A control method for a double-rotor variable speed system based on an intermediate motor

Abstract

The application discloses a control method of a double-rotor variable speed system based on a middle motor, which comprises a main shaft and a five-way shell, wherein the main shaft is coaxially and movably connected with the five-way shell; the control method further comprises a double-rotor planetary gear transmission system, wherein the double-rotor planetary gear transmission system comprises a planetary gear train, a first fixed-rotor set and a second fixed-rotor set; the planetary gear train comprises a sun gear, a first planetary gear, a second planetary gear, a planetary gear carrier and an output gear ring; the first fixed-rotor set comprises two states of a generator and a motor, and the second fixed-rotor set is always in the state of the motor; in a normal horizontal driving state, the first fixed-rotor set is in the state of the generator; when full-speed or high-tooth-plate load torque operation is needed, the first fixed-rotor set is changed into the state of the motor; the application realizes stepless speed change of the middle motor of an electric-assisted bicycle through the cooperation of the first fixed-rotor set which can be switched between the state of the generator and the state of the motor and the second fixed-rotor set which is always in the state of the motor.

Description

Technical Field

[0001] This invention belongs to the field of mid-drive motor technology for electric bicycles. Background Technology

[0002] As mid-drive motors gradually become the mainstream power source for e-bikes, riders are paying more attention to the riding experience. Currently, most mid-drive motors use external gearboxes or increase the number of internal gears to achieve gear shifting. This approach complicates installation and operation, increases the motor's structural complexity, and raises the failure rate. Furthermore, the limited number of gears restricts the number of gear levels during shifting, resulting in a choppy and uneven shifting process. Additionally, existing solutions generate reverse braking torque during braking, causing a momentary impact on the transmission system, resulting in a jerky feeling for the rider and a poor riding experience. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the present invention provides a control method based on a mid-mounted motor dual-rotor transmission system. The first stator and rotor group, which can switch between generator and motor states, works in conjunction with the second stator and rotor group, which is always in motor state, to achieve stepless speed change of the mid-mounted motor of the electric bicycle and improve the rider's riding experience.

[0004] Technical Solution: To achieve the above objectives, the present invention provides a control method for a mid-mounted motor dual-rotor transmission system, comprising a main shaft and a bottom bracket housing, wherein the main shaft and the bottom bracket housing are coaxially rotatably coupled, and the two ends of the main shaft are directly connected to the pedal cranks; it also includes a planetary gear train, a first stator-rotor assembly, and a second stator-rotor assembly, wherein the planetary gear train includes a sun gear, a first planet gear, a second planet gear, a planetary gear carrier, and an output gear ring; the main shaft is unidirectionally coaxially coupled with the planetary gear carrier via a one-way clutch; the first stator-rotor assembly includes a first stator and a first rotor, and the second stator-rotor assembly includes a second stator and a second rotor; both the first stator and the second stator are fixed on the bottom bracket housing, the first rotor is coaxially and synchronously coupled with the sun gear, the second rotor is coaxially and synchronously coupled with the planetary gear carrier, and the output gear ring is synchronized with the front sprocket of an electric-assisted bicycle;

[0005] Its features include: the first stator and rotor assembly includes both generator and motor states, while the second stator and rotor assembly is always in motor state;

[0006] Under normal riding conditions, the first stator and rotor assembly enters generator mode, and the human pedal crank performs work on the main shaft. In motor mode, the second rotor of the second stator and rotor assembly performs work on the planetary gear carrier. Under stable conditions, the front sprocket and the first rotor of the first stator and rotor assembly adaptively distribute the speed.

[0007] Based on normal riding conditions, during the braking process, at the beginning of the braking process, the circuit containing the stator winding of the first stator and rotor group, which is in generator mode, is disconnected.

[0008] Furthermore, under normal driving conditions, the output speed of the output gear ring is changed by altering the external impedance of the first stator and rotor assembly in the generator state.

[0009] Furthermore, under normal driving conditions, the output torque of the output gear ring is changed by altering the output torque of the second rotor of the second stator and rotor assembly.

