GB2566488A

GB2566488A - An energy comparison module

Info

Publication number: GB2566488A
Application number: GB1714838.8A
Authority: GB
Inventors: Tam Louis
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-09-15
Filing date: 2017-09-15
Publication date: 2019-03-20
Anticipated expiration: 2037-09-15
Also published as: GB201714838D0; DE102018215342A1; GB2566488B

Abstract

An energy comparison module for a brake system of a vehicle is configured to: calculate a remaining energy conversion capacity of a braking means to perform braking of a vehicle; and compare the remaining energy conversion capacity of a braking means to an energy of the vehicle. At least one vehicle function can be activated in response to the comparison. The vehicle function includes: warning the driver, performing intermittent braking, increasing regenerative braking, reducing a gear of the vehicle and adjusting a navigational route. The remaining energy conversion capacity of the braking means is preferably calculated by integrating a braking temperature. Energy of the vehicle may include kinetic energy based on vehicle speed, and potential energy based on altitude. This allows accurate monitoring of brake capacity to mitigate brake fade and reduced braking performance.

Description

AN ENERGY COMPARISON MODULE

TECHNICAL FIELD

The present disclosure relates to an energy comparison module. Particularly, but not exclusively, the disclosure relates to an energy comparison module of a vehicle. Aspects of the invention relate to an energy comparison module, a brake system, a vehicle and a method.

BACKGROUND

When operating a vehicle there is a need to monitor a capability of a braking means of the vehicle in order to determine whether the braking means is able to reduce the speed of the vehicle sufficiently when a user of the vehicle applies the braking means.

Existing vehicles monitor how long a braking means has a temperature above a temperature threshold, and if the temperature remains above the temperature threshold for a certain time, provide warnings and take subsequent compensatory actions within the vehicle.

However, such known methods merely infer when brake fade and reduced performance is likely to occur.

It is an aim of the present invention to mitigate a problem of the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide an energy comparison module, a brake system, a vehicle and a method as claimed in the appended claims.

According to an aspect of the invention, there is provided an energy comparison module for a brake system of a vehicle, the controller configured to calculate a remaining energy conversion capacity of a braking means to perform braking of a vehicle and compare the remaining energy conversion capacity of a braking means to an energy of a vehicle comprising the braking means.

Advantageously, comparison of the energy of the vehicle in relation to the remaining energy conversion capacity allows for the controller to use the remaining energy conversion capacity of the braking means to accurately identify any potential issues and pre-emptively take action to overcome them.

Optionally, the controller is configured to output a control signal to modify at least one vehicle function in dependence on the comparison of the remaining energy conversion capacity of a braking means to the energy of the vehicle comprising the braking means.

Optionally, modifying the at least one vehicle function comprises switching the vehicle function between an inactive state and an active state.

Switching between an inactive state and an active state of at least one vehicle function beneficially uses the at least one vehicle function when necessary and thereby conserve resources of the vehicle.

Optionally, the at least one vehicle function is an assistive vehicle function that acts to assist a user or driver of the vehicle to operate the vehicle so that the vehicle can be slowed.

Optionally, the controller is configured to calculate the remaining energy conversion capacity by integrating a temperature of the braking means. Optionally, a function of the temperature of the braking means is integrated. Optionally, a product of the function of the temperature and mass of the braking means is integrated. Optionally, the integration is carried out between a current temperature of the braking means and a limit temperature of the braking means. The limit temperature of the braking means may be the temperature at which the braking means experiences brake fade. Alternatively, the limit temperature may be offset from the temperature at which the braking means experiences brake fade or offset from the temperature at which the braking means experiences boiling, for example, if the braking means is brake fluid, the boiling point of the brake fluid.

Optionally, the controller is configured to determine whether the remaining energy conversion capacity of the braking means is sufficient to reduce the energy of the vehicle to less than or equal to an energy threshold. In a slight variation, the controller may be configured to determine whether the energy of the vehicle exceeds a threshold representing a certain proportion of the remaining energy conversion capacity.

