JP6054645B2 - Electric assist vehicle - Google Patents

Description

  The present invention relates to an electric assist vehicle that assists a driving force by an electric motor with respect to a driving force by human power.

  An example of the electrically assisted vehicle is an electrically assisted bicycle. In recent years, the power-assisted bicycle has been spread as a means of transportation due to its convenience, along with an increase in health consciousness and environmental awareness.

  In the electrically assisted bicycle, when a person steps on the pedal, the pedaling force is detected as a pedaling torque by a torque sensor, and an auxiliary torque for assisting the pedaling torque is generated by the motor based on this detection.

  Therefore, the electric assist bicycle is driven by a torque obtained by combining the pedaling torque and the auxiliary torque, and can travel without giving an excessive load to a person even when climbing or headwind, so that human power can be reduced. .

JP 2004-345400 A JP 2011-168241 A JP 2011-178341 A

  In the case of the electric assist bicycle as described above, a magnetostrictive torque sensor is generally used as a torque sensor. This magnetostrictive torque sensor is composed of a magnetostrictive material having a magnetostrictive effect and a detection coil, and uses the property that the permeability changes when stress is applied to the magnetostrictive material.

  Therefore, when the pedaling force is applied to the magnetostrictive material, the magnetic permeability of the magnetostrictive material changes, and this change is detected by the detection coil. That is, when a large pedal force is applied to the magnetostrictive material, the detected waveform becomes large, and when a small pedal force is applied, the detected waveform becomes small. The pedaling torque is detected by the change in the detected waveform.

  Such a magnetostrictive torque sensor requires a magnetostrictive material and a detection coil, and requires a signal processing circuit for supplying an excitation signal to the detection coil, which may increase the cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrically assisted vehicle capable of avoiding an increase in cost by estimating torque due to human power without using a torque sensor. To do.

The electrically assisted vehicle according to claim 1 is a vehicle that assists the driving force by the electric motor with the driving force by human power, the human power torque estimating means for estimating the torque by human power from the driving state of the electric motor, and the human power Motor control means having motor torque calculation means for calculating drive torque by the electric motor based on the output from the torque estimation means, and the human power torque estimation means uses a disturbance observer to estimate the torque by human power. When viewed from the electric motor, a disturbance torque as a force applied from the outside of the electric motor is estimated .

  The electrically assisted vehicle is not limited to the electrically assisted bicycle. The present invention can be applied to a vehicle that assists driving force by human power by electric drive, and can be applied to, for example, a wheelchair or a luggage carrier.

  The driving state of the electric motor is grasped by detecting, for example, the voltage or angular velocity of the electric motor as a detection element. However, this detection element is not particularly limited.

The motor control means is preferably configured around a microcomputer, but may be configured using a DSP (digital signal processor) or the like, and the configuration is not particularly limited.
According to this invention, it is possible to estimate the torque due to human power without using a torque sensor.

The electrically assisted vehicle according to claim 2 is the electrically assisted vehicle according to claim 1 , wherein the human power torque estimating means detects a voltage of at least an electric motor to estimate a torque due to human power. .

The electrically assisted vehicle according to claim 3 is the electrically assisted vehicle according to claim 1 or 2 , wherein the human torque estimating means calculates a running load torque from an estimated value of torque by human power for the immediately preceding rotation. , And the torque by instantaneous human power is estimated from the difference between the estimated value of the disturbance torque and the estimated value of the running load torque.
According to this invention, the increase or decrease in torque due to human power is reflected in a timely manner with little delay.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the electrically assisted vehicle which can avoid that cost becomes high by estimating the torque by human power, without using a torque sensor.

1 is a system configuration diagram showing an electrically assisted bicycle according to an embodiment of the present invention. It is a control block block diagram of the same electrically assisted bicycle. It is a block diagram which shows control of the electric motor in the electric assist bicycle. It is explanatory drawing which shows the calculation flow which estimates the pedaling torque in the same electrically assisted bicycle. It is a graph which shows the relationship between the pedaling torque and crank angle in the same electrically assisted bicycle. In the same electrically assisted bicycle, a simulation result of an estimated pedaling torque is shown and is a graph showing a vehicle speed. FIG. 6 is a graph showing a simulation result of an estimated pedaling torque in the electric assist bicycle, and showing a fluctuation state of the pedaling torque. It is a graph which shows the assist ratio by an electric motor.

