JPS6341318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in electric vehicles, etc., which are powered by a battery or a power source and are driven by a DC motor via a chopper, and particularly relates to a method for controlling electric motor drive torque with respect to the amount of depression of the accelerator pedal of an electric vehicle. It is related to.

In an engine vehicle, when the transmission gear is constant, the driving torque and maximum speed change depending on the amount of depression of the accelerator pedal (referred to as the amount of accelerator depression), and this change changes the driving characteristics of the vehicle as perceived by the driver. That is, it is closely related to so-called feeling.

On the other hand, even in an electric vehicle, it is desirable that the feeling when stepping on the accelerator is similar to that of a conventional engine vehicle.

On the other hand, conventionally, for controlling this type of electric vehicle, a method as shown in FIG. 1 has been used as an example. In FIG. 1, reference numeral 1 denotes a DC motor for driving an electric vehicle, and one end of its armature 1a is connected to the positive electrode of a battery 3 via an armature chopper 2.
Moreover, the armature current detection resistor 4 is connected to the other end of the armature 1a.
are inserted in series and connected to the negative electrode of the battery 3. 5 is a freewheeling diode for the armature 1a.

One end of the shunt field winding 1b of the motor 1 is connected to the negative pole of the battery 3 via a field chopper 6, and a field current detection resistor 7 is inserted into the other end.
The voltage generated at both terminals is input to the control amplifier 8 of the field chopper 6. 9 is a conductivity regulator for the field chopper, and 10 is a freewheeling diode for the shunt field winding 1b.

11 is a control amplifier for armature chopper 2, 12
is the conduction rate regulator of the armature chopper 2. One input terminal of the control amplifier 11 receives an armature current command voltage V _I representing a vehicle accelerator command from a current setting device 13 that is linked with the accelerator pedal A, and the other input terminal receives an armature current command voltage V I representing a vehicle accelerator command. A detection voltage V _C of the armature current I _M of the electric motor 1 by the detection resistor 4 is applied differentially with respect to the accelerator command input voltage V _I.

14 is an amplifier for field current command, and the accelerator command input voltage V _I and the detection armature current signal V _C are differentially applied to its input terminal, and an amplifier with the same polarity as the detection voltage V _C is applied differentially to its input terminal. A bias voltage ΔV _C0 is applied. The output of the field current command amplifier 14 passes through a limiter 15 and becomes an input to the field chopper control amplifier 8.

Figure 2 shows the respective voltage values of the accelerator command input voltage VI _{, VI1 , VI2} , _VI3 , _VI4 , according to the circuit system shown in Figure 1.
A characteristic diagram shows the relationship between (V _I1 < V _I2 < V _I3 < V _I4 ), the corresponding torque values T ₁ , T ₂ , T ₃ , T ₄ of the electric motor 1, and the motor speed N. In the figure, N ₀ represents the base speed of the motor, and N ₄ represents the maximum speed. In addition, a typical load torque T _L used to explain the subsequent operation is also described.

Next, the operation of the control system shown in FIG. 1 will be explained with reference to FIG.

Initially, when the accelerator command input voltage V _I is 0, the armature chopper control amplifier 11 and the duty ratio regulator 12 are both inactive, and the chopper 2 is in a non-operating state.
It is in the OFF state, and both the armature current I _M and the detected armature current signal V _C are 0.

On the other hand, among the inputs of the field current command amplifier 14, the accelerator command input voltage V _I and the armature current signal V _C are 0, but the bias input ΔV _C0 is input with the same polarity as V _C , and the field current The current command amplifier 14 is PI
Since an amplifier with a high static gain such as a regulator is used, the output V _F of the field current command amplifier 14
is at the maximum value (saturation value) and is input to the limiter 15, whose output V _F1 becomes the maximum limit value V _FI1 .

V _F1 becomes an input to the field chopper control amplifier 8, drives the field chopper 6 through the conductivity regulator 9, and controls the field current I _F. The field current I _F is detected by the field current detection resistor 7, and is fed back to the field chopper control amplifier 8 as a detected field current signal V _R to generate a strong field current corresponding to the input V _F1 = V _FI1 . I _FI1 .

At this time, of course, both the armature voltage V _M and the motor rotational speed N are 0, and FIG. 3 shows this state between time points t ₀ and t ₁ .

Next, at time t ₁ , when the accelerator command input voltage V _I is set to V _I1 for running, the input V _I1 is input to the armature chopper control amplifier 11.
The armature chopper 2 operates through the conductivity regulator 12, and a current I _M flows through the armature circuit.