In both cases, what is important is that a comparison between the remaining energy conversion capacity and the energy of the vehicle is carried out to determine whether the braking means has sufficient capability to reduce the energy of the vehicle to a desired energy level. A threshold level can be set for either the remaining energy conversion capacity or the energy of the vehicle and the determination made based on the comparison of the threshold level of the remaining energy conversion capacity or the energy of the vehicle with the amount of the other entity. For example, if a threshold level is set in the energy of the vehicle, the comparison step compares the other entity, namely, the remaining energy conversion capacity of the braking means, to the threshold.

Advantageously, using the energy of the vehicle to determine whether the remaining energy conversion capacity of the braking means is sufficient to reduce the energy of the vehicle to a desired amount, rather than merely considering the length of time that the braking means has been above a certain temperature, allows for appropriate at least one vehicle functions to be activated which improves speed at which a reduction in energy of the vehicle can be achieved.

In addition, using the energy of the vehicle reduces computation resources of the vehicle due to energy of the vehicle not requiring high frequency re-calculation, contrary to the temperature of the braking means. This is due to the energy calculation only needing performing ten times a second instead of 100 times a second as per the temperature calculation. This would therefore be approximately a ten times reduction in computational time/resource required. This factor could be reduced further.

Optionally, if the controller determines that the remaining energy conversion capacity of the braking means is sufficient to reduce the energy of the vehicle to less than or equal to an energy threshold, the controller is configured not to output the control signal to cause switching between an inactive state and an active state of at least one vehicle function.

Optionally, if the controller determines that the remaining energy conversion capacity of the braking means to perform braking is not sufficient to reduce the energy of the vehicle to less than or equal to an energy threshold, the controller is configured to output the control signal to cause switching between an inactive state and an active state of at least one vehicle function.

Optionally, the controller is configured to output a control signal to cause switching from an inactive state to an active state of at least one assistive vehicle function in dependence on the comparison of the remaining energy conversion capacity of a braking means to the energy of the vehicle comprising the braking means.

Optionally, the energy of a vehicle comprising the braking means is equivalent to the energy required to halt the vehicle.

Optionally, the energy of a vehicle comprising the braking means comprises at least one of the following: kinetic energy of the vehicle; and kinetic energy and gravitational potential energy of the vehicle.

Advantageously, taking into account the gravitational potential energy of the vehicle makes a more accurate comparison with the remaining energy conversion capacity that can predict a future energy state of the vehicle using navigational mapping.

Optionally, the kinetic energy is calculated based on speed of the vehicle.

Optionally, the gravitational potential energy is calculated based on altitude of the vehicle.

Optionally, a predicted change of the gravitational potential energy may be calculated based on a gradient estimation of a predicted route of the vehicle determined using navigational mapping. Optionally, the predicted change of the gravitational potential energy may be used to determine a specific at least one vehicle function to activate.

Optionally, the at least one vehicle function is a function that reduces at least one of the kinetic energy and the gravitational potential energy.

Optionally, the at least one vehicle function may be one of the following: performing intermittent braking, increasing regenerative braking, reducing a gear of the vehicle, and adjusting a navigational route.

According to further aspect of the invention, there is provided a brake system for a vehicle, the brake system comprising the energy comparison module and a braking means to perform braking of a vehicle.

Optionally, the braking means comprises at least one of the following: a brake disc; a brake fluid; a brake calliper; and a regenerative braking system.

Optionally, a vehicle comprises the braking means.

According to further aspect of the invention, there is provided a method for causing activation of a vehicle function, the method comprising calculating a remaining energy conversion capacity of a braking means to perform braking of a vehicle and comparing the remaining energy conversion capacity to an energy of a vehicle comprising the braking means.

Advantageously, the comparison of the energy of the vehicle in relation to the remaining energy conversion capacity allows for the controller to use the remaining energy conversion capacity of the braking means to accurately identify any potential issues and pre-emptively take action to overcome them.