Hereinafter, an electrically assisted vehicle according to an embodiment of the present invention will be described with reference to FIGS. 1 to 8. FIG. 1 is a system configuration diagram illustrating an electric assist bicycle as an electric assist vehicle, FIG. 2 is a control block configuration diagram of the electric assist bicycle, and FIG. 3 is a configuration diagram illustrating control of an electric motor. 4 shows a calculation flow for estimating pedaling torque, FIG. 5 shows the relationship between pedaling torque and crank angle, and FIGS. 6 and 7 show simulation results of the estimated pedaling torque. FIG. 8 shows the assist ratio by the electric motor.

  As shown in FIG. 1, the electrically assisted bicycle 1 includes a frame 2, a front wheel 3, a rear wheel 4, an electric motor 5, a motor controller 6 as motor control means, and a battery 7.

  The frame 2 is configured by connecting a head tube 21, a seat tube 22, and a down tube 23. The head tube 21 is a member that is positioned at the front portion and extends in the vertical direction, and a down tube 23 that extends obliquely downward from the middle portion of the head tube 21 is connected to the head tube 21. A seat tube 22 extending in the vertical direction is connected to the rear end portion of the down tube 23.

A pair of front forks 24 extending downward is connected to the lower end portion of the head tube 21, and a handle 26 is rotatably held at the upper end portion via a handle stem 25. A seat post 28 having a saddle 27 is attached to the upper end of the seat tube 22 so that the vertical position can be adjusted.
The front wheel 3 is pivotally supported at the lower end of the front fork 24 and can be steered by operating the handle 26.

  The rear wheel 4 is supported by a pair of seat stays 41 that extend obliquely downward from the upper end of the seat tube 22 toward the rear, and a pair of rear stays 42 that extend rearward from the lower end of the seat tube 22.

  A crank 44 having a pedal 43 is disposed at the lower end of the seat tube 22. The pedal depression force by the driver riding on the electrically assisted bicycle 1 is transmitted to the crank 44, whereby the crank 44 can be rotated. This rotational driving force is transmitted to the rear wheel 4 by the chain 45.

  The electric motor 5 is a brushless DC motor and has an IPMSM (interior permanent magnet synchronous motor) structure in which a permanent magnet is embedded in a rotor, and is of a direct drive system incorporated in a hub of the front wheel 3. . The electric motor 5 functions as an auxiliary torque (assist torque) generation source.

  The electric motor 5 may be an inner rotor type or an outer rotor type, and can be appropriately employed. Further, the position of the electric motor 5 may be incorporated in the hub of the rear wheel 4, and may be a center mount system positioned near the crank 44.

  The motor controller 6 includes a circuit board and electronic components such as a microcomputer and an IC mounted on the circuit board. The motor controller 6 is housed in a box-like case and disposed on the lower surface side of the pair of rear stays 42. The motor controller 6 has a function of controlling the motor 5 as a whole.

  The battery 7 is a rechargeable secondary battery such as a nickel metal hydride battery or a lithium ion battery. The battery 7 is housed in a battery case that is detachably attached to the rear surface of the seat tube 22. The battery 7 is connected to the motor 5 and the motor controller 6 and supplies power to them.

  Next, an outline of a control block configuration of the electrically assisted bicycle 1 will be described with reference to FIGS. 2 and 3. FIG. 2 mainly shows the flow of the driving force, and FIG. 3 shows the control configuration of the electric motor 5.

As shown in FIG. 2, the pedaling force by the driver of the electrically assisted bicycle 1 is transmitted to the rear wheel 4 as the pedaling torque τ _man through the crank 44. On the other hand, the motor torque τ _motor that assists the pedal depression force is transmitted to the front wheels 3 from the motor 5 that is supplied with electric power from the battery 7 and controlled by the motor controller 6. In this case, the motor torque τ _motor is determined based on the pedaling torque τ _man , and the assist force acts.

