DE102015225959A1 - Interface to the electric power steering with variable active damping - Google Patents

Abstract

The invention relates to a method for regulating an engine torque for a steering assistance of a motor vehicle by means of a control unit which is connected to an electric motor, comprising the steps: receiving a desired torque by means of the control unit determining a setpoint torque and transmitting this setpoint torque to a motor control unit of the control unit wherein the target torque is formed from a sum of a plurality of factors including a target assist torque determined based on the desired torque and a drive-dependent additional torque, characterized in that the sum further comprises a damping torque by means of which the target torque is variably reducible.

Description

The invention relates to a method and a system for controlling an engine torque for a steering assistance of a motor vehicle according to the preambles of the independent claims.

Systems for steering assistance of a motor vehicle are known from the prior art, in which an electric motor generates a support torque based on a desired steering torque and thus facilitates the steering of the motor vehicle. With the arrival of assistance systems and in particular the automated driving, the coordination between the driver assistance systems and the steering assistance is becoming increasingly important.

From practice it is known that the use of steering assistive or mitlenkenden driver assistance systems, such. As Emergency Steer Assist, can cause that in certain driving situations, the support of the steering is too large, especially if the driver overreacts. Since each driver reacts differently, the co-steering assistance system can not adjust to the different reactions of a driver, it is necessary to provide a way to intercept an overreaction of the driver. The influence of the driver is only one example of external forces and suggestions acting on the assistance system, which are to be controlled in a suitable manner in the sense of a high control quality. Due to the merger of several systems or control units, however, there is the disadvantage that the signal transmission speed between the control units in driving situations, eg. As dangerous situations, may be too slow to build a real-time responsive control system.

It is therefore an object of the invention to provide a method and a system with which the aforementioned disadvantages can be overcome.

The object is achieved according to a first aspect of the invention by means of a method of the type mentioned, wherein the sum to the target torque further comprises a damping torque by means of which the target torque is variably reduced. The target torque for the steering motor includes, as a component, a damping torque whose height is variably adjustable or reducible. Further advantageous embodiments are the subject of the dependent claims, which are expressly made by reference to the subject invention.

The invention is based on the basic idea that a variable damping torque can be used to mitigate the amplitudes of the target torque due to the driving situation, so as to intercept an overreaction or sudden changes in the desired torque smoothly or smoothly. The steering assistance feels particularly fluid and even in this way. The variable adjustability of the damping torque at the same time helps to adjust the steering assistance, if necessary, so high, so that a driver does not have to spend too much force to steer the vehicle. If necessary, the variable adjustability of the damping torque allows a slight overshooting of the recommendation of the assistance function by the driver.

The method according to the invention is advantageously further developed in that the damping torque is determined as a function of the angular velocity of the electric motor.

The method according to the invention is advantageously further developed in that the damping torque is determined as a function of a driving situation-dependent damping level or damping level.

The method according to the invention is advantageously further developed in that the damping torque is determined as a function of a preferably constant damping factor.

M_attn:

Dämpfungsdrehmoment

φ_Motor:

Motorwinkelgeschwindigkeit

f_attn:

Dämpfungsfaktor

l_attn:

Dämpfungslevel

The method according to the invention is advantageously developed by calculating the amount of damping torque using the following equation: M_attn = φ_motor · f_attn · l_attn With

M_attn:

damping torque

φ_Motor:

Motor angular velocity

f_attn:

damping factor

l_attn:

attenuation level

The method according to the invention is advantageously further developed in that the damping torque is determined by means of the control unit, in particular with the sampling rate of the signal of the motor angular velocity.

The method according to the invention is advantageously further developed by filtering the damping torque before addition to the desired torque by means of a high-pass filter.

The method according to the invention is advantageously further developed in that the damping torque before addition to the desired torque is generally filtered by a filter function with characteristic transmission behavior for realizing a frequency response correction of the resulting angular velocity control loop. In this way, in addition to the function of active damping, it is possible to effectively limit the maximum angular velocity. The height of the limitation of the angular velocity is selectable in a wide range, regardless of the amount of limitation of the additional torque.

