Vehicle on-demand hold control
Patent Information
- Authority / Receiving Office
- GB · GB
- Patent Type
- Patents
- Current Assignee / Owner
- JAGUAR LAND ROVER LTD
- Filing Date
- 2024-03-29
- Publication Date
- 2026-06-15
Smart Images
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Abstract
Description
TECHNICAL FIELD The present disclosure relates to vehicle on-demand hold control. Aspects of the invention relate to a control system, a foundation brake system, a vehicle, a method and computer-readable instructions. BACKGROUND It is known to provide vehicles having foundation brake systems configured to perform “hold” operations when a vehicle is stationary. Such hold operations involve applying enough brake force to keep the vehicle stationary, even if a driver reduces or ends a foundation brake input (for example takes their foot of a brake pedal). Hold operations are typically ended when the vehicle receives an input to move off (for example a driver actuating an accelerator pedal), and which point the foundation brakes are released, allowing the vehicle to move. Hold operations may be started automatically (for example every time a vehicle speed reaches zero and the vehicle is in a forward drive mode / gear). In addition, it is known to provide “on-demand hold” functionality. In this case, rather than automatically performing a hold operation whenever vehicle speed is zero, hold operations are only performed responsive to a particular driver input, and subject to the vehicle speed being zero. Such driver inputs are generally made via the same means a driver usually uses to cause operation of the foundation brakes (e.g., a brake pedal), and often involve requiring t a driver to make a request a brake force above a threshold force (for example by applying a pressure above a threshold pressure to a brake pedal. However, it can be difficult for a driver to know if they have successfully made an input that exceeds the applicable threshold. This is particularly true for road vehicle electronic brake systems (e.g., electrohydraulic brake systems), wherein brake pedal resistance differs to traditional vacuum brake systems, providing drivers with different feedback behaviour. There is a desire to improve techniques for detecting and recognising driver inputs to request on-demand hold, to ensure that deliberate driver inputs are recognised more accurately. Similarly, there is a desire to improve filtering of driver foundation brake inputs that were not made for the purposes of requesting on-demand hold, to avoid false-positive input recognition. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide an control system for controlling a foundation brake system of a vehicle, a foundation brake system of a vehicle, a vehicle, a method of controlling a foundation brake system of a vehicle and computer readable instructions as claimed in the appended claims According to an aspect of the present invention there is provided a vehicle control system configured to: • determine that a vehicle speed is below a threshold speed; • in dependence on determining that the vehicle speed is below the threshold speed, detect an increase in driver foundation brake demand; • in dependence on detecting the increase in driver foundation brake demand, determine a first value based on a rate of increase of driver foundation brake demand; • in dependence on determining the first value indicating the rate of increase of the driver foundation brake demand satisfies one or more first criteria (e.g., the first value exceeds a threshold or indicates that the rate of increase is greater than a threshold rate of increase), monitor for a decrease in driver foundation brake demand; • while monitoring for the decrease in driver foundation brake demand, detect the decrease in driver foundation brake demand; • in dependence on detecting the decrease in driver foundation brake demand, determine a second value based on a rate of decrease of driver foundation brake demand; and • in dependence on determining the second value indicating the rate of decrease of the driver foundation brake demand satisfies one or more second criteria (e.g., the magnitude of the second value exceeds a threshold or indicates that the rate of decrease is greater than a threshold rate of decrease), command the foundation brake system to perform a vehicle hold operation. According to another aspect of the present invention there is provided a control system for controlling a foundation brake system of a vehicle, the control system comprising one or more processors collectively configured to: • determine that a vehicle speed is below a threshold speed (e.g., based on a signal received from sensors or systems elsewhere on the vehicle); • in dependence on determining that the vehicle speed is below the threshold speed, detect an increase in driver foundation brake demand (e.g., a driver input to request an increase in brake force delivered by one or more foundation brakes, such as an increased pressure applied to a vehicle brake pedal); • in dependence on detecting the increase in driver foundation brake demand, determine a first value based on a rate of increase of driver foundation brake demand (e.g., corresponding to or based on an absolute rate of increase, a magnitude of rate of increase, an average rate of increase ora cumulative rate of increase); • in dependence on determining the first value indicating the rate of increase of the driver foundation brake demand exceeding a threshold rate of increase, monitor for a decrease in driver foundation brake demand; • while monitoring for the decrease in driver foundation brake demand, detect the decrease in driver foundation brake demand; • in dependence on detecting the decrease in driver foundation