[0010] Furthermore, let the power of the human input end be p1, the input power of the second stator and rotor group be p2, the output power of the generator state of the first stator and rotor group be p3, and the output power of the output gear ring (8) be p4. In an ideal state, p1+p2=p3+p4, and p3 and p4 are automatically adaptively allocated and enter a stable state.

[0011] Under normal horizontal driving conditions, when the first stator and rotor assembly enters generator mode and runs smoothly, let the speed of the sun gear be n1, the speed of the output ring gear be n2, the speed of the planetary gear carrier be n3, the torque of the sun gear be T1, the torque of the output ring gear be T2, the torque of the planetary gear carrier be T3, the number of teeth of the sun gear be z1, and the number of teeth of the output ring gear be z2. Then, the speeds and torques of the three components satisfy the following relationship:

[0012] n1= n3•(1 + z2 / z1) - (z2 / z1)•n2;

[0013] This constraint relationship indicates that the rotational speeds of the sun gear and the output ring gear are coupled by this linear relationship;

[0014] At the same time, according to the principle of planetary gear transmission, the following conditions are met under stable conditions:

[0015] T1:T2:T3=z1:z2:(z1+z2);

[0016] p1 + p2 = p3 + p4 expands to: p1 + p2 = T3•n3 = T a •n1+T2•n2;

[0017] Let the current speed of the first stator and rotor assembly in generator mode be n, the reverse braking torque be T1, and the braking stiffness coefficient be K. Then the reverse braking torque of the first stator and rotor assembly in generator mode satisfies:

[0018] T1 = K•n;

[0019] Wherein, the braking stiffness coefficient K represents the coefficient that the reverse braking torque T1 of the first stator and rotor group changes with the speed n of the first stator and rotor group when it is in generator state; the larger the external impedance, the smaller K is.

[0020] Under normal and stable driving conditions, based on the above formula combination, the output speed of the output gear ring is adjusted by individually controlling the external impedance adjustment K value of the first stator and rotor group in the generator state.

[0021] Furthermore, under normal and stable driving conditions, based on the above formula combination, by controlling the output torque of the second rotor of the second stator and rotor assembly, i.e. the torque T3 of the planetary gear carrier, the torque T2 of the output gear ring is adjusted, i.e., the output torque of the output gear ring is changed.

[0022] Furthermore, when full speed or high gear load torque is required, the first stator and rotor assembly is converted into an electric motor.

[0023] Furthermore, it also includes a torque sensor capable of detecting the spindle torque; the output gear ring is coaxially and synchronously engaged with the gear disc;

[0024] Furthermore, when the main shaft is stationary and the planetary gear carrier is rotating normally, the one-way clutch is in an over-engaged state; when the main shaft rotates, the one-way clutch is in a locked state, and the main shaft drives the planetary gear carrier to rotate synchronously.

[0025] Furthermore, the first planetary gear and the second planetary gear are coaxially and integrally connected, with the first planetary gear meshing with the sun gear and the second planetary gear meshing with the output ring gear.

[0026] Furthermore, a stator fixing bracket is fixed on the five-way housing, the stator fixing bracket including a first stator fixing bracket and a second stator fixing bracket, the first stator fixing bracket and the second stator fixing bracket being coaxially fixedly connected; one end of the sun gear is rotatably engaged with the first stator fixing bracket through a fixed sun gear first bearing, and the other end of the sun gear is rotatably engaged with the second stator fixing bracket through a fixed sun gear second bearing; the second rotor is rotatably engaged with the second stator fixing bracket through a fixed rotor bearing.

[0027] Furthermore, the first stator is fixed to the inner side of the first stator fixing bracket and the second stator fixing bracket, and the second stator is fixed to the outer side of the first stator fixing bracket and the second stator fixing bracket, ensuring that the first stator, the second stator, the first stator fixing bracket, the second stator fixing bracket and the bottom bracket are coaxial with the bottom bracket housing.

