Motor control system, and electric bicycle

Abstract

To make it easy to maintain an appropriate motor output at the time of motor control.SOLUTION: A motor control system 100 performs vector control on a motor 1 that generates driving force for propelling an electric bicycle in a forward direction. The motor control system 100 includes: an inverter 3 that converts a DC current from a DC power supply 2 into an AC current and supplies it to the motor 1; two or less detection resistors 4 for detecting two-phase currents out of three phase-currents flowing through the motor 1; and a control unit 5 for controlling the inverter 3 based on the two phase-currents detected by the two or less detection resistors 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a motor control system for controlling a motor provided in an electric bicycle, and to an electric bicycle. [Background Art]

[0002] Patent Document 1 discloses an electrically power assisted bicycle that can travel by adding an auxiliary driving force generated by a motor to human driving force from the pedaling force of a pedal. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. WO2014 / 009995 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] An object of the present disclosure is to provide a motor control system and an electric bicycle that facilitate maintaining an appropriate motor output during motor control. [Means for Solving the Problem]

[0005] To achieve the above object, a motor control system according to one aspect of the present disclosure is a motor control system that performs vector control on a motor which generates driving force for propelling an electric bicycle in a forward direction, the motor control system comprising: an inverter that converts a direct current from a DC power supply into an alternating current and supplies the alternating current to the motor; two or less detection resistors for detecting currents of two phases among three-phase currents flowing through the motor; and a control unit that controls the inverter based on the two-phase currents detected by the two or less detection resistors.

[0006] Further, an electric bicycle according to one aspect of the present disclosure includes the above motor control system, and the motor that adds driving force for causing a vehicle body to travel by the motor control system. [Effects of the Invention]

[0007] The motor control system etc. described herein has the advantage of making it easier to maintain an appropriate motor output when controlling the motor. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the overall configuration including the motor control system according to the embodiment. [Figure 2] Figure 2 is a block diagram showing the configuration of the control unit according to the embodiment. [Figure 3] Figure 3 is a side view illustrating an electric assist bicycle according to an embodiment. [Figure 4] Figure 4 is a schematic diagram illustrating a motor unit according to an embodiment. [Figure 5] Figure 5 is a side view illustrating a specific small motorized bicycle according to an embodiment. [Figure 6] Figure 6 is a flowchart showing an example of the operation of the motor control system according to the embodiment. [Figure 7] Figure 7 shows an example of waveforms during low-speed motor operation and low-modulation inverter operation. [Figure 8] Figure 8 shows an example of waveforms during high-speed motor operation and high-modulation inverter operation. [Figure 9] Figure 9 shows an example of a waveform during one period of electrical angle. [Figure 10] Figure 10 is a block diagram showing the configuration of a motor control system according to the first modified example. [Figure 11] Figure 11 is a block diagram showing the configuration of a motor control system according to a second modified example. [Modes for carrying out the invention]

[0009] (Knowledge that forms the basis of this disclosure) First, the inventor's perspective is explained below.

[0010] In recent years, permanent magnet motors have been widely used in electric assist bicycles and other applications. Permanent magnet motors are typically driven by motor control devices that output three-phase AC, and vector control is frequently used for this control. This vector control method independently controls the currents of the motor's two orthogonal axes (d-axis and q-axis). However, detecting the currents of these two orthogonal axes requires detecting at least two phase currents. One known technique for detecting these two phase currents is to use two DCCTs (Direct Current-Current Transformers).

[0011] However, DCCTs have the drawbacks of being relatively expensive components, thus significantly impacting the product price, and being relatively large components, thus occupying a large area on the circuit board. Therefore, the inventor considered using a shunt resistor (sensing resistor), which is a relatively inexpensive component, thus having little impact on the product price, and is a relatively small component, thus not occupying much area on the circuit board, for detecting the phase current of two phases.

[0012] While it is possible to detect two-phase currents using a single shunt resistor, there is a challenge in detecting these currents, for example, when the motor is stopped or operating at low speed.

[0013] Specifically, during low-speed motor operation and low-modulation inverter operation, or during high-speed motor operation and high-modulation inverter operation, the phase voltages of two-phase or three-phase systems become close together, which can result in periods where the detection of two-phase currents becomes impossible. Numerous studies and proposals have been made to enable the detection of two-phase currents even during such periods.

[0014] For example, Document 1 (Japanese Patent Publication No. 3664040) discloses a technique (hereinafter also referred to as "pulse shift") for extending the current detection period by correcting at least one of the two voltage command values ​​with a small difference to different voltage command values ​​in the first and second halves of a 1 PWM (Pulse Width Modulation) period when the difference between the two phase voltage command values ​​is small.

[0015] Furthermore, for example, document 2 (Japanese Patent Publication No. 4429338) discloses a technique for creating a voltage command vector consisting of a vector of the combined voltages of each phase voltage of a three-phase system, correcting the created voltage command vector, and controlling a motor according to the corrected voltage command vector, as well as a technique for correcting the voltage command vector so that the corrected voltage command vector is a vector outside the region where the current flowing through the motor cannot be detected.

[0016] Furthermore, for example, document 3 (Japanese Patent Publication No. 5311864) discloses a technique in which a period of undetectable time is set for when the phase current for two phases cannot be detected from the voltage difference between two of the U-phase, V-phase, and W-phase voltages of a motor, and the motor is controlled within that period based on past voltage command values ​​that have been stored in advance.

[0017] However, especially when the motor is stopped, operating at low speed, or when the inverter is at low modulation, the phase voltages of all three phases (in other words, the inverter output voltages) are small, and the difference between the phase voltages is also small. Therefore, in such situations, none of the technologies described in the above references 1 to 3 can reliably detect the phase currents of two phases over a long period of time, resulting in the problem that the motor cannot be started or controlled at all. For this reason, in electric assist bicycles and the like, motor vector control using a technology that detects the phase currents of two phases with a single shunt resistor has not yet been put into practical use.

[0018] In view of the above, the inventor has created this disclosure. Specifically, the purpose of this disclosure is to provide a motor control system and an electric bicycle that can perform stable vector control of a motor using a technique that detects two-phase currents with a single shunt resistor at all operating times, from when the motor stops to when it is operating at high speed, even in applications where the operating range of the motor is extremely wide, such as electric assist bicycles. In other words, the purpose of this disclosure is to provide a motor control system and an electric bicycle that make it easier to maintain an appropriate motor output when controlling the motor.

[0019] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are all specific examples of this disclosure. Therefore, the numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure. Accordingly, any components in the following embodiments that are not described in an independent claim will be described as optional components.

[0020] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, for example, the scale and other aspects may not necessarily match in each figure. Also, in each figure, substantially identical components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0021] The motor control system and electric bicycle according to the embodiment will be described below.

[0022] (Embodiment) <Structure> [Motor control system] First, the motor control system 100 according to the embodiment will be described. Figure 1 is a schematic diagram showing the overall configuration including the motor control system 100 according to the embodiment. As shown in Figure 1, the motor control system 100 is a system that receives power from a DC power supply 2 and vector-controls a motor 1 that generates a driving force to propel the electric bicycle 10 (described later) in the forward direction. The motor control system 100 includes an inverter 3, a detection resistor (shunt resistor) 4, a control unit 5, and a capacitor (noise reduction element) C1.

[0023] Motor 1 is a three-phase permanent magnet synchronous motor. Motor 1 comprises a rotor 11 having permanent magnets and a stator 12 having U-phase, V-phase, and W-phase armature windings (stator windings) 13u, 13v, and 13w. The armature windings 13u, 13v, and 13w are all Y-connected around a neutral point 14. The unconnected ends of the armature windings 13u, 13v, and 13w that are not connected to the neutral point 14 are connected to terminals 15u, 15v, and 15w, respectively. In the example shown in Figure 1, the wiring of the armature windings in motor 1 is Y-connected, but it can be replaced with a delta connection or the like.

[0024] DC power supply 2 is the battery provided by the electric bicycle 10, which will be described later. Hereafter, DC power supply 2 will also be referred to as "battery 2". DC power supply 2 has a high-potential positive output terminal 21 and a low-potential negative output terminal 22, and outputs a DC voltage between the positive output terminal 21 and the negative output terminal 22.

[0025] Inverter 3 is a PWM inverter and comprises a half-bridge circuit for the U phase, a half-bridge circuit for the V phase, and a half-bridge circuit for the W phase. These three half-bridge circuits form a switching circuit for driving the motor 1. Each half-bridge circuit has a pair of switching elements connected in series. In each half-bridge circuit, the pair of switching elements is connected in series between the positive output terminal 21 and the negative output terminal 22 of the DC power supply 2. Therefore, a DC voltage from the DC power supply 2 is applied to each half-bridge circuit. In other words, inverter 3 has three half-bridge circuits corresponding to the three phases, and each of the three half-bridge circuits has a pair of switching elements.

[0026] In this embodiment, each pair of switching elements in the half-bridge circuit is an n-channel enhancement-type MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). However, each pair of switching elements in the half-bridge circuit may be a field-effect transistor other than the MOSFET, or it may be an IGBT (Insulated Gate Bipolar Transistor), for example.