Therefore, the pedaling force due to human power is reduced by the torque (τ _man + τ _motor ) obtained by combining the pedaling torque τ _man and the motor torque τ _motor, and the electrically assisted bicycle 1 travels.

In the present embodiment, a detection mechanism such as a torque sensor for detecting the pedaling torque τ _man is not provided. Therefore, the pedaling torque τ _man is estimated and determined from the driving state of the electric motor 5 by the motor controller 6 as described later.

  As shown in FIG. 3, the control configuration of the electric motor 5 includes an electric motor 5, an inverter circuit 51 that drives the electric motor 5, a motor controller 6 as a motor control unit that is configured around a microcomputer, And an output transistor control circuit 52 as a drive signal generation circuit system. A motor drive state detection circuit 55 is connected between the electric motor 5 and the motor controller 6.

  The electric motor 5 has a U-phase, V-phase, and W-phase, which are three-phase windings, and includes a rotor 53 having a structure in which a permanent magnet is embedded, and a Hall IC 54 that detects the rotational position of the rotor 53.

  The inverter circuit 51 is bridge-connected using a plurality of switching elements of transistors Q1 to Q6, for example, IGBTs. This switching element is driven by a pulse width modulated (PWM) signal output from the output transistor control circuit 52, that is, a drive signal.

  The output transistor control circuit 52 is connected to the motor controller 6 and is driven under the control of the motor controller 6. Furthermore, the electric motor 5 is connected to the motor controller 6. In addition, a battery 7 and a smoothing capacitor C that supply power to the electric motor 5 are connected between both ends of the inverter circuit 51.

In such a configuration, the current from the battery 7 is switched by the transistors Q1 to Q6 in the block of the inverter circuit 51 based on the output signal from the motor controller 6, and the U phase and V phase which are the windings of the electric motor 5 are switched. The rotor 53 is driven to rotate by generating a motor torque τ _motor . For example, when the transistors Q1 and Q6 are turned on and the others are turned off, a current flows from the U phase to the V phase of the winding, and the U phase and the V phase are excited.

  The motor drive state detection circuit 55 has a function of detecting the drive state of the electric motor 5, detects the voltage V, current I and angular velocity ω of the electric motor 5, and converts these values into digital value signals. And sent to the motor controller 6.

  The motor controller 6 is mainly composed of a microcomputer, and executes various controls according to an operation program stored in the memory. The motor controller 6 includes state detection means 61, human torque estimation means 62, motor torque calculation means 63, and motor torque output means 64.

The state detection means 6 receives the information sent from the motor drive state detection circuit 55. In the present embodiment, the received information includes the voltage V and the angular velocity ω of the electric motor 5, specifically, the voltage V (V _q ) of the armature winding and the angular velocity ω of the rotor 53. The state detection unit 6 transmits the received information to the human power torque estimation unit 62.

The manpower torque estimating means 62 is a pedaling torque estimating means, and calculates and estimates the pedaling torque using the information on the voltage V and the angular velocity ω of the electric motor 5 transmitted from the state detecting means 6. Then, the estimated pedaling torque τ _man is output to the motor torque calculating means 63.

The motor torque calculation means 63 is a means for calculating the motor torque τ _motor as the assist torque, and the motor torque τ _motor is calculated and determined based on the value of the pedaling torque τ _man transmitted from the human power torque estimation means 62. The In this calculation, a predetermined calculation formula is used with reference to a traveling speed (vehicle speed) and a coefficient stored in the memory. The calculated motor torque τ _motor is sent to the motor torque output means 64.

The motor torque output means 64 creates the motor torque τ _motor transmitted from the motor torque calculation means 63 as a motor torque command and sends it to the output transistor control circuit 52. Therefore, the output transistor control circuit 52 drives the inverter circuit 51 according to the motor torque command, and the electric motor 5 is driven with the motor torque τ _motor based on the motor torque command.
Next, operations of the manpower torque estimating means 62 and the motor torque calculating means 63 will be described with reference to FIGS.

