Driving control system for electric vehicles

Abstract

To provide a travel control device for an electric vehicle, capable of preventing a rapid decrease in vehicle speed not intended by a driver when an accelerator opening decreases, and allowing the driver to drive a vehicle without impairing operability.SOLUTION: When a vehicle speed is higher than a prescribed speed, and a change rate of an accelerator opening is less than a prescribed change rate (YES in Step S5), an ECU causes a driving motor to generate non-one-pedal drive braking torque with which the vehicle speed gradually decreases (Step S9). The ECU includes: a driving region in which one-pedal drive braking torque is generated when the accelerator opening decreases; and a braking region in which the non-one-pedal drive braking torque is generated when the accelerator opening decreases. The ECU causes the driving motor to generate the non-one-pedal drive braking torque when: the accelerator opening decreases within the driving region; the vehicle speed is higher than the prescribed speed; and the change rate of the accelerator opening is less than the prescribed change rate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a driving control device for an electric vehicle.

Background Art

[0002] Patent Document 1 describes a technique in which, when the accelerator is off, a driving force in the opposite direction to the rotation direction of the drive motor (a driving force in the regeneration direction) is generated in the drive motor. According to the technique described in Patent Document 1, the vehicle can be stopped and held in a stopped state without operating the brake. Such a function enables adjustment of vehicle acceleration, deceleration, and stop only by operating the accelerator pedal, and is sometimes called one-pedal driving.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case described in Patent Document 1, when the driver eases the depression of the accelerator pedal during traveling at a certain speed or higher, the vehicle suddenly decelerates contrary to the driver's intention, and such vehicle behavior is significantly different from that of a general vehicle that performs coasting (coast driving) with gentle deceleration when the accelerator pedal is released, so there is a risk of impairing the operability.

[0005] Therefore, an object of the present invention is to provide a control device for an electric vehicle that can prevent an unintended sudden decrease in vehicle speed when the accelerator opening decreases and allows the driver to drive the vehicle without impairing the operability.

Means for Solving the Problems

[0006] To solve the above problems, the present invention is mounted on an electric vehicle equipped with a drive motor for driving, and the accelerator pedal The accelerator opening range includes a first range in which driving torque is generated according to the accelerator opening, and a second range in which the accelerator opening is smaller than that of the first range and braking torque is generated according to the accelerator opening, and within the second range A driving control device for an electric vehicle, comprising a control unit that generates a first braking torque in the drive motor such that the vehicle speed decreases at a first rate of decrease when the accelerator opening is reduced, wherein the control unit is The accelerator opening is within the first region, The aforementioned vehicle speed is greater than the specified vehicle speed, and The vehicle speed change rate changed from a state where it was smaller than the specified vehicle speed change rate to a state where the accelerator opening decreased and it was in the second region. In that case, the vehicle speed decreases at a second rate of decrease that is smaller than the first rate of decrease. Slowly The invention is characterized by generating a second braking torque that decreases in the drive motor. [Effects of the Invention]

[0007] Thus, according to the present invention, it is possible to provide a control device for an electric vehicle that can prevent a sudden decrease in vehicle speed unintended by the driver when the accelerator opening is reduced, and allows the driver to operate the vehicle without impairing operability. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a diagram showing the configuration of an electric vehicle according to one embodiment of the present invention. [Figure 2] Figure 2 is a flowchart showing the procedure for switching to one-pedal drive using a driving control device for an electric vehicle according to one embodiment of the present invention. [Figure 3] Figure 3 is a flowchart showing the procedure for determining the one-pedal drive suspension condition by a driving control device for an electric vehicle according to one embodiment of the present invention. [Figure 4] Figure 4 is a time chart showing the changes in the vehicle state when a one-pedal drive switching operation is performed by a driving control device for an electric vehicle according to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] A driving control device for an electric vehicle according to one embodiment of the present invention is mounted on an electric vehicle equipped with a drive motor for driving, and includes a control unit that generates a first braking torque to the drive motor that reduces the vehicle speed by a first rate of decrease when the accelerator pedal opening decreases, wherein the control unit generates a second braking torque to the drive motor that reduces the vehicle speed by a second rate of decrease that is smaller than the first rate of decrease when the vehicle speed is greater than a specified vehicle speed and the rate of change of the accelerator opening is smaller than the specified rate of change. As a result, the driving control device for an electric vehicle according to one embodiment of the present invention can prevent a sudden decrease in vehicle speed that is not intended by the driver when the accelerator opening decreases, and the driver can drive the vehicle without impairing operability. [Examples]

[0010] Hereinafter, with reference to the drawings, an electric vehicle equipped with a driving control device according to an embodiment of the present invention will be described in detail.

