JPS5915243B2 - Chip control device for electric vehicles - Google Patents

Description

[Detailed Description of the Invention] The present invention gently reduces the motor current when the train decelerates to a certain speed during braking in a chopper-controlled train that uses regenerative braking, etc., so that there is no drop in braking force caused by air brake equipment with poor response characteristics. This invention relates to a chopper control device that aims to perform smooth switching.

Recent DC electric vehicles are increasingly equipped with chopper control devices that can significantly reduce power consumption through regenerative braking.

- However, since it is other power-running vehicles that absorb the regenerative energy, it must be assumed that the regenerative load will always fluctuate.

Therefore, since a predetermined braking force may not be obtained with only regenerative braking, the braking device must be backed up by another braking device such as an air brake and constantly perform supplementary calculations.

A chopper-controlled vehicle that uses both regenerative brakes and air brakes will be described below.

As shown in FIG. 1, the brake torque command is converted into a command value Ip in a pattern generation circuit 1, and torque conversion 3 is performed by the output of a chopper control circuit 2.

This torque-converted output is detected as a brake torque caused by a motor current such as a regenerative brake, and is calculated in a brake torque command and comparison circuit 4. Supplemented by applying the brakes.

In a chopper-controlled vehicle that uses a combination of regenerative brakes and air brakes that performs supplementary calculations as described above, if there is sufficient regenerative load, when the brake is commanded, the motor current of the electric vehicle will change to the vehicle speed (Figure 2 a). decreases, and the chopper conductivity (
The commanded constant current is automatically controlled until the braking force (Fig. 2b) reaches the maximum conduction rate, and the specified constant braking force (Fig. 2C
) can be obtained.

However, when the maximum conduction rate is reached just before the motor stops, the motor's starting force decreases, and it becomes impossible to control the flow of a constant current against the internal resistance of the circuit, and the motor current rapidly attenuates.

Because the attenuation of this motor current is fast, an air brake system with poor response characteristics cannot keep up with the attenuation of this electric braking force due to the large dead time and rise time constant, and the total braking force will be reduced as shown in Figure 2. Not only did this cause the vehicle to dip, reducing ride comfort, but it also caused a safety issue as the braking force decreased just before the vehicle came to a stop.

Therefore, the air brake system used together with the chopper control system that uses regenerative braking requires an expensive brake system with good response characteristics, and even if a conventional air brake system is used, it does not have good response. For this reason, various measures have been taken, such as installing a relay valve (explanation is omitted) for each truck, which increases the price and complicates the system.

The present invention eliminates these drawbacks by modifying a very small part of the chopper control circuit, thereby slowing down the change in motor current before stopping, and making it possible to regenerate even when combined with a general air brake device that has poor response characteristics. This is intended to smooth the transition between the brake and air brake and eliminate the drop in braking force.

An embodiment of the present invention will be described below based on the drawings.

FIG. 3 shows an embodiment of a chopper control device for brake current control according to the present invention, in which 1 is a pattern generation circuit that generates a command value Ip based on a brake torque command, and 6 is a pattern generation circuit 1. A comparison circuit 7 compares and calculates the command value Ip supplied from the motor current IM and the output of the brake control circuit 9, which will be described later.
A current control circuit (A
CR), 8 is a chopper main circuit that controls the motor current in response to the output of the current control circuit I, and 9 is the output of the current control circuit γ and a vehicle speed signal e.

This is a brake control circuit (LMT) which inputs a brake control signal and supplies a brake control signal to the comparator circuit 6.

First, conventional general current control will be explained.

As is well known, the relational expression in the main circuit during regenerative braking is expressed as follows.

EM-ES(1-r)-(1) FM: Motor generated voltage ES: Power supply voltage r: Conductivity ratio Also, the conductivity ratio r, which is the output of the main circuit, can also be expressed as follows.

r = 1 - Gl - (Ip - IM) - (2) G1: Current control system ACR gain ■ P two command pattern ■ M: Motor current signal 1: Chopper main circuit conversion coefficient The motor generated voltage is Under certain conditions, it can be expressed as follows.

2・v for EM= (3) V: 2 for vehicle speed: Coefficient (1) j (2) From equation (3), 2 for IES−
・V IP−IM=−・□ (4) The relational expression GI Kl・gs is derived, and this characteristic is shown in FIG. 4.

As can be seen from this figure, the deviation IP-IM between the motor current IM and the command value IP increases as the vehicle speed V decreases if the power supply voltage Es is kept constant.

In the figure, ■ indicates the characteristics of the current control circuit.

Originally, this chopper current control circuit was designed to increase the gain G1 to minimize this deviation (Ip-IM) and increase constant current control accuracy, but due to stability issues in the control system, G1 was It cannot be increased unnecessarily, so in reality, the gain value is set to a finite value.

Therefore, the deviation of IP-IM also has a numerical coefficient with respect to the absolute value of IP.