The detected value V _C of the armature current I _M is fed back to the armature chopper control amplifier 11, and is controlled so that the current I _M =I _M1 corresponds to the input V _I =V _I1 . I _M =
If the value of V _C corresponding to I _M1 is V _C1 , then since an amplifier with high static gain such as a PI regulator is used as the armature chopper control amplifier 11, approximately V _I1
=V _C1 .

Among the inputs to the field current command amplifier 14,
Since V _I1 and V _C1 have different polarities and are almost equal in value, they cancel each other out, and only △V _C0 is input to the field current command amplifier 14, V _F becomes the maximum value (saturation value), and the output V of the limiter 15 _F1 is limited to an upper limit value V _FI1 , and the field current I _F is controlled to a stronger field current I _F1 .

Here, when the armature current I _M1 flows, the motor rotation speed N increases and the armature voltage V _M also increases. As the armature voltage V _M increases, the current flow rate of the armature chopper 2 increases by controlling I _M =I _M1 until the current flow rate reaches 1 and the armature chopper 2 reaches the point t ₂ when is shorted. During this time, the field current I _F is controlled to a stronger field current I _F1 . Of course,
As shown in Figure 3, the conditions for the electric motor to accelerate are that the driving torque T of the electric motor is equal to the load torque T _L
It needs to be bigger.

At time _t2 , when the chopper 2 is completely short-circuited and the armature voltage V _M becomes equal to the power supply voltage V _B ,
Note that if T > T _L , the electric motor is further accelerated and N increases, and Equation (1) E _M = K ₁ NΦ≒K ₂ NI _F ... (1) Φ: Magnetic flux K ₁ , K ₂ : Constant Due to the relationship, the back electromotive force E _M of the motor increases.

Therefore, equation (2) V _B ≒ V _M = I _M · R _A + E _M ... (2) R _A : I _M decreases due to the armature circuit resistance.

Detect armature current signal when armature current I _M decreases
When V _C also decreases and the condition of V _I −V _C −△V _C0 >0 is satisfied, the field current command amplifier 14
is no longer saturated and the output voltage V _F of the amplifier 14 begins to decrease, and the limit value of the limiter 15 is also released and its output voltage V _FI decreases below the upper limit value V _FI1 . When the output voltage V _FI of limiter 15 decreases, the field current I _F becomes
I decreases from _F1 , and the back electromotive force E _M of the motor also decreases,
From the relationship in equation (2), the armature current I _M increases, and V _I −V _C
−△V _C0 <0.

In this way, by the action of the field current command amplifier 14, the field current I _F decreases while maintaining the relationship of formula (3): V _I −V _C −△V _C0 ≒0 ...(3) go.
Here, if the motor current value corresponding to the bias voltage △V _C0 is △I _M , then when V _I = V _I1 is set,
According to the relationship in equation (3), in the weak field control range after the chopper 2 is short-circuited, control is performed so that I _M =I _M1 -ΔI _M as shown in FIG. Now, if △V _C0 <<V _C , then △I _M <<I _M1 , and the armature current I _M is controlled to approximately I _M1 in the entire range.

In this way, in the range of conditions T>T _L , the field current I _F decreases and the motor rotation speed N increases, but as shown in equation (4), T=K ₃・Φ・I _M ≒K ₄・I _F・I _M ...(4) K ₃ , K ₄ : According to the relationship between constants, if the field current I _F decreases, the generated torque T of the electric motor 1 also decreases, and at the time t ₃ when T=T _L , the motor vehicle The acceleration stops and the rotational speed settles at N _O4 . If the load torque is even smaller, it will be accelerated to a higher speed, and depending on the value of the additional torque, the rotational speed may reach the maximum rotation speed _N4 .

Further, when the load torque T _L is even larger, the speed becomes even lower, and depending on the characteristics of the load torque, the control may be performed within the field strength range.

In such a control system, when comparing the torque-speed characteristic with respect to the accelerator command input voltage and the load torque characteristic representing the running resistance of the vehicle, there are the following problems.This point will be explained based on Fig. 2. do.

(1) When accelerating to speed N _O4 with load characteristic T _L and operating at N _O4 , accelerator command input voltage V _I can be set to V _I1 from the beginning and acceleration can be performed with torque T ₁ , but the acceleration torque (T ₁ - T _L ) is small and acceleration performance is poor. Therefore, when the traveling speed is low, the accelerator pedal is depressed greatly to increase the accelerator command input voltage V _I to V _I2 or V _I3 , and the torque T ₂ or T It is necessary to accelerate at ₃ , and as the speed approaches N _O4 , release the accelerator pedal to return _VI to _VI1 .

(2) In the low speed range, the torque-speed characteristic and the load torque characteristic are almost parallel, making it difficult to set the low speed by operating the accelerator pedal. This problem is particularly severe when the load torque is small.

