Motor driving device and driving method thereof

Abstract

The invention provides a motor driving device and a driving method thereof. The motor controller determines a switching condition according to the treading torque and the gear ratio, and switches a mode for controlling the motor to a magnetic field steering control mode, a six-step square wave control mode or a simulation six-step square wave control mode according to whether the rotating speed of the motor meets the switching condition or not.

Description

Technical Field

[0001] The present invention relates to a driving device, and in particular to a motor driving device and a driving method thereof. Background Art

[0002] Field-oriented control (FOC) uses motor speed to estimate angles, offering advantages such as quietness and high efficiency. However, at low speeds, such as during startup, unstable speeds often lead to angle estimation errors, resulting in improper motor rotation. To address this issue, an additional mechanism, such as six-step square-wave control or simulated six-step square-wave control, can be added to ensure proper motor rotation even at low speeds.

[0003] When motors are used in electric vehicles, the timing for switching the motor control mechanism varies depending on the vehicle's conditions. Therefore, how to switch the motor control mechanism at the appropriate time for different electric vehicles is an important issue. Summary of the Invention

[0004] The present invention provides a motor driving device and a driving method thereof, which can switch the control mechanism of the motor at an appropriate time to ensure that the motor can rotate normally at a low speed (starting).

[0005] The motor drive device of the present invention is suitable for driving the motor of an electric assisted vehicle. The motor drive device includes a torque sensor, a gear ratio sensor, and a motor controller. The torque sensor senses the pedaling torque of the electric assisted vehicle. The gear ratio sensor senses the gear ratio of the electric assisted vehicle. The motor controller determines a switching condition based on the pedaling torque and gear ratio. Depending on whether the motor speed meets the switching condition, the controller switches to a field-guided control mode, a six-step square wave control mode, or a simulated six-step square wave control mode.

[0006] In one embodiment of the present invention, the switching condition is a speed threshold value. When the motor speed is greater than or equal to the speed threshold value, the motor controller enters the magnetic field oriented control mode. When the motor speed is less than the speed threshold value, the motor controller enters the six-step square wave control mode or the simulated six-step square wave control mode.

[0007] In one embodiment of the present invention, the rotation speed threshold is 5% of the maximum rotation speed of the motor.

[0008] In one embodiment of the present invention, the motor controller further determines the switching condition according to the riding environment of the electric-assisted vehicle.

[0009] In one embodiment of the present invention, the riding environment condition of the electric-assisted vehicle includes a road slope.

[0010] The present invention also provides a method for driving a motor drive device suitable for driving a motor of an electric-assisted vehicle. The method comprises the following steps: sensing the pedaling torque of the electric-assisted vehicle; sensing the gear ratio of the electric-assisted vehicle; determining a switching condition based on the pedaling torque and the gear ratio; and switching to a field-guided control mode, a six-step square wave control mode, or a simulated six-step square wave control mode based on whether the motor speed meets the switching condition.

[0011] In one embodiment of the present invention, the switching condition is a speed threshold value, and the driving method of the motor drive device includes: when the speed of the motor is greater than or equal to the speed threshold value, the motor controller enters a magnetic field oriented control mode; when the speed of the motor is less than the speed threshold value, the motor controller enters a six-step square wave control mode or a simulated six-step square wave control mode.

[0012] In one embodiment of the present invention, the speed threshold is 5% of the maximum speed of the motor.

[0013] In one embodiment of the present invention, the driving method of the motor driving device includes determining a switching condition according to a riding environment of the electric-assisted vehicle.

[0014] In one embodiment of the present invention, the riding environment condition of the electric-assisted vehicle includes a road slope.

[0015] Based on the above, the present invention's embodiments determine switching conditions based on the pedaling torque and gear ratio of the electric vehicle. Depending on whether the motor speed meets the switching conditions, the control mode switches to either the field-guided control mode, the six-step square-wave control mode, or the simulated six-step square-wave control mode. This approach, by determining the timing of motor control mode switching based on the electric vehicle's usage, specifications, and motor speed, effectively ensures normal motor rotation at low speeds.

[0016] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a motor drive device according to an embodiment of the present invention;

[0018] Figure 2 is a flow chart of a driving method of a motor driving device according to an embodiment of the present invention;

[0019] Figure 3 is a flow chart of a driving method of a motor driving device according to another embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to make the content of the present invention more clearly understood, the following embodiments are given as examples of how the present invention can be truly implemented. In addition, wherever possible, components / members with the same reference numerals are used in the drawings and embodiments to represent the same or similar parts.

