Drive force control device

Abstract

To provide a drive force control device capable of maintaining straight-line stability when one or two motors fail while a vehicle is in motion.SOLUTION: A drive force control device is used in a vehicle mounted with at least one set of a pair of bilaterally symmetrical wheels, each independently driven by a motor and drive force of the motors being individually controlled. The drive force control device executes control, with respect to the one set of motors in which left and right motors have a differential motor rotation speed equal to or greater than a threshold, to adjust the motor rotation speeds to match a lower motor rotation speed for a predetermined period, then shuts down the motor with the lower motor rotation speed, and corrects drive force of the remaining motor.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a driving force control device. [Background technology]

[0002] Patent Document 1 discloses a driving force control device for an independently driven wheel vehicle that, when some of the wheels of the independently driven vehicle become unable to drive while driving, corrects the target driving force for each wheel so that the ratio between the total driving force of the left wheels and the total driving force of the right wheels is the same when normal and when the wheels are unable to drive, and continues torque control, thereby enabling driving and ensuring safety. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-119647 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the driving force control device for an independently driven wheel vehicle disclosed in Patent Document 1, if one or two motors fail and the required torque cannot be output, a difference in rotation speed will occur between the left and right wheels, causing the vehicle to lose straight-line stability and potentially resulting in unintended turning.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a driving force control device that can maintain straight-line running when one or two motors fail while the vehicle is running. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the driving force control device of the present invention is used in a vehicle having at least one pair of wheels arranged symmetrically left and right, with the wheels driven independently by individual motors, and is a driving force control device that controls the driving force of the motors individually, and is characterized in that for a pair of motors where the difference in motor rotation speed between the left and right motors is greater than or equal to a threshold, it controls the rotation speed to match the motor rotation speed of the motor with the lower motor rotation speed for a predetermined period of time, then shuts down the motor with the lower motor rotation speed, and corrects the driving force of the remaining motor. [Effects of the Invention]

[0007] The driving force control device according to the present invention has the effect of being able to maintain straight-line running even when one or two motors fail while the vehicle is running. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a vehicle according to an embodiment. [Figure 2] FIG. 2 is a flowchart showing an example of control performed by a controller in a vehicle according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of a driving force control device according to the present invention will be described, but the present invention is not limited to the embodiment.

[0010] FIG. 1 is a diagram showing a schematic configuration of a vehicle 10 according to an embodiment. As shown in FIG. 1, the vehicle 10 according to the embodiment includes at least one pair of wheels 1 arranged symmetrically. That is, the vehicle 10 is an electric vehicle in which four motors 2FR, 2FL, 2RR, and 2RL are arranged inside four wheels 1FR, 1FL, 1RR, and 1RL on the front, rear, left, and right sides, respectively, as driving power sources. The vehicle 10 is an independent drive vehicle that can travel by independently driving the four motors 2FR, 2FL, 2RR, and 2RL. In the following description, when there is no need to distinguish between the wheels 1FR, 1FL, 1RR, and 1RL, they will also be simply referred to as wheels 1. In the following description, when there is no need to distinguish between the motors 2FR, 2FL, 2RR, and 2RL, they will also be simply referred to as motors 2.

[0011] Each wheel 1 is driven by power output from a corresponding motor 2. The motor 2 is an electric motor that functions as a power source for driving. Each motor 2FR, 2FL, 2RR, 2RL is provided with an inverter 3FR, 3FL, 3RR, 3RL, respectively. In the following description, when there is no need to distinguish between the inverters 3FR, 3FL, 3RR, 3RL, they will also be referred to simply as inverter 3. The inverter 3 is electrically connected to a battery (not shown). The vehicle 10 is also equipped with a controller 5, which is a driving force control device that controls the drive of each motor 2 by torque control or rotation speed control.

[0012] The controller 5 performs various controls (drive control, braking control, and turning control) for the motor 2 based on signals input from the rotation speed sensors 4FR, 4FL, 4RR, and 4RL, accelerator sensor, brake sensor, and steering angle sensor mounted on the vehicle 10. The rotation speed sensors 4FR, 4FL, 4RR, and 4RL are sensors that detect the rotation speeds of the motors 2FR, 2FL, 2RR, and 2RL. The accelerator sensor is a sensor that detects the amount of depression of the accelerator pedal (accelerator operation amount). The brake sensor is a sensor that detects the amount of depression of the brake pedal (brake operation amount). The steering angle sensor is a sensor that detects the steering angle of the steering wheel.