[0028] Beneficial Effects: This invention provides a control method for a mid-drive dual-rotor transmission system. By coordinating a first stator-rotor group that can switch between generator and motor modes with a second stator-rotor group that always remains in motor mode, it achieves stepless speed regulation for the mid-drive motor of an electric-assist bicycle. The number of gear levels is unlimited, the shifting process is smooth and seamless, and the riding experience is excellent. A torque sensor is installed within the motor to acquire real-time pedaling information and adjust the assist level according to the rider's pedaling force, ensuring the rider always rides with the most comfortable pedaling force. During braking in normal riding conditions, at the initial stage of braking, the circuit containing the stator winding of the first stator-rotor group (in generator mode) is disconnected, achieving a shock-free transition to the front sprocket. The first stator-rotor group functions as both a generator and a motor. During normal operation, it operates as a generator, recovering energy by converting mechanical energy into electrical energy stored in the battery, extending the electric-assist bicycle's range. When full speed or high load is required, the first stator-rotor switches to motor mode, working with the second stator-rotor to output driving torque to meet high load demands. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the control method of a dual-rotor speed change system based on a mid-mounted motor according to the present invention. Detailed Implementation

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] like Figure 1 As shown, the present invention provides a control method for a mid-mounted motor dual-rotor transmission system, comprising a main shaft 1 and a bottom bracket housing 2 that rotate coaxially. The main shaft 1 has pedal cranks connected to both ends, serving as the human input terminals. The bottom bracket housing 2 is fixed to the bottom bracket of the frame, and the sprocket is connected to the rear wheel of the electric bicycle via a chain, transmitting power to the wheel.

[0032] This includes a torque sensor 3 that can detect the torque of the main shaft 1. The torque sensor 3 is used to detect the pedaling torque of the main shaft 1. The torque sensor can obtain the pedaling torque, providing a more accurate basis for motor assist control, so that the assist output can be matched with the rider's actual pedaling force in real time.

[0033] The present invention also includes a dual-rotor planetary gear transmission system, which comprises a planetary gear train, a first stator-rotor assembly, and a second stator-rotor assembly. The planetary gear train includes a sun gear 4, first planet gears 5, second planet gears 6, a planet carrier 7, and an output ring gear 8. The first stator-rotor assembly includes a first stator 11 and a first rotor 21, and the second stator-rotor assembly includes a second stator 12 and a second rotor 22. Both the first stator 11 and the second stator 12 are fixed to the bottom bracket housing 2. The first rotor 21 is coaxially and synchronously engaged with the sun gear 4, and the second rotor 22 is coaxially and synchronously engaged with the planet carrier 7.

[0034] A stator fixing bracket is fixed on the bottom bracket housing 2. The stator fixing bracket includes a first stator fixing bracket 31 and a second stator fixing bracket 32, which are coaxially fixedly connected. The first stator 11 is fixed inside the first stator fixing bracket 31 and the second stator fixing bracket 32, and the second stator 12 is fixed outside the first stator fixing bracket 31 and the second stator fixing bracket 32, ensuring that the first stator 11, the second stator 12, the first stator fixing bracket 31, the second stator fixing bracket 32, and the bottom bracket housing 2 are coaxial.

[0035] One end of the sun gear 4 is rotatably engaged with the first stator fixing bracket 31 via a fixed sun gear first bearing 41, and the other end of the sun gear 4 is rotatably engaged with the second stator fixing bracket 32 ​​via a fixed sun gear second bearing 42. The two ends of the sun gear 4 are supported by two bearings respectively, forming a stable double-support structure. This ensures that the sun gear 4 maintains a stable rotational posture when subjected to meshing forces and transmitting torque, reducing gear overload and wear.

[0036] The second rotor 22 of the second stator and rotor assembly rotates with the second stator fixed bracket 32 ​​via a fixed rotor bearing 43. The first planetary gear 5 and the second planetary gear 6 are coaxially connected, with the first planetary gear 5 meshing with the sun gear 4 and the second planetary gear 6 meshing with the output gear ring 8.

