DE-102010027896-B4 - Control unit for an electric vehicle

Abstract

Control unit for an electric vehicle (10) comprising a brake control device (50) for stabilizing vehicle behavior by controlling a friction brake (24) of a vehicle wheel (14, 15, 16, 17): an electric motor (11) which is controlled in a state in which current flows, in which the vehicle wheel (14, 15, 16, 17) is driven by a torque when current flows, and a regenerative state in which the vehicle wheels (14, 15, 16, 17) are braked by a regenerative torque, a slip determination device (50) for determining whether the brake control device (50) is to be actuated on the basis of a slip tendency of the vehicle wheel (14, 15, 16, 17) or not, and a motor control device (40) for controlling a drive state of the electric motor (11) on the basis of a determination result from the slip determination device (50), wherein the motor control means (40) prevents regenerative braking by the electric motor (11) when it has been determined that the result of the determination by the slip determination means (50) is abnormal, wherein the motor control means (40) controls the electric motor (11) to a torque during current flow which is not greater than a predetermined value when it has been determined that the result of the determination by the slip determination means (50) is abnormal, characterized by the fact that the control unit further comprises a vehicle wheel speed sensor (51, 52, 53, 54), wherein the engine control means (40) determines that the determination result of the slip determination means (50) is abnormal if an output voltage of the vehicle wheel speed sensor (51, 52, 53, 54) is outside a predetermined range and/or, wherein the control unit further comprises a brake control unit (50), which includes slip determination means (50) and an EV control unit (40), which includes the engine control means (40) and communicates with the brake control unit (50), wherein the engine control means (40) determines that the determination result from the slip determination means (50) is abnormal if a An abnormality in the communication between the brake control unit (50) and the EV control unit (40) was detected.

Inventors

• Minoru Yuki

Assignees

• Subaru Corporation

Dates

Publication Date

20260513

Application Date

20100419

Priority Date

20090420

Claims (4)

1. Control unit for an electric vehicle (10) comprising a brake control device (50) for stabilizing vehicle behavior by controlling a friction brake (24) of a vehicle wheel (14, 15, 16, 17), comprising: an electric motor (11) controlled to a current-flow state in which the vehicle wheel (14, 15, 16, 17) is driven by a current-flowing torque, and controlled to a regenerative state in which the vehicle wheels (14, 15, 16, 17) are braked by a regenerative torque, a slip-determining means (50) for determining whether the brake control device (50) is to be actuated based on a slip tendency of the vehicle wheel (14, 15, 16, 17), and a motor control means (40) for controlling a drive state of the electric motor (11) based on a The control unit (40) determines the result of the slip determination means (50), wherein the engine control means (40) prevents regenerative braking by the electric motor (11) when the result of the slip determination means (50) is determined to be abnormal, and wherein the engine control means (40) controls the electric motor (11) to a torque during current flow that is not greater than a predetermined value when the result of the slip determination means (50) is determined to be abnormal, characterized in that the control unit further comprises a vehicle wheel speed sensor (51, 52, 53, 54), wherein the engine control means (40) determines that the result of the slip determination means (50) is abnormal when an output voltage of the vehicle wheel speed sensor (51, 52, 53, 54) is outside a predetermined range and/or, and wherein the control unit further comprises a brake control unit. (50) comprises the slip determination means (50) and an EV control unit (40) which includes the engine control means (40) and communicates with the brake control unit (50), wherein the engine control means (40) determines that the determination result of the slip determination means (50) is abnormal if an abnormality in the communication between the brake control unit (50) and the EV control unit (40) has been detected.
2. Control unit for an electric vehicle (10) according to Claim 2 , wherein the torque is controlled based on a driving condition when current flows through the electric motor (11).
3. Control unit for an electric vehicle (10) according to Claim 2 or 3 , wherein the motor control means (40) controls a torque acting on the vehicle wheel (14, 15, 16, 17) towards zero by controlling the electric motor (11) to the torque during current flow which is not greater than the predetermined value.
4. Control unit for an electric vehicle (10) according to one of the Claims 1 until 3 , wherein the brake control device (50) is an anti-lock brake control device (50) to prevent the vehicle wheel (14, 15, 16, 17) from locking during vehicle braking.

