JP3810130B2 - Vehicle with electric motor and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a vehicle with an electric motor in which a human power drive system and an electric drive system are provided in parallel, and the output of the electric drive system is controlled in response to a change in the output of the human power drive system, and a control method used therefor, It is about.
[0002]
[Prior art]
A vehicle such as a bicycle that detects a driving force by human power from, for example, a pedaling force and controls an output of an electric motor in response to a change in the pedaling force is known (Japanese Patent Laid-Open No. 50-125438, Japanese Utility Model Laid-Open No. 56-76590). No. 2, JP-A-2-74491). In other words, when the burden of human power is large, the driving force of the electric motor is also increased to reduce the burden of human power, so that the vehicle can travel easily.
[0003]
[Problems of the prior art]
In this type of vehicle, it is conceivable to add a transmission with a variable reduction ratio to the human power drive system.
[0004]
In this case, there are a method of providing a transmission on the downstream side (drive wheel side) from the resultant force point of the output of the human power drive system and the output of the electric motor, and a method of providing a transmission upstream of the resultant force point. It is done. According to the system in which the transmission is interposed downstream from the former resultant force point, the ratio of the pedaling force torque and the electric motor torque does not change even if the transmission gear ratio changes. Therefore, there is no inconvenience because even if the speed reduction ratio of the transmission changes, only the vehicle speed changes and the burden ratio of the pedal effort does not change.
[0005]
However, in the system in which the transmission is interposed upstream from the latter resultant force point, there arises a problem that the burden of the pedaling force changes depending on the transmission gear ratio. For example, when the transmission is at a high speed (the reduction ratio is small), the pedal force torque increases, and the motor torque increases accordingly. However, since the reduction ratio between the motor and the drive wheels is fixed, the drive torque of the drive wheels Will increase. For this reason, the ratio of the driving torque by the motor to the driving torque due to the pedaling force (motor assist rate) increases.
[0006]
On the contrary, when the transmission is at a low speed (the reduction ratio is large), the pedaling force torque is reduced, and the motor torque is also reduced accordingly. For this reason, since the driving torque of the driving wheel is also reduced, the motor assist rate is reduced . Thus because auxiliary index for pressing torque of the motor due to the shifting operation of the transmission is changed, a problem that desirable drive feeling can not be obtained.
[0007]
OBJECT OF THE INVENTION
The present invention has been made in view of such circumstances, and when a transmission is provided in the human power drive system upstream of the resultant force point of the human power drive system and the electric drive system, the motor assistance accompanying the speed change operation of the transmission is provided. It is a first object of the present invention to provide a control method for a vehicle with an electric motor that can prevent a significant change in the rate and obtain a desired driving feeling. A second object is to provide a vehicle with an electric motor.
[0008]
[Structure of the invention]
According to the present invention, a first object is to provide a vehicle with an electric motor in which a human power drive system and an electric drive system are provided in parallel, and the output of the electric motor of the electric drive system is controlled in response to a change in the driving force due to human power. In this control method, a transmission having a variable reduction ratio is interposed in the human power drive system upstream of the resultant force point of the human power driving force and the motor driving force, and the auxiliary ratio of the motor to the human power driving torque is set to a reduction ratio of the transmission. This is achieved by a vehicle motor-equipped vehicle control method characterized in that a target value of a motor torque is obtained so as to change depending on the size of the motor, and the output of the electric motor is controlled to the target value.
[0009]
A second object is to provide a vehicle with an electric motor that is provided with a human drive system and an electric drive system in parallel, and controls the output of the electric motor of the electric drive system in response to a change in the output of the human drive system. Torque detection means for detecting human power drive torque of the human power drive system, a transmission with a variable reduction ratio interposed in the human power drive system upstream of the resultant force point of the human power drive system and the electric drive system, A reduction ratio detection means for detecting a reduction ratio; a motor torque target value calculation means for obtaining a target value of the motor torque so as to change a motor auxiliary rate with respect to the human drive torque according to the magnitude of the reduction ratio of the transmission ; and Motor torque actual value detecting means for obtaining the actual value of the electric motor torque, and output control for controlling the output of the electric motor so that the motor torque actual value matches the motor torque target value. It is achieved by an electric motor with vehicle, characterized in that it comprises a means.
[0010]
Here, the motor torque target value calculating means can obtain the motor torque target value by adding the coefficient determined by the reduction ratio to the human power torque. It is also possible to store in advance a conversion map, a conversion equation, etc. for each reduction ratio, and select a conversion map or conversion equation to be used according to the reduction ratio to obtain the target value.
