JP2022114547A - Control apparatus for electric vehicle - Google Patents

Abstract

To provide a control apparatus for an electric vehicle capable of suppressing the occurrence of regeneration loss of energy in consideration of load state and/or towing state.SOLUTION: A control apparatus for an electric vehicle includes a motor with at least power generating function and is configured to brake the electric vehicle with regenerative torque of the motor during deceleration. The control apparatus includes a controller for controlling the electric vehicle. The controller calculates a center of gravity H(H_add) of the vehicle and a drive wheel distance L(L_add), which is a distance from the center of gravity to a drive wheel 2, estimates a load on the drive wheel 2 on the basis of the calculated center of gravity H(H_add) and drive wheel distance L(L_add;), and sets an amount of regeneration of the motor on the basis of the estimated load.SELECTED DRAWING: Figure 2

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric vehicle that controls the amount of regeneration of a motor connected to drive wheels.

Patent Literature 1 describes a regenerative braking control device for an electric vehicle configured to recover energy while achieving good brake feeling during deceleration. The control device described in Patent Document 1 is configured to brake the vehicle with braking torque from a mechanical braking device (friction braking device) and regenerative braking (regenerative torque) from a motor. Specifically, the maximum braking torque (ideal braking torque) within a range in which the wheels do not lock is estimated, the mechanical braking torque is set to be smaller than the ideal braking torque, and the difference between the ideal braking torque and the mechanical braking torque is determined. is set as regenerative braking torque. The above ideal braking torque is estimated based on the vehicle weight and vehicle height (or the height of the center of gravity) of the electric vehicle.

Japanese Patent Application Laid-Open No. 2010-200590

In an electric vehicle, it is desired to set the regeneration amount of the motor to be large. The amount of regeneration is set according to the vehicle weight of the vehicle, and in the control device described in Patent Document 1, the ideal braking torque is estimated based on the vehicle weight, and the vehicle is braked by the mechanical braking torque and the regenerative braking torque. is configured to However, the weight of a towing vehicle such as a truck changes greatly depending on the loading condition of cargo handling. For example, if a target regeneration amount is set according to a large load, when the load becomes small, the regenerative torque braking amount may become excessive and the drive wheels may slip. On the other hand, if the target regeneration amount is set according to the state where the load is small, the regeneration amount becomes small when the load is large, and the regeneration efficiency is lowered. Also, even with the same load capacity and vehicle weight, depending on the shape of the load, the position and method of loading or towing, the limit value of the slip of the drive wheels will change, and the amount of regeneration will also change. . In such a case, depending on the loading state of the vehicle or the towing state, the efficiency of energy regeneration may be reduced, resulting in energy regeneration loss.

The present invention has been conceived with a focus on the above technical problems, and provides a control device for an electric vehicle that can suppress the occurrence of energy regeneration loss in consideration of the loading state and traction state. It is intended to provide

To achieve the above object, the present invention provides a control apparatus for an electric vehicle, which includes a motor having at least a power generation function, and is configured to brake the vehicle by regenerative torque of the motor during deceleration. The controller calculates the center of gravity position of the electric vehicle and the driving wheel distance, which is the distance from the center of gravity position to the driving wheels, and based on the calculated center of gravity position and driving wheel distance, the driving The load acting on the wheel is estimated, and the amount of regeneration of the motor is set based on the estimated load.

According to the present invention, the center of gravity of the vehicle and the drive wheel distance, which is the distance from the center of gravity to the drive wheels, are calculated, and the load acting on the drive wheels is estimated from the calculated parameter values. It is configured to grasp the deceleration limit value (slip limit) to the extent that slip does not occur. The amount of regeneration of the motor is set according to the load acting on the drive wheels and the deceleration limit value. Therefore, as described above, even if the load acting on the drive wheels differs depending on the load capacity, the shape of the object to be loaded with the same load capacity, or the position and method of loading or towing, the load It is possible to set the amount of regeneration according to the state and traction state. That is, it is possible to set an appropriate amount of regeneration according to the state of the vehicle, and as a result, it is possible to avoid or suppress generation of regeneration loss. In other words, it is possible to avoid or suppress a decrease in energy efficiency.

1 is a diagram schematically showing a vehicle targeted by an embodiment of the present invention; FIG. FIG. 4 is a diagram for explaining a center of gravity position and a drive wheel distance; FIG. 10 is a diagram for calculating a variation in driving wheel distance; FIG. 10 is a diagram for calculating a variation in the center of gravity position and drive wheel distance;

Embodiments of the present invention will be described with reference to the drawings. It should be noted that the embodiment shown below is merely an example when the present invention is embodied, and does not limit the present invention.

A vehicle targeted by the embodiments of the present invention is an electric vehicle including at least a motor having a power generation function and a battery capable of supplying and receiving electric power to and from the motor. Alternatively, it may be a hybrid vehicle further equipped with an engine as a power source.