First, the operation of the human power torque estimating means 62 will be described. The human torque estimating means 62 estimates the pedaling torque τ _man and also estimates its instantaneous value. For this reason, as shown in FIG. 4, the following arithmetic expression is used to derive the estimation result.
First, a steady state circuit equation of the motor, that is, a voltage equation is expressed by Equations (1) and (2), an equation of motion is expressed by Equation (3), and a torque equation is expressed by Equation (4).

式（４）の右辺第１項は、磁石のトルクであり、第２項は、リラクタンストルクである。

The first term on the right side of Equation (4) is the torque of the magnet, and the second term is the reluctance torque.

Here, in the above equation, V _d is the d-axis voltage of the armature winding, V _q is the q-axis voltage of the armature winding, R is the resistance of the armature winding, and L _d is the d-axis of the armature winding. Inductance, L _q is q-axis inductance of armature winding, P is differential operator d / dt, I _d is d-axis current of armature winding, I _q is q-axis current of armature winding, p is pole Logarithm, ω is the angular velocity of the rotor, Ψ is the permanent magnet field (linkage magnetic flux), J is the moment of inertia of the rotor, τ _motor is the torque generated by the motor (> 0), τ _man is the pedaling torque of the person (> 0), τ _load is a running load torque (> 0), and τ _dis described later is a disturbance torque viewed from the motor.

Then, for the sake of simplicity, assuming that the electrical time constant is sufficiently short, and I _d = 0 and L _d = L _q , the voltage equation, the equation of motion and the torque equation are expressed by the following equations.

τ_dis＝τ_load−τ_man、Ｋ＝ｐΨとおいて上式を整理すると、制御対象モデルは、式（７）で表わされる。

When the above equation is arranged with τ _dis = τ _load −τ _man and K = pΨ, the controlled object model is expressed by equation (7).

この制御対象モデルを用いて、外乱トルクτ_disを推定するため、外乱オブザーバを構築する（式（８））。

Using this controlled object model, a disturbance observer is constructed in order to estimate the disturbance torque τ _dis (formula (8)).

g is a disturbance observer gain (disturbance estimation cutoff angular frequency), and is set sufficiently large. τ _dis is an estimated value (function of time t) of disturbance torque as seen from the motor. That is, τ _dis is a disturbance torque as a force applied from the outside of the motor when viewed from the motor, and is a full load torque. Accordingly, the full load torque includes the traveling load torque τ _load and the pedaling torque τ _man . S represents Laplace transform.

In the disturbance observer, the instantaneous value of the disturbance torque τ _dis can be estimated as shown in Expression (9). The disturbance torque τ _dis is an estimated value (a function of the crank angle θ) of the disturbance torque viewed from the motor, and is stored in the memory as a function of the crank angle θ described later.

Since the estimated value of the disturbance torque τ _dis as described above includes the running load torque τ _load and the human pedaling torque τ _man , it is necessary to separate and extract the human pedaling torque τ _man from here. . The human pedaling torque τ _man is usually a periodic function of two cycles as shown in FIG. 5 with respect to the crank angle θ.

FIG. 5 is a graph showing the relationship between the pedaling torque τ _man and the crank angle θ. The vertical axis represents torque (N · m), and the horizontal axis represents crank angle (θ). Further, the rotational position of the crank 44 corresponding to the crank angle is shown in the upper part of the graph.

When the electrically assisted bicycle 1 travels, for example, when a pedal depression force is applied to one pedal 43, the crank 44 rotates in the clockwise direction. The magnitude of the pedaling torque τ _man becomes substantially 0 when one pedal 43 reaches the top dead center or the bottom dead center, that is, when the crank angle θ is 0 degree or 180 degrees, and the crank angle θ is 90 It tends to be substantially maximum when the angle is 270 degrees.
Therefore, a torque component having a cycle twice the crank angle θ can be extracted by performing the following calculation.

