DE102018211460A1 - Generating the braking force of an electric auxiliary drive of a vehicle as a function of a pedal position - Google Patents

Abstract

The invention relates to a possibility for generating a braking force (T) of an electrical auxiliary drive (1) of a vehicle which can be driven with a pedal (4A). The braking force (T) is generated as a function of a pedal position (α, β) of the pedal (4A).

Description

The invention relates to a method and a device and a computer program product, each of which is used to generate a braking force that is generated by an electrical auxiliary drive of a vehicle that can be driven by a pedal.

Vehicles with an electric auxiliary drive are widely known, for example so-called electric bicycles (e-bikes, pedelecs). Here, the auxiliary drive with an auxiliary drive force supports the drive force applied by a user of the vehicle himself by muscles. Muscle strength is typically applied using a vehicle pedal, usually a foot pedal. Such vehicles can appear in many forms, for example as a bicycle, tandem, tricycle, etc. Water or aircraft with auxiliary drive are also possible.

It is known to operate the auxiliary electric drive of such a vehicle as a generator when the vehicle is to be decelerated anyway. The regenerative operation creates a braking force that decelerates the vehicle. As a rule, a brake system of the vehicle must be actuated for this purpose, for example by actuating a brake lever. This can be uncomfortable for the user of the vehicle, particularly in continuous operation, for example on longer downhill gradients, since he has to constantly exert a certain force in order to operate the brake system sufficiently.

The object of the present invention is to improve the prior art in this regard.

This object is achieved by the features specified in the main claims. Preferred embodiments thereof can be found in the subclaims.

It has been recognized that many users of auxiliary vehicle vehicles take a pedal position that is comfortable and / or skillful for the user on longer downhill gradients. It was also recognized that it is easier for the user to hold this pedal position than to operate the vehicle's brake system permanently.

It is therefore proposed that in a vehicle with an electrical auxiliary drive the pedal position of a pedal that can be used to drive the vehicle is used to set a braking force generated by the auxiliary drive. In other words, the braking force is generated as a function of the pedal position of the pedal with which the vehicle can be driven. In particular, a corresponding, specific braking force is therefore assigned to one or more specific pedal positions. However, other influencing factors, so-called parameters, can also be included in the determination of the braking force.

The braking force is understood to mean a force which tends to reduce the speed of the vehicle. The braking force therefore acts counter to the direction of travel of the vehicle.

• • Ermitteln der Pedalposition,
• • Ermitteln der Bremskraft oder einer damit korrespondierenden Größe (beispielsweise einer Bremsleistung oder eines Bremsmoments des Hilfsantriebs) mittels der Pedalposition.
• • Ausgeben der ermittelten Bremskraft oder der damit korrespondierenden Größe.
• • Erzeugen der Bremskraft mittels des Hilfsantriebs.

The proposed method can have at least the following steps:

• Determining the pedal position,
• • Determining the braking force or a corresponding quantity (for example a braking power or a braking torque of the auxiliary drive) by means of the pedal position.
• • Output of the determined braking force or the corresponding size.
• • Generating the braking force using the auxiliary drive.

The electric auxiliary drive is understood to mean a drive device of the vehicle which is set up to support the (user) driving force generated by the user of the vehicle by muscles and introduced by means of the pedal by an (auxiliary) driving force generated electrically by the drive device. Such an auxiliary drive can also be referred to as an auxiliary motor. In particular, a drive train of the vehicle is designed to combine these two drive forces into a total drive force. Such an electrical auxiliary drive is designed in particular as an electric motor, for example as a synchronous or asynchronous machine. Accordingly, the auxiliary drive, together with the pedal, is coupled in terms of drive technology to an output of the vehicle in order to drive it. This output of the vehicle is in particular a drivable vehicle wheel.

• • Einstellen der Bremskraft.
• • Einleiten der (Benutzer-)Antriebskraft.

The pedal is in particular a foot pedal, that is to say a pedal designed for actuation with one foot. But it can also be a hand pedal, i.e. a handle for driving the vehicle. Since the vehicle can be driven by means of the pedal, it is not just a simple adjustment device for the braking force. In the present case, it fulfills at least a double function:

• • Setting the braking force.
• • Initiation of the (user) driving force.

