Patent Description:
Electrical vehicles may be equipped with multiple driving motors which can be used as braking means, in particular as regenerative brakes. Regenerative brakes produce electric current from kinetic energy to recuperate, when braking, a portion of the energy from the motion of the vehicle.

Such vehicles may further be equipped with dissipative non-frictional brakes, for example eddy current brakes or electric retarders. This kind of brakes may use resistive losses from eddy currents induced in moving parts to remove kinetic energy from the vehicle and dissipate it as heat.

Furthermore, such vehicles may additionally be equipped with frictional brakes as well.

Each of these brakes has a different operating capability in terms of achievable torque, force and/or acceleration. Furthermore, regenerative brakes may have varying operating capabilities in that they each may have a specific regeneration efficiency.

When a desired brake function is to be achieved with such diverse braking means, various goals, some of which are contradictory, need to be accounted for. For example, a steer-by-brake situation is to be avoided or one of the braking means on its own may not be able to provide a sufficient brake function.

Utilization of the brakes may have stability implications for the whole vehicle. For example, if brakes on left and right sides of a vehicle effect diverging braking torque, they may drag the vehicle in one direction. This effect is called steer-by-brake and is one of the steering modes of tracked vehicles but disadvantageous in wheeled vehicles as their regular steering mechanism is rendered ineffective by the effect.

It is suggested in <CIT> to prioritize multiple brakes of a vehicle according to their braking effect and temporal availability to provide a required brake function at a defined time. In particular, brakes that allow controlling a magnitude of their effected brake function are to be prioritized higher than other brakes.

Given the above, the invention aims to improve utilization of said brakes to effect not only a desired brake parameter, e.g. braking torque, but to do so taking into account specific needs of electric vehicles.

This is achieved by a method according to claim <NUM> and a braking system according to claim <NUM>.

The problem is solved by a method for controlling a multitude of braking means of a vehicle to effect a desired brake function quantified as a desired brake parameter, wherein each of the braking means is controllable by an actuation parameter to effect at least a portion of said desired brake function, comprising the steps: Determine, for each braking means, a brake capability representing a maximum brake function achievable with the braking means; Determine, for each braking means, an actuation priority, wherein the actuation priority is determined from at least one predetermined operating parameter of the braking means and/or the vehicle; in order from highest priority to lowest priority of the braking means, Allocate, to each braking means, the actuation parameter, wherein the actuation parameter is chosen between the brake capability and the quantity of the desired brake parameter not yet allocated to other braking means, whichever is lower. When determining the actuation priority, the higher the regeneration efficiency is of regenerational brake device of the braking means, the higher its priority will be relative to other braking means comprising regenerational brake devices.

In this way, brakes that are more desirable to use in a particular braking situation are preferentially utilized as they have a higher priority. In this way, preferred braking means can be used before other, less preferred, braking means. Furthermore, higher regeneration efficiency of a braking means will lead to that braking means being used preferentially.

In further embodiments, the desired brake parameter, the maximum actuation parameter and/or the actuation parameter each are expressed as one of the following: a torque, a force, a retardation.

These kinds of parameter are easily measurable and available as inputs and/or outputs of braking means, brake devices and/or sensors.

In further embodiments, when determining the actuation priority, braking means comprising a non-frictional brake devices are determined to have a higher priority than braking means comprising frictional brake devices.

Preferring non-frictional brake devices allows for better longevity of frictional brake devices as this kind of brake device deteriorates through use.

In further embodiments, when determining the actuation priority, braking means comprising regenerational brake devices are determined to have a higher priority than braking means comprising dissipational brake devices.

In particular for electric vehicles, regenerating some electric energy from a braking action allows the electric vehicles to cover larger distances before requiring a recharge.

In further embodiments, when determining the actuation priority, one or more of the following parameters is taken into account: type or types of braking device comprised in the braking means, efficiency of regenerational brake devices comprised in the braking means, recuperation ratio of regenerational brake devices comprised in the braking means, current vehicle speed, current dynamic vehicle state, state of charge of a traction battery, axle load of the vehicle, individual loads on each axle of the vehicle, brake device response time, brake device response brake force, configurable priority value.

With these parameters, the distribution of the braking function to the appropriate and/or preferred braking means can be carried out with specific, in particular with closed-loop control goals in mind.