Τ _man obtained in equation (12) represents an approximate estimated value of pedaling torque estimated from the previous crank angle of 360 degrees (one rotation). Therefore, it is possible to estimate the pedaling torque τ _man using the equation (12) and to determine the motor torque τ _motor based on this.

However, this estimate, just before since pedaling torque tau _man is estimated from the crank angle one rotation of the case or the like suddenly increased pedaling torque tau _man during travel, the increase in the estimated value immediately Not reflected. For this reason, it is preferable that the increase is reflected in the estimated value in a timely manner.

Therefore, by further development of the estimation, the running load, for example, inclined, air resistance of the road surface is assumed to not rapidly change, the following equation immediately before a crank angle one rotation of the pedaling torque tau _man of The running load torque τ _load is estimated from the estimated value, and the instantaneous pedaling torque τ _man is estimated from the difference between the estimated value of the disturbance torque τ _{dis and} the estimated value of the running load torque τ _load .
The average running load torque τ _load for the immediately preceding crank angle of one rotation is obtained as shown in Equation (13).

この走行負荷トルクτ_loadは、直前のクランク角３６０度分（１回転分）から推定した走行負荷トルクの近似推定値（平均値）を表わしている。
そして、式（１４）によって、瞬時のペダリングトルクτ_manを推定する。

This traveling load torque τ _load represents an approximate estimated value (average value) of the traveling load torque estimated from the crank angle of 360 degrees (one rotation) immediately before.
Then, the instantaneous pedaling torque τ _man is estimated by the equation (14).

A simulation was performed based on the instantaneous pedaling torque τ _man thus estimated. The results will be described with reference to FIGS. The figure shows a state when the bicycle is run without assistance by the motor, FIG. 6 shows the vehicle speed, and FIG. 7 shows the pedaling torque τ _man .
In FIG. 6, the vertical axis represents speed (km / h) and the horizontal axis represents time (s). A state in which the speed gradually increases from the start is shown.

In FIG. 7, the vertical axis represents pedaling torque τ _man (N · m), and the horizontal axis represents time (s). Further, the actual pedaling torque τ _man is indicated by a broken line, and the pedaling torque τ _man estimated above is indicated by a solid line. Further, the traveling load torque τ _load is indicated by a one-dot chain line.

FIG. 7 shows the state of the pedaling torque τ _man corresponding to FIG. 6, and the actual pedaling torque τ _man is increased at the time t = 3 (s), but this fluctuation is estimated with almost no error. It can be seen that the pedaling torque τ _man follows and is estimated stably with good accuracy.

Using the equation (14) derived as described above, the manpower torque estimating means 62 estimates the instantaneous pedaling torque τ _man . The estimated value is sent to the motor torque calculation means 63.

Specifically, an arithmetic expression necessary for the processing is stored in the memory, and the human torque estimating unit 62 transmits the q-axis voltage V _q and the rotation of the armature winding of the electric motor 5 transmitted from the state detecting unit 6. The disturbance torque τ _dis is estimated by the disturbance observer using information on the driving state of the angular velocity ω of the child 53, and finally the instantaneous pedaling torque τ _man is estimated.

Next, the operation of the motor torque calculation means 63 will be described. The motor torque calculation means 63 calculates and determines the motor torque τ _motor based on the estimated value of the instantaneous pedaling torque τ _man transmitted from the human power torque estimation means 62.

  Specifically, it is determined with reference to the traveling speed and coefficient (assist ratio) stored in the memory. As shown in FIG. 8, the upper limit value of the motor torque as the assist torque in the electrically assisted bicycle is defined by regulations such as the Road Traffic Act.

  FIG. 8 is a graph showing the assist ratio by the electric motor, in which the vertical axis shows the output ratio and the horizontal axis shows the traveling speed (km / h). Further, the transmission relationship of the driving force in the electrically assisted bicycle is shown corresponding to the graph.

