DE102017221986A1 - Method and control device for operating an electric vehicle or a hybrid vehicle - Google Patents

Abstract

Method and control device for operating an electric vehicle or a hybrid vehicle with an electric machine comprising a drive unit, wherein when there is no accelerator operation, via a creep and hill start function on the electric machine, an actual torque is provided on the output, which from a control side of the creep and hill start function requested target torque (2) is dependent. In accordance with the invention, a change in the acceleration (5) that is formed depending on the actual torque at the output is determined. Depending on the acceleration change, a maximum permissible creep and hill-start torque (3) is determined. Then, when requested by the creep and hill start function target torque (2) is smaller than the maximum allowable creep and hill start torque (3), the requested by the creep and hill start function target torque (2) is left unchanged. Then, when requested by the creep and hill start function target torque (2) is greater than the maximum allowable creep and hill start torque (3), requested by the creep and hill start function target torque (2) to zero or in reduced to about zero.

Description

The invention relates to a method for operating an electric vehicle or a hybrid vehicle. Furthermore, the invention relates to a control device for operating an electric vehicle or a hybrid vehicle.

Then, when a driver of an electric vehicle or hybrid vehicle on the driver side, the accelerator pedal, which is also called the accelerator pedal, an actual torque is provided depending on the driver's pedal operation and thus depending on a driver's request via an electric machine of the electric vehicle or hybrid vehicle. The actual torque provided as a function of a driver request can already be monitored by a simple safety function.

There are electric vehicles and hybrid vehicles known that use a creep and hill start function. About a creep and hill start function when the driver side is no accelerator pedal operation, an actual torque on the output provided, which is dependent on a control side requested by the creep and hill start function target torque. This should then, when the vehicle is operated in the plane, a Ankriechen the vehicle are made possible. Then, when the vehicle is operated uphill on a slope, this is to prevent rolling back of the vehicle in the slope and preferably also a Ankriechen of the vehicle in the slope are made possible.

Then, when an electric vehicle or hybrid vehicle uses such a creep and hill start function, a high actual torque can be provided at the output via the electric machine. So far, it is difficult to monitor the control unit provided via a creep and hill start function on the output torque, since typically in vehicles no tilt sensor is installed, could be detected by the metrology, whether the vehicle operated in a plane or uphill in a slope becomes.

However, depending on whether an electric vehicle or hybrid vehicle is operating in a plane or uphill on a hillside, one and the same actual moment has different effects with respect to the acceleration of the vehicle. For example, if the vehicle is operated in a plane and too high a torque is provided for too long a time, undesirable uncontrolled acceleration of the vehicle may be caused. This is a disadvantage. There is therefore a need to monitor the actual torque provided at a power take-off via a creeping and hill-start function with regard to its admissibility or safety.

From the DE 10 2015 202 107 A1 For example, a method for canceling creep torque in a hybrid vehicle is known. According to this prior art it is proposed to apply a creep torque to vehicle wheels and subsequently apply braking torque to the wheels. In response to the braking torque exceeding a calibrated threshold, the electric machine is prevented from generating the creep torque.

On this basis, the invention is based on the object to provide a novel method and a control device for operating an electric vehicle or a hybrid vehicle.

This object is achieved by a method and a control device according to the main claims. According to the invention, a change in acceleration that forms as a function of the actual torque at the output is determined. Depending on the acceleration change, a maximum permissible creep and hill-start torque is determined. Then, if the requested by the creep and hill start function torque is less than the maximum allowable creep and hill start torque, the requested by the creep and hill start function target torque is left unchanged. Then, when requested by the creep and hill start function target torque is greater than the maximum allowable creep and hill start torque, the requested by the creep and hill start function target torque is reduced to zero or about zero. The control unit is designed to carry out the individual steps of the method.

The method and control device according to the invention allow a simple and reliable safety-side monitoring of an actual torque provided via a creeping and hill-start function with the aid of an electric machine (for example a synchronous or asynchronous machine) at the output of an electric vehicle or hybrid vehicle. As a result, an uncontrolled acceleration of the hybrid vehicle or electric vehicle can be avoided. It is determined depending on the actual moment at the output forming acceleration change. Depending on this change in acceleration, a maximum permissible creep and hill-start torque is determined, wherein the control-requested desired torque is compared with the maximum permissible creep and hill-start torque to decide whether the target torque left unchanged or to zero or about zero is reduced.

With the present invention, if the requested by the creep and hill start function target torque is greater than the maximum allowable creep and hill start torque, that of the creep and hill start function Requested desired torque step-like or ramp-like reduced to zero or approximately zero. Thus, an uncontrolled acceleration of the motor vehicle can be safely and reliably avoided.

