JPH08334439A - Chassis dynamometer for electric automobile - Google Patents

Abstract

PURPOSE: To faithfully evaluate regenerative braking function in a wide application range by providing a chassis dynamometer for a four-wheel drive and letting it simulate a regenerative braking as brake dynamometers for the four wheels in a decelerating mode. CONSTITUTION: The chassis dynamometer 1 for electric automobile is constituted of a chassis dynamometer composed of two rollers 12, 13 and dynamometers 14, 15, a temperature adjuster 5, and two battery simulators 4 to secure resolution of load control, realize larger real inertia, and secure space efficiency. The dynamometers simulate the corresponding total running resistances and inertia drive shafts of the vehicle in a case except braking, however, in the case of decelerating and braking, respective dynamometers 14, 15 simulate the running resistances and the inertias of respective shafts so that respective speeds are controlled to be equalized each other. Therefore, the brake of a nondriving wheel is equally acted as the one in the real running so that the brake of the vehicle including regenerative braking can be faithfully simulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chassis dynamometer for testing electric vehicles.

[0002]

2. Description of the Related Art In testing electric vehicles, chassis dynamometers are widely used not only for evaluation of power performance but also for evaluation of energy consumption rate and mileage per charge. Generally, since a chassis dynamometer has been widely used for exhaust gas testing of an internal combustion engine vehicle, evaluation of an electric vehicle is generally performed on a chassis dynamometer prepared for an internal combustion engine vehicle.

However, since electric vehicles are generally highly efficient, a chassis dynamometer for electric vehicles, which is evaluated, is required to have sufficient accuracy both for simulating inertia and running resistance. In addition, since cooling of a general-purpose internal combustion engine vehicle is performed by a radiator, in a test on a chassis dynamometer, if the radiator is sufficiently cooled, cooling of other parts does not become a problem. For this reason, there are not a few facilities equipped with spot-like blowers that are designed only for radiator cooling. However, electric vehicles generally do not have radiators, and at the present time, there are scattered elements such as motors, controllers, and batteries that require cooling, so cooling that is closer to actual driving conditions is required. Becomes Further, the chassis dynamometer for an electric vehicle has to evaluate the efficiency of the vehicle including the effect of regenerative braking, and therefore it is necessary to be able to simulate regenerative braking.

That is, the electric vehicle is designed to have a low running resistance for the purpose of improving energy efficiency, and a chassis dynamometer for evaluating this requires high accuracy and resolution for simulating the running resistance. (High-precision load control). In addition, since the center of evaluation is energy efficiency when driving in a city, similarly high accuracy and resolution are required for the simulation of the vehicle mass including the equivalent inertia of the rotating portion (high-precision inertia control).

On the other hand, for the purpose of improving the resolution of inertia simulation of the chassis dynamometer and simplifying the system, it has become common practice in recent chassis dynamometers to employ electrical inertia simulation.

[0006]

However, since the electric vehicle is equipped with the battery, its mass is about 1.5 times larger than that of an internal combustion engine vehicle of the same level. Therefore,
When testing a heavy electric vehicle with this type of chassis dynamometer, it is necessary to set a larger dynamometer capacity in order to electrically simulate a large vehicle mass, and as a result the running resistance resolution is reduced. Inconvenience occurs.

FIG. 7 shows a control method of a vehicle and a dynamometer when a driving cycle test simulating driving in a city is carried out on a general-purpose chassis dynamometer. Since the general-purpose chassis dynamometer is for exhaust gas testing, it can be seen that the control method during deceleration differs greatly from the actual running state. That is, the vehicle is not controlled except for fully closing the accelerator, and the speed of the test vehicle is controlled by the dynamometer. When an electric vehicle is tested by this method, the brake pedal of the vehicle is not operated during deceleration.Therefore, regenerative braking of the vehicle can be performed at this level only if it has a function to simulate the braking force equivalent to engine braking. It works, but no further regenerative braking works. Even if the vehicle under test has a function of controlling regenerative braking according to the magnitude of the brake stroke or the pedal effort, this function does not work. Therefore, when testing a vehicle having such a function, the speed of the vehicle must be controlled by braking the vehicle by operating the brake pedal with an actuator.