[0027] The half-bridge circuit for the U-phase includes a high-potential switching element 31u (hereinafter also referred to as the upper arm 31u), a low-potential switching element 32u (hereinafter also referred to as the lower arm 32u), and two diodes 33u and 34u. The drain of the upper arm 31u is connected to the positive output terminal 21 of the DC power supply 2, and its source is connected to terminal 15u of the motor 1. A PWM signal (also referred to as a "pulse width modulation signal") GHu from the control unit 5 is input to the gate of the upper arm 31u. The drain of the lower arm 32u is connected to terminal 15u of the motor 1, and its source is connected to the negative output terminal 22 of the DC power supply 2 via a detection resistor 4. A PWM signal GLu from the control unit 5 is input to the gate of the lower arm 32u.

[0028] Diode 33u is connected in parallel to upper arm 31u, with its anode connected to the source of upper arm 31u and its cathode connected to the drain of upper arm 31u. Diode 34u is connected in parallel to lower arm 32u, with its anode connected to the source of lower arm 32u and its cathode connected to the drain of lower arm 32u. Both diodes 33u and 34u function as freewheeling diodes.

[0029] The half-bridge circuit for the V phase includes a high-potential switching element 31V (hereinafter also referred to as the upper arm 31V), a low-potential switching element 32V (hereinafter also referred to as the lower arm 32V), and two diodes 33V and 34V. The drain of the upper arm 31V is connected to the positive output terminal 21 of the DC power supply 2, and its source is connected to the terminal 15V of the motor 1. The gate of the upper arm 31V is input to the PWM signal GHv from the control unit 5. The drain of the lower arm 32V is connected to the terminal 15V of the motor 1, and its source is connected to the negative output terminal 22 of the DC power supply 2 via the detection resistor 4. The gate of the lower arm 32V is input to the PWM signal GLv from the control unit 5.

[0030] Diode 33V is connected in parallel to upper arm 31V with its anode connected to the source of upper arm 31V and its cathode connected to the drain of upper arm 31V. Diode 34V is connected in parallel to lower arm 32V with its anode connected to the source of lower arm 32V and its cathode connected to the drain of lower arm 32V. Both diodes 33V and 34V function as freewheeling diodes.

[0031] The half-bridge circuit for the W phase includes a high-potential switching element 31w (hereinafter also referred to as the upper arm 31w), a low-potential switching element 32w (hereinafter also referred to as the lower arm 32w), and two diodes 33w and 34w. The drain of the upper arm 31w is connected to the positive output terminal 21 of the DC power supply 2, and its source is connected to the terminal 15w of the motor 1. The gate of the upper arm 31w is input to the PWM signal GHw from the control unit 5. The drain of the lower arm 32w is connected to the terminal 15w of the motor 1, and its source is connected to the negative output terminal 22 of the DC power supply 2 via the detection resistor 4. The gate of the lower arm 32w is input to the PWM signal GLw from the control unit 5.

[0032] Diode 33w is connected in parallel to upper arm 31w, with its anode connected to the source of upper arm 31w and its cathode connected to the drain of upper arm 31w. Diode 34w is connected in parallel to lower arm 32w, with its anode connected to the source of lower arm 32w and its cathode connected to the drain of lower arm 32w. Both diodes 33w and 34w function as freewheeling diodes.

[0033] Inverter 3 drives the control terminals (in this case, gates) of each switching element of inverter 3 based on the three-phase PWM signals provided by control unit 5. Of the six PWM signals GHu, GLu, GHv, GLv, GHw, and GLw supplied from control unit 5 to inverter 3, PWM signals GHu and GLu, GHv and GLv, and GHw and GLw are complementary inverses of each other. That is, ignoring the dead time required to prevent the upper and lower arms of the same phase from being turned on simultaneously, in each half-bridge circuit, when the upper arm is on, the lower arm is off, and when the upper arm is off, the lower arm is on. Hereafter, unless otherwise specified, the above dead time will be ignored.

[0034] The DC voltage from the DC power supply 2 applied to the inverter 3 is converted into, for example, a pulse-width modulated three-phase AC voltage by the switching operation of each switching element in the inverter 3. When this three-phase AC voltage is applied to the motor 1, current corresponding to the three-phase AC voltage flows through each armature winding 13u, 13v, and 13w, driving the motor 1.

[0035] The detection resistor 4 is connected to the wire, i.e., the busbar M, that connects the negative output terminal 22 of the DC power supply 2 to the source (low potential) of the lower arm 32u, 32v, 32w of the inverter 3. L It is located on the busbar M L The current flowing through the busbar (hereinafter also referred to as the "busbar current") is detected. Since the busbar current has a DC component, it is also possible to interpret the busbar current as equivalent to a DC current. In other words, in this embodiment, the motor control system 100 is equipped with two or fewer detection resistors for detecting the current of two of the three phases of current flowing through the motor 1, and the two or fewer detection resistors are connected to the wire (busbar M) that connects the DC power supply 2 and the inverter 3. L This is a single detection resistor 4 provided in the control unit 5. The detection resistor 4 provides the control unit 5 with a signal indicating the current value of the detected bus current (hereinafter also referred to as the "current detection signal").

[0036] Here, the three-phase currents flowing through motor 1 refer to the U-phase current, which flows through armature winding 13u; the V-phase current, which flows through armature winding 13v; and the W-phase current, which flows through armature winding 13w. For each of the U-phase, V-phase, and W-phase currents, the polarity of the current flowing from terminals 15u, 15v, and 15w towards the neutral point 14 is positive, and the polarity of the current flowing from the neutral point 14 towards terminals 15u, 15v, and 15w is negative.

[0037] Note that the detection resistor 4 is not limited to the arrangement described above; for example, it may be placed in the wire connecting the positive output terminal 21 of the DC power supply 2 and the drains (high potential) of the upper arms 31u, 31v, and 31w of the inverter 3.

[0038] The control unit 5 is implemented, for example, by a microcontroller, and consists of a non-volatile memory where the program is stored, a volatile memory (storage unit) which is a temporary storage area for executing the program, input / output ports, a processor for executing the program, etc. The control unit 5 may also be implemented by a dedicated electronic circuit. In this embodiment, the control unit 5 has the function of performing pulse shift control used in the PWM control unit 58, which will be described later.

[0039] The control unit 5 generates and outputs the three-phase PWM signals GHu, GLu, GHv, GLv, GHw, and GLw while referring to the current detection signal from the detection resistor 4. Figure 2 is a block diagram showing the configuration of the control unit 5 according to the embodiment. As shown in Figure 2, the control unit 5 sets the target value Iqm of the q-axis current of the motor 1. * The torque generated by motor 1 is controlled by controlling the following. The control unit 5 includes a current control unit 51, a first coordinate transformation unit 52, a second coordinate transformation unit 53, a position / velocity estimation unit 54, a magnetic flux control unit 55, a motor current detection unit 56, a two-phase modulation conversion unit 57, and a PWM control unit 58.

[0040] The current control unit 51 controls the motor currents of two orthogonal axes (d-axis and q-axis) in a rotating coordinate system. Specifically, the current control unit 51 uses, for example, proportional-integral control to control the q-axis current Iqm provided by the first coordinate transformation unit 52 and the target value Iqm of the q-axis current. * The command value Vqm of the q-axis voltage is set such that the difference between it and zero converges to zero. * The current control unit 51 calculates and outputs the d-axis current Idm provided by the first coordinate transformation unit 52 and the target value Idm of the d-axis current provided by the magnetic flux control unit 55, for example, by using proportional-integral control. * The command value Vdm of the d-axis voltage is set such that the difference between it and zero converges to zero. * Calculate and output the result.

[0041] Both the first coordinate conversion unit 52 and the second coordinate conversion unit 53 perform mutual conversion between a rotating coordinate system (dq coordinate system) and a stationary coordinate system (uvw coordinate system). Specifically, the first coordinate conversion unit 52 coordinate-converts the U-phase current Iu, V-phase current Iv, and W-phase current Iw supplied from the motor current detection unit 56 onto the dq axis based on the rotor position θe indicating the position of the rotor 11 supplied from the position / speed estimation unit 54, thereby calculating and outputting a d-axis current Idm and a q-axis current Iqm.

[0042] Further, the second coordinate conversion unit 53 uses the d-axis voltage command value Vdm supplied from the current control unit 51 based on the rotor position θe supplied from the position / speed estimation unit 54 * and the q-axis voltage command value Vqm * to perform coordinate conversion onto the uvw axis, thereby obtaining a U-phase voltage command value Vu0 * , a V-phase voltage command value Vv0 * , and a W-phase voltage command value Vw0 * which are calculated and output.

[0043] The position / speed estimation unit 54 receives the d-axis current Idm and q-axis current Iqm supplied from the first coordinate conversion unit 52, and the d-axis voltage command value Vdm supplied from the current control unit 51 * and the q-axis voltage command value Vqm * by reference to these values, for example using proportional-integral control, estimates and outputs the rotor position θe and the rotation speed (in other words, rotational speed) nm of the motor 1.

