Auxiliary power output control method and system for electric bicycle assist vehicle mode

Abstract

The application discloses an auxiliary power output control method and system for an electric bicycle assist vehicle mode, and the method comprises the following steps: measuring the pitch angle, acceleration and speed of the electric bicycle during driving; during riding, when the rider stops pedaling, updating a second-order system model according to the pitch angle, acceleration, speed and direct-current brushless motor torque of the electric bicycle during driving; when the rider pedals the electric bicycle, calculating the torque output by the expected direct-current brushless motor according to the second-order system model, the pitch angle, acceleration, speed of the electric bicycle and the torque applied to the electric bicycle pedal by the rider, and driving the direct-current brushless motor to rotate according to the calculation result of the torque output by the expected direct-current brushless motor to output auxiliary torque. The application greatly reduces the manufacturing cost of the electric bicycle and improves the riding experience of the rider.

Description

Technical Field

[0001] This invention belongs to the field of electric bicycle technology, specifically relating to an auxiliary power output control method and system that can meet multiple working conditions. Background Technology

[0002] In today's society, electric bicycles are widely used due to their unique convenience. Common operating modes include electric vehicle mode, e-bike mode, and bicycle mode. Among these, e-bike mode, as an important riding mode for electric bicycles, is receiving increasing attention in transportation, medical rehabilitation, and fitness and leisure.

[0003] In the assisted mode of an electric bicycle, sensors installed on the bicycle monitor the load applied by the rider to the pedals and transmit the signal to the controller. Upon receiving the signal, the controller issues commands to the motor based on certain calculations. The motor, upon receiving the control signal, provides a certain amount of power assistance to the electric bicycle through a mechanical transmission device. The power assistance control methods for electric bicycles can be mainly divided into two categories:

[0004] 1. Using a torque sensor to detect the dynamic torque applied by the rider to the pedals of an electric bicycle, and the controller controlling the motor's auxiliary power output according to the input torque, this method has high accuracy, good real-time performance, and can achieve a smooth transition of motor output, resulting in a better riding experience. However, in practical applications, the torque sensor needs to be installed on the bottom bracket of the electric bicycle, which requires certain modifications to the bottom bracket structure, increasing costs and reducing the economic benefits of the electric bicycle.

[0005] 2. Using a speed sensor to monitor the pedal speed of the electric bicycle by the rider. The amount of auxiliary power output by the motor increases with the increase of pedal speed. Although this method is relatively low cost, it may cause the controller to misjudge the working status of the electric bicycle in certain environments. For example, when going uphill or against the wind, when more auxiliary power is needed, the power will decrease because the rider cannot apply a large speed to the pedal. Summary of the Invention

[0006] This invention provides a method and system for controlling the auxiliary power output of an electric bicycle in assisted mode. The method measures the riding state of the electric bicycle using sensors, updates the real-time second-order system model of the electric bicycle during riding by combining the input and output characteristics of the motor, and controls the auxiliary power output of the electric bicycle based on this model.

[0007] To achieve the above objectives, the present invention provides an auxiliary power output control method for an electric bicycle in a power-assisted mode, comprising the following steps:

[0008] S1. The brushless DC motor used in electric bicycles is calibrated to obtain the motor torque-speed characteristic curves under different duty cycle drive signals at rated voltage.

[0009] S2. Measure the pitch angle, acceleration, and speed of the electric bicycle during its operation;

[0010] S3. During the ride, detect whether the rider makes a pedaling motion;

[0011] S4. When the rider stops pedaling, the detected pedal speed of the electric bicycle is 0, which slows down the electric bicycle. The second-order system model is updated based on the pitch angle, acceleration, speed and DC brushless motor torque of the electric bicycle during the ride.

[0012] S5. When the rider steps on the electric bicycle pedal, the pedal speed is detected to be non-zero. Based on the second-order system model, the electric bicycle pitch angle, acceleration, speed, and the rider's desired torque to be applied to the electric bicycle pedal, the torque expected to be output by the brushless DC motor is calculated.

