase and active short-circuit control are performed alternately, and the second phase and switching to the no-load state are performed alternately, it is also possible to provide fewer or more control pulses with different pulse widths than three.

[0046] In a drive system comprising two electric motors 11 and 12 similar to or identical to those of the drive unit 10, which are used to continuously adjust the gear ratio of the planetary transmission 15, under certain driving conditions, even if a fault signal f s Even if a safety-critical failure is notified via [the appropriate means], controlling the second electric motor E2 with an active short circuit may be disadvantageous in some cases. Therefore, during the normal operation of the drive unit 10, it is clearly possible that the second rotor shaft 4 will be driven by the second electric motor 12 to rotate at a negative rotational speed and therefore in a negative rotational direction. In such cases, it is observed that an active short circuit may be disadvantageous.

[0047] Therefore, for example, in a modified embodiment of Figure 1, the system is configured to check which rotational direction the rotor shaft 4 of the second electric motor 12 is rotating in before the (initial) control by active short circuit, and consequently the control sequence shown in Figure 4, can be started. Regarding the second rotor shaft 4, the sensor signal S 115 If a negative rotational speed is notified to the sensor device 115 via the sensor signal S, control by active short circuit is not performed (initially). 115Only when it is notified that the second rotor shaft 4 of the second electric motor 12 has stopped or is rotating in the positive rotation direction via [the relevant component], the control by active short circuit is performed for the first time. Here, when a failure occurs and thus the electric drive device no longer operates properly, it is also utilized that the driver of the electric bicycle F applies a driving force (continuously) to the pedal fixed to the pedal crank 1A by manual operation, and the rotor shaft 4 is accelerated in the positive rotation direction after a relatively short time.

[0048] In this way, via the sensor signal S 115 it is notified that the operating parameters of the drive system characterizing the running state of the electric bicycle F are satisfied. The operation by active short circuit is executed only when the corresponding criteria are met.

[0049] Regarding a modified embodiment of the proposed control method, the above-mentioned procedure for controlling the first and second electric motors 11, 12 during a failure will be described again with reference to FIG. 5.

[0050] According to this, in the first step S1, first the detection of a safety-related failure is defined. Therefore, here the failure signal f s is generated and thus it is confirmed whether it exists. In the second step S2, first based on the sensor signal S 115 it is confirmed whether the rotational speed of the second electric motor 12, and thus the second rotor shaft, is 0 or more, that is, whether the rotor shaft 4 is rotating in the forward rotation direction. If not, first wait further and continue to monitor the rotational speed.

[0051] When the rotational speed of the second electric motor 12 or the rotor shaft 4 is 0 or more, the (initial) control by active short circuit is performed. As particularly described with reference to FIG. 4, in the process of the control sequence controlled by the control device 8, the pulse duration of the control pulse for the active phase and thus the active short circuit is continuously decreased until a no-load state is maintained. [Explanation of Symbols]

[0052] 1 Drive shaft 10 Drive Unit 11. First electric motor 12. Second electric motor 15 Planetary transmission 16 (3-axis) planetary gear stage 17 Sun Gear 18 Ring Gear 19 Planetary Carrier 2 Output shafts 20 Planetary gears 21 First shaft row 22 Second shaft row 23 Third shaft row 25 Housing 26 Main Housing 27 Centerland 28 Motor cover 29. Gearbox cover 3. First rotor shaft 30 Axis 31 First spur gear stage 32 Second spur gear stage 33 Third spur gear stage 34. Fourth spur gear stage 35 First arrangement plane 36. Second arrangement plane 37 Third arrangement plane 38. The fourth arrangement plane 39. Fifth arrangement plane 4. Second rotor shaft 40 Freewheel 5. First connecting shaft 6. Second connecting shaft 7. Third connecting shaft 8. Control Unit 80PI(D) Controller 80 B6 Bridge 9. Energy storage devices 102 Operation section 110 (bicycle) frame 111 Front Wheel 112 Rear wheel 113 Belt / Chain 114 Wheel Sensor 115 Sensor device F Electric Bicycle f s failure signal PW1, PW2, PW3 pulse width T period S 115 First signal

Claims

1. A drive system for electric bicycles (F), A drive shaft (1) for applying driving force to drive the electric bicycle (F) by human operation, An output shaft (2) for transmitting the aforementioned driving force to the wheels (112) of the electric bicycle (F), At least one electric motor (11, 12) for generating assist force by external power operation, A transmission (15) connects the drive shaft (1) and the output shaft (2) and transmits the assist force to the output shaft (2), A control device (8) for controlling at least one electric motor (11, 12), wherein at least one fault signal (f ｓ A control device (8) configured to switch at least one of the electric motors (11, 12) to an unloaded state in response to ), It has, The control device (8) receives the at least one fault signal (f ｓ A drive system characterized in that, in response to the above, it is configured to control at least one electric motor (11, 12) using an active short circuit before switching to the no-load state.

