AT525681A1 - Method for selectively connecting a mechanical friction brake to an electrodynamic brake - Google Patents

Abstract

The invention relates to a method for selectively connecting a mechanical friction brake (BRn) to an electrodynamic brake (EDBn) in a vehicle (1), comprising, during a first phase (6), simultaneous full braking of all electrodynamic brakes ( EDBn) and thereby measuring the respective braking current (Ibn) of each electrodynamic brake (EDBn), measuring the deceleration (a) of the vehicle (1) and determining the total braking force (Fg) of all electrodynamic brakes (EDB); during a second phase (7), successive individual activation of each electrodynamic brake (EDBn) with the respective braking current (Fbn), measuring the respective deceleration (a) of the vehicle (1) and determining the braking force (Fn) of each electrodynamic brake (EDBn); and for each electrodynamic brake (EDBn) whose braking force (Fn) is less than one Nth of the total braking force (Fg), switching on the friction brake (BRn).

Description

AT PATENT Scripture ay No.

(73) Patent owner: DATASOFT Embedded GmbH 3100 St. Pölten (AT)

(54) "Title: Method for selectively connecting a mechanical friction brake to an electrodynamic brake

(61) Addendum to Patent No. (66) Conversion of (62) Separate application from (division):

(30) Priority(s):

(72) Inventor:

(22) (21) Filing date, file number: (60) Dependency: (42) Start of patent term: Longest possible term:

(45) Issue Date:

(56) References considered for the assessment of patentability:

Form PA 35 [23

08956 DATASOFT Embedded GmbH

3100 St. Pölten (AT)

The present invention relates to a method for selectively connecting a mechanical friction brake to an electrodynamic brake in a vehicle, in particular an electrically operated vehicle.

In many electrically operated vehicles such as electrically operated cars, trucks or rail vehicles, e.g. trams, the electric drive motors of the wheels are used as electrodynamic brakes by switching them to generator operation. If the braking force of the electrodynamic brakes is not sufficient, mechanical friction brakes are often used as additional brakes. It is known from WO 22009/077835 A1 to control the braking force of such a friction brake as a function of the available braking force of the electrodynamic brake, the latter being determined from the braking current of the electrodynamic brake. However, this solution is unable to detect faulty electrodynamic brakes where the braking current is not correctly related to the braking force generated. Also, the known solutions often require a previous calibration run and cannot be used during operation

become.

This object is achieved with a method for selectively engaging a mechanical friction brake to an electrodynamic brake in a vehicle having a number N > 1 of electrodynamic brakes, comprising

in a first phase, while the vehicle is moving: simultaneous full braking of all electrodynamic brakes and thereby measuring the respective braking current of each electrodynamic brake, measuring the deceleration of the vehicle and determining the total braking force of all electrodynamic brakes as a product of deceleration and current mass of the vehicle;

in a second phase, while the vehicle is moving: sequentially applying each electrodynamic brake individually with the respective previously measured braking current, thereby measuring the respective deceleration of the vehicle and determining the braking force of each electrodynamic brake as a product of jeach deceleration and current mass of the vehicle;

for each electrodynamic brake whose determined braking force, possibly taking into account a tolerance, is less than one Nth of the total braking force: switching on the

Friction brake to this electrodynamic brake for the ak-

The method of the invention allows a faulty electrodynamic brake to be detected while the vehicle is in operation and a mechanical friction brake to be selectively switched on as an additional brake for this purpose, for example in order to have the maximum possible braking force available in the event of emergency braking. Risks and necessary corrective measures resulting from a faulty electrodynamic brake can be determined at any time during runtime and thus recognized much earlier. Residual risks, such as those defined in the standard ISO 61508 for industry, ISO 26262 for automotive, or EN 50126 for railway, and other standards present in today's implementations, can be managed with the method of the invention significantly reduced and the quality of the realization optimized. The requirements for the functional safety of the vehicle are thus implemented with a significantly higher degree of reliability and quality than is the case with the solutions available today. The method of the invention is not based solely on measuring the braking currents during operation, but conversely on subjecting the electrodynamic brakes to braking currents previously measured in a first phase during full braking. This allows

errors that result from insufficient implementation of the braking

In principle, the method of the invention can also be used if a plurality of electrodynamic brakes are assigned to one wheel of a vehicle. However, the vehicle is preferably a multi-wheeled vehicle and each wheel is assigned an electrodynamic brake and a friction brake, so that the braking forces are evenly distributed over the wheels during operation.

Said emergency braking to determine the total braking force of all electrodynamic brakes preferably consists in each electrodynamic brake being actuated in such a way that it exerts its greatest possible braking force at which the wheel assigned to it is just not locked.