[0013] S6. Based on the desired output torque and speed of the brushless DC motor, and combined with the torque-speed characteristic curve, output a PWM signal to drive the brushless DC motor to rotate and provide auxiliary torque output.

[0014] Furthermore, in step S2, the initial pitch angle, pitch velocity, and acceleration in the direction of travel of the electric bicycle are detected by the inertial measurement unit, and the pitch angle, acceleration, and speed of the bicycle during travel are calculated based on the initial pitch angle, pitch velocity, and acceleration in the direction of travel.

[0015] Furthermore, in step S3, a Hall sensor is used to detect whether the rider is pedaling.

[0016] Furthermore, in step S3, the expression for the second-order system model is:

[0017] (1)

[0018] in, m For quality coefficient, i ( t This refers to the real-time pitch angle of the electric bicycle. c The damping coefficient is... v ( t (This refers to the real-time speed of the electric bicycle.) R The radius of the electric bicycle wheel. M 电机 This is the output torque of the brushless DC motor. M 人To apply torque to the pedals of an electric bicycle by the rider, n 电机 This refers to the transmission ratio from the DC brushless motor to the electric bicycle wheel. n 人 This refers to the transmission ratio from the pedals to the wheels of an electric bicycle. m Let g be the kinetic friction factor between the electric bicycle and the road surface, and g be the acceleration due to gravity.

[0019] Furthermore, in step S4, updating the second-order system model based on the pitch angle, acceleration, velocity, and DC brushless motor torque of the electric bicycle during operation includes the following steps:

[0020] collection t 1. t 2. t 3. Real-time pitch angle of electric bicycle at three time points i ( t 1) i ( t 2) i ( t 3) The acceleration of the electric bicycle in the direction of travel. a ( t 1) a ( t 2) a ( t 3) With real-time speed v ( t 1) v ( t 2) v ( t 3) Substituting the above values ​​into the second-order system model yields equation (2). Based on equation (2), the quality coefficient is... m Damping coefficient c and the dynamic friction factor between electric bicycles and the road surface m Recalculate and update the real-time second-order model of the electric bicycle;

[0021] (2)

[0022] in, for t At moment 1, the output torque of the brushless DC motor is... for t At time 2, the output torque of the brushless DC motor is... for t At time 3, the output torque of the brushless DC motor is given, where g is the acceleration due to gravity.

[0023] Furthermore, t 1. t 2. t3. The interval time is greater than 0.5s.

[0024] Furthermore, in step S4, the calculation method for calculating the desired output torque of the brushless DC motor based on the second-order system model of the electric bicycle during operation, the electric bicycle's pitch angle, acceleration, velocity, and the rider's desired torque applied to the electric bicycle pedals is as follows:

[0025]

[0026] in, i ( t ) for the real-time pitch angle of electric bicycles, a ( t () represents the acceleration in the direction of travel of the electric bicycle. v ( t ) represents the real-time speed of the electric bicycle in the direction of travel. M’ 人 The torque that the rider expects to apply to the pedals of the electric bicycle. M’ 电机 Let g be the desired output torque of the brushless DC motor, and g be the acceleration due to gravity.

[0027] An auxiliary power output control system for an electric bicycle in a power-assisted mode includes an electric bicycle pedal, an inertial measurement unit, a Hall sensor, an AD conversion circuit, a control circuit, and a switching power supply circuit.

[0028] The inertial measurement unit is fixedly mounted on the frame of the electric bicycle, and the Hall sensor is mounted on the pedal of the electric bicycle. Both the inertial measurement unit and the Hall sensor are connected to the AD conversion circuit, which is connected to the control circuit. The control circuit is connected to the switching power supply circuit, which is connected to the DC brushless motor.