The braking force can be generated by generating the electrical auxiliary drive as a generator is operated. An electric current generated by the auxiliary drive can then be supplied to a rechargeable traction battery of the vehicle. As a result, the traction battery can be charged (again) and electrical energy can thus be stored for later motor operation of the auxiliary drive. The electric auxiliary drive is then operated in a recuperation mode. The set braking force then corresponds to a recuperation level. The recuperation level is a measure of the amount of electrical power supplied from the auxiliary electric drive to the traction battery. In this case, the braking force is synonymous with the recuperation level. Instead of the braking force, the recuperation level can be set.

Alternatively, the electrical current generated by the electrical auxiliary drive as a generator can be conducted via an electrical braking resistor and the electrical energy generated can thus be given off as heat.

Alternatively, the braking force can also be generated by short-circuiting the auxiliary electric drive. For example, for this purpose, at least two phase lines of the auxiliary drive can be connected to one another at least temporarily in a conductive manner.

The vehicle user is understood to be, in particular, an occupant of the vehicle who at least temporarily contributes his muscle power to drive the vehicle and uses the pedal for this purpose. This can be a driver of the vehicle or a fellow occupant, such as a passenger on a tandem (also referred to here as a stoker or heater).

As indicated at the beginning, the vehicle can be a land, water or aircraft. In particular, the vehicle is a vehicle for road traffic. In particular, the vehicle is a bicycle. A bicycle is also to be understood as a bicycle derivative, such as a tandem, tricycle, recumbent, etc. The vehicle is in particular a so-called electric bicycle (e-bike, pedelec).

The pedal is preferably rotatably connected to a pedal arm. The pedal arm is then rotatably arranged to a frame of the vehicle. Pedal arm and pedal can together form a pedal crank or a hand crank. In this way, the muscle strength can simply be increased. In addition, the pedal can simply be moved into the corresponding pedal position in order to apply the corresponding braking force. The frame can be a bicycle frame. The pedal arm can be rotatably mounted in the bicycle frame. For this purpose, the pedal arm can be rotatably mounted in the auxiliary drive, which in turn is designed for attachment to the frame.

The pedal position can form an angle between the pedal and the pedal arm. For example, the angle enclosed between a support surface of the pedal and a longitudinal axis of the pedal arm and variable in crank operation can be used as the pedal position. In order to brake, the pedal is therefore positioned in a certain angle or angular range relative to the pedal arm. If a foot pedal is used as the pedal, the foot resting on the pedal can be inclined, for example, in order to adjust the pedal position for braking and thus to bring about the corresponding braking force. For example, an inclination of the foot backwards in the direction of the verses may be required in order to adjust the pedal position for braking.

Alternatively or additionally, the pedal position can form an angle between the pedal arm and the frame of the vehicle. This angle also defines the position of the pedal in relation to the vehicle frame and can therefore also be understood as a pedal position. For example, the angle enclosed between the longitudinal axis of the pedal arm and the frame or a specific frame element (seat tube, down tube, top tube, chain stay, seat stay, etc.) and variable in crank operation can be used as the pedal position. In order to brake, the pedal is positioned together with the pedal arm in a certain angle or angular range relative to the frame or the respective frame element. If a foot pedal is used as the pedal, the pedal arm can be rotated, for example, by a corresponding actuation of the pedal, in order to set the pedal position for braking and thus the corresponding braking force, for example by turning the pedal arm into the horizontal position.

The pedal position can also be formed by the angle between the pedal and the pedal arm in conjunction with the angle between the pedal arm and the frame of the vehicle. Thus, one or more specific combinations of these angles can form a pedal position that triggers the braking force.

In principle, it is possible to use a different size as the pedal position, which defines the current position or position of the pedal relative to another component of the vehicle or a roadway of the vehicle.

The pedal position is determined in particular by means of a corresponding position sensor determined. If the pedal position is an angle, an appropriate angle sensor is preferably used. Such an angle sensor can be arranged in a bottom bracket of the vehicle. Such an angle sensor can also be arranged in a pedal bearing of the vehicle. A rotor position sensor of the electrical auxiliary drive can also serve as an angle sensor, in particular when the pedal arm is coupled to the auxiliary drive in a rotationally fixed manner. Such a rotor position sensor is used to determine a rotor of the auxiliary drive, which is used to drive the vehicle.