[0011]
[Action]
Since the motor torque target value is changed according to the reduction ratio of the transmission, motor torque suitable for the reduction ratio can be output. For example, when the transmission is capable of shifting in three stages of high, medium, and low speeds, the motor auxiliary rate is decreased at the high speed (the reduction ratio is small) compared to that at the medium speed. On the other hand, when the speed is low (the reduction ratio is large), the motor auxiliary rate is increased as compared with the middle speed.
[0012]
Thus, by changing the motor assist rate according to the reduction ratio, the range of change in the motor assist rate at the time of shifting can be reduced. As a result, the running feeling can be improved.
[0013]
Embodiment
1 is a side view of a bicycle according to an embodiment of the present invention, FIG. 2 is a diagram showing a control system thereof, FIG. 3 is a conceptual diagram of a torque detection portion, and FIG. 4 is an explanatory diagram of a principle of torque detection. 5, 6 and 7 are explanatory diagrams of different interpolation methods, and FIG. 8 is an explanatory diagram of the moving averaging process.
[0014]
In FIG. 1, reference numeral 10 denotes a main frame, which has a head pipe 12, a main tube 14, a down tube 16, a seat tube 18, a chain stay 20, a back stay 22 and the like. A front fork 24 and a steering handle bar 26 are steerably held on the head pipe 12, and a front wheel 28 is attached to the front fork 24.
[0015]
A saddle 30 is held at the upper end of the seat tube 18 and a bottom bracket 32 is fixed to the lower end. A crankshaft 34 is rotatably held horizontally by the bottom bracket 32. A left crank arm 36 and a right crank arm 38 are fixed to the left end and the right end of the crank shaft 34, respectively. These crank arms 36 and 38 serve as input means for a human-powered drive system. A torque detecting means 40 shown in FIG. 3 is attached to the right end of the crankshaft 34.
[0016]
The torque detecting means 40 is fixed to the right end of the crankshaft 34, and is integrated with the right crank arm 38, and an output side rotating body 44 that is held on the crankshaft 34 so as to be slightly rotatable. And an elastic material 46 that is compressed when the rotation is transmitted from the rotating body 42 to the rotating body 42. Here, the rotating bodies 42 and 44 are provided with 20 teeth 42A and 44A opposed to each other in the rotation direction at equal intervals, and an elastic material 46 is sandwiched between the teeth 42A and 44A, respectively. Yes. Therefore, there are 20 elastic members 46 in total.
[0017]
The outer periphery of the output side rotating body 44 is a chain sprocket. Reference numeral 48 denotes a rear wheel, and the rotation of the output side rotator 44 is transmitted to the rear wheel 48 via the chain 50, the exterior transmission 52, and a free wheel clutch (not shown).
[0018]
Therefore, when a pedaling force is applied to the crank arms 36 and 38, the input side rotating body 42 rotates the output side rotating body 44 in the same direction while compressing the elastic member 46, and drives the rear wheel 48. Since the amount of compression of the elastic member 46 at this time is proportional to or corresponds to the pedaling force, the amount of change in the phase difference between the rotating bodies 42 and 44 is proportional to or corresponds to the pedaling force.
[0019]
In this embodiment, this phase difference is obtained by detecting the passage of 20 permanent magnets 54 and 56 fixed to the rotating bodies 42 and 44 along the circumference by the Hall elements 58 and 60, respectively. The hall elements 58 and 60 detect the permanent magnets 54 and 56 each time the rotating bodies 42 and 44 rotate 360 ° / 20, respectively, and pulse-shaped first and second angle detection signals 58A and 60A (FIG. 4), respectively. Is output.
[0020]
When the pedaling force is now 0, the phase difference between the rotating bodies 42 and 44, that is, the phase difference between the permanent magnets 54 and 56 is defined as θ ₀ . If the phase difference when the pedaling force F (F ≠ 0) is applied is θ ₁ , the deformation amount Δθ of the elastic material 46 is (θ ₀ −θ ₁ ), and this deformation amount Δθ is That is, the amount of change Δθ of the phase difference θ. Therefore, the pedaling force torque, that is, the manpower driving torque T can be known from this Δθ. A speed detector 62 (see FIG. 1) for detecting the rotational speed of the crankshaft 34 is attached in the vicinity of the torque detecting means 40.
[0021]
1 and 2, 64 is an electric motor, and for example, a permanent magnet type DC motor can be used. In this motor 64, the rotor rotates in the field of a permanent magnet, and the output driving torque can be controlled by changing the armature current. The rotation speed can be controlled by the armature voltage. The rotation of the motor 64 is directly transmitted to the rear wheel 48 via the belt type speed reducer 66.