[0029] The control circuit incorporates a second-order system model of the electric bicycle. This model is updated based on data from Hall sensors, inertial measurement units, and the torque of the brushless DC motor. The circuit then calculates the desired output torque of the brushless DC motor based on the updated model, the electric bicycle's pitch angle, acceleration, speed, and the rider's desired torque applied to the pedals. Finally, based on the calculated torque and the brushless DC motor's speed, and combined with the electric bicycle's torque-speed characteristic curve, a PWM signal is output to drive the brushless DC motor and provide auxiliary torque output.

[0030] Furthermore, a signal processing circuit is connected between the inertial measurement unit and the Hall sensor and the AD conversion circuit.

[0031] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0032] This invention eliminates the need for torque sensors in the control scheme design and system construction, significantly reducing the manufacturing cost of electric bicycles. An inertial measurement unit (IMU) is used to monitor the electric bicycle's riding status in real time. Based on this monitoring and combined with a real-time second-order system model of the electric bicycle, the output torque of the brushless DC motor is controlled. This ensures that the torque applied to the pedals by the rider remains essentially constant under different road conditions, terrain, and load conditions. When encountering situations such as climbing hills, the rider does not need to increase the torque applied to the pedals and can still ride normally, thereby improving the riding experience.

[0033] The second-order system model provided by this invention is established based on the actual second-order differential equations of an electric bicycle during its operation. Since the magnitude of displacement does not affect the operation of the electric bicycle during its operation, the displacement term is not included in the model establishment process. This second-order system model has high reliability and achieves precise control of the motor output torque to the greatest extent without changing the structure of the electric bicycle. This allows the rider to maintain a constant torque on the pedals under different usage conditions, thereby improving the rider's riding experience.

[0034] Furthermore, during the model update process, this invention recalculates the model parameters based on the electric bicycle's state at three time points. By solving the system of equations, the second-order system model of the electric bicycle is updated. This method has a fast solution speed and does not cause long pauses during riding due to model updates, greatly improving the rider's riding experience. Attached Figure Description

[0035] Figure 1 This is a structural block diagram of the present invention;

[0036] Figure 2 This is a flowchart of the present invention.

[0037] In the attached diagram: 1-Electric bicycle frame, 2-Electric bicycle pedals, 3-Inertial measurement unit, 4-Hall sensor, 5-Signal processing circuit, 6-AD conversion circuit, 7-Control circuit, 8-Switching power supply circuit, 9-DC brushless motor. Detailed Implementation

[0038] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Example 1

[0041] Reference Figure 1 An auxiliary power output control system for an electric bicycle in a power-assisted mode includes: an electric bicycle pedal 2, an inertial measurement unit 3, a Hall sensor 4, a signal processing circuit 5, an AD conversion circuit 6, a control circuit 7, and a switching power supply circuit 8.

[0042] The inertial measurement unit 3 is fixedly installed on the electric bicycle frame 1, and the Hall sensor 4 is installed at the electric bicycle pedal 2. Both the inertial measurement unit 3 and the Hall sensor 4 are connected to the signal processing circuit 5. The signal processing circuit 5 is connected to the AD conversion circuit 6. The AD conversion circuit 6 is connected to the control circuit 7. The control circuit 7 is connected to the switching power supply circuit 8. The switching power supply circuit 8 is connected to the DC brushless motor 9.

[0043] The bicycle frame 1 is the frame on which the various components of the electric bicycle are mounted. In this invention, it is used to mount the inertial measurement unit 3.

[0044] The electric bicycle pedal 2 is used to provide power to the electric bicycle during riding and serves as the basis for activating auxiliary power.

[0045] Inertial measurement unit 3 is used to detect the initial pitch angle of the electric bicycle. i (0) Pitch angular velocity oh θ ( t and acceleration in the direction of travel a ( t ).

[0046] Hall sensor 4 is used to detect the pedal position of the electric bicycle at various times.

[0047] The signal processing circuit 5 is used to process the signals from the inertial measurement unit 3 and the Hall sensor 4, including but not limited to filtering and amplification, so that the output analog signal is compatible with the input of the AD conversion circuit 6.

[0048] The AD conversion circuit 6 converts the analog signals from the inertial measurement unit 3 and the Hall sensor 4, which have been processed by the signal processing circuit 5, into digital signals compatible with the control circuit 7.