Another problem arises even when the speed during deceleration is controlled by operating the brake pedal and braking the vehicle. For testing a two-wheel drive (2WD) vehicle, a general chassis dynamometer of a one-roller / one-dynamometer system is generally used. In tests using these chassis dynamometers, only the drive shaft is set on the rollers of the chassis dynamometer, and this dynamometer simulates the mass and running resistance of the entire vehicle including the non-drive shaft. However, since the non-driving wheels do not rotate, the brakes on the non-driving wheels do not work, and during deceleration, the kinetic energy of the entire vehicle is absorbed by the mechanical brakes and regenerative braking of the driving wheels via the driving wheels, and is collected in the actual running state. More energy than this can be recovered in the battery.

In order to eliminate this contradiction, SAEJ1634 stipulates a method of correcting the effect of regenerative braking and the one-charge running distance on the basis of the difference in brake capacity of each axis. However, that method also has the following problems. That is, since the efficiency of regenerative braking depends on the charging state of the driving battery and the rotation speed of the motor, the efficiency of regenerative braking greatly changes depending on the charging state of the driving battery and the rotation speed of the motor. Therefore, in the evaluation test of electric vehicles,
It is essential to control the vehicle speed during deceleration by controlling all brakes of the vehicle by controlling the brake pedal.

Next, one of the problems that arise when testing an electric vehicle with a general-purpose chassis dynamometer designed for an internal combustion engine vehicle is the cooling method. Cooling devices for general-purpose chassis dynamometers are often designed to cool vehicle radiators, but electric vehicles have many components, some of which are cooled by the vehicle running. Many are based on. Therefore, the cooling device needs to realize a cooling state equivalent to the actual traveling state.

Next, one of the things that make the test results of an electric vehicle unstable is the state of the battery. Since there are so many factors that affect the battery condition, it is very difficult to conduct a test in which the battery condition is always constant. In particular, a test at a high discharge rate has a great influence on the battery condition, so a test that requires a long time such as a speed-output characteristic test, or a test that is performed at a condition close to the maximum output such as a maximum speed test or an uphill test. Then, it is almost impossible to obtain stable data under the condition that the battery condition is constant. Therefore, in order to evaluate the characteristics of the vehicle itself under a constant battery condition, a battery simulator capable of performing tests with the battery state fixed is indispensable.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a chassis dynamometer for an electric vehicle which can faithfully simulate regenerative braking.

[0013]

To solve this problem, the chassis dynamometer for an electric vehicle of the present invention includes a chassis dynamometer for four-wheel drive, and in the deceleration mode, regenerative braking is performed as a four-wheel brake dynamometer. It is characterized by simulating and operating as a single-axis chassis dynamo for drive wheels in other modes.

[0014]

Operation: A chassis dynamometer for an electric vehicle is constructed based on the chassis dynamometer for a four-wheel drive vehicle. This chassis dynamometer has 4
It faithfully simulates regenerative braking as a wheel brake dynamometer, and operates as a general chassis dynamometer in other modes.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings showing an embodiment.

In FIG. 1, reference numeral 1 is a chassis dynamometer for an electric vehicle. The chassis dynamometer 1 for an electric vehicle includes a chassis dynamometer 2, a flywheel 3, a battery simulator 4, a temperature adjusting device 5, and a control device 6. The temperature adjusting device 5 includes an air circulating device 7 and an air adjusting device 8. The chassis dynamometer 2 includes mechanical brakes on both front and rear axes of the vehicle 11,
A chassis dynamometer for a four-wheel drive vehicle (4WD) is required in order to accurately evaluate all the functions of a brake composed of an electric brake of a drive shaft. There are three types of chassis dynamometers for four-wheel drive vehicles, depending on the configuration of the roller and the dynamometer. That is, a 4-roller / 4-dynamometer system that uses one roller / dynamometer pair for each wheel, a 2-roller / 2-dynamometer system that has a pair of rollers and dynamometer for each axis, and two rollers and one dynamo There are three types of two-roller / one-dynamometer system in which meters are mechanically connected.