Optionally, the method comprises outputting a control signal to cause modify at least one vehicle function in dependence on the comparison of the remaining energy conversion capacity of a braking means to the energy of the vehicle comprising the braking means.

Optionally modifying the at least one vehicle function comprises switching the vehicle function between an inactive state and an active state.

Switching between an inactive state and an active state of at least one vehicle function beneficially uses the at least one vehicle function when necessary and thereby conserves resources of the vehicle.

Optionally, the calculating comprises integrating a temperature of the braking means. Optionally, the calculating comprises integrating a function of the temperature of the braking means. Optionally, the calculating comprises integrating a product of the function of the temperature and mass of the braking means. Optionally, the integrating is carried out between a current temperature of the braking means and a limit temperature of the braking means. The limit temperature of the braking means may be the temperature at which the braking means experiences brake fade. Alternatively, the limit temperature may be offset from the temperature at which the braking means experiences brake fade.

Optionally, the method comprises determining whether the remaining energy conversion capacity of the braking means to perform braking is sufficient to reduce the energy of the vehicle to less than or equal to an energy threshold.

In addition, using the energy of the vehicle reduces computation resources of the vehicle due to energy of the vehicle not requiring high frequency re-calculation, contrary to the temperature of the braking means.

Optionally, the method comprises calculating the kinetic energy of the vehicle using a speed of the vehicle.

Optionally, the method comprises calculating the gravitational potential energy of the vehicle using altitude of the vehicle. Optionally, the altitude of the vehicle is determined from navigational mapping.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

Figure 1 is a schematic illustration of a brake system, in accordance with an embodiment of the invention.

Figure 2 is a further schematic illustration of a brake system of Figure 1, in accordance with an embodiment of the invention.

Figure 3 is a flow chart of a method, in accordance with an embodiment of the invention.

Figure 4 is a flow chart of a method, in accordance with a further embodiment of the invention.

Figure 5 is a flow chart of a method, in accordance with a further embodiment of the invention.

Figure 6 is a table illustrating a relationship between vehicle energy thresholds and vehicle functions, in accordance with an embodiment of the claimed invention.

Figure 7 is a flow chart of a method, in accordance with a further embodiment of the invention.

Figure 8 is a table listing vehicle energy differences and vehicle functions, in accordance with an embodiment of the invention.

Figure 9 is a side view of a vehicle in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

Figure 1 is a schematic illustration of a brake system 200. The brake system 200 has an energy comparison module 100 coupled to a braking means 150 that performs braking of a vehicle 300 (as shown in Figure 9).

The energy comparison module 100 calculates an estimate of a remaining energy conversion capacity of the braking means 150. The energy comparison module 100 also compares the remaining energy conversion capacity of the braking means 150 to an energy of a vehicle 300 comprising the braking means 150. The energy comparison module 100 outputs a control signal 120 to modify least one vehicle function in dependence on the comparison of the remaining energy conversion capacity of the braking means 150 to the energy of the vehicle 300 comprising the braking means 150. Modifying a vehicle function can include switching said function between an inactive state and an active state.

The braking means 150 is a brake disc. The brake disc 150 may have an attached fluidbased brake calliper.

Figure 2 illustrates the brake system 200 of Figure 1 coupled to a vehicle function driver 320 within a vehicle 300 (shown in more detail in Figure 9). Both the brake system 200 and the vehicle function driver 320 are part of the vehicle 300. More specifically, the controller 100 is coupled to the vehicle function driver 320 in order to provide the control signal 120 to the vehicle function driver 320.

The energy comparison module 100 calculates the estimate of the remaining energy conversion capacity based on integration of a temperature of the braking means 150. The temperature of the braking means may be measured using sensors or calculated by first determining the net energy change in the braking means 150 and then determining a temperature change in the braking means 150.