In further embodiments, where a braking means comprises multiple brake devices, the actuation parameter is distributed among the brake devices according to predefined and/or calculated distribution ratios.

Such ratios may, for example, take into account constructional differences between the brake devices or may just result in an equal distribution.

In further embodiments, when multiple braking means are determined to have the same actuation priority, in the Allocate step, the brake capabilities of the multiple braking means determined to have the same actuation priority are conflated and the actuation parameter allocated to the multiple braking means distributed to the braking devices according to predefined and/or calculated allocation ratios.

Such ratios may, for example take into account constructional differences between the braking means or the positioning of the braking means, for example on different sides of the vehicle.

The problem is also solved by a braking system of a vehicle, comprising a first braking means comprising at least one frictional brake device, a second braking means comprising at least one regenerative brake device and a control device, wherein the control device is configured to implement the method according to any of the previous embodiments.

Such a braking system improves maintenance intervals and the range, in particular of electric vehicles.

Embodiments of the disclosure are now described in detail. Referring to the drawing, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of "a," "an," and "the" includes plural reference, the meaning of "in" includes "in" and "on. " Relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. In the drawing:.

The braking system <NUM> of an electric vehicle comprises a first braking means <NUM>, a second braking means <NUM> and a third braking means <NUM>. The braking system <NUM> further comprises a control device <NUM> configured to control the braking means <NUM>, <NUM>, <NUM>.

The first braking means <NUM> comprises a frictional brake device. The second braking means <NUM> comprises a non-frictional dissipational brake device. The third braking means <NUM> comprises a non-frictional regenerational brake device.

In further embodiments, each of the braking means <NUM>, <NUM>, <NUM> may comprise one or more brake devices.

Each of the braking means <NUM>, <NUM>, <NUM> is controllable by means of an actuation parameter which may, for example, be transmitted mechanically (e.g. displacement, brake pedal), electrically (e.g. as a voltage) or electronically (e.g. digitally via a communication bus or by direct connection). The control device <NUM> is configured to provide the actuation parameter to the braking means <NUM>, <NUM>, <NUM> such that the braking means <NUM>, <NUM>, <NUM> to gather effect the desired brake function.

When the vehicle needs to brake, the control device <NUM> carries out a method for controlling the multitude of braking means <NUM>, <NUM>, <NUM> to effect the desired brake function. The desired brake function is usually communicated to the control device <NUM> as a representation of a desired braking parameter to be controlled. Examples for such desired braking parameters may be e.g. a desired braking force, a desired braking torque or a desired braking retardation/acceleration.

Each of the braking means <NUM>, <NUM>, <NUM> has a brake capability. Such a brake capability represents a maximum brake function achievable with a braking means. This maximum brake function may, for example, be represented as a maximum brake torque. The maximum brake torque of each braking means may be dependent on a dynamic state of the vehicle, in particular on its speed. The control device <NUM> determines, in a first step, for each braking means <NUM>, <NUM>, <NUM> the brake capability representing a maximum brake function achievable with said braking means <NUM>, <NUM>, <NUM>.

In further embodiments, the brake capability may, for example, be also determined by a measured dynamic state of the vehicle, for example a wheel slip, an allowed slip or slip stiffness and/or a state of charge of a traction battery of the vehicle. This may help to avoid ABS activity and/or overcharging the traction battery.

In a second step, the control device <NUM> determines, for each braking means <NUM>, <NUM>, <NUM>, an actuation priority, wherein the actuation priority is determined from at least one predetermined operating parameter of the braking means <NUM>, <NUM>, <NUM> and/or the vehicle.

In further embodiments, the predetermined operating parameter may, for example, be the kind of brake device comprised in the braking means. For example, for an electric vehicle, it may be expedient to achieve as much of the desired brake parameter as possible using regenerational brake devices as comprised in the braking means <NUM>. Furthermore, it may be expedient to achieve as much of the desired brake parameter as possible using non-frictional brake devices as comprised in the braking means <NUM>, <NUM>.

These considerations would, in that particular case, lead to the braking means <NUM> having the highest priority, the braking means <NUM> having the second highest priority and the braking means <NUM> having the third highest priority.