The two-roller / one-dynamometer system is easy to control, but has some mechanical problems. That is, since the power that circulates between the two shafts is generated, the fluctuation of the mechanical loss due to this power cannot be ignored and there is a problem in accuracy. Further, in this system, it is difficult to separately measure the driving force and the braking force of each axis, and therefore it is impossible to grasp the circulating power. Since there are few fluctuations in mechanical loss and the control and measurement of braking / driving force for each axis can be performed independently, here, two rollers 12, 13 and 2 are used.
2 rollers consisting of two dynamometers 14 and 15
A 2-dynamometer chassis dynamometer is used. Of course, adoption of a 4-roller, 4-dynamometer system is also conceivable.

For the above reasons, the 2WD, 2 dynamometer type chassis dynamometer for 4WD is adopted. As shown in FIG. 1, the system configuration includes the chassis dynamometer for 4WD, a temperature adjusting device 5 that creates a temperature condition equivalent to an actual running state, and a battery simulator 4 that realizes a battery state with good repeatability.

As described above, in order to secure the load control resolution, the chassis dynamometer for an electric vehicle should realize a larger actual inertia and suppress the capacity of the dynamometer to a necessary and sufficient size. The outer rotor type chassis dynamometer has a large inertia compared to its size and capacity, so we adopted this in consideration of space efficiency. Since FR trucks are generally used as small trucks, in order to support small trucks, two removable flywheels equivalent to 0.8 tons were prepared on the rear axle side. The outer roller type dynamometer with a roller is a transistor inverter-controlled induction machine called a roller dynamometer. The inner stator has a primary winding and the outer movable part is provided with a secondary winding. The oscillating mechanism causes the stator shaft to rotate without friction, and the torque generated in the stator shaft is detected by the high-accuracy load cell attached to the torque arm. The roller torque (corresponding to driving force / braking force) is controlled by a dynamometer so that the output of the load meter becomes equal to the running resistance and the acceleration / deceleration resistance due to inertia.

The running resistance is loaded with a value that compensates for mechanical loss of the chassis dynamometer and the vehicle. On the other hand, the inertia is controlled by a value obtained by correcting the actual inertia such as the inertia of the roller, the flywheel, and the rotating portion of the vehicle. The force used for absorption or driving during acceleration / deceleration by the inertia is calculated as the product of the corrected inertia and the acceleration / deceleration of the vehicle. Table 1 outlines the specifications of the chassis dynamometer 2.
Shown in

[0021]

[Table 1] Next, in order to create a cooling state equivalent to the actual running state, the temperature adjusting device 5 is prepared. This sends temperature-controlled cooling air to the lower part of the vehicle in which the motor, controller and battery are arranged, and the wind speed is equivalent to the speed of the vehicle. After cooling the vehicle, the cooling air is guided into the pit by an exhaust fan installed at the rear of the vehicle, cools the main body of the dynamometer, and then is kept at a constant temperature by the heat exchanger and is blown from the blower. Since this device is for an electric vehicle with no exhaust gas, it does not force the introduction of fresh air. The upper limit of wind speed was set to 80 km / h in consideration of the usage environment of electric vehicles. The temperature that can be temperature controlled is 5 ° C to 40 ° C. However, due to the capacity limitation of the refrigerator, when the test is performed in the entire test range, the above temperature is within the range of -5 ° C to + 10 ° C from the external temperature. Guaranteed. The test vehicle can be soaked by operating the cooling device alone.

A battery simulator 4 is provided in order to realize a test that is not affected by the instability of the actual battery. This subsystem consists of two battery simulators. One is based on a motor generator (MG) type DC power supply device, and the other is based on a static high-capacity DC power supply device. Both have real resistance to simulate discharge resistance, and electromotive force and internal resistance can be controlled by computer instructions. In the MG type, in addition to this, the charging resistance can be controlled independently.