The method according to the invention is advantageously further developed in that the attenuation level is determined by means of a second control device.

The method according to the invention is developed in an advantageous manner by virtue of the fact that the damping level has an initial value of 1 or 100% and is reduced depending on the driving situation.

The method according to the invention is developed in an advantageous manner in that the attenuation level in evasion maneuvers or maneuvers in the range of a few seconds has a value of less than 0.2 or 20%, preferably 0.1 or 10%, particularly preferably 0.

The method according to the invention is advantageously further developed in that the rate of change of the value of the damping level, preferably depending on the driving situation, is limited.

The method according to the invention is developed in an advantageous manner by limiting the damping torque at a maximum value or by means of a gradient.

The method according to the invention is advantageously further developed by setting the maximum value as a function of a minimum setpoint torque.

The method according to the invention is advantageously developed further in that the damping torque is set or reduced aperiodically to the desired torque in the event of a sudden desired torque. Particularly advantageous is a development of the method according to the invention, in which the damping torque is applied such that at a sudden additional torque and load-free steering, the resulting engine speed creeping, aperiodic or slightly overshoot their end value approaches. An aperiodic course is particularly favorable here.

The method according to the invention is developed in an advantageous manner by adjusting the damping torque in such a way that a driver assistance function for the driver is continuously or without jerky torques.

• – ein erstes Steuergerät zum Ermitteln eines Solldrehmoments und Ansteuern eines elektrischen Motors mit dem Solldrehmoment,
• – ein zweites Steuergerät zum Durchführen von Fahrmanövern oder Fahrassistenzfunktionen, das über eine Schnittstelle mit dem ersten Steuergerät verbunden ist, und eine Vorgabe für das Soll-Unterstützungsmoments an das erste Steuergerät bereitstellt,

wobei das erste Steuergerät dem Solldrehmoment ein Dämpfungsdrehmoment addiert mittels dessen das Solldrehmoment variabel verringerbar ist. The object is further achieved by means of a system for controlling an engine torque for a steering assistance of a motor vehicle, comprising

• A first control unit for determining a setpoint torque and driving an electric motor with the setpoint torque,
• A second control device for carrying out driving maneuvers or driving assistance functions, which is connected via an interface to the first control device and provides a specification for the desired assisting torque to the first control device,

wherein the first controller adds a damping torque to the target torque by means of which the target torque is variably reduced.

The system according to the invention is further developed in an advantageous manner in that the first control unit determines the damping torque.

The method according to the invention is advantageously further developed by an external computing unit, an interface module or interface that determines the damping torque and transmits it to the first control unit.

The invention will be described below with reference to an embodiment and a figure. It shows:

1 a schematic representation of an embodiment of the system according to the invention on which the inventive method is executable.

1 shows a system S for controlling an engine torque, for a steering assistance of a motor vehicle. The system S comprises a first control unit S1 for determining a setpoint torque M_Des and driving an electric motor M with the setpoint torque M_Des. It is in this embodiment, a steering controller or Electrical Power Steering (EPS). Strictly speaking, the engine is not part of the first control unit S1. The first control unit receives a desired torque, which maps the steering request of the driver. From this, a target assist torque based on predefined curves or tables C. The desired torque M_Des is determined by means of the sum of a plurality of torque components and transmitted to a motor control unit μC of the control unit. The target torque comprises the target assist torque M_C, which is determined on the basis of the desired torque and a driving situation-dependent additional torque M_ST. The latter is limited by limiting units U_Sat, U_Sat 2.

Furthermore, the system S comprises a second control unit S2 for performing driving maneuvers or driving assistance functions. Execution means in the sense of the invention the determination of the data and specifications for a driving maneuver. The second control device S2 is connected to the first control device S1 via an interface I and provides a specification for the desired assist torque M_ST to the first control device.

