JP2005124287A - Drive control arrangement for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive control arrangement in which occurrence of slip is suppressed while acceleration performance and hill climbing performance are improved. <P>SOLUTION: If it is judged that the temporal change of an acceleration open degree &theta; is small on a low &mu; path for a vehicle, for example, comprising a motor as a driving source (step S3&rarr;S5), a target motor torque T used for controlling the motor torque in a step S9 is periodically changed between 0 and k&theta; (k is a constant)(step S7). <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention relates to a drive control device that controls drive force applied to wheels in a vehicle.

In an electric vehicle, linear output torque characteristics can be realized with respect to the stroke of the accelerator pedal. Therefore, torque characteristics that match the acceleration operation of the driver can be realized, and driving feeling is improved. On the other hand, when the road surface condition is bad due to snow accumulation, freezing, etc., the low rotational torque is large, so there is a problem that slip is likely to occur and the accelerator operation is difficult. Patent Document 1 is a technique that suppresses such slip and ensures steering stability even on a low μ road with low frictional resistance. Specifically, the acceleration of the wheel is calculated from the number of rotations of the motor, and the presence or absence of slip is determined from this and the current torque command value. Suppress.
JP-A-8-182118

  However, in this technology, slip is estimated only from the relationship between wheel acceleration and torque command value, and the torque is limited. Therefore, it cannot be said that the available torque is fully utilized, and sufficient acceleration performance and Climbing performance cannot be obtained.

  Accordingly, an object of the present invention is to provide a drive control device that improves acceleration performance and climbing performance while suppressing the occurrence of slip.

  In order to solve the above-described problems, a vehicle drive control device according to the present invention is a vehicle drive control device that controls a drive force applied to wheels by a drive means. A μ road determination means is provided, and when it is determined that the road is a low μ road, the driving force that is actually applied to the wheels is vibrated and changed within a predetermined torque range according to the accelerator operation amount of the driver. And

  The low μ road can be determined by determining a slip state or the like. When it is determined that the road is a low μ road, the driving force applied to the wheels is periodically increased or decreased within a predetermined torque range according to the accelerator operation amount of the driver, thereby periodically increasing and decreasing the torque. Switch.

  For example, the low μ road determination means determines that the road has a low μ road when the slip ratio of the wheel is equal to or greater than a predetermined value. After reaching this predetermined value, the drive torque may be reduced until the slip ratio becomes 0, and after reaching zero, the drive torque may be increased.

  This driving means is preferably an electric motor. The electric motor may be mounted inside the wheel.

  In this way, by periodically switching between torque increase and decrease, it is possible to travel using the maximum possible torque while suppressing continuation of slip, so that acceleration performance and climbing performance can be ensured. it can.

  When the slip ratio reaches a predetermined value, the drive torque is reduced to automatically suppress the slip. When the slip ratio becomes zero, that is, when the friction between the slope and the road surface is in a rolling friction state, the drive force is reduced. By increasing the driving force, the driving force can be efficiently transmitted to the road surface, and acceleration performance and climbing performance are improved.

  By using the electric motor as the driving means, it becomes easy to periodically switch between increasing and decreasing torque. Further, when the electric motor is mounted inside the wheel, the maximum torque can be utilized for each wheel, so that the effect of improving acceleration performance and climbing performance can be obtained.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.

FIG. 1 is a schematic configuration diagram of a vehicle equipped with a vehicle drive control device according to the present invention. This vehicle is an in-wheel motor type electric vehicle in which electric motors 4 _FR , 4 _FL , 4 _RR , 4 _RL are independently provided as drive sources in the four wheels (FR, FL, RR, RL). . Each wheel FR, FL, RR, RL is provided with a brake device 5 _FR , 5 _FL , 5 _RR , 5 _RL and a wheel speed sensor 6 _FR , 6 _FL , 6 _RR , 6 _RL for detecting the wheel speed, respectively. Is done.

The motor control device 1 corresponding to the control unit of the vehicle drive control device according to the present invention includes each electric motor 4 _FR , 4 _FL , 4 _RR , 4 _RL and each wheel speed sensor 6 _FR , 6 _FL , 6 _RR. 6 _RL and the battery 2 are connected, and output signals of an accelerator pedal stroke sensor 7 for detecting an accelerator pedal opening, a steering angle sensor 8 for detecting a steering amount, and a shift switch 9 for detecting a shift setting state are inputted. Has been. On the other hand, the brake control device 3 is connected to each brake device 5 _FR , 5 _FL , 5 _RR , 5 _RL and receives an output signal of the brake pedal stroke sensor 10 for detecting the brake pedal opening. . The motor control device 1 and the brake control device 3 are connected so as to transmit information to each other.