[0049] Control circuit 7 is used to calculate the data measured by inertial measurement unit 3 and Hall sensor 4, based on the initial pitch angle. i (0) Pitch angular velocity oh θ ( t Calculate the real-time pitch angle of an electric bicycle using the quaternion method. i ( t According to the acceleration in the direction of travel a ( t The real-time speed of an electric bicycle is calculated using an integral method. v ( t The control circuit 7 determines whether the rider is pedaling based on the position of the electric bicycle pedal 2 at various times.

[0050] The control circuit 7 can calculate the output speed based on the rotor position information detected by the Hall sensor built into the brushless DC motor 9;

[0051] The control circuit 7 internally stores a real-time second-order system model of the electric bicycle during riding and the torque that the rider expects to apply to the electric bicycle pedals 2. M’ 人 :

[0052] (1)

[0053] in, m For quality coefficient, c The damping coefficient is... R The radius of the electric bicycle wheel. M 电机 The output torque of the brushless DC motor 9 M 人 To apply torque to the electric bicycle pedal 2 by the rider, n电机 The transmission ratio of a DC brushless motor to the wheel of an electric bicycle is 9. n 人 The transmission ratio from pedal 2 to wheel of the electric bicycle. m Let g be the kinetic friction factor between the electric bicycle and the road surface, and g be the acceleration due to gravity.

[0054] Control circuit 7 can update the second-order model of the electric bicycle in real time, as follows:

[0055] During riding, when the rider perceives changes in road width, terrain, or load (i.e., the second-order system model of the electric bicycle is no longer applicable), they stop pedaling. The electric bicycle continues forward due to its inertia. At this time, Hall sensor 4 detects that the pedal speed is 0, and the duty cycle of the PWM signal received by the brushless DC motor 9 decreases to 0.05 or another value, causing the electric bicycle to begin decelerating. M 人 Both are 0 in size. M 电机 The value can be obtained based on the torque-speed characteristic curve of the DC brushless motor 9 and its speed. When the Hall sensor 4 detects that the speed of the electric bicycle pedal 2 is 0, the control circuit 7 collects... t 1. t 2. t 3. Real-time pitch angle of electric bicycle at three time points i ( t 1) i ( t 2) i ( t 3) Acceleration in the direction of travel a ( t 1) a ( t 2) a ( t 3) With real-time speed v ( t 1) v ( t 2) v ( t 3) Substituting the above values ​​into equation (1) yields equation (2). t 1. t 2. t 3. If the interval time is greater than 0.5s, the quality coefficient is based on equation (2). m Damping coefficient c and the dynamic friction factor between electric bicycles and the road surface m Recalculate and update the real-time second-order model of the electric bicycle.

[0056] (2)

[0057] in, for t At moment 1, the brushless DC motor outputs 9 torques. for t At time 2, the brushless DC motor outputs 9 torques. for t At time 3, the DC brushless motor outputs 9 torque.

[0058] Control circuit 7 can be based on the real-time second-order system model of the electric bicycle and the real-time pitch angle of the electric bicycle. i ( t acceleration in the direction of travel a ( t Real-time speed v ( t ), the torque that the rider expects to apply to the electric bicycle pedal 2 M’ 人 Calculate the desired output torque of the brushless DC motor 9. M’ 电机 The calculation method is as follows.

[0059] (3)

[0060] The control circuit 7 obtains the duty cycle of the output PWM signal based on the built-in torque-speed characteristic curve of the electric bicycle and the speed of the DC brushless motor, and completes the PWM signal output.

[0061] The switching power supply circuit 8 can output a drive voltage to the brushless DC motor 9 based on the PWM signal output by the control circuit 7.

[0062] The DC brushless motor 9 is used to output torque and assist the rider in riding the electric bicycle in the electric bicycle-assist model.

[0063] In addition, the DC brushless motor 9 was calibrated in advance to determine its torque-speed characteristic curves under different PWM signal duty cycles.