  By convention, the magnitude of human power (crank rotation output (pedaling torque)) and motor power (drive assist output (motor torque)) is 1: 2, and in terms of ratio, the motor power is up to about 67%. Is allowed. However, this ratio can be applied only when the traveling speed is up to 10 km / h.

Further, it is stipulated that the motor force is gradually decreased from 10 km / h to 24 km / h, and the motor force is reduced to 0 when the traveling speed reaches 24 km / h.
Therefore, the running speed and the coefficient are stored in the memory so that the motor torque τ _motor is determined within such a prescribed range.

When the electrically assisted bicycle 1 configured as described above is operated, the driving state of the electric motor 5 is grasped by detecting the voltage V and the angular velocity ω of the electric motor 5, and the instantaneous pedaling torque τ _man is estimated to estimate the motor. Torque τ _motor is determined.

Therefore, the pedaling force due to human power is reduced by the combined torque of the pedaling torque τ _man and the motor torque τ _motor that assists the pedaling torque τ _man, and a comfortable running performance can be obtained.

In addition, when applying the technique for estimating the magnetic pole position of the rotor 53 without using the Hall IC 54, the angular velocity ω can be estimated and obtained. Therefore, in this case, when estimating the pedaling torque τ _man , it is not necessary to detect the angular velocity ω, and the driving state of the electric motor 5 is grasped by detecting the voltage V of the electric motor 5. .

As described above, according to the present embodiment, the torque due to human power, that is, the pedaling torque τ _man is estimated from the driving state of the electric motor 5, so that a torque sensor or the like for detecting the pedaling torque τ _man is omitted. It is possible to avoid an increase in cost.

Further, since the disturbance torque τ _dis is estimated by the disturbance observer when estimating the pedaling torque τ _man , it is possible to estimate a disturbance state quantity that is difficult to detect.

Further, since the estimated pedaling torque τ _man is an instantaneous value, an increase or decrease in the pedaling torque τ _man is reflected in a timely manner with little delay, and an appropriate traveling state can be realized.
Furthermore, an electrically assisted bicycle can be configured by replacing the front wheel of a normal bicycle with a wheel with a motor incorporating the motor control device of the above embodiment.

  In addition, this invention is not limited to the structure of the said embodiment, A various deformation | transformation is possible in the range which does not deviate from the summary of invention. Moreover, the said embodiment is shown as an example and is not intending limiting the range of invention.

  For example, in the above-described embodiment, an electrically assisted bicycle has been described as an example. However, the present invention is not limited to this, and the present invention can be applied to various vehicles that electrically assist driving force by human power. It can be applied to human-powered wheelchairs, luggage carriers, three-wheeled and four-wheeled vehicles, fitness equipment and the like.

1 ... Electric assist vehicle (electric assist bicycle)
2 ... Frame 3 ... Front wheel 4 ... Rear wheel 5 ... Electric motor 6 ... Motor control means (motor controller)
7 ... Battery 51 ... Inverter circuit 52 ... Output transistor control circuit 53 ... Rotor 54 ... Hall IC
55 ... Motor drive state detection circuit 61 ... State detection means 62 ... Human power torque estimation means 63 ... Motor torque calculation means 64 ... Motor torque output means

Claims (3)

A vehicle that assists a driving force by an electric motor to a driving force by human power,
Comprising the manpower torque estimating means for estimating the torque by human power from the drive state of the electric motor, the motor control means and a motor torque calculation means for calculating a driving torque by the electric motor based on an output from the manpower torque estimating means ,
The human power torque estimating means estimates a disturbance torque as a force applied from the outside of the electric motor when viewed from the electric motor by a disturbance observer when estimating the torque due to the human power . The electrically assisted vehicle according to claim 1 , wherein the human power torque estimating means estimates a torque due to human power by detecting at least a voltage of the electric motor. The human torque estimation means estimates the running load torque from the estimated value of torque due to human power for one rotation immediately before, and calculates the torque due to instantaneous human power from the difference between the estimated value of disturbance torque and the estimated value of running load torque. The electrically assisted vehicle according to claim 1 , wherein the electrically assisted vehicle is estimated.

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