[0011] In Figure 1, a vehicle 1 according to one embodiment of the present invention is composed of an engine 2, a transmission 3, a clutch 26, a drive motor 4 for driving, drive wheels 5, and an ECU (Electronic Control Unit) 10 as a control unit that comprehensively controls the vehicle 1.

[0012] Engine 2 has multiple cylinders. In this embodiment, engine 2 is configured to perform a series of four strokes for each cylinder, consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0013] Engine 2 is connected to an alternator 20 and an air conditioning compressor 21. The alternator 20 and the air conditioning compressor 21 are connected to the crankshaft 2A of engine 2 via a belt 22 and are operated by the power of engine 2. The alternator 20 generates alternating current. The air conditioning compressor 21 compresses the refrigerant for air conditioning.

[0014] The transmission 3 is configured to shift the rotation output from the engine 2 and drive the drive wheels 5 via the drive shaft 6.

[0015] The clutch 26 is provided between the crankshaft 2A of the engine 2 and the input shaft 3A of the transmission 3. The clutch 26 can be switched between an engaged state in which power transmission is performed between the engine 2 and the transmission 3, and a released state in which power transmission is not performed between the engine 2 and the transmission 3.

[0016] The drive motor 4 is provided between the output shaft 3B of the transmission 3 and the drive shaft 6. The drive motor 4 is driven by the electric power generated by the alternator 20 using the power of the engine 2, or the electric power stored in a battery (not shown). The drive motor 4 consists of a motor generator and also functions as a generator that performs regenerative power generation using the deceleration energy of the vehicle 1.

[0017] The vehicle 1 constitutes a hybrid system that can run using the power of at least one of the engine 2 and the drive motor 4. Therefore, the vehicle 1 is an electric vehicle that can run by the motor torque of the drive motor 4.

[0018] The ECU 10 is composed of a computer unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, an input port, and an output port.

[0019] In the ROM of these computer units, a program for making the computer unit function as the ECU 10 is stored together with various constants, various maps, etc.

[0020] That is, by the CPU executing the program stored in the ROM using the RAM as a working area, these computer units function as the ECU10 in the present embodiment.

[0021] Various sensors such as an accelerator opening sensor 51, a vehicle speed sensor 52, and a changeover switch 53 are connected to the input ports of the ECU10. The accelerator opening sensor 51 detects the depression amount (operation amount) of the accelerator pedal 50 as the accelerator opening and outputs a detection signal to the ECU10. The vehicle speed sensor 52 detects the vehicle speed of the vehicle 1 (hereinafter also referred to as the vehicle speed) from the rotational speed of the drive wheels 5 etc. and outputs a detection signal to the ECU10. The changeover switch 53 is a switch for the driver to switch the one-pedal drive mode ON or OFF, and outputs a detection signal to the ECU10.

[0022] When the accelerator opening of the accelerator pedal 50 decreases, the ECU10 generates a first one-pedal drive braking torque as a first torque at which the vehicle speed decreases at a first decrease rate in the drive motor 4. The one-pedal drive braking torque is a braking torque generated by the drive motor 4. Thus, the ECU10 realizes the so-called one-pedal drive function capable of significantly decelerating the vehicle 1 without operating a brake pedal not shown. With this one-pedal drive function, the driver can accelerate and decelerate the vehicle 1 only by operating the accelerator pedal 50 (hereinafter also referred to as an accelerator operation). Note that the ECU10 may control not only to decelerate the vehicle 1 by the one-pedal drive braking torque but also to cause the vehicle 1 to come to a stop after deceleration.