The deceleration of the vehicle in both the first and second phase of the method can be measured in any manner known in the art, for example by evaluating the speed profile of the vehicle. However, it is particularly favorable if the deceleration of the vehicle is measured using an inertial measuring device mounted on the vehicle.

The method of the invention is suitable for any type of electrodynamic brakes, for example eddy current brakes, which are attached to the wheels independently of the drive. In a particularly advantageous embodiment of the

Each electrodynamic brake is protected by an as

Generator-powered drive motor of the associated wheel formed.

The mass of the vehicle used to calculate the total braking force in the first phase and the individual braking forces of the electrodynamic brakes in the second phase can be determined in various ways. Either it is already known at all or it can be calculated, for example, from the dead weight and the payload or the number of passengers in the vehicle. Or the mass is measured in each case, e.g. by axle load sensors or weight sensors on the wheels or chassis of the vehicle, by electronic passenger counters, etc.

It is particularly favorable if the current mass of the vehicle is determined from the driving force of all drive motors when the vehicle is accelerated and the acceleration of the vehicle measured in the process. All that is required for this is a measurement of the acceleration of the vehicle, for example with the aid of the aforementioned inertial measuring device. The drive force mentioned is preferably determined from the drive currents of all the drive motors measured during the acceleration mentioned.

The invention is explained below with reference to exemplary embodiments illustrated in the enclosed drawings

explained in more detail. In the drawings shows:

7723

2 shows the method of the invention in a flow chart; and

3 shows the optional step of measuring the vehicle mass in a flowchart.

1 schematically shows, in the form of a block diagram, a vehicle 1 with a plurality of electrodynamic brakes EDB1, EDB2, . . . , generally EDBna (n=1 . An electrodynamic brake EDBn could also be assigned to a wheel axle with several wheels, or more than one electrodynamic brake EDB» could also be assigned to one wheel.

The vehicle 1 can be any vehicle, including an autonomously driving vehicle, for example a car or truck with an internal combustion engine as the drive, and the electrodynamic brakes EDBa are eddy current brakes that are separate from the drive. As a rule, the vehicle 1 is an electrically driven vehicle, in particular a rail vehicle, e.g. a train or a tram, and the electrodynamic brakes EDB,1 are each driven by an electric drive motor Mı, Mz, .. , generally Mn, of the vehicle 1 is formed.

The respective drive and braking operation of the drive motor

re Ma or electrodynamic brakes EDBna is replaced by a re-

A mechanical friction brake BRn that can be switched on is assigned to each electrodynamic brake EDB,a. When a friction brake BRana is connected to the electrodynamic brake EDBna assigned to it, the braking force Fn exerted on the vehicle 1 by the electrodynamic brake EDB and the braking force Fn exerted on the vehicle 1 by the friction brake BR» add up.

The (starting) driving and braking operation of the vehicle 1 is controlled by an electronic controller 3 to which a corresponding driving or braking control signal C is supplied by a driving operation controller 4 . The driving operation controller 4 can, for example, be a hand lever and/or pedal for controlling the acceleration a (a>0) or deceleration a (a<0) of the vehicle 1 .

The actual acceleration or deceleration of the vehicle 1 is measured by an inertial measurement unit (IMU) 5 mounted on the vehicle 1 and supplied to the controller 3 as a measured value. The controller 3 receives measured values of the drive currents Ian on further inputs

of the drive motors Mn in motor operation and the braking currents

In the event of reduced performance or a failure of one (or more) of the electrodynamic brakes EDB», the controller 3 causes the activation of the respectively assigned friction brake BRn via a control signal Sn. In order to detect a faulty, i.e. poorly performing or failing, electrodynamic brake EDBna and to activate the corresponding activation of the friction brake BR, the controller 3 carries out the method now described with reference to FIG.

According to FIG. 2, some preparatory steps are initially carried out in a first phase 6, during which vehicle 1 is driving, and then in a second phase 7/7, during which vehicle 1 is driving, a faulty electrodynamic brake EDBna is detected and the associated mechanical friction brake BR switch on.

The current mass m of the vehicle 1 is measured in an (optional) step 8 before or during the first phase 6 . If the current mass m of the vehicle 1 before or in the

first phase 6 is known, for example if no passenger

te are in the tram and the weight of the driver is negligible, so that the dead weight of the vehicle 1 can be used as the current mass m, step 8 can be omitted, the mass m is then known in advance. The current mass m can be measured in step 8 in a wide variety of ways, for example by counting or weighing the passengers, e.g. with an electronic passenger counter, or the transported load and adding it to the vehicle's own mass, using weight sensors on the wheels or chassis of the vehicle 1 or by means of the inertial measuring device 5, as will be explained in detail later with reference to FIG.