In this vehicle, when the driver operates the accelerator pedal, the motor control device 1 determines each wheel FR, FL, based on the accelerator opening θ detected by the accelerator pedal stroke sensor 7 and the shift setting state in the shift switch 9. The drive torque to be applied to RR and RL is calculated, and the operation of each electric motor 4 _FR , 4 _FL , 4 _RR , 4 _RL is controlled so that the obtained drive torque is obtained. For example, when the target torque T of the motor is set to be proportional to the accelerator pedal stroke (accelerator pedal opening θ) as shown in FIG. 2, a drive torque characteristic that matches the pedal operation of the driver can be realized. .

In addition, when the brake pedal is operated, the brake control device 3 uses the brake devices 5 _FR , 5 _FL , 5 _RR , 5 _RL to drive the wheels FR, FL, The braking force to be applied to RR and RL is controlled. At this time, each electric motor 4 _FR , 4 _FL , 4 _RR , 4 _RL may function as a generator to perform regenerative power generation, collect it as electric power, and store it in the battery 2.

  Specific drive torque control in the present embodiment will be described with reference to FIGS. FIG. 3 is a process flowchart of the drive torque control, and FIGS. 4 and 5 are graphs showing examples of time changes of the accelerator stroke and the motor torque at the start operation on the high μ road and the low μ road, respectively.

  This drive torque control is repeatedly executed by the motor control device 1 at a predetermined timing while the power switch of the vehicle is turned on.

  First, the accelerator opening θ is read from the output of the accelerator pedal stroke sensor 7, and the estimated road surface friction coefficient μ information is read (step S1). Here, the estimated road surface friction coefficient μ can be estimated from the slip state of each wheel FR, FL, RR, RL during traveling so far and the relationship between the applied driving force and the actual wheel speed. Of course, another means for measuring the road surface friction coefficient may be provided.

  The obtained μ is compared with the threshold value μth (step S3). Only when μ is smaller than μth, whether or not the absolute value of the time variation dθ / dt of the accelerator opening is smaller than the threshold value α. Is determined (step S5). If μ ≧ μth or | dθ / dt | ≧ α, the process proceeds to step S6. If μ <μth and | dθ / dt | <α, the process proceeds to step S7. To do.

  When μ ≧ μth, that is, when the vehicle is not traveling on a low μ road, or when | dθ / dt | ≧ α, that is, when the accelerator pedal is operating at a high speed and decelerating, the low μ road The current time t is set to a variable t0 representing the constant accelerator stroke travel start time at (step S6), and kθ (k is set based on the setting state of the shift switch 9 to the target motor torque T in proportion to the accelerator opening θ. A constant determined by the shift state to be set is set (step S8).

  On the other hand, when μ <μth and | dθ / dt | <α, that is, when traveling on a low μ road, the operation speed of the accelerator pedal is low, and the accelerator stroke is substantially constant, The target motor torque T is obtained by multiplying k.theta. (T-t0) by k.theta. (K is a constant determined by the set shift state based on the set state of the shift switch 9) proportional to the accelerator opening degree .theta. (Step S7). ). That is, the target motor torque T is periodically changed from kθ → 0 → kθ in a predetermined cycle f (= 2 × π / ω).

The operation of the electric motors 4 _FR , 4 _FL , 4 _RR , 4 _RL is controlled so that the target motor torque T obtained in steps S 7, S 8 is applied to each wheel FR, FL, RR, RL (step S 9). Exit.

If the road is not a low μ road (referred to as a high μ road relative to a low μ road), the driver depresses the accelerator pedal at a constant speed when starting, and the accelerator opening θ is constant at θ ₁ from time t ₁ . And The time change of the accelerator opening θ at this time is as shown in FIG. At this time, according to the present embodiment, the motor torque T applied by each of the electric motors 4 _FR , 4 _FL , 4 _RR , 4 _RL is also monotonous until time t ₁ , similarly to the time change of the accelerator opening θ. It increases, and a constant motor torque kθ ₁ is obtained after time t ₁ . As a result, the necessary maximum torque can be exhibited, start / acceleration performance can be ensured, and climbing performance during climbing can also be exhibited.