brake demand, determine a second value based on a rate of decrease of driver foundation brake demand (e.g., corresponding to or based on an absolute rate of decrease, a magnitude of rate of decrease, an average rate of decrease or a cumulative rate of decrease); and • in dependence on determining the second value indicating the rate of decrease of the driver foundation brake demand exceeding a threshold rate of decrease, command the foundation brake system to perform a vehicle hold operation (e.g., cause the foundation brakes to keep the vehicle stationary even if a driver ends an input to the foundation brake system, until the driver make an input to request movement of the vehicle such as via an accelerator pedal). Optionally, the one or more processors are configured to, in dependence on determining that the vehicle speed is below the threshold speed, monitor for an increase in driver foundation brake demand, and further detect the increase in driver foundation brake demand in dependence on monitoring for the increase. Advantageously, by comparing values based on rates of change of driver foundation brake demand, the control system provides an on-demand hold input mechanism that can be easily and reliably performed by a driver. In addition, by looking at both the rates of increase and decrease in driver brake demand, the control system effectively disambiguates between deliberate driver on-demand hold inputs, and other inputs that might inadvertently cause activation on on-demand hold functionality in prior art systems. Optionally, the one or more processors are collectively configured to: in dependence on determining that the magnitude of the first value exceeds the first predetermined threshold: monitor for the decrease in driver foundation brake demand during a first predetermined length of time (e.g., time period) after determining that the magnitude of the first value exceeds the first predetermined threshold. The first predetermined length of time advantageously provides a filter for distinguishing between deliberate attempts to activate on-demand hold from sudden increases in brake demand for other reasons. Furthermore, adjustment of the first length of time provides an effective means for tuning input recognition, adapting the response of the control system according to analysis of driver inputs. Optionally, the one or more processors are collectively configured to: • in dependence on detecting the increase in driver foundation brake demand: measure the rate of increase of driver foundation brake demand during a second predetermined length of time (e.g., time period) after detecting the increase in driver foundation brake demand; and determine the first value based on the rate of increase of driver foundation brake demand measured during the second predetermined length of time; and / or • in dependence on detecting the decrease in driver foundation brake demand: measure the rate of decrease of driver foundation brake demand during a third predetermined length of time (e.g., time period) after detecting the decrease in driver foundation brake demand; and determine the second value based on the rate of decrease of driver foundation brake demand measured during the third predetermined length of time. Beneficially, use of the second and / or third predetermined lengths of time provide further means for distinguishing deliberate driver requests for on-demand hold. Again, adjustment of the second and / or third predetermined lengths of time provides a means for effectively tuning the input recognition. In an embodiment, the first value is a sum of measured rates of change of driver foundation brake demand measured at intervals during the increase in driver foundation brake demand, and / or wherein the second value is a sum of measured rates of change of driver foundation brake demand measured at intervals during the decrease in driver foundation brake demand. In another embodiment, the first value is a first absolute rate of change of driver foundation brake demand measured during the increase in driver foundation brake demand, and / or wherein the second value is a second absolute rate of change of driver foundation brake demand measured during the decrease in driver foundation brake demand. Optionally, the one or more processors is collectively configured to: determine the second value based on the rate of decrease of driver foundation brake demand further in dependence on detecting that the driver foundation brake demand exceeded a first threshold demand during the increase in driver foundation brake demand, and command the foundation brake system to perform the vehicle hold operation further in dependence on detecting that the driver foundation brake demand fell below a second threshold demand during the decrease in driver foundation brake demand. Advantageously either embodiment above provides a more repeatably achievable set of criteria for a driver to activate on-demand hold than prior art systems utilizing a foundation brake demand threshold only. Optionally, the one or more processors are collectively configured to, in dependence on determining that the second value is below the second threshold, determine that the vehicle is stationary; and command the foundation brake system to perform a vehicle hold operation further in dependence on the determination that the vehicle is stationary. Advantageously, it is confirmed that the vehicle is stationary after a driver request for on-demand hold has been detected, rather than before. This ensures that early / pre-emptive inputs, made by a driver before the vehicle has detected that it is stationary, are effectively recognised. This is in contrast to prior art systems that require confirmation a vehicle is stationary prior to