[0023] Even when the accelerator opening decreases, when the vehicle speed is greater than the specified vehicle speed and the change rate of the accelerator opening is smaller than the specified change rate, the ECU10 has a second decrease rate smaller than the first decrease rate at which the vehicle speed gently decreases at a second decrease rate. braking ​​The drive motor 4 generates non-one-pedal drive braking torque (coasting torque) as torque. Non-one-pedal drive braking torque is motor torque that enables coasting (coasting) accompanied by a gradual decrease in vehicle speed, similar to the operation of releasing the accelerator pedal in a typical vehicle that does not have a one-pedal drive specification. Therefore, in this embodiment, if the driver quickly releases the accelerator pedal 50, the vehicle speed of vehicle 1 decreases as if the brakes were applied, and if the driver slowly releases the accelerator pedal 50 when the vehicle speed is greater than the specified vehicle speed, coasting is performed. The first rate of decrease due to the generation of one-pedal drive braking torque and the second rate of decrease due to the generation of non-one-pedal drive braking torque are values ​​that change depending on the drag force (air resistance, etc.) acting on vehicle 1 and the amount of decrease in accelerator opening.

[0024] As shown in Figure 4, the ECU 10 has two regions for accelerator opening: a first region that generates driving torque corresponding to the accelerator opening, and a second region that generates braking torque corresponding to the accelerator opening, which is a region with a smaller accelerator opening than the drive region. The drive region and the braking region are separated by a boundary opening. As a result, when the accelerator opening decreases within the drive region, the vehicle speed decreases in accordance with the decrease in driving torque, and when the accelerator opening decreases within the braking region, the braking torque for one-pedal drive mode and the braking torque for non-one-pedal drive mode are set, and the vehicle decelerates according to the set braking torque.

[0025] If the accelerator opening decreases within the driving range, and the vehicle speed is greater than the specified vehicle speed and the rate of change in the accelerator opening is less than the specified rate of change, the ECU10 sets a one-pedal drive hold condition and generates drive torque corresponding to the accelerator opening in the drive motor 4.

[0026] Furthermore, when the non-one-pedal drive braking torque is set, the ECU10 generates the non-one-pedal drive braking torque in the drive motor 4 if the accelerator opening decreases from the drive region to the braking region.

[0027] When the accelerator opening increases from the braking region to the driving region, the ECU10 cancels the generation of non-one-pedal drive braking torque to the drive motor 4.

[0028] When the accelerator pedal 50 is released, the ECU 10 generates a one-pedal drive braking torque in the drive motor 4 if the accelerator opening decreases at a rate greater than the specified rate of change from the drive range.

[0029] Referring to Figure 2, the one-pedal drive switching operation by the driving control device according to this embodiment will be described. This one-pedal drive switching operation starts when the ECU 10 starts operating and is performed at a preset time interval. In the following description, one-pedal drive mode is the braking torque mode in which the driver's one-pedal drive mode selector switch 53 is selected in the ON state and the accelerator opening is within the braking range and a predetermined braking torque is generated in the drive motor 4. One-pedal drive hold is a state in which, even if the driver has selected the one-pedal drive mode selector switch 53 to the ON state, the drive motor 4 does not generate one-pedal drive braking torque, but exceptionally generates non-one-pedal drive braking torque. One-pedal drive hold condition is the condition for exceptionally generating non-one-pedal drive braking torque in the drive motor 4. One-pedal drive hold request is a request for exceptionally generating non-one-pedal drive braking torque in the drive motor 4.

[0030] In step S1, the ECU10 determines whether the driver's one-pedal drive mode toggle switch 53 (in the diagram, the switch is denoted as SW) is ON or OFF.

[0031] If the ECU 10 determines in step S1 that the state of the changeover switch 53 is ON, then in step S2 it determines whether or not one-pedal drive hold is set.

[0032] If the ECU10 determines in step S2 that the one-pedal drive hold condition is not set, it determines in step S3 whether or not the one-pedal drive hold condition is set. In step S3, the one-pedal drive hold condition determination process (see Figure 3), which will be described later, is executed. Setting the one-pedal drive hold condition means that this condition is met, and releasing the one-pedal drive hold condition means that this condition is not met.

[0033] If the ECU10 determines in step S3 that the one-pedal drive hold condition has been set, in step S4 it determines whether the rate of change in the accelerator opening is in the deceleration direction or not.