A braking torque causing the braking force and / or a braking power causing the braking force is preferably determined as a function of the pedal position. The braking force is then generated by means of the electrical auxiliary drive in accordance with the braking torque and / or the braking force. The braking torque is the torque generated by the electric drive (for example, as a generator) for braking the vehicle. The braking power is the power generated by the electric drive (for example, as a generator) for braking the vehicle. The braking torque and the braking power thus bring about the braking force. If the braking power is first determined, it can then be converted into the associated braking torque for the electrical auxiliary drive, for example by mathematical division with a speed of the auxiliary drive. This means that a specific braking force can be generated that exactly matches the current pedal position.

There are various options for determining the braking torque and / or the braking power. For example, this can be done using characteristic curves or maps or determination formulas. The use of a lookup table has proven to be particularly advantageous for this. As a result, the braking torque can be determined robustly. Such a lookup table is also easy to apply. The pedal position serves as the input to the lookup table. The braking torque associated with the pedal position or the braking power associated with the pedal position is output as the output of the lookup table.

The braking torque and / or the braking force is preferably limited. In this way, an disadvantageously high braking force can be prevented, which leads, for example, to an unsafe driving state of the vehicle. This limitation is made by at least one parameter other than the pedal position. In particular, the lookup table is used to determine a first value for the braking torque or the braking power, which is dependent on the pedal position. This first value is then reduced depending on one or more other parameters. A limit for the braking torque (braking torque limit) or for the braking power (braking power limit) can be determined independently of the pedal position, i.e. depending on one or more of the other parameters. The (first) value for the braking torque or the braking power determined as a function of the pedal position is limited to this limit if the braking torque or the braking power exceeds this limit.

• • ein Ladezustand einer Traktionsbatterie des Fahrzeugs,
• • eine Temperatur des Hilfsantriebs,
• • die Höhe eines durch das Aufbringen des Bremsmoments oder der Bremsleistung von dem Hilfsantrieb erzeugten elektrischen Stroms,
• • ein Schlupfzustand zumindest eines von dem Hilfsantrieb antreibbaren Fahrzeugrades des Fahrzeugs.

The at least one other parameter is in particular at least one of the following:

• A state of charge of a traction battery of the vehicle,
• A temperature of the auxiliary drive,
• The amount of an electric current generated by the application of the braking torque or the braking power by the auxiliary drive,
• A slip state of at least one vehicle wheel of the vehicle that can be driven by the auxiliary drive.

Other parameters that are not explicitly mentioned here can also be used. The at least one other parameter can, for example, be determined and / or provided by an engine or battery management system of the vehicle.

The braking force is preferably generated as a function of a rotational speed of the electrical auxiliary drive. Alternatively or additionally, the braking force is generated as a function of a rotational speed of a vehicle wheel of the vehicle. In this way, an unsafe driving state of the vehicle can be prevented. The speed of the electrical auxiliary drive is in particular a rotor speed of a rotor of the electrical auxiliary drive. A rotor speed sensor or a rotor position sensor of the auxiliary drive can therefore be used to determine the speed of the electrical auxiliary drive. A wheel speed sensor can also be used to determine the speed of the vehicle wheel. The speed is also understood to mean a variable corresponding to the speed, such as an angular speed. In particular, a braking power is first determined as a function of the pedal position and this braking power is divided by the speed. A braking torque is thus determined as the quotient of braking power and speed.

The braking torque is then output to the electrical auxiliary drive and made available by it, thus generating the braking force.

The vehicle preferably has a brake system. This is particularly a service brake, such as a disc brake or rim brake or Coaster brake. The brake system can be operated, for example, by operating a brake lever. The braking force generated by the auxiliary electric drive is now also dependent on the actuation of the braking system. The braking force generated by the auxiliary drive can thus be reduced or increased when the brake system is actuated. The total braking force generated jointly by the brake system and the electrical auxiliary drive can thus be distributed in a targeted manner, for example between several vehicle wheels. An unsafe driving state of the vehicle can thus be prevented.