monitoring for on-demand hold requests, in which such early / pre-emptive requests are not typically recognised / detected. Optionally, the one or more processors are collectively configured to detect the increase in driver foundation brake demand in dependence on determining that an amount of variation in driver brake demand prior to the increase in driver foundation brake demand is below a variation threshold. Beneficially this provides a further means for distinguishing deliberate driver on-demand hold request inputs. Optionally, the one or more processors are collectively configured to monitor for the increase in driver foundation brake demand further in dependence on confirming that a drive selection input has not been made within a preceding fourth predetermined length of time; wherein the drive selection input comprises an input to change from a first vehicle drive mode of a plurality of vehicle drive modes to a second vehicle drive mode of the plurality of vehicle drive modes. For example, the plurality of vehicle drive modes includes a forward drive mode and a reverse drive mode. Optionally the plurality of vehicle drive modes also includes a neutral drive mode and a park drive mode. This advantageously reduces the chance that a foundation brake input made during low speed manoeuvring is incorrectly interpreted as an on-demand hold request (e.g., a false-positive input detection). According to an aspect of the present invention there is provided a control system comprising one or more controllers collectively comprising at least one electronic processor having an electrical input for receiving an input signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein; and wherein the at least one electronic processor is configured to access the at least one memory device and execute the instructions thereon so as to: • determine that a vehicle speed is below a threshold speed; • in dependence on determining that the vehicle speed is below the threshold speed, detect an increase in driver foundation brake demand; • in dependence on detecting the increase in driver foundation brake demand, determine a first value based on a rate of increase of driver foundation brake demand; • in dependence on determining the first value indicating the rate of increase of the driver foundation brake demand exceeding a threshold rate of increase, monitor for a decrease in driver foundation brake demand; • while monitoring for the decrease in driver foundation brake demand, detect the decrease in driver foundation brake demand; • in dependence on detecting the decrease in driver foundation brake demand, determine a second value based on a rate of decrease of driver foundation brake demand; and • in dependence on determining the second value indicating the rate of decrease of the driver foundation brake demand exceeding a threshold rate of decrease, command a foundation brake system to perform a vehicle hold operation. In another aspect of the present invention there is provided a foundation brake system comprising the control system above and one or more foundation brakes configured to provide a braking torque to one or more vehicle wheels. Optionally the one or more foundation brakes comprise one or more electrohydraulic brakes. The present driver on-demand hold input recognition provisions are particularly effective for electrohydraulic brakes, in which driver feedback via the brake pedal differs from that of traditional vacuum actuated brake systems. In yet another aspect of the present invention, there is provided a vehicle comprising the foundation brake system and / or the control system above. In a further aspect of the present invention, there is provided a method for operating a vehicle foundation braking system comprising: • determining that a vehicle speed is below a threshold speed; • in dependence on determining that the vehicle speed is below the threshold speed, detecting an increase in driver foundation brake demand; • in dependence on detecting the increase in driver foundation brake demand, determining a first value based on a rate of increase of driver foundation brake demand; • in dependence on determining the first value indicating the rate of increase of the driver foundation brake demand exceeding a threshold rate of increase, monitoring for a decrease in driver foundation brake demand; • while monitoring for the decrease in driver foundation brake demand, detecting the decrease in driver foundation brake demand; • in dependence on detecting the decrease in driver foundation brake demand, determining a second value based on a rate of decrease of driver foundation brake demand; and • in dependence on determining the second value indicating the rate of decrease of the driver foundation brake demand exceeding a threshold rate of decrease, commanding the foundation brake system to perform a vehicle hold operation. Optionally, the method comprises, in dependence on determining that the second value is below the second threshold, determining that the vehicle is stationary; and commanding the foundation brake system to perform a vehicle hold operation further in dependence on the determination that the vehicle is stationary. In a still further aspect of the present invention, there are provided computer readable instructions which, when executed by a computer, are arranged to perform the method above. 