[0034] If the ECU10 determines in step S4 that the rate of change in the accelerator opening is in the deceleration direction, in step S5 it determines whether the rate of change in the accelerator opening is smaller than the specified rate of change.

[0035] If the ECU10 determines in step S5 that the rate of change in accelerator opening is less than the specified rate of change, it sets a request to suspend one-pedal driving in step S6.

[0036] Subsequently, in step S7, the ECU10 determines whether or not the accelerator opening is within the braking range.

[0037] If the ECU10 determines in step S7 that the accelerator opening is within the braking range, it sets the one-pedal drive to hold in step S8.

[0038] Subsequently, in step S9, ECU10 sets the non-one-pedal drive braking torque (switching the braking torque to non-one-pedal torque), and then completes this operation.

[0039] If the ECU10 determines in step S7 that the accelerator opening is not within the braking range, it sets the non-one-pedal drive braking torque in step S9 and terminates the operation.

[0040] If the ECU10 determines in step S3 that no one-pedal drive hold condition has been set, or if it determines in step S4 that the rate of change in accelerator opening is not in the deceleration direction, or if it determines in step S5 that the rate of change in accelerator opening is not less than the specified rate of change, then in step S10 the one-pedal drive hold request is canceled.

[0041] Subsequently, in step S11, ECU10 sets the one-pedal drive braking torque (switching the braking torque to one-pedal drive), and then completes this operation.

[0042] If the ECU10 determines in step S2 that one-pedal drive hold is set, in step S12 it determines whether the accelerator opening is within the drive range.

[0043] If the ECU 10 determines in step S12 that the accelerator opening is within the driving range, it cancels the one-pedal drive hold request in step S13, and cancels the one-pedal drive hold in step S14.

[0044] Subsequently, in step S11, ECU10 sets the one-pedal drive braking torque (switching the braking torque to one-pedal drive), and then completes this operation.

[0045] If the ECU 10 determines in step S1 that the state of the changeover switch 53 is not ON, or if it determines in step S12 that the accelerator opening is not within the drive range, in step S9 it sets the non-one-pedal drive braking torque (switches the braking torque to the non-one-pedal torque) and ends the operation.

[0046] Referring to Figure 3, the one-pedal drive hold condition determination process by the driving control device according to this embodiment will be described.

[0047] In step S21, the ECU10 determines whether the driver's one-pedal drive mode toggle switch 53 (in the diagram, the switch is denoted as SW) is ON or OFF.

[0048] If the ECU 10 determines in step S21 that the state of the changeover switch 53 is ON, then in step S22 it determines whether the accelerator opening is greater than the specified opening within the drive range.

[0049] If the ECU10 determines in step S22 that the accelerator opening is greater than a specified opening within the driving range, it determines in step S23 whether the vehicle speed is greater than a specified vehicle speed.

[0050] If the ECU10 determines in step S23 that the vehicle speed is greater than the specified vehicle speed, it then determines in step S24 whether the rate of change of vehicle speed is less than the specified rate of change.

[0051] If the ECU10 determines in step S24 that the rate of change of vehicle speed is less than the specified rate of change, in step S25 it determines whether the conditions regarding the accelerator opening, vehicle speed, and rate of change of vehicle speed have continued for the specified time.

[0052] If the ECU10 determines in step S25 that the specified time has been maintained, it sets the one-pedal drive hold condition in step S26 and terminates the current operation.

[0053] If the ECU 10 determines in step S22 that the accelerator opening is not greater than a specified opening within the driving range, or in step S23 that the vehicle speed is not greater than a specified vehicle speed, or in step S24 that the rate of change of vehicle speed is not less than a specified rate of change, or in step S25 that it has not continued for a specified time, then in step S27 it determines whether a one-pedal drive hold request has been set.

[0054] If ECU10 determines in step S27 that a one-pedal drive hold request has been set, it terminates this operation.

[0055] If the ECU 10 determines in step S27 that no one-pedal drive hold request has been set, or if it determines in step S21 that the state of the changeover switch 53 is not ON, it will release the one-pedal drive hold condition in step S28 and terminate this operation.