These can be used independently, and the MG type is used to simulate a power battery.
By using a static type for simulating an energy battery, it is possible to operate as a hybrid battery.

Next, the test of the electric vehicle using the chassis dynamometer for the electric vehicle having the above-mentioned structure is conducted as follows.

A control sequence for the two dynamometers and the vehicle is shown in FIG. Except during braking, it is simulated by the chassis dynamometer corresponding to the total running resistance of the vehicle and the inertia drive shaft. The chassis dynamometer corresponding to the non-driving shaft does not perform torque control, but this dynamometer is controlled so that the drum speed matches the roller speed on the driving shaft side (speed follow-up control).

During braking, the running resistance and inertia are set separately in the two dynamometers. That is,
Each dynamometer independently simulates the running resistance and inertia of each axis. Further, the respective speeds are controlled so as to be equal to each other. By switching the control of the chassis dynamometer during braking in this way, the brakes of the non-driving wheels operate in the same way as during actual running, so that the vehicle brake including regenerative braking can be faithfully simulated.

FIG. 3 shows the concept of control by taking an FR vehicle as an example.
(I) and (III) are the systems described here.
Is a mode used in the chassis dynamometer mode except when braking. (II) is a four-wheel brake dynamometer mode and is used during braking. On the contrary,
(III) shows the case where the vehicle brake is used on the chassis dynamometer of a general-purpose 1-roller / 1-dynamometer. (IV) is a method in which the vehicle brake is not used as in the exhaust gas test of an internal combustion engine vehicle on the same chassis dynamometer (speed control by the dynamometer).
It shows the case of testing.

(Experimental example) In order to analyze the simulated state of regenerative braking, a one-charge mileage test was carried out by each of these control methods using a delivery electric truck. In consideration of the usage mode for delivery, 10 traveling modes were adopted and the ambient temperature was kept constant at 25 ° C. 4 to 6 show changes in the braking / driving force of the front wheels and the rear wheels, the total braking / driving force, and the voltage / current of the battery during 10-mode traveling. 4 (a) and 4 (b) are the results of the system proposed here (corresponding to ((I) + (II) in FIG. 3) including the above-described brake simulation, and FIG.
(C) and (d) are when the vehicle brake is used on a general-purpose 1-roller / 1-dynamometer chassis dynamometer (corresponding to (III) in Fig. 3), and Fig. 6 (e) is based on the exhaust gas test. When the vehicle brake is not used (Fig. 3
(Corresponding to (IV)).

The test vehicle has a function of selecting the rate of regenerative braking, and FIGS. 4 (a) and 5 (c) are examples in which the strength of regenerative braking is increased (High position). 5) and FIG. 5D are examples in which this is weakened (Low position).

FIG. 4 showing a complete simulation of the brake.
As for (a) and (b), when the regenerative braking shown in FIG. 4 (b) is weak, the braking force ratio between the front and rear wheels is close to the original brake capacity ratio of the vehicle. It can be seen that the simulation of power is accurate. Strong regenerative braking Fig. 4
In (a), the rear wheel (drive shaft) side has a large value only in the high speed range. Since the used regenerative braking operation algorithm of the vehicle is designed to give priority to the regenerative braking, it can be seen that the vehicle is speed-controlled by the ON / OFF control of the regenerative braking in the regenerative braking operation region.

The braking force of the front wheels fluctuates in anti-phase with the fluctuation of the braking force of the rear wheels due to regenerative braking. This occurs because the front wheel roller follows the speed change of the rear wheel roller that rapidly changes due to ON / OFF of regenerative braking, and this fluctuation of the front wheel braking force signal does not mean the fluctuation of the braking force itself. .