According to an advantageous development, the maximum permissible creep and hill-start torque is determined such that the same is the smaller, the greater the acceleration change that forms on the output. This can be an uncontrolled acceleration of the motor vehicle can be avoided.

According to an advantageous development, the requested by the creep and hill start function target torque is detected with a first cycle time. The depending on the actual moment at the output forming acceleration change and the maximum permissible creep and hill start torque are determined in a second cycle time, which is an adjustable multiple greater than the first cycle time, the comparison between the maximum allowable creep and Hill start torque and the requested by the creep and hill start function target torque is preferably carried out in the second cycle time. This can be an uncontrolled acceleration of the motor vehicle can be avoided.

According to an advantageous development, the maximum permissible creep and hill-start torque is determined by means of a characteristic stored on the control side. Hereby, the maximum allowable creep and hill start torque can be determined particularly reliable and easy.

The invention allows a simple and robust, safety-side verification of the actual torque provided by an electric machine at an output depending on a creep and hill-start function, which torque is dependent on the requested desired torque. The invention does not require a sensor of an inclination of the motor vehicle.

• 1 eine Kennlinie zur Durchführung der Erfindung;
• 2 ein erstes Zeitdiagramm zur Verdeutlichung der Erfindung;
• 3 ein zweites Zeitdiagramm zur Verdeutlichung der Erfindung; und
• 4 ein drittes Zeitdiagramm zur Verdeutlichung der Erfindung.

Preferred developments emerge from the subclaims and the following description. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

• 1 a characteristic for carrying out the invention;
• 2 a first timing diagram to illustrate the invention;
• 3 a second time chart to illustrate the invention; and
• 4 a third time chart to illustrate the invention.

The invention relates to a method for operating an electric vehicle or a hybrid vehicle with a drive unit comprising an electric machine. Furthermore, the invention relates to a control device for carrying out the method.

The present invention relates to details of a creep and hill start function of an electric vehicle or hybrid vehicle in which a torque is provided on the output via the electric machine.

Then, when the driver side is no accelerator pedal operation and preferably also on the driver side there is no brake pedal operation, an actual torque at the output of the vehicle is provided via a creeper and hill start function on the electric machine of the drive unit. This actual torque provided at the output is dependent on a desired torque requested by the creep and hill-start function on the control side.

On the control side of the creep and hill start function, the requested target torque can also be calculated or output control side, although there is no accelerator operation but a brake pedal operation. Only then, when no more brake pedal operation is present or the brake pedal operation decreases, the requested by the creep and Berganfahrfunktion control side target torque is converted into an actual torque on the output.

In order to increase the safety of a creep and hill start function of an electric vehicle or a hybrid vehicle in which an actual torque is provided via an electric machine at the output, it is proposed according to the invention to determine a change in acceleration which is dependent on the actual torque at the output.

An acceleration of the vehicle can be determined from a measured speed of the vehicle, wherein the acceleration is the first time derivative of the speed. The acceleration change is the first time derivative of the acceleration or the second time derivative of the velocity.

Depending on the determined acceleration change, a maximum permissible creep and hill-start torque is determined. This is preferably done via a control-side stored map or a control-side stored characteristic. So shows 1 by way of example, such a characteristic stored on the control side 1 in which the acceleration change Δa is a maximum permissible creep and hill-start torque M _MAX is applied.

Then, when the requested by the creep and hill start function target torque is smaller than the dependent on the acceleration change determined maximum allowable creep and hill start torque, requested by the creep and hill start function target torque is left unchanged and based on the same at the output an actual moment provided.

On the other hand, if the desired torque required by the creep and hill-start function on the control side is greater than the maximum permissible creep and hill-start torque determined by the acceleration change, the desired torque requested by the creep and hill-start function is set to zero or approximately reduced to zero. The drive via the electric machine of the drive unit is then switched off.

With the invention, a simple and robust safety function for the crawl and hill start function is possible. The function does not require any sensors, with which the inclination, in which a motor vehicle is operated, would have to be determined. Accordingly, the method according to the invention requires no knowledge of a gradient or slope in which the hybrid vehicle or electric vehicle is located.

Further details of the invention are described below with reference to the signal flow diagrams of 2 to 4 described.

In 2 . 3 and 4 are over the time t several temporal curves 2 . 3 . 4 and 5 applied, namely with the temporal curve 2 a time course of a requested by the creep and Berganfahrfunktion control side target torque, with the temporal curve 3 a time course of a determined depending on an acceleration change maximum allowable creep and starting torque M _MAX , with the temporal curve 4 a time course of the speed of the electric vehicle or hybrid vehicle. and with the temporal curve 5 a time course of acceleration of the electric vehicle or hybrid vehicle.