FIG. 1 shows a specific example of an electric vehicle according to an embodiment of the invention. An electric vehicle (hereinafter referred to as vehicle) Ve shown in FIG. 1 transmits driving torque output from a motor 1 as a driving force source to rear wheels 2 to generate driving force. In other words, FIG. 1 shows the configuration of a rear wheel drive vehicle in which the rear wheels 2 serve as driving wheels. The vehicle Ve in the embodiment of the present invention may be a front wheel drive vehicle in which the front wheels 3 are driving wheels. Alternatively, it may be a four-wheel (all-wheel) drive vehicle in which both the front wheels 3 and the rear wheels 2 are driving wheels. When an engine is mounted as a driving force source, a transmission (not shown) is provided on the output side of the engine so that the driving torque output by the driving force source is transmitted to the drive wheels via the transmission. can be configured to

The motor (MG) 1 is composed of, for example, a permanent magnet synchronous motor or an induction motor. Therefore, the motor 1 generates drive torque when supplied with electric power, and generates power when it is forced to rotate by the running inertia force of the vehicle Ve. The negative torque accompanying the power generation becomes the braking force (braking torque) of the vehicle Ve.

A motor 1 is connected to a power supply 4 . The power supply device 4 supplies electric power to the motor 1 and has a power storage device for storing electric power generated by the motor 1, an inverter for converting voltage or frequency, and the like.

An output shaft (rotor shaft) of the motor 1 is connected to a differential gear 5 as a final reduction gear. The differential gear 5 is configured to output drive torque for running to the rear wheels (driving wheels) 2 . The front wheels 3 are steered wheels and are connected to a steering mechanism 6 .

A braking device 7 is provided for each of the front wheels 3 and the rear wheels 2 . The brake device 7 is similar to a conventionally known brake mechanism, and may be a friction brake such as a disc brake, a drum brake, or a powder brake. That is, the brake device 7 is configured to generate a braking force in a direction to stop the rotation of the front wheels 3 and the rear wheels 2 by generating frictional force by hydraulic pressure, electromagnetic force, or the like.

Further, a pedal 8 is provided for manipulating driving conditions such as acceleration and deceleration. The pedals 8 may be two pedals, an accelerator pedal and a brake pedal, or may be a so-called one-pedal acceleration/deceleration operation device.

An electronic control unit (hereinafter referred to as ECU) 9 is provided for controlling the motor 1, the power supply 4, the brake device 7, and the like. The ECU 9 corresponds to the "controller" in the embodiment of the present invention, and is composed mainly of a microcomputer, performs calculations using input data, pre-stored data and programs, and outputs the calculation results. as a control command signal. The input data includes, for example, vehicle speed, acceleration, accelerator opening, which is the amount of drive demand, brake pedal force, road surface friction coefficient μ, vehicle weight, wheel speed of each wheel, position of the center of gravity of the vehicle Ve (or height of the center of gravity). ), the distance from the center of gravity to the driving wheels (driving wheel distance), on/off of the towing switch, the number of revolutions and torque of the motor 1, and other various sensor values. The pre-stored data is a map or the like that determines the regenerative braking torque based on the position of the center of gravity and the driving wheel distance. The ECU 7 outputs a torque (driving torque, regenerative torque) command signal for the motor 1, a braking torque command signal for the brake device, and the like as control command signals. Although the example of FIG. 1 shows an example in which one ECU is provided, a plurality of ECUs may be provided, for example, for each device to be controlled or for each control content.

In the electric vehicle Ve configured in this way, it is preferable to set the regeneration amount of the motor to be large. On the other hand, in a towing vehicle such as a truck, the amount of regeneration changes depending on the loading condition of cargo handling. For example, when the load capacity is large, when the load capacity is small, or even if the load capacity and vehicle weight are the same, the slip limit value of the drive wheels changes depending on the shape of the load, the position and method of loading or towing. As a result, the amount of regeneration also changes. In such a case, the efficiency of energy regeneration may be reduced, resulting in energy regeneration loss. Therefore, in the embodiment of the present invention, the amount of regeneration is set according to the towing state (or loading state) of the vehicle.

Specifically, the ECU 7 is configured to calculate the upper limit deceleration that can be regenerated by the motor 1 . In other words, it is configured to calculate a deceleration limit value (slip limit value) at which the rear wheel 2 does not slip.

FIG. 2 is a diagram for explaining the center-of-gravity position of the vehicle Ve and the distance between the center-of-gravity position and the drive wheels (hereinafter simply referred to as the drive-wheel distance). FIG. FIG. 2B is a diagram for explaining the center-of-gravity position H_base and the driving wheel distance Lr_base in the case where the center-of-gravity position H_base and the driving wheel distance Lr_base are shown in FIG. FIG. 2C is a diagram for explaining H_add(a) and driving wheel distance Lr_add(a), and FIG. It is a figure for demonstrating H_add(b) and driving wheel distance Lr_add(b).

In the embodiment of the present invention, the amount of regeneration in the state of no towing shown in FIG. 2(a) is set as a reference state. and the driving wheel distance Lr_add. In other words, the correction values for these three parameters are calculated. Then, the load acting on the driving wheels is obtained based on these correction values. Then, based on the load acting on the drive wheels (that is, the rear wheels 2), a slip limit value (deceleration at which no slip occurs) is obtained, and a target regeneration amount is set. The ellipses in (a) to (c) of FIG. 2 indicate the friction limit (slip limit). In other words, it indicates the magnitude of the load applied between the rear wheel 2 and the road surface (friction circle range).