[0044] The magnetic flux control unit 55 executes maximum torque control of the motor 1 or flux-weakening control of the motor 1 based on the rotation speed nm of the motor 1 supplied from the position / speed estimation unit 54. When performing maximum torque control, the magnetic flux control unit 55 outputs a d-axis current target value Idm * as zero. On the other hand, when performing flux-weakening control, the magnetic flux control unit 55 outputs the d-axis current target value Idm * as a negative value.

[0045] The motor current detection unit 56 samples the detection signal (instantaneous current) idc detected by the detection resistor 4 twice within one PWM period according to the timing signals SP1 and SP2 for current detection output from the PWM control unit 58 (see Figure 9(f)) and performs A / D (Analog to Digital) conversion. Here, one PWM period corresponds to one period of the carrier signal, which is a reference triangular wave. Then, the motor current detection unit 56 calculates (detects) the U-phase current Iu, V-phase current Iv, and W-phase current Iw for each PWM period based on the two converted digital detection signals and the energizing mode signal Vmode provided by the two-phase modulation conversion unit 57. Here, when calculating the phase currents Iu, Iv, and Iw of each phase, the motor current detection unit 56 utilizes the fact that the sum of the U-phase current Iu, V-phase current Iv, and W-phase current Iw is zero, as needed. The energizing mode signal Vmode is the voltage command value Vu0 of the U-phase. * , V-phase voltage command value Vv0 * , and the voltage command value Vw0 for the W phase * These are control signals divided into six categories, determined by their relative magnitudes (see Figure 9(f)).

[0046] The two-phase modulation conversion unit 57 performs two-phase modulation by using a so-called up-and-down method, setting one of the U-phase, V-phase, and W-phase as the fixed phase for every electrical angle π / 3, and turning on the upper or lower arm of the fixed phase. Specifically, the two-phase modulation conversion unit 57 receives the voltage command value Vu0 of the U-phase from the second coordinate conversion unit 53. * , V-phase voltage command value Vv0 * , and the voltage command value Vw0 for the W phase * By using this as input and superimposing the zero-sequence voltage, a two-phase modulated U-phase voltage command value Vu1 is obtained. * , V-phase voltage command value Vv1 * , and the voltage command value Vw1 for the W phase * Convert and output.

[0047] In this embodiment, the two-phase modulation conversion unit 57 performs two-phase modulation by using the so-called up-and-down method, setting one of the U-phase, V-phase, and W-phase as the fixed phase for every electrical angle π / 3, and turning on either the upper or lower arm of the fixed phase. However, it is not limited to this. For example, the two-phase modulation conversion unit 57 may perform two-phase modulation by using the so-called down-and-down method, setting one of the U-phase, V-phase, and W-phase as the fixed phase for every electrical angle 2π / 3, and turning on the lower arm of the fixed phase. Alternatively, for example, the two-phase modulation conversion unit 57 may perform two-phase modulation by using the so-called up-and-down method, setting one of the U-phase, V-phase, and W-phase as the fixed phase for every electrical angle 2π / 3, and turning on the upper arm of the fixed phase. In other words, the two-phase modulation conversion unit 57 converts the voltage command values ​​of each of the three phases by using two-phase modulation, setting one of the three phases as the fixed phase, and turning on either one of the pair of switching elements corresponding to the fixed phase, and outputs it to the PWM control unit 58.

[0048] The PWM control unit 58 receives a carrier signal which is a reference triangular wave and a two-phase modulated U-phase voltage command value Vu1 provided by the two-phase modulation conversion unit 57. * , V-phase voltage command value Vv1 * , and the voltage command value Vw1 for the W phase * Based on this, six PWM signals GHu, GLu, GHv, GLv, GHw, and GLw are generated. In addition, the PWM control unit 58 performs pulse shift control, which will be described later in the <Operation> section, for each PWM period.

[0049] In other words, the PWM control unit 58 provides a PWM signal (six PWM signals GHu, GLu, GHv, GLv, GHw, GLw) to each control terminal (gate) of all the switching elements (six switching elements 31u, 32u, 31v, 32v, 31w, 32w) of the inverter 3, which turns the corresponding switching element on or off. The PWM control unit 58 also generates a PWM signal for each of the switching elements based on a voltage command value which is the target voltage to be applied to the motor 1 and a carrier signal which is a reference triangular wave. Furthermore, if the difference in voltage command values ​​of at least two of the three phases is less than or equal to a predetermined value, the PWM control unit 58 corrects the difference in voltage command values ​​of at least two phases to be larger in the first half of the PWM period, and corrects the voltage command values ​​of at least two phases to the opposite extent in the second half of the PWM period.

[0050] Furthermore, the PWM control unit 58 generates timing signals SP1 and SP2 by setting the timer that generates the timing signals SP1 and SP2.

[0051] As shown in Figure 1, capacitor C1 is installed between the DC power supply 2 and the inverter 3 and is a noise suppression element that removes noise that may flow into the detection resistor 4. Specifically, the first end of capacitor C1 is connected to the positive output terminal 21 of the DC power supply 2 and the high-potential input terminal of the inverter 3, and the second end is connected to the negative output terminal 22 of the DC power supply 2 and the low-potential input terminal of the inverter 3.

[0052] [Electric bicycle] Next, an electric bicycle 10 using the motor control system 100 will be described. The electric bicycle 10 is a vehicle that can travel on a road surface using electric power, and is, for example, an electric assist bicycle or a specific small motorized bicycle such as a so-called electric kick scooter. The electric bicycle 10 may be a vehicle that does not require the user to have a driver's license.

[0053] In this embodiment, the electric assist bicycle 20 shown in Figure 3 and the specific small motorized bicycle 30 shown in Figure 5 are used as examples of electric bicycles 10, but the electric bicycle 10 is not limited to these. For example, the electric bicycle 10 may be a three-wheeled bicycle in which either the front wheel or the rear wheel is a single wheel and the other is a two-wheeled bicycle.

[0054] <Electric-assisted bicycle> Figure 3 is a side view illustrating an electric assist bicycle 20 according to an embodiment. The electric assist bicycle 20 shown in Figure 3 is an electric assist bicycle that assists the user's pedaling force with the auxiliary driving force of the motor 1. In other words, the electric assist bicycle 20 (electric bicycle 10) comprises a motor control system 100 and a motor 1 that adds driving force to propel the vehicle body 200. Note that the electric assist bicycle 20 may have independent human power driving that provides power to the wheels by pedaling force and auxiliary driving force that provides power to the wheels by the motor 1, and may be a bicycle that can be driven (self-propelled) with only the motor 1.

[0055] The electric assist bicycle 20 consists of a frame 200 equipped with a motor control system 100.

[0056] The vehicle body 200 includes a frame 201, a front wheel 203, a rear wheel 206, a saddle 205, a handlebar 202, pedals 208, a crank 209, a chain 207, a gear shifter, a motor unit 204, and a battery 2.

[0057] Frame 201 is the framework of the electric assist bicycle 20. Frame 201 is made of a metal such as aluminum alloy, iron, chromium-molybdenum steel, steel, or titanium. Frame 201 may also be made of carbon or synthetic resin.

[0058] Frame 201 includes a head tube 201a, a top tube 201b, a down tube 201c, a seat tube 201d, a chainstay 201e, and a seatstay 201f. Frame 201 may also have a suspension system.

[0059] The front fork 201g and handlebars 202 are attached to the head tube 201a so as to be able to rotate freely around an axis along the longitudinal direction of the head tube 201a. The front wheel 203 is rotatably attached to the front fork 201g. By turning the handlebars 202 left or right, the direction of the front wheel 203, which is supported by the front fork 201g, can be rotated left or right.

[0060] The top tube 201b and down tube 201c connect to the head tube 201a and seat tube 201d, respectively. Battery 2 is detachably mounted on the down tube 201c, and motor units 204 are provided on both the down tube 201c and the seat tube 201d.

[0061] The seat tube 201d holds the saddle 205. The saddle 205 is mounted on the seat tube 201d so as to be movable along the longitudinal direction of the seat tube 201d. The lower end of the seat tube 201d is connected to the rear end of the down tube 201c. In the fore-aft direction, the seat tube 201d is located between the front wheel 203 and the rear wheel 206.

[0062] One end of the chainstay 201e is connected to the lower end of the seat tube 201d. The other end of the seatstay 201f is connected to the upper end of the seat tube 201d. The other end of the chainstay 201e and the other end of the seatstay 201f are connected, and the rear wheel 206 and the rear sprocket, which is linked to the axle of the rear wheel 206, are attached to this part. A chain 207 is stretched between the rear sprocket and the front sprocket. As a result, the rotational force of the front sprocket, which is rotated when the pedal 208 is pressed, is transmitted to the rear wheel 206 via the chain 207 and the rear sprocket. In this embodiment, the pedal 208, the front sprocket, the rear sprocket, and the chain 207 form a rear-wheel drive mechanism that relies on human power.

[0063] The front wheel 203 has a tire 203a for the vehicle body 200 to travel on. The front wheel 203 is the front wheel of two wheels arranged in the front-to-rear direction. The front wheel 203 is supported by the front fork 201g so that it can rotate around an axis along the left-to-right direction. The front wheel 203 may also receive power from the motor unit 204, and for example, a motor may be provided to provide the driving force to rotate the front wheel 203.