A device for generating a braking force of an electric auxiliary drive of a vehicle that can be driven with a pedal is also proposed. The device is designed to operate the auxiliary electric drive such that it generates the braking force as a function of the pedal position, as suggested. The device is thus designed to carry out the proposed method. The device can be a control device for the electrical auxiliary drive. If the vehicle is an electric bicycle, the device can thus be a bicycle computer that is used to control the electric auxiliary drive. It is therefore not necessary for the device to generate the braking force itself. It is sufficient that the device triggers the generation of the braking force by the auxiliary electric drive.

The device accordingly has means to carry out the method. The device can thus have a data memory in which the commands for carrying out the method are stored. The device can thus have a processor by means of which the corresponding braking force and / or the corresponding braking torque and / or the corresponding braking power is determined from the pedal position. The device can also have the means for determining the pedal position, in particular one or more angle sensors. The device can also have an interface (input) to maintain the pedal position. The device can have an interface (output) in order to output the determined braking force or the determined braking torque or the determined braking power to the auxiliary drive so that it generates the corresponding braking force.

A computer program product is also proposed. The computer program product has commands in detail which, when executed by a computing unit (for example a control unit), cause the computing unit to carry out the proposed method. The computer program product can consist of a commercially available data memory which has the special commands for carrying out the proposed method.

• 1 ein Fahrzeug mit einem elektrischen Hilfsantrieb,
• 2 eine Tretkurbel mit einem Pedal,
• 3 eine Vorgehensweise zur Ermittlung eines Bremsmoments.

The invention is explained in more detail below with reference to figures, from which further preferred embodiments and further preferred features of the invention can be gathered. The following are shown in a schematic representation:

• 1 a vehicle with an electric auxiliary drive,
• 2 a crank with a pedal,
• 3 a procedure for determining a braking torque.

1 shows a vehicle designed as an electric bicycle. Accordingly, it has an electric motor as an electrical auxiliary drive 1 on. The vehicle is operated by a user 2 hazards. The auxiliary drive 1 thus supports that of the user 2 Muscle-generated (user) driving force with an (auxiliary) driving force generated by an electric motor. The auxiliary drive takes the necessary electrical energy 1 a traction battery 5 , These drive forces add up to a total drive force in the drive train of the vehicle (not shown in more detail). For application of the driving force by the user 3 is a pedal crank 4 intended. In principle, instead of the pedal crank 4 a hand crank can also be provided.

The auxiliary drive 1 is exemplary in the area of a bottom bracket on a frame 3 arranged of the vehicle. It is also possible, for example, for the electrical auxiliary drive 1 is arranged on a front wheel hub or a rear wheel hub of the vehicle.

The crank 4 is exemplary in 2 shown. It consists of two pedals in a manner known per se 4A and each pedal 4A a pedal arm 4B together. The pedals 4A are in the corresponding pedal arm 4B each rotatably supported by a pedal bearing. The pedal arms 4A are rigidly connected to each other and to the frame 3 pivoted on the bottom bracket. The pedals 4A serve as a footrest for the user 2 , Between pedal 4A and associated pedal arm 4B there is an angle α on. The angle is in the detail α between a contact surface of the pedal 4A for each user's foot 2 and a longitudinal axis of the associated pedal arm 4B in front. Between pedal arm 4B and the frame makes an angle β on. The angle is in the detail β between the longitudinal axis of the pedal arm 4B and the frame or a frame element.

The angle α can both by the inclination of the on the pedal 4A resting foot, as well as by turning the pedal crank 4 to be influenced. The angle β can be done by turning the crank 4 to be influenced. The angles α . β can be determined, for example, by angle sensors. The angles α . β each provide a measure of the position of the pedal 4A , so they can both be understood individually or in combination with each other as "pedal position".

The electric auxiliary drive 1 is designed not only to generate the electromotive driving force but also to be operated as a generator. This creates the auxiliary drive 1 a braking torque that is in a braking force acting on the vehicle F _b manifests. This braking force F _b brakes the vehicle. Recuperation can be performed in generator mode. This means that the electrical energy generated as a generator at least in part of the traction battery 5 is fed. The auxiliary drive 1 generated braking force F _b corresponds to a recuperation level of the vehicle.