[0022]
That is, in this embodiment, the resultant force point where the outputs of the electric drive system and the human power drive system merge is the rear wheel 48. Therefore, the transmission 52 is interposed in the human power drive system upstream of the resultant force point (rear wheel 48). In FIG. 1, reference numeral 68 denotes a case for accommodating a battery, a control device, and the like.
[0023]
Next, the control device 70 will be described with reference to FIG. The control device 70 is constituted by a microcomputer. FIG. 2 is a block diagram showing functions formed by the software. In FIG. 2, reference numerals 72 and 74 denote input interfaces, and the first and second angle detection signals 58A and 60A detected by the torque detection means 40 are input to the torque calculation means 76 via the interface 72. A phase difference change amount Δθ and an input driving torque T are obtained.
[0024]
Here, the torque detection means 40 obtains the torque T at every fixed interval (360 ° / 20 = θ _f ) between the permanent magnets 54 and 56. Therefore, the actual torque T cannot be known during this interval θ _f . Therefore, in the present invention, the torque T during the interval θ _f is estimated by the interpolation means 80 described later, and a continuous estimated torque value is output. The torque estimation value is regarded as an actual torque value, and the following processing is performed.
[0025]
Note in fact the estimated value of the torque is determined for each operation cycle of the computer can be regarded as continuous from sufficiently short compared to the time between the intervals theta _f. The output of the speed detector 62 is input to the speed calculation means 78 via the interface 74, and the crankshaft rotation speed (N) is obtained.
[0026]
On the other hand, the rotational speed of the rear wheel 48 is detected by a vehicle speed detector 79. The output of the vehicle speed detector 79 is input to the vehicle speed calculation means 79b via the input interface 79a, where the vehicle speed Sp is obtained. That is, since the vehicle speed detector 79 detects the rotational speed of the rear wheel 48, the vehicle speed Sp is obtained by adding a predetermined coefficient in consideration of the diameter of the rear wheel 48.
[0027]
Based on the calculated vehicle speed Sp and the crankshaft rotational speed N, the reduction ratio calculation means 79c calculates the reduction ratio R of the transmission 52. The obtained reduction ratio R and the actual torque value (estimated value) output from the interpolation means 80 are input to the motor torque target value calculating means 82, where the motor torque target value is obtained.
[0028]
In this motor torque target value calculation means 82, for example, the coefficient determined by the reduction ratio R can be obtained by integrating the actual torque value (T). This coefficient may be a fixed value or a variable that varies depending on other factors such as the state of charge of the battery.
[0029]
Further, the motor torque target value calculating means 82 may store a conversion map or a conversion formula in advance for each reduction ratio R, and select and use a conversion map or conversion formula corresponding to the detected reduction ratio R. .
[0030]
The result is input to the correction calculation means 84. The correction calculation means 84 performs appropriate correction. For example, as the crankshaft rotation speed (N) and vehicle speed (Sp) obtained by the speed calculation means 78 increase, the motor assist force is gradually decreased to prevent the vehicle speed from becoming excessive.
[0031]
Further, when the pedaling force becomes zero during traveling, a voltage for reducing the current of the motor 64 and causing no-load rotation (no-load rotation voltage) is applied. That is, the motor 64 has a built-in one-way clutch, keeps the motor rotating near the motor speed to which the clutch is connected, and can quickly apply the motor driving force to the rear wheel 48 when the target value of the motor assist force increases again. To do.
[0032]
Further, when the bicycle is started, the crankshaft speed (N) and the vehicle speed Sp are 0, and the reduction ratio R cannot be estimated. At this time, correction is preferably performed so that the target value does not become 0. For example, at this time, even if the crankshaft speed (N) and the vehicle speed Sp are actually zero or almost zero, a certain value other than zero is used as the initial value. Alternatively, an initial value of the reduction ratio R may be set. In this way, the motor auxiliary force can be output in response to the torque input from the pedal even when the vehicle starts.
[0034]
The target value of the motor torque corrected in this way is input to the comparator 86, and a difference from the torque T _M (actual value) of the motor 64 is obtained. Then, the driving torque of the motor 64 is controlled so that this difference becomes zero. That is, the output control means 88 outputs a signal corresponding to this difference to the motor driver 92 via the output interface 90. In the driver 92, for example, power supplied from the battery 94 to the motor 64 is controlled by a pulse width control method (PWM).