The present invention eliminates the above-mentioned drawbacks, and provides a torque control method for a DC motor suitable for an electric vehicle, which has acceleration characteristics similar to those of an engine vehicle and improves speed controllability in a low speed range. The purpose is to

In order to achieve this object, in this invention, the upper limit value of the current flow rate of the armature chopper is changed in accordance with the accelerator command input voltage _VI , so that the generated torque of the electric motor is at the upper limit value corresponding to the accelerator command input voltage. The torque is controlled so that the generated torque changes rapidly above a certain speed as shown in FIG.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram showing an embodiment of the present invention, in which the same components as those in FIG. 1 are given the same reference numerals and explanations of those parts will be omitted.

In this embodiment, as compared to the control system shown in FIG. An amplifier 17 that amplifies the output of the current setting device 13 so that _L can be changed by the output signal of the current setting device 13
is configured such that the output thereof is applied to the limiter 16. And output limit value V _L of limiter 16
limits the maximum value of the input to the conduction rate regulator 12, limits the maximum conduction value of the armature chopper 2,
This limits the maximum armature voltage of the armature 1a.

When the accelerator command input voltage V _I is the maximum value V _I4 , the gain of the amplifier 17 described above is set to the limiter control voltage V _L
If the value is selected so that the chopper 2 for the armature is just short-circuited, the characteristics representing the relationship between the accelerator command input voltage V _I , the motor torque, and the motor speed will be as shown in FIG. The reason why the characteristics shown in FIG. 5 are achieved by providing the limiter 16 is as described below.

The relational expression (2) when the maximum value of the conduction rate α is limited to 1 or less is as follows.

αV _B =V _M =IM・RA+EM ……(5) Therefore, even if the chopper is not completely short-circuited (that is, even if α<1), the motor speed will be the rotational speed corresponding to the limit value of the conduction rate. When this happens, the field will shift to field-weakening control.

Also, from equation (5), the back electromotive force EM of the motor is the conduction rate α
Since the minimum value of the field current is limited to a constant V _FI2 , the motor rotation speed cannot be increased any further from equation (1).

Therefore, the maximum rotational speeds N1, N2, N3, and N4 correspond to the conduction rate α. In the case of this control method, the operation can be expressed as shown in FIG. 6, similar to FIG. Third
In order to clarify the difference in the operation of both methods in comparison with the figure, it is assumed that the load torque T _L has the same characteristics as in Fig. 3, and the final attained speed N ₃ of the electric motor is also N _O4 in Fig. 3. shall be equal to Further, in FIGS. 2 and 5 showing the characteristics of both types, typical indicated values indicated by the signs of V _I , T, and N represent the same value.

At time t ₁ in Fig. 6, the accelerator command input voltage V _I
When V _I3 is taken, the armature chopper control amplifier 11 operates so that the armature current I _M becomes a value I _M3 that matches this input value, the motor 1 accelerates, and the rotational speed N increases. As the rotational speed N increases, the armature induced voltage V _M increases, but the armature current I _M always remains I _M3
The armature chopper control amplifier 11 operates so that
2 to increase the conduction rate of the armature chopper 2.

When the output of the armature chopper control amplifier 11 increases and reaches the limit value V _L = V _L3 corresponding to V _I3 at time t ₂ , the input of the duty regulator 12 is limited to V _L3 and the chopper The conduction rate of No. 2 is also fixed at that value, and the armature voltage V _M is fixed at the voltage V _M3 corresponding to the conduction rate. At this time, if T > T _L , the motor rotation speed N will further increase and the armature current I _M will decrease for the same reason as the operation shown in Fig. 3, but the field current command amplifier 14 will operate and I _F The electric motor is controlled to weaken the field so as to decrease the value of I=I _M3 -ΔI _M. When T>T _L , the rotational speed N increases,
The field current I _F continues to decrease and at time t ₃ the field current I _F
When becomes the weakest field value I _F2 , the armature current I _M becomes I _M3 −△
It decreases from I _M and settles down at time t ₄ when it reaches a value equivalent to the load torque, and the rotational speed becomes N ₃ .

On the other hand, if the accelerator command input voltage V _I is set to V _I1 which is smaller than V _I3 in order to drive at a low speed, the upper limit value V _L of the limiter 16 will also be lowered in accordance with the above-mentioned command input voltage V _I1 . Therefore, the maximum conductivity of the conductivity regulator 12 also decreases corresponding to the above V _L1 , and the armature current I _M supplied from the armature chopper 2 also decreases, resulting in a change in the speed - torque of the motor 1. Characteristic is the fifth
Curve A, represented by T ₁ −N ₁ in the figure, is obtained, and the motor speed, and hence the vehicle's traveling speed, is the intersection of T _L and the above curve A. As you can see from this figure 5, the load
In a range where T _L is small and the speed is low, for example, the motor rotation speed is limited to a low value N ₁ , making it easy to adjust the low speed running.