[0037] The main shaft 1 is coupled to the planetary gear carrier 7 via a one-way coaxial transmission via a one-way clutch 9. When the main shaft 1 is stationary and the planetary gear carrier 7 is rotating normally, the one-way clutch 9 is in an overrunning state; when the main shaft 1 rotates, the one-way clutch 9 is in a locked state, and the main shaft 1 drives the planetary gear carrier 7 to rotate synchronously. This one-way clutch 9 ensures that the human input end is coupled to the transmission system only when the rider actively pedals. When the motor is driving but the rider is not pedaling, the one-way clutch 9 automatically overruns and disengages, and the main shaft 1 remains stationary and does not rotate, effectively avoiding the problem of the crank following the rotation.

[0038] The output gear ring 8 is coaxial and synchronously engaged with the sprocket. The sprocket is connected to the bicycle's rear wheel via a chain, transmitting power to the wheel.

[0039] The following is in conjunction with the appendix Figure 1 The specific implementation methods of the control method of the present invention will be described in detail below:

[0040] The core control logic of this invention is as follows: A torque sensor 3 is installed inside the motor. The torque sensor 3 detects the pedaling torque of the main shaft 1. The controller determines the current operating state based on the obtained pedaling torque information. If it is determined to be normal level driving, the controller sets the first stator and rotor group to generator mode, while the second stator and rotor group remains in motor mode, and the system enters power balance mode. If it is determined to be a high load demand such as climbing or rapid acceleration, the controller switches the first stator and rotor group to motor mode, which drives the system together with the second stator and rotor group.

[0041] The first stator and rotor assembly includes both generator and motor states, while the second stator and rotor assembly is always in motor state.

[0042] Under normal driving conditions, the first stator and rotor assembly enters generator mode. Let the power input from the manual input be p1, the input power of the second stator and rotor assembly be p2, the output power of the first stator and rotor assembly in generator mode be p3, and the output power of the output gear ring 8 be p4. Ideally, p1 + p2 = p3 + p4, and p3 and p4 automatically and adaptively distribute themselves, reaching a stable state. This power balance reflects the energy flow of the system during normal driving: part of the energy input from the manual input and battery input is used to drive the gear ring, and the other part is converted into electrical energy recovery through the generator mode of the first stator and rotor assembly, achieving rational energy distribution and efficient utilization.

[0043] Under normal riding conditions, during the braking process, at the beginning of the braking process, the controller controls the circuit containing the stator winding of the first stator and rotor group in generator mode to be disconnected.

[0044] Under normal riding conditions, the first stator and rotor assembly operates as a generator. The stator winding circuit is closed, and when the first rotor 21 rotates, it cuts the magnetic field, generating an induced electromotive force and forming a loop current, thus producing a reverse braking torque. This reverse braking torque is transmitted to the output ring gear 8 and the front sprocket through the planetary gear train, achieving energy recovery. When the rider applies the brakes, if the stator winding circuit remains closed during the initial braking phase, the first rotor 21 will continue to generate an induced current and reverse braking torque during its inertial rotation. This braking torque will be transmitted to the front sprocket through the planetary gear train, causing a momentary impact on the transmission system.

[0045] After the stator winding circuit is disconnected during the initial braking phase, no current flows through the circuit, and the rotation of the first rotor 21 does not generate reverse braking torque. Therefore, during the initial braking phase, there is no additional braking torque superimposed on the transmission system, the front sprocket is not subjected to impact force, and the braking process is smooth and without jerking at the start. By disconnecting the stator winding circuit, the electromagnetic braking effect of the generator is temporarily cut off during the initial braking phase, allowing the mechanical braking system to take over the control power. After the braking process continues and the mechanical braking is fully engaged, the controller recloses the stator winding circuit to restore the normal energy recovery function.