[0064] Example 2

[0065] Reference Figure 2 A method for controlling the auxiliary power output in the electric bicycle assist mode includes the following steps:

[0066] S1. Calibrate the DC brushless motor used in electric bicycles and determine the motor torque-speed characteristic curves of different duty cycle drive signals (PWM signals) under rated voltage;

[0067] S2. An inertial measurement unit is installed on the electric bicycle. The test signal measured by the inertial measurement unit is processed by the control circuit to obtain the pitch angle, acceleration and speed of the electric bicycle during the driving process.

[0068] S3. Install Hall sensors on the pedals of electric bicycles to detect whether the rider is pedaling.

[0069] S4. The control circuit internally stores a second-order system model of the electric bicycle during its operation. During the ride, when the rider perceives changes in road width, terrain, or load, they stop pedaling. The electric bicycle continues to move forward due to its inertia. At this time, the Hall sensor detects that the pedal speed is 0, and the duty cycle of the PWM signal of the brushless DC motor decreases, causing the electric bicycle to begin to decelerate. The control circuit can update the second-order system model based on the pitch angle, acceleration, speed, and torque of the brushless DC motor during the electric bicycle's operation.

[0070] S5. After the second-order system model update is completed, the rider can continue to perform normal riding actions. When the rider steps on the electric bicycle pedal, the Hall sensor detects that the electric bicycle pedal speed is not 0. The control circuit calculates the expected output torque of the DC brushless motor based on the second-order system model of the electric bicycle during the riding process, the electric bicycle pitch angle, acceleration, speed, and the rider's expectation to apply torque to the electric bicycle pedal.

[0071] S6. Based on the calculated torque of the desired brushless DC motor output and the speed of the brushless DC motor, the control circuit outputs a PWM signal in conjunction with the torque-speed characteristic curve. After passing through the switching power supply circuit, the signal drives the brushless DC motor to rotate and output auxiliary torque. This ensures that the torque applied to the electric bicycle pedal by the rider remains relatively constant under different riding conditions such as road conditions, terrain, and load. When encountering situations such as climbing hills, the rider does not need to increase the torque applied to the electric bicycle pedal, thereby improving the rider's riding experience.

[0072] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for controlling the auxiliary power output in the power-assisted mode of an electric bicycle, characterized in that, Includes the following steps: S1. The brushless DC motor used in electric bicycles is calibrated to obtain the motor torque-speed characteristic curves under different duty cycle drive signals at rated voltage. S2. Measure the pitch angle, acceleration, and speed of the electric bicycle during its operation; S3. During the ride, detect whether the rider makes a pedaling motion; S4. When the rider stops pedaling, the detected pedal speed of the electric bicycle is 0, which slows down the electric bicycle. The second-order system model is updated based on the pitch angle, acceleration, speed and DC brushless motor torque of the electric bicycle during the ride. S5. When the rider pedals the electric bicycle, the pedal speed is detected to be non-zero. Based on the second-order system model, the electric bicycle pitch angle, acceleration, speed, and the rider's desired torque to be applied to the electric bicycle pedal, the torque expected to be output by the brushless DC motor is calculated. S6. Based on the desired output torque and speed of the brushless DC motor, and combined with the torque-speed characteristic curve, output a PWM signal to drive the brushless DC motor to rotate and provide auxiliary torque output.

2. The auxiliary power output control method for an electric bicycle in power-assisted mode according to claim 1, characterized in that, In step S2, the initial pitch angle, pitch velocity, and acceleration in the direction of travel of the electric bicycle are detected by the inertial measurement unit. Based on the initial pitch angle, pitch velocity, and acceleration in the direction of travel, the pitch angle, acceleration, and speed of the bicycle during travel are calculated.

3. The auxiliary power output control method for an electric bicycle in power-assisted mode according to claim 1, characterized in that, In step S3, a Hall sensor is used to detect whether the rider is pedaling.