Thereafter, by the same operation, the upper limit value V _L of the limiter 16 is set in accordance with the accelerator command input voltages V _I2 and V _I3 .
changes, the current flow rate of the armature chopper 2 is also limited to a value corresponding to the upper limit value, and the speed-torque characteristic of the motor 1 remains constant for each specified input voltage as shown in Figure 5. At higher speeds, the torque decreases rapidly. Therefore, speed control can be performed stably even in the low torque and low speed region.

Furthermore, if the accelerator command input voltage V _I is set to the maximum V _I4 , the V _I =V _I4 characteristic shown in FIG. 2 will be the same, and the maximum torque and rotational speed characteristics will be sufficiently covered. Even for larger load torques T _LA and T _LB , by adjusting the accelerator command input voltage V _I as shown in Fig. 5, the speed can be set to a value determined by the intersection of the torque-speed characteristic and the load torque characteristic. .

As described in detail above, according to the present invention, the current flow rate of the chopper can be controlled by the accelerator command input voltage so that the maximum current flow rate limit value of the chopper for controlling the armature current of a driving DC motor of an electric vehicle, etc. Since a limiter that can freely adjust the output limit value is provided before the regulator, it is easy to adjust the low speed at low load torque, and the acceleration performance is greatly improved.

Therefore, when the present invention is applied to the drive system of an electric vehicle, when the vehicle accelerates or decelerates, the speed increases or decelerates approximately corresponding to the amount of depression of the accelerator pedal. It eliminates the need for the driver to press down heavily and then return to the original position, and the acceleration characteristics can be approximated to those of an engine vehicle, providing acceleration and deceleration characteristics that match the driver's feeling.

Note that the control method of the present invention is not limited to electric vehicles.
It can also be applied to electric railway train control chips, etc.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a conventional torque control method for a DC motor in an electric vehicle, and Figure 2 is an operating characteristic curve for the torque control method shown in Figure 1.
Figure 3 is an explanatory diagram of the operation of the main parts of the circuit in Figure 1;
The figure is a circuit diagram showing one embodiment of the torque control method of the present invention, FIG. 5 is an operating characteristic curve of a DC motor according to the control method of FIG. 4, and FIG. 6 is the operation of the main part of the embodiment of FIG. 4. It is an explanatory diagram. 1...Electric motor, 2...Armature chopper, 3...
...Battery, 4...Armature current detection resistor, 6...
Field chopper, 7...Field current detection resistor, 8...
... field chopper control amplifier, 11 ... armature chopper control amplifier, 9, 12 ... duty ratio regulator, 13 ... current setting device, 14 ... field current command amplifier, 16 ... limiter , 17...Amplifier.

Claims (1)

[Claims] 1. A current setting device that outputs a command voltage specifying an armature current of a DC motor, and a current setting device into which the command voltage of the current setting device is input and a detection voltage of the armature current is input differentially. an armature chopper amplifier to which the output of the armature chopper amplifier is input and which is inserted into a closed circuit between the DC power supply, the armature winding, and a detection resistor; and an armature chopper that controls the current flow rate. A field current in which a command voltage of the duty ratio regulator and the current setting device is inputted, and a detected voltage of the armature current and a bias voltage having the same polarity as the detected voltage are differentially inputted to the command voltage. a command amplifier, a field chopper control amplifier to which the field current command amplifier output is input and a field current detection voltage is differentially input; and a field chopper control amplifier to which the field chopper control amplifier output is input. In the torque control system for a DC motor, the DC motor is equipped with a DC power source, a field current flow rate regulator that controls the current flow rate of a field chopper inserted into a closed circuit between a field winding, and a detection resistor. A limiter is provided between the armature chopper amplifier and the armature conductivity regulator, and the limiter changes the upper limit of the conductivity according to the magnitude of the command voltage of the current setting device, thereby reducing the torque generated by the DC motor. A torque control method for a DC motor, characterized in that an upper limit is limited to a magnitude corresponding to a command voltage of the current setting device. 2. In the torque control method for a DC motor as set forth in claim 1, the DC motor is mounted on an electric vehicle, and the current setting device adjusts the accelerator command input voltage in conjunction with the accelerator pedal of the electric vehicle. Torque control method for DC motors. 3. A torque control method for a DC motor according to claim 1, wherein the DC motor is mounted on an electric railway vehicle.