[0013] During drive control of the motors 2FR, 2FL, 2RR, and 2RL, the controller 5 calculates a motor torque command value for each of the motors 2FR, 2FL, 2RR, and 2RL based on a signal (accelerator operation amount) input from an accelerator sensor, and outputs a signal (torque command) indicating the motor torque command value to each of the inverters 3FR, 3FL, 3RR, and 3RL. Each of the inverters 3FR, 3FL, 3RR, and 3RL passes a predetermined current (excitation current) to each of the motors 2FR, 2FL, 2RR, and 2RL based on the torque command input from the controller 5. During braking control, the controller 5 causes each of the motors 2FR, 2FL, 2RR, and 2RL to function as a generator based on a signal (brake operation amount) input from a brake sensor, thereby performing regenerative braking. At this time, the power generated by each of the motors 2FR, 2FL, 2RR, and 2RL can be charged to the battery. Furthermore, during turning control, in order to stabilize the posture of the vehicle 10 during turning, the controller 5 changes the output balance of the front, rear, left and right motors 2FR, 2FL, 2RR, 2RL based on the signal (steering angle) input from the steering angle sensor, thereby enabling assistance in turning the vehicle 10.

[0014] FIG. 2 is a flowchart showing an example of control performed by the controller 5 in the vehicle 10 according to the embodiment.

[0015] First, while the vehicle 10 is traveling, the controller 5 monitors the rotation speeds (motor rotation speeds) of the motors 2FR, 2FL, 2RR, and 2RL based on the detection results of the rotation speed sensors 4FR, 4FL, 4RR, and 4RL (step S1). Next, the controller 5 compares the four motor rotation speeds (the rotation speeds of the motors 2FR, 2FL, 2RR, and 2RL) (step S2). Next, the controller 5 determines whether all four motor rotation speeds match (step S3). Note that matching of the motor rotation speeds does not necessarily mean that the motor rotation speeds are the same; it is determined that the motor rotation speeds match when the difference between the compared motor rotation speeds is less than a preset threshold, and that there is a deviation when the difference between the compared motor rotation speeds is equal to or greater than the threshold.

[0016] If it is determined that all four motor rotation speeds match (Yes in step S3), the controller 5 controls the torque of the four motors 2FR, 2FL, 2RR, and 2RL as normal running (step S4). Thereafter, the controller 5 ends the series of controls. On the other hand, if it is determined that all four motor rotation speeds do not match (No in step S3), the controller 5 determines whether all four motor rotation speeds are different (step S5).

[0017] If it is determined that the rotation speeds of all four motors are different (Yes in step S5), the controller 5 shuts down the four motors and sets them to Ready OFF (step S6). Then, the controller 5 ends the series of controls. On the other hand, if it is determined that the rotation speeds of all four motors are not different (No in step S5), the controller 5 determines whether only one motor rotation speed is different (step S7).

[0018] If it is determined that only one motor rotation speed deviates (Yes in step S7), the controller 5 temporarily switches the torque control to rotation speed control for the three normal motors 2, and controls them so that the rotation speed matches that of the failed motor 2 for a predetermined period of time (step S8). This allows measures to be taken to avoid unintended turning of the vehicle 10, making it possible to maintain the straight-line running of the vehicle 10. Next, the controller 5 shuts down at least one failed motor 2 (step S9). For example, in a first example, only the failed motor 2 is shut down. Alternatively, in a second example, the failed motor 2 and the motor 2 on the opposite side are shut down. That is, if vehicle 1FR fails, motors 2FR and 2FL are shut down. Furthermore, if motor 2RL fails, motors 2RR and 2RL are shut down.