[0064] The rear wheel 206 has a tire 206a for the vehicle body 200 to travel on. The rear wheel 206 is the rear wheel of two wheels arranged in the front-to-rear direction. The rear wheel 206 is supported so that it can rotate around an axis along the left-to-right direction. The rear wheel 206 may also receive power from the motor unit 204, for example, a motor that provides the driving force to rotate the rear wheel 206 may be provided. The rear wheel 206 has a rear sprocket. The rear sprocket is connected to the front sprocket via a chain 207. In this embodiment, power output from the motor unit 204 is transmitted to the rear wheel 206.

[0065] The saddle 205 is the part where the user sits. The saddle 205 is movably mounted on the seat tube 201d.

[0066] The handlebars 202 change the steering angle of the electric assist bicycle 20, for example, when a user is operating the electric assist bicycle 20. A pair of grips and a pair of brake levers are provided at both ends of the handlebars 202. The pair of grips are the parts that the user holds with their hands when riding in a proper posture. The pair of grips are also held with the hands when pushing or supporting the electric assist bicycle 20 while walking, and receive a forward pushing force. One brake lever applies a mechanical braking force to the front wheel 203 by driving the front brake device. The other brake lever applies a mechanical braking force to the rear wheel 206 by driving the rear brake device.

[0067] The pedal 208 receives the user's pedaling force, for example, when the user is riding the electric assist bicycle 20. The pedal 208 is attached to the end of each crank arm 209a in the longitudinal direction, on the side opposite to the crank axis 209b. The pedal 208 is rotatably mounted to the crank arm 209a. The axis of rotation of the pedal 208 is approximately parallel to the axis of rotation of the crank axis 209b of the crank 209.

[0068] The crank 209 has a crank shaft 209b, a pair of crank arms 209a, and a front sprocket. One crank arm 209a is provided on each of the left and right sides of the motor unit 204, and is fixed to both ends of the crank shaft 209b which extends in the left-right direction. One end of the crank arm 209a is rotatably fixed to the crank shaft 209b, and the pedal 208 is rotatably fixed to the other end of the crank arm 209a. When pedaling force is applied to the pedal 208, the crank arm 209a rotates around the crank shaft 209b, and the human-powered driving force resulting from this rotation is transmitted to the rear wheel 206 via the front sprocket and chain 207. When the electric assist bicycle 20 operates in assist mode, the human-powered driving force based on pedaling force and the auxiliary driving force from the motor 1 added to the human-powered driving force are transmitted to the rear wheel 206. The front sprocket is attached to the crank axle 209b of the crank arm 209a. When the user presses down on the pedal 208, the front sprocket rotates via the crank arm 209a and the crank axle 209b. The rotation of the front sprocket causes the rear sprocket to rotate via the chain 207, and the rear wheel 206 to rotate as well.

[0069] The chain 207 transmits the rotational force of the front sprocket, which is rotated when the pedal 208 is pressed, and the auxiliary driving force output from the motor unit 204, to the rear sprocket. The chain 207 is a power transmission body such as a belt, shaft, wire, or gear.

[0070] The transmission is composed of well-known transmission mechanisms such as planetary gears and multi-stage gears, which have multiple drive force transmission paths with different gear ratios. The transmission can shift between, for example, a low gear, a medium gear, or a high gear by switching the drive force transmission paths. The transmission may be configured to switch the drive force transmission paths manually, or it may be configured to switch the drive force transmission paths electrically.

[0071] The motor unit 204 comprises a motor 1 and a motor control system 100, and is mounted on the vehicle body 200. The motor unit 204 outputs auxiliary driving force, adding auxiliary drive to the pedaling force, which is the human-powered driving force, and transmits it to the rear wheels 206 via the chain 207.

[0072] Figure 4 is a schematic diagram illustrating a motor unit 204 according to an embodiment. Figure 4(a) is a cross-sectional view of the motor unit 204 taken from a plane along the vertical direction. Figure 4(b) is a cross-sectional view of the motor unit 204 taken from a plane along the horizontal direction. The motor unit 204 is a unit in which the motor 1 and the motor control system 100 are housed in a resin or metal housing 204A. Inside the housing 204A are the motor 1 and a circuit board 204B on which various components constituting the motor control system 100 are mounted. As shown in Figure 4, various components including the crankshaft 209b and the motor 1 are housed inside the housing 204A. For this reason, it is necessary to house the circuit board 204B using the limited space inside the housing 204A, and miniaturization of the circuit board 204B is required.

[0073] Motor 1 adds auxiliary driving force to propel the vehicle body 200. Motor 1 is powered by electricity from battery 2, based on control by motor control system 100. Motor 1 rotates the rear wheel 206 by transmitting rotational torque as auxiliary driving force to the rear sprocket via chain 207. Rotational torque is auxiliary driving force, which is the driving force by motor 1 added to human power driving force, and auxiliary driving force, which is the auxiliary force applied to the force used to push or support the electric assist bicycle 20 while walking. When the assist mode is running, motor 1 adds auxiliary driving force to the human power driving force based on the force applied to pedal 208.

[0074] The motor control system 100 drives the motor 1 according to the operating mode of the electric assist bicycle 20. For example, when the assist mode is activated, the motor control system 100 determines the magnitude of the auxiliary driving force generated by the motor 1 based on the pedaling force applied to the pedal 208 and the speed of the electric assist bicycle 20. The motor control system 100 also supplies power from the battery 2 to the motor 1 and the headlights, etc.

[0075] In this embodiment, the motor control system 100 is housed inside the casing of the motor unit 204, but is not limited to this. The motor control system 100 may be provided separately from the motor unit 204.

[0076] Battery 2 is a rechargeable battery that stores power for driving motor 1. Battery 2 is, for example, a secondary battery, but it may also be a capacitor or the like. Battery 2 is electrically connected to motor 1. Specifically, battery 2 supplies power to motor 1.

[0077] <Specific Small Motorized Bicycle> Figure 5 is a side view illustrating a specific small motorized bicycle 30 according to an embodiment. The specific small motorized bicycle 30 shown in Figure 5 does not have pedals and is a bicycle that can be driven (self-propelled) solely by the driving force of the motor 1. In other words, the specific small motorized bicycle 30 (electric bicycle 10) comprises a motor control system 100 and a motor 1 that adds driving force to propel the vehicle body 300.

[0078] The specified small motorized bicycle 30 consists of a vehicle body 300 equipped with a motor control system 100.

[0079] The vehicle body 300 includes a frame 301, a front wheel 303, a rear wheel 306, a saddle 305, a handlebar 302, a chain 308, a gear shifter, a motor unit 304, and a battery 2.

[0080] The frame 301 is the framework of the specified small motorized bicycle 30. The frame 301 is made of a metal such as aluminum alloy, iron, chromium-molybdenum steel, steel, or titanium. The frame 301 may also be made of carbon or synthetic resin.

[0081] The frame 301 has a head tube 301a, a down tube 301b, a seat tube 301c, a bottom tube 301d, and a chainstay 301e. The frame 301 may also have a suspension system.

[0082] The front fork 301f and handlebars 302 are attached to the head tube 301a so as to be able to rotate freely around an axis along the longitudinal direction of the head tube 301a. The front wheel 303 is rotatably attached to the front fork 301f. By turning the handlebars 302 left or right, the direction of the front wheel 303, which is supported by the front fork 301f, can be rotated left or right.

[0083] The down tube 301b connects the head tube 301a and the bottom tube 301d. Battery 2 is detachably attached to the down tube 301b, and motor units 304 are provided on both the down tube 301b and the bottom tube 301d.

[0084] The seat tube 301c holds the saddle 305. The saddle 305 is mounted on the seat tube 301c so as to be movable along the longitudinal direction of the seat tube 301c. The lower end of the seat tube 301c is connected to the rear end of the bottom tube 301d. In the front-to-rear direction, the seat tube 301c is located between the front wheel 303 and the rear wheel 306.

[0085] One end of the chainstay 301e is connected to the lower end of the seat tube 301c. The other end of the chainstay 301e is attached to the rear wheel 306 and the rear sprocket 307, which is linked to the axle of the rear wheel 306. A chain 308 is stretched between the rear sprocket 307 and the front sprocket 309. As a result, the rotational force of the front sprocket 309, which is rotated by the driving force generated by the motor 1, is transmitted to the rear wheel 306 via the chain 308 and the rear sprocket 307.

[0086] The front wheel 303 has a tire 303a for the vehicle body 300 to travel on. The front wheel 303 is the front wheel of two wheels arranged in the front-to-rear direction. The front wheel 303 is supported by the front fork 301f so that it can rotate around an axis along the left-to-right direction. The front wheel 303 may also receive power from the motor unit 304, and for example, a motor may be provided to provide the driving force to rotate the front wheel 303.

[0087] The rear wheel 306 has a tire 306a for the vehicle body 300 to travel on. The rear wheel 306 is the rear wheel of two wheels arranged in the front-to-back direction. The rear wheel 306 is supported so that it can rotate about an axis along the left-to-right direction. The rear wheel 306 has a rear sprocket 307. The rear sprocket 307 is connected to the front sprocket 309 via a chain 308.