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, in which: Figure 1 shows a representation of a vehicle in accordance with an embodiment of the present invention; Figure 2 shows a schematic representation of the vehicle of figure 1; Figure 3 shows a method of controlling a foundation brake system in accordance with the present invention; and Figure 4 shows an example graph of a driver foundation brake demand corresponding to a request to activate on-demand vehicle hold. Figure 5 shows an example graph of a rate of change of driver foundation brake demand corresponding to a request to activate on-demand vehicle hold. DETAILED DESCRIPTION A vehicle 10 in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figures 1 and 2. With reference to Figure 2, the vehicle 10 of Figure 1 is illustrated schematically. The vehicle 10 includes a control system 100 and a foundation brake system 110 configured to deliver braking torque to one or more wheels 120. The foundation brake system 110 comprises one or more foundation brakes 112 (for example friction brakes) configured to apply a force that acts to resist motion of the wheels 120 (for example a force between brake pads and a brake disc in the case of calliper brakes). The vehicle 10 further comprises a driver foundation brake input system 130, for example comprising a brake pedal, via which a driver of the vehicle 10 demands a brake force to be applied by the foundation brakes 112. The foundation brake input system 130 may be part of the foundation brake system 110. The foundation brake system 110 may be an electrohydraulic brake system, wherein the driver foundation brake input system 130 outputs electrical signals used to control actuation of the foundation brakes 112. The control system 100 comprises a controller 101. The control system 100 as illustrated in Figure 1 comprises one controller 101, although it will be appreciated that this is merely illustrative. The controller 101 comprises processing means 102 and memory means 103. The processing means 102 may be one or more electronic processing device 102 which operably executes computer-readable instructions. The memory means 103 may be one or more memory device 103. The memory means 103 is electrically coupled to the processing means 102. The memory means 103 is configured to store instructions, and the processing means 102 is configured to access the memory means 103 and execute the instructions stored thereon. The control system 100 is configured to receive a signal indicative of a driver brake demand from the driver foundation brake input system 130. The control system 100 is configured to then output a control signal to the foundation brake system 110 to activate on-demand hold. The control system 100 comprises an input means 104 and an output means 105. The input means 104 may comprise an electrical input 104 of the control system 100. The output means 105 may comprise an electrical output 105 of the control system 100. The input 104 is arranged to receive the signal indicative of driver brake demand from the driver foundation brake input system 130. The processing means 102 is configured to determine whether the signal indicative of driver brake demand corresponds to a request to activate on-demand hold (as described in more detail below) - if so, the controller outputs a control signal via the output means 105, to the foundation brake system 110, the control signal instructing the foundation brake system 110 to perform a vehicle hold operation. As used herein, a vehicle hold operation means the actuation of vehicle foundation brakes so as to cause the vehicle 10 to remain stationary, without the driver having to maintain an input to the driver foundation brake input system 130. For example, when the foundation brake system 110 performs a vehicle hold operation, the vehicle 10 remains stationary even if the driver stops pressing a brake pedal. This is sometimes referred to as “auto-hold”. As illustrated, the vehicle further comprises a drive mode input system 140. The drive mode input system 140 is configured to receive a driver input, for example via a gear select lever, and change the drive mode of the vehicle responsive to the driver input. For example, the drive modes may include a forward direction drive mode, a reverse drive direction mode and a neutral drive mode. The control system 100 may further receive a signal indicative of a change in drive mode (for example forward, reverse or neutral) from the drive mode input system 140 via the input means 104. As illustrated, the vehicle 10 further comprises one or more sensors 150 configured to determine whether the vehicle 10 is stationary. The control system 100 may further receive a signal from the one or more sensors 150, via the input means 104, the signal indicative of whether the vehicle 10 is stationary. Figure 3 illustrates a method 300 according to an embodiment of the invention. The method 300 is a method of controlling a foundation brake system 110 of a vehicle 10, such as the foundation brake system 110 of the vehicle 10 illustrated in Figure 2. In particular, the method 300 is a method of selectively causing the foundation brake system 110 of performing a vehicle hold operation. The method 300 may be performed by the control system 100 illustrated in Figure 2. In particular, the memory 103 may comprise computer-readable instructions which, when executed by the processor 102, perform the method 300 according to an embodiment of the invention. Figure 4 shows a graph 400 of an example driver brake input D plotted against time t corresponding to a driver request to activate on-demand hold, in accordance with the method 300 of figure 3. The method 300 begins at step S-302, in which it is determined whether the vehicle speed is less than a threshold speed, such as at time tO. For example, the control system 100 receives a signal indicative of the speed of the vehicle 10 from the one or more sensors 150, and compares the speed indicated by the signal with the threshold speed. In examples, the threshold speed is 1.5 km / h, 1.0 km / h, 0.5 km / h, 0.45 km / h, or less. The use of the speed threshold in this