[0021] Figure 1 This is a schematic diagram of a motor drive device according to an embodiment of the present invention. Figure 1 The motor drive device 100 is adapted to drive a motor 108 , which may be, for example, a motor of an electric bicycle. The motor drive device 100 may include a torque sensor 102 , a gear ratio sensor 104 , and a motor controller 106 . The motor controller 106 is coupled to the torque sensor 102 , the gear ratio sensor 104 , and the motor 108 .

[0022] The torque sensor 102 is used to sense the pedaling torque of the electric vehicle, and the gear ratio sensor 104 is used to sense the gear ratio of the electric vehicle. In some embodiments, the gear ratio sensor 104 can be implemented as an electronic transmission, for example. The shift information provided by the electronic transmission can be used to determine the current gear ratio of the electric vehicle. The motor controller 106 can determine a switching condition for switching the control mode of the motor controller 106 based on the pedaling torque and gear ratio, and switch the control mode of the motor controller 106 based on whether the speed of the motor 108 meets the switching condition. The control modes of the motor controller 106 can include, for example, a field-oriented control mode, a six-step square wave control mode, and a simulated six-step square wave control mode.

[0023] The field-guided control mode offers advantages of quietness and high efficiency, but is prone to angle estimation errors at low speeds and under heavy loads, potentially preventing the motor 108 from rotating properly. The six-step square-wave control mode is noisier, but provides the greatest starting force, ensuring a successful start of the motor 108. In the simulated six-step square-wave control mode, the 360-degree motor electrical angle is divided into six states and a current feedback mechanism is used instead of a control mechanism that estimates angle changes based on motor speed. Therefore, the simulated six-step square-wave control mode offers operating noise and starting force levels between the field-guided control mode and the six-step square-wave control mode.

[0024] Furthermore, the switching condition can be, for example, a speed threshold of the motor 108, whose default value can be set to, for example, 5% of the maximum speed of the motor 108. When the speed of the motor 108 is less than the speed threshold, the motor controller 106 can enter a simulated six-step square wave control mode (in other embodiments, the six-step square wave control mode can also be entered) to ensure normal operation of the motor 108 at low speeds. When the speed of the motor 108 is greater than or equal to the speed threshold, the speed tends to stabilize, and the motor controller 106 can enter a field-oriented control mode. The motor controller 106 can adjust the speed threshold based on the pedaling torque and gear ratio. For example, when the pedaling torque is greater or the gear ratio (the ratio of the front gear to the rear gear) of the electric bicycle is smaller (i.e., a light gear ratio), it indicates that the user is experiencing a situation where high torque output is required to cope with a heavy load. Therefore, the motor controller 106 can increase the speed threshold, for example, to 10% of the maximum speed of the motor 108, to ensure that the motor 108 spends more time in the starting state and avoid the dilemma of being unable to output torque. On the contrary, when the pedaling torque is smaller or the gear ratio (the ratio of the front gear to the rear gear) of the electric bicycle is larger (i.e., a heavy gear ratio), the user may only need to cope with light or medium loads. The motor controller 106 can lower the speed threshold value, allowing the motor controller 106 to enter the magnetic field guidance control mode with less noise and vibration earlier.

[0025] In this way, the switching timing (switching conditions) of the motor control mode is determined based on the usage status (pedaling torque), specifications (gear ratio) and speed of the electric assisted vehicle, and the motor 108. This can effectively ensure that the motor controller 106 switches to the appropriate control mode at the appropriate time to control the motor 108 in response to different electric assisted vehicle specifications and different usage statuses, and ensure that the motor 108 can rotate normally at low speeds.

[0026] In some embodiments, the motor controller 106 may determine the switching conditions based not only on the pedaling torque and gear ratio, but also on the riding environment of the electric vehicle, such as the slope of the road on which the electric vehicle is riding and the road conditions (e.g., road surface smoothness (gravel or asphalt)). For example, when the electric vehicle is traveling uphill, the speed threshold may be increased based on the road slope, or the speed threshold may be increased or decreased based on the road surface smoothness.

[0027] Figure 2This is a flow chart of a driving method of a motor drive device according to an embodiment of the present invention. The driving method of the motor drive device can be used, for example, to drive the motor of an electric assisted vehicle. As can be seen from the above embodiment, the driving method of the motor drive device may include the following steps. First, the pedaling torque of the electric assisted vehicle is sensed (step S202), and the gear ratio of the electric assisted vehicle is sensed (step S204). Then, the switching condition is determined based on the pedaling torque and the gear ratio (step S206), and then the mode of controlling the motor is switched to the magnetic field oriented control mode, the six-step square wave control mode, or the simulated six-step square wave control mode based on whether the motor speed meets the switching condition (step S208).