[0046] The more crucial role of this control method lies in its energy transfer perspective. During braking, the kinetic energy of the wheel is constantly dissipated as heat through friction between the brake pads and the ground. If the stator winding circuit remains closed, the first rotor 21, constrained by electromagnetic resistance, continuously generates reverse braking torque, converting mechanical energy into electrical energy. At this time, the mechanical energy corresponding to the heat energy converted from friction is constrained by electromagnetic resistance and cannot be dissipated through the free rotation of the rotor. It is forced to be transmitted in reverse through the planetary gear system to the output gear ring 8, where it is superimposed with the mechanical braking torque, generating an impact. However, after the stator winding circuit of the first stator and rotor assembly is disconnected at the initial stage of braking, the current in the circuit is zero, the electromagnetic resistance disappears, and the first rotor 21 is freed from electromagnetic constraint and enters a free rotation state. At this time, the mechanical energy corresponding to the heat energy converted from friction is no longer constrained by electromagnetic resistance. A portion of this energy can be transmitted in reverse through the planetary gear system to the first rotor 21, converting it into the kinetic energy of the first rotor 21's free rotation and gradually dissipating, rather than being concentrated on the output gear ring 8. This method eliminates the superimposed impact of electromagnetic braking force and mechanical braking force on the output gear ring 8 by disconnecting the stator winding circuit during the initial braking stage and converting part of the heat energy into the kinetic energy dissipation of the rotor's free rotation.

[0047] When the system detects a demand for full-speed operation or high torque load on the gears, such as when an e-bike is climbing a hill or accelerating rapidly, the controller switches the first stator-rotor assembly from generator mode to electric motor mode. At this time, both the first and second stator-rotor assemblies jointly output driving torque, which is vector-superimposed in the planetary gear train, resulting in maximum system power output. During normal, stable riding, the first stator-rotor assembly always operates in generator mode, while the second stator-rotor assembly acts as the primary drive motor. Only under high-torque load conditions such as climbing hills or rapid acceleration does the first stator-rotor assembly switch to electric motor mode to meet power demands. This mode switching is automatically determined and executed by the controller based on load requirements; the switching process is rapid and smooth, imperceptible to the rider.

[0048] During normal level driving, the output speed of the output ring gear 8 can be continuously changed by adjusting the external impedance of the first stator and rotor assembly in generator mode. Changes in external impedance directly alter the reverse braking torque and power generation of the first stator and rotor assembly, thus affecting the power balance distribution and causing continuous changes in the speed of the output ring gear 8. This adjustment process is entirely achieved through electrical parameters and does not involve any mechanical shifting, resulting in a smooth and shock-free gear change process.

[0049] During normal operation, the output torque of the output ring gear 8 can be continuously changed by adjusting the output torque of the second rotor 22 of the second stator-rotor assembly. The output torque of the second rotor 22 of the second stator-rotor assembly directly determines the input torque of the planetary gear carrier 7, thus affecting the output torque of the output ring gear 8. Its output torque can be precisely controlled by adjusting the drive current of the second rotor 22 of the second stator-rotor assembly. Speed ​​regulation and torque regulation are independently handled by the first stator-rotor assembly and the second stator-rotor assembly, respectively, achieving control of speed and torque.

[0050] Under normal horizontal driving conditions, when the first stator and rotor assembly is in generator mode and the system is running smoothly, let the speed of the sun gear 4 be n1, the speed of the output ring gear 8 be n2, the speed of the planetary gear carrier 7 be n3, the torque of the sun gear 4 be T1, the torque of the output ring gear 8 be T2, the torque of the planetary gear carrier 7 be T3, the number of teeth of the sun gear 4 be z1, and the number of teeth of the output ring gear 8 be z2. The kinematic constraints between the three are as follows:

[0051] n1= n3•(1 + z2 / z1) - (z2 / z1)•n2;

[0052] This equation shows that there is a linear coupling relationship between the rotational speeds of the sun gear 4 and the output ring gear 8, and the two cannot change independently. In a differential gear train, only two of the three basic components—the sun gear, the output ring gear, and the planetary carrier—can move independently, while the third is determined by this constraint relationship.