In addition, the vehicle 1 a braking system 7 have, such as a friction brake, such as a disc or rim or coaster brake.

It is provided that the electrical auxiliary drive 1 generated braking force F _b based on the pedal position of the pedal 4A is set. This is the device 6 intended. This can be, for example, a control device for controlling the auxiliary drive 1 act, such as a bike computer. The control unit can therefore also be used to carry out further functions of the vehicle. For example, the device 6 via a battery management system for the traction battery 5 feature.

In the device 6 a lookup table for determining a braking torque and / or a braking power as a function of the pedal position is preferably stored. To do this, the lookup table uses the pedal position, for example the angle α or β fed. The lookup table then gives the corresponding braking torque or the corresponding braking power for the auxiliary drive 1 out.

The braking force F _b can also be influenced by other parameters, i.e. influencing factors. For example, the braking torque and / or the braking power can be limited in this way. Such parameters can be: a state of charge of the traction battery 5 , a temperature of the auxiliary drive 1 , the height of one from the auxiliary drive 1 generated electrical current at the brake, a slip state of the auxiliary drive 1 drivable vehicle wheel of the vehicle (for example blocking the vehicle wheel), a speed of the auxiliary drive 1 , an actuation of the brake system 7 of the vehicle.

3 shows a preferred procedure for determining a braking torque generated by an auxiliary drive of a vehicle T _m depending on a pedal position α . β , This may be the vehicle after 1 act. The procedure can accordingly be carried out by the device 6 be executed, which has appropriate means, such as in particular interfaces, stored commands and a computing unit (processor etc.).

How out 3 can be seen, the pedal position (here, for example, at least one of the angles α . β ) a lookup table "LUT" (block 8th ) fed. The lookup table gives a braking power corresponding to the pedal position P _b for the auxiliary drive.

The braking torque P _b is then limited if necessary (block 9 ). For example, a maximum charging current for the traction battery should be taken into account in order to protect the traction battery. A temperature of the auxiliary drive should also be taken into account in order to protect it. Therefore, a braking power limit (maximum permissible braking power) is set by another function, not shown in detail. P _lim determined and the limitation (Block 9 ) fed. This other function can take into account parameters other than the pedal position for the limitation, in particular parameters from a battery management system or from temperature monitoring of the auxiliary drive or motor parameters of the auxiliary drive or other system evaluations. If the braking power determined using the lookup table P _b the braking power limit P _lim the value of the braking power of P _b on P _lim limited. The braking power limited in this way, if necessary, is from the block 9 as P _blim output.

miteinbezogen. Das auf diese Art ermittelte Bremsmoment T_m wird vom Block 10 ausgeben. Beispielsweise wird das Bremsmoment T_m an ein Steuergerät des Hilfsantriebs ausgegeben, das dafür sorgt, dass der Hilfsantrieb dieses Bremsmoment T_m erzeugt. Beispielsweise werden dazu die Leistungsschalter einer Motorsteuerung des Hilfsantriebs vom Steuergerät entsprechend angesteuert.From the limited braking force if necessary P _blim then the braking torque that matches the pedal position T _m determined (block 10 ). Here, the speed n _{m of} the auxiliary drive is determined using equation Eq. 1 $$T_m=\frac{P_{blim}}{n_m}$$

involved. The braking torque determined in this way T _m is from the block 10 output. For example, the braking torque T _m to a control unit of the auxiliary drive, which ensures that the auxiliary drive applies this braking torque T _m generated. For example, the circuit breakers of a motor control of the auxiliary drive are controlled accordingly by the control unit.

It is possible to combine this procedure with other procedures for determining the braking torque T _m or braking performance P _b . P _blim to combine.

It is possible to determine or output the braking torque T _m to be prevented if necessary by setting or removing a software flag provided for this purpose. The software flag can be set or removed, for example, by the user of the vehicle using a corresponding user input interface.