[0028] The switching condition may be, for example, a motor speed threshold value, and its default value may be, for example, 5% of the maximum motor speed, but is not limited thereto. Figure 3 As shown, after step S204, a speed threshold value can be determined based on the pedaling torque and gear ratio (step S302). For example, the speed threshold value can be increased as the pedaling torque increases or the gear ratio of the electric vehicle decreases, such as by adjusting the speed threshold value to 10% of the maximum speed of the motor 108. This ensures that the motor spends more time in the starting state and avoids the dilemma of being unable to output torque. For another example, the speed threshold value can be lowered as the pedaling torque decreases or the gear ratio of the electric vehicle increases, thereby enabling the early entry into the magnetic field-guided control mode with less noise and vibration. In some embodiments, the switching condition can be further determined based on the riding environment of the electric vehicle, such as determining the speed threshold value based on the slope of the road on which the electric vehicle is located.

[0029] After determining the speed threshold, the process then determines whether the motor speed is greater than or equal to the speed threshold (step S304). If the motor speed is greater than or equal to the speed threshold, the motor control mode can be switched to the field-oriented control mode (step S306). If the motor speed is less than the speed threshold, the motor control mode can be switched to the six-step square wave control mode or the simulated six-step square wave control mode (step S308). After steps S306 and S308, the process returns to step S304 to switch the motor mode at any time based on the determination result of step S304.

[0030] In summary, the embodiments of the present invention determine switching conditions based on the pedaling torque and gear ratio of the electric vehicle. Depending on whether the motor speed meets the switching conditions, the control mode switches to the field-guided control mode, the six-step square-wave control mode, or the simulated six-step square-wave control mode. This approach, by determining the timing of motor control mode switching based on the electric vehicle's usage, specifications, and motor speed, effectively ensures normal motor rotation at low speeds.

[0031] Although the present invention has been disclosed above by way of embodiments, they are not intended to limit the present invention. Any person skilled in the art may make slight changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A motor drive device suitable for driving a motor of an electric vehicle, characterized in that: The motor drive device comprises: a torque sensor for sensing the pedaling torque of the electric assisted vehicle; a gear ratio sensor for sensing the gear ratio of the electric-assisted vehicle; and The motor controller determines a switching condition according to the pedaling torque and the gear ratio, and switches to a magnetic field oriented control mode, a six-step square wave control mode, or a simulated six-step square wave control mode according to whether the motor speed meets the switching condition.

2. The motor drive device according to claim 1, wherein: The switching condition is a speed threshold value. When the speed of the motor is greater than or equal to the speed threshold value, the motor controller enters the magnetic field oriented control mode. When the speed of the motor is less than the speed threshold value, the motor controller enters the six-step square wave control mode or the simulated six-step square wave control mode.

3. The motor drive device according to claim 2, wherein: The speed threshold is 5% of the maximum speed of the motor.

4. The motor drive device according to claim 1, wherein: The motor controller further determines the switching condition according to a riding environment of the electric-assisted vehicle.

5. The motor drive device according to claim 4, characterized in that: The riding environment conditions of the electric-assisted vehicle include the road slope.

6. A method for driving a motor drive device, suitable for driving a motor of an electric vehicle, characterized in that: The driving method of the motor driving device includes: sensing a pedaling torque of the electric-assisted vehicle; sensing a gear ratio of the electric-assisted vehicle; determining a switching condition according to the pedaling torque and the gear ratio; and The control mode is switched to the magnetic field oriented control mode, the six-step square wave control mode or the simulated six-step square wave control mode according to whether the rotation speed of the motor meets the switching condition.

7. The driving method of the motor driving device according to claim 6, wherein: The switching condition is a speed threshold value, and the driving method of the motor driving device includes: When the speed of the motor is greater than or equal to the speed threshold value, the motor controller enters the magnetic field oriented control mode; when the speed of the motor is less than the speed threshold value, the motor controller enters the six-step square wave control mode or the simulated six-step square wave control mode.

8. The driving method of the motor driving device according to claim 7, characterized in that: The speed threshold is 5% of the maximum speed of the motor.

9. The driving method of the motor driving device according to claim 6, wherein: include: The switching condition is determined according to a riding environment of the electric-assisted vehicle.

10. The driving method of the motor driving device according to claim 9, wherein: The riding environment conditions of the electric-assisted vehicle include the road slope.

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