The energy comparison module 100 compares the remaining energy conversion capacity of the braking means 150 to an energy of a vehicle 300 comprising the braking means 150.

Following the comparison, the energy comparison module 100 determines whether the remaining energy conversion capacity of the braking means 150 is sufficient to reduce the energy of the vehicle 300 to less than or equal to an energy threshold.

If the energy comparison module 100 determines that the remaining energy conversion capacity of the braking means 150 is sufficient to reduce the energy of the vehicle 300 to less than or equal to an energy threshold: the energy comparison module 100 does not output the control signal 120 to cause switching between an inactive state and an active state of at least one vehicle function.

On the other hand, if the energy comparison module 100 determines that the remaining energy conversion capacity of the braking means 150 to perform braking is not sufficient to reduce the energy of the vehicle 300 to less than or equal to an energy threshold, the energy comparison module 100 outputs the control signal 120 to cause switching from an inactive state and an active state of at least one vehicle function.

The energy comparison module 100 sends the control signal 120 to the vehicle function driver 320. The vehicle function driver 320 switches at least one vehicle function from an inactive state to an active state.

The energy of a vehicle 300 is the kinetic energy and gravitational potential energy of the vehicle 300. The energy required to halt the vehicle 300 is equal to the sum of all the kinetic energy and a proportion of the gravitational energy. The kinetic energy is calculated based on speed of the vehicle 300. The gravitational potential energy is calculated based on an altitude of the vehicle determined, for example, using navigational mapping, such as GPS mapping.

The at least one vehicle function may be an assistive function to reduce at least one of the kinetic energy and the gravitational potential energy. The at least one vehicle function is increased engine braking, but may be one or more of the following: providing a user warning, performing intermittent braking, re-routing of a navigation system of the vehicle, and limiting the maximum power output of a powertrain of the vehicle.

Figure 3 is a flow chart illustrating a method 400 carried out by the controller 100 of Figures 1 and 2. At step S420 the energy comparison module 100 calculates an estimate of a remaining energy conversion capacity of the braking means 150 to perform braking of a vehicle 300. At step S440 the energy comparison module 100 compares the remaining energy conversion capacity of the braking means 150 to an energy of a vehicle 300 comprising the brake system 200.

Figure 4 is a flow chart illustrating further steps of the method 400 of Figure 3.

In the calculation at step S420 the energy comparison module 100 integrates a temperature of the braking means 150 to determine the remaining energy conversion capacity of the braking means 150. More specifically, the remaining energy conversion capacity is calculated by integrating a product of a function of the temperature and mass of the braking means 150. The integrating is carried out between a current temperature of the braking means 150 and a limit temperature of the braking means 150.

The current temperature of the braking means 150 is measured using sensors. Alternatively, the temperature of the braking means 150 may be calculated by first determining the net energy change in the braking means 150 and then determining a temperature change in the braking means 150. The limit temperature of the braking means 150 is the temperature at which the braking means 150 experiences brake fade. Alternatively, the limit temperature may be offset from the temperature at which the braking means 150 experiences brake fade.

The integration of calculation at step S420 uses the following formula:

Remaining energy conversion capacity =

Where, Tcurrent = current temperature of braking means; Tiimit = limit temperature of braking means 150; m = mass of braking means; cp(T) = function of energy required to raise 1 unit mass 1 unit of temperature, where cp(T) can be any integral function of temperature, for example a polynomial (A + BT + CT²), an exponential (Ae^BT), or a logarithmic term (In (BT)). The limit temperature of the braking means 150 may be the temperature at which the braking means 150 experiences brake fade. Alternatively, the limit temperature may be offset from the temperature at which the braking means 150 experiences brake fade.

The integration is performed for each braking means 150 of the vehicle 300 and the products of the integrations are summed to give an overall value for the remaining energy conversion capacity. For instance, where the braking means 150 is a disc brake, the integration is performed for each of the disc brakes of the vehicle, and the products of each integration summed. As an example, when the vehicle is a car with four disc brakes, the integration is performed four times.