Next, as shown in FIG. 3, the brake control circuit 9
Current control when (LMT) is added will be explained.

Symbol e shown in FIG. indicates a voltage value corresponding to the speed (hereinafter referred to as a vehicle speed signal), and this control circuit 9 receives the output of the current control circuit 7 and the vehicle speed signal e.

The difference is amplified with a gain G2 and fed back to the current control circuit 7 as a negative input.

Deviation when adding brake control circuit 9 (Ip-IM)
is expressed by the following equation (5).

I 2°V to ES- (-8° "IP-IM=-・□+ --eo) GI Kl・Es Kl・gsG2...
・・・・・・(5) G2: Gain of LMT circuit K s −K 2・V Here, output value of current control circuit 8 Kani 1・
Es Vehicle speed signal e.

If the speed when it becomes equal to is Vo, then gs- is 2・VQ K1. ES o (6).

e in equation (6).

Substituting into equation (5) and summarizing, I Es- has 2-
V K2 Ip-IM-1・□+G2・GI Kl・Els Kl・ES(Vo-
V)・・・(7) (7)・It becomes like the formula.

Here, it is assumed that the brake control circuit 9 has a detection function that generates an output only when (output value of the current control circuit γ)≧eo.

In other words, in equation (7), 1.gs is output only when the vehicle speed becomes smaller than vfJzv□ and becomes 2 G 2 ·-(Vo-'y), h, Q K.

FIG. 5 shows the characteristics of equation (7) based on the present invention, and the vehicle speed v
When hv, the conventional characteristic ■ is shown, (Ip-IM) is kept small, and when the vehicle speed V is decelerated to vVo, the term 2G2・□ffo-V) is added to the conventional characteristic line. It can be seen that K1·gs (Ip-IM) increases due to the superposition.

That is, in the figure, ■ indicates the characteristic of the brake control circuit 9, and ■ indicates the characteristic based on the current control circuit 7 and the brake control circuit 9.

In other words, the motor current will gradually decrease.

In other words, as shown in Fig. 6a-C, the speed, flow rate, and braking force change, thereby making the switching between regenerative braking and air braking smooth even when combined with an air braking device with poor response, and improving overall performance. It is possible to eliminate dips in braking force.

FIG. 7 shows a specific example of the circuit shown in FIG. 3, particularly the brake control circuit 9, in which 10 is an operational amplifier;
It is composed of a few simple circuits: 11 is a diode, and 12 to 14 are resistors.

In this circuit, the gain G2 of the brake control circuit 9 and the feedback start speed VO of the brake control circuit 9 are controlled by resistors 12 to 1.
Easy to set up with 4 combinations.

Further, when the speed V is higher than Vo, the output of the brake control circuit 9 is not output.

In other words, Es- is 2・V (-e (1) ・G2 <0 or (7) 2 is 1
G2- (Vo-v) <oc- of ES 2 is 1·ES for brake control. The detection function of not outputting the output IF of the circuit 9 can be easily achieved by the diode 11.

As described above, according to the present invention, switching between regenerative braking and air braking is smooth, the total braking force does not drop, safety problems are solved, and riding comfort can be improved.

At the same time, there is no need to use a complicated and expensive brake device with good response characteristics, which is used with conventional chopper devices, and it is possible to perform brake control with good performance using an inexpensive air brake.

In the above explanation, a regenerative brake type chopper control device is used, but it is natural that similar effects can be obtained with other electric brake type chopper control devices such as a power generation brake.

Furthermore, there is an input (
eo) can be inputted not only at a constant voltage but also at a voltage proportional to the speed.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a conventional chopper control device for an electric vehicle, Fig. 2 a to C are control characteristic diagrams showing the operation of each part of Fig. 1, and Fig. 3 shows an embodiment of the present invention. 4 is a characteristic diagram showing the speed-deviation characteristics of the circuit shown in FIG. 1, FIG. 5 is a characteristic diagram showing the speed-deviation characteristics of the circuit shown in FIG. 3, and FIGS. 6 a to C are FIG. 3 is a control characteristic diagram showing the operation of each part, and FIG. 7 is a circuit diagram showing a specific example of the main part of FIG. Note that the same reference numerals in the figures indicate the same or corresponding parts. In the figure, 1 is a pattern generation circuit, 6 is a comparison circuit, 7 is a current control circuit, 8 is a chopper main circuit, and 9 is a brake control circuit.

Claims (1)

[Claims] 1. A current control circuit that controls the current of a motor that drives an electric vehicle is provided, and when the vehicle speed of the electric vehicle decreases to a predetermined value due to regenerative braking, the air brake is applied and the electric brake is gradually reduced. In a chopper control device for an electric vehicle that controls current, the difference between the vehicle speed signal of the electric vehicle and the output signal of the current control circuit is amplified to obtain a control signal, and the control signal is output only when the current is equal to or less than the predetermined value. A chopper control device for an electric vehicle, comprising a brake control circuit that causes feedback input to the current control circuit.