2. The control device (8) uses an active short circuit for a predetermined period of time before switching to the no-load state to signal at least one electric motor (11, 12) to the at least one fault signal (f ｓ The drive system according to claim 1, characterized in that it is configured to control in response to ).

3. The control device (8) is A control sequence in which a first control using an active short circuit and a subsequent first switch to a no-load state are followed by at least one further control using an active short circuit and at least one further switch to a no-load state, The at least one electric motor (11, 12) is controlled by the at least one fault signal (f ｓ The drive system according to claim 1 or 2, characterized in that it is configured to control in response to ).

4. The drive system according to claim 3, characterized in that a predetermined first time period for the first control using the active short circuit is longer than a second time period for at least one further control using the active short circuit.

5. The control device (8) is A control sequence in which at least one electric motor (11, 12) is controlled in an active short circuit state, and at least one electric motor (11, 12) is switched to an unloaded state, is performed alternately. The at least one electric motor (11, 12) is controlled by the at least one fault signal (f ｓ The drive system according to claim 3 or 4, characterized in that it is configured to control in response to ).

6. The drive system according to claim 5, characterized in that the length of the first phase of the control sequence decreases over time, and in particular decreases continuously.

7. The control device (8) alternates between first and second phases for a predetermined total time period, and the at least one fault signal (f ｓ The drive system according to claim 5 or 6, characterized in that it is configured to control at least one electric motor (11, 12) in response to ).

8. The control device (8) alternates between first and second phases, and the at least one fault signal (f ｓ The drive system according to claim 6 or 7, characterized in that it is configured to control at least one electric motor (11, 12) in response to the first phase until the length of the first phase decreases over time and reaches a threshold.

9. The drive system according to any one of claims 5 to 8, characterized in that the control device (8) is configured to periodically control the at least one electric motor (11, 12) by active short circuit using control pulses.

10. The drive system according to claims 6 and 9, characterized in that the control device (8) is configured to reduce the duty cycle of the control pulse over time during the control sequence.

11. The control device (8) is Only if at least one additional criterion is met, in particular if an additional criterion related to the operating parameters of the drive system is met, The drive system according to any one of the preceding claims, characterized in that it is configured to control at least one electric motor (11, 12) using an active short circuit.

12. The drive system according to claim 11, characterized in that the control device (8) is configured to control the at least one electric motor (11, 12) using an active short circuit only when the rotational speed of the at least one electric motor (12) exceeds a threshold.

13. The drive system according to any one of the preceding claims, wherein the drive system comprises a first electric motor (11) and a second electric motor (12), the transmission comprises at least one planetary transmission (15) whose gear ratio is adjustable using the first and second electric motors (11, 12), and the torque generated by the first electric motor (11) is at least partially transmittable to the output shaft (2).

14. The drive system according to claims 12 and 13, characterized in that the control device (8) is configured to control the first and second electric motors (11, 12) using an active short circuit only when the rotational speed of the second electric motor (12) exceeds a threshold.

15. The drive system according to any one of the preceding claims, characterized in that the control device (8) comprises a B6 bridge circuit (80) for controlling the at least one electric motor (11, 12).

16. The at least one fault signal (f ｓ ) via The position of the rotor (3, 4) of at least one of the electric motors (11, 12) is no longer detectable or undeterminable, and In the case of magnetic field direction control of at least one electric motor (11, 12) by the control device (8), phase current measurement is no longer available. A drive system according to any one of the prior claims, characterized in that at least one of the following is notified.

17. A method for controlling the drive system of an electric bicycle (F), wherein in the drive system, A drive shaft (1) is provided for applying driving force to drive an electric bicycle (F) by human operation. An output shaft (2) is provided for transmitting the aforementioned driving force to the wheel (112) of the electric bicycle (F). At least one electric motor (11, 12) is provided to generate assist force by external power operation. A transmission (15) is provided to connect the drive shaft (1) and the output shaft (2) and to transmit the assist force to the output shaft (2). The at least one electric motor (11, 12) can be switched to a no-load state in response to at least one fault signal (f ｓ ) The at least one fault signal (f ｓ A method characterized in that, in response to the above, at least one electric motor (11, 12) is controlled using an active short circuit before switching to the no-load state.

18. A computer program product comprising instructions that, when executed by at least one processor of a control device for a drive system of an electric bicycle (F) equipped with an electric drive unit (10), cause the at least one processor to perform the method according to claim 17.

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