Further, the driving wheel distance Lr_add is calculated according to whether the wheels (wheels of the towed object) are the towed object 10 contacting the road surface, or whether the load is not in contact with the road surface. good. Further, the driving wheel distance Lr_add may be calculated according to only the increase/decrease in the distance of the vehicle in the front-rear direction, or may be calculated in consideration of the increase/decrease in the height direction of the vehicle. Furthermore, when the towed object 10 moves laterally during travel, it is possible to avoid slipping during turning, etc., and in a normal case where the towed object 10 does not move during travel. In comparison, the correction value may be set smaller.

The magnitude of the friction limit ar of the rear wheel (driving wheel) 2 indicated by the friction circles in FIGS. 2(a) to 2(c) can be expressed as follows. First, the load Wr and the load change amount dw of the rear wheels 2, which are regenerative wheels, are:
Wr=M×g×(L−Lr)/L (1)
dw=(M×ar×H)/L (2)
becomes. Note that M indicates the vehicle weight, g indicates the gravitational acceleration, L indicates a predetermined wheel base, and μ indicates the friction coefficient of the road surface. Using these formulas to find the friction limit ar of the rear wheel 2,
M×ar=μ×(Wr×dW)
= μ × (M × g × (L-Lr) / L + (M × ar × H) / L)
Finally, the friction limit ar of the rear wheel 2 is
ar x (1-(μ x H)/L) = g x (μ x (L-Lr)/L)
and further rearranging,
ar=g×(μ×(L−Lr))/(L−μ×H) (3)
becomes.

Calculating the friction limit ar in the examples of FIGS. 2(b) and 2(c) from equation (3), the driving wheel distance Lr_add is greater in FIG. 2(b) than in FIG. The height H_add of the center of gravity position is smaller than that of FIG. 2(b) and that of FIG. 2(c). Therefore, the friction limit ar is larger in FIG. 2(b) than in FIG. 2(c), and therefore the friction circle (slip limit) is also larger in FIG. 2(b). In other words, even when towing objects of the same load, the one who tows from the rear of the vehicle as shown in FIG. The amount of regeneration is greater than

Thus, in the embodiment of the present invention, the amount of regeneration that varies depending on the towing position and method is calculated from the position of the center of gravity, the drive wheel distance, and the load acting on the drive wheels (rear wheels) 2 to the friction limit (that is, the slip limit). is configured to ask for and set Therefore, it is possible to set an appropriate amount of regeneration according to the state of the vehicle Ve, and as a result, it is possible to avoid or suppress generation of regeneration loss. In short, the friction limit ar changes depending on the above-described center-of-gravity position H_add and drive wheel distance Lr_add, thereby changing the amount of power that can be regenerated. Therefore, by setting the target amount of regeneration according to the friction limit ar, it is possible to avoid or suppress a decrease in energy regeneration efficiency.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above examples, and may be modified as appropriate within the scope of achieving the object of the present invention. As described above, the friction limit ar changes depending on the vehicle weight M_add, the center-of-gravity position H_add, and the drive wheel distance L_add, which are the amount of change from the reference value, and accordingly the amount of regeneration also changes. Therefore, the method of calculating the friction limit ar is not limited to the above example.

For example, the vehicle weight M_add may be calculated from the drive power required during acceleration. Further, the drive wheel distance L_add may be calculated according to the amount of change in the acceleration sensor, the amount of vertical lift of the vehicle, or the amount of change in the viewing angle of the vehicle-mounted camera. For example, as shown in FIG. 3, the change margin of the driving wheel distance L_add is calculated based on the acceleration and the sensor value for an arbitrary number of times (for example, four times). Further, as shown in FIG. 4, an in-vehicle camera 11 in front of the vehicle may detect the amount of change in the center-of-gravity position H_add and display the amount of change on a display (for example, a display of a navigation system) 12 . In this case, the center-of-gravity position H_add and the driving wheel distance L_add are corrected according to the amount of change indicated by the solid line with respect to the reference indicated by the broken line. FIG. 4(a) shows the change with respect to the reference during acceleration without traction, and FIG. 4(b) shows the change with respect to the reference during acceleration with traction. showing change.

1 motor 2 rear wheel (drive wheel)
3 front wheels 4 power supply 5 differential gear 6 steering mechanism 7 brake device 8 pedal 9 electronic control unit (ECU)
10 towed object 11 in-vehicle camera 12 display Ve vehicle

Claims (1)

A control device for an electric vehicle, which includes a motor having at least a power generation function, and is configured to brake the vehicle by regenerative torque of the motor during deceleration,
A controller that controls the electric vehicle,
The controller is
calculating the position of the center of gravity of the electric vehicle and the drive wheel distance, which is the distance from the position of the center of gravity to the drive wheels;
estimating the load acting on the drive wheel based on the calculated position of the center of gravity and the distance between the drive wheels;
A control device for an electric vehicle, wherein the amount of regeneration of the motor is set based on the estimated load.

Images