way allows the control system 100 to start monitoring for a driver input to activate on-demand hold before the vehicle 10 is completely stationary. This in turn allows the control system 100 to recognise driver inputs to activate on-demand hold made as the vehicle 10 is reaching a standstill, reducing the chance that a driver input is not acted upon by the vehicle 10. Optionally, the method includes determining whether a drive mode of the vehicle 10 is being changed at step S-304. For example, the control system 100 determines whether a signal has been received from the drive mode input system 140 indicative of the drive mode being changed (for example from a forward drive mode to a reverse drive mode, or vice versa). If it is determined that the drive mode of the vehicle 10 is being changed, the method ends and / or returns to step S-302. Advantageously, this allows the control system 100 to filter out signals from the driver foundation brake input system 130 that might superficially look like a request for on-demand vehicle hold but is due to driver brake inputs made during a change in drive mode. Accordingly, the accuracy of driver on-demand hold requests is improved. If it is determined that the drive mode of the vehicle 10 is not being changed, the method 300 proceeds to step S-306. In alternative embodiments, step S-304 may be performed at a different point in the method 300, for example after step S-324 described below. The method 300 optionally further includes determining that an amount of variation in driver brake demand D prior to the increase in driver foundation brake demand D is below a variation threshold (for example, driver foundation brake demand D remains non-zero (to confirm the driver continues to make a foundation brake demand) and substantially constant, e.g., varies by no more than 5%, or no more than 1%, over a predetermined length of time) prior to proceeding to step S-306. Beneficially this helps distinguish deliberate driver on-demand hold requests from inputs associated with, or characteristic of, foundation brake operation during normal driving. Although optional step S-304 is illustrated as occurring after steps S-302, step S-304 may alternatively occur before or contemporaneously with step S-302. If the vehicle speed is less than the threshold speed (and optionally if it is determined that the drive mode of the vehicle is not being changed), the control system 100 begins to monitor for an increase in driver brake demand D (that is, an increase in the brake force demanded by the driver), for example between tO and t1. At step S-306 it is determined that the driver brake demand has increased, for example at t1. For example, the control system 100 receives a signal from the driver foundation brake input system 130 indicative of the driver having demanded increased foundation brake force (e.g., by increasing pressure on a brake pedal). Optionally step S-306 is only performed if the driver brake demand D increases by more than a certain amount, or at or above a certain rate. Responsive to determining the increase in driver brake demand, a first value based on a rate of increase of the driver brake demand is determined at step S-308. For example, the control system 100 is configured to identify the rate of change of driver brake demand D based on the signal received from the driver foundation brake input system 130 and use the rate of change to calculate the first value. The first value is optionally the rate of increase of driver brake demand D, an average rate of increase of driver brake demand D, a cumulative rate of increase of driver brake demand D, orthe magnitude(s) thereof. Optionally, the rate of increase of driver foundation brake demand D is measured over a predetermined length of time t1 to t2 at step S-310, starting after the increase has been determined in step S-306, and the first value is determined based on the rate of increase of driver foundation brake demand measured during the predetermined time period at step S-312. For example, a detected / received rate of change of driver foundation brake demand is first filtered, for example using a moving average window, before using the filtered rate to calculate the first value. In an example, the first value is, oris determined based on, an average or cumulative rate of increase of driver brake demand D over that predetermined length of time 402 (that is, a sum of measured rates of change of driver foundation brake demand measured at intervals during the increase in driver foundation brake demand D and / or between times t1 and t2). In one example, the intervals correspond to a frequency of 50Hz or higher. At step S-314, it is determined whether the determined first value is indicative of the rate of increase of driver brake demand having exceeded a threshold rate of increase, for example between time t1 and time t2. If it is determined that the rate of increase of the driver brake demand has not exceeded the threshold, the method 300 ends or returns to step S-302. Thus, the invention beneficially distinguishes between a deliberate, quick increase in brake force demand by the driver and more gradual increases corresponding to different driver intention. If it is determined that that the rate of increase of the driver brake demand has exceeded the threshold, the method proceeds to step S-316, in which the control system 100 monitors for a decrease in driver input demand, for example based on a signal received from the driver foundation brake input system 130. In some examples, the first value corresponds to, or is calculated based on, the maximum value of the rate of increase of driver brake demand (e.g., during the predetermined length of time 402). In this case, it is further determined whether the