[0019] Next, the controller 5 switches the motors 2 that are not shut down from rotation speed control to torque control, corrects the driving force, and drives the vehicle 10 (step S10). For example, in the first example, the three motors 2 that are not failing are controlled so that the left and right torque balances are consistent. That is, if motor 2FR fails, the torque of motor 2RR is set to "torque of motor 2FL + torque of motor 2RL." At this time, the torque of motor 2RR is output taking into account the braking torque due to the induced voltage of the failed motor 2FR. Note that the braking torque is generated when the rotation speed of motor 2FR increases and the input voltage to inverter 3FR < induced voltage (ω Φ)" holds when the rotational angular velocity is ω and the magnetic flux is Φ. Also, in the second example, the two motors 2 on the front and rear sides that are not failing are used for driving. That is, if motor 2FR on the front wheels fails, the two motors 2RR and 2RL on the rear wheels are driven. Moreover, if the motor 2RL on the rear wheel side fails, the two motors 2FR and 2FL on the front wheel side are driven.

[0020] The processing in steps S9 and S10 is a procedure for maintaining the torque balance between the left and right in order to respond to the driver's accelerator request when the motor 2 that has not been shut down is returned to torque control.

[0021] After executing the process of step S10, the controller 5 ends the series of controls.

[0022] On the other hand, if it is determined in step S7 that not only one motor rotation speed is deviating (No in step S7), the controller 5 determines that the two motor rotation speeds are the same and that the other two motor rotation speeds are deviating (step S11). Next, the controller 5 temporarily switches the two normal motors 2 from torque control to rotation speed control, and controls them for a predetermined period of time so that their rotation speeds match the rotation speed of the lower of the two failed motors 2 (step S12). This allows measures to be taken to avoid unintended turning of the vehicle 10, making it possible to maintain the straight-line running of the vehicle 10.

[0023] Next, the controller 5 shuts down the two failed motors 2 (step S13). For example, if motor 2FR and motor 2FL have failed, the controller 5 shuts down motor 2FR and motor 2FL. Also, if motor 2RR and motor 2RL have failed, the controller 5 shuts down motor 2RR and motor 2RL.

[0024] Next, the controller 5 returns the two motors 2 that are not shut down from the rotation speed control to the torque control, corrects the driving force, and runs the vehicle 10 (step S14). For example, if the motors 2FR and 2FL on the front wheels fail and shut down, the motors 2RR and 2RL on the rear wheels are driven by torque control. If the motors 2RR and 2RL on the rear wheels fail and shut down, the motors 2FR and 2FL on the front wheels are driven by torque control. If the motor 2FR on the front wheels and the motor 2RL on the rear wheels fail and shut down, the motors 2FL on the front wheels and the motor 2RR on the rear wheels are driven by torque control. If the motor 2FL on the front wheels and the motor 2RR on the rear wheels fail and shut down, the motor 2FR on the front wheels and the motor 2RL on the rear wheels are driven by torque control.

[0025] The processing in steps S13 and S14 is a procedure for maintaining the torque balance between the left and right motors in order to respond to the driver's accelerator request when the two motors 2 that have not been shut down are returned to torque control.

[0026] After executing the process of step S14, the controller 5 ends the series of controls.

[0027] The controller 5 according to the embodiment is a driving force control device used in a vehicle 10 having at least one pair of symmetrically arranged wheels 1, with the wheels 1 driven independently by individual motors 2, and controls the driving force of each of the motors 2 individually. For example, for a pair of motors 2 where the difference in motor rotation speed between the left and right motors is equal to or exceeds a threshold, the controller controls the rotation speed to match the lower motor rotation speed for a predetermined period, then shuts down the motor 2 with the lower motor rotation speed and corrects the driving force of the remaining motor 2. In this way, the controller 5 according to the embodiment can maintain straight-line running even when one or two motors 2 fail while the vehicle 10 is traveling. [Explanation of symbols]

[0028] 1,1FR,1FL,1RR,1RL wheels 2, 2FR, 2FL, 2RR, 2RL motor 3,3FR,3FL,3RR,3RL inverter 4FR, 4FL, 4RR, 4RL RPM sensor 5 Controller 10 vehicles

Claims

[Claim 1] A driving force control device is used in a vehicle having at least one pair of wheels arranged symmetrically on the left and right, the wheels being independently driven by individual motors, the driving force control device individually controlling the driving forces of the motors, A driving force control device characterized by performing control for a pair of motors in which the difference between the left and right motor rotation speeds is equal to or exceeds a threshold value to match the rotation speed of the motor with the lower rotation speed for a predetermined period of time, then shutting down the motor with the lower rotation speed and correcting the driving force of the remaining motor.

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