The control device <NUM> will then, in a third step, go through the braking means <NUM>, <NUM>, <NUM> in order from highest priority to lowest priority and allocate an actuation parameter to each of the braking means <NUM>, <NUM>, <NUM>. Each of the actuation parameters represents a portion of the desired brake function to be effected by each of the braking means <NUM>, <NUM>, <NUM>. The actuation parameter for each braking means <NUM>, <NUM>, <NUM> is chosen between the brake capability, as this represents the maximum brake function that can be affected by each of the braking means <NUM>, <NUM>, <NUM> and the quantity of the desired brake parameter not allocated to other braking means, whichever is lower.

To further illustrate this method, the following example calculations resulting from the method will be shown. Each of these examples is not based on actual measurements but constructed only to better show how to carry out the method. The values given herein are also not measured but given for illustration purposes only.

The first braking means <NUM>, which comprises a frictional brake device, may, for example, have a maximum brake torque between <NUM> and <NUM> depending on the speed that the vehicle is moving at.

The second braking means <NUM> may, for example, have a maximum brake torque of <NUM>. The third braking means <NUM> may, for example, have a maximum brake torque of <NUM>.

In a first example, the driver of the vehicle may press the brake pedal such that the desired brake torque is <NUM>.

The control device <NUM> has determined the highest priority braking means to be the regenerational third braking means <NUM>, the second highest priority braking means to be the dissipational second braking means <NUM> and the third highest priority braking means to be the frictional third braking means <NUM>. The control device <NUM> may, for example, keep information about the priorities of the braking means <NUM>, <NUM>, <NUM> in a memory as an ordered list.

The control device <NUM> starts by allocating an actuation parameter to the (regenerational) third braking means <NUM> because the third braking means <NUM> has the highest priority. The maximum brake torque of the third braking means <NUM> is <NUM>, which is smaller than the desired brake torque of <NUM>. The control device <NUM> allocates the maximum value of <NUM> to the third braking means <NUM>.

The control device <NUM> then allocates the remaining desired brake torque of <NUM> as the actuation parameter to the second braking means <NUM>, which is the braking means <NUM>, <NUM>, <NUM> having the next lower priority, wherein the allocated desired brake torque of <NUM> is lower than the maximum brake torque of the second braking means <NUM>.

The braking means <NUM>, <NUM>, <NUM> having the next lower priority is the frictional first braking means <NUM> which, in this example, is allocated an actuation parameter representing <NUM> as all of the desired brake torque has already been allocated to higher priority braking means <NUM>, <NUM>. Thus, in this case, no further brake function beyond that which has already been allocated is necessary to achieve the desired brake function.

The braking means <NUM>, <NUM>, <NUM> will then, according to the actuation parameters transmitted to them, effect a braking torque.

In another example, when the desired braking torque is <NUM> or less, only the regenerational third braking means <NUM> will be allocated and receive an actuation parameter representing more braking torque than <NUM>.

In yet another example, when the desired braking torque exceeds the combined maximum braking torque of the second and third braking means <NUM>, <NUM>, the remaining braking torque will be allocated to the first frictional braking means <NUM>.

In further embodiments, multiple regenerational first braking means <NUM> may be present. These first braking means <NUM> may have different efficiencies. When determining the actuation priority of the braking means <NUM>, <NUM>, <NUM>, the control device <NUM> will determine first braking means <NUM> having a higher efficiency to have a higher priority relative to other first braking means <NUM> having a lower efficiency.

In further embodiments, when multiple braking means <NUM>, <NUM>, <NUM> are present, they may be located on different axles of the vehicle. If, in this situation, any of the braking means <NUM>, <NUM>, <NUM> have the same priority, the control device <NUM> will, for example, allocate the actuation parameter according to the load present on each of the axles. In particular, the control device <NUM> will, for example, allocate more of the actuation parameter to braking means <NUM>, <NUM>, <NUM> located on the axle having a higher load.

In further embodiments, when, more generally, multiple braking means <NUM>, <NUM>, <NUM> are arranged on different sides of the vehicle, for example some braking means <NUM>, <NUM>, <NUM> are arranged on the left side of the vehicle while other braking means <NUM>, <NUM>, <NUM> are arranged on the right side of the vehicle, the control device <NUM> will, for example, allocate the actuation parameter such that the braking parameter on each side of the vehicle is balanced. In this way, a situation wherein the vehicle is steered into a particular direction by unbalanced braking is avoided. In these embodiments, the actuation parameter may, for example, be distributed among the brake devices and/or the braking means <NUM>, <NUM>, <NUM> according to predefined or calculated distribution ratios and/or allocation ratios. For example, when a vehicle is currently driving in a curve, a distribution or allocation ratio may be calculated to distribute or allocate <NUM>% of the braking torque (braking parameter) on one side and <NUM>% of the braking torque (braking parameter) on the other side of the vehicle.