2 shows the curves 2 . 3 . 4 and 5 for a situation in which the electric vehicle or hybrid vehicle is up in the mountain and crawls uphill. From the electric machine of the drive unit of the electric vehicle or hybrid, an actual torque is provided on the output of the vehicle, which is requested by a control unit from the creep and Berganfahrfunktion requested control torque 2 is dependent. The actual torque provided at the output effects a starting of the motor vehicle while increasing the speed in the sense of the curve 4 , as well as under acceleration according to the curve 5 , Depending on the determined or developing acceleration change .DELTA.a is about the characteristic 1 the 1 the maximum permissible creep and hill-start torque M _MAX or 3 is determined, which in the case of Berganfahren the 2 is constant. It lies in 2 The requested by the creep and Berganfahrfunktion control side target torque 2 always below the maximum permissible creep and hill-start torque 3 , The requested torque requested by the creep and hill start function 2 is therefore permanently smaller than the maximum permissible creep and hill start torque 3 , In this case, the requested torque is requested by the creep and hill start function 2 unchanged allowed to provide actual torque as a function of the output via the electric machine.

3 shows the curves 2 . 3 . 4 and 5 for a situation in which the electric vehicle or hybrid vehicle is to crawl in the plane. For this purpose, then turn of the creep and Berganfahrfunktion control side, a target torque 2 requested, as a function of which the electric machine of the electric vehicle or hybrid vehicle at the output an actual torque builds up or provides. This actual moment leads to a change of the speed 4 as well as change of acceleration 5 of the motor vehicle. Depending on the acceleration change that is being formed, the characteristic curve is changed again 1 the 1 the maximum permissible creep and hill-start torque 3 determined. Also in 3 is the requested torque requested by the creep and hill start function 2 permanently smaller than the maximum permissible creep and hill-start torque 3 so that requested by the creep and hill start function target torque 2 left unchanged and provided depending on the output actual moment.

4 shows a malfunction of the creep and hill start function, which can be detected by the method according to the invention, in particular when, for example, a desired torque is requested for Ankriechen in the plane, which is too high and is actually only allowed for a hill start function. 4 clarified with the curve 2 the dependent on the creep and hill start function control side requested target torque. Depending on this target torque 2 At the output an actual torque is provided, which leads to the change of the speed 4 as well as to the change of the acceleration 5 at the output leads. Depending on the determined acceleration change Δa is again using the characteristic curve 1 the 1 the maximum permissible creep and hill-start torque 3 determined.

In 4 At time t1, the requested torque is requested by the creep and hill-start function 2 greater than the maximum permissible creep and hill-start torque 3 , This is in 4 even at the time t2, ie a defined debounce time .DELTA.t after the time t1. the case so that then requested by the creep and hill start function target torque 2 is not left unchanged, but rather is reduced according to the invention to zero or approximately zero. In approximately zero means that the target torque may deviate a defined amount from zero.

In 4 becomes when the requested by the creep and hill start function target torque 2 greater than the maximum permissible creep and hill-start torque 3 is, the target moment 2 ramped down to zero or about zero.

However, it is also possible, the target moment 2 gradually reduce.

From the characteristic stored on the control side 1 the 1 follows that the maximum permissible creep and hill start torque 3 or. M _MAX is determined such that the same is the smaller, the greater the acceleration change forming at the output .DELTA.a is.

In a particularly preferred embodiment of the invention, the requested by the creep and hill start function target torque 2 detected with a first cycle time, in particular every 10 ms. The depending on the actual torque at the output forming acceleration change and depending on the maximum allowable creep and hill start torque 3 are determined in a second cycle time which is adjustable by an integer multiple times greater than the first cycle time. The second cycle time is in particular 300 ms. The comparison of the requested by the creep and hill start function target torque 2 with the maximum permissible creep and hill-start torque determined as a function of the acceleration change 3 takes place in particular in the cycle of the second cycle time. If there is a sustained change in acceleration as a result of the change in acceleration determined within the second cycle time, the requested target torque is required 2 too high, so that no more torque is to be built on the output more.

The invention further relates to a control device for operating an electric vehicle or hybrid vehicle, wherein the control device is used to carry out the method according to the invention.