[0035]
The actual value of the torque T _M of the motor 64 is obtained from the current I of the motor 64. Here, the current I of the motor 64 is obtained by detecting the armature current with a current detector 96 using a shunt resistor or the like. For example, the output of the detector 96 is input to the current detection means 100 via the input interface 98, and the armature current I is obtained here. In this case, the current detection means 100 becomes the actual value detection means of the motor torque.
[0036]
Next, a processing method of the interpolation unit 80 will be described. Various methods can be considered as the interpolation method. The simplest method uses the linear approximation shown in FIG. In FIG. 5, the horizontal axis t represents time, and the vertical axis T represents torque T. Times t ₁ , t ₂ ... Indicate detection time points, and the intervals correspond to the angular intervals of the permanent magnets 54 and 56. Instead of this time t, the rotation angle θ of the crankshaft 34 may be taken.
[0037]
In FIG. 5, t ₁ , t ₂ ... Are detection times by the torque detecting means 40, and the detected value (detected torque) T at this time is represented by T ₁ , T ₂ . The straight line L ₁ connecting the detection points A and B at t ₁ and t ₂ now has a slope m ₁ = (T ₂ −T ₁ ) / (t ₂ −t ₁ ). Therefore, between the next detection points B and C at t ₂ and t ₃ , the torque T is approximated by a straight line L ₁ having the slope m ₁ .
[0038]
That is, during t ₂ <t <t ₃ , the estimation is performed using a straight line, T = T ₂ + m ₁ t. Similarly, during t ₃ <t <t ₄ , the estimation is performed using a straight line, T = T ₃ + m ₂ t. In this way, the calculation is performed while sequentially changing the straight line.
[0039]
The method shown in FIG. 6 is approximated by quadratic curves K ₁ (t), K ₂ (t),. For example, a quadratic function of T = at ² + bt + c≡K (t) is set, and simultaneous with respect to the detection points A (t ₁ , T ₁ ), B (t ₂ , T ₂ ), C (t ₃ , T ₃ ) The coefficient abc can be obtained by solving the equation. In this way, the function K ₁ (t) is determined, and is estimated by T = K ₁ (t) between t ₃ and t ₄ .
[0040]
If slopes of two straight lines passing through the detection points A and B and B and C are m ₁ and m ₂ , respectively, 2a = (m ₂ −m ₁ ) / (t ₃ −t ₂ ), b = m ₂ It becomes. That is, the slope change rate 2a = {(m ₂ −m ₁ ) / (t ₃ −t ₂ ) on the approximate straight line (T = m ₂ t + T ₃ ) of the slope m ₂ passing through the detection point C in the method of FIG. } To which a correction term at ² is added.
[0041]
In the method of FIG. 7, a sine curve is stored in advance, a sine curve on which detection points A, B, C... Are obtained is determined, and an approximate value is determined by this curve. For example, the sine curve can be uniquely determined by knowing the maximum value T _M and the minimum value T _m of the detection points A, B.
[0042]
In general, when starting from the time when the vehicle is stopped, one pedal is near the top dead center. Therefore, it is considered that the torque T decreases along the sine curve from the first detection point S at the start. The period of the sine curve at this time can be known using the crankshaft rotation speed detected by the speed detector 62 (FIG. 1). According to this method, the torque T immediately after starting can be estimated with high accuracy, and smoother operation is possible.
[0043]
In the interpolation method described above, the detection values T ₁ , T ₂ , T ₃ ... At the detection points A, B, C... Do not match the estimated values obtained immediately before the detection points A, B, C. If this difference is large, the target value of the motor drive torque will fluctuate greatly at the detection points A, B,.
[0044]
Therefore, it is preferable to add a correction process to reduce this difference. FIG. 8 shows an example of the correction method. This method uses a moving average value. That is, an estimated value (approximate torque) Tb (t) at a certain time t is converted into a certain number (n) of estimated values Tb (t−τ), Tb (t−2τ),. An arithmetic average value Tc (t) of Tb (t−nτ) is obtained, and this average value Tc (t) is replaced with an estimated value Tb (t) at this time point t.
[0045]
Here, τ is a time interval (t ₂ −t ₁ ), (t ₃ −t ₂ ),... Of the detection points A, B..., And if the rotation speed of the crankshaft 34 is constant (t ₂ −t ₁ ), (T ₃ −t ₂ ),... Is constant and τ is constant. Since the rotational speed of the crankshaft 34 actually changes, τ is no longer a constant. Therefore, at this time, it is necessary to change τ for each interval between the detection points A, B.
