Load estimation and torque compensation system for electric power-assisted bicycle

Abstract

The utility model discloses a load estimation and torque compensation system for an electric power-assisted bicycle. The load estimation and torque compensation system comprises a motor control circuit connected with a three-phase brushless direct current motor of the electric power-assisted bicycle, the switching elements are arranged in a full-bridge inverter structure, and each pair of switching elements is used for controlling the phase current of the motor; and the plurality of current sampling resistors are respectively connected to the lower end of the motor phase current and are used for collecting current signals and feeding back the current signals to the control circuit. According to the load estimation and torque compensation system based on the motor current and the rotating speed signal, the output torque of the motor is adjusted in time by estimating the load change on the motor shaft, the purpose of automatically increasing assisting power under the condition of uphill or load increase is achieved, and compared with an existing IMU sensor scheme, the load estimation and torque compensation system based on the motor current and the rotating speed signal has the advantages of being simple in structure and convenient to use. According to the utility model, no additional sensor is needed, and load estimation can be realized by using existing motor signals, so that the system cost and complexity are effectively reduced.

Description

Technical Field

[0001] The utility model relates to the field of electric power-assisted bicycles, and in particular to a load estimation and torque compensation system for electric power-assisted bicycles. Background Art

[0002] Currently, most electric-assisted bicycle control systems rely on pedaling force and frequency to adjust the motor's output power. However, riding on a sloped road or when loaded significantly increases riding resistance. Even with the same pedaling force and frequency, it becomes difficult for riders to maintain a constant speed, which degrades the riding experience.

[0003] Some existing solutions use inertial measurement units (IMUs) or gravity sensors to detect changes in the bicycle's angle or acceleration and compensate for the motor's output torque based on these physical quantities. However, while these solutions can effectively improve power assist, they are expensive and increase system complexity, making them unsuitable for cost-sensitive applications.

[0004] Therefore, there is an urgent need for a technical solution that can realize motor load estimation and torque compensation without increasing additional hardware costs, so as to improve the adaptability of electric-assisted bicycles under different road conditions. Utility Model Content

[0005] In order to solve the above problems, the utility model provides a load estimation and torque compensation system for an electric-assisted bicycle, which realizes real-time estimation and torque compensation of the motor load torque through a control circuit and a feedback mechanism, and utilizes a feedforward gain adjustment device to ensure the stability of the system when the load changes, avoiding system oscillation. It not only improves the power-assisting effect of the electric-assisted bicycle, but also significantly reduces the production and maintenance costs, and has broad application prospects.

[0006] The utility model is realized by the following technical solution: a load estimation and torque compensation system for an electric power-assisted bicycle, comprising:

[0007] a motor control circuit connected to a three-phase brushless DC motor of an electric power-assisted bicycle;

[0008] a group of switching elements arranged in a full-bridge inverter structure, wherein each pair of switching elements is used to control a phase current of the motor;

[0009] Multiple current sampling resistors are connected to the lower ends of the motor phase currents to collect current signals and feed them back to the control circuit;

[0010] A feedback controller, the feedback controller comprising:

[0011] A load estimation device, configured to receive the current signal and the speed signal of the motor, estimate the load torque of the motor by calculation, and dynamically adjust the output torque of the motor according to changes in the load torque;

[0012] The feedback controller further includes a signal input terminal connected to a motor speed sensor, for receiving a motor speed signal and adjusting the output of the motor based on the signal.

[0013] As a preferred technical solution, a feedforward gain adjustment device is further included, and the feedforward gain adjustment device includes:

[0014] A signal conditioner is used to receive the current signal and speed signal from the motor and dynamically adjust the feedforward gain according to the actual load change;

[0015] a gain control circuit, the gain control circuit comprising an adjustable amplifier and a connection resistor, the amplifier being configured to adjust the gain of the feedforward signal according to an input signal;

[0016] A fine-tuning controller is manually operable to adjust an initial setting of the feedforward gain.