In further embodiments, for example, braking means <NUM>, <NUM>, <NUM> of the same kind located on the same axle but on different sides of the vehicle are determined to have the same priority. In this case, the actuation parameters, and thus the brake parameter to be effected may, for example, be distributed equally between braking means <NUM>, <NUM>, <NUM> situated on the same axle.

Due to this described prioritization of brake the braking means <NUM>, <NUM>, <NUM>, for example, for small desired brake parameters, only one of the braking means <NUM>, <NUM>, <NUM> will be utilized. When, for example, the desired brake parameters exceeds the capabilities of said one braking means <NUM>, <NUM>, <NUM>, another of the braking means <NUM>, <NUM>, <NUM> will also become utilized. When, for example, the desired brake parameter rises further, further braking means <NUM>, <NUM>, <NUM> will be utilized as necessary.

Embodiments may for example prefer non-frictional, regenerational brakes determining a higher priority for them, to extend the range of the vehicle and extend any maintenance intervals. Frictional first braking means <NUM> may, for example, only be utilized when the brake capability of all the other braking means <NUM>, <NUM> is not sufficient to effect the desired brake parameter.

The term "highest priority" may have different representations according to how priority is represented. Where priority is represented for example as a number, the highest priority may, for example, be represented by the highest number or may, for example, be represented by the lowest number.

The term "operating capability" may, for example, refer to a maximum of a braking parameter attainable by the brake device, for example a maximum torque and/or a maximum force and/or a maximum acceleration.

The actuation parameter, the desired brake parameter and/or the maximum brake function may be represented in any suitable manner. In different embodiments, they may be represented, for example, as a torque value, a percentage of a reference value, an integer or floating point number.

The methods described above may be performed by a properly programmed general purpose computer alone or in connection with a special purpose computer. Such processing may be performed by a single platform or by a distributed processing platform. In addition, such processing and functionality can be implemented in the form of special purpose hardware or in the form of software or firmware being run by a general-purpose or network processor. Data handled in such processing or created as a result of such processing can be stored in any memory as is conventional in the art. By way of example, such data may be stored in a temporary memory, such as in the RAM of a given computer system or subsystem. In addition, or in the alternative, such data may be stored in longer-term storage devices, for example, magnetic disks, rewritable optical disks, solid state drives, and so on. For purposes of the disclosure herein, a computer-readable media may comprise any form of data storage mechanism, including such existing memory technologies as well as hardware or circuit representations of such structures and of such data.

Claim 1:
Method for controlling a multitude of braking means (<NUM>, <NUM>, <NUM>) of a vehicle to effect a desired brake function quantified as a desired brake parameter, wherein each of the braking means (<NUM>, <NUM>, <NUM>) is controllable by an actuation parameter to effect at least a portion of said desired brake function, comprising the steps:
Determine, for each braking means (<NUM>, <NUM>, <NUM>), a brake capability representing a maximum brake function achievable by the braking means (<NUM>, <NUM>, <NUM>);
Determine, for each braking means (<NUM>, <NUM>, <NUM>), an actuation priority, wherein the actuation priority is determined from at least one predetermined operating parameter of the braking means (<NUM>, <NUM>, <NUM>) and/or the vehicle;
in order from highest priority to lowest priority of the braking means (<NUM>, <NUM>, <NUM>), Allocating, to each braking means (<NUM>, <NUM>, <NUM>), the actuation parameter, wherein the actuation parameter is chosen between the brake capability and the quantity of the desired brake parameter not yet allocated to other braking means (<NUM>, <NUM>, <NUM>),
whichever is lower, characterized in that when determining the actuation priority, the higher a regeneration efficiency of regenerational brake devices of a braking means (<NUM>, <NUM>, <NUM>), the higher its priority relative to other braking (<NUM>, <NUM>, <NUM>) means comprising regenerational brake devices.