absolute value of the driver foundation brake demand D exceeds a first threshold demand D1 at step S-314. Proceeding to step S-316 is then further dependent on the absolute value of the driver foundation brake demand D having exceeded a first threshold demand D1. In an example, the control system 100 monitors for a decrease in driver brake demand D for a further predetermined length of time 404 (e.g., from t2 to t4). Advantageously, this further helps distinguish deliberate driver inputs, based on the decrease in foundation brake demand D being made within a certain time of detecting the initial increase in demand D. While monitoring for the decrease in driver foundation brake demand D, at step S-317 a decrease in driver foundation brake demand D is detected (for example by the control system 100 based on a signal from the driver foundation brake input system 130 at time t3). Responsive to determining the decrease in driver brake demand, a second value based on a rate of decrease of the driver brake demand is determined at step S-318. For example, the control system 100 is configured to identify the rate of change of driver brake demand D based on the signal received from the driver foundation brake input system 130 and use the rate of change to calculate the second value. The second value is optionally the rate of decrease of driver brake demand D, an average rate of decrease of driver brake demand D, a cumulative rate of decrease of driver brake demand D, or the magnitude(s) thereof. Optionally, the rate of decrease of driver foundation brake demand D is measured over a further predetermined length of time 406 (e.g., t3 to t5) at step S-320, starting after the increase has been determined in step S-317, and the second value is determined based on the rate of decrease of driver foundation brake demand D measured during this further predetermined time period at steps S-322. Again, a detected / received rate of change of driver foundation brake demand may first be filtered, for example using a moving average window, before using the filtered rate to calculate the second value. In an example, the second value is, or is determined based on, an average or cumulative rate of decrease of driver brake demand D over the further predetermined length of time (that is, a sum of measured rates of change of driver foundation brake demand measured at intervals during the decrease in driver foundation brake demand D and / or between times t3 and t5). In one example, the intervals correspond to a frequency of 50Hz or higher. At step S-324, it is determined whether the determined second value is indicative of the rate of decrease of driver brake demand having exceeded a threshold rate of decrease, for example between time t3 and time t5. If it is determined that the rate of decrease of the driver brake demand has not exceeded the threshold, the method 300 ends or returns to step S-302. This advantageously further enhances discrimination between a deliberate, quick increase and then decrease in brake force demand by the driver and other inputs for more gradual decreases corresponding to different driver intentions. In an example, the control system 100 monitors for a decrease in driver brake demand D for a further predetermined length of time 404 (e.g., from t2 to t4). Advantageously, this further helps distinguish deliberate driver inputs, based on the decrease in foundation brake demand D being made within a certain time of detecting the initial increase in demand D. In some examples, the second value corresponds to, or is calculated based on, the maximum value of the rate of decrease of driver brake demand (e.g., during the predetermined length of time 406). In this case, it is optionally further determined whether the absolute value of the driver foundation brake demand D fell below a second threshold demand D2 at step S-324. Proceeding to step S-325 or S-326 (discussed below) is then further dependent on the absolute value of the driver foundation brake demand D having fallen below the second threshold demand D2. The present invention therefore provides an on-demand hold request input that is based on a rate of change of driver brake demand D. Beneficially, it is easier for a driver to successfully make such an input as compared to traditional on-demand hold inputs based only on an absolute brake force / brake pedal pressure value. This is particularly the case for electronic brake systems, where resistance to driver brake pedal input is typically provided using a mechanical spring coupled to the pedal, and it can be difficult for a driver to judge whether they have applied sufficient pressure to the pedal to overcome any given threshold. As a result, the present invention is capable of recognising a greater percentage of attempted driver on-demand hold inputs. Moreover, the present invention analyses not only the rate of change of an increase in foundation brake demand D, but also a subsequent decrease. Advantageously, this provides for enhanced disambiguation between deliberate driver on-demand hold inputs, and other inputs involving an increase in foundation brake demand (for example a driver naturally increasing pressure on a brake pedal as the vehicle becomes stationary then resting their foot on the brake pedal, or a driver making a sudden increase in brake pressure to avoid a hazard as the vehicle is close to becoming stationary). It is further noted that, advantageously, the use of the optional predetermined lengths of time 402, 404, 406 provides fortunability of the system. For example, the respective predetermined lengths of time 402, 404, 406 can be individually chosen / adapted based on empirical data obtained during testing to ensure effective recognition of deliberate driver on-demand