[0017] As a preferred technical solution, the gain control circuit is physically connected to the feedback controller and performs gain adjustment according to a real-time feedback signal from the motor to ensure that the output torque of the motor matches the actual load change.

[0018] As a preferred technical solution, the switching element controls the three phase currents of the motor and performs feedback regulation based on the signal collected by the current sampling resistor.

[0019] As a preferred technical solution, the switching element is a MOSFET or an IGBT, the motor is a brushless DC motor, and the entire system controls the three-phase currents of the motor through the switching element.

[0020] The beneficial effects of the present invention are as follows: the present invention proposes a load estimation and torque compensation system based on motor current and speed signals. The system estimates the load changes on the motor shaft and adjusts the motor's output torque in a timely manner, thereby automatically increasing the power assist when going uphill or when the load increases. Compared with existing IMU sensor solutions, the present invention does not require additional sensors and can achieve load estimation using existing motor signals, thereby effectively reducing system cost and complexity.

[0021] Real-time estimation and torque compensation of the motor load torque are achieved through the control circuit and feedback mechanism, and the feedforward gain adjustment device is used to ensure the stability of the system when the load changes and avoid system oscillation. This not only improves the power-assisting effect of the electric-assisted bicycle, but also significantly reduces the production and maintenance costs, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 It is a simulation schematic diagram of the utility model;

[0024] Figure 2 This is a system block diagram of the utility model;

[0025] Figure 3 This is the control principle diagram of the utility model. DETAILED DESCRIPTION

[0026] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0027] Any feature disclosed in this specification (including any appended claims, abstract and drawings), unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0028] like Figure 2 and Figure 3 As shown, the present invention provides a load estimation and torque compensation system for an electric-assisted bicycle. This system can accurately and dynamically adjust the motor's output torque under different road and load conditions, thereby improving the riding experience. The system includes a motor control circuit connected to the electric-assisted bicycle's three-phase brushless DC motor, a switching element, a current sampling resistor, a feedback controller, and a feedforward gain adjustment device.

[0029] The motor control circuit is connected to the motor and achieves torque control by adjusting the motor's output. The motor is a three-phase brushless DC motor, and the system controls the motor's phase current through switching elements. The switching elements are arranged in a full-bridge inverter structure, with each pair of switching elements used to control the motor's phase current. Specifically, the switching elements can be MOSFETs or IGBTs, and each switching element receives a control signal from the control circuit to adjust the motor's output. The operating frequency of the switching elements is achieved through pulse width modulation (PWM), and the PWM signal controls the on and off time of the switching elements to control the operating state of the motor.

[0030] To monitor the motor's operating status, the present invention incorporates multiple current sampling resistors located below the motor's phase current sensors. Each current sampling resistor collects the motor's phase current signal and feeds the collected signal back to the motor control circuit. The current sampling resistors are designed with appropriate resistance values ​​to effectively reflect changes in the motor's phase current, ensuring accurate current signal acquisition. After the current signal is collected, it is processed by an amplifier circuit and fed back to the controller for subsequent control and adjustment.

[0031] The core control device of this system is the feedback controller, which receives speed and current signals from the motor and estimates the motor's load torque based on these signals. The load estimation device estimates the current motor load by constructing a kinematic model of the motor. The basic principle of load estimation is to use the motor's current and speed signals to calculate using the following formula:

[0032]

[0033] System output:

[0034] y=v n (2)

[0035] Let:

[0036] It is called the state transfer matrix, dt represents the execution cycle, k is the physical quantity related to the motor parameters, and the coefficient of converting current into torque;

[0037] It is called the control matrix, and k is the same as k in the above formula.

[0038] It is called the band estimation matrix, vn represents the n-th velocity, an represents the n-th acceleration, and TLn represents the n-th axial load. From (2), we know that y = HX; thus, we can know that the prediction matrix H is:

[0039]

[0040] The input observation value is the motor speed V, which is a one-dimensional data.