[0053] Meanwhile, according to the principle of planetary gear transmission, the torque distribution of the system in a steady state satisfies:

[0054] T1:T2:T3=z1:z2:(z1+z2);

[0055] This relationship indicates that the torque of the planetary gear carrier 7 is equal to the sum of the torques of the sun gear 4 and the output ring gear 8. The torque input to the first rotor 21 of the first stator-rotor assembly via the sun gear 4 and the torque input to the second rotor 22 of the second stator-rotor assembly via the planetary gear carrier 7 converge at the output ring gear 8, jointly determining the output torque of the gear disc.

[0056] Furthermore, the power balance relationship p1+p2=p3+p4 can be expanded as follows:

[0057] p1+p2=T3·n3=T1·n1+T2·n2;

[0058] This expansion quantitatively describes the power distribution path of each power source in the transmission system. The controller calculates the power distribution of each node in real time based on this relationship to ensure that the system always operates in the optimal efficiency range.

[0059] Let the current speed of the first stator and rotor assembly in generator mode be n, the reverse braking torque be T1, and the braking stiffness coefficient be K. Then the reverse braking torque satisfies:

[0060] T1 = K•n;

[0061] Here, K is determined by the generator dynamic load controller and is used to control the external impedance of the first stator and rotor assembly. This linear relationship indicates that the higher the rotational speed, the greater the reverse braking torque and the greater the power generation. The generator dynamic load controller changes the value of K by adjusting the external impedance in real time. When the external impedance increases, K decreases, and both the reverse braking torque and power generation at the same rotational speed decrease. By continuously adjusting the external impedance, precise control of power generation can be achieved.

[0062] Under normal and stable driving conditions, based on the above formula combination, the external impedance of the first stator and rotor assembly is individually controlled by the generator dynamic load controller to adjust the K value, thereby adjusting the output speed of the output ring gear 8. Specifically, from the kinematic constraint relationship n1 = n3•(1 + z2 / z1) - (z2 / z1)•n2, it can be seen that under the given planetary gear carrier speed n3, there is a definite linear relationship between the speed n1 of the sun gear 4 and the speed n2 of the output ring gear 8. The speed n1 of the first rotor 21 of the first stator and rotor assembly is determined by the generator state characteristic T1 = K•n of the first stator and rotor assembly. When the external impedance changes, the K value changes, and the reverse braking torque T1 of the first rotor 21 of the first stator and rotor assembly changes accordingly, and its speed n1 changes accordingly. Through the kinematic constraint relationship, the change of n1 will cause a continuous change in the speed n2 of the output ring gear 8, ultimately achieving continuous stepless adjustment of the output speed of the gear plate. During this adjustment process, the first stator and rotor assembly always maintains the generator state, without any mechanical gear shifting operation, and the speed change process is continuous, stepless, smooth and without jamming.

[0063] By controlling the output torque of the second rotor 22 of the second stator-rotor assembly, i.e., the torque T3 of the planetary gear carrier 7, the torque T2 of the output ring gear 8 is adjusted, thus changing the output torque of the gear disc. From the torque distribution relationship T1:T2:T3=z1:z2:(z1+z2), it can be seen that when the torque T1 of the sun gear 4 is fixed, the torque T2 of the output ring gear 8 is proportional to the torque T3 of the planetary gear carrier 7. By adjusting the input current of the second rotor 22 of the second stator-rotor assembly to change T3, T2 can be linearly changed, achieving precise control of the gear disc's output torque. This torque control is independent of the aforementioned speed control, together forming a complete continuously variable transmission (CVT) control strategy.

[0064] In practical implementation, the control method described in this invention is achieved through the following steps:

[0065] The controller first collects the pedaling torque of the main shaft in real time through torque sensor 3, and combines it with signals such as vehicle speed, load, and battery status to determine the current operating status. If it is determined to be normal level driving, the controller sets the first stator and rotor assembly to generator mode, while the second stator and rotor assembly remains in motor mode, and the system enters power balance mode; if it is determined to be a high load demand such as climbing or rapid acceleration, the controller switches the first stator and rotor assembly to motor mode, which works together with the second stator and rotor assembly to drive the vehicle.