The procedure can be linked to a braking system of the vehicle in order to increase the braking power of the vehicle and / or to achieve an advantageous distribution of the braking power to the wheels of the vehicle.

In the 3 blocks shown 8th . 9 . 10 can be designed as separate hardware or software modules that perform the corresponding functions. You can in the device 6 the 1 be provided.

• • Verbesserung der Energieeffizienz des elektrischen Antriebssystems des Fahrzeugs (Traktionsbatterie, Hilfsantrieb, etc.) und damit Erhöhung der Reichweite.
• • Reduzierung der Nutzung der Bremsanlage und damit Verbesserung deren Lebensdauer.
• • Einbeziehung von vorhandenen Batterie- und Motorgrenzen, um deren Leistungsfähigkeit zu Berücksichtigen und um das elektrische Antriebssystem innerhalb seiner zulässigen thermischen Grenzen zu betreiben.

The particular advantages of this approach can be the following:

• • Improving the energy efficiency of the vehicle's electric drive system (traction battery, auxiliary drive, etc.) and thus increasing the range.
• • Reduction of the use of the brake system and thus improvement of its service life.
• • Inclusion of existing battery and motor limits in order to take their performance into account and to operate the electric drive system within its permissible thermal limits.

LIST OF REFERENCE NUMBERS

1

electric auxiliary drive

2

user

3

frame

4

crank

4A

pedal

4B

pedal arm

5

traction battery

6

contraption

7

braking system

8th

block

9

block

10

block

α, β

Angle, pedal position

F _b

braking force

P _b

brake horsepower

P _lim

Braking power limit

P _blim

limited braking power if necessary

T _m

braking torque

Claims (10)

Method for generating a braking force (F _b ) by means of an electrical auxiliary drive (1) of a vehicle that can be driven with a pedal (4A), characterized in that the braking force (F _b ) is dependent on a pedal position (α, β) of the pedal (4A) is produced. Procedure according to Claim 1 , wherein the pedal (4A) is rotatably connected to a pedal arm (4B) and the pedal arm (4B) is rotatably arranged to a frame (3) of the vehicle, and wherein the pedal position (α, β) by • one between the pedal ( 4A) and the pedal arm (4B) present angle (α) is formed, and / or • an angle (β) is formed between the pedal arm (4B) and the frame (3) of the vehicle. A method effecting braking power (P _b) (α, β) according to one of the preceding claims, wherein a braking force (F _b) effecting braking torque (T _m) and / or the braking force (F _b) depending on the pedal position is determined, and wherein the braking force (F _b ) is generated in accordance with the determined braking torque (T _m ) and / or the determined braking power (P _b ) by means of the electrical auxiliary drive (1). Procedure according to Claim 3 , the braking torque (T _lim ) and / or the braking power (P _b ) being determined using a lookup table. Procedure according to Claim 3 or 4 , the braking torque (T _lim ) and / or the braking power (P _b ) being limited by at least one parameter (P _lim ) other than the pedal position (α, β). Procedure according to Claim 5 , the at least one other parameter being at least one of the following: a state of charge of a traction battery (5) of the vehicle, a temperature of the auxiliary drive (1), the level of a braking torque (T _m ) or the braking power (P _b ) electrical current generated by the auxiliary drive (1), a slip state of at least one vehicle wheel of the vehicle which can be driven by the auxiliary drive (1). Method according to one of the preceding claims, wherein the braking force (F _b ) in dependence a rotational speed (n _m ) of the vehicle, in particular a rotational speed (n _m ) of the auxiliary drive (1) and / or the rotational speed of a vehicle wheel of the vehicle. Method according to one of the preceding claims, wherein the vehicle has a braking system (7), the braking force (F _b ) being generated as a function of an actuation of the braking system (7). Device (6) for generating a braking force (F _b ) by means of an electrical auxiliary drive (1) of a vehicle drivable with a pedal (4A), characterized in that the device (6) is designed to apply the electrical auxiliary drive (1) in this way operate that this generates the braking force (F _b ) according to the method according to any one of the preceding claims. Computer program product with instructions which, when executed by a computing unit (6), cause the computing unit (6) to carry out the method according to one of the Claims 1 to 8th performs.

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