[0041] Load observation principle:

[0042] The kinematic model can obtain an estimated rotational speed, and then the motor position sensor can obtain a measured speed. By measuring the difference between the speed and the theoretical speed, the kinematic model can be continuously updated until the estimated speed of the kinematic model is basically consistent with the measured speed. At this time, the TL in the estimated state represents the load on the motor shaft.

[0043] The adjustable feedforward gain is set to prevent system instability. Generally speaking, the feedforward control cannot be 100% feedforward, otherwise it will easily cause system instability. It should be adjusted according to actual conditions.

[0044] The specific iterative process is as follows:

[0045] X_=F*X+B*u; X_ is the prior estimate calculated based on the theoretical model

[0046] P=F*P*F'+Q; P is the prior error covariance calculation

[0047] K=P*H' / (H*P_*H'+R); K optimal value iteration coefficient

[0048] X=X_+K*(VH*X_); optimal estimate of X

[0049] P=(eye(3)-K*H)*P_;P posterior error covariance is updated

[0050] Through continuous iteration, the value of TL can be calculated

[0051] The simulation is performed under the condition that TL is always equal to 1, and the results are as follows Figure 1 shown.

[0052] This utility model proposes a load estimation and torque compensation system based on motor current and speed signals. By estimating the load changes on the motor shaft, the system promptly adjusts the motor's output torque to automatically increase power assistance when going uphill or when the load increases. Compared with existing IMU sensor solutions, this utility model does not require additional sensors and can achieve load estimation using existing motor signals, thereby effectively reducing system cost and complexity.

[0053] Real-time estimation and torque compensation of the motor load torque are achieved through the control circuit and feedback mechanism, and the feedforward gain adjustment device is used to ensure the stability of the system when the load changes and avoid system oscillation. This not only improves the power-assisting effect of the electric-assisted bicycle, but also significantly reduces the production and maintenance costs, and has broad application prospects.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that do not require creative effort should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined in the claims.

Claims

1. A load estimation and torque compensation system for an electric power-assisted bicycle, characterized in that: include: a motor control circuit connected to a three-phase brushless DC motor of an electric power-assisted bicycle; a group of switching elements arranged in a full-bridge inverter structure, wherein each pair of switching elements is used to control a phase current of the motor; Multiple current sampling resistors are connected to the lower ends of the motor phase currents to collect current signals and feed them back to the control circuit; A feedback controller, the feedback controller comprising: A load estimation device, configured to receive the current signal and the speed signal of the motor, estimate the load torque of the motor by calculation, and dynamically adjust the output torque of the motor according to changes in the load torque; The feedback controller further includes a signal input terminal connected to a motor speed sensor, for receiving a motor speed signal and adjusting the output of the motor based on the signal.

2. The load estimation and torque compensation system for an electric-assisted bicycle according to claim 1, characterized in that: The invention further comprises a feedforward gain adjustment device, wherein the feedforward gain adjustment device comprises: A signal conditioner is used to receive the current signal and speed signal from the motor and dynamically adjust the feedforward gain according to the actual load change; a gain control circuit, the gain control circuit comprising an adjustable amplifier and a connection resistor, the amplifier being configured to adjust the gain of the feedforward signal according to an input signal; A fine-tuning controller is manually operable to adjust an initial setting of the feedforward gain.

3. The load estimation and torque compensation system for an electric-assisted bicycle according to claim 2, characterized in that: The gain control circuit is physically connected to the feedback controller and performs gain adjustment based on a real-time feedback signal from the motor to ensure that the output torque of the motor matches the actual load change.

4. The load estimation and torque compensation system for an electric-assisted bicycle according to claim 1, characterized in that: The switching element controls the three phase currents of the motor and performs feedback regulation based on the signal collected by the current sampling resistor.

5. The load estimation and torque compensation system for an electric-assisted bicycle according to claim 1, characterized in that: The switching element is a MOSFET or an IGBT, the motor is a brushless DC motor, and the entire system controls the three-phase currents of the motor through the switching element.

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