[0056] Referring to Figure 4, the changes in the vehicle state during the one-pedal drive switching operation will be explained. In Figure 4, the vertical axis represents the mode of the one-pedal drive mode selection switch 53 by the driver, vehicle speed, accelerator opening, setting or release of the one-pedal drive hold condition, setting or release of the one-pedal drive hold request, setting or release of the one-pedal drive hold, and braking torque, while the horizontal axis represents time.

[0057] At time t0, the accelerator opening is kept constant within the drive range, and vehicle 1 is traveling at a constant speed. In this state, the one-pedal drive hold condition, the one-pedal drive hold request, and the one-pedal drive hold are all released. Also, the braking torque is set to one-pedal drive.

[0058] At time t1, the one-pedal drive deactivation condition is set. Here, the one-pedal drive deactivation condition is set when the accelerator opening is greater than a specified opening within the driving range, the vehicle speed is greater than a specified vehicle speed, the rate of change of vehicle speed is less than a specified rate of change, and these conditions continue for a specified time.

[0059] Subsequently, at time t2, the accelerator opening begins to decrease gradually. At this point, the one-pedal drive hold condition is set, and a request to hold the one-pedal drive is set because the rate of change in the accelerator opening is in the deceleration direction and the rate of change in the accelerator opening is smaller than the specified rate of change. Also, since the accelerator opening is in the drive region and not the braking region, the braking torque is switched to non-one-pedal drive.

[0060] Subsequently, at time t3, one-pedal drive hold is set. Here, one-pedal drive hold is set in response to the accelerator opening dropping into the braking range. The accelerator opening continues to decrease, and after time t3, the accelerator opening becomes zero (the accelerator pedal 50 is released).

[0061] Subsequently, at time t4, the accelerator opening increases while remaining within the braking range. Here, since the accelerator opening is within the braking range, the vehicle speed continues to decrease.

[0062] Subsequently, at time t5, the accelerator pedal 50 is released again, and the accelerator opening decreases to zero.

[0063] Subsequently, at time t6, the accelerator opening increases to the drive range. This cancels the one-pedal drive hold request, the one-pedal drive hold is released, and the one-pedal hold condition is released. Therefore, the braking torque is switched to one-pedal drive.

[0064] Subsequently, at time t7, the accelerator opening decreases rapidly to the braking region. Here, because the rate of change in accelerator opening is greater than the specified rate of change, the braking torque is maintained for one-pedal driving, and the vehicle speed begins to decrease as if the brakes had been applied. After time t7, the vehicle speed decreases to a value less than the specified vehicle speed.

[0065] Subsequently, at time t8, the accelerator opening increases to within the drive range. As a result, the vehicle speed increases.

[0066] Thus, in this embodiment, when the accelerator pedal opening of the accelerator pedal 50 decreases, the ECU 10 generates a one-pedal drive braking torque in the drive motor 4 that reduces the vehicle speed by a first rate of decrease. Furthermore, when the vehicle speed is greater than the specified vehicle speed and the rate of change of the accelerator pedal opening is less than the specified rate of change, the ECU 10 generates a non-one-pedal drive braking torque in the drive motor 4 that reduces the vehicle speed by a second rate of decrease that is smaller than the first rate of decrease.

[0067] As a result, at low vehicle speeds or when the accelerator pedal is quickly released, the vehicle speed decreases at the first rate due to the generation of one-pedal drive braking torque, allowing the driver to adjust the vehicle speed using only the accelerator pedal without having to operate the brakes.

[0068] On the other hand, in coasting conditions where the vehicle speed is greater than the specified vehicle speed, if the accelerator pedal 50 is released gradually, the vehicle speed will decrease gradually at the second rate of decrease due to the generation of non-one-pedal drive braking torque, allowing the driver to coast the vehicle 1.

[0069] As a result, it is possible to prevent a sudden decrease in vehicle speed that is not intended by the driver when the accelerator opening is reduced, allowing the driver to drive vehicle 1 without compromising operability.

[0070] Furthermore, in this embodiment, the ECU 10 has a range of accelerator openings, which includes a drive range in which a drive torque corresponding to the accelerator opening is generated when the accelerator opening decreases, and a braking range in which the accelerator opening is smaller than that of the drive range, and in which the ECU 10 selects and generates a braking torque for one-pedal drive mode and a braking torque for non-one-pedal drive mode when the accelerator opening decreases.