hold inputs and filtering of other inputs to avoid false-positive driver on-demand hold input recognition. Further, the control system 100 can be updated in situ by updating the predetermined lengths of time 402, 404, 406 if required. An example graph 500 illustrating a particular implementation of the method 300 of figure 3 is shown in figure 5, in which the rate of change in driver braking demand (dD) is plotted against time t dD / dt. In this example, the first value is, or is calculated based on, the rate of change in driver brake demand dD / dt. At step S-314, it is determined whether the determined first value exceeds a first threshold rate, dD / dt1. If it is determined that that the rate of increase of the driver brake demand has exceeded the first threshold dD / dt1, the method proceeds to step S-316, in which the control system 100 monitors for a decrease in driver input demand. In this example, the control system 100 only activates an on demand hold operation if the rate of change of driver demand is determined to have fallen below a second threshold dD / dt2 at step S-318 within a predetermined time period 504 starting when the rate of change exceeded the first threshold dD / dt1. In the illustrated example, the system determines (step S-314) that the rate of change of driver brake demand exceeds the first threshold dD / dt1 at time t6, and predetermined time period 504 begins - because the rate of change of driver brake demand is determined (step S-324) to have fallen below the second threshold dD / dt2 before the time period 504 ends at time t7, the method proceeds to step S-325. Determining that the rate of decrease of the driver brake demand has exceeded the threshold, corresponds to the control system 100 determining that a driver input to request on-demand hold has been made. In an example, the method 300 then proceeds to step S-325, in which it is determined that the vehicle 10 is stationary. It is desirable that the vehicle 10 is completely stationary before the foundation brake system 110 performs any on-demand hold operation, to avoid the vehicle 10 behaving in a manner unexpected to the driver. Advantageously, by confirming that the vehicle 10 is stationary after the driver on-demand hold request input has been detected (as opposed to confirming that the vehicle 10 is stationary before starting to monitor for a driver on-demand hold request input), the method improves driver input detection and recognition as noted above. The inventors have discovered that driver perception of vehicle speed can subtly differ from actual vehicle speed. For example, a human driver may interpret a vehicle as being stationary before the vehicle has actually become stationary, or before vehicle systems have detected and registered that the vehicle is stationary. It is therefore possible for a driver to perceive a vehicle as being stationary and start making an input to request on-demand hold before that vehicle has registered that it is stationary. In prior art systems, in which it is typically confirmed that a vehicle is stationary before starting to monitor for a driver on-demand hold request input, such inputs would not be recognised, or would be ignored. This in turn provides inaccurate feedback to the driver, in that the vehicle would not behave in a manner corresponding to the input they had made. In contrast, in the present case confirming the vehicle 10 is stationary at step S-325 ensures that “early” driver inputs are not missed, and the vehicle 10 responds as the driver expects. If it is determined that that the rate of decrease of the driver brake demand has exceeded the threshold, the method proceeds to step S-326, in which the foundation brake system is commanded to perform a vehicle hold operation. For example, the control system 100 sends a control signal to the foundation brake system 110 (for example via output means 105). In response to this control signal, the foundation brake system 110 actuates the foundation brakes 112, applying enough brake force to keep the vehicle 10 stationary. The foundation brake system 110 further causes the foundation brakes 112 to maintain enough brake force to keep the vehicle 10 stationary even if the driver reduces their brake demand D, for example to zero (e.g., lifting their foot off a brake pedal of driver foundation brake input system 130), until the driver makes a further input to increase the speed of the vehicle (e.g., via an accelerator pedal). It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.
Claims
1. A control system for controlling a foundation brake system of a vehicle, the control system comprising one or more processors collectively configured to:determine that a vehicle speed is below a threshold speed;in dependence on determining that the vehicle speed is below the threshold speed, detect an increase in driver foundation brake demand;in dependence on detecting the increase in driver foundation brake demand, determine a first value based on a rate of increase of driver foundation brake demand;in dependence on determining the first value indicating the rate of increase of the driver foundation brake demand exceeding a threshold rate of increase, monitor for a decrease in driver foundation brake demand;while monitoring for the decrease in driver foundation brake demand, detect the decrease in driver foundation brake demand;in dependence on detecting the decrease in driver foundation brake demand, determine a second value based on a rate of decrease of driver foundation brake demand; andin dependence on determining the second value indicating the rate of decrease of the driver foundation brake demand exceeding a threshold rate of decrease, command the foundation brake system to perform a vehicle hold operation.