[0088] The saddle 305 is the part where the user sits. The saddle 305 is movably mounted on the seat tube 301c.

[0089] The handlebars 302 change the steering angle of the specified small motorized bicycle 30, for example, when a user operates the specified small motorized bicycle 30. A pair of grips and a pair of brake levers are provided at both ends of the handlebars 302. The pair of grips are the parts that the user holds with their hands when riding in a proper posture. The pair of grips are also held with the hands when pushing or supporting the specified small motorized bicycle 30 while walking, and receive a forward pushing force. One brake lever applies a mechanical braking force to the front wheel 303 by driving the front brake device. The other brake lever applies a mechanical braking force to the rear wheel 306 by driving the rear brake device.

[0090] The chain 308 transmits the driving force output from the motor unit 304 to the rear sprocket 307 via the front sprocket 309. The chain 308 is a power transmission body such as a belt, shaft, wire, or gear.

[0091] The transmission is composed of well-known transmission mechanisms such as planetary gears and multi-stage gears, which have multiple drive force transmission paths with different gear ratios. The transmission can shift between, for example, a low gear, a medium gear, or a high gear by switching the drive force transmission paths. The transmission may be configured to switch the drive force transmission paths manually, or it may be configured to switch the drive force transmission paths electrically.

[0092] The motor unit 304 comprises a motor 1 and a motor control system 100, and is mounted on the vehicle body 300. While the structure of the motor unit 304 will not be described in detail here, like the motor unit 204 of the electric assist bicycle 20, the motor 1 and the motor control system 100 are housed in a resin or metal casing to form a unit. Therefore, in the motor unit 304, it is necessary to house the circuit board on which the various components constituting the motor control system 100 are mounted, utilizing the limited space inside the casing, thus requiring miniaturization of the circuit board.

[0093] Motor 1 provides the driving force necessary to propel the vehicle body 300. Motor 1 is powered by electricity from battery 2, based on control by motor control system 100. Motor 1 rotates the rear wheel 306 by transmitting rotational torque, which is the driving force, to the rear sprocket 307 via the front sprocket 309 and chain 308. The rotational torque is the driving force provided by motor 1.

[0094] The motor control system 100 drives the motor 1 according to the operating mode of the specified small motorized bicycle 30. For example, the motor control system 100 determines the magnitude of the driving force generated by the motor 1 based on the speed of the specified small motorized bicycle 30, etc. The motor control system 100 also supplies power from the battery 2 to the motor 1 and the headlights, etc.

[0095] In this embodiment, the motor control system 100 is housed inside the casing of the motor unit 304, but is not limited to this. The motor control system 100 may be provided separately from the motor unit 304.

[0096] Battery 2 is a rechargeable battery that stores power for driving motor 1. Battery 2 is, for example, a secondary battery, but it may also be a capacitor or the like. Battery 2 is electrically connected to motor 1. Specifically, battery 2 supplies power to motor 1.

[0097] Furthermore, the position of the motor unit 304 is not limited to the frame 301; for example, it may be located on the front wheel 303 or the rear wheel 306. In other words, the specific small motorized bicycle 30 may be configured to propel itself using a hub motor.

[0098] <Operation> The operation of the motor control system 100 according to the embodiment will be described below with reference to Figure 6. Figure 6 is a flowchart showing an example of the operation of the motor control system 100 according to the embodiment. Here, in particular, the pulse shift control by the PWM control unit 58 will be described. The PWM control unit 58 shifts the PWM signal of each switching element by correcting the voltage command value in the first half of the PWM period (i.e., the period of the carrier signal) and correcting the voltage command value in the opposite way in the second half of the PWM period. That is, in the first half of the PWM period, the pulse width is widened by correcting the voltage command value to secure the current detection period. Then, in the second half of the PWM period, the average value of the voltage command value in the PWM period is made to match the average value of the voltage command value when pulse shift control is not performed by correcting the voltage command value in the opposite way in the first half.

[0099] Here, the current detection period is the period during the first half of the PWM period (i.e., the period of the carrier signal) for sampling the detection signal (instantaneous current) idc detected by the detection resistor 4 and performing A / D (Analog to Digital) conversion. In order to accurately acquire the detection signal idc, it is preferable to sample the detection signal during the period when the ringing associated with the switching of the switching element has subsided and the current is flowing stably. For this reason, the minimum allowable value PWmin of the current detection period is set to a length that takes into account the ringing occurrence period, and is preferably about 10 μs.

[0100] In typical pulse shift control in three-phase modulation, the phase voltage of the U-phase, V-phase, and W-phase is used as a reference to correct the voltage command value of the phase with the maximum voltage (hereinafter also referred to as the "maximum voltage phase") and the voltage command value of the phase with the minimum voltage (hereinafter also referred to as the "minimum voltage phase"). In contrast, in this embodiment, the pulse shift control by the PWM control unit 58 corrects the voltage command value Vu1 of the two-phase modulated U-phase. * , V-phase voltage command value Vv1 * , and the voltage command value Vw1 for the W phase *This is performed on the following. In other words, in the pulse shift control in this embodiment, the voltage command values ​​of the non-fixed phases among the minimum voltage phase and maximum voltage phase, and the voltage command values ​​of the intermediate voltage phases are corrected with reference to a fixed phase which is either the minimum voltage phase or the maximum voltage phase.

[0101] In the following explanation, pulse shift amount d1 represents the magnitude of the shift in the voltage command value of the unfixed phase among the maximum voltage phase and minimum voltage phase. Also, in the following explanation, pulse shift amounts d2 and d3 represent the magnitude of the shift in the voltage command value of the intermediate voltage phase. Also, in the following explanation, "PWmin" represents the minimum allowable value of the current detection period (in μs). Also, in the following explanation, "Vmax" represents the voltage command value of the maximum voltage phase (in %), "Vmid" represents the voltage command value of the intermediate voltage phase (in %), and "Vmin" represents the voltage command value of the minimum voltage phase (in %).

[0102] The following describes the processing of the PWM control unit 58 during the first half (S1:Yes) of the PWM period (i.e., the period of the carrier signal). First, the PWM control unit 58 resets the pulse shift amounts d1, d2, and d3 to zero (S2). Next, the PWM control unit 58 calculates the pulse shift amount d1 using the following formula (1) (S3).

[0103] d1 = 2 * PWmin - (Vmax - Vmin) ... (1)

[0104] Then, if the pulse shift amount d1 is zero or less (S4: No), the PWM control unit 58 does not perform pulse shift control based on the pulse shift amount d1 because the difference between the voltage command value Vmax of the maximum voltage phase and the voltage command value Vmin of the minimum voltage phase is large enough to secure two current detection periods. Therefore, it performs the next step S8.

[0105] On the other hand, if the pulse shift amount d1 is greater than zero (S4:Yes), the PWM control unit 58 performs pulse shift control based on the pulse shift amount d1 because the difference between the voltage command value Vmax of the maximum voltage phase and the voltage command value Vmin of the minimum voltage phase is not large enough to secure two current detection periods. Here, if the voltage command value Vmin of the minimum voltage phase is -100%, that is, if the minimum voltage phase is a fixed phase due to two-phase modulation (S5:Yes), the PWM control unit 58 adds the pulse shift amount d1 to the voltage command value Vmax of the maximum voltage phase, which is not fixed due to two-phase modulation (S6). On the other hand, if the voltage command value Vmax of the maximum voltage phase is 100%, that is, if the maximum voltage phase is a fixed phase due to two-phase modulation (S5:No), the PWM control unit 58 subtracts the pulse shift amount d1 from the voltage command value Vmin of the minimum voltage phase, which is not fixed due to two-phase modulation (S7).

[0106] Next, the PWM control unit 58 calculates the pulse shift amount d2 using the following formula (2) (S8).

[0107] d2 = PWmin - (Vmax - Vmid) ... (2)

[0108] Furthermore, the PWM control unit 58 calculates the pulse shift amount d3 using the following formula (3) (S9).

[0109] d3 = PWmin - (Vmid - Vmin) ... (3)

[0110] Then, if the pulse shift amount d2 is zero or less (S10: No), the PWM control unit 58 does not perform pulse shift control based on the pulse shift amount d2 because the difference between the voltage command value Vmax of the maximum voltage phase and the voltage command value Vmid of the intermediate voltage phase is large enough to ensure the current detection period, and instead performs the next step S12.

[0111] On the other hand, if the pulse shift amount d2 is greater than zero (S10: Yes), the PWM control unit 58 performs pulse shift control based on the pulse shift amount d2 because the difference between the voltage command value Vmax of the maximum voltage phase and the voltage command value Vmid of the intermediate voltage phase is not large enough to secure the current detection period. Specifically, the PWM control unit 58 subtracts the pulse shift amount d2 from the voltage command value Vmid of the intermediate voltage phase (S11).

[0112] Furthermore, if the pulse shift amount d3 is zero or less (S12: No), the PWM control unit 58 does not perform pulse shift control based on the pulse shift amount d3, because the difference between the voltage command value Vmid of the intermediate voltage phase and the voltage command value Vmin of the minimum voltage phase is large enough to ensure the current detection period, and thus terminates processing in the first half of the PWM period.