Description

Cross-reference to related registrations The present application claims priority of Japanese patent application no. 2009-101876 , which was submitted on April 20, 2009, and which is incorporated herein in its entirety. Background of the invention Field of invention The present invention relates to a control unit for an electric vehicle, which includes a brake control device for stabilizing the behavior of a vehicle or vehicle behavior by controlling a friction brake of a vehicle wheel. Description of the state of the art In an electric vehicle that includes an electric motor to drive a wheel, the electric motor acts as a generator during braking, thus braking the vehicle using regenerative torque generated by the electric motor. However, the braking force obtained through regenerative braking using the electric motor is affected by battery characteristics, etc. Therefore, a braking force of the required strength is typically ensured with consistency by using a friction brake, such as a disc brake, in addition to regenerative braking. Furthermore, when regenerative braking and a friction brake are used in combination, it is important to coordinate the regenerative and friction brakes. Furthermore, an electric vehicle is also equipped with a braking control device, such as an anti-lock braking system (ABS). The braking control device estimates the vehicle's behavior based on signals from a wheel speed sensor, an acceleration sensor, etc., and stabilizes the vehicle's behavior by applying the friction brakes to control the braking force applied to each wheel. Additionally, when another braking control device, such as the ABS, is active, a motor control unit simultaneously performs torque control on the electric motor. By controlling the electric motor in this way, coordinated with the braking control device, the vehicle's behavior is further stabilized. However, if an abnormality occurs in a control system, such as in the vehicle's wheel speed sensor or in a communication network, the motor control unit may not be able to determine the operating state of the brake control device, and therefore the brake control device and the electric motor cannot be properly coordinated. For example, if coordinated control of the brake control device and the electric motor becomes difficult, regenerative torque may be generated by the electric motor even though ABS control is active. If the electric motor is controlled in this way, the vehicle's wheels may lock up, leading to instability in vehicle behavior, and as a result, the steering stability of the electric vehicle may deteriorate. document JP H11-45 03 A This reveals a regenerative braking device that receives target value information for the regenerative braking torque from a hydraulic braking device, and the regenerative braking torque is controlled to approximate a target value for the regenerative braking torque in the regenerative braking device. The hydraulic braking device receives information about the actual regenerative braking torque value from the regenerative braking device, and the vehicle's braking system is controlled to achieve a hydraulic braking torque target value in the hydraulic braking system, the magnitude of which is the difference between the actual regenerative braking torque and the overall braking torque target value. If the information about the actual regenerative braking torque value is not received normally, the regenerative braking torque target value is reduced and set to zero. Since the vehicle is braked only by the hydraulic deceleration torque, the vehicle's braking system can be excellently controlled to ensure that the overall braking torque reaches the target overall deceleration torque. document DE 10 2007 022 849 A1 Disclosing a device for influencing the driving behavior of a vehicle. The vehicle's efficiency can be improved by providing a system comprising several electric machines, each assigned to one of the vehicle's wheels and capable of operating either as a motor or generator. The electric machines are preferably connected to a control unit that can individually control them to accelerate, decelerate, and/or generate a yaw moment about the vehicle's vertical axis. document DE 44 35 953 A1 Disclosing an electrically powered vehicle with a drive system comprising at least one electric motor, which is controlled and monitored by an electronic control unit to drive at least one vehicle wheel in a drive mode of the motor and to optionally contribute to the overall braking torque when the motor is operated in a braking mode. It also includes a hydraulic braking system, which is actuated by the driver and which acts on at least one of the front wheels of the vehicle, wherein the hydraulic braking torque generated by the driver through the hydraulic braking system is adjusted such that, in order to modulate the overall braking torque acting on the vehicle wheels, the change in the electric braking torque is arranged to remain