[0046]
If this correction process is performed, for example, even if the approximate curve Tb1 starting from the detection point A in FIG. 8 becomes Tb ₁ (t ₂ ) (≠ T ₂ ) at the detection time B2 of the detection point B, thereafter, the correction torque Tc riding a (t) slide into close gradually in the following approximate curve Tb _2. Therefore, the change in the estimated torque value at the detection points B, C... Becomes smooth.
[0047]
Of course, a part of the estimated value used for the calculation of the moving average may be replaced with the detected value.
[0048]
In the embodiment described above, the manual driving torque (T) is intermittently detected, continuous torque is estimated by interpolation processing, and this estimated value is used as an actual value. However, the present invention may of course be detected by a torque detecting means for continuously detecting the human driving torque. The crankshaft rotational speed (N) and the vehicle speed Sp are used to obtain the reduction ratio R, but the reduction ratio for each gear stage of the transmission 66 is stored in advance, and the gear stage to be used is detected by a sensor. Then, the reduction ratio corresponding to the detected gear position may be read from the memory.
[0049]
【The invention's effect】
As described above, the reduction ratio of the transmission is detected, and the motor torque target value is set so that the assist ratio of the motor with respect to the manual driving torque is changed depending on the magnitude of the reduction ratio of the transmission. Therefore, even if the reduction ratio of the transmission interposed in the human power drive system upstream of the resultant force point of both drive systems changes, the auxiliary ratio of the electric motor is made appropriate to the reduction ratio. Can be set to For this reason, a desirable running feeling can be obtained.
[0050]
According to the invention of claim 2, a vehicle with an electric motor for carrying out the method of the invention of claim 1 is obtained. Here, the motor torque target value calculation means can obtain the coefficient determined by the reduction ratio of the transmission by adding it to the manual driving torque.
Alternatively, a conversion map or conversion formula may be stored in advance, and a conversion map or conversion formula corresponding to the reduction ratio may be selected and used.
[Brief description of the drawings]
FIG. 1 is a side view of a bicycle according to an embodiment of the present invention. FIG. 2 is a diagram showing its control system. FIG. 3 is a conceptual diagram of a torque detection portion. Illustration of interpolation method (linear approximation) [FIG. 6] Illustration of interpolation method (quadratic curve approximation) [FIG. 7] Illustration of interpolation method (sine curve approximation) [FIG. 8] Illustration of moving averaging process [FIG. Explanation of symbols]
34 Crankshaft 36, 38 Crank arm 40 as input means for manual drive system Torque detection means 48 Rear wheel (the resultant force point of both drive systems)
52 Transmission 64 Electric motor 70 Control device 82 Motor torque target value calculation means 84 Correction calculation means 88 Output control means 100 Motor current detection means T as actual motor torque value detection means T Manual driving torque (stepping force torque)
R Reduction ratio

Claims (4)

In a method for controlling a vehicle with an electric motor, in which a manpower driving system and an electric driving system are provided in parallel and the output of the electric motor of the electric driving system is controlled in response to a change in driving force due to manpower, the manpower driving force and the motor driving The motor torque so that the auxiliary ratio of the motor with respect to the manual driving torque is changed depending on the size of the reduction ratio of the transmission by interposing a transmission with a variable reduction ratio in the manual driving system upstream of the resultant force point. And a control method for a vehicle with an electric motor, wherein the output of the electric motor is controlled to the target value. In a vehicle with an electric motor that provides a human drive system and an electric drive system in parallel and controls the output of the electric motor of the electric drive system in response to a change in the output of the human drive system, the human drive torque of the human drive system A torque detection means for detecting the transmission, a transmission with a variable reduction ratio interposed in the manual drive system upstream of the resultant force of the manual drive system and the electric drive system, and a reduction ratio for detecting the reduction ratio of the transmission Detecting means; motor torque target value calculating means for determining a target value of the motor torque so as to change the motor auxiliary ratio with respect to the manual driving torque depending on the reduction ratio of the transmission; and an actual value of the torque of the electric motor Motor torque actual value detecting means for obtaining the motor torque, and output control means for controlling the output of the electric motor so that the motor torque actual value matches the motor torque target value. Vehicles with an electric motor which is characterized in.   3. The vehicle with an electric motor according to claim 2, wherein the motor torque target value calculating means obtains the motor torque target value by adding a coefficient determined by the reduction ratio to the manual driving torque.   3. The electric motor according to claim 2, wherein the motor torque target value calculation means has a conversion map or conversion formula stored in advance for each reduction ratio, and obtains the motor torque target value using the conversion map or conversion formula corresponding to the detected reduction ratio. With vehicle.

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