At step S430 the energy comparison module 100 calculates the energy of the vehicle 300. As in Figure 3, at step S440 the energy comparison module 100 compares the remaining energy conversion capacity of the braking means 150 to the estimated energy of vehicle 300. At step S460 the energy comparison module determines whether the remaining energy conversion capacity of the braking means 150 to perform braking is sufficient to reduce the energy of the vehicle 300 to less than or equal to an energy threshold. At step S480 the energy comparison module 100 outputs a control signal 120 to cause switching between an inactive state and an active state of at least one vehicle function in dependence on the comparison of the remaining energy conversion capacity of the braking means 150 to the energy of the vehicle 300.

The energy threshold is a proportion of the energy of the vehicle, for example, a percentage of the energy of the vehicle.

Figure 5 is a flow chart of the determination step S460 of method 400. At S451 the energy threshold is Thi. At step S461 the energy comparison module 100 determines whether the remaining energy conversion capacity of the braking means 150 is sufficient to reduce the energy of the vehicle to less than or equal to energy threshold Thi.

As an example, the vehicle 300 may have a mass of 600kg and be travelling at 30 miles per hour (13.4 metres per second), giving a kinetic energy of the vehicle 300 as approximately 54 000 Joules, J. The vehicle 300 may be at a height of 50 metres, giving a gravitational potential energy of approximately 290 000 Joules, J. Therefore, the energy of the vehicle is approximately 344 000 Joules, J. The energy threshold Thi of the energy of the vehicle is set at 100 000 J. The energy comparison module 100 determines whether the remaining energy conversion capacity of the braking means 150 is sufficient to reduce the energy of the vehicle from 344 000 J to less than or equal to the threshold energy 100 000 J.

Alternatively, instead of using a vehicle energy threshold, a threshold of the remaining energy conversion capacity of the braking means 150 may be set and the controller 100 may determine whether the energy of the vehicle 300 exceeds the threshold of the remaining energy conversion capacity. The threshold of the remaining energy conversion capacity is a proportion of the remaining energy conversion capacity, for example, a percentage of the remaining energy conversion capacity. The threshold of the remaining energy conversion capacity of the braking means 150 may be offset from zero.

If the remaining energy conversion capacity of the braking means 150 is sufficient to reduce the energy of the vehicle 300 to less than or equal to the energy threshold Thi, no action is required, step S470. However, if the remaining energy conversion capacity of the braking means 150 is insufficient to reduce the energy of the vehicle 300 to less than or equal to the energy threshold Thi, action is taken to activate at least one vehicle function, step S464.

In a slight variation, there may be more than one energy threshold to which the energy comparison module 100 compares the remaining energy conversion capacity of the braking means 150. Each energy threshold is associated with a different at least one vehicle function that is activated in response to a control signal 120 sent by the controller 100.

Figure 6 is a table illustrating vehicle energy thresholds and corresponding vehicle functions. Energy threshold Thi corresponds to Function 1. Energy threshold Th₂ corresponds to Function 2. Energy threshold Th₃ corresponds to Function 3.

Energy threshold Thi may be 75 % of the vehicle energy, energy threshold Th₂ may be 50 % of the vehicle energy, and energy threshold Th₃ maybe 25 % of the vehicle energy. Function 3, associated with energy threshold Th₃, is required to reduce the energy of the vehicle by a greater amount than either of Function 1 or 2 because energy threshold Th₃ is lower than energy threshold Thi and Energy threshold Th₂.

Function 3 is lowering of a gear of the vehicle. Function 2 is increasing regenerative braking. Function 1 is performing intermittent braking.

The percentages associated with each threshold may be increased or reduced. Indeed, one of the thresholds may be set at 100% to determine whether the braking means 150 is sufficient, on its own, to bring the vehicle 300 to a halt.