In step 9 of the first phase 6, full braking of the vehicle 1 is now carried out. For this purpose, all N electrodynamic brakes EDBn are fully braked at the same time, for example by moving the driving operation controller 4 to a special emergency braking position, triggering an emergency brake button connected to the controller 3 or the like. "Emergency braking" of an electrodynamic brake EDB is understood to mean its actuation to achieve its greatest possible (individual) braking force F, at which the wheel assigned to it is just not locked, i.e. similar to emergency braking with an anti-lock braking system (ABS). Alternatively, full braking of all electrodynamic brakes EDBf1 can also consist in a ma- applied by controller 3 via control signals Cna

maximum actuation of each electrodynamic brake EDB»1

is triggered, regardless of whether the respective assigned wheel is locked or not.

During full braking step 9, on the one hand the respective braking currents Ibn of the electrodynamic EDBn are measured (step 10), for example by measuring the currents flowing in the load resistors Rn, and on the other hand the deceleration a of the vehicle 1 is measured (step 11), e.g. using the inertial measuring device 5.

It goes without saying that the full braking step 9 does not necessarily have to be carried out until the vehicle 1 has come to a complete standstill (velocity v=0); on the contrary, it is actually desirable to only carry out the full braking in step 9 for so long that there is sufficient time to be able to measure the braking currents Ibn in step 10 and the deceleration a in step 11. The full braking step 9 can therefore also be very short and only slightly reduce the speed v of the vehicle 1, for example to only 90% or 80% of the speed v of the vehicle 1 before the full braking step 9. Optionally, full braking step 9 takes care of this worn that the speed v of the vehicle 1 does not fall below 30%, preferably not below 50%, particularly preferably not below 75% of the initial speed v, because the measured braking currents Ibn generally decrease with decreasing speed, which distorts the measurement result. In the best case, the speed v of the vehicle 1 in full

braking step 9 only reduced as little as possible.

Then, in a step 12, the total braking force Fg is determined as the product of the measured deceleration a and the current mass m of the vehicle 1 as Fyg=M*a. Since the current mass m of the vehicle 1 is only required in this step 12, it goes without saying that the (optional) step 8 can also be carried out at a different point before step 12.

The emergency braking step 9—and in particular the entire first phase 6—can optionally be carried out at any time during operation of the vehicle 1, for example shortly before entering a station in the case of a rail vehicle.

After the first phase 6, the vehicle 1 is now ready for any one (or more) second phase(s) 7, which can be carried out at any one or more later points in time.

The second phase 7 can take place immediately after the first phase 6, for example during one and the same journey of the vehicle 1 between two stations, or at a considerable time interval. For example, the first phase 6 can be carried out once a week or once a day, for example in the morning, and the second phase 7 often during the day. Or phases 6 and 7 are repeated alternately or in a regular pattern, e.g. the second phase 7 at regular time intervals and the first phase 6 after every second, third,

fourth etc. phase 7 or at the beginning or end of each first,

second, third, etc. consecutive trip of the vehicle 1.

In the second phase 7, the current mass m is first measured again in an (optional) step 13 as in step 8, if not previously known, can be taken over unchanged from the first phase 6 or can be calculated in some other way. Step 13 can also be carried out as described later in detail with reference to FIG. 3 .

In phase 7/7, in a loop 14 that runs over all N electrodynamic brakes EDBn, steps 15 to 19 are carried out for each electrodynamic brake EDB,1, as follows.

In step 15, the respective electrodynamic brake EDBn is actuated, specifically with that braking current Ibn that was previously measured in step 10 in the first phase 6. During the actuation of this individual electrodynamic brake EDBn, the deceleration caused in each case on the vehicle 1 is measured (step 16).

The individual braking force Fn of the respective electrodynamic brake EDB,a considered in the loop run is then determined as the product of the measured individual deceleration an and the current mass m of the vehicle 1 as Fa=m−an (step 17). Since the mass m is only required here, step 13 in phase 7 can be carried out at any point before the respective calculation step 17 of loop 14.

are performed, for example immediately before.

Then, in step 18, it is checked whether the individual braking force Fn of the electrodynamic brake EDB1 under consideration is less than one Nth of the total braking force Fy of all electrodynamic brakes EDBna previously determined in step 12 of the first phase 6. The comparison in step 18 can optionally be carried out taking into account a corresponding tolerance, for example 45% or +%*10%. For example, the "smaller" case of comparison step 18 is given when the individual braking force Fn is less than 0.95 times (tolerance: -5%) or 0.90 times (tolerance: -10%) of Fgy/ N is.