2. The control system of claim 1, wherein the one or more processors are collectively configured to:in dependence on determining that the magnitude of the first value exceeds the first predetermined threshold:monitor for the decrease in driver foundation brake demand during a first predetermined length of time after determining that the magnitude of the first value exceeds the first predetermined threshold.
3. The control system of claim 1 or claim 2, wherein the one or more processors are collectively configured to:in dependence on detecting the increase in driver foundation brake demand:measure the rate of increase of driver foundation brake demand during a second predetermined length of time after detecting the increase in driver foundation brake demand; anddetermine the first value based on the rate of increase of driver foundation brake demand measured during the second predetermined length of time; and / orin dependence on detecting the decrease in driver foundation brake demand:measure the rate of decrease of driver foundation brake demand during a third predetermined length of time after detecting the decrease in driver foundation brake demand; anddetermine the second value based on the rate of decrease of driver foundation brake demand measured during the third predetermined length of time.
4. The control system of any preceding claim, wherein the first value is a sum of measured rates of change of driver foundation brake demand measured at intervals during the increase in driver foundation brake demand, and / orwherein the second value is a sum of measured rates of change of driver foundation brake demand measured at intervals during the decrease in driver foundation brake demand.
5. The control system of claims 1 to 3, wherein the first value is a first absolute rate of change of driver foundation brake demand measured during the increase in driver foundation brake demand, and / orwherein the second value is a second absolute rate of change of driver foundation brake demand measured during the decrease in driver foundation brake demand.
6. The control system of claim 5, wherein the one or more processors is collectively configured to: determine the second value based on the rate of decrease of driver foundation brake demand further in dependence on detecting that the driver foundation brake demand exceeded a first threshold demand during the increase in driver foundation brake demand, andcommand the foundation brake system to perform the vehicle hold operation further in dependence on detecting that the driver foundation brake demand fell below a second threshold demand during the decrease in driver foundation brake demand.
7. The control system of any preceding claim, wherein the one or more processors are collectively configured to, in dependence on determining that the second value is below the second threshold, determine that the vehicle is stationary; andcommand the foundation brake system to perform a vehicle hold operation further in dependence on the determination that the vehicle is stationary.
8. The control system of any preceding claim, wherein the one or more processors are collectively configured to detect the increase in driver foundation brake demand in dependence on determining that an amount of variation in driver brake demand prior to the increase in driver foundation brake demand is below a variation threshold.
9. The control system of any preceding claim, wherein the one or more processors are collectively configured to monitor for the increase in driver foundation brake demand further in dependence on confirming that a drive selection input has not been made within a preceding fourth predetermined length of time;wherein the drive selection input comprises an input to change from a first vehicle drive mode of a plurality of vehicle drive modes to a second vehicle drive mode of the plurality of vehicle drive modes.
10. A foundation brake system comprising the control system of any preceding claim and one or more foundation brakes configured to provide a braking torque to one or more vehicle wheels.11.The foundation brake system of claim 10, wherein the one or more foundation brakes comprise one or more electrohydraulic brakes.
12. A vehicle comprising the foundation brake system of claim 10 or claim 11, or the control system of any of claims 1 to 9.
13. A method for operating a vehicle foundation braking system comprising:determining that a vehicle speed is below a threshold speed;in dependence on determining that the vehicle speed is below the threshold speed, detecting an increase in driver foundation brake demand;in dependence on detecting the increase in driver foundation brake demand, determining a first value based on a rate of increase of driver foundation brake demand;in dependence on determining the first value indicating the rate of increase of the driver foundation brake demand exceeding a threshold rate of increase, monitoring for a decrease in driver foundation brake demand;while monitoring for the decrease in driver foundation brake demand, detecting the decrease in driver foundation brake demand;in dependence on detecting the decrease in driver foundation brake demand, determining a second value based on a rate of decrease of driver foundation brake demand; andin dependence on determining the second value indicating the rate of decrease of the driver foundation brake demand exceeding a threshold rate of decrease, commanding(S-326) the foundation brake system to perform a vehicle hold operation.
14. The method of claim 13, comprising, in dependence on determining that the second value is below the second threshold, determining that the vehicle is stationary; andcommanding the foundation brake system to perform a vehicle hold operation further in dependence on the determination that the vehicle is stationary.
15. Computer readable instructions which, when executed by a computer, are arranged to perform a method according to claim 13 or claim 14.