A case where a brake actuator is used in the general-purpose chassis dynamometer for 2WD shown in FIGS. 5C and 5D will be examined. As mentioned above, 2WD
In the mode, the amplitude of the regenerative braking force should obviously increase, but the battery current data in FIG. 5 (c) shows that the current during regenerative braking is almost the same as in FIG. 4 (a). . It can be inferred that the brake control algorithm giving priority to regenerative braking produced this result. Similarly, the level of regenerative braking in FIG. 5 (d) is equivalent to that in FIG. 4 (b). In this vehicle, the effect of regenerative braking does not depend on the magnitude of inertia, and is a constant value determined by the vehicle. in this way,
2W for vehicles with certain braking algorithms
It can be seen that it is not appropriate to estimate the effect of regenerative braking based on the general test results of the D chassis dynamometer.

A brake control device that prioritizes regenerative braking for the purpose of improving efficiency and safety of a brake system including regenerative braking has been proposed (Y. Kabuyama, “Isuzu
“ELF” -1.25 ton payload electric delivery vehicl
e, ”Paper No. 13.11, presented at EVS11, Florence,
Italy (September 1992) and A. Giorgetti, L. Cave
stro, M. Rampazzo, “A Light weight braking system
for electric vehicles, ”paper No.12.07, presented
at EVS11, Florence, Italy (september 1992)).
In this system, the ratio of the braking force distributed to the mechanical brakes of the front and rear wheels and the regenerative braking of the drive shaft dynamically changes according to the vehicle condition. Faithful imitation is essential. Similarly, mechanical brakes also employ a brake system via a control system for impact, and considering high efficiency and safety, it is obvious that such a smart brake is essential.

Next, FIG. 6 (e) will be examined in the case of performing control for a general internal combustion engine vehicle in which speed control is performed on the dynamometer side during deceleration. During braking, the absorption force of the dynamometer is equivalent to the braking force, and regenerative braking is not operating at all (whether the regenerative braking rate selection switch is set to High or Low).

The results of the one-charge mileage test under each condition are shown in Table 2. Since the algorithm for controlling regenerative braking gives priority to regenerative braking, the effect of regenerative braking does not depend on the simulation of braking but only on the level of regenerative braking. Therefore, it can be understood that the method of estimating the effect of regeneration from the result of the general-purpose one-roller / one-dynamometer chassis dynamometer may lead to an erroneous result.

[0036]

[Table 2]

[0037]

As is apparent from the above description, according to the present invention, a chassis dynamometer for an electric vehicle, which has a wide range of applications applicable to light vehicles to small trucks and which enables faithful evaluation of regenerative braking function, is provided. Can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory perspective view showing a configuration of a chassis dynamometer for an electric vehicle.

FIG. 2 is an explanatory diagram showing a control sequence on a chassis dynamometer for an electric vehicle.

FIG. 3 is an explanatory diagram showing various controls of a chassis dynamometer for an electric vehicle and a vehicle.

FIG. 4 is a graph showing braking / driving force during a mode test on a chassis dynamometer for an electric vehicle.

FIG. 5 is a graph showing braking / driving force during a mode test on a general-purpose chassis dynamometer.

FIG. 6 is a graph showing braking / driving force during a mode test on a general-purpose chassis dynamometer.

FIG. 7 is an explanatory view showing a control sequence during a mode test on a general-purpose chassis dynamometer.

[Explanation of symbols]

 1 Chassis Dynamometer for Electric Vehicles 2 Chassis Dynamometer 3 Flywheel 4 Battery Simulator 5 Temperature Controller 6 Controller 7 Air Circulator 8 Air Conditioner 11 Vehicle 12 Roller 13 Roller 14 Dynamometer 15 Dynamometer

Claims (3)

[Claims] 1. A four wheel drive chassis dynamometer is provided to simulate regenerative braking as a four wheel brake dynamometer in a deceleration mode, and to operate as a uniaxial chassis dynamometer for drive wheel shafts in other modes. Chassis dynamometer for electric vehicles. 2. The chassis dynamometer for an electric vehicle according to claim 1, further comprising a temperature adjusting device that creates a temperature condition equivalent to an actual running state. 3. The chassis dynamometer for an electric vehicle according to claim 1, further comprising a battery simulator.