The control unit then determines, if there is no accelerator operation, a setpoint torque via a creep and hill start function. Furthermore, if there is no brake pedal operation, then this requested target torque 2 implemented by the electric machine to provide an actual torque to output. The control unit determines a dependent on the actual moment at the output forming acceleration change and depending on the acceleration change a maximum allowable creep and hill start torque 3 , The control unit compares the setpoint torque 2 with the maximum permissible creep and hill-start torque 3 , Then, if requested by the creep and hill start function target torque 2 less than the maximum permissible creep and hill-start torque 3 is, the controller leaves the requested target torque 2 unchanged. Then, on the other hand, if the requested target moment 2 greater than the maximum allowable creep and hill start torque, the controller reduces the requested target torque to zero or approximately zero.

The control unit is preferably an electronic engine control unit for the electric machine. This control device comprises means for carrying out the method according to the invention, namely hardware-side means and software-side means. The hardware-side means include data interfaces in order to exchange data with the modules involved in the execution of the method according to the invention, for example with the electric machine. Furthermore, the hardware resources include a processor for data processing and a memory for data storage. The software resources include program modules for carrying out the method according to the invention.

LIST OF REFERENCE NUMBERS

1

curve

2

Course of the requested setpoint torque

3

Course of the maximum permissible creep and hill-start torque

4

Course of the speed

5

Course of the acceleration

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102015202107 A1 [0006]

Claims (10)

Method for operating an electric vehicle or a hybrid vehicle with a drive unit comprising an electric machine, wherein when there is no accelerator pedal operation, an actual torque is provided on the output via a creep and hill start function via the electric machine, which is a control side of the creep and Berganfahrfunktion requested setpoint torque (2) is dependent, characterized in that a depending on the actual torque at the output forming acceleration change is determined, depending on the acceleration change, a maximum permissible creep and hill start torque (3) is determined, then if the desired torque (2) requested by the creep and hill-start function is less than the maximum permissible creep and hill-start torque (3), the desired torque (2) requested by the creep and hill-start function is left unchanged, then that requested by the crawl and hill start function e target torque (2) is greater than the maximum allowable creep and hill start torque (3), the requested by the creep and hill start function target torque (2) is reduced to zero or approximately zero. Method according to Claim 1 , characterized in that when the requested by the creep and hill start function desired torque (2) is greater than the maximum allowable creep and hill start torque (3), the requested by the creep and hill start function target torque (2) is reduced stepwise or ramped to zero or approximately zero. Method according to Claim 1 or 2 , characterized in that the maximum permissible creep and hill start torque (3) is determined such that the same is the smaller, the greater is the acceleration change forming at the output. Method according to one of Claims 1 to 3 , characterized in that the maximum allowable creep and hill start torque (3) by means of a control side stored characteristic (1) is determined. Method according to one of Claims 1 to 4 , characterized in that the requested by the creep and hill start function target torque (2) is detected with a first cycle time, depending on the actual torque at the output forming acceleration change and the maximum permissible creep and hill start torque (3) in one second cycle time is greater than the first cycle time by an adjustable multiple. Control unit for operating an electric vehicle or a hybrid vehicle with a drive unit comprising an electric machine, wherein the control unit, if there is no accelerator operation, via a creep and hill start function on the control side a desired torque (2) requests, depending on the electric machine at the output an actual torque provides, characterized in that the control unit determines a depending on the actual torque on the output forming acceleration change, the control unit depending on the acceleration change a maximum allowable creep and hill start torque (3) determined, the controller then, if that of the creep and hill start function requested target torque (2) is less than the maximum allowable creep and hill start torque (3), the requested by the creep and hill start function target torque (2) unchanged, the control unit, if that of the creep and hill start function requested setpoint torque (2) is greater than the maximum permissible creep and hill-start torque (3), which reduces the desired torque (2) requested by the creep and hill-start function to zero or approximately zero. Control unit after Claim 6 , characterized in that the control unit determines the maximum permissible creep and hill-start torque (3) by means of a characteristic curve (1) stored on the control side. Control unit after Claim 6 or 7 , characterized in that the control unit determines the maximum permissible creep and hill starting torque (3) such that the same is the smaller, the greater is the acceleration change forming at the output. Control unit according to one of Claims 6 to 8th , characterized in that the control unit, when the requested by the creep and hill start function target torque (2) is greater than the maximum permissible creep and hill start torque (3), the requested by the creep and hill start function target torque ( 2) step-like or ramp-like reduced to zero or approximately zero. Control unit according to one of Claims 6 to 9 , characterized in that the control unit detects the requested torque (2) requested by the creep and hill-start function with a first cycle time, the control unit determines the acceleration change which forms as a function of the actual torque at the output and the maximum permissible creep and hill-start torque (3) in a second cycle time which is greater than the first cycle time by an adjustable multiple.

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