φ_Motor

für Motorwinkelgeschwindigkeit,

f_attn

für den Dämpfungsfaktor, und

l_attn

für den Dämpfungslevel

steht. Um einen negatives Drehmoment zu bewirken wird die Motorwinkelgeschwindigkeit φ_Motor mit –1 multipliziert. Dieser wiederum wird mit dem Dämpfungsfaktor f_attn multipliziert, das je nach Fahrzeug eingestellt wird und einen konstanten Wert annehmen kann. Das Produkt davon wird mit dem Dämpfungslevel l_attn multipliziert. Der Dämpfungslevel wird in diesem Ausführungsbeispiel von dem zweiten Steuergerät S2 vorgegeben und kann fahrsituationsabhängig unterschiedlich eingestellt sein. Das über den Kommunikationsbus gesendete Dämpfungslevel l_attn bzw. das Signal dazu skaliert die mittels des Applikationsparameters definierte zulässige Maximaldämpfung bzw. den Dämpfungsfaktor f_attn im Bereich von 0% bis 100%. In addition, the first control unit S1 adds a damping torque M_attn to the setpoint torque, wherein the setpoint torque can be variably reduced by means of the damping torque M_attn. The amount of the damping torque M_attn is calculated by the following equation: M_attn = φ_motor · f_attn · l_attn in which

φ_Motor

for motor angular velocity,

f_attn

for the damping factor, and

l_attn

for the damping level

stands. To cause a negative torque, the motor angular velocity φ_motor is multiplied by -1. This in turn is multiplied by the attenuation factor f_attn, which is set depending on the vehicle and can assume a constant value. The product of this is multiplied by the attenuation level l_attn. The attenuation level is specified in this embodiment by the second control unit S2 and can be adjusted depending on the driving situation. The attenuation level l_attn sent over the communication bus or the signal for this purpose scales the permissible maximum attenuation defined by the application parameter or the attenuation factor f_attn in the range from 0% to 100%.

Instead of assuming a constant value, the damping factor can also assume a value which is determined as a function of driving or vehicle parameters, such as, for example, Vehicle speed, power of the electric motor, etc.

The system is designed such that the first control unit determines the damping torque M_attn. Thus, the damping torque M_attn can be determined with the same clock rate with which the first control unit S1 operates or the motor angular velocity is detected. In other words, the damping torque M_attn can be determined with a higher clock rate than the specification of the damping level l_attn. In this way, undesirable delays in the provision of the signal or value of the damping torque can be prevented. The operating speed of the control loop is not unnecessary in this way by the slower operating speed or latency of the interface I, z. B. CAN interface, or the second control unit S2 limited.

Alternatively, the system S may also be designed such that an external computing unit, an interface module or interface determines the damping torque M_attn and transmits it to the first control unit S1. In this case, it is important to provide that the operating speed or sampling rate of the first control unit is maintained as far as possible.

Advantageously, the damping torque M_attn is filtered before the addition with the aid of a high-pass filter, so that for reasons of control dynamics in areas of quasi-constant engine angular velocity of the full control range of engine torque is available for Aktorbeschleunigung.

Also, by means of a limiter U_Sat, the maximum damping torque can be limited to maximum values or gradually.

The variability of the active damping has the advantage that fades and fades for the driver, as e.g. occur during function input and output, are comfortable and practically jerk-free executable.

In contrast to a permanently set active damping, a variably adjustable active damping has the advantage that it can be changed depending on the situation in favor of higher control dynamics. The background is that the maximum from the outside specifiable accelerating EPS engine torque is always limited and high setpoint gradient of a steering angle setpoint z. B. lead to high active damping moments that still counteract the accelerating moment and thus further limit the achievable dynamics. Due to the variability of the active damping this z. B. only selectively activated shortly before reaching the steering angle setpoint. In this way, the actuating torque potential of the EPS actuator can be largely completely exhausted.