[0113] On the other hand, if the pulse shift amount d3 is greater than zero (S12: Yes), the PWM control unit 58 performs pulse shift control based on the pulse shift amount d3 because the difference between the voltage command value Vmid of the intermediate voltage phase and the voltage command value Vmin of the minimum voltage phase is not large enough to secure the current detection period. Specifically, the PWM control unit 58 adds the pulse shift amount d3 to the voltage command value Vmid of the intermediate voltage phase (S13). Then, the PWM control unit 58 finishes processing in the first half of the PWM period.

[0114] Next, we will explain the processing of the PWM control unit 58 in the latter half of the PWM period (S1: No). First, if the pulse shift amount d1 is zero or less (S14: No), the PWM control unit 58 does not perform pulse shift control based on the pulse shift amount d1 in the first half of the PWM period, so it executes the next step S18 without doing anything in particular. On the other hand, if the pulse shift amount d1 is greater than zero (S14: Yes), the PWM control unit 58 performs the opposite correction to that of the first half of the PWM period, because it performed pulse shift control based on the pulse shift amount d1 in the first half of the PWM period. Here, if the voltage command value Vmin of the voltage minimum phase is -100%, that is, if the voltage minimum phase is fixed by two-phase modulation (S15: Yes), the PWM control unit 58 subtracts the pulse shift amount d1 from the voltage command value Vmax of the voltage maximum phase, which is not fixed by two-phase modulation (S16). On the other hand, if the voltage command value Vmax of the maximum voltage phase is 100%, that is, if the maximum voltage phase is fixed by two-phase modulation (S15: No), the PWM control unit 58 adds the pulse shift amount d1 to the voltage command value Vmin of the minimum voltage phase which is not fixed by two-phase modulation (S17).

[0115] Next, if the pulse shift amount d2 is zero or less (S18: No), the PWM control unit 58 does not perform any pulse shift control based on the pulse shift amount d2 in the first half of the PWM period, and therefore executes the next step S20 without doing anything in particular. On the other hand, if the pulse shift amount d2 is greater than zero (S18: Yes), the PWM control unit 58 performs the opposite correction to that of the first half of the PWM period, since it has performed pulse shift control based on the pulse shift amount d2 in the first half of the PWM period. Specifically, the PWM control unit 58 adds the pulse shift amount d2 to the voltage command value Vmid of the voltage intermediate phase (S19).

[0116] Next, if the pulse shift amount d3 is zero or less (S20: No), the PWM control unit 58 does not perform any special actions because it has not performed pulse shift control based on the pulse shift amount d3 in the first half of the PWM period, and terminates processing in the second half of the PWM period. On the other hand, if the pulse shift amount d3 is greater than zero (S20: Yes), the PWM control unit 58 performs the opposite correction to that in the first half of the PWM period because it has performed pulse shift control based on the pulse shift amount d3 in the first half of the PWM period. Specifically, the PWM control unit 58 subtracts the pulse shift amount d3 from the voltage command value Vmid of the voltage intermediate phase (S21). Then, the PWM control unit 58 terminates processing in the second half of the PWM period.

[0117] The following describes specific examples of operation by the motor control system 100 according to the embodiment, using Figures 7 and 8. Figure 7 shows an example of waveforms when the motor 1 is operating at a low speed and the inverter 3 is at low modulation (here, the rotational speed of the motor 1 is nm = 400 rpm and the q-axis current Iqm = 20 A). Figure 8 shows an example of waveforms when the motor 1 is operating at a high speed and the inverter 3 is at high modulation (here, the rotational speed of the motor 1 is nm = 2000 rpm and the q-axis current Iqm = 20 A).

[0118] Figures 7(a) and 8(a) show the voltage command values ​​Vu0 for the U, V, and W phases before two-phase modulation, respectively. * ,Vv0 * ,Vw0 * These are waveform diagrams. Figures 7(b) and 8(b) show the voltage command values ​​Vu1 for the U, V, and W phases after two-phase modulation, respectively. * ,Vv1 * VW1 * These are waveform diagrams. Figures 7(c) and 8(c) show the voltage command values ​​Vu2 for the U-phase, V-phase, and W-phase after pulse shift control has been performed, respectively. * ,Vv2 * VW2 *These are waveform diagrams. Figure 7(d) and Figure 8(d) are waveform diagrams of the six PWM signals GHu, GHv, GHw, GLu, GLv, and GLw, respectively. Figure 7(e) and Figure 8(e) are waveform diagrams of the phase currents Iu, Iv, and Iw of the U-phase, V-phase, and W-phase, respectively, as well as the detection signal idc and the inverted detection signal -idc.

[0119] In Figures 7 and 8, "CA" represents the waveform of the carrier signal. In Figures 7 and 8, the left dashed line represents the detection timing of the detection signal idc based on the timing signal SP1, and the right dashed line represents the detection timing of the detection signal idc based on the timing signal SP2.

[0120] As shown in Figure 7(a), during low-speed operation of motor 1 and low-modulation operation of inverter 3, the voltage command value Vu0 of each phase * ,Vv0 * ,Vw0 * The voltage command values ​​Vu0 of at least two phases are always small and close together. * ,Vv0 * ,Vw0 * The difference is less than or equal to a predetermined value). And in the motor control system 100 according to an embodiment that employs a method of detecting the current with one detection resistor 4, the voltage command value Vu0 of each phase is such that * ,Vv0 * ,Vw0 * Even if all of these values ​​are close to zero, it is necessary to detect the current flowing through the detection resistor 4 twice per PWM cycle, that is, when two of the three phase switching elements are turned on simultaneously, and when only one phase switching element is turned on.

[0121] In the specific example shown in Figure 7, the U phase is the phase with the lowest voltage, the V phase is the phase with the intermediate voltage, and the W phase is the phase with the highest voltage. Also, as shown in Figure 7(b), the U phase is the fixed phase due to two-phase modulation. And, as shown in Figure 7(c), the voltage command value Vw1 of the W phase, which is the phase with the highest voltage and is not the fixed phase, is controlled by pulse shift control. * It is corrected to the maximum extent and Vw2 *Furthermore, the voltage command value Vv1 of the V-phase, which is the intermediate voltage phase. * This is further corrected to Vv2 * That's how it is.

[0122] As a result, as shown in Figure 7(d), the rising edge (or falling edge) of the PWM signal for either the non-fixed phase (maximum voltage phase and minimum voltage phase in this case, the maximum voltage phase) and the intermediate voltage layer are close together. Therefore, starting from the point when these two phases of PWM signal rise (or fall), the non-fixed phase voltage phase continues for a period of at least 2 PWmin, and the intermediate voltage layer continues for a period of at least PWmin. Thus, in the PWM period, there are consecutive periods when both phases of switching elements are on simultaneously and periods when only one phase of switching element is on, and each period is guaranteed to last at least PWmin.

[0123] Here, as shown in Figure 7(e), a detection signal idc of "-Iu (=Iv+Iw)" can be detected during the period when the V-phase and W-phase switching elements are ON, and a detection signal idc of "Iw" can be detected during the period when the W-phase switching element is ON.

[0124] On the other hand, during high-speed operation of motor 1 and high-modulation operation of inverter 3, pulse shift control is not performed except when the voltage command values ​​of two of the three phases are close together. However, as shown in Figure 8(a), the voltage command values ​​Vv0 of two phases (here, V phase and W phase) * ,Vw0 * When the two phases are always small and close together (i.e., the two-phase voltage command value Vv0 * ,Vw0 * If the difference is less than or equal to a predetermined value, pulse shift control is performed as shown in Figure 7.

[0125] In the specific example shown in Figure 8, the U phase is the phase with the lowest voltage, the V phase is the phase with the highest voltage, and the W phase is the phase with the intermediate voltage. Also, as shown in Figure 8(b), the U phase is the fixed phase due to two-phase modulation. And, as shown in Figure 8(c), the voltage command value Vv1 of the V phase, which is the phase with the highest voltage and is not the fixed phase. * Vv2 remains unchanged * Therefore, the voltage command value Vw2 is the voltage command value of the W phase, which is the voltage intermediate phase. * Only Vw2 is corrected by pulse shift control. * That's how it is.

[0126] As a result, as shown in Figure 8(d), in the first half of the PWM period, the non-fixed phase voltage phase continues for a minimum of 2PWmin, and the voltage intermediate layer continues for a minimum of PWmin. Therefore, in the PWM period, there are consecutive periods in which both phase switching elements are turned on simultaneously and periods in which only one phase switching element is turned on, and each of these periods is guaranteed to last for a minimum of PWmin.

[0127] Here, as shown in Figure 8(e), a detection signal idc of "-Iu (=Iv+Iw)" can be detected during the period when the V-phase and W-phase switching elements are ON, and a detection signal idc of "Iv" can be detected during the period when the V-phase switching element is ON.