4. The auxiliary power output control method for an electric bicycle in power-assisted mode according to claim 1, characterized in that, In step S3, the expression for the second-order system model is: （1） in, m For quality coefficient, θ ( t This refers to the real-time pitch angle of the electric bicycle. c The damping coefficient is... v ( t (This refers to the real-time speed of the electric bicycle.) R The radius of the electric bicycle wheel. M 电机 This is the output torque of the brushless DC motor. M 人 To apply torque to the pedals of an electric bicycle by the rider, n 电机 This refers to the transmission ratio from the DC brushless motor to the electric bicycle wheel. n 人 This refers to the transmission ratio from the pedals to the wheels of an electric bicycle. μ Let g be the kinetic friction factor between the electric bicycle and the road surface, and g be the acceleration due to gravity.

5. The auxiliary power output control method for an electric bicycle in power-assisted mode according to claim 1, characterized in that, In step S4, updating the second-order system model based on the pitch angle, acceleration, velocity, and DC brushless motor torque of the electric bicycle during operation includes the following steps: collection t 1. t 2. t 3. Real-time pitch angle of electric bicycle at three time points θ ( t 1) θ ( t 2) θ ( t 3) The acceleration of the electric bicycle in the direction of travel. a ( t 1) a ( t 2) a ( t 3) With real-time speed v ( t 1) v ( t 2) v ( t 3) Substituting the above values ​​into the second-order system model yields equation (2). Based on equation (2), the quality coefficient is... m Damping coefficient c and the dynamic friction factor between electric bicycles and the road surface μ Recalculate and update the real-time second-order model of the electric bicycle; （2） in, for t At moment 1, the output torque of the brushless DC motor is... for t At time 2, the output torque of the brushless DC motor is... for t At time 3, the output torque of the brushless DC motor is given, where g is the acceleration due to gravity.

6. The auxiliary power output control method for an electric bicycle in power-assisted mode according to claim 5, characterized in that, t 1. t 2. t 3. The interval time is greater than 0.5s.

7. The auxiliary power output control method for an electric bicycle in power-assisted mode according to claim 1, characterized in that, In step S4, the calculation method for calculating the desired output torque of the brushless DC motor based on the second-order system model of the electric bicycle during operation, the electric bicycle's pitch angle, acceleration, velocity, and the rider's desired torque applied to the electric bicycle pedals is as follows: in, θ ( t ) for the real-time pitch angle of electric bicycles, a ( t () represents the acceleration in the direction of travel of the electric bicycle. v ( t ) represents the real-time speed of the electric bicycle in the direction of travel. M’ 人 The torque that the rider expects to apply to the pedals of the electric bicycle. M’ 电机 Let g be the desired output torque of the brushless DC motor, and g be the acceleration due to gravity.

8. An auxiliary power output control system for an electric bicycle in a power-assisted mode, characterized in that, It includes electric bicycle pedals, inertial measurement unit, Hall sensor, AD conversion circuit, control circuit and switching power supply circuit; The inertial measurement unit is fixedly mounted on the frame of the electric bicycle, and the Hall sensor is mounted on the pedal of the electric bicycle. Both the inertial measurement unit and the Hall sensor are connected to the AD conversion circuit, which is connected to the control circuit. The control circuit is connected to the switching power supply circuit, which is connected to the DC brushless motor. The control circuit incorporates a second-order system model of the electric bicycle. This model is updated based on data from Hall sensors, inertial measurement units, and the torque of the brushless DC motor. The circuit then calculates the desired output torque of the brushless DC motor based on the updated model, the electric bicycle's pitch angle, acceleration, speed, and the rider's desired torque applied to the pedals. Finally, based on the calculated torque and the brushless DC motor's speed, and combined with the electric bicycle's torque-speed characteristic curve, a PWM signal is output to drive the brushless DC motor and provide auxiliary torque output.

9. The auxiliary power output control system for an electric bicycle in power-assisted mode according to claim 8, characterized in that, A signal processing circuit is connected between the inertial measurement unit and the Hall sensor and the AD conversion circuit.

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