Advantageously, the variable damping torque is used to reduce the damping at high setpoint dynamics in order to achieve a low-distortion consequences of the controlled variable also in the vicinity of the manipulated variable limitation.

Advantageously, the variable damping torque is used to make it comfortable and easy for the driver to hide the driver assistance function.

Advantageously, the variable damping torque is used to selectively limit the steering wheel angular velocity to always ensure controllability by the driver.

Advantageously, the variable damping moment is used to increase the stability of the closed loop in the presence of realized gradient limits at the requesting torque input M_ST.

It is conceivable to design the system or the method according to the invention such that the damping torque M_attn, when additional moments are required, adds this to the input instead of the output of the EPS functions.

Claims (20)

A method for controlling an engine torque for a steering assistance of a motor vehicle by means of a control unit, which is connected to an electric motor, comprising the steps: - Receiving a desired torque by means of the control unit, - Determining a target torque and transmit this target torque to a motor control unit of the control unit, said Target torque is formed from a sum of several factors, comprising a target assist torque, which is determined on the basis of the desired torque and a driving situation-dependent additional torque, characterized in that the sum further comprises a damping torque, by means of which the target torque is variably reduced.  The method of claim 1, wherein the damping torque is determined in dependence on the angular velocity of the electric motor.  Method according to one of the preceding claims, wherein the damping torque is determined as a function of a driving situation-dependent damping level or damping level.  Method according to one of the preceding claims, wherein the damping torque is determined as a function of a, preferably constant, damping factor. Method according to one of the preceding claims, wherein the amount of the damping torque is calculated using the following equation: M_attn = φ_motor · f_attn · l_attn with M_attn: damping torque φ_motor: motor angular velocity f_attn: damping factor l_attn: damping level  Method according to one of the preceding claims, wherein the damping torque is determined by means of the control device, in particular with the sampling rate of the signal of the motor angular velocity.  Method according to one of the preceding claims, wherein the damping torque is filtered before addition to the target torque by means of a high-pass filter. Method according to one of the preceding claims, wherein the damping torque (M_attn) before the addition to the target torque by a linear or non-linear filter function to obtain a frequency response correction of the resulting angular velocity control loop is filtered.  Method according to one of the preceding claims, wherein the attenuation level is determined by means of a second control device.  Method according to one of the preceding claims, wherein the attenuation level has an initial value of 1 or 100% and is reduced depending on the driving situation.  Method according to one of the preceding claims, wherein the attenuation level in evasion maneuvers or driving maneuvers in the range of a few seconds has a value of less than 0.2 or 20%, preferably 0.1 or 10%, particularly preferably 0.  Method according to one of the preceding claims, wherein the rate of change of the value of the damping level, preferably depending on the driving situation, is limited.  Method according to one of the preceding claims, wherein the damping torque is limited at a maximum value or by means of a gradient.  Method according to the preceding claim, wherein the maximum value is set in dependence on a minimum target torque. Method according to one of the preceding claims, wherein the damping torque is set or reduced aperiodisch to the desired torque at a desired jump-like torque. Method according to one of the preceding claims, wherein the damping torque is parameterized such that in the load-free case with a sudden desired torque, the angular velocity of the engine creeps, aperiodic or slightly overshoot their final value approaches.  Method according to one of the preceding claims, wherein the damping torque is set in such a way that the intervention of a driver assistance function for the driver occurs continuously or without jerky torques. A system for controlling an engine torque, for a steering assistance of a motor vehicle, comprising - a first control unit for determining a desired torque and driving an electric motor with the target torque, - a second control unit for performing driving maneuvers or driving assistance functions, which is connected via an interface with the first control unit is, and provides a specification for the target assist torque to the first control unit, characterized in that by means of the first control unit, a damping torque is added to the target torque, by means of which the target torque is variably reduced.  System according to the preceding claim, wherein the first control unit determines the damping torque.  The system of claim 16, wherein an external computing unit, an interface module or an interface that determines the damping torque and transmitted to the first control unit.

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