The use of multiple thresholds provides a hierarchy of vehicle functions that allows activation of less power intensive vehicle functions when the braking means is required to reduce the vehicle energy by a smaller amount, for example, energy threshold Thi at 75 % of the vehicle energy. This saves power resources of the vehicle 300. Multiple thresholds also provide a way of activating a vehicle function with a more significant effect on the energy of the vehicle when the braking means is required to reduce the vehicle energy by a greater amount, for example, energy threshold Th₃ at 25 % of the vehicle energy.

Figure 7 is a further flow chart illustrating the determination step S460 of method 400 and possible further steps of method 400. Figure 7 illustrates an alternative to the step of the NO, N, branch of Figure 5.

Like in Figure 5, at step S461 the energy comparison module 100 determines whether the remaining energy conversion capacity of the braking means 150 is sufficient to reduce the energy of the vehicle 300 to less than or equal to an energy threshold, in this case a desired energy threshold - energy threshold Th₃at 25 % of the vehicle energy.

If the remaining energy conversion capacity of the braking means 150 is sufficient to reduce the energy of the vehicle 300 to less than or equal to the desired energy threshold Th₃, no action is required, step S470.

However, if the remaining energy conversion capacity of the braking means 150 is insufficient to reduce the energy of the vehicle 300 to less than or equal to the desired energy threshold Th₃, at step S462 a determination is carried out to determine a reachable energy threshold associated with the remaining energy conversion capacity. At step S463 a further determination is carried out to determine an energy difference between the desired energy threshold Th₃ and the reachable energy threshold. After, at step S464 at least one vehicle function associated with the determined energy difference is activated.

Determining a reachable energy threshold and activating a vehicle function that corresponds to the energy difference between the reachable energy threshold and the desired energy threshold allows the braking means 150 to share the burden of reducing the energy of the vehicle with an activated vehicle function. In this way, the level of severity of the vehicle function that is activated may be reduced and power resources of the vehicle 300 saved.

Alternatively, instead of using a vehicle energy threshold, a threshold of the remaining energy conversion capacity of the braking means 150 may be set and the controller 100 may determine whether the energy of the vehicle 300 exceeds the threshold of the remaining energy conversion capacity.

Figure 8 is a table listing energy differences and corresponding vehicle functions. The magnitude of the energy difference is associated with an at least one vehicle function. The bigger the energy difference the more influential the associated at least one vehicle function is on reducing the vehicle energy.

In this instance, when the energy difference is less than or equal to 20 % of the desired energy threshold, Function 4 is activated. Function 4 is re-routing of a navigational system.

When the energy difference is greater than 20 % and less than or equal to 40 % of the desired energy threshold, Function 5 is activated. Function 5 is performing intermittent braking.

When the energy difference is greater than 40 % and less than or equal to 60 % of the desired energy threshold, Function 6 is activated. Function 6 is increasing regenerative braking.

When the energy difference is greater than 60 % of the desired energy threshold, Function 7 is activated. Function 7 is reducing a gear of the vehicle 300.

Figure 9 illustrates a vehicle 300 with the brake system 200 of Figures 1 and 2.

Whilst the vehicle functions have been described as one or more of performing intermittent braking, increasing regenerative braking, reducing a gear of the vehicle, and adjusting navigational route, the vehicle functions may be any vehicle functions that act to assist a user or driver of the vehicle to operate the vehicle so that the vehicle can be slowed.

The remaining energy conversion capacity has been described as being calculated through an integration of a product of mass and a temperature function for the braking means. Alternatively, the remaining energy conversion capacity may be retrieved from a look up table storing temperature values for the braking means with corresponding remaining energy conversion capacity values.

The multiple vehicle functions may be associated with corresponding energy thresholds such that a hierarchy of vehicle functions is provided that is ordered from least power intensive to most power intensive. Alternatively, the hierarchy of vehicle functions may be ordered from those having least effect on the vehicle energy to those having greatest effect on the vehicle energy.