[0128] Figure 9 shows an example of a waveform at one electrical angle period. Figure 9(a) shows the voltage command values ​​Vu0 for the U, V, and W phases before two-phase modulation. * ,Vv0 * ,Vw0 * Figure 9(b) shows the waveforms of the U-phase, V-phase, and W-phase voltage Vu1 after two-phase modulation. * ,Vv1 * VW1 * This is a waveform diagram. Figure 9(c) shows the voltage command values ​​Vu2 for the U, V, and W phases after pulse shift control has been performed. * ,Vv2 * VW2 *Figure 9(d) shows the waveforms of the six PWM signals GHu, GHv, GHw, GLu, GLv, and GLw. Figure 9(e) shows the waveforms of the phase currents Iu, Iv, and Iw of the U, V, and W phases. Figure 9(f) shows the waveforms of the timing signals SP1 and SP2, and the energization mode signal Vmode. As shown in Figure 9, the motor control system 100 according to the embodiment can stably detect the two phase currents at all times, including when the motor 1 is stopped, operating at low speed, and operating at high speed, so that the control of each phase current does not break down and the current flowing through the motor 1 can be stabilized.

[0129] In other words, the motor control system 100 according to this embodiment can perform stable vector control of the motor 1 using a technique that detects the two-phase current using a single detection resistor 4, even in applications where the operating range of the motor 1 is extremely wide, such as electric assist bicycles, and during all operating times from when the motor 1 is stopped to when it is operating at high speed.

[0130] [Effects and Effects] The following describes the effects and advantages of the motor control system 100 according to the embodiment. First, the problems of electric bicycles such as electric assist bicycles or specific small motorized bicycles will be described. In other words, in such electric bicycles, if the motor unit including the motor and motor control system becomes relatively large, the maneuverability of the electric bicycle deteriorates, making it difficult to park, etc. In addition, in such electric bicycles, lowering the mounting position of the motor unit in order to ensure footing reduces the minimum ground clearance, which reduces the tipping angle and makes it easier to tip over when turning.

[0131] In contrast, the motor control system 100 according to this embodiment is equipped with only two or fewer detection resistors 4 for detecting two-phase current. Therefore, by reducing the number of current sensors (detection resistors 4), the number of auxiliary components can also be reduced, and the area of ​​the circuit board on which the current sensors and auxiliary components are mounted can be reduced, thus enabling miniaturization of the motor unit. Consequently, it is possible to improve the maneuverability of the electric bicycle and make it easier to park, etc. Furthermore, by miniaturizing the motor unit, the mounting position of the motor unit can be raised and the minimum ground clearance can be increased, which increases the tipping angle and makes it less likely for the electric bicycle to tip over when turning, thus improving safety.

[0132] Here, electric bicycles, particularly electric assist bicycles, present the following challenges. Specifically, in a bicycle, the pedal load applied by the rider does not generate driving force at the upper and lower pivot points of the crank, but the driving force is maximized when the crank is in the front-to-back position. Therefore, pedaling generates a sinusoidal driving force. On the other hand, challenges related to disturbances during bicycle operation include, for example, vibrations due to road surface conditions, vibrations due to tire condition, or vibrations due to chain condition. Furthermore, challenges during motor control include variations in current sensors due to temperature characteristics or individual characteristics.

[0133] Electric assist bicycles require motor output with an appropriate assist ratio and responsiveness to support the driving force generated by pedaling. However, when assisting this driving force with motor output, it may become difficult to maintain an appropriate motor output due to the aforementioned disturbances during bicycle operation or variations in the current sensor during motor control. If an appropriate motor output cannot be maintained, this will be affected on the pedal side, causing a change in the driving force generated by pedaling. Attempting to provide motor output assistance with an appropriate assist ratio to compensate for this changed driving force will only exacerbate further fluctuations in motor output.

[0134] Thus, in electric assist bicycles, there is a problem in that the appropriate assist ratio may not be maintained due to disturbances during bicycle operation or variations in the current sensor during motor control.

[0135] To address these challenges, the motor control system 100 according to this embodiment reduces the number of current sensors (detection resistors 4), which are a problem during motor control. This reduces the impact of variations in the current sensors during motor control, making it easier to maintain an appropriate motor output when controlling motor 1. As a result, it not only makes it easier to maintain an appropriate assist ratio for an electric assist bicycle, but also makes it easier to realize an electric assist bicycle with appropriate responsiveness and a comfortable ride.

[0136] (Other variations, etc.) Although the present disclosure has been described above based on embodiments, the present disclosure is not limited to these embodiments.

[0137] <First variation> Figure 10 is a block diagram showing the configuration of the motor control system 100A according to the first modified example. The motor control system 100A according to this modified example differs from the motor control system 100 according to the embodiment in that, as shown in Figure 10, it further includes a low-pass filter 59A and a power supply current detection unit 59B.

[0138] The low-pass filter 59A removes the high-frequency components of the detection signal idc and outputs the detection signal idc', from which the high-frequency components have been removed, to the power supply current detection unit 59B. While the low-pass filter 59A is preferably configured in hardware, it may also be configured using a combination of hardware and software.

[0139] The power supply current detection unit 59B detects the average current flowing through the DC power supply 2 based on the detection signal idc' input from the low-pass filter 59A.

[0140] In this modified example, it is possible to detect both the current flowing through the motor 1 and the current flowing through the DC power supply 2 based on the current flowing from either the positive or negative side of the DC power supply 2. Therefore, in electric bicycles 10 such as electric assist bicycles, for example, it is possible to reduce the number of parts, or simplify, miniaturize, and reduce the cost of the circuit. That is, for example, if the maximum value of the power supply current flowing through the DC power supply 2 is limited, then if the current flowing through the motor 1 is detected using two detection resistors 4, a separate power supply current detection circuit would be required. On the other hand, in this modified example, the busbar M L A single detection resistor 4 positioned in this configuration allows for the detection of the current flowing through the motor 1, and the power supply current can also be detected using the low-pass filter 59A and the power supply current detection unit 59B. Therefore, in this modified example, if the low-pass filter 59A and the power supply current detection unit 59B are implemented in software, a separate detection circuit becomes unnecessary, and the above-mentioned advantages such as a reduction in the number of components can be enjoyed.

[0141] <Second variation> Figure 11 is a block diagram showing the configuration of the motor control system 100B according to the second modified example. The motor control system 100B according to this modified example differs from the motor control system 100 according to the embodiment in that, as shown in Figure 11, it has two detection resistors 4 (a first detection resistor 41 and a second detection resistor 42) instead of one detection resistor 4. Furthermore, the motor control system 100B according to this modified example differs from the motor control system 100 according to the embodiment in that the two-phase modulation conversion unit 57 performs two-phase modulation using a so-called downward method rather than an upward method. In addition, the motor control system 100B according to this modified example differs from the motor control system 100 according to the embodiment in that the PWM control unit 58 does not perform pulse shift control.

[0142] The first detection resistor 41 and the second detection resistor 42 are connected in series to two of the following half-bridge circuits: the U-phase half-bridge circuit, the V-phase half-bridge circuit, and the W-phase half-bridge circuit. In this modified example, the first detection resistor 41 is connected in series to the source of the U-phase lower arm 32u, and the second detection resistor 42 is connected in series to the source of the V-phase lower arm 32v.

[0143] The two-phase modulation conversion unit 57 performs two-phase modulation by using a so-called lower method, setting one of the U-phase, V-phase, and W-phase as the fixed phase at every electrical angle of 2π / 3, and turning on the lower arm of the fixed phase.

[0144] Therefore, in the motor control system 100B according to this modified example, the lower arms 32u, 32v, and 32w of each phase are always in the ON state, and the current can always be detected by the first detection resistor 41 and the second detection resistor 42. In other words, in the motor control system 100B according to this modified example, the phase currents of the two phases can be detected by the first detection resistor 41 and the second detection resistor 42 at any time, whether the motor 1 is stopped, operating at low speed, or operating at high speed.

[0145] In the motor control system 100B according to this modified example, as described above, the two-phase currents can always be detected by the first detection resistor 41 and the second detection resistor 42, so it is not necessary to perform pulse shift control as in the motor control system 100 according to the embodiment. However, in order to stably detect the two-phase currents, it is preferable to ensure that the minimum ON width of each of the lower arms 32u, 32v, and 32w is at least a predetermined length (for example, 3 μs).

[0146] As described above, the motor control system 100B according to this modified example has two detection resistors 4, so compared to a configuration with three detection resistors to detect the current of each phase, the number of current sensors (detection resistors 4), which is a challenge during motor control, is reduced, and the influence of variations in the current sensors during motor control can be reduced, which has the advantage of making it easier to maintain an appropriate motor output when controlling the motor 1.

[0147] In addition, the motor control system 100B according to this modified example may employ, for example, spatial vector modulation or third-harmonic superposition instead of two-phase modulation. In this case as well, it is possible to detect the two-phase currents using the first detection resistor 41 and the second detection resistor 42.

[0148] <Other variations> In the above embodiment, a detection resistor 4 is used as the current sensor, but the embodiment is not limited to this. For example, if miniaturization of the substrate area in the motor units 204 and 304 is not a priority, a current transformer may be used as the current sensor instead of the detection resistor 4.

[0149] Furthermore, the motor control system 100 and the processing units used in the electric bicycle 10 according to the above embodiment are typically implemented as LSIs, which are integrated circuits. These may be individually integrated into a single chip, or some or all of them may be integrated into a single chip.