In the present embodiment, in the case of a low μ road, when the time change of the accelerator opening θ as shown in FIG. 5A is realized, the motor torque is set to kθ ₁ and 0 after time t _1. Is periodically changed by the period f. By periodically changing the torque in this way, it is possible to use high torque up to near the slip limit, and at the same time, even if slip occurs due to torque input exceeding the slip limit, the torque subsequently decreases Then, since the tire can surely grip the road surface below the slip limit, it is possible to prevent the slip from continuing. Further, by periodically changing the torque, it is possible to apply the torque more efficiently than when the torque is constant, and the start / acceleration performance and the climbing performance are improved.

  Further, such vibration torque can be automatically applied, and the driver does not need to perform an advanced accelerator operation, so even an unskilled driver can exhibit the performance of the vehicle. It becomes possible.

  In the above description, the case where the present invention is applied to an electric vehicle having a drive source independently in each wheel has been described as an example, but the electric motor may be provided not on the wheel but on the vehicle body side. In addition, an electric motor as a drive source is not arranged independently for each wheel, but a drive force is applied to the drive wheels by a distributing means such as a differential gear from a drive source common to a plurality of drive wheels, and further to all drive wheels. It may be configured to distribute.

  Further, the present invention is not limited to an electric vehicle, but a series type hybrid vehicle that generates electric power by an internal combustion engine and drives an electric motor by the electric power, and a parallel type having an internal combustion engine and an electric motor as drive sources. It is also possible to apply to other hybrid vehicles. Furthermore, the present invention can also be applied to a type of vehicle that has a drive source other than an electric motor, such as an internal combustion engine and an external combustion engine, independently for each drive wheel.

  Here, the driving force is periodically oscillated with a cosine wave period. However, the periodic oscillation of the driving force is not limited to this method, and the sawtooth wave shape and the cycle itself may be periodically changed. Good. Further, here, the driving force is periodically changed from 0 to a predetermined torque. However, the minimum torque at the time of this periodic fluctuation is not limited to 0, and the maximum torque is also normally applied. It may be different from the torque value.

  For example, the wheel slip rate is monitored, and when the slip rate reaches a predetermined value or more, the drive torque is reduced, and when the slip rate becomes 0, the drive torque is increased again to apply the drive torque in a vibrational manner. May be. In this case, the slip ratio can be effectively suppressed to a predetermined value or less by torque limitation. Further, by increasing the driving torque when the slip ratio is 0, the driving force can be transmitted from the wheel to the road surface in a state of rolling friction between the wheel and the road surface, so that the driving force is efficiently transmitted to the road surface. This improves the starting performance and climbing performance.

It is a schematic block diagram of the vehicle carrying the vehicle drive control apparatus which concerns on this invention. It is a graph which shows the example of a setting of the target torque T of the motor of an accelerator pedal stroke (accelerator pedal opening degree (theta)). It is a process flowchart of the drive torque control in the apparatus of FIG. It is a graph which shows an example of each time change of the accelerator stroke at the time of start operation in a high micro road, and motor torque. It is a graph which shows an example of each time change of the accelerator stroke at the time of start operation in a low micro road, and motor torque.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Motor control device, 2 ... Battery, 3 ... Brake control device, 4 ... Electric motor, 5 ... Brake device, 6 ... Wheel speed sensor, 7 ... Accelerator pedal stroke sensor, 8 ... Steering angle sensor, 9 ... Shift switch, 10: Brake pedal stroke sensor, FR, FL, RR, RL ... Wheels.

Claims (4)

In the vehicle drive control device for controlling the drive force applied to the wheels by the drive means,
Comprising a low μ road determination means for determining whether the traveling road is a low μ road,
A drive control device for a vehicle, characterized in that, when it is determined that the road is a low μ road, the driving force actually applied to the wheel is changed in a vibration manner within a predetermined torque range according to the accelerator operation amount of the driver. .   The low μ road determination means determines a low μ road when the slip ratio of the wheel is equal to or greater than a predetermined value, and the vibrational driving force change between the predetermined torque ranges has a slip ratio. 2. The vehicle drive control device according to claim 1, wherein after the predetermined value is reached, the drive torque is reduced until the slip ratio becomes zero, and the drive torque is increased after the slip ratio becomes zero. 3. .   The vehicle drive control device according to claim 1, wherein the drive means is an electric motor.   4. The vehicle drive control device according to claim 3, wherein the electric motor is mounted inside a wheel.

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