If comparison step 18 is not fulfilled (branch "n"), i.e. the individual braking force Fn of an electrodynamic brake EDBna is equal or approximately equal (e.g. at least 0.95 or 0.90 times) the Nth part of the total braking force Fg of all electrodynamic brakes EDBn1a, then the considered electrodynamic brake EDBn is obviously in order and the loop 14 is continued, if not already ended. If, on the other hand, the comparison step 18 shows that the individual braking force Fa—possibly within the specified tolerance—is smaller than Fy/N (branch “y”), then the associated mechanical friction brake BR is switched on to the electrodynamic brake EDB1 by means of the control signal Fn ( step 19).

Will now in this (or a later) phase 7 be a

Brake actuation (step 20) required, then this is done

using the respective friction brake BRn - i.e. to the extent required after step 18 and switched on in step 19. With regard to an electrodynamic brake EDB1a under consideration, brake actuation 20 can also be a continuation of the current brake actuation of step 15, or a later, separate brake actuation.

3 shows a possible embodiment of the optional measuring steps 8 and 13 for measuring the respective current mass m of the vehicle 1. For this purpose, the vehicle 1 can initially be accelerated in a step 21 during the first or second phase 6, 7 (a>0) are, in that the drive motors Ma or the electrodynamic brakes EDBn1 are operated by an electric motor. At the same time, both the individual drive currents Ian (step 22) and the acceleration a of the vehicle 1 (step 23) are measured during the acceleration.

Then in step 24 for each drive motor Ma

from the drive current Ian supplied to it - for example using stored tables or a function £() - the respective drive force Fan is determined, e.g. to Fan = £f(Ian),

and the sum of all the driving forces Fan is calculated as the driving force Fag of all the driving motors Mn. From the total driving force Fag, the current mass m of the vehicle 1 can now be calculated in step 25 by dividing it by the measured acceleration a

be determined.

The transmission of all signals C, Cns a, Ian, Ibn, Sn exchanged between the components of the vehicle 1 in the described method can be secured according to the desired safety requirements, in particular according to a standardized safety integrity level (SIL). e.g. SIL 4 according to the IEC 61508 standard or derived standards such as 15026262 ASIL-D for the automotive sector, EN50126 or EN50129 (EN5012x for short) for the railway sector or general cybersecurity and privacy standards such as ISO021434, UNECE or the like. The invention is not limited to the illustrated embodiments, but includes all variants, modifications and combinations thereof that are in the

fall under the attached claims.

Claims (7)

Patent Claims: A method for selectively engaging a mechanical friction brake (BRn) to an electrodynamic brake (EDBn) in a vehicle (1) having a number N > 1 of electrodynamic brakes, comprising in a first phase (6), while the vehicle (1) is driving: simultaneous full braking of all electrodynamic brakes (EDBn) and measuring the respective braking current (Ibn) of each electrodynamic brake (EDB1), measuring the deceleration (a) of the vehicle (1 ) and determining the total braking force (Fy) of all electrodynamic brakes (EDBa) as a product of deceleration (a) and current mass (m) of the vehicle (1); in a second phase (7), while the vehicle (1) is driving: sequentially actuating each electrodynamic brake (EDBn) individually with the respective previously measured braking current (Fbn), thereby measuring the respective deceleration (an) of the vehicle (1) and determining the braking force (Fn) of each electrodynamic brake (EDB1a) as a product of the respective deceleration (an) and the current mass (m) of the vehicle (1); For each electrodynamic brake (EDBn) whose determined braking force (Fan), possibly taking into account a tolerance, is less than one Nth of the total braking force (Fgy): Switching on the friction brake (BRan) to this electrodynamic brake (EDB1n) for the current one or a next brake activation of this electrodynamic brake (EDB\). 2. The method according to claim 1, characterized in that the vehicle (1) is a multi-wheeled vehicle and each wheel is assigned an electrodynamic brake (EDBn) and a friction brake (BRn). 3. The method as claimed in claim 2, characterized in that the full braking of an electrodynamic brake (EDBn) is its actuation to produce its greatest possible braking force at which the wheel assigned to it is not yet locked. 4. The method as claimed in one of claims 1 to 3, characterized in that the deceleration (a, an) of the vehicle (1) is measured by means of an inertial measuring device (5) mounted on the vehicle (1). 5. Method according to one of Claims 1 to 4, characterized in that each electrodynamic brake (EDB»n) is formed by a drive motor (Ma) operated as a generator for the associated wheel. 6. The method according to claim 5, characterized in that the current mass (m) of the vehicle (1) from the driving force (Fag) of all drive motors (Ma) when the vehicle (1) accelerates and an acceleration (a) of the Vehicle (1) is determined. 7. The method according to claim 6, characterized in that said drive force (Fag) from the drive currents (Ian) measured during said acceleration of all drive motors (Man) is determined.