Claims

1. An energy comparison module for a brake system of a vehicle, the controller configured to:

calculate a remaining energy conversion capacity of a braking means to perform braking of a vehicle;

compare the remaining energy conversion capacity of a braking means to an energy of a vehicle comprising the braking means; and output a control signal to modify at least one vehicle function in dependence on the comparison of the remaining energy conversion capacity of the braking means to the energy of the vehicle comprising the braking means.

2. The energy comparison module of claim 1, wherein the controller is configured to:

calculate the remaining energy conversion capacity by integrating a temperature of the braking means.

3. The energy comparison module of any preceding claim, wherein modifying at least one vehicle function comprises switching the vehicle function between an inactive state and an active state.

4. The energy comparison module of any preceding claim, wherein the controller is configured to: determine whether the remaining energy conversion capacity of the braking means is sufficient to reduce the energy of the vehicle to less than or equal to an energy threshold.

5. The energy comparison module of claim 4, wherein if the controller determines that the remaining energy conversion capacity of the braking means is sufficient to reduce the energy of the vehicle to less than or equal to an energy threshold: the controller is configured to not output the control signal to cause switching between an inactive state and an active state of at least one vehicle function.

6. The energy comparison module of claim 4 or 5, wherein if the controller determines that the remaining energy conversion capacity of the braking means to perform braking is not sufficient to reduce the energy of the vehicle to less than or equal to an energy threshold: the controller is configured to output the control signal to cause switching between an inactive state and an active state of at least one vehicle function.

7. The energy comparison module of any preceding claim, wherein the controller is configured to output the control signal to cause switching from an inactive state to an active state of the at least one assistive vehicle function.

8. The energy comparison module of any preceding claim, wherein the energy of a vehicle comprising the braking means is equivalent to the energy required to halt the vehicle.

9. The energy comparison module of any preceding claim, wherein the energy of a vehicle comprising the braking means comprises at least one of the following: kinetic energy of the vehicle; and gravitational potential energy of the vehicle.

10. The energy comparison module of claim 9, wherein the kinetic energy is calculated based on speed of the vehicle.

11. The energy comparison module of claim 9 or 10, wherein the gravitational potential energy is calculated based on an altitude of the vehicle.

12. The energy comparison module of any of claims 9 to 11, wherein when the energy of the vehicle comprises the kinetic energy and the gravitational potential energy of the vehicle, the at least one vehicle function is a function to reduce at least one of the kinetic energy and the gravitational potential energy.

13. The energy comparison module according to claim 12 wherein the at least one vehicle function limits the maximum power output of a powertrain of the vehicle.

14. A brake system for a vehicle, the brake system comprising:

the energy comparison module of any of claims 1 to 11; and a braking means to perform braking of a vehicle.

15. The brake system of claim 14, wherein the braking means to perform braking of a vehicle is at least one of the following: a brake disc; a brake fluid; a regenerative braking system.

16. A vehicle comprising the brake system of claim 14 or 15.

17. A method, the method comprising:

calculating a remaining energy conversion capacity of a braking means to perform braking of a vehicle;

comparing the remaining energy conversion capacity of a braking means to an energy of a vehicle comprising the braking means; and outputting a control signal to modify at least one vehicle function in dependence on the comparison of the remaining energy conversion capacity of a braking means to the energy of the vehicle comprising the braking means.

18. The method of claim 17, wherein the calculating comprises integrating a temperature of the braking means.

19. The method of claim 17, wherein modifying at least one vehicle function comprises switching the vehicle function between an inactive state and an active state.

20. The method of any of claims 17 to 19, comprising determining whether the remaining energy conversion capacity of the braking means to perform braking is sufficient to reduce the energy of the vehicle to less than or equal to an energy threshold.

21. The method of any of claims 17 to 20, comprising calculating the energy of the vehicle.

22. A non-transitory computer readable medium comprising computer readable instructions that, when executed by a processor, cause performance of the method of claim 17.