[0071] If the accelerator opening decreases within the driving range, and the vehicle speed is greater than the specified vehicle speed, and the rate of change of the accelerator opening is less than the specified rate of change, the ECU 10 generates a drive torque corresponding to the accelerator opening in the drive motor 4.

[0072] Furthermore, if the non-one-pedal drive braking torque is selected and the accelerator opening decreases further from the driving region to the braking region, the ECU10 generates the non-one-pedal drive braking torque in the drive motor 4.

[0073] As a result, for example, if the accelerator opening decreases during coasting and the vehicle enters the braking zone, braking torque is generated in non-one-pedal drive mode, allowing vehicle 1 to continue coasting. Therefore, a sudden decrease in vehicle speed when the accelerator opening decreases can be suppressed, allowing the driver to operate vehicle 1 without compromising operability.

[0074] Furthermore, in this embodiment, when the accelerator opening increases from the braking region to the driving region, the ECU 10 cancels the generation of non-one-pedal drive braking torque to the drive motor 4.

[0075] As a result, when the accelerator opening increases from the braking region to the driving region, the generation of non-one-pedal drive braking torque for coasting is released, allowing the driver to drive vehicle 1 without compromising operability.

[0076] Furthermore, in this embodiment, if the accelerator opening decreases from the drive region at a rate greater than a specified rate of change due to the release of the accelerator pedal 50, the ECU 10 generates a one-pedal drive braking torque in the drive motor 4.

[0077] As a result, when the accelerator pedal 50 is released quickly, the vehicle speed decreases due to the generation of one-pedal drive braking torque. Therefore, by adjusting the speed of the accelerator pedal 50 release operation, the driver can switch between one-pedal drive braking torque, which reduces the vehicle speed in the same way as when the brakes are applied, and non-one-pedal drive braking torque, which allows the vehicle 1 to coast. Thus, the driver can operate the vehicle 1 without compromising operability.

[0078] While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims. [Explanation of symbols]

[0079] 1 vehicle (electric vehicle) 4. Drive motor 10 ECU (control unit) 50 Accelerator pedal

Claims

1. It is mounted on an electric vehicle equipped with a drive motor for propulsion, As a range of accelerator pedal opening, A first region that generates driving torque according to the accelerator opening, It has a second region in which the accelerator opening is smaller than the first region, and in which braking torque is generated according to the accelerator opening, A driving control device for an electric vehicle, comprising a control unit that generates a first braking torque in the drive motor such that the vehicle speed decreases at a first rate of decrease when the accelerator opening decreases within the second region, The control unit, A driving control device for an electric vehicle, characterized in that, when the accelerator opening is within the first region, the vehicle speed is greater than a specified vehicle speed, and the rate of change of vehicle speed is less than the rate of change of vehicle speed, the accelerator opening decreases and the vehicle speed changes to the second region, the device generates a second braking torque in the drive motor that causes the vehicle speed to decrease gradually at a second rate of decrease smaller than the first rate of decrease.

2. The control unit, The driving control device for an electric vehicle according to claim 1, characterized in that, when the accelerator opening is within the first region, the vehicle speed is greater than a specified vehicle speed, and the rate of change of the vehicle speed is smaller than the rate of change of the specified vehicle speed, and as a result of the accelerator opening continuing to decrease while the rate of change of the accelerator opening remains smaller than the rate of change of the specified accelerator opening, the accelerator opening changes to a state in the second region, the second braking torque is generated in the drive motor.

3. The control unit, The driving control device for an electric vehicle according to claim 2, characterized in that the accelerator opening is within the second region, and even if the rate of change of the accelerator opening exceeds the specified rate of change of accelerator opening while the second braking torque is being generated, the device continues to generate the second braking torque in the drive motor.

4. The control unit, The electric vehicle driving control device according to claim 2 or 3, characterized in that, if the accelerator opening is within the second region and the accelerator opening increases and returns to the first region while the second braking torque is being generated, the generation of the second braking torque by the drive motor is released.

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