[0066] After entering normal driving state, the controller adjusts the external impedance of the first stator and rotor group through the generator dynamic load controller to change the K value, thereby changing the speed n1 of the first rotor 21 of the first stator and rotor group. The speed n2 of the output gear ring 8 is adjusted through the kinematic constraint relationship n1=n3•(1 + z2 / z1) - (z2 / z1)•n2, so as to realize stepless adjustment of the output speed of the gear plate.

[0067] Alternatively, the controller can change the torque T3 of the planetary gear carrier 7 by adjusting the drive current of the second rotor 22 of the second stator and rotor group, and adjust the torque T2 of the output gear ring 8 by the torque distribution relationship T1:T2:T3=z1:z2:(z1+z2), thereby realizing the independent adjustment of the output torque of the gear plate.

[0068] The controller continuously monitors the values ​​of p1, p2, p3, and p4, and by fine-tuning the external impedance and the second rotor current of the second stator and rotor group, it ensures that the system always satisfies the power balance relationship of p1+p2=p3+p4 and remains stable.

[0069] In this invention, torque sensor 3 is used to detect the pedaling torque of the main shaft 1. During riding, the main shaft 1 rotates as the rider pedals, the torque sensor acquires the pedaling torque, and the controller determines the current riding state. When the rider's pedaling torque is large, it indicates that the rider has a strong intention to accelerate, and the controller increases the drive current of the first rotor 21 and the second rotor 22 to increase the motor output power; when the pedaling speed is slow or stops, the controller reduces or stops the motor output, achieving coordinated operation between power assist and manual pedaling.

[0070] Under normal riding conditions, during the braking process, at the initial stage, the controller disconnects the circuit containing the stator winding of the first stator-rotor assembly (acting as a generator). Once the braking process has continued and mechanical braking has fully engaged, the controller recloses the stator winding circuit, restoring normal energy recovery functionality.

[0071] The above are the preferred embodiments described in this invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A control method for a dual-rotor transmission system based on a mid-mounted motor, comprising a main shaft (1) and a five-way housing (2), wherein the main shaft (1) and the five-way housing (2) are coaxially rotated together, and the two ends of the main shaft (1) are directly connected to foot cranks; further comprising a planetary gear train, a first stator-rotor group and a second stator-rotor group, wherein the planetary gear train comprises a sun gear (4), a first planetary gear (5), a second planetary gear (6), a planetary gear carrier (7), and an output gear ring (8); the main shaft (1) is connected to the planetary gear carrier (8) via a one-way clutch (9). 7) Unidirectional coaxial transmission; the first stator and rotor assembly includes a first stator (11) and a first rotor (21), and the second stator and rotor assembly includes a second stator (12) and a second rotor (22); the first stator (11) and the second stator (12) are both fixed on the five-way housing (2), the first rotor (21) is coaxially and synchronously engaged with the sun gear (4), the second rotor (22) is coaxially and synchronously engaged with the planetary gear carrier (7), and the output gear ring (8) is synchronously engaged with the front sprocket of the electric-assisted bicycle; Its features are: The first stator and rotor assembly includes both generator and motor states, while the second stator and rotor assembly is always in motor state. In normal riding conditions, the first stator and rotor assembly enters generator mode, and human power is applied to the main shaft by pedaling the crank. In motor mode, the second rotor (22) of the second stator and rotor assembly applies power to the planetary gear carrier (7). In a stable state, the front sprocket and the first rotor (21) of the first stator and rotor assembly adaptively distribute the speed. Based on normal riding conditions, during the braking process, at the beginning of the braking process, the circuit containing the stator winding of the first stator and rotor group, which is in generator mode, is disconnected.

2. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 1, characterized in that: Under normal driving conditions, the output speed of the output gear ring (8) is changed by altering the external impedance of the first stator and rotor assembly in the generator state.

3. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 1, characterized in that: Under normal driving conditions, the output torque of the output gear ring (8) is changed by changing the output torque of the second rotor (22) of the second stator and rotor group.

4. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 1, characterized in that: Let the power of the human input end be p1, the input power of the second stator and rotor group be p2, the output power of the generator state of the first stator and rotor group be p3, and the output power of the output gear ring (8) be p4. In an ideal state, p1+p2=p3+p4, and p3 and p4 are automatically adaptively allocated and enter a stable state. Under normal horizontal driving conditions, when the first stator and rotor set enters generator state and runs smoothly, let the speed of the sun gear (4) be n1, the speed of the output ring gear (8) be n2, the speed of the planetary gear carrier (7) be n3, the torque of the sun gear (4) be T1, the torque of the output ring gear (8) be T2, the torque of the planetary gear carrier (7) be T3, the number of teeth of the sun gear (4) be z1, and the number of teeth of the output ring gear (8) be z2. Then the speeds and torques of the three satisfy the following relationship: n1= n3•(1 + z2 / z1) - (z2 / z1)•n2; This constraint relationship indicates that the rotational speeds of the sun gear (4) and the output gear ring (8) are coupled by this linear relationship; At the same time, according to the principle of planetary gear transmission, the following conditions are met under stable conditions: T1:T2:T3=z1:z2:(z1+z2); p1 + p2 = p3 + p4 expands to: p1 + p2 = T3•n3 = T a •n1+T2•n2; Let the current speed of the first stator and rotor assembly in generator mode be n, the reverse braking torque be T1, and the braking stiffness coefficient be K. Then the reverse braking torque of the first stator and rotor assembly in generator mode satisfies: T1 = K•n; Wherein, the braking stiffness coefficient K represents the coefficient that the reverse braking torque T1 of the first stator and rotor group changes with the speed n of the first stator and rotor group when it is in generator state; the larger the external impedance, the smaller K is. Under normal and stable driving conditions, based on the above formula combination, the output speed of the output gear ring (8) is adjusted by individually controlling the external impedance adjustment K value of the first stator and rotor group under the generator state.

5. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 4, characterized in that: Under normal and stable driving conditions, based on the above formula combination, by controlling the output torque of the second rotor (22) of the second stator and rotor group, that is, the torque T3 of the planetary gear carrier (7), the torque T2 of the output gear ring (8) is adjusted, that is, the output torque of the output gear ring (8) is changed.

6. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 1, characterized in that: When full speed or high gear load torque is required, the first stator and rotor assembly is converted into an electric motor.

7. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 6, characterized in that: It also includes a torque sensor (3) that can detect the torque of the spindle (1); the output gear ring (8) is coaxially and synchronously engaged with the gear disk.

8. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 7, characterized in that: When the main shaft (1) is stationary and the planetary gear carrier (7) is rotating normally, the one-way clutch (9) is in an over-engaged state; when the main shaft (1) rotates, the one-way clutch (9) is in a locked state, and the main shaft (1) drives the planetary gear carrier (7) to rotate synchronously.

9. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 8, characterized in that: The first planetary gear (5) and the second planetary gear (6) are coaxially connected. The first planetary gear (5) meshes with the sun gear (4), and the second planetary gear (6) meshes with the output gear ring (8).

10. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 9, characterized in that: The five-way housing (2) is fixed with a stator fixing bracket, which includes a first stator fixing bracket (31) and a second stator fixing bracket (32). The first stator fixing bracket (31) and the second stator fixing bracket (32) are coaxially fixedly connected. One end of the sun gear (4) is rotatably engaged with the first stator fixing bracket (31) through a fixed sun gear first bearing (41), and the other end of the sun gear (4) is rotatably engaged with the second stator fixing bracket (32) through a fixed sun gear second bearing (42). The second rotor (22) is rotatably engaged with the second stator fixing bracket (32) through a fixed rotor bearing (43).

11. The control method for a dual-rotor transmission system based on a mid-mounted motor according to claim 10, characterized in that: The first stator (11) is fixed inside the first stator fixing bracket (31) and the second stator fixing bracket (32), and the second stator (12) is fixed outside the first stator fixing bracket (31) and the second stator fixing bracket (32), ensuring that the first stator (11), the second stator (12), the first stator fixing bracket (31), the second stator fixing bracket (32) and the five-way housing (2) are coaxial.

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