[0150] Furthermore, integrated circuit implementation is not limited to LSIs; it may also be achieved using dedicated circuits or general-purpose processors. Field-Programmable Gate Arrays (FPGAs), which can be programmed after LSI manufacturing, or reconfigurable processors, which allow for the reconfiguration of the connections and settings of circuit cells within the LSI, may also be used.

[0151] In each of the above embodiments, each component may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may also be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0152] Furthermore, all figures used above are illustrative to illustrate the present disclosure, and the embodiments of this disclosure are not limited to the figures exemplified.

[0153] Furthermore, the division of functional blocks in the block diagram is just one example; multiple functional blocks can be implemented as a single functional block, a single functional block can be divided into multiple parts, or some functions can be moved to other functional blocks. In addition, the functions of multiple functional blocks with similar functions can be processed in parallel or time-sharing by a single piece of hardware or software.

[0154] Furthermore, the order in which each step in the flowchart is performed is illustrative for the purpose of specifically illustrating this disclosure, and may be in a different order. Also, some of the above steps may be performed simultaneously (in parallel) with other steps.

[0155] Furthermore, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of the embodiments without departing from the spirit of this disclosure.

[0156] (summary) As described above, the motor control systems 100, 100A, and 100B according to the first embodiment are motor control systems that vector-control a motor 1 that generates a driving force to propel the electric bicycle 10 in the forward direction. The motor control systems 100, 100A, and 100B include an inverter 3 that converts a DC current from a DC power supply 2 into an AC current and supplies it to the motor 1, two or fewer detection resistors 4 for detecting the current of two of the three phases of current flowing through the motor 1, and a control unit 5 that controls the inverter 3 based on the two or fewer phases of current detected by the two or fewer detection resistors 4.

[0157] According to this, reducing the number of detection resistors 4 reduces the influence of variations in the current sensor (detection resistor 4) during motor control, which has the advantage of making it easier to maintain an appropriate motor output when controlling motor 1.

[0158] Furthermore, in the motor control systems 100 and 100A according to the second embodiment, in the first embodiment, two or fewer detection resistors 4 are connected to the wire (busbar M) that connects the DC power supply 2 and the inverter 3. L This is a single detection resistor 4 provided in ).

[0159] According to this, compared to the case where there are two detection resistors 4, the number of detection resistors 4 is further reduced, which has the advantage of further reducing the effect of variations in the current sensor (detection resistor 4) during motor control, and making it easier to maintain an appropriate motor output when controlling motor 1.

[0160] Furthermore, in the motor control systems 100 and 100A according to the third embodiment, in the second embodiment, the inverter 3 has three half-bridge circuits corresponding to each of the three phases, and each of the three half-bridge circuits has a pair of switching elements. The motor control systems 100 and 100A further include a PWM control unit 58 that provides PWM signals (six PWM signals GHu, GLu, GHv, GLv, GHw, GLw) to each control terminal (gate) of all the switching elements (six switching elements 31u, 32u, 31v, 32v, 31w, 32w) of the inverter 3 to turn the corresponding switching element on / off. The PWM control unit 58 generates a PWM signal for each of all the switching elements based on a voltage command value which is the target value of the voltage applied to the motor 1 and a carrier signal which is a reference triangular wave. Furthermore, if the difference in voltage command values ​​of at least two of the three phases is less than or equal to a predetermined value, the PWM control unit 58 corrects the voltage command values ​​of at least two phases to increase them in the first half of the PWM period, and corrects the voltage command values ​​of at least two phases to the opposite extent in the second half of the PWM period.

[0161] According to this, the two-phase current can be stably detected when the motor 1 is stopped, operating at low speed, or operating at high speed. As a result, the control of each phase current does not break down, and the current flowing through the motor 1 can be stabilized.

[0162] Furthermore, in the motor control systems 100 and 100A according to the fourth embodiment, the third embodiment further includes a two-phase modulation conversion unit 57 that converts the voltage command values ​​of each of the three phases by two-phase modulation, in which one of the three phases is designated as a fixed phase and one of the pair of switching elements corresponding to the fixed phase is turned on, and outputs the result to the PWM control unit 58.

[0163] According to this, the two-phase current can be detected more stably when the motor 1 is stopped, operating at low speed, or operating at high speed. As a result, the control of each phase current does not break down, and the current flowing through the motor 1 can be further stabilized.

[0164] Furthermore, the motor control system 100A according to the fifth embodiment further includes a power supply current detection unit 59B that detects the average current of the current flowing through the DC power supply 2 based on the current flowing through one detection resistor 4, in any one of the second to fourth embodiments.

[0165] This method has the advantage of being able to detect both the current flowing through motor 1 and the current flowing through DC power supply 2 based on the current flowing from either the positive or negative terminal of DC power supply 2.

[0166] Furthermore, the motor control systems 100 and 100A according to the sixth embodiment further include a noise suppression element (capacitor C1) provided between the DC power supply 2 and the inverter 3 in any one of the second to fourth embodiments.

[0167] According to this, there is an advantage in that the two-phase current can be detected more stably by removing noise that may flow into one detection resistor 4. Another advantage is that the number of noise reduction elements can be reduced compared to the case where two detection resistors 4 are provided.

[0168] Furthermore, the electric bicycle 10 according to the seventh embodiment comprises a motor control system 100, 100A, 100B according to any one of the first to sixth embodiments, and a motor 1 that adds driving force to propel the vehicle body 200 by the motor control systems 100, 100A, 100B.

[0169] According to this, there is an advantage in that it is easier to maintain an appropriate motor output when controlling motor 1. [Explanation of Symbols]

[0170] 100, 100A, 100B Motor Control System 1 motor 2. DC power supply (battery) 3 Inverter 10 Electric bicycles 4. Detection Resistance 5. Control Unit 57 Two-phase modulation conversion section 58 PWM control unit 59B Power supply current detection unit C1 Capacitor (noise reduction element)

Claims

1. A motor control system that vector-controls a motor that generates driving force to propel an electric bicycle forward, An inverter that converts a DC current from a DC power supply into an AC current and supplies it to the motor, Two or fewer detection resistors for detecting the current of two of the three phases of current flowing through the motor, The system includes a control unit that controls the inverter based on the two-phase current detected by the two or fewer detection resistors, The two or fewer detection resistors mentioned above are one detection resistor provided in the wire connecting the DC power supply and the inverter. The inverter has three half-bridge circuits, each corresponding to one of the three phases. Each of the three half-bridge circuits has a pair of switching elements, The control unit, The inverter includes a PWM control unit that provides a PWM signal to each control terminal of all the switching elements to turn the corresponding switching element on or off. The PWM control unit generates the PWM signal for each of the switching elements based on a voltage command value which is the target voltage to be applied to the motor and a carrier signal which is a reference triangular wave. The PWM control unit, when the difference in the voltage command values ​​of at least two of the three phases is less than or equal to a predetermined value, corrects the difference in the voltage command values ​​of at least two phases to be larger in the first half of the PWM cycle, and corrects the voltage command values ​​of at least two phases to the opposite extent in the second half of the PWM cycle compared to the first half. The control unit, The system further includes a two-phase modulation conversion unit that converts the voltage command value of each of the three phases by two-phase modulation, in which one of the three phases is designated as a fixed phase and one of the pair of switching elements corresponding to the fixed phase is turned on, and outputs the result to the PWM control unit. The fixed phase is either the minimum voltage phase or the maximum voltage phase among the three phases. The voltage command value corrected by the PWM control unit includes the voltage command value of the phase that is not the fixed phase among the minimum voltage phase and the maximum voltage phase, and the voltage command value of the intermediate voltage phase where the voltage is in the middle. The PWM control unit, when the minimum allowable value of the current detection period is PWmin, the voltage command value of the maximum voltage phase is Vmax, the voltage command value of the intermediate voltage phase is Vmid, and the voltage command value of the minimum voltage phase is Vmin, The first pulse shift amount d1 is calculated by d1 = 2 * PWmin - (Vmax - Vmin), The second pulse shift amount d2 is calculated using the formula d2 = PWmin - (Vmax - Vmid), The third pulse shift amount d3 is calculated using the formula d3 = PWmin - (Vmid - Vmin), In the first half of the aforementioned PWM period, If the first pulse shift amount d1 is greater than zero, and the lowest voltage phase is the fixed phase, the first pulse shift amount d1 is added to the voltage command value of the highest voltage phase; if the highest voltage phase is the fixed phase, the first pulse shift amount d1 is subtracted from the voltage command value of the lowest voltage phase. If the second pulse shift amount d2 is greater than zero, the second pulse shift amount d2 is subtracted from the voltage command value of the intermediate phase of the voltage. If the third pulse shift amount d3 is greater than zero, the third pulse shift amount d3 is added to the voltage command value of the intermediate voltage phase. Motor control system.

2. The system further includes a power supply current detection unit that detects the average current flowing through the DC power supply based on the current flowing through one of the detection resistors. The motor control system according to claim 1.

3. The system further includes a noise reduction element provided between the DC power supply and the inverter. The motor control system according to claim 1.

4. A motor control system according to any one of claims 1 to 3, The motor, which adds a driving force